U.S. patent application number 10/611260 was filed with the patent office on 2004-05-20 for window frame-guided stage mechanism.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Lee, Martin E..
Application Number | 20040095085 10/611260 |
Document ID | / |
Family ID | 23650430 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040095085 |
Kind Code |
A1 |
Lee, Martin E. |
May 20, 2004 |
WINDOW FRAME-GUIDED STAGE MECHANISM
Abstract
A guided stage mechanism suitable for supporting a reticle in a
photolithography machine includes a stage movable in the X-Y
directions on a base. Laterally surrounding the stage is a
rectangular window frame guide which is driven in the X-axis
direction on two fixed guides by means of motor coils on the window
frame guide co-operating with magnetic tracks fixed on the base.
The stage is driven inside the window frame guide in the Y-axis
direction by motor coils located on the stage co-operating with
magnetic tracks located on the window frame guide. Forces from the
drive motors of both the window frame guide and the stage are
transmitted through the center of gravity of the stage, thereby
eliminating unwanted moments of inertia. Additionally, reaction
forces caused by the drive motors are isolated from the projection
lens and the alignment portions of the photolithography machine.
This isolation is accomplished by providing a mechanical support
for the stage independent of the support for its window frame
guide. The window frame guide is a hinged structure capable of a
slight yawing (rotational) motion due to hinged flexures which
connect the window frame guide members.
Inventors: |
Lee, Martin E.; (Saratoga,
CA) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Assignee: |
Nikon Corporation
|
Family ID: |
23650430 |
Appl. No.: |
10/611260 |
Filed: |
July 2, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10611260 |
Jul 2, 2003 |
|
|
|
09964550 |
Sep 28, 2001 |
|
|
|
6683433 |
|
|
|
|
09964550 |
Sep 28, 2001 |
|
|
|
09836273 |
Apr 18, 2001 |
|
|
|
6316901 |
|
|
|
|
09836273 |
Apr 18, 2001 |
|
|
|
09192153 |
Nov 12, 1998 |
|
|
|
6246202 |
|
|
|
|
09192153 |
Nov 12, 1998 |
|
|
|
08416558 |
Apr 4, 1995 |
|
|
|
5874820 |
|
|
|
|
Current U.S.
Class: |
318/135 |
Current CPC
Class: |
G03F 7/70358 20130101;
Y10T 74/20201 20150115; G03F 7/70825 20130101; G03F 7/70716
20130101; G03F 7/709 20130101; G03F 7/70833 20130101 |
Class at
Publication: |
318/135 |
International
Class: |
H02P 001/00 |
Claims
What is claimed is:
1. An exposure apparatus that exposes a pattern of a mask onto an
object by a projection system, comprising: a frame that has a
support member to support the projection system and a suspended
member that is suspended from the support member; a first base that
is coupled to the support member, the first base having a first
horizontal plane; a second base that is coupled to the suspended
member such that the suspended member receives the weight of the
second base, the second base having a second horizontal plane that
is located below the first horizontal plane; a mask stage that is
movably supported by the first horizontal plane to retain the mask,
the mask stage having a first reflective member; an object stage
that is movably supported by the second horizontal plane to retain
the object, the object stage having a second reflective member; a
first linear motor that has a first member coupled to the mask
stage and a second member to move the mask stage parallel to the
first horizontal plane; a second linear motor that moves the object
stage parallel to the second horizontal plane; a first
interferometer system that cooperates with the first reflective
member to detect a position of the mask stage, the first
interferometer system being supported by the frame; a second
interferometer system that cooperates with the second reflective
member to detect a position of the object stage, the second
interferometer system being supported by the frame; and a reaction
frame that is dynamically isolated from the frame to receive a
reaction force caused by a movement of the mask stage, the reaction
frame having a member that is located above the suspended member
and coupled to the second member of the first linear motor.
2. The exposure apparatus of claim 1, wherein the first linear
motor moves the mask stage in a first direction parallel to the
first horizontal plane.
3. The exposure apparatus of claim 2, further comprising a third
linear motor having a coil and a magnet to move the mask stage in a
second direction different from the first direction, one of the
coil and the magnet being coupled to the reaction frame.
4. The exposure apparatus of claim 3, wherein the first
interferometer system detects the position of the mask stage with
regard to the first direction.
5. The exposure apparatus of claim 4, further comprising a third
interferometer system that detects the position of the mask stage
with regard to the second direction.
6. The exposure apparatus of claim 5, wherein the first
interferometer system is supported by the support member of the
frame.
7. The exposure apparatus of claim 6, wherein the second
interferometer system is supported by the support member of the
frame.
8. The exposure apparatus of claim 7, wherein the third
interferometer system is supported by the support member of the
frame.
9. The exposure apparatus of claim 8, wherein the second member of
the first linear motor is movable along a guide that is coupled to
the reaction frame.
10. The exposure apparatus of claim 9, wherein the reaction frame
receives a reaction force caused by a movement of the object
stage.
11. The exposure apparatus of claim 1, wherein the first
interferometer system is supported by the support member of the
frame.
12. The exposure apparatus of claim 1, wherein the second
interferometer system is supported by the support member of the
frame.
13. The exposure apparatus of claim 1, wherein the second member of
the first linear motor is movable along a guide that is coupled to
the reaction frame.
14. An exposure apparatus that exposes a pattern of a mask onto an
object by a projection system, comprising: supporting means having
a support member for supporting the projection system and a
suspended member that is suspended from the support member; first
guiding means having a first horizontal plane; second guiding means
having a second horizontal plane; mask holding means for retaining
the mask, the mask holding means being movably supported by the
first horizontal plane and having a first reflective member; object
holding means for retaining the object, the object holding means
being movably supported by the second horizontal plane and having a
second reflective member; first moving means for moving the mask
holding means parallel to the first horizontal plane, the first
moving means having a first member coupled to the mask holding
means and a second member; second moving means for moving the
object holding means parallel to the second horizontal plane; first
position detecting means for detecting a position of the mask
holding means and cooperating with the first reflective member;
second position detecting means for detecting a position of the
object holding means and cooperating with the second reflective
member; and reaction-force-receiving means for receiving a reaction
force caused by a movement of the mask holding means, the
reaction-force-receiving means being dynamically isolated from the
supporting means and having a member that is located above the
suspended member and coupled to the second member of the first
moving means.
15. An exposure method that exposes a pattern of a mask onto an
object by a projection system, comprising the steps of: providing a
frame that has a support member to support the projection system
and a suspended member that is suspended from the support member;
providing a first base that is coupled to the support member, the
first base having a first horizontal plane; providing a second base
that is coupled to the suspended member such that the suspended
member receives the weight of the second base, the second base
having a second horizontal plane that is located below the first
horizontal plane; moving a mask stage having a first reflective
member by a first linear motor, the mask stage being movably
supported by the first horizontal plane to retain the mask and the
first linear motor having a first member coupled to the mask stage
and a second member; moving an object stage having a second
reflective member by a second linear motor, the object stage being
movably supported by the second horizontal plane to retain the
object; detecting a position of the mask stage by a first
interferometer system that cooperates with the first reflective
member, the first interferometer system being supported by the
frame; detecting a position of the object stage by a second
interferometer system that cooperates with the second reflective
member, the second interferometer system being supported by the
frame; and receiving in a reaction frame, a reaction force caused
by a movement of the mask stage, the reaction frame is dynamically
isolated from the frame, the reaction frame having a member that is
located above the suspended member and coupled to the second member
of the first linear motor.
16. The method of claim 15, wherein the first linear motor moves
the mask stage in a first direction parallel to the first
horizontal plane.
17. The method of claim 16, further comprising moving the mask
stage in a second direction different from the first direction by a
third linear motor having a coil and a magnet, one of the coil and
the magnet being coupled to the reaction frame.
18. The method of claim 17, wherein the first interferometer system
detects the position of the mask stage with regard to the first
direction.
19. The method of claim 18, further comprising detecting the
position of the mask stage with regard to the second direction by a
third interferometer system.
20. The method of claim 19, wherein the first interferometer system
is supported by the support member of the frame.
21. The method of claim 20, wherein the second interferometer
system is supported by the support member of the frame.
22. The method of claim 21, wherein the third interferometer system
is supported by the support member of the frame.
23. The method of claim 22, further comprising moving the second
member of the first linear motor along a guide that is coupled to
the reaction frame.
24. The method of claim 23, further comprising the reaction frame
receiving a reaction force caused by a movement of the object
stage.
25. The method of claim 15, wherein the first interferometer system
is supported by the support member of the frame.
26. The method of claim 15, wherein the second interferometer
system is supported by the support member of the frame.
27. The method of claim 15, further comprising moving the second
member of the first linear motor along a guide that is coupled to
the reaction frame.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to precision motion stages and more
specifically to a stage suitable for use in a photolithography
machine and especially adapted for supporting a reticle.
[0003] 2. Description of the Prior Art
[0004] Photolithography is a well known field especially as applied
to semiconductor fabrication. In photolithography equipment a stage
(an X-Y motion device) supports the reticle (i.e., mask) and a
second stage supports the semiconductor wafer, i.e. the work piece
being processed. Sometimes only a single stage is provided, for the
wafer or the mask.
[0005] Such stages are essential for precision motion in the X-axis
and Y-axis directions and often some slight motion is provided for
adjustments in the vertical (Z-axis) direction. A reticle stage is
typically used where the reticle is being scanned in a scanning
exposure system, to provide smooth and precise scanning motion in
one linear direction and insuring accurate, reticle to wafer
alignment by controlling small displacement motion perpendicular to
the scanning direction and a small amount of "yaw" (rotation) in
the X-Y plane. It is desirable that such an X-Y stage be relatively
simple and be fabricated from commercially available components in
order to reduce cost, while maintaining the desired amount of
accuracy. Additionally, many prior art stages include a guide
structure located directly under the stage itself. This is not a
desirable in a reticle stage since it is essential that a light
beam be directed through the reticle and through the stage itself
to the underlying projection lens. Thus a stage is needed which
does not include any guides directly under the stage itself, since
the stage itself must define a fairly large central passage for the
light bean.
[0006] Additionally, many prior art stages do not drive the stage
through its center of gravity which undesirably induces a twisting
notion in the stage, reducing the frequency response of the stage.
Therefore there is a need for an improved stage and especially one
suitable for a reticle stage.
SUMMARY
[0007] A precision motion stage mechanism includes the stage itself
which moves in the X-Y plane on a flat base. The stage is laterally
surrounded by a "window frame" guide structure which includes four
members attached at or near their corners to form a rectangular
structure. The attachments are flexures which are a special type of
hinge allowing movement to permit slight distortion of the
rectangle. In one version these flexures are thin stainless steel
strips attached in an "X" configuration, allowing the desired
degree of hinge movement between any two adjacent connected window
frame members.
[0008] The window frame guide structure moves on a base against two
spaced-apart and parallel fixed guides in e.g. the X axis
direction, being driven by motor coils mounted on two opposing
members of the window frame cooperating with magnetic tracks fixed
on the base.
[0009] The window frame in effect "follows" the movement of the
stage and carries the magnetic tracks needed for movement of the
stage in the Y axis direction. (It is to be understood that
references herein to the X and Y axes directions are merely
illustrative and for purposes of orientation relative to the
present drawings and are not to be construed as limiting.)
[0010] The stage movement in the direction perpendicular (the Y
axis direction) to the direction of movement of the window frame is
accomplished by the stage moving along the other two members of the
window frame. The stage is driven relative to the window frame by
motor coils mounted on the stage and cooperating with magnetic
tracks mounted in the two associated members of the window
frame.
[0011] To minimize friction, the stage is supported on the base by
air bearings or other fluid bearings mounted on the underside of
the stage. Similarly fluid bearings support the window frame
members on their fixed guides. Additionally, fluid bearings load
the window frame members against the fixed guides and load the
stage against the window frame. So as to allow slight yaw movement,
these loading bearings are spring mounted. The stage itself defines
a central passage. The reticle rests on a chuck mounted on the
stage. Light from an illuminating source typically located above
the reticle passes to the central passage through the reticle and
chuck to the underlying projection lens.
[0012] It is to be understood that the present stage, with suitable
modifications, is not restricted to supporting a reticle but also
may be used as a wafer stage and is indeed not limited to
photolithography applications but is generally suited to precision
stages.
[0013] An additional aspect in accordance with the present
invention is that the reaction force of the stage and window frame
drive motors is not transmitted to the support frame of the
photolithography apparatus projection lens but is transmitted
independently directly to the earth's surface by an independent
supporting structure. Thus the reaction forces caused by movement
of the stage do not induce undesirable movement in the projection
lens or other elements of the photolithography machine.
[0014] This physically isolating the stage reaction forces from the
projection lens and associated structures prevents these reaction
forces from vibrating the projection lens and associated
structures. These structures include the interferometer system used
to determine the exact location of the stage in the X-Y plane and
the wafer stage. Thus the reticle stage mechanism support is spaced
apart from and independently supported from the other elements of
the photolithography machine and extends to the surface of the
earth.
[0015] Advantageously, the reaction forces from operation of the
four motor coils for moving both the stage and its window frame are
transmitted through the center of gravity of the stage, thereby
desirably reducing unwanted moments of force (i.e., torque). The
controller controlling the power to the four drive motor coils
takes into consideration the relative position of the stage and the
frame and proportions the driving force accordingly by a
differential drive technique.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a top view of the present window frame guided
stage.
[0017] FIG. 2 shows a side view of the window frame guided stage
and associated structures.
[0018] FIGS. 3A and 3B show enlarged views of portions of the
structure of FIG. 2.
[0019] FIG. 4 shows a top view of a photolithography apparatus
including the present window frame guided stage.
[0020] FIG. 5 shows a side view of the photolithography apparatus
of FIG. 4.
[0021] FIGS. 6A and 6B show a flexure hinge structure as used e.g.
in the present window frame guided stage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] FIG. 1 shows a top view of a stage mechanism in accordance
with the present invention. See also copending commonly owned and
invented U.S. patent application Ser. No. 08/221,375 entitled
"Guideless Stage with Isolated Reaction Stage" filed Apr. 1, 1994,
original docket no. NPI0500 which is incorporated herein by
reference and shows a related method of supporting elements of a
stage mechanism so as to isolate reaction forces from the
projection lens and other parts of a photolithography
apparatus.
[0023] The stage 10 is (in plan view) a rectangular structure of a
rigid material (e.g., steel, aluminum, or ceramic). Two
interferometry mirrors 14A and 14B located on stage 10 interact
conventionally with respectively laser beams 16A and 16B.
Conventionally, laser beams 16A are two pairs of laser beams and
laser beams 16B are one pair of laser beam, for three independent
distance measurements. The underside of stage 10 defines a relieved
portion 22 (indicated by a dotted line, not being visible in the
plane of the drawing). A reticle 24 is located on stage 10 and held
by conventional reticle vacuum groove 26 formed in the upper
surface of chuck plate 28. Stage 10 also defines a central aperture
30 (passage) below the location of reticle 24. Central aperture 30
allows the light (or other) beam which penetrates through reticle
24 to enter the underlying projection lens, as described further
below. (It is to be understood that the reticle 24 itself is not a
part of the stage mechanism.) Moreover if the present stage
mechanism is to be used for other than a reticle stage, i.e. for
supporting a wafer, aperture 30 is not needed.
[0024] Stage 10 is supported on a conventional rectangular base
structure 32 of e.g. granite, steel, or aluminum, and having a
smooth planar upper surface. The left and right edges (in FIG. 1)
of base structure 32 are shown as dotted lines, being overlain by
other structures (as described below) in this view. In operation,
stage 10 is not in direct physical contact with its base structure
32; instead, stage 10 is vertically supported by, in this example,
conventional bearings such as gas bearings. In one embodiment three
air bearings 36A, 36B and 36C are used which may be of a type
commercially available.
[0025] In an alternative air bearing/vacuum structure, the vacuum
portion is physically separated from and adjacent to the air
bearing portion. It is to be understood that the vacuum and
compressed air are provided externally via tubing in a conventional
cable bundle and internal tubing distribution system (not shown in
the drawings for simplicity). In operation stage 10 thereby floats
on the air bearings 36A, 36B, 36C approximately 1 to 3 micrometers
above the flat top surface of base structure 32. It is to be
understood that other types of bearings (e.g. air bearing/magnetic
combination type) may be used alternatively.
[0026] Stage 10 is laterally surrounded by the "window frame guide"
which is a four member rectangular structure. The four members as
shown in FIG. 1 are (in the drawing) the top member 40A, the bottom
member 40B, the lefthand member 40C, and the righthand member 40D.
The four members 40A-40D are of any material having high specific
stiffness (stiffness to density ratio) such as aluminum or a
composite material. These four members 40A-40D are attached
together by hinge structures which allow non-rigid movement of the
four members relative to one another in the X-Y plane and about the
Z-axis as shown in the drawing, this movement also referred to as a
"yaw" movement. Th hinge is described in detail below, each hinge
44A, 44B, 44C and 44D being e.g. one or more metal flexures
allowing a slight flexing of the window frame guide structure.
[0027] The window frame guide structure moves in the X axis (to the
left and right in FIG. 1) supported on horizontal surfaces of fixed
guides 46A and 46B, and supported on vertical surfaces of fixed
guides 64A, 64B. (It is to be understood that each pair of fixed
guides 46A, 64A and 46B, 64B could be e.g. a single L-shaped fixed
guide, or other configurations of fixed guides may be used.)
Mounted on window frame guide member 40A are two air bearings 50A
and 50B that cause the member 40A to ride on its supporting fixed
guide member 46A. Similarly air bearings 52A and 52B are mounted on
the member 40B, allowing member 40B to ride on its supporting fixed
guide member 46B. Air bearings 50A, 50B, 52A, 52B are similar to
air bearings 36A, etc.
[0028] The window frame guide is driven along the X axis on fixed
guides 46A and 46B, 64A and 64B by a conventional linear motor,
which includes a coil 60A which is mounted on window frame guide
member 40A. Motor coil 60A moves in a magnetic track 62A which is
located in (or along) fixed guide 64A. Similarly, motor coil 60B
which is mounted on window frame guide member 40B moves in magnetic
track 62B which is located in fixed guide 64B. The motor coil and
track combinations are part no. 1M-310 from Trilogy Company of
Webster Tex. These motors are also called "linear commutator
motors". The tracks 62A, 62B are each a number of permanent magnets
fastened together. The electric wires which connect to the motor
coils are not shown but are conventional. Other types of linear
motors may be substituted. It is to be understood that the
locations of the motor coils and magnetic tracks for each motor
could be reversed, so that for instance the magnetic tracks are
located on stage 10 and the corresponding motor coils on the window
frame guide members, at a penalty of reduced performance.
[0029] Similarly, stage 10 moves along the Y axis in FIG. 1 by
means of motor coils 68A and 68B mounted respectively on the left
and right edges of stage 10. Motor coil 68A moves in magnetic track
70A mounted in window frame guide member 40C. Motor coil 68B moves
in magnetic track 70B mounted in window frame guide member 40D.
[0030] Also shown in FIG. 1 are air bearings 72A, 72B and 72C. Air
bearing 72A is located on window frame guide member 40A and
minimizes friction between window frame guide member 40A and its
fixed guide 64A. Similarly two air bearings 72B and 72C on window
frame guide member 40B minimize its friction with the fixed guide
64B. The use of a single air bearing 72A at one end and two
opposing air bearings 72B and 72C at the other end allows a certain
amount of yaw (rotation in the X-Y plane about the Z-axis) as well
as limited motion along the Z-axis. In this case, typically air
bearing 72A is gimbal mounted, or gimbal mounted with the gimbal
located on a flexure so as to allow a limited amount of
misalignment between the member 40A and fixed guide 64A.
[0031] The use of the air bearing 72A opposing bearings 72B and 72C
provides a loading effect to keep the window frame guide in its
proper relationship to fixed guides 64A, 64B. Similarly, an air
bearing 76A loads opposing air bearings 76B and 76C, all mounted on
side surfaces of the stage 10, in maintaining the proper location
of stage 10 relative to the opposing window frame guide members 40B
and 40D. Again, in this case one air bearing such as 76A is gimbal
mounted to provide a limited amount of misalignment, or gimbal
mounted with the gimbal on a flexure (spring). Air bearings 72A,
72B, 72C and 76A, 76B, and 76C are conventional air bearings.
[0032] The outer structure 80 in FIG. 1 is the base support
structure for the fixed guides 46A, 46B, 64A, 64B and the window
frame guide members 40A, . . . , 40D of the stage mechanism, but
does not support stage base structure 32. Thus underlying support
is partitioned so the reaction force on base support structure 80
does not couple into the stage base structure 32. Base support
structure 80 is supported by its own support pillars or other
conventional support elements (not shown in this drawing) to the
ground, i.e. the surface of the earth or the floor of a building.
An example of a suitable support structure is disclosed in
above-referenced U.S. patent application Ser. No. 08/221,375 at
FIGS. 1, 1B, 1C. This independent support structure for this
portion of stage mechanism provides the above-described advantage
of transmitting the reaction forces of the reticle stage mechanism
drive motors away from the frame supporting the other elements of
the photolithography apparatus, especially away from the optical
elements including the projection lens and from the wafer stage,
thereby minimizing vibration forces on the projection lens due to
reticle stage movement. This is further described below.
[0033] The drive forces for the stage mechanism are provided as
close as possible through the stage mechanism center of gravity. As
can be understood, the center of gravity of the stage mechanism
moves with the stage 10. Thus the stage 10 and the window frame
guide combine to define a joint center of gravity. A first
differential drive control (not shown) for motor coils 60A, 60B
takes into account the location of the window frame guide to
control the force exerted by each motor coil 60A, 60B to keep the
effective force applied at the center of gravity. A second
conventional differential drive control (not shown) for motor coils
68A, 68B takes into account the location of stage 10 to control the
force exerted by each motor coil 68A, 68B to keep the effective
force applied at the center of gravity. It is to be understood that
since stage 10 has a substantial range of movement, that the
differential drive for the motor coils 60A, 60B has a wide
differential swing. In contrast, the window frame guide has a more
limited range of movement, hence the differential drive for the
motor coils 68A, 68B has a much lesser differential swing,
providing a trim effect. Advantageously, use of the window frame
guide maintains the reaction forces generated by movement of the
reticle stage mechanism in a single plane, thus making easier to
isolate these forces from other parts of the photolithography
apparatus.
[0034] FIG. 2 shows a cross-sectional view through line 2-2 of FIG.
1. The structures shown in FIG. 2 which are also in FIG. 1 have
identical reference numbers and are not described herein. Also
shown in FIG. 2 is the illuminator 90 which is a conventional
element shown here without detail, and omitted from FIG. 1 for
clarity. Also shown without detail in FIG. 2 is the upper portion
of the projection lens (barrel) 92. It is to be understood that the
lower portion of the projection lens and other elements of the
photolithography apparatus are not shown in FIG. 2, but are
illustrated and described below.
[0035] The supporting structure 94 for the projection lens 92 is
also shown in FIG. 2. As can be seen, structure 94 is separated at
all points by a slight gap 96 from the base support structure 80
for the reticle stage mechanism. This gap 96 isolates vibrations
caused by movement of the reticle stage mechanism from the
projection lens 92 and its support 94. As shown in FIG. 2, stage 10
is not in this embodiment a flat structure but defines the
underside relieved portion 22 to accommodate the upper portion of
lens 92. Magnetic track 70A is mounted on top of the window frame
guide 40B and similarly magnetic track 70B is mounted on top of the
opposite window frame guide member 40D.
[0036] FIGS. 3A and 3B are enlarged views of portions of FIG. 2,
with identical reference numbers; FIG. 3A is the left side of FIG.
2 and FIG. 3B is the right side of FIG. 2. Shown in FIG. 3A is the
spring mounting 78 for air bearing 76A. Air bearing 78A being
spring mounted to a side surface of stage 10, this allows a certain
amount of yaw (rotation in the X-Y plane about the Z-axis) as well
as limited motion along the Z-axis. A gimbal mounting may be used
in place of or in addition to the spring 78. The spring or gimbal
mounting thereby allows for a limited amount of misalignment
between stage 10 and members 40C, 40D (not shown in FIG. 3A).
[0037] FIG. 4 is a top view of a photolithography apparatus
including the stage mechanism of FIGS. 1 and 2 and further
including, in addition to the elements shown in FIG. 1, the
supporting base structure 100 which supports the photolithography
apparatus including frame 94 except for the reticle stage
mechanism. (Not all the structures shown in FIG. 1 are labelled in
FIG. 4, for simplicity.) Base structure 100 supports four vertical
support pillars 102A, 102B, 102C and 102D connected to structure 94
by respectively bracket structures 106A, 106B, 106C and 106D. It is
to be appreciated that the size of the base structure 100 is fairly
large, i.e. approximately 3 meters top to bottom in one embodiment.
Each pillar 102A, 102B, 102C, 102D includes an internal
conventional servo mechanism (not shown) for leveling purposes.
Also shown in FIG. 4 are the supports 108 and 110 for respectively
laser interferometer units (beam splitter etc.) 112A, 112B, 112C.
FIG. 4 will be further understood with reference to FIG. 5 which
shows a view of FIG. 4 through cross-sectional line 5-5 of FIG.
4.
[0038] In FIGS. 4 and 5 the full extent of the supporting structure
94 can be seen along with its support pillars 102A, 102C which rest
on the base structure 100 which is in contact with the ground via a
conventional foundation (not shown). The independent support
structure for the reticle stage base support structure 80 is shown,
in FIG. 4 only (for clarity) and similarly includes a set of four
pillars 114A, 114B, 114C, 114D with associated bracket structures
116A, 116B, 116C, 116D, with the pillars thereby extending from the
level of base support structure 80 down to the base structure
100.
[0039] The lower portion of FIG. 5 shows the wafer stage 120 and
associated support structures 122, 124. The elements of wafer stage
120 conventionally include (not labelled in the drawing) a base,
the stage itself, fixed stage guides located on the base, magnetic
tracks located on the fixed stage guides, and motor coils fitting
in the magnetic tracks and connected to the stage itself. Laser
beams from laser 124 mounted on support 126 locate lens 92 and the
stage itself by interferometry.
[0040] FIG. 6A shows detail of one of the window frame guide hinged
flexure structures, e.g. 44C, in a top view (corresponding to FIG.
1). Each of hinges 44A, 44B, 44C and 44D is identical. These
flexure hinges have the advantage over a mechanical-type hinge of
not needing lubrication, not exhibiting histeresis (as long as the
flexure is not bent beyond its mechanical tolerance) and not having
any mechanical "slop", as well as being inexpensive to
fabricate.
[0041] Each individual flexure is e.g. 1/4 hard 302 stainless steel
approximately 20 mils (0.02 inch) thick and can sustain a maximum
bend of 0.5 degree. The width of each flexure is not critical; a
typical width is 0.5 inch. Two, three or four flexures are used at
each hinge 44A, 44B, 44C and 44D in FIG. 1. The number of flexures
used at each hinge is essentially determined by the amount of space
available, i.e., the height of the window frame guide members. The
four individual flexures 130A, 130B, 130C, 130D shown in FIG. 6A
(and also in a 90.degree. rotated view in FIG. 68) are each
attached by clamps 136A, 136B, 136C, 136D to adjacent frame members
(members 40 and 40D in FIGS. 6A and 6B) by conventional screws
which pass through holes in the individual flexures 130A, 1308,
130C, 130D and through the clamps and are secured in corresponding
threaded holes in frame members 40B and 40D.
[0042] Note that the frame members 40B, 40D of FIGS. 6A and 6B
differ somewhat from those of FIG. 1 in terms of the angular
(triangular) structures at the ends of frame members 405, 40D and
to which the metal flexures 130A, 130B, 130C, 130D are mounted. In
the embodiment of FIG. 1, these angular structures are dispensed
with, although their presence makes screw mounting of the flexures
easier.
[0043] In an alternate embodiment, the window frame guide is not
hinged but is a rigid structure. To accommodate this rigidity and
prevent binding, one of bearings 72C or 72B is eliminated, and the
remaining bearing moved to the canter of member 40B, mounted on a
gimbal with no spring. The other bearings (except those mounted on
stage 10) are also gimballed.
[0044] This disclosure is illustrative and not limiting; further
modifications will be apparent to one skilled in the art in light
of this disclosure and are intended to fall within the scope of the
appended claims.
* * * * *