U.S. patent application number 11/896448 was filed with the patent office on 2008-04-24 for movable body drive method and movable body drive system, pattern formation method and apparatus, exposure method and apparatus, and device manufacturing method.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Yuichi Shibazaki.
Application Number | 20080094592 11/896448 |
Document ID | / |
Family ID | 39136023 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080094592 |
Kind Code |
A1 |
Shibazaki; Yuichi |
April 24, 2008 |
Movable body drive method and movable body drive system, pattern
formation method and apparatus, exposure method and apparatus, and
device manufacturing method
Abstract
During the drive of a stage, positional information in a
movement plane of a stage is measured by three encoders that
include at least one each of an X encoder and a Y encoder of an
encoder system, and a controller switches an encoder used for a
measurement of positional information of a stage in the movement
plane from an encoder to an encoder so that the position of the
stage in the movement plane is maintained before and after the
switching. Therefore, although the switching of the encoder used
for controlling the position of the stage is performed, the
position of the stage in the movement plane is maintained before
and after the switching, and a correct linkage becomes
possible.
Inventors: |
Shibazaki; Yuichi;
(Kumagaya-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
NIKON CORPORATION
TOKYO
JP
|
Family ID: |
39136023 |
Appl. No.: |
11/896448 |
Filed: |
August 31, 2007 |
Current U.S.
Class: |
355/53 ;
310/12.06; 310/12.19; 355/67; 355/77; 356/509 |
Current CPC
Class: |
G03F 7/70775 20130101;
G03F 9/7088 20130101; G03F 7/70341 20130101; G03F 7/7085 20130101;
G03F 7/70725 20130101 |
Class at
Publication: |
355/053 ;
310/012; 355/067; 355/077; 356/509 |
International
Class: |
G03B 27/42 20060101
G03B027/42; G01B 11/02 20060101 G01B011/02; G03B 27/54 20060101
G03B027/54; H02K 41/00 20060101 H02K041/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2006 |
JP |
2006-237045 |
Sep 1, 2006 |
JP |
2006-237491 |
Sep 1, 2006 |
JP |
2006-237606 |
Claims
1. A movable body drive method in which a movable body is driven in
a movement plane including a first axis and a second axis
orthogonal to each other, the method comprising: a measuring
process in which positional information of the movable body in the
movement plane is measured using at least one encoder of an encoder
system including a plurality of encoders having a head that
irradiates a detection light on a grating and receives the
detection light from the grating; and a switching process in which
at least one of an encoder used for position control of the movable
body is switched to another encoder so as to maintain a position of
the movable body in the movement plane before and after the
switching.
2. The movable body drive method according to claim 1 wherein in
the switching process, a measurement value of a newly used encoder
is predicted so that a result of position measurement of the
movable body is continuously linked before and after the switching,
and the predicted value is set as an initial value of the
measurement value of the newly used encoder.
3. The movable body drive method according to claim 2 wherein in
order to predict the measurement value of the newly used encoder, a
predetermined theoretical formula that includes a rotation angle of
the movable body in the movement plane as a parameter and a
required number of measurement values of active encoders including
an encoder which will be suspended later are used.
4. The movable body drive method according to claim 3 wherein when
predicting the measurement value of the newly used encoder, a value
obtained from a measurement result of a measurement unit different
from the encoder system is used as the rotation angle of the
movable body in the movement plane.
5. The movable body drive method according to claim 1 wherein in
the measuring process, at least two encoders of the encoder system
is used to measure the positional information of the movable body
in the movement plane, and in the switching process, the encoder
used for position control of the movable body is switched from an
encoder of the at least two encoders to another encoder.
6. The movable body drive method according to claim 5 wherein in
the measuring process, three encoders are used to measure
positional information of the movable body in the movement plane in
directions of three degrees of freedom, and in the switching
process, the encoder used for position control of the movable body
is switched from an encoder of the at least two encoders to another
encoder so as to maintain a position of the movable body in
directions of the three degrees of freedom before and after the
switching.
7. The movable body drive method according to claim 1 wherein on
the movable body, at least one each of a first grating having a
periodic direction parallel to the first axis and a second grating
having a periodic direction parallel to the second axis is placed,
and a head of each encoder is placed external to the movable
body.
8. The movable body drive method according to claim 7 wherein on
the movable body, a pair of the first gratings having a direction
parallel to the first axis serving as a longitudinal direction is
placed in a direction parallel to the second axis serving as a
longitudinal direction at a predetermined distance.
9. The movable body drive method according to claim 1 wherein as
each of the encoders, a reflection type optical encoder is
used.
10. The movable body drive method according to claim 1 wherein in
the switching process, when the switching is performed, positional
information of the movable body in the movement plane is computed
according to a computing formula that uses an affine transformation
relation based on the measurement values of an at least the two
encoders used for position control of the movable body before
switching, and an initial value of the measurement value of the
another encoder is decided so as to satisfy the computation
result.
11. The movable body drive method according to claim 10 wherein in
the switching process, the initial value is decided taking into
consideration at least one of correction information of the
measurement value of the another encoder corresponding to a
relative movement of a head of the another encoder with respect to
the corresponding grating and of correction information of the
pitch of the corresponding grating.
12. The movable body drive method according to claim 1, the method
further comprising: a scheduling process in which a combination of
encoders subject to the switching is made and a switching timing is
prepared based on a movement course of the movable body, prior to
the switching.
13. The movable body drive method according to claim 1 wherein in
the switching process, an output of each encoder of the encoder
system is constantly taken in, and a switching operation of
switching from one encoder of the at least two encoders to another
encoder is also executed in synchronization with a timing of
position control of the movable body.
14-152. (canceled)
153. A pattern formation method, comprising: a mount process in
which an object is mounted on a movable body that can move in a
movement plane; and a drive process in which the movable body is
driven by the movable body drive method according to claim 1, to
form a pattern on the object.
154. A device manufacturing method including a pattern formation
process wherein in the pattern formation process, a pattern is
formed on a substrate using the pattern formation method according
to claim 153.
155. An exposure method in which a pattern is formed on an object
by an irradiation of an energy beam wherein for relative movement
of the energy beam and the object, a movable body on which the
object is mounted is driven, using the movable body drive method
according to claim 1.
156. A movable body drive method in which a movable body is driven
in a movement plane, the method comprising: an intake process in
which measurement data corresponding to a detection signal of at
least one head of an encoder system including a plurality of heads
that measure positional information of the movable body within the
movement plane is taken in at a predetermined control sampling
interval when the movable body is driven in a predetermined
direction in the movement plane; and a drive process in which the
movable body is driven so as to correct a measurement error of the
head due to a measurement delay that accompanies propagation of the
detection signal, based on a plurality of data which include the
most recent measurement data that was taken in the latest and
previous measurement data including at least data just before the
most recent measurement data, and information of a delay time that
accompanies propagation of the detection signal through a
propagation path.
157. The movable body drive method according to claim 156 wherein
in the intake process, the positional information of the movable
body is measured using the plurality of heads of the encoder
system, and measurement data corresponding to a detection signal of
each head is also taken in at the control sampling interval, and in
the drive process, the movable body is driven so as to correct
respective measurement errors of the plurality of heads due to the
measurement delay, based on the plurality of data for each of the
plurality of heads and the information on the delay time.
158. The movable body drive method according to claim 156 wherein
in the intake process, the positional information of the movable
body is measured sequentially using a plurality of heads of the
encoder system arranged apart in the predetermined direction, and
measurement data corresponding to the detection signal of each head
is taken in at the control sampling interval.
159. The movable body drive method according to claim 156 wherein
in the drive process, one of an approximation straight line and an
approximate curve that shows the temporal change of the position of
the movable body is obtained, using the plurality of data for the
head, and based on one of the approximation straight line and the
approximate curve, and information of the delay time of the head,
the movable body is driven so as to correct the measurement error
of the head due to the measurement delay.
160. The movable body drive method according to claim 156 wherein
the positional information of the movable body in the movement
plane is measured furthermore by an interferometer system, the
method further comprising: a delay time acquisition process in
which a delay time acquisition processing of driving the movable
body in a predetermined direction, taking in a detection signal of
the head and a detection signal of the interferometer system
simultaneously at a predetermined sampling timing for at least one
head of the encoder system during the drive, and acquiring
information of the delay time of the at least one head based on
both detection signals, with the detection signal of the
interferometer system serving as a reference are executed.
161. The movable body drive method according to claim 160 wherein
in the delay time acquisition process, the delay time acquisition
processing is executed for all heads in the encoder system.
162. The movable body drive method according to claim 160 wherein
in the delay time acquisition process, on the delay time
acquisition processing, information of the delay time of the head
is computed based on an intensity difference of the detection
signal of the head and the detection signal of the interferometer
system.
163. A pattern formation method, comprising: a mount process in
which an object is mounted on a movable body that can move in a
movement plane; and a drive process in which the movable body is
driven by the movable body drive method according to claim 156, to
form a pattern on the object.
164. A device manufacturing method including a pattern formation
process wherein in the pattern formation process, a pattern is
formed on a substrate using the pattern formation method according
to claim 163.
165. An exposure method in which a pattern is formed on an object
by an irradiation of an energy beam wherein for relative movement
of the energy beam and the object, a movable body on which the
object is mounted is driven, using the movable body drive method
according to claim 156.
166. An exposure method in which an object on a movable body that
moves in a movement plane is sequentially exchanged, and a pattern
is formed respectively on each object by sequentially exposing the
object after exchange, wherein each time the exchange of the object
is performed on the movable body, position control of the movable
body in the movement plane is started once more, using at least
three encoders of an encoder system that measures positional
information of the movable body in the movement plane within a
predetermined effective area including an exposure position.
167. The exposure method according to claim 166 wherein as each
encoder of the encoder system, an encoder is used that measures the
positional information of the movable body in the measurement
direction by irradiating a detection light on a grating placed on a
surface parallel to the movement plane of the movable body and
receiving the light from each grating.
168. The exposure method according to claim 166 wherein even while
exchange of the object is performed on the movable body,
measurement of the positional information of the movable body in
the measurement direction is continued using a specific encoder of
the encoder system.
169. The exposure method according to claim 166 wherein the
positional information of the movable body in the movement plane is
measured by an interferometer system, whereby when the movable body
moves outside the effective area from inside the effective area,
position control of the movable body in the movement plane is
switched from the position control using the encoder system to the
position control using the interferometer system, and when the
movable body moves inside the effective area from outside the
effective area, position control of the movable body in the
movement plane is switched from the position control using the
interferometer system to the position control using the encoder
system.
170. The exposure method according to claim 169 wherein after
having moved the movable body once near a position decided
beforehand based on a measurement value of the interferometer
system, by finely moving the movable body and at a point where an
absolute phase of each of the at least three encoders respectively
become a value that was decided beforehand, position control of the
movable body in the movement plane using the at least three
encoders is started once more.
171. The exposure method according to claim 166, wherein each time
the exchange of the object is performed on the movable body, prior
to beginning detection of a mark formed on the object using a mark
detection system, position control of the movable body in the
movement plane using the at least three encoders is started once
more.
172. A device manufacturing method including a pattern formation
process in which a pattern is sequentially formed on a plurality of
objects, using the exposure apparatus according to claim 171.
173. A movable body drive method in which a movable body is driven
in a movement plane, the method comprising: an execution process in
which of an encoder system including a plurality of encoders
respectively having a head that irradiates a detection light on a
grating and receives the detection light from the grating and
measures positional information of the movable body in the movable
plane, an output of each encoder is constantly taken in, and an
operation of switching an encoder used for position control of the
movable body from an encoder that has been used for position
control of the movable body to another encoder, at a timing in
synchronization with the position control of the movable body is
executed.
174. A movable body drive method in which a movable body is driven
in a movement plane including a first axis and a second axis
orthogonal to each other, the method comprising: a measuring
process in which positional information of the movable body in the
movement plane is measured using at least one encoder of an encoder
system including a plurality of encoders respectively having a head
that irradiates a detection light on a grating and receives the
detection light from the grating; a scheduling process in which a
combination of encoders subject to a switching where an encoder
used for position control of the movable body is switched from an
arbitrary encoder to another encoder is made and a switching timing
is prepared, based on a movement course of the movable body; and a
switching process in which the arbitrary encoder is switched to the
another encoder based on the contents prepared in the
scheduling.
175. The movable body drive method according to claim 174 wherein
in the measuring process, three encoders are used to measure
positional information of the movable body in the movement plane in
directions of three degrees of freedom, and in the scheduling
process, a combination of encoders subject to a switching where an
encoder is switched from an arbitrary encoder of the three encoders
to another encoder is made and a switching timing is prepared,
based on a movement course of the movable body.
176. The movable body drive method according to claim 174 wherein
in the switching process, an output of each encoder of the encoder
system is constantly taken in, and a switching operation of
switching from the arbitrary encoder to another encoder is also
executed in synchronization with a timing of position control of
the movable body.
177. A movable body drive system in which a movable body is driven
in a movement plane including a first axis and a second axis
orthogonal to each other, the system comprising: an encoder system
having a plurality of encoders respectively having a head that
irradiates a detection light on a grating and receives the
detection light from the grating, including a first encoder used
for measuring positional information of the movable body in a
direction parallel to the first axis; and a controller that
measures positional information of the movable body in the movement
plane using at least one encoder of the encoder system, and also
switches at least one of an encoder used for measurement of the
positional information of the movable body in the movement plane to
another encoder so as to maintain a position of the movable body in
the movement plane before and after the switching.
178. The movable body drive system according to claim 177 wherein
the controller predicts a measurement value of a newly used encoder
so that a result of position measurement of the movable body is
continuously linked before and after the switching, and sets the
predicted value as an initial value of the measurement value of the
newly used encoder.
179. The movable body drive system according to claim 178 wherein
in order to predict the measurement value of the newly used
encoder, the controller uses a predetermined theoretical formula
that includes a rotation angle of the movable body in the movement
plane as a parameter and a required number of measurement values of
active encoders including an encoder which will be suspended
later.
180. The movable body drive system according to claim 179, the
system further comprising: a measurement unit that measures
positional information of the movable body in a rotation direction
in the movement plane, wherein when predicting the measurement
value of the newly used encoder, the controller uses a value
obtained from a measurement result of the measurement unit as the
rotation angle of the movable body in the movement plane.
181. The movable body drive system according to claim 177 wherein
the encoder system has a total of three encoders or more including
at least one each of the first encoder and a second encoder used
for measurement of positional information of the movable body in a
direction parallel to the second axis, and the controller measures
positional information of the movable body in the movement plane,
using at least two encoders which at least include one each of the
first encoder and the second encoder, and also switches the encoder
used for the measurement of the positional information of the
movable body from an encoder of one of the at least two encoders to
another encoder.
182. The movable body drive system according to claim 181 wherein
the controller switches from an encoder of one of three encoders
that measure positional information of the movable body in
directions of three degrees of freedom in the movement plane to
another encoder, so as to maintain a position of the movable body
in directions of three degrees of freedom in the movement plane
before and after the switching.
183. The movable body drive system according to claim 177 wherein
on the movable body, at least one each of a first grating having a
periodic direction parallel to the first axis and a second grating
having a periodic direction parallel to the second axis is placed,
and the encoder system includes at least one each of a first head
unit and a second head unit placed external to the movable body,
whereby the first head unit has a plurality of heads placed in a
direction intersecting the first grating at a predetermined
interval, and the second head unit has a plurality of heads placed
in a direction intersecting the second grating at a predetermined
interval.
184. The movable body drive system according to claim 183 wherein
on the movable body, a pair of the first gratings having a periodic
direction parallel to the first axis is placed in a direction of
the second axis at a predetermined distance, and the encoder system
includes a pair of the first head units corresponding to each of
the pair of first gratings.
185. The movable body drive system according to claim 177 wherein
each of the encoders is a reflection type optical encoder.
186. The movable body drive system according to claim 177 wherein
on the switching, the controller computes the positional
information of the movement plane of the movable body by a
computing formula using the affine transformation relation based on
the measurement value of at least the two encoders used for
position control of the movable body before the switching, and
decides an initial value of the measurement value of the another
encoder so as to satisfy the computation results.
187. The movable body drive system according to claim 186 wherein
the controller determines the initial value, taking into
consideration at least one of correction information of the
measurement value of the another encoder corresponding to a
relative movement of a head of the another encoder in a direction
besides the measurement direction with respect to the corresponding
grating and of correction information of the pitch of the
corresponding grating.
188. The movable body drive system according to claim 177 wherein
the controller makes a combination of encoders subject to the
switching and prepares a switching timing based on a movement
course of the movable body.
189. The movable body drive system according to claim 177 wherein
the controller constantly takes in measurement values of each
encoder of the encoder system, and also executes an operation to
switch the encoder used for control of the movable body from an
encoder of either of at least the two encoders used for position
control of the movable body to another encoder in synchronization
with the timing of the position control of the movable body.
190. A pattern formation apparatus, the apparatus comprising: a
movable body on which an object is mounted, and is movable in a
movement plane holding the object; and a movable body drive system
according to claim 177 that drives the movable body to perform
pattern formation with respect to the object.
191. The pattern formation apparatus according to claim 190, the
apparatus further comprising: an interferometer system that
measures positional information of the movable body; a mark
detection system that detects a mark located on the movable body
holding the object; and a switching unit that switches a
measurement unit used for position control of the movable body
prior to a measurement of a plurality of marks on the object by the
mark detection system, from the interferometer system to the
encoder system.
192. An exposure apparatus that forms a pattern on an object by an
irradiation of an energy beam, the apparatus comprising: a
patterning unit that irradiates the energy beam on the object; and
the movable body drive system according to claim 177, wherein the
movable body drive system drives the movable body on which the
object is mounted for relative movement of the energy beam and the
object.
193. A movable body drive system in which a movable body is driven
in a movement plane, the system comprising: an encoder system
including a plurality of heads that measure positional information
of the movable body in the movement plane; and a controller that
takes in measurement data corresponding to a detection signal of at
least one head of an encoder system at a predetermined control
sampling interval when the movable body is driven in a
predetermined direction in the movement plane, and drives the
movable body so that the measurement error of the head due to a
measurement delay that accompanies propagation of the detection
signal is corrected, based on a plurality of data that include the
most recent measurement data that was taken in the latest and
previous measurement data including at least data just before the
most recent measurement data, and information of a delay time that
accompanies propagation of the detection signal through a
propagation path.
194. The movable body drive system according to claim 193 wherein
the controller measures positional information of the movable body,
using a plurality of heads of the encoder system, and takes in
measurement data corresponding to a detection signal of each head
at the control sampling interval, and drives the movable body so as
to correct respective measurement errors of the plurality of heads
due to the measurement delay, based on the plurality of data for
each of the plurality of heads and the information on the delay
time.
195. The movable body drive system according to claim 193 wherein
the plurality of heads of the encoder system includes a plurality
of heads placed apart in the predetermined direction, and the
controller measures the positional information of the movable body
sequentially using a plurality of heads of the encoder system
placed apart in the predetermined direction, and takes in
measurement data corresponding to the detection signal of each head
at the control sampling interval.
196. The movable body drive system according to claim 193 wherein
the controller obtains one of an approximation straight line and an
approximate curve that shows the temporal change of the position of
the movable body, using the plurality of data for the head, and
based on one of the approximation straight line and the approximate
curve, and information of the delay time of the head, drives the
movable body so as to correct the measurement error of the head due
to the measurement delay.
197. The movable body drive system according to claim 193 wherein
the system further comprises an interferometer system that measures
positional information of the movable body in the movement plane,
and also further comprises a processing unit that executes a delay
time acquisition process in which a delay time acquisition
processing of driving the movable body in a predetermined
direction, taking in a detection signal of the head and a detection
signal of the interferometer system simultaneously at a
predetermined sampling timing during this drive for at least one
head of the encoder system, and acquiring information of the delay
time of the at least one head based on both detection signals, with
the detection signal of the interferometer system serving as a
reference are executed.
198. The movable body drive system according to claim 197 wherein
the processing unit executes the delay time acquisition processing
for all heads in the encoder system.
199. The movable body drive system according to claim 197 wherein
the processing unit computes information of the delay time of the
head based on an intensity difference of the detection signal of
the head and the detection signal of the interferometer system on
the delay time acquisition processing.
200. A pattern formation apparatus, the apparatus comprising: a
movable body on which an object is mounted, and is movable in a
movement plane holding the object; and a movable body drive system
according to claim 193 that drives the movable body to perform
pattern formation with respect to the object.
201. The pattern formation apparatus according to claim 200, the
apparatus further comprising: an interferometer system that
measures positional information of the movable body; a mark
detection system that detects a mark located on the movable body
holding the object; and a switching unit that switches a
measurement unit used for position control of the movable body
prior to a measurement of a plurality of marks on the object by the
mark detection system, from the interferometer system to the
encoder system.
202. An exposure apparatus that forms a pattern on an object by an
irradiation of an energy beam, the apparatus comprising: a
patterning unit that irradiates the energy beam on the object; and
the movable body drive system according to claim 193, wherein the
movable body drive system drives the movable body on which the
object is mounted for relative movement of the energy beam and the
object.
203. A movable body drive system in which a movable body is driven
in a movement plane, the system comprising: an encoder system
including a plurality of heads that measure positional information
of the movable body in the movement plane; an interferometer system
that measures positional information of the movable body in the
movement plane; a processing unit that executes a delay time
acquisition processing of driving the movable body in a
predetermined direction, taking in a detection signal of each head
and a detection signal of the interferometer system simultaneously
at a predetermined sampling timing for a plurality of heads of the
encoder system during the drive, and based on both detection
signals, acquiring information of the delay time of the detection
signals of the respective plurality of heads that accompanies the
propagation through the propagation path, with the detection signal
of the interferometer system serving as a reference; and a
controller that drives the movable body, based on measurement data
corresponding to the respective detection signals of the plurality
of heads of the encoder system and information of a delay time of
the plurality of heads, respectively.
204. A pattern formation apparatus, the apparatus comprising: a
movable body on which an object is mounted, and is movable in a
movement plane holding the object; and a movable body drive system
according to claim 203 that drives the movable body to perform
pattern formation with respect to the object.
205. The pattern formation apparatus according to claim 204, the
apparatus further comprising: an interferometer system that
measures positional information of the movable body; a mark
detection system that detects a mark located on the movable body
holding the object; and a switching unit that switches a
measurement unit used for position control of the movable body
prior to a measurement of a plurality of marks on the object by the
mark detection system, from the interferometer system to the
encoder system.
206. An exposure apparatus that sequentially exchanges an object on
a movable body that moves in a movement plane, and forms a pattern
respectively on each object by sequentially exposing the object
after exchange, the apparatus comprising: an encoder system
including at least three encoders that measure positional
information of the movable body in the movement plane in a
predetermined effective area including an exposure position; and a
controller that starts position control of the movable body in the
movement plane using at least three encoders of the encoder system
once more, each time exchange of the object is performed on the
movable body.
207. The exposure apparatus according to claim 206 wherein on a
surface parallel to the movement plane of the movable body, a
plurality of gratings is placed that include at least one each of a
first grating having a longitudinal direction in a first axis
direction and a second grating having a longitudinal direction in a
second axis direction which intersect with the first axis direction
in the surface parallel to the movement plane, and the encoder
system has at least three encoders respectively including a head
that irradiates detection light on each of the gratings and
receives the light from each grating individually.
208. The exposure apparatus according to claim 206 wherein the
controller continues measurement of the positional information of
the movable body in the measurement direction using a specific
encoder of the encoder system even while exchange of the object is
performed on the movable body.
209. The exposure apparatus according to claim 206, the apparatus
further comprising: an interferometer system that measures
positional information of the movable body in the movement plane,
wherein when the movable body moves outside the effective area from
inside the effective area, the controller switches position control
of the movable body in the movement plane from the position control
using the encoder system to the position control using the
interferometer system, and when the movable body moves inside the
effective area from outside the effective area, the controller
switches the position control of the movable body in the movement
plane from the position control using the interferometer system to
the position control using the encoder system.
210. The exposure apparatus according to claim 209 wherein after
having moved the movable body once near a position determined
beforehand based on a measurement value of the interferometer
system, the controller finely moves the movable body and at a point
where an absolute phase of each of the at least three encoders
respectively become a value that was decided beforehand, starts
position control of the movable body in the movement plane using
the at least three encoders once more.
211. The exposure apparatus according to claim 206, the apparatus
further comprising: a mark detection system that detects a mark
formed on the object, wherein each time the exchange of the object
is performed on the movable body, prior to beginning detection of a
mark formed on the object using a mark detection system, the
controller starts position control of the movable body in the
movement plane using the at least three encoders once more.
212. A movable body drive system in which a movable body is driven
in a movement plane, the system comprising: an encoder system
including a plurality of encoders respectively having a head that
irradiates a detection light on a grating and receives the
detection light from the grating and measures positional
information of the movable body in the movable plane; and a
controller that constantly takes in an output of each encoder of
the encoder system, and also executes an operation to switch the
encoder used for control of the movable body from an encoder that
has been used for position control of the movable body to another
encoder in synchronization with the timing of the position control
of the movable body.
213. A pattern formation apparatus, the apparatus comprising: a
movable body on which the object is mounted, and is movable in a
movement plane holding the object; and a movable body drive system
according to claim 212 that drives the movable body to perform
pattern formation with respect to the object.
214. The pattern formation apparatus according to claim 213, the
apparatus further comprising: an interferometer system that
measures positional information of the movable body; a mark
detection system that detects a mark located on the movable body
holding the object; and a switching unit that switches a
measurement unit used for position control of the movable body
prior to a measurement of a plurality of marks on the object by the
mark detection system, from the interferometer system to the
encoder system.
215. An exposure apparatus that forms a pattern on an object by an
irradiation of an energy beam, the apparatus comprising: a
patterning unit that irradiates the energy beam on the object; and
the movable body drive system according to claim 212 wherein the
movable body drive system drives the movable body on which the
object is mounted for relative movement of the energy beam and the
object.
216. A movable body drive system in which a movable body is driven
in a movement plane including a first axis and a second axis
orthogonal to each other, the system comprising: an encoder system
including a plurality of encoders having a head that irradiates a
detection light on a grating and receives the detection light from
the grating and measures positional information of the movable body
in the movable plane; and a controller that makes a combination of
encoders subject to a switching where an encoder used for position
control of the movable body is switched from an arbitrary encoder
to another encoder and prepares a switching timing, based on a
movement course of the movable body.
217. The movable body drive system according to claim 216 wherein
the controller makes a combination of encoders subject to a
switching where an encoder is switched from an arbitrary encoder of
three encoders of the encoder system that measure positional
information of the movable body in directions of three degrees of
freedom in the movement plane to another encoder and prepares a
switching timing, based on a movement course of the movable
body.
218. The movable body drive system according to claim 216 wherein
the controller constantly takes in the output of each encoder of
the encoder system and executes an operation of switching an
encoder used for position control of the movable body from an
arbitrary encoder that has been used for position control of the
movable body to another encoder, at a timing in synchronization
with the position control of the movable body.
219. A pattern formation apparatus, the apparatus comprising: a
movable body on which the object is mounted, and is movable in a
movement plane holding the object; and a movable body drive system
according to claim 216 that drives the movable body to perform
pattern formation with respect to the object.
220. The pattern formation apparatus according to claim 219, the
apparatus further comprising: an interferometer system that
measures positional information of the movable body; a mark
detection system that detects a mark located on the movable body
holding the object; and a switching unit that switches a
measurement unit used for position control of the movable body
prior to a measurement of a plurality of marks on the object by the
mark detection system, from the interferometer system to the
encoder system.
221. An exposure apparatus that forms a pattern on an object by an
irradiation of an energy beam, the apparatus comprising: a
patterning unit that irradiates the energy beam on the object; and
the movable body drive system according to claim 216, wherein the
movable body drive system drives the movable body on which the
object is mounted for relative movement of the energy beam and the
object.
222. An exposure apparatus that exposes an object with an energy
beam, the apparatus comprising: a movable body that holds the
object and is movable at least in a first and second directions
which are orthogonal in a predetermined plane; an encoder system in
which one of a grating section and a head unit is arranged on a
surface of the movable body where the object is held and the other
is arranged facing the surface of the movable body, and positional
information of the movable body in the predetermined plane is
measured by a head that faces the grating section of a plurality of
heads of the head unit; and a controller that decides the
positional information which should be measured by a head after a
switching, during the switching of the head used for the
measurement that accompanies the movement of the movable body,
based on positional information measured by a head before the
switching and positional information of the movable body in a
direction different from the first and second directions.
223. The exposure apparatus according to claim 222 wherein the
positional information which should be measured by the head after
the switching is decided so that a position of the movable body in
the predetermined plane is maintained before and after the
switching.
224. The exposure apparatus according to claim 222 wherein the
measurement is continued while switching the head used for the
measurement to another head during the movement of the movable
body, and the measurement of the positional information of the
movable body is performed by the another head using the positional
information that has been decided.
225. The exposure apparatus according to claim 222 wherein
positional information measured by the head before the switching is
corrected, based on positional information of the movable body in
the different direction, and the positional information that has
been corrected is set as an initial value of the positional
information measured by the head after the switching.
226. The exposure apparatus according to claim 222 wherein the
different direction includes the rotational direction in the
predetermined plane.
227. The exposure apparatus according to claim 226 wherein
positional information of the movable body in the different
direction is obtained from the measurement information of the
encoder system.
228. The exposure apparatus according to claim 222 wherein the
grating section is arranged with the first direction serving as a
longitudinal direction, and the head unit has the plurality of
heads placed apart in the second direction.
229. The exposure apparatus according to claim 222 wherein the
grating section has a pair of a first grating section whose
longitudinal direction is the first direction and is placed apart
in the second direction and a pair of a second grating section
whose longitudinal direction is the second direction and is placed
apart in the first direction, and the head unit has a pair of a
first head unit having a plurality of a first head placed apart in
the second direction that face the pair of the first grating
section on exposure and a pair of a second head unit having a
plurality of a second head placed apart in the first direction that
face the pair of the second grating section on exposure.
230. The exposure apparatus according to claim 229 wherein
positional information of the movable body in the first and second
directions is measured by at least three of the pair of the first
head units and the pair of the second head units.
231. The exposure apparatus according to claim 222 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
232. The exposure apparatus according to claim 222 wherein the
grating section is arranged on a surface of the movable body, and
the head unit is arranged facing the surface of the movable
body.
233. The exposure apparatus according to claim 222 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
234. The exposure apparatus according to claim 233 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
235. The exposure apparatus according to claim 233 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
236. The exposure apparatus according to claim 233 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
237. The exposure apparatus according to claim 233 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
238. The exposure apparatus according to claim 222 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
239. The exposure apparatus according to claim 238 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
240. The exposure apparatus according to claim 238 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
241. The exposure apparatus according to claim 238 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
242. The exposure apparatus according to claim 222 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
243. The exposure apparatus according to claim 242 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
244. The exposure apparatus according to claim 242 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
245. The exposure apparatus according to claim 222, the apparatus
further comprising: a measurement system that measures the
positional information of the movable body in a third direction
orthogonal to the predetermined plane by a sensor which faces the
grating section of a plurality of sensors arranged on the same side
as the head unit, wherein the position of the movable body in the
third direction is controlled based on measurement information of
the measurement system.
246. The exposure apparatus according to claim 245 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
247. The exposure apparatus according to claim 245 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
248. The exposure apparatus according to claim 247 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
249. The exposure apparatus according to claim 245, the apparatus
further comprising: a position measuring unit that measures
positional information of the object in the third direction,
wherein in a measurement operation of a surface position
information of the object, the encoder system, the measurement
system, and the position measuring unit are used.
250. The exposure apparatus according to claim 245, the apparatus
further comprising: a mark detection system that detects a mark on
the object, wherein in a detection operation of the mark, the
encoder system and the mark detection system are used.
251. The exposure apparatus according to claim 222, the apparatus
further comprising: an interferometer system that measures
positional information of the movable body in at least the first
and second directions, wherein to drive the movable body, the
measurement information of the encoder system is used in an
exposure operation, and the measurement information of the
interferometer system is used in an operation that is different
from the exposure operation.
252. The exposure apparatus according to claim 251 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
253. The exposure apparatus according to claim 251, wherein at
least a part of the measurement information of the interferometer
system is used in the exposure operation.
254. The exposure apparatus according to claim 222 wherein of a
plurality of heads of the encoder system, the position of the
movable body in the predetermined plane is controlled, based on
positional information of the head used for the measurement of the
positional information of the movable body in a plane parallel to
the predetermined plane, and the measurement information of the
encoder system.
255. The exposure apparatus according to claim 222 wherein the
positional information of a plurality of heads of the head unit in
a surface parallel to the predetermined plane is measured.
256. An exposure apparatus that exposes an object with an energy
beam, the apparatus comprising: a movable body that holds the
object and is movable at least in a first and second directions
which are orthogonal in a predetermined plane; an encoder system in
which one of a grating section and a head unit is arranged on a
surface of the movable body where the object is held and the other
is arranged facing the surface of the movable body, and positional
information of the movable body in the predetermined plane is
measured by a head that faces the grating section of a plurality of
heads of the head unit; and a controller that continues the
measurement while switching the head used for the measurement to
another head during the movement of the movable body, and controls
a position of the movable body in the predetermined plane, based on
measurement information of the encoder system measured by the
another head and positional information of the movable body in a
direction different from the first and second directions on the
switching.
257. The exposure apparatus according to claim 256 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the positional information of the movable body in the different
direction.
258. The exposure apparatus according to claim 256 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
positional information of the movable body in the different
direction so as to compensate for a measurement error of the
encoder system caused by displacement of the movable body in the
different direction on the switching, while the movable body is
driven based on the measurement information of the encoder
system.
259. The exposure apparatus according to claim 256 wherein
positional information measured by the head before the switching is
set as an initial value of positional information measured by the
another head.
260. The exposure apparatus according to claim 256 wherein the
different direction includes the rotational direction in the
predetermined plane.
261. The exposure apparatus according to claim 260 wherein
positional information of the movable body in the different
direction is obtained from the measurement information of the
encoder system.
262. The exposure apparatus according to claim 256 wherein the
grating section is arranged with the first direction serving as a
longitudinal direction, and the head unit has the plurality of
heads placed apart in the second direction.
263. The exposure apparatus according to claim 256 wherein the
grating section has a pair of a first grating section whose
longitudinal direction is the first direction and is placed apart
in the second direction and a pair of a second grating section
whose longitudinal direction is the second direction and is placed
apart in the first direction, and the head unit has a pair of a
first head unit having a plurality of a first head placed apart in
the second direction that face the pair of the first grating
section on exposure and a pair of a second head unit having a
plurality of a second head placed apart in the first direction that
face the pair of the second grating section on exposure.
264. The exposure apparatus according to claim 263 wherein
positional information of the movable body in the first and second
directions is measured by at least three of the pair of the first
head units and the pair of the second head units.
265. The exposure apparatus according to claim 256 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
266. The exposure apparatus according to claim 256 wherein the
grating section is arranged on a surface of the movable body, and
the head unit is arranged facing the surface of the movable
body.
267. The exposure apparatus according to claim 256 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
268. The exposure apparatus according to claim 267 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
269. The exposure apparatus according to claim 267 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
270. The exposure apparatus according to claim 267 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
271. The exposure apparatus according to claim 267 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
272. The exposure apparatus according to claim 256 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
273. The exposure apparatus according to claim 272 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
274. The exposure apparatus according to claim 272 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
275. The exposure apparatus according to claim 272 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
276. The exposure apparatus according to claim 256 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
277. The exposure apparatus according to claim 276 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
278. The exposure apparatus according to claim 276 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
279. The exposure apparatus according to claim 256, the apparatus
further comprising: a measurement system that measures the
positional information of the movable body in a third direction
orthogonal to the predetermined plane by a sensor which faces the
grating section of a plurality of sensors arranged on the same side
as the head unit, wherein the position of the movable body in the
third direction is controlled based on measurement information of
the measurement system.
280. The exposure apparatus according to claim 279 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
281. The exposure apparatus according to claim 279 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
282. The exposure apparatus according to claim 281 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
283. The exposure apparatus according to claim 279, the apparatus
further comprising: a position measuring unit that measures
positional information of the object in the third direction,
wherein in a measurement operation of a surface position
information of the object, the encoder system, the measurement
system, and the position measuring unit are used.
284. The exposure apparatus according to claim 279, the apparatus
further comprising: a mark detection system that detects a mark on
the object, wherein in a detection operation of the mark, the
encoder system and the mark detection system are used.
285. The exposure apparatus according to claim 256, the apparatus
further comprising: an interferometer system that measures
positional information of the movable body in at least the first
and second directions, wherein to drive the movable body, the
measurement information of the encoder system is used in an
exposure operation, and the measurement information of the
interferometer system is used in an operation that is different
from the exposure operation.
286. The exposure apparatus according to claim 285 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
287. The exposure apparatus according to claim 285, wherein at
least a part of the measurement information of the interferometer
system is used in the exposure operation.
288. The exposure apparatus according to claim 256 wherein of a
plurality of heads of the encoder system, the position of the
movable body in the predetermined plane is controlled, based on
positional information of the head used for the measurement of the
positional information of the movable body in a plane parallel to
the predetermined plane, and the measurement information of the
encoder system.
289. The exposure apparatus according to claim 256 wherein the
positional information of a plurality of heads of the head unit in
a surface parallel to the predetermined plane is measured.
290. An exposure apparatus that exposes an object with an energy
beam, the apparatus comprising: a movable body that holds the
object and is movable at least in a first and second directions
which are orthogonal in a predetermined plane; an encoder system in
which one of a grating section and a head unit is arranged on a
surface of the movable body where the object is held and the other
is arranged facing the surface of the movable body, and positional
information of the movable body in the first and second directions,
and rotational direction in the predetermined plane is measured by
at least three heads that face the grating section of a plurality
of heads of the head unit; and a controller that continues the
measurement while switching the three heads used for the
measurement to three heads having at least one different head
during the movement of the movable body, and during the switching,
decides position information that should be measured by at least
one head of the three heads after the switching which are different
from the three heads before the switching, based on positional
information measured by the three heads before the switching.
291. The exposure apparatus according to claim 290 wherein the
positional information which should be measured by the at least one
head after the switching is decided so that the position of the
movable body in the predetermined plane is maintained before and
after the switching.
292. The exposure apparatus according to claim 290 wherein the
positional information that has been decided is set as an initial
value of the positional information measured by the at least one
head after the switching so as to continuously link the positional
information of the movable body that is measured before and after
the switching.
293. The exposure apparatus according to claim 290 wherein the
grating section has a pair of a first grating section whose
longitudinal direction is the first direction and is placed apart
in the second direction and a pair of a second grating section
whose longitudinal direction is the second direction and is placed
apart in the first direction, and the head unit has a pair of a
first head unit having a plurality of a first head placed apart in
the second direction that face the pair of the first grating
section on exposure and a pair of a second head unit having a
plurality of a second head placed apart in the first direction that
face the pair of the second grating section on exposure, whereby
positional information of the movable body is measured by at least
three of the pair of the first head units and the pair of the
second head units.
294. The exposure apparatus according to claim 290 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
295. The exposure apparatus according to claim 290 wherein the
grating section is arranged on a surface of the movable body, and
the head unit is arranged facing the surface of the movable
body.
296. The exposure apparatus according to claim 290 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
297. The exposure apparatus according to claim 296 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
298. The exposure apparatus according to claim 296 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
299. The exposure apparatus according to claim 296 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
300. The exposure apparatus according to claim 296 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
301. The exposure apparatus according to claim 290 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
302. The exposure apparatus according to claim 301 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
303. The exposure apparatus according to claim 301 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
304. The exposure apparatus according to claim 301 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
305. The exposure apparatus according to claim 290 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
306. The exposure apparatus according to claim 305 wherein one of
the measurement information of the encoder system and a target
position where the movable body is positioned is corrected, based
on the correction information.
307. The exposure apparatus according to claim 305 wherein the
object is exposed by the energy beam via a mask, and at the time of
the exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
308. The exposure apparatus according to claim 290, the apparatus
further comprising: a measurement system that measures the
positional information of the movable body in a third direction
orthogonal to the predetermined plane by a sensor which faces the
grating section of a plurality of sensors arranged on the same side
as the head unit, wherein the position of the movable body in the
third direction is controlled based on measurement information of
the measurement system.
309. The exposure apparatus according to claim 308 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
310. The exposure apparatus according to claim 308 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
311. The exposure apparatus according to claim 310 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
312. The exposure apparatus according to claim 308, the apparatus
further comprising: a position measuring unit that measures
positional information of the object in the third direction,
wherein in a measurement operation of a surface position
information of the object, the encoder system, the measurement
system, and the position measuring unit are used.
313. The exposure apparatus according to claim 308, the apparatus
further comprising: a mark detection system that detects a mark on
the object, wherein in a detection operation of the mark, the
encoder system and the mark detection system are used.
314. The exposure apparatus according to claim 290, the apparatus
further comprising: an interferometer system that measures
positional information of the movable body in at least the first
and second directions, wherein to drive the movable body, the
measurement information of the encoder system is used in an
exposure operation, and the measurement information of the
interferometer system is used in an operation that is different
from the exposure operation.
315. The exposure apparatus according to claim 314 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
316. The exposure apparatus according to claim 314, wherein at
least a part of the measurement information of the interferometer
system is used in the exposure operation.
317. The exposure apparatus according to claim 290 wherein of a
plurality of heads of the encoder system, the position of the
movable body in the predetermined plane is controlled, based on
positional information of the head used for the measurement of the
positional information of the movable body in a plane parallel to
the predetermined plane, and the measurement information of the
encoder system.
318. The exposure apparatus according to claim 290 wherein the
positional information of a plurality of heads of the head unit in
a surface parallel to the predetermined plane is measured.
319. An exposure apparatus that exposes an object with an energy
beam, the apparatus comprising: a movable body that holds the
object and is movable at least in a first and second directions
which are orthogonal in a predetermined plane; an encoder system in
which one of a grating section and a head unit is arranged on a
surface of the movable body where the object is held and the other
is arranged facing the surface of the movable body, and positional
information of the movable body in the predetermined plane is
measured by a head that faces the grating section of a plurality of
heads of the head unit; and a controller that controls a position
of the movable body in the predetermined plane, based on positional
information of the head used for measuring the positional
information in a surface parallel to the predetermined plane and
measurement information of the encoder system.
320. An exposure apparatus that exposes an object with an energy
beam, the apparatus comprising: a movable body that holds the
object and is movable at least in a first and second directions
which are orthogonal in a predetermined plane; an encoder system in
which one of a grating section and a head unit is arranged on a
surface of the movable body where the object is held and the other
is arranged facing the surface of the movable body, and positional
information of the movable body in the predetermined plane is
measured by a head that faces the grating section of a plurality of
heads of the head unit; and a controller that measures positional
information of the plurality of heads of the head unit in a surface
parallel to the predetermined plane and controls a position of the
movable body in the predetermined plane, based on positional
information that has been measured and measurement information of
the encoder system.
321. An exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby positional information of the movable
body is measured using an encoder system in which one of a grating
section and a head unit is arranged on a surface of the movable
body where the object is mounted and the other is arranged facing
the surface of the movable body, and positional information of the
movable body in the predetermined plane is measured by a head that
faces the grating section of a plurality of heads of the head unit,
and the positional information which should be measured by a head
after a switching during the switching of the head used for the
measurement that accompanies the movement of the movable body is
decided, based on positional information measured by a head before
the switching and positional information of the movable body in a
direction different from the first and second directions.
322. The exposure method according to claim 321 wherein the
positional information which should be measured by the head after
the switching is decided so that a position of the movable body in
the predetermined plane is maintained before and after the
switching.
323. The exposure method according to claim 321 wherein the
measurement is continued while switching the head used for the
measurement to another head during the movement of the movable
body, and the measurement of the positional information of the
movable body is performed by the another head using the positional
information that has been decided.
324. The exposure method according to claim 321 wherein positional
information measured by the head before the switching is corrected,
based on positional information of the movable body in the
different direction, and the positional information that has been
corrected is set as an initial value of the positional information
measured by the head after the switching.
325. The exposure method according to claim 321 wherein the
different direction includes the rotational direction in the
predetermined plane.
326. The exposure method according to claim 325 wherein positional
information of the movable body in the different direction is
obtained from the measurement information of the encoder
system.
327. The exposure method according to claim 321 wherein the grating
section is arranged with the first direction serving as a
longitudinal direction, and the head unit has the plurality of
heads placed apart in the second direction.
328. The exposure method according to claim 321 wherein the grating
section has a pair of a first grating section whose longitudinal
direction is the first direction and is placed apart in the second
direction and a pair of a second grating section whose longitudinal
direction is the second direction and is placed apart in the first
direction, and the head unit has a pair of a first head unit having
a plurality of a first head placed apart in the second direction
that face the pair of the first grating section on exposure and a
pair of a second head unit having a plurality of a second head
placed apart in the first direction that face the pair of the
second grating section on exposure.
329. The exposure method according to claim 328 wherein positional
information of the movable body in the first and second directions
is measured by at least three of the pair of the first head units
and the pair of the second head units.
330. The exposure method according to claim 321 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
331. The exposure method according to claim 321 wherein the grating
section is arranged on a surface of the movable body, and the head
unit is arranged facing the surface of the movable body.
332. The exposure method according to claim 321 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
333. The exposure method according to claim 332 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
334. The exposure method according to claim 332 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
335. The exposure method according to claim 332 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
336. The exposure method according to claim 332 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
337. The exposure method according to claim 321 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
338. The exposure method according to claim 337 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
339. The exposure method according to claim 337 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
340. The exposure method according to claim 337 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
341. The exposure method according to claim 321 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
342. The exposure method according to claim 341 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
343. The exposure method according to claim 341 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
344. The exposure method according to claim 321 wherein a
measurement system is further used to measure the positional
information of the movable body in a third direction orthogonal to
the predetermined plane by a sensor which faces the grating of a
plurality of sensors arranged on the same side as the head unit,
and the position of the movable body in the third direction is
controlled based on measurement information of the measurement
system.
345. The exposure method according to claim 344 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
346. The exposure method according to claim 344 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
347. The exposure method according to claim 346 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
348. The exposure method according to claim 344 wherein in a
measurement operation of a surface position information of the
object, in addition to the encoder system and the measurement
system, a position measuring unit is further used to measure the
positional information of the object in the third direction.
349. The exposure method according to claim 344 wherein in a
detection operation of the mark, the encoder system and the mark
detection system are used.
350. The exposure method according to claim 321 wherein to drive
the movable body, the measurement information of the encoder system
is used in an exposure operation, and the measurement information
of the interferometer system that measures the positional
information of the movable body in at least the first and second
directions is used in an operation that is different from the
exposure operation.
351. The exposure method according to claim 350 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
352. The exposure method according to claim 350 wherein at least a
part of the measurement information of the interferometer system is
used in the exposure operation.
353. The exposure method according to claim 321 wherein a position
of the movable body in the predetermined plane is controlled, based
on positional information of the head used for measuring the
positional information of the movable body in a surface parallel to
the predetermined plane of the plurality of heads in the encoder
system and measurement information of the encoder system.
354. The exposure method according to claim 321 wherein positional
information of the plurality of heads of the head unit in a surface
parallel to the predetermined plane is measured.
355. A device manufacturing method including a lithography process
wherein in the lithography process, an exposure method according to
claim 321 is used to expose a sensitive object mounted on the
movable body, and to form a pattern on the sensitive object.
356. An exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby positional information of the movable
body is measured using an encoder system in which one of a grating
section and a head unit is arranged on a surface of the movable
body where the object is mounted and the other is arranged facing
the surface of the movable body, and positional information of the
movable body in the predetermined plane is measured by a head that
faces the grating section of a plurality of heads of the head unit,
and the measurement is continued while switching the head used for
the measurement to another head during the movement of the movable
body, and a position of the movable body in the predetermined plane
is controlled based on measurement information of the encoder
system measured by the another head and positional information of
the movable body in a direction different from the first and second
directions on the switching.
357. The exposure method according to claim 356 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
positional information of the movable body in the different
direction.
358. The exposure method according to claim 356 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
positional information of the movable body in the different
direction so as to compensate for a measurement error of the
encoder system caused by displacement of the movable body in the
different direction on the switching, while the movable body is
driven based on the measurement information of the encoder
system.
359. The exposure method according to claim 356 wherein positional
information measured by the head before the switching is set as an
initial value of positional information measured by the another
head.
360. The exposure method according to claim 356 wherein the
different direction includes the rotational direction in the
predetermined plane.
361. The exposure method according to claim 360 wherein positional
information of the movable body in the different direction is
obtained from the measurement information of the encoder
system.
362. The exposure method according to claim 356 wherein the grating
section is arranged with the first direction serving as a
longitudinal direction, and the head unit has the plurality of
heads placed apart in the second direction.
363. The exposure method according to claim 356 wherein the grating
section has a pair of a first grating section whose longitudinal
direction is the first direction and is placed apart in the second
direction and a pair of a second grating section whose longitudinal
direction is the second direction and is placed apart in the first
direction, and the head unit has a pair of a first head unit having
a plurality of a first head placed apart in the second direction
that face the pair of the first grating section on exposure and a
pair of a second head unit having a plurality of a second head
placed apart in the first direction that face the pair of the
second grating section on exposure.
364. The exposure method according to claim 363 wherein positional
information of the movable body in the first and second directions
is measured by at least three of the pair of the first head units
and the pair of the second head units.
365. The exposure method according to claim 356 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
366. The exposure method according to claim 356 wherein the grating
section is arranged on a surface of the movable body, and the head
unit is arranged facing the surface of the movable body.
367. The exposure method according to claim 356 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
368. The exposure method according to claim 367 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
369. The exposure method according to claim 367 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
370. The exposure method according to claim 367 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
371. The exposure method according to claim 367 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
372. The exposure method according to claim 356 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
373. The exposure method according to claim 372 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
374. The exposure method according to claim 372 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
375. The exposure method according to claim 372 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
376. The exposure method according to claim 356 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
377. The exposure method according to claim 376 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
378. The exposure method according to claim 376 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
379. The exposure method according to claim 356 wherein a
measurement system is further used to measure the positional
information of the movable body in a third direction orthogonal to
the predetermined plane by a sensor which faces the grating of a
plurality of sensors arranged on the same side as the head unit,
and the position of the movable body in the third direction is
controlled based on measurement information of the measurement
system.
380. The exposure method according to claim 379 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
381. The exposure method according to claim 379 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
382. The exposure method according to claim 381 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
383. The exposure method according to claim 379 wherein in a
measurement operation of a surface position information of the
object, in addition to the encoder system and the measurement
system, a position measuring unit is further used to measure the
positional information of the object in the third direction.
384. The exposure method according to claim 379 wherein in a
detection operation of the mark, the encoder system and the mark
detection system are used.
385. The exposure method according to claim 356 wherein to drive
the movable body, the measurement information of the encoder system
is used in an exposure operation, and the measurement information
of the interferometer system that measures the positional
information of the movable body in at least the first and second
directions is used in an operation that is different from the
exposure operation.
386. The exposure method according to claim 385 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
387. The exposure method according to claim 385 wherein at least a
part of the measurement information of the interferometer system is
used in the exposure operation.
388. The exposure method according to claim 356 wherein a position
of the movable body in the predetermined plane is controlled, based
on positional information of the head used for measuring the
positional information of the movable body in a surface parallel to
the predetermined plane of the plurality of heads in the encoder
system and measurement information of the encoder system.
389. The exposure method according to claim 356 wherein positional
information of the plurality of heads of the head unit in a surface
parallel to the predetermined plane is measured.
390. A device manufacturing method including a lithography process
wherein in the lithography process, an exposure method according to
claim 356 is used to expose a sensitive object mounted on the
movable body, and to form a pattern on the sensitive object.
391. An exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby positional information of the movement
body is measured using an encoder system in which one of a grating
section and a head unit is arranged on a surface of the movable
body where the object is held and the other is arranged facing the
surface of the movable body and which also measures positional
information of the movable body in the first direction, the second
direction, and rotational direction in the predetermined plane with
at least three heads that face the grating section of a plurality
of heads of the head unit, and the measurement is continued while
switching the three heads used for the measurement to three heads
having at least one different head during the movement of the
movable body, and during the switching, position information that
should be measured by at least one head of the three heads after
the switching which are different from the three heads before the
switching is decided, based on positional information measured by
the three heads before the switching.
392. The exposure method according to claim 391 wherein the
positional information which should be measured by the at least one
head after the switching is decided so that the position of the
movable body in the predetermined plane is maintained before and
after the switching.
393. The exposure method according to claim 391 wherein the
positional information that has been decided is set as an initial
value of the positional information measured by the at least one
head after the switching so as to continuously link the positional
information of the movable body that is measured before and after
the switching.
394. The exposure method according to claim 391 wherein the grating
section has a pair of a first grating section whose longitudinal
direction is the first direction and is placed apart in the second
direction and a pair of a second grating section whose longitudinal
direction is the second direction and is placed apart in the first
direction, and the head unit has a pair of a first head unit having
a plurality of a first head placed apart in the second direction
that face the pair of the first grating section on exposure and a
pair of a second head unit having a plurality of a second head
placed apart in the first direction that face the pair of the
second grating section on exposure, whereby positional information
of the movable body is measured by at least three of the pair of
the first head units and the pair of the second head units.
395. The exposure method according to claim 391 wherein the
switching is performed in a state where the head before the
switching and the head after the switching both face the grating
section.
396. The exposure method according to claim 391 wherein the grating
section is arranged on a surface of the movable body, and the head
unit is arranged facing the surface of the movable body.
397. The exposure method according to claim 391 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to at least
one of the head unit and the grating section and the measurement
information of the encoder system.
398. The exposure method according to claim 397 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least optical properties of
the head unit.
399. The exposure method according to claim 397 wherein the
correction information compensates for the measurement error of the
encoder system that occurs due to at least one of flatness and
formation error of the grating section.
400. The exposure method according to claim 397 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
401. The exposure method according to claim 397 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
402. The exposure method according to claim 391 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to
displacement of the movable body in the direction that is different
from the first and second directions on the measurement and the
measurement information of the encoder system.
403. The exposure method according to claim 402 wherein the
different direction includes at least one of a direction orthogonal
to the predetermined plane, a rotational direction around an axis
orthogonal to the predetermined plane, and a rotational direction
around an axis parallel to the predetermined plane.
404. The exposure method according to claim 402 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
405. The exposure method according to claim 402 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
406. The exposure method according to claim 391 wherein the
position of the movable body in the predetermined plane is
controlled, based on correction information to compensate for the
measurement error of the encoder system that occurs due to gradient
of the movable body with respect to the predetermined plane and the
measurement information of the encoder system.
407. The exposure method according to claim 406 wherein one of the
measurement information of the encoder system and a target position
where the movable body is positioned is corrected, based on the
correction information.
408. The exposure method according to claim 406 wherein the object
is exposed by the energy beam via a mask, and at the time of the
exposure, a position of the mask is controlled based on the
correction information so as to compensate for the measurement
error, while the movable body is driven based on the measurement
information of the encoder system.
409. The exposure method according to claim 391 wherein a
measurement system is further used to measure the positional
information of the movable body in a third direction orthogonal to
the predetermined plane by a sensor which faces the grating of a
plurality of sensors arranged on the same side as the head unit,
and the position of the movable body in the third direction is
controlled based on measurement information of the measurement
system.
410. The exposure method according to claim 409 wherein the
measurement system measures the positional information in the third
direction and inclination information of the movable body with a
plurality of sensors that face the grating section.
411. The exposure method according to claim 409 wherein of
positional information of the movable body in directions of six
degrees of freedom, positional information in directions of three
degrees of freedom including the first direction, the second
direction and a rotational direction in the predetermined plane is
measured by the encoder system, and positional information in the
remaining directions of three degrees of freedom is measured by the
measurement system.
412. The exposure method according to claim 411 wherein the
position of the movable body in at least the exposure operation is
controlled, based on the positional information measured in
directions of six degrees of freedom.
413. The exposure method according to claim 409 wherein in a
measurement operation of a surface position information of the
object, in addition to the encoder system and the measurement
system, a position measuring unit is further used to measure the
positional information of the object in the third direction.
414. The exposure method according to claim 409 wherein in a
detection operation of the mark, the encoder system and the mark
detection system are used.
415. The exposure method according to claim 391 wherein to drive
the movable body, the measurement information of the encoder system
is used in an exposure operation, and the measurement information
of the interferometer system that measures the positional
information of the movable body in at least the first and second
directions is used in an operation that is different from the
exposure operation.
416. The exposure method according to claim 415 wherein in a
detection operation of a mark and/or the surface position
information of the object, the measurement information of the
encoder system is used.
417. The exposure method according to claim 415 wherein at least a
part of the measurement information of the interferometer system is
used in the exposure operation.
418. The exposure method according to claim 391 wherein a position
of the movable body in the predetermined plane is controlled, based
on positional information of the head used for measuring the
positional information of the movable body in a surface parallel to
the predetermined plane of the plurality of heads in the encoder
system and measurement information of the encoder system.
419. The exposure method according to claim 391 wherein positional
information of the plurality of heads of the head unit in a surface
parallel to the predetermined plane is measured.
420. A device manufacturing method including a lithography process
wherein in the lithography process, an exposure method according to
claim 391 is used to expose a sensitive object mounted on the
movable body, and to form a pattern on the sensitive object.
421. An exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby one of a grating section and a head
unit is arranged on a surface of the movable body where the object
is held and the other is arranged facing the surface of the movable
body, and the position of the movable body in the predetermined
plane is controlled, based on measurement information of an encoder
system that measures positional information of the movable body in
the predetermined plane by a head that faces the grating section of
a plurality of heads of the head unit, and positional information
of the head used to measure the positional information in a surface
parallel to the predetermined plane.
422. A device manufacturing method including a lithography process
wherein in the lithography process, an exposure method according to
claim 421 is used to expose a sensitive object mounted on the
movable body, and to form a pattern on the sensitive object.
423. An exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby of an encoder system in which one of a
grating section and a head unit is arranged on a surface of the
movable body where the object is held and the other is arranged
facing the surface of the movable body, and positional information
of the movable body in the predetermined plane is measured by a
head that faces the grating section of a plurality of heads of the
head unit, the positional information of a plurality of heads of
the head unit in a surface parallel to the predetermined plane is
measured, and based on measured positional information and the
measurement information of the encoder system, the position of the
movable body in the predetermined plane is controlled.
424. A device manufacturing method including a lithography process
wherein in the lithography process, an exposure method according to
claim 423 is used to expose a sensitive object mounted on the
movable body, and to form a pattern on the sensitive object.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to movable body drive methods
and movable body drive systems, pattern formation methods and
apparatuses, exposure methods and apparatuses, and device
manufacturing methods, and more particularly to a movable body
drive method in which a movable body is driven within a movement
plane and a movable body drive system, a pattern formation method
using the movable body drive method and a pattern formation
apparatus equipped with the movable body drive system, an exposure
method using the movable body drive method and an exposure
apparatus equipped with the movable body drive system, and a device
manufacturing method in which the pattern formation method is
used.
[0003] 2. Description of the Background Art
[0004] Conventionally, in a lithography process for manufacturing
microdevices (electron devices and the like) such as semiconductor
devices and liquid crystal display devices, exposure apparatuses
such as a projection exposure apparatus by a step-and-repeat method
(a so-called stepper) and a projection exposure apparatus by a
step-and-scan method (a so-called scanning stepper (which is also
called a scanner) are relatively frequently used.
[0005] In this kind of exposure apparatus, in order to transfer a
pattern of a reticle (or a mask) on a plurality of shot areas on a
wafer, a wafer stage holding the wafer is driven in an XY
two-dimensional direction, for example, by linear motors and the
like. Especially in the case of a scanning stepper, not only the
wafer stage but also a reticle stage is driven in by predetermined
strokes in a scanning direction by linear motors and the like.
Position measurement of the reticle stage and the wafer stage is
generally performed using a laser interferometer whose stability of
measurement values is good for over a long time and has a high
resolution.
[0006] However, requirements for a stage position control with
higher precision are increasing due to finer patterns that
accompany higher integration of semiconductor devices, and now,
short-term variation of measurement values due to temperature
fluctuation of the atmosphere on the beam optical path of the laser
interferometer has come to occupy a large percentage in the overlay
budget.
[0007] Meanwhile, as a measurement unit besides the laser
interferometer used for position measurement of the stage, an
encoder can be used, however, because the encoder uses a scale,
which lacks in mechanical long-term stability (drift of grating
pitch, fixed position drift, thermal expansion and the like), it
makes the encoder have a drawback of lacking measurement value
linearity and being inferior in long-term stability when compared
with the laser interferometer.
[0008] In view of the drawbacks of the laser interferometer and the
encoder described above, various proposals are being made (refer to
Kokai (Japanese Patent Unexamined Application Publication) No.
2002-151405, Kokai (Japanese Patent Unexamined Application
Publication) No. 2004-101362 and the like) of a unit that measures
the position of a stage using both a laser interferometer and an
encoder (a position detection sensor which uses a diffraction
grating) together.
[0009] Further, the measurement resolution of the conventional
encoder was inferior when compared with an interferometer, however,
recently, an encoder which has a nearly equal or a better
measurement resolution than a laser interferometer has appeared
(for example, refer to Kokai (Japanese Patent Unexamined
Application Publication) No. 2005-308592), and the technology to
put the laser interferometer and the encoder described above
together is beginning to gather attention.
[0010] However, in the case position measurement is performed of
the movement plane of the wafer stage of the exposure apparatus
that moves two-dimensionally holding a wafer using an encoder, for
example, in order to avoid an unnecessary increase in the size of
the wafer stage and the like, it becomes essential to switch the
encoder used for control while the wafer stage is moving using a
plurality of encoders, or in other words, to perform a linkage
between the plurality of encoders. However, as it can be easily
imagined, for example, when considering the case when a grating is
placed on the wafer stage, it is not so easy to perform linkage
between a plurality of encoders while the wafer stage is being
moved, especially while precisely the wafer stage is being moved
two-dimensionally along a predetermined path.
[0011] Further, by repeating the linkage operation, the position
error of the wafer stage may grow large with the elapse of time due
to the accumulation of the error which occurs when linkage is
performed, and the exposure accuracy (overlay accuracy) may
consequently deteriorate.
[0012] Meanwhile, it is conceivable that the position of the wafer
stage does not necessarily have to be measured using an encoder
system in the whole movable range of the wafer stage.
[0013] Now, the propagation speed in the cable of an electrical
signal such as the detection signal of the head of the encoder, or
more specifically, the photoelectric conversion signal of the light
receiving element is limited, and the length of the cable through
which the detection signal of the encoder propagates is generally
from several meters to 10 m, and in quite a few cases exceeds 10 m.
When considering that a signal propagates through the cable of such
a length at the speed of light, the influence of the delay time
that accompanies the propagation is at a level that cannot be
ignored.
SUMMARY OF THE INVENTION
[0014] The present invention has been made in consideration of the
circumstances described above, and according to the first aspect of
the present invention, there is provided a first movable body drive
method in which a movable body is driven in a movement plane
including a first axis and a second axis orthogonal to each other,
the method comprising: a measuring process in which positional
information of the movable body in the movement plane is measured
using at least one encoder of an encoder system including a
plurality of encoders having a head that irradiates a detection
light on a grating and receives the detection light from the
grating; and a switching process in which at least one of an
encoder used for position control of the movable body is switched
to another encoder so as to maintain a position of the movable body
in the movement plane before and after the switching.
[0015] According to this method, while the movable body is driven,
positional information of the movable body in the movement plane is
measured using at least two encoders of the encoder system, and the
encoder used for position control of the movable body is switched
from at least one of an encoder used for position control of the
movable body to another encoder so as to maintain the position of
the movable body in the movement plane before and after the
switching. Therefore, although the switching of the encoder used
for the control of the position of the movable body is performed,
the position of the movable body in the movement plane is
maintained before and after the switching, and a precise linkage
becomes possible. Accordingly, it becomes possible to move the
movable body two-dimensionally precisely along a predetermined
course, while performing the linkage between a plurality of
encoders.
[0016] According to the second aspect of the present invention,
there is provided a second movable body drive method in which a
movable body is driven in a movement plane, the method comprising:
an intake process in which measurement data corresponding to a
detection signal of at least one head of an encoder system
including a plurality of heads that measure positional information
of the movable body within the movement plane is taken in at a
predetermined control sampling interval when the movable body is
driven in a predetermined direction in the movement plane; and a
drive process in which the movable body is driven so as to correct
a measurement error of the head due to a measurement delay that
accompanies propagation of the detection signal, based on a
plurality of data which include the most recent measurement data
that was taken in the latest and previous measurement data
including at least data just before the most recent measurement
data, and information of a delay time that accompanies propagation
of the detection signal through a propagation path.
[0017] According to this method, when the movable body is driven in
a predetermined direction in the movement plane, measurement data
corresponding to the detection signal of at least one head of an
encoder system which measures positional information of the movable
body in the movement plane are taken in at a predetermined control
sampling interval, and the movable body is driven so that a
measurement error of the head due to a measurement delay that
accompanies the propagation of the detection signal is corrected
drives movable body so that it is corrected, based on a plurality
of data including the most recent measurement data taken in the
latest and previous data including at least data just before the
most recent measurement data (one control sampling interval
earlier), and information of a delay time that accompanies
propagation of the detection signal through a propagation path.
Accordingly, it becomes possible to drive movable body with high
precision in the desired direction, without being affected by the
measurement delay that accompanies the propagation of the detection
signal of the head of the encoder through the propagation path.
[0018] According to the third aspect of the present invention,
there is provided a pattern formation method, comprising: a mount
process in which an object is mounted on a movable body that can
move in a movement plane; and a drive process in which the movable
body is driven by the movable body drive method according to one of
the first and second movable body drive methods, to form a pattern
on the object.
[0019] According to this method, by forming a pattern on the object
mounted on the movable body which is driven using one of the first
and second movable body drive methods of the present invention, it
becomes possible to form a desired pattern on the object.
[0020] According to a fourth aspect of the present invention, there
is provided a first device manufacturing method including a pattern
formation process wherein in the pattern formation process, a
pattern is formed on a substrate using the pattern formation method
according to the pattern formation method of the present
invention.
[0021] According to a fifth aspect of the present invention, there
is provided a first exposure method in which a pattern is formed on
an object by an irradiation of an energy beam wherein for relative
movement of the energy beam and the object, a movable body on which
the object is mounted is driven, using one of the first and second
movable body drives method of the present invention.
[0022] According to this method, for relative movement of the
energy beam irradiated on the object and the object, the movable
body on which the object is mounted is driven with good precision,
using one of the first and second movable body drive methods of the
present invention. Accordingly, it becomes possible to form a
desired pattern on the object by scanning exposure.
[0023] According to a sixth aspect of the present invention, there
is provided a second exposure method in which an object on a
movable body that moves in a movement plane is sequentially
exchanged, and a pattern is formed respectively on each object by
sequentially exposing the object after exchange, wherein each time
the exchange of the object is performed on the movable body,
position control of the movable body in the movement plane is
started once more, using at least three encoders of an encoder
system that measures positional information of the movable body in
the movement plane within a predetermined effective area including
an exposure position.
[0024] According to this method, each time the exchange of the
object is performed on the movable body, position control of the
movable body in the movement plane using at least three encoders of
an encoder system that measures positional information of the
movable body in the movement plane in an effective area is started
once more. Therefore, each time the object exchange is performed,
the position error of the movable body is canceled out, so that the
position error of the movable body does not increase with the
passage of time. Accordingly, it becomes possible to measure the
positional information of the movable body in the movement plane in
a predetermined effective area including the exposure position by
the encoder system with good precision for over a long time, which
makes it possible to maintain the exposure precision for over a
long period of time.
[0025] According to a seventh aspect of the present invention,
there is provided a third movable body drive method in which a
movable body is driven in a movement plane, the method comprising:
an execution process in which of an encoder system including a
plurality of encoders respectively having a head that irradiates a
detection light on a grating and receives the detection light from
the grating and measures positional information of the movable body
in the movable plane, an output of each encoder is constantly taken
in, and an operation of switching an encoder used for position
control of the movable body from an encoder that has been used for
position control of the movable body to another encoder, at a
timing in synchronization with the position control of the movable
body is executed.
[0026] According to this method, when the movable body is driven,
the output of each encoder of the encoder system is constantly
taken in, and an operation of switching an encoder used for the
position control of the movable body from an encoder that has been
used for position control of the movable body to another encoder is
executed at a timing in synchronization with the position control
of the movable body. Therefore, the switching of the encoder will
not have to be performed at a high speed, and a highly precise
hardware for the switching will not be necessary, which
consequently will make cost reduction possible.
[0027] According to an eighth aspect of the present invention,
there is provided a fourth movable body drive method in which a
movable body is driven in a movement plane including a first axis
and a second axis orthogonal to each other, the method comprising:
a measuring process in which positional information of the movable
body in the movement plane is measured using at least one encoder
of an encoder system including a plurality of encoders respectively
having a head that irradiates a detection light on a grating and
receives the detection light from the grating; a scheduling process
in which a combination of encoders subject to a switching where an
encoder used for position control of the movable body is switched
from an arbitrary encoder to another encoder is made and a
switching timing is prepared, based on a movement course of the
movable body; and a switching process in which the arbitrary
encoder is switched to the another encoder based on the contents
prepared in the scheduling.
[0028] According to this method, a combination of encoders subject
to a switching where an encoder used for position control of the
movable body is switched from an arbitrary encoder to another
encoder is made and a switching timing is prepared, based on a
movement course of the movable body. And when the movable body is
moving, the positional information of the movable body in the
movement plane is measured using at least one encoder of the
encoder system, and based on the contents made out in the
scheduling above, the switching from an arbitrary encoder to
another encoder is performed. According to this, a reasonable
encoder switching according to the target track of the movable body
becomes possible.
[0029] According to a ninth aspect of the present invention, there
is provided a first movable body drive system in which a movable
body is driven in a movement plane including a first axis and a
second axis orthogonal to each other, the system comprising: an
encoder system having a plurality of encoders respectively having a
head that irradiates a detection light on a grating and receives
the detection light from the grating, including a first encoder
used for measuring positional information of the movable body in a
direction parallel to the first axis; and a controller that
measures positional information of the movable body in the movement
plane using at least one encoder of the encoder system, and also
switches at least one of an encoder used for measurement of the
positional information of the movable body in the movement plane to
another encoder so as to maintain a position of the movable body in
the movement plane before and after the switching.
[0030] According to this system, when the movable body is driven,
the positional information of the movable body in the movement
plane is measured by at least two encoders which at least includes
include one each of the first encoder and the second encoder of the
encoder system, and the controller switches the encoder used for
measurement of the positional information of the movable body in
the movement plane from an encoder of either of the at least two
encoders to another encoder so that the position of the movable
body in the movement plane is maintained before and after the
switching. Therefore, although the switching of the encoder used
for controlling the position of the movable body is performed, the
position of the movable body in the movement plane is maintained
before and after the switching, which allows an accurate linkage.
Accordingly, it becomes possible to move the movable body
two-dimensionally, precisely along a predetermined course, while
performing linkage between a plurality of encoders.
[0031] According to a tenth aspect of the present invention, there
is provided a second movable body drive system in which a movable
body is driven in a movement plane, the system comprising: an
encoder system including a plurality of heads that measure
positional information of the movable body in the movement plane;
and a controller that takes in measurement data corresponding to a
detection signal of at least one head of an encoder system at a
predetermined control sampling interval when the movable body is
driven in a predetermined direction in the movement plane, and
drives the movable body so that the measurement error of the head
due to a measurement delay that accompanies propagation of the
detection signal is corrected, based on a plurality of data that
include the most recent measurement data that was taken in the
latest and previous measurement data including at least data just
before the most recent measurement data, and information of a delay
time that accompanies propagation of the detection signal through a
propagation path.
[0032] According to this system, when the movable body is driven by
the controller in a predetermined direction in the movement plane,
the measurement data corresponding to the detection signal of at
least one head of the encoder system are taken in at a
predetermined control sampling interval, and the movable body is
driven so as to correct the measurement error of the head due to a
measurement delay that accompanies propagation of the detection
signal, based on a plurality of data that include the most recent
measurement data that was taken in the latest and previous
measurement data including at least data just before the most
recent measurement data, and information of a delay time that
accompanies propagation of the detection signal through a
propagation path. According to this, it becomes possible to drive
the movable body with high precision in the desired direction
without being affected by the measurement delay that accompanies
the detection signals of the head of the encoder propagating
through the propagation path.
[0033] According to an eleventh aspect of the present invention,
there is provided a third movable body drive system in which a
movable body is driven in a movement plane, the system comprising:
an encoder system including a plurality of heads that measure
positional information of the movable body in the movement plane;
an interferometer system that measures positional information of
the movable body in the movement plane; a processing unit that
executes a delay time acquisition processing of driving the movable
body in a predetermined direction, taking in a detection signal of
each head and a detection signal of the interferometer system
simultaneously at a predetermined sampling timing for a plurality
of heads of the encoder system during the drive, and based on both
detection signals, acquiring information of the delay time of the
detection signals of the respective plurality of heads that
accompanies the propagation through the propagation path, with the
detection signal of the interferometer system serving as a
reference; and a controller that drives the movable body, based on
measurement data corresponding to the respective detection signals
of the plurality of heads of the encoder system and information of
a delay time of the plurality of heads, respectively.
[0034] According to this system, the processing unit executes a
delay time acquisition process in which a delay time acquisition
processing of driving the movable body in a predetermined
direction, taking in a detection signal of each head and a
detection signal of the interferometer system simultaneously at a
predetermined sampling timing for at least a plurality of heads of
the encoder system during the drive, and based on both detection
signals, acquiring information of the delay time of the detection
signals of the respective plurality of heads that accompanies the
propagation through the propagation path, with the detection signal
of the interferometer system serving as a reference are executed.
Accordingly, it becomes possible for the processing unit itself to
obtain information of the delay time on each of the plurality of
heads with the detection signal of the interferometer system
serving as a reference. Then, the controller drives the movable
body based on the measurement data corresponding to each detection
signal of the plurality of heads of the encoder system and
information of the delay time for each of the plurality of heads
that has been obtained. Accordingly, even if the delay time is
different for each head, it becomes possible to drive the movable
body using each encoder of the encoder system with good precision,
without being affected by the difference of the delay time between
the plurality of heads.
[0035] According to a twelfth aspect of the present invention,
there is provided a first pattern formation apparatus, the
apparatus comprising: a movable body on which an object is mounted,
and is movable in a movement plane holding the object; and a
movable body drive system according to any one of the first to
third movable body drive systems of the present invention that
drives the movable body to perform pattern formation with respect
to the object.
[0036] According to this apparatus, by generating a pattern on an
object on the movable body driven by any one of the first to third
movable body drive systems of the present invention with a
patterning unit, it becomes possible to form a desired pattern on
the object.
[0037] According to a thirteenth aspect of the present invention,
there is provided a first exposure apparatus that forms a pattern
on an object by an irradiation of an energy beam, the apparatus
comprising: a patterning unit that irradiates the energy beam on
the object; and the movable body drive system according to any one
of the first to third movable body drive systems of the present
invention, wherein the movable body drive system drives the movable
body on which the object is mounted for relative movement of the
energy beam and the object.
[0038] According to this apparatus, for relative movement of the
energy beam irradiated on the object from the patterning unit and
the object, the movable body on which the object is mounted is
driven by any one of the first to third movable body drive system
of the present invention. Accordingly, it becomes possible to form
a desired pattern on the object by scanning exposure.
[0039] According to a fourteenth aspect of the present invention,
there is provided a second exposure apparatus that sequentially
exchanges an object on a movable body that moves in a movement
plane, and forms a pattern respectively on each object by
sequentially exposing the object after exchange, the apparatus
comprising: an encoder system including at least three encoders
that measure positional information of the movable body in the
movement plane in a predetermined effective area including an
exposure position; and a controller that starts position control of
the movable body in the movement plane using at least the three
encoders of the encoder system once more, each time exchange of the
object is performed on the movable body.
[0040] According to this apparatus, each time the exchange of the
object is performed on the movable body by the controller, position
control of the movable body in the movement plane using at least
three encoders of an encoder system that measure positional
information in the movement plane of the movable body in the
effective area is started once more. Therefore, each time the
object exchange is performed, the position error of the movable
body is canceled out, so that the position error of the movable
body does not increase with the passage of time. Accordingly, it
becomes possible to measure the positional information of the
movable body in the movement plane in a predetermined effective
area including the exposure position by the encoder system with
good precision for over a long time, which makes it possible to
maintain the exposure precision for over a long period of time.
[0041] According to a fifteenth aspect of the present invention,
there is provided a fourth movable body drive system in which a
movable body is driven in a movement plane, the system comprising:
an encoder system including a plurality of encoders respectively
having a head that irradiates a detection light on a grating and
receives the detection light from the grating and measures
positional information of the movable body in the movable plane;
and a controller that constantly takes in an output of each encoder
of the encoder system, and also executes an operation to switch the
encoder used for control of the movable body from an encoder that
has been used for position control of the movable body to another
encoder in synchronization with the timing of the position control
of the movable body.
[0042] According to the system, when the movable body is driven,
the controller constantly takes in the output of each encoder of
the encoder system, and executes an operation of switching an
encoder used for position control of the movable body from an
encoder that has been used for position control of the movable body
to another encoder at a timing in synchronization with the position
control of the movable body. Therefore, the switching of the
encoder will not have to be performed at a high speed, and a highly
precise hardware for the switching will not be necessary, which
consequently will make cost reduction possible.
[0043] According to a sixteenth aspect of the present invention,
there is provided a fifth movable body drive system in which a
movable body is driven in a movement plane including a first axis
and a second axis orthogonal to each other, the system comprising:
an encoder system including a plurality of encoders having a head
that irradiates a detection light on a grating and receives the
detection light from the grating and measures positional
information of the movable body in the movable plane; and a
controller that makes a combination of encoders subject to a
switching where an encoder used for position control of the movable
body is switched from an arbitrary encoder to another encoder and
prepares a switching timing, based on a movement course of the
movable body.
[0044] According to this system, the controller makes a combination
of encoders subject to a switching where an encoder used for
position control of the movable body is switched from an arbitrary
encoder to another encoder and prepares a switching timing, based
on a movement course of the movable body. And when the movable body
is moving, the positional information of the movable body in the
movement plane is measured using at least one encoder of the
encoder system, and based on the contents made out in the
scheduling above, the switching from an arbitrary encoder to
another encoder is performed. According to this, a reasonable
encoder switching according to the target track of the movable body
becomes possible.
[0045] According to a seventeenth aspect of the present invention,
there is provided a second pattern formation apparatus, the
apparatus comprising: a movable body on which the object is
mounted, and is movable in a movement plane holding the object; and
a movable body drive system according to one of the fourth and
fifth movable body drive systems of the present invention that
drives the movable body to perform pattern formation with respect
to the object.
[0046] According to this apparatus, by generating a pattern on the
object on the movable body driven smoothly by one of the fourth and
fifth movable body drive systems of the present invention with a
patterning unit, it becomes possible to form a pattern on the
object with good precision.
[0047] According to an eighteenth aspect of the present invention,
there is provided a third exposure apparatus that forms a pattern
on an object by an irradiation of an energy beam, the apparatus
comprising: a patterning unit that irradiates the energy beam on
the object; and the movable body drive system according to one of
the fourth and fifth movable body drive systems of the present
invention, wherein the movable body drive system drives the movable
body on which the object is mounted for relative movement of the
energy beam and the object.
[0048] According to this apparatus, for relative movement of the
energy beam irradiated on the object from the patterning unit and
the object, the movable body on which the object is mounted is
driven with good precision by one of the fourth and fifth movable
body drive system of the present invention. Accordingly, it becomes
possible to form a pattern on the object with good precision by
scanning exposure.
[0049] According to a nineteenth aspect of the present invention,
there is provided a fourth exposure apparatus that exposes an
object with an energy beam, the apparatus comprising: a movable
body that holds the object and is movable at least in a first and
second directions which are orthogonal in a predetermined plane; an
encoder system in which one of a grating section and a head unit is
arranged on a surface of the movable body where the object is held
and the other is arranged facing the surface of the movable body,
and positional information of the movable body in the predetermined
plane is measured by a head that faces the grating section of a
plurality of heads of the head unit; and a controller that decides
the positional information which should be measured by a head after
a switching, during the switching of the head used for the
measurement that accompanies the movement of the movable body,
based on positional information measured by a head before the
switching and positional information of the movable body in a
direction different from the first and second directions.
[0050] According to the apparatus, before and after the switching
of the head used for position measurement of the movable body that
accompanies the movement of the movable body, the position of the
movable body is maintained, which allows a smooth switching of the
head. Accordingly, it becomes possible to drive the movable body
two-dimensionally accurately at least within the predetermined
plane, while performing switching between a plurality of heads,
which in turn allows exposure of the object on the movable body to
be performed with good precision.
[0051] According to a twentieth aspect of the present invention,
there is provided a fifth exposure apparatus that exposes an object
with an energy beam, the apparatus comprising: a movable body that
holds the object and is movable at least in a first and second
directions which are orthogonal in a predetermined plane; an
encoder system in which one of a grating section and a head unit is
arranged on a surface of the movable body where the object is held
and the other is arranged facing the surface of the movable body,
and positional information of the movable body in the predetermined
plane is measured by a head that faces the grating section of a
plurality of heads of the head unit; and a controller that
continues the measurement while switching the head used for the
measurement to another head during the movement of the movable
body, and controls a position of the movable body in the
predetermined plane, based on measurement information of the
encoder system measured by the another head and positional
information of the movable body in a direction different from the
first and second directions on the switching.
[0052] According to this, it becomes possible to drive the movable
body two-dimensionally accurately at least within the predetermined
plane, while performing switching between a plurality of heads,
which in turn allows exposure of the object on the movable body to
be performed with good precision.
[0053] According to a twenty-first aspect of the present invention,
there is provided a sixth exposure apparatus that exposes an object
with an energy beam, the apparatus comprising: a movable body that
holds the object and is movable at least in a first and second
directions which are orthogonal in a predetermined plane; an
encoder system in which one of a grating section and a head unit is
arranged on a surface of the movable body where the object is held
and the other is arranged facing the surface of the movable body,
and positional information of the movable body in the first and
second directions, and rotational direction in the predetermined
plane is measured by at least three heads that face the grating
section of a plurality of heads of the head unit; and a controller
that continues the measurement while switching the three heads used
for the measurement to three heads having at least one different
head during the movement of the movable body, and during the
switching, decides position information that should be measured by
at least one head of the three heads after the switching which are
different from the three heads before the switching, based on
positional information measured by the three heads before the
switching.
[0054] According to the apparatus, before and after the switching
of the head used for position measurement of the movable body that
accompanies the movement of the movable body, the position
(including rotation in the predetermined plane) of the movable body
is maintained, which allows a smooth switching of the head.
Accordingly, it becomes possible to drive the movable body
two-dimensionally accurately at least within the predetermined
plane, while performing switching between a plurality of heads,
which in turn allows exposure of the object on the movable body to
be performed with good precision.
[0055] According to a twenty-second aspect of the present
invention, there is provided a seventh exposure apparatus that
exposes an object with an energy beam, the apparatus comprising: a
movable body that holds the object and is movable at least in a
first and second directions which are orthogonal in a predetermined
plane; an encoder system in which one of a grating section and a
head unit is arranged on a surface of the movable body where the
object is held and the other is arranged facing the surface of the
movable body, and positional information of the movable body in the
predetermined plane is measured by a head that faces the grating
section of a plurality of heads of the head unit; and a controller
that controls a position of the movable body in the predetermined
plane, based on positional information of the head used for
measuring the positional information in a surface parallel to the
predetermined plane and measurement information of the encoder
system.
[0056] According to the apparatus, it becomes possible to drive the
movable body two-dimensionally accurately at least within the
predetermined plane, which in turn allows exposure of the object on
the movable body to be performed with good precision, without being
affected by the measurement error of the encoder system due to the
shift (for example, shift from the design position) of position of
the head used for the measurement of the positional information in
a surface parallel to the predetermined plane.
[0057] According to a twenty-third aspect of the present invention,
there is provided an eighth exposure apparatus that exposes an
object with an energy beam, the apparatus comprising: a movable
body that holds the object and is movable at least in a first and
second directions which are orthogonal in a predetermined plane; an
encoder system in which one of a grating section and a head unit is
arranged on a surface of the movable body where the object is held
and the other is arranged facing the surface of the movable body,
and positional information of the movable body in the predetermined
plane is measured by a head that faces the grating section of a
plurality of heads of the head unit; and a controller that measures
positional information of the plurality of heads of the head unit
in a surface parallel to the predetermined plane and controls a
position of the movable body in the predetermined plane, based on
positional information that has been measured and measurement
information of the encoder system.
[0058] According to the apparatus, it becomes possible to drive the
movable body two-dimensionally accurately at least within the
predetermined plane, which in turn allows exposure of the object on
the movable body to be performed with good precision. According to
a twenty-fourth aspect of the present invention, there is provided
third exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby positional information of the movable
body is measured using an encoder system in which one of a grating
section and a head unit is arranged on a surface of the movable
body where the object is mounted and the other is arranged facing
the surface of the movable body, and positional information of the
movable body in the predetermined plane is measured by a head that
faces the grating section of a plurality of heads of the head unit,
and the positional information which should be measured by a head
after a switching during the switching of the head used for the
measurement that accompanies the movement of the movable body is
decided, based on positional information measured by a head before
the switching and positional information of the movable body in a
direction different from the first and second directions.
[0059] According to this method, before and after the switching of
the head used for position measurement of the movable body that
accompanies the movement of the movable body, the position of the
movable body is maintained, which allows a smooth switching of the
head. Accordingly, it becomes possible to drive the movable body
two-dimensionally accurately at least within the predetermined
plane, while performing switching between a plurality of heads,
which in turn allows exposure of the object on the movable body to
be performed with good precision.
[0060] According to a twenty-fifth aspect of the present invention,
there is provided a fourth exposure method of exposing an object
with an energy beam wherein the object is mounted on a movable body
that can move in at least a first and second direction which are
orthogonal in a predetermined plane, whereby positional information
of the movable body is measured using an encoder system in which
one of a grating section and a head unit is arranged on a surface
of the movable body where the object is mounted and the other is
arranged facing the surface of the movable body, and positional
information of the movable body in the predetermined plane is
measured by a head that faces the grating section of a plurality of
heads of the head unit, and the measurement is continued while
switching the head used for the measurement to another head during
the movement of the movable body, and a position of the movable
body in the predetermined plane is controlled based on measurement
information of the encoder system measured by the another head and
positional information of the movable body in a direction different
from the first and second directions on the switching.
[0061] According to the method, it becomes possible to drive the
movable body two-dimensionally accurately at least within the
predetermined plane, while performing switching between a plurality
of heads, which in turn allows exposure of the object on the
movable body to be performed with good precision. According to a
twenty-sixth aspect of the present invention, there is provided a
fifth exposure method of exposing an object with an energy beam
wherein the object is mounted on a movable body that can move in at
least a first and second direction which are orthogonal in a
predetermined plane, whereby positional information of the movement
body is measured using an encoder system in which one of a grating
section and a head unit is arranged on a surface of the movable
body where the object is held and the other is arranged facing the
surface of the movable body and which also measures positional
information of the movable body in the first direction, the second
direction, and rotational direction in the predetermined plane with
at least three heads that face the grating section of a plurality
of heads of the head unit, and the measurement is continued while
switching the three heads used for the measurement to three heads
having at least one different head during the movement of the
movable body, and during the switching, position information that
should be measured by at least one head of the three heads after
the switching which are different from the three heads before the
switching is decided, based on positional information measured by
the three heads before the switching.
[0062] According to this method, before and after the switching of
the head used for position measurement of the movable body that
accompanies the movement of the movable body, the position
(including rotation in the predetermined plane) of the movable body
is maintained, which allows a smooth switching of the head.
Accordingly, it becomes possible to drive the movable body
two-dimensionally accurately at least within the predetermined
plane, while performing switching between a plurality of heads,
which in turn allows exposure of the object on the movable body to
be performed with good precision.
[0063] According to a twenty-seventh aspect of the present
invention, there is provided a sixth exposure method of exposing an
object with an energy beam wherein the object is mounted on a
movable body that can move in at least a first and second direction
which are orthogonal in a predetermined plane, whereby one of a
grating section and a head unit is arranged on a surface of the
movable body where the object is held and the other is arranged
facing the surface of the movable body, and the position of the
movable body in the predetermined plane is controlled, based on
measurement information of an encoder system that measures
positional information of the movable body in the predetermined
plane by a head that faces the grating section of a plurality of
heads of the head unit, and positional information of the head used
to measure the positional information in a surface parallel to the
predetermined plane.
[0064] According to the method, it becomes possible to drive the
movable body two-dimensionally accurately at least within the
predetermined plane, which in turn allows exposure of the object on
the movable body to be performed with good precision, without being
affected by the measurement error of the encoder system due to the
shift (for example, shift from the design position) of position of
the head used for the measurement of the positional information in
a surface parallel to the predetermined plane.
[0065] According to a twenty-eighth aspect of the present
invention, there is provided a seventh exposure method of exposing
an object with an energy beam wherein the object is mounted on a
movable body that can move in at least a first and second direction
which are orthogonal in a predetermined plane, whereby of an
encoder system in which one of a grating section and a head unit is
arranged on a surface of the movable body where the object is held
and the other is arranged facing the surface of the movable body,
and positional information of the movable body in the predetermined
plane is measured by a head that faces the grating section of a
plurality of heads of the head unit, the positional information of
a plurality of heads of the head unit in a surface parallel to the
predetermined plane is measured, and based on measured positional
information and the measurement information of the encoder system,
the position of the movable body in the predetermined plane is
controlled.
[0066] According to the method, it becomes possible to drive the
movable body two-dimensionally accurately at least within the
predetermined plane, which in turn allows exposure of the object on
the movable body to be performed with good precision.
[0067] According to a twenty-ninth aspect of the present invention,
there is provided a second device manufacturing method including a
lithography process wherein in the lithography process, a sensitive
object mounted on the movable body is exposed using the exposure
method according to one of the third and seventh exposure method of
the present invention, and a pattern is formed on the sensitive
object.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] In the accompanying drawings;
[0069] FIG. 1 is a view schematically showing the configuration of
an exposure apparatus related to an embodiment;
[0070] FIG. 2 is a planar view showing a stage unit in FIG. 1;
[0071] FIG. 3 is a planar view showing the placement of various
measuring apparatuses (such as encoders, alignment systems, a
multipoint AF system, and Z sensors) that are equipped in the
exposure apparatus in FIG. 1;
[0072] FIG. 4A is a planar view showing a wafer stage, and FIG. 4B
is a schematic side view of a partially sectioned wafer stage
WST;
[0073] FIG. 5A is a planar view showing a measurement stage, and
FIG. 5B is a schematic side view showing a partial cross section of
the measurement stage;
[0074] FIG. 6 is a block diagram showing a main configuration of a
control system of the exposure apparatus related to an
embodiment;
[0075] FIG. 7A is a view showing an example of a configuration of
an encoder, and FIG. 7B is a view showing the case when a laser
beam LB having a sectional shape extending narrowly in the periodic
direction of grating RG is used as a detection light;
[0076] FIG. 8A is a view showing a Doppler effect which the light
scattered by a movement plane receives, and FIG. 8B is a view for
explaining a relation between incoming light and diffraction light
with respect to a reflection type diffraction grating of a beam in
the encoder head;
[0077] FIG. 9A is a view showing a case when a measurement value
does not change even if a relative movement in a direction besides
the measurement direction occurs between a head of an encoder and a
scale, and FIG. 9B is a view showing a case when a measurement
value changes when a relative movement in a direction besides the
measurement direction occurs between a head of an encoder and a
scale;
[0078] FIGS. 10A to 10D are views used for describing the case when
the measurement value of the encoder changes and the case when the
measurement values do not change, when a relative movement in the
direction besides the measurement direction occurs between the head
and the scale;
[0079] FIGS. 11A and 11B are views for explaining an operation to
acquire correction information to correct a measurement error of an
encoder (a first encoder) due to the relative movement of the head
and the scale in the direction besides the measurement
direction;
[0080] FIG. 12 is a graph showing a measurement error of the
encoder with respect to the change in the Z position in pitching
amount .theta.x=.alpha.;
[0081] FIG. 13 is a view for explaining an operation to acquire
correction information to correct a measurement error of another
encoder (a second encoder) due to the relative movement of the head
and the scale in the direction besides the measurement
direction;
[0082] FIG. 14 is a view for describing a calibration process of a
head position;
[0083] FIG. 15 is a view for explaining a calibration process to
obtain an Abbe offset quantity;
[0084] FIG. 16 is a view for explaining an inconvenience that
occurs in the case a plurality of measurement points on the same
scale is measured by a plurality of heads;
[0085] FIG. 17 is a view for explaining a method to measure the
unevenness of the scale (No. 1);
[0086] FIGS. 18A to 18D are views for explaining a method to
measure the unevenness of the scale (No. 2);
[0087] FIG. 19 is a view for describing an acquisition operation of
correction information of the grating pitch of the scale and the
correction information of the grating deformation;
[0088] FIG. 20 is a view for explaining a method to obtain a delay
time that accompanies a propagation of the detection signal of each
Y head through a cable;
[0089] FIG. 21 is a view for describing an example of a correction
method of the measurement error of the encoder due to the
measurement delay that accompanies a propagation of the detection
signal of each head through a cable;
[0090] FIGS. 22A and 22B are views for explaining a concrete method
to convert a measurement value of the encoder that has been
corrected into a position of wafer stage WST;
[0091] FIGS. 23A and 23B are views for describing a carryover of
position measurement of the wafer table in the XY plane by a
plurality of encoders which respectively include a plurality of
heads placed in the shape of an array and the measurement value
between the heads;
[0092] FIGS. 24A to 24E are views for explaining a procedure of an
encoder switching;
[0093] FIG. 25 is a view for explaining the switching process of
the encoder used for position control of the wafer stage in the XY
plane;
[0094] FIG. 26 is a view conceptually showing position control of
the wafer stage, intake of the count value of the encoder, and an
encoder switching timing;
[0095] FIG. 27 is a view showing a state of the wafer stage and the
measurement stage where exposure to a wafer on the wafer stage is
performed by a step-and-scan method;
[0096] FIG. 28 is a view showing the state of both stages just
after the stages shifted from a state where the wafer stage and the
measurements stage are distanced to a state where both stages are
in contact after exposure has been completed;
[0097] FIG. 29 is a view showing a state where the measurement
stage moves in the -Y direction and the wafer stage moves toward an
unloading position, while maintaining the positional relation
between the wafer table and the measurement table in the Y-axis
direction;
[0098] FIG. 30 is a view showing a state of the wafer stage and the
measurement stage when the measurement stage arrives at a position
where Sec-BCHK (an interval) is performed;
[0099] FIG. 31 is a view showing a state of the wafer stage and the
measurement stage when the wafer stage moves from the unloading
position to a loading position, in parallel with the Sec-BCHK
(interval) being performed;
[0100] FIG. 32 is a view showing a state of the wafer stage and the
measurement stage when the measurement stage moves to an optimal
scrum waiting position and a wafer is loaded on a wafer table;
[0101] FIG. 33 is a view showing a state of both stages when the
wafer stage has moved to a position where the Pri-BCHK former
process is performed while the measurement stage is waiting at the
optimal scrum waiting position;
[0102] FIG. 34 is a view showing a state of the wafer stage and the
measurement stage when alignment marks arranged in three first
alignment shot areas are being simultaneously detected using
alignment systems AL1, AL2.sub.2 and AL2.sub.3;
[0103] FIG. 35 is view showing a state with a wafer stage and the
measurement stage when the focus calibration former process is
performed;
[0104] FIG. 36 is a view showing a state of the wafer stage and the
measurement stage when alignment marks arranged in five second
alignment shot areas are being simultaneously detected using
alignment systems AL1 and AL2.sub.1 to AL2.sub.4;
[0105] FIG. 37 is a view showing a state of the wafer stage and the
measurement stage when at least one of the Pri-BCHK latter process
and the focus calibration latter process is being performed;
[0106] FIG. 38 is a view showing a state of the wafer stage and the
measurement stage when alignment marks arranged in five third
alignment shot areas are being simultaneously detected using
alignment systems AL1 and AL2.sub.1 to AL2.sub.4;
[0107] FIG. 39 is a view showing a state of the wafer stage and the
measurement stage when alignment marks arranged in three fourth
alignment shot areas are being simultaneously detected using
alignment systems AL1, AL2.sub.2 and AL2.sub.3;
[0108] FIG. 40 is a view showing a state of the wafer stage and the
measurement stage when the focus mapping has ended;
[0109] FIG. 41 is a flow chart for explaining an embodiment of the
device manufacturing method; and
[0110] FIG. 42 is a flow chart which shows a concrete example of
step 204 of FIG. 41.
DESCRIPTION OF THE EMBODIMENTS
[0111] Hereinafter, an embodiment of the present invention will be
described, referring to FIGS. 1 to 40.
[0112] FIG. 1 shows a schematic configuration of an exposure
apparatus 100 related to the embodiment.
[0113] Exposure apparatus 100 is a scanning exposure apparatus of
the step-and-scan method, namely the so-called scanner. As it will
be described later, a projection optical system PL is arranged in
the embodiment, and in the description below, a direction parallel
to an optical axis AX of projection optical system PL will be
described as the Z-axis direction, a direction within a plane
orthogonal to the Z-axis direction in which a reticle and a wafer
are relatively scanned will be described as the Y-axis direction, a
direction orthogonal to the Z-axis and the Y-axis will be described
as the X-axis direction, and rotational (inclination) directions
around the X-axis, the Y-axis, and the Z-axis will be described as
.theta.x, .theta.y, and .theta.z directions, respectively.
[0114] Exposure apparatus 100 includes an illumination system 10, a
reticle stage RST that holds a reticle R that is illuminated by an
illumination light for exposure (hereinafter, referred to as
"illumination light" or "exposure light") IL from illumination
system 10, a projection unit PU that includes projection optical
system PL that projects illumination light IL emitted from reticle
R on a wafer W, a stage unit 50 that has a wafer stage WST and a
measurement stage MST, their control system, and the like. On wafer
stage WST, wafer W is mounted.
[0115] Illumination system 10 is configured including a light
source, an illuminance uniformity optical system, which includes an
optical integrator and the like, and n illumination optical system
that has a reticle blind and the like (none of which are shown), as
is disclosed in, for example, Kokai (Japanese Patent Unexamined
Application Publication) No. 2001-313250 (the corresponding U.S.
Patent Application Publication No. 2003/0025890 description) and
the like. In illumination system 10, a slit-shaped illumination
area extending in the X-axis direction which is set on reticle R
with a reticle blind (a masking system) is illuminated by
illumination light (exposure light) IL with a substantially uniform
illuminance. In this case, as illumination light IL, for example,
an ArF excimer laser beam (wavelength 193 nm) is used. Further, as
the optical integrator, for example, a fly-eye lens, a rod
integrator (an internal reflection type integrator), a diffractive
optical element or the like can be used.
[0116] On reticle stage RST, reticle R on which a circuit pattern
or the like is formed on its pattern surface (the lower surface in
FIG. 1) is fixed, for example, by vacuum chucking. Reticle stage
RST is finely drivable or movable in within an XY plane by a
reticle stage drive section 11 (not shown in FIG. 1, refer to FIG.
6) that includes a linear motor or the like, and reticle stage RST
is also drivable in a predetermined scanning direction (in this
case, the Y-axis direction, which is the lateral direction of the
page surface in FIG. 1) at a designated scanning speed.
[0117] The positional information (including rotation information
in the .theta.z direction) of reticle stage RST in the movement
plane is constantly detected, for example, at a resolution of
around 0.5 to 1 nm by a reticle laser interferometer (hereinafter
referred to as a "reticle interferometer") 116, via a movable
mirror 15 (the mirrors actually arranged are a Y movable mirror
that has a reflection surface which is orthogonal to the Y-axis
direction and an X movable mirror that has a reflection surface
orthogonal to the X-axis direction). The measurement values of
reticle interferometer 116 are sent to a main controller 20 (not
shown in FIG. 1, refer to FIG. 6). Main controller 20 computes the
position of reticle stage RST in the X-axis direction, Y-axis
direction, and the .theta.z direction based on the measurement
values of reticle interferometer 116, and also controls the
position (and velocity) of reticle stage RST by controlling reticle
stage drive section 11 based on the computation results.
Incidentally, instead of movable mirror 15, the edge surface of
reticle stage RSV can be mirror polished so as to form a reflection
surface (corresponding to the reflection surface of movable mirror
15). Further, reticle interferometer 116 can measure positional
information of reticle stage RST related to at least one of the
Z-axis, .theta.x, or .theta.y directions.
[0118] Projection unit PU is placed below reticle stage RST in FIG.
1. Projection unit PU includes a barrel 40, and projection optical
system PL that has a plurality of optical elements which are held
in a predetermined positional relation inside barrel 40. As
projection optical system PL, for example, a dioptric system is
used, consisting of a plurality of lenses (lens elements) that is
disposed along an optical axis AX, which is parallel to the Z-axis
direction. Projection optical system PL is, for example, a
both-side telecentric dioptric system that has a predetermined
projection magnification (such as one-quarter, one-fifth, or
one-eighth times). Therefore, when illumination light IL from
illumination system 10 illuminates illumination area IAR, a reduced
image of the circuit pattern (a reduced image of a part of the
circuit pattern) of the reticle is formed within illumination area
IAR, with illumination light IL that has passed through reticle R
which is placed so that its pattern surface substantially coincides
with a first plane (an object plane) of projection optical system
PL, in an area conjugate to illumination area IAR on wafer W
(exposure area) whose surface is coated with a resist (a sensitive
agent) and is placed on a second plane (an image plane) side, via
projection optical system PL (projection unit PU) and liquid Lq
(refer to FIG. 1). And by reticle stage RST and wafer stage WST
being synchronously driven, the reticle is relatively moved in the
scanning direction (the Y-axis direction) with respect to
illumination area IAR (illumination light IL) while wafer W is
relatively moved in the scanning direction (the Y-axis direction)
with respect to the exposure area (illumination light IL), thus
scanning exposure of a shot area (divided area) on wafer W is
performed, and the pattern of the reticle is transferred onto the
shot area. That is, in the embodiment, the pattern is generated on
wafer W according to illumination system 10, the reticle, and
projection optical system PL, and then by the exposure of the
sensitive layer (resist layer) on wafer W with illumination light
IL, the pattern is formed on wafer W. Although it is not shown in
the drawings, projection unit PU is mounted on a barrel platform
supported by three struts via a vibration isolation mechanism,
however, as is disclosed in, for example, the pamphlet of
International Publication No. WO 2006/038952 and the like,
projection unit PU can be supported by suspension with respect to a
mainframe member (not shown) placed above projection unit PU or
with respect to a base member on which reticle stage RST is
placed.
[0119] Further, in exposure apparatus 100 of the embodiment, in
order to perform exposure applying the liquid immersion method, a
nozzle unit 32 that constitutes part of a local liquid immersion
unit 8 is arranged so as to enclose the periphery of the lower end
portion of barrel 40 that holds an optical element that is closest
to an image plane side (wafer W side) that constitutes projection
optical system PL, which is a lens (hereinafter, also referred to a
"tip lens") 191 in this case. In the embodiment, as shown in FIG.
1, the lower end surface of nozzle unit 32 is set to be
substantially flush with the lower end surface of tip lens 191.
Further, nozzle unit 32 is equipped with a supply opening and a
recovery opening of liquid Lq, a lower surface to which wafer W is
placed facing and at which the recovery opening is arranged, and a
supply flow channel and a recovery flow channel that are connected
to a liquid supply pipe 31A and a liquid recovery pipe 31B
respectively. As shown in FIG. 3, liquid supply pipe 31A and liquid
recovery pipe 31B are inclined at an angle of 45 degrees with
respect to the X-axis direction and the Y-axis direction in a
planer view (when viewed from above) and are symmetrically placed
with respect to a straight line LV in the Y-axis direction that
passes through optical axis AX of projection optical system PL.
[0120] One end of a supply pipe (not shown) is connected to liquid
supply pipe 31A while the other end of the supply pipe is connected
to a liquid supply unit 5 (not shown in FIG. 1, refer to FIG. 6),
and one end of a recovery pipe (not shown) is connected to liquid
recovery pipe 31B while the other end of the recovery pipe is
connected to a liquid recovery unit 6 (not shown in FIG. 1, refer
to FIG. 6).
[0121] Liquid supply unit 5 includes a liquid tank, a compression
pump, a temperature controller, a valve for controlling supply/stop
of the liquid to liquid supply pipe 31A, and the like. As the
valve, for example, a flow rate control valve is preferably used so
that not only the supply/stop of the liquid but also the adjustment
of flow rate can be performed. The temperature controller adjusts
the temperature of the liquid within the liquid tank to nearly the
same temperature, for example, as the temperature within the
chamber (not shown) where the exposure apparatus is housed.
Incidentally, the tank for supplying the liquid, the compression
pump, the temperature controller, the valve, and the like do not
all have to be equipped in exposure apparatus 100, and at least
part of them can also be substituted by the equipment or the like
available in the plant where exposure apparatus 100 is
installed.
[0122] Liquid recovery unit 6 includes a liquid tank, a suction
pump, a valve for controlling recovery/stop of the liquid via
liquid recovery pipe 31B, and the like. As the valve, a flow rate
control valve is preferably used corresponding to the valve of
liquid supply unit 5. Incidentally, the tank for recovering the
liquid, the suction pump, the valve, and the like do not all have
to be equipped in exposure apparatus 100, and at least part of them
can also be substituted by the equipment or the like available in
the plant where exposure apparatus 100 is installed.
[0123] In the embodiment, as the liquid described above, pure water
(hereinafter, it will simply be referred to as "water" besides the
case when specifying is necessary) that transmits the ArF excimer
laser light (light with a wavelength of 193 nm) is to be used. Pure
water can be obtained in large quantities at a semiconductor
manufacturing plant or the like without difficulty, and it also has
an advantage of having no adverse effect on the photoresist on the
wafer, to the optical lenses or the like.
[0124] Refractive index n of the water with respect to the ArF
excimer laser light is around 1.44. In the water the wavelength of
illumination light IL is 193 nm.times.1/n, shorted to around 134
nm.
[0125] Liquid supply unit 5 and liquid recovery unit 6 each have a
controller, and the respective controllers are controlled by main
controller 20 (refer to FIG. 6). According to instructions from
main controller 20, the controller of liquid supply unit 5 opens
the valve connected to liquid supply pipe 31A to a predetermined
degree to supply water Lq (refer to FIG. 1) to the space between
tip lens 191 and wafer W via liquid supply pipe 31A, the supply
flow channel and the supply opening. Further, when the water is
supplied, according to instructions from main controller 20, the
controller of liquid recovery unit 6 opens the valve connected to
liquid recovery pipe 31B to a predetermined degree to recover water
Lq from the space between tip lens 191 and wafer W into liquid
recovery unit 6 (the liquid tank) via the recovery opening, the
recovery flow channel and liquid recovery pipe 31B. During the
supply and recovery operations, main controller 20 gives commands
to the controllers of liquid supply unit 5 and liquid recovery unit
6 so that the quantity of water supplied to the space between tip
lens 191 and wafer W constantly equals the quantity of water
recovered from the space. Accordingly, a constant quantity of water
Lq is held (refer to FIG. 1) in the space between tip lens 191 and
wafer W. In this case, water Lq held in the space between tip lens
191 and wafer W is constantly replaced.
[0126] As is obvious from the above description, in the embodiment,
local liquid immersion unit 8 is configured including nozzle unit
32, liquid supply unit 5, liquid recovery unit 6, liquid supply
pipe 31A and liquid recovery pipe 31B, and the like. Local liquid
immersion unit 8 fills liquid Lq in the space between tip lens 191
and wafer W by nozzle unit 32, so that a local liquid immersion
space (equivalent to a liquid immersion area 14) which includes the
optical path space of illumination light IL is formed. Accordingly,
nozzle unit 32 is also called a liquid immersion space formation
member or a containment member (or, a confinement member).
Incidentally, part of local liquid immersion unit 8, for example,
at least nozzle unit 32 may also be supported in a suspended state
by a main frame (including the barrel platform) that holds
projection unit PU, or may also be arranged at another frame member
that is separate from the main frame. Or, in the case projection
unit PU is supported in a suspended state as is described earlier,
nozzle unit 32 may also be supported in a suspended state
integrally with projection unit PU, but in the embodiment, nozzle
unit 32 is arranged on a measurement frame that is supported in a
suspended state independently from projection unit PU. In this
case, projection unit PU does not have to be supported in a
suspended state.
[0127] Incidentally, also in the case measurement stage MST is
located below projection unit PU, the space between a measurement
table (to be described later) and tip lens 191 can be filled with
water in a similar manner to the manner described above.
[0128] Incidentally, in the description above, one liquid supply
pipe (nozzle) and one liquid recovery pipe (nozzle) were arranged
as an example, however, the present invention is not limited to
this, and a configuration having multiple nozzles as is disclosed
in, for example, the pamphlet of International Publication No. WO
99/49504, may also be employed, in the case such an arrangement is
possible taking into consideration a relation with adjacent
members. Further, the lower surface of nozzle unit 32 can be placed
near the image plane (more specifically, a wafer) of projection
optical system PL rather than the outgoing plane of tip lens 191,
or, in addition to the optical path of the image plane side of tip
lens 191, a configuration in which the optical path on the object
plane side of tip lens 191 is also filled with liquid can be
employed. The point is that any configuration can be employed, as
long as the liquid can be supplied in the space between optical
member (tip lens) 191 in the lowest end constituting projection
optical system PL and wafer W. For example, the liquid immersion
mechanism disclosed in the pamphlet of International Publication
No. WO 2004/053955, or the liquid immersion mechanism disclosed in
the EP Patent Application Publication No. 1 420 298 can also be
applied to the exposure apparatus of the embodiment.
[0129] Referring back to FIG. 1, stage unit 50 is equipped with
wafer stage WST and measurement stage MST that are placed above a
base board 12, an interferometer system 118 (refer to FIG. 6)
including Y interferometers 16 and 18 that measure position
information of stages WST and MST, an encoder system (to be
described later) that is used for measuring position information of
wafer stage WST on exposure or the like, a stage drive system 124
(refer to FIG. 6) that drives stages WST and MST, and the like.
[0130] On the bottom surface of each of wafer stage WST and
measurement stage MST, a noncontact bearing (not shown), for
example, a vacuum preload type hydrostatic air bearing
(hereinafter, referred to as an "air pad") is arranged at a
plurality of points. Wafer stage WST and measurement stage MST are
supported in a noncontact manner via a clearance of around several
.mu.m above base board 12, by static pressure of pressurized air
that is blown out from the air pad toward the upper surface of base
board 12. Further, stages WST and MST are independently drivable in
two-dimensional directions, which are the Y-axis direction (a
horizontal direction of the page surface of FIG. 1) and the X-axis
direction (an orthogonal direction to the page surface of FIG. 1)
in a predetermined plane (the XY plane), by stage drive system
124.
[0131] To be more specific, on a floor surface, as shown in the
planar view in FIG. 2, a pair of Y-axis stators 86 and 87 extending
in the Y-axis direction are respectively placed on one side and the
other side in the X-axis direction with base board 12 in between.
Y-axis stators 86 and 87 are each composed of, for example, a
magnetic pole unit that incorporates a permanent magnet group that
is made up of a plurality of sets of a north pole magnet and a
south pole magnet that are placed at a predetermined distance and
alternately along the Y-axis direction. At Y-axis stators 86 and
87, two Y-axis movers 82 and 84, and two Y-axis movers 83 and 85
are respectively arranged in a noncontact engaged state. In other
words, four Y-axis movers 82, 84, 83 and 85 in total are in a state
of being inserted in the inner space of Y-axis stator 86 or 87
whose XZ sectional surface has a U-like shape, and are severally
supported in a noncontact manner via a clearance of, for example,
around several .mu.m via the air pad (not shown) with respect to
corresponding Y-axis stator 86 or 87. Each of Y-axis movers 82, 84,
83 and 85 is composed of, for example, an armature unit that
incorporates armature coils placed at a predetermined distance
along the Y-axis direction. That is, in the embodiment, Y-axis
movers 82 and 84 made up of the armature units and Y-axis stator 86
made up of the magnetic pole unit constitute moving coil type
Y-axis linear motors respectively. Similarly, Y-axis movers 83 and
85 and Y-axis stator 87 constitute moving coil type Y-axis linear
motors respectively. In the following description, each of the four
Y-axis linear motors described above is referred to as a Y-axis
linear motor 82, a Y-axis linear motor 84, a Y-axis linear motor 83
and a Y-axis linear motor 85 as needed, using the same reference
codes as their movers 82, 84, 83 and 85.
[0132] Movers 82 and 83 of two Y-axis linear motors 82 and 83 out
of the four Y-axis linear motors are respectively fixed to one end
and the other end in a longitudinal direction of an X-axis stator
80 that extends in the X-axis direction. Further, movers 84 and 85
of the remaining two Y-axis linear motors 84 and 85 are fixed to
one end and the other end of an X-axis stator 81 that extends in
the X-axis direction. Accordingly, X-axis stators 80 and 81 are
driven along the Y-axis by a pair of Y-axis linear motors 82 and 83
and a pair of Y-axis linear motors 84 and 85 respectively.
[0133] Each of X-axis stators 80 and 81 is composed of, for
example, an armature unit that incorporates armature coils placed
at a predetermined distance along the X-axis direction.
[0134] One X-axis stator, X-axis stator 81 is arranged in a state
of being inserted in an opening (not shown) formed at a stage main
section 91 (not shown in FIG. 2, refer to FIG. 1) that constitutes
part of wafer stage WST. Inside the opening of stage main section
91, for example, a magnetic pole unit, which has a permanent magnet
group that is made up of a plurality of sets of a north pole magnet
and a south pole magnet placed at a predetermined distance and
alternately along the X-axis direction, is arranged. This magnetic
pole unit and X-axis stator 81 constitute a moving magnet type
X-axis linear motor that drives stage main section 91 in the X-axis
direction. Similarly, the other X-axis stator, X-axis stator 80 is
arranged in a state of being inserted in an opening formed at a
stage main section 92 (not shown in FIG. 2, refer to FIG. 1) that
constitutes part of measurement stage MST. Inside the opening of
stage main section 92, a magnetic pole unit, which is similar to
the magnetic pole unit on the wafer stage WST side (stage main
section 91 side), is arranged. This magnetic pole unit and X-axis
stator 80 constitute a moving magnet type X-axis linear motor that
drives measurement stage MST in the X-axis direction.
[0135] In the embodiment, each of the linear motors described above
that constitute stage drive system 124 is controlled by main
controller 20 shown in FIG. 6. Incidentally, each linear motor is
not limited to either one of the moving magnet type or the moving
coil type, and the types can appropriately be selected as
needed.
[0136] Incidentally, by making thrust forces severally generated by
a pair of Y-axis linear motors 84 and 85 be slightly different,
yawing (rotation quantity in the .theta.z direction) of wafer stage
WST can be controlled. Further, by making thrust forces severally
generated by a pair of Y-axis linear motors 82 and 83 be slightly
different, yawing of measurement stage MST can be controlled.
[0137] Wafer stage WST includes stage main section 91 previously
described and a wafer table WTB that is mounted on stage main
section 91. Wafer table WTB and stage main section 91 are finely
driven relative to base board 12 and X-axis stator 81 in the Z-axis
direction, the .theta.x direction, and the .theta.y direction by a
Z leveling mechanism (not shown) (including, for example, a voice
coil motor and the like). More specifically, wafer table WTB is
finely movable in the Z-axis direction and can also be inclined
(tilted) with respect to the XY plane (or the image plane of
projection optical system PL). Incidentally, in FIG. 6, stage drive
system 124 is shown including each linear motor, the Z leveling
mechanism, and the drive system of measurement stage MST described
above. Further, wafer table WTB can also be configured finely
movable in at least one of the X-axis, the Y-axis, and the .theta.z
directions.
[0138] On wafer table WTB, a wafer holder (not shown) that holds
wafer W by vacuum suction or the like is arranged. The wafer holder
may also be formed integrally with wafer table WTB, but in the
embodiment, the wafer holder and wafer table WTB are separately
configured, and the wafer holder is fixed inside a recessed portion
of wafer table WTB, for example, by vacuum suction or the like.
Further, on the upper surface of wafer table WTB, a plate (liquid
repellent plate) 28 is arranged, which has the surface (liquid
repellent surface) substantially flush with the surface of a wafer
mounted on the wafer holder to which liquid repellent processing
with respect to liquid Lq is performed, has a rectangular outer
shape (contour), and has a circular opening that is formed in the
center portion and is slightly larger than the wafer holder (a
mounting area of the wafer). Plate 28 is made of materials with a
low coefficient of thermal expansion, such as glasses or ceramics
(such as Zerodur (the brand name) of Schott AG, Al.sub.2O.sub.3, or
TiC), and on the surface of plate 28, a liquid repellent film is
formed by, for example, fluorine resin materials, fluorine series
resin materials such as polytetrafluoroethylene (Teflon.RTM.),
acrylic resin materials, or silicon series resin materials.
Further, as shown in a planer view of wafer table WTB (wafer stage
WST) in FIG. 4A, plate 28 has a first liquid repellent area 28a
whose outer shape (contour) is rectangular enclosing a circular
opening, and a second liquid repellent area 28b that has a
rectangular frame (annular) shape placed around the first liquid
repellent area 28a. On the first liquid repellent area 28a, for
example, at the time of an exposure operation, at least part of a
liquid immersion area 14 that is protruded from the surface of the
wafer is formed, and on the second liquid repellent area 28b,
scales for an encoder system (to be described later) are formed.
Incidentally, at least part of the surface of plate 28 does not
have to be flush with the surface of the wafer, that is, may have a
different height from that of the surface of the wafer. Further,
plate 28 may be a single plate, but in the embodiment, plate 28 is
configured by combining a plurality of plates, for example, first
and second liquid repellent plates that correspond to the first
liquid repellent area 28a and the second liquid repellent area 28b
respectively. In the embodiment, pure water is used as liquid Lq as
is described above, and therefore, hereinafter the first liquid
repellent area 28a and the second liquid repellent area 28b are
also referred to as a first water repellent plate 28a and a second
water repellent plate 28b.
[0139] In this case, exposure light IL is irradiated to the first
water repellent plate 28a on the inner side, while exposure light
IL is hardly irradiated to the second water repellent plate 28b on
the outer side. Taking this fact into consideration, in the
embodiment, a first water repellent area to which water repellent
coat having sufficient resistance to exposure light IL (light in a
vacuum ultraviolet region, in this case) is applied is formed on
the surface of the first water repellent plate 28a, and a second
water repellent area to which water repellent coat having
resistance to exposure light IL inferior to the first water
repellent area is applied is formed on the surface of the second
water repellent plate 28b. In general, since it is difficult to
apply water repellent coat having sufficient resistance to exposure
light IL (light in a vacuum ultraviolet region, in this case) to a
glass plate, it is effective to separate the water repellent plate
into two sections in this manner, i.e. the first water repellent
plate 28a and the second water repellent plate 28b around it.
Incidentally, the present invention is not limited to this, and two
types of water repellent coat that have different resistance to
exposure light IL may also be applied on the upper surface of the
same plate in order to form the first water repellent area and the
second water repellent area. Further, the same kind of water
repellent coat may be applied to the first and second water
repellent areas. For example, only one water repellent area may
also be formed on the same plate.
[0140] Further, as is obvious from FIG. 4A, at the end portion on
the +Y side of the first water repellent plate 28a, a rectangular
cutout is formed in the center portion in the X-axis direction, and
a measurement plate 30 is embedded inside the rectangular space
(inside the cutout) that is enclosed by the cutout and the second
water repellent plate 28b. A fiducial mark FM is formed in the
center in the longitudinal direction of measurement plate 30 (on a
centerline LL of wafer table WTB), and a pair of aerial image
measurement slit patterns (slit-shaped measurement patterns) SL are
formed in the symmetrical placement with respect to the center of
fiducial mark FM on one side and the other side in the X-axis
direction of fiducial mark FM. As each of aerial image measurement
slit patterns SL, an L-shaped slit pattern having sides along the
Y-axis direction and X-axis direction can be used, as an
example.
[0141] Further, as shown in FIG. 4B, at the wafer stage WST section
below each of aerial image measurement slit patterns SL, an
L-shaped housing 36 in which an optical system containing an
objective lens, a mirror, a relay lens and the like is housed is
attached in a partially embedded state penetrating through part of
the inside of wafer table WTB and stage main section 91. Housing 36
is arranged in pairs corresponding to the pair of aerial image
measurement slit patterns SL, although omitted in the drawing.
[0142] The optical system inside housing 36 guides illumination
light IL that has been transmitted through aerial image measurement
slit pattern SL along an L-shaped route and emits the light toward
a -Y direction. Incidentally, in the following description, the
optical system inside housing 36 is described as a
light-transmitting system 36 by using the same reference code as
housing 36 for the sake of convenience.
[0143] Moreover, on the upper surface of the second water repellent
plate 28b, multiple grid lines are directly formed in a
predetermine pitch along each of four sides. More specifically, in
areas on one side and the other side in the X-axis direction of the
second water repellent plate 28b (both sides in the horizontal
direction in FIG. 4A), Y scales 39Y.sub.1 and 39Y.sub.2 are formed,
respectively. Y scales 39Y.sub.1 and 39Y.sub.2 are each composed of
a reflective grating (e.g. diffraction grating) having a periodic
direction in the Y-axis direction in which grid lines 38 having the
longitudinal direction in the X-axis direction are formed in a
predetermined pitch along a direction parallel to the Y-axis
(Y-axis direction).
[0144] Similarly, in areas on one side and the other side in the
Y-axis direction of the second water repellent plate 28b (both
sides in the vertical direction in FIG. 4A), X scales 39X.sub.1 and
39X.sub.2 are formed respectively. X scales 39X.sub.1 and 39X.sub.2
are each composed of a reflective grating (e.g. diffraction
grating) having a periodic direction in the X-axis direction in
which grid lines 37 having the longitudinal direction in the Y-axis
direction are formed in a predetermined pitch along a direction
parallel to the X-axis (X-axis direction).
[0145] As each of the scales, the scale made up of a reflective
diffraction grating RG (refer to FIG. 7) that is created by, for
example, hologram or the like on the surface of the second water
repellent plate 28b is used. In this case, each scale has gratings
made up of narrow slits, grooves or the like that are marked at a
predetermined distance (pitch) as graduations. The type of
diffraction grating used for each scale is not limited, and not
only the diffraction grating made up of grooves or the like that
are mechanically formed, but also, for example, the diffraction
grating that is created by exposing interference fringe on a
photosensitive resin may be used. However, each scale is created by
marking the graduations of the diffraction grating, for example, in
a pitch between 138 nm to 4 .mu.m, for example, a pitch of 1 .mu.m
on a thin plate shaped glass. These scales are covered with the
liquid repellent film (water repellent film) described above.
Incidentally, the pitch of the grating is shown much wider in FIG.
4A than the actual pitch, for the sake of convenience. The same is
true also in other drawings.
[0146] In this manner, in the embodiment, since the second water
repellent plate 28b itself constitutes the scales, a glass plate
with low-thermal expansion is to be used as the second water
repellent plate 28b. However, the present invention is not limited
to this, and a scale member made up of a glass plate or the like
with low-thermal expansion on which a grating is formed may also be
fixed on the upper surface of wafer table WTB, by a plate spring
(or vacuum suction) or the like so as to prevent local
shrinkage/expansion. In this case, a water repellent plate to which
the same water repellent coat is applied on the entire surface may
be used instead of plate 28. Or, wafer table WTB may also be formed
by a low thermal expansion material, and in such a case, a pair of
Y scales and a pair of X scales may be directly formed on the upper
surface of wafer table WTB.
[0147] Incidentally, in order to protect the diffraction grating,
it is also effective to cover the grating with a glass plate with
low thermal expansion that has liquid repellency. In this case, the
thickness of the glass plate, for example, is 1 mm, and the glass
plate is set on the upper surface of the wafer table WST so that
its surface is at the same height same as the wafer surface.
Accordingly, the distance between the surface of wafer W held on
wafer stage WST and the grating surface of the scale in the Z-axis
direction is 1 mm.
[0148] Incidentally, a lay out pattern is arranged for deciding the
relative position between an encoder head and a scale near the edge
of the scale (to be described later). The lay out pattern is
configured from grid lines that have different reflectivity, and
when the encoder head scans the pattern, the intensity of the
output signal of the encoder changes. Therefore, a threshold value
is determined beforehand, and the position where the intensity of
the output signal exceeds the threshold value is detected. Then,
the relative position between the encoder head and the scale is
set, with the detected position as a reference.
[0149] In the embodiment, main controller 20 can obtain the
displacement of wafer stage WST in directions of six degrees of
freedom (the Z, X, Y, .theta.z, .theta.x, and .theta.y directions)
in the entire stroke area from the measurement results of
interferometer system 118 (refer to FIG. 6). In this case,
interferometer system 118 includes X interferometers 126 to 128, Y
interferometer 16, and Z interferometers 43A and 43B.
[0150] To the -Y edge surface and the -X edge surface of wafer
table WTB, mirror-polishing is applied, respectively, and a
reflection surface 17a and a reflection surface 17b shown in FIG. 2
are formed. By severally projecting an interferometer beam
(measurement beam) to reflection surface 17a and reflection surface
17b and receiving a reflected light of each beam, Y interferometer
16 and X interferometers 126, 127, and 128 (X interferometers 126
to 128 are not shown in FIG. 1, refer to FIG. 2) of interferometer
system 118 (refer to FIG. 6) measure a displacement of each
reflection surface from a datum position (generally, a fixed mirror
is placed on the side surface of projection unit PU, and the
surface is used as a reference surface), that is, positional
information of wafer stage WST within the XY plane, and the
measurement values are supplied to main controller 20. In the
embodiment, as it will be described later on, as each
interferometer a multiaxial interferometer that has a plurality of
measurement axes is used with an exception for a part of the
interferometers.
[0151] Meanwhile, to the side surface on the -Y side of stage main
section 91, a movable mirror 41 having the longitudinal direction
in the X-axis direction is attached via a kinematic support
mechanism (not shown), as shown in FIGS. 1 and 4B.
[0152] A pair of Z interferometers 43A and 43B (refer to FIGS. 1
and 2) that configures a part of interferometer system 118 (refer
to FIG. 6) and irradiates measurement beams on movable mirror 41 is
arranged facing movable mirror 41. To be more specific, as it can
be seen when viewing FIGS. 2 and 4B together, movable mirror 41 is
designed so that the length in the X-axis direction is longer than
reflection surface 17a of wafer table WTB by at least the interval
of Z interferometers 43A and 43B. Further, movable mirror 41 is
composed of a member having a hexagonal cross-section shape as in a
rectangle and an isosceles trapezoid that has been integrated.
Mirror-polishing is applied to the surface on the -Y side of
movable mirror 41, and three reflection surfaces 41b, 41a, and 41c
are formed.
[0153] Reflection surface 41a configures the edge surface on the -Y
side of movable mirror 41, and reflection surface 41a is parallel
with the XZ plane and also extends in the X-axis direction.
Reflection surface 41b configures a surface adjacent to the +Z side
of reflection surface 41a, and reflection surface 41b is parallel
with a plane inclined in a clockwise direction in FIG. 4B at a
predetermined angle with respect to the XZ plane and also extends
in the X-axis direction. Reflection surface 41c configures a
surface adjacent to the -Z side of reflection surface 41a, and is
arranged symmetrically with reflection surface 41b, with reflection
surface 41b in between.
[0154] As it can be seen when viewing FIGS. 1 and 2 together, Z
interferometers 43A and 43B are placed apart on one side and the
other side of Y interferometer 16 in the X-axis direction at a
substantially equal distance and at positions slightly lower than Y
interferometer 16, respectively.
[0155] From each of the Z interferometers 43A and 43B, as shown in
FIG. 1, measurement beam B1 along the Y-axis direction is projected
toward reflection surface 41b, and measurement beam B2 along the
Y-axis direction is projected toward reflection surface 41c (refer
to FIG. 4B). In the embodiment, fixed mirror 47A having a
reflection surface orthogonal to measurement beam B1 reflected off
reflection surface 41b and a fixed mirror 47B having a reflection
surface orthogonal to measurement beam B2 reflected off reflection
surface 41c are arranged, each extending in the X-axis direction at
a position distanced apart from movable mirror 41 in the
-Y-direction by a predetermined distance in a state where the fixed
mirrors do not interfere with measurement beams B1 and B2.
[0156] Fixed mirrors 47A and 47B are supported, for example, by the
same support body (not shown) arranged in the frame (not shown)
which supports projection unit PU. Incidentally, fixed mirrors 47A
and 47B can be arranged in the measurement frame or the like
previously described. Further, in the embodiment, movable mirror 41
having three reflection surfaces 41b, 41a, and 41c and fixed
mirrors 47A and 47B were arranged, however, the present invention
is not limited to this, and for example, a configuration in which a
movable mirror having an inclined surface of 45 degrees is arranged
on the side surface of stage main section 91 and a fixed mirror is
placed above wafer stage WST can be employed. In this case, the
fixed mirror can be arranged in the support body previously
described or in the measurement frame.
[0157] Y interferometer 16, as shown in FIG. 2, projects
measurement beams B4.sub.1 and B4.sub.2 on reflection surface 17a
of wafer table WTB along a measurement axis in the Y-axis direction
spaced apart by an equal distance to the -X side and the +X side
from a straight line that is parallel to the Y-axis which passes
through the projection center (optical axis AX, refer to FIG. 1) of
projection optical system PL, and by receiving each reflected
light, detects the position of wafer table WTB in the Y-axis
direction (a Y position) at the irradiation point of measurement
beams B4.sub.1 and B4.sub.2. Incidentally, in FIG. 1, measurement
beams B4.sub.1 and B4.sub.2 are representatively shown as
measurement beam B4.
[0158] Further, Y interferometer 16 projects a measurement beam B3
toward reflection surface 41a along a measurement axis in the
Y-axis direction with a predetermined distance in the Z-axis
direction spaced between measurement beams B4.sub.1 and B4.sub.2,
and by receiving measurement beam B3 reflected off reflection
surface 41a, detects the Y position of reflection surface 41a (more
specifically wafer stage WST) of movable mirror 41.
[0159] Main controller 20 computes the Y position (or to be more
precise, displacement A Y in the Y-axis direction) of reflection
surface 17a, or more specifically, wafer table WTB (wafer stage
WST), based on an average value of the measurement values of the
measurement axes corresponding to measurement beams B4.sub.1 and
B4.sub.2 of Y interferometer 16. Further, main controller 20
computes displacement (yawing amount) .DELTA..theta.z.sup.(Y) in
the .theta.z direction of wafer stage WST, based on a difference of
the measurement values of the measurement axes corresponding to
measurement beams B4.sub.1 and B4.sub.2. Further, main controller
20 computes displacement (pitching amount) .DELTA..theta.x in the
.theta.x direction of wafer stage WST, based on the Y position
(displacement .DELTA.Y in the Y-axis direction) of reflection
surface 17a and reflection surface 41a.
[0160] Further, as shown in FIG. 2, X interferometer 126 projects
measurement beams B5.sub.1 and B5.sub.2 on wafer table WTB along
the dual measurement axes spaced apart from straight line LH
previously described by the same distance, and based on the
measurement values of the measurement axes corresponding to
measurement beams B5.sub.1 and B5.sub.2, main controller 20
computes a position (an X position, or to be more precise,
displacement .DELTA.X in the X-axis direction) of wafer stage WST
in the X-axis direction. Further, main controller 20 computes
displacement (yawing amount) .DELTA.z.sup.(X) of wafer stage WST in
the .theta.z direction from a difference of the measurement values
of the measurement axes corresponding to measurement beams B5.sub.1
and B5.sub.2. Incidentally, .DELTA..theta.z.sup.(X) obtained from X
interferometer 126 and .DELTA..theta.z.sup.(Y) obtained from Y
interferometer 16 are equal to each other, and represents
displacement (yawing amount) .DELTA..theta.z of wafer stage WST in
the .theta.z direction.
[0161] Further, as is indicated in a dotted line in FIG. 2, a
measurement beam B7 is emitted from X interferometer 128 along a
measurement axis parallel to the X-axis. X interferometer 128
actually projects measurement beam B7 on reflection surface 17b of
wafer table WTB located in the vicinity of an unloading position UP
and a loading position LP along a measurement axis, which is
parallel to the X-axis and joins unloading position UP and loading
position LP (refer to FIG. 3) as in the description later on.
Further, as shown in FIG. 2, a measurement beam B6 from X
interferometer 127 is projected on reflection surface 17b of wafer
table WTB. Measurement beam B6 is actually projected on reflection
surface 17b of wafer table WTB along a measurement axis parallel to
the X-axis that passes through the detection center of a primary
alignment system AL1.
[0162] Main controller 20 can obtain displacement .DELTA.X of wafer
table WTB in the X-axis direction from the measurement values of
length measurement beam B6 of X interferometer 127 and the
measurement values of length measurement beam B7 of X
interferometer 128. However, the three X interferometers 126, 127,
and 128 are placed differently regarding the Y-axis direction, and
X interferometer 126 is used at the time of exposure as shown in
FIG. 27, X interferometer 127 is used at the time of wafer
alignment as shown in FIG. 34 and the like, and X interferometer
128 is used at the time of wafer loading shown in FIG. 32 and wafer
unloading shown in FIG. 30.
[0163] Further from Z interferometers 43A and 43B, measurement
beams B1 and B2 that proceed along the Y-axis are projected toward
movable mirror 41, respectively. These measurement beams B1 and B2
are incident on reflection surfaces 41b and 41c of movable mirror
41, respectively, at a predetermined angle of incidence (the angle
is to be .theta./2). Then, measurement beams B1 and B2 are
reflected off reflection surfaces 41b and 41c, respectively, and
are incident on the reflection surfaces of fixed mirrors 47A and
47B perpendicularly. And then, measurement beams B1 and B2, which
were reflected off the reflection surface of fixed mirrors 47A and
47B, are reflected off reflection surfaces 41b and 41c again
(returns the optical path at the time of incidence), respectively,
and are received by Z interferometers 43A and 43B.
[0164] In this case, when displacement of wafer stage WST (more
specifically movable mirror 41) in the Y-axis direction is
.DELTA.Yo and displacement in the Z-axis direction is .DELTA.Zo, an
optical path length change .DELTA.L1 of measurement beam B1 and an
optical path length change .DELTA.L2 of measurement beam B2
received at of Z interferometers 43A and 43B can respectively be
expressed as in formulas (1) and (2) below.
.DELTA.L1=.DELTA.Yo*(1+cos .theta.)-.DELTA.Zo*sin .theta. (1)
.DELTA.L2=.DELTA.Yo*(1+cos .theta.)+.DELTA.Zo*sin .theta. (2)
[0165] Accordingly, from formulas (1) and (2), .DELTA.Zo and
.DELTA.Yo can be obtained using the following formulas (3) and (4).
.DELTA.Zo=(.DELTA.L2-.DELTA.L1)/2 sin .theta. (3)
.DELTA.Yo=(.DELTA.L1+.DELTA.L2)/{2(1+cos .theta.)} (4)
[0166] Displacements .DELTA.Zo and .DELTA.Yo above can be obtained
with Z interferometers 43A and 43B. Therefore, displacement which
is obtained using Z interferometer 43A is to be .DELTA.ZoR and
.DELTA.YoR, and displacement which is obtained using Z
interferometer 43B is to be .DELTA.ZoL and .DELTA.YoL. And the
distance between measurement beams B1 and B2 projected by Z
interferometers 43A and 43B, respectively, in the X-axis direction
is to be a distance D (refer to FIG. 2). Under such premises,
displacement (yawing amount) .DELTA..theta.z of movable mirror 41
(more specifically wafer stage WST) in the .theta.z direction and
displacement (rolling amount) .DELTA..theta.y of movable mirror 41
(more specifically wafer stage WST) in the .theta.y direction can
be obtained by the following formulas (5) and (6).
.DELTA..theta.z.apprxeq.(.DELTA.YoR-.DELTA.YoL)/D (5)
.DELTA..theta.y.apprxeq.(.DELTA.ZoL-.DELTA.ZoR)/D (6)
[0167] Accordingly, by using the formulas (3) to (6) above, main
controller 20 can compute displacement of wafer stage WST in four
degree of freedom, .DELTA.Zo, .DELTA.Yo, .DELTA..theta.z, and
.DELTA..theta.y, based on the measurement results of Z
interferometers 43A and 43B.
[0168] In the manner described above, from the measurement results
of interferometer system 118, main controller 20 can obtain
displacement of wafer stage WST in directions of six degrees of
freedom (Z, X, Y, .theta.z, .theta.x, and .theta.y directions).
Incidentally, in the embodiment, interferometer system 118 could
measure the positional information of wafer stage WST in directions
of six degrees of freedom, however, the measurement direction is
not limited to directions of six degrees of freedom, and the
measurement direction can be directions of five degrees of freedom
or less.
[0169] Incidentally, as the main error cause of an interferometer,
there is an effect of air fluctuation which occurs by a temperature
change and a temperature gradient of the atmosphere on a beam
optical path. When a wavelength .lamda. of light changes from
.lamda. to .lamda.+.DELTA..lamda. by air fluctuation, because the
change of a phase difference K.DELTA.L due to a minute change
.DELTA..lamda. of this wavelength is wave number K=2.pi./.lamda.,
2.pi..DELTA.L .DELTA..lamda./.lamda..sup.2 can be obtained. In this
case, when wavelength of light .lamda.=1 .mu.m and minute change
.DELTA..lamda.=1 nm, the phase change becomes 2.pi.*100 with
respect to an optical path difference .DELTA.L=100 mm. This phase
change corresponds to displacement which is 100 times the
measurement unit. In the case the optical path length which is set
is long as is described, the interferometer is greatly affected by
the air fluctuation which occurs in a short time, and is inferior
in short-term stability. In such a case, it is desirable to use an
encoder.
[0170] Incidentally, in the embodiment, the case has been described
where wafer stage WST (91, WTB) is a single stage that can move in
six degrees of freedom, however, the present invention is not
limited to this, and wafer stage WST can be configured including
stage main section 91 which can move freely in the XY plane, and
wafer table WTB mounted on stage main section 91 that can be finely
driven relative to stage main section 91 at least in the Z-axis
direction, the .theta.x direction, and the .theta.y direction. In
this case, movable mirror 41 described earlier is arranged in wafer
table WTB. Further, instead of reflection surface 17a and
reflection surface 17b, a movable mirror consisting of a plane
mirror can be arranged in wafer table WTB.
[0171] However, in the embodiment, positional information
(positional information in directions of three degrees of freedom
including rotary information in the .theta.z direction) of wafer
stage WST (wafer table WTB) in the XY plane is mainly measured by
an encoder system described later on, and the measurement values of
interferometer 16, 126, and 127 are used secondarily as backup or
the like, such as in the case of correcting (calibrating) a
long-term change (due to, for example, temporal deformation of a
scale) of the measurement values of the encoder system, and in the
case of output abnormality in the encoder system. Incidentally, in
the embodiment, of the positional information of wafer stage WST in
directions of six degrees of freedom, positional information in
directions of three degrees of freedom including the X-axis
direction, the Y-axis direction and the .theta.z direction is
measured by the encoder system described later on, and the
remaining directions of three degrees of freedom, or more
specifically, the positional information in the Z-axis direction,
the .theta.x direction, and the E y direction is measured by a
measurement system which will also be described later that has a
plurality of Z sensors. Positional information of the remaining
directions of three degrees of freedom can be measured by both the
measurement system and interferometer system 118. For example,
positional information in the Z-axis direction and the .theta.y
direction can be measured by the measurement system, and positional
information in the .theta.x direction can be measured by
interferometer system 118.
[0172] Incidentally, at least part of interferometer system 118
(such as an optical system) may be arranged at the main frame that
holds projection unit PU, or may also be arranged integrally with
projection unit PU that is supported in a suspended state as is
described above, however, in the embodiment, interferometer system
118 is to be arranged at the measurement frame described above.
[0173] Measurement stage MST includes stage main section 92
previously described, and measurement table MTB mounted on stage
main section 92. Measurement table MTB is mounted on stage main
section 92, via the Z leveling mechanism (not shown). However, the
present invention is not limited to this, and for example,
measurement stage MST can employ the so-called coarse and fine
movement structure in which measurement table MTB can be finely
driven in the X-axis direction, the Y-axis direction, and the
.theta.z direction with respect to stage main section 92, or
measurement table MTB can be fixed to stage main section 92, and
all of measurement stage MST including measurement table MTB and
stage main section 92 can be configured drivable in directions of
six degrees of freedom.
[0174] Various measurement members are arranged at measurement
table MTB (and stage main section 92). As such measurement members,
for example, as shown in FIGS. 2 and 5A, members such as an uneven
illuminance measuring sensor 94 that has a pinhole-shaped
light-receiving section which receives illumination light IL on an
image plane of projection optical system PL, an aerial image
measuring instrument 96 that measures an aerial image (projected
image) of a pattern projected by projection optical system PL, a
wavefront aberration measuring instrument 98 by the Shack-Hartman
method that is disclosed in, for example, the pamphlet of
International Publication No. WO 03/065428 and the like are
employed.
[0175] As wavefront aberration measuring instrument 98, the one
disclosed in, for example, the pamphlet of International
Publication No. WO 99/60361 (the corresponding EP Patent
Application Publication No. 1 079 223) can also be used. As
irregular illuminance sensor 94, the configuration similar to the
one that is disclosed in, for example, Kokai (Japanese Unexamined
Patent Application Publication) No. 57-117238 (the corresponding
U.S. Pat. No. 4,465,368) and the like can be used. Further, as
aerial image measuring instrument 96, the configuration similar to
the one that is disclosed in, for example, Kokai (Japanese
Unexamined Patent Application Publication) No. 2002-014005 (the
corresponding U.S. Patent Application Publication No. 2002/0041377)
and the like can be used. Incidentally, three measurement members
(94, 96 and 98) are to be arranged at measurement stage MST in the
embodiment, however, the types and/or the number of measurement
members are/is not limited to them. As the measurement members, for
example, measurement members such as a transmittance measuring
instrument that measures a transmittance of projection optical
system PL, and/or a measuring instrument that observes local liquid
immersion unit 8, for example, nozzle unit 32 (or tip lens 191) or
the like may also be used. Furthermore, members different from the
measurement members such as a cleaning member that cleans nozzle
unit 32, tip lens 191 or the like may also be mounted on
measurement stage MST.
[0176] In the embodiment, as it can be seen from FIG. 5A, the
sensors that are frequently used such as irregular illuminance
sensor 94 and aerial image measuring instrument 96 are placed on a
centerline CL (Y-axis passing through the center) of measurement
stage MST. Therefore, in the embodiment, measurement using these
sensors can be performed by moving measurement stage MST only in
the Y-axis direction without moving the measurement stage in the
X-axis direction.
[0177] In addition to each of the sensors described above, an
illuminance monitor that has a light-receiving section having a
predetermined area size that receives illumination light IL on the
image plane of projection optical system PL may also be employed,
which is disclosed in, for example, Kokai (Japanese Unexamined
Patent Application Publication) No. 11-016816 (the corresponding
U.S. Patent Application Publication No. 2002/0061469) and the like.
The illuminance monitor is also preferably placed on the
centerline.
[0178] Incidentally, in the embodiment, liquid immersion exposure
is performed in which wafer W is exposed with exposure light
(illumination light) IL via projection optical system PL and liquid
(water) Lq, and accordingly irregular illuminance sensor 94 (and
the illuminance monitor), aerial image measuring instrument 96 and
wavefront aberration measuring instrument 98 that are used in
measurement using illumination light IL receive illumination light
IL via projection optical system PL and water. Further, only part
of each sensor such as the optical system may be mounted on
measurement table MTB (and stage main section 92), or the entire
sensor may be placed on measurement table MTB (and stage main
section 92).
[0179] As shown in FIG. 5B, a frame-shaped attachment member 42 is
fixed to the end surface on the -Y side of stage main section 92 of
measurement stage MST. Further, to the end surface on the -Y side
of stage main section 92, a pair of photodetection systems 44 are
fixed in the vicinity of the center position in the X-axis
direction inside an opening of attachment member 42, in the
placement capable of facing a pair of light-transmitting systems 36
described previously. Each of photodetection systems 44 is composed
of an optical system such as a relay lens, a light receiving
element such as a photomultiplier tube, and a housing that houses
them. As it can be easily imagined from FIGS. 4B and 5B and the
description so far, in the embodiment, in a state where wafer stage
WST and measurement stage MST are closer together within a
predetermined distance in the Y-axis direction (including a contact
state), illumination light IL that has been transmitted through
each aerial image measurement slit pattern SL of measurement plate
30 is guided by each light-transmitting system 36 and received by
the light-receiving element of each photodetection system 44. That
is, measurement plate 30, light-transmitting systems 36 and
photodetection systems 44 constitute an aerial image measuring unit
45 (refer to FIG. 6), which is similar to the one disclosed in
Kokai (Japanese Unexamined Patent Application Publication) No.
2002-014005 (the corresponding U.S. Patent Application Publication
No. 2002/0041377) referred to previously, and the like.
[0180] On attachment member 42, a confidential bar (hereinafter,
shortly referred to as a "CD bar") 46 that is made up of a
bar-shaped member having a rectangular sectional shape and serves
as a reference member is arranged extending in the X-axis
direction.
[0181] CD bar 46 is kinematically supported on measurement stage
MST by a full-kinematic mount structure. Since CD bar 46 serves as
a prototype standard (measurement standard), an optical glass
ceramic that has a low thermal expansion, such as Zerodur (the
brand name) of Schott AG is employed as the material. The flatness
degree of the upper surface (the surface) of CD bar 46 is set high
to be around the same level as a so-called datum plane plate.
Further, as shown in FIG. 5A, a reference grating (e.g. diffraction
grating) 52 whose periodic direction is the Y-axis direction is
respectively formed in the vicinity of the end portions on one side
and the other side in the longitudinal direction of CD bar 46. The
pair of reference gratings 52 are formed placed apart from each
other at a predetermined distance (which is to be "L") in the
symmetrical placement with respect to the center in the X-axis
direction of CD bar 46, that is, centerline CL described above. For
example, distance L is distance more than 400 mm incidentally.
[0182] Further, on the upper surface of CD bar 46, a plurality of
reference marks M are formed in the placement as shown in FIG. 5A.
The plurality of reference marks M are formed in three-row arrays
in the Y-axis direction in the same pitch, and the array of each
row is formed being shifted from each other by a predetermined
distance in the X-axis direction. As each of reference marks M, a
two-dimensional mark having a size that can be detected by a
primary alignment system and secondary alignment systems (to be
described later) is used. Reference mark M may also be different in
shape (constitution) from fiducial mark FM, but in the embodiment,
reference mark M and fiducial mark FM have the same constitution
and also they have the same constitution with that of an alignment
mark of wafer W. Incidentally, in the embodiment, the surface of CD
bar 46 and the surface of measurement table MTB (which may include
the measurement members described above) are also covered with a
liquid repellent film (water repellent film) severally.
[0183] Also on the +Y end surface and the -X end surface of
measurement table MTB, reflection surfaces 19a and 19b are formed
similar to wafer table WTB as is described above (refer to FIGS. 2
and 5A). By projecting an interferometer beam (measurement beam),
as shown in FIG. 2, on reflection surfaces 19a and 19b and
receiving a reflected light of each interferometer beam, a Y
interferometer 18 and an X interferometer 130 (X-axis
interferometer 130 is not shown in FIG. 1, refer to FIG. 2) of
interferometer system 118 (refer to FIG. 6) measure a displacement
of each reflection surface from a datum position, that is,
positional information of measurement stage MST (e.g. including at
least positional information in the X-axis and Y-axis directions
and rotation information in the .theta.z direction), and the
measurement values are supplied to main controller 20.
[0184] In exposure apparatus 100 of the embodiment, in actual, a
primary alignment system AL1 is placed on straight line LV passing
through the center of projection unit PU (optical axis AX of
projection optical system PL, which also coincides with the center
of exposure area IA in the embodiment) and being parallel to the
Y-axis, and has a detection center at a position that is spaced
apart from the optical axis at a predetermined distance on the -Y
side as shown in FIG. 3, although omitted in FIG. 1 from the
viewpoint of avoiding intricacy of the drawing. Primary alignment
system AL1 is fixed to the lower surface of a main frame (not
shown) via a support member 54. On one side and the other side in
the X-axis direction with primary alignment system AL1 in between,
secondary alignment systems AL2.sub.1 and AL2.sub.2, and AL2.sub.3
and AL2.sub.4 whose detection centers are substantially
symmetrically placed with respect to straight line LV are severally
arranged. That is, five alignment systems AL1 and AL2.sub.1 to
AL2.sub.4 are placed so that their detection centers are placed at
different positions in the X-axis direction, that is, placed along
the X-axis direction.
[0185] As is representatively shown by secondary alignment system
AL2.sub.4, each secondary alignment system AL2.sub.n (n=1 to 4) is
fixed to a tip (turning end) of an arm 56.sub.n (n=1 to 4) that can
turn around a rotation center O as the center in a predetermined
angle range in clockwise and anticlockwise directions in FIG. 3. In
the embodiment, a part of each secondary alignment system AL2.sub.n
(e.g. including at least an optical system that irradiates an
alignment light to a detection area and also leads the light that
is generated from a subject mark within the detection area to a
light-receiving element) is fixed to arm 56.sub.n and the remaining
section is arranged at the main frame that holds projection unit
PU. The X-positions of secondary alignment systems AL2.sub.1,
AL2.sub.2, AL2.sub.3 and AL2.sub.4 are severally adjusted by
rotating around rotation center O as the center. In other words,
the detection areas (or the detection centers) of secondary
alignment systems AL2.sub.1, AL2.sub.2, AL2.sub.3 and AL2.sub.4 are
independently movable in the X-axis direction. Accordingly, the
relative positions of the detection areas of primary alignment
system AL1 and secondary alignment systems AL2.sub.1, AL2.sub.2,
AL2.sub.3 and AL2.sub.4 are adjustable in the X-axis direction.
Incidentally, in the embodiment, the X-positions of secondary
alignment systems AL2.sub.1, AL2.sub.2, AL2.sub.3 and AL2.sub.4 are
to be adjusted by the rotation of the arms. However, the present
invention is not limited to this, and a drive mechanism that drives
secondary alignment systems AL2.sub.1, AL2.sub.2, AL2.sub.3 and
AL2.sub.4 back and forth in the X-axis direction may also be
arranged. Further, at least one of secondary alignment systems
AL2.sub.1, AL2.sub.2, AL2.sub.3 and AL2.sub.4 can be moved not only
in the X-axis direction but also in the Y-axis direction.
Incidentally, since part of each secondary alignment system
AL2.sub.n is moved by arm 56.sub.n, positional information of the
part that is fixed to arm 56.sub.n is measurable by a sensor (not
shown) such as, for example, an interferometer or an encoder. The
sensor may only measure position information in the X-axis
direction of secondary alignment system AL2.sub.n, or may be
capable of measuring position information in another direction, for
example, the Y-axis direction and/or the rotation direction
(including at least one of the .theta.x and .theta.y
directions).
[0186] On the upper surface of each arm 56.sub.n, a vacuum pad
58.sub.n (n=1 to 4) that is composed of a differential evacuation
type air bearing is arranged. Further, arm 56.sub.n is rotated by a
rotation drive mechanism 60.sub.n (n=1 to 4, not shown in FIG. 3,
refer to FIG. 6) that includes a motor or the like, in response to
instructions of main controller 20. Main controller 20 activates
each vacuum pad 58.sub.n to fix each arm 56.sub.n to a main frame
(not shown) by suction after rotation adjustment of arm 56.sub.n.
Thus, the state of each arm 56.sub.n after rotation angle
adjustment, that is, a desired positional relation of four
secondary alignment systems AL2.sub.1 to AL2.sub.4 with respect to
primary alignment system AL1 is maintained.
[0187] Incidentally, in the case a portion of the main frame facing
arm 56.sub.n is a magnetic body, an electromagnet may also be
employed instead of vacuum pad 58.
[0188] In the embodiment, as each of primary alignment system AL1
and four secondary alignment systems AL2.sub.1 to AL2.sub.4, for
example, an FIA (Field Image Alignment) system by an image
processing method is used that irradiates a broadband detection
beam that does not expose resist on a wafer to a subject mark, and
picks up an image of the subject mark formed on a light-receiving
plane by the reflected light from the subject mark and an image of
an index (an index pattern on an index plate arranged within each
alignment system) (not shown), using an imaging device (such as
CCD), and then outputs their imaging signals. The imaging signal
from each of primary alignment system AL1 and four secondary
alignment systems AL2.sub.1 to AL2.sub.4 is supplied to main
controller 20 in FIG. 6.
[0189] Incidentally, each of the alignment systems described above
is not limited to the FIA system, and an alignment sensor, which
irradiates a coherent detection light to a subject mark and detects
a scattered light or a diffracted light generated from the subject
mark or makes two diffracted lights (e.g. diffracted lights of the
same order or diffracted lights being diffracted in the same
direction) generated from the subject mark interfere and detects an
interference light, can naturally be used alone or in combination
as needed. Further, five alignment systems AL1 and AL2.sub.1 to
AL2.sub.4 are to be arranged in the embodiment. However, the number
of alignment systems is not limited to five, but may be the number
equal to or more than two and equal to or less than four, or may be
the number equal to or more than six, or may be the even number,
not the odd number. Moreover, in the embodiment, five alignment
systems AL1 and AL2.sub.1 to AL2.sub.4 are to be fixed to the lower
surface of the main frame that holds projection unit PU, via
support member 54. However, the present invention is not limited to
this, and for example, the five alignment systems may also be
arranged on the measurement frame described earlier. Further,
because alignment systems AL1 and AL2.sub.1 to AL2.sub.4 detect
alignment marks on wafer W and reference marks on and CD bar 46, in
the embodiment, the systems will also be simply referred to as a
mark detection system.
[0190] In exposure apparatus 100 of the embodiment, as shown in
FIG. 3, four head units 62A to 62D of the encoder system are placed
in a state of surrounding nozzle unit 32 on all four sides. In
actual, head units 62A to 62D are fixed to the foregoing main frame
that holds projection unit PU in a suspended state via a support
member, although omitted in FIG. 3 from the viewpoint of avoiding
intricacy of the drawings. Incidentally, for example, in the case
projection unit PU is supported in a suspended state, head units
62A to 62D may be supported in a suspended state integrally with
projection unit PU, or may be arranged at the measurement frame
described above.
[0191] Head units 62A and 62C are respectively placed on the +X
side and -X side of projection unit PU having the longitudinal
direction in the X-axis direction, and are also placed apart at the
substantially same distance from optical axis AX of projection
optical system PL symmetrically with respect to optical axis AX of
projection optical system PL. Further, head units 62B and 62D are
respectively placed on the +Y side and -Y side of projection unit
PU having the longitudinal direction in the Y-axis direction and
are also placed apart at the substantially same distance from
optical axis AX of projection optical system PL.
[0192] As shown in FIG. 3, head units 62A and 62C are each equipped
with a plurality of (six in this case) Y heads 64 that are placed
at a predetermined distance on a straight line LH that passes
through optical axis AX of projection optical system PL and is
parallel to the X-axis, along the X-axis direction. Head unit 62A
constitutes a multiple-lens (six-lens in this case) Y linear
encoder (hereinafter, shortly referred to as a "Y encoder" or an
"encoder" as needed) 70A (refer to FIG. 6) that measures the
position in the Y-axis direction (the Y-position) of wafer stage
WST (wafer table WTB) using Y scale 39Y.sub.1 described above.
Similarly, head unit 62C constitutes a multiple-lens (six-lens, in
this case) Y linear encoder 70C (refer to FIG. 6) that measures the
Y-position of wafer stage WST (wafer table WTB) using Y scale
39Y.sub.2 described above. In this case, a distance between
adjacent Y heads 64 (i.e. measurement beams) equipped in head units
62A and 62C is set shorter than a width in the X-axis direction of
Y scales 39Y.sub.1 and 39Y.sub.2 (to be more accurate, a length of
grid line 38). Further, out of a plurality of Y heads 64 that are
equipped in each of head units 62A and 62C, Y head 64 located
innermost is fixed to the lower end portion of barrel 40 of
projection optical system PL (to be more accurate, to the side of
nozzle unit 32 enclosing tip lens 191) so as to be placed as close
as possible to the optical axis of projection optical system
PL.
[0193] As shown in FIG. 3, head unit 62B is equipped with a
plurality of (seven in this case) X heads 66 that are placed on
straight line LV at a predetermined distance along the Y-axis
direction. Further, head unit 62D is equipped with a plurality of
(eleven in this case, out of eleven X heads, however, three X heads
that overlap primary alignment system AL1 are not shown in FIG. 3)
X heads 66 that are placed on straight line LV at a predetermined
distance. Head unit 62B constitutes a multiple-lens (seven-lens, in
this case) X linear encoder (hereinafter, shortly referred to as an
"X encoder" or an "encoder" as needed) 70B (refer to FIG. 6) that
measures the position in the X-axis direction (the X-position) of
wafer stage WST (wafer table WTB) using X scale 39X.sub.1 described
above. Further, head unit 62D constitutes a multiple-lens
(eleven-lens, in this case) X linear encoder 70D (refer to FIG. 6)
that measures the X-position of wafer stage WST (wafer table WTB)
using X scale 39X.sub.2 described above. Further, in the
embodiment, for example, at the time of alignment (to be described
later) or the like, two X heads 66 out of eleven X heads 66 that
are equipped in head unit 62D simultaneously face X scale 39X.sub.1
and X scale 39X.sub.2 respectively in some cases. In these cases, X
scale 39X.sub.1 and X head 66 facing X scale 39X.sub.1 constitute X
linear encoder 70B, and X scale 39X.sub.2 and X head 66 facing X
scale 39X.sub.2 constitute X linear encoder 70D.
[0194] Herein, some of eleven X heads 66, in this case, three X
heads are attached to the lower surface side of support member 54
of primary alignment system AL1. Further, a distance between
adjacent X heads 66 (measurement beams) that are equipped in each
of head units 62B and 62D is set shorter than a width in the Y-axis
direction of X scales 39X.sub.1 and 39X.sub.2 (to be more accurate,
a length of grid line 37). Further, X head 66 located innermost out
of a plurality of X heads 66 that are quipped in each of head units
62B and 62D is fixed to the lower end portion of the barrel of
projection optical system PL (to be more accurate, to the side of
nozzle unit 32 enclosing tip lens 191) so as to be placed as close
as possible to the optical axis of projection optical system
PL.
[0195] Moreover, on the -X side of secondary alignment system
AL2.sub.1 and on the +X side of secondary alignment system
AL2.sub.4, Y heads 64y.sub.1 and 64y.sub.2 are respectively
arranged, whose detection points are placed on a straight line
parallel to the X-axis that passes through the detection center of
primary alignment system AL1 and are substantially symmetrically
placed with respect to the detection center. The distance between Y
heads 64y.sub.1 and 64y.sub.2 is set substantially equal to
distance L described previously. Y heads 64y.sub.1 and 64y.sub.2
face Y scales 39Y.sub.2 and 39Y.sub.1 respectively in a state where
the center of wafer W on wafer stage WST is on straight line LV as
shown in FIG. 3. On an alignment operation (to be described later)
or the like, Y scales 39Y.sub.2 and 39Y.sub.1 are placed facing Y
heads 64y.sub.1 and 64y.sub.2 respectively, and the Y-position (and
the .theta.z rotation) of wafer stage WST is measured by Y heads
64y.sub.1 and 64y.sub.2 (i.e. Y encoders 70C and 70A composed of Y
heads 64y.sub.1 and 64y.sub.2).
[0196] Further, in the embodiment, at the time of baseline
measurement of the secondary alignment systems (to be described
later) or the like, a pair of reference gratings 52 of CD bar 46
face Y heads 64y.sub.1 and 64y.sub.2 respectively, and the
Y-position of CD bar 46 is measured at the position of each of
reference gratings 52 by Y heads 64y.sub.1 and 64y.sub.2 and facing
reference gratings 52. In the following description, encoders that
are composed of Y heads 64y.sub.1 and 64y.sub.2 facing reference
gratings 52 respectively are referred to as Y-axis linear encoders
70E and 70F (refer to FIG. 6).
[0197] Six linear encoders 70A to 70F described above measure the
positional information of wafer stage WST in each measurement
direction at a resolution of, for example, around 0.1 nm, and the
measurement values (measurement information) are supplied to main
controller 20. Main controller 20 controls the position within the
XY plane of wafer table WTB based on the measurement values of
linear encoders 70A to 70D, and also controls the rotation in the
.theta.z direction of CD bar 46 based on the measurement values of
linear encoders 70E and 70F. Incidentally, the configuration and
the like of the linear encoder will be described further later in
the description.
[0198] In exposure apparatus 100 of the embodiment, a position
measuring unit that measures positional information of wafer W in
the Z-axis direction is arranged. As shown in FIG. 3, in the
embodiment, as the position measuring unit, a multipoint focal
position detecting system (hereinafter, shortly referred to as a
"multipoint AF system") by an oblique incident method is arranged,
which is composed of an irradiation system 90a and a photodetection
system 90b, and has the configuration similar to the one disclosed
in, for example, Kokai (Japanese Unexamined Patent Application
Publication) No. 06-283403 (the corresponding U.S. Pat. No.
5,448,332) and the like. In the embodiment, as an example,
irradiation system 90a is placed on the -Y side of the -X end
portion of head unit 62C and photodetection system 90b is placed on
the -Y side of the +X end portion of head unit 62A in a state of
opposing irradiation system 90a.
[0199] A plurality of detection points of the multipoint AF system
(90a, 90b) are placed at a predetermined distance along the X-axis
direction on the surface to be detected, although it is omitted in
the drawings. In the embodiment, the plurality of detection points
are placed, for example, in the arrangement of a matrix having one
row and M columns (M is a total number of detection points) or
having two rows and N columns (N is a half of a total number of
detection points). In FIG. 3, the plurality of detection points to
which a detection beam is severally irradiated are not individually
shown, but are shown as an elongate detection area (beam area) AF
that extends in the X-axis direction between irradiation system 90a
and photodetection system 90b. Since the length of detection area
AF in the X-axis direction is set to around the same as the
diameter of wafer W, position information (surface position
information) in the Z-axis direction across the entire surface of
wafer W can be measured by only scanning wafer W in the Y-axis
direction once. Further, since detection area AF is placed between
liquid immersion area 14 (exposure area IA) and the detection areas
of the alignment systems (AL1, AL2.sub.1, AL2.sub.2, AL2.sub.3 and
AL2.sub.4) in the Y-axis direction, the detection operations of the
multipoint AF system and the alignment systems can be performed in
parallel. The multipoint AF system may also be arranged on the main
frame that holds projection unit PU or the like, but is to be
arranged on the measurement frame described earlier in the
embodiment.
[0200] Incidentally, the plurality of detection points are to be
placed in one row and M columns, or two rows and N columns, but the
number(s) of rows and/or columns is/are not limited to these
numbers. However, in the case the number of rows is two or more,
the positions in the X-axis direction of detection points are
preferably made to be different even between the different rows.
Moreover, the plurality of detection points is to be placed along
the X-axis direction. However, the present invention is not limited
to this, and all of or some of the plurality of detection points
may also be placed at different positions in the Y-axis direction.
For example, the plurality of detection points may also be placed
along a direction that intersects both of the X-axis and the
Y-axis. That is, the positions of the plurality of detection points
only have to be different at least in the X-axis direction.
Further, a detection beam is to be irradiated to the plurality of
detection points in the embodiment, but a detection beam may also
be irradiated to, for example, the entire area of detection area
AF. Furthermore, the length of detection area AF in the X-axis
direction does not have to be nearly the same as the diameter of
wafer W.
[0201] In the embodiment, in the vicinity of detection points
located at both ends out of a plurality of detection points of the
multipoint AF system, that is, in the vicinity of both end portions
of beam area AF, one each pair of surface position sensors for Z
position measurement (hereinafter, shortly referred to as "Z
sensors"), that is, a pair of Z sensors 72a and 72b and a pair of Z
sensors 72c and 72d are arranged in the symmetrical placement with
respect to straight line LV. Z sensors 72a to 72d are fixed to the
lower surface of a main frame (not shown). As Z sensors 72a to 72d,
a sensor that irradiates a light to wafer table WTB from above,
receives the reflected light and measures position information of
the wafer table WTB surface in the Z-axis direction orthogonal to
the XY plane, as an example, an optical displacement sensor (sensor
by an optical pickup method), which has the configuration like an
optical pickup used in a CD drive unit, is used. Incidentally, Z
sensors 72a to 72d may also be arranged on the measurement frame
described above or the like.
[0202] Moreover, head unit 62C is equipped with a plurality of (in
this case six each, which is a total of twelve) Z sensors
74.sub.i,j (i=1, 2, j=1, 2, . . . , 6), which are placed
corresponding to each other along two straight lines at a
predetermined distance, the straight lines being parallel to
straight line LH and are located on one side and the other side of
straight line LH in the X-axis direction that connects a plurality
of Y heads 64. In this case, Z sensors 74.sub.1,j and 74.sub.2,j
that make a pair are disposed symmetrical to straight line LH.
Furthermore, the plurality of pairs (in this case, six pairs) of Z
sensors 74.sub.1,j and 74.sub.2,j and a plurality of Y heads 64 are
placed alternately in the X-axis direction. As each Z sensor
74.sub.i,j, a sensor by an optical pickup method similar to Z
sensors 72a to 72d is used.
[0203] In this case, the distance between each pair of Z sensors
74.sub.1,j and 74.sub.2,j that are located symmetrically with
respect to straight line LH is set to be the same distance as the
distance between Z sensors 74a and 74b previously described.
Further, a pair of Z sensors 74.sub.1,4 and 74.sub.2,4 are located
on the same straight line in the Y-axis direction as Z sensors 72a
and 72b.
[0204] Further, head unit 62A is equipped with a plurality of
(twelve in this case) Z sensors 76.sub.p,q (p=1, 2 and q=1, 2, . .
. , 6) that are placed symmetrically to a plurality of Z sensors
74.sub.i,j with respect to straight line LV. As each Z sensor
76.sub.p,q, a sensor by an optical pickup method similar to Z
sensors 72a to 72d is used. Further, a pair of Z sensors 76.sub.1,3
and 76.sub.2,3 are located on the same straight line in the Y-axis
direction as Z sensors 72c and 72d. Incidentally, Z sensors
74.sub.i,j and 76.sub.p,q are installed, for example, at the
mainframe or the measurement frame previously described. Further,
in the embodiment, the measurement system that has Z sensors 72a to
72d, and 74.sub.i,j and 76.sub.p,q measures positional information
of wafer stage WST in the Z-axis direction using one or a plurality
of Z sensors that face the scale previously described. Therefore,
in the exposure operation, Z sensors 74.sub.i,j and 76.sub.p,q used
for position measurement are switched, according to the movement of
wafer stage WST. Furthermore, in the exposure operation, Y scale
39Y.sub.1 and at least one Z sensor 76.sub.p,q face each other, and
Y scale 39Y.sub.2 and at least one Z sensor 74.sub.i,j also face
each other. Accordingly, the measurement system can measure not
only positional information of wafer stage WST in the Z-axis
direction, but also positional information (rolling) in the
.theta.y direction. Further, in the embodiment, each Z sensor of
the measurement system detects a grating surface (a formation
surface of a diffraction grating) of the scale, however, the
measurement system can also detect a surface that is different from
the grating surface, such as, for example, a surface of the cover
glass that covers the grating surface.
[0205] Incidentally, in FIG. 3, measurement stage MST is omitted
and a liquid immersion area that is formed by water Lq held in the
space between measurement stage MST and tip lens 191 is shown by a
reference code 14. Further, in FIG. 3, a reference code 78
indicates a local air-conditioning system that blows dry air whose
temperature is adjusted to a predetermined temperature to the
vicinity of a beam path of the multipoint AF system (90a, 90b) by,
for example, downflow as is indicated by outline arrows in FIG. 3.
Further, a reference code UP indicates an unloading position where
a wafer on wafer table WTB is unloaded, and a reference code LP
indicates a loading position where a wafer is loaded on wafer table
WTB. In the embodiment, unloading position UP and loading position
LP are set symmetrically with respect to straight line LV.
Incidentally, unloading position UP and loading position LP may be
the same position.
[0206] FIG. 6 shows the main configuration of the control system of
exposure apparatus 100. The control system is mainly configured of
main controller 20 composed of a microcomputer (or workstation)
that performs overall control of the entire apparatus. In a memory
34 which is an auxiliary memory connecting to main controller 20,
correction information, which will be described below, is stored.
Incidentally, in FIG. 6, various sensors such as irregular
illuminance sensor 94, aerial image measuring instrument 96 and
wavefront aberration measuring instrument 98 that are arranged at
measurement stage MST are collectively shown as a sensor group
99.
[0207] In the embodiment, by using encoder systems 70A to 70F
(refer to FIG. 6), main controller 20 can measure a position
coordinate of wafer stage WST in directions of three degree of
freedom (X, Y, .theta.z), in an effective stroke range of wafer
stage WST, namely in an area where wafer stage WST moves for
alignment and exposure operation.
[0208] The configuration of encoders 70A to 70F will be described
now, focusing on Y encoder 70A that is enlargedly shown in FIG. 7A,
as a representative. FIG. 7A shows one Y head 64 of head unit 62A
that irradiates a detection light (measurement beam) to Y scale
39Y.sub.1.
[0209] Y head 64 is mainly composed of three sections, which are an
irradiation system 64a, an optical system 64b and a photodetection
system 64c.
[0210] Irradiation system 64a includes a light source that emits a
laser beam LB in a direction inclined at an angle of 45 degrees
with respect to the Y-axis and Z-axis, for example, a semiconductor
laser LD, and a converging lens L1 that is placed on the optical
path of laser beam LB emitted from semiconductor laser LD.
[0211] Optical system 64b is equipped with a polarization beam
splitter PBS whose separation plane is parallel to an XZ plane, a
pair of reflection mirrors R1a and R1b, lenses L2a and L2b, quarter
wavelength plates (hereinafter, referred to as a .lamda./4 plate)
WP1a and WP1b, refection mirrors R2a and R2b, and the like.
[0212] Photodetection system 64c includes a polarizer (analyzer), a
photodetector, and the like.
[0213] In Y encoder 70A, laser beam LB emitted from semiconductor
laser LD is incident on polarization beam splitter PBS via lens L1,
and is split by polarization into two beams LB.sub.1 and LB.sub.2.
Beam LB.sub.1 having been transmitted through polarization beam
splitter PBS reaches reflective diffraction grating RG that is
formed on Y scale 39Y.sub.1, via reflection mirror R1a, and beam
LB.sub.2 reflected off polarization beam splitter PBS reaches
reflective diffraction grating RG via reflection mirror R1b.
Incidentally, "split by polarization" in this case means the
splitting of an incident beam into a P-polarization component and
an S-polarization component.
[0214] Predetermined-order diffraction beams that are generated
from diffraction grating RG due to irradiation of beams LB.sub.1
and LB.sub.2, for example, the first-order diffraction beams are
severally converted into a circular polarized light by .lamda./4
plates WP1b and WP1a via lenses L2b and L2a, and reflected by
reflection mirrors R2b and R2a and then the beams pass through
.lamda./4 plates WP1b and WP1a again and reach polarization beam
splitter PBS by tracing the same optical path in the reversed
direction.
[0215] Each of the polarization directions of the two beams that
have reached polarization beam splitter PBS is rotated at an angle
of 90 degrees with respect to the original direction. Therefore,
the first-order diffraction beam of beam LB.sub.1 that was
previously transmitted through polarization beam splitter PBS is
reflected off polarization beam splitter PBS and is incident on
photodetection system 64c, and also the first-order diffraction
beam of beam LB.sub.2 that was previously reflected off
polarization beam splitter PBS is transmitted through polarization
beam splitter PBS and is synthesized concentrically with the
first-order diffraction beam of beam LB.sub.1 and is incident on
photodetection system 64c.
[0216] Then, the polarization directions of the two first-order
diffraction beams described above are uniformly arranged by the
analyzer inside photodetection system 64c and the beams interfere
with each other to be an interference light, and the interference
light is detected by the photodetector and is converted into an
electric signal in accordance with the intensity of the
interference light.
[0217] Then, when Y scale 39Y.sub.1 (more specifically, wafer stage
WST) moves in a measurement direction (in this case, the Y-axis
direction), the phase of the two beams changes, respectively, which
changes the intensity of the interference light. This change in the
intensity of the interference light is detected by photodetection
system 64c, and positional information corresponding to the
intensity change is output as a measurement value of Y encoder 70A.
Other encoders 70B, 70C, 70D, 70E, and 70F are also configured
similarly with encoder 70A.
[0218] As is obvious from the above description, in encoders 70A to
70F, since the optical path lengths of the two beams to be
interfered are extremely short and also are almost equal to each
other, the influence by air fluctuations can mostly be ignored.
Incidentally, as each encoder, an encoder having a resolution of,
for example, around 0.1 nm is used.
[0219] Incidentally, in the encoders of the embodiment, as shown in
FIG. 7B, laser beam LB having a sectional shape that is elongated
in the periodic direction of grating RG may also be used, as a
detection light. In FIG. 7B, beam LB is overdrawn largely compared
to grating RG.
[0220] Incidentally, as another form of the encoder head, there is
a type in which only optical system 64b is included in the encoder
head and irradiation system 64a and photodetection system 64c are
physically separate from optical system 64b. In this type of
encoder, the three sections are optically connected via an optical
fiber.
[0221] Next, a measurement principle of an encoder will be
explained in detail, with Y encoder 70A shown in FIG. 7A serving as
an example. First of all, a relation between the intensity of
interference light that is synthesized from two return beams
LB.sub.1 and LB.sub.2 and displacement (relative displacement with
Y head 64) of Y scale 39Y.sub.2 is derived.
[0222] When the two beams (beam) LB.sub.1 and LB.sub.2 are
scattered by reflection grating RG that moves, the beams are
subject to a frequency shift by a Doppler effect, or in other
words, undergo a Doppler shift. FIG. 8A shows a scatter of light by
the moving reflection surface DS. However, vectors k.sub.0 and
k.sub.1 in the drawing are to be parallel with a YZ plane, and
reflection surface DS is to be parallel to the Y-axis and
perpendicular to the Z-axis.
[0223] Supposing that reflection surface DS moves at a velocity
vector v=vy+vz, or more specifically, moves in the +Y direction at
a speed Vy (=|vy|) and also in the +Z direction at a speed Vz
(=|vz|). To this reflection surface, the light of wave number
vector k.sub.0 is incident at an angle .theta..sub.0, and the light
of wave number vector k.sub.1 is scattered at an angle
.theta..sub.1. However, |k.sub.0|=|k.sub.1|=k. The Doppler shift
(frequency difference of scattered light k.sub.1 and incident light
k.sub.0) f.sub.D that incident light k.sub.0 undergoes is given in
the next formula (7). 2 .times. .times. .PI. .times. .times. f D =
( k 1 .times. - k .times. 0 ) * v = 2 .times. .times. KVy .times.
.times. cos .function. [ ( .theta. 1 .times. - .theta. 0 ) / 2 ]
.times. cos .times. .times. .theta. + 2 .times. .times. KVz .times.
.times. cos .function. [ ( .theta. 1 .times. - .theta. 0 ) / 2 ]
.times. sin .times. .times. .theta. ( 7 ) ##EQU1##
[0224] In this case, since
.theta.=.pi./2-(.theta..sub.1+.theta..sub.0)/2, the above formula
is transformed so as to obtain the following formula (8).
2.pi.f.sub.D=KVy(sin .theta..sub.1+sin .theta..sub.0)+KVz(cos
.theta..sub.1+cos .theta..sub.0) (8)
[0225] Reflection surface DS is displaced during time .DELTA.t by
displacement vector v.DELTA.t, or more specifically, displaced in
the +Y direction by a distance .DELTA.Y=Vy.DELTA.t and in the +Z
direction by a distance .DELTA.Z=Vz.DELTA.t. And with this
displacement, the phase of scattered light k.sub.1 shifts by
.phi.=2.pi.f.sub.D.DELTA.t. When substituting formula (8), phase
shift .phi. can be obtained from the following formula (9).
.phi.=K.DELTA.Y(sin .theta..sub.1+sin .theta..sub.0)+K.DELTA.z(cos
.theta..sub.1+cos .theta..sub.1) (9)
[0226] In this case, a relation (a diffraction condition) expressed
as in the following formula is valid between incident angle
.theta..sub.0 and scattering angle .theta..sub.1. sin
.theta..sub.1+sin .theta..sub.0=.pi..lamda./p (10)
[0227] However, .lamda. is the wavelength of the light, p is the
pitch of the diffraction grating, and n is the order of
diffraction. Incidentally, order of diffraction n becomes positive
to a diffraction light scattered (generated) in the +Y direction,
and becomes negative to a diffraction light generated in the
-Y-direction, with a zero order diffraction light of scattering
angle (diffraction angle) -.theta..sub.0 serving as a reference.
When formula (10) is substituted into formula (9), phase shift
.phi. can be rewritten as in formula (II) below.
.phi.=2.pi.n.DELTA.Y/p+K.DELTA.Z(cos .theta..sub.1+cos
.theta..sub.0) (11)
[0228] As is obvious from formula (II) above, if reflection surface
DS stops, or more specifically, .DELTA.Y=.DELTA.Z=0, phase shift
.phi. also becomes zero.
[0229] Using formula (II), phase shift of the two beams LB.sub.1
and LB.sub.2 are obtained. First of all, phase shift of beam
LB.sub.1 will be considered. In FIG. 8B, supposing that beam
LB.sub.1, which was reflected off reflection mirror R1a, is
incident on reflection grating RG at an angle .theta..sub.a0, and a
n.sub.a.sup.th order diffraction light is to be generated at an
angle .theta..sub.a1. When the diffraction light is generated, the
phase shift that the diffraction light undergoes becomes the same
form as the right-hand side of formula (II). And the return beam,
which is reflected off reflection mirror R2a and follows the return
path, is incident on reflection grating RG at an angle
.theta..sub.a1. Then, a diffraction light is generated again. In
this case, the diffraction light that occurs at angle
.theta..sub.a0 and moves toward reflection mirror R1a following the
original optical path is an n.sub.a.sup.th order diffraction light,
which is a diffraction light of the same order as the diffraction
light generated on the outward path. Accordingly, the phase shift
which beam LB.sub.1 undergoes on the return path is equal to the
phase shift which beam LB.sub.1 undergoes on the outward path.
Accordingly, the total phase shift which beam LB.sub.1 undergoes is
obtained as in the following formula (12).
.phi..sub.1=4.pi.n.sub.a.DELTA.Y/p+2K.DELTA.Z(cos
.theta..sub.a1+cos .theta..sub.a0) (12)
[0230] However, a diffraction condition was given as in the next
formula (13). sin .theta..sub.a1+sin
.theta..sub.a0=n.sub.a.lamda./p (13)
[0231] Meanwhile, beam LB.sub.2 is incident on reflection grating
RG at an angle .theta..sub.b0, and an n.sub.b.sup.th order
diffraction light is generated at an angle .theta..sub.b1.
Supposing that this diffraction light is reflected off reflection
mirror R2b and returns to reflection mirror R1b following the same
optical path. The total phase shift which beam LB.sub.2 undergoes
can be obtained as in the next formula (14), similar to formula
(12). .phi..sub.2=4.pi.n.sub.b.DELTA.Y/p+2K.DELTA.Z(cos
.theta..sub.b1+cos .theta..sub.b0) (14)
[0232] However, a diffraction condition was given as in the next
formula (15). sin .theta..sub.b1+sin
.theta..sub.b0=n.sub.b.lamda./p (15)
[0233] Intensity I of the interference light synthesized by the two
return beams LB.sub.1 and LB.sub.2 is dependent on a phase
difference .phi. between the two return beams LB.sub.1 and LB.sub.2
in the light receiving position of the photodetector, by
I.varies.1+cos .phi.. However, the intensity of the two beams
LB.sub.1 and LB.sub.2 was to be equal to each other. In this case,
phase difference .phi. can be obtained as a sum of a difference
(more specifically .phi..sub.2-.phi..sub.1) of phase shifts due to
Y and Z displacements of each reflection grating RG of the two
beams LB.sub.1 and LB.sub.2 and a phase difference (K.DELTA.L) due
to optical path difference .DELTA.L of the two beams LB.sub.1 and
LB.sub.2, using a formula (12) and formula (14) as in the following
formula (16).
.phi.=K.DELTA.L+4.pi.(n.sub.b-n.sub.a).DELTA.Y/p+2K.DELTA.Zf(.theta..sub.-
a0, .theta..sub.a1, .theta..sub.b0, .theta..sub.b1)+.phi..sub.0
(16)
[0234] In this case, a geometric factor, which is to be decided
from the placement of reflection mirrors R1a, R1b, R2a, and R2b and
diffraction conditions (13) and (15), was expressed as in the
following formula (17). f(.theta..sub.a0, .theta..sub.a1,
.theta..sub.b0, .theta..sub.b1)=cos .theta..sub.b1+cos
.theta..sub.b0-cos .theta..sub.a1-cos .theta..sub.a0 (17)
[0235] Further, in formula (16) above, a constant phase term, which
is to be decided by other factors (e.g., a definition of the
reference position of displacements .DELTA.L, .DELTA.Y, and
.DELTA.Z), was expressed as .phi..sub.0.
[0236] In this case, the encoder is to be configured so as to
satisfy optical path difference .DELTA.L=0 and a symmetry shown in
the following formula (18). .theta..sub.a0=.theta..sub.b0,
.theta..sub.a1=.theta..sub.b1 (18)
[0237] In such a case, inside the parenthesis of the third term on
the right-hand side of formula (16) becomes zero, and also at the
same time n.sub.b=-n.sub.a (=n), therefore, the following formula
(19) can be obtained.
.phi..sub.sym(.DELTA.Y)=2.pi..DELTA.Y/(p/4n)+.phi..sub.0 (19)
[0238] From formula (19) above, it can be seen that phase
difference .phi..sub.sym is not dependent on wavelength .lamda. of
the light. And, it can be seen that intensity I of the interference
light repeats strong and weak intensities each time displacement
.DELTA.Y is increased or decreased by a measurement unit (also
referred to as a measurement pitch) of p/4n. Therefore, the number
of times is measured of the strong and weak intensities of the
interference light that accompanies displacement .DELTA.Y from a
predetermined reference position. And by using a counting value
(count value) c.sub..DELTA.Y, a measurement value c.sub..DELTA.Y of
displacement .DELTA.Y is computed from formula (20) below.
C.sub..DELTA.Y=(p/4n)*c.sub..DELTA.Y (20)
[0239] Furthermore, by splitting a sinusoidal intensity change of
the interference light using interpolation instrument (an
interpolator), its phase .phi.'(=.phi..sub.sym % 2.pi.) can be
measured. In this case, measurement value c.sub..DELTA.Y of
displacement .DELTA.Y is computed according to the following
formula (21).
C.sub..DELTA.Y=(p/4n)*[c.sub..DELTA.Y+(.phi.'-.phi..sub.0)/2.pi.]
(21)
[0240] In formula (21) above, constant phase term .phi..sub.0 is to
be a phase offset (however, 0.ltoreq..phi..sub.0<2.pi.), and
phase .phi..sub.sym (.DELTA.Y=0) at the reference position of
displacement .DELTA.Y is to be kept.
[0241] As it can be seen from the description so far above, by
using an interpolation instrument together, displacement .DELTA.Y
can be measured at a measurement resolution whose measurement unit
is (p/4.pi.) or under. The measurement resolution in this case is
decided from an interpolation error or the like, due to a shift of
an intensity change I(.DELTA.Y)=I(.phi..sub.sym(.DELTA.Y)) of the
interference light from an ideal sinusoidal waveform according to
displacement .DELTA.Y, which is a discretization error (also
referred to as a quantization error) determined from a split unit
of phase .phi.'. Incidentally, because the discretization unit of
displacement .DELTA.Y is, for example, one in several thousand of
measurement unit (p/4n), which is sufficiently small about 0.1 nm,
measurement value c.sub..DELTA.Y of the encoder will be regarded as
a continuous quantity unless it is noted otherwise.
[0242] Meanwhile, when wafer stage WST moves in a direction
different from the Y-axis direction and a relative motion (a
relative motion in a direction besides the measurement direction)
occurs between head 64 and Y scale 39Y.sub.1 in a direction besides
the direction that should be measured, in most cases, a measurement
error occurs in Y encoder 70A due to such motion. In the
description below, a mechanism of the generation of a measurement
error will be considered, based on the measurement principle of the
encoder described above.
[0243] In this case, the change of phase difference .phi. indicated
by formula (16) above in two cases shown in FIGS. 9A and 9B will be
considered, as a simple example. First of all, in the case of FIG.
9A, an optical axis of head 64 coincides with the Z-axis direction
(head 64 is not inclined). Supposing that wafer stage WST was
displaced in the Z-axis direction (.DELTA.Z.noteq.0, .DELTA.Y=0).
In this case, because there are no changes in optical path
difference .DELTA.L, there are no changes in the first term on the
right-hand side of formula (16). The second term becomes zero,
according to a supposition .DELTA.Y=0. And, the third term becomes
zero because it satisfies the symmetry of formula (18).
Accordingly, no change occurs in phase difference .phi., and
further no intensity change of the interference light occurs. As a
consequence, the measurement values of the encoder also do not
change.
[0244] Meanwhile, in the case of FIG. 9B, the optical axis of head
64 is inclined (head 64 is inclined) with respect to the Z-axis.
Supposing that wafer stage WST was displaced in the Z-axis
direction from this state (.DELTA.Z.noteq.0, .DELTA.Y=0). In this
case as well, because there are no changes in optical path
difference .DELTA.L, there are no changes in the first term on the
right-hand side of formula (16). And, the second term becomes zero,
according to supposition .DELTA.Y=0. However, because the head is
inclined the symmetry of formula (18) will be lost, and the third
term will not become zero and will change in proportion to Z
displacement .DELTA.Z. Accordingly, a change occurs in phase
difference .phi., and as a consequence, the measurement values
change. Incidentally, even if head 64 is not gradient, for example,
the symmetry of formula (18) is lost depending on the optical
properties (such as telecentricity) of the head, and count values
change likewise. More specifically, characteristic information of
the head unit, which is a generation factor of the measurement
error of the encoder system, includes not only the gradient of the
head but also the optical properties as well.
[0245] Further, although it is omitted in the drawings, in the case
wafer stage WST is displaced in a direction perpendicular to the
measurement direction (the Y-axis direction) and the optical axis
direction (the Z-axis direction), (.DELTA.X.noteq.0, .DELTA.Y=0,
.DELTA.Z=0), the measurement values do not change as long as the
direction (longitudinal direction) in which the grid line of
diffraction grating RG faces is orthogonal to the measurement
direction, however, in the case the direction is not orthogonal,
sensitivity occurs with a gain proportional to the angle.
[0246] Next, a case will be considered in which wafer stage WST
rotates (the inclination changes), using FIGS. 10A to 10D. First of
all, in the case of FIG. 10A, the optical axis of head 64 coincides
with the Z-axis direction (head 64 is not inclined). Even if wafer
stage WST is displaced in the +Z direction and moves to a condition
shown in FIG. 10B from this state, the measurement value of the
encoder does not change since the case is the same as in FIG. 9A
previously described.
[0247] Next, suppose that wafer stage WST rotates around the X-axis
from the state shown in FIG. 10B and moves into a state shown in
FIG. 10C. In this case, since the head and the scale do not perform
relative motion, or more specifically, because a change occurs in
optical path difference .DELTA.L due to the rotation of wafer stage
WST even though .DELTA.Y=.DELTA.Z=0, the measurement values of the
encoder change. That is, a measurement error occurs in the encoder
system due to an inclination (tilt) of wafer stage WST.
[0248] Next, suppose that wafer stage WST moves downward from a
state shown in FIG. 10C and moves into a state shown in FIG. 10D.
In this case, a change in optical path difference .DELTA.L does not
occur because wafer stage WST does not rotate. However, because the
symmetry of formula (18) has been lost, phase difference .phi.
changes by Z displacement .DELTA.Z through the third term on the
right-hand side of formula (16). Accordingly, the measurement
values of the encoder change. Incidentally, the count value of the
encoder in the case of FIG. 10D will be the same as the count value
in the case of FIG. 10A.
[0249] According to a result of a simulation that the inventors and
the like performed, it became clear that the measurement values of
the encoder have sensitivity not only to the displacement of the
scale in the Y-axis direction, which is the measurement direction
but also have sensitivity to an attitude change in the .theta.x
direction (the pitching direction) and the .theta.z direction (the
yawing direction), and moreover, depend on the position change in
the Z-axis direction in the case such as when the symmetry has been
lost as is previously described. That is, the theoretical
description previously described agreed with the result of the
simulation.
[0250] Therefore, in the embodiment, correction information to
correct the measurement error of each encoder caused by the
relative motion of the head and the scale in the direction besides
the measurement direction is acquired as follows.
[0251] a. First of all, main controller 20 drives wafer stage WST
via stage drive system 124, while monitoring the measurement values
of Y interferometer 16 of interferometer system 118, X
interferometer 126, and Z interferometers 43A and 43B, and as shown
in FIGS. 11A and 11B, makes Y head 64 located farthest to the -X
side of head unit 62A face an arbitrary area (an area circled in
FIG. 11A) AR of Y scale 39Y.sub.1 on the upper surface of wafer
table WTB.
[0252] b. Then, based on the measurement values of Y interferometer
16 and Z interferometers 43A and 43B, main controller 20 drives
wafer table WTB (wafer stage WST) so that a rolling amount .theta.y
and yawing amount .theta.z of wafer table WTB (wafer stage WST)
both become zero while a pitching amount .theta.x also becomes a
desired value .alpha..sub.0 (in this case, .alpha..sub.0=200
.mu.rad), irradiates a detection light on area AR of Y scale
39Y.sub.1 from head 64 above after the drive, and stores the
measurement values which correspond to a photoelectric conversion
signal from head 64 which has received the reflected light in an
internal memory.
[0253] c. Next, while maintaining the attitude (pitching amount
.theta.x=.alpha..sub.0, yawing amount .theta.z=0, rolling amount
.theta.y=0) of wafer table WTB (wafer stage WST) based on the
measurement values of Y interferometer 16 and Z interferometers 43A
and 43B, main controller 20 drives wafer table WTB (wafer stage
WST) within a predetermined range, such as, for example, the range
of -100 .mu.m to +100 .mu.m in the Z-axis direction as is indicated
by an arrow in FIG. 11B, sequentially takes in the measurement
values corresponding to the photoelectric conversion signals from
head 64 which has received the reflected light at a predetermined
sampling interval while irradiating a detection light on area AR of
Y scale 39Y.sub.1 from head 64 during the drive, and stores the
values in the internal memory.
d. Next, main controller 20 changes pitching amount .theta.x of
wafer table WTB (wafer stage WST) to
(.alpha.=.alpha..sub.0-.DELTA..alpha.), based on the measurement
values of Y interferometer 16.
e. Then, as for the attitude after the change, main controller 20
repeats an operation similar to c. described above.
[0254] f. Then, main controller 20 alternately repeats the
operations of d. and e described above, and for a range where
pitching amount .theta.x is, for example, -200
.mu.rad<.theta.x<+200 .mu.rad, takes in the measurement
values of head 64 within the Z drive range described above at
.DELTA..alpha.(rad), at an interval of, for example, 40
.mu.rad.
[0255] g. Next, by plotting each data within the internal memory
obtained by the processes b. to e. described above on a
two-dimensional coordinate system whose horizontal axis indicates a
Z position and vertical axis indicates an encoder count value,
sequentially linking plot points where the pitching amounts are the
same, and shifting the horizontal axis in the vertical axis
direction so that a line (a horizontal line in the center) which
indicates a zero pitching amount passes through the origin, main
controller 20 can obtain a graph (a graph that shows a change
characteristic of the measurement values of the encoder (head)
according to the Z leveling of the wafer stage) like the one shown
in FIG. 12.
[0256] The values of the vertical axis at each point on the graph
in FIG. 12 is none other than the measurement error of the encoder
in each Z position, in pitching amount .theta.x=.alpha.. Therefore,
main controller 20 sees pitching amount .theta.x, the Z position,
and the encoder measurement error at each point on the graph in
FIG. 12 as a table data, and stores the table data in memory 34
(refer to FIG. 6) as stage position induced error correction
information. Or main controller 20 sees the measurement error as a
function of Z position z and pitching amount .theta.x, and obtains
the function computing an undetermined coefficient, for example, by
the least-squares method, and stores the function in memory 34 as
stage position induced error correction information.
[0257] h. Next, main controller 20 drives wafer stage WST in the
-X-direction by a predetermined amount via stage drive system 124
while monitoring the measurement values of X interferometer 126 of
interferometer system 118, and as shown in FIG. 13, makes Y head 64
located second from the edge on the -X side of head unit 62A (the Y
head next to Y head 64 whose data has already been acquired in the
process described above) face area AR previously described (the
area circled in FIG. 13) of Y scale 39Y.sub.1 on the upper surface
of wafer table WTB.
i. Then, main controller 20 performs a process similar to the ones
described above on Y head 64, and stores correction information of
Y encoder 70A configured by head 64 and Y scale 39Y.sub.1 in memory
34.
[0258] j. Hereinafter, in a similar manner, main controller 20
respectively obtains correction information of Y encoder 70A
configured by each remaining Y head 64 of head unit 62A and Y scale
39Y.sub.1, correction information of X encoder 70B configured by
each X head 66 of head unit 62B and X scale 39X.sub.1, correction
information of Y encoder 70C configured by each X head 64 of head
unit 62C and Y scale 39Y.sub.2, and correction information of X
encoder 70D configured by each X head 66 of head unit 62D and X
scale 39X.sub.2, and stores them in memory 34.
[0259] In this case, it is important that the same area on X scale
39X.sub.1 is used on the measurement using each X head 66 of head
unit 62B described above, the same area on Y scale 39Y.sub.2 is
used on the measurement using each Y head 64 of head unit 62C, and
the same area in X scale 39X.sub.2 is used on the measurement using
each Y head 66 of head unit 62D. The reason for this is because if
the correction (including the curve correction of reflection
surfaces 17a and 17b, and reflection surfaces 41a, 41b, and 41c) of
each interferometer of interferometer system 118 has been
completed, the attitude of wafer stage WST can be set to a desired
attitude anytime based on the measurement values of the
interferometers, and by using the same location of each scale, even
if the scale surface is inclined, the measurement error caused by
the effect of the inclination does not occur between the heads.
[0260] Further, main controller 20 performs the measurement
described above for Y heads 64y.sub.1 and 64y.sub.2 using the same
area on Y scale 39Y.sub.2 and 39Y.sub.1, respectively, which is the
same as each Y head 64 of head units 62C and 64A described above,
obtains correction information of encoder 70C configured by Y head
64y.sub.1 which faces Y scale 39Y.sub.2 and correction information
of encoder 70A configured by Y head 64y.sub.2 which faces Y scale
39Y.sub.1, and stores the information in memory 34.
[0261] Next, in a similar procedure as in the case described above
where the pitching amount was changed, main controller 20
sequentially changes yawing amount .theta.z of wafer stage WST for
a range of -200 .mu.rad<.theta.z<+200 .mu.rad and drives
wafer table WTB (wafer stage WST) in the Z-axis direction at each
position within a predetermined range, such as, for example, within
-100 .mu.m.about.+100 .mu.m, while maintaining both the pitching
amount and the rolling amount of wafer stage WST at zero, and
during the drive, sequentially takes in the measurement values of
the head at a predetermined sampling interval and stores them in
the internal memory. Such a measurement is performed for all heads
64 or 66, and in a procedure similar to the one described earlier,
by plotting each data within the internal memory on the
two-dimensional coordinate system whose horizontal axis indicates
the Z position and vertical axis indicates the encoder count value,
sequentially linking plot points where the yawing amounts are the
same, and shifting the horizontal axis so that a line (a horizontal
line in the center) which indicates a zero pitching amount passes
through the origin, main controller 20 can obtain a graph similar
to the one shown in FIG. 12. Then, main controller 20 sees yawing
amount .theta.z, Z position z, and the encoder measurement error at
each point on the graph as a table data, and stores the table data
in memory 34 as correction information. Or, main controller 20 sees
the measurement error as a function of Z position z and yawing
amount .theta.z, and obtains the function computing an undetermined
coefficient, for example, by the least-squares method, and stores
the function in memory 34 as correction information.
[0262] In this case, the measurement error of each encoder in the
case both the pitching amount and the yawing amount of wafer stage
WST are not zero when wafer stage WST is at Z position z can safely
be considered to be a simple sum of the measurement error that
corresponds to the pitching amount described above and the
measurement error that corresponds to the yawing amount (a linear
sum) when wafer stage WST is at Z position z. The reason for this
is, as a result of simulation, it has been confirmed that the
measurement error (count value) linearly changes according to the
change of the Z position, even when the yawing is changed.
[0263] Hereinafter, to simplify the description, as for the Y heads
of each Y encoder, a function of pitching amount .theta.x, yawing
amount .theta.z, and Z position z of wafer stage WST that expresses
a measurement error .DELTA.y as shown in the next formula (22) is
to be obtained, and to be stored in memory 34. Further, as for the
X heads of each X encoder, a function of rolling amount .theta.y,
yawing amount .theta.z, and Z position z of wafer stage WST that
expresses a measurement error .DELTA.x as shown in the next formula
(23) is to be obtained, and to be stored in memory 34.
.DELTA.y=f(z, .theta.x, .theta.z)=.theta.x(z-a)+.theta.z(z-b) (22)
.DELTA.x=g(z, .theta.y, .theta.z)=.theta.y(z-c)+.theta.z(z-d)
(23)
[0264] In formula (22) above, a is a Z-coordinate of a point where
each straight line intersects on the graph in FIG. 12, and b is a
Z-coordinate of a point where each straight line intersects on a
graph similar to FIG. 12 in the case when the yawing amount is
changed so as to acquire the correction information of the Y
encoder. Further, in formula (23) above, c is a Z-coordinate of a
point where each straight line intersects on a graph similar to
FIG. 12 in the case when the rolling amount is changed so as to
acquire the correction information of the X encoder, and d is a
Z-coordinate of a point where each straight line intersects on a
graph similar to FIG. 12 in the case when the yawing amount is
changed so as to acquire the correction information of the X
encoder.
[0265] Incidentally, because .DELTA.y and .DELTA.x described above
show the degree of influence of the position of wafer stage WST in
the direction besides the measurement direction (e.g. the .theta.x
direction, the .theta.y direction, the .theta.z direction and the
Z-axis direction) on the measurement values of the Y encoder or the
X encoder, in the present specification, it will be referred to as
a stage position induced error, and because the stage position
induced error can be used as it is as correction information, the
correction information will be referred to as stage position
induced error correction information.
[0266] Next, a calibration process of a head position for acquiring
a position coordinate of each head in the XY plane, especially the
position coordinate in the direction besides the measurement
direction, which becomes a premise in processes such as a process
to convert the measurement value of an encoder to be described
later into positional information of wafer stage WST in the XY
plane and a linkage process among a plurality of encoders, will be
described. In this case, as an example, a calibration process of
the position coordinate in the direction besides the measurement
direction (the X-axis direction) orthogonal to the measurement
direction of Y head 64 configuring each head unit 62A and 62C will
be described.
[0267] First of all, on starting this calibration process, main
controller 20 drives wafer stage WST so that Y scales 39Y.sub.1 and
39Y.sub.2 are located below head units 62A and 62C, respectively.
For example, as shown in FIG. 14, Y head 64.sub.A3, which is the
third head from the left of head unit 62A, and Y head 64.sub.C5,
which is the second head from the right of head unit 62C, are made
to face Y scales 39Y.sub.1 and 39Y.sub.2, respectively.
[0268] Next, based on the measurement values of measurement beams
B4.sub.1 and B4.sub.2 of Y interferometer 16, or the measurement
values of Z interferometers 43A and 43B, main controller 20 rotates
wafer stage WST only by a predetermined angle (the angle being
.theta.) within the XY plane with optical axis AX of projection
optical system PL serving as a center as shown by an arrow RV in
FIG. 14, and acquires the measurement values of encoders 70A and
70C configured by Y heads 64.sub.A3 and 64.sub.C5 and Y scales
39Y.sub.1 and 39Y.sub.2 facing Y heads 64.sub.A3 and 64.sub.C5,
respectively, which can be obtained during the rotation. In FIG.
14, vectors MA and MB, which correspond to the measurement values
measured during the rotation of wafer stage WST by Y heads
64.sub.A3 and 64.sub.C5, are respectively shown.
[0269] In this case, because .theta. is a very small angle,
MA=b*.theta. and MB=a*.theta. are valid, and a ratio MA/MB of the
magnitude of vectors MA and MB are equal to a ratio a/b, which is a
ratio of the distance from the rotation center to Y heads 64.sub.A3
and 64.sub.C5.
[0270] Therefore, main controller 20 computes distances b and a, or
more specifically, the X-coordinate values of Y heads 64.sub.A3 and
64.sub.C5, based on predetermined angle .theta. obtained from the
measurement values of encoders 70A and 70C and the measurement
values of interferometer beams B4.sub.1 and B4.sub.2, respectively,
or, furthermore performs a calculation based on the X-coordinate
values that have been calculated, and computes the positional shift
amount (more specifically, correction information of the positional
shift amount) of Y heads 64.sub.A3 and 64.sub.C5 in the X-axis
direction with respect to the design position.
[0271] Further, in the case wafer stage WST is located at the
position shown in FIG. 14, in actual practice, head units 62B and
62D face X scales 39X.sub.1 and 39X.sub.2, respectively.
Accordingly, on the rotation of wafer stage WST described above,
main controller 20 simultaneously acquires the measurement values
of X scales 39X.sub.1 and 39X.sub.2 and encoders 70B and 70D, which
are configured by one X head 66 each of head units 62B and 62D that
respectively face X scale 39X.sub.1 and 39X.sub.2. Then, in a
manner similar to the description above, main controller 20
computes the Y-coordinate values of one X head 66 each that
respectively face X scale 39X.sub.1 and 39X.sub.2, or, furthermore
performs a calculation based on the computation result, and
computes the positional shift amount (more specifically, correction
information of the positional shift amount) of the X heads in the
Y-axis direction with respect to the design position.
[0272] Next, main controller 20 moves wafer stage WST in the X-axis
direction at a predetermined pitch, and by performing a processing
similar to the procedure described above at each positioning
position, main controller 20 can obtain the X-coordinate values, or
the positional shift amount (more specifically, correction
information of the positional shift amount) in the X-axis direction
with respect to the design position also for the remaining Y heads
of head units 62A and 62C.
[0273] Further, by moving wafer stage WST in the Y-axis direction
at a predetermined pitch from the position shown in FIG. 14 and
performing a processing similar to the procedure described above at
each positioning position, main controller 20 can obtain the
Y-coordinate values, or the positional shift amount (more
specifically, correction information of the positional shift
amount) in the Y-axis direction with respect to the design position
also for the remaining Y heads of head units 62B and 62D.
[0274] Further, in a method similar to Y head 64 described above,
main controller 20 acquires the X-coordinate values or the
positional shift amount (more specifically, correction information
of the positional shift amount) in the X-axis direction with
respect to the design position, also for Y heads 64y.sub.1 and
y.sub.2.
[0275] In the manner described above, main controller 20 can
acquire the X-coordinate values or the positional shift amount
(more specifically, correction information of the positional shift
amount) in the X-axis direction with respect to the design position
for all Y heads 64, 64y.sub.1, and 64y.sub.2, and the Y-coordinate
values or the positional shift amount (more specifically,
correction information of the positional shift amount) in the
Y-axis direction with respect to the design position also for all X
heads 66, therefore, the information that has been acquired is
stored in a storage unit, such as, for example, memory 34. The
X-coordinate values or the Y coordinate values or the positional
shift amount in the X-axis direction or the Y-axis direction with
respect to the design position of each head stored in memory 34,
will be used such as when converting the measurement values of an
encoder into positional information within the XY plane of wafer
stage WST, as it will be described later on. Incidentally, on
converting the measurement values of an encoder into positional
information within the XY plane of wafer stage WST or the like
described later on, design values are used for the Y coordinate
values of each Y head, and the X-coordinate values of each X head.
This is because since the influence that the position coordinates
of each head in the measurement direction has on the control
accuracy of the position of wafer stage WST is extremely weak, (the
effectiveness to the control accuracy is extremely slow), it is
sufficient enough to use the design values.
[0276] Now, when there is an error (or a gap) between the height
(the Z position) of each scale surface (the grating surface) on
wafer table WTB and the height of a reference surface including the
exposure center (it is the center of exposure area IA previously
described and coincides with optical axis AX of projection optical
system PL in the embodiment), the so-called Abbe error occurs in
the measurement values of the encoder on rotation (pitching or
rolling) around an axis (an X-axis or a Y-axis) parallel to the XY
plane of wafer stage WST, therefore, this error needs to be
corrected. In this case, the reference surface is a surface that
serves as a reference to displacement .DELTA.Zo of wafer stage WST
in the Z-axis direction measured by interferometer system 118, and
in the embodiment, the surface is to coincide with the image plane
of projection optical system PL.
[0277] For the correction of the error described above, it is
necessary to accurately obtain the difference of height (the
so-called Abbe offset quantity) of each scale surface (the grating
surface) with respect to the reference surface of wafer stage WST.
This is because correcting the Abbe errors due to the Abbe offset
quantity described above is necessary in order to accurately
control the position of wafer stage WST within the XY plane using
an encoder system. By taking into consideration such points, in the
embodiment, main controller 20 performs calibration for obtaining
the Abbe offset quantity described above in the following
procedure.
[0278] First of all, on starting this calibration processing, main
controller 20 drives wafer stage WST and moves Y scales 39Y.sub.1
and 39Y.sub.2 so that Y scales 39Y.sub.1 and 39Y.sub.2 are located
under head units 62A and 62C, respectively. In this case, for
example, as shown in FIG. 15, Y head 64.sub.A3 being the third head
from the left of head unit 62A faces area AR which is a specific
area on Y scale 39Y.sub.1 where Y head 64.sub.A3 had faced when
acquiring the stage position induced error correction information
in the previous description. Further, in this case, as shown in
FIG. 15, Y head 64.sub.C4 being the fourth head from the left of
head unit 62C faces an area which is a specific area on Y scale
39Y.sub.2 where Y head 64.sub.C4 had faced when acquiring the stage
position induced error correction information in the previous
description.
[0279] Next, based on measurement results of Y interferometer 16
which uses interferometer beams B4.sub.1, B4.sub.2 and B3
previously described, main controller 20 tilts wafer stage WST
around an axis that passes the exposure center and is parallel to
the X-axis so that pitching amount .DELTA..theta.x becomes zero in
the case displacement (pitching amount) .DELTA..theta.x of wafer
stage WST in the .theta.x direction with respect to the XY plane is
not zero, based on the measurement results of Y interferometer 16
of interferometer system 118. Because all the corrections of each
interferometer of interferometer system 118 have been completed at
this point, such pitching control of wafer stage WST becomes
possible.
[0280] Then, after such adjustment of the pitching amount of wafer
stage WST, main controller 20 acquires measurement values y.sub.A0
and y.sub.C0 of encoders 70A and 70C, configured by Y scales
39Y.sub.1 and 39Y.sub.2 and Y heads 64.sub.A3 and 64.sub.C4 that
face Y scales 39Y.sub.1 and 39Y.sub.2, respectively.
[0281] Next, based on measurement results of Y interferometer 16,
using interferometer beams B4.sub.1, B4.sub.2 and B3, main
controller 20 tilts wafer stage WST at an angle .phi. around the
axis that passes the exposure center and is parallel to the X-axis,
as shown by arrow Rx in FIG. 15. Then, main controller 20 acquires
measurement values y.sub.A1 and y.sub.C1 of encoders 70A and 70C,
configured by Y scales 39Y.sub.1 and 39Y.sub.2 and Y heads
64.sub.A3 and 64.sub.C4 that face Y scales 39Y.sub.1 and 39Y.sub.2,
respectively.
[0282] Then, based on measurement values Y.sub.A0, y.sub.C0, and
Y.sub.A1, Y.sub.C1 of encoders 70A and 70C acquired above, and
angle .phi. above, main controller 20 computes the so-called Abbe
offset quantities h.sub.A and h.sub.C of Y scales 39Y.sub.1 and
39Y.sub.2.
[0283] In this case, because .phi. is a very small angle, sin
.phi.=.phi. and cos .phi.=1 are valid.
h.sub.A=(y.sub.A1-y.sub.A0)/.phi. (24)
h.sub.C=(y.sub.C1-y.sub.C0)/.phi. (25)
[0284] Next, after adjusting the pitching amount of wafer stage WST
so that pitching amount .DELTA..theta.x becomes zero, main
controller 20 drives wafer stage WST if necessary in the X-axis
direction, and makes a predetermined X head 66 of head units 62B
and 62D face the specific area on X scales 39X.sub.1 and 39X.sub.2
where each X head 66 had faced when acquiring the stage position
induced error correction information in the previous
description.
[0285] Next, main controller 20 performs a calculation of formula
(6) previously described, using the output of Z interferometers 43A
and 43B previously described, and in the case displacement (rolling
amount) .DELTA..theta.y of wafer stage WST in the .theta.y
direction with respect to the XY plane is not zero, main controller
20 tilts wafer stage WST around an axis that passes the exposure
center and is parallel to the Y-axis so that rolling amount
.DELTA..theta.y becomes zero. Then, after such adjustment of the
rolling amount of wafer stage WST, main controller 20 acquires
measurement values x.sub.B0 and x.sub.D0 of encoders 70B and 70D,
configured by X scales 39X.sub.1 and 39X.sub.2 and each X head 66,
respectively.
[0286] Next, main controller 20 tilts wafer stage WST at angle
.phi. around the axis that passes the exposure center and is
parallel to the Y-axis, based on the output of Z interferometers
43A and 43B, and acquires measurement values x.sub.B1 and x.sub.D1
of encoders 70B and 70D, configured by X scales 39X.sub.1 and
39X.sub.2 and each X head 66, respectively.
[0287] Then, based on measurement values x.sub.B0, x.sub.D0, and
x.sub.B1, x.sub.D1 of encoders 70B and 70D acquired above, and
angle .phi. above, main controller 20 computes the so-called Abbe
offset quantities h.sub.B and h.sub.D of X scales 39X.sub.1 and
39X.sub.2. In this case, .phi. is a very small angle.
h.sub.B=(x.sub.B1-X.sub.B0)/.phi. (26)
h.sub.D=(x.sub.D1-x.sub.D0)/.phi. (27)
[0288] As it can be seen from formulas (24) and (25) above, when
the pitching amount of wafer stage WST is expressed .phi.x, then
Abbe errors .DELTA.A.sub.A and .DELTA.A.sub.C of Y encoders 70A and
70C that accompany the pitching of wafer stage WST can be expressed
as in the following formulas (28) and (29).
.DELTA.A.sub.A=h.sub.A*.phi.x (28) .DELTA.A.sub.C=h.sub.C*.phi.x
(29)
[0289] As it can be seen from formulas (26) and (27) above, when
the rolling amount of wafer stage WST is expressed .phi.y, then
Abbe errors .DELTA.A.sub.B and .DELTA.A.sub.D of X encoders 70B and
70D that accompany the rolling of wafer stage WST can be expressed
as in the following formulas (30) and (31).
.DELTA.A.sub.B=h.sub.B*.phi.y (30) .DELTA.A.sub.D=h.sub.D*.phi.y
(31)
[0290] Main controller 20 stores the quantities h.sub.A to h.sub.D
or formulas (28) to (31) obtained in the manner described above in
memory 34. Accordingly, on the actual position control of wafer
stage WST such as during lot processing and the like, main
controller 20 is able to drive (perform position control of) wafer
stage WST with high precision in an arbitrary direction within the
XY plane while correcting the Abbe errors included in the
positional information of wafer stage WST within the XY plane (the
movement plane) measured by the encoder system, or, more
specifically, measurement errors of Y encoders 70A and 70C
corresponding to the pitching amount of wafer stage WST caused by
the Abbe offset quantities of the surface of Y scales 39Y.sub.1 and
39Y.sub.2 (the grating surface) with respect to the reference
surface previously described, or measurement errors of X encoders
70B and 70D corresponding to the rolling amount of wafer stage WST
caused by the Abbe offset quantities of the surface of X scales
39X.sub.1 and 39X.sub.2 (the grating surface) with respect to the
reference surface previously described.
[0291] Now, in the case the optical axis of the heads of the
encoder substantially coincides with the Z-axis, and the pitching
amount, rolling amount, and yawing amount of wafer stage WST are
all zero, as it is obvious from formulas (22) and (23) above,
measurement errors of the encoder described above due to the
attitude of wafer table WTB are not supposed to occur, however,
even in such a case, the measurement errors of the encoder are not
actually zero. This is because the surface of Y scales 39Y.sub.1
and 39Y.sub.2, and X scales 39X.sub.1 and 39X.sub.2 (the surface of
the second water repellent plate 28b) is not an ideal plane, and is
somewhat uneven. When the surface of the scale (to be more precise,
the diffraction grating surface, and including the surface of a
cover glass in the case the diffraction grating is covered with the
cover glass) is uneven, the scale surface will be displaced in the
Z-axis direction (move vertically), or be inclined with respect to
the heads of the encoder even in the case when wafer stage WST
moves along a surface parallel to the XY plane. This consequently
means none other that a relative motion occurs in the direction
besides the measurement direction between the head and the scale,
and as it has already been described, such a relative motion
becomes a cause of the measurement error.
[0292] Further, as shown in FIG. 16, for example, in the case of
measuring a plurality of measurement points P.sub.1 and P.sub.2 on
the same scale 39x using a plurality of heads 66A and 66B, when the
tilt of the optical axis of the plurality of heads 66A and 66B is
different and there is also an unevenness (including inclination)
to the surface of scale 39X, as is obvious from
.DELTA.X.sub.A.noteq..DELTA.X.sub.B shown in FIG. 16, the influence
that the unevenness has on the measurement values will differ for
each head depending on the tilt difference. Accordingly, in order
to remove such difference in the influence, it will be necessary to
obtain the unevenness of the surface of scale 39X. The unevenness
of the surface of scale 39X may be measured, for example, using a
measurement unit besides the encoder such as the Z sensor
previously described, however, in such a case, because the
measurement accuracy of the unevenness is set according to the
measurement resolution of the measurement unit, in order to measure
the unevenness with high precision, a possibility may occur of
having to use a sensor that has higher precision and an expensive
sensor must become use than the sensor which is necessary for an
original purpose as a Z sensor to measure unevenness in high
accuracy.
[0293] Therefore, in the embodiment, a method of measuring the
unevenness of the surface of a scale using the encoder system
itself is employed. Following is a description of the method.
[0294] As shown in a graph (an error characteristics curve) of FIG.
12, which shows a change characteristic of the measurement values
of the encoder (a head) corresponding to the Z leveling of wafer
stage WST previously described, only one point can be found in the
Z-axis direction for each encoder head where the head has no
sensibility to the tilt operation of wafer stage WST, or more
specifically, a singular point where the measurement error of the
encoder becomes zero regardless of the angle of inclination of
wafer stage WST to the XY plane. If this point can be found by
moving wafer stage WST similarly as when acquiring the stage
position induced error correction information previously described,
the point (a Z position) can be positioned the singular point with
respect to the encoder head. If such operation to find the singular
point is performed on a plurality of measurement points on the
scale, the shape (unevenness) of the surface of the scale can be
obtained.
[0295] (a) Therefore, main controller 20 first of all drives wafer
stage WST via stage drive system 124, while monitoring the
measurement values of Y interferometer 16 of interferometer system
118, X interferometer 126, and Z interferometers 43A and 43B, and
as shown in FIG. 17, makes an arbitrary Y head of head unit 62A,
such as for example, Y head 64.sub.A2 in FIG. 17, face the vicinity
of the end section of Y scale 39Y.sub.1 on the +Y side. Then, main
controller 20 changes the pitching amount (.theta.x rotation
quantity) of wafer stage WST at the position in at least two stages
as is previously described, and in a state where the attitude of
wafer stage WST at the time of change is maintained for every
change, main controller 20 scans (moves) wafer stage WST in the
Z-axis direction in a predetermined stroke range while irradiating
a detection light on a point of Y scale 39Y.sub.1 subject to
measurement from Y head 64.sub.A2, and samples the measurement
results of Y head 64.sub.A2 (encoder 70A) that faces Y scale
39Y.sub.1 during the scan (movement). Incidentally, the sampling
above is performed while maintaining the yawing amount (and rolling
amount) of wafer stage WST at zero.
[0296] Then, by performing a predetermined operation based on the
sampling results, main controller 20 obtains an error
characteristics curve (refer to FIG. 12) at the point described
above subject to the measurement of encoder 70A corresponding to
the Z position of wafer stage WST for a plurality of attitudes, and
sets the intersecting point of the plurality of error
characteristics curves, or more specifically, sets the point where
the measurement error of encoder 70A above becomes zero regardless
of the angle of inclination of wafer stage WST with respect to the
XY plane as the singular point at the measurement point, and
obtains Z positional information z.sub.1 (refer to FIG. 18A) of the
singular point.
[0297] (b) Next, main controller 20 steps wafer stage WST in the +Y
direction by a predetermined amount via stage drive system 124
while maintaining the pitching amount and rolling amount of wafer
stage WST at zero, while monitoring the measurement values of Y
interferometer 16 of interferometer system 118, X interferometer
126, and Z interferometers 43A and 43B. This step movement is
performed at a speed slow enough so that measurement errors caused
by air fluctuation of the interferometers can be ignored.
(c) Then, at a position after the step movement, as in (a) above,
main controller 20 obtains a Z positional information z.sub.p (in
this case, p=2) of the singular point of encoder 70A above at the
position.
[0298] After this operation, by repeating the operations similar to
the ones described in (b) and (c) above, main controller 20 obtains
a Z positional information z.sub.p (p=2, 3 . . . , i, . . . k, . .
. n) in a plurality of (e.g. n-1) measurement points set at a
predetermined interval in the Y-axis direction on scale
39Y.sub.1.
[0299] FIG. 18B shows a z positional information z.sub.i of the
singular point at the i-th measurement point that was obtained in
the manner described above, and FIG. 18C shows a z positional
information z.sub.k of the singular point at the k.sup.th
measurement point.
[0300] (d) Then, based on Z positional information z.sub.1,
z.sub.2, . . . z.sub.n of the singular point obtained for each of
the plurality of measurement points above, main controller 20
obtains the unevenness of scale 39Y.sub.1. As shown in FIG. 18D, if
one end of a double-sided arrow showing Z position z.sub.p of the
singular point in each measurement point on scale 39Y.sub.1 is made
to coincide with a predetermined reference line, the curve which
links the other end of each double-sided arrow indicates the shape
of the surface (unevenness) of scale 39Y.sub.1. Accordingly, main
controller 20 obtains function z=f.sub.1(y) that expresses this
unevenness by performing curve fitting (a least square
approximation) on the point at the other end of each double-sided
arrow, and is stored in memory 34. Incidentally, y is a
Y-coordinate of wafer stage WST measured with Y interferometer
16.
[0301] (e) In a similar manner described above, main controller 20
obtains function z=f.sub.2(y) that expresses the unevenness of Y
scale 39Y.sub.2, function z=g.sub.1(x) that expresses the
unevenness of X scale 39X.sub.1, and, function z=g.sub.2(x) that
expresses the unevenness of X scale 39X.sub.2, respectively, and
stores them in memory 34. Incidentally, x an X-coordinate of wafer
stage WST measured with X interferometer 126.
[0302] In this case, at each measurement point on each scale, when
an error characteristics curve whose measurement error always
becomes zero is obtained regardless of the change of Z in the case
of obtaining the error characteristics curve (refer to FIG. 12)
described above, the pitching amount (or rolling amount) of wafer
stage WST at the point when the error characteristics curve was
obtained corresponds to an inclined quantity of the scale surface
at the measurement point. Accordingly, in the method above,
information on inclination at each measurement point can also be
obtained, in addition to the height information of the scale
surface. This arrangement allows fitting with higher precision when
the curve fitting described above is performed.
[0303] Now, the scale of the encoder lacks in mechanical long-term
stability, such as in the diffraction grating deforming due to
thermal expansion or other factors by the passage of use time, or
the pitch of the diffraction grating changing partially or
entirely. Therefore, because the errors included in the measurement
values grow larger with the passage of use time, it becomes
necessary to correct the errors. Hereinafter, an acquisition
operation of correction information of the grating pitch and of
correction information of the grating deformation performed in
exposure apparatus 100 of the embodiment will be described, based
on FIG. 19.
[0304] In FIG. 19, measurement beams B4.sub.1 and B4.sub.2 are
arranged symmetric to straight line LV previously described, and
the substantial measurement axis of Y interferometer 16 coincides
with straight line LV, which passes through the optical axis of
projection optical system PL and is parallel to the Y-axis
direction. Therefore, according to Y interferometer 16, the Y
position of wafer table WTB can be measured without Abbe error.
Similarly, measurement beams B5.sub.1 and B5.sub.2 are arranged
symmetric to straight line LH previously described, and the
substantial measurement axis of X interferometer 126 coincides with
straight line LH, which passes through the optical axis of
projection optical system PL and is parallel to the X-axis
direction. Therefore, according to X interferometer 126, the X
position of wafer table WTB can be measured without Abbe error.
[0305] First of all, an acquisition operation of correction
information of the deformation (curve of the grid line) of the grid
line of the X scale, and correction information of the grating
pitch of the Y scale will be described. In this case, to simplify
the description, reflection surface 17b is to be an ideal plane.
Further, prior to this acquisition operation, a measurement of the
unevenness information of the surface of each scale described above
is performed, and function z=f.sub.1(y) that expresses the
unevenness of Y scale 39Y.sub.1, function z=f.sub.2(y) that
expresses the unevenness of Y scale 39Y.sub.2, function
z=g.sub.1(x) that expresses the unevenness of X scale 39X.sub.1,
and function z=g.sub.2(x) that expresses the unevenness of X scale
39X.sub.2, are to be stored in memory 34.
[0306] First of all, main controller 20 reads function
z=f.sub.1(y), function z=f.sub.2(y), function z=g.sub.1(x) and
function z=g.sub.2(x) stored in memory 34 into the internal
memory.
[0307] Next, at a speed low enough so that the short-term variation
of the measurement values of Y interferometer 16 can be ignored and
also in a state where the measurement value of X interferometer 126
is fixed to a predetermined value, main controller 20 moves wafer
stage WST based on the measurement values of Y interferometer 16,
and Z interferometers 43A and 43B, for example, in at least one
direction of the +Y direction and the -Y-direction with in the
effective stroke range mentioned earlier as is indicated by arrow F
and F' in FIG. 19, in a state where the pitching amount, the
rolling amount, and the yawing amount are all maintained at zero.
During this movement, while correcting the measurement values (the
output) of Y linear encoders 70A and 70C using the function
z=f.sub.1(y) and function z=f.sub.2(y) described above,
respectively, main controller 20 takes in the measurement values
after the correction and the measurement values (or to be more
precise, measurement values of interferometer beams B4.sub.1 and
B4.sub.2) of Y interferometer 16 at a predetermined sampling
interval, and based on each measurement value that has been taken
in, obtains a relation between the measurement values of Y linear
encoders 70A and 70C (output of encoder 70A--the measurement values
corresponding to function f.sub.1(y), output of encoder 70C--the
measurement values corresponding to function f.sub.2(y)) and the
measurement values of Y interferometer 16. More specifically, in
the manner described above, main controller 20 obtains a grating
pitch (the distance between adjacent grid lines) of Y scales
39Y.sub.1 and 39Y.sub.2 which are sequentially placed opposing head
units 62A and 62C with the movement of wafer stage WST and
correction information of the grating pitch. As the correction
information of the grating pitch, for example, in the case a
horizontal axis shows the measurement values of the interferometer
and a vertical axis shows the measurement values (the measurement
values whose errors due to the unevenness of the scale surface has
been corrected) of the encoder, a correction map which shows the
relation between the two using a curve can be obtained. Because the
measurement values of Y interferometer 16 in this case are obtained
when wafer stage WST was scanned at an extremely low speed as was
previously described, the measurement values hardly include any
short-term variation errors due to air fluctuation, as well as
long-term variation errors, and it can be said that the measurement
values are accurate values in which the errors can be ignored.
[0308] Further, during the movement of wafer stage WST described
above, by statistically processing the measurement values (the
measurement values of X linear encoders 70B and 70D) obtained from
a plurality of X heads 66 of head units 62B and 62D placed
sequentially opposing X scales 39X.sub.1 and 39X.sub.2 with the
movement, such as, for example, averaging (or performing weighted
averaging), main controller 20 also obtains correction information
of the deformation (warp) of grid lines 37 which sequentially face
the plurality of X heads 66. This is because in the case reflection
surface 17b is an ideal plane, the same blurring pattern should
appear repeatedly in the process when wafer stage WST is sent in
the +Y direction or the -Y-direction, therefore, if averaging or
the like is performed on the measurement data acquired with the
plurality of X heads 66, it becomes possible to precisely obtain
correction information of the deformation (warp) of grid lines 37
which sequentially face the plurality of X head 66.
[0309] Incidentally, in a normal case where reflection surface 17b
is not an ideal plane, by measuring the unevenness (warp) of the
reflection surface and obtaining the correction data of the curve
in advance and performing movement of wafer stage WST in the +Y
direction or the -Y-direction while controlling the X position of
wafer stage WST, based on the correction data instead of fixing the
measurement value of X interferometer 126 to the predetermined
value on the movement of wafer stage WST in the +Y direction or the
-Y-direction described above, wafer stage WST can be made to move
precisely in the Y-axis direction. In this manner, the same
correction information of the grating pitch of the Y scale and the
correction information of the deformation (warp) of grid lines 37
can be obtained as in the description above. Incidentally, the
measurement data acquired with the plurality of X heads 66
described above is a plurality of data at different location
references of reflection surface 17b, and because X heads 66
measure deformation (warp) of the same grid line 37, there is a
collateral effect of the curve correction residual of the
reflection surface being averaged and approaching its true value
(in other words, by averaging the measurement data (curve
information of grid line 37) acquired by the plurality of X heads,
the effect of the curve residual can be weakened) by the averaging
or the like described above.
[0310] Next, acquisition operations of correction information of
deformation (curve of the grid lines) of the grid lines of the Y
scale and correction information of the grating pitch of the X
scale will be described. In this case, to simplify the description,
reflection surface 17a is to be an ideal plane. In this case, a
processing as in the case of the correction described above, but
with the X-axis direction and the Y-axis direction interchanged,
should be performed.
[0311] More specifically, at a speed low enough so that the
short-term variation of the measurement values of X interferometer
126 can be ignored and also in a state where the measurement value
of Y interferometer 16 is fixed to a predetermined value, main
controller 20 moves wafer stage WST based on the measurement values
of Y interferometer 16, and Z interferometers 43A and 43B, for
example, in at least one direction of the +X direction and the
-X-direction with in the effective stroke range mentioned earlier,
in a state where the pitching amount, the rolling amount, and the
yawing amount are all maintained at zero. During this movement,
while correcting the measurement values of X linear encoders 70B
and of 70D using the function z=g.sub.1(x) and function
z=g.sub.2(x) described above, respectively, main controller 20
takes in the measurement values after the correction and the
measurement values of X interferometer 126 at a predetermined
sampling interval, and based on each measurement value that has
been taken in, obtains a relation between the measurement values of
X linear encoders 70B and 70D (output of encoder 70B--the
measurement values corresponding to function g.sub.1(x), output of
encoder 70D--the measurement values corresponding to function
g.sub.2(x)) and the measurement values of X interferometer 126.
More specifically, in the manner described above, main controller
20 obtains a grating pitch (the distance between adjacent grid
lines) of X scales 39X.sub.1 and 39X.sub.2 which are sequentially
placed opposing head units 62B and 62D with the movement of wafer
stage WST and the correction information of the grating pitch. As
the correction information of the grating pitch, for example, in
the case a horizontal axis shows the measurement values of the
interferometer and a vertical axis shows the measurement values
(the measurement values whose errors due to the unevenness of the
scale surface has been corrected) of the encoder, a map which shows
the relation between the two using a curve can be obtained. Because
the measurement values of X interferometer 126 in this case are
obtained when wafer stage WST was scanned at an extremely low speed
as was previously described, the measurement values hardly include
any short-term variation errors due to air fluctuation, as well as
long-term variation errors, and it can be said that the measurement
values are accurate values in which the errors can be ignored.
[0312] Further, during the movement of wafer stage WST described
above, by statistically processing the measurement values (the
measurement values of Y linear encoders 70A and 70C) obtained from
a plurality of Y heads 64 of head units 62A and 62C placed
sequentially opposing Y scales 39Y.sub.1 and 39Y.sub.2 with the
movement, such as, for example, averaging (or performing weighted
averaging), main controller 20 also obtains correction information
of the deformation (warp) of grid lines 38 which sequentially face
the plurality of Y heads 64. This is because in the case reflection
surface 17a is an ideal plane, the same blurring pattern should
appear repeatedly in the process when wafer stage WST is sent in
the +X direction or the -X-direction, therefore, if averaging or
the like is performed on the measurement data acquired with the
plurality of Y heads 64, it becomes possible to precisely obtain
correction information of the deformation (warp) of grid lines 38
which sequentially face the plurality of Y head 64.
[0313] Incidentally, in a normal case where reflection surface 17a
is not an ideal plane, by measuring the unevenness (warp) of the
reflection surface and obtaining the correction data of the curve
in advance and performing movement of wafer stage WST in the +X
direction or the -X-direction while controlling the Y position of
wafer stage WST, based on the correction data instead of fixing the
measurement value of Y interferometer 16 to the predetermined value
on the movement of wafer stage WST in the +X direction or the
-X-direction described above, wafer stage WST can be made to move
precisely in the X-axis direction. In this manner, the same
correction information of the grating pitch of the X scale and the
correction information of the deformation (warp) of grid lines 38
can be obtained as in the description above.
[0314] As is described above, main controller 20 obtains correction
information on grating pitch of the Y scales and correction
information on deformation (warp) of grating lines 37, and
correction information on grating pitch of the X scales and
correction information on deformation (warp) of grating lines 38 at
each predetermined timing, for example, with respect to each lot,
or the like.
[0315] And, during processing of the lot, main controller 20
performs movement control of wafer stage WST in the Y-axis
direction, using Y scales 39Y.sub.1 and 39Y.sub.2 and head units
62A and 62C, or more specifically, using Y linear encoders 70A and
70C, while correcting the measurement values obtained from head
units 62A and 62C (more specifically, the measurement values of
encoders 70A and 70C), based on correction information of the
grating pitch and correction information of the deformation (warp)
of grid line 38 referred to above, stage position induced error
correction information corresponding to the Z position of wafer
stage WST measured by interferometer system 118, pitching amount
.DELTA..theta.x, and yawing amount .DELTA..theta.z, and correction
information of the Abbe error that corresponds to pitching amount
.DELTA..theta.x of wafer stage WST caused by the Abbe offset
quantity of the surface of Y scales 39Y.sub.1 and 39Y.sub.2. By
this operation, it becomes possible for main controller 20 to
perform movement control of wafer stage WST in the Y-axis direction
with good precision using Y linear encoders 70A and 70C, without
being affected by temporal change of the grating pitch of the Y
scale and the warp of each grating (line) that make up the Y scale,
without being affected by the change of position of wafer stage WST
in the direction besides the measurement direction (relative motion
between the head and the scale in the direction besides the
measurement direction), and without being affected by the Abbe
error.
[0316] Further, during processing of the lot, main controller 20
performs movement control of wafer stage WST in the X-axis
direction, using X scales 39X.sub.1 and 39X.sub.2 and head units
62B and 62D, or more specifically, using X linear encoders 70B and
70D, while correcting the measurement values obtained from head
units 62B and 62D (more specifically, the measurement values of
encoders 70B and 70D), based on correction information of the
grating pitch and correction information of the deformation (warp)
of grid line 37 referred to above, stage position induced error
correction information corresponding to the Z position of wafer
stage WST measured by interferometer system 118, rolling amount
.theta.y, and yawing amount .theta.z, and correction information of
the Abbe error that corresponds to rolling amount .DELTA..theta.y
of wafer stage WST caused by the Abbe offset quantity of the
surface of X scales 39X.sub.1 and 39X.sub.2. By this operation, it
becomes possible for main controller 20 to perform movement control
of wafer stage WST in the X-axis direction with good precision
using X linear encoders 70B and 70D, without being affected by
temporal change of the grating pitch of the X scale and the warp of
each grating (line) that make up the X scale, without being
affected by the change of position of wafer stage WST in the
direction besides the measurement direction (relative motion
between the head and the scale in the direction besides the
measurement direction), and without being affected by the Abbe
error.
[0317] Incidentally, in the description above, the case has been
described where the correction information of the grating pitch and
the grid line warp was acquired for both the Y scale and the X
scale, however, the present invention is not limited to this, and
the correction information of the grating pitch and the grid line
warp can be acquired only for either the Y scale or the X scale, or
the correction information of only either the grating pitch or the
grid line warp can be acquired for both the Y scale and the X
scale. For example, in the case where only the acquisition of the
correction information of the warp of grid line 37 of the X scale
is performed, wafer stage WST can be moved in the Y-axis direction
based on the measurement values of Y linear encoders 70A and 70C,
without necessarily using Y interferometer 16. Similarly, in the
case where only the acquisition of the correction information of
the warp of grid line 38 of the Y scale is performed, wafer stage
WST can be moved in the X-axis direction based on the measurement
values of X linear encoders 70B and 70D, without necessarily using
X interferometer 126. Further, either one of the stage position
induced error previously described or the measurement error
(hereinafter also referred to as a scale induced error) of the
encoder which occurs due to the scale (for example, degree of
flatness of the grating surface (surface smoothness) and/or grating
formation error (including pitch error, grid line warp and the
like) can be compensated.
[0318] Now, on actual exposure, wafer stage WST is driven by main
controller 20 via stage drive system 124 at a speed in which the
short-term variation of the measurement values due to air
fluctuation on the optical path of the beam of the interferometer
cannot be ignored. Accordingly, it becomes important to perform
position control of wafer stage WST based on the measurement values
of the encoder system. For example, when wafer stage WST is scanned
in the Y-axis direction during exposure, main controller 20 drives
stage drive system 124 based on the measurement values of a pair of
Y heads 64 (a Y encoder) which faces Y scales 39Y.sub.1 and
39Y.sub.2, respectively. In doing so, in order to move wafer stage
WST accurately in Y-axis direction via wafer stage drive system 124
based on the measurement values of the pair of Y heads 64 (the Y
encoder), it is necessary to make sure that the measurement error
caused by the measurement delay that accompanies each detection
signal (a photoelectric conversion signal by the light receiving
element) of the pair of Y heads 64 propagating through the cable
does not affect the position control of wafer stage WST. Further,
for example, on the stepping operation or the like between shots of
wafer stage WST performed between exposure of a shot area on wafer
W and exposure of the adjacent shot area, main controller 20 also
has to control the position of wafer stage WST in the X-axis
direction, based on the measurement values of a pair of X heads 66
(an X encoder) which face X scales 39X.sub.1 and 39X.sub.2,
respectively. In this case, it is necessary to make sure that the
measurement error caused by the measurement delay that accompanies
each detection signal (a photoelectric conversion signal by the
light receiving element) of the pair of X heads 66 propagating
through the cable does not affect the position control of wafer
stage WST. Further, in order to expose all the shot areas on wafer
W, a linkage operation between a plurality of encoders is
essential, which will be described later in the description.
Accordingly, it becomes necessary to obtain the information of the
delay time that accompanies the detection signals (photoelectric
conversion signals by the light receiving element) of all the Y
heads 64 and X heads 66 in the encoder system and the pair of Y
heads 64y.sub.1 and 64y.sub.2 propagating through the cable in
advance.
[0319] On the other hand, in addition to the encoder system,
exposure apparatus 100 of the embodiment can also measure
positional information of wafer stage WST in the XY plane by
interferometer system 118. More specifically, in exposure apparatus
100, simultaneous measurement of positional information of wafer
stage WST in the Y-axis direction using each Y head of the encoder
system and Y interferometer 16 and simultaneous measurement of
positional information of positional information of wafer stage WST
in the X-axis direction using each X head of the encoder system and
X interferometer 126 are possible.
[0320] Therefore, as in the following procedure, main controller 20
acquires the information of the delay time that accompanies the
detection signals (photoelectric conversion signals by the light
receiving element) of all the Y heads 64 and X heads 66 in the
encoder system and the pair of Y heads 64y.sub.1 and 64y.sub.2
propagating through the cable, for example, during the start-up
period of the apparatus.
[0321] First of all, main controller 20 moves wafer stage WST to
the position so that one head of Y heads 64 in each head unit 62A
and 62C faces Y scales 39Y.sub.1 and 39Y.sub.2, respectively.
[0322] Next, main controller 20 drives wafer stage WST at a
predetermined speed, such as, for example, at a speed as in the
scanning exposure, in the +Y direction or the -Y-direction, while
controlling the X position of wafer stage WST based on Y
interferometer 16, X interferometer 126, and the warp correction
data of reflection surface 17b, and also in a state where the
pitching amount, the rolling amount, and the yawing amount are all
maintained at zero, based on the measurement values of Y
interferometer 16 and Z interferometers 43A and 43B. During this
drive, main controller 20 takes in detection signals from the two Y
heads 64 that face Y scales 39Y.sub.1 and 39Y.sub.2, and an output
signal of Y interferometer 16 simultaneously and at a predetermined
sampling interval, in a storage unit, such as, for example, memory
34.
[0323] As a result of this, for example, an output signal C1 of Y
interferometer 16 and a detection signal C2 of each Y head 64 both
expressed in a sine curve are obtained, as shown in FIG. 20. In
FIG. 20, the horizontal axis shows time t, and the vertical axis
shows signal intensity I. Incidentally, FIG. 20 shows both signals
after having normalized at least one of the signals so that the
peak value and the bottom value of both signals C1 and C2 become
the same value.
[0324] Then, main controller 20 obtains intersecting points Q1 and
Q2 of a straight line parallel to the vertical axis shown in FIG.
20 and both signals C1 and C2, obtains distance (difference in
intensity) .DELTA.I of points Q1 and Q2, and then multiplies a
predetermined coefficient .gamma. to intensity difference .DELTA.I
and obtains a delay time .delta. of each Y head 64 that accompanies
signal C2 propagating through the cable, with signal C1 serving as
a reference. In this case, coefficient .gamma. is a coefficient for
converting difference .DELTA.I of intensity obtained by experiment
or the like in advance into delay time .delta..
[0325] In this case, as a matter of course, main controller 20
obtains delay time .delta. for each of the two Y heads 64 that
respectively oppose Y scales 39Y.sub.1 and 39Y.sub.2.
[0326] Next, main controller 20 moves wafer stage WST in the
-X-direction (or the +X direction) only by a distance to the
adjacent Y head, and in a procedure similar to the description
above, main controller 20 obtains delay time .delta. for each of
the two Y heads 64 that respectively oppose Y scales 39Y.sub.1 and
39Y.sub.2. Hereinafter, main controller 20 repeats the same
procedure as in the description above, and obtains delay time
.delta. of all the Y heads 64, and Y heads 64y.sub.1 and 64y.sub.2.
Incidentally, in the description above, delay time .delta. was
obtained at a time with two Y heads as a set, however, the present
invention is not limited to this, and delay time .delta. can be
obtained for each Y head in the same procedure as in the
description above.
[0327] Further, in the case of obtaining information of the delay
time that accompanies the detection signals (photoelectric
conversion signals by the light receiving element) of each X head
66 in the encoder system propagating through the cable, main
controller 20 performs a processing in which the X-axis direction
and the Y-axis direction are interchanged in the case of the
correction described above. Incidentally, details on this
processing will be omitted. In the manner described above, main
controller 20 obtains the information of delay time that
accompanies the propagation of the detection signals of each Y head
through the cable which uses the measurement values of Y
interferometer 16 as a reference, and the information of delay time
that accompanies the propagation of the detection signals of each X
head through the cable which uses the measurement values of X
interferometer 126 as a reference, respectively, and stores the
information in memory 34.
[0328] Next, an example of a correction method of a measurement
error in an encoder caused by a measurement delay that accompanies
the detection signals of each head propagating through the cable is
described, referring to FIG. 21. FIG. 21 shows a temporal change
curve y=y(t) that indicates an example of a temporal change of a
position in the Y-axis direction of wafer stage WST which is
decelerating at a predetermined acceleration (deceleration) from a
predetermined speed v.sub.0, and an approximation straight line
y=y.sub.cal(t), which is used to correct the measurement error. In
this case, temporal change curve y=y(t) is a curve (a curve which
is a least squares approximation of the measurement values of Y
interferometer 16 obtained at a predetermined measurement sampling
interval) showing a change of position of wafer stage WST in the
Y-axis direction measured by a measurement unit, Y interferometer
16 in this case, which serves as a reference for delay time .delta.
that accompanies the propagation of the detection signals of each Y
head through the cable. Approximation straight line y=y.sub.cal(t)
is a straight line that joins together point S1 and point S2 on
temporal change curve y=y(t). When the current time is expressed as
t, point S1 is a point corresponding to the latest measurement
values of the Y encoder (Y head) that main controller 20 acquires
at current time t, located on temporal change curve y=y(t) at a
time (t-.delta.), which is earlier than the current time by only
delay time .delta.. Further, point S2 is a point corresponding to
the measurement values of the Y encoder (Y head) that main
controller 20 has acquired at time (t-.DELTA.t), which is earlier
than current time t by one control sampling interval .DELTA.t
(.DELTA.t, for example, is 96 .mu.s), or more specifically, a point
corresponding to the measurement values of the previous Y encoder
(Y head), located on temporal change curve y=y(t) at time
(t-.DELTA.t-.delta.). Accordingly, main controller 20 can compute
approximation straight line y=y.sub.cal(t), based on the latest
measurement values of the Y encoder (Y head) which main controller
20 acquires at current time t and the measurement values of the
previous Y encoder (Y head).
[0329] In this case, approximation straight line y=y.sub.cal(t) can
be expressed as in formula (32) below. y = y cal .function. ( t ) =
y .function. ( t - .delta. ) + y .function. ( t - .delta. ) - y
.function. ( t - .delta. - .DELTA. .times. .times. t ) .DELTA.
.times. .times. t .times. .delta. ( 32 ) ##EQU2##
[0330] Further, because temporal change curve y=y(t) is a curve
that shows an example of a position change of wafer stage WST in
the Y-axis direction decelerating at a predetermined acceleration
(deceleration) a from a predetermined speed v.sub.0, it can be
expressed, as an example, as in formula (33) below.
y=y(t)=v.sub.0t-1/2at.sup.2 (33)
[0331] Accordingly, the correction error shown in FIG. 21, or more
specifically, a difference (y.sub.cal(t)-y(t)) between y=y(t) and
y=y.sub.cal(t) at current time t can be expressed as in formula
(34) below. y cal .function. ( t ) - y .function. ( t ) = a .times.
.times. .delta. .function. ( .delta. + .DELTA. .times. .times. t )
2 .apprxeq. a .times. .times. .delta..DELTA. .times. .times. t 2 (
34 ) ##EQU3##
[0332] In the case of deceleration (acceleration) a=20 [m/s.sup.2],
delay time .delta.=100 [ns], and one control sampling interval
.DELTA.t=96 [.mu.sec], the correction error results to be 0.1 nm,
which is a quantity that will not cause any problems for the time
being. More specifically, if delay time .delta. of each Y head is
precisely obtained, the measurement errors of the encoder due to
the measurement delay (delay time) can be corrected software wise
by the method described above.
[0333] More specifically, by locating points S1 and S2 on temporal
change curve y=y(t) at time t and time (t-.DELTA.t), computing the
approximation straight line y=y.sub.cal(t) that passes through
points S1 and S2, and obtaining a y-coordinate value of a point on
approximation straight line y=y.sub.cal(t) at time t, based on the
measurement values of each Y head of the encoder system and the
measurement values which are one control sampling interval earlier,
main controller 20 can correct the measurement errors by the
measurement delay that accompanies the detection signals of each Y
head propagating through the cable, and can correct the influence
of the measurement delay of each Y head of the encoder system.
[0334] Further, main controller 20 can also correct the influence
of the measurement delaying (delay time .delta.) on each X head 66
of the encoder system in a manner similar to the description
above.
[0335] As other generation factors of measurement errors,
temperature fluctuation (air fluctuation) of the atmosphere on the
beam optical path can be considered. Phase difference .phi. between
the two return beams LB.sub.1 and LB.sub.2 depend on optical path
difference .DELTA.L of the two beams, according to the first term
on the right-hand side of formula (16). Suppose that wavelength
.lamda.0 of the light changes to .lamda.+.DELTA..lamda. by air
fluctuation. By minute change .DELTA..lamda. of this wavelength,
the phase difference changes by minute amount
.DELTA..phi.=2.pi..DELTA.L.DELTA..lamda./.lamda..sup.2. In this
case, when the wavelength of light .lamda.=1 .mu.m and minute
change .DELTA..lamda.=1 nm, then phase change .DELTA..phi.=2.pi.
with respect to optical path difference .DELTA.L=1 mm. This phase
change is equivalent to 1 when it is converted into a count value
of the encoder. Further, when it is converted into displacement, it
is equivalent to p/2 (n.sub.b-n.sub.a). Accordingly, if
n.sub.b=-n.sub.a=1, in the case of p=1 .mu.m, a measurement error
of 0.25 .mu.m will occur.
[0336] In the actual encoder, because the optical path length of
the two beams which are made to interfere is extremely short,
wavelength change .DELTA..lamda. due to the air fluctuation is
extremely small. Furthermore, optical path difference .DELTA.L is
designed to be approximately 0, in an ideal state where the optical
axis is orthogonal to the reflection surface. Therefore, the
measurement errors due to the air fluctuation can be substantially
ignored. The fluctuation is remarkably small when compared with the
interferometer, and is superior in short-term stability.
[0337] In exposure apparatus 100 of the embodiment, for example, at
the time of start-up of the apparatus, main controller 20 can
perform a series of calibration processing described earlier, or
more specifically, A. acquisition processing of the stage position
induced error correction information, B. head position calibration
processing, C. calibration processing to obtain Abbe offset
quantity, D. processing for obtaining the shape (unevenness) of the
surface of the scale, E. acquisition processing of correction
information of the grating pitch of the scale and the correction
information of the grating deformation, and F. acquisition
processing of the correction information of the measurement errors
due to the measurement delay, a plurality of times, or repeated in
the order previously described or in a different order. On this
repetition, the various calibrations from the second time onward
can be performed, using the various information that has been
measured until the previous time.
[0338] For example, on the acquisition processing of the stage
position induced error correction information described above, for
example, the pitching (or the rolling) of wafer table WTB (wafer
stage WST) has to be adjusted by making wafer stage WST perform a
.theta.x rotation (or a .theta.y rotation) around a point where Z
position z=0 serves as a center, and as the premise, the Abbe
offset quantity previously described of Y scales 39Y.sub.1 and
39Y.sub.2 (or, X scales 39X.sub.1 and 39X.sub.2) will have to be
known. Therefore, in the first acquisition process of the stage
position induced error correction information, A. acquisition
processing of the stage position induced error correction
information can be performed in the procedure described above,
using design values of Y scales 39Y.sub.1 and 39Y.sub.2 (or, X
scale 39X.sub.1 and 39X.sub.2) as the Abbe offset quantity, and
then, after performing B. head position calibration processing and
C. calibration processing to obtain Abbe offset quantity, D.
processing for obtaining the shape (unevenness) of the surface of
the scale and E. acquisition processing of correction information
of the grating pitch of the scale and the correction information of
the grating deformation can be performed, and then, when the second
A. acquisition process of the stage position induced error
correction information is performed, wafer stage WST can be made to
perform a ex rotation (or a .theta.y rotation) around a point where
Z position z=0 serves as a center, based on the Abbe offset
quantity which is actually obtained in the manner described above,
and the stage position induced error correction information can be
acquired in the procedure previously described. By the processing
described above, it becomes possible to acquire the stage position
induced error correction information that is not affected by the
errors to the design values of the Abbe offset quantity in the
second measurement.
[0339] Next, a switching process of the encoder used for position
control of wafer stage WST in the XY plane that is executed during
the actual processing or the like, or more specifically, a linkage
process between a plurality of encoders will be described, after
processing such as the acquisition of the stage position induced
error correction information, unevenness measurement of the surface
of the scale, the acquisition of correction information of the
grating pitch of the scale and the correction information of the
grating deformation, and the acquisition of the Abbe offset
quantity of the scale surface and the like are performed in
advance.
[0340] In this case, first of all, prior to describing the linkage
process of the plurality of encoders, a concrete method of
converting the corrected measurement values of the encoder into the
position of wafer stage WST, which is the premise, will be
described, using FIGS. 22A and 22B. In this case, in order to
simplify the description, the degrees of freedom of wafer stage WST
is to be three degrees of freedom (X, Y, and .theta.z).
[0341] FIG. 22A shows a reference state where wafer stage WST is at
the origin of coordinates (X, Y, .theta.z)=(0,0,0). From this
reference state, wafer stage WST is driven within a range where
encoders (Y heads) Enc1 and Enc2 and encoder (X head) Enc3 do not
move away from the scanning areas of their opposing scales
39Y.sub.1 and 39Y.sub.2 and 39X.sub.1. The state where wafer stage
WST is moved to position (X, Y, .theta.z) in the manner described
above is shown in FIG. 22B.
[0342] Here, supposing that the position coordinates (X, Y) of the
measurement points of encoders Enc1, Enc2, and Enc3 on the XY
coordinate system are (p.sub.1, q.sub.1), (p.sub.2, q.sub.2), and
(p.sub.3, q.sub.3), respectively. Then, as X coordinate values
p.sub.1 and p.sub.2 of encoders Enc1 and Enc2 and Y coordinate
values q.sub.3 of Enc3, the positional information which was
acquired in the case of the calibration of the head position
described earlier is read from memory 34 and is used, whereas as Y
coordinate values q.sub.1 and q.sub.2 of encoders Enc1 and Enc2 and
X coordinate values p.sub.3 of Enc3, the positional information of
design values is read from memory 34 and is used.
[0343] The X head and the Y head respectively measure the relative
distance from central axes LL and LW of wafer stage WST.
Accordingly, measurement values C.sub.X and C.sub.Y of the X head
and the Y head can be expressed, respectively, as in the following
formulas (35a) and (35b). C.sub.X=r'*ex' (35a) C.sub.Y=r'*ey'
(35b)
[0344] In this case, ex' and ey' are X' and Y' unit vectors in a
relative coordinate system (X', Y', .theta.z') set on wafer stage
WST, and have a relation as in the following Y formula (36) with
.theta.x and .theta.y, which are X, Y unit vectors in a reference
coordinate system (X, Y, .theta.z). ( ex ' ey ' ) = ( cos .times.
.times. .theta. z sin .times. .times. .theta. z - sin .times.
.times. .theta. z cos .times. .times. .theta. z ) .times. ( ex ey )
( 36 ) ##EQU4##
[0345] Further, r' is a position vector of the encoder in the
relative coordinate system, and r' is given r'=r-(O'-O), using
position vector r=(p, q) in the reference coordinate system.
Accordingly, formulas (35a) and (35b) can be rewritten as in the
next formulas (37a) and (37b). C.sub.X=(p-X)cos .theta.z+(q-Y)sin
.theta.z (37a) C.sub.Y=-(p-X)sin .theta.z+(q-Y)cos .theta.z
(37b)
[0346] Accordingly, as shown in FIG. 22B, when wafer stage WST is
located at the coordinate (X, Y, .theta.z), the measurement values
of three encoders can be expressed theoretically in the next
formulas (38a) to (38c) (also referred to as a relationship of the
affine transformation). C.sub.1=-(p.sub.1-X)sin
.theta.z+(q.sub.1-Y)cos .theta.z (38a) C.sub.2=-(p.sub.2-X)sin
.theta.z+(q.sub.2-Y)cos .theta.z (38b) C.sub.3=(p.sub.3-X)cos
.theta.z+(q.sub.3-Y)sin .theta.z (38c)
[0347] Incidentally, in the reference state of FIG. 22A, according
to simultaneous formulas (38a) to (38c), C.sub.1=q.sub.1,
C.sub.2=q.sub.2, and C.sub.3=p.sub.3. Accordingly, in the reference
state, if the measurement values of the three encoders Enc1, Enc2,
and Enc3 are initialized to q.sub.1, q.sub.2, and p.sub.3
respectively, then the three encoders will show theoretical values
given by formulas (38a) to (38c) with respect to displacement (X,
Y, .theta.z) of wafer stage WST from then onward.
[0348] In simultaneous formulas (38a) to (38c), three formulas are
given to the three variables (X, Y, .theta.z). Accordingly, if
dependent variables C.sub.1, C.sub.2, and C.sub.3 are given in the
simultaneous formulas (38a) to (38c), variables X, Y, and .theta.z
can be obtained. In this case, when approximation
sin..theta.z.apprxeq..theta.z is applied, or even if an
approximation of a higher order is applied, the formulas can be
solved easily. Accordingly, the position of wafer stage WST (X, Y,
.theta.z) can be computed from measurement values C.sub.1, C.sub.2,
and C.sub.3 of the encoder.
[0349] In exposure apparatus 100 of the embodiment which is
configured in the manner described above, because the placement of
the X scales and Y scales on wafer table WTB and the arrangement of
the X heads and Y heads which were described above were employed,
in the effective stroke range (more specifically, in the
embodiment, the range in which the stage moves for alignment and
exposure operation) of wafer stage WST, at least one X head 66 in
the total of 18 X heads belonging to head units 62B and 62D must
face at least one of X scale 39X.sub.1 and 39X.sub.2, and at least
one Y head 64 each, or Y head 64y.sub.1 and 64y.sub.2 belonging to
head units 62A and 62C, also respectively face Y scales 39Y.sub.1
and 39Y.sub.2, respectively, as illustrated in FIGS. 23A and 23B.
That is, at least one each of the corresponding heads is made to
face at least the three out of the four scales.
[0350] Incidentally, in FIGS. 23A and 23B, the head which faces the
corresponding X scale or Y scale is shown surrounded in a
circle.
[0351] Therefore, in the effective stroke range of wafer stage WST
referred to earlier, by controlling each motor that configures
stage drive system 124, based on at least a total of three
measurement values of the encoders, which are encoders 70A and 70C,
and at least one of encoders 70B and 70D, main controller 20 can
control positional information (including rotation in the .theta.z
direction) of wafer stage WST in the XY plane with high accuracy.
Because the effect of the air fluctuation that the measurement
values of encoder 70A to 70D receive is small enough so that it can
be ignored when compared with an interferometer, the short-term
stability of the measurement affected by the air fluctuation is
remarkably good when compared with the interferometer.
[0352] Further, when wafer stage WST is driven in the X-axis
direction as is shown by an outlined arrow in FIG. 23A, Y heads 64
that measure the position of wafer stage WST in the Y-axis
direction are sequentially switched, as is indicated by arrows
e.sub.1 and e.sub.2 in the drawing, to the adjacent Y heads 64. For
example, the heads are switched from Y heads 64 surrounded by a
solid circle to Y heads 64 that are surrounded by a dotted circle.
Therefore, before or after this switching, linkage process of the
measurement values which will be described later on is
performed.
[0353] Further, when wafer stage WST is driven in the Y-axis
direction as is shown by an outlined arrow in FIG. 23B, X heads 66
that measure the position of wafer stage WST in the X-axis
direction are sequentially switched to the adjacent X heads 66. For
example, the heads are switched from X heads 66 surrounded by a
solid circle to X heads 66 that are surrounded by a dotted circle.
Therefore, before or after this switching, linkage process of the
measurement values is performed.
[0354] The switching procedure of will now be described here, based
on FIGS. 24A to 24E, with the switching from Y heads 64.sub.3 to
64.sub.4 shown by arrow e.sub.1 in FIG. 23A serving as an
example.
[0355] In FIG. 24A, a state before the switching is shown. In this
state, Y head 64.sub.3 facing the scanning area (the area where the
diffraction grating is arranged) on Y scale 39Y.sub.2 is operating,
and Y head 64.sub.4 which has moved away from the scanning area is
suspended. The operating head is indicated here, using a solid
black circle, and the suspended head is indicated by an outlined
circle. Then, main controller 20 monitors the measurement values of
Y head 64.sub.3 which is operating. The head whose measurement
values are monitored, here, is shown in a double rectangular
frame.
[0356] Then, wafer stage WST moves in the +X direction.
Accordingly, Y scale 39Y.sub.2 is displaced to the right. In this
case, in the embodiment, as is previously described, the distance
between the two adjacent Y heads is set smaller than the effective
width (width of the scanning area) of Y scale 39Y.sub.2 in the
X-axis direction. Accordingly, as shown in FIG. 24B, a state occurs
where Y heads 64.sub.3 and 64.sub.4 face the scanning area of Y
scale 39Y.sub.2. Therefore, main controller 20 makes sure that Y
head 64.sub.4, which is suspended, has faced the scanning area
along with Y head 64.sub.3 that is operating, and then activates
the suspended Y head 64.sub.4. However, main controller 20 does not
yet start monitoring the measurement values at this point.
[0357] Next, as shown in FIG. 24C, while Y head 64.sub.3, which
will be suspended later faces the scanning area, main controller 20
computes a reference position of Y head 64.sub.4, which has been
restored, from the measurement values of the active encoder heads
including Y head 64.sub.3. Then, main controller 20 sets the
reference position as an initial value of the measurement value of
Y head 64.sub.4. Incidentally, details on the computation of the
reference position and the setting of the initial value will be
described later in the description.
[0358] Main controller 20 switches the encoder head whose
measurement values are monitored from Y head 64.sub.3 to Y head
64.sub.4 simultaneously with the setting of the initial value
above. After the switching has been completed, main controller 20
suspends the operation of Y head 64.sub.3 before it moves off the
scanning area as shown in FIG. 24D. By the operation described
above, all the operations of switching the encoder heads are
completed, and hereinafter, as shown in FIG. 24E, the measurement
values of Y head 64.sub.4 are monitored by main controller 20.
[0359] In the embodiment, the distance between adjacent Y heads 64
that head units 62A and 62C have is, for example, 70 mm (with some
exceptions), and is set smaller than the effective width (e.g. 76
mm) of the scanning area of Y scales 39Y.sub.1 and 39Y.sub.2 in the
X-axis direction. Further, for example, the distance between
adjacent X heads 66 that head units 62B and 62D have is, for
example, 70 mm (with some exceptions), and is set smaller than the
effective width (e.g. 76 mm) of the scanning area of X scales
39X.sub.1 and 39X.sub.2 in the Y-axis direction. Accordingly, the
switching operation of Y heads 64 and X heads 66 can be performed
smoothly as in the description above.
[0360] Incidentally, in the embodiment, the range in which both
adjacent heads face the scale, or more specifically, the moving
distance of wafer stage WST from a state shown in FIG. 24B to a
state shown in FIG. 24D, for example, is 6 mm. And at the center,
or more specifically, when wafer stage WST is located at the
position shown in FIG. 24C, the head that monitors the measurement
values is switched. This switching operation is completed by the
time the head which is to be suspended moves off the scanning area,
or more specifically, while wafer stage WST moves in an area by a
distance of 3 mm during the state shown in FIG. 24C until the state
shown in FIG. 24D. For example, in the case the movement speed of
the stage is 1 m/sec, then the switching operation of the head is
to be completed within 3 msec.
[0361] Next, the linkage process when the encoder head is switched,
or more specifically, the initial setting of the measurement values
will be described, focusing mainly on the operation of main
controller 20.
[0362] In the embodiment, as is previously described, three
encoders (the X heads and the Y heads) constantly observe wafer
stage WST within the effective stroke range of wafer stage WST, and
when the switching process of the encoder is performed, four
encoders will be made to observe wafer stage WST, as shown in FIG.
25.
[0363] At the moment when the switching process (linkage) of the
encoder used for the position control of wafer stage WST within the
XY plane is to be performed, encoders Enc1, Enc2, Enc3 and Enc4 are
positioned above scales 39Y.sub.1, 39Y.sub.2, 39X.sub.1, and
39X.sub.2, respectively, as shown in FIG. 25. When having a look at
FIG. 25, it looks as though the encoder is going to be switched
from encoder Enc1 to encoder Enc4, however, as is obvious from the
fact that the measurement direction is different in encoder Enc1
and encoder Enc4, it does not have any meaning even if the
measurement values (count values) of encoder Enc1 are given without
any changes as the initial value of the measurement values of
encoder Enc4.
[0364] Therefore, in the embodiment, main controller 20 switches
from measurement/servo by the three encoders Enc1, Enc2 and Enc3 to
measurement/servo by the three encoders Enc2, Enc3 and Enc4. More
specifically, as it can be seen from FIG. 25, this method is
different from the concept of a normal encoder linkage, and in this
method the linkage is made not from one head to another head, but
from a combination of three heads (an encoder) to a combination of
another three heads (an encoder). Incidentally, in the three heads
and another three heads, the different head is not limited to one.
Further, in FIG. 25, encoder Enc3 was switched to encoder Enc4,
however, instead of encoder Enc4, for example, the encoder can be
switched, for example, to the encoder adjacent to encoder Enc3.
[0365] First of all, main controller 20 solves the simultaneous
formulas (38a) to (38c) based on the measurement values C.sub.1,
C.sub.2, and C.sub.3 of encoders Enc1, Enc2, and Enc3, and computes
positional information (X, Y, .theta.z) of wafer stage WST within
the XY plane.
[0366] Next, main controller 20 substitutes X and .theta.z computed
above into the affine transformation of the next formula (39), and
determines the initial value of the measurement values of encoder
(X head) Enc4. C.sub.4=(p.sub.4-X)cos .theta.z+(q.sub.4-Y)sin
.theta.z (39)
[0367] In formula (39) above, p.sub.4 and q.sub.4 are the
X-coordinate value and the Y-coordinate value at the measurement
point of encoder Enc4. As Y coordinate value q.sub.4 of encoder
Enc4, the positional information which was acquired on calibration
of the head position previously described is read from memory 34
and is used, while as X-coordinate value p.sub.4 of encoder Enc4,
the design position information is read from memory 34 and is
used.
[0368] By giving initial value C.sub.4 as an initial value of
encoder Enc4, linkage will be completed without any contradiction,
having maintained the position (X, Y, .theta.z) of wafer stage WST
in directions of three degree of freedom. From then onward, the
following simultaneous formulas (38b) to (38d) are solved, using
the measurement values C.sub.2, C.sub.3, and C.sub.4 of encoders
Enc2, Enc3, and Enc4 which are used after the switching, and a
position coordinate (X, Y, .theta.z) of wafer stage WST is
computed. C.sub.2=-(p.sub.2-X)sin .theta.z+(q.sub.2-Y)cos .theta.z
(38b) C.sub.3=(p.sub.3-X)cos .theta.z+(q.sub.3-Y)sin .theta.z (38c)
C.sub.4=(p.sub.4-X)cos .theta.z+(q.sub.4-Y)sin .theta.z (38d)
[0369] Incidentally, in the case the fourth encoder is a Y head,
simultaneous formulas (38b) (38c) (38e) that use the following
theoretical formula (38e) instead of theoretical formula (38d) can
be used. C.sub.4=-(p.sub.4-X)sin .theta.z+(q.sub.4-Y)cos .theta.z
(38e)
[0370] However, because measurement value C.sub.4 computed above is
a measurement value of a corrected encoder whose measurement errors
of the various encoders previously described have been corrected,
main controller 20 performs inverse correction on measurement value
C.sub.4 and computes a raw value C.sub.4' which is the value before
correction, and determines raw value C.sub.4' as the initial value
of the measurement value of encoder Enc4, using the stage position
induced error correction information, the correction information of
the grating pitch of the scale (and the correction information of
the grating deformation), the Abbe offset quantity (the Abbe error
correction information) and the like previously described.
[0371] In this case, the inverse correction refers to the
processing of computing measurement value C.sub.4' based on
measurement value C.sub.4, under the hypothesis that the
measurement value of the encoder after correcting measurement value
C.sub.4' is C.sub.4, when measurement value C.sub.4', on which no
correction has been performed, is corrected using the stage
position induced error correction information, the scale induced
error correction information (e.g., correction information of the
grating pitch of the scale (and correction information of the
grating deformation), and the Abbe offset quantity (Abbe error
correction information) and the like.
[0372] Now, the position control interval (control sampling
interval) of wafer stage WST, as an example, is 96 [.mu.sec],
however, the measurement interval (measurement sampling interval)
of an interferometer or an encoder has to be at a much higher
speed. The reason why the sampling of the interferometer and the
encoder has to be performed at a higher-speed than the control
sampling is because both the interferometer and the encoder count
the intensity change (fringe) of the interference light, and when
the sampling becomes rough, measurement becomes difficult.
[0373] However, with the position servo control system of wafer
stage WST, the system updates the current position of wafer stage
WST at every control sampling interval of 96 [.mu.sec], performs
calculation to set the position to a target position, and outputs
thrust command values and the like. Accordingly, the positional
information of the wafer stage is necessary at every control
sampling interval of 96 [.mu.sec], and the positional information
in between the sampling intervals will not be necessary in the
position control of wafer stage WST. The interferometer and the
encoder merely perform sampling at a high speed so as not to lose
track of the fringe.
[0374] Therefore, in the embodiment, at all times while wafer stage
WST is located in the effective stroke range previously described,
main controller 20 continues to receive the measurement values
(count values) from each encoder (a head) of the encoder system,
regardless of whether or not the encoder watches the scale. And,
main controller 20 performs the switching operation (linkage
operation between the plurality of encoders) previously described,
in synchronization with the timing of the position control of the
wafer stage performed every 96 [.mu.sec]. In such an arrangement,
the switching operation of an electrically high-speed encoder will
not be required, which means that costly hardware to realize such a
high-speed switching operation does not necessarily have to be
arranged. FIG. 26 conceptually shows the timing of position control
of wafer stage WST, the uptake of the count values of the encoder,
and the switching of the encoder, which are performed in the
embodiment. In FIG. 26, reference code CSCK shows a generation
timing of a sampling clock of the position control of wafer stage
WST, and reference code MSCK shows a generation timing of a
measurement sampling clock of the encoder (and the interferometer).
Further, reference code CH typically shows the switching (linkage)
of the encoder.
[0375] Incidentally, main controller 20 performs the correction of
the measurement errors due to delay time .delta. for each head,
each time at the generation timing of the sampling clock of the
position control of the wafer stage, regardless of whether or not
the switching of the encoder is performed. Accordingly, based on
the measurement values of the three encoders whose measurement
errors due to the measurement delay have been corrected, the
position (X, Y, .theta.z) of wafer stage WST is to be
controlled.
[0376] Now, in the description above, the switching that could be
performed from one combination of heads (encoders) to another
combination of heads (encoders), and the timing when the switching
can be performed are to be known, however, they also must be known
in the actual sequence as well. It is also preferable to prepare
the scheduling of the timing to carry out the linkage in
advance.
[0377] Therefore, in the embodiment, main controller 20 prepares
the schedule for the switching (the switching from one combination
of three heads (e.g., Enc1, Enc2, and Enc3) to another combination
of three heads (e.g., Enc4, Enc2, and Enc3), and the timing of the
switch) of the three encoders (heads) which are used for measuring
the positional information of wafer stage WST in directions of
three degrees of freedom (X, Y, .theta.z) within the XY plane,
based on the movement course (target track) of wafer stage WST, and
stores the scheduling result in the storage unit such as memory
34.
[0378] In this case, if a retry (redoing) is not considered, the
contents of the schedule in every shot map (an exposure map)
becomes constant, however, in actual practice, because a retry must
be considered, it is preferable for main controller 20 to
constantly update the schedule slightly ahead while performing the
exposure operation.
[0379] Incidentally, in the embodiment above, because the
description was made related to the principle of the switching
method of the encoder used for position control of wafer stage WST,
expressions such as encoder (head) Enc1, Enc2, Enc3, and Enc4 were
used, however, it goes without saying that head Enc1 and Enc2
indicate either Y head 64 of head units 62A and 62C or a pair of Y
heads 64y.sub.1 and 64y.sub.2, representatively, and heads Enc3 and
Enc4 indicates X head 66 of head unit 62B and 62D,
representatively. Further, for similar reasons, in FIGS. 22A, 22B
and 25, the placement of encoders (heads) Enc1, Enc2, Enc3 and the
like is shown differently from the actual placement (FIG. 3 and the
like).
[0380] <<Generalization of Switching and Linkage
Principle>>
[0381] In the embodiment, in order to measure the position
coordinates of wafer stage WST in directions of three degree of
freedom (X, Y, .theta.z), among the X encoders (heads) and Y
encoders (heads) that constitute encoder systems 70A to 70D, at
least three heads which at least include one X head and at least
two Y heads are constantly used. Therefore, when the head which is
to be used is switched along with the movement of wafer stage WST,
a method of switching from a combination of three heads to another
combination of three heads is employed, so as to continuously link
the measurement results of the stage position before and after the
switching. This method will be referred to as a first method.
[0382] However, when considering the basic principle of the
switching and linkage process from a different point of view, it
can also be viewed as a method of switching one head of the three
heads that are used to another head. This method will be referred
to as a second method. Therefore, the second method will be
described, with the switching and linkage process from Y heads
64.sub.3 to 64.sub.4 shown in FIGS. 24A to 24E, serving as an
example.
[0383] The basic procedure of the switching process is similar to
the procedure described above, and while both the first head
64.sub.3 which will be suspended later and the second head 64.sub.4
which will be newly used face the corresponding scale 39Y.sub.2, as
shown in figure of FIG. 24A or more 24E, main controller 20
executes the restoration of the second head 64.sub.4 and the
setting of the measurement values (linkage process), and the
switching (and suspension of the first head 64.sub.3) of the head
monitoring the measurement value.
[0384] When the measurement value is set (linkage process), main
controller 20 predicts a measurement value C.sub.Y4 of the second
head 64.sub.4 using a measurement value C.sub.Y3 of the first head
64.sub.3. In this case, according to the theoretical formula (37b),
measurement values C.sub.Y3 and C.sub.Y4 of Y heads 64.sub.3 and
64.sub.4 follow formulas (39a) and (39b) below.
C.sub.Y3=-(p.sub.3-X)sin .theta.z+(q.sub.3-Y)cos .theta.z (39a)
C.sub.Y4=-(p.sub.4-X)sin .theta.z+(q.sub.4-Y)cos .theta.z (39b) In
this case, (p.sub.3, q.sub.3) and (p.sub.4, q.sub.4) are the X and
Y setting positions (or to be more precise, the X and Y positions
of the measurement points) of Y heads 64.sub.3 and 64.sub.4.
[0385] To make it more simple, suppose that the Y setting positions
of Y heads 64.sub.3 and 64.sub.4 are equal (q.sub.3=q.sub.4). Under
this supposition, formula (40) below can be obtained by formulas
(39a) and (39b) above. C.sub.Y4=C.sub.Y3+(p.sub.3-p.sub.4)sin
.theta.z (40) Accordingly, by substituting the measurement value of
first head 64.sub.3 which will be suspended later into C.sub.Y3 on
the right-hand side of formula (40) above and obtaining C.sub.Y4 on
the left-hand side, the measurement value of the second head
64.sub.4 which will be newly used can be predicted.
[0386] Predicted value C.sub.Y4 that has been obtained is to be set
as the initial value of the measurement value of the second head
64.sub.4 at a proper timing. After the setting, the first head
64.sub.3 is suspended when it moves off scale 39Y.sub.2, which
completes the switching and linkage process.
[0387] Incidentally, when the measurement value of the second head
64.sub.4 is predicted using formula (40) above, a value of rotation
angle .theta.z, which is obtained from the measurement results of
another head that is active, should be substituted into variable
.theta.z. In this case, another head that is active is not limited
to the first head 64.sub.3 which is subject to switching, but
includes all the heads that provide the measurement results
necessary to obtain rotation angle .theta.z. In this case, because
the first head 64.sub.3 is a head of head unit 62C, rotation angle
.theta.z can be obtained using the first head 64.sub.3, and for
example, one of the heads of head unit 62A that faces Y scale
39Y.sub.1 during the switching. Or, a value of rotation angle
.theta.z, which can be obtained from the measurement results of X
interferometer 126 of interferometer system 118, Y interferometer
16, or Z interferometer 43A and 43B and the like can be substituted
into variable .theta.z.
[0388] Incidentally, the switching and linkage process between Y
heads was explained as an example here, however, the switching and
linkage process between X heads, and further, also the switching
and linkage process between two heads belonging to different head
units such as between the X head and the Y head can also be
explained similarly as the second method.
[0389] Therefore when the principle of the linkage process is
generalized, the measurement value of another head newly used is
predicted so that the results of the position measurement of wafer
stage WST is linked continuously before and after the switching,
and the predicted value is set as the initial value of the
measurement values of the second head. In this case, in order to
predict the measurement values of another head, theoretical
formulas (37a) and (37b) and the measurement values of the active
heads including the head which will be suspended later subject to
the switching will be used as required. However, for the rotation
angle in the .theta.z direction of wafer stage WST which is
necessary on the linkage, a value which is obtained from the
measurement results of interferometer system 118 can be used.
[0390] As is described above, even if it is premised that at least
three heads are constantly used to measure the position of wafer
age WST in directions of three degree of freedom (X, Y, .theta.z)
as in the preceding first method, if focusing on only the two heads
which are direct objects of the switching and linkage process
without referring to the concrete procedure of predicting the
measurement value of another head newly used, the observation on
the second method where one head out of the three heads used is
switched to another head can be realized.
[0391] Incidentally, the description so far was made on the premise
that the position of wafer stage WST in directions of three degrees
of freedom (X, Y, .theta.z) was measured using at least three
heads. However, even in the case of measuring the position of two
or more in directions of m degrees of freedom (the choice of the
degrees of freedom is arbitrary) using at least m heads, it is
obvious that the observation of the second method where one head
out of m heads used is switched to another head can be realized, as
in the description above.
[0392] Next, a description will be made in which under a specific
condition, an observation of a method (to be referred to as a third
method) where a combination of two heads is switched to a
combination of another two heads can be consistently realized.
[0393] In the example above, as shown in FIGS. 24A to 24E,
switching and linkage process between heads 64.sub.3 and 64.sub.4
is executed, while Y heads 64.sub.3 and 64.sub.4 each face the
corresponding Y scale 39Y.sub.2. During this operation, according
to the placement of the scale and the head employed in exposure
apparatus 100 of the embodiment, one Y head (expressed as 64.sub.A)
of head unit 62A faces Y scale 39Y.sub.1 and measures relative
displacement of Y scale 39Y.sub.1 in the Y-axis direction.
Therefore, a switching and linkage process will be considered from
a first combination of Y heads 64.sub.3 and 64.sub.A to a second
combination of Y heads 64.sub.4 and 64.sub.A.
[0394] According to theoretical formula (37b), a measurement value
C.sub.YA of Y head 64.sub.A follows formula (39c) below.
C.sub.YA=-(p.sub.A-X)sin .theta.z+(q.sub.A-Y)cos .theta.z (39c)
[0395] In this case, (p.sub.A, q.sub.A) is the X and Y setting
position (or to be more precise, the X and Y positions of the
measurement point) of Y head 64.sub.A. To make it more simple,
suppose that Y setting position q.sub.A of Y head 64.sub.A is equal
to Y setting positions q.sub.3 and q.sub.4 of Y heads 64.sub.3 and
64.sub.4 (q.sub.A=q.sub.3=q.sub.4).
[0396] When theoretical formulas (39a) and (39c), which measurement
values C.sub.Y3 and C.sub.YA of Y heads 64.sub.3 and 64.sub.A of
the first combination follow, are substituted into theoretical
formula (39b), which measurement value C.sub.Y3 of Y head 64.sub.4
that is newly used follows, formula (41) below is derived.
C.sub.Y4=(1-c)C.sub.Y3-c*C.sub.YA (41)
[0397] However, constant C=(p.sub.3-p.sub.4)/(q.sub.A-q.sub.3).
Accordingly, by substituting the measurement values of Y heads
64.sub.3 and 64.sub.A into C.sub.Y3 and C.sub.YA on the right-hand
side of formula (41) above and obtaining C.sub.Y4 on the left-hand
side, the measurement value of Y head 64.sub.4 newly used can be
predicted.
[0398] Predicted value C.sub.Y4 that has been obtained is to be set
as the initial value of the measurement value of Y head 64.sub.4 at
a proper timing. After the setting, Y head 64.sub.3 is suspended
when it moves off scale 39Y.sub.2, which completes the switching
and linkage process.
[0399] Incidentally, according to the placement of the scale and
the head employed in exposure apparatus 100 of the embodiment, at
least one X head 66 faces X scale 39X.sub.1 or 39X.sub.2 and
measures the relative displacement in the X-axis direction. Then,
according to the measurement results of the three heads, which are
one X head 66 two Y heads 64.sub.3 and 64.sub.A, the position of
wafer stage WST in directions of three degrees of freedom (X, Y,
.theta.z) is computed. However, in the example of the switching and
linkage process described above, X head 66 merely plays the role of
a spectator, and the observation of the third method where a
combination of two heads, Y heads 64.sub.3 and 64.sub.A is switched
to a combination of another two heads, Y head 64.sub.4 and
64.sub.A, is consistently realized.
[0400] Accordingly, under the premise that the use of three heads
is indispensable to measure the position of wafer stage WST in
directions of three degrees of freedom (X, Y, .theta.z), the first
method was proposed as a general method of the switching and
linkage process that could be applied to every case, regardless of
the placement of the scale and the head employed in exposure
apparatus 100 of the embodiment. And, based on the concrete
placement of the scale and the head employed in exposure apparatus
100 of the embodiment and the concrete procedure of the linkage
process, the observation of the third method could be realized
under a particular condition.
[0401] Incidentally, in addition to the first method, in the
switching and linkage process of the encoder head by the second and
third methods described above, the measurement value of another
head to be newly used was predicted so that the position coordinate
of wafer stage WST which is monitored is continuously linked before
and after the switching, and this predicted value was set as an
initial value for the measurement value of another head. Instead of
the processing above, the measurement error of another head
including the measurement error generated by the switching and
linkage process can be computed and the correction data can be
made. And, while the another head is being used, the correction
data that has been made can be used for servo drive control of
wafer stage WST. In this case, based on the correction data,
positional information of wafer stage WST measured by the another
head can be corrected, or a target position of wafer stage WST for
servo control can be corrected. Furthermore, in the exposure
operation, servo drive control of the reticle stage is performed,
following the movement of wafer stage WST. Therefore, based on the
correction data, instead of correcting the servo control of wafer
stage WST, the follow-up servo control of the reticle stage can be
corrected. Further, according to these control system, the
measurement value of the head before the switching may be set as an
initial value of another head without any changes. Incidentally,
when making the correction data, not only the encoder system but
also other measurement systems that the exposure apparatus in the
embodiment has, such as the interferometer systems, should be
appropriately used.
[0402] Next, a parallel processing operation that uses wafer stage
WST and measurement stage MST in exposure apparatus 100 of the
embodiment will be described based on FIGS. 27 to 40. Incidentally,
during the operation below, main controller 20 performs the
open/close control of each valve of liquid supply unit 5 of local
liquid immersion unit 8 and liquid recovery unit 6 in the manner
previously described, and water is constantly filled in the space
right under tip lens 191 of projection optical system PL. However,
in the description below, for the sake of simplicity, the
explanation related to the control of liquid supply unit 5 and
liquid recovery unit 6 will be omitted. Further, many drawings are
used in the operation description hereinafter, however, reference
codes may or may not be given to the same member for each drawing.
More specifically, the reference codes written are different for
each drawing, however, such members have the same configuration
regardless of the indication of the reference codes. The same can
be said for each drawing used in the description so far.
[0403] FIG. 27 shows a state where exposure by the step-and-scan
method is being performed on wafer W (in this case, as an example,
the wafer is a wafer midway of a certain lot (one lot contains 25
or 50 wafers)) on wafer stage WST. In this state, measurement stage
MST can wait at a withdrawal position where it avoids bumping into
wafer stage WST, however, in the embodiment, measurement stage MST
is moving, following wafer stage WST while keeping a predetermined
distance. Therefore, when measurement stage MST moves into a
contact state (or a proximity state) with wafer stage WST after the
exposure has been completed, the same distance as the predetermined
distance referred to above will be enough to cover the movement
distance.
[0404] During this exposure, main controller 20 controls the
position (including the .theta.z rotation) of wafer table WTB
(wafer stage WST) within the XY plane, based on the measurement
values of at least three encoders out of two X heads 66 (X encoders
70B and 70D) shown surrounded by a circle in FIG. 27 facing X
scales 39X.sub.1 and 39X.sub.2, respectively, and two Y heads 64 (Y
encoders 70A and 70C) shown surrounded by a circle in FIG. 27
facing Y scales 39Y.sub.1 and 39Y.sub.2, respectively, the pitching
amount or rolling amount, and yawing amount of wafer stage WST
measured by interferometer system 118, the stage position induced
error correction information (correction information obtained by
formula (22) or formula (23) previously described) of each encoder
corresponding to the Z position, the correction information of the
grating pitch of each scale and correction information of the warp
of the grid line, and the Abbe offset quantity (Abbe error
correction information). Further, main controller 20 controls the
position of wafer table WTB in the Z-axis direction, the .theta.y
rotation (rolling), and the ex rotation (pitching), based on
measurement values of one pair each of Z sensors 74.sub.1,j and
74.sub.2,j, and 76.sub.1,q and 76.sub.2,q that face one end and the
other end (in the embodiment, Y scales 39Y.sub.1 and 39Y.sub.2) of
the wafer table WTB surface in the X-axis direction. Incidentally,
the position of wafer table WTB in the Z-axis direction and the
.theta.y rotation (rolling) can be controlled based on the
measurement value of Z sensors 74.sub.1,j, 74.sub.2,j, 76.sub.1,q,
and 76.sub.2,q, and the .theta.x rotation (pitching) can be
controlled based on the measurement values of Y interferometer 16.
In any case, the control (focus leveling control of wafer W) of the
position of wafer table WTB in the Z-axis direction, the .theta.y
rotation, and the .theta.x rotation during this exposure is
performed, based on results of a focus mapping performed in advance
by the multipoint AF system previously described.
[0405] Main controller 20 performs the exposure operation described
above, based on results of wafer alignment (e.g. Enhanced Global
Alignment (EGA)) that has been performed beforehand and on the
latest baseline and the like of alignment systems AL1, and
AL2.sub.1 to AL2.sub.4, by repeating a movement operation between
shots in which wafer stage WST is moved to a scanning starting
position (an acceleration starting position) for exposure of each
shot area on wafer W, and a scanning exposure operation in which a
pattern formed on reticle R is transferred onto each shot area by a
scanning exposure method. Incidentally, the exposure operation
described above is performed in a state where water is retained in
the space between tip lens 191 and wafer W. Further, exposure is
performed in the order from the shot area located on the -Y side to
the shot area located on the +Y side in FIG. 27. Incidentally,
details on the EGA method are disclosed, for example, in U.S. Pat.
No. 4,780,617 and the like.
[0406] And before the last shot area on wafer W is exposed, main
controller 20 controls stage drive system 124 based on the
measurement value of Y interferometer 18 while maintaining the
measurement value of X interferometer 130 to a constant value, and
moves measurement stage MST (measurement table MTB) to the position
shown in FIG. 28. When the measurement stage is moved, the edge
surface of CD bar 46 (measurement table MTB) on the -Y side touches
the edge surface of wafer table WTB on the +Y side. Incidentally,
measurement table MTB and wafer table WTB can be separated, for
example, at around 300 .mu.m in the Y-axis direction while
monitoring, for example, the interferometer that measures the
position of each table in the Y-axis direction or the measurement
values of the encoder so as to maintain a non-contact state
(proximity state). After wafer stage WST and measurement stage MST
are set to the positional relation shown in FIG. 28 during the
exposure of wafer W, both stages are moved while maintaining this
positional relation.
[0407] Subsequently, as shown in FIG. 29, main controller 20 begins
the operation of driving measurement stage MST in the -Y-direction,
and also begins the operation of driving wafer stage WST toward
unloading position UP, while maintaining the positional relation of
wafer table WTB and measurement table MTB in the Y-axis direction.
When the operations begin, in the embodiment, measurement stage MST
is moved only in the -Y direction, and wafer stage WST is moved in
the -Y direction and the -X direction. Further, at the beginning
stage of the movement, main controller 20 controls the position
(including the .theta.z rotation) of wafer table WTB (wafer stage
WST) in the XY plane, based on the measurement values of three
encoders.
[0408] When main controller 20 simultaneously drives wafer stage
WST and measurement stage MST in the manner described above, the
water (water of liquid immersion area 14 shown in FIG. 29) which
was retained in the space between tip lens 191 of projection unit
PU and wafer W sequentially moves over wafer W.fwdarw.plate
28.fwdarw.CD bar 46.fwdarw.measurement table MTB, along with the
movement of wafer stage WST and measurement stage MST to the -Y
side. Incidentally, during the movement above, wafer table WTB and
measurement table MTB maintain the contact state (or proximity
state) previously described. Incidentally, FIG. 29 shows a state
just before the water of liquid immersion area 14 is moved over to
CD bar 46 from plate 28. Further, in the state shown in FIG. 29,
main controller 20 controls the position (including the .theta.z
rotation) of wafer table WTB (wafer stage WST) within the XY plane,
based on the measurement values (and the stage position induced
error correction information, the correction information of the
grating pitch of the scale and the correction information of the
grid line of encoders 70A, 70B or 70D stored in memory 34,
corresponding to the pitching amount, rolling amount, yawing
amount, and the Z position of wafer stage WST measured by
interferometer system 118) of the three encoders 70A, 70B, and
70D.
[0409] When wafer stage WST and measurement stage MST are driven
simultaneously, slightly in the directions above furthermore from
the state shown in FIG. 29, respectively, because the position
measurement of wafer stage WST (wafer table WTB) by Y encoder 70A
(and, 70C) will no longer be possible, main controller 20 switches
the control of the Y position and the .theta.z rotation of wafer
stage WST (wafer table WTB) just before this, from a control based
on the measurement values of Y encoders 70A and 70C to a control
based on the measurement values of Y interferometer 16 and Z
interferometers 43A and 43B. Then, after a predetermined time
later, measurement stage MST reaches a position where baseline
measurement (hereinafter appropriately referred to as Sec-BCHK
(interval)) of the secondary alignment system is performed at a
predetermined interval (in this case, at each wafer exchange) as
shown in FIG. 30. Then, main controller 20 stops measurement stage
MST at the position, and drives wafer stage WST furthermore toward
unloading position UP and then stops wafer stage WST at unloading
position UP, while measuring the X position of wafer stage WST
using X head 66 (X linear encoder 70B) shown in FIG. 30 surrounded
by a circle that faces X scale 39X.sub.1 and also measuring the
position in the Y-axis direction and the .theta.z rotation measure
using Y interferometer 16 and Z interferometers 43A and 43B.
Incidentally, in the state shown in FIG. 30, the water is retained
in the space between measurement table MTB and tip lens 191.
[0410] Subsequently, as shown in FIGS. 30 and 31, main controller
20 adjusts the .theta.z rotation of CD bar 46, based on the
measurement values of Y-axis linear encoders 70E and 70F configured
by Y heads 64y.sub.1 and 64y.sub.2 shown in FIG. 31 surrounded by a
circle that face a pair of reference grids 52 on CD bar 46
supported by measurement stage MST, respectively, and also adjusts
the XY position of CD bar 46, based on the measurement value of
primary alignment system AL1 which detects reference mark M located
on or in the vicinity of center line CL of measurement table MTB.
Then, in this state, main controller 20 performs the Sec-BCHK
(interval) in which the baseline (the relative position of the four
secondary alignment systems with respect to primary alignment
system AL1) of the four secondary alignment systems AL2.sub.1 to
AL2.sub.4 is obtained by simultaneously measuring reference mark M
on CD bar 46 located within the field each secondary alignment
system, respectively, using the four secondary alignment systems
AL2.sub.1 to AL2.sub.4. In parallel with this Sec-BCHK (an
interval), main controller 20 gives a command to a drive system of
an unload arm (not shown) so that wafer W on wafer stage WST
suspended at unload position UP is unloaded, and also drives wafer
stage WST in the +X direction so that the stage is moved to loading
position LP, while keeping a vertical movement pin CT (not shown in
FIG. 30, refer to FIG. 31) elevated by a predetermined amount,
which was driven upward on the unloading.
[0411] Next, as shown in FIG. 32, main controller 20 moves
measurement stage MST to an optimal waiting position (hereinafter
referred to as "optimal scrum waiting position")), which is the
optimal waiting position for moving measurement stage MST from the
state distanced from wafer stage WST into the contact state (or
proximity state) previously described with wafer stage WST. In
parallel with this, main controller 20 gives a command to a drive
system of a load arm (not shown) so that a new wafer W is loaded on
wafer table WTB. In this case, because vertical movement pin CT is
maintaining the state of being elevated by a predetermined amount,
wafer loading can be performed in a short period of time when
compared with the case when vertical movement pin CT is driven
downward and is housed inside the wafer holder. Incidentally, FIG.
32 shows a state where wafer W is loaded on wafer table WTB.
[0412] In the embodiment, the optimal scrum waiting position of
measurement stage MST referred to above is appropriately set
according to the Y-coordinate of alignment marks arranged on the
alignment shot area on the wafer. Further, in the embodiment, the
optimal scrum waiting position is decided so that wafer stage WST
can move into the contact state (or proximity state) at the
position where wafer stage WST stops for wafer alignment.
[0413] Next, main controller 20 moves wafer stage WST from loading
position LP, to a position (more specifically, a position where the
former process of base line measurement (Pri-BCHK) of the primary
alignment system is performed) in the field (detection area) of
primary alignment system AL1 where fiducial mark FM on measurement
plate 30 shown in FIG. 33 is positioned. On this operation, by
irregular control based on the measurement values of Encoder 70B
for the X-axis direction, and Y interferometer 16 and Z
interferometer 43A and 43B for the Y-axis direction and the
.theta.z rotation, main controller 20 controls the position of
wafer table WTB (wafer stage WST) in the XY plane. And, when wafer
stage WST arrives at the position shown in FIG. 33 where the former
process of Pri-BCHK is performed, main controller 20 switches the
position control of wafer stage WST in the XY plane from the
irregular control described above to the position control using the
three encoders (heads) in the following procedure.
[0414] In a state where wafer stage WST has been moved to the
position shown in FIG. 33 where of the former process of Pri-BCHK
is performed, two X heads 66 (of the heads, head 66 that faces X
scale 39X.sub.2 is shown surrounded by a circle) of head unit 62D
face X scales 39X.sub.1 and 39X.sub.2, respectively, and two Y
heads 64y.sub.2 and 64y.sub.1, which are shown in FIG. 33
surrounded by a circle, face Y scales 39Y.sub.1 and 39Y.sub.2,
respectively. In this state, main controller 20 selects the two Y
heads 64y.sub.2 and 64y.sub.1 and X head 66 that faces X scale
39X.sub.2 (these three selected heads will hereinafter be referred
to as origin heads), and finely moves wafer stage WST within the XY
plane so that an absolute phase of each origin head will be the
initial value for each origin head that has been decided
beforehand. In this case, the initial value of the absolute phase
of each origin head is decided to be the measurement values of the
absolute phase of Y heads 64y.sub.2 and 64y.sub.1 which were
obtained after adjusting .theta.z rotation of wafer stage WST in
advance so as to make the .theta.z rotational error of wafer stage
WST become a value close to zero as much as possible, and the
measurement value of the absolute phase of the remaining origin
head 66 which was measured at the same time with the measurement
values of the Y heads. Incidentally, at the point when the fine
movement described above is started, the position of wafer stage
WST within the XY plane is driven so that the value that the
measurement value of each origin head decided beforehand fits
within a range of one fringe of the interference fringe.
[0415] Then, at a point when the absolute phase of the three origin
heads 66, 64y.sub.2 and 64y.sub.1 each become the initial value,
main controller 20 begins the position control of wafer stage WST
within the XY plane again, using origin heads (Y heads) 64y.sub.2
and 64y.sub.1 (encoders 70A and 70C) which face Y scales 39Y.sub.1
and 39Y.sub.2, respectively, and origin head (X head) 66 (encoder
70D) which face X scale 39X.sub.2. That is, in the manner described
above, main controller 20 switches the position control of wafer
stage WST in the XY plane at the position where of the former
process of Pri-BCHK is performed from the irregular control
previously described to the position control based on the
measurement values of encoders 70A, 70C and 70D corresponding to
the three origin heads 66, 64y.sub.2 and 64y.sub.1. The position
control based on the measurement values of encoders 70A, 70C and
70D is performed by controlling the position of wafer stage WST
within the XY plane, based on the measurement values of encoders
70A, 70C and 70D, the stage position induced error correction
information (the correction information that is obtained from
formulas (22) and (23) previously described) of each encoder which
corresponds to the pitching amount or rolling amount, yawing
amount, and the Z position of wafer stage WST measured by
interferometer system 118, the correction information of the
grating pitch and the correction information of the grid line of
each scale, and the Abbe offset quantity (Abbe error correction
information).
[0416] Subsequently, main controller 20 performs the former process
of Pri-BCHK in which fiducial mark FM is detected using primary
alignment system AL1. At this point in time, measurement stage MST
is waiting at the optimal scrum waiting position described
above.
[0417] Next, while controlling the position of wafer stage WST
based on the measurement values of at least the three encoders and
each correction information described above, main controller 20
begins the movement of wafer stage WST in the +Y direction toward a
position where the alignment marks arranged in three first
alignment shot areas are detected.
[0418] Then, when wafer stage WST reaches the position shown in
FIG. 34, main controller 20 stops wafer stage WST. Prior to this,
main controller 20 activates (turns on) Z sensors 72a to 72d at the
point when Z sensors 72a to 72d begins to move over wafer table WTB
or at the point before, and measures the Z position and the
inclination (.theta.y rotation and .theta.x rotation) of wafer
table WTB.
[0419] After wafer stage WST is stopped as in the description
above, main controller 20 detects the alignment marks arranged in
the three first alignment shot areas substantially at the same time
and also individually (refer to the star-shaped marks in FIG. 34),
using primary alignment system AL1, and secondary alignment systems
AL2.sub.2 and AL2.sub.3, and makes a link between the detection
results of the three alignment systems AL1, AL2.sub.2, and
AL2.sub.3 and the measurement values (measurement values after the
correction according to each correction information) of at least
the three encoders above at the time of the detection, and stores
them in the internal memory.
[0420] As in the description above, in the embodiment, the shift to
the contact state (or proximity state) between measurement stage
MST and wafer stage WST is completed at the position where
detection of the alignment marks of the first alignment shot areas
is performed, and from this position, main controller 20 begins to
move both stages WST and MST in the +Y direction (step movement
toward the position for detecting alignment marks arranged in five
second alignment shot areas) in the contact state (or proximity
state). Prior to starting the movement of both stages WST and MST
in the +Y direction, as shown in FIG. 34, main controller 20 begins
irradiation of a detection beam from irradiation system 90 of the
multipoint AF system (90a, 90b) toward wafer table WTB.
Accordingly, a detection area of the multipoint AF system is formed
on wafer table WTB.
[0421] Then, when both stages WST and MST reach the position shown
in FIG. 35 during the movement of both stages WST and MST in the +Y
direction, main controller 20 performs the former process of the
focus calibration, and obtains the relation between the measurement
values (surface position information on one side and the other side
of wafer table WTB in the X-axis direction) of Z sensors 72a, 72b,
72c, and 72d, in a state where a straight line (center line) in the
Y-axis direction passing through the center (substantially
coinciding with the center of wafer W) of wafer table WTB coincides
with straight line LV previously described, and the detection
results (surface position information) of a detection point (the
detection point located in or around the center, among a plurality
of detection points) on the surface of measurement plate 30 of the
multipoint AF system (90a, 90b). At this point, liquid immersion
area 14 is located in the vicinity of the border of CD bar 46 and
wafer table WTB. More specifically, liquid immersion area 14 is in
a state just before it is passed over to wafer table WTB from CD
bar 46.
[0422] Then, when both stages WST and MST move further in the +Y
direction and reach the position shown in FIG. 36 while maintaining
the contact state (or proximity state), the alignment marks
arranged in the five second alignment shot areas are detected
substantially at the same time and also individually (refer to the
star-shaped marks in FIG. 3), using the five alignment systems AL1,
and AL2.sub.1 to AL2.sub.4 and a link is made between the detection
results of the five alignment systems AL1, and AL2.sub.1 to
AL2.sub.4 and the measurement values (measurement values after the
correction according to each correction information) of the three
encoders 70A, 70C, and 70D at the time of the detection, and stored
in the internal memory. At this point in time, since the X head
that faces X scale 39X.sub.1 and is located on straight line LV
does not exist, main controller 20 controls the position within the
XY plane of wafer table WTB based on the measurement values of X
head 66 facing X scale 39X.sub.2 (X linear encoder 70D) and Y
linear encoders 70A and 70C.
[0423] As is described above, in the embodiment, the positional
information (two-dimensional positional information) of a total of
eight alignment marks can be detected at the point when the
detection of the alignment marks in the second alignment shot areas
is completed. Therefore, at this stage, main controller 20 can
perform a statistical computation such as the one disclosed in, for
example, Kokai (Japanese Unexamined Patent Application Publication)
No. 61-44429 (the corresponding U.S. Pat. No. 4,780,617) and the
like, to obtain the scaling (shot magnification) of wafer W, and
can adjust the optical properties of projection optical system PL,
such as for example, the projection magnification, by controlling
an adjustment 68 (refer to FIG. 6) based on the shot magnification
which has been computed. Adjustment unit 68 adjusts the optical
properties of projection optical system PL, for example, by driving
a particular movable lens that configures projection optical system
PL, or changing gas pressure in an airtight chamber formed between
particular lenses that configure projection optical system PL or
the like.
[0424] Further, after the simultaneous detection of the alignment
marks arranged in the five second alignment shot areas is
completed, main controller 20 starts again movement in the +Y
direction of both stages WST and MST in the contact state (or
proximity state), and at the same time, starts the focus mapping
using Z sensors 72a to 72d and the multipoint AF system (90a, 90b),
as is shown in FIG. 36.
[0425] Then, when both stages WST and MST reach the position with
which measurement plate 30 is located directly below projection
optical system PL shown in FIG. 37, main controller 20 performs the
Pri-BCHK latter process and the latter process of the focus
calibration. In this case, the Pri-BCHK latter process refers to a
processing in which a projected image (aerial image) of a pair of
measurement marks on reticle R projected by projection optical
system PL is measured, using aerial image measurement unit 45
previously described which has aerial image measurement slit
pattern SL formed on measurement plate 30, and the measurement
results (aerial image intensity depending on the XY position of
wafer table WTB) are stored in the internal memory. In this
processing, the projected image of the pair of measurement marks is
measured in an aerial image measurement operation by the slit scan
method, using a pair of aerial image measurement slit patterns SL,
respectively, similar to the method disclosed in, U.S. Patent
Application Publication No. 2002/0041377 and the like. Further, the
latter process of the focus calibration refers to a processing in
which main controller 20 measures the aerial image of a measurement
mark formed on a mark plate (not shown) on reticle R or on reticle
stage RST using aerial image measurement unit 45, while controlling
the position (Z position) of measurement plate 30 (wafer table WTB)
related to the optical axis direction of projection optical system
PL, based on the surface position information of wafer table WTB
(wafer stage WST) measured by Z sensors 72a, 72b, 72c, and 72d, and
then measures the best focus position of projection optical system
PL based on the measurement results, as shown in FIG. 37. For
example, the measurement operation of the projected image of the
measurement mark is disclosed in, for example, the pamphlet of
International Publication No. WO 05/124834 and the like. While
moving measurement plate 30 in the Z-axis direction, main
controller 20 takes in the measurement values of Z sensors
74.sub.1,4, 74.sub.2,4, 76.sub.1,3, and 76.sub.2,3 in
synchronization with taking in the output signal from aerial image
measurement unit 45. Then, main controller 20 stores the values of
Z sensors 74.sub.1,4, 74.sub.2,4, 76.sub.1,3, and 76.sub.2,3
corresponding to the best focus position of projection optical
system PL in a memory (not shown). Incidentally, the reason why the
position (Z position) related to the optical axis direction of
projection optical system PL of measurement plate 30 (wafer stage
WST) is controlled using the surface position information measured
in the latter process of the focus calibration by Z sensors 72a,
72b, 72c, and 72d is because the latter process of the focus
calibration is performed during the focus mapping previously
described.
[0426] In this case, because liquid immersion area 14 is formed
between projection optical system PL and measurement plate 30
(wafer table WTB), the measurement of the aerial image is performed
via projection optical system PL and water Lq. Further, because
measurement plate 30 and the like is installed in wafer stage WST
(wafer table WTB), and the light receiving element and the like is
installed in measurement stage MST, the measurement of the aerial
image is performed while maintaining the contact state (or
proximity state) of wafer stage WST and measurement stage MST, as
shown in FIG. 37. By the measurement described above, measurement
values (more specifically, surface position information of wafer
table WTB) of Z sensors 74.sub.1,4, 74.sub.2,4, 76.sub.1,3, and
76.sub.2,3 corresponding to the best focus position of projection
optical system PL are obtained, in a state where the straight line
(the center line) in the Y-axis direction passing through the
center of wafer table WTB coincides with straight line LV
previously described.
[0427] Then, main controller 20 computes the baseline of primary
alignment system AL1, based on the results of the former process of
Pri-BCHK and the results of the latter process of Pri-BCHK
described above. With this, based on the relation between the
measurement values (surface position information of wafer table
WTB) of Z sensors 72a, 72b, 72c, and 72d obtained in the former
process of the focus calibration described above and the detection
results (surface position information) of the detection point on
the surface of measurement plate 30 of the multipoint AF system
(90a, 90b), and the measurement values (more specifically, surface
position information of wafer table WTB) of Z sensors 74.sub.1,4,
74.sub.2,4, 76.sub.1,3, and 76.sub.2,3 corresponding to the best
focus position of projection optical system PL which are obtained
in the latter process of the focus calibration described above,
main controller 20 obtains the offset at a representative detection
point (the detection point located in or around the center, among a
plurality of detection points) of the multipoint AF system (90a,
90b) with respect to the best focus position of projection optical
system PL and adjusts the detection origin of the multipoint AF
system, for example, by an optical method so that the offset
becomes zero.
[0428] In this case, from the viewpoint of improving throughput,
only one processing of the latter process of Pri-BCHK described
above and the latter process of the focus calibration can be
performed, or the procedure can move on to the next processing
without performing both processing.
[0429] As a matter of course, in the case the latter process of
Pri-BCHK is not performed, the former process of Pri-BCHK described
earlier also does not have to be performed, and in this case, main
controller 20 only has to move wafer stage WST from loading
position LP to a position where the alignment marks arranged in the
first alignment shot areas are detected. Incidentally, in the case
Pri-BCHK processing is not performed, the baseline which is
measured by a similar operation just before the exposure of a wafer
exposed earlier than wafer W subject to exposure is used. Further,
when latter process of the focus calibration is not performed,
similar to the baseline, the best focus position of projection
optical system PL which is measured just before the exposure of a
preceding wafer is used.
[0430] Incidentally, in the state shown in FIG. 37, the focus
mapping previously described is being continued.
[0431] When wafer stage WST reaches the position shown in FIG. 38
by movement in the +Y direction of both stages WST and MST in the
contact state (or proximity state) described above, main controller
20 stops wafer stage WST at that position, while also making
measurement stage MST continue the movement in the +Y direction.
Then, main controller 20 almost simultaneously and individually
detects the alignment marks arranged in the five third alignment
shot areas AS (refer to star-shaped marks in FIG. 38) using five
alignment systems AL1 and AL2.sub.1 to AL2.sub.4, links the
detection results of five alignment systems AL1 and AL2.sub.1 and
AL2.sub.4 and the measurement values of the four encoders at the
time of the detection and stores them in the internal memory. At
this point in time, the focus mapping is being continued.
[0432] Meanwhile, after a predetermined period of time from the
suspension of wafer stage WST described above, measurement stage
MST and wafer stage WST moves from the contact state (or proximity
state) into a separation state. After moving into the separation
state, main controller 20 stops the movement of measurement stage
MST when measurement stage MST reaches an exposure start waiting
position where measurement stage MST waits until exposure is
started.
[0433] Next, main controller 20 starts to move wafer stage WST in
the +Y direction toward a position where alignment marks arranged
in three fourth alignment shot areas are detected. At this point in
time, the focus mapping is being continued. Meanwhile, measurement
stage WST is waiting at the exposure start waiting position
described above.
[0434] Then, when wafer stage WST reaches the position shown in
FIG. 39, main controller 20 immediately stops wafer stage WST, and
almost simultaneously and individually detects the alignment marks
arranged in the three fourth alignment shot areas on wafer W (refer
to star-shaped marks in FIG. 39) using primary alignment system AL1
and secondary alignment systems AL2.sub.2 and AL2.sub.3, links the
detection results of three alignment systems AL1, AL2.sub.2 and
AL2.sub.3 and the measurement values of the four encoders at the
time of the detection, and stores them in the internal memory. Also
at this point in time, the focus mapping is being continued, and
measurement stage MST is still waiting at the exposure start
waiting position. Then, using the detection results of a total of
16 alignment marks and the measurement values (measurement values
after the correction by each correction information) of the
corresponding encoders obtained in the manner described above, main
controller 20 computes array information (coordinate values) of all
the shot areas on wafer W on a coordinate system (for example, an
XY coordinate system whose origin is placed at the center of wafer
table WTB) that is set by the measurement axes of the four
encoders, using the EGA method disclosed in, for example, U.S. Pat.
No. 4,780,617 and the like.
[0435] Next, main controller 20 continues the focus mapping while
moving wafer stage WST in the +Y direction again. Then, when the
detection beam from the multipoint AF system (90a, 90b) moves off
the wafer W surface, as is shown in FIG. 40, main controller 20
ends the focus mapping. After that, based on the results of the
wafer alignment (EGA) described earlier performed in advance, the
latest baselines of the five alignment systems AL1 and AL2.sub.1 to
AL2.sub.4, and the like, main controller 20 performs exposure by
the step-and-scan method in a liquid immersion exposure and
sequentially transfers a reticle pattern to a plurality of shot
areas on wafer W. Afterwards, similar operations are repeatedly
performed so as to expose the remaining wafers within the lot.
[0436] As discussed in detail above, according to exposure
apparatus 100 related to the embodiment, the positional information
(including the .theta.z rotation) of wafer stage WST within the XY
plane is measured by three encoders, which at least include one
each of an X encoder and a Y encoder of the encoder system, while
wafer stage WST is being driven. Then, main controller 20 switches
an encoder (a head) used for measuring the positional information
of wafer stage WST in the XY plane from one of the encoders of the
three encoders to another encoder, so that the position of wafer
stage WST within the XY plane is maintained before and after the
switching. Because of this, although the encoder which is used for
the control of the position of wafer stage WST has been switched,
the position of wafer stage WST within the XY plane is maintained
before and after the switching, which makes an accurate linkage
possible. Further, also on the switching of the encoder, main
controller 20 uses the measurement values of each encoder whose
measurement errors of the head (encoder) due to the measurement
delay previously described have been corrected. Accordingly, it
becomes possible to move wafer stage WST two-dimensionally,
precisely along a predetermined course, while performing linkage
between a plurality of encoders.
[0437] Further, according to exposure apparatus 100 related to the
embodiment, for example, while the lot is being processed, main
controller 20 measures the positional information (including the
.theta.z rotation) of wafer stage WST within the XY plane (the
movement plane) by three heads (encoders), which at least include
one each of an X head (X encoder) and a Y head (Y encoder) of the
encoder system. Then, based on the measurement results of the
positional information and the positional information ((X, Y)
coordinate value) in the movement plane of the three heads used for
measuring the positional information, main controller 20 drives
wafer stage WST within the XY plane. In this case, main controller
20 drives wafer stage WST within the XY plane, while computing the
positional information of wafer stage WST within the XY plane using
the affine transformation relation. Accordingly, it becomes
possible to control the movement of wafer stage WST with good
precision while switching the head (encoder) used for control
during the movement of wafer stage WST, using the encoder system
including head units 62A to 62D which respectively have a plurality
of Y heads 64 or a plurality of X heads 66.
[0438] Further, according to exposure apparatus 100 of the
embodiment, while wafer stage WST is being driven, main controller
20 takes in the output of each encoder (a head) of the encoder
system constantly (at a predetermined measurement sampling
interval), as well as executes an operation where the encoder used
for position control of wafer stage WST is switched from an encoder
(a head) that has been used for position control of wafer stage WST
to another encoder (a head) in synchronization with the timing of
the position control of wafer stage WST. Therefore, the switching
of the encoder no longer has to be performed at a high speed in
synchronization with the measurement sampling where the output of
the interferometer and the encoder is taken in, and a highly
precise hardware for the switching will not be necessary, which
consequently will make cost reduction possible.
[0439] Further, according to exposure apparatus 100 of the
embodiment, main controller 20 can make out a combination of
encoders subject to the switching of the encoder used for position
control of wafer stage WST from an arbitrary encoder of the encoder
system to another encoder and prepare a schedule in advance for the
timing of the switching, based on the movement course of wafer
stage WST. Then, during the movement of wafer stage WST, main
controller 20 measures the positional information of wafer stage
WST within the XY plane using the three encoders of the encoder
system, and based on the contents above that have been scheduled,
the switching from the arbitrary encoder to the another encoder is
performed. According to this, a reasonable encoder switching
according to the target track of wafer stage WST becomes
possible.
[0440] Further, according to exposure apparatus 100 of the
embodiment, in the case of moving wafer stage WST in a
predetermined direction, such as, for example, the Y-axis direction
at the time of wafer alignment time or exposure, wafer stage WST is
driven in the Y-axis direction, based on the measurement
information of the encoder system, the positional information
(including inclination information, e.g., rotation information in
the .theta.x direction) of wafer stage WST in a direction different
from the Y-axis direction, the characteristic information (e.g.,
the degree of flatness of the grating surface, and/or a grating
formation error) of the scale, and the correction information of
the Abbe error due to the Abbe offset quantity of the scale. More
specifically, wafer stage WST is driven to compensate for the
measurement errors of the encoder system (encoders 70A and 70C)
caused by the displacement (including the inclination) of wafer
stage WST in a direction different from the Y-axis direction and
the scale. In the embodiment, main controller 20 drives wafer stage
WST in the Y-axis direction, based on the measurement values of
encoders 70A and 70C which measure the positional information of
wafer stage WST in a predetermined direction, such as, for example,
in the Y-axis direction, the positional information of wafer stage
WST in a direction different from the Y-axis direction at the time
of the measurement (direction besides the measurement direction),
such as, for example, the stage position induced error correction
information (the correction information which is computed by
formula (22) previously described) that corresponds to the
positional information of wafer stage WST in the .theta.x
direction, .theta.z direction, and the Z-axis direction measured by
Y interferometer 16 and Z interferometers 43A and 43B of
interferometer system 118, the correction information (the
correction information which takes into consideration the
unevenness (degree of flatness) of the Y scale) of the grating
pitch of the Y scale, the correction information of the warp of
grid line 38 of the Y scale, and the correction information of the
Abbe error due to the Abbe offset quantity of the Y scale. In the
manner described above, stage drive system 124 is controlled and
wafer stage WST is driven in the Y-axis direction, based on the
measurement values of encoders 70A and 70C which are corrected
according to each correction information of the relative
displacement of scales 39Y.sub.1 and 39Y.sub.2 and Y head 64 in the
direction besides the measurement direction, the measurement errors
of encoders 70A and 70C, due to the grating pitch of Y scales
39Y.sub.1 and 39Y.sub.2 the warp of grid line 38, and the Abbe
error due to the Abbe offset quantity of the Y scale. In this case,
the measurement values (count values) of encoders 70A and 70C are
the same results as when an ideal grating (diffraction grating) is
measured with an ideal encoder (head). An ideal grating
(diffraction grating), here, refers to a grating whose surface of
the grating is parallel to the movement plane (the XY plane) of the
stage and is a completely flat surface, and the pitch direction of
the grating is parallel to the beam of the interferometer and the
distance between the grid lines is completely equal. An ideal
encoder (head) refers to a head whose optical axis is perpendicular
to the movement plane of the stage and whose measurement values do
not change by Z displacement, leveling, yawing and the like.
[0441] Further, in the case wafer stage WST is moved in the X-axis
direction, wafer stage WST is driven in the X-axis direction, based
on the measurement information of the encoder system, the
positional information (including inclination information, e.g.,
rotation information in the .theta.y direction) of wafer stage WST
in a direction different from the X-axis direction, the
characteristic information (e.g., the degree of flatness of the
grating surface, and/or a grating formation error) of the scale,
and the correction information of the Abbe error due to the Abbe
offset quantity of the scale. More specifically, wafer stage WST is
driven to compensate for the measurement errors of the encoder
system (encoders 70B and 70D) caused by the displacement (including
the inclination) of wafer stage WST in a direction different from
the X-axis direction. In the embodiment, main controller 20 drives
wafer stage WST in the X-axis direction, based on the measurement
values of encoders 70B and 70D which measure the positional
information of wafer stage WST in the X-axis direction, the
positional information of wafer stage WST in a direction different
from the X-axis direction at the time of the measurement (direction
besides the measurement direction), such as, for example, the stage
position induced error correction information (the correction
information which is computed by formula (23) previously described)
that corresponds to the positional information of wafer stage WST
in the .theta.y direction, .theta.z direction, and the Z-axis
direction measured by Z interferometers 43A and 43B of
interferometer system 118, the correction information (the
correction information which takes into consideration the
unevenness (degree of flatness) of the X scales) of the grating
pitch of the X scales, the correction information of the warp of
grid line 37 of the X scales, and the correction information of the
Abbe error due to the Abbe offset quantity of X scales 39X.sub.1
and 39X.sub.2. In the manner described above, stage drive system
124 is controlled and wafer stage WST is driven in the X-axis
direction, based on the measurement values of encoders 70B and 70D
which are corrected according to each correction information of the
relative displacement of X scales 39X.sub.1 and 39X.sub.2 and X
head 66 in the direction besides the measurement direction, the
measurement errors of encoders 70B and 70D, due to the grating
pitch of X scales 39X.sub.1 and 39X.sub.2 the warp of grid line 37,
and the Abbe error due to the Abbe offset quantity of X scales
39X.sub.1 and 39X.sub.2. In this case, the measurement values of
encoders 70B and 70D are the same results as when an ideal grating
(diffraction grating) is measured with an ideal encoder (head).
[0442] Accordingly, it becomes possible to drive wafer stage WST
using an encoder in a desired direction with good precision,
without being affected by the relative motion in directions other
than the direction (measurement direction) of the head and the
scale to be measured, without being affected by the Abbe error,
without being affected by the unevenness of the scale, and without
being affected by the grating pitch of the scale and the grating
warp.
[0443] Further, according to exposure apparatus 100 of the
embodiment, when the pattern of reticle R is formed in each shot
area on the wafer, exposure by the step-and-scan method is
performed, and during the exposure operation of this step-and-scan
method, main controller 20 performs the linkage operation between
the plurality of encoders, between the encoders (between
combinations of the encoders) in accordance with the schedule set
in advance, at a timing in accordance with the schedule, in
synchronization with the timing of the position control of wafer
stage WST.
[0444] Further, according to exposure apparatus 100 related to the
embodiment, when wafer stage WST is driven in a predetermined
direction within the XY plane by main controller 20, the
measurement data corresponding to the detection signals of a total
of three heads including at least one of the encoder systems, such
as, for example, an X head and a Y head, is taken in at a
predetermined control sampling interval (for example, 96
[.mu.sec]), respectively, and based on the measurement data which
was taken in the latest and the data just before the latest data
(one control sampling interval earlier) for each head, and the
information of delay time .delta. that accompanies the detection
signals propagating through the cable (propagation path), wafer
stage WST is driven so that the measurement errors of the head
(encoder) due to the measurement delay that accompanies the
detection signals propagating delay the cable (propagation path)
are corrected. According to this, it becomes possible to drive
wafer stage WST with high precision in the desired direction
without being affected by the measurement delay that accompanies
the detection signals of the head of the encoder propagating
through the cable (propagation path).
[0445] For example, in exposure apparatus 100 of the embodiment, in
the case wafer stage WST is driven in the Y-axis, the positional
information of wafer stage WST is measured using a total of three
heads (encoders) that include encoders 70A and 70C each having a
pair of Y heads 64 which faces Y scales 39Y.sub.1 and 39Y.sub.2,
respectively. On this measurement, even if delay time .delta.
between the pair of Y heads 64 that each faces Y scales 39Y.sub.1
and 39Y.sub.2 is different, because main controller 20 drives wafer
stage WST so that the measurement errors of the head (encoder) due
to delay time .delta. are corrected, there consequently is no risk
of the .theta.z rotational error occurring in wafer stage WST
according to the difference in delay time described above between
the pair of Y heads 64.
[0446] Further, in the embodiment, prior to the drive of wafer
stage WST described above, for example, such as at the startup time
of the apparatus, main controller 20 drives wafer stage WST in a
predetermined direction (e.g. the Y-axis direction (or the X-axis
direction)) within the XY plane, and during the drive, for a
plurality of Y heads 64 (or X heads 66) of the encoder system, such
as for example, a pair, takes in the detection signals of each head
and detection signals of Y interferometer 16 (or X interferometer
126) of interferometer system 118 in memory 34 simultaneously at a
predetermined sampling timing, and based on both of the detection
signals, executes a delay time acquisition process of acquiring
information of the delay time for each head the with the detection
signals of the corresponding interferometer serving as a reference.
In the manner described above, it becomes possible for exposure
apparatus 100 (main controller 20) itself to acquire the
information of the delay time of the detection signals of each of
the plurality of heads with the detection signals of the
corresponding interferometer of interferometer system 118 serving
as a reference.
[0447] Then, based on the information of the delay time for each of
the plurality of heads of the encoder system that has been
acquired, and the measurement data corresponding to the detection
signals of each of the plurality of heads, main controller 20
drives wafer stage WST in the manner described above. Accordingly,
even if the delay time is different for each head, it becomes
possible to drive wafer stage WST using each encoder of the encoder
system with good precision, without being affected by the
difference of the delay time between the plurality of heads.
[0448] Further, according to exposure apparatus 100 of the
embodiment, when main controller 20 completes the exposure of wafer
W on wafer stage WST, wafer stage WST is sequentially moved to
unloading position UP and then to loading position LP, and
unloading of wafer W that has been exposed from wafer stage WST and
loading of a new wafer W on wafer stage WST, or more specifically,
exchange of wafer W is performed on wafer stage WST. Each time the
exchange of wafer W is completed, main controller 20 sets the
position of wafer stage WST at the processing position where the
former process of Pri-BCHK described earlier is performed, and
starts the position control of wafer stage WST within the XY plane
using the three encoders of the encoder system once more, according
to the procedure previously described. Therefore, even if the
linkage process (the switching process of the encoder used for the
position control of wafer stage WST in the XY plane) between the
plurality of encoders previously described is repeatedly performed,
the position error (the cumulative error which is accumulated each
time the linkage process is performed) of wafer stage WST that
accompanies the linkage process is canceled each time exchange of
wafer W is performed, so the position error of wafer stage WST
never accumulates beyond a permissible level. Accordingly, the
encoder system makes it possible to measure the positional
information of wafer stage WST within the XY plane in the effective
area previously described that includes the exposure position with
good precision for over a long period, which in turn makes it
possible to maintain the exposure precision for over a long period
of time.
[0449] Further, in the embodiment, main controller 20 starts the
position control of wafer stage WST within the XY plane using the
three encoders of the encoder system once more, in a state in which
yawing of wafer stage WST is adjusted to a position where the
absolute phase of a pair of origin heads 64y.sub.2 and 64y.sub.1
which are spaced apart by distance L (.gtoreq.400 mm) becomes the
initial value that has been decided in advance. Because of this,
the yawing error of wafer stage WST based on the measurement values
of three origin heads at the control starting point within the XY
plane of wafer stage WST can be set approximately to 0, and as a
result, the shift of the baseline of the primary alignment system
in the X-axis direction that accompanies the yawing error of wafer
stage WST, chip rotation (rotational error of the shot area on
wafer W), and the generation of overlay error that accompanies the
chip rotation can be effectively controlled.
[0450] Further, in the embodiment, each time exchange of wafer W is
performed on wafer stage WST, prior to starting the EGA alignment
measurement, or to be more specific, prior to the measurement of
the alignment marks arranged in the three first alignment shot
areas on wafer W by alignment systems AL1, AL2.sub.2, and
AL2.sub.3, main controller 20 begins the position control of wafer
stage WST within the XY plane using the three encoders once more.
Therefore, even if there are some errors in the measurement values
of the X position and the Y position of wafer stage WST measured by
the encoder at the point in time when position control of wafer
stage WST within the XY plane using the three encoders is started
once more, the errors are consequently canceled by the EGA
performed next.
[0451] Further, in the embodiment, as shown in FIGS. 30, 31, and
32, main controller 20 continues the measurement of the positional
information of wafer stage WST in the X-axis direction, which is
the measurement direction of X encoder 70B, even while exchange of
wafer W is being performed on wafer stage WST, using X encoder 70B
(X head 66, which is a head of head unit 62D that faces X scale
39X.sub.2) of the encoder system. Therefore, X interferometer 128,
which measures the X position of wafer stage WST in the vicinity of
unloading position UP and loading position LP, does not necessarily
have to be arranged. However, in the embodiment, X interferometer
128 is arranged for the purpose of backup, such as at the time of
abnormality of the encoder.
[0452] Further, according to exposure apparatus 100 of the
embodiment, for relative movement between illumination light IL
irradiated on wafer W via reticle R, projection optical system PL,
and water Lq from illumination system 10 and wafer W, main
controller 20 drives wafer stage WST on which wafer W is placed
with good precision, based on the measurement values of each
encoder described above, the stage position induced error
correction information of each encoder corresponding to the
positional information of the wafer stage in the direction besides
the measurement direction at the time of the measurement, the
correction information of the grating pitch of each scale and the
correction information of the grid line, and the correction
information of the Abbe error due to the Abbe offset quantity of
each scale.
[0453] Accordingly, by scanning exposure and liquid immersion
exposure, it becomes possible to form a desired pattern of reticle
R in each shot area on the wafer with good precision.
[0454] Further, in the embodiment, as it has been described earlier
based on FIGS. 33 and 34, prior to the measurement (EGA alignment
measurement) of the alignment marks arranged in the three first
alignment shot areas on wafer W by alignment systems AL1,
AL2.sub.2, and AL2.sub.3, main controller 20 switches the
measurement unit used for the position control of wafer stage WST
from interferometer system 118 to the encoder system (switches the
control of the position of wafer table WTB within the XY plane from
the irregular control previously described to the control based on
the measurement values of at least three encoders out of encoders
70B and 70D and encoders 70A and 70C). According to this, even if
there are some errors in the measurement values of the X position
and the Y position of wafer stage WST by the encoder system just
after the switching, there is an advantage of the errors being
consequently canceled by the EGA performed next.
[0455] Further, according to the embodiment, on acquiring the stage
position induced error correction information of the measurement
values of the encoder previously described, main controller 20
changes wafer stage WST into a plurality of different attitudes,
and for each attitude, in a state where the attitude of wafer stage
WST is maintained based on the measurement results of
interferometer system 118, moves wafer stage WST in the Z-axis
direction in a predetermined stroke range while irradiating a
detection light from head 64 or 66 of the encoder on the specific
area of scales 39Y.sub.1, 39Y.sub.2, 39X.sub.1 or 39X.sub.2, and
samples the measurement results of the encoder during the movement.
According to this, change information (for example, an error
characteristics curve as shown in the graph in FIG. 12) of the
measurement values of the encoder corresponding to the position in
the direction (Z-axis direction) orthogonal to the movement plane
of wafer stage WST for each attitude can be obtained.
[0456] Then, by performing a predetermined operation based on this
sampling result, namely the change information of the measurement
values of the encoder corresponding to the position of wafer stage
WST in the Z-axis direction for each attitude, main controller 20
obtains the correction information of the measurement values of the
encoder corresponding to the positional information of wafer stage
WST in the direction besides the measurement direction.
Accordingly, the stage position induced error correction
information for correcting the measurement errors of the encoder
due to a relative change between the head and the scale in the
direction besides the measurement direction can be determined by a
simple method.
[0457] Further, in the embodiment, in the case of deciding the
correction information above, for a plurality of heads that
configure the same head unit, such as, for example, a plurality of
Y heads 64 that configure head unit 62A, because a detection light
is irradiated from each Y head 64 on the same specific area of the
corresponding Y scale 39Y.sub.1, the sampling described above is
performed on the measurement results of the encoder, and the stage
position induced error correction information of each encoder
configured by each Y head 64 and Y scale 39Y.sub.1 is determined
based on the sampling result, by using this correction information,
a geometric error which occurs because of the gradient of the head
is also consequently corrected. In other words, when main
controller 20 obtains by the correction information with the
plurality of encoders corresponding to the same scale as the
object, it obtains the correction information of the encoder
serving as the object taking into consideration the geometric error
which occurs by the gradient of the head of the object encoder when
wafer stage WST is moved in the Z-axis direction. Accordingly, in
the embodiment, a cosine error caused by different gradient angles
in a plurality of heads is also not generated. Further, even if a
gradient does not occur in Y head 64, for example, when a
measurement error occurs in an encoder caused by the optical
properties (telecentricity) of the head or the like, obtaining the
correction information similarly can prevent the measurement error
from occurring, which in turn prevents the deterioration of the
position control precision of wafer stage WST. That is, in the
embodiment, wafer stage WST is driven so as to compensate for the
measurement errors (hereinafter also referred to as a head induced
error) of the encoder system which occur due to the head unit.
Incidentally, for example, correction information of the
measurement values of the encoder system can be computed, based on
the characteristic information (for example, including the gradient
of the head and/or the optical properties and the like) of the head
unit.
[0458] Incidentally, in the embodiment above, on the switching of
the encoder used for position control of wafer stage WST, the case
has been described where of the three encoders (head) that measure
the positional information of wafer stage WST within the movement
plane in directions of three degrees of freedom, one encoder (head)
was switched to another encoder (head) so that the position (X, Y,
.theta.z) of wafer stage WST within the XY plane (movement plane)
in directions of three degrees of freedom is maintained before and
after the switching, however, the present invention is not limited
to this. For example, in the case when a movable body is not
allowed to rotate within the movement plane, the degree of freedom
that the movable body has is only two degrees of freedom (X, Y) in
the movement plane, however, the present invention can be applied
even to such a case. More specifically, in this case, an encoder
system that includes a total of three or more encoders including at
least one each of a first encoder which measures positional
information of the movable body in a direction that is parallel to
a first axis within the movement plane and a second encoder which
measures positional information of the movable body in a direction
parallel to a second axis orthogonal to the first axis in the
movement plane can be used by a controller, and the controller can
switch an encoder used for measurement of the positional
information of the movable body within the movement plane from an
encoder of either of at least two encoders that include each one of
the first encoder and the second encoder to another encoder, so as
to maintain the position of the movable body within the movement
plane before and after the switching. In the case of such an
arrangement, the position of the movable body within the movement
plane before and after the switching is maintained although the
switching of the encoder used for controlling the position of the
movable body is performed, which allows a precise linkage to be
performed, which in turn makes it possible to perform linkage
between a plurality of encoders while moving the movable body
two-dimensionally precisely along a predetermined course. Further,
similar to the embodiment above, the controller can make out a
combination of the encoders subject to the switching and prepare
the schedule for the switching timing based on the movement course
of the movable body, as well as constantly takes in the measurement
values of each encoder of the encoder system, and the controller
can also execute an operation to switch the encoder used for
control of the movable body from an encoder of either of at least
the two encoders used for position control of the movable body to
another encoder in synchronization with the timing of the position
control of the movable body.
[0459] Further, on the switching described above, the controller
can compute the positional information of the movement plane of the
movable body by a computing formula using the affine transformation
relation based on the measurement value of at least the two
encoders used for position control of the movable body before the
switching, and can decide the initial value of the measurement
value of the another encoder so as to satisfy the computed
results.
[0460] Incidentally, in the embodiment above, a movable body drive
system was described in which an encoder system including an a
plurality of encoders which measure the positional information of a
wafer stage that moves within a two-dimensional plane is equipped,
and main controller 20 constantly takes in the output of each
encoder of the encoder system and executes an operation of
switching an encoder used for position control of the movable body
from an encoder that has been used for position control of the
movable body to another encoder, at a timing in synchronization
with the position control of the movable body, however, besides
such a system, for example, in a movable body drive system equipped
with the encoder system including a plurality of encoders which
measure the positional information of a movable body that moves
only in a one-dimensional direction, the controller can constantly
take in the output of each encoder of the encoder system and
execute an operation of switching an encoder used for position
control of the movable body from an encoder that has been used for
position control of the movable body to another encoder, at a
timing in synchronization with the position control of the movable
body. Even in such a case, the switching of the encoder will not
have to be performed at a high speed, and a highly precise hardware
for the switching will not be necessary, which consequently will
make cost reduction possible.
[0461] Further, in the embodiment above, the case has been
described where main controller 20 makes out a combination of the
encoders subject to the switching of the encoder from an arbitrary
encoder out of the three encoders of the encoder system that
measures the positional information of wafer stage WST in
directions of three degrees of freedom within the movement plane
(XY plane) to another encoder and prepares the schedule for the
switching timing based on the movement course of the movable body,
however, the present invention is not limited to this. For example,
there are movable bodies in which the movement of the movable body
is allowed only in directions of two degrees of freedom or in a
direction of one degree of freedom, however, even in a movable body
drive system that drives such a movable body within the movement
plane, if the system is equipped with an encoder system including a
plurality of encoders for measuring the positional information of
the movable body within the movement plane, it is desirable to make
out a combination of the encoders subject to the switching of the
encoder from an arbitrary encoder of the encoder system used for
position control of the movable body to another encoder and prepare
the schedule for the switching timing based on the movement course
of the movable body, similar to the embodiment described above.
According to this, a reasonable encoder switching according to the
target track of the movable body becomes possible. Further, in this
case as well, the controller can constantly take in the output of
each encoder of the encoder system and execute an operation of
switching an encoder used for position control of the movable body
from an encoder that has been used for position control of the
movable body to another encoder, at a timing in synchronization
with the position control of the movable body.
[0462] When wafer stage WST is moved in the X-axis direction, in
the embodiment above, for example, the switching of the head and
linkage process of head unit 62A and head unit 62C is performed
simultaneously, or a part of the process is performed in parallel,
however, the process can be performed in head units 62A and 62C at
a different timing. In this case, for example, the distance between
adjacent heads is to be the same in head units 62A and 62C, and the
position of head units 62A and 62C placed in the X-axis direction
can be shifted.
[0463] Incidentally, in the embodiment above, an invention related
to the switching of the head of the encoder and the linkage of the
measurement value, an invention related to the correction of
various measurement errors (e.g., stage position induced error,
head induced error, scale induced error, Abbe error and the like)
of the encoder system, an invention (invention about the reset of
the encoder system) in which the position control of the wafer
stage using the encoder system was started once more after every
wafer exchange, an invention related to the switching timing in
which the switching operation of the encoder (head) is executed at
a timing in synchronization with the position control of the wafer
stage, an invention to prepare the schedule for the switching
timing based on the movement course of the wafer stage, an
invention associated with the correction of the measurement errors
of the encoder head due to the measurement delay that accompanies
the propagation of the detection signal and the like were carried
out by the same exposure apparatus. However, the inventions above
can be executed alone or in any combination.
[0464] Further, in combination with the head switching/the linkage
process previously described, a correction of the stage position
induced error, the head induced error, the scale induced error and
the Abbe error previously described or a combination of two or more
of the corrections can also be performed.
[0465] Incidentally, in the embodiment above, the case has been
described where main controller 20 computes an approximation
straight line (for example, refer to straight line y=Y.sub.cal(t)
shown in FIG. 10) with respect to the temporal change (for example,
refer to temporal change curve y=y(t) shown in FIG. 10) of the
position of wafer stage WST, based on the latest measurement values
of each encoder (head) acquired at current time t and the
measurement values of each encoder just before the latest
measurement value (one control sampling interval), and drives wafer
stage WST using the approximation straight line so that the
measurement errors due to the measurement delay that accompanies
the propagation of the detection signal of each head of the encoder
system through the propagation path are corrected, however, the
present invention is not limited to this. More specifically, in the
present invention, in addition to the latest measurement data and
the measurement data just before the latest measurement data (one
control sampling interval), the controller can compute a secondary
approximate curve of the temporal change curve of the position of
the movable body using measurement data two measurements before the
latest measurement data (two control sampling interval), and can
drive wafer stage WST so that the measurement errors due to the
measurement delay that accompanies the propagation of the detection
signal of each head of the encoder system through the propagation
path are corrected based on the approximation curve. The important
thing is the controller should drive the movable body based on a
plurality of data which includes the latest measurement data of the
head of the encoder system and previous data including at least the
measurement data just before the latest measurement data and on
information of the delay time that accompanies the propagation the
detection signal of the head through the cable, so that the
measurement errors due to the measurement delay of the head are
corrected.
[0466] Further, in the embodiment above, based on the detection
signals of each Y head (each or, X head) of the encoder system and
the detection signals of Y interferometer 16 (or X interferometer
126), main controller 20 performed the delay time acquisition
process in which the information of the delay time of each Y head
(or each X head) was acquired with the detection signals of Y
interferometer 16 (or X interferometer 126) serving as a reference,
however, the present invention is not limited to this, and by
obtaining the difference of the delay time that accompanies the
propagation of the detection signal of one of the X heads (or Y
heads) through the cable and the delay time that accompanies the
propagation of the detection signal of other X heads (or Y heads),
information of the delay time for other X heads (or Y head) can be
acquired with the detection signals of the one X head (or Y head)
above serving as a reference.
[0467] Further, in the embodiment above, main controller 20
performed the delay time acquisition process on all heads of the
encoder system, however, the present invention is not limited to
this, and the delay time acquisition process can be performed on
some heads.
[0468] Further, in the embodiment above, as it has been described
referring to FIG. 20, on the delay time acquisition process, main
controller 20 obtained the information of the delay time based on
intensity difference .DELTA.I of each head, e.g. detection signal
C2 of Y head 64 and the corresponding interferometer, e.g. output
signal C1 of Y interferometer 16, and computed the information of
delay time .delta. above for Y head 64, however, the present
invention is not limited to this, and the information of the delay
time can be obtained directly, from the shift of both signals in
the temporal axis direction.
[0469] Incidentally, in the embodiment above, the case has been
described where all heads of head unit 62D except for one head 66
no longer face the scale at the unloading position and the loading
position, and the position measurement of the wafer stage within
the XY plane by the encoder system could no longer be performed
physically, however, the present invention is not limited to this.
More specifically, even if the position measurement of the wafer
stage within the XY plane by the encoder system can be continued
even at the unloading position and the loading position, it is
desirable to begin the position measurement and position control of
wafer stage WST using the three encoders once more, at any point
while wafer stage WST returns from the wafer exchange position to
the alignment area, similar to the embodiment above. By doing so,
the cumulative error of the wafer stage position that accompanies
the linkage process repeatedly performed between a plurality of
encoders can be canceled regularly.
[0470] Incidentally, in the embodiment above, in order to simplify
the description, main controller 20 had control over each part of
the exposure apparatus such as the stage system, the interferometer
system, the encoder system and the like, however, the present
invention is not limited to this, and it is a matter of course that
at least a part of the control performed by main controller 20 can
be shared with a plurality of controllers. For example, a stage
controller, which controls wafer stage WST based on the measurement
values of the encoder system, the Z sensor and the interferometer
system, can be arranged to operate under main controller 20.
Further, the control that main controller 20 performs does not
necessarily have to be realized by hardware, and the control can be
realized by software using a computer program that sets the
operation of main controller 20 or each operation of some
controllers that share the control as previously described.
[0471] Incidentally, the configuration and the placement of the
encoder system, the interferometer system, the multipoint AF
system, the Z sensor and the like in the embodiment above is an
example among many, and it is a matter of course that the present
invention is not limited to this. For example, in the embodiment
above, an example was indicated of a case where the pair of Y
scales 39Y.sub.1 and 39Y.sub.2 used for the measurement of the
position in the Y-axis direction and the pair of X scales 39X.sub.1
and 39X.sub.2 used for the measurement of the position in the
X-axis direction are arranged on wafer table WTB, and corresponding
to the scales, the pair of head units 62A and 62C is placed on one
side and the other side of the X-axis direction of projection
optical system PL, and the pair of head units 62B and 62D is placed
on one side and the other side of the Y-axis direction of
projection optical system PL. However, the present invention is not
limited to this, and of Y scales 39Y.sub.1 and 39Y.sub.2 used for
the measurement of the position in the Y-axis direction and X
scales 39X.sub.1 and 39X.sub.2 used for the measurement of the
position in the X-axis direction, at least one of the scales can be
arranged singularly on wafer table WTB, without being a pair, or,
of the pair of head units 62A and 62C and the pair of head units
62B and 62D, at least one of the head units can be arranged,
singularly. Further, the extension direction of the scale and the
extension direction of the head unit are not limited to an
orthogonal direction such as the X-axis direction and the Y-axis
direction in the embodiment above, and it can be any direction as
long as the directions intersect each other. Further, the periodic
direction of the diffraction grating can be a direction orthogonal
to (or intersecting with) the longitudinal direction of each scale,
and in such a case, a plurality of heads of the corresponding head
unit should be placed in a direction orthogonal to the periodic
direction of the diffraction grating. Further, each head unit can
have a plurality of heads placed without any gap in a direction
orthogonal to the periodic direction of the diffraction
grating.
[0472] Further, in the embodiment above, the case has been
described where the X scale and the Y scale were placed on a
surface parallel to the XY plane of wafer stage WST, or to be more
concrete, on the upper surface, however, the present invention is
not limited to this, and the grating can be placed, as a matter of
course, on the lower surface, or on the side surface of wafer stage
WST. Or an encoder system having a configuration in which a head is
arranged on a wafer stage, and a two-dimensional grating (or a
one-dimensional grating section which is arranged
two-dimensionally) placed external to the movable body can be
employed. In this case, when a Z sensor is placed on the wafer
stage upper surface, the two-dimensional grating (or the
one-dimensional grating section which is arranged
two-dimensionally) can also be used as a reflection surface
reflecting the measurement beam from a Z sensor.
[0473] Incidentally, in the embodiment above, rotation information
(pitching amount) of wafer stage WST in the .theta.x direction was
measured by interferometer system 118, however, for example, the
pitching amount can be obtained from the measurement values of
either of the pair of Z sensors 74.sub.i,j or 76.sub.p,q. Or,
similar to head units 62A and 62C, for example, one Z sensor or a
pair of Z sensors can be arranged in proximity each head of head
units 62B and 62D, and the pitching amount can be obtained from X
scales 39X.sub.1 and 39X.sub.2 and the measurement value of the Z
sensors that face the scales, respectively. Accordingly, it becomes
possible to measure the positional information of wafer stage WST
in directions of six degrees of freedom, or more specifically, the
X-axis, Y-axis, Z-axis, .theta.x, .theta.y, and .theta.z directions
using the encoder and the Z sensor previously described, without
using interferometer system 118. The measurement of the positional
information of wafer stage WST in directions of six degrees of
freedom using the encoder and the Z sensor previously described can
be performed not only in the exposure operation but also in the
alignment operation and/or the focus mapping operation previously
described.
[0474] Further, in the embodiment above, the measurement values of
the encoder system were corrected based on the correction
information previously described so as to compensate for the
measurement errors of the encoder system that occur due to
displacement (relative displacement of the head and the scale) of
wafer stage WST in a direction different from a predetermined
direction in which wafer stage WST is driven, however, the present
invention is not limited to this, and the target position for
setting the position of wafer stage WST based on the correction
information previously described can be corrected, for example,
while driving wafer stage WST based on the measurement values of
the encoder system. Or, especially in the exposure operation, the
position of reticle stage RST can be corrected based on the
correction information previously described, while, for example,
driving wafer stage WST based on the measurement values of the
encoder system.
[0475] Further, in the embodiment above, wafer stage WST was driven
based on the measurement value of the encoder system, for example,
in the case of exposure, however, for example, an encoder system
the measures the position of reticle stage RST can be added, and
reticle stage RST can be driven based on the correction information
that corresponds to the measurement values of the encoder system
and the positional information of the reticle stage in the
direction besides the measurement direction measured by reticle
interferometer 116.
[0476] Further, in the embodiment above, the case has been
described where the apparatus is equipped with one fixed primary
alignment system and four movable secondary alignment systems, and
alignment marks arranged in the 16 alignment shot areas on the
wafer are detected by the sequence according to the five alignment
systems. However, the secondary alignment system does not need to
be movable, and, further, the number of the secondary alignment
systems does not matter. The important thing is that there is at
least one alignment system that can detect the alignment marks on
the wafer.
[0477] Incidentally, in the embodiment above, the exposure
apparatus which is equipped with measurement stage MST separately
from wafer stage WST was described as in the exposure apparatus
disclosed in the pamphlet of International Publication No. WO
2005/074014, however, the present invention is not limited to this,
and for example, as is disclosed in, for example, Kokai (Japanese
Patent Unexamined Application Publication) No. 10-214783 and the
corresponding U.S. Pat. No. 6,341,007, and in the pamphlet of
International Publication No. WO 98/40791 and the corresponding
U.S. Pat. No. 6,262,796 and the like, even in an exposure apparatus
by the twin wafer stage method that can execute the exposure
operation and the measurement operation (e.g., mark detection by
the alignment system) almost in parallel using two wafer stages, it
is possible to perform the position control of each wafer stage the
encoder system (refer to FIG. 3 and the like) previously described.
By appropriately setting the placement and length of each head unit
not only during the exposure operation but also during the
measurement operation, the position control of each wafer stage can
be performed continuing the use of the encoder system previously
described, however, a head unit that can be used during the
measurement operation can be arranged, separately from head units
(62A to 62D) previously described. For example, four head units can
be placed in the shape of a cross with one or two alignment systems
in the center, and during the measurement operation above, the
positional information of each wafer stage WST can be measured
using these head units and the corresponding scales. In the
exposure apparatus by the twin wafer stage method, at least two
scales each is arranged in the two wafer stages, respectively, and
when the exposure operation of the wafer mounted on one of the
wafer stages is completed, in exchange with the stage, the other
wafer stage on which the next wafer that has undergone mark
detection and the like at the measurement position is mounted is
placed at the exposure position. Further, the measurement operation
performed in parallel with the exposure operation is not limited to
the mark detection of wafers and the like by the alignment system,
and instead of this, or in combination with this, the surface
information (step information) of the wafer can also be
detected.
[0478] Incidentally, in the embodiment above, the case has been
described where Sec-BCHK (interval) is performed using CD bar 46 on
the measurement stage MST side while each wafer is exchanged on the
wafer stage WST side, however, the present invention is not limited
to this, and at least one of an illuminance irregularity
measurement (and illuminance measurement), aerial image
measurement, wavefront aberration measurement and the like can be
performed using a measuring instrument (measurement member) of
measurement stage MST, and the measurement results can be reflected
in the exposure of the wafer performed later on. To be more
concrete, for example, projection optical system PL can be adjusted
by adjustment unit 68 based on the measurement results.
[0479] Further, in the embodiment above, a scale can also be placed
on measurement stage MST, the position control of the measurement
stage can be performed using the encoder system (head unit)
previously described. More specifically, the movable body that
performs the measurement of positional information using the
encoder system is not limited to the wafer stage.
[0480] Incidentally, when reducing the size and weight of wafer
stage WST is taken into consideration, it is desirable to place the
scale as close as possible to wafer W on wafer stage WST, however,
when the size of the wafer stage is allowed to increase, by
increasing the size of the wafer stage and increasing the distance
between the pair of scales that is placed facing the stage,
positional information of at least two each in the X-axis and
Y-axis directions, that is, a total of four positional information,
can be measured constantly during the exposure operation. Further,
instead of increasing the size of the wafer stage, for example, a
part of the scale can be arranged so that it protrudes from the
wafer stage, or, by placing the scale on the outer side of wafer
stage main body using an auxiliary plate on which at least one
scale is arranged, the distance between the pair of scales that
face the stage can be increased as in the description above.
[0481] Further, in the embodiment above, in order to prevent
deterioration in the measurement accuracy caused by adhesion of a
foreign material, contamination, and the like to Y scales 39Y.sub.1
and 39Y.sub.2, and X scales 39X.sub.1 and 39X.sub.2, for example, a
coating can be applied on the surface so as to cover at least the
diffraction grating, or a cover glass can be arranged. In this
case, especially in the case of a liquid immersion type exposure
apparatus, a liquid repellent protection film can be coated on the
scale (a grating surface), or a liquid repellent film can be formed
on the surface (upper surface) of the cover glass. Furthermore, the
diffraction grating was formed continually on substantially the
entire area in the longitudinal direction of each scale, however,
for example, the diffraction grating can be formed intermittently
divided into a plurality of areas, or each scale can be configured
by a plurality of scales. Further, in the embodiment above, an
example was given in the case where an encoder by the diffraction
interference method is used as the encoder, however, the present
invention is not limited to this, and methods such as the so-called
pickup method, the magnetic method and the like can be used, and
the so-called scan encoders whose details are disclosed in, for
example, U.S. Pat. No. 6,639,686 and the like, can also be
used.
[0482] Further, in the embodiment above, as the Z sensor, instead
of the sensor by the optical pick-up method referred to above, for
example, a sensor configured by a first sensor (the sensor can be a
sensor by the optical pick-up method or other optical displacement
sensors) that projects a probe beam on a measurement object surface
and optically reads the displacement of the measurement object
surface in the Z-axis direction by receiving the reflected light, a
drive section that drives the first sensor in the Z-axis direction,
and a second sensor (e.g. encoders and the like) that measures the
displacement of the first sensor in the Z-axis direction can be
used. In the Z sensor having the configuration described above, a
mode (the first servo control mode) in which the drive section
drives the first sensor in the Z-axis direction based on the output
of the first sensor so that the distance between the measurement
object surface, such as the surface of the scale and the first
sensor in the Z-axis direction is always constant, and a mode (the
first servo control mode) in which a target value of the second
sensor is given from an external section (controller) and the drive
section maintains the position of the first sensor in the Z-axis
direction so that the measurement values of the second sensor
coincides with the target value can be set. In the case of the
first servo control mode, as the output of the Z sensor, the output
of the measuring section (the second sensor) can be used, and in
the case of the second servo control mode, the output of the second
sensor can be used. Further, in the case of using such a Z sensor,
and when an encoder is employed as the second sensor, as a
consequence, the positional information of wafer stage WST (wafer
table WTB) in directions of six degrees of freedom can be measured
using an encoder. Further, in the embodiment above, as the Z
sensor, a sensor by other detection methods can be employed.
[0483] Further, in the embodiment above, the configuration of the
plurality of interferometers used for measuring the positional
information of wafer stage WST and their combination are not
limited to the configuration and the combination previously
described. The important thing is that as long as the positional
information of wafer stage WST of the direction except for the
measurement direction of the encoder system can be measured, the
configuration of the interferometers and their combination does not
especially matter. The important thing is that there should be a
measurement unit (it does not matter whether it is an
interferometer or not) besides the encoder system described above
that can measure the positional information of wafer stage WST in
the direction except for the measurement direction of the encoder
system. For example, the Z sensor previously described can be used
as such a measurement unit.
[0484] Further, in the embodiment above, the Z sensor was arranged
besides the multipoint AF system, however, for example, in the case
the surface position information of the shot area subject to
exposure of wafer W can be detected with the multipoint AF system
on exposure, then the Z sensor does not necessarily have to be
arranged.
[0485] Incidentally, in the embodiment above, pure water (water)
was used as the liquid, however, it is a matter of course that the
present invention is not limited to this. As the liquid, liquid
that is chemically stable, having high transmittance to
illumination light IL and safe to use, such as a
fluorine-containing inert liquid may be used. As the
fluorine-containing inert liquid, for example, Fluorinert (the
brand name of 3M United States) can be used. The
fluorine-containing inert liquid is also excellent from the point
of cooling effect. Further, as the liquid, liquid which has a
refractive index higher than pure water (a refractive index is
around 1.44), for example, liquid having a refractive index equal
to or higher than 1.5 can be used. As this type of liquid, for
example, a predetermined liquid having C--H binding or O--H binding
such as isopropanol having a refractive index of about 1.50,
glycerol (glycerin) having a refractive index of about 1.61, a
predetermined liquid (organic solvent) such as hexane, heptane or
decane, or decalin (decahydronaphthalene) having a refractive index
of about 1.60, or the like can be cited. Alternatively, a liquid
obtained by mixing arbitrary two or more of these liquids may be
used, or a liquid obtained by adding (mixing) the predetermined
liquid to (with) pure water can be used. Alternatively, as the
liquid, a liquid obtained by adding (mixing) base or acid such as
H.sup.+, Cs.sup.+, K.sup.+, Cl.sup.-, SO.sub.4.sup.2-, or
PO.sub.4.sup.2- to (with) pure water can be used. Moreover, a
liquid obtained by adding (mixing) particles of Al oxide or the
like to (with) pure water can be used. These liquids can transmit
ArF excimer laser light. Further, as the liquid, liquid, which has
a small absorption coefficient of light, is less
temperature-dependent, and is stable to a projection optical system
(tip optical member) and/or a photosensitive agent (or a protection
film (top coat film), an antireflection film, or the like) coated
on the surface of a wafer, is preferable. Further, in the case an
F.sub.2 laser is used as the light source, fomblin oil can be
selected.
[0486] Further, in the embodiment above, the recovered liquid may
be reused, and in this case, a filter that removes impurities from
the recovered liquid is preferably arranged in a liquid recovery
unit, a recovery pipe or the like.
[0487] Further, in the embodiment above, the case has been
described where the exposure apparatus is a liquid immersion type
exposure apparatus, however, the present invention is not limited
to this, and it can also be applied to a dry type exposure
apparatus that performs exposure of wafer W without liquid
(water).
[0488] Further, in the embodiment above, the case has been
described where the present invention is applied to a scanning
exposure apparatus by a step-and-scan method or the like. However,
the present invention is not limited to this, but may also be
applied to a static exposure apparatus such as a stepper. Even with
the stepper or the like, by measuring the position of a stage on
which an object subject to exposure is mounted by encoders,
generation of position measurement error caused by air fluctuations
can substantially be nulled likewise. Further, with the stepper or
the like, the switching of the encoder used for position control of
the stage can be performed as is previously described, and a
combination of the encoders (heads) subject to the switching can be
made out and the schedule for the switching timing prepared.
Further, the timing of the switching operation can be in
synchronization with the timing of the position control of the
stage. Furthermore, it becomes possible to set the position of the
stage with high precision based on the measurement values of the
encoder and each of the correction information previously
described, and as a consequence, it becomes possible to transfer a
reticle pattern onto an object with high precision. Further, the
present invention can also be applied to a reduction projection
exposure apparatus by a step-and-stitch method that synthesizes a
shot area and a shot area, an exposure apparatus by a proximity
method, a mirror projection aligner, or the like.
[0489] Further, the magnification of the projection optical system
in the exposure apparatus of the embodiment above is not only a
reduction system, but can also be either an equal magnifying system
or a magnifying system, and projection optical system PL is not
only a dioptric system, but can also be either a catoptric system
or a catadioptric system, and in addition, the projected image may
be either an inverted image or an upright image. Moreover, the
exposure area to which illumination light IL is irradiated via
projection optical system PL is an on-axis area that includes
optical axis AX within the field of projection optical system PL.
However, for example, as is disclosed in the pamphlet of
International Publication No. WO 2004/107011, the exposure area can
also be an off-axis area that does not include optical axis AX,
similar to a so-called inline type catadioptric system, in part of
which an optical system (catoptric system or catadioptric system)
that has plural reflection surfaces and forms an intermediate image
at least once is arranged, and which has a single optical axis.
Further, the illumination area and exposure area described above
are to have a rectangular shape. However, the shape is not limited
to rectangular, and can also be circular arc, trapezoidal,
parallelogram or the like.
[0490] Incidentally, a light source of the exposure apparatus in
the embodiment above is not limited to the ArF excimer laser, but a
pulse laser light source such as a KrF excimer laser (output
wavelength: 248 nm), an F.sub.2 laser (output wavelength: 157 nm),
an Ar.sub.2 laser (output wavelength: 126 nm) or a Kr.sub.2 laser
(output wavelength: 146 nm), or an extra-high pressure mercury lamp
that generates an emission line such as a g-line (wavelength: 436
nm) or an i-line (wavelength: 365 nm) can also be used. Further, a
harmonic wave generating unit of a YAG laser or the like can also
be used. Besides the sources above, as is disclosed in, for
example, the pamphlet of International Publication No. WO
1999/46835 (the corresponding U.S. Pat. No. 7,023,610), a harmonic
wave, which is obtained by amplifying a single-wavelength laser
beam in the infrared or visible range emitted by a DFB
semiconductor laser or fiber laser as vacuum ultraviolet light,
with a fiber amplifier doped with, for example, erbium (or both
erbium and ytteribium), and by converting the wavelength into
ultraviolet light using a nonlinear optical crystal, can also be
used.
[0491] Further, in the embodiment above, illumination light IL of
the exposure apparatus is not limited to the light having a
wavelength equal to or more than 100 nm, and it is needless to say
that the light having a wavelength less than 100 nm can be used.
For example, in recent years, in order to expose a pattern equal to
or less than 70 nm, development of an EUV exposure apparatus that
makes an SOR or a plasma laser as a light source generate an EUV
(Extreme Ultraviolet) light in a soft X-ray range (e.g. a
wavelength range from 5 to 15 nm), and uses a total reflection
reduction optical system designed under the exposure wavelength
(e.g. 13.5 nm) and the reflective mask is underway. In the EUV
exposure apparatus, the arrangement in which scanning exposure is
performed by synchronously scanning a mask and a wafer using a
circular arc illumination can be considered, and therefore, the
present invention can also be suitably applied to such an exposure
apparatus. Besides such an apparatus, the present invention can
also be applied to an exposure apparatus that uses charged particle
beams such as an electron beam or an ion beam.
[0492] Further, in the embodiment above, a transmissive type mask
(reticle), which is a transmissive substrate on which a
predetermined light shielding pattern (or a phase pattern or a
light attenuation pattern) is formed, is used. Instead of this
reticle, however, as is disclosed in, for example, U.S. Pat. No.
6,778,257, an electron mask (which is also called a variable shaped
mask, an active mask or an image generator, and includes, for
example, a DMD (Digital Micromirror Device) that is a type of a
non-emission type image display device (spatial light modulator) or
the like) on which a light-transmitting pattern, a reflection
pattern, or an emission pattern is formed according to electronic
data of the pattern that is to be exposed can also be used. In the
case of using such a variable shaped mask, because the stage on
which a wafer or a glass plate is mounted moves relatively with
respect to the variable shaped mask, by driving the stage based on
the measurement values of an encoder and each correction
information previously described while measuring the position of
the stage within the movement plane using the encoder system and
performing the linkage operation between a plurality of encoders
previously described, an equivalent effect as the embodiment
described above can be obtained.
[0493] Further, as is disclosed in, for example, the pamphlet of
International Publication No. WO 2001/035168, the present invention
can also be applied to an exposure apparatus (lithography system)
that forms line-and-space patterns on a wafer by forming
interference fringes on the wafer.
[0494] Moreover, the present invention can also be applied to an
exposure apparatus that synthesizes two reticle patterns via a
projection optical system and almost simultaneously performs double
exposure of one shot area by one scanning exposure, as is disclosed
in, for example, Kohyo (published Japanese translation of
International Publication for Patent Application) No. 2004-519850
(the corresponding U.S. Pat. No. 6,611,316).
[0495] Further, an apparatus that forms a pattern on an object is
not limited to the exposure apparatus (lithography system)
described above, and for example, the present invention can also be
applied to an apparatus that forms a pattern on an object by an
ink-jet method.
[0496] Incidentally, an object on which a pattern is to be formed
(an object subject to exposure to which an energy beam is
irradiated) in the embodiment above is not limited to a wafer, and
can be other objects such as a glass plate, a ceramic substrate, a
film member, or a mask blank.
[0497] The use of the exposure apparatus is not limited only to the
exposure apparatus for manufacturing semiconductor devices, but the
present invention can also be widely applied to an exposure
apparatus for transferring a liquid crystal display device pattern
onto a rectangular glass plate and an exposure apparatus for
producing organic ELs, thin-film magnetic heads, imaging devices
(such as CCDs), micromachines, DNA chips, and the like. Further,
the present invention can be applied not only to an exposure
apparatus for producing microdevices such as semiconductor devices,
but can also be applied to an exposure apparatus that transfers a
circuit pattern onto a glass plate or silicon wafer to produce a
mask or reticle used in a light exposure apparatus, an EUV exposure
apparatus, an X-ray exposure apparatus, an electron-beam exposure
apparatus, and the like.
[0498] Incidentally, the movable body drive system, the movable
body drive method, or the deciding method of the present invention
can be applied not only to the exposure apparatus, but can also be
applied widely to other substrate processing apparatuses (such as a
laser repair apparatus, a substrate inspection apparatus and the
like), or to apparatuses equipped with a movable body such as a
stage that moves within a two-dimensional plane such as a position
setting apparatus for samples or a wire bonding apparatus in other
precision machines.
[0499] Further, the exposure apparatus (the pattern forming
apparatus) of the embodiment above is manufactured by assembling
various subsystems, which include the respective constituents that
are recited in the claims of the present application, so as to keep
predetermined mechanical accuracy, electrical accuracy and optical
accuracy. In order to secure these various kinds of accuracy,
before and after the assembly, adjustment to achieve the optical
accuracy for various optical systems, adjustment to achieve the
mechanical accuracy for various mechanical systems, and adjustment
to achieve the electrical accuracy for various electric systems are
performed. A process of assembling various subsystems into the
exposure apparatus includes mechanical connection, wiring
connection of electric circuits, piping connection of pressure
circuits, and the like among various types of subsystems. Needless
to say, an assembly process of individual subsystem is performed
before the process of assembling the various subsystems into the
exposure apparatus. When the process of assembling the various
subsystems into the exposure apparatus is completed, a total
adjustment is performed and various kinds of accuracy as the entire
exposure apparatus are secured. Incidentally, the making of the
exposure apparatus is preferably performed in a clean room where
the temperature, the degree of cleanliness and the like are
controlled.
[0500] Incidentally, the disclosures of the various publications,
the pamphlets of the International Publications, and the U.S.
Patent Application Publication descriptions and the U.S. patent
descriptions that are cited in the embodiment above and related to
exposure apparatuses and the like are each incorporated herein by
reference.
[0501] Next, an embodiment of a device manufacturing method in
which the exposure apparatus (pattern forming apparatus) described
above is used in a lithography process will be described.
[0502] FIG. 41 shows a flowchart of an example when manufacturing a
device (a semiconductor chip such as an IC or an LSI, a liquid
crystal panel, a CCD, a thin film magnetic head, a micromachine,
and the like). As is shown in FIG. 41, first of all, in step 201
(design step), function and performance design of device (such as
circuit design of semiconductor device) is performed, and pattern
design to realize the function is performed. Then, in step 202 (a
mask making step), a mask (reticle) is made on which the circuit
pattern that has been designed is formed. Meanwhile, in step 203 (a
wafer fabrication step), wafers are manufactured using materials
such as silicon.
[0503] Next, in step 204 (wafer processing step), the actual
circuit and the like are formed on the wafer by lithography or the
like in a manner that will be described later, using the mask and
the wafer prepared in steps 201 to 203. Then, in step 205 (device
assembly step), device assembly is performed using the wafer
processed in step 204. Step 205 includes processes such as the
dicing process, the bonding process, and the packaging process
(chip encapsulation), and the like when necessary.
[0504] Finally, in step 206 (an inspecting step), tests are
performed on a device made in step 205, such as the operation check
test, durability test and the like. After these processes, the
devices are completed and are shipped out.
[0505] FIG. 42 is a flowchart showing a detailed example of step
204 described above. In FIG. 42, in step 211 (an oxidation step),
the surface of wafer is oxidized. In step 212 (CDV step), an
insulating film is formed on the wafer surface. In step 213 (an
electrode formation step), an electrode is formed on the wafer by
deposition. In step 214 (an ion implantation step), ions are
implanted into the wafer. Each of the above steps 211 to step 214
constitutes the preprocess in each step of wafer processing, and
the necessary processing is chosen and is executed at each
stage.
[0506] When the above-described preprocess ends in each stage of
wafer processing, post-process is executed as follows. First of
all, in the post-process, first in step 215 (a resist formation
step), a photosensitive agent is coated on the wafer. Then, in step
216 (exposure step), the circuit pattern of the mask is transferred
onto the wafer by the exposure apparatus (pattern forming
apparatus) described above and the exposure method (pattern forming
method) thereof. Next, in step 217 (development step), the wafer
that has been exposed is developed, and in step 218 (etching step),
an exposed member of an area other than the area where resist
remains is removed by etching. Then, in step 219 (resist removing
step), when etching is completed, the resist that is no longer
necessary is removed.
[0507] By repeatedly performing the pre-process and the
post-process, multiple circuit patterns are formed on the
wafer.
[0508] By using the device manufacturing method of the embodiment
described above, because the exposure apparatus (pattern forming
apparatus) in the embodiment above and the exposure method (pattern
forming method) thereof are used in the exposure step (step 216),
exposure with high throughput can be performed while maintaining
the high overlay accuracy. Accordingly, the productivity of highly
integrated microdevices on which fine patterns are formed can be
improved.
[0509] While the above-described embodiments of the present
invention are the presently preferred embodiments thereof, those
skilled in the art of lithography systems will readily recognize
that numerous additions, modifications, and substitutions may be
made to the above-described embodiments without departing from the
spirit and scope thereof. It is intended that all such
modifications, additions, and substitutions fall within the scope
of the present invention, which is best defined by the claims
appended below.
* * * * *