U.S. patent number RE48,429 [Application Number 16/003,207] was granted by the patent office on 2021-02-09 for substrate holding method, substrate holding apparatus, exposure apparatus and exposure method.
This patent grant is currently assigned to NIKON CORPORATION. The grantee listed for this patent is NIKON CORPORATION. Invention is credited to Go Ichinose.
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United States Patent |
RE48,429 |
Ichinose |
February 9, 2021 |
Substrate holding method, substrate holding apparatus, exposure
apparatus and exposure method
Abstract
A wafer holding apparatus for holding a wafer including a wafer
holder on which the wafer is placed; and a lift pin that is
configured to be lifted up and down with respect to the wafer
holder in a direction along a normal line of a placement surface of
the wafer, the lift pin includes a tip part, the tip part includes:
a bottom part that forms a suction region for sucking a rear
surface of the wafer; and a convex part that supports the rear
surface of the wafer in the suction region. When a substrate is
placed on a target position, it is possible to prevent a local
deterioration of flatness of the substrate even if the substrate is
large.
Inventors: |
Ichinose; Go (Fukaya,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NIKON CORPORATION |
Tokyo |
N/A |
JP |
|
|
Assignee: |
NIKON CORPORATION (Tokyo,
JP)
|
Family
ID: |
51933154 |
Appl.
No.: |
16/003,207 |
Filed: |
June 8, 2018 |
PCT
Filed: |
May 23, 2013 |
PCT No.: |
PCT/JP2013/064414 |
371(c)(1),(2),(4) Date: |
January 04, 2016 |
PCT
Pub. No.: |
WO2014/188572 |
PCT
Pub. Date: |
November 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
14892336 |
May 23, 2013 |
9865494 |
Jan 9, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/6875 (20130101); H01L 21/68742 (20130101); G03F
7/707 (20130101); H01L 21/6875 (20130101); G03F
7/20 (20130101); G03F 7/70733 (20130101); G03F
7/20 (20130101); G03F 7/70733 (20130101); G03F
7/707 (20130101); H01L 21/6838 (20130101); H01L
21/68742 (20130101); H01L 21/6838 (20130101) |
Current International
Class: |
G03F
7/20 (20060101); H01L 21/683 (20060101); H01L
21/687 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2010-226039 |
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Oct 2010 |
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JP |
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2012026262 |
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Mar 2012 |
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WO |
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Other References
Aug. 7, 2019 Notice of Allowance issued in U.S. Appl. No.
15/845,654. cited by applicant .
May 2, 2017 Office Action Issued in U.S. Appl. No. 14/892,336.
cited by applicant .
Sep. 5, 2017 Notice of Allowance issued in U.S. Appl. No.
14/892,336. cited by applicant .
Dec. 13, 2017 Office Action issued in European Application No. 13
885 187.8. cited by applicant .
Feb. 13, 2019 Office Action issued in U.S. Appl. No. 15/845,654.
cited by applicant .
Apr. 18, 2018 Office Action issued in Taiwan Patent Application No.
103118054. cited by applicant .
Aug. 31, 2018 Office Action issued in U.S. Appl. No. 15/845,654.
cited by applicant .
May 20, 2019 Office Action issued in Taiwanese Patent Application
No. 107139756. cited by applicant .
Oct. 25, 2018 Office Action issued in European Application No.
13885187.8. cited by applicant .
Nov. 29, 2018 Office Action issued in Chinese Patent Application
No. 201380078446.X. cited by applicant .
Dec. 8, 2016 Search Report issued in European Application No.
13885187.8. cited by applicant .
Jun. 2, 2017 Office Action issued in Chinese Application No.
201380078446.X. cited by applicant.
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Primary Examiner: Doerrler; William C
Attorney, Agent or Firm: Oliff PLC
Claims
The invention claimed is:
1. A substrate holding apparatus for holding a substrate, the
apparatus comprising: a substrate holding part on which the
substrate is placed; and a supporting member that is configured to
be lifted up and down with respect to the substrate holding part,
an end part of the supporting member including: a suction part for
sucking a rear surface of the substrate; and a supporting part that
supports the rear surface of the substrate, wherein the suction
part includes a wall part that surrounds the supporting part.
2. The substrate holding apparatus according to claim 1, wherein
the end part of the supporting member includes a plurality of
supporting parts.
3. The substrate holding apparatus according to claim 1, wherein
the wall part is formed to have a rimmed shape.
4. The substrate holding apparatus according to claim 1, wherein
the suction part includes a bottom part that is formed below an
upper end of the wall part in a lift direction of the supporting
member, the supporting part is placed at the bottom part.
5. The substrate holding apparatus according to claim 4, wherein
the supporting part is formed at the bottom part to have a
truncated conical shape.
6. The substrate holding apparatus according to claim 4, wherein a
plurality of supporting parts are placed at the bottom part
concentrically.
7. The substrate holding apparatus according to claim 1, wherein an
upper end of the supporting part is formed to have a circular
shape.
8. The substrate holding apparatus according to claim 1, wherein
the suction part includes a bottom part that is formed below an
upper end of the wall part in a lift direction of the supporting
member, an outer shape of the wall part is a circular shape having
a diameter of 5 mm to 15 mm and width of the wall part is 0.05 mm
to 0.6 mm, a shape of an upper end of the supporting part is a
circular shape having a diameter of 0.05 mm to 0.6 mm, the
supporting member includes a bar-shaped part that is coupled to the
bottom part, and a cross-sectional area of the bar-shaped part
along a surface that intersects a direction along the lift
direction is smaller than a cross-sectional area of the outer shape
of the wall part along the intersecting surface.
9. The substrate holding apparatus according to claim 1, wherein
the supporting part includes a wall-shaped member, a shape of an
end surface of the wall-shaped member includes a curved shape.
10. The substrate holding apparatus according to claim 9, wherein
the curved shape is a circular arc shape.
11. The substrate holding apparatus according to claim 1, wherein
the supporting part includes at least one ring-like wall-shaped
member.
12. The substrate holding apparatus according to claim 1, wherein a
plurality of supporting members are placed along a circumference of
a circle having predetermined diameter.
13. The substrate holding apparatus according to claim 1, wherein
the substrate has a circular shape having a diameter of
approximately 450 mm, and a plurality of supporting members are
placed at the substrate holding part along a circumference of a
circle having a diameter of 180 mm to 350 mm.
14. The substrate holding apparatus according to claim 1, wherein
the suction part sucks the substrate by using suction force that is
caused by negative pressure.
15. The substrate holding apparatus according to claim 1, wherein
the supporting member includes: a bar-shaped part that is coupled
to the end part; and a hinge part that allows the end part to
incline with respect to the bar-shaped part in a lift
direction.
16. The substrate holding apparatus according to claim 1, wherein
an opening is formed at at least one portion of the suction part
and the suction part includes a bottom part that is formed below an
upper end of the wall part in a lift direction of the supporting
member, and a passage is formed in the supporting member, a
pressure in the passage can be set to negative pressure and the
passage communicates with the opening.
17. The substrate holding apparatus according to claim 16, wherein
the supporting part is placed at the bottom part.
18. The substrate holding apparatus according to claim 16, wherein
the end part of the supporting member includes a plurality of
supporting parts, and the plurality of supporting parts are placed
around the opening concentrically.
19. The substrate holding apparatus according to claim 16, wherein
the supporting part is placed at the bottom part and includes at
least one ring-like wall-shaped member that surrounds the opening,
and a second opening is formed at a region of the bottom part
between the wall part and the wall-shaped member, the passage
communicates with the second opening.
20. An exposure apparatus that projects a pattern with exposure
light and exposes a substrate with the exposure light via the
pattern, comprising: the substrate holding apparatus according to
claim 1 for holding the substrate that is an exposed target; and a
stage that moves with the substrate holding apparatus being placed
thereon.
21. A method of manufacturing a device, the method comprising:
forming a pattern of a photosensitive layer on a substrate by using
the exposure apparatus according to claim 20; and processing the
substrate on which the pattern is formed.
22. A substrate holding method that uses the substrate holding
apparatus according to claim 1, comprising: moving the end part of
the supporting member of the substrate holding apparatus to an
upside of the substrate holding part; receiving the substrate at
the end part of the supporting member; sucking the substrate by the
suction part; lifting down the end part of the supporting member
with respect to the substrate holding part; stopping the suction of
the substrate by the suction part; and delivering the substrate
from the end part of the supporting member to the substrate holding
part.
23. A substrate holding apparatus for holding a substrate,
comprising: a substrate holding part on which the substrate is
placed; and a supporting member that is configured to be lifted up
with respect to the substrate holding part, an end part of the
supporting member including: a looped first supporting part that
supports a rear surface of the substrate; and a second supporting
part that supports the rear surface of the substrate in a region
surrounded by the first supporting part.
24. An exposure method of projecting a pattern with exposure light
and exposing a substrate with the exposure light via the pattern,
comprising: holding the substrate by using the substrate holding
method according to claim 22; and moving the substrate to an
exposure position.
25. A method of manufacturing a device, the method comprising:
forming a pattern of a photosensitive layer on a substrate by using
the exposure method according to claim 24; and processing the
substrate on which the pattern is formed.
26. A substrate holding apparatus for holding a substrate,
comprising: a substrate holding part on which the substrate is
placed; and a supporting member that is configured to be lifted up
and down with respect to the substrate holding part, an end part of
the supporting member including: a porous member that includes a
space part and allows a pressure of at least one portion of the
space part to be a negative pressure to suck a rear surface of the
substrate; and a wall part that is formed to surround at least one
portion of the porous member.
27. The substrate holding method according to claim 22, wherein the
substrate starts to be sucked to the substrate holding part when
the substrate is delivered to the substrate holding part.
28. The substrate holding apparatus according to claim 23, wherein
the end part of the supporting member includes a plurality of the
second supporting parts.
29. The substrate holding apparatus according to claim 23, wherein
the first supporting part is formed to have a rimmed shape.
30. The substrate holding apparatus according to claim 23, wherein
the end part of the supporting member includes a bottom part that
is formed below an upper end of the first supporting part in a lift
direction of the supporting member, the second supporting part is
placed at the bottom part.
31. The substrate holding apparatus according to claim 30, wherein
the second supporting part is formed at the bottom part to have a
truncated conical shape.
32. The substrate holding apparatus according to claim 30, wherein
a plurality of the second supporting parts are placed at the bottom
part concentrically.
33. The substrate holding apparatus according to claim 23, wherein
an upper end of the second supporting part is framed to have a
circular shape.
34. The substrate holding apparatus according to claim 23, wherein
the end part of the supporting member includes: a bottom part that
is formed below an upper end of the first supporting part in a lift
direction of the supporting member, an outer shape of the first
supporting part is a circular shape having a diameter of 5 mm to 15
mm and width of the first supporting part is 0.05 mm to 0.6 mm, a
shape of an upper end of the second supporting part is a circular
shape having a diameter of 0.05 mm to 0.6 mm, the supporting member
includes a bar-shaped part that is coupled to the bottom part, and
a cross-sectional area of the bar-shaped part along a surface that
intersects a direction along the lift direction is smaller than a
cross-sectional area of the outer shape of the first supporting
part along the intersecting surface.
35. The substrate holding apparatus according to claim 23, wherein
the second supporting part includes a wall-shaped member, a shape
of an end surface of the wall-shaped member includes a curved
shape.
36. Use substrate holding apparatus according to claim 35, wherein
the curved shape is a circular arc shape.
37. The substrate holding apparatus according to claim 23, wherein
the second supporting part includes at least one ring-like
wall-shaped member.
38. The substrate holding apparatus according to claim 23, wherein
a plurality of the supporting members are placed along a
circumference of a circle having predetermined diameter.
39. The substrate holding apparatus according to claim 23, wherein
the substrate has a circular shape having a diameter of
approximately 450 mm, and a plurality of the supporting members are
placed at the substrate holding part along a circumference of a
circle having a diameter of 180 mm to 350 mm.
40. The substrate holding apparatus according to claim 23, wherein
the supporting member includes: a bar-shaped part that is coupled
to the end part; and a hinge part that allows the end part to
incline with respect to the bar-shaped part in a lift
direction.
.Iadd.41. A substrate holding apparatus for holding a substrate,
the apparatus comprising: a substrate holding part on which the
substrate is placed; and a supporting member that is configured to
be lifted up and down with respect to the substrate holding part,
an end part of the supporting member including: a suction part for
sucking a rear surface of the substrate; and a supporting part that
supports the rear surface of the substrate, wherein the suction
part includes (i) a wall part that surrounds the supporting part
and (ii) a suction hole for forming a negative pressure space that
causes suction force in vacuum-sucking the substrate. .Iaddend.
Description
TECHNICAL HELD
The present invention relates to a substrate holding technology
that holds a substrate, an exposure technology using this substrate
holding technology and a device manufacturing technology using this
exposure technology.
BACKGROUND ART
In order to hold a circular semiconductor wafer (hereinafter, it is
referred to as a "wafer" simply) for example as a substrate that is
an exposed target, what we call a pin-chuck type of wafer holder in
which three lift pins (center pins) for example that is capable of
being lifted up and down (going up and down) for carrying a wafer
are disposed between many pin-shaped small protruding parts is used
by an exposure apparatus such as what we call a stepper or a
scanning stepper that is used in a photolithography process for
manufacturing an electronic device (a micro device) such as a
semiconductor element. Moreover, a SEMI standards (Semiconductor
Equipment and Materials International standards) for a diameter of
the wafer becomes larger at a rate of 1.25 times to 1.5 times per
every several years to be 125 mm, 150 mm, 200 mm and then 300
mm.
The lift pin that is placed in the conventional wafer holder is a
bar-shaped component in which a size of its tip part that contacts
with the wafer is approximately same as a size of a lower part
below the tip part, and an exhaust hole for vacuum suction using
suction force that is generated at a negative pressure region is
formed at a center portion thereof (for example, refer to a Patent
Literature 1).
CITATION LIST
Patent Literature
Patent Literature 1: U.S. Pat. No. 6,590,633
SUMMARY OF INVENTION
Technical Problem
Recently, the SEMI standards proceeds with a standardization of the
wafer having a diameter of 450 min to improve so throughput in
manufacturing the electronic device. If the wafer becomes larger in
this manner, the conventional method of simply allowing the
bar-shaped three lift pins for holding the wafer to lift and
carrying the wafer to a placement surface of the wafer holder (an
upper surface of many protruding portions) may not generate
adequate suction force to the wafer and may lead to local
deformation (distortion) of the wafer at a position of the lift
pin. If the wafer is locally distorted in this manner, residual
distortion or the like of the wafer may lead to a partial gap (a
space) between the wafer and the placement surface for the wafer.
If there is the partial gap between the wafer and the placement
surface for the wafer in this manner, flatness of an exposed region
of the wafer may deteriorate and exposure accuracy (resolution or
the like) may partially deteriorate.
An aspect of the present invention considers this condition and its
object is to suppress the local deterioration of the flatness of a
substrate in placing the substrate that is a held target at a
target position even if the substrate is large.
Solution to Problem
According to a first aspect of the present invention, there is
provided a substrate holding apparatus for holding a substrate,
including: a substrate holding part on which the substrate is
placed; and a supporting member that is configured to be lifted up
and down with respect to the substrate bolding part, an end part of
the supporting member including; a suction part that forms a
suction region for sucking a rear surface of the substrate; and a
supporting part that supports the rear surface of the substrate in
the suction region.
According to a second aspect, there is provided a substrate holding
apparatus for holding a substrate, including: a substrate holding
part on which the substrate is placed; and a supporting member that
is configured to be lifted up and down with respect to the
substrate holding part, an end part of the supporting member
including: a porous member that includes a space part and allows a
pressure of at least one portion of the space part to be a negative
pressure to suck a rear surface of the substrate; and a wall part
that is formed to surround at least one portion of the porous
member.
According to a third aspect, there is provided a substrate holding
apparatus for holding a substrate, including: a substrate holding
part on which the substrate is placed; and a supporting member that
is configured to be lifted up with respect to the substrate holding
part, an end part of the supporting member including: a ring-like
first supporting part that supports a rear surface of the
substrate; and a second supporting part that supports the rear
surface of the substrate in a region surrounded by the first
supporting part.
According to a fourth aspect, there is provided an exposure
apparatus that projects pattern with exposure light and exposes a
substrate with the exposure light via the pattern, including: the
substrate holding apparatus in the aspect of the present invention
for holding the substrate that is an exposed target; and a stage
that moves with the substrate holding apparatus being placed
thereon.
According to a fifth aspect, there is provided a substrate holding
method that uses the substrate holding apparatus in the aspect of
the present invention, including: moving the end part of the
supporting member of the substrate holding apparatus to an upside
of the substrate holding part; receiving the substrate at the end
part of the supporting member; sucking the substrate by the suction
part; lifting down the end part of the supporting member with
respect to the substrate holding part; stopping the suction of the
substrate by the suction part; and delivering the wafer from the
end part of the supporting member to the substrate holding
part.
According to a sixth aspect, there is provided an exposure method
of projecting pattern with exposure light and exposing a substrate
with the exposure light via the pattern, including: holding the
substrate by using the substrate holding method in the aspect of
the present invention; and moving the substrate to an exposure
position.
According to a seventh aspect, there is provided a method of
manufacturing device including: forming a pattern of a
photosensitive layer on a substrate by using the exposure apparatus
or the exposure method in the aspect of the present invention; and
processing the substrate on which the pattern is formed.
Advantageous Effects of Invention
According to the aspects of the present invention, since the
supporting parts that supports the rear surface of the substrate in
the suction region, the porous member that sucks the rear surface
of the substrate or the second supporting part that supports the
rear surface of the substrate in the region surrounded by the
ring-like first supporting part is placed at the end part of the
supporting member, it is possible to prevent the local deformation
of the wafer when the end part of the supporting member supports
the substrate. Thus, when the substrate as a held target is placed
on a target position, it is possible to prevent a local
deterioration of flatness of the substrate even if the substrate is
large.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram illustrating an outline of a structure of an
exposure apparatus EX in a first embodiment.
FIG. 2 is a plan view illustrating a wafer stage in FIG. 1
FIG. 3 is a block diagram illustrating a control system and the
like of the exposure apparatus in FIG. 1
FIG. 4(A) is a plan view illustrating a wafer holder apparatus in
FIG. 1, and FIG. 4(B) is a diagram illustrating a cross-sectional
view of FIG. 4(A) that is observed from the front and a control
part.
FIG. 5(A) is an enlarged plan view illustrating a lift pin of the
wafer holding apparatus, FIG. 5(B) is a vertical cross-sectional
view illustrating the lift pin in FIG. 5(A) from which one portion
is omitted, FIG. 5(C) is an enlarged plan view illustrating a lift
pin in the modified example, and FIG. 5(D) is a vertical
cross-sectional view illustrating the lift pin in another modified
example from which one portion is omitted.
FIG. 6 is a flow chart illustrating one example of an exposure
method including a method of holding the wafer.
FIG. 7(A) is a cross-sectional view illustrating a state where the
wafer is carried to the lift pin, and FIG. 7(B) is a
cross-sectional view illustrating a state where a center part of
the wafer contacts with a wafer holder.
FIG. 8(A) is an enlarged cross-sectional view illustrating one
portion of the wafer that is supported by the lid pin in the
embodiment, and
FIG. 8(B) is an enlarged cross-sectional view illustrating one
portion of the wafer that is supported by the lift pin in the
modified example.
FIG. 9 is a plan view illustrating a water holding apparatus in the
modified example.
FIG. 10(A) is an enlarged plan view illustrating a lift pin in the
modified example, FIG. 10(B) is a vertical crass-sectional view
illustrating the lift pin in FIG. 10(A) from which one portion is
omitted, FIG. 10(C) is an enlarged plan view illustrating a lift
pin in another modified example, FIG. 10(D) is a vertical
cross-sectional view illustrating the lift pin in FIG. 10(C) from
which one portion is omitted, and FIG. 10(E) is an enlarged plan
view illustrating a lift pin in additional another modified
example.
FIG. 11(A) is an enlarged plan view illustrating a lift pin in
another modified example, FIG. 11(B) is an enlarged plan view
illustrating a lift pin in additional another modified example, and
FIG. 11(C) is an enlarged plan view illustrating a lift pin in
another modified example.
FIG. 12(A) is an enlarged plan view illustrating a lift pin in a
second embodiment, and FIG. 12(B) is a vertical cross-sectional
view illustrating the lift pin in FIG. 11(A) from which one portion
is omitted.
FIG. 13 is a flowchart illustrating one example of a method for
manufacturing an electronic device.
DESCRIPTION OF EMBODIMENTS
First Embodiment
With reference to FIG. 1 to FIG. 8(B), a first embodiment of the
present invention will be explained. FIG. 1 illustrate an outline
of a structure of an exposure apparatus EX that includes a wafer
holding apparatus (a substrate holding apparatus) in the present
embodiment. The exposure apparatus EX is a scan-exposure type of
projection exposure apparatus that includes scanning stepper (a
scanner). The exposure apparatus EX includes a projection optical
system PL (a projection unit PU). Hereinafter, the embodiment will
be explained under the condition where a Z axis is set to he
parallel to an optical axis AX of the projection optical system PL,
a Y axis is set to be along a direction in which a scanning of a
reticle R relative to a wafer (a semiconductor wafer) W is
performed in a surface that is perpendicular to the Z axis, and a X
axis is set to be along a direction that is perpendicular to the Z
axis and the Y axis. Moreover, rotational directions around axes
that are parallel to the X axis, the Y axis and the Z axis
respectively are referred to as a .theta.X direction, a .theta.Y
direction and a .theta.Z direction, respectively. In the present
embodiment, a plane (a XY plane) that is perpendicular to the Z
axis is approximately parallel to a horizontal plane, and -Z
direction is a direction of an approximately vertical line.
The exposure apparatus EX includes: an illumination system ILS that
is disclosed in United States Patent Application Publication No.
2003/0025890 for example; and a reticle state RST that holds the
reticle R (a mask) that is illuminated by illumination light
(exposure light) IL for exposure (for example, ArF excimer laser
light having wavelength of 193 nm, harmonic wave of solid-state
laser (semiconductor laser or the like) or the like) from the
illumination system ILS. Moreover, the exposure apparatus EX
includes: the projection unit PU including the projection optical
system PL that exposes the wafer W (a substrate) with the
illumination light IL emitted from the reticle R; a wafer holding
apparatus 8 that holds the wafer W (refer to FIG. 3); a wafer stage
WST that moves while supporting a mechanical unit of the wafer
holding apparatus 8; and a control system and the like (see FIG.
3).
The reticle R is held on an upper surface of the reticle stage RST
by vacuum suction or the like and circuit pattern and the like is
formed on a pattern surface (a lower surface) of the reticle R. The
reticle stage RST is finely movable in the XY plane on a
not-illustrated reticle base by a reticle stage driving system 25
in FIG. 3 including a linear motor or the like for example, and is
movable at a designated scan speed in a scan direction (a Y
direction).
Position information (including positions in a X direction and the
Y direction and rotational angle in the OZ direction) of the
reticle stage RST in a moving surface is continuously detected by a
reticle interferometer 24 including a reticle interferometer via a
movable mirror 22 (or end surface of the stage that is
mirror-polished) with a resolution of 0.5 nm to 0.1 nm, for
example. The detected value of the reticle interferometer 24 is
outputted to a main control apparatus 20 including a computer in
FIG. 3. The main control apparatus 20 controls the reticle stage
driving system 25 on the basis of the detected value and thus
controls the position and speed of the reticle stage RST.
In FIG. 1, the projection unit PU that is placed below the reticle
stage RST includes: lens barrel 40; and the projection optical
system PL having a plurality of optical elements that are held to
have a predetermined positional relationship in the lens barrel 40.
A planar frame (hereinafter, it is referred to as a "measurement
frame") 16 is supported by a not-illustrated frame body via a
plurality of vibration isolating apparatuses (not illustrated), and
the projection unit PL is placed in an opening that is formed at
the measurement frame 16 via a flange part FL. The projection
optical system PL is a both-sides telecentric system and has a
predetermined projection magnification .beta. (for example, a
reduction magnification such as 1/4 times, 1/5 times or the
like).
When a illumination region IAR of the reticle R is to illuminated
with the illumination light IL from the illumination system ILS,
the illumination light IL that passes through the reticle R
generates an image of the circuit pattern in the illumination
region IAR at an exposed region IA (a region that is conjugate to
the illumination region IAR) in one shot region of the wafer W via
the projection optical system PL. The wafer W includes, as one
example, a large circular base material that includes the
semiconductor such as a silicon and has a diameter of 300 mm, 450
mm or the like and on which photoresist (photosensitive material)
having a thickness of tens of nanometer to 200 nm is coated. A
thickness of the base material having the diameter of 300 mm is 775
.mu.m, for example. A thickness of the base material having the
diameter of 450 mm is 900 .mu.m to 1100 .mu.m (for example, about
925 .mu.m) at present, for example.
Moreover, in order to allow the exposure apparatus EX to expose by
using liquid immersion method, a nozzle unit 32 that is one portion
of a local liquid immersion apparatus 38 is placed to surround a
lower end part of the lens barrel 40 holding a front end lens that
is the optical element being closest to an image plane (the wafer
W) and constituting the projection optical system PL. The nozzle
unit 32 is coupled to a liquid supply apparatus 34 and a liquid
recovery apparatus 36 (refer to FIG. 3) via a supply pipe 31A that
is for supplying liquid Lq (for example, purified water) for the
exposure and a recovery pipe 31B. Incidentally, if the liquid
immersion type of exposure apparatus is not used, the above
described local liquid immersion apparatus 38 may not be
provided.
Moreover, the exposure apparatus EX includes: a special image
measurement system (not illustrated) that measures a position of an
image of an alignment mark (a reticle mark) of the reticle R
generated by the projection optical system PL to align the reticle
R; an image processing type (PIA system) of alignment system AL,
for example, that is used to align the wafer W; an oblique incident
type of automatic focusing sensor (hereinafter, it is referred to
as a "multipoint AF system") 90 (refer to FIG. 3) for multipoint
that includes an light emitting system 90a and a light detecting
system 90b and that measures Z positions of plurality of parts of a
front surface of the wafer W; and an encoder 6 (refer to FIG. 3)
that is to measure position information of the wafer stage WST. The
special image measurement system is placed in the wafer stage WST,
for example.
The alignment system AL includes five alignment systems ALc, ALb,
ALa, Ald and ALe that are placed at approximate equal intervals
along the X direction (non-scan direction) in a region that is
placed to be away from the projection optical system PL in -Y
direction and whose length is about the diameter of the wafer W, as
illustrated in FIG. 2 as one example. The alignment system AL is
configured to simultaneously detect wafer marks at different
positions on the wafer W by using five alignment systems ALa to
ALe. Moreover, a loading position LP that corresponds to a center
position of the wafer stage WST when the wafer W is loaded and an
unloading position UP that corresponds to the center position of
the wafer stage WST when the wafer W is unloaded are respectively
set at positions that are away from the alignment systems ALa to
ALe in -Y direction and that are respectively shifted in -X
direction and +X direction. A wafer carriage robot WLD (refer to
FIG. 1) that loads the wafer W is placed near the loading position
LP and a wafer carriage robot (not illustrated) that unloads the
wafer W is placed near the unloading position UP.
Moreover, in FIG. 2, the light emitting system 90a and the light
detecting system 90b of the multipoint AF system 90 are placed
along a region that is between the alignment systems ALa to ALe and
the projection optical system PL, for example. According to this
arrangement, the wafer stage WST is driven to move the wafer W in
the Y direction to an exposure start position that is below the
projection optical system PL after the wafer W is loaded on the
wafer stage WST, and thus the multipoint AF system 90 is capable of
efficiently measuring a distribution of the Z positions of the
front surface of the wafer W and the alignment systems ALa to ALe
is capable of efficiently measuring the positions of the plurality
of wafer marks (mark or the like that is formed in each shot region
of the wafer W). A measurement result of the multipoint AF system
90 and a measurement result of the alignment system AL are
outputted to the main control apparatus 20.
In FIG. 1, the wafer stage WST is supported in a non-contact manner
by an upper surface WBa that is parallel to a XY surface of a base
plate WB via a plurality of non-illustrated vacuum pre-loadable
pneumatic static pressure bearings (air pads). The wafer stage WST
is movable in the X direction and the Y direction by a stage
driving system 18 (refer to FIG. 3) including a planar motor or two
pairs of linear motors that are orthogonal to each other, for
example. The wafer stage WST includes: a stage body 30 which is
moved in the X direction and the Y direction; a wafer table WTB
that is placed, as a Z stage, on the stage body 30; and a Z stage
driving unit that is placed in the stage body 30 and that finely
adjusts the Z position and tilt angles in the .theta.X direction
and the .theta.Y direction of the wafer table WTB relative to the
stage body 30. A wafer holder 54 that holds the wafer W by vacuum
suction or the like on a placement surface that is approximately
parallel to the XY surface is placed inside an opening placed at a
center of the wafer table WTB. The mechanical unit 50 (refer le
FIG. 3) of the wafer holding apparatus 8 is configured to include
the wafer holder 54. Incidentally, the water stage body 30 itself
may be configured to move as a six degrees of freedom stage (in X,
Y, Z, .theta.X, .theta.Y and .theta.Z. directions) by the planar
motor or the like.
Moreover, plate-shaped plate body 28 having high flatness is placed
on an upper surface of the wafer table WTB, the plate body 28 has a
surface that is subjected to the liquid-repellent process for the
liquid Lq and that is at the same level as the front surface of the
wafer W, an outer shape (a contour) of the plate body 28 is
rectangular and a circular opening that is larger than a placement
region for the wafer W is formed at a center position of the plate
body 28.
Incidentally, in what we call the liquid immersion type of exposure
apparatus including the above described local liquid immersion
apparatus 38, as illustrated in a plane view of the wafer stage WST
in FIG. 2, the plate body 28 further includes: a plate part (liquid
repellent plate) 28b that surrounds the circular opening 28a, that
has a rectangular outer shape and that has a surface being
subjected to the liquid-repellent process; and a periphery part 28c
that surrounds the plate part 28b. One pair of two-dimensional
diffraction gratings 12A and 12B and one pair of two-dimensional
diffraction gratings 12C and 12D are placed on an upper surface of
the periphery part 28c. The pair of two-dimensional diffraction
gratings 12A and 12B is elongated in the X direction to sandwich
the plate part 28b in the Y axis direction. The pair of
two-dimensional diffraction gratings 12C and 12D is elongated in
the Y direction to sandwich the plate part 28b in the X axis
direction. Each of the diffraction gratings 12A to 12D is a
reflective type of diffraction grating having a two-dimensional
grating pattern whose periodical direction is the X direction and
the Y direction and whose cycle is about 1 .mu.m.
In FIG. 1, a plurality of three-axis detection heads 14 that
irradiate the diffraction gratings 12C and 12D with laser light
(measurement light) for the measurement and that measure a relative
(three-dimensional) position relative to the diffraction grating in
the X direction, the Y direction and the Z direction are placed on
a bottom surface of the measurement frame 16 to sandwich the
projection optical system PL in the X direction (refer to FIG. 2).
Moreover, a plurality of three-axis detection heads 14 that
irradiate the diffraction gratings 12A and 12B with the laser light
for the measurement and that measure the relative three-dimensional
position relative to the diffraction grating are placed on the
bottom surface of the measurement frame 16 to sandwich the
projection optical system PL in the Y direction (refer to FIG. 2).
Moreover, there are also provided one laser source or a plurality
of laser sources (not illustrated) for supplying the laser light
(the measurement light and reference light) to the plurality of
detection heads 14.
In FIG. 2, during a period during which the wafer W is exposed via
the projection optical system PL, two detection heads 14 in a row
A1 in the Y direction irradiate the diffraction grating 12A or 12B
with the measurement light and supplies to a respective one
measurement processing unit 42 (refer to FIG. 3) detection signal
of interfering light generated by interference between the
reference light and diffracted light generated from the diffraction
gratings 12A and 12B. In parallel to this, two detection heads 14
in a row A2 in the X direction irradiate the diffraction grating
12C or 12D with the measurement light and supplies to a respective
one measurement processing unit 42 (refer to FIG. 3) detection
signal of interfering light generated by interference between the
reference light and diffracted light generated from the diffraction
gratings 12C and 12D. These measurement processing units 42 for the
detection heads 14 in the row A1 and the row A2 calculate the
relative positions (relative movement amounts) in the X direction,
the Y direction and the Z direction of the wafer stage WST (the
wafer W) relative to the measurement frame 16 (the projection
optical system PL) at a resolution of 0.5 nm to 0.1 nm for example,
and supply the calculated value to a switching unit 80A and a
switching unit 80B. The switching units 80A and 80B for the
calculated value supply to the main control apparatus 20
information of the relative positions that are supplied from the
measurement processing units 42 corresponding to the detection
heads 14 that face the diffraction gratings 12A to 12D.
The three-axis encoder 6 is constructed of the plurality of
detection heads 14 in the row A1 and the row A2, the laser source
(not illustrated), the plurality of measurement processing units
42, the switching units 80A and 80B and the diffraction gratings
12A to 12D. A detailed structure of each of this encoder and five
alignment systems are disclosed in United States Patent Application
Publication No. 2008/094593, for example. The main control
apparatus 20 obtains information relating to positions in the X
direction, the Y direction and the Z direction and the rotational
angle in the OZ direction and the like of the wafer stage WST (the
wafer W) relative to the measurement frame 16 (the projection
optical system PL) on the basis of information of the relative
positions that are supplied from the encoder 6 and moves the wafer
stage WST on the basis of this information by using the stage
driving system 18.
Incidentally, a laser interferometer that measures the
three-dimensional position of the wafer stage WST may he provided
in addition to or instead of the encoder 6 and the wafer stage WST
may be moved by using the measurement value of the laser
interferometer.
When the exposure apparatus EX performs the exposure, the reticle R
and the wafer W are aligned firstly as a basic operation. Then, the
image of the pattern of the reticle R is transferred onto one shot
region by starting to illuminate the reticle R with the
illumination light IL and performing a scanning exposure operation
that projects the image of one portion of the pattern of the
reticle R on one shot region on the front surface of the wafer W
via the projection optical system while synchronously moving
(synchronously scanning) the reticle stage RST and the wafer stage
WST in the Y direction with the projection magnitude .beta. of the
projection optical system PL being set as a speed ratio. Then, an
operation (a step movement operation) that moves the wafer W in the
X direction and the Y direction via the wafer stage WST and the
above described scanning exposure operation are repeated and thus
the image of the pattern is transferred onto all shot regions of
the wafer W by a step-and-scan method and the liquid immersion
method.
At this time, optical path lengths of the measurement light and the
diffracted light in each detection head 14 of the encoder 6 are
shorter than that of the laser interferometer. Thus, the image of
the pattern of the reticle R can be transferred onto the wafer W
highly precisely. Incidentally, in the present embodiment, the
detection heads 14 are placed at a side of the measurement frame 16
and the diffraction gratings 12A to 12D are placed at a side of the
wafer stage WST. As another structure, the diffraction gratings 12A
to 12D may be placed at the side of the measurement frame 16 and
the detection heads 14 may be placed at the side of the wafer stage
WST
Next, the structure and the operation of the wafer holding
apparatus 8 in the present embodiment will be explained in detail.
The wafer holding apparatus 8 includes: the mechanical unit 50
including the wafer holder 54 that is placed in the wafer stage
WST; and a wafer holder control system 51 that controls an
operation of the mechanical unit 50 under the control of the main
control apparatus 20.
FIG. 4(A) is a plan view illustrating the wafer holder apparatus 8
in FIG. 1. FIG. 4(B) illustrates a vertical cross-sectional view (a
cross-sectional view that is observed from the front) of a center
portion of FIG. 4(A) in the X direction and the wafer holder
control system 51. In FIG. 4(B), the Z stage 53 that is made of a
metal having a low expansion rate, for example, is supported on an
upper surface of the stage body 30 via driving units (not
illustrated) at three positions each of which uses a voice coil
motor method, for example, and allows the movement in Z direction.
The stage 53 corresponds to the wafer table WTB FIG. 1.
The Z stage 53 is a rectangular box-shaped member whose upper part
is opened. The wafer holder 54 is fixed at an inner surface 53a
that is approximately parallel to the XY plane and is in a concaved
part at center of the Z stage 53. The wafer W is held by the wafer
holder 54. The diffraction gratings 12A to 12D are fixed at an
upper surface of a side wall part of the Z stage 53 via the plate
body 28.
Moreover, a bottom part of the wafer holder 54 has a circular and
planar plate-like shape. A side wall part 54c that has a closed
ring-like shape is integrally formed on an upper surface of the
bottom part. A size of the aide wall part 54c is slightly smaller
than an edge part of a periphery of the wafer W that is a held
target. The side wall part 54c supports a periphery part of the
wafer W. If the diameter of the wafer W is 300 mm or 450 mm, the
side wall part 54c is formed so that its outer diameter is slightly
smaller than 300 mm or 450 mm. The wafer holder 54 is made of a
material having a very low thermal expansion rate, for example, as
one example. A super low expansion glass (for example, ULE (a trade
name) of Corning company), a glass-ceramic having a super low
expansion rate (for example, Zerodur (a trade name) of Schott
company), a silicon carbide (SiC) or the like can be used as this
material.
Moreover, as illustrated in FIG. 4(A), a plurality of pin-shaped
protruding parts 54b are integrally formed at positions
corresponding to grid points of two-dimensional grid having an
equilateral-triangular shape as a basic shape, for example, in a
region that is surrounded by the side wall part 54c on the bottom
part of the wafer holder 54. A distance between plural adjacent
protruding parts 54b is several mm (for example, about 3 mm), for
example. Upper surfaces of the plurality of protruding parts 54b
and the side wall part 54c are processed to have an extremely high
flatness to contact with same plane (approximately, the XY plane).
A surface including the upper surfaces of the plurality of
protruding parts 54b and the side wall part 54c corresponds to the
placement surface 54a for the wafer W. The wafer W that is the
exposed target is placed on the placement surface 54a so that a gap
between a rear surface of the wafer W and the upper surfaces of the
plurality of protruding parts 54b and the side wall part 54c is not
generated as much as possible. The wafer holder 54 can be
manufactured by performing an integral molding and then a polishing
and the like of front surfaces of the protruding parts 54b and the
like, for example. Incidentally, for the simple illustration, FIG.
4(a) illustrates the wafer W by two-dot chain line.
Moreover, a suction hole 55A is formed at an approximate center of
a region that is surrounded by the side wall part 54c on an upper
surface of the wafer holder 54. A plurality of first surrounding
suction holes 55B are formed at approximate equal angle intervals
along a first circumference C1 that surrounds the suction hole 55A.
A plurality of second surrounding suction holes 55C are formed at
approximate equal angle intervals along a second circumference C2
that surrounds the suction hole 55A at the center and that is
larger than the first circumference C1. A plurality of third
surrounding suction holes 55D are formed at approximate equal angle
intervals along a third circumference C3 that surrounds the suction
hole 55A at the center and that is larger than the second
circumference C2. The suction holes 55A to 55D are formed in a
region between the plurality of protruding parts 54b. Incidentally,
the suction holes 55A at the center or at the vicinity of the
center may not be necessarily formed.
In the present embodiment, the number of each of the first to third
surrounding suction holes 55B to 55D is preferably larger than six,
in order to suck the rear surface of the wafer W at the placement
surface 54a more uniformly and stably. However, the number of each
of the first to third surrounding suction holes 55B to 55D may be
any number. The numbers of the first to third surrounding suction
holes 55B to 55D may be different from one another. As illustrated
in FIG. 4(b), the suction holes 55A, 55B, 55C and 55D communicate
with exhaust pipes 61B1, 61B2, 61B3 and 61B4 that are placed inside
the stage body 30 via exhaust passages a1 and a2 and the like that
are independent from one another and that are inside the bottom
part of the wafer holder 54 and exhaust passages a11, a21, a31 and
a41 that are independent from one another and that are inside the Z
stage 53, respectively. The exhaust pipes 61B1 to 61B4 are coupled
to a vacuum pump 62 that is outside the wafer stage WST via an
exhaust pipe 61A having flexibility.
Valves (hereinafter, each is referred to as a "suction valve") V11,
V12, V13 and V14 that are to start the vacuum suction and valves
(hereinafter, each is referred to as a "suction stop valve") V21,
V22, V23 and V24 that are to allow the insides of the exhaust pipes
61B1 to 61B4 to communicate with air to stop the vacuum suction are
attached to the exhaust pipes 61B1, 61B2, 61B3 and 61B4,
respectively. The wafer holder control system 51 controls the
opening and the closing of each of the valves V11 to V14 and the
valves V21 to V24. The bottom part of the wafer holder 54 at which
the plurality of suction holes 55A to 55D are formed, the exhaust
pipes 61A and 61B1 to 61B4 and the vacuum pump 62 constitute a
suction unit (a second suction part) for the wafer holder 54 that
holds the wafer W at the placement surface 54a of the wafer holder
54 by the vacuum suction. This suction unit is one portion of
entire suction unit 52. In the present embodiment, the wafer holder
control system 51 is capable of controlling timings for the vacuum
suction of the wafer W and for the stop of the vacuum suction via
the suction holes 55A to 55D independently of one another.
Incidentally, the vacuum suction of the wafer W and the stop of the
vacuum suction via the suction holes 55A to 55D may he
synchronously performed at the same timing.
Moreover, a plurality of members (hereinafter, each is referred to
as a "lift pin") each of which elongates in the Z direction and can
be lifted up and down (go up and down) in the Z direction while
holding the wafer W by the vacuum suction are placed at approximate
equal angle intervals along a circumference CT between the first
circumference C1 and the second circumference C2 in the region of
the wafer holder 54 that is surrounded by the side wall part 54c,
for example. Incidentally, the lift pin 44 are placed near the
center of the wafer holder 54 and thus the lift pin 44 can be
referred to as a center pin or an up-and-down pin. At least three
lift pins 44 are preferably placed to stably support the wafer W.
However, the number of the lift pins 44 is not limited to this
number. The number of the lift pins 44 may be larger or smaller
than three, for example. Moreover, the number of the lift pins 44
may he an integral multiple of three such as six or nine, for
example. In the present embodiment, three lift pins 44 are placed
at a positions P1, P2 and P3 that are arranged at approximate equal
angle intervals along the circumference CT, respectively. FIG. 4(B)
illustrates the lift pins 44 in the positions P1 and P3.
If the diameter of the wafer W is 450 mm, a diameter of the
circumference CT along which the plurality of lift pins 44 are
placed is preferably 180 mm to 350 mm (2/3 times to 7/9 times of
the diameter of the wafer W), for example, to stably support the
wafer W by the plurality of lift pins 44. If the diameter of the
wafer W is 450 mm, the diameter of the circumference CT may be set
about 200 mm, for example.
Moreover, the diameter of the circumference CT along which the lift
pins 44 are placed may be set so that deflection amount of the
wafer W is minimized when the plurality of lift pins 44 support the
wafer W, namely, so that the wafer W is supported at positions that
correspond to what we call Bessel points. The diameter of the
circumference CT representing the positions that correspond to the
Bessel points in the case where the diameter of the wafer W is 450
mm is about 280 mm to 310 mm.
The lift pin 44 includes: an axis part 45 that has an elongated and
cylindrical (bar-like) external appearance and that is inserted in
an opening formed in the wafer holder 54 and the Z stage 53; and a
tip part 46 that is coupled to an upper end of the axis part 45 and
that faces the wafer W as the held target to support the wafer W,
for example. A suction hole (passage) 45a is formed in a center of
the axis part 45. The suction hole 45a includes a circular through
hole for forming a negative pressure space that causes suction
force (attracting force) in vacuum-sucking the wafer W. An outer
shape of the tip part 46 is a circular dish-like shape having a
diameter that is larger than a diameter of the axis part 45, for
example, and a center part of the tip part 46 communicates with the
suction hole 45a. A circular cut part (a counter boring part) 54d
(refer to FIG. 7(A)) having a size and depth that allows the tip
part 46 to be in it is formed at a position that is on the surface
of the wafer holder 54 at which the plurality of protruding part
54b are formed and that has the opening through which the axis part
45 of the lift pin 44 passes. When the wafer W is placed on the
placement surface 54a of the wafer holder 54 on the plurality of
protruding part 54b and the wafer W is exposed, the axis parts 45
of the plurality of lift pills 44 are down toward -Z direction and
one portion of the tip part 46 is in the cut part 54d of the wafer
holder 54 (in a position that is below the protruding parts 54d in
the Z direction). Thus, even if a size (thickness) of the tip part
46 in the Z direction is larger than a size (a thickness) of the
protruding part 54b in the Z direction, the tip part 46 is capable
of certainly moving to a position (cut part 54d) that is away from
the wafer W. However, if the size of the tip part 46 in the Z
direction is smaller than the size (the thickness) of the
protruding part 54b in the Z direction, the cm part 54b may not be
necessarily formed.
Moreover, in FIG. 4(B), each of the suction holes 45a in the axis
parts 45 of the plurality of lift pins 44 communicates with an
exhaust pipe 61A having flexibility via an exhaust pipe 60 having
flexibility in the stage body 30 and a fixed exhaust pipe 61C. The
exhaust pipe 61A communicates with the vacuum pump 62. The suction
hole of the lift pin 44 at the position P2 in FIG. 4(A) also
communicates with the exhaust pipe 61C. A suction valve V3 that is
to start the vacuum suction by the lift pins 44 and a suction stop
valve V4 that is to stop the vacuum suction are attached to the
exhaust pipe 61C. The wafer holder control system 51 controls the
opening and the closing of each of the valves V3 and V4. The
exhaust pipes 60 and 61C, the valves V3 and V4 and the vacuum pump
62 constitute a suction unit (a first suction part) that holds the
wafer W at the tip parts 46 of the plurality of lift pins 44 by the
vacuum suction. This suction unit is one portion of entire suction
unit 52. Incidentally, a plurality of vacuum pumps may be provided
and the first and second suction units may he coupled to the vacuum
pumps, respectively and independently from each other. In the
present embodiment, the first to third surrounding suction holes
55B to 55D are placed at positions having approximate same angle in
the circumferential direction. The plurality of lift pins 44 are
placed along the circumferential direction between the plurality of
suction holes 55B and 55C.
Moreover, the axis part 45 and the tip part 46 of the lift pin 44
are integrally formed as one example, however, the axis part 45 and
the tip part 46 may be coupled to each other by bond or the like
after the axis part 45 and the tip part 46 are formed separately.
The lift pin 44 can be formed of the material having a very low
thermal expansion rate such as the silicon carbide (SiC), a ceramic
made of the silicon carbide, the super low expansion glass or the
glass-ceramic having a super low expansion rate, for example, as
with the wafer holder 54.
As illustrated in FIG. 4(B), each of the axis parts 45 of the
plurality of lift pins 44 is lifted up and down (goes up and down)
with respect to the wafer holder 54 in the Z direction by a driving
unit 56 that is placed at a side of a bottom surface of the Z stage
53. A driving mechanism using a voice coil motor method, a rack and
pinion method or the like can be used as the driving unit 56.
Moreover, position sensors 57 such as optical linear encoders or
the like, for example, are placed. The position sensors 57 measure
positions of the axis parts 45 of the plurality of lift pins 44 in
the Z direction separately. The measured values by the position
sensors 57 for the plurality of lift pins 44 are supplied to the
wafer holder control system 51. The wafer holder control system 51
separately controls each of the positions of the plurality of lift
pins 44 in the Z direction via respective one driving unit 56 on
the basis of the measurement result of the plurality of position
sensors 57.
Moreover, if the tip part 46 of the lift pin 44 contacts with the
rear surface of the wafer W when the lift pin 44 is being lifted
up, driving force of corresponding one driving unit 56 increases
and driving current increases, for example. Thus, the wafer holder
control system 51 monitors the driving currents of the driving
units 56 and thus is capable of determining whether the lift pin 44
contacts with the wafer W on the basis of the variation of the
driving currents, for example. Incidentally, the plurality of lift
pins 44 are synchronously moved in the Z direction to be at the
same height, however, the plurality of lift pins may be lifted up
and down by one driving unit, for example. The wafer holder 54, the
plurality of lift pins 44, the driving units 56 for these and the
suction unit 52 constitute the mechanical unit 50 (refer to FIG. 3)
of the wafer holding apparatus 8.
Next, with reference to FIG. 5(A) to FIG. 5(D), the lift pin 44 of
the wafer holding apparatus 8 in the present embodiment will he
explained in detail. In the below explanation relating to the lift
pin 44, the diameter of the wafer W that is the held target is
regarded as 450 mm.
FIG. 5(A) is an enlarged plan view illustrating the lift pin 44 in
FIG. 4(B). FIG. 5(B) is a vertical cross-sectional view
illustrating the lift pin 44 in FIG. 5(A) from which one portion of
the axis part 45 is omitted.
As illustrated in FIG. 5(A) and FIG. 5(B), the tip part 46 that is
placed at the upper end of the axis part 45 of the lift pin 44
includes: a circular-disk-shaped bottom part 46a having an opening
(this is also referred to as the "suction hole 45a") communicating
with the suction hole 45a in the axis part 45; a convex and
circular wall part 46b that is placed at a periphery of the bottom
part 46a; and a plurality of convex parts 46c that are formed in a
suction region 46s on an upper surface of the bottom part 46a
surrounded by the wall part 46b and that are formed in a region
outside the suction hole 45a. The plurality of convex parts 46c
have truncated conical shapes that are same as each other, for
example. Thus, even if the convex parts 46c repeatedly contact with
the wafer, the convex parts 46c do not deform. Moreover, as
illustrated in FIG. 5(A), the plurality of convex parts 46c are
arranged along a first circumference and a second circumference
whose centers correspond to the circular suction hole 45a.
Incidentally, the plurality of convex parts 46c may be firmed along
one circumference that surrounds the suction hole 45a, and
moreover, may be formed along three or more circumferences that
surround the suction hole 45a.
Moreover, upper surfaces of the plurality of convex parts 46c and
an upper surface of the wall part 46b at the tip part 46 are
processed to have high flatness to contact with same plane (virtual
plane) Q1.
For example, an outer shape of the wall part 46b of the tip part 46
is preferably a circular shape having a diameter .phi.3 (refer to
FIG. 5(A)) of 5 mm to 15 mm and width (thickness) t1 (refer to FIG.
5(B) of the wall part 46b is preferably 0.05 mm to 0.6 mm.
Moreover, the diameter .phi.3 of the outer shape of the wall part
46b is more preferably 6 mm to 9 mm. In this case, a shape of a tip
of each of the plurality of convex parts 46c is preferably a
circular shape having a diameter .phi.4 (refer to FIG. 5(B)) of
0.05 mm to 0.6 mm. Moreover, height h1 (refer to FIG. 5(B) of each
of the wall part 46b and the convex parts 46c is preferably 20
.mu.m to 500 .mu.m.
Moreover, a cross-sectional area of the axis part 45 is set to be
smaller than a cross-sectional area of the outer shape of the wall
part 46b of the tip part 46. If the shape of the wall part 46b is
the circular shape having the diameter .phi.3 of 5 mm to 15 mm, an
outer shape of the axis part 45 is a circular shape having a
diameter .phi.2 (refer to FIG. 5(B)) of 3 mm to 5 mm and a shape of
the suction hole 45a is a circular shape having a diameter .phi.1
(refer to FIG. 5(B)) of 1 mm to 2 mm. For example, if the diameter
of the outer shape of the wall part 46b is about 8 mm, the diameter
of the outer shape of the axis part 45 may be about 5 mm.
Incidentally, the outer shape of the axis part 45 may be a
polygonal shape or the like having a cross-sectional area that is
close to that of the circle having the diameter .phi.2. Similarly,
the outer shape of the wall part 46b may be also a polygonal shape
or the like having a cross-sectional area that is close to that of
the circle having the diameter .phi.3. The lift pin 44 having this
tip part 46 can he manufactured by molding a material and then
polishing the upper surfaces of the wall part 46b and the convex
parts 46c, for example. Moreover, the wall part 46b and the convex
parts 46c at the tip part 46 of the lift pin 44 may be formed by
etching or CVD.
Moreover, in the present embodiment, since the rear surface of the
wafer W is sucked and supported by the lift pins 44, a part (a
front surface) of the tip part 46 of each lift pin 44 that contacts
with the wafer W is preferably slippery in order to prevent a local
deformation such as warp, curve or the like of the wafer W
supported by the lift pins 44. For this purpose, the front surface
of the tip part 46 of each lift pin 44 is subjected to a process
for reducing friction. The process on the front surface for
reducing the friction includes, as one example, a forming of a DLC
(Diamond Like Carbon) film.
Incidentally, the arrangement of the plurality of convex parts 46c
at the tip part 46 is not limited to the arrangement along the
circumference. As illustrated by the lift pins 44 in FIG. 5(C), the
convex parts 46 may be placed at grid points of two-dimensional
grid having an equilateral-triangular shape (a square shape may be
used) as a basic shape, for example, respectively. The plurality of
convex parts 46c may be placed randomly,
Moreover, as illustrated by convex parts 46d of the lift pin 44B in
FIG. 5(D), the shape of each of the plurality of convex parts of
the lift pin that contact with the wafer W may be a truncated
conical shape having two (three or more) steps. The height of this
convex part 46d is preferably 50 .mu.m to 500 .mu.m, for example.
Moreover, the convex part 46c may not be solid and may has a
tube-like shape (alternatively, pipe-like shape), for example. In
this case, an upper end of the convex part has a ring-like shape
surrounding the opening, for example, and the ring-like-shaped part
contacts with the rear surface of the wafer. Moreover, an inside of
the tube (the pipe) may he allowed to communicate with the opening
at the bottom part as a passage and thus the wafer may he sucked by
the tip of the convex part 46c.
Moreover, as illustrated by the lift pin 44B in FIG. 5(D), the
height of the wall part 46b at the tip part 46 may be lower by gap
.delta. than the height of the convex part 46d (a height of plane
Q1). The gap .delta. is 50 nm to several micrometer, for example.
if the height of the wall part 46b is lower than the height of the
convex part 46d, air flows through a gap between the wall part 46b
and the wafer W when the suction hole 45a sucks the air and thus
the wafer W can be stably sucked by Bernoulli effect in some cases.
Moreover, the height of not entire circumference of the wall part
46b but one portion thereof may be lower than the height of the
convex part 46d (the height of the plane Q1).
Next, with reference to a flowchart in FIG. 6, one example of a
holding method of holding the wafer by using the wafer holding
apparatus 8 and an exposure method using this holding method in the
exposure apparatus EX in the present embodiment will be explained.
The operation in this method is controlled by the main control
apparatus 20 and the wafer holder control system 51. Firstly, the
reticle R is loaded on the reticle stage RST in FIG. 1 and the
reticle R is aligned at step 102 in FIG. 6. Then, the wafer stage
WST moves to the loading position LP in FIG. 2 wider the condition
where the wafer W is not loaded, and the wafer carriage robot WLD
(a wafer loading system) in FIG. 1 carries the nova-exposed and
resist-coated wafer Won the wafer stage WST (step 104). At this
time, the wafer W that is placed at a folk type of wafer arm (not
illustrated) at a tip part of the wafer carriage robot WLD moves
above the wafer holder 54 that is fixed to the wafer stage WST. At
this state, the suction unit 52 of the wafer holding apparatus 8
stops the suction (including the suction by the lift pins 44) and
the tip parts 46 of the lift pins 44 are located below the wafer
W.
Then, as illustrated in FIG. 7(A), the wafer holder control system
51 starts the vacuum suction operation by the suction holes 45a
while synchronously lifting up (moving toward +Z direction) all
lift pins 44. After tips (the upper surface of the tip part 46) of
the lift pins 44 contact with the rear surface of the wafer W, the
lift pins 44 are slightly lifted up and then stop (step 106). At
this time, the wafer W is sucked by the tips of the lift pins 44
and the position of the wafer W relative to the lift pins 44 does
not change. At this time, the wafer W is carried from the wafer arm
to the lift pins 44. Under this condition, the wafer arm moves
toward -Y direction (step 110).
Then, all lift pins 44 are synchronously lifted down at same speed
under the condition where the wafer W is supported (step 112),
Then, as illustrated in FIG. 7(B), the suction unit 52 starts the
vacuum suction via the suction holes 55A to 55D of the wafer holder
54 when the tips (the upper surfaces of the tip parts 46) of the
lift pins 44 are close to the placement surface 54a, and the
suction of the wafer W by the lift pins 44 stops when the tips of
the lift pins 44 reach the placement surface 54a (step 114). The
lift pins 44 stop at a position at which the tip parts 46 are below
the placement surface 54a (at which the tip parts 46 are in the cut
parts 54d). Then, as illustrated in FIG. 5(B), the rear surface of
the wafer W is placed on the placement surface 54a of the wafer
holder 54 and the wafer W is carried from the lift pins 44 to the
wafer holder 54 (step 116).
At this time, the suction of the wafer by the suction hole 55A at
the center of the wafer holder 54 may be performed and then the
suction of the wafer by the surrounding suction holes 55B, 55C and
55D may be sequentially performed to gradually expand an area at
which the suction is performed. For this operation, even if the
wafer W is large substrate (450 mm wafer) such as a
circular-disk-shaped substrate having the diameter of 450 mm, for
example, the wafer W does not deform, warp, curve or the like in a
wrinkle-like manner easily and the gap is not generated partially
between the rear surface of the wafer W and the placement surface
54a (the upper surfaces of the wall part 54c and the plurality of
protruding parts 54b), and thus the wafer W is held by the wafer
holder 54 to have high flatness.
Moreover, in the present embodiment, as illustrated in FIG. 8(A),
the plurality of convex parts 46c are placed to surround the
suction hole 45a in the region (the suction region) surrounded by
the wall part 46b at the tip part 46 of each lift pin 44. Thus, the
large wafer W can be supported more stably by enlarging the outer
shape of the wall part 46b, and the suction force (the attracting
force) can be increased by enlarging an area size of the negative
region and thus the large wafer W can be held by larger suction
force stably. Moreover, even when the pressure in the suction
region becomes negative by the suction (the vacuum suction), it is
possible to prevent the wafer W to locally deform because the
convex parts 46c in the suction region support the rear surface of
the wafer W. Thus, the residual distortion of the wafer W decreases
more when the wafer W is carried from the lift pins 44 to the wafer
holder 54.
On the other hand, as illustrated by a lift pin 74 in a comparison
example in FIG. 8(B), if the convex part is not placed inside a
wall part 46Hb placed at a periphery of a bottom part 46Ha of a tip
part 46H, the vacuum suction possibly causes the local distortion
of the wafer W and this distortion may lead to the residual
distortion when the wafer W is carried to the wafer holder 54.
Then, the wafer W is aligned by the alignment system AL during a
period during which the wafer stage WST moves to allow the wafer W
to move to an underside of the projection optical system PL (an
exposing position) (step 118). The image of the pattern of the
reticle R scanning-exposes each shot region on the wafer W by
moving the wafer W on the basis of the result of the alignment
(step 120), Then, the wafer stage WST moves to the unloading
position UP, the suction unit 52 of the wafer holding apparatus 8
stops sucking the wafer W, the wafer W is lifted up by the lift
pins 44, and the wafer W is carried to the wafer carriage robot
(not illustrated) for the unload, and thus the wafer W is unloaded
(step 122). The unloaded wafer W is carried to a coater/developer
(not illustrated) and then is developed. Then, if next wafer is
exposed (step 124), the operation from the step 104 to the step
S122 is repeated.
As described above, according to the exposure method in the present
embodiment, since the outer shape of the tip part 46 of the lift
pin 44 is large, the wafer W can he supported in a state where the
wafer W is stably sucked and supported, even when the wafer W is
large. Moreover, since the plurality of convex parts 46c are placed
in the region (the suction region) surrounded by the wall part 46b
at the tip part 46 of the lift pin 44 and the local deformation of
the wafer W is prevented when the lift pins 44 suck and support the
wafer W, the high flatness of the wafer W can be maintained when
the wafer W is carried to the wafer holder 54. Therefore, high
throughput can be achieved by using the large wafer W and the image
of the pattern of the reticle R can be transferred highly precisely
by maintaining high exposure accuracy (resolution or the like) at
all surface of the wafer W.
As described above, the exposure apparatus EX in the present
embodiment includes the wafer holding apparatus 8 that holds the
wafer W (the substrate). The wafer holding apparatus 8 includes:
the wafer holder 54 (a substrate holding part) on which wafer W is
placed; and the lift pin 44 (a supporting member) that is
configured to be lifted up and down with respect to the wafer
holder 54, the tip part 46 (an end part) of the lift pin 44
includes: the bottom part 46a (a suction part) that forms the
suction region 46s for sucking the rear surface of the wafer W; and
the convex part 46c (a supporting part) that supports the rear
surface of the wafer W in the suction region 46s.
Moreover, from another point of view, the wafer holding apparatus 8
includes: the wafer holder 54 (a substrate holding part) on which
wafer W is placed; and the lift pin 44 (a supporting member) that
is configured to be lifted up and down with respect to the wafer
holder 54, the tip part 46 (an end part) of the lift pin 44
includes: the wall part 46b (a first supporting part) that supports
the rear surface of the wafer W and that is ring-like; and the
concave part 46c (a second supporting part) that supports the rear
surface of the wafer W in the suction region (a region) surrounded
by the wall part 46b.
Moreover, the method of holding the wafer W by the wafer holding
apparatus 8 includes: the step 106 in which the tip portions 46
(the end parts) of the lift pins 44 contact the wafer W and the
lift pins 44 suck the wafer W; the step 112 at which the tip
portions 46 of the lift pins 44 are lifted down in the Z direction
to a side of the wafer holder 54; and the step 114 at which the
suction unit 52 stops sucking the wafer W via the lift pins 44.
According to the present embodiment, the convex part 46c (the
supporting part or the second supporting part) is in the suction
region 46s that is surrounded by the wall part 46b of the tip part
46 when the tip part 46 (the end part) of the lift pin 44 supports
the wafer W by the suction for example, and thus the local
deformation of the wafer W at the tip part 46 can be prevented.
Therefore, even if the wafer W is large, it is possible to stably
support the wafer W by enlarging the tip part 46 of the lift pin 44
and it is possible to suppress the local deterioration of the
flatness of the wafer W when the wafer W is placed at the wafer
holder 54 (a target position).
Moreover, in the present embodiment, the lift pin 44 is movable in
the Z direction (in a direction along a normal line of the
placement surface 54a) through the placement surface 54a fur the
wafer W of the wafer holder 54, and the lift pin 44 includes: the
axis part 45 (a bar-shaped part) in which the suction hole 45a (it
is also referred to as a first opening or passage) through which
exhausts the air by a first suction part is formed; and the tip
part 46 that is placed at a tip part of the axis part 45 to support
the wafer W and the tip part 46 includes: the bottom part 46a that
is configured to face the wafer W via a predetermined gap; the
convex wall part 46b that is placed at the button part 46a so as to
surround at least one portion of a surface of the button part 46a
that is configured to thee the wafer W; and the plurality of convex
parts 46c that are placed at a region of the bottom part 46a
surrounded by the wall part 46b and that is configured to support
the wafer W, a region that is surrounded by the bottom part 46a and
the wall part 46b communicates with the suction hole (the passage)
45a of the axis part 45. Thus, the tip part of the lift pin 44 is
capable of stably holding the rear surface of the wafer W by the
vacuum suction.
Moreover, the exposure apparatus EX in the present embodiment is an
exposure apparatus that projects the pattern of the reticle R with
the illumination light IL (exposure light) for the exposure and
exposes the wafer W with the illumination light IL via the pattern,
the exposure apparatus EX includes: the wafer holding apparatus 8
for holding the wafer W that is the exposed target; and the wafer
stage WST that moves with holding the wafer holder 54 of the wafer
holding apparatus 8. Moreover, the exposure method by the exposure
apparatus EX includes: the steps 106 to 116 in which the wafer
holding apparatus 8 holds the wafer W; and the step 118 in which
the held wafer W moves to an exposure position.
According to the exposure apparatus EX or the exposure method in
the present embodiment, the high throughput can be achieved by
using the large wafer W, for example, and it is possible to stably
support the wafer W when the wafer W is carried from the wafer
carriage robot WLD to the wafer holder 54 and it is possible to
maintain the high flatness of the wafer W when the wafer W is
placed on the wafer holder 54. Thus, the high exposure accuracy can
be achieved.
Incidentally, the above described embodiment can be modified as
described below. Incidentally, when the following modifications are
explained, a part in FIG. 9 to FIG. 10(E) that corresponds to the
part in FIG. 4(A) to FIG. 5(B) has a same or similar reference
number and its detailed explanation will be omitted.
Firstly, in the above described embodiment, the wafer holding
apparatus 8 has three lift pins 44, for example. On the other
hands, as illustrated by a wafer holding apparatus 8A in the
modified example in FIG. 9, the lift pin 44 may be placed at the
center of the region of the wafer holder 54 surrounded by the side
wall 54c and the plurality of (for example, six) lift pins 44 may
be placed at equal angle intervals along the circumference CT
surrounding the center, and the wafer W may be carried by the
plurality of lift pins 44.
In this modified example, for example, a Z position of the tip of
the lift pin 44 at the center may be slightly lower than Z
positions of the tips of the plurality of lift pins 44 surrounding
it, arid the wafer W may be carried to the wafer holder 54 by
lifting down these lift pins 44 under the condition where the wafer
W is sucked to be convex toward a side of the wafer holder 54,
According to this, even if the wafer W is the wafer having the
diameter of 450 mm, it is possible to certainly prevent the
occurrence of the wrinkle or the like when the wafer W is placed on
the wafer holder 54. Moreover, a bar-shaped member that is movable
in the Z direction without the suction unit may be used instead of
the lift pin 44 at the center.
Moreover, in the above described embodiment, the convex parts 46c
having the truncated conical shapes are placed inside the wall part
46b of the tip part 46. On the other hand, as illustrated by a lift
pin 44C in the modified example in FIG. 10(A), a plurality of
convex parts 46e1 and 46e2 having curved wall-like shapes (or
circular arc shapes) may be placed in the suction region 46s
surrounded by the wall part 46b of the tip part 46 to surround the
suction hole 45 and the wafer W may be supported by their upper
surfaces (end parts). FIG. 10(B) is a vertical cross-sectional view
of the lift pin 44C in FIG. 10(A). As illustrated in FIG. 10(B),
the axis part 45 of the lift pin 44C has, at a position that is
closed to the tip part 46, an elastic hinge part 45b that is
configured to elastically incline and at which the diameter is
smaller. Moreover, the upper surfaces of the convex parts 46e1 and
46e1 and the upper surface of the wall part 46b contact with same
plane Q1, however, the height of the upper surface of the wall part
46b may be slightly lower.
Even when the lift pin 44C in the modified example, the convex
parts 46e1 and 46e2 is capable of preventing the local deformation
of the wafer W. Moreover, since the elastic hinge part 45b is
placed, the tip part 46 is capable of easily inclining (is allowed
to incline) by the elastic deformation in accordance with the wafer
W when the wafer W deforms due to its own weight. Thus, the local
deformation of the wafer W can be reduced more in some cases.
Moreover, as illustrated by a lift pin 44D in another modified
example in FIG. 10(C), a plurality of (or one may be possible)
ring-like convex parts 46f1 and 46f2 may be placed concentrically
in the region of the tip part 46 surrounded by the wall part 46b to
surround the suction hole 45a. FIG. 10(D) is a vertical
cross-sectional view of the lift pin 44D in FIG. 10(C). As
illustrated in FIG. 10(D), an opening 46g1 that communicates with
the suction hole 45a is formed at a region of the tip part 46 of
the lift pin 44D between the convex parts 46f1 and 46f2, and an
opening 46g2 that communicates with the suction hole 45a is formed
between the convex part 46f2 and the wall part 46b. According to
this, the air can be simultaneously and appropriately exhausted
from a space between the wall part 46b and the convex part 46f2, a
space between the convex parts 46f1 and 46f2 and a space inside the
convex part 46f1 when the wafer W is placed on the tip part 46, and
thus the wafer W can be stably sucked. In addition, the convex
parts 46f1 and 46f2 is capable of preventing the local deformation
of the wafer W.
Moreover, as illustrated by a lift pin 64 in additional another
modified example in FIG. 10(E), a tip part 65 having branch toward
three direction, for example, may be coupled to the upper end of
the axis part 45, the wall part 65b may be placed to surround an
outline of the tip part 65, and a plurality of convex parts 65c may
be placed in the region (suction region) surrounded by the wall
part 65b to surround the suction hole 45a. Even when this lift pin
64 is used, the wafer W can be lifted up and down without locally
deforming the wafer W.
Moreover, as illustrated by a lift pin 44C1 in the modified example
in FIG. 11(A), a plurality of convex parts 46e1 and 46e2 having
curved wall-like shapes, for example, may be placed in the region
of the tip part 46 surrounded by the wall part 46b to surround the
suction hole 45a, and at least one portion of the wall-like convex
parts 46e1 and 46e2 may be a convex part 46e3 having one end
coupled to the wall part 46b.
Moreover, as illustrated by a lift pin 44C2 in another modified
example in FIG. 11(B), a plurality of wall-like convex parts 46e4
may be radially placed in the region of the tip part 46 surrounded
by the wall part 46b to surround the suction hole 45a. In an
example in FIG. 11(B), end parts of the wall-like convex parts 46e4
are coupled to the wall part 46b, however, the end part of the
convex part 46e4 may be placed to be away from the wall part 46b.
In the lift pin 44C2, the wall part 46b is formed to have a rimmed
shape (ring-like shape) while the plurality. of convex parts 46e4
are placed radially.
Moreover, as illustrated by a lift pin 44C3 in another modified
example in FIG. 11(C), the plurality of convex parts 46c having the
truncated conical shapes may be placed in the region of the tip
part 46 surrounded by the wall part 46b, and a plurality of convex
parts 46c1 may be placed to be coupled to the wall part 46b and the
shape of the half of the convex part 46c1 is the truncated conical
shapes. According to this, the plurality of convex parts 46c and
46c1 can be placed at all grid points of the two-dimensional grid
having a regular grid in the region of the lift pin 44C3 surrounded
by the wall part 46b.
Even when the lift pins 44C1 to 44C3 in these modified examples are
used, the wafer IV can be lifted up and down without locally
deforming the wafer W
Incidentally, in the lift pins 44, 44A, 44B, 64, 44C3 and the like,
a cylindrical or prismatic (for example, a hexagonal prismatic)
convex part having a cross-sectional area larger than an area of
the upper surface of the convex parts 46c may be placed instead of
the convex part 46c having the truncated conical shape or the
truncated conical shape with steps. Moreover, the convex part 46c
may be formed to have a tube-like shape (for example, a circular
tube-like shape or a polygonal tube-like shape) instead of the
cylindrical shape or the prismatic shape.
Moreover, in the above described embodiment, the suction unit 52
holds the wafer W by the vacuum suction at the wafer holder 54 via
the suction holes 55A to 55D and the like, however, the wafer W may
be held at the wafer holder 54 by electrostatic attraction. If the
electrostatic attraction is performed, the placement surface of the
wafer holder 54 may be planar without placing the plurality of
protruding parts 54b on the upper surface of the wafer holder 54
and the planar surface may support the wafer W.
Second Embodiment
A second embodiment will be explained with reference to FIG. 12(A)
and FIG. 12(B). A basic structure of an exposure apparatus in the
present embodiment is same as that of the exposure apparatus EX in
FIG. 1. A structure of a wafer holding apparatus is also same as
that in the above described embodiment, however, a structure of the
lift pin is different. Incidentally, a part in FIG. 12(A) and FIG.
12(B) that corresponds to the part in FIG. 5(A) and FIG. 5(B) has a
same or similar reference number and its detailed explanation will
be omitted.
FIG. 12(A) is an enlarged plan view illustrating a lift pin 44E in
the present embodiment that is configured to suck and support the
wafer W. FIG. 12(B) is a vertical cross-sectional view illustrating
the lift pin 44E in FIG. 12(A) from which one portion of the axis
part 45 is omitted. In FIG. 12(A) and FIG. 12(B), the lift pin 44E
(supporting member) includes: the axis part 45 (bar-shaped member)
in which the suction hole 45a is formed; and a tip part 46A that is
coupled to the tip of the axis part 45 to support the wafer W. And,
the tip part 46A includes: a bottom part 46Aa; a circular wall-part
46Ab that is placed at a periphery of the bottom part 46Aa; a
contacting part (facing part) 48 that is fixed in a region
surrounded by the wall part 46Ab, that is made of a breathable
porous member and that is configured to face the wafer W, and the
contacting part 48 communicates with the suction hole 45a (the
first opening) in the axis part 45. The wall part 46Ab is formed to
have an outer shape that is larger than the outer shape of the axis
part 45. Moreover, a porous ceramic can be used as the contacting
part 48, for example. An upper surfaces of the wall part 46Ab and
the contacting part 48 are processed to have high flatness.
The outer shape of the wall part 46Ab of the tip part 46A is
preferably a circular shape baying a diameter of 5 mm to 15 mm,
width (thickness) of the wall part 46Ab is preferably 0.05 mm to
0.6 mm, as one example. Incidentally, the outer shape of a convex
part 46Ac may be a polygonal shape or the like. Moreover, the upper
surface of the contacting part 48 and the upper surface of the wall
part 46Ab are at the same height (on same plane Q1). Another
structure is same as that in FIG. 4(A) and FIG. 4(B).
And, when the lift pin 44E in the present embodiment is used
instead of the lift pin 44 in FIG. 4(A), the wafer holding
apparatus in the present embodiment (a substrate holding apparatus)
for holding the wafer W includes: the wafer holder 54 (a substrate
holding part) on which the wafer W is placed; and a lift pin 44E (a
supporting member) that is configured to be lifted up and down with
respect to the wafer holder 54. And, the tip part 46A (an end part)
of the lift pin 44E includes: the contacting part 48 made of the
porous member that includes a space part and that allows a pressure
of at least one portion of the space part to be a negative pressure
to suck the rear surface of the wafer; and the wall part 46Ab that
is formed to surround entire circumference (or at least one
portion) of the contacting part 48.
According to the present embodiment, when the wafer W is supported
by the tip part 46A of the lift pin 44E, the wafer W can be sucked
by sucking the air by the suction unit 52 in FIG. 4(B), for
example, via the contacting part 48 (the porous member) in the tip
part 46A. Moreover, it is possible to prevent the local deformation
of the wafer W at the tip part 46A, because a front surface of the
contacting part 48 in the region of the tip part 46A surrounded by
the wall part 46Ab is planar. Thus, even if the wafer W is large
(for example, the wafer having the diameter of 450 mm), it is
possible to stably support the wafer W by enlarging the tip part
46A of the lift pin 44E and it is possible to suppress the local
deterioration of the flatness of the wafer W when the wafer W is
placed at the placement surface 54a (the target position) of the
wafer holder 54 in FIG. 4(B).
Incidentally, in the present embodiment, a height of the wall part
46Ab of the lift pin 44E may be lower by 50 nm to several
micrometer, for example, than a height of the contacting part 48.
If the height of the wall part 46Ab may be lower than that of the
contacting part 48, the air flows through a gap between the wall
part 46Ab and the wafer W when the suction hole 45a sucks the air
and thus the wafer W can be stably sucked by Bernoulli effect in
some cases.
Moreover, even in the present embodiment, a film (for example, the
Diamond Like Carbon film) that allows easy slip may be formed on a
surface (facing surface) of the tip part 46A that contacts with the
wafer W and that is made of the silicon carbide ceramic, for
example.
Moreover, an elastic hinge part may be placed at the axis part 45
of the lift pin 44E and the tip part 46A may be configured to
elastically deform in accordance with the water W.
By the way, for example, in an apparatus that does not require a
high accuracy of the position of the wafer W in a direction along
the XY plane, it may be assumed that the wafer is placed on the
holding part and is not sucked. In this case, if a space or the
like that does not support the wafer is under the wafer, it may be
assumed that the wafer deforms by its own weight at this position
and the flatness of the wafer locally deteriorates.
Thus, in this case, in an apparatus that includes the holding part
on which the wafer is placed: and the supporting member that is
configured to be lifted up and down with respect to the holding
part, a ring-like first supporting part that supports the rear
surface of the wafer and a second supporting part that supports the
rear surface of the wafer in a region surrounded by the first
supporting part may be placed at an end part of the supporting
member. According to this, it is possible to prevent the local
deterioration of the flatness of the wafer W.
Moreover, the wafer W is circular shape having the diameter of 300
mm to 450 mm in the above described embodiment, however, the
diameter of the wafer W may be any value, and the diameter of the
wafer W may be smaller than 300 mm or larger than 450 mm.
Moreover, when an electronic device (or a micro device) such as a
semiconductor device or the like is manufactured by using the
exposure apparatus EX or the exposure method in the above described
each embodiment, the electronic device is manufactured through a
step 221 at which function and performance of the electronic device
is designed, a step 222 at which the mask (the reticle) based on
the step for the design is manufactured, a step 223 at which the
substrate (the wafer) that is the base material of the device is
manufactured and it is coated with the resist, a substrate
processing step 224 including a process of exposing the substrate
(the photosensitive substrate) with the pattern of the reticle by
using the exposure apparatus (the exposure method) in the above
described embodiment, a process of developing the exposed
substrate, a process of heating (curing) and etching the developed
substrate and the like, a device assembling step 225 (including a
process such as a dicing process, a bonding process, a packaging
process and the like), an inspection step 226 and the like.
In other words, a method of manufacturing the device includes
forming a pattern of a photosensitive layer on the substrate by
using the exposure apparatus EX or the exposure method in the above
described embodiment; and processing (developing or the like) the
substrate on which the pattern is formed. At this time, according
to the exposure apparatus EX or the exposure method in the above
described embodiment, since the substrate can be held on the wafer
stage with high flatness even if the substrate is large, it is
possible to improve the throughput in manufacturing the electronic
device and it is possible to manufacture the electronic device with
high accuracy while maintaining high accuracy of the exposure.
Incidentally, the present invention can be employed not only for
the above described scan-exposure type of projection exposure
apparatus (the scanner) but also for a step-and-repeat type of
projection exposure apparatus (a stepper or the like). Furthermore,
the present invention can be also employed for a dry-exposure type
of exposure apparatus other than the liquid immersion type of
exposure apparatus.
Moreover, the present invention is not limited to the exposure
apparatus for manufacturing the semiconductor device, and can be
widely employed for an exposure apparatus for a display apparatus
such as a liquid crystal element that is formed on a square glass
plate, a plasma display or the like and an exposure apparatus for
manufacturing various devices such as an imaging element (CCD or
the like), a micro machine, a thin film magnetic head, a DNA chip
and the like, for example. Furthermore, the present invention can
be employed for an exposure apparatus when a mask (a photomask, a
reticle or the like) on which mask pattern for various devices is
formed is manufactured by using photolithography process.
Incidentally, the present invention is not limited to the above
described embodiments, and various constitutions can be employed
without departing from the essence of the present invention.
DESCRIPTION OF REFERENCE CODES
EX1 exposure apparatus
R reticle
W wafer
WST wafer stage
8, 8A wafer holding apparatus
44 to 44E lift pin
45 axis part
45a suction hole
46 tip part
46b wall part
46c convex part
52 suction unit
54 wafer holder
56 driving unit
62 vacuum pump
* * * * *