U.S. patent number RE43,576 [Application Number 12/318,821] was granted by the patent office on 2012-08-14 for dual stage lithographic apparatus and device manufacturing method.
This patent grant is currently assigned to ASML Netherlands B.V.. Invention is credited to Jozef Petrus Henricus Benschop, Erik Roelof Loopstra, Marinus Aart Van Den Brink.
United States Patent |
RE43,576 |
Van Den Brink , et
al. |
August 14, 2012 |
**Please see images for:
( Certificate of Correction ) ** |
Dual stage lithographic apparatus and device manufacturing
method
Abstract
The invention relates to a dual stage lithographic apparatus,
wherein two substrate stages are constructed and arranged for
mutual cooperation in order to perform a joint scan movement. The
joint scan movement brings the lithographic apparatus from a first
configuration, wherein immersion liquid is confined between a first
substrate held by the first stage of the stages and a projection
system of the apparatus, to a second configuration, wherein the
immersion liquid is confined between a second substrate held by the
second stage of the two stages and the projection system, such that
during the joint scan movement the liquid is essentially confined
within the space with respect to the projection system.
Inventors: |
Van Den Brink; Marinus Aart
(Moergestel, NL), Benschop; Jozef Petrus Henricus
(Veldhoven, NL), Loopstra; Erik Roelof (Eindhoven,
NL) |
Assignee: |
ASML Netherlands B.V.
(Veldhoven, NL)
|
Family
ID: |
46613654 |
Appl.
No.: |
12/318,821 |
Filed: |
January 8, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11101631 |
Apr 8, 2005 |
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Reissue of: |
11135655 |
May 24, 2005 |
7161659 |
Jan 9, 2007 |
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Current U.S.
Class: |
355/53; 355/72;
355/30 |
Current CPC
Class: |
G03F
7/70733 (20130101); G03F 7/70341 (20130101) |
Current International
Class: |
G03B
27/42 (20060101); G03B 27/52 (20060101); G03B
27/58 (20060101) |
Field of
Search: |
;355/30,52,53,55,67,72,75 ;356/399-401 ;250/548 |
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|
Primary Examiner: Nguyen; Hung Henry
Attorney, Agent or Firm: Pillsbury Winthrop Shaw Pittman
LLP
Parent Case Text
RELATED APPLICATION
The present application is a Continuation In Part Application of
U.S. application Ser. No. 11/101,631, filed on Apr. 8, 2005 now
abandoned.
Claims
The invention claimed is:
1. A lithographic apparatus comprising: a support constructed to
support a patterning device, the patterning device being capable of
imparting a radiation beam with a pattern in its cross-section to
form a patterned radiation beam; a measuring system configured to
measure characteristics of substrates in a metrology station of the
apparatus; a projection system configured to project the patterned
radiation beam onto a substrate in an exposure station of the
apparatus; a liquid confinement system configured to at least
partly confine liquid in a space between the projection system and
the substrate; a positioning system and at least two substrate
stages, each stage constructed to hold a .[.substrates.].
.Iadd.substrate.Iaddend., wherein the positioning system is
constructed to move the stages between the metrology station and
the exposure station, and wherein the positioning system is
constructed to position one of the stages holding a substrate
during exposure in the exposure station on the basis of at least
one measured characteristic of that substrate; wherein the stages
are constructed and arranged for mutual cooperation in order to
perform a joint scan movement to bring the lithographic apparatus
from a first situation, wherein the liquid is confined between a
first substrate held by a first stage of the two stages and the
projection system, towards a second situation, wherein the liquid
is confined between a second substrate held by a second stage of
the two stages and the projection system, such that during the
joint scan movement the liquid is essentially confined within the
space with respect to the projection system.
2. The lithographic apparatus according to claim 1, wherein each of
the first stage and second stage has an immersion cross edge at or
near a side of the stage which is constructed and arranged to
cooperate with an immersion cross edge of another stage during the
joint scan movement.
3. The lithographic apparatus according to claim 2, wherein each
immersion cross edge comprises an essentially plane surface.
4. The lithographic apparatus according to claim 2, wherein the
positioning system is constructed and arranged to position the
respective stages during their joint scan movement such that
surfaces of their respective immersion cross edges remain at an
essentially mutual constant distance, wherein the distance is in
the range of zero to about 1 millimeter.[., wherein a preferred
distance is about 0.1 millimeter.]..
5. The lithographic apparatus according to claim 2, wherein at
least one of the respective stages is provided with a channel
system having an opening in a surface of the immersion cross edge
of the stage, wherein the channel system is constructed and
arranged to generate a flow of gas and/or liquid along the
immersion cross edge during the joint scan movement.
6. The lithographic apparatus according to claim 2, wherein at
least one of the respective stages is provided with a liquid gutter
under its immersion cross edge, wherein the liquid gutter is
capable of catching liquid possibly dripped along the immersion
cross edge.
7. The lithographic apparatus according to claim 2, wherein at
least one of the respective stages is provided with an
interferometer-mirror near the immersion cross edge, wherein the
interferometer-mirror is staggered with respect to the immersion
cross edge .[.and preferably placed in a niche of the stage in
order to protect the interferometer-mirror.]..
8. The lithographic apparatus according to claim 6, wherein at
least one of the respective stages is provided with an
interferometer-mirror near the immersion cross edge, wherein the
interferometer-mirror is placed at a level below that of the liquid
gutter in order to protect the interferometer-mirror.
9. The lithographic apparatus according to claim 1, further
comprising an exposure station situated between a first metrology
station and a second metrology station such that alternately
substrates measured by the first metrology station and substrates
measured by the second metrology station may be fed towards the
exposure station.
10. The lithographic apparatus according to claim 1, further
comprising a base frame configured to carry a metro frame which
supports the measuring system and the projection system, wherein
the metro frame is dynamically isolated from the base frame, and
wherein the measuring system comprises at least one encoder plate
configured to cooperate with an encoder head placed at one of the
stages to measure the position of that stage.
11. The lithographic apparatus according to claim 10, wherein the
at least one encoder plate extends in the exposure station and the
metrology station.
12. The lithographic apparatus according to claim 10, further
comprising a machine frame .[.which is preferably separated from
the base frame, wherein the machine frame is provided with.].
.Iadd.having .Iaddend.a first part of a planar motor to cooperate
with respective second parts of the planar motor in the respective
stages, wherein the positioning system is constructed and arranged
to control the planar motor in order to position the respective
stages between the metrology station and the exposure station.
13. The lithographic apparatus according to claim 10, further
comprising a machine frame .[.which is preferably separated from
the base frame, wherein the machine frame has.]. .Iadd.having
.Iaddend.two essentially parallel guides extending in a first
direction in a horizontal plane, wherein each guide is coupled to
an element which can be moved along the guide by means of a motor,
and wherein each element is coupled to a stage of the respective
stages by means of a motor to move that stage in a second direction
directed in the horizontal plane and perpendicular to the first
direction, wherein the positioning system is constructed and
arranged to control the motors in order to move the stage in the
plane.
14. A lithographic product with a lithographic apparatus according
to claim 1.
.Iadd.15. A lithographic apparatus comprising: a substrate stage
configured to support a substrate and a second stage; a liquid
confinement system configured to at least partly confine liquid in
a space between a projection system and the substrate stage, a
substrate supported by the substrate stage, or both; the substrate
stage and the second stage constructed and arranged for mutual
cooperation to perform a joint movement wherein the liquid in the
liquid confinement structure is transferred from being confined by
the substrate or the substrate stage or both to being confined by
the second stage, the liquid crossing an edge of the substrate
stage and an opposing edge of the second stage, wherein the
substrate stage, the second stage, or both, comprises a channel
system in fluid communication with an opening defined by the edge
of the stage, the channel system constructed and arranged to
generate a fluid flow along the edge during the joint movement, the
fluid flow including liquid from the liquid confinement
structure..Iaddend.
.Iadd.16. A lithographic apparatus comprising: a substrate stage
configured to support a substrate and a second stage; a liquid
confinement system configured to at least partly confine liquid in
a space between a projection system and the substrate stage, a
substrate supported by the substrate stage, or both; the substrate
stage and the second stage constructed and arranged for mutual
cooperation to perform a joint movement wherein the liquid in the
liquid confinement structure is transferred from being confined by
the substrate or the substrate stage or both to being confined by
the second stage, the liquid crossing an edge of the substrate
stage and an opposing edge of the second stage, wherein the
substrate stage, the second stage, or both, comprises a gutter
located under the edge of the respective stage, the gutter
constructed and arranged to collect liquid from the liquid
confinement structure flowing down one or both edges during the
joint movement..Iaddend.
.Iadd.17. A lithographic apparatus comprising: a substrate stage
configured to support a substrate and a second stage; a liquid
confinement system configured to at least partly confine liquid in
a space between a projection system and the substrate stage, a
substrate supported by the substrate stage, or both; the substrate
stage and the second stage constructed and arranged for mutual
cooperation to perform a joint movement wherein the liquid in the
liquid confinement structure is transferred from being confined by
the substrate or the substrate stage or both to being confined by
the second stage, the liquid crossing an edge of the substrate
stage and an opposing edge of the second stage, wherein the
substrate stage, the second stage, or both, comprises a fluid
extraction system constructed and arranged to collect liquid
flowing between the edges during the joint movement. .Iaddend.
.Iadd.18. A lithographic apparatus comprising: a substrate stage
configured to support a substrate, the substrate stage having an
edge; a further stage having a corresponding edge, the
corresponding edge constructed and arranged to mutually co-operate
with the edge when the substrate stage and the further stage are
arranged adjacently to define a gap; and a liquid confinement
structure configured to at least partly confine immersion liquid in
a space between a projection system and a substrate, the substrate
stage, or both, wherein, during a joint movement of the substrate
stage and the further stage, confinement of liquid in the space by
the substrate stage, the substrate or both is replaced by the
further stage, and the substrate stage, the further stage, or both,
comprises a fluid extraction system constructed and arranged to
collect immersion liquid in the gap during the joint
movement..Iaddend.
.Iadd.19. The lithographic apparatus of claim 18, wherein the fluid
extraction system comprises a gutter constructed and arranged to
collect immersion liquid under the substrate stage, the further
stage or both flowing from the gap before, during and/or after
joint movement..Iaddend.
.Iadd.20. The lithographic apparatus of claim 19, wherein the
gutter is attached to the substrate stage and/or the further
stage..Iaddend.
.Iadd.21. The lithographic apparatus of claim 20, wherein the
gutter is located under the edge of the stage to which it is
attached..Iaddend.
.Iadd.22. The lithographic apparatus of claim 18, wherein the fluid
extraction system comprises a channel system comprised in the
substrate stage, the further stage or both and which is in fluid
communication with an opening defined in the edge, the
corresponding edge or both, the channel system constructed and
arranged to generate a fluid flow along the gap during the joint
movement..Iaddend.
.Iadd.23. The lithographic apparatus of claim 22, wherein the fluid
flow comprises liquid and gas away from the gap..Iaddend.
.Iadd.24. The lithographic apparatus of claim 18, further
comprising a positioning system comprising a motor to move the
substrate stage and/or the further stage and constructed and
arranged to control the motor during the joint movement so that the
distance between the edge and the corresponding edge is
controlled..Iaddend.
.Iadd.25. The lithographic apparatus of claim 24, wherein the
distance between the edge and the corresponding edge is controlled
to be in the range of 0 to 1 mm..Iaddend.
.Iadd.26. The lithographic apparatus of claim 24, wherein the
positioning system comprises an interferometer system comprising a
mirror located on the edge or the corresponding edge..Iaddend.
.Iadd.27. The lithographic apparatus of claim 26, wherein the
mirror is on a surface staggered away from the edge or the
corresponding edge..Iaddend.
.Iadd.28. The lithographic apparatus of claim 26, wherein the
mirror is located in a protective niche defined in the edge or the
corresponding edge..Iaddend.
.Iadd.29. The lithographic apparatus of claim 26, wherein the
mirror is located underneath the fluid extraction
system..Iaddend.
.Iadd.30. The lithographic apparatus of claim 18, wherein the
further stage is a substrate stage configured to support a further
substrate..Iaddend.
.Iadd.31. The lithographic apparatus of claim 18, wherein the
further stage is an actuated closing stage. .Iaddend.
.Iadd.32. A device manufacturing method, comprising: supporting a
substrate on a substrate table, wherein the substrate table is
laterally movable with respect to an adjacent table; at least
partly confining immersion liquid in a space between a projection
system and the substrate table, the substrate or both; jointly
moving the substrate table with the adjacent table, the adjoining
edges of the substrate table and the adjacent table mutually
cooperating to define a gap, so that the liquid in the space is
contained by the adjacent table instead of the substrate table; and
collecting immersion liquid in the gap during joint movement using
a fluid extraction system. .Iaddend.
.Iadd.33. The lithographic apparatus according to claim 7, wherein
the interferometer-mirror is in a niche of the stage in order to
protect the interferometer-mirror..Iaddend.
Description
FIELD
The present invention relates to a multi stage lithographic
apparatus and a method for manufacturing a device with the multi
stage lithographic apparatus.
BACKGROUND
A lithographic apparatus is a machine that applies a desired
pattern onto a substrate, usually onto a target portion of the
substrate. A lithographic apparatus can be used, for example, in
the manufacture of integrated circuits (ICs). In that instance, a
patterning device, which is alternatively referred to as a mask or
a reticle, may be used to generate a circuit pattern to be formed
on an individual layer of the IC. This pattern can be transferred
onto a target portion (e.g. comprising part of, one, or several
dies) on a substrate (e.g. a silicon wafer). Transfer of the
pattern is typically via imaging onto a layer of
radiation-sensitive material (resist) provided on the substrate. In
general, a single substrate will contain a network of adjacent
target portions that are successively patterned. Known lithographic
apparatus include so-called steppers, in which each target portion
is irradiated by exposing an entire pattern onto the target portion
at one time, and so-called scanners, in which each target portion
is irradiated by scanning the pattern through a radiation beam in a
given direction (the "scanning"-direction) while synchronously
scanning the substrate parallel or anti-parallel to this direction.
It is also possible to transfer the pattern from the patterning
device to the substrate by imprinting the pattern onto the
substrate.
There is an ongoing development in improving current lithographic
apparatus. An aspect herewith is to increase the throughput
(throughput is related to the number of substrates that can be
processed in a certain time by a lithographic apparatus). For
example, Dual Stage Lithographic apparatus generally have a larger
throughput than Single stage apparatus since a substrate on a first
substrate stage may be measured in a metrology station while
another substrate on a second substrate stage is exposed in an
exposure station on the basis of data measured previously in the
metrology station. Another aspect is to improve the capability of
lithographic apparatus to transfer patterns with smaller structures
(but with a given quality) on substrates. For example, an Immersion
lithographic apparatus is capable of transferring patterns with
smaller structures in comparison with non-immersion lithographic
apparatus (see for example EP 1486827, incorporated herein by
reference).
In U.S. Pat. No. 5,969,441 (incorporated herein by reference) a
Dual Stage lithographic apparatus is described that is provided
with "H-drives" (see for example FIGS. 4, 5: respective X-actuators
105 and 107 connected to respective sets of opposite Y-actuators
109, 111 and 113, 115) for its substrate stages (substrate holders
11, 13). The described Dual Stage yields a relatively high
throughput but a disadvantage is that the substrate stages need a
"stage-swap" (according to the transition between FIG. 4 and FIG. 5
wherein substrate holder 11 is uncoupled from unit 25 and coupled
to unit 27 and wherein substrate holder 13 is uncoupled from unit
27 and coupled to unit 25) for passing each other while moving
between the metrology station and the exposure station (column 16,
lines 47 52). The apparatus has the disadvantage that the
stage-swap takes time, thus yielding a decreased throughput.
In U.S. Pat. No. 6,341,007 (incorporated herein by reference) (see
in particular FIGS. 2, 3, 4) a Dual Stage lithographic apparatus is
described that is provided with one exposure station situated
between two metrology stations. The substrates in the batch are
measured alternately in the metrology stations before exposure in
the exposure station. The stages can not pass each other while
moving between the metrology stations and the exposure station (see
FIG. 3). A disadvantage of this lithographic apparatus is that it
requires two metrology stations. Therefore, there is a necessity of
providing a double substrate conveying path. The extra metrology
station and the extra conveying path yield an expensive
lithographic apparatus. Furthermore, the system layout takes
relatively much (floor)-space in the facrories (large footprint). A
further disadvantage is that this concept yields problems of a
logistics nature. Furthermore, the lithographic apparatus is not
suitable for immersion lithographic applications such that it is
not capable to project relatively small structures on the
substrates.
SUMMARY
It is desirable to at least partially alleviate one of the
mentioned disadvantages. In particular it is an aspect of the
invention to provide a lithographic apparatus with a relatively
high throughput and the capability of transferring patterns with
relatively small structures on substrates.
In order to meet the desire the invention proposes a lithographic
apparatus comprising:
a support constructed to support a patterning device, the
patterning device being capable of imparting a radiation beam with
a pattern in its cross-section to form a patterned radiation
beam;
a measuring system for measuring characteristics of substrates in a
metrology station of the apparatus;
a projection system configured to project the patterned radiation
beam onto a substrate in an exposure station of the apparatus;
a liquid confinement system for confining liquid between a final
element of the projection system and the substrate;
a positioning system and at least two substrate stages constructed
to hold substrates, wherein the positioning system is constructed
for moving the stages between the metrology station and the
exposure station, and wherein the positioning system is constructed
for positioning one of the stages holding a substrate during
exposure in the exposure station on the basis of at least one
measured characteristic of that substrate;
wherein the stages are constructed and arranged for mutual
cooperation in order to perform a joint scan movement for bringing
the lithographic apparatus from a first situation, wherein the said
liquid is confined between a first substrate held by the first
stage of the said stages and the final element, towards a second
situation, wherein the said liquid is confined between a second
substrate held by the second stage of the two stages and the final
element, such that during the joint scan movement the liquid is
essentially confined within said space with respect to the final
element. The joint scan movement yields an increased throughput
compared to conventional immersion lithographic apparatus wherein a
separate closing disc is used for confining the liquid between the
transfer from the said first situation and the said second
situation.
In order to meet the desire the invention proposes a lithographic
apparatus comprising:
a support constructed to support a patterning device, the
patterning device being capable of imparting a radiation beam with
a pattern in its cross-section to form a patterned radiation
beam;
a measuring system for measuring characteristics of substrates in a
metrology station of the apparatus;
a projection system configured to project the patterned radiation
beam onto a substrate in an exposure station of the apparatus;
a positioning system for positioning at least two substrate stages
of the lithographic apparatus, wherein the stages are constructed
to hold substrates;
a machine frame which is provided with a first part of a planar
motor for cooperating with respective second parts of the planar
motor in the respective stages, wherein the positioning system is
constructed and arranged to control the planar motor for moving the
stages between the metrology station and the exposure station and
for moving each of the said stages in the exposure station in six
degrees of freedom on the basis of at least one measured
characteristic of the substrate on the stage, wherein the machine
frame is constructed and arranged to allow the stages to pass each
other while moving between the metrology station and the exposure
station. Since the stages can pass each other there is no need for
a "stage-swap". In this way an apparatus is provided with a
relatively high throughput while having only one metrology station
and only one exposure station, and wherein the apparatus has a
relatively small "footprint".
In order to meet the desire the invention proposes a lithographic
apparatus comprising:
a support constructed to support a patterning device, the
patterning device being capable of imparting a radiation beam with
a pattern in its cross-section to form a patterned radiation
beam;
a measuring system for measuring characteristics of substrates in a
metrology station of the apparatus;
a projection system configured to project the patterned radiation
beam onto a substrate in an exposure station of the apparatus;
a positioning system and at least two stages constructed to hold
substrates, wherein the positioning system is constructed for
moving the stages between the metrology station and the exposure
station, and wherein the positioning system is constructed for
positioning one of the stages holding a substrate during exposure
in the exposure station on the basis of at least one measured
characteristic of that substrate,
a machine frame having two essentially parallel guides extending in
a first direction in a horizontal plane, wherein each guide is
coupled to an element which can be moved along the guide by means
of a motor, and wherein each element is coupled to a stage by means
of a motor for moving the stage in a second direction directed in
the horizontal plane and perpendicular to the first direction,
wherein the positioning system is constructed and arranged for
controlling the motors in order to move the stages in the plane,
wherein the machine frame is constructed and arranged to allow the
stages to pass each other while moving between the metrology
station and the exposure station. Since the stages can pass each
other there is no need for a "stage-swap". In this way an apparatus
is provided with a relatively high throughput while having only one
metrology station and only one exposure station, and wherein the
apparatus has a relatively small "footprint".
In order to meet the desire the invention proposes a lithographic
apparatus comprising:
a support constructed to support a patterning device, the
patterning device being capable of imparting a radiation beam with
a pattern in its cross-section to form a patterned radiation
beam;
a measuring system for measuring characteristics of substrates in a
metrology station of the apparatus;
a projection system configured to project the patterned radiation
beam onto a substrate in an exposure station of the apparatus;
a positioning system and at least two stages constructed to hold
substrates, wherein the positioning system is constructed for
moving the stages between the metrology station and the exposure
station, and wherein the positioning system is constructed for
positioning one of the stages holding a substrate during exposure
in the exposure station on the basis of at least one measured
characteristic of that substrate;
a base frame carrying a metro frame which supports the measuring
system and the projection system, wherein the metro frame is
dynamically isolated from the base frame, and wherein the measuring
system comprises an encoder system extending in both the metrology
station and the exposure station for measuring the position of the
stages. The said encoder system for example reduces the need of
frequent TIS alignments (aligning masks/reticles on the one hand
with substrates on the other hand via Transmission Image Sensors
such as described in EP 1510870, incorporated herein by reference,
see in particular FIGS. 8A, 8B). The reduction of the necessity of
frequent TIS-alignments increases throughput of the lithographic
apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described, by way of
example only, with reference to the accompanying schematic drawings
in which corresponding reference symbols indicate corresponding
parts, and in which:
FIG. 1A schematically depicts a lithographic apparatus according to
an embodiment of the invention in a side-view;
FIG. 1B shows a stage of the lithographic apparatus according to
FIG. 1A;
FIG. 2 is a schematic side-view of a metrology station of the
lithographic apparatus according to the invention;
FIG. 3 is a schematic side-view of an exposure station of the
lithographic apparatus according to the invention;
FIG. 4 is a schematic top-view of a first embodiment of the drive
and stage configuration of the dual stage immersion lithography
apparatus according to FIG. 1A;
FIG. 5 is a schematic top-view of the apparatus of FIG. 4 showing a
joint scan movement;
FIG. 6 is a schematic top-view of a second embodiment of the drive
and stage configuration of the dual stage immersion lithography
apparatus according to FIG. 1A;
FIG. 7 is a schematic top-view of the apparatus of FIG. 6 showing a
joint scan movement;
FIG. 8 is a schematic top-view of a third embodiment of the drive
and stage configuration of the dual stage immersion lithography
apparatus according to FIG. 1A, wherein the lithographic apparatus
performs a joint scan movement;
FIG. 9 is a schematic side-view showing two substrate stages in a
vertical cross section, wherein the stages perform a joint scan
movement;
FIG. 10 is a schematic vertical cross section of a first embodiment
of the stages in FIG. 9;
FIG. 11 is a schematic vertical cross section of a second
embodiment of the stages in FIG. 9;
FIG. 12 is a schematic vertical cross section of a third embodiment
of the stages in FIG. 9;
FIG. 13 is a schematic vertical cross section of a fourth
embodiment of the stages in FIG. 9;
FIG. 14 is a schematic vertical cross section of a fifth embodiment
of the stages in FIG. 9.
DETAILED DESCRIPTION
FIG. 1A schematically depicts a lithographic apparatus according to
one embodiment of the invention. The apparatus comprises:
an illumination system (illuminator) 2 configured to condition a
radiation beam 4 (e.g. UV radiation).
a support structure (e.g. a mask table) 6 constructed to support a
patterning device (e.g. a mask) 8 and coupled to a first positioner
10 configured to accurately position the patterning device in
accordance with certain parameters;
a substrate table (e.g. a wafer table) WT constructed to hold a
substrate (e.g. a resist-coated wafer) 14 and coupled (via a mirror
block MB) to a second positioner 16 configured to accurately
position the substrate in accordance with certain parameters;
and
a projection system (e.g. a refractive projection lens system) 18
configured to project a pattern imparted to the radiation beam 4 by
patterning device 8 onto a target portion C (e.g. comprising one or
more dies) of the substrate 14.
The illumination system may include various types of optical
components, such as refractive, reflective, magnetic,
electromagnetic, electrostatic or other types of optical
components, or any combination thereof, for directing, shaping, or
controlling radiation.
The support structure supports, i.e. bears the weight of, the
patterning device. It holds the patterning device in a manner that
depends on the orientation of the patterning device, the design of
the lithographic apparatus, and other conditions, such as for
example whether or not the patterning device is held in a vacuum
environment. The support structure can use mechanical, vacuum,
electrostatic or other clamping techniques to hold the patterning
device. The support structure may be a frame or a table, for
example, which may be fixed or movable as required. The support
structure may ensure that the patterning device is at a desired
position, for example with respect to the projection system. Any
use of the terms "reticle" or "mask" herein may be considered
synonymous with the more general term "patterning device."
The term "patterning device" used herein should be broadly
interpreted as referring to any device that can be used to impart a
radiation beam with a pattern in its cross-section such as to
create a pattern in a target portion of the substrate. It should be
noted that the pattern imparted to the radiation beam may not
exactly correspond to the desired pattern in the target portion of
the substrate, for example if the pattern includes phase-shifting
features or so called assist features. Generally, the pattern
imparted to the radiation beam will correspond to a particular
functional layer in a device being created in the target portion,
such as an integrated circuit.
The patterning device may be transmissive or reflective. Examples
of patterning devices include masks, programmable mirror arrays,
and programmable LCD panels. Masks are well known in lithography,
and include mask types such as binary, alternating phase-shift, and
attenuated phase-shift, as well as various hybrid mask types. An
example of a programmable mirror array employs a matrix arrangement
of small mirrors, each of which can be individually tilted so as to
reflect an incoming radiation beam in different directions. The
tilted mirrors impart a pattern in a radiation beam which is
reflected by the mirror matrix.
The term "projection system" used herein should be broadly
interpreted as encompassing any type of projection system,
including refractive, reflective, catadioptric, magnetic,
electromagnetic and electrostatic optical systems, or any
combination thereof, as appropriate for the exposure radiation
being used, or for other factors such as the use of an immersion
liquid or the use of a vacuum. Any use of the term "projection
lens" herein may be considered as synonymous with the more general
term "projection system".
As here depicted, the apparatus is of a transmissive type (e.g.
employing a transmissive mask). Alternatively, the apparatus may be
of a reflective type (e.g. employing a programmable mirror array of
a type as referred to above, or employing a reflective mask).
The lithographic apparatus may be of a type having two (dual stage)
or more substrate tables (and/or two or more mask tables). In such
machines the additional tables may be used in parallel, or
preparatory steps may be carried out on one or more tables while
one or more other tables are being used for exposure.
The lithographic apparatus may also be of a type wherein at least a
portion of the substrate may be covered by a liquid having a
relatively high refractive index, e.g. water, so as to fill a space
between the projection system and the substrate. An immersion
liquid may also be applied to other spaces in the lithographic
apparatus, for example, between the mask and the projection system.
Immersion techniques are well known in the art for increasing the
numerical aperture of projection systems. The term "immersion" as
used herein does not mean that a structure, such as a substrate,
must be submerged in liquid, but rather only means that liquid is
located between the projection system and the substrate during
exposure.
Referring to FIG. 1A, the illuminator 2 receives a radiation beam
from a radiation source 20. The source and the lithographic
apparatus may be separate entities, for example when the source is
an excimer laser. In such cases, the source is not considered to
form part of the lithographic apparatus and the radiation beam is
passed from the source 20 to the illuminator 2 with the aid of a
beam delivery system 22 comprising, for example, suitable directing
mirrors and/or a beam expander. In other cases the source may be an
integral part of the lithographic apparatus, for example when the
source is a mercury lamp. The source 20 and the illuminator 2,
together with the beam delivery system 22 if required, may be
referred to as a radiation system.
The illuminator 2 may comprise an adjuster 24 for adjusting the
angular intensity distribution of the radiation beam. Generally, at
least the outer and/or inner radial extent (commonly referred to as
.sigma.-outer and .sigma.-inner, respectively) of the intensity
distribution in a pupil plane of the illuminator can be adjusted.
In addition, the illuminator 2 may comprise various other
components, such as an integrator 26 and a condenser 28. The
illuminator may be used to condition the radiation beam, to have a
desired uniformity and intensity distribution in its
cross-section.
The radiation beam 4 is incident on the patterning device (e.g.,
mask 8), which is held on the support structure (e.g., mask table
6), and is patterned by the patterning device. Having traversed the
mask 8, the radiation beam 4 passes through the projection system
18, which focuses the beam onto a target portion C of the substrate
14. With the aid of the second positioner 16 and position sensor 30
(e.g. an interferometric device, linear encoder or capacitive
sensor), the substrate table WT of a wafer stage St can be moved
accurately, e.g. so as to position different target portions C in
the path of the radiation beam 4. For this, known measure &
Control algorithms with feedback and/or feedforward loops may be
used. Similarly, the first positioner 10 and another position
sensor (which is not explicitly depicted in FIG. 1A) can be used to
accurately position the mask 8 with respect to the path of the
radiation beam 4, e.g. after mechanical retrieval from a mask
library, or during a scan. In general, movement of the mask table 6
may be realized with the aid of a long-stroke module (coarse
positioning) and a short-stroke module (fine positioning), which
form part of the first positioner 10. Similarly, movement of the
substrate table WT may be realized using a long-stroke module and a
short-stroke module, which form part of the second positioner 16.
In the case of a stepper (as opposed to a scanner) the mask table 6
may be connected to a short-stroke actuator only, or may be fixed.
Mask 8 and substrate 14 may be aligned using mask alignment marks
M1, M2 and substrate alignment marks P1, P2. Although the substrate
alignment marks as illustrated occupy dedicated target portions,
they may be located in spaces between target portions (these are
known as scribe-lane alignment marks). Similarly, in situations in
which more than one die is provided on the mask 8, the mask
alignment marks may be located between the dies.
FIG. 1B shows a substrate stage St (also called substrate chuck)
for the lithographic apparatus according to FIG. 1A. The stage St
comprises the non-stationary parts of the second positioner 16, a
mirror block MB, and the substrate table WT mounted to the mirror
block MB. In this example the mirror block MB is provided with
interferometer-mirrors which are arranged for cooperation with
interferometers for measuring the position of the mirror block
MB.
The second positioner 16 is arranged for positioning the mirror
block MB and the substrate table WT. The second positioner 16
comprises the short stroke module (which is provided with a short
stroke motor ShM) and the long stroke module (which is provided
with a long stroke motor LoM).
The long stroke motor LoM comprises a stationary part LMS that can
be mounted to a stationary frame or a balance mass (not shown) and
a non-stationary part LMM that is displaceable relative to the
stationary part. The short stroke motor ShM comprises a first
non-stationary part SMS (that may be mounted to the non-stationary
part LMM of the long stroke motor) and a second non-stationary part
SMM (that may be mounted to the mirror block MB).
It should be noted that the mask table 6 and the first positioner
10 (see FIG. 1A) may have a similar structure as depicted in FIG.
1B.
A so-called dual stage (multi stage) machine may be equipped with
two (or more) stages as described. Each stage can be provided with
an object table (such as the substrate table WT). In such an
arrangement, a preparatory step such as the measurement of a height
map of the substrate disposed on one of the object tables can be
performed in parallel with the exposure of the substrate disposed
on another object table. In order to expose a substrate that
previously has been measured, the stages may change position from
the measurement location to the exposure location (and vice versa).
As an alternative, the object tables can be moved from one stage to
an other.
The apparatus depicted in FIG. 1A could be used in at least one of
the following modes: 1. In step mode, the mask table 6 and the
substrate table WT are kept essentially stationary, while an entire
pattern imparted to the radiation beam is projected onto a target
portion C at one time (i.e. a single static exposure). The
substrate table WT is then shifted in the X and/or Y direction so
that a different target portion C can be exposed. In step mode, the
maximum size of the exposure field limits the size of the target
portion C imaged in a single static exposure. 2. In scan mode, the
mask table 6 and the substrate table WT are scanned synchronously
while a pattern imparted to the radiation beam is projected onto a
target portion C (i.e. a single dynamic exposure). The velocity and
direction of the substrate table WT relative to the mask table 6
may be determined by the (de-)magnification and image reversal
characteristics of the projection system 18. In scan mode, the
maximum size of the exposure field limits the width (in the
non-scanning direction) of the target portion in a single dynamic
exposure, whereas the length of the scanning motion determines the
height (in the scanning direction) of the target portion. 3. In
another mode, the mask table 6 is kept essentially stationary
holding a programmable patterning device, and the substrate table
WT is moved or scanned while a pattern imparted to the radiation
beam is projected onto a target portion C. In this mode, generally
a pulsed radiation source is employed and the programmable
patterning device is updated as required after each movement of the
substrate table WT or in between successive radiation pulses during
a scan. This mode of operation can be readily applied to maskless
lithography that utilizes programmable patterning device, such as a
programmable mirror array of a type as referred to above.
Combinations and/or variations on the above described modes of use
or entirely different modes of use may also be employed.
FIG. 4 is a schematic top-view of an embodiment of a drive and
stage configuration of the lithographic apparatus schematically
shown in FIG. 1A. The part is defined by a plane indicated in FIG.
1A by the line LL. The lithographic apparatus comprises a first
metrology station 32.1, a second metrology section 32.2 and an
exposure station 34 which is situated between the metrology
stations 32.1, 32.2.
In FIG. 2 a schematic side view of a metrology station 32 is
provided. The metrology station is supported by a base frame 36
which carries a metro frame 38. The base frame 36 may be placed
directly on the floor in a factory. The base frame 36 and the metro
frame 38 are dynamically isolated by isolation means 40 (the
isolation means 40 may be passive isolation means such as
airmounts, active isolation means such a pneumatic pistons or
combinations thereof). Due to the dynamical isolation, it is
prevented that vibrations or other disturbance movements in the
base frame transfer into the metro frame (the disturbances will at
least be reduced to a relatively large amount). The metro frame and
elements which are connected to it are sometimes called the "silent
world".
FIG. 2 also shows a (substrate) stage 42 holding a substrate 14 and
a measuring system 44 comprising a height measurement sensor 46 and
a position sensor 30. In this example, the position sensor 30 is
capable of measuring the position of the stage 42 in six degrees of
freedom. The measuring system 44 is carried by the metro frame and
is therefore part of the silent world. The sensors 46, 30 may be
used for measuring a characteristic (height map) of the substrate
14 held by the stage 42. The height map is used later during
exposure in the exposure station 34.
The position sensor 30 for measuring the position of the stage 42
may be an interferometer sensor 48.1 which is capable of directing
interferometer measurement beams 50 towards interferometer mirrors
52 attached to the stage 42. As an alternative, the position sensor
may be an encoder system 48.2 for measuring the position of the
stage 42. However, it is noted here that combinations of
interferometers and encoders, whereby the interferometer system
measures different parameters than the encoder are also
possible.
In the presented example of FIG. 2 the encoder system 48.2 is an
encoder plate which is attached to the metro frame 38. The stage 42
is provided with encoder heads 54 which are capable of cooperating
with the encoder plate 48.2 for measuring the position of the stage
42. Note that the encoder plate is provided with a cut-away to let
the height measurement sensor 46 directing a light measurement beam
through the cut-away on the surface of the substrate 8 for
measuring the height of the surface of the substrate. Preferably,
each corner (at or near each corner) of the upper surface of the
stage 42 is provided with an encoder head 54. The position of the
stage can be measured at any location under the cut-away with the
encoder system 48.2.
FIG. 3 is a schematic side view of an exposure station 34. The
exposure station 34 is supported by the base frame 36. The base
frame carries the metro frame 38, the metro frame 38 is dynamically
isolated from the base frame 36 by the isolation means 40. The
projection system 18 is supported by the metro frame 38 via
supporting members 56 (the supporting members 56 may also be
dynamical isolation means). In this example the metro frame 38
carries the position sensor 30 (an interferometer 48.1 and/or an
encoder system 48.2, whereby it is noted that the encoder system
48.2 is provided with a cut away for the projection system 18).
However, it is noted that the position sensor 30 may also be
carried by the projection system 18 (or, equivalently, by a frame
attached to the projection system 18).
If the position sensor 30 is an encoder plate 48.2, then this
encoder plate may extend both in the exposure station 34 and the
metrology station 32. In an advanced embodiment there is only one
encoder plate which extends completely from the metrology station
32 to the exposure station 34.
A reticle stage or mask stage 6 is located above the projection
system 18. The position of the reticle stage and the position of
the mask/reticle are measured by a measuring system 60. The
measuring system 60 cooperates with the position sensor 30 in order
to align the mask/reticle with the substrate 14 under the
projection system 18. Aligning the mask/reticle to the substrate is
usually performed according to zero point sensors and TIS-alignment
techniques (see for a description EP 1510870). For applying the
TIS-alignment it is required that the position of the substrate
with respect to the base frame 36 is known within a certain
accuracy (rough indication as starting point for the fine TIS
measurements) such that the substrate is in the capture range of
the TIS sensor.
Generally, interferometer sensors measure relative positions (by
counting fringes). In order to obtain absolute position
measurements via the interferometer sensor the interferometer
sensors can be "zerod" by means of a so-called zeroing-operation,
which means that a reference point is defined in order to obtain
absolute position measurements. Defining such a reference point is
of special interest in a multi-stage apparatus, since in such an
apparatus it frequently occurs that one stage eclipses another
stage yielding a loss of an already defined reference point. If
this happens it may be necessary to define a new reference point
(according to a new zeroing operation) has to be defined which
costs time and reduces throughput. However, the application of the
encoder plate may yield an absolute measurement system which
reduces or even eliminates the necessary zeroing operations which
is beneficial for throughput. Furthermore, if the encoder plate has
a high accuracy, the frequency of TIS-alignments itself may also be
reduced or even eliminated (at least partly replaced by the encoder
measurements), such that the throughput of the corresponding
apparatus is further increased.
As shown in FIG. 4, the stages holding substrates can be exchanged
between, on the one hand, the metrology stations 32.1, 32.2 and, on
the other hand, the exposure station 34. This will be described in
more detail hereinafter. FIG. 4 schematically depicts two guides
62.1, 62.2 which extend in a first direction (the X-direction) in a
horizontal plane. The guides 62 may be attached to the base frame
36, but it is preferred to attach the guides 62 to a machine frame
which is completely separated (thus no dynamical coupling) from the
said base frame 36, the metro frame 38 and the projection lens
18.
Each guide 62 is coupled to elements 64 which can be moved along
the guide 62 in the first direction (X-direction) by means of a
motor of the positioning system. In the configuration of FIG. 4
each stage 42.1, 42.2 is coupled to two elements 64. Each stage can
be moved in the horizontal plane in the Y-direction (which is
essentially perpendicular to the first direction) by motors in the
elements 64. In a preferred embodiment the motors in the guides 62
and/or in the elements 64 cooperate with balance masses in order to
reduce effects of reaction forces. The stages 42.1, 42.2 may be
supported by the base frame 36 via an air bearing which yields a
dynamical isolation of the base frame 26 and the stages 42.1, 42.2.
It is noted that as an alternative of the described drive
configuration a planar motor configuration may be applied.
In the configuration of FIG. 4 the stages can not pass each other.
Therefore, the working sequence of the lithographic apparatus which
belongs to this configuration is as follows. A substrate 14.1 is
provided on the first stage 42.1 via a first substrate convey path
to the first metrology station 32.1. Then this substrate is
measured (see FIG. 2, measurement system 44, generation of a height
map) in the metrology station 32.1 while being scanned in the
horizontal plane (the stage 42.1 is moved in the horizontal plane
for this). The position of the stages 42.1, 42.2 is, in the example
of FIG. 4, measured by an interferometer system 48.1. Next the
stage is transferred to the exposure station 34 in order to expose
the substrate 14.1 held by the stage 42.1. The exposure is based on
the measured height map of the substrate 14.1, wherein the stage
42.1 holding the substrate is positioned by the positioning system.
(It is noted that the said motors are capable of positioning the
stage in six degrees of freedom, however within a limited range,
under the projection system 18). At the same time, the other stage
42.2 is in the second metrology station 32.2 and holds a substrate
14.2 which is measured. The substrate 14.2 has been supplied via a
second substrate convey path. After the exposure of substrate 14.1
has been performed the stage 42.1 with the exposed substrate moves
to the first metrology station 32.1, the exposed substrate 14.1 is
conveyed via the first substrate convey path, and a new substrate
to be measured is loaded on the stage 42.1 via the first substrate
convey path. At the same time the substrate 14.2 held by the stage
42.2 is exposed. The sequence continues in this way. It is clear
that the configuration requires a double substrate convey path.
It is noted that the beams of the interferometers sometimes have to
bridge relatively great distances between the interferometer system
and the interferometer-mirror attached to the stage (see FIG. 4,
interferometer beams in the X-direction). This decreases the
accuracy of the measurement in this direction, since pressure
variations in the air disturb the interferometer measurement beam
(this effect increases with an increased distance). Application of
the discussed encoder system 48.2 alleviates this disadvantage and
may yield higher measurement accuracies.
FIG. 6 schematically depicts another dual stage concept in a
top-view defined by the line LL in FIG. 1. In this concept stages
with substrates 42.1, 42.2 can be exchanged between the metrology
station 32 and the exposure station 34. The concept is provided
with two guides 62.1, 62.2 which extend in a first direction (the
X-direction) in a horizontal plane. The guides 62 may be attached
to the base frame 36, but it is preferred to attach the guides 62
to a machine frame which is completely separated (thus no dynamical
coupling) from the said base frame 36, the metro frame 38 and the
projection lens 18. Each guide 62 carries an element 64 which can
be moved along the guide 62 in the first direction (X-direction) by
means of a motor (part of and) controlled by the positioning
system. In this example the elements 64 are T-elements which are
part of a so-called "T-drive". Each stage 42.1, 42.2 is coupled to
one T-element 64, wherein the T-element 64 can move the stage to
which it is coupled in the Y-direction by a motor which may be
present in the element 64. The motor is (preferably part of and)
controlled by the positioning system. In a preferred embodiment the
motors in the guides 62 and/or in the elements 64 cooperate with
balance masses in order to reduce effects of reaction forces. It is
noted that the stages 42.1, 42.2 may be supported by the base frame
36 via a dynamically isolating air bearing.
The dual stage concept according to FIG. 6 allows the stages 42.1
and 42.2 to pass each other while being moved between the metrology
station 32 and the exposure station 34. This concept based on the
T-drives does not require a stage swap (in contrast to the H-drive
concept described in U.S. Pat. No. 5,969,441). Therefore a
relatively high throughput can be achieved since a continuous
transfer movement of the stages is possible without a stop for a
swap.
As an alternative of the depicted "T-drive system" (guides 62.1,
62.2 and T-elements 64 in FIG. 6) a planar motor configuration can
be used. According to the planar motor configuration the
lithographic apparatus is provided with a machine frame with coils
and/or magnets (the first part of the planar motor) for cooperating
with magnets and/or coils in the said stages 42.1, 42.2 (the
respective second parts of the planar motor) such that the
positioning system can move each of the said stages 42.1, 42.2
between the metrology station 32 and the exposure station 34. Such
a planar motor can also be used to position the stages in the
exposure station 34 in six degrees of freedom. The machine frame
may be part of the base frame 36 (then the coils and/or magnets)
are integrated in the base frame 36, or the machine frame is
separated (dynamically isolated) from the base frame 36. The planar
motor is under control of the positioning system.
According to an embodiment of the lithographic apparatus according
to the invention there is provided an immersion liquid 66 between a
final optical (lens) element of the projection system 18 and a
target portion of the substrate 14 (FIG. 3). The application of
immersion fluid yields the advantage that during exposure smaller
structures of patterns can be transferred from the reticle or mask
to substrates 14 than in a comparable system without immersion
fluid. The lithographic apparatus has a liquid confinement system
for confining liquid between a final element of the projection
system and the substrate. The liquid confinement system comprises a
so-called immersion hood 68 (see FIG. 9). The immersion fluid may
be kept in place during illumination by the immersion hood 68. The
immersion hood 68 may comprise a mechanical contact-seal and/or may
also comprise a contact-less seal which operation is based on
guiding a pressure-gas-flow towards the fluid to be confined
(combinations are possible).
After exposure of a substrate the stage holding it has to move
away, for example towards a metrology station. Since it is desired
that the immersion fluid 66 is kept in its space under the final
element of the projection system 18, special measures have to be
taken before the stage can be moved away from its position under
the space of the immersion liquid 66. A possibility is to use a
separate closing disc or a separate small closing stage (unable to
hold a substrate) which closes the space at the bottom, until a
stage holding a substrate to be exposed takes the place of the
closing disc/closing stage.
However, the said closing disc/closing stage yields extra take-over
operations which cost valuable time and which appear to decrease
the throughput of the lithographic apparatus significantly.
Therefore, it is an aspect of the invention to prevent the
necessity of a closing disc (or closing stage) and to provide a
lithographic apparatus wherein the stages are constructed and
arranged for mutual cooperation in order to perform a joint scan
movement for bringing the lithographic apparatus from a first
situation, wherein the said liquid is confined between a first
substrate held by the first stage of the said stages and the final
element, towards a second situation, wherein the said liquid is
confined between a second substrate held by the second stage of the
two stages and the final element, such that during the joint scan
movement the liquid is essentially confined within said space with
respect to the final element.
The said joint scan movement of the stages 42.1 and 42.2 is
illustrated schematically in FIG. 9 (the arrows 71 indicate the
direction of movement of the stages with respect to the projection
system 18). The joint scan movement is performed such that the
liquid 66 stays confined in its space under the final lens element
70. At the bottom of the space the stages 42.1, 42.2 confine the
liquid 66. At the sides it is the immersion hood (which preferably
stays in an essentially fixed position with respect to the
projection system 18) which confines the liquid 66.
In an advanced embodiment the respective first stage 42.1 and
second stage 42.2 have respective immersion cross edges 72.1, 72.2
(situated at or near a side of the relevant stage, see FIG. 9),
wherein the immersion cross edges are constructed and arranged to
cooperate with each other during the joint scan movement.
Preferably each immersion cross edge 72 comprises one or more
essentially plane and smooth surface(s). Thus, it is possible to
perform the said joint scan movement in such a way that a
well-defined space is obtained between plane surfaces of different
immersion cross edges (for example a space defined by parallel
surfaces). In FIG. 9 an example is provided wherein the cooperating
immersion cross edges of the stages define a space with a mutual
distance D during the joint scan movement.
A different shape of the immersion cross edges 72.1, 72.2 is shown
in FIG. 10. In FIG. 10 the stage 42.1 shows an immersion cross edge
with respectively a vertical plane A, a horizontal plane B and a
vertical plane C. These planes are constructed to cooperate with
respective planes D, E, F of the immersion cross edge 72.2.
The lithographic apparatus according to the invention may comprise
a control system (using a feedback and/or a feedforward loop) that
may be fed with position measurements (actually the term position
measurement may include position, velocity, acceleration and/or
jerk measurements) of the stages (the measurements may be performed
by the measurement system 44) for calculating setpoint-signals for
the relevant motors. The motors are controlled during the joint
scan movement of the stages by the positioning system according to
the setpoint-signals such that the mutual constant distance D
between the planes of the respective immersion cross edges
corresponds to a pre-determined function. The pre-determined
function may be chosen such that the space between the immersion
cross edges functions a liquid channel character (see below for
further description).
According to an embodiment of the lithographic apparatus, the
positioning system is constructed and arranged to control the
motors for moving the stages such that stage 42.1 pushes the stage
42.2 gently during the joint scan movement. Herewith, a control
system (using a feedback and/or a feedforward loop) of the
positioning system is fed with position measurements (actually the
term position measurement may include position, velocity,
acceleration and/or jerk measurements) of the stages (performed by
the measurement system 44) and calculates setpoint-signals for the
relevant motors. Next, motors are controlled by the positioning
system according to the setpoint-signals such that the mutual
constant distance D between the planes of the respective immersion
cross edges is essentially zero.
According to a preferred embodiment of the lithographic apparatus,
the positioning system is constructed and arranged to control the
motors for moving the stages such that during the joint scan
movement the said mutual distance D is larger than zero but smaller
that 1 millimeter. A favorable mutual distance D appears to be
between 0.05 and 0.2 millimeter. A distance D in this
distance-range is especially favorable if one of the stages is
provided with a channel system 74 leading to and from an opening
the immersion cross edge, wherein the channel system 74 is
constructed and arranged for generating a flow of gas and/or liquid
along the immersion cross edge during the joint scan movement. The
generation of this flow is of importance to reduce the chance that
bubbles (bubbles deteriorate the projection of patterns on the
substrate) are generated in the immersion liquid 66. A stable and
well controlled distance D results in a stable and well favorable
flow thereby avoiding the generation of bubbles in the immersion
liquid during the joint scan movement.
The application of a channel system 74 may yield (during the joint
scan movement) a gas flow from under the stages 42 (see for example
FIG. 11 with indication G) and a liquid flow from above the stages
(see for example FIG. 11 with indication L). Then a mixture of gas
and liquid will be drained away via the channel system 74 (see
indication L/G). Flexible tubes may be connected to the (channel
system 74 of the) stage for further transport of the mixture
L/G.
In the example of FIG. 11 each stage (42.1 respectively 42.2) has a
channel system (74.1 respectively 74.2), wherein each channel
system leads to an opening in a plane surface of the immersion
cross edge (72.1 respectively 72.2). In the example of FIG. 10 only
the stage 42.2 is provided with a channel system 74, wherein the
channel system 74 has three openings in the surface E of the
immersion cross edge 72.2. Little arrows in the channel system 74
show the direction of the flow during the joint scan movement.
FIG. 10, 13, 14 show a configuration wherein the stages 42.1, 42.2
are provided with a water gutter 76.1, 76.2 under the immersion
cross edges 72.1, 72.2. The water gutter is capable of catching
liquid possible dripped along the immersion cross edge before,
during and after the joint scan movement. Application of only one
water gutter attached to only one of the stages is in principle
sufficient for only catching liquid during the joint scan
movement.
The said interferometer system 48.1 uses interferometer-mirrors
attached to the stages for position measuring. In the example of
FIG. 4 it does not make sense for the interferometer system 48.1 to
have interferometer mirrors 52 on the stages at the sides of the
immersion cross edges. However, for the drive and stage
configuration in FIG. 6, it may be advantageous to have an
interferometer-mirrors 52 at the stages at the sides of the
immersion cross edges (for example to have relative short distances
of the interferometer beam, which generally yields relative high
measurement accuracies). This also holds for the configuration of
FIG. 8, for example in the situation whereby the stage 42.1 visits
the exposure station 34 (the immersion cross edge is at the side of
the positive X-direction, and in the left X-direction is a
relatively long interferometer beam path). In these case it is
preferred that the stages are provided with an
interferometer-mirror 52 at the immersion cross edge. It is noted
that the chance on contamination (liquid flow) and or damage
arising during the joint scan movement is greater than for the
other interferometer-mirrors. Therefore it is advantageous to
stagger the interferometer-mirror with respect to the immersion
cross edge as indicated in FIG. 12. As an alternative the
interferometer-mirrors 52 are placed it in a protective niche of
the stage, as indicated in FIG. 13. Another alternative is to place
the interferometer-mirror 52 below the said water gutter 76 which
catches liquid (and possible contamination). FIG. 14 shows an
example of a combination of the mentioned measures whereby the
interferometer-mirrors are both staggered with respect to the
immersion cross edge 72 and placed at a level under the water
gutter 76. In this way the interferometers stay clean and undamaged
which yield a reliable performance of the measurement system.
Although specific reference may be made in this text to the use of
lithographic apparatus in the manufacture of ICs, it should be
understood that the lithographic apparatus described herein may
have other applications, such as the manufacture of integrated
optical systems, guidance and detection patterns for magnetic
domain memories, flat-panel displays, liquid-crystal displays
(LCDs), thin-film magnetic heads, etc. The skilled artisan will
appreciate that, in the context of such alternative applications,
any use of the terms "wafer" or "die" herein may be considered as
synonymous with the more general terms "substrate" or "target
portion", respectively. The substrate referred to herein may be
processed, before or after exposure, in for example a track (a tool
that typically applies a layer of resist to a substrate and
develops the exposed resist), a metrology tool and/or an inspection
tool. Where applicable, the disclosure herein may be applied to
such and other substrate processing tools. Further, the substrate
may be processed more than once, for example in order to create a
multi-layer IC, so that the term substrate used herein may also
refer to a substrate that already contains multiple processed
layers.
Although specific reference may have been made above to the use of
embodiments of the invention in the context of optical lithography,
it will be appreciated that the invention may be used in other
applications, for example imprint lithography, and where the
context allows, is not limited to optical lithography. In imprint
lithography a topography in a patterning device defines the pattern
created on a substrate. The topography of the patterning device may
be pressed into a layer of resist supplied to the substrate
whereupon the resist is cured by applying electromagnetic
radiation, heat, pressure or a combination thereof. The patterning
device is moved out of the resist leaving a pattern in it after the
resist is cured.
The terms "radiation" and "beam" used herein encompass all types of
electromagnetic radiation, including ultraviolet (UV) radiation
(e.g. having a wavelength of or about 365, 355, 248, 193, 157 or
126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a
wavelength in the range of 5-14 20 nm), as well as particle beams,
such as ion beams or electron beams.
The term "lens", where the context allows, may refer to any one or
combination of various types of optical components, including
refractive, reflective, magnetic, electromagnetic and electrostatic
optical components.
While specific embodiments of the invention have been described
above, it will be appreciated that the invention may be practiced
otherwise than as described. For example, the invention may take
the form of a computer program containing one or more sequences of
machine-readable instructions describing a method as disclosed
above, or a data storage medium (e.g. semiconductor memory,
magnetic or optical disk) having such a computer program stored
therein.
The descriptions above are intended to be illustrative, not
limiting. Thus, it will be apparent to one skilled in the art that
modifications may be made to the invention as described without
departing from the scope of the claims set out below.
* * * * *