U.S. patent application number 11/289472 was filed with the patent office on 2006-04-20 for stage system, exposure apparatus, and device manufacturing method.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Kotaro Akutsu, Mitsuru Inoue, Nobushige Korenaga.
Application Number | 20060082755 11/289472 |
Document ID | / |
Family ID | 33296823 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060082755 |
Kind Code |
A1 |
Akutsu; Kotaro ; et
al. |
April 20, 2006 |
Stage system, exposure apparatus, and device manufacturing
method
Abstract
A stage system that can meet enlargement of a stroke and thus,
particularly, that can be suitably incorporated into an electron
beam exposure apparatus. The stage system includes a first fixed
guide having a plane along X and Y directions, a first movable
guide to be guided by the first fixed guided (the first movable
guide having a Y guide 3f extending in the Y direction), a second
fixed guide having a plane along X and Y directions, a second
movable guide to be guided by the second fixed guide (the second
movable guide having an X guide extending in the X direction), and
a central movable member to be guided in the X and Y directions by
the Y guide and the X guide.
Inventors: |
Akutsu; Kotaro; (Soka-shi,
JP) ; Korenaga; Nobushige; (Utsunomiya-shi, JP)
; Inoue; Mitsuru; (Utsunomiya-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
33296823 |
Appl. No.: |
11/289472 |
Filed: |
November 30, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10862383 |
Jun 8, 2004 |
|
|
|
11289472 |
Nov 30, 2005 |
|
|
|
Current U.S.
Class: |
355/72 ;
355/75 |
Current CPC
Class: |
G03F 7/70816 20130101;
H02K 2201/18 20130101; G03F 7/70808 20130101; G03F 7/70716
20130101; H01J 2237/20292 20130101; H02K 41/031 20130101; H02K
16/00 20130101; G03F 7/70758 20130101; H02K 1/278 20130101; H01J
37/20 20130101; H01J 2237/3175 20130101 |
Class at
Publication: |
355/072 ;
355/075 |
International
Class: |
G03B 27/58 20060101
G03B027/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2003 |
JP |
2003-165512 |
Claims
1. A stage system, comprising: a first fixed guide having a first
guide surface being parallel to or approximately parallel to a
first direction and a second direction being orthogonal to or
approximately orthogonal to the first direction; a first movable
guide to be guided by said first fixed guide and having three
freedoms of straight motions in the first and second directions and
a motion in a rotational direction about a third direction being
orthogonal to or approximately orthogonal to the first and second
directions, said first movable guide having a first guide extending
in the second direction; a second fixed guide having a second guide
surface being parallel to or approximately parallel to the first
and second directions; a second movable guide to be guided by said
second fixed guide and having three freedoms of straight motions in
the first and second directions and a motion in a rotational
direction about the third direction, said second movable guide
having a second guide extending in the first direction; and a
central movable member to be guided in the first and second
directions by means of said first and second guides.
2-15. (canceled)
Description
[0001] This application is a divisional application of copending
U.S. patent application Ser. No. 10/862,383, filed on Jun. 8,
2004.
FIELD OF THE INVENTION AND RELATED ART
[0002] This invention relates to a stage system to be used in
various measuring instruments, or in a projection exposure
apparatus, for a semiconductor lithography process, for moving and
positioning a substrate, such as a wafer, at a high speed and with
a high precision. The stage system of the present invention is best
suited for a stage system particularly to be used in an electron
beam exposure apparatus, in which an electron beam is used to
perform pattern drawing for direct patterning of a wafer or reticle
exposure, or in an EUV (extreme ultraviolet) exposure apparatus
using EUV light as exposure light in which the stage system is used
in a vacuum ambience.
[0003] The manufacture of devices such as semiconductor devices,
for example, is based on lithography technology in which various
patterns formed on a mask are transferred to a wafer in a reduced
scale, by use of light. Extremely high precision is required in
relation to the mask pattern to be used in such lithography
technology, and an electron beam exposure apparatus is used to make
such a mask. Further, an electron beam exposure apparatus is used
also in a case wherein a pattern is to be directly formed on a
wafer without using a mask.
[0004] As regards such an electron beam exposure apparatus, there
is a point beam type apparatus wherein an electron beam to be used
is shaped into a spot-like shape, and a variable rectangle-beam
type apparatus wherein an electron beam has a rectangular section
of various size, for example. In these types of exposure apparatus,
however, generally, the apparatus comprises an electron gun unit
for producing an electron beam, an electron optical system for
directing the produced electron beam to a sample, a stage system
for scanningly moving the whole surface of the sample with respect
to the electron beam, and an objective deflector for positioning
the electron beam upon the sample very precisely.
[0005] The region that can be positioned by use of an objective
deflector has only a small size of about a few millimeters, to
suppress the aberration of the electron optical system as much as
possible. To the contrary, as regards the size of the sample, for a
silicon wafer, it is about 200-300 mm in diameter, and for a glass
substrate to be used as a mask, it is about 150 mm square. So, the
electron beam exposure apparatuses include a stage system by which
the whole surface of the sample can be scanned with the electron
beam.
[0006] In electron beam exposure apparatuses, since the positioning
response of the electron beam is extraordinarily high, generally,
they use a system in which the attitude of the stage or a
positional deviation thereof is measured and the measured value is
fed back to the positioning of the electron beam through the
deflector, rather than attempting to improve the mechanical control
characteristic of the stage. Also, since the stage is disposed in a
vacuum chamber and, furthermore, there is a restriction that a
change in a magnetic field that may influence the positioning
precision of the electron beam must be avoided, generally, the
stage is disposed by use of a limited element of a contact type,
such as rolling guides or ball screw actuators.
[0007] Such contact type elements involve a problem of lubrication
and dust creation, for example. Japanese Laid-Open Patent
Application No. 2002-252166 shows a countermeasure therefor, and
FIG. 10 illustrates it, that is, a stage having two freedoms of
movement in a planar direction, using vacuum air guides and linear
motors. In the example of FIG. 10, very smooth acceleration can be
accomplished and, yet, with respect to the positioning direction,
external disturbance from the guide is very small. In the
illustrated example, the stage comprises an X slider, a Y slider
and an X-Y slider, wherein the X slider and the Y slider are
confined with respect to rotation about the Z axis, by means of
radial bearings.
[0008] FIG. 11 shows an example of a stage, to be used in an
atmosphere, corresponding to a stage disclosed in Japanese
Laid-Open Patent Application No. 2002-8971. In the example of FIG.
11, like the example of FIG. 10, the stage comprises an X slider (X
guide bar 28), a Y slider (Y guide bar 29), and an X-Y slider, but
the X slider and the Y slider are not confined with respect to
rotation about the Z axis.
[0009] As regards the election beam exposure apparatus, there is a
known example disclosed in Japanese Laid-Open Patent Application
No. H09-330867. In the apparatus of this document, a plurality of
electron beams are projected upon the surface of a sample along
design coordinates and the electron beams are deflected along the
design coordinates to thereby scan the sample surface.
Additionally, in accordance with a pattern to be drawn, the
electron beams are individually turned on and off to thereby draw
the pattern. In such a multiple electron-beam type exposure
apparatus, a desired pattern can be drawn by use of plural electron
beams, and thus, the throughput can be improved.
[0010] FIG. 12 illustrates a general structure of a multiple
electron-beam type exposure apparatus. Denoted at 501a, 501b, and
501c are electron guns by which a plurality of electron beams can
be individually turned on and off. Denoted at 100 is a reduction
electron optical system for reducing and projecting the electron
beams from the electron guns 501a, 501b and 501c, onto a wafer 305.
Denoted at 306 is a deflector for scanning the plural electron
beams projected to the wafer 305.
[0011] FIG. 13 illustrates the action as a wafer is scanned with
plural electron beams, in the exposure apparatus of FIG. 12. White
small circles depict beam reference positions BS1, BS2 and BS3
whereat the electron beams are incident, as they are not deflected
by the deflector 306. These beam reference positions BS1-BS3 are
placed along a design orthogonal coordinate system (Xs, Ys).
[0012] On the other hand, the electron beams are scanned
(scanningly deflected) also along a design orthogonal coordinate
system (Xs, Ys) while taking the beam reference positions as a
reference, to scan associated exposure fields EF1, EF2 and EF3,
respectively. In this stage, the stage which carries the wafer 350
thereon is scanningly moved mainly in the Y direction, as denoted
at 200 in FIG. 13, to perform sequential exposures of zones of the
wafer.
SUMMARY OF THE INVENTION
[0013] Enlargement of the wafer diameter has been required in
lithography, and thus, the stroke of the apparatus should be
enlarged. In the example of FIG. 10, there is a difficulty in
setting the orthogonality of confining axes for confining each of
the X and Y sliders at opposite sides. This leads to a difficulty
in improvement of the precision or enlargement of the stroke.
[0014] In the example of FIG. 11, on the other hand, if there is a
tilt of a base table, for example, it may cause unwanted motion in
the X or Y direction. Furthermore, the arrangement itself cannot be
used in a vacuum ambience.
[0015] It is accordingly an object of the present invention to
provide a high-precision stage system that can meet enlargement of
the stroke.
[0016] In accordance with an aspect of the present invention, to
achieve this object, there is provided a stage system, comprising a
first fixed guide having a first guide surface being parallel to or
approximately parallel to a first direction and a second direction
being orthogonal to or approximately orthogonal to the first
direction, a first movable guide to be guided by the first fixed
guide and having three freedoms of movement of straight motions in
the first and second directions and a motion in a rotational
direction about a third direction being orthogonal to or
approximately orthogonal to the first and second directions, the
first movable guide having a first guide extending in the second
direction, a second fixed guide having a second guide surface being
parallel to or approximately parallel to the first and second
directions, a second movable guide to be guided by the second fixed
guide and having three freedoms of movement of straight motions in
the first and second directions and a motion in a rotational
direction about the third direction, the second movable guide
having a second guide extending in the first direction, and a
central movable member to be guided in the first and second
directions by means of the first and second guides.
[0017] In accordance with another aspect of the present invention,
there is provided a stage system comprising a first fixed guide
having a first guide surface being parallel to or approximately
parallel to a first direction and a second direction being
orthogonal to or approximately orthogonal to the first direction, a
first movable guide to be guided by the first fixed guide and
having a first guide extending in the second direction, a second
fixed guide having a second guide surface being parallel to or
approximately parallel to the first and second directions, a second
movable guide to be guided by the second fixed guide and having a
second guide extending in the first direction, a third fixed guide
having a third guide surface being parallel to or approximately
parallel to the first and second guide surfaces, and a central
movable member to be guided in the first and second directions by
means of the first and second guides, and also to be guided by the
third fixed guide in a third direction being orthogonal to or
approximately orthogonal to the first and second directions,
wherein the central movable member is attracted to the third fixed
guide by means of a permanent magnet unit having a magnetic
shield.
[0018] In accordance with the present invention, a high-precision
stage system that can meet enlargement of the stroke can be
accomplished. Further, since the fixed guide (guide surface) is
divided into plural guides, even if a magnetic preload is used,
magnets can be magnetically shielded effectively. Thus, the stage
system can be well incorporated into an electron beam exposure
apparatus.
[0019] These and other objects, features and advantages of the
present invention will become more apparent upon a consideration of
the following description of the preferred embodiments of the
present invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic view of a main portion of an electron
beam exposure apparatus according to an embodiment of the present
invention.
[0021] FIG. 2 is a perspective view of a main portion of a stage
system in the FIG. 1 embodiment.
[0022] FIG. 3 is a diagram for explaining a stage control system of
the stage system of the FIG. 2 example.
[0023] FIGS. 4A and 4B are schematic views for explaining operation
of a linear motor of the stage system of FIG. 2.
[0024] FIG. 5 is a schematic view of a stage system according to a
second embodiment of the present invention.
[0025] FIGS. 6A-6D are schematic views for explaining a base
arrangement for supporting sliders in the stage system of FIG.
2.
[0026] FIG. 7 is a schematic view for explaining another example of
the base arrangement.
[0027] FIGS. 8A and 8B are schematic views, explaining a further
example of the base arrangement.
[0028] FIGS. 9A and 9B illustrate an exhaust system in the stage
system of FIG. 2.
[0029] FIG. 10 is a perspective view of a stage system of a first
conventional example.
[0030] FIGS. 11A and 11B are schematic views, showing a stage
system of a second conventional example.
[0031] FIG. 12 is a schematic view of a general structure of a
multiple electron-beam exposure apparatus.
[0032] FIG. 13 is a schematic view for explaining the action as a
wafer is scanned with a plurality of electron beams, in the
exposure apparatus of FIG. 12.
[0033] FIG. 14 is a flow chart for explaining device manufacturing
processes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The present invention may take the following preferred
forms.
[0035] That is, a stage system in one preferred form of the present
invention comprises a first fixed guide (1a, 1c: reference numerals
are those used in the embodiments to be described later), having a
plane (first guide surface) being parallel to or approximately
parallel to a first direction (X direction) and a second direction
(Y direction) being orthogonal to or approximately orthogonal to
the first direction, a first movable guide (3) to be guided by the
first fixed guide and having three freedoms of movement, including
a motion in a rotational direction about a third direction being
orthogonal to or approximately orthogonal to the first and second
directions (the first movable guide having a guide 3f extending in
the Y direction), a second fixed guide (1b, 1d) having a plane
(second guide surface) being parallel to or approximately parallel
to the first and second directions, a second movable guide (2) to
be guided by the second fixed guide and having three freedoms of
movement in the first, second and third directions (the second
movable guide having a guide 2f extending in the X direction, and a
central movable member (4) to be guided in the X and Y directions
by means of the Y guide 3f and X guide 2f.
[0036] Preferably, the stage system may further comprise (i) a
first actuator group (34m) for driving the first movable guide (3)
in three-freedom of movement directions (the first actuator group
including a first X actuator for driving the first movable guide in
the X direction with a relatively long stroke, and a first Y
actuator for driving the first movable guide in the second
direction with a relatively short stroke), and (ii) a second
actuator group (24m) for driving the second movable guide (2) at
least in two-freedom of movement directions of X and Y (the second
actuator group including a second Y actuator for driving the second
movable guide in the Y direction with a relatively long stroke, and
a second X actuator for driving the second movable guide in the X
direction with a relatively short stroke).
[0037] Moreover, preferably, the stage system may further comprise
a third fixed guide (1) having a plane extending in the X and Y
directions. The central movable member (4) may be guided by the
third fixed guide. The upper surfaces of the first, second and
third fixed guides, functioning as a guide surface, may be parallel
to or approximately parallel to each other. These guides may
comprise a static pressure bearing. The actuators may comprise a
non-contact linear motor. On that occasion, the first X actuator
may use a Y-direction magnetic flux component of a permanent magnet
134 mag group (X movable element), while the first Y actuator may
use an X-direction magnetic flux component of the permanent magnet
group. The second Y actuator may use an X-direction magnetic flux
component of a permanent magnet group (Y movable element), while
the second X actuator may use a Y-direction magnetic flux component
of the permanent magnet group.
[0038] Moreover, the stage system may preferably further comprise a
third fixed guide (1) having a plane in the X and Y directions, and
the central movable member (4) may be guided by the third fixed
guide. A first magnet (39) may apply a preload to the first movable
guide (3) with respect to the first fixed guide (1a, 1c), and a
second magnet (29) may apply a preload to the second movable guide
(2) with respect to the second fixed guide (1b, 1d). A third magnet
(49) may apply a preload to the central movable member (4) with
respect to the third fixed guide (1). The first, second and third
magnets may have magnetic shields (39sh, 29sh, 49sh),
respectively.
[0039] When the magnetic resistance of a magnetic path defined
inside each magnetic shield and the first, second and third magnets
is Re, and the magnetic resistance of a magnetic path defined
interactively between the first, second and third magnets is Rr,
there may be a relation Re<Rr.
[0040] Preferably, the actuators may comprise non-contact linear
motors, having a magnetic shield. The first Y actuator or the
second X actuator may comprise an electromagnet.
[0041] A stage system in a second preferred form of the present
invention comprises a first fixed guide (1a, 1c) having a plane
(first guide surface) being parallel to or approximately parallel
to a first direction (X direction) and a second direction (Y
direction) being orthogonal to or approximately orthogonal to the
first direction, a first movable guide (3) to be guided by the
first fixed guide (the first movable guide having a Y guide 3f
extending in the Y direction, a second fixed guide (1b, 1d) having
a plane (second guide surface) being parallel to or approximately
parallel to the first and second directions, a second movable guide
(2) to be guided by the second fixed guide (the second movable
guide having an X guide 2f extending in the X direction), a third
fixed guide (1) having a third guide surface being parallel to or
approximately parallel to the first and second guide surfaces, and
a central movable member (4) to be guided in the X and Y directions
by means of the Y guide (3f) and the X guide (2f), and also to be
guided by the third fixed guide (1) in a third direction being
orthogonal to or approximately orthogonal to the first and second
direction, wherein the central movable member is attracted to the
third fixed guide by means of a permanent magnet (1) unit having a
magnetic shield.
[0042] Preferred embodiments of the present invention will now be
described with reference to the attached drawings.
[0043] FIG. 1 is a schematic view of a main portion of an electron
beam exposure apparatus according to an embodiment of the present
invention. Denoted in FIG. 1 at 300 is a vacuum sample chamber, and
denoted at 301 is an electron gun having a cathode 301a, a grid
301b and an anode 301c. Electrons emitted from the cathode 301a
produce a crossover image between the grid 301b and the anode 301c
(hereinafter, the crossover image will be referred to as a light
source).
[0044] Electrons emitted from this light source are formed into an
approximately parallel electron beam by means of a condenser lens
302 having a front focal point position placed at the light source
position. The approximately parallel electron beam is then incident
on an element electron optical system array 303. The element
electron optical system array 303 includes a plurality of element
electron optical systems each comprising a blanking electrode, an
aperture and an electron lens. These element electron optical
systems are arrayed along a direction perpendicular to the optical
axis of a reduction electron optical system 100, which is parallel
to the Z axis. Details of the element electron optical system array
303 will be described later.
[0045] The element electron optical system array 303 functions to
produce a plurality of intermediate images of the light source, and
these intermediate images are projected in a reduced scale by the
reduction electron optical system 100, whereby light source images
are formed upon a wafer 305. Here, the components of the element
electron optical system array 303 are set so that the spacing of
the light source images formed on the wafer 305 has a size
corresponding to a multiple, by an integral number, of the size of
the light source. Further, the element electron optical system 303
functions to assure that the positions of the light source images
with respect to the optical axis directions are different in
accordance with the field curvature of the reduction electron
optical system 100. Also, the element electron optical system
functions to correct aberration to be produced as the intermediate
images are projected on the wafer 305 by the reduction electron
optical system 100.
[0046] The reduction electron optical system 100 includes two-stage
type symmetric magnetic tablets, comprising a first projection lens
(341, 343) and a second projection lens (342, 344). When the focal
length of the first projection lens (341, 343) is f1 while the
focal length of the second projection lens (342, 44) is f2, the
distance between these two lenses is equal to f1+f2.
[0047] The object point on the optical axis is at the focal point
position of the first projection lens (341, 343), and the image
point thereof is focused on the focal point of the second
projection lens (342, 344). This image is reduced at -f2/f1. Also,
since the magnetic fields of these two lenses are determined so
that they act in mutually opposite directions, theoretically,
except five aberrations of spherical aberration, isotropic
astigmatism, isotropic coma aberration, field curvature aberration,
and longitudinal chromatic aberration, the remaining Seidel's
aberration and chromatic aberration concerning rotation and
magnification can be cancelled.
[0048] Denoted at 306 is a deflector for deflecting plural electron
beams from the element electron optical system array 303 so as to
shift plural light source images upon the wafer 305 in the X and Y
directions by the same displacement amount. While not shown in the
drawing, the deflector 306 comprises a main deflector to be used
when the deflection width is wide, and a sub-deflector to be used
when the deflection width is narrow. The main deflector is an
electromagnetic type deflector, while the sub-deflector is an
electrostatic type deflector.
[0049] Denoted at 307 is a dynamic focus coil for correcting a
deviation of the focus position of the light source image, based on
deflection aberration to be produced when the deflector 306 is
operated. Denoted at 308 is a dynamic coil, which serves, like the
dynamic focus coil 307, to correct astigmatism of deflection
aberration to be produced by the deflection. Denoted at 99 is an
alignment scope having an off-axis management, for detecting a mark
already formed on the wafer.
[0050] Denoted at 310 is a top stage for carrying a wafer 305
thereon. For observation of the whole surface of the wafer 305
through the alignment scope 99, the top stage 310 should have a
stroke corresponding to the wafer diameter, just underneath the
alignment scope 99.
[0051] Denoted at 4 is an X-Y slider for carrying the top stage 310
thereon and being movable in the X and Y directions, which are
orthogonal to the optical axis (Z axis). The X-Y slider will be
explained in greater detail, in conjunction with FIG. 2. The X-Y
slider 4 comprises an X-Y slider-(y) 41 and an X-Y slider-(x) 42.
At the bottom of the X-Y slider-(y) 41, there is a vacuum-proof
bearing 43 disposed opposed to the top face 1f of a stage base 1.
Also, inside the side wall of the X-Y slider-(y) 41, there is a
similar vacuum-proof bearing 44 disposed to sandwich a Y guide
3f.
[0052] Further, inside the side wall of the X-Y slider-(x) 42,
there is a similar vacuum-proof bearing 45 disposed to sandwich an
X guide 2f. The Y guide 3f is formed at opposite side walls of the
beam 32 (providing X slider 3), in the lengthwise direction. The X
guide 2f is formed at the opposite side walls of a Y beam
(providing Y slider 2), in the lengthwise direction. The X slider 3
having the Y guide 3f and the Y slider 2 having the X guide 2f are
formed in a grid-like shape as shown in FIG. 3.
[0053] When the X-Y slider 4 is to be moved in the X direction, the
X slider 3 is moved in the X direction by which it can be moved
smoothly along the X guide 2f and the stage base top face 1f. When
the X-Y slider 4 is to be moved in the Y direction, the Y slider 2
is moved in the Y direction by which it can be moved smoothly along
the Y guide 3f and the stage base top face 1f.
[0054] The Y slider 2 will now be explained. The Y slider 2 has a Y
beam 22 including the X guide 2f, as well as a Y foot 21 and a Y
foot 21' disposed on the opposite side with respect to the X
direction. At the bottom of the Y foot 21 (21'), there is a
vacuum-proof bearing 23 disposed opposed to the top face of a beam
base 1b (1d).
[0055] The top face of the beam base 1b (1d) is parallel to or
approximately parallel to the stage base top face 1f. The Y slider
2 can move smoothly in the Y direction by a required stroke, within
the range of the top face of the beam base 1b (1d), and also it can
move smoothly in the direction and a rotational direction about the
Z axis (hereinafter, "Z-axis rotational direction"). Thus, the Y
slider 2 can move with a long stroke in the Y direction and with a
short stroke in the X direction. Thus, adding the Z-axis rotational
direction, it can move with three freedoms of movement.
[0056] Also, there are linear motor movable elements 24m disposed
at the opposite sides with respect to the X direction, for driving
the Y slider 2 in the Y direction. Each linear motor movable
element 24m contains a permanent magnet therein, and a magnetic
shield cover is mounted thereon to prevent leakage of magnetic
field into the stage space. A linear motor for moving the Y slider
2 in the X direction is also housed in the movable element 24m.
Details will be described later, with reference to FIG. 4.
[0057] The Y foot 21 is provided with a reflection mirror 26 for
measuring the position in the Y direction and a reflection mirror
26x for measuring the position in the X direction, while the Y foot
21' is provided with a reflection mirror 26' for measuring the
position in the Y direction. Thus, by use of interferometer systems
126, 126' and 126x, the position (x, y, .theta.z) of the Y slider 2
in the directions of X, Y and Z-axis rotation can be measured.
[0058] Similarly, the X slider 3 will now be described. The X
slider 3 includes an X beam 32 having the Y guide 3f, and an X foot
31 and an X foot 31' disposed on opposite sides with respect to the
Y direction. At the bottom of the X foot 31 (31'), there is a
vacuum-proof bearing 33 disposed opposed to the top face of a beam
base 1a (1c).
[0059] The top face of the beam base 1a (1c) is parallel to or
approximately parallel to the stage base top face 1f. The X slider
can move smoothly in the X direction by a required stroke, within
the range of the top face of the beam base 1a (1c), and also it can
move smoothly in the Y direction and the Z-axis rotational
direction. Thus, the X slider 3 can move with a long stroke in the
X direction and with a short stroke in the Y direction. Thus,
adding the Z-axis rotational direction, it can move with three
freedoms of movement. Also, there are linear motor movable elements
34m disposed at the opposite sides with respect to the Y direction,
for driving the X slider in the X direction.
[0060] Each linear motor movable element 34m contains a permanent
magnet therein, and a magnetic shield cover is mounted thereon to
prevent leakage of a magnetic field into the stage space. A linear
motor for moving the X slider in the Y direction is also housed in
the movable element 34m.
[0061] The X foot 31 is provided with a reflection mirror 36 for
measuring the position in the X direction, while the X foot 31' is
provided with a reflection mirror 36y for measuring the position in
the Y direction and a reflection mirror 36' for measuring the
position in the X direction. Thus, by use of interferometer systems
136, 136' and 136y, the position (x, y, .theta.z) of the X slider 3
in the directions of X, Y and Z-axis rotation can be measured.
[0062] FIG. 3 is a diagram of a control system for the X and Y
sliders. The values of the interferometer systems 136, 136' and
136y corresponding to the X slider 3 are converted by an X slider
computing unit 130 into the X-direction position x, Y-direction
position y and Z-axis rotational direction .theta.z of the X slider
3, and they are applied as a feedback signal to an X slider
controller 131. The X slider controller 131 calculates a driver
designated value (Xfx, Xfx', Xfy) and, by applying an electrical
current to a coil array provided in an associated X stator 34s,
driving forces Xfx and Xfx' in the X and Z-axis rotational
directions, as well as a driving force Xfy in the Y direction, are
produced.
[0063] Similarly, the values of the interferometer systems 126,
126' and 126x corresponding to the Y slider 2 are converted by a Y
slider computing unit 120 into the X-direction position x and
Y-direction position y of the Y slider 2, and they are applied as a
feedback signal to a Y slider controller 121. The Y slider
controller 121 calculates a driver designated value (Yfy, Yfx) and,
by applying an electrical current to a coil array provided in an
associated Y stator 24s, driving forces Yfy in the Y direction, as
well as a driving force Yfx in the X direction, are produced. In
the control system of this embodiment, the Z-axis rotation of the X
slider 3 is controllably confined, while the Z-axis rotation of the
Y slider 2 follows the rotation of the X slider 3.
[0064] As described above, three freedoms of movement of the X
slider and two freedoms of movement of the Y slider are
controllably confined, by which three freedoms of movement of the
X-Y slider 4 can be controlled. Here, the X-direction position of
the X-Y slider 4 can be regarded as being substantially equivalent
to the X-direction position of the X slider 3, and the Y-direction
position of the X-Y slider can be regarded as being substantially
equivalent to the Y-direction position of the Y slider 2. Also, the
Z-axis rotation thereof can be regarded as being substantially
equivalent to the Z-axis rotation of the X slider 3. Measurement
for these rough-motion sliders can be performed in various
combinations and, as an example, the X-Y slider 4 can be measured
directly by use of an interferometer.
[0065] Further, while the positional information of the Y slider 2
regarding the rotational direction is not specifically used in this
embodiment as a measured value, a control may be added by using
velocity information in the rotational direction.
[0066] Referring now to FIGS. 4A and 4B, the linear motor to be
used in the present invention will be explained while taking the
linear motor 34 of the X slider 3 as an example. As described
hereinbefore, the linear motor 34 has a movable element 34m and a
stator 34s. The movable element 34m comprises a movable magnet 134
mag and a magnetic shield 134sh. The stator 34 comprises coil
arrays 134a, 134b, 134c, 134d and 134e, which are disposed along
the stroke direction. Each coil has a two-layer structure. There is
a jacket 134j for covering the coil arrays, to prevent the coil
arrays from being bared inside the vacuum sample chamber. The
movable magnet 134 mag includes X-direction magnetized magnets,
which are alternately sandwiched between Y-direction magnetized
magnets, to provide a magnetic flux distribution near a sine wave
in the coil space.
[0067] FIG. 4A illustrates a state in which a driving force acts in
the X direction. A Y-direction largest magnetic flux By is being
produced at the coil b. At this moment, by supplying electrical
currents of the same phase to the coils 134b.sub.--u and
134b.sub.--d, due to the Lorentz's force, a force is applied to the
movable element 34m in the X direction.
[0068] FIG. 4B illustrates a state in which a driving force acts in
the Y direction. An X-direction largest magnetic flux Bx is being
produced at the coil c, in opposite directions at the positions of
the coils 134b.sub.--u and 134b.sub.--d. At this moment, by
applying electrical currents of opposite phases to the coils
13b.sub.--u and 134b.sub.--d, due to the Lorentz's force, a force
is applied to the movable element 34m in the Y direction. Although
this force in the Y direction may be weak as compared with the
force in the X direction, there does not occur a particular problem
since the force in the Y direction is not used for acceleration of
the X slider.
[0069] FIG. 5 illustrates an electromagnet arrangement, as a second
embodiment, for applying a driving force in the Y direction for the
X slider and a driving force in the X direction for the Y slider.
The X foot 31 and X foot 31' of the X slider 3 are provided with a
linear motor movable element 34m'' for applying an X-direction
driving force and, additionally, the X foot 31' is provided with an
electromagnet unit 34m' for applying a Y-direction driving force.
The electromagnet unit 34m' includes an E-shaped core 234EM, a coil
234co and a magnetic shield 234sh, at the movable side, which are
fixed to the X foot 31' by a non-magnetic material 235. Also, there
is a magnetic material bar 234I at the fixed side, which is fixed
to the beam base 1c by a non-magnetic material 236. In the
electromagnetic unit 34m', the X slider 3 can be driven in the Y
direction by selectively applying and controlling a voltage to
opposed coils.
[0070] The Y foot 21 and the Y foot 21' of the Y slider 2 are
provided with a linear motor movable element 24m'' for applying a
Y-direction driving force and, additionally, the Y foot 31' is
provided with an electromagnet unit 24m' for applying an
X-direction driving force. The electromagnet unit 24m' includes an
E-shaped core 224EM, a coil 224co and a magnetic shield 224sh, at
the movable side, which are fixed to the Y foot 21' by a
non-magnetic material 235. Also, there is a magnetic material bar
(I-shaped core) 224I at the fixed side, which is fixed to the beam
base 1d by an I-shaped core mounting member 236 made of a
non-magnetic material. In the electromagnetic unit 24m', the Y
slider 2 can be driven in the X direction by selectively applying
and controlling a voltage to opposed coils.
[0071] Referring now to FIGS. 6A-6D, the structure at the bottom
faces of the sliders will be explained. FIG. 6A illustrates the
whole structure as viewed from the bottom, for explaining the base
arrangement for supporting the sliders. FIG. 6B illustrates a
single bottom pad. As has been described with reference to FIG. 2,
at the bottom of the X-Y slider-(y) 41, there is a vacuum-proof
bearing 43 disposed opposed to the top surface 1f of the stage base
1. At the bottom of the Y foot 21 (21'), there is a vacuum-proof
bearing 23 disposed opposed to the top surface of the beam base 1b
(1d). At the bottom of the X foot 31 (31'), there is a vacuum-proof
bearing 33 disposed opposed to the top surface of the beam base 1a
(1c). Details of such pads are such as shown in FIG. 6B.
Specifically, each pad comprises a static-pressure bearing portion
51 in which a fluid is discharged through a porous material, a
labyrinth portion 52 for preventing leakage of the discharged fluid
into the ambience, and an exhaust bore 53. The labyrinth portion
includes a plurality of lands 52L and grooves 52g, for providing a
fluid resistance without contact.
[0072] In order to attain a desired rigidity in a static-pressure
bearing, generally, a preload is applied to the static-pressure
bearing. In this embodiment, a preload is applied on the basis of
an attraction force of a permanent magnet. The preload application
may be made by a simple float-type preload such as a vacuum preload
(in a case wherein the ambience is at atmosphere or a reduced
pressure ambience) or a magnet preload, or a confinement type load
in which a preload is applied while a static-pressure bearing is
disposed opposed.
[0073] In this embodiment, since the system is used in a vacuum
ambience, the simple float-type preload based on a magnet preload
is used. In FIG. 6, denoted at 29 is a permanent magnet fixed to
the Y foot, and denoted at 39 is a permanent magnet fixed to the X
foot. Denoted at 49 is a permanent magnet fixed to the X-Y
slider-(y) 41 (FIG. 2). These magnets are covered by magnetic
shields 29sh, 39sh and 49sh, for preventing leakage of their
magnetic shield. Since the confinement-type preload is not used,
only the bearing surface and the guide surface are the precision
required surface.
[0074] On the other hand, a structure such as a confinement-type
preload is used as shown in FIG. 2, that is a vacuum-proof bearing
45 is provided at the opposite sides of the inside wall of the X-Y
slider-(x) 42 to sandwich the opposed X guide 2f therebetween. On
that occasion, regarding the precision required surface, the
parallelism of the opposite sides of the bearing 45 at the X-Y
slider side, as well as the parallelism of the opposite faces of
the X guide 2f, should be controlled. However, the rigidity will be
improved in this case.
[0075] Further, when permanent magnets are used in an electron beam
exposure apparatus as in the present embodiment, in addition to
covering each permanent magnet by use of a magnetic shield, the
following measures may be done. That is, in FIG. 6A, the bases (1,
1a, 1b, 1c, 1d) of magnetic materials, which are the object to be
attracted by the respective permanent magnets, are magnetically
isolated from each other.
[0076] More specifically, the preload magnet 49 of the X-Y slider
is disposed opposed to the stage base 1, and the preload magnet 29
of the Y slider is disposed opposed to the beam base 1b (1d). The
preload magnet 39 of the X slider is disposed opposed to the beam
base 1a (1c). The bases 1, 1a, 1b, 1c and 1d of them are disposed
with a certain mutual magnetic resistance.
[0077] The effect of this structure will be explained, in
conjunction with FIGS. 6C and 6D. FIG. 6C shows a case wherein the
bases are not magnetically isolated, and FIG. 6D shows a case
wherein the bases are isolated. If they are not isolated, in
addition to magnetic circuits L1 produced by the respective
magnets, a magnetic circuit L2 is produced between plural magnets
and this leaks outwardly beyond the shields 29sh, 39sh and 49sh. On
the other hand, if magnetic isolation is provided (that is, the
magnetic resistance is enlarged sufficiently high), the magnetic
flux leakage between plural magnets can be reduced as much as
possible.
[0078] FIG. 7 illustrates the base arrangement according to a
second embodiment, as viewed from the bottom. In FIG. 7, the base
1' to which the respective permanent magnets are disposed opposed
is formed integrally. There is a slit Is between movable regions of
the sliders, to increase the magnetic resistance between plural
magnets, such that magnetic flux leakage to be produced between
plural magnets is minimized. In the arrangement of FIG. 7, the
precision setting at the guide surface 1f of the base 1' is
easy.
[0079] FIG. 8A shows the base arrangement according to a third
embodiment, as viewed from the bottom. In FIG. 8A, in the bottom
pad movable region of each slider, a common base 1'' and the
magnetic material base 1m to which the permanent magnets 29 and 29
of the sliders 2 and 3 are magnetically isolated from each
other.
[0080] FIG. 8B illustrates the Y foot 21 as seen from the side
thereof. The Y-bottom pad 23, including a labyrinth portion, uses
the top face 1f of the common base 1'' as a guide surface. The
attracting permanent magnet 29 for applying a preload to the
Y-bottom pad 23 and the magnetic shield 29sh are disposed opposed
to the magnetic material base 1m being magnetically isolated from
the common base 1'',
[0081] As shown in FIG. 8A, while the attracting magnet of the X-Y
slider 4 is disposed opposed to the common base 1'', since the
common base 1'' and the magnetic material base 1m are magnetically
isolated from each other, magnetic flux leakage to be produced
between plural magnets can be reduced as much as possible.
Furthermore, generally, the flatness precision may be looser at the
surface opposed to the permanent magnet than at the surface to be
opposed to the bearing portion, and, therefore, the arrangement is
advantageous with respect to machining and assembling.
[0082] FIGS. 9A and 9B are schematic views for explaining the flow
of fluids collected by exhaust bores 53' and 53'' of lateral pads
44 and 45 of the X-Y slider 4. In the electron beam exposure
apparatus according to this embodiment of the present invention, as
has been described with reference to FIGS. 1 and 2, an alignment
scope 99 is disposed in the X direction such that, for observation
of the whole surface of the wafer through the alignment scope, the
top stage should have a stroke, just below the alignment scope,
that corresponds to the wafer diameter. The distance from the
center of the projection optical system to the alignment scope is
called a "base line", and, in this arrangement, the X-direction
stroke Xst is longer than the Y-direction stroke Yst by the base
line (i.e., Xst>Yst). Thus, the following measures are taken, in
this embodiment.
[0083] The fluid discharged from the Y lateral pad 45 is collected
by the exhaust bore 53' formed in the labyrinth portion grooves 52g
(FIG. 6). The collected fluid is discharged to the labyrinth
portion groove 52g of the X lateral pad 44 through a pipe 55
provided in the X-Y slider 4 and the X lateral pad 44. The thus
discharged fluid and the fluid discharged from the X lateral pad 44
are mixed with each other. The thus combined fluid is collected
through an exhaust bore 53'' formed in the X beam 32. The collected
fluid is discharged outwardly of the vacuum sample chamber 300
(FIG. 1) through a pipe 56 formed in the X beam 32 and the X foot
31 (31') and from a flexible tube 38 connected to the X foot 31
(31').
[0084] The labyrinth portion groove 52g of the Y lateral pad 44
should have a length the same as or larger than the Y-direction
stroke Yst. Although the X-direction stroke is still longer, since,
in this embodiment, the fluid discharged from the X lateral pad 45
is collected at the X-Y slider 4 side, it is not necessary for the
labyrinth portion groove 52g of the X lateral pad to have a length
the same as the X-direction stroke Xst. Therefore, the size of the
X-Y slider structure including the lateral pads 44 and 45 can be
held to be small.
[0085] Next, semiconductor device manufacturing processes using an
exposure apparatus described above, will be explained.
[0086] FIG. 13 is a flow chart for explaining a general procedure
for manufacturing semiconductor devices. Step 1 is a design process
for designing a circuit of a semiconductor device. Step 2 is a
process for making a mask on the basis of the circuit pattern
design. Step 3 is a process for preparing a wafer by using a
material such as silicon. Step 4 is a wafer process, which is
called a pre-process, wherein, by using the thus prepared mask and
wafer, a circuit is formed on the wafer in practice, in accordance
with lithography. Step 5 subsequent to this is an assembling step,
which is called a post-process, wherein the wafer having been
processed at step 4 is formed into semiconductor chips. This step
includes an assembling (dicing and bonding) process and a packaging
(chip sealing) process. Step 6 is an inspection step wherein an
operation check, a durability check, and so on, for the
semiconductor devices produced by step 5, are carried out. With
these processes, semiconductor devices are produced, and they are
shipped (step 7).
[0087] Step 4 described above includes an oxidation process for
oxidizing the surface of a wafer, a CVD process for forming an
insulating film on the wafer surface, an electrode forming process
for forming electrodes upon the wafer by vapor deposition, an ion
implanting process for implanting ions to the wafer, a resist
process for applying a resist (photosensitive material) to the
wafer, an exposure process for printing, by exposure, the circuit
pattern of the mask on the wafer through the exposure apparatus
described above, a developing process for developing the exposed
wafer, an etching process for removing portions other than the
developed resist image, and a resist separation process for
separating the resist material remaining on the wafer after being
subjected to the etching process. By repeating these processes,
circuit patterns are superposedly formed on the wafer.
[0088] Although the foregoing description has been made with
reference to examples in which the present invention is applied to
an electron beam exposure apparatus, with appropriate modification
of the structure, the present invention can be applied to a
vacuum-ambience exposure apparatus that does not use an electron
beam, for example, an EUV exposure apparatus in which EUV (extreme
ultraviolet) light is used as exposure light. Furthermore, the
stage of the present invention can be used not only in a vacuum,
but also in a desired gas ambience.
[0089] If an electron beam is not used, since it is not necessary
to consider the problem of a change in magnetic field in that case,
there is no necessity of providing a magnetic shield to the linear
motor or the permanent magnet. Further, it is unnecessary to
magnetically isolate the base tables (bases) from each other.
[0090] On the other hand, even in an electron beam exposure
apparatus, when the X slider and/or the Y slider is made on the
basis of the confinement-type preload as described hereinbefore, it
is not necessary to magnetically isolate the base tables from each
other.
[0091] While the invention has been described with reference to the
structures disclosed herein, it is not confined to the details set
forth and this application is intended to cover such modifications
or changes as may come within the purposes of the improvements or
the scope of the following claims.
* * * * *