U.S. patent application number 09/210801 was filed with the patent office on 2001-08-16 for stage apparatus, exposure apparatus using the same, and a device manufacturing method.
Invention is credited to ITOH, HIROSHI, KORENAGA, NOBUSHIGE.
Application Number | 20010013927 09/210801 |
Document ID | / |
Family ID | 18466397 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013927 |
Kind Code |
A1 |
ITOH, HIROSHI ; et
al. |
August 16, 2001 |
STAGE APPARATUS, EXPOSURE APPARATUS USING THE SAME, AND A DEVICE
MANUFACTURING METHOD
Abstract
A stage apparatus includes a base having a reference plane, a
stage mounted on the base, a plurality of static-pressure bearings
forming a gap between the reference plane and the stage, a
plurality of preloading mechanisms producing a preload between the
stage and the reference plane, a guideless motor for driving the
stage and a controller for controlling driving of the stage in (i)
at least one of a direction at perpendicular to the reference plane
and in a tilting direction by controlling at least one of the
static-pressure bearings and the preloading mechanism, and (ii) in
a direction within the reference plane by the guideless motor.
Positioning of the stage in a Z-direction and in tilting directions
can be carried out by electromagnets and air pads. Positioning in
directions (X, Y, .theta.) within a plane parallel to the reference
plane of the base can be accomplished by guideless motors.
Inventors: |
ITOH, HIROSHI; (TOKYO,
JP) ; KORENAGA, NOBUSHIGE; (UTSUNOMIYA-SHI,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
18466397 |
Appl. No.: |
09/210801 |
Filed: |
December 15, 1998 |
Current U.S.
Class: |
355/53 |
Current CPC
Class: |
G03F 7/70716 20130101;
G03F 7/70758 20130101 |
Class at
Publication: |
355/53 |
International
Class: |
G03B 027/42 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 1997 |
JP |
359807/1997 |
Claims
What is claimed is:
1. A stage apparatus comprising: a base having a reference plane; a
stage mounted on said base; a plurality of static-pressure bearings
forming a gap between the reference plane and said stage; a
plurality of preloading mechanisms producing a preload between said
stage and the reference plane; a guideless motor for driving said
stage; and a controller for controlling driving of said stage in
(i) at least one of a direction at perpendicular to the reference
plane and in a tilting direction by controlling at least one of
said static-pressure bearings and said preloading mechanism, and
(ii) in a direction within the reference plane by said guideless
motor.
2. A stage apparatus according to claim 1, wherein said stage has a
monolithic structure.
3. A stage apparatus according to claim 1, further comprising a
measuring instrument provided substantially integrally with said
base.
4. A stage apparatus according to claim 1, further comprising a
measuring instrument using a member from which vibration has been
eliminated from said base as a reference.
5. A stage apparatus according to claim 1, further comprising a
measuring instrument for measuring a position of said stage in a
direction within the reference plane.
6. A stage apparatus according to claim 1, further comprising a
measuring instrument for measuring a position of said stage in one
of a direction at perpendicular to the reference plane and in a
tilting direction.
7. A stage apparatus according to claim 6, wherein a change in the
thrust produced by said guideless motor is estimated on the basis
of an output of said measuring instrument, and said controller
controls at least one of an estimated thrust value of said
guideless motor and a preload of said preloading mechanism.
8. A stage apparatus according to claim 1, further comprising a gap
gauge for measuring a gap between the reference plane and said
stage.
9. A stage apparatus according to claim 1, wherein said controller
controls a position of said stage in a direction at perpendicular
to the reference plane and in a tilting direction by controlling
said preloading mechanism.
10. A stage apparatus according to claim 9, wherein said controller
sends an instruction value to said preloading mechanism based on a
sum of a certain offset value and a control instructing value.
11. A stage apparatus according to claim 1, wherein said plurality
of preloading mechanisms are at least three in number.
12. A stage apparatus according to claim 1, wherein said preloading
mechanism comprises an electromagnet.
13. A stage apparatus according to claim 1, wherein said guideless
motor is an induction motor using said base as a stator.
14. A stage apparatus according to claim 13, wherein said base has
a conductive layer and a magnetic layer formed thereunder.
15. A stage apparatus according to claim 1, wherein said guideless
motor is a flat pulse motor using said base as a stator.
16. An exposure apparatus comprising: a base having a reference
plane; a stage mounted on said base; a plurality of static-pressure
bearings forming a gap between the reference plane and said stage;
a plurality of preloading mechanisms producing a preload between
said stage and the reference plane; a guideless motor for driving
of said stage; a controller for controlling driving of said stage
in (i) at least one of a direction at right angles to the reference
plane and in a tiling direction by controlling at least one of said
static-pressure bearings and said preloading mechanism, and (ii) in
a direction within the reference plane by said guideless motor; and
an exposure apparatus for exposing a device held by said stage.
17. An exposure apparatus according to claim 16, wherein said stage
has a monolithic structure.
18. An exposure apparatus according to claim 16, further comprising
a measuring instrument provided substantially integrally with said
base.
19. An exposure apparatus according to claim 16, further comprising
a measuring instrument using a member from which vibration has been
eliminated from said base as a reference.
20. An exposure apparatus according to claim 16, further comprising
a measuring instrument for measuring a position of said stage in a
direction within the reference plane.
21. An exposure apparatus according to claim 16, further comprising
a measuring instrument for measuring a position of said stage in
one of a direction at right angles to the reference plane and in a
tilting direction.
22. An exposure apparatus according to claim 21, wherein a change
in the thrust produced by said guideless motor is estimated on the
bases of an output of said measuring instrument, and said
controller controls at least one of an estimated thrust value of
said guideless motor and a preload of said preloading
mechanism.
23. An exposure apparatus according to claim 16, further comprising
a gap gauge for measuring a gap between the reference plane and
said stage.
24. An exposure apparatus according to claim 16, wherein said
guideless motor is a flat pulse motor using said base as a
stator.
25. A device manufacturing method comprising: providing a base
having a reference plane; mounting a stage on the base; forming a
gap between the reference plane and the stage by a plurality of
static-pressure bearings; producing a preload between the stage and
the reference plane by a plurality of preloading mechanisms;
driving the stage by a guideless motor; controlling, using a
controller, driving of the stage in (i) at least one of a direction
at right angles to the reference plane and in a tilting direction
by controlling at least one of the static-pressure bearings and the
preloading mechanism, and (ii) in a direction within the reference
plane by the guideless motor; and exposing a wafer, mounted on the
stage, to a pattern on a mask, to produce a device.
26. A device manufacturing method according to claim 25, wherein
the stage has a monolithic structure.
27. A device manufacturing method according to claim 25, further
comprising providing a measuring instrument substantially
integrally with the base.
28. A device manufacturing method according to claim 25, further
comprising providing a measuring instrument using a member from
which vibration has been eliminated from the base as a
reference.
29. A device manufacturing method according to claim 25, further
comprising providing a measuring instrument for measuring a
position of the stage in a direction within the reference
plane.
30. A device manufacturing method according to claim 25, further
comprising providing a measuring instrument for measuring a
position of the stage in one of a direction at right angles to the
reference plane and in a tilting direction.
31. A device manufacturing method according to claim 30, wherein a
change in the thrust produced by the guideless motor is estimated
on the basis of an output of the measuring instrument, and said
controlling step controls at least one of an estimated thrust value
of the guideless motor and a preload of the preloading
mechanism.
32. A device manufacturing method according to claim 25, further
comprising providing a gap gauge for measuring a gap between the
reference plane and the stage.
33. A device manufacturing method according to claim 25, wherein
the guideless motor is a flat pulse motor using the base as a
stator.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a stage apparatus for
performing positioning by mounting an object, and particularly, to
a stage apparatus suitably applicable to a semiconductor exposure
apparatus. The invention also relates to an exposure apparatus
using the aforementioned stage apparatus and a device manufacturing
method for manufacturing a device, such as a semiconductor device,
using such an exposure apparatus.
[0003] 2. Description of the Related Art
[0004] FIG. 10 is a schematic diagram of a wafer stage of a
conventional semiconductor exposure apparatus. Three translational
axes (X, Y and Z directions) relative to a reference coordinate
system and three rotational axes (.theta..sub.x, .theta..sub.y,
.theta..sub.z) around the three translational axes, respectively,
will hereinafter be referred to as six degree-of-freedom
positions.
[0005] In FIG. 10, reference numeral 41 represents a base supported
on a floor F via dampers 51A and 51B; and 43 a Y-stage movable in
the Y-direction on a reference plane on the base 41 by the action
of a Y-linear motor 46 producing a thrust in the Y-direction along
a fixed guide 42 fixed to the base 41. The base 41 and the fixed
guide 42 are not in contact with the Y-stage 43, being connected by
air pads 44a to 44c serving as static-pressure bearings. The
Y-stage 43 has an X-direction guide, and guides 97 X-stage 45
mounted on the Y-stage 43 in the X-direction. An X-linear motor
stator producing a force in the X-direction is provided on the
Y-stage 43 and drives, together with the X-linear motor movable
part (rotor), the X-stage 45 in the X-direction. The base 41 and
the X-guide are connected by an air pad serving as a static
pressure bearing with the X-stage 45, and are not in contact
therewith.
[0006] A tilting stage 48 is mounted on the X-stage 45. The tilting
stage 48 travels in the Z-direction and rotates in the three
rotational axes (.theta..sub.x, .theta..sub.y, .theta..sub.z)
directions by the thrust produced by a motor (not shown). A stage
substrate 51 including a wafer chuck is mounted on the tilting
stage 48 to hold a wafer 53, which is an object to be exposed. A
measuring mirror for measuring positions in the X-direction and the
Y-direction is provided on the stage substrate. (Only measuring
mirror 49a for measuring in the X-direction and Y-direction is
shown.)
[0007] The stage apparatus of a semiconductor exposure apparatus
performs positioning using the six degree-of-freedom positions in
the in-plane directions (X, Y, .theta..sub.z) and in the vertical
directions (Z, .theta..sub.x, .theta..sub.y), and performs exposure
for a chip. Positions in the in-plane direction (X, Y,
.theta..sub.z) are measured with a laser interferometer 50 integral
with a lens mirror cylinder (not shown). For positions in the
tilting directions (Z, .theta..sub.x, .theta..sub.y), a position in
the Z-direction and an angle of the rotational component are
measured with an alignment measuring system (not shown), integral
with the lens mirror cylinder.
[0008] In FIG. 10, the laser interferometer 50 is connected to the
base 41 on the assumption that the lens mirror cylinder (not shown)
is integral with the base 41. Although the measuring instrument for
the Z-direction is omitted, it is possible to measure positions in
the tilting directions (Z, .theta..sub.x, .theta..sub.y) by
measuring three points on the substrate stage or the wafer from the
lens mirror cylinder.
[0009] Positioning in the six-axis directions is accomplished by
providing a servo system for each axis. Drive instruction values to
a Y-direction linear motor and an X-direction linear motor serving
as actuators for the X-direction and the Y-direction of the stage
are calculated with a compensator on the basis of positional
information of the laser interferometer 50 to drive the X-stage and
the Y-stage, respectively. The tilting stage 48 is driven by
calculating drive instruction values by the compensator to an
actuator for the tilting stage 48 in response to measured values of
the Z-direction position, the angles in the rotating directions
(.theta..sub.x, .theta..sub.y) and in the
.theta..sub.z-direction.
[0010] It is thus possible to control the six degree-of-freedom
positions of the three translational axes (X, Y, Z) and the three
rotational axes to arbitrary positions relative to the lens mirror
cylinder serving as a reference point of the stage, thus permitting
highly accurate positioning.
[0011] In the stage apparatus of such a semiconductor exposure
apparatus, a high positioning accuracy is required because of a
high resolution of the line width to be exposed. Also, the
semiconductor exposure apparatus, being production equipment, is
required to provide a high throughput. In order to satisfy this
requirement, it is necessary to have a high response of the servo
system of the stage, and to be capable of traveling at a high
speed. In order to improve the response of the servo system, the
mechanical system of the stage must have a high rigidity. With a
low rigidity of the stage, it is impossible to improve the band of
the servo system, and inability to rapidly respond to a target
position decreases throughput. A low band of the servo system
results in a decrease in the ability to inhabit disturbances, and
makes it impossible to accomplish highly accurate positional
control.
[0012] The aforementioned conventional stage is composed of a base
supporting the entire stage apparatus, a Y-stage conducting travel
in the Y-direction, an X-stage conducting travel in the
X-direction, a tilting stage conducting travel in the tilting
direction and a substrate stage for holding a wafer, these stages
forming a unit thus leading to a lower mechanical rigidity. This
arrangement, however, creates a resonance point determined by the
rigidity of air portions connecting these stages and the mass of
the configuration. The stage system, therefore, has a servo band
restricted by this resonance point, and cannot improve
response.
SUMMARY OF THE INVENTION
[0013] The present invention has an object to provide a high-speed
and high-accuracy stage apparatus having a wide servo band by
achieving a higher resonance point of the mechanical system thereof
in a simple configuration with a positionally controllable
stage.
[0014] The stage apparatus includes a base having a reference
plane, a stage mounted on the base, a plurality of static-pressure
bearings forming a gap between the reference plane and the stage, a
plurality of preloading mechanisms producing a preload between the
stage and the reference plane, a guideless motor for driving the
stage, and a controller for controlling driving of the stage in (i)
at least one of a direction at perpendicular to the reference plane
and in a tilting direction by controlling at least one of the
static-pressure bearings and the preloading mechanism, and (ii) in
an in-plane direction by the use of the guideless motor.
[0015] The above-mentioned stage should preferably have a
monolithic structure.
[0016] It is desirable to control positions in the direction at
perpendicular to the reference plane of the stage and in the
tilting direction by controlling the preloading mechanism.
[0017] In another aspect, the present invention provides an
exposure apparatus that includes a base having a reference plane, a
stage mounted on the base, a plurality of static-pressure bearings
forming a gap between the reference plane and the stage, a
plurality of preloading mechanisms producing a preload between the
stage and the reference plane, a guideless motor for driving the
stage, a controller for controlling driving of the stage in (i) at
least one of a direction at perpendicular to the reference plane
and in a tilting direction by controlling at least one of the
static-pressure bearings and the preloading mechanism, and (ii) in
a direction within the reference plane by the guideless motor, and
an exposure apparatus for exposing a device held by the stage.
[0018] In yet another aspect, the present invention provides a
device manufacturing method that includes providing a base having a
reference plane, mounting a stage on the base, forming a gap
between the reference plane and the stage by a plurality of
static-pressure bearings, producing a preload between the stage and
the reference plane by a plurality of preloading mechanisms,
driving the stage by a guideless motor, controlling, using a
controller, driving of the stage in (i) at least one of a direction
at perpendicular to the reference plane and in a tilting direction
by controlling at least one of the static-pressure bearings and the
preloading mechanism and (ii) in a direction within the reference
plane by the duideless motor, and exposing a wafer, mounted on the
stage, to a pattern on a mask to produce a device.
[0019] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention and, together with the description, serve to explain
the principles of the invention.
[0021] FIG. 1 is a schematic view of a stage apparatus of a first
embodiment of the present invention;
[0022] FIGS. 2A through 2D are schematic views of a stage substrate
of the stage apparatus of the first embodiment of the
invention;
[0023] FIG. 3 is a configuration diagram of a servo system of the
stage apparatus of the first embodiment of the invention;
[0024] FIGS. 4A through 4D are descriptive views of the principle
of driving a flat pulse motor used in a stage apparatus of a second
embodiment of the invention;
[0025] FIG. 5 is a configuration diagram of a servo system of a
stage apparatus of a third embodiment of the invention;
[0026] FIG. 6 is a schematic view of a substrate stage of a stage
apparatus of a fourth embodiment of the invention;
[0027] FIG. 7 is a schematic view of an exposure apparatus of a
fifth embodiment of the invention;
[0028] FIG. 8 is a flow chart of a semiconductor device
manufacturing method;
[0029] FIG. 9 is a flowchart of a wafer process used in the
semiconductor device manufacturing method; and
[0030] FIG. 10 is a schematic view of a conventional stage
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Preferred embodiments of the present invention will now be
described in detail in accordance with the accompanying
drawings.
First Embodiment
[0032] FIG. 1 is a schematic diagram of a stage apparatus of the
invention. In FIG. 1, reference numeral 1 represents a substrate
stage; 2 a base, supported by a damper (not shown); and 7a to 7f
measuring instruments for measuring at least six positions for
determining the six degree-of-freedom positions of the stage 1.
Positions in the in-plane directions (X, Y, .theta..sub.z) are
measured by the use of laser interferometers (in-plane position
measuring instruments) 7a to 7c, integral with a lens barrel. For
tilting directions in a direction at perpendicular to the reference
plane and rotating directions (Z, .theta..sub.x, .theta..sub.y)
having axes within the reference plane, the position in the
Z-direction and the angle of the rotational component are measured
by alignment meters (vertical position measuring instruments)
integral with the lens barrel, formed integrally with the measuring
instruments 7a to 7f, for determining the six degree-of-freedom
positions of the stage and may be provided integrally with the base
or may be vibration-removed from the base by a damper.
[0033] FIGS. 2A through 2D illustrate a configuration of a
substrate stage serving as the stage main body of the present
invention. In FIG. 2, reference numeral 1 represents the substrate
stage main body. As shown in FIG. 2, the stage 1 is composed of a
single substrate stage to provide a monolithic structure. A mirror
4 for reflecting a laser beam of the laser interferometers 7a to 7c
(shown in FIG. 1), for detecting a position in the horizontal
direction and a wafer chuck 5 for holding a wafer, are provided on
the upper surface of this stage. Air pads 17 to 19 serving as
static-pressure bearings for creating a gap between the reference
plane 3 of the base 2 and the stage 1 by discharging air, and
electromagnets 14 to 16 serving as preloading mechanisms for
producing a preload between the stage and the reference plane are
provided on the lower surface of the substrate stage 1. The base 2
is, therefore, made of a magnetic material such as steel so as to
be attracted by the electromagnets. Although the air pads and the
electromagnets are arranged at the same positions, the arrangement
of the air pads and the electromagnets is not limited to this
arrangement.
[0034] Needles (rotors) 10 to 13 of an induction motor serving as a
guideless motor for driving the substrate stage 1 are provided on
four sides of the substrate stage 1. In this case, the base 2 plays
the role of a stator.
[0035] In this embodiment, by driving two opposite induction motors
(10 and 12, for example) from among the four induction motors 10 to
13 provided on the substrate stage 1 in reverse directions, it is
possible to achieve driving in the rotating direction
(.theta..sub.z) around a direction vertical to the reference plane
3 of the base 2. That is, the substrate stage 1 can be positioned
in the desired directions within the reference plane 3 (X, Y,
.theta..sub.z) of the base 2 by driving the plurality of induction
motors 10 to 13.
[0036] Since the substrate stage 1 is driven in directions (X, Y,
.theta..sub.z) within the reference plane 3 of the base 2 by the
use of the induction motors 10 to 13, the number of induction
motors 10 to 13 should preferably be at least three. The number of
induction motors, which may be four, as in this embodiment, is,
therefore, not limited to four.
[0037] As described above, the base 2 is made of a magnetic
material such as steel. The base 2 is made of a magnetic material
in order to produce an attraction force by feeding current to the
electromagnets 14 to 16. Relative to the induction motors 10 to 13
producing a thrust in directions (X, Y, .theta..sub.z) within the
reference plane 3 of the base 2, the base 2, serving as a stator,
must be conductive. For properly feeding current, the conductor
should preferably be a conductive material having the smallest
possible electrical resistance. It is, therefore, desirable to form
a surface layer of the base 2 from a conductive material having a
small electrical resistance, such as aluminum or copper, and a
layer thereunder from a magnetic material. The base material is
not, however, limited to this. With this configuration, current
necessary for the induction motors 10 to 13 of the base can be
minimized, thus providing a stage apparatus having a high
efficiency with small heat generation.
[0038] FIG. 3 illustrates a configuration of a servo system of the
stage apparatus of the present invention. Operations of this servo
system will now be described.
[0039] First, target position instruction values (21d to 26d) for
the six axes (X, Y, Z, .theta..sub.x, .theta..sub.y, .theta..sub.z)
relative to coordinates of the reference position are given. Six
values of stage position information (6a to 6f) measured from a
coordinate system at the reference position are converted by a
noninteracting compensator 27 into values of the current positions
(21e to 26e) of coordinate systems for the six degrees-of-freedom.
Differences (21c to 26c) between the target position instruction
values and the current positions measured from the reference
position are determined and entered into compensators (21b to 26b).
A PID compensator is usually used as this type of compensator.
Values of thrust for the six axes are determined at this point, and
values of instructed thrust to the actuator are determined from
these values of thrust and from noninteracting compensator 20.
[0040] Feeding current to the induction motor needles (rotors) 10
to 13 produces thrust in the directions (X, Y, .theta..sub.z)
within the reference plane 3 of the base 2. The values of current
(10a to 13a) fed to the induction motor needles (rotors) are
calculated from the target thrust and supplied by drives (10b to
13b). Thrust in the direction (Z) at perpendicular to the reference
plane 3 and thrust in the tilting directions (.theta..sub.x,
.theta..sub.y) are controlled by means of electromagnets (14 to 16)
and air pads (17 to 19). Thrust in a direction away from the
reference plane 3 of the base 2 is controlled by means of pressure
and air flow rate (17a to 19a) via valves (17b to 19b), and thrust
in a direction toward the reference plane 3 is controlled by
feeding current (14a to 16a) to the electromagnets (14 to 16) via
drivers (14b to 16b).
[0041] For controlling the position of the substrate stage 1 in a
direction (Z) at perpendicular to the reference plane and tilting
directions (.theta..sub.x, .theta..sub.y), the number of the
electromagnets and static-pressure bearings should preferably be at
least three, but is not limited to three.
[0042] Blocks (14d to 16d) are vertical thrust determiners for
determining which of the electromagnets (14 to 16) or the air pads
(17 to 19) are to be driven in accordance with a positive or
negative target thrust. When values of the target thrust determined
by the vertical thrust determiners (14d to 16d) are in a direction
toward the stage base, the substrate stage 1 is driven by feeding
current (14a to 16a) by the drivers (14b to 16b) to the
electromagnets (14 to 16). When target values of the thrust are in
a direction away from the base, the substrate stage 1 is driven by
feeding air (17a to 19a) via valves (17b to 19b). Upon application
of the thrust, the stage 1 travels, and the position thereof at
this point is measured by the measuring instrument. The measured
position is fed back, and the same operations are repeated.
[0043] According to this embodiment, it is possible to position the
substrate stage 1 in a direction (Z) at perpendicular to the
reference plane of the base and in tilting directions
(.theta..sub.x, .theta..sub.y) by controlling the thrust produced
from the air pads (static-pressure bearings) and the electromagnets
(preloading means) provided on the substrate stage 1. It is,
therefore, possible to position Z-tilting of a wafer, which is the
object of exposure with a simpler configuration as compared to the
conventional art, thus providing a stage apparatus having lighter
weight and smaller size.
[0044] Along with this, it is possible to move the substrate stage
1, which has a monolithic structure in six-axis directions (X, Y,
Z, .theta..sub.x, .theta..sub.y, .theta..sub.z) by using induction
motors for driving the substrate stage 1 in the directions (X, Y,
.theta..sub.z) within the reference plane 3 of the base 2. This
improves the conventional laminated stage apparatus, and permits
improvement of rigidity of the stage apparatus. It is possible to
improve the response of the servo system, ensuring a rapid response
to a target position. Thus, it is possible to provide a high-speed
and high-accuracy stage apparatus.
[0045] The surface layer of the base 2 is made of a material having
a low electrical resistance, such as aluminum, and the layer
thereunder is made of a magnetic material. This minimizes the
current that is required by the induction motor of the base 2. As a
result, a stage apparatus having a high energy efficiency with
small heat generation is provided.
Second Embodiment
[0046] In the aforementioned embodiment, the induction motors have
been used for driving in directions (X, Y, .theta..sub.z) within
the reference plane 3 of the base 2. In the present embodiment,
also, four guideless motors are provided for the substrate stage 1,
as in the preceding stage apparatus, provided that, in the present
embodiment, flat pulse motors, with which it is easier to obtain a
larger thrust than with induction motors, are used as the guideless
motors.
[0047] Because the stage apparatus of this embodiment has the same
configuration as in the preceding embodiment, further description
thereof is omitted here.
[0048] The principle of driving a general flat pulse motor is
illustrated in FIGS. 4A through 4D.
[0049] First, fixed teeth 8 having a pitch P are provided on the
upper surface of the base 2 in the present embodiment. A needle
(rotor) of the flat pulse motor is composed of a permanent magnet
9a, a movable tooth 9b1, another movable tooth 9b2, and coils 9c1
and 9c2 wound on the individual movable teeth. Each of the movable
teeth 9b1 and 9b2 is composed of a pair of small teeth spaced apart
from each other by 1.5 P (i.e., spaced apart by 180.degree. with
respect to an electrical angle, with the pitch P as a reference).
The movable teeth 9b1 and 9b2 are connected by the permanent magnet
9a provided as shown. The movable tooth 9b1 and the movable tooth
9b2 have a positional shift of 4.25 P (i.e., an electrical angle of
90.degree.). For each of the movable teeth 9b1 and 9b2, the coils
9c1 and 9c2 are wound to form a counterphase to the two small teeth
so that one of the two small teeth is magnetized vertically upward,
and the other, vertically downward.
[0050] In this configuration, the coils 9c1 and 9c2 are
magnetically excited in the sequence shown in FIGS. 4A through 4D,
and the flow of magnetic flux of the permanent magnet 8 is
sequentially distributed. The pulse motor needle (rotor), as a
whole, moves in one direction. These figures show the principle of
the motor based on a current variation in four steps. Actually,
however, the motor is operated as a synchronous motor by
continuously following the four steps with a sinusoidal current
waveform to ensure continuous travel. While these figures
illustrate a one-dimensional operation, the fixed teeth 8 provided
on the base 2 are not actually comb-shaped, but take a lattice
form, thus permitting operations as shown, in the X and
Y-directions.
[0051] In this embodiment, by driving two opposite pulse motors (10
and 12, for example) from among the four pulse motors 10 to 13
provided on the substrate stage 1 in reverse directions, it is
possible to achieve driving in the rotating direction
(.theta..sub.z) around a vertical direction with respect to the
reference plane 3 of the base 2. That is, the substrate stage 1 can
be positioned in the directions within the reference plane (X, Y,
.theta..sub.z) of the base 2 by driving the plurality of pulse
motors 10 to 13.
[0052] Since the substrate stage 1 is driven in directions (X, Y,
.theta..sub.z) within the reference plane 3 of the base 2 by the
use of the pulse motors 10 to 13, the number of pulse motors should
preferably be at least three. The member of pulse motors in this
embodiment is four. This number, however, is not limited to
four.
[0053] An air jet port from the static-pressure bearings 17 to 19
is provided between the fixed teeth and the motor needles (rotors).
To ensure a stable air flow, recesses of the fixed teeth 8 are
filled with a resin to achieve a mechanically flat, but
magnetically concave/convex surface.
[0054] The servo system is the same as that in the preceding first
embodiment, so that the flat pulse motor is controlled in place of
the induction motor.
[0055] The same advantages as in the preceding embodiment can be
expected. It is possible to position the substrate stage 1 in a
direction (Z) at perpendicular to the reference plane of the base 2
and in tilting directions (.theta..sub.x, .theta..sub.y) by
controlling the thrust produced from the air pads (static-pressure
bearings) and the electromagnets (preloading mechanism) provided on
the substrate stage 1. It is, therefore, possible to position in
the Z and tilting directions of a wafer, which is the object of
exposure, with a simpler configuration as compared to the
conventional art, thus permitting a stage apparatus of lighter
weight and smaller size.
[0056] Along with this, it is possible to move the substrate stage
1, which has a monolithic structure, in six-axis directions (X, Y,
Z, .theta..sub.x, .theta..sub.y, .theta..sub.z) by using pulse
motors for driving the substrate stage in directions (X, Y,
.theta..sub.z) within the reference plane 3 of the base 2. This
improves the conventional laminated stage apparatus, and improves
rigidity of the stage apparatus. Also, it is possible to improve
the response of the servo system, ensuring rapid response to a
target position. Thus it is possible to provide a stage apparatus
having high-speed and high-accuracy.
Third Embodiment
[0057] In the preceding stage apparatus, the ascending force of the
stage substrate has been controlled through the control of the
static-pressure bearings. It is, however, difficult to accurately
control an ascending force or positioning of the stage substrate
through the control of air. This is caused by a low response of
air, in general. In the present embodiment, therefore, air of the
static-pressure bearings is used for production of the ascending
force to a certain degree, and control of the ascending force, the
descending force and positioning of the stage substrate are
accomplished by means of the electromagnets. Driving in the
directions within the reference plane 3 of the base 2, in this
embodiment, may be by means of induction motors or by means of flat
pulse motors.
[0058] While air is injected under a certain pressure or at a
certain flow rate, a certain offset current is fed to the
electromagnets to generate a preload sufficient to offset the
ascending force of air, and the position of balance is used as the
origin in the vertical direction. When the current instruction
value to be fed to the electromagnets is expressed as a sum of the
offset current and the control instruction value, the control
instruction value becomes negative when causing the stage substrate
to descend from the foregoing stage origin, and when causing the
stage substrate to ascend, on the contrary, the control instruction
value becomes positive, thus permitting control of the thrust in
the vertical direction. According to this practice, control of the
force in a direction (Z) at right angles to the stage substrate and
in tilting directions (.theta..sub.x, .theta..sub.y) can be
adjusted by means of electromagnets. This provides a stage
apparatus having a higher response than in the practice based on
air control. This provides another advantage of a simpler air
control system.
[0059] FIG. 5 illustrates a configuration of a servo system of the
second embodiment of the invention.
[0060] First, target position instruction values (21d to 26d) for
the six axes (X, Y, Z, .theta..sub.x, .theta..sub.y, .theta..sub.z)
relative to coordinates of the reference position are given. Six
values of stage position information (6a to 6f) measured from a
coordinate system at the reference position are converted by a
noninteracting compensator 27 into values of the current positions
(21e to 26e) of coordinate systems for the six degrees-of-freedom.
Differences (21c to 26c) between the target position instruction
values and the current positions measured from the reference
position are determined and entered into compensators (21b to 26b).
A PID compensator is usually used as such a compensator. Values of
thrust for the six axes (21a to 26a) are determined at this point,
and values of instructed thrust to the actuator are determined from
these values of thrust and the noninteracting compensator 20.
Feeding current to the induction motor (or flat pulse motor) rotors
(10 to 13) produces thrust in the directions (X, Y, .theta..sub.z)
within the reference plane of the base. Values of current (10a to
13a) fed to the induction motor rotors are calculated from the
target thrust and supplied by drivers (10b to 13b). Thrust in the
direction (Z) at perpendicular to the reference plane and thrust in
the tilting directions (.theta..sub.x, .theta..sub.y) are
controlled by means of electromagnets (14 to 16). Current
instruction values (14a to 16a) of thrust in a direction (Z) at
perpendicular to the reference plane 3 of the base 2 and tilting
directions (.theta..sub.x, .theta..sub.y) are determined by adding
offset current (14h to 16h) to the thrust instruction values (14e
to 16e). At this point, air (17a to 19a) of air pads (17 to 19),
serving as static-pressure bearings, is fed through valves (17b to
19b) under a certain pressure at a certain flow rate as specified
by air instruction values (17c to 19c).
[0061] According to the stage apparatus of this embodiment, in
which the supply of air for the static-pressure bearings is kept
constant at a certain level, and positional control in a direction
(Z) at perpendicular to the reference plane 3 of the base 2 and in
tilting directions (.theta..sub.x, .theta..sub.y) is accomplished
by the electromagnets, it is possible to conduct highly accurate
positioning with a high response. Because air supply is constant
and satisfactory, design of the mechanical and control systems for
the supply of air can be simplified, thereby providing a stage
apparatus having a lighter weight, a smaller size and a lower
cost.
Fourth Embodiment
[0062] FIG. 6 illustrates a substrate stage of a fourth embodiment
of the invention. Air pads (17 to 19) serving as static-pressure
bearings and electromagnets (14 to 16) provided on the back of the
substrate stage 1 are the same as in the preceding embodiment.
Therefore, a further description is omitted here. A description of
an induction motor or a flat pulse motor provided on a side of the
stage substrate 1, being the same as in the preceding embodiment,
is also omitted.
[0063] Gap measuring gauges (30 to 32) for measuring the gap in the
vertical directions (Z, .theta..sub.x, .theta..sub.y) between the
substrate stage 1 and the base 2 are provided on the back of the
substrate stage of the present embodiment. This permits accurate
measurement of the positional relationship in the vertical
direction between the substrate stage 1 and the base 2.
[0064] Since induction motors (10 to 13) are used for driving in
the in-plane directions (X, Y, .theta..sub.z) in the present
invention, a change in the gap between the base 2 and the substrate
stage 1 leads to a change in the distance between the stators of
the induction motors and the rotors of the induction motors
provided on the stage substrate, hence to a change in the motor
thrust. If the gap in the vertical direction can be measured, it is
possible to determine the thrust applied to the substrate stage 1.
Because the thrust in directions (X, Y, .theta..sub.z) within the
reference plane 3 of the base 2 is generated by the induction
motors, it is possible to linearize the thrust produced by the
induction motors relative to the target thrust instruction value by
vector control by measuring the plane direction positional
relationship between the stage having the induction motors and the
base 2 serving as a stator. It is also possible to estimate a
variation in the thrust generated by the induction motors from the
measured results, and to control the thrust instruction value of
the induction motors and the preload of the preloading mechanism.
Further, it is possible to provide a stage apparatus that is not
susceptible to any influence of base vibration, by controlling the
current of the electromagnets, so as to remove a vibration
component of the base 2, on the basis of the measured results.
Fifth Embodiment
[0065] An embodiment of a scanning type exposure apparatus mounting
one of the stage apparatuses of the aforementioned embodiments as a
reticle stage or a wafer stage will now be described with reference
to FIG. 7.
[0066] A reticle stage base 71a supporting a reticle stage 73 is
integral with a frame 94 provided on a base 92 supporting a wafer
stage 93. Exposure light for exposing a wafer W on the wafer stage
93 via a reticle on the reticle stage 73 is produced from a light
source 95 (shown by a broken line).
[0067] The frame 94 supports the reticle stage base 71a, and also
supports a projection optical system 96 between the reticle stage
73 and the wafer stage 93. Since a stator 75 of a linear motor,
which accelerates and decelerates the reticle stage 73, is
supported by the frame 94 and a separate supporting frame 90, a
reaction force to the driving force of the motor of the reticle
stage 73 is transferred to the wafer stage 93. There is, therefore,
no risk of causing a disturbance of the driving section, or causing
vibration of the projection optical system 96.
[0068] The wafer stage 93 is scanned in synchronization with the
reticle stage 73 by the driving section. During scanning of the
reticle stage 73 and the wafer stage 93, the positions of these
stages are continuously detected by interferometers 97 and 98, and
the results of the detection are fed back to the driving sections
of the reticle stage 73 and the wafer stage 93, respectively. It
is, therefore, possible to accurately synchronize the scanning
starting positions of these stages, and at the same time, to
control the scanning speed in the constant-speed scanning area at a
high accuracy.
Sixth Embodiment
[0069] An embodiment of a method manufacturing of a semiconductor
device by the utilization of the aforementioned exposure apparatus
will now be described. FIG. 8 illustrates a flow chart for
manufacturing a semiconductor device 1a semiconductor chip, such as
an IC or an LSI, a liquid crystal panel, a CCD, a thin-film
magnetic head, or a micro-machine). At step S11 (circuit design),
circuits for the semiconductor device are designed. At step S12
(manufacture of a mask), a mask having a circuit pattern thus
designed and formed thereon is manufactured. At step S13
(manufacture of a wafer), on the other hand, a wafer serving as a
substrate is manufactured by the use of a material such as silicon.
At step S14 (wafer process), called a pre-process, an actual
circuit is formed on the wafer by lithography, by the use of the
thus manufactured mask and wafer. In the next step S15 (assembly),
called a post-process, a semiconductor chip is produced by the use
of the wafer manufactured at step S14, and includes an assembly
step (dicing, bonding), a packaging step (sealing of a chip) and
the like. At step S16 (inspection), an operation confirming test, a
durability test and other inspections are carried out on the
semiconductor device manufactured at step S15. Through these steps,
the semiconductor devices are completed and shipped (step S17).
[0070] FIG. 9 illustrates a detailed flow chart of the
aforementioned wafer process. At step S21 (oxidation), the wafer
surface is oxidized. At step S22 (chemical vapor deposition--CVD),
an insulating film is formed on the wafer surface. At step S23
(forming electrodes), electrodes are formed on the wafer by vapor
deposition. At step S24 (ion implantation), ions are implanted into
the wafer. At step S25 (resist processing), a photosensitive agent
is coated onto the wafer. At step S26 (exposure), the circuit
pattern described above is printed on the wafer and exposed by the
exposure apparatus described above. At step S27 (development), the
exposed wafer is developed. At step S28 (etching), portions other
than the developed resist image are scraped off. At step S29
(resist peeling), any portions of the resist becoming unnecessary
after the completion of etching are removed. By repeating these
steps, multiple circuit patterns are formed on the wafer. According
to the manufacturing method of this embodiment, it is possible to
manufacture a semiconductor device having a high degree of
integration.
[0071] Except as otherwise disclosed herein, the various components
shown in outline or in block form in the figures are individually
well known and their internal construction and operation are not
critical either to the making or using of this invention or to a
description of the best mode of the invention.
[0072] While the present invention has been described with respect
to what is at present considered to be the preferred embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments. To the contrary, the invention is intended
to cover various modifications and equivalent arrangements included
within the spirit and scope of the appended claims. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
* * * * *