U.S. patent application number 09/814633 was filed with the patent office on 2001-11-29 for high performance stage assembly.
Invention is credited to Poon, Alex Ka Tim, Watson, Douglas.
Application Number | 20010045810 09/814633 |
Document ID | / |
Family ID | 23872815 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045810 |
Kind Code |
A1 |
Poon, Alex Ka Tim ; et
al. |
November 29, 2001 |
High performance stage assembly
Abstract
A stage assembly (10) for moving and positioning one or more
objects (24) for an exposure apparatus (28) is provided herein. The
stage assembly (10) includes a fine stage (14) and a coarse stage
(18). The fine stage (14) includes a holder (15) that retains the
object (24). The stage assembly (10) also includes a fine Y mover
(32) and a fine X mover (34) that precisely move the fine stage
(14) relative to the coarse stage (18). Uniquely, the fine movers
(32), (34) are positioned on only one side of the holder (15). With
this design, the resulting stage assembly (10) has a relatively low
mass and a relatively high servo bandwidth. Further, with this
design, the stage assembly (10) is readily accessible for service
and a measurement system (16) can be easily positioned near the
fine stage (14). The stage assembly (10) can also include an
anti-gravity mechanism (40) that minimizes distortion of a stage
base (12) that supports the fine stage (14) as the fine stage (14)
moves above the stage base (12). Additionally, the stage assembly
(10) can include a reaction assembly (20) that reduces the amount
of reaction forces transferred from the coarse stage (18).
Inventors: |
Poon, Alex Ka Tim; (San
Ramon, CA) ; Watson, Douglas; (Campbell, CA) |
Correspondence
Address: |
Steven G. Roeder
The Law Office of Steven G. Roeder
5560 Chelsea Avenue
La Jolla
CA
92037
US
|
Family ID: |
23872815 |
Appl. No.: |
09/814633 |
Filed: |
March 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09814633 |
Mar 22, 2001 |
|
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|
09471740 |
Dec 23, 1999 |
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6281655 |
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Current U.S.
Class: |
318/649 |
Current CPC
Class: |
Y10T 74/20012 20150115;
G03F 7/70716 20130101 |
Class at
Publication: |
318/649 |
International
Class: |
B64C 017/06 |
Claims
What is claimed is:
1. A stage apparatus for positioning an object, the stage apparatus
comprising: a first stage including a first frame and a first
supporting member that supports the first frame, the first frame
holding the object and positioning the object; and a second stage
including a second frame and a second supporting member that
supports the second frame, the second frame being connected with
the first frame in a non-contact manner and positioning the first
frame, and the second supporting member is provided independently
from the first supporting member of the first stage.
2. The stage apparatus of claim 1, wherein the first stage is a
fine stage that positions the object with a first precision, and
the second stage is a coarse stage that positions the first frame
of the first stage with a second precision that is lower than the
first precision.
3. The stage apparatus of claim 1, wherein the first stage
positions the object within a first movable region and the second
stage positions the first frame of the first stage within a second
movable region that is larger than the first movable region.
4. The stage apparatus of claim 1, further comprising a vibration
damper device disposed between the first supporting member and the
second supporting member.
5. The stage apparatus of claim 4, wherein the vibration damper
device prevents a vibration, which is generated by a movement of
the second stage, from propagating to the first support member.
6. The stage apparatus of claim 4, wherein the vibration damper
device is a reaction assembly that reduces a reaction force
generated by the movement of the second stage.
7. The stage apparatus of claim 1, further comprising a measurement
system that measures a position of the first frame of the first
stage, wherein the measurement system is connected to the first
supporting member.
8. The stage apparatus of claim 1, further comprising a first mover
that causes a relative movement between the first frame of the
first stage and the second stage, wherein the first mover connect
the first stage and the second stage in a non-contract manner.
9. The stage apparatus of claim 8, wherein the first mover
generates driving force by utilizing a magnetic field.
10. The stage apparatus of claim 9, wherein the first mover has at
least one electromagnet that generates the driving force.
11. The stage apparatus of claim 8, further comprising a second
mover that causes a relative movement between the second frame and
the second supporting member along the direction substantially
parallel to the direction of driving force of the first mover, and
wherein (i) a first portion of the first mover is connected to the
first frame, (ii) a second portion of the first mover is connected
to the second frame, (iii) a first portion of the second mover is
connected to the second frame, and (iv) a second portion of the
second mover is connected to the second supporting member.
12. The stage apparatus of claim 11, wherein the second mover
connects the second frame and the second supporting member in a
non-contact manner.
13. The stage apparatus of claim 12, wherein the second supporting
member supports the second frame in a non-contact manner.
14. The stage apparatus of claim 1, wherein the first supporting
member supports the first frame in a non-contact manner.
15. The stage apparatus of claim 14, wherein the first stage
further comprises a fluid bearing disposed between the first frame
and the first supporting member.
16. An exposure apparatus for positioning an object, the exposure
apparatus comprising: an illumination source; and a stage
apparatus, the stage apparatus comprising: a first stage including
a first frame and a first supporting member that supports the first
frame, the first frame holding the object and positioning the
object; a second stage including a second frame and a second
supporting member that supports the second frame, the second frame
being connected with the first frame of the first stage in a
non-contact manner and positioning the first frame, and the second
supporting member is provided independently from the first
supporting member of the first stage.
17. The exposure apparatus of claim 16, further comprising an
apparatus frame that holds the illumination source, wherein the
apparatus frame is construed integrally with the first supporting
member of the first stage and is independent of the second
supporting member of the second stage.
18. The exposure apparatus of claim 16, wherein the object is a
reticle having a pattern, and the first stage and the second stage
position the reticle.
19. A device manufactured with the exposure apparatus according to
claim 16.
20. A wafer on which an image has been formed by the exposure
apparatus according to claim 16.
21. A method for making a stage apparatus, the method comprising
the steps of: providing a first stage including a first frame and a
first supporting member that supports the first frame, the first
frame holding an object and positioning the object; and providing a
second stage including a second frame and a second supporting
member that supports the second frame, the second frame being
connected with the first frame in a non-contact manner and
positioning the first frame, an the second supporting member is
provided independently from the first supporting member.
22. The method of claim 21, wherein the first stage is a fine stage
that positions the object with a first precision; and the second
stage is a coarse stage that positions the first frame of the first
stage with a second precision that is lower than the first
precision.
23. The method of claim 21, wherein the first stage positions the
object within a first movable region; and the second stage
positions the first frame of the first stage within a second
movable region that is larger than the first movable region.
24. The method of claim 21, further comprising the step of
disposing a vibration damper device between the first supporting
member and the second supporting member.
25. The method of claim 24, wherein the vibration damper device
prevents a vibration, which is generated by a movement of the
second stage, from propagating to the first support member.
26. The method of claim 24, wherein the vibration damper device is
a reactive assembly that reduces a reaction force generated by the
movement of the second stage.
27. The method of claim 21, further comprising the step of
connecting a measurement system to the first supporting member so
that the measurement system measures a position of the first frame
of the first stage.
28. The method of claim 21, further comprising the step of coupling
a first mover to at least one of the first stage and the second
stage so that the first mover connects the first stage and the
second stage in a non-contact manner and causes a relative movement
between the first frame of the first stage and the second
stage.
29. The method of claim 28, wherein the first mover generates
driving force by utilizing a magnetic field.
30. The method of claim 29, wherein the first mover has at least
one electromagnet that generates the driving force.
31. The method of claim 28, further comprising the step of coupling
a second mover to the second stage so that the second mover causes
a relative movement between the second frame and the second
supporting member along the direction substantially parallel to the
direction of driving force of the first mover, wherein: (i) the
step of coupling the first mover includes the steps of connecting a
first portion of the first mover to the first frame, and connecting
a second portion of the first mover to the second frame, and (ii)
the step of coupling the second mover includes the steps of
connecting a first portion of the second mover to the second frame,
and connecting a second portion of the second mover to the second
supporting member.
32. The method of claim 31, wherein the second mover connects the
second frame and the second supporting member in a non-contact
manner.
33. The method of claim 32, wherein the second supporting member
supports the second frame in a non-contact manner.
34. The method of claim 21, wherein the first supporting member
supports the first frame in a non-contact manner.
35. The method of claim 34, wherein the first stage further
comprises a fluid bearing disposed between the first frame and the
first supporting member.
36. A method for making an exposure apparatus including the steps
of: providing an illumination source; and providing a stage
apparatus, the step of providing the stage apparatus further
comprising the steps of: providing a first stage including a first
frame and a first supporting member that supports the first frame,
the first frame holding an object and positioning the object; and
providing a second stage including a second frame and a second
supporting member that supports the second frame, the second frame
being connected with the first frame in a non-contact manner and
positioning the first frame, and the second supporting member is
provided independently from the first supporting member.
37. The method of claim 36, further comprising the step of
providing an apparatus frame that supports the illumination source,
the apparatus frame being construed integrally with the first
supporting member of the first stage and is independent of the
second supporting member of the second stage.
38. The method of claim 36, wherein the object is a reticle having
a pattern, the first stage and the second stage positioning the
reticle.
39. A method of making a device including at least an exposure
process, wherein the exposure process utilizes the exposure
apparatus made by the method of claim 36.
40. A method of making a wafer utilizing the exposure apparatus
made by the method of claim 36.
Description
RELATED APPLICATION
[0001] This application is a continuation of application Ser. No.
09/471,740 filed on Dec. 23, 1999, entitled "HIGH PERFORMANCE STAGE
ASSEMBLY" which is currently pending. The contents of application
Ser. No. 09/471,740 is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to a stage for an exposure
apparatus. More specifically, the present invention is directed to
a low mass, high performance stage for an exposure apparatus.
BACKGROUND
[0003] Exposure apparatuses 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 retaining a reticle, a lens assembly and a
wafer stage retaining a semiconductor wafer. The reticle stage and
the wafer stage are supported above a ground with an apparatus
frame. Typically, one or more motors precisely position the wafer
stage and one or more motors precisely position the reticle stage.
The images transferred onto the wafer from the reticle are
extremely small. Accordingly, the precise relative positioning of
the wafer and the reticle is critical to the manufacturing of high
density, semiconductor wafers.
[0004] A typical reticle stage includes a coarse stage and a fine
stage. The coarse stage is used for relatively large movements of
the reticle and the fine stage is used for relatively small,
precise movements of the reticle. Existing reticle stages typically
utilize a pair of spaced apart fine Y motors to move the fine stage
along a Y axis and a pair of spaced apart coarse Y motors to move
the coarse stage along the Y axis.
[0005] Unfortunately, existing reticle stages that utilize both a
coarse stage and a fine stage have a relatively large total mass.
As a result of the large mass, large motors are needed to move and
position the fine stage and the coarse stage. These motors occupy
valuable space near the stage, consume large amounts of electric
current and generate a significant amount of heat. The heat is
subsequently transferred to the surrounding environment, including
the air surrounding the motors and the other components positioned
near the motors. The heat changes the index of refraction of the
surrounding air. This reduces the accuracy of any metrology system
used to monitor the positions of the stages and degrades machine
positioning accuracy. Additionally, the heat causes expansion of
the other components of the device. This further degrades the
accuracy of the device.
[0006] Moreover, a large mass, reticle stage has a relatively low
resonant frequency and a low servo bandwidth. As a result of the
low resonant frequency and low servo bandwidth, external forces
and/or small reaction forces can easily vibrate and distort the
reticle stage. This will influence the position of the reticle
stage and the performance of the exposure apparatus.
[0007] Additionally, the multiple motors required for both the
coarse stage and the fine stage complicates the layout of the
reticle stage and the system required to control both the coarse
stage and the fine stage.
[0008] In light of the above, it is an object of the present
invention to provide a stage assembly that has a relatively low
mass, a relatively high resonance frequency and a relatively high
servo bandwidth. Another object is to provide a stage assembly that
is relatively simple to control, allows space for service access,
and allows space for a measurement system. Still another object is
to provide a stage assembly that utilizes efficient motors to move
the components of the stage assembly. Yet another object is to
provide a low mass stage assembly that can simultaneously carry two
reticles. Another object is to provide a stage assembly that
offsets the mass of a fine stage to minimize distortion to a stage
base and a lens assembly. Another object is to provide a stage that
utilizes reaction force cancellation to minimize the forces
transferred to a mounting frame. Still another object is to provide
an exposure apparatus capable of manufacturing high density,
semiconductor wafers. Yet another object is to provide a stage
assembly having a guideless fine stage and a guideless coarse
stage.
SUMMARY
[0009] The present invention is directed to a stage assembly for
moving an object that satisfies these needs. The stage assembly
includes a fine stage and a coarse stage. The fine stage includes a
holder that retains the object. As provided herein, the stage
assembly can be used to precisely position one or more objects
during a manufacturing and/or an inspection process.
[0010] The stage assembly includes a fine Y mover and a fine X
mover that precisely move the fine stage relative to the coarse
stage. Additionally, the stage assembly can also include a coarse Y
mover and a coarse X mover that move the coarse stage relative to a
reaction assembly. Uniquely, the fine movers and the coarse movers
are positioned on only one side of the holder. With this design,
the fine stage has a relatively low mass and a relatively high
servo bandwidth. Because of the low mass, smaller movers can be
used to move the fine stage. Because of the high servo bandwidth,
external forces and small reaction forces are less likely to
influence the position of the fine stage. This allows for more
accurate positioning of the object by the stages and the production
of higher quality wafers. Further, with this design, the stage
assembly is easily accessible for service and the measurement
system can be easily positioned near the fine stage.
[0011] Moreover, both the fine stage and the coarse stage are
guideless along the X axis, along the Y axis and about the Z axis.
More specifically, both the fine stage and the coarse stage are not
constrained along the Y axis, the X axis and about the Z axis.
Stated another way, each stage can be moved with at least three
degrees of freedom. With this design, the movers control the
position of the stages along the X axis, along the Y axis and about
the Z axis. This allows for more accurate positioning of the stages
and better performance of the stage assembly.
[0012] Further, the stage assembly can also include an anti-gravity
mechanism that urges the fine stage upwards towards the coarse
stage. This minimizes distortion to a stage base that supports the
fine stage as the fine stage moves above the stage base.
[0013] Additionally, the stage assembly can include a mounting
frame that supports the reaction assembly and allows the reaction
assembly to move relative to the mounting frame. With this design,
the reaction assembly reduces the amount of reaction forces from
the coarse movers that are transferred to the ground.
[0014] The present invention is also directed to a method for
moving an object, a method for manufacturing a stage assembly, a
method for manufacturing an exposure apparatus and a method for
manufacturing a wafer and a device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The novel features of this invention, as well as the
invention itself, both as to its structure and its operation, will
be best understood from the accompanying drawings, taken in
conjunction with the accompanying description, in which similar
reference characters refer to similar parts, and in which:
[0016] FIG. 1 is an upper perspective view of a stage assembly
having features of the present invention;
[0017] FIG. 2 is front plan view of the stage assembly of FIG. 1,
with a stage base and a measurement system omitted for clarity;
[0018] FIG. 3 is a side plan view of the stage assembly of FIG. 1,
with the stage base and the measurement system omitted for
clarity;
[0019] FIG. 4 is an exploded perspective view of the stage assembly
of FIG. 1, without the stage base and the measurement system;
[0020] FIG. 5 is a top, partly exploded, perspective view of a fine
stage having features of the present invention;
[0021] FIG. 6 is a bottom perspective view of the fine stage of
FIG. 5;
[0022] FIG. 7 is a perspective view of a mover having features of
the present invention;
[0023] FIG. 8 is an exploded perspective view of the mover of FIG.
7;
[0024] FIG. 9 is a cross-sectional view taken on line 9-9 of FIG.
3;
[0025] FIG. 10 is a perspective view of the view of FIG. 9;
[0026] FIG. 11 is a side perspective view, in partial cut-away of
the stage assembly of FIG. 1;
[0027] FIG. 12 is another side perspective view of the stage
assembly of FIG. 1;
[0028] FIG. 13 is an illustration of an exposure apparatus having
features of the present invention;
[0029] FIG. 14 is a flow chart that outlines a process for
manufacturing a device in accordance with the present invention;
and
[0030] FIG. 15 is a flow chart that outlines device processing in
more detail.
DESCRIPTION
[0031] Referring initially to FIGS. 1-4, a stage assembly 10 having
features of the present invention includes a stage base 12, a fine
stage 14 including a holder 15, a measurement system 16, a coarse
stage 18, a reaction assembly 20 and a mounting frame 22. The stage
assembly 10 is useful for precisely positioning one or more objects
24 during a manufacturing and/or inspection process.
[0032] The type of object 24 positioned and moved by the stage
assembly 10 can be varied. In the embodiments provided herein, each
object 24 is a reticle 26 and the stage assembly 10 is useful as
part of an exposure apparatus 28 (illustrated in FIG. 13) for
precisely positioning each reticle 26 during the manufacture of a
semiconductor wafer 30 (illustrated in FIG. 13). Alternately, for
example, the stage assembly 10 can be used to retain a reticle
during reticle manufacturing, an object under an electron
microscope (not shown), an object during a precision measurement
operation, or an object during a precision manufacturing
operation.
[0033] As an overview, the stage assembly 10 also includes a fine Y
mover 32, a fine X mover 34, a coarse Y mover 36, a coarse X mover
38 and an anti-gravity mechanism 40. The fine Y mover 32 and the
fine X mover 34 precisely move the fine stage 14 relative to the
coarse stage 18. The coarse Y mover 36 (illustrated in FIGS. 9 and
10) and the coarse X mover 38 move the coarse stage 18 relative to
the reaction assembly 20. The anti-gravity mechanism 40 minimizes
distortion of the stage base 12 as the fine stage 14 moves above
the stage base 12.
[0034] The fine stage movers 32, 34 and the coarse stage movers 36,
38 are uniquely positioned on only one side of the holder 15. With
this design, the fine stage 14 has a relatively low mass and a
relatively high servo bandwidth. Because of the low mass, smaller
movers 32, 34 can be used to move the fine stage 14. The smaller
movers 32, 34 generate less heat and consume less energy. Because
of the high servo bandwidth, external forces and small reaction
forces are less likely to influence the position of the fine stage
14. This allows for more accurate positioning of the object 24 by
the stages 14,18 and the production of higher quality wafers 30.
Further, with this design, the stage assembly 10 is readily
accessible for service and the measurement system 16 can be easily
positioned near the fine stage 14.
[0035] Some of the Figures provided herein include a coordinate
system that designates an X axis, a Y axis and a Z axis. It should
be understood that the coordinate system is merely for reference
and can be varied. For example, the X axis can be switched with the
Y axis.
[0036] Importantly, as provided herein, both the fine stage 14 and
the coarse stage 18 are guideless along the X axis, along the Y
axis and about the Z axis. More specifically, both the fine stage
14 and the coarse stage 18 are not constrained along the Y axis,
the X axis and about the Z axis. Stated another way, each stage
14,18 can be moved with at least three degrees of freedom. With
this design, the fine movers 32, 34 precisely control the position
of the fine stage 14 along the X axis, along the Y axis and about
the Z axis and the coarse movers 36, 38 control the position of the
coarse stage 18 along the X axis, along the Y axis and about the Z
axis. This allows for more accurate control over the positions of
the stages 12, 14 and better performance of the stage assembly
10.
[0037] The stage base 12 supports the fine stage 14 during
movement. The design of the stage base 12 can be varied to suit the
design requirements of the stage assembly 10. In the embodiment
illustrated in FIG. 1, the stage base 12 is a generally rectangular
shaped plate. The stage base 12 includes a planar upper base
surface 42 and an opposed, lower base surface 44. The stage base 12
also includes a base aperture 46 and a lens cut-out 48. The base
aperture 46 extends through the stage base 12 and allows for the
passage of light through the stage base 12. The lens cut-out 48 is
somewhat cylindrical shaped and extends partly into the stage base
12 from the lower base surface 44. The lens cut-out 48 allows for
the positioning of a lens assembly 50 (illustrated in FIG. 13) near
the first stage 14.
[0038] The fine stage 14 precisely positions the one or more
objects 24. The design of fine stage 14 and the degrees of freedom
of the fine stage 14 relative to the stage base 12 can be varied.
In the embodiment illustrated in the figures, the fine stage 14 is
guideless and moved by the fine movers 32, 34 with a limited range
of motion along the X axis, the Y axis and about the Z axis (theta
Z) relative to the coarse stage 18. Referring to FIGS. 4-6, the
fine stage 14 includes a fine frame 52, a first portion 54 of the
fine Y mover 32, a first portion 56 of the fine X mover 34, a first
portion 58 of the anti-gravity mechanism 40 and a first potion 60
of the measurement system 16.
[0039] The combination of the fine stage 14 and the one or more
objects 24 have a combined center of gravity 61 (illustrated as a
dot in FIGS. 9 and 10). Importantly, the fine Y mover 32 engages
the fine stage 14 near the combined center of gravity 61. This
minimizes the coupling of acceleration of the fine Y mover 32 to
movement along the X axis and about the Z axis of the fine stage
14. Stated another way, this minimizes the forces on the fine stage
14 along the X axis and about the Z axis, generated by the fine Y
mover 32. With this design, the fine Y mover 32 does not tend to
move the fine stage 14 along the X axis or rotate the fine stage 14
about the Z axis. As a result of this design, the force required to
move the fine stage 14 along the X axis and about the Z axis is
minimized. This allows for the use of a smaller and lighter, fine X
mover 34.
[0040] The fine frame 52 is generally rectangular shaped and
includes a fine frame bottom 62, a fine frame top 64, a first fine
frame side 66, a second fine frame side 68 substantially opposite
the first fine frame side 66, a front fine frame side 70 and a rear
fine frame side 72 substantially opposite the front fine frame side
70. The fine frame 52 is preferably made of a ceramic material
having a low rate of thermal expansion.
[0041] The fine frame bottom 62 includes a plurality of spaced
apart fluid outlets (not shown) and a plurality of spaced apart
fluid inlets (not shown). Pressurized fluid (not shown) is released
from the fluid outlets towards the stage base 12 and a vacuum is
pulled in the fluid inlets to create a vacuum preload type, fluid
bearing between the fine frame 52 and the stage base 12. The vacuum
preload type, fluid bearing maintains the fine stage 14 spaced
apart along the Z axis relative to the stage base 12 and allows for
motion of the fine stage 14 along the X axis, the Y axis and about
the Z axis relative to the stage base 12. The vacuum preload fluid
bearing maintains a high stiffness connection between the fine
stage 14 and the stage base 12 along the Z axis, about the X axis
and about the Y axis, despite the approximately zero net gravity
force of the fine stage 14 as a result of the anti-gravity
mechanism 40. Alternately, the fine stage 14 can be supported above
the stage base 12 by alternate ways such as magnetic type bearing
(not shown).
[0042] The fine frame 52 also includes one or more holders 15, a
mid-wall 74 and a stiffener 76. Each holder 15 retains and secures
one of the objects 24, e.g. reticles 26, to the fine stage 14. In
the embodiment illustrated in the figures, each holder 15 is a
rectangular shaped cut-out with vacuum chucks on either side. Each
holder 15 includes a first holder side 78, an opposed second holder
side 80, a front holder side 82 and a rear holder side 84. The
number of holders 15 can be varied. For example, in the embodiment
illustrated in the Figures, the fine stage 14 includes two spaced
apart holders 15. Because of the unique design provided herein, a
relatively low mass stage assembly 10 that retains two reticles 26
can be manufactured. Alternately, the fine stage 14 could include a
single holder 15 for retaining only one reticle 26.
[0043] Importantly, as provided below, the required stroke of the
coarse stage 18 along the Y axis will vary according to the number
of objects 24 retained by the fine stage 14. More specifically, the
stroke of the coarse stage 18 along the Y axis will need to be
increased as the number of objects 24 is increased.
[0044] The mid-wall 74 extends upwardly from the fine frame top 64
and secures the first portion 54 of the fine Y mover 32 and the
first portion 58 of the anti-gravity mechanism 40 to the fine frame
52. In the embodiment illustrated n the Figures, the mid-wall 74 is
a flat, planar wall. The mid-wall 74 includes a plurality of spaced
apart wall apertures 86 that extend transversely through the
mid-wall 74. As illustrated in FIG. 5, the mid-wall 74 also
includes a plurality of pairs of spaced apart pins 88 and a
plurality of spaced apart internally threaded apertures 90 for
securing the first portion 54 of the fine Y mover 32 and the first
portion 58 of the anti-gravity mechanism 40 to the mid-wall 74.
[0045] The mid-wall 74 extends along the Y axis between the first
fine frame side 66 and the first holder side 78. The mid-wall 74 is
preferably extends near the combined center of gravity 61 so that
the fine Y mover 32 is maintained near the combined center of
gravity 61. In the embodiments provided herein, the combined center
of gravity 61 is near the mid-wall 74 approximately half way
between the front fine frame side 70 and the rear fine frame side
72. With this design, the force from the fine Y mover 32 is
directed through the combined center of gravity 61.
[0046] The stiffener 76 provides stiffness to the fine stage 14 and
inhibits bending and flexing of the fine stage 14. Additionally,
the stiffener 76 adds mass to the fine stage 14 so that the
combined center of gravity 61 is near the mid-wall 74. The design
and location of the stiffener 76 can be varied to suit the design
of the fine stage 14. In the embodiment illustrated in the Figures,
the stiffener 76 is rectangular "U" shaped and extends along the
first fine frame side 66. The first portion 56 of the fine X mover
34 is secured to the stiffener 76 near the front fine frame side 70
and the rear fine frame side 72.
[0047] Preferably, the fine stage 14 includes one or more stage
openings 92 that are strategically positioned to lighten the mass
of the fine stage 14 and balance the mass of the fine stage 14,
without compromising the structural strength of the fine stage 14.
The number and design of the stage openings 92 can be varied. In
the embodiment illustrated in the Figures, the fine stage 14
includes four, rectangular shaped stage openings 92 that extend
partly into the fine frame top 64. The stage openings 92 are
located between the mid-wall 74 and the first fine frame side 66 of
the fine frame 52.
[0048] As provided above, the fine movers 32, 34 move the fine
stage 14 with a limited range of motion along the X axis, the Y
axis and about the Z axis relative to the coarse stage 18. More
specifically, the fine Y mover 32 moves the fine stage 14 relative
to the coarse stage 18 along the Y axis and the fine X mover 34
moves the fine stage 14 relative to the coarse stage 18 along the X
axis and around the theta Z axis.
[0049] The design of each fine movers 32, 34 can be varied to suit
the design requirements of the stage assembly 10. In the embodiment
illustrated in the Figures, each fine Y mover 32 includes the first
portion 54 that is secured to the fine stage 14 and a second
portion 94 that is secured to the coarse stage 18. The first
portion 54 and the second portion 94 of the fine Y mover 32
interact to selectively move the fine stage 14 along the Y
axis.
[0050] Somewhat similarly, each fine X mover 34 includes the first
portion 56 that is secured to the fine stage 14 and a second
portion 96 that is secured to the coarse stage 18. The first
portion 56 and the second portion 96 of the fine X mover 34
interact to selectively move the fine stage 14 along the X axis and
about the Z axis.
[0051] In the embodiment illustrated in the Figures, the fine Y
mover 32 and the fine X mover 34 each include a plurality of spaced
apart pairs of opposed, attraction only actuators 98. More
specifically, the fine Y mover 32 includes five, spaced apart pairs
of opposed, attraction only actuators 98 and the fine X mover 34
includes two, spaced apart pairs of opposed, attraction only
actuators 98.
[0052] The attraction only type actuators 98 consume less power and
generate less heat than a voice coil motor or a linear motor. This
minimizes the need to cool the fine movers 32, 34. Further, because
the fine movers 32, 34 are each located on only on side of the
holder 15, any heat from the fine movers 32, 34 can be easily
directed away from the measurement system 16.
[0053] FIGS. 7 and 8 illustrate a perspective view of a preferred
attraction only actuator 98. More specifically, FIG. 7 illustrates
a perspective view of a type of attraction only actuator 98
commonly referred to as an E/I core actuator and FIG. 8 illustrates
an exploded perspective view of the E/I core actuator. Each E/I
core actuator is essentially an electo-magnetic attractive device.
Each E/I core actuator includes an E shaped core 100, a tubular
coil 102, and an I shaped core 104. The E core 100 and the I core
104 are each made of a magnetic material such as iron. The coil 102
is positioned around the center bar of the E core 100. Current (not
shown) directed through the coil 102 creates an electromagnetic
field that attracts the I core 104 towards the E core 100. The
amount of current determines the amount of attraction.
[0054] In the embodiments provided herein, (i) the I core 104 of
each attraction only actuator 98 is considered the first portion
54, 56 of each fine mover 32, 34 and is secured to the fine stage
14, and (ii) the E core 100 and coil 102 of each attraction only
actuator 98 is considered the second portion 94, 96 of each fine
mover 32, 34 and is secured to the coarse stage 18.
[0055] Specifically, the fine Y mover 32 includes five pairs of
spaced apart, I cores 104 (ten total I cores) secured to the
mid-wall 74 and five pairs of spaced apart, E cores 100 and coils
102 (ten total E cores and ten coils 102) secured to the coarse
stage 18. The fine Y mover 32 is preferably centered on the
combined center of gravity 61.
[0056] Somewhat similarly, the fine X mover 34 includes two sets of
two spaced apart, I cores 104 (four total I cores) and two sets of
two spaced apart, E cores 100 and coils 102 (four total E cores 100
and coils 102). One of the sets of I cores 104 is secured to each
end of the stiffener 76 and the two sets of E cores 100 and coils
102 are secured to the coarse stage 18.
[0057] This arrangement is preferred because no electrical wires
associated with the fine movers 32, 34 are directly connected to
the fine stage 14. This reduces interference to the fine stage 14.
Alternately, the mounting of the attraction only actuators 98 could
be reversed. In this proposed configuration, the I cores 104 would
be attached to the coarse stage 18 while the E cores 100 and coils
102 would be secured to the fine stage 14.
[0058] The anti-gravity mechanism 40 offsets the weight of the fine
stage 14 and minimizes distortion of the stage base 12 as the fine
stage 14 moves relative to the stage base 14. More specifically,
the anti-gravity mechanism 40 pulls upward on the fine stage 14 as
the fine stage 14 moves relative to the stage base 12 to inhibit
the location of the fine stage 14 from influencing the stage base
12.
[0059] In the embodiment illustrated in the Figures, the
anti-gravity mechanism 40 includes a pair of spaced apart
attraction only actuators 106. Each attraction only actuator 106
includes the first portion 58 that is secured to the top of the
mid-wall 74 and a second portion 108 that is secured to the coarse
stage 18.
[0060] Preferably, each attraction only actuator 106 is an E/I core
actuator as described above. With this design, two spaced apart I
cores 104 are secured to the top of the mid-wall 74 and two spaced
apart E cores 100 and coils 102 are secured to the coarse stage 18.
Alternately, the mounting of the I core 104 and the E core 100 can
be reversed.
[0061] Importantly, the anti-gravity mechanism 40 is also
positioned near the combined center of gravity 61 and the fine Y
mover 32 so that the anti-gravity mechanism 40 can lift the fine
stage 14 along the Z axis to counteract the influence of fine stage
14 on the stage base 12. Further, the amount of attraction
generated by the anti-gravity mechanism 40 can be adjusted by
adjusting the current to the coil 102.
[0062] The measurement system 16 monitors the position of the fine
stage 14 relative to the stage base 12. With this information, the
position of the fine stage 14 can be adjusted. The design of the
measurement system 16 can be varied. In the embodiment illustrated
in FIG. 1, the measurement system 16 includes the first portion 60
that is part of and mounted to the fine stage 14 and a second
portion 110.
[0063] Referring to FIG. 1, the first portion 60 of the measurement
system 16 includes a X interferometer mirror 112 and a pair of
spaced apart Y interferometer mirrors 114 while the second portion
110 includes a X interferometer block 116 and a Y interferometer
block 118. Alternately, these components can be reversed.
[0064] The X interferometer block 116 interacts with the X
interferometer mirror 112 to monitor the location of the fine stage
14 along the X axis. More specifically, the X interferometer block
116 generates a measurement signal (not shown) that is reflected
off of the X interferometer mirror 112. With this information, the
location of the fine stage 14 along the X axis can be monitored. In
the embodiment illustrated in the Figures, the X interferometer
mirror 112 is rectangular shaped and extends along the second fine
frame side 68 of the fine frame 52. The X interferometer block 116
is positioned away from the fine stage 14. The X interferometer
block 116 can be secured to an apparatus frame 120 (illustrated in
FIG. 13) or some other location that is isolated by vibration.
[0065] The Y interferometer mirrors 114 interact with the Y
interferometer block 118 to monitor the position of the fine stage
14 along the Y axis and about the Z axis (theta Z). More
specifically, the Y interferometer block 118 generates a pair of
spaced apart measurement signals (not shown) that are reflected off
of the Y interferometer mirrors 114. With this information, the
location of the fine stage 14 along the Y axis and about the Z axis
can be monitored. In the embodiment illustrated in the Figures,
each Y interferometer mirror 114 is somewhat "V" shaped and is
positioned along the rear fine frame side 72 of the fine frame 52.
The Y interferometer block 118 is positioned away from the fine
stage 14. The Y interferometer block 118 can be secured to an
apparatus frame 120 or some other location that is isolated from
vibration.
[0066] Importantly, because the fine movers 32, 34 and the coarse
movers 36, 38 are positioned on only one side of the holder 15, the
measurement system 16 can be easily positioned near the fine stage
14.
[0067] The coarse stage 18 keeps the second portion of the fine Y
mover 94 and the second portion of the fine X mover 96 near the
fine stage 14 over the long stroke. This allows for the use of
relatively short travel, efficient fine Y mover 32 and fine X mover
34.
[0068] The design of coarse stage 18 and the degrees of freedom of
the coarse stage 18 relative to the reaction assembly 20 can be
varied. In the embodiment illustrated in the figures, the coarse
stage 18 is guideless in the planar degrees of freedom and is moved
by the coarse movers 36, 38 a relatively long displacement along
the Y axis and a relatively short displacement along the X axis and
around the Z axis (theta Z). More specifically, the coarse stage 18
illustrated in the Figures is moved by the coarse Y mover 36
relative to the reaction assembly 20 a relatively long displacement
along the Y axis. Further, the coarse stage 18 is moved by the
coarse X mover 38 a relatively short displacement along the X axis
and around the Z axis (theta Z).
[0069] Further, in the embodiments illustrated in the Figures, the
coarse stage 18 is positioned above the fine stage 14.
[0070] Referring to FIGS. 4, and 9-12, the coarse stage 18 includes
a coarse frame 122, the second portion 94 of the fine Y mover 32,
the second portion 96 of the fine X mover 34, the second portion
108 of the anti-gravity mechanism 40, a first portion 124 of the
coarse Y mover 36, and a first portion 126 of the coarse X mover
38.
[0071] The combination of the fine stage 14, the objects 24 and the
coarse stage 18 have a combination center of gravity 128
(illustrated as a dot in FIGS. 9 and 10). Importantly, the coarse Y
mover 36 engages the coarse stage 18 near the combination center of
gravity 128. This minimizes the coupling of acceleration of the
coarse Y mover 36 to movement along the X axis and about the Z axis
of the coarse stage 18. Stated another way, this minimizes the
forces on the coarse stage 18 along the X axis and about the Z
axis, generated by the coarse Y mover 36. With this design, the
coarse Y mover 36 does not tend to move the coarse stage 18 along
the X axis or rotate the coarse stage 18 about the Z axis. As a
result of this design, the force required to move the coarse stage
18 along the X axis and about the Z axis is minimized. This allows
for the use of a smaller, lighter mass, coarse X mover 38.
[0072] The coarse frame 122 illustrated in the Figures is generally
rectangular tube shaped and includes a coarse frame bottom 130, a
coarse frame top 132, a first coarse frame side 134 and a second
coarse frame side 136 substantially opposite the first coarse frame
side 134. The coarse frame 122 can be made of a number of
materials, including a ceramic material or aluminum.
[0073] The coarse frame bottom 130 supports the second portion 96
of the fine X mover 34 and the first portion 124 of the coarse Y
mover 36. More specifically, a pair of attachment plates 138
cantilever downward from coarse frame bottom 130 intermediate the
coarse frame sides 134, 136. One of the attachment plates 138 is
positioned on the front of the coarse stage 18 while the other
attachment plate 138 is positioned on the rear of the coarse stage
18. The second portion 96 of the fine X mover 34 (e.g., a pair of E
cores 100 and a pair of coils 102) is attached to each attachment
plate 138.
[0074] The first portion 124 of the coarse Y mover 36 is secured to
the coarse frame bottom 130 and extends along the length of the
coarse stage bottom 130 between the front and rear of the coarse
stage 18. In the embodiment illustrated in the Figures, a
rectangular shaped, attachment bar 140 is positioned between and
used to secure the first portion 124 of the coarse Y mover 36 to
the coarse frame bottom 130. The attachment bar 140 is secured to
the first portion 124 of the coarse Y mover 36 and the coarse frame
bottom 130 with an attachment bolt (not shown).
[0075] In the embodiment provided herein, the combination center of
gravity 128 is near the center of the first portion 124 of the
coarse Y mover 36 approximately half way between the front and the
rear of the coarse stage 18.
[0076] In the embodiments provided herein, the coarse frame top 132
is supported between a pair of spaced apart bearing plates 142 of
the reaction assembly 20. The coarse frame top 132 is generally
planar shaped and includes an upper surface 144 and a lower surface
146. The upper surface 144 and the lower surface 146 of the coarse
frame top 132 each include a plurality of spaced apart fluid
outlets (not shown). Pressurized fluid (not shown) is released from
the fluid outlets towards the bearing plates 142 of the reaction
assembly 20 to create a fluid bearing between the coarse frame top
132 and the bearing plates 142. The fluid bearing maintains the
coarse frame top 132 spaced between the bearing plates 142 and
allows for relatively large movement of the coarse stage 18
relative to the reaction assembly 20 along the Y axis, and smaller
movement along the X axis and about the Z axis relative to the
reaction assembly 20. Alternately, the coarse stage 18 can be
supported by the reaction assembly 20 by other ways such as
magnetic type bearing (not shown). In another alternate embodiment,
the coarse stage 18 can be supported by the reaction assembly 20
having only one bearing plate with a vacuum preload type fluid
bearing (not shown).
[0077] The first coarse frame side 134 extends between coarse frame
bottom 130 and the coarse frame top 132 and secures the first
portion 126 of the coarse X mover 34 to the coarse stage 18. In the
embodiment illustrated in the Figures, the first portion 126 is
positioned intermediate the coarse frame bottom 130 and the coarse
frame top 132.
[0078] The second coarse frame side 136 extends between coarse
frame bottom 130 and the coarse frame top 132 and secures the
second portion 94 of the fine Y mover 32 and the second portion 108
of the anti-gravity mechanism 40 to the coarse stage 18. More
specifically, a side attachment plate 148 cantilevers downward from
the second coarse frame side 136 and a pair of spaced apart, three
beam assemblies 150 extend transversely from the second coarse
frame side 136. The second portion 94 of the fine Y mover 32 (e.g.,
ten spaced apart E cores 100 and ten coils 102) is secured to the
side attachment plate 148. The second portion 108 of the
anti-gravity mechanism 40 (e.g., two spaced apart E cores 100 and
two coils 102) is retained by the three beam assemblies 150 to the
second coarse frame side 136.
[0079] The design of each coarse movers 36, 38 can be varied to
suit the design requirements of the stage assembly 10. In the
embodiment illustrated in the Figures, each coarse Y mover 36
includes the first portion 124 that is secured to the coarse stage
18 and a second portion 152 that is secured to the reaction
assembly 20. The first portion 124 and the second portion 152 of
the coarse Y mover 36 interact to selectively move the coarse stage
18 along the Y axis. Somewhat similarly, each coarse X mover 38
includes two of the first portion 126 that is secured to the coarse
stage 18 and a second portion 154 that is secured to the reaction
assembly 20. The first portions 126 and the second portion 154 of
the coarse X mover 38 interact to selectively move the coarse stage
18 along the X axis and about the Z axis.
[0080] In the embodiment illustrated in the Figures, the coarse Y
mover 36 is a linear motor. In this embodiment, the first portion
124 of the coarse Y mover 36 includes a plurality of spaced apart
coils (not shown) aligned in a coil array (not shown) while the
second portion 152 of the coarse Y mover 36 includes a pair of
spaced apart Y magnet arrays 156. Each Y magnet array 156 is
positioned on one of the sides of the coil array. The coil array
extends the length of the coarse frame 122 and is disposed within a
generally "T" shaped Y coil frame 158 that also extends the length
of the coarse frame 122. The Y magnet arrays 156 extend
substantially parallel along the length of the bearing plates 142
and are retained by the reaction assembly 20. Alternately, the
configuration of the coil array and the magnet array can be
reversed.
[0081] It should be noted that the coarse Y mover 36 is designed to
allow for movement along the X axis and about the Z axis. Referring
to FIG. 9, each Y magnet array 156 is sized to provide space for
the Y coil frame 156 along the X axis and about the Z axis.
[0082] The desired stroke of the coarse Y mover 36 along the Y axis
will vary according to the number of objects 24 retained by the
fine stage 14. More specifically, the stroke of the coarse Y mover
along the Y axis will need to be increased as the number of objects
24 is increased. A suitable stroke of a single reticle 26 is
between approximately 250 millimeters and 350 millimeters while a
suitable stroke for two reticles 26 is between approximately 450
millimeters and 550 millimeters.
[0083] Importantly, the coarse Y mover 36 engages the coarse stage
18 near the combination center of gravity 128. As a result of this
design, the force required to move the coarse stage 18 along the X
axis and about the Z axis is minimized. This allows for the use of
a smaller, lighter mass, coarse X mover 38.
[0084] In the embodiment illustrated in the Figures, the coarse X
mover 38 includes a pair of spaced apart voice coil actuators. In
this embodiment, the first portion 126 of the coarse X mover 38
includes a pair of spaced apart coils (not shown) and the second
portion 154 of the coarse X mover 38 includes a pair of X magnet
arrays 160. Each coil is disposed within a generally "T" shaped X
coil frame 162. The X magnet arrays 160 extend substantially
parallel along the length of the reaction assembly 20 and are
retained by the reaction assembly 20. Alternately, the
configuration of the coil array and the magnet array can be
reversed.
[0085] The reaction assembly 20 reduces and minimizes the amount of
reaction forces from the coarse movers 36, 38 that is transferred
through the mounting frame 22 to the ground 164. The reaction
assembly 20 is supported above the mounting frame 22 by a fluid
bearings as provided below. Through the principle of conservation
of momentum, movement of the coarse stage 18 with the coarse Y
mover 36 in one direction, moves the reaction assembly 20 in the
opposite direction along the Y axis. The reaction forces along the
X axis and about the Z axis from the coarse X mover 38 are
relatively small and are transferred directly to the mounting plate
174 through the second portion of the coarse X mover 154.
[0086] The design of the reaction assembly 20 can be varied to suit
the design requirements of the stage assembly 10. In the embodiment
illustrated in the Figures, the reaction assembly 20 includes the
pair of spaced apart bearing plates 142, a "U" shaped bracket 166,
a "L" shaped bracket 168, a bottom plate 170, a pair of end blocks
172, a mounting plate 174 and a trim mover 176. The bearing plates
142, the "U" shaped bracket 166, the "L" shaped bracket 168, and
the bottom plate 170 each extend between and are supported by the
end blocks 172. The end blocks 172 are mounted to the mounting
plate 174.
[0087] As provided above, the bearing plates 142 provide a fluid
bearing surface for supporting the coarse stage 18. The "U" shaped
bracket 166 supports the second portion 152 of the coarse Y mover
36. More specifically, the "U" shaped bracket 166 supports the pair
of Y magnets arrays 156 on each side of the first portion 124 of
the coarse Y mover 36. The "L" shaped bracket 168 and the bottom
plate 170 support the "U" shaped bracket 166 and secure the "U"
shaped bracket 166 to the lower bearing plate 142. The "L" shaped
bracket 168 can include a passageway for directing a circulating
fluid (not shown) for cooling the coarse Y mover 36.
[0088] The mounting plate 174 is generally planar shaped and
includes a body section 178 and a pair of spaced apart transverse
sections 180. The second portion 154 of the coarse X mover 38 (i.e.
the X magnet arrays 160) is secured to the top of the body section
178 and each end block 172 is attached to the top of each of the
transverse sections 180. The mounting plate 174 also includes (i)
three, spaced apart, upper Z bearing components 184, (ii) two,
spaced apart, upper X bearing components 186, and (iii) two, space
apart, preload magnets 188.
[0089] Two of the upper Z bearing components 184 extends downward
from the bottom of each transverse section 180 and the other upper
Z bearing component 184 extends downward from the bottom of the
body section 178. The upper Z bearing components 184 interact with
three, spaced apart lower Z bearing components 190 that are secured
to the mounting frame 22. More specifically, pressurized fluid is
released between the corresponding Z bearing components 184, 190 to
create a fluid bearing that maintains the reaction assembly 20
spaced apart from the mounting frame 22 along the Z axis. The fluid
bearing also allows for relative motion between the reaction
assembly 20 and the mounting frame 22 so that reaction forces from
the coarse movers 36, 38 are not transferred to the mounting frame
22 and the ground 164. Alternately, the reaction assembly 20 can be
supported above the mounting frame 22 by other ways such as
magnetic type bearing (not shown).
[0090] The upper X bearing components 186 extend downward from the
bottom of the body section 178. Each upper X bearing component 186
is positioned between a pair of spaced apart lower X bearing
components 192 that are secured to the mounting frame 22.
Pressurized fluid is released from the lower X bearing components
192 against the upper X bearing component 186 to create a fluid
bearing that maintains the reaction assembly 20 properly spaced
relative to the mounting frame 22 along the X axis. The fluid
bearing also allows for relative motion between the reaction
assembly 20 and the mounting frame 22 so that reaction forces from
the coarse movers 36, 38 are not transferred to the mounting frame
22 and the ground 164. Alternately, the reaction assembly 20 can be
supported above the mounting frame 22 along the X axis by other
ways such as magnetic type bearing (not shown).
[0091] The spaced apart preload magnets 188 extend downward from
the bottom of the body section 178. The preload magnets 188 are
attracted to mounting frame 22 and urge the reaction assembly 20
towards the mounting frame 22. This loads the fluid bearing created
between the corresponding Z bearing components 184, 190.
Alternately, for example, a vacuum could be created between the
reaction assembly 20 and the mounting frame 22 to load the fluid
bearing.
[0092] The trim mover 176 is used to make minor corrections along
the Y axis to the position of the reaction assembly 20 relative to
the mounting frame 22. The design of the trim mover 176 can be
varied. For example, the trim mover 176 can be a rotary motor, a
voice coil motor or a linear motor. In the embodiment illustrated
in the Figures, the trim mover 176 is a rotary motor connected to
both the reaction assembly 20 and the mounting frame 22.
[0093] The trim mover 176 includes a body 194 and a tab 196 that is
moved by rotation of the motor. The body 194 of the trim mover 176
is mounted to one of the preload magnets 188 of the reaction
assembly 20 and the tab 196 is mounted to the mounting frame 22.
With this design, rotation of the trim mover 176 can move the tab
196 and make minor corrections along the Y axis to the position of
the reaction assembly 20 relative to the mounting frame 22.
Preferably, the trim mover 176 includes an encoder (not shown) that
provides information regarding the position of the reaction
assembly 20 relative to the mounting frame 22 along the Y axis.
[0094] Preferably, the mass ratio of the reaction assembly 20 to
the combination fine stage 14 and coarse stage 18 is high. This
will minimize the movement of the reaction assembly and minimize
the required travel of the trim mover 176.
[0095] The mounting frame 22 is rigid and supports the reaction
assembly 20 above the ground 164. The design of the mounting frame
22 can be varied to suit the design requirements of the stage
assembly 10 and the exposure apparatus 28. In the embodiment
illustrated in the Figures, the mounting frame 22 includes a pair
of side brackets 198 that are maintained apart by a back bracket
200. One of the lower Z bearing components 190 is secured to each
of the side brackets 198 and the other lower Z bearing component
190 is secured to the back bracket 200. The two pairs of spaced
apart lower X bearing components 192 are also secured to the back
bracket 200.
[0096] The mounting frame 22 can be secured to the ground 164 in a
number of alternate ways. For example, as illustrated in FIG. 13,
the mounting frame 22 can be secured with a separate reaction frame
202 to the ground 164. Alternately, because of the use of the
reaction assembly 20, the mounting frame 22 can be secured to the
apparatus frame 120 with some of the other components of the
exposure apparatus 28.
[0097] FIG. 13 is a schematic view illustrating an exposure
apparatus 28 useful with the present invention. The exposure
apparatus 28 includes an apparatus frame 120, an illumination or
irradiation source 204, the reticle stage assembly 10, the lens
assembly 50, and a wafer stage 206.
[0098] The exposure apparatus 28 is particularly useful as a
lithographic device which transfers a pattern (not shown) of an
integrated circuit from the reticle 26 onto the semiconductor wafer
30. The exposure apparatus 28 mounts to the ground 164, i.e., a
floor, a base or some other supporting structure.
[0099] The apparatus frame 120 is rigid and supports the components
of the exposure apparatus 28. The design of the apparatus frame 120
can be varied to suit the design requirements for the rest of the
exposure apparatus 28. The apparatus frame 120 illustrated in FIG.
13, supports the stage base 12, the wafer stage 206, the lens
assembly 50, and the illumination source 204 above the ground 164.
Alternately, for example, separate, individual structures (not
shown) can be used to support the wafer stage 206, the illumination
source 204 and the lens assembly 50 above the ground 164.
[0100] The illumination source 204 emits the beam of light energy
which selectively illuminates different portions of the reticle 26
and exposes the wafer 30. In FIG. 13, the illumination source 204
is illustrated as being supported above the reticle stage assembly
10. Typically, however, the illumination source 204 is secured to
one of the sides of the apparatus frame 120 and the energy beam
from the illumination source 204 is directed to above the reticle
stage assembly 10.
[0101] The lens assembly 50 projects and/or focuses the light
passing through reticle 26 to the wafer 30. Depending upon the
design of the apparatus 28, the lens assembly 50 can magnify or
reduce the image illuminated on the reticle 26.
[0102] The reticle stage assembly 10 holds and positions the
reticle 26 relative to the lens assembly 50 and the wafer 30.
Similarly, the wafer stage 206 holds and positions the wafer 30
with respect to the projected image of the illuminated portions of
the reticle 26. In FIG. 13, the wafer stage 206 is positioned by
linear motors 208. Depending upon the design, the apparatus 28 can
also include additional motors to move the wafer stage 206. In this
embodiment, the position of the wafer stage 206 is monitored by an
interferometer system 214. The interferometer system 214 comprises
a moving mirror 210 disposed on the top surface of the wafer stage
206 and a wafer interferometer 212 connected to the apparatus frame
120. The wafer interferometer 212 generates a measurement beam 216
toward the moving mirror 210, and detects the beam reflected from
the moving mirror 210. The linear motors 208 drive the wafer stage
206 based on the result of the monitoring of the interferometer
system 214.
[0103] There are a number of different types of lithographic
devices. For example, the exposure apparatus 28 can be used as
scanning type photolithography system that exposes the pattern from
the reticle 26 onto the wafer 30, with the reticle 26 and wafer 30
moving synchronously. In a scanning type lithographic device, the
reticle 26 is moved perpendicular to an optical axis of the lens
assembly 50 by the reticle stage assembly 10 and the wafer 30 is
moved perpendicular to the optical axis of the lens assembly 50 by
the wafer stage 206. Scanning of the reticle 26 and the wafer 30
occurs while the reticle 26 and the wafer 30 are moving
synchronously.
[0104] Alternately, the exposure apparatus 28 can be a
step-and-repeat type photolithography system that exposes the
reticle 26 while the reticle 26 and the wafer 30 are stationary. In
the step and repeat process, the wafer 30 is in a constant position
relative to the reticle 26 and the lens assembly 50 during the
exposure of an individual field. Subsequently, between consecutive
exposure steps, the wafer 30 is consecutively moved by the wafer
stage 206 perpendicular to the optical axis of the lens assembly 50
so that the next field of the wafer 30 is brought into position
relative to the lens assembly 50 and the reticle 26 for exposure.
Following this process, the images on the reticle 26 are
sequentially exposed onto the fields of the wafer 30 so that the
next field of the wafer 30 is brought into position relative to the
lens assembly 50 and the reticle 26.
[0105] However, the use of the exposure apparatus 28 provided
herein is not limited to a photolithography system for
semiconductor manufacturing. The exposure apparatus 28, 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. Further, the present invention can also be applied
to a proximity photolithography system that exposes a mask pattern
by closely locating a mask and a substrate without the use of a
lens assembly. Moreover, the stage assembly 10 provided herein can
be used in other devices, including other semiconductor processing
equipment, machine tools, metal cutting machines, and inspection
machines.
[0106] The illumination source 204 can be g-line (436 nm), i-line
(365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm)
and F.sub.2 laser (157 nm). Alternately, the illumination source
204 can also use charged particle beams such as x-ray and electron
beam. For instance, in the case where an electron beam is used,
thermionic emission type lanthanum hexaboride (LaB.sub.6) or
tantalum (Ta) can be used as an electron gun. Furthermore, in the
case where an electron beam is used, the structure could be such
that either a mask is used or a pattern can be directly formed on a
substrate without the use of a mask.
[0107] In terms of the magnification of the lens assembly 50
included in the photolithography system, the lens assembly 50 need
not be limited to a reduction system. It could also be a lx or
magnification system.
[0108] With respect to a lens assembly 50, when far ultra-violet
rays such as the excimer laser is used, glass materials such as
quartz and fluorite that transmit far ultra-violet rays is
preferable to be used. When the F.sub.2 type laser or x-ray is
used, the lens assembly 50 should preferably be either catadioptric
or refractive (a reticle should also preferably be a reflective
type), and when an electron beam is used, electron optics should
preferably consist of electron lenses and deflectors. The optical
path for the electron beams should be in a vacuum.
[0109] Also, with an exposure device that employs vacuum
ultra-violet radiation (VUV) of wavelength 200 nm or lower, use of
the catadioptric type optical system can be considered. Examples of
the catadioptric type of optical system include the disclosure
Japan Patent Application Disclosure No.8-171054 published in the
Official Gazette for Laid-Open Patent Applications and its
counterpart U.S. Pat. No. 5,668,672, as well as Japan Patent
Application Disclosure 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. Japan Patent Application Disclosure No.8-334695
published in the Official Gazette for Laid-Open Patent Applications
and its counterpart U.S. Pat. No. 5,689,377 as well as Japan Patent
Application Disclosure 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. As far as is permitted, the
disclosures in the above-mentioned U.S. patents, as well as the
Japan patent applications published in the Official Gazette for
Laid-Open Patent Applications are incorporated herein by
reference.
[0110] Further, in photolithography systems, when linear motors
(see U.S. Pat. Nos. 5,623,853 or 5,528,118) are used in a wafer
stage or a mask (reticle) stage, the linear motors can be either an
air levitation type employing air bearings or a magnetic levitation
type using Lorentz force or reactance force. Additionally, the
stage could move along a guide, or it could be a guideless type
stage which uses no guide. As far as is permitted, the disclosures
in U.S. Pat. Nos. 5,623,853 and 5,528,118 are incorporated herein
by reference.
[0111] Alternatively, one of the stages could be driven by a planar
motor, which drives the stage by 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 one of
the magnet unit or the armature coil unit is connected to the stage
and the other unit is mounted on the moving plane side of the
stage.
[0112] Movement of the stages as described above generates reaction
forces which can affect performance of the photolithography system.
Reaction forces generated by the wafer (substrate) stage motion can
be mechanically released to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,528,118 and published
Japanese Patent Application Disclosure 8-166475. Additionally,
reaction forces generated by the reticle (mask) stage motion can be
mechanically released to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,874,820 and published
Japanese Patent Application Disclosure No. 8-330224. As far as is
permitted, the disclosures in U.S. Pat. Nos. 5,528,118 and
5,874,820 and Japanese Patent Application Disclosure Nos. 8-166475
and 8-330224 are incorporated herein by reference.
[0113] As described above, a photolithography system according to
the above described embodiments can be built by assembling various
subsystems, including each element listed in the appended claims,
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 is also 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,
total adjustment is performed to make sure that every 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.
[0114] Further, semiconductor devices can be fabricated using the
above described systems, by the process shown generally in FIG. 14.
In step 301 the device's function and performance characteristics
are designed. Next, in step 302, a mask (reticle) having a pattern
is designed according to the previous designing step, and in a
parallel step 303 a wafer is made from a silicon material. The mask
pattern designed in step 302 is exposed onto the wafer from step
303 in step 304 by a photolithography system described hereinabove
in accordance with the present invention. In step 305 the
semiconductor device is assembled (including the dicing process,
bonding process and packaging process), then finally the device is
inspected in step 306.
[0115] FIG. 15 illustrates a detailed flowchart example of the
above-mentioned step 304 in the case of fabricating semiconductor
devices. In FIG. 15, in step 311 (oxidation step), the wafer
surface is oxidized. In step 312 (CVD step), an insulation film is
formed on the wafer surface. In step 313 (electrode formation
step), electrodes are formed on the wafer by vapor deposition. In
step 314 (ion implantation step), ions are implanted in the wafer.
The above mentioned steps 311-314 form the preprocessing steps for
wafers during wafer processing, and selection is made at each step
according to processing requirements.
[0116] 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,
firstly, in step 315 (photoresist formation step), photoresist is
applied to a wafer. Next, in step 316, (exposure step), the
above-mentioned exposure device is used to transfer the circuit
pattern of a mask (reticle) to a wafer. Then, in step 317
(developing step), the exposed wafer is developed, and in step 318
(etching step), parts other than residual photoresist (exposed
material surface) are removed by etching. In step 319 (photoresist
removal step), unnecessary photoresist remaining after etching is
removed.
[0117] Multiple circuit patterns are formed by repetition of these
preprocessing and post-processing steps.
[0118] While the particular stage assembly 10 as shown and
disclosed herein is fully capable of obtaining the objects and
providing the advantages herein before stated, it is to be
understood that it is merely illustrative of the presently
preferred embodiments of the invention and that no limitations are
intended to the details of construction or design herein shown
other than as described in the appended claims.
* * * * *