U.S. patent application number 11/253597 was filed with the patent office on 2006-02-16 for environmental system including vacuum scavenge for an immersion lithography apparatus.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Andrew J. Hazelton, Michael Sogard.
Application Number | 20060033899 11/253597 |
Document ID | / |
Family ID | 33162259 |
Filed Date | 2006-02-16 |
United States Patent
Application |
20060033899 |
Kind Code |
A1 |
Hazelton; Andrew J. ; et
al. |
February 16, 2006 |
Environmental system including vacuum scavenge for an immersion
lithography apparatus
Abstract
An environmental system controls an environment in a gap between
an optical assembly and a device and includes a fluid barrier and
an immersion fluid system. The fluid barrier is positioned near the
device. The immersion fluid system delivers an immersion fluid that
fills the gap and collects the immersion fluid that is directly
between the fluid barrier and the device. The fluid barrier can
include a scavenge inlet that is positioned near the device, and
the immersion fluid system can include a low pressure source that
is in fluid communication with the scavenge inlet. The fluid
barrier confines any vapor of the immersion fluid and prevents it
from perturbing a measurement system. Additionally, the
environmental system can include a bearing fluid source that
directs a bearing fluid between the fluid barrier and the device to
support the fluid barrier relative to the device.
Inventors: |
Hazelton; Andrew J.; (Tokyo,
JP) ; Sogard; Michael; (Menlo Park, CA) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
NIKON CORPORATION
TOKYO
JP
|
Family ID: |
33162259 |
Appl. No.: |
11/253597 |
Filed: |
October 20, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11237799 |
Sep 29, 2005 |
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11253597 |
Oct 20, 2005 |
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PCT/IB04/02704 |
Mar 29, 2004 |
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11237799 |
Sep 29, 2005 |
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60462112 |
Apr 10, 2003 |
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60484476 |
Jul 1, 2003 |
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Current U.S.
Class: |
355/53 |
Current CPC
Class: |
G03F 7/70875 20130101;
G03F 7/70775 20130101; G03F 7/709 20130101; G03F 7/70816 20130101;
G03F 7/70866 20130101; G03F 7/2041 20130101; G03F 7/70341
20130101 |
Class at
Publication: |
355/053 |
International
Class: |
G03B 27/42 20060101
G03B027/42 |
Claims
1. A lithographic projection apparatus comprising: a projection
system, a space between said projection system and a substrate
being filled with a liquid; a liquid confinement structure
extending along at least a part of the boundary of said space; and
a gas seal between said structure and the surface of said
substrate.
2. Apparatus according to claim 1, wherein said gas seal comprises
a gas bearing.
3. Apparatus according to claim 2, wherein said gas bearing is
configured to support said structure over said substrate.
4. Apparatus according to claim 3, wherein said gas seal comprises
a gas inlet formed in a face of said structure that opposes said
substrate to supply gas and a first gas outlet formed in a face of
said structure that opposes said substrate to extract gas.
5. Apparatus according to claim 4, wherein said gas seal comprises
a gas supply to provide gas to said gas inlet and a vacuum device
to extract gas from said first gas outlet.
6. Apparatus according to claim 4, wherein said first gas outlet
comprises a groove in the face of said structure.
7. Apparatus according to claim 4, wherein said gas seal comprises
a second gas outlet formed in a face of said structure that opposes
said substrate to extract gas.
8. Apparatus according to claim 7, wherein said first and second
gas outlets are formed on opposite sides of said gas inlet.
9. Apparatus according to claim 4, wherein said gas inlet is
located further outward from said projection system than is said
first gas outlet.
10. Apparatus according to claim 4, wherein said gas inlet and said
first gas outlet each comprises a groove in said face of said
structure.
11. Apparatus according to claim 2, wherein said gas seal comprises
a gas inlet formed in a face of said structure that opposes said
substrate to supply gas and a first gas outlet formed in a face of
said structure that opposes said substrate to extract gas.
12. Apparatus according to claim 11, wherein said gas seal
comprises a gas supply to provide gas to said gas inlet and a
vacuum device to extract gas from said first gas outlet.
13. Apparatus according to claim 11, wherein said first gas outlet
comprises a groove in the face of said structure.
14. Apparatus according to claim 11, wherein said gas seal
comprises a second gas outlet formed in a face of said structure
that opposes said substrate to extract gas.
15. Apparatus according to claim 14, wherein said first and second
gas outlets are formed on opposite sides of said gas inlet.
16. Apparatus according to claim 11, wherein said gas inlet is
located further outward from said projection system than is said
first gas outlet.
17. Apparatus according to claim 11, wherein said gas inlet and
said first gas outlet each comprises a groove in said face of said
structure.
18. Apparatus according to claim 1, wherein said gas seal comprises
a first gas outlet and a second gas outlet formed in a face of said
structure that opposes said substrate to extract gas.
19. Apparatus according to claim 18, wherein said first and second
gas outlets each comprises a groove in said face of said
structure.
20. Apparatus according to claim 18, wherein said gas seal
comprises a gas inlet formed in a face of said structure that
opposes said substrate to supply gas.
21. Apparatus according to claim 20, wherein said first and second
gas outlets are formed on opposite sides of said gas inlet.
22. Apparatus according to claim 20, wherein said gas inlet
comprises a groove in said face of said structure.
23. Apparatus according to claim 20, wherein said gas seal
comprises a gas supply to provide gas to said gas inlet and a
vacuum device to extract gas from said first and second gas
outlets.
24. Apparatus according to claim 20, wherein said second gas outlet
is located further outward from the projection system than is said
first gas outlet, and said gas inlet is located further outward
from the projection system than is said first gas outlet.
25. Apparatus according to claim 24, wherein said first and second
gas outlets are formed on opposite sides of said gas inlet.
Description
RELATED APPLICATION
[0001] This is a Divisional of application Ser. No. 11/237,799
filed Sep. 29, 2005, which in turn is a Continuation of
International Application No. PCT/IB2004/002704 filed Mar. 29,
2004, which claims the benefit of U.S. Provisional Patent
Application No. 60/462,112 filed on Apr. 10, 2003 and U.S.
Provisional Patent Application No. 60/484,476 filed on Jul. 1,
2003. The disclosures of these applications are incorporated herein
by reference in their entireties.
BACKGROUND
[0002] Lithography exposure apparatus are commonly used to transfer
images from a reticle onto a semiconductor wafer during
semiconductor processing. A typical exposure apparatus includes an
illumination source, a reticle stage assembly that positions a
reticle, an optical assembly, a wafer stage assembly that positions
a semiconductor wafer, and a measurement system that precisely
monitors the position of the reticle and the wafer.
[0003] Immersion lithography systems utilize a layer of immersion
fluid that completely fills a gap between the optical assembly and
the wafer. The wafer is moved rapidly in a typical lithography
system and it would be expected to carry the immersion fluid away
from the gap. This immersion fluid that escapes from the gap can
interfere with the operation of other components of the lithography
system. For example, the immersion fluid and its vapor can
interfere with the measurement system that monitors the position of
the wafer.
SUMMARY
[0004] The invention is directed to an environmental system for
controlling an environment in a gap between an optical assembly and
a device that is retained by a device stage. The environmental
system includes a fluid barrier and an immersion fluid system. The
fluid barrier is positioned near the device and encircles the gap.
The immersion fluid system delivers an immersion fluid that fills
the gap.
[0005] In one embodiment, the immersion fluid system collects the
immersion fluid that is directly between the fluid barrier and at
least one of the device and the device stage. In this embodiment,
the fluid barrier includes a scavenge inlet that is positioned near
the device, and the immersion fluid system includes a low pressure
source that is in fluid communication with the scavenge inlet.
Additionally, the fluid barrier can confine and contain the
immersion fluid and any of the vapor from the immersion fluid in
the area near the gap.
[0006] In another embodiment, the environmental system includes a
bearing fluid source that directs a bearing fluid between the fluid
barrier and the device to support the fluid barrier relative to the
device. In this embodiment, the fluid barrier includes a bearing
outlet that is positioned near the device. Further, the bearing
outlet is in fluid communication with the bearing fluid source.
[0007] Additionally, the environmental system can include a
pressure equalizer that allows the pressure in the gap to be
approximately equal to the pressure outside the fluid barrier. In
one embodiment, for example, the pressure equalizer is a channel
that extends through the fluid barrier.
[0008] Moreover, the device stage can include a stage surface that
is in approximately the same plane as an exposed surface of the
device. As an example, the device stage can include a device holder
that retains the device, a guard that defines the stage surface,
and a mover assembly that moves one of the device holder and the
guard so that the exposed surface of the device is approximately in
the same plane as the stage surface. In one embodiment, the mover
assembly moves the guard relative to the device and the device
holder. In another embodiment, the mover assembly moves the device
holder and the device relative to the guard.
[0009] The invention also is directed to an exposure apparatus, a
wafer, a device, a method for controlling an environment in a gap,
a method for making an exposure apparatus, a method for making a
device, and a method for manufacturing a wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will be described in conjunction with the
following drawings of exemplary embodiments in which like reference
numerals designate like elements, and in which:
[0011] FIG. 1 is a side illustration of an exposure apparatus
having features of the invention;
[0012] FIG. 2A is a cut-away view taken on line 2A-2A of FIG.
1;
[0013] FIG. 2B is a cut-away view taken on line 2B-2B of FIG.
2A;
[0014] FIG. 2C is a perspective view of a containment frame having
features of the invention;
[0015] FIG. 2D is an enlarged detailed view taken on line 2D-2D in
FIG. 2B;
[0016] FIG. 2E is an illustration of the portion of the exposure
apparatus of FIG. 2A with a wafer stage moved relative to an
optical assembly;
[0017] FIG. 3 is a side illustration of an injector/scavenge source
having features of the invention;
[0018] FIG. 4A is an enlarged detailed view of a portion of another
embodiment of a fluid barrier;
[0019] FIG. 4B is an enlarged detailed view of a portion of another
embodiment of a fluid barrier;
[0020] FIG. 4C is an enlarged detailed view of a portion of another
embodiment of a fluid barrier;
[0021] FIG. 5A is a cut-away view of a portion of another
embodiment of an exposure apparatus;
[0022] FIG. 5B is an enlarged detailed view taken on line 5B-5B in
FIG. 5A;
[0023] FIG. 6 is a perspective view of one embodiment of a device
stage having features of the invention;
[0024] FIG. 7A is a perspective view of another embodiment of a
device stage having features of the invention;
[0025] FIG. 7B is a cut-away view taken on line 7B-7B in FIG.
7A;
[0026] FIG. 8A is a flow chart that outlines a process for
manufacturing a device in accordance with the invention; and
[0027] FIG. 8B is a flow chart that outlines device processing in
more detail.
DETAILED DESCRIPTION OF EMBODIMENTS
[0028] FIG. 1 is a schematic illustration of a precision assembly,
namely an exposure apparatus 10 having features of the invention.
The exposure apparatus 10 includes an apparatus frame 12, an
illumination system 14 (irradiation apparatus), an optical assembly
16, a reticle stage assembly 18, a device stage assembly 20, a
measurement system 22, a control system 24, and a fluid
environmental system 26. The design of the components of the
exposure apparatus 10 can be varied to suit the design requirements
of the exposure apparatus 10.
[0029] A number of Figures include an orientation system that
illustrates an X axis, a Y axis that is orthogonal to the X axis,
and a Z axis that is orthogonal to the X and Y axes. It should be
noted that these axes can also be referred to as the first, second
and third axes.
[0030] The exposure apparatus 10 is particularly useful as a
lithographic device that transfers a pattern (not shown) of an
integrated circuit from a reticle 28 onto a semiconductor wafer 30
(illustrated in phantom). The wafer 30 is also referred to
generally as a device or work piece. The exposure apparatus 10
mounts to a mounting base 32, e.g., the ground, a base, or floor or
some other supporting structure.
[0031] There are a number of different types of lithographic
devices. For example, the exposure apparatus 10 can be used as a
scanning type photolithography system that exposes the pattern from
the reticle 28 onto the wafer 30 with the reticle 28 and the wafer
30 moving synchronously. In a scanning type lithographic device,
the reticle 28 is moved perpendicularly to an optical axis of the
optical assembly 16 by the reticle stage assembly 18 and the wafer
30 is moved perpendicularly to the optical axis of the optical
assembly 16 by the wafer stage assembly 20. Irradiation of the
reticle 28 and exposure of the wafer 30 occur while the reticle 28
and the wafer 30 are moving synchronously.
[0032] Alternatively, the exposure apparatus 10 can be a
step-and-repeat type photolithography system that exposes the
reticle 28 while the reticle 28 and the wafer 30 are stationary. In
the step and repeat process, the wafer 30 is in a constant position
relative to the reticle 28 and the optical assembly 16 during the
exposure of an individual field. Subsequently, between consecutive
exposure steps, the wafer 30 is consecutively moved with the wafer
stage assembly 20 perpendicularly to the optical axis of the
optical assembly 16 so that the next field of the wafer 30 is
brought into position relative to the optical assembly 16 and the
reticle 28 for exposure. Following this process, the images on the
reticle 28 are sequentially exposed onto the fields of the wafer
30, and then the next field of the wafer 30 is brought into
position relative to the optical assembly 16 and the reticle
28.
[0033] However, the use of the exposure apparatus 10 provided
herein is not limited to a photolithography system for
semiconductor manufacturing. The exposure apparatus 10, for
example, can be used as an LCD photolithography system that exposes
a liquid crystal display device pattern onto a rectangular glass
plate or a photolithography system for manufacturing a thin film
magnetic head.
[0034] The apparatus frame 12 supports the components of the
exposure apparatus 10. The apparatus frame 12 illustrated in FIG. 1
supports the reticle stage assembly 18, the wafer stage assembly
20, the optical assembly 16 and the illumination system 14 above
the mounting base 32.
[0035] The illumination system 14 includes an illumination source
34 and an illumination optical assembly 36. The illumination source
34 emits a beam (irradiation) of light energy. The illumination
optical assembly 36 guides the beam of light energy from the
illumination source 34 to the optical assembly 16. The beam
illuminates selectively different portions of the reticle 28 and
exposes the wafer 30. In FIG. 1, the illumination source 34 is
illustrated as being supported above the reticle stage assembly 18.
Typically, however, the illumination source 34 is secured to one of
the sides of the apparatus frame 12 and the energy beam from the
illumination source 34 is directed to above the reticle stage
assembly 18 with the illumination optical assembly 36.
[0036] The illumination source 34 can be a light source such as a
mercury g-line source (436 nm) or i-line source (365 nm), a KrF
excimer laser (248 nm), an ArF excimer laser (193 nm) or a F.sub.2
laser (157 nm). The optical assembly 16 projects and/or focuses the
light passing through the reticle 28 onto the wafer 30. Depending
upon the design of the exposure apparatus 10, the optical assembly
16 can magnify or reduce the image illuminated on the reticle 28.
It also could be a 1.times. magnification system.
[0037] When far ultra-violet radiation such as from the excimer
laser is used, glass materials such as quartz and fluorite that
transmit far ultra-violet rays can be used in the optical assembly
16. The optical assembly 16 can be either catadioptric or
refractive.
[0038] Also, with an exposure device that employs radiation of
wavelength 200 nm or lower, use of the catadioptric type optical
system can be considered. Examples of the catadioptric type of
optical system are shown in Japanese Laid-Open Patent Application
Publication No. 8-171054 and its counterpart U.S. Pat. No.
5,668,672, as well as Japanese Laid-Open Patent Application
Publication No. 10-20195 and its counterpart U.S. Pat. No.
5,835,275. In these cases, the reflecting optical device can be a
catadioptric optical system incorporating a beam splitter and
concave mirror. Japanese Laid-Open Patent Application Publication
No. 8-334695 and its counterpart U.S. Pat. No. 5,689,377 as well as
Japanese Laid-Open Patent Application Publication No. 10-3039 and
its counterpart U.S. patent application Ser. No. 873,605
(Application Date: Jun. 12, 1997) also use a reflecting-refracting
type of optical system incorporating a concave mirror, etc., but
without a beam splitter, and can also be employed with this
invention. The disclosures of the above-mentioned U.S. patents and
application, as well as the Japanese Laid-Open patent applications
publications are incorporated herein by reference in their
entireties.
[0039] In one embodiment, the optical assembly 16 is secured to the
apparatus frame 12 with one or more optical mount isolators 37. The
optical mount isolators 37 inhibit vibration of the apparatus frame
12 from causing vibration to the optical assembly 16. Each optical
mount isolator 37 can include a pneumatic cylinder (not shown) that
isolates vibration and an actuator (not shown) that isolates
vibration and controls the position with at least two degrees of
motion. Suitable optical mount isolators 37 are sold by Integrated
Dynamics Engineering, located in Woburn, Mass. For ease of
illustration, two spaced apart optical mount isolators 37 are shown
as being used to secure the optical assembly 16 to the apparatus
frame 12. However, for example, three spaced apart optical mount
isolators 37 can be used to kinematically secure the optical
assembly 16 to the apparatus frame 12.
[0040] The reticle stage assembly 18 holds and positions the
reticle 28 relative to the optical assembly 16 and the wafer 30. In
one embodiment, the reticle stage assembly 18 includes a reticle
stage 38 that retains the reticle 28 and a reticle stage mover
assembly 40 that moves and positions the reticle stage 38 and
reticle 28.
[0041] Somewhat similarly, the device stage assembly 20 holds and
positions the wafer 30 with respect to the projected image of the
illuminated portions of the reticle 28. In one embodiment, the
device stage assembly 20 includes a device stage 42 that retains
the wafer 30, a device stage base 43 that supports and guides the
device stage 42, and a device stage mover assembly 44 that moves
and positions the device stage 42 and the wafer 30 relative to the
optical assembly 16 and the device stage base 43. The device stage
42 is described in more detail below.
[0042] Each stage mover assembly 40, 44 can move the respective
stage 38, 42 with three degrees of freedom, less than three degrees
of freedom, or more than three degrees of freedom. For example, in
alternative embodiments, each stage mover assembly 40, 44 can move
the respective stage 38, 42 with one, two, three, four, five or six
degrees of freedom. The reticle stage mover assembly 40 and the
device stage mover assembly 44 can each include one or more movers,
such as rotary motors, voice coil motors, linear motors utilizing a
Lorentz force to generate drive force, electromagnetic movers,
planar motors, or other force movers.
[0043] Alternatively, one of the stages could be driven by a planar
motor that drives the stage by an electromagnetic force generated
by a magnet unit having two-dimensionally arranged magnets and an
armature coil unit having two-dimensionally arranged coils in
facing positions. With this type of driving system, either the
magnet unit or the armature coil unit is connected to the stage
base and the other unit is mounted on the moving plane side of the
stage.
[0044] Movement of the stages as described above generates reaction
forces that can affect performance of the photolithography system.
Reaction forces generated by the wafer (substrate) stage motion can
be mechanically transferred to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,528,100 and Japanese
Laid-Open Patent Application Publication No. 8-136475.
Additionally, reaction forces generated by the reticle (mask) stage
motion can be mechanically transferred to the floor (ground) by use
of a frame member as described in U.S. Pat. No. 5,874,820 and
Japanese Laid-Open Patent Application Publication No. 8-330224. The
disclosures of U.S. Pat. Nos. 5,528,100 and 5,874,820 and Japanese
Laid-Open Patent Application Publication Nos. 8-136475 and 8-330224
are incorporated herein by reference in their entireties.
[0045] The measurement system 22 monitors movement of the reticle
28 and the wafer 30 relative to the optical assembly 16 or some
other reference. With this information, the control system 24 can
control the reticle stage assembly 18 to precisely position the
reticle 28 and the device stage assembly 20 to precisely position
the wafer 30. The design of the measurement system 22 can vary. For
example, the measurement system 22 can utilize multiple laser
interferometers, encoders, mirrors, and/or other measuring devices.
The stability of the measurement system 22 is essential for
accurate transfer of an image from the reticle 28 to the wafer
30.
[0046] The control system 24 receives information from the
measurement system 22 and controls the stage mover assemblies 40,
44 to precisely position the reticle 28 and the wafer 30.
Additionally, the control system 24 can control the operation of
the environmental system 26. The control system 24 can include one
or more processors and circuits.
[0047] The environmental system 26 controls the environment in a
gap 246 (illustrated in FIG. 2B) between the optical assembly 16
and the wafer 30. The gap 246 includes an imaging field 250
(illustrated in FIG. 2A). The imaging field 250 includes the area
adjacent to the region of the wafer 30 that is being exposed and
the area in which the beam of light energy travels between the
optical assembly 16 and the wafer 30. With this design, the
environmental system 26 can control the environment in the imaging
field 250.
[0048] The desired environment created and/or controlled in the gap
246 by the environmental system 26 can vary according to the wafer
30 and the design of the rest of the components of the exposure
apparatus 10, including the illumination system 14. For example,
the desired controlled environment can be a fluid such as water.
The environmental system 26 is described in more detail below.
[0049] A photolithography system (an exposure apparatus) according
to the embodiments described herein can be built by assembling
various subsystems in such a manner that prescribed mechanical
accuracy, electrical accuracy, and optical accuracy are maintained.
In order to maintain the various accuracies, prior to and following
assembly, every optical system is adjusted to achieve its optical
accuracy. Similarly, every mechanical system and every electrical
system are adjusted to achieve their respective mechanical and
electrical accuracies. The process of assembling each subsystem
into a photolithography system includes mechanical interfaces,
electrical circuit wiring connections and air pressure plumbing
connections between each subsystem. Needless to say, there also is
a process where each subsystem is assembled prior to assembling a
photolithography system from the various subsystems. Once a
photolithography system is assembled using the various subsystems,
a total adjustment is performed to make sure that accuracy is
maintained in the complete photolithography system. Additionally,
it is desirable to manufacture an exposure system in a clean room
where the temperature and cleanliness are controlled.
[0050] FIG. 2A is a cut-away view taken on line 2A-2A in FIG. 1
that illustrates a portion of the exposure apparatus 10 including
the optical assembly 16, the device stage 42, the environmental
system 26, and the wafer 30. The imaging field 250 (illustrated in
phantom) also is illustrated in FIG. 2A.
[0051] In one embodiment, the environmental system 26 fills the
imaging field 250 and the rest of the gap 246 (illustrated in FIG.
2B) with an immersion fluid 248 (illustrated in FIG. 2B). As used
herein, the term "fluid" shall mean and include a liquid and/or a
gas, including any fluid vapor.
[0052] The design of the environmental system 26 and the components
of the environmental system 26 can be varied. In the embodiment
illustrated in FIG. 2A, the environmental system 26 includes an
immersion fluid system 252 and a fluid barrier 254. In this
embodiment, (i) the immersion fluid system 252 delivers and/or
injects the immersion fluid 248 into the gap 246 and captures the
immersion fluid 248 flowing from the gap 246, and (ii) the fluid
barrier 254 inhibits the flow of the immersion fluid 248 away from
near the gap 246.
[0053] The design of the immersion fluid system 252 can vary. For
example, the immersion fluid system 252 can inject the immersion
fluid 248 at one or more locations at or near the gap 246 and/or
the edge of the optical assembly 16. Alternatively, the immersion
fluid 248 may be injected directly between the optical assembly 16
and the wafer 30. Further, the immersion fluid system 252 can
scavenge the immersion fluid 248 at one or more locations at or
near the gap 246 and/or the edge of the optical assembly 16. In the
embodiment illustrated in FIG. 2A, the immersion fluid system 252
includes four spaced apart injector/scavenge pads 258 (illustrated
in phantom) positioned near the perimeter of the optical assembly
16 and an injector/scavenge source 260. These components are
described in more detail below.
[0054] FIG. 2A also illustrates that the optical assembly 16
includes an optical housing 262A, a last optical element 262B, and
an element retainer 262C that secures the last optical element 262B
to the optical housing 262A.
[0055] FIG. 2B is a cut-away view of the portion of the exposure
apparatus 10 of FIG. 2A, including (i) the optical assembly 16 with
the optical housing 262A, the last optical element 262B, and the
element retainer 262C, (ii) the device stage 42, and (iii) the
environmental system 26. FIG. 2B also illustrates the gap 246
between the last optical element 262B and the wafer 30, and that
the immersion fluid 248 (illustrated as circles) fills the gap 246.
In one embodiment, the gap 246 is approximately 1 mm.
[0056] In one embodiment, the fluid barrier 254 contains the
immersion fluid 248, including any fluid vapor 249 (illustrated as
triangles) in the area near the gap 246 and forms and defines an
interior chamber 263 around the gap 246. In the embodiment
illustrated in FIG. 2B, the fluid barrier 254 includes a
containment frame 264 (also referred to herein as a surrounding
member), a seal 266, and a frame support 268. The interior chamber
263 represents the enclosed volume defined by the containment frame
264, the seal 266, the optical housing 262A and the wafer 30. The
fluid barrier 254 restricts the flow of the immersion fluid 248
from the gap 246, assists in maintaining the gap 246 full of the
immersion fluid 248, allows for the recovery of the immersion fluid
248 that escapes from the gap 246, and contains any vapor 249
produced from the fluid. In one embodiment, the fluid barrier 254
encircles and runs entirely around the gap 246. Further, in one
embodiment, the fluid barrier 254 confines the immersion fluid 248
and its vapor 249 to a region on the wafer 30 and the device stage
42 centered on the optical assembly 16.
[0057] Containment of both the immersion fluid 248 and its vapor
249 can be important for the stability of the lithography tool. For
example, stage measurement interferometers are sensitive to the
index of refraction of the ambient atmosphere. For the case of air
with some water vapor present at room temperature and 633 nm laser
light for the interferometer beam, a change of 1% in relative
humidity causes a change in refractive index of approximately
10.sup.-8. For a 1 m total beam path, this can represent an error
of 10 nm in stage position. If the immersion fluid 248 is water, a
droplet of water 7 mm in diameter evaporating into a 1 m.sup.3
volume changes the relative humidity by 1%. Relative humidity is
typically monitored and corrected for by the control system 24, but
this is based on the assumption that the relative humidity is
uniform, so that its value is the same in the interferometer beams
as at the monitoring point. However, if droplets of water and its
attendant vapor are scattered around on the wafer and stage
surfaces, the assumption of uniform relative humidity may not be
valid.
[0058] In addition to the risk to the interferometer beams, water
evaporation may also create temperature control problems. The heat
of vaporization of water is about 44 kJ/mole. Evaporation of the 7
mm drop mentioned above will absorb about 430 J which must be
supplied by the adjacent surfaces.
[0059] FIG. 2C illustrates a perspective view of one embodiment of
the containment frame 264. In this embodiment, the containment
frame 264 is annular ring shaped and encircles the gap 246
(illustrated in FIG. 2B). Additionally, in this embodiment, the
containment frame 264 includes a top side 270A, an opposite bottom
side 270B (also referred to as a first surface) that faces the
wafer 30, an inner side 270C that faces the gap 246, and an outer
side 270D. The terms top and bottom are used merely for
convenience, and the orientation of the containment frame 264 can
be rotated. The containment frame 264 can have another shape.
Alternatively, for example, the containment frame 264 can be
rectangular frame shaped or octagonal frame shaped.
[0060] Additionally, as provided herein, the containment frame 264
may be temperature controlled to stabilize the temperature of the
immersion fluid 248.
[0061] Referring back to FIG. 2B, the seal 266 seals the
containment frame 264 to the optical assembly 16 and allows for
some motion of the containment frame 264 relative to the optical
assembly 16. In one embodiment, the seal 266 is made of a flexible,
resilient material that is not influenced by the immersion fluid
248. Suitable materials for the seal 266 include rubber, Buna-N,
neoprene, Viton or plastic. Alternatively the seal 266 may be a
bellows made of a metal such as stainless steel or rubber or a
plastic.
[0062] FIG. 2D illustrates an enlarged view of a portion of FIG.
2B, in partial cut-away. The frame support 268 connects and
supports the containment frame 264 to the apparatus frame 12 and
the optical assembly 16 above the wafer 30 and the device stage 42.
In one embodiment, the frame support 268 supports all of the weight
of the containment frame 264. Alternatively, for example, the frame
support 268 can support only a portion of the weight of the
containment frame 264. In one embodiment, the frame support 268 can
include one or more support assemblies 274. For example, the frame
support 268 can include three spaced apart support assemblies 274
(only two are illustrated). In this embodiment, each support
assembly 274 extends between the apparatus frame 12 and the top
side 270A of the containment frame 264.
[0063] In one embodiment, each support assembly 274 is a flexure.
As used herein, the term "flexure" shall mean a part that has
relatively high stiffness in some directions and relatively low
stiffness in other directions. In one embodiment, the flexures
cooperate (i) to be relatively stiff along the X axis and along the
Y axis, and (ii) to be relatively flexible along the Z axis. The
ratio of relatively stiff to relatively flexible is at least
approximately 100/1, and can be at least approximately 1000/1.
Stated another way, the flexures can allow for motion of the
containment frame 264 along the Z axis and inhibit motion of the
containment frame 264 along the X axis and the Y axis. In this
embodiment, each support assembly 274 passively supports the
containment frame 264.
[0064] Alternatively, for example, each support assembly 274 can be
an actuator that can be used to adjust the position of the
containment frame 264 relative to the wafer 30 and the device stage
42. Additionally, the frame support 268 can include a frame
measurement system 275 that monitors the position of the
containment frame 264. For example, the frame measurement system
275 can monitor the position of the containment frame 264 along the
Z axis, about the X axis, and/or about the Y axis. With this
information, the support assemblies 274 can be used to adjust the
position of the containment frame 264. In this embodiment, each
support assembly 274 can actively adjust the position of the
containment frame 264.
[0065] In one embodiment, the environmental system 26 includes one
or more pressure equalizers 276 that can be used to control the
pressure in the chamber 263. Stated another way, the pressure
equalizers 276 inhibit atmospheric pressure changes or pressure
changes associated with the fluid control from creating forces
between the containment frame 264 and the wafer 30 or the last
optical element 262B. For example, the pressure equalizers 276 can
cause the pressure on the inside of the chamber 263 and/or in the
gap 246 to be approximately equal to the pressure on the outside of
the chamber 263. For example, each pressure equalizer 276 can be a
channel that extends through the containment frame 264. In one
embodiment, a tube 277 (only one is illustrated) is attached to the
channel of each pressure equalizer 276 to convey any fluid vapor
away from the measurement system 22 (illustrated in FIG. 1). In
alternative embodiments, the pressure equalizer 276 allows for a
pressure difference of less than approximately 0.01, 0.05, 0.1,
0.5, or 1.0 PSI.
[0066] FIG. 2B also illustrates several injector/scavenge pads 258.
FIG. 2D illustrates one injector/scavenge pad 258 in more detail.
In this embodiment, each of the injector/scavenge pads 258 includes
a pad outlet 278A and a pad inlet 278B that are in fluid
communication with the injector/scavenge source 260. At the
appropriate time, the injector/scavenge source 260 provides
immersion fluid 248 to the pad outlet 278A that is released into
the chamber 263 and draws immersion fluid 248 through the pad inlet
278B from the chamber 263.
[0067] FIGS. 2B and 2D also illustrate that the immersion fluid 248
in the chamber 263 sits on top of the wafer 30. As the wafer 30
moves under the optical assembly 16, it will drag the immersion
fluid 248 in the vicinity of a top, device surface 279 of the wafer
30 with the wafer 30 into the gap 246.
[0068] In one embodiment, referring to FIGS. 2B and 2D, the device
stage 42 includes a stage surface 280 that has approximately the
same height along the Z axis as the top, exposed surface 279 of the
wafer 30. Stated another way, in one embodiment, the stage surface
280 is in approximately the same plane as the exposed surface 279
of the wafer 30. In alternative embodiments, for example,
approximately the same plane shall mean that the planes are within
approximately 1, 10, 100 or 500 microns. As a result thereof, the
distance between the bottom side 270B of the containment frame 264
and the wafer 30 is approximately equal to the distance between the
bottom side 270B of the containment frame 264 and the device stage
42. In one embodiment, for example, the device stage 42 can include
a disk shaped recess 282 for receiving the wafer 30. Some
alternative designs of the device stage 42 are discussed below.
[0069] FIG. 2D illustrates that a frame gap 284 exists between the
bottom side 270B of the containment frame 264 and the wafer 30
and/or the device stage 42 to allow for ease of movement of the
device stage 42 and the wafer 30 relative to the containment frame
264. The size of the frame gap 284 can vary. For example, the frame
gap 284 can be between approximately 5 .mu.m and 3 mm. In
alternative examples, the frame gap 284 can be approximately 5, 10,
50, 100, 150, 200, 250, 300, 400, or 500 microns.
[0070] In certain embodiments, the distance between the bottom side
270B and at least one of the wafer 30 and/or the device stage 42 is
shorter than a distance between the end surface (e.g., the last
optical element 262B or the bottom of the optical housing 262A) of
the optical assembly 16 and at least one of the wafer 30 and/or the
device stage 42.
[0071] Additionally, a wafer gap 285 can exist between the edge of
the wafer 30 and the wafer stage 42. In one embodiment, the wafer
gap 285 is as narrow as possible to minimize leakage when the wafer
30 is off-center from the optical assembly 16 and lying partly
within and partly outside the fluid containment frame 264 region.
For example, in alternative embodiments, the wafer gap 285 can be
approximately 1, 10, 50, 100, 500, or 1000 microns.
[0072] FIG. 2D also illustrates that some of the immersion fluid
248 flows between the containment frame 264 and the wafer 30 and/or
the device stage 42. In one embodiment, the containment frame 264
includes one or more scavenge inlets 286 that are positioned at or
near the bottom side 270B of the containment frame 264. The one or
more scavenge inlets 286 are in fluid communication with the
injector/scavenge source 260 (illustrated in FIG. 2B). With this
design, the immersion fluid 248 that escapes in the frame gap 284
can be scavenged by the injector/scavenge source 260. In the
embodiment illustrated in FIG. 2D, the bottom side 270B of the
containment frame 264 includes one scavenge inlet 286 that is
substantially annular groove shaped and is substantially concentric
with the optical assembly 16. Alternatively, for example, the
bottom side 270B of the containment frame 264 can include a
plurality of spaced apart annular groove shaped, scavenge inlets
286 that are substantially concentric with the optical assembly 16
to inhibit the immersion fluid 248 from completely exiting the
frame gap 284. Still alternatively, a plurality of spaced apart
apertures oriented in a circle can be used instead of an annular
shaped groove.
[0073] In one embodiment, the injector/scavenge source 260 applies
a vacuum and/or partial vacuum on the scavenge inlet 286. The
partial vacuum draws the immersion fluid 248 between (i) a small
land area 288 on the bottom side 270B, and (ii) the wafer 30 and/or
the device stage 42. The immersion fluid 248 in the frame gap 284
acts as a fluid bearing 289A (illustrated as an arrow) that
supports the containment frame 264 above the wafer 30 and/or the
device stage 42, allows for the containment frame 264 to float with
minimal friction on the wafer 30 and/or the device stage 42, and
allows for a relatively small frame gap 284. With this embodiment,
most of the immersion fluid 248 is confined within the fluid
barrier 254 and most of the leakage around the periphery is
scavenged within the narrow frame gap 284.
[0074] Additionally, the environmental system 26 can include a
device for creating an additional fluid bearing 289B (illustrated
as an arrow) between the containment frame 264 and the wafer 30
and/or the device stage 42. For example, the containment frame 264
can include one or more bearing outlets 290A that are in fluid
communication with a bearing fluid source 290B of a bearing fluid
290C (illustrated as triangles). In one embodiment, the bearing
fluid 290C is air. In this embodiment, the bearing fluid source
290B provides pressurized air 290C to the bearing outlet 290A to
create the aerostatic bearing 289B. The fluid bearings 289A, 289B
can support all or a portion of the weight of the containment frame
264. In alternative embodiments, one or both of the fluid bearings
289A, 289B support approximately 1, 5, 10, 20, 30, 40, 50, 60, 70,
80, 90, or 100 percent of the weight of the containment frame 264.
In one embodiment, the concentric fluid bearings 289A, 289B are
used to maintain the frame gap 284.
[0075] Depending upon the design, the bearing fluid 290C can have
the same composition or a different composition than the immersion
fluid 248. However, some of the bearing fluid 290C may escape from
the fluid barrier 254. In one embodiment, the type of bearing fluid
290C is chosen so that the bearing fluid 290C and its vapor do not
interfere with the measurement system 22 or temperature stability
of the exposure apparatus 10.
[0076] In another embodiment, the partial vacuum in the scavenge
inlets 286 pulls and urges the containment frame 264 toward the
wafer 30. In this embodiment, the fluid bearing 289B supports part
of the weight of the containment frame 264 as well as opposes the
pre-load imposed by the partial vacuum in the scavenge inlets
286.
[0077] In addition, the pressurized air 290C helps to contain the
immersion fluid 248 within the containment frame 264. As provided
above, the immersion fluid 248 in the frame gap 284 is mostly drawn
out through the scavenge inlets 286. In this embodiment, any
immersion fluid 248 that leaks beyond the scavenge inlets 286 is
pushed back to the scavenge inlets 286 by the bearing fluid
290C.
[0078] The frame gap 284 may vary radially, from the inner side
270C to the outer side 270D, to optimize bearing and scavenging
functions.
[0079] In FIG. 2D, the bearing outlet 290A is substantially annular
groove shaped, is substantially concentric with the optical
assembly 16 and the scavenge inlet 286, and has a diameter that is
greater than the diameter of the scavenge inlet 286. Alternatively,
for example, the bottom side 270B of the containment frame 264 can
include a plurality of spaced apart annular groove shaped, bearing
outlets 290A that are substantially concentric with the optical
assembly 16. Still alternatively, a plurality of spaced apart
apertures oriented in a circle can be used instead of an annular
shaped groove. Alternatively, for example, a magnetic type bearing
could be used to support the containment frame 264.
[0080] As illustrated in FIGS. 2B and 2D, the wafer 30 is centered
under the optical assembly 16. In this position, the fluid bearings
289A, 289B support the containment frame 264 above the wafer 30.
FIG. 2E is an illustration of the portion of the exposure apparatus
10 of FIG. 2A with the device stage 42 and the wafer 30 moved
relative to the optical assembly 16. In this position, the wafer 30
and the device stage 42 are no longer centered under the optical
assembly 16, and the fluid bearings 289A, 289B (illustrated in FIG.
2D) support the containment frame 264 above the wafer 30 and the
device stage 42.
[0081] FIG. 3 is a first embodiment of the injector/scavenge source
260. In this embodiment, the injector/scavenge source 260 includes
(i) a low pressure source 392A, e.g. a pump, having an inlet that
is at a vacuum or partial vacuum that is in fluid communication
with the scavenge inlet 286 (illustrated in FIG. 2D) and the pad
inlets 278B (illustrated in FIGS. 2B and 2D) and a pump outlet that
provides pressurized immersion fluid 248, (ii) a filter 392B in
fluid communication with the pump outlet and that filters the
immersion fluid 248, (iii) a de-aerator 392C in fluid communication
with the filter 392B and that removes any air, contaminants, or gas
from the immersion fluid 248, (iv) a temperature control 392D in
fluid communication with the de-aerator 392C and that controls the
temperature of the immersion fluid 248, (v) a reservoir 392E in
fluid communication with the temperature control 392D and that
retains the immersion fluid 248, and (vi) a flow controller 392F
that has an inlet in fluid communication with the reservoir 392E
and an outlet in fluid communication with the pad outlets 278A
(illustrated in FIGS. 2B and 2D), the flow controller 392F
controlling the pressure and flow to the pad outlets 278A. The
operation of these components can be controlled by the control
system 24 (illustrated in FIG. 1) to control the flow rate of the
immersion fluid 248 to the pad outlets 278A, the temperature of the
immersion fluid 248 at the pad outlets 278A, the pressure of the
immersion fluid 248 at the pad outlets 278A, and/or the pressure at
the scavenge inlets 286 and the pad inlets 278B.
[0082] Additionally, the injector/scavenge source 260 can include
(i) a pair of pressure sensors 392G that measure the pressure near
the pad outlets 278A, the scavenge inlets 286 and the pad inlets
278B, (ii) a flow sensor 392H that measures the flow to the pad
outlets 278A, and/or (iii) a temperature sensor 392I that measures
the temperature of the immersion fluid 248 delivered to the pad
outlets 278A. The information from these sensors 392G-392I can be
transferred to the control system 24 so that that control system 24
can appropriately adjust the other components of the
injector/scavenge source 260 to achieve the desired temperature,
flow and/or pressure of the immersion fluid 248.
[0083] The orientation of the components of the injector/scavenge
source 260 can be varied. Further, one or more of the components
may not be necessary and/or some of the components can be
duplicated. For example, the injector/scavenge source 260 can
include multiple pumps, multiple reservoirs, temperature
controllers or other components. Moreover, the environmental system
26 can include multiple injector/scavenge sources 260.
[0084] The rate at which the immersion fluid 248 is pumped into and
out of the chamber 263 (illustrated in FIG. 2B) can be adjusted to
suit the design requirements of the system. Further, the rate at
which the immersion fluid 248 is scavenged from the pad inlets 278B
and the scavenge inlets 286 can vary. In one embodiment, the
immersion fluid 248 is scavenged from the pad inlets 278B at a
first rate and is scavenged from the scavenge inlets 286 at a
second rate. As an example, the first rate can be between
approximately 0.1-5 liters/minute and the second rate can be
between approximately 0.01-0.5 liters/minute. However, other first
and second rates can be utilized.
[0085] The rates at which the immersion fluid 248 is pumped into
and out of the chamber 263 can be adjusted to (i) control the
leakage of the immersion fluid 248 below the fluid barrier, (ii)
control the leakage of the immersion fluid 248 from the wafer gap
285 when the wafer 30 is off-center from the optical assembly 16,
and/or (iii) control the temperature and purity of the immersion
fluid 248 in the gap 246. For example, the rates can be increased
in the event the wafer 30 is off-center, the temperature of the
immersion fluid 248 becomes too high and/or there is an
unacceptable percentage of contaminants in the immersion fluid 248
in the gap 246.
[0086] The type of immersion fluid 248 can be varied to suit the
design requirements of the apparatus 10. In one embodiment, the
immersion fluid 248 is water. Alternatively, for example, the
immersion fluid 248 can be a fluorocarbon fluid, Fomblin oil, a
hydrocarbon oil, or another type of oil. More generally, the fluid
should satisfy certain conditions: 1) it must be relatively
transparent to the exposure radiation; 2) its refractive index must
be comparable to that of the last optical element 262B; 3) it
should not react chemically with components of the exposure system
10 with which it comes into contact; 4) it must be homogeneous; and
5) its viscosity should be low enough to avoid transmitting
vibrations of a significant magnitude from the stage system to the
last optical element 262B.
[0087] FIG. 4A is an enlarged view of a portion of another
embodiment of the fluid barrier 454A, a portion of the wafer 30,
and a portion of the device stage 42. In this embodiment, the fluid
barrier 454A is somewhat similar to the corresponding component
described above and illustrated in FIG. 2D. However, in this
embodiment, the containment frame 464A includes two concentric,
scavenge inlets 486A that are positioned at the bottom side 470B of
the containment frame 464A. The two scavenge inlets 486A are in
fluid communication with the injector/scavenge source 260
(illustrated in FIG. 2B). With this design, the immersion fluid 248
that escapes in the frame gap 284 can be scavenged by the
injector/scavenge source 260. In this embodiment, the bottom side
470B of the containment frame 464 includes two scavenge inlets 486A
that are each substantially annular groove shaped and are
substantially concentric with the optical assembly 16.
[0088] With this design, the injector/scavenge source 260 applies a
vacuum or partial vacuum on the scavenge inlets 486A. The partial
vacuum draws the immersion fluid 248 between a small land area 488
on the bottom side 470B and the wafer 30 and/or the device stage
42. In this embodiment, the majority of the immersion fluid 248
flows under the land 488 and into the inner scavenge inlet 486A.
Additionally, the immersion fluid 248 not removed at the inner
scavenge inlet 486A is drawn into the outer scavenge inlet
486A.
[0089] FIG. 4B is an enlarged view of a portion of another
embodiment of the fluid barrier 454B, a portion of the wafer 30,
and a portion of the device stage 42. In this embodiment, the fluid
barrier 454B is somewhat similar to the corresponding component
described above and illustrated in FIG. 2D. However, in this
embodiment, the containment frame 464B includes one bearing outlet
490B and two scavenge inlets 486B that are positioned at the bottom
side 470B. The scavenge inlets 486B are in fluid communication with
the injector/scavenge source 260 (illustrated in FIG. 2B) and the
bearing outlet 490B is in fluid communication with the bearing
fluid source 290B (illustrated in FIG. 2D). However, in this
embodiment, the bearing outlet 490B is positioned within and
concentric with the scavenge inlets 486B. Stated another way, the
bearing outlet 490B has a smaller diameter than the scavenge inlets
486B, and the bearing outlet 490B is closer to the optical assembly
16 than the scavenge inlets 486B. Further, with this design, the
bearing fluid 290C (illustrated in FIG. 2D) can be a liquid that is
the same in composition as the immersion fluid 248. With this
design, the bearing fluid 290C in the frame gap 284 can be
scavenged by the injector/scavenge source 260 via the scavenge
inlets 486B.
[0090] FIG. 4C is an enlarged view of a portion of another
embodiment of the fluid barrier 454C, a portion of the wafer 30,
and a portion of the device stage 42. In this embodiment, the fluid
barrier 454C is somewhat similar to the corresponding component
described above and illustrated in FIG. 2D. However, in this
embodiment, the containment frame 464C includes one bearing outlet
490C and two scavenge inlets 486C that are positioned at the bottom
side 470B. The scavenge inlets 486C are in fluid communication with
the injector/scavenge source 260 (illustrated in FIG. 2B) and the
bearing outlet 490C is in fluid communication with the bearing
fluid source 290B (illustrated in FIG. 2D). However, in this
embodiment, the bearing outlet 490C is positioned between the two
scavenge inlets 486C. Stated another way, the inner scavenge inlet
486C has a smaller diameter than the bearing outlet 490C, and the
bearing outlet 490C has a smaller diameter than the outer scavenge
inlet 486C. With this design, the inner scavenge inlet 486C is
closer to the optical assembly 16 than the bearing outlet 490C.
[0091] It should be noted that in each embodiment, additional
scavenge inlets and addition bearing outlets can be added as
necessary.
[0092] FIG. 5A is a cut-away view of a portion of another
embodiment of the exposure apparatus 510, including the optical
assembly 516, the device stage 542, and the environmental system
526 that are similar to the corresponding components described
above. FIG. 5A also illustrates the wafer 30, the gap 546, and that
the immersion fluid 548 fills the gap 546. FIG. 5B illustrates an
enlarged portion of FIG. 5A taken on line 5B-5B.
[0093] However, in the embodiment illustrated in FIGS. 5A and 5B,
the fluid barrier 554 includes an inner barrier 555 in addition to
the containment frame 564, the seal 566, and the frame support 568.
In this embodiment, the inner barrier 555 is annular ring shaped,
encircles the bottom of the optical assembly 516, is concentric
with the optical assembly 516, and is positioned within the
containment frame 564 adjacent to the seal 566.
[0094] The inner barrier 555 can serve several purposes. For
example, the inner barrier 555 can limit the amount of immersion
fluid 548 escaping to the containment frame 564, reducing the
scavenging requirements at the scavenge inlets 586, and also
reducing the leakage of immersion fluid 548 into the wafer gap 285
when the wafer 30 is off-center from the optical assembly 516 and
lying partly within and partly outside the fluid containment frame
564 region. With this design, the fluid injection/scavenge pads 558
can be used to recover the majority of the immersion fluid 548 from
the chamber 563. Additionally, if the immersion fluid 548 is
maintained at or near the level of the top of the inner barrier
555, pressure surges associated with injection of the immersion
fluid 548 can be reduced, because excess immersion fluid 548
overflows the top of the inner barrier 555, creating a static
pressure head. Some pressure surge may remain even in this
situation due to surface tension effects. These effects can be
reduced by increasing the height of the inner barrier 555 shown in
FIG. 5B. For example, if the immersion fluid is water, the height
should preferably be several mm or more. Additionally, the
remaining pressure surge can be reduced or eliminated by adjusting
the "wettability" of the surfaces of inner barrier 555 and optical
assembly 516 in contact with the immersion fluid 548 to reduce
surface tension forces. In one embodiment, the inner barrier 555
can maintain a significant fluid height difference with a gap of
approximately 50 .mu.m between the bottom of the inner barrier 55
and the top of the wafer 30 or the device stage 42.
[0095] FIG. 6 is a perspective view of one embodiment of a device
stage 642 with a wafer 630 positioned above the device stage 642.
In this embodiment, the device stage 642 includes a device table
650, a device holder 652, a guard 654, and a guard mover assembly
656. In this embodiment, the device table 650 is generally
rectangular plate shaped. The device holder 652 retains the wafer
630. In this embodiment, the device holder 652 is a chuck or
another type of clamp that is secured to the device table 650. The
guard 654 surrounds and/or encircles the wafer 630. In one
embodiment, the guard 654 is generally rectangular plate shaped and
includes a circular shaped aperture 658 for receiving the wafer
630.
[0096] In one embodiment, the guard 654 can include a first section
660 and a second section 662. One or more of the sections 660, 662
can be moved, removed or recessed to provide easy access for
loading and removing the wafer 630.
[0097] The guard mover assembly 656 secures the guard 654 to the
device table 650, and moves and positions the guard 654 relative to
the device table 650, the device holder 652, and the wafer 630.
With this design, the guard mover assembly 656 can move the guard
654 so that the top, stage surface 680 of the guard 654 is
approximately at the same Z height as the top exposed surface 679
of the wafer 630. Stated another way, the guard mover assembly 656
moves the guard 654 so that the stage surface 680 is approximately
in the same plane as the exposed surface 679 of the wafer 630. As a
result thereof, the guard 654 can be moved to adjust for wafers 630
of alternative heights.
[0098] The design of the guard mover assembly 656 can be varied.
For example, the guard mover assembly 656 can include one or more
rotary motors, voice coil motors, linear motors, electromagnetic
actuators, and/or other type of force actuators. In one embodiment,
the guard mover assembly 656 moves and positions the guard 654
along the Z axis, about the X axis and about the Y axis under the
control of the control system 24 (illustrated in FIG. 1). A sensor
681 (illustrated as a box) can be used to measure the relative
heights of the guard surface 680 and the wafer top surface 679.
Information from the sensor 681 can be transferred to the control
system 24 (illustrated in FIG. 1) which uses information from the
height sensor 681 to control the guard mover assembly 656.
[0099] FIG. 7A is a perspective view of another embodiment of a
device stage 742 with a wafer 730 positioned above the device stage
742. FIG. 7B is a cut-away view taken from FIG. 7A. In this
embodiment, the device stage 742 includes a device table 750, a
device holder 752, a guard 754, and a holder mover assembly 756. In
this embodiment, the device table 750 is generally rectangular
plate shaped. The device holder 752 retains the wafer 730. The
guard 754 is generally rectangular plate shaped and includes a
circular shaped aperture 758 for the wafer 730. In this embodiment,
the guard 754 is fixedly secured to the device table 750. The
holder mover assembly 756 secures the device holder 752 to the
device table 750 and moves and positions the device holder 752
relative to the device table 750 and the guard 754. With this
design, the holder mover assembly 756 can move the device holder
752 and the wafer 730 so that the top stage surface 780 of the
guard 754 is approximately at the same Z height as the top exposed
surface 779 of the wafer 730. A sensor 781 can be used to measure
the relative heights of the top stage surface 780 and the top
exposed surface 779 of the wafer 730. The information from the
sensor 781 can be transferred to the control system 24 (illustrated
in FIG. 1) which uses information from the height sensor to control
the holder mover assembly 756.
[0100] For example, the holder mover assembly 756 can include one
or more rotary motors, voice coil motors, linear motors,
electromagnetic actuators, and/or other types of force actuators.
In one embodiment, the holder mover assembly 756 moves and
positions the device holder 752 and the wafer 730 along the Z axis,
about the X axis and about the Y axis under the control of the
control system 24 (illustrated in FIG. 1).
[0101] Semiconductor devices can be fabricated using the above
described systems, by the process shown generally in FIG. 8A. In
step 801 the device's function and performance characteristics are
designed. Next, in step 802, a mask (reticle) having a pattern is
designed according to the previous designing step, and in a
parallel step 803 a wafer is made from a silicon material. The mask
pattern designed in step 802 is exposed onto the wafer from step
803 in step 804 by a photolithography system described hereinabove
in accordance with the invention. In step 805 the semiconductor
device is assembled (including the dicing process, bonding process
and packaging process). Finally, the device is then inspected in
step 806.
[0102] FIG. 8B illustrates a detailed flowchart example of the
above-mentioned step 804 in the case of fabricating semiconductor
devices. In FIG. 8B, in step 811 (oxidation step), the wafer
surface is oxidized. In step 812 (CVD step), an insulation film is
formed on the wafer surface. In step 813 (electrode formation
step), electrodes are formed on the wafer by vapor deposition. In
step 814 (ion implantation step), ions are implanted in the wafer.
The above mentioned steps 811-814 form the preprocessing steps for
wafers during wafer processing, and selection is made at each step
according to processing requirements.
[0103] At each stage of wafer processing, when the above-mentioned
preprocessing steps have been completed, the following
post-processing steps are implemented. During post-processing,
first, in step 815 (photoresist formation step), photoresist is
applied to a wafer. Next, in step 816 (exposure step), the
above-mentioned exposure device is used to transfer the circuit
pattern of a mask (reticle) to a wafer. Then in step 817
(developing step), the exposed wafer is developed, and in step 818
(etching step), parts other than residual photoresist (exposed
material surface) are removed by etching. In step 819 (photoresist
removal step), unnecessary photoresist remaining after etching is
removed. Multiple circuit patterns are formed by repetition of
these preprocessing and post-processing steps.
[0104] While the exposure apparatus 10 as shown and described
herein is fully capable of providing the advantages described
herein, it is merely illustrative of embodiments of the invention.
No limitations are intended to the details of construction or
design herein shown.
* * * * *