U.S. patent application number 12/142649 was filed with the patent office on 2009-01-01 for optical integrator, illumination optical device, aligner, and method for fabricating device.
Invention is credited to Osamu Tanitsu.
Application Number | 20090002664 12/142649 |
Document ID | / |
Family ID | 38188422 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090002664 |
Kind Code |
A1 |
Tanitsu; Osamu |
January 1, 2009 |
OPTICAL INTEGRATOR, ILLUMINATION OPTICAL DEVICE, ALIGNER, AND
METHOD FOR FABRICATING DEVICE
Abstract
An optical integrator is able to keep down a light-quantity loss
in modified illumination with an illumination optical apparatus. An
optical integrator of a wavefront division type according to the
present invention has a plurality of refracting surface regions
which refract incident light, and a plurality of deflecting surface
regions provided corresponding to the plurality of refracting
surface regions and adapted for changing a traveling direction of
the incident light. The plurality of refracting surface regions
include a plurality of first refracting surface regions includes an
arcuate contour with the center projecting in a first direction,
and a plurality of second refracting surface regions includes an
arcuate contour with the center projecting in a second
direction.
Inventors: |
Tanitsu; Osamu;
(Kumagaya-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
38188422 |
Appl. No.: |
12/142649 |
Filed: |
June 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2006/322767 |
Nov 15, 2006 |
|
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12142649 |
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Current U.S.
Class: |
355/67 ;
359/618 |
Current CPC
Class: |
G02B 3/0068 20130101;
G03F 7/70108 20130101; G02B 3/0062 20130101; G02B 27/10 20130101;
G03F 7/70075 20130101 |
Class at
Publication: |
355/67 ;
359/618 |
International
Class: |
G03B 27/54 20060101
G03B027/54; G02B 27/10 20060101 G02B027/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2005 |
JP |
P2005-367647 |
Claims
1. An optical integrator of a wavefront division type comprising: a
plurality of refracting surface regions which refract incident
light, wherein the plurality of refracting surface regions comprise
a plurality of first refracting surface regions including an
arcuate contour with the center projecting in a first direction,
and a plurality of second refracting surface regions including an
arcuate contour with the center projecting in a second direction
different from the first direction.
2. The optical integrator according to claim 1, wherein the first
direction and the second direction are opposed to each other.
3. The optical integrator according to claim 2, wherein the first
refracting surface regions and the second refracting surface
regions are continuously formed.
4. The optical integrator according to claim 2, wherein the contour
of the plurality of first refracting surface regions and the
contour of the plurality of second refracting surface regions are
substantially symmetric with respect to a third direction
orthogonal to the first direction.
5. The optical integrator according to claim 2, wherein at least
either of the plurality of first refracting surface regions and the
plurality of second refracting surface regions include the contour
curved in an arcuate shape.
6. The optical integrator according to claim 5, wherein the contour
curved in the arcuate shape corresponds to a contour of a partial
region along a circumferential direction of an annular region.
7. The optical integrator according to claim 2, wherein at least
either of the plurality of first refracting surface regions and the
plurality of second refracting surface regions include a contour
bent in an arcuate shape.
8. The optical integrator according to claim 1, wherein a number of
the plurality of first refracting surface regions is substantially
equal to a number of the plurality of second refracting surface
regions.
9. The optical integrator according to claim 1, wherein the
plurality of refracting surface regions comprise a plurality of
third refracting surface regions including an arcuate contour with
the center projecting in a third direction orthogonal to the first
direction, and a plurality of fourth refracting surface regions
including an arcuate contour with the center projecting in a fourth
direction opposite to the third direction.
10. The optical integrator according to claim 9, wherein the
contour of the plurality of third refracting surface regions and
the contour of the plurality of fourth refracting surface regions
are substantially symmetric with respect to the first
direction.
11. The optical integrator according to claim 9, wherein at least
either of the plurality of third refracting surface regions and the
plurality of fourth refracting surface regions include a contour
curved in an arcuate shape.
12. The optical integrator according to claim 11, wherein the
contour curved in the arcuate shape corresponds to a contour of a
partial region along a circumferential direction of an annular
region.
13. The optical integrator according to claim 9, wherein at least
either of the plurality of third refracting surface regions and the
plurality of fourth refracting surface regions include a contour
bent in an arcuate shape.
14. The optical integrator according to claim 9, wherein a number
of the plurality of third refracting surface regions is
substantially equal to a number of the plurality of fourth
refracting surface regions.
15. The optical integrator according to claim 11, further
comprising a plurality of deflecting surface regions provided
corresponding to the plurality of refracting surface regions and
adapted for changing a traveling direction of the incident light,
wherein the plurality of deflecting surface regions further
comprise a plurality of third deflecting surface regions including
an arcuate contour with the center projecting in the third
direction corresponding to the plurality of third refracting
surface regions, and a plurality of fourth deflecting surface
regions including an arcuate contour with the center projecting in
the fourth direction corresponding to the plurality of fourth
refracting surface regions, and wherein the plurality of third
deflecting surface regions include a planar shape defined by a
third normal inclined with respect to the third direction, and the
plurality of fourth deflecting surface regions further include a
planar shape defined by a fourth normal inclined with respect to
the fourth direction and reversely to the third normal.
16. The optical integrator according to claim 1, comprising a
plurality of deflecting surface regions provided corresponding to
the plurality of refracting surface regions and adapted for
changing a traveling direction of the incident light.
17. The optical integrator according to claim 16, wherein the
plurality of refracting surface regions are formed on an entrance
side of a single optical member, and wherein the plurality of
deflecting surface regions are formed on an exit side of the single
optical member and are adapted to change the traveling direction of
the light including passed through the plurality of refracting
surface regions.
18. The optical integrator according to claim 16, wherein the
plurality of deflecting surface regions comprise a plurality of
first deflecting surface regions including an arcuate contour with
the center projecting in the first direction corresponding to the
plurality of first refracting surface regions, and a plurality of
second deflecting surface regions including an arcuate contour with
the center projecting in the second direction corresponding to the
plurality of second refracting surface regions, and wherein the
plurality of first deflecting surface regions include a planar
shape defined by a first normal inclined with respect to the first
direction, and the plurality of second deflecting surface regions
include a planar shape defined by a second normal inclined with
respect to the second direction and reversely to the first
normal.
19. The optical integrator according to claim 16, wherein the
plurality of refracting surface regions further comprise a
plurality of fifth refracting surface regions including a contour
substantially different from the arcuate contour, and wherein the
plurality of deflecting surface regions further comprise a
plurality of fifth deflecting surface regions including a contour
corresponding to the plurality of fifth refracting surface regions
and a planar shape substantially parallel to the first
direction.
20. The optical integrator according to claim 16, wherein the
plurality of deflecting surface regions are formed on an entrance
side of a single optical member and adapted to change the traveling
direction of the incident light, and wherein the plurality of
refracting surface regions are formed on an exit side of the single
optical member so as to correspond to the plurality of deflecting
surface regions.
21. The optical integrator according to claim 1, wherein each of
the plurality of refracting surface regions includes a convex shape
or a concave shape.
22. The optical integrator according to claim 1, wherein the
plurality of refracting surface regions are formed on a single
optical member, and wherein the single optical member is made of a
fluoride crystal material.
23. The optical integrator according to claim 22, said optical
integrator being formed by processing a plane-parallel plate made
of a fluoride crystal material.
24. The optical integrator according to claim 22, wherein the
plurality of refracting surface regions are formed on a single
optical member, and wherein the single optical member is made of a
fluoride crystal material of the cubic system and includes a
crystal plane {111} directed to a traveling direction of the
incident light.
25. The optical integrator according to claim 1, said optical
integrator being made of an optical material with optical
activity.
26. The optical integrator according to claim 25, wherein the
optical material is rock crystal and a crystal optic axis of the
rock crystal is matched with the traveling direction of the
incident light.
27. An optical integrator of a wavefront division type which forms
a far field pattern of a predetermined shape on the basis of
incident light, comprising: a plurality of wavefront dividing
regions which divide a wavefront of the incident light, wherein the
plurality of wavefront dividing regions comprise a plurality of
first wavefront dividing regions including an arcuate contour with
the center projecting in a first direction, and a plurality of
second wavefront dividing regions including an arcuate contour with
the center projecting in a second direction different from the
first direction.
28. The optical integrator according to claim 27, wherein the far
field pattern of the predetermined shape includes a first region of
a portion along a circumferential direction of an annular region,
and a second region of another portion along the circumferential
direction of the annular region.
29. The optical integrator according to claim 28, wherein the far
field pattern of the predetermined shape is formed by light
including a direction of polarization along the circumferential
direction of the annular region.
30. The optical integrator according to claim 27, said optical
integrator being made of an optical material with optical
activity.
31. The optical integrator according to claim 30, wherein the
optical material is rock crystal and a crystal optic axis of the
rock crystal is matched with a traveling direction of the incident
light.
32. The optical integrator according to claim 27, further
comprising a plurality of deflecting surface regions provided
corresponding to the plurality of wavefront dividing regions and
adapted for changing a traveling direction of the incident
light.
33. An optical integrator of a wavefront division type which forms
a far field pattern of a predetermined shape on the basis of
incident light, comprising: a plurality of refracting surface
regions which refract the incident light, and a plurality of
deflecting surface regions provided corresponding to the plurality
of refracting surface regions and adapted for changing a traveling
direction of the incident light, wherein the far field pattern is
formed by a beam including passed through the refracting surface
regions and the deflecting surface regions and is localized in an
annular region, and wherein a direction of polarization of the beam
to form the far field pattern is set in a circumferential direction
of the annular region.
34. A method for manufacturing an optical integrator of a wavefront
division type, comprising: preparing an optically transparent
substrate; and forming a plurality of wavefront dividing regions in
a surface of the optically transparent substrate, wherein the
forming the plurality of wavefront dividing regions comprises:
forming a plurality of first wavefront dividing regions including
an arcuate contour with the center projecting in a first direction,
and forming a plurality of second wavefront dividing regions
including an arcuate contour with the center projecting in a second
direction different from the first direction.
35. The method according to claim 34, wherein the forming the
plurality of wavefront dividing regions comprises forming a
plurality of refracting surface regions which refract incident
light.
36. The method according to claim 35, further comprising forming a
plurality of deflecting surface regions which change a traveling
direction of the incident light, so as to correspond to the
plurality of refracting surface regions, in another surface
different from the surface of the optically transparent
substrate.
37. An optical integrator manufactured by the method as set forth
in claim 34.
38. An illumination optical apparatus which illuminates an
illumination target surface on the basis of light from a light
source, comprising: the optical integrator as set forth in claim 1,
which is disposed in an optical path between the light source and
the illumination target surface.
39. The illumination optical apparatus according to claim 38,
further comprising: a second optical integrator disposed in an
optical path of a beam from the optical integrator; and a
light-guide optical system which guides light from the second
optical integrator to the illumination target surface in a
superimposed manner.
40. The illumination optical apparatus according to claim 38,
wherein the light source supplies a substantially parallel
beam.
41. An exposure apparatus comprising the illumination optical
apparatus as set forth in claim 38, which illuminates a
predetermined pattern, said exposure apparatus being adapted to
effect exposure of a photosensitive substrate with the
predetermined pattern.
42. A device manufacturing method comprising: exposing the
photosensitive substrate with the predetermined pattern, using the
exposure apparatus as set forth in claim 41; and developing the
photosensitive substrate after the exposing.
43. An illumination optical apparatus which illuminates an
illumination target surface on the basis of light from a light
source, comprising: the optical integrator as set forth in claim
27, which is disposed in an optical path between the light source
and the illumination target surface.
44. The illumination optical apparatus according to claim 43,
further comprising: a second optical integrator disposed in an
optical path of a beam from the optical integrator; and a
light-guide optical system which guides light from the second
optical integrator to the illumination target surface in a
superimposed manner.
45. The illumination optical apparatus according to claim 43,
wherein the light source supplies a substantially parallel
beam.
46. An exposure apparatus comprising the illumination optical
apparatus as set forth in claim 43, which illuminates a
predetermined pattern, said exposure apparatus being adapted to
effect exposure of a photosensitive substrate with the
predetermined pattern.
47. A device manufacturing method comprising: exposing of the
photosensitive substrate with the predetermined pattern, using the
exposure apparatus as set forth in claim 46; and developing the
photosensitive substrate after the exposing.
48. An illumination optical apparatus which illuminates an
illumination target surface on the basis of light from a light
source, comprising: the optical integrator as set forth in claim
33, which is disposed in an optical path between the light source
and the illumination target surface.
49. The illumination optical apparatus according to claim 48,
further comprising: a second optical integrator disposed in an
optical path of a beam from the optical integrator; and a
light-guide optical system which guides light from the second
optical integrator to the illumination target surface in a
superimposed manner.
50. The illumination optical apparatus according to claim 48,
wherein the light source supplies a substantially parallel
beam.
51. An exposure apparatus comprising the illumination optical
apparatus as set forth in claim 48, which illuminates a
predetermined pattern, said exposure apparatus being adapted to
effect exposure of a photosensitive substrate with the
predetermined pattern.
52. A device manufacturing method comprising: exposing of the
photosensitive substrate with the predetermined pattern, using the
exposure apparatus as set forth in claim 51; and developing the
photosensitive substrate after the exposing.
53. An illumination optical apparatus which illuminates an
illumination target surface on the basis of light from a light
source, comprising: the optical integrator as set forth in claim
37, which is disposed in an optical path between the light source
and the illumination target surface.
54. The illumination optical apparatus according to claim 53,
further comprising: a second optical integrator disposed in an
optical path of a beam from the optical integrator; and a
light-guide optical system which guides light from the second
optical integrator to the illumination target surface in a
superimposed manner.
55. The illumination optical apparatus according to claim 53,
wherein the light source supplies a substantially parallel
beam.
56. An exposure apparatus comprising the illumination optical
apparatus as set forth in claim 53, which illuminates a
predetermined pattern, said exposure apparatus being adapted to
effect exposure of a photosensitive substrate with the
predetermined pattern.
57. A device manufacturing method comprising: exposing of the
photosensitive substrate with the predetermined pattern, using the
exposure apparatus as set forth in claim 56; and developing the
photosensitive substrate after the exposing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/JP2006/322767 filed on Nov. 15, 2006, the
contents of which are incorporated herein by reference.
International Application No. PCT/JP2006/322767 claims priority to
Japanese Patent Application No. 2005-367647 filed on Dec. 21, 2005,
the contents of which are incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] One embodiment of the present invention relates to an
optical integrator, illumination optical apparatus, exposure
apparatus, and device manufacturing method. More particularly, the
present invention relates to an optical integrator suitably
applicable to illumination optical apparatus in exposure apparatus
used for manufacturing such devices as semiconductor devices,
imaging devices, liquid-crystal display devices, and thin-film
magnetic heads, for example, by lithography.
[0004] 2. Description of the Related Art
[0005] In a typical exposure apparatus of this type, a beam emitted
from a light source is guided into a fly's eye lens as an optical
integrator of a wavefront division type, to form a secondary light
source consisting of a large number of illuminants on or near a
rear focal plane of the fly's eye lens. Beams from the secondary
light source are guided through an aperture stop disposed on or
near the rear focal plane of the fly's eye lens, to be limited, and
they are then incident to a condenser lens. The aperture stop
limits the shape or size of the secondary light source to a desired
shape or size in accordance with a desired illumination condition
(exposure condition).
[0006] The beams condensed by the condenser lens illuminate a mask
with a predetermined pattern therein in a superimposed manner.
Light transmitted by the pattern of the mask travels through a
projection optical system to form an image thereof on a wafer. In
this manner, the mask pattern is projected (or transferred) onto
the wafer to effect exposure thereof. Sine the pattern formed in
the mask is a highly integrated pattern, a uniform illuminance
distribution must be achieved on the wafer in order to accurately
transfer this microscopic pattern onto the wafer.
[0007] A conventional technique proposed for improving illuminance
uniformity on the wafer is a configuration in which two fly's eye
lenses are arranged in tandem in the illumination optical apparatus
for illuminating the mask, i.e., a double fly's eye configuration.
The double fly's eye configuration described in U.S. Reissued Pat.
No. 34,634.
[0008] In recent years, attention is being directed toward modified
illumination techniques in which the aperture stop located on the
exit side of the fly's eye lens has an aperture (light transmitting
portion) set in an annular or multi-pole (dipole, quadrupole, or
the like) shape to limit the shape of the secondary light source to
the annular or multi-pole shape, thereby improving the depth of
focus and the resolving power of the projection optical system. In
the conventional technology of the double fly's eye configuration,
a rectangular illumination field is formed on the entrance surface
of the second fly's eye lens by action of the first fly's eye lens
(light-source-side fly's eye lens) and the secondary light source
of the rectangular shape is similarly formed on or near the rear
focal plane of the second fly's eye lens.
[0009] For implementing the modified illumination (annular
illumination or multi-pole illumination) in this case, the beams
from the relatively large rectangular secondary light source formed
by the second fly's eye lens are limited by the aperture stop
having the aperture of an annular shape or multi-pole shape.
Namely, the conventional technology had the problem that the
aperture stop blocked a considerable amount of the beams from the
secondary light source in the modified illumination, without
contribution to illumination (exposure), and the light-quantity
loss at the aperture stop caused reduction in illuminance on the
mask and on the wafer and, in turn, reduction in throughput as
exposure apparatus.
[0010] An object of the invention is to provide an optical
integrator capable of keeping down the light-quantity loss, for
example, in the modified illumination with illumination optical
apparatus. Another object of the present invention is to provide an
illumination optical apparatus capable of illuminating an
illumination target surface under a desired illumination condition,
using the optical integrator capable of keeping down the
light-quantity loss in the modified illumination. Still another
object of the present invention is to provide an exposure apparatus
and device manufacturing method capable of implementing good
exposure under a desired illumination condition, using the
illumination optical apparatus for illuminating a mask under a
desired illumination condition.
SUMMARY
[0011] For purposes of summarizing the invention, certain aspects,
advantages, and novel features of the invention have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the invention may be embodied or
carried out in a manner that achieves or optimizes one advantage or
group of advantages as taught herein without necessary achieving
other advantages as may be taught or suggested herein.
[0012] A first embodiment of the present invention provides an
optical integrator of a wavefront division type comprising:
[0013] a plurality of refracting surface regions which refract
incident light,
[0014] wherein the plurality of refracting surface regions comprise
a plurality of first refracting surface regions including an
arcuate contour with the center projecting in a first direction,
and a plurality of second refracting surface regions including an
arcuate contour with the center projecting in a second direction
different from the first direction.
[0015] A second embodiment of the present invention provides an
optical integrator of a wavefront division type which forms a far
field pattern of a predetermined shape on the basis of incident
light, comprising:
[0016] a plurality of wavefront dividing regions which divide a
wavefront of the incident light,
[0017] wherein the plurality of wavefront dividing regions comprise
a plurality of first wavefront dividing regions including an
arcuate contour with the center projecting in a first direction,
and a plurality of second wavefront dividing regions including an
arcuate contour with the center projecting in a second direction
different from the first direction.
[0018] A third embodiment of the present invention provides an
optical integrator of a wavefront division type which forms a far
field pattern of a predetermined shape on the basis of incident
light, comprising:
[0019] a plurality of refracting surface regions which refract the
incident light, and a plurality of deflecting surface regions
provided corresponding to the plurality of refracting surface
regions and adapted for changing a traveling direction of the
incident light,
[0020] wherein the far field pattern is formed by a beam including
passed through the refracting surface regions and the deflecting
surface regions and is localized in an annular region, and
[0021] wherein a direction of polarization of the beam to form the
far field pattern is set in a circumferential direction of the
annular region.
[0022] A fourth embodiment of the present invention provides a
method for manufacturing an optical integrator of a wavefront
division type, comprising:
[0023] preparing an optically transparent substrate; and
[0024] forming a plurality of wavefront dividing regions in a
surface of the optically transparent substrate,
[0025] wherein the forming the plurality of wavefront dividing
regions comprises:
[0026] forming a plurality of first wavefront dividing regions
including an arcuate contour with the center projecting in a first
direction, and forming a plurality of second wavefront dividing
regions including an arcuate contour with the center projecting in
a second direction different from the first direction.
[0027] A fifth embodiment of the present invention provides an
illumination optical apparatus which illuminates an illumination
target surface on the basis of light from a light source,
comprising:
[0028] the optical integrator of any one of the first aspect to the
third aspect disposed in an optical path between the light source
and the illumination target surface, or the optical integrator
manufactured by the manufacturing method of the fourth
embodiment.
[0029] A sixth embodiment of the present invention provides an
exposure apparatus comprising the illumination optical apparatus of
the fifth embodiment which illuminates a predetermined pattern, the
exposure apparatus being adapted to effect exposure of a
photosensitive substrate with the predetermined pattern. A seventh
embodiment of the present invention provides a device manufacturing
method comprising: exposing the photosensitive substrate with the
predetermined pattern, using the exposure apparatus of the sixth
embodiment; and developing the photosensitive substrate after the
exposing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] A general architecture that implements the various features
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0031] FIG. 1 is a drawing schematically showing a configuration of
an exposure apparatus according to an embodiment of the present
invention.
[0032] FIG. 2 is a perspective view schematically showing a
configuration of a cylindrical micro fly's eye lens.
[0033] FIG. 3 is a drawing schematically showing a configuration of
a micro fly's eye lens for dipole illumination according to the
embodiment, wherein (a) is a view from the light source side and
(b) a view from the mask side.
[0034] FIG. 4 includes (a) a sectional view along line A-A in FIGS.
3 (a) and (b) a sectional view along line B-B in FIG. 3 (a).
[0035] FIG. 5 is a drawing schematically showing a secondary light
source of a dipole shape formed on the back of the cylindrical
micro fly's eye lens in the embodiment.
[0036] FIG. 6 is a drawing to illustrate a configuration and action
of a micro fly's eye lens for dipole illumination in a first
modification example.
[0037] FIG. 7 is a drawing to illustrate a configuration and action
of a micro fly's eye lens for dipole illumination in a second
modification example.
[0038] FIG. 8 is a drawing to illustrate a configuration and action
of a micro fly's eye lens for dipole illumination in a third
modification example.
[0039] FIG. 9 is a view from the light source side of a micro fly's
eye lens for quadrupole illumination in a fourth modification
example.
[0040] FIG. 10 is a view from the mask side of the micro fly's eye
lens for quadrupole illumination in the fourth modification
example.
[0041] FIG. 11 is sectional views of the micro fly's eye lens for
quadrupole illumination in the fourth modification example.
[0042] FIG. 12 is a drawing schematically showing a secondary light
source of a cross-shaped quadrupole shape formed with the micro
fly's eye lens for quadrupole illumination in the fourth
modification example.
[0043] FIG. 13 is a drawing schematically showing a secondary light
source of a cross-shaped double quadrupole shape and a secondary
light source of an X-shaped double quadrupole shape.
[0044] FIG. 14 is a drawing schematically showing a configuration
of a micro fly's eye lens for tripole illumination in a fifth
modification example, wherein (a) is a view from the light source
side and (b) a view from the mask side.
[0045] FIG. 15 is a drawing schematically showing a secondary light
source of a tripole shape formed with the micro fly's eye lens for
tripole illumination in the fifth modification example and a
configuration of an aperture stop for defining a center pole.
[0046] FIG. 16 is a drawing schematically showing a configuration
of a micro fly's eye lens for pentapole illumination in a sixth
modification example, wherein (a) is a view from the light source
side and (b) a view from the mask side.
[0047] FIG. 17 is a drawing schematically showing a secondary light
source of a pentapole shape formed with the micro fly's eye lens
for pentapole illumination in the sixth modification example.
[0048] FIG. 18 is a drawing to illustrate another technique for
forming a circular surface illuminant of a center pole in the
tripole illumination or the pentapole illumination.
[0049] FIG. 19 is a view from the light source side of a micro
fly's eye lens for quadrupole illumination with a circumferential
polarization state in a seventh modification example.
[0050] FIG. 20 is a view from the mask side of the micro fly's eye
lens for quadrupole illumination with the circumferential
polarization state in the seventh modification example.
[0051] FIG. 21 is a sectional view of the micro fly's eye lens for
quadrupole illumination with the circumferential polarization state
in the seventh modification example.
[0052] FIG. 22 is a drawing schematically showing a secondary light
source of a cross-shaped quadrupole shape formed with the micro
fly's eye lens for quadrupole illumination with the circumferential
polarization state in the seventh modification example.
[0053] FIG. 23 is a flowchart to illustrate an embodiment of a
method for manufacturing the micro fly's eye lens for modified
illumination according to each of the embodiment and the
modification examples.
[0054] FIG. 24 is a flowchart of a method for obtaining
semiconductor devices as micro devices.
[0055] FIG. 25 is a flowchart of a method for obtaining a
liquid-crystal display device as a micro device.
DESCRIPTION OF THE EMBODIMENTS
[0056] Embodiments of the present invention will be described on
the basis of the accompanying drawings. FIG. 1 is a drawing
schematically showing a configuration of an exposure apparatus
according to an embodiment of the present invention. In FIG. 1, the
Z-axis is set along a direction of a normal to a wafer W being a
photosensitive substrate, the Y-axis along a direction parallel to
the plane of FIG. 1 in a surface of the wafer W, and the X-axis
along a direction normal to the plane of FIG. 1 in the surface of
the wafer W. With reference to FIG. 1, the exposure apparatus of
the present embodiment has a light source 1 for supplying exposure
light (illumination light).
[0057] The light source 1 can be, for example, an ArF excimer laser
light source for supplying light at the wavelength of 193 nm, a KrF
excimer laser light source for supplying light at the wavelength of
248 nm, or the like. Light emitted from the light source 1 is
expanded into a beam of a required sectional shape by a shaping
optical system 2, travels via an automatic axis tracking unit
2a-2c, thereafter travels through a polarization state switch 3 and
a micro fly's eye lens 4 for multi-pole illumination (dipole
illumination, quadrupole illumination, or the like), and is then
incident to an afocal lens 5. A detailed configuration and action
of the micro fly's eye lens 4 for multi-pole illumination will be
described later.
[0058] The automatic axis tracking unit is composed of at least one
path folding mirror 2a having two or more rotation axes, an angular
deviation detector 2b for detecting an angular deviation from the
optical axis of the light from the light source 1, and a driver 2c
for rotating (or inclining) the path folding mirror 2a so as to
correct the angular deviation, based on an output from the angular
deviation detector 2b, and has a function to keep the angular
deviation of light incident to the micro fly's eye lens 4 described
below, within a predetermined permissible range.
[0059] The polarization state switch 3 is provided with the
following components arranged in the order named from the light
source side: a quarter wave plate 3a a crystal optic axis of which
is arranged as rotatable around the optical axis AX and which
converts elliptically polarized light incident thereinto, into
linearly polarized light; a half wave plate 3b a crystal optic axis
of which is arranged as rotatable around the optical axis AX and
which changes a direction of polarization of the linearly polarized
light incident thereinto; a depolarizer (depolarizing element) 3c
which can be set in or off an illumination optical path. The
polarization state switch 3, in a state in which the depolarizer 3c
is set off the illumination optical path, has a function to convert
the light from the light source 1 into linearly polarized light
with a desired polarization direction and let the linearly
polarized light into the micro fly's eye lens 4, and, in a state in
which the depolarizer 3c is set in the illumination optical path,
has a function to convert the light from the light source 1 into
substantially unpolarized light and let the unpolarized light into
the micro fly's eye lens 4.
[0060] The afocal lens 5 is an afocal system (afocal optic) so set
that a front focal position of a front lens unit 5a thereof is
approximately coincident with a position of the micro fly's eye
lens 4 and that a rear focal position of a rear lens unit 5b
thereof is approximately coincident with a position of a
predetermined plane 6 indicated by a dashed line in the drawing.
The micro fly's eye lens 4 for multi-pole illumination, as
described later, functions as an optical integrator of a wavefront
division type and, when a parallel beam of a rectangular cross
section is incident thereinto, it functions to form a light
intensity distribution of a multi-pole shape (dipole shape,
quadrupole shape, or the like) on the pupil plane of the afocal
lens 5.
[0061] Therefore, a nearly parallel beam incident into the micro
fly's eye lens 4 forms a light intensity distribution of a
multi-pole shape on the pupil plane of the afocal lens 5 and is
then emitted in an angular distribution of the multi-pole shape
from the afocal lens 5. A conical axicon system 7 is disposed on or
near the pupil plane in the optical path between the front lens
unit 5a and the rear lens unit 5b of the afocal lens 5. A
configuration and action of the conical axicon system 7 will be
described later.
[0062] The beam passing through the afocal lens 5 travels through a
zoom lens 8 for variation in .sigma.-value (.sigma. value=mask-side
numerical aperture of illumination optical apparatus/mask-side
numerical aperture of projection optical system) to enter a
cylindrical micro fly's eye lens 9. The cylindrical micro fly's eye
lens 9, as shown in FIG. 2, is composed of a first fly's eye member
9a disposed on the light source side, and a second fly's eye member
9b disposed on the mask side. Cylindrical lens groups 9aa and 9ba
arrayed in the X-direction are formed each at a pitch p1 in a
light-source-side surface of the first fly's eye member 9a and in a
light-source-side surface of the second fly's eye member 9b,
respectively.
[0063] On the other hand, cylindrical lens groups 9ab and 9bb
arrayed in the Z-direction are formed each at a pitch p2 (p2>p1)
in a mask-side surface of the first fly's eye member 9a and in a
mask-side surface of the second fly's eye member 9b, respectively.
When attention is focused on refraction in the X-direction (or
refraction in the XY plane) of the cylindrical micro fly's eye lens
9, a parallel beam incident along the optical axis AX is
wavefront-divided at the pitch p1 along the X-direction by the
cylindrical lens group 9aa formed on the light source side of the
first fly's eye member 9a and is condensed by its refracting
surface, and thereafter divided wavefront sections are condensed by
refracting surfaces of the corresponding cylindrical lenses in the
cylindrical lens group 9ba formed on the light source side of the
second fly's eye member 9b, to be converged on the rear focal plane
of the cylindrical micro fly's eye lens 9.
[0064] On the other hand, when attention is focused on refraction
in the Z-direction (or refraction in the YZ plane) of the
cylindrical micro fly's eye lens 9, the parallel beam incident
along the optical axis AX is wavefront-divided at the pitch p2
along the Z-direction by the cylindrical lens group 9ab formed on
the mask side of the first fly's eye member 9a and condensed by its
refracting surface, and thereafter divided wavefront sections are
condensed by refracting surfaces of the corresponding cylindrical
lenses in the cylindrical lens group 9bb formed on the mask side of
the second fly's eye member 9b, to be converged on the rear focal
plane of the cylindrical micro fly's eye lens 9.
[0065] As described above, the cylindrical micro fly's eye lens 9
is composed of the first fly's eye member 9a and the second fly's
eye member 9b each of which has the cylindrical lens groups
disposed on both side faces, and exhibits an optical function
similar to that of a micro fly's eye lens in which a large number
of rectangular microscopic refracting surfaces having the size of
p1 in the X-direction and the size of p2 in the Z-direction are
integrally formed vertically and horizontally and densely. With the
cylindrical micro fly's eye lens 9, it is feasible to hold down
change in distortion due to variation in surface shape of
microscopic refracting surfaces, e.g., to keep down influence of a
manufacturing error of the large number of microscopic refracting
surfaces integrally formed by etching, on the illuminance
distribution.
[0066] The position of the predetermined plane 6 is located near
the front focal position of the zoom lens 8 and the entrance
surface of the cylindrical micro fly's eye lens 9 is located near
the rear focal position of the zoom lens 8. In other words, the
zoom lens 8 keeps the predetermined plane 6 and the entrance
surface of the cylindrical micro fly's eye lens 9 substantially in
the Fourier transform relation and, therefore, keeps the pupil
plane of the afocal lens 5 optically substantially conjugate with
the entrance surface of the cylindrical micro fly's eye lens 9.
[0067] Accordingly, for example, an illumination field of a
multi-pole shape centered on the optical axis AX is formed on the
entrance surface of the cylindrical micro fly's eye lens 9 as on
the pupil plane of the afocal lens 5. The overall shape of this
illumination field of a multi-pole shape similarly varies depending
upon the focal length of the zoom lens 8. The rectangular
microscopic refracting surfaces as wavefront division units in the
cylindrical micro fly's eye lens 9 are similar to a shape of an
illumination field to be formed on the mask M (or a shape of an
exposure region to be formed on the wafer W eventually).
[0068] A beam incident into the cylindrical micro fly's eye lens 9
is two-dimensionally divided and a secondary light source having a
light intensity distribution substantially identical with the
illumination field formed by the incident beam, i.e., a secondary
light source consisting of substantial surface illuminants of the
multi-pole shape centered on the optical axis AX is formed on or
near the rear focal plane of the cylindrical micro fly's eye lens 9
(therefore, on an illumination pupil). Beams from the secondary
light source formed on or near the rear focal plane of the
cylindrical micro fly's eye lens 9 are then incident to an aperture
stop 10 disposed near it.
[0069] The aperture stop 10 has an aperture (light transmitting
portion) of a multi-pole shape corresponding to the secondary light
source of the multi-pole shape formed on or near the rear focal
plane of the cylindrical micro fly's eye lens 9. The aperture stop
10 is so arranged that it can be set in or off the illumination
optical path and that it can be switched to one of other aperture
stops with an aperture different in size and shape. The aperture
stops can be switched, for example, by such a method as a
well-known turret method or slide method. The aperture stop 10 is
located at a position optically substantially conjugate with an
entrance pupil plane of a projection optical system PL described
below, to define a range of contribution of the secondary light
source to illumination.
[0070] Light beams from the secondary light source limited by the
aperture stop 10 travel through a condenser optical system 11 to
illuminate a mask blind 12 in a superimposed manner. In this
manner, a rectangular illumination field according to the shape and
focal length of the rectangular microscopic refracting surfaces as
wavefront division units in the cylindrical micro fly's eye lens 9
is formed on the mask blind 12 as an illumination field stop. The
beams passing through a rectangular aperture (light transmitting
portion) of the mask blind 12 are condensed by an imaging optical
system 13 to illuminate the mask M with a predetermined pattern
therein in a superimposed manner. Namely, the imaging optical
system 13 forms an image of the rectangular aperture of the mask
blind 12 on the mask M.
[0071] A beam transmitted by the pattern of the mask M held on a
mask stage MS travels through the projection optical system PL to
form an image of the mask pattern on the wafer (photosensitive
substrate) W held on a wafer stage WS. In this configuration, the
pattern of the mask M is sequentially transferred into each of
exposure areas on the wafer W by carrying out one-shot exposure or
scan exposure while two-dimensionally driving and controlling the
wafer stage WS and, therefore, two-dimensionally driving and
controlling the wafer W in the plane (XY plane) perpendicular to
the optical axis AX of the projection optical system PL.
[0072] Modified illuminations of various forms can be implemented,
for example, by setting a micro fly's eye lens with an appropriate
property like a micro fly's eye lens for annular illumination or a
micro fly's eye lens for circular illumination in the illumination
optical path, instead of the micro fly's eye lens 4 for multi-pole
illumination. The micro fly's eye lens can be switched to another,
for example, by such a method as the well-known turret method or
slide method.
[0073] The conical axicon system 7 is composed of a first prism
member 7a with a plane on the light source side and a refracting
surface of a concave conical shape on the mask side, and a second
prism member 7b with a plane on the mask side and a refracting
surface of a convex conical shape on the light source side, which
are arranged in order from the light source side. The refracting
surface of the concave conical shape of the first prism member 7a
and the refracting surface of the convex conical shape of the
second prism member 7b are complementarily formed so as to abut on
each other. At least one of the first prism member 7a and the
second prism member 7b is arranged as movable along the optical
axis AX to make the distance variable between the refracting
surface of the concave conical shape of the first prism member 7a
and the refracting surface of the convex conical shape of the
second prism member 7b. For easier understanding, the action of the
conical axicon system 7 and the action of the zoom lens 8 will be
described with focus on the secondary light source of an annular
shape or quadrupole shape.
[0074] In a state in which the concave conical refracting surface
of the first prism member 7a and the convex conical refracting
surface of the second prism member 7b are in contact with each
other, the conical axicon system 7 functions as a plane-parallel
plate and has no effect on the annular or quadrupolar secondary
light source formed. However, as the concave conical refracting
surface of the first prism member 7a is separated away from the
convex conical refracting surface of the second prism member 7b,
the outside diameter (inside diameter) of the annular or
quadrupolar secondary light source varies while the width of the
annular or quadrupolar secondary light source (half of a difference
between the outside diameter and the inside diameter of the annular
secondary light source; half of a difference between a diameter
(outside diameter) of a circle circumscribed to the quadrupolar
secondary light source and a diameter (inside diameter) of a circle
inscribed in the quadrupolar secondary light source) is kept
constant. Namely, the separation results in varying the annular
ratio (inside diameter/outside diameter) and the size (outside
diameter) of the annular or quadrupolar secondary light source.
[0075] The zoom lens 8 has a function to similarly enlarge or
reduce the overall shape of the annular or quadrupolar secondary
light source. For example, when the focal length of the zoom lens 8
is increased from a minimum to a predetermined value, the overall
shape of the annular or quadrupolar secondary light source is
similarly enlarged. In other words, the action of the zoom lens 8
is to vary both the width and size (outside diameter), without
change in the annular ratio of the annular or quadrupolar secondary
light source. In this manner, the annular ratio and size (outside
diameter) of the annular or quadrupolar secondary light source can
be controlled by the actions of the conical axicon system 7 and the
zoom lens 8.
[0076] FIG. 3 is a drawing schematically showing a configuration of
a micro fly's eye lens for dipole illumination according to the
present embodiment, wherein (a) is a view from the light source
side and (b) a view from the mask side. FIG. 4 (a) is a sectional
view along line A-A in FIG. 3 (a) and FIG. 4 (b) a sectional view
along line B-B in FIG. 3 (a). The micro fly's eye lens 4 for dipole
illumination in the present embodiment is constructed as a single
optical member (optically transparent member) made, for example, of
fluorite (CaF.sub.2: calcium fluoride).
[0077] The following refracting surface regions are formed on the
entrance side (light source side) of the micro fly's eye lens 4, as
shown in FIG. 3 (a): a large number of first refracting surface
regions 4a having an arcuate contour with the center projecting in
the -X-direction (first direction); and a large number of second
refracting surface regions 4b having an arcuate contour with the
center projecting in the +X-direction (second direction). Each of
the arcuate contours of the first refracting surface regions 4a and
the second refracting surface regions 4b corresponds to a contour
of a partial region along a circumferential direction of an annular
region.
[0078] More specifically, the arcuate contour of the first
refracting surface regions 4a and the second refracting surface
regions 4b, as described below with reference to FIG. 5,
corresponds to an arcuate contour defined by two parallel line
segments (corresponding to 20e, 20f in FIG. 5) separated by an
equal distance from a center of an annular region, an inside circle
of the annular region (corresponding to 20d in FIG. 5), and an
outside circle of the annular region (corresponding to 20c in FIG.
5). It is, however, noted that when the arcuate contour defined by
the two line segments and two circles is faithfully applied to the
refracting surface regions 4a, 4b, the refracting surface regions
4a, 4b cannot be closely packed along the X-direction, different
from the closely packed arrangement shown in FIG. 3 (a), because
the curvature of the inside arc is slightly different from that of
the outside arc.
[0079] For easier understanding of the configuration, it is assumed
in the present embodiment that the arcuate contour of each
refracting surface region 4a, 4b is not one faithfully
corresponding to a contour of a partial region along the
circumferential direction of the annular region, but is an arcuate
contour obtained by making the curvature of the inside arc
coincident with that of the outside arc or by making the curvature
of the outside arc coincident with that of the inside arc, from an
arcuate shape as a part of the annular region. In passing, in a
case where the faithful arcuate contour obtained from the annular
region is applied to the refracting surface regions 4a, 4b, a small
crescent region between two refracting surface regions adjacent to
each other along the X-direction is formed as a shield region
covered by a light blocking material, e.g., chromium.
[0080] Each refracting surface region 4a, 4b has a convex shape (or
concave shape) and has a function to refract incident light. In
general, the surface shape of each refracting surface region 4a, 4b
can be one of various surface shapes, for example, including a part
of a spherical surface, a part of a rotationally symmetric
aspherical surface, a part of a rotationally asymmetric aspherical
surface (toric surface or the like), and so on. For simpler
description, it is assumed in the present embodiment that each
refracting surface region 4a, 4b has, for example, a spherical
convex shape symmetric with respect to each center axis parallel to
the optical axis AX, as shown in FIGS. 4 (a) and (b).
[0081] For simpler description, it is also assumed in the present
embodiment that the spherical curvature of the first refracting
surface regions 4a is equal to that of the second refracting
surface regions 4b and that the contour of the first refracting
surface regions 4a is equal to the contour of the second refracting
surface regions 4b. Namely, the contour of the first refracting
surface regions 4a and the contour of the second refracting surface
regions 4b are symmetric with respect to the Z-direction (third
direction) and, in turn, are opposite to each other along the
X-direction. In this case, the first refracting surface regions 4a
and the second refracting surface regions 4b are continuously
formed and no border line extending in the X-direction actually
appears between the first refracting surface regions 4a and the
second refracting surface regions 4b. However, a border line is
illustrated between the first refracting surface regions 4a and the
second refracting surface regions 4b for clarity of the drawing in
FIG. 3 (a). In the configuration wherein the first refracting
surface regions 4a and the second refracting surface regions 4b are
continuously formed and wherein there is no level difference
between the first refracting surface regions 4a and the second
refracting surface regions 4b, it is feasible to reduce (or
suppress) occurrence of unwanted light that directly passes through
the micro fly's eye lens 4 (or that travels straight to be
transmitted).
[0082] On the other hand, the following deflecting surface regions
are formed on the exit side (mask side) of the micro fly's eye lens
4, as shown in FIG. 3 (b): a large number of first deflecting
surface regions 4c of an arcuate contour densely arranged along the
X-direction so as to correspond to the large number of first
refracting surface regions 4a; and a large number of second
deflecting surface regions 4d of an arcuate contour densely
arranged along the X-direction so as to correspond to the large
number of second refracting surface regions 4b. Each deflecting
surface region 4c, 4d has a planar shape inclined with respect to
the X-direction, and has a function to change a traveling direction
of light having passed through each corresponding refracting
surface region 4a, 4b.
[0083] More specifically, each first deflecting surface region 4c,
as shown in FIG. 4 (a), has a planar shape with an up slope
relative to the +X-direction, i.e., a planar shape inclined so as
to be projecting toward the mask side with respect to the
+X-direction. On the other hand, each second deflecting surface
region 4d, as shown in FIG. 4 (b), has a planar shape with an up
slope relative to the -X-direction, i.e., a planar shape inclined
so as to be projecting toward the mask side with respect to the
-X-direction. In other words, each first deflecting surface region
4c has a planar shape defined by a first normal 4ca inclined
relative to the X-direction, and each second deflecting surface
region 4d has a planar shape defined by a second normal 4da
inclined reversely to the first normal 4ca and relative to the
X-direction.
[0084] In FIG. 3 (b), for easier understanding of the
configuration, each deflecting surface region 4c, 4d is provided
with an arrow for indicating the up slope direction of the planar
shape. Namely, each first deflecting surface region 4c is provided
with an arrow directed in the +X-direction and each second
deflecting surface region 4d is provided with an arrow directed in
the -X-direction. For clarity of the drawing, FIG. 3 shows only
some of the large number of refracting surface regions 4a, 4b and
deflecting surface regions 4c, 4d forming the micro fly's eye lens
4. This also applies to FIG. 6 (a), FIG. 7 (a), FIG. 8 (a), FIG. 9,
FIG. 10, FIG. 14, FIG. 16, and FIG. 18 associated with FIG. 3.
[0085] The micro fly's eye lens 4 is formed, for example, by
physically processing a plane-parallel plate made of fluorite
(e.g., micromachining, processing with a die in a high temperature
state, or the like). At this time, the plane-parallel plate made of
fluorite belonging to the cubic system may be one with the crystal
plane {111} directed to the optical axis AX (i.e., to the traveling
direction of the incident light to each refracting surface region
4a, 4b). This crystal plane arrangement improves easiness and
stability of processing and well suppresses influence of
birefringence of fluorite. When the crystal plane arrangement is
one with the crystal plane {100} directed to the optical axis AX
(i.e., to the traveling direction of the incident light to each
refracting surface 4a), it is also feasible to well suppress the
influence of birefringence of fluorite.
[0086] In the micro fly's eye lens 4 for dipole illumination in the
present embodiment, the nearly parallel beam of the rectangular
shape incident thereto from the light source 1 is wavefront-divided
by the large number of wavefront dividing regions, i.e., the large
number of arcuate first refracting surface regions (first wavefront
dividing regions) 4a and the large number of arcuate second
refracting surface regions (second wavefront dividing regions) 4b.
A beam refracted by each first refracting surface region 4a is
guided to each corresponding first deflecting surface region 4c and
a beam refracted by each second refracting surface region 4b is
guided to each corresponding second deflecting surface region
4d.
[0087] Beams guided through the respective first refracting surface
regions 4a to the respective corresponding first deflecting surface
regions 4c and beams guided through the respective second
refracting surface regions 4b to the respective corresponding
second deflecting surface regions 4d form a light intensity
distribution of a dipole shape arranged in the X-direction and in
symmetry with respect to the optical axis AX on the pupil plane of
the afocal lens 5, in a superimposed manner. In this way, an
illumination field of a dipole shape arranged in the X-direction
and in symmetry with respect to the optical axis AX is formed on
the entrance surface of the cylindrical micro fly's eye lens 9 as
on the pupil plane of the afocal lens 5, as described above.
Furthermore, a secondary light source of a dipole shape consisting
of a pair of substantial surface illuminants 20a and 20b arranged
in the X-direction and in symmetry with respect to the optical axis
AX, as shown in FIG. 5, is formed on or near the rear focal plane
of the cylindrical micro fly's eye lens 9.
[0088] The pair of surface illuminants 20a and 20b have an arcuate
contour defined by an outside circle 20c of an annular region
centered on the optical axis AX, an inside circle 20d of the
annular region, and two parallel line segments 20e and 20f
separated by an equal distance from the optical axis AX. However,
since in the present embodiment the faithful arcuate contour
obtained from the annular region is not applied to each refracting
surface region 4a, 4b as described above, the pair of surface
illuminants 20a and 20b have the contour slightly different from
the contour of the arcuate shape defined by the two circles 20c and
20d and the two line segments 20e and 20f.
[0089] In this manner, the beams guided through the respective
first refracting surface regions 4a to the respective corresponding
first deflecting surface regions 4c are deflected by the first
deflecting surface regions 4c with the planar shape of the up slope
relative to the +X-direction to illuminate a light intensity
distribution corresponding to one arcuate surface illuminant 20a
among the secondary light source of the dipole shape, in a
superimposed manner. The beams guided through the respective second
refracting surface regions 4b to the respective corresponding
second deflecting surface regions 4d are deflected by the second
deflecting surface regions 4d with the planar shape of the up slope
relative to the -X-direction to form a light intensity distribution
corresponding to the other arcuate surface illuminant 20b among the
secondary light source of the dipole shape, in a superimposed
manner. For making the light intensity on the surface illuminant
20a substantially coincident with the light intensity on the
surface illuminant 20b, the number of first refracting surface
regions 4a may be approximately equal to the number of second
refracting surface regions 4b.
[0090] In FIG. 5, for clarity of the drawing, the rectangular
microscopic refracting surfaces as wavefront division units in the
cylindrical micro fly's eye lens 9 are indicated by dashed lines
and the number of refracting surfaces depicted is much smaller than
the actual number. This also applies to FIG. 6 (b), FIG. 7 (b),
FIG. 8 (b), FIG. 12, FIG. 13, FIG. 15 (a), and FIG. 17 associated
with FIG. 5.
[0091] As described above, the micro fly's eye lens 4 for dipole
illumination in the present embodiment is provided with the large
number of arcuate first refracting surface regions 4a and second
refracting surface regions 4b as wavefront dividing regions. It
also has the large number of arcuate first deflecting surface
regions 4c corresponding to the large number of first refracting
surface regions 4a and the large number of arcuate second
deflecting surface regions 4d corresponding to the large number of
arcuate second refracting surface regions 4b. The arcuate contour
of the first refracting surface regions 4a and the arcuate contour
of the second refracting surface regions 4b are symmetric with
respect to the Z-direction (or opposite to each other along the
X-direction), and the first refracting surface regions 4a and
second deflecting surface regions 4d have beam deflecting actions
opposite to each other along the X-direction.
[0092] Accordingly, the beams guided through the respective first
refracting surface regions 4a to the respective corresponding first
deflecting surface regions 4c and the beams guided through the
respective second refracting surface regions 4b to the respective
corresponding second deflecting surface regions 4d are deflected by
the first deflecting surface regions 4c and by the second
deflecting surface regions 4d, respectively, to form the secondary
light source of the dipole shape consisting of the pair of arcuate
surface illuminants 20a and 20b on or near the rear focal plane of
the cylindrical micro fly's eye lens 9. The first surface
illuminant 20a is formed in an arcuate first region being a portion
along the circumferential direction of the annular region centered
on the optical axis AX and the second surface illuminant 20b is
formed in an arcuate second region being a portion along the
circumferential direction of the annular region and being symmetric
with the first region with respect to the optical axis AX.
[0093] Namely, the pair of arcuate surface illuminants 20a and 20b
constituting the secondary light source of the dipole shape occupy
arcuate regions extending along the peripheral edge of the circular
illumination pupil centered on the optical axis AX and opposed to
each other on both sides of the optical axis AX, and have so-called
forms stuck to the peripheral edge of the circular illumination
pupil. In this way, the micro fly's eye lens 4 for dipole
illumination in the present embodiment has the function to form the
far field pattern of the dipole shape having the first region of a
portion along the circumferential direction of the annular region
and the second region of another portion along the circumferential
direction of the annular region, based on the incident light.
[0094] As a result, the present embodiment is able to hold down the
light-quantity loss at the aperture stop 10, while only a small
amount of beams from the secondary light source of the dipole shape
(20a, 20b) is blocked by the aperture of the dipole shape of the
aperture stop 10. Since in the present embodiment the dipole light
intensity distribution of any desired shape is formed by the micro
fly's eye lens 4 having the very small wavefront dividing surfaces
and the cylindrical micro fly's eye lens 9 having the very small
unit wavefront dividing surfaces, the secondary light source of the
dipole shape (20a, 20b) does not always have to be limited by the
aperture stop 10, according to circumstances.
[0095] Since in the present embodiment the pair of arcuate surface
illuminants 20a and 20b constituting the secondary light source of
the dipole shape have the forms stuck to the peripheral edge of the
circular illumination pupil, for example, the mask pattern having
the pitch direction in a direction optically corresponding to the
X-direction on the illumination pupil can be illuminated with a
beam of a high NA corresponding to a maximum numerical aperture
(NA) of the illumination optical apparatus and, in turn, the
pattern image can be formed with high contrast on the wafer W.
[0096] For forming the pattern image with high contrast, the
annular ratio of the dipole secondary light source (20a, 20b) (or
the diameter of the inside circle 20d/the diameter of the outside
circle 20c in FIG. 5) may be set, for example, to 8/10 or more. For
forming the pattern image with high contrast and ensuring a
sufficient superposition tolerance of beams onto the arcuate
surface illuminants 20a, 20b, an angle subtended at the optical
axis AX by the arcuate surface illuminants 20a, 20b (or an angle
between two line segments 20g and 20h connecting the optical axis
AX with the two ends of the arcuate surface illuminant 20a in FIG.
5) .theta. may be, for example, in the range of approximately
35.degree. to 40.degree..
[0097] In passing, a conventional fly's eye lens having only the
wavefront division function forms a secondary light source of a
rectangular shape (or a regular hexagonal shape or the like)
similar to the shape of the wavefront dividing surfaces of the
fly's eye lens. For this reason, for forming the pattern image with
high contrast in the conventional technology, it is necessary to
limit a beam from the secondary light source of the rectangular
shape by an aperture of a dipole shape with a large annular ratio,
which results in occurrence of a large light-quantity loss at the
aperture stop.
[0098] Since in the present embodiment the micro fly's eye lens 4
for dipole illumination is constructed as a single optical member
(optically transparent member) made of fluorite, or since the
plurality of refracting surface regions 4a, 4b and the plurality of
deflecting surface regions 4c, 4d are integrally formed in the
single optical member (optically transparent member) made of
fluorite, sufficient durability can be ensured even against light
(pulsed light) in the ultraviolet region of short wavelengths like
the ArF excimer laser light and the KrF excimer laser light. In
passing, a conventional fly's eye lens made of silica glass is
easily damaged by irradiation energy of light (particularly, pulsed
light) in the ultraviolet region of short wavelengths and cannot
ensure sufficient durability.
[0099] In this manner, the illumination optical apparatus of the
present embodiment is able to keep down the light-quantity loss at
the aperture stop 10 in the modified illumination such as the
dipole illumination and to stably illuminate the mask (illumination
target surface) M under a desired illumination condition, using the
micro fly's eye lens (optical integrator) 4 with the sufficient
durability to light in the ultraviolet region of short wavelengths.
The exposure apparatus of the present embodiment is able to stably
perform good exposure under a desired illumination condition, using
the illumination optical apparatus for stably illuminating the mask
M under a desired illumination condition.
[0100] In the above-described embodiment, the large number of first
refracting surface regions 4a of the arcuate shape with the center
projecting in the -X-direction and the large number of second
refracting surface regions 4b of the arcuate shape with the center
projecting in the +X-direction are densely arranged along the
X-direction. Namely, the projecting direction of the center of the
first refracting surface regions 4a and the projecting direction of
the center of the second refracting surface regions 4b are set
opposite to each other along one straight line. However, without
having to be limited to this, it is also possible to adopt a
configuration example in which the projecting direction of the
center of the first refracting surface regions and the projecting
direction of the center of the second refracting surface regions
are not set opposite to each other along one straight line. In this
case, however, the pair of arcuate surface illuminants constituting
the secondary light source of the dipole shape are not formed at
positions symmetric with respect to the optical axis.
[0101] In the above-described embodiment, each of the first
refracting surface regions 4a and the second refracting surface
regions 4b has the parallel type arcuate contour defined
approximately by the two parallel line segments separated by the
same distance from the center of the annular region, the inside
circle of the annular region, and the outside circle of the annular
region. However, without having to be limited to this, the same
effect as in the above embodiment is also obtained in a
modification example in which a nonparallel type arcuate contour
defined approximately by two line segments extending radially at a
predetermined angle from the center of the annular region, the
inside circle of the annular region, and the outside circle of the
annular region is applied to the first refracting surface regions
and the second refracting surface regions.
[0102] FIG. 6 is a drawing to illustrate a modification example in
which the nonparallel type arcuate contour is applied to the first
refracting surface regions and the second refracting surface
regions. With reference to FIG. 6 (a), a micro fly's eye lens 41
for dipole illumination in the first modification example has a
large number of first refracting surface regions 41a having a
nonparallel type arcuate contour with the center projecting in the
-X-direction, and a large number of second refracting surface
regions 41b having a nonparallel type arcuate contour with the
center projecting in the +X-direction. The micro fly's eye lens 41
also has a large number of nonparallel type arcuate first
deflecting surface regions 41c corresponding to the large number of
first refracting surface regions 41a, and a large number of
nonparallel type arcuate second deflecting surface regions 41d
corresponding to the large number of arcuate second refracting
surface regions 41b though they are not illustrated in the
drawing.
[0103] In this manner, the secondary light source of the dipole
shape consisting of a pair of nonparallel type arcuate surface
illuminants 21a and 21b arranged in the X-direction and in symmetry
with respect to the optical axis AX is formed as shown in FIG. 6
(b), by action of the micro fly's eye lens 41 in the first
modification example. Each of the pair of surface illuminants 21a
and 21b has an arcuate contour defined approximately by an outside
circle 21c of an annular region centered on the optical axis AX, an
inside circle 21d of the annular region, and two line segments 21e
and 21f extending radially from the optical axis AX. In the first
modification example, for permitting closely packed arrangement of
the first refracting surface regions 41a and the second refracting
surface regions 41b along the X-direction, it is also preferable to
apply a contour resulting from slight modification of the faithful
arcuate shape obtained from the annular region, to the first
refracting surface regions 41a and the second refracting surface
regions 41b.
[0104] Namely, it is preferable to apply to the first refracting
surface regions 41a and the second refracting surface regions 41b,
an arcuate contour obtained by making the curvature of the inside
arc coincident with that of the outside arc or by making the
curvature of the outside arc coincident with that of the inside
arc, from the arcuate shape defined by the two line segments
extending radially from the center of the annular region
(corresponding to 21e, 21f in FIG. 6 (b)), the inside circle of the
annular region (corresponding to 21d in FIG. 6 (b)), and the
outside circle of the annular region (corresponding to 21c in FIG.
6 (b)).
[0105] In the above-described embodiment, each of the first
refracting surface regions 4a and the second refracting surface
regions 4b has the arcuate contour corresponding to a partial
region along the circumferential direction of the annular region.
However, without having to be limited to this, it is also possible
to apply to at least either of the first refracting surface regions
and the second refracting surface regions, generally, an arcuate
contour with the center projecting in a predetermined direction,
e.g., a contour curved in an arcuate shape or a contour bent in an
arcuate shape. Specifically, the same effect as in the
aforementioned embodiment is also achieved by applying a contour
bent in a chevron shape as shown in FIG. 7 or a contour bent in a
compressed chevron shape as shown in FIG. 8, to the first
refracting surface regions and the second refracting surface
regions.
[0106] With reference to FIG. 7 (a), a micro fly's eye lens 42 for
dipole illumination in the second modification example is arranged
so that each of first refracting surface regions 42a and second
refracting surface regions 42b has a contour of a hexagonal shape
bent in a chevron shape. Accordingly, a secondary light source of a
dipole shape consisting of a pair of surface illuminants 22a and
22b of a hexagonal shape bent in a chevron shape as arranged in the
X-direction and in symmetry with respect to the optical axis AX is
formed as shown in FIG. 7 (b), by action of the micro fly's eye
lens 42 in the second modification example.
[0107] With reference to FIG. 8 (a), a micro fly's eye lens 43 for
dipole illumination in the third modification example is arranged
so that each of first refracting surface regions 43a and second
refracting surface regions 43b has a contour of an octagonal shape
bent in a compressed chevron shape. Accordingly, a secondary light
source of a dipole shape consisting of a pair of surface
illuminants 23a and 23b of an octagonal shape bent in a compressed
chevron shape as arranged in the X-direction and in symmetry with
respect to the optical axis AX is formed as shown in FIG. 8 (b), by
action of the micro fly's eye lens 43 in the third modification
example.
[0108] As described above, a variety of modification examples can
be contemplated as to the contours, the number, the arrangement,
etc. of the first refracting surface regions and the second
refracting surface regions in the micro fly's eye lens 4 for dipole
illumination in the embodiment shown in FIGS. 3 to 5.
[0109] The above description shows the examples of the dipole
illumination, but, without having to be limited to it, a micro
fly's eye lens for quadrupole illumination can also be implemented
based on a configuration similar to that in the embodiment in FIGS.
3 to 5. A micro fly's eye lens for quadrupole illumination in the
fourth modification example will be described below with reference
to FIGS. 9 to 12. With reference to FIG. 9, the following
refracting surface regions are formed on the entrance side (light
source side) of the micro fly's eye lens 44 for quadrupole
illumination in the fourth modification example: a large number of
first refracting surface regions 44a of an arcuate shape with the
center projecting in the -X-direction; a large number of second
refracting surface regions 44b of an arcuate shape with the center
projecting in the +X-direction; a large number of third refracting
surface regions 44c of an arcuate shape with the center projecting
in the +Z-direction; and a large number of fourth refracting
surface regions 44d of an arcuate shape with the center projecting
in the -Z-direction.
[0110] The first refracting surface regions 44a and the second
refracting surface regions 44b have respective configurations
corresponding to the first refracting surface regions 4a and the
second refracting surface regions 4b in the micro fly's eye lens 4
for dipole illumination shown in FIGS. 3 to 5. The third refracting
surface regions 44c have a configuration obtained by rotating the
first refracting surface regions 44a by 90.degree. clockwise in the
drawing, and the fourth refracting surface regions 44d have a
configuration obtained by rotating the second refracting surface
regions 44b by 90.degree. clockwise in the drawing. Regions 44e
hatched in the drawing are shield regions between the first and
second refracting surface regions 44a, 44b and the third and fourth
refracting surface regions 44c, 44d.
[0111] On the other hand, the following deflecting surface regions
are formed on the exit side (mask side) of the micro fly's eye lens
44 for quadrupole illumination, as shown in FIG. 10: a large number
of arcuate first deflecting surface regions 44f densely arranged
along the X-direction corresponding to the large number of first
refracting surface regions 44a; a large number of arcuate second
deflecting surface regions 44g densely arranged along the
X-direction corresponding to the large number of second refracting
surface regions 44b; a large number of arcuate third deflecting
surface regions 44h densely arranged along the Z-direction
corresponding to the large number of third refracting surface
regions 44c; a large number of arcuate fourth deflecting surface
regions 44i densely arranged along the Z-direction corresponding to
the large number of fourth refracting surface regions 44d. Regions
44j hatched in the drawing are shield regions between the first and
second deflecting surface regions 44f, 44g and the third and fourth
deflecting surface regions 44h, 44i. The exit-side shield regions
44j are provided corresponding to the entrance-side shield regions
44e.
[0112] With reference to FIGS. 10 and 11, the first deflecting
surface regions 44f have a planar shape with an up slope relative
to the +X-direction as the first deflecting surface regions 4c in
the micro fly's eye lens 4 for dipole illumination, and the second
deflecting surface regions 44g have a planar shape with an up slope
relative to the -X-direction as the second deflecting surface
regions 4d. The third deflecting surface regions 44h have a
configuration obtained by rotating the first deflecting surface
regions 44f by 90.degree. counterclockwise in the drawing, and the
fourth deflecting surface regions 44i have a configuration obtained
by rotating the second deflecting surface regions 44g by 90.degree.
counterclockwise in the drawing. Namely, the third deflecting
surface regions 44h have a planar shape with an up slope relative
to the -Z-direction and the fourth deflecting surface regions 44i
have a planar shape with an up slope relative to the
+Z-direction.
[0113] In this manner, the secondary light source is formed in a
cross-shaped quadrupole shape consisting of a pair of arcuate
surface illuminants 24a and 24b arranged in the X-direction and in
symmetry with respect to the optical axis AX and a pair of arcuate
surface illuminants 24c and 24d arranged in the Z-direction and in
symmetry with respect to the optical axis AX, as shown in FIG. 12,
by action of the micro fly's eye lens 44 in the fourth modification
example. For approximately matching light intensities on the
respective surface illuminants 24a-24d with each other, it is
preferable to make the number of first refracting surface regions
44a, the number of second refracting surface regions 44b, the
number of third refracting surface regions 44c, and the number of
fourth refracting surface regions 44d approximately equal to each
other.
[0114] In the fourth modification example, for example, a mask
pattern with the pitch direction along a direction optically
corresponding to the X-direction on the illumination pupil and a
mask pattern with the pitch direction along a direction optically
corresponding to the Z-direction on the illumination pupil can be
illuminated with beams of a high NA corresponding to the maximum
numerical aperture (NA) of the illumination optical apparatus, so
that pattern images can be formed with high contrast on the wafer
W.
[0115] It is also possible to apply other appropriate arcuate
contours as shown in the first modification example to the third
modification example, to the micro fly's eye lens 44 for quadrupole
illumination in the fourth modification example. Namely, various
modification examples can be contemplated as to the contours,
numbers, arrangement, etc. of the respective refracting surface
regions in the fourth modification example and various modification
examples can also be contemplated as to the surface shape of each
deflecting surface region and others.
[0116] Specifically, in the fourth modification example each
deflecting surface region 44f-44i has a planar shape defined by a
normal of one kind. Namely, the large number of first deflecting
surface regions 44f have their respective planar shapes parallel to
each other; the large number of second deflecting surface regions
44g have their respective planar shapes parallel to each other; the
large number of third deflecting surface regions 44h have their
respective planar shapes parallel to each other; the large number
of fourth deflecting surface regions 44i have their respective
planar shapes parallel to each other. However, without having to be
limited to this, a secondary light source of a cross-shaped double
quadrupole shape as shown in FIG. 13 (a), i.e., a secondary light
source of an octupole shape can be formed, for example, based on a
configuration in which each deflecting surface region has a shape
of planes defined by normals of two kinds.
[0117] For forming a secondary light source of an X-shaped double
quadrupole shape as shown in FIG. 13 (b), it is necessary to define
a shape of planes of each deflecting surface region by normals of
two kinds and to rotate the arrangement of the large number of
refracting surface regions and deflecting surface regions by
45.degree. around the Y-axis, in the micro fly's eye lens 44 for
quadrupole illumination in the fourth modification example. In the
embodiment of FIGS. 3 to 5 and the first modification example to
the third modification example, the planar shape of each deflecting
surface region can be defined by normals of two kinds, when
necessary, to form a secondary light source of a double dipole
shape (not shown).
[0118] Furthermore, a micro fly's eye lens for tripole illumination
can be realized based on a configuration similar to that in the
embodiment of FIGS. 3 to 5. The micro fly's eye lens for tripole
illumination according to the fifth modification example will be
described below with reference to FIGS. 14 and 15. With reference
to FIG. 14 (a), the following refracting surface regions are formed
on the entrance side (light source side) of the micro fly's eye
lens 45 for tripole illumination according to the fifth
modification example: a large number of first refracting surface
regions 45a of an arcuate shape with the center projecting in the
-X-direction; a large number of second refracting surface regions
45b of an arcuate shape with the center projecting in the
+X-direction. A large number of third refracting surface regions
45c are formed between two adjacent first refracting surface
regions 45a and between two adjacent second refracting surface
regions 45b.
[0119] The first refracting surface regions 45a and the second
refracting surface regions 45b have respective configurations
corresponding to those of the first refracting surface regions 4a
and the second refracting surface regions 4b in the micro fly's eye
lens 4 for dipole illumination shown in FIGS. 3 to 5. On the other
hand, the third refracting surface regions 45c have a contour of a
nearly rectangular shape (or an arcuate shape close to a square)
obtained by dividing each arcuate region corresponding to the first
refracting surface regions 45a and the second refracting surface
regions 45b in the Z-direction (FIG. 14 shows an example of
division into five equal parts). The third refracting surface
regions 45c have a convex shape (or concave shape) as the first
refracting surface regions 45a and the second refracting surface
regions 45b, and have a function to refract incident light.
[0120] In general, it is possible to apply various surface shapes,
for example, including a part of a spherical surface, a part of a
rotationally symmetric aspherical surface, and a part of a
rotationally asymmetric aspherical surface (e.g., a toric surface)
to the surface shape of each third refracting surface region 45c,
as in the case of the first refracting surface regions 45a and the
second refracting surface regions 45b. For simpler description, it
is assumed in the fifth modification example that each third
refracting surface region 45c has a spherical convex shape
symmetric with respect to each center axis parallel to the optical
axis AX, for example.
[0121] On the other hand, the following deflecting surface regions
are formed on the exit side (mask side) of the micro fly's eye lens
45 for tripole illumination, as shown in FIG. 14 (b): a large
number of arcuate first deflecting surface regions 45d arranged
along the X-direction corresponding to the large number of first
refracting surface regions 45a; a large number of arcuate second
deflecting surface regions 45e arranged along the X-direction
corresponding to the large number of second refracting surface
regions 45b; a large number of nearly rectangular third deflecting
surface regions 45f arranged corresponding to the large number of
third refracting surface regions 45c.
[0122] The first deflecting surface regions 45d have a planar shape
with an up slope relative to the +X-direction as the first
deflecting surface regions 4c in the micro fly's eye lens 4 for
dipole illumination, and the second deflecting surface regions 45e
have a planar shape with an up slope relative to the -X-direction
as the second deflecting surface regions 4d. On the other hand, the
third deflecting surface regions 45f have a planar shape
perpendicular to the optical axis AX (and, therefore, perpendicular
to the Y-axis) and have a function to transmit rays incident
through the corresponding third refracting surface regions 45c and
in parallel with the optical axis AX, without change in their
traveling direction.
[0123] Accordingly, nearly parallel beams guided through the
respective third refracting surface regions 45c to the respective
corresponding third deflecting surface regions 45f are not
substantially subjected to deflection in the respective third
deflecting surface regions 45f, to form a light intensity
distribution of a nearly circular shape centered on the optical
axis AX on the illumination pupil plane, in a superimposed manner.
In this way, a secondary light source of a tripole shape is formed
as one consisting of a pair of arcuate surface illuminants 25a and
25b arranged in the X-direction and in symmetry with respect to the
optical axis AX, and a surface illuminant 25c of a nearly circular
shape centered on the optical axis AX, as shown in FIG. 15 (a), by
action of the micro fly's eye lens 45 in the fifth modification
example.
[0124] For obtaining an accurate light intensity distribution of a
circular shape centered on the optical axis AX on the illumination
pupil plane, it is preferable to limit light reaching the surface
illuminant 25c of the center pole or light from the surface
illuminant 25c, by a circular aperture (light transmitting portion)
of an aperture member 10aa for the center pole in an aperture stop
10a shown in FIG. 15 (b). The aperture stop 10a is provided with an
outside aperture member 10ab having a circular aperture defined by
a circle circumscribed to the pair of arcuate surface illuminants
25a and 25b. The aperture member 10aa for the center pole is held
by four chord members 10ac extending radially from the outside
aperture member 10ab to the inside.
[0125] Similarly, a micro fly's eye lens for pentapole illumination
can be realized based on a configuration similar to that in the
fourth modification example of FIGS. 9 to 12. The micro fly's eye
lens for pentapole illumination according to the sixth modification
example will be described below with reference to FIGS. 16 and 17.
With reference to FIG. 16 (a), the following refracting surface
regions are formed on the entrance side (light source side) of the
micro fly's eye lens 46 for pentapole illumination in the sixth
modification example: a large number of first refracting surface
regions 46a of an arcuate shape with the center projecting in the
-X-direction; a large number of second refracting surface regions
46b of an arcuate shape with the center projecting in the
+X-direction; a large number of third refracting surface regions
46c of an arcuate shape with the center projecting in the
+Z-direction; a large number of fourth refracting surface regions
46d of an arcuate shape with the center projecting in the
-Z-direction. Furthermore, a large number of fifth refracting
surface regions 46e are formed between two adjacent first
refracting surface regions 46a, between two adjacent second
refracting surface regions 46b, between two adjacent third
refracting surface regions 46c, and between two adjacent fourth
refracting surface regions 46d.
[0126] The first refracting surface regions 46a to the fourth
refracting surface regions 46d have respective configurations
corresponding to the first refracting surface regions 44a to the
fourth refracting surface regions 44d in the micro fly's eye lens
44 for quadrupole illumination shown in FIGS. 9 to 12. On the other
hand, the fifth refracting surface regions 46e have a contour of a
nearly rectangular shape (or an arcuate shape close to a square)
obtained by dividing an arcuate region corresponding to the first
refracting surface regions 46a and the second refracting surface
regions 46b in the Z-direction (FIG. 16 shows an example of
division into five equal parts), or a contour of a nearly
rectangular shape (or an arcuate shape close to a square) obtained
by dividing an arcuate region corresponding to the third refracting
surface regions 46c and the fourth refracting surface regions 46d
in the X-direction (FIG. 16 shows an example of division into five
equal parts).
[0127] Namely, the fifth refracting surface regions 46e formed
between two adjacent first refracting surface regions 46a and
between two adjacent second refracting surface regions 46b have a
configuration corresponding to that of the third refracting surface
regions 45c in the fifth modification example. The fifth refracting
surface regions 46e formed between two adjacent third refracting
surface regions 46c and between two adjacent fourth refracting
surface regions 46d have a configuration obtained by rotating the
third refracting surface regions 45c in the fifth modification
example by 90.degree. in the drawing. The fifth refracting surface
regions 46e have a convex shape (or concave shape) as the third
refracting surface regions 45c in the fifth modification example,
and have a function to refract incident light. Shield regions 46f
are provided between the first and second refracting surface
regions 46a, 46b and the third and fourth refracting surface
regions 46c, 46d.
[0128] On the other hand, the following regions are formed on the
exit side (mask side) of the micro fly's eye lens 46 for pentapole
illumination, as shown in FIG. 16 (b): a large number of arcuate
first deflecting surface regions 46g arranged along the X-direction
corresponding to the large number of first refracting surface
regions 46a; a large number of arcuate second deflecting surface
regions 46h arranged along the X-direction corresponding to the
large number of second refracting surface regions 46b; a large
number of arcuate third deflecting surface regions 46i arranged
along the Z-direction corresponding to the large number of third
refracting surface regions 46c; a large number of arcuate fourth
deflecting surface regions 46j arranged along the Z-direction
corresponding to the large number of fourth refracting surface
regions 46d; a large number of nearly rectangular fifth deflecting
surface regions 46k arranged corresponding to the large number of
fifth refracting surface regions 46e; shield regions 46m arranged
corresponding to the shield regions 46f.
[0129] The first deflecting surface regions 46g have a planar shape
with an up slope relative to the +X-direction as the first
deflecting surface regions 44f in the micro fly's eye lens 44 for
quadrupole illumination; the second deflecting surface regions 46h
have a planar shape with an up slope relative to the -X-direction
as the second deflecting surface regions 44g; the third deflecting
surface regions 46i have a planar shape with an up slope relative
to the -Z-direction as the third deflecting surface regions 44h;
the fourth deflecting surface regions 46j have a planar shape with
an up slope relative to the +Z-direction as the fourth deflecting
surface regions 44i. On the other hand, the fifth deflecting
surface regions 46k have a planar shape perpendicular to the
optical axis AX (and, therefore, perpendicular to the Y-axis) as
the third deflecting surface regions 45f in the micro fly's eye
lens 45 for tripole illumination, and have a function to transmit
rays incident through the corresponding fifth refracting surface
regions 46e and in parallel with the optical axis AX, without
change in their traveling direction.
[0130] Accordingly, nearly parallel beams guided through the
respective fifth refracting surface regions 46e to the respective
corresponding fifth deflecting surface regions 46k are not
substantially subjected to deflection in the respective fifth
deflecting surface regions 46k, to form a light intensity
distribution of a nearly circular shape centered on the optical
axis AX on the illumination pupil plane, in a superimposed manner.
In this manner, a secondary light source of a pentapole shape is
formed as one consisting of a pair of arcuate surface illuminants
26a and 26b arranged in the X-direction and in symmetry with
respect to the optical axis AX, a pair of arcuate surface
illuminants 26c and 26d arranged in the Z-direction and in symmetry
with respect to the optical axis AX, and a surface illuminant 26e
of a nearly circular shape centered on the optical axis AX, as
shown in FIG. 17, by action of the micro fly's eye lens 46 in the
sixth modification example. In the sixth modification example, for
obtaining an accurate light intensity distribution of a circular
shape centered on the optical axis AX on the illumination pupil
plane, it is also preferable to limit light reaching the surface
illuminant 26e of the center pole or light from the surface
illuminant 26e, by the circular aperture of the center-pole
aperture member 10aa of the aperture stop 10a shown in FIG. 15
(b).
[0131] It is also possible to apply other appropriate arcuate
contours as shown in the first modification example to the third
modification example, to the micro fly's eye lens 45 for tripole
illumination in the fifth modification example and the micro fly's
eye lens 46 for pentapole illumination in the sixth modification
example. Namely, in the fifth modification example, various
modification examples can be contemplated as to the contours,
numbers, arrangement, etc. of the respective refracting surface
regions except for the third refracting surface regions 45c. In the
sixth modification example, various modification examples can be
contemplated as to the contours, numbers, arrangement, etc. of the
respective refracting surface regions except for the fifth
refracting surface regions 46e.
[0132] In the fifth modification example and the sixth modification
example, the third refracting surface regions 45c and the fifth
refracting surface regions 46e for illuminating the surface
illuminant of the center pole in the superimposed manner have the
nearly rectangular contour resulting from division of the arcuate
region adjacent to other refracting surface regions. However,
without having to be limited to this, various modification examples
can be contemplated as to the contour, number, arrangement, etc. of
the center-pole refracting surface regions for forming the surface
illuminant of the center pole in the superimposed manner. As an
example, FIG. 18 shows a configuration example in which the
refracting surface regions for the center pole are set in a
circular contour.
[0133] In the configuration example of FIG. 18, a large number of
circular refracting surface regions 52 for the center pole are
formed between two adjacent refracting surface regions 51, on the
entrance side (light source side) of the micro fly's eye lens. The
refracting surface regions 51 correspond to the first refracting
surface regions 45a or the second refracting surface regions 45b in
the fifth modification example. Alternatively, the refracting
surface regions 51 correspond to the first refracting surface
regions 46a, the second refracting surface regions 46b, the third
refracting surface regions 46c, or the fourth refracting surface
regions 46d in the sixth modification example. On the other hand,
the refracting surface regions 52 for the center pole are formed in
juxtaposition so as to be adjacent to each other in the arcuate
regions corresponding to the refracting surface regions 51.
Hatching is given to regions except for the center-pole refracting
surface regions 52 in the arcuate regions between two adjacent
refracting surface regions 51, and the hatched regions 53 are
shield regions.
[0134] The refracting surface regions 52 for the center pole have a
convex shape (or concave shape) as the third refracting surface
regions 45c in the fifth modification example and the fifth
refracting surface regions 46e in the sixth modification example,
and have a function to refract incident light. Specifically, the
refracting surface regions 52 for the center pole have, for
example, a spherical convex shape symmetric with respect to each
center axis parallel to the optical axis AX. On the exit side (mask
side) of the micro fly's eye lens, though not shown, a large number
of circular center-pole deflecting surface regions are provided
corresponding to the large number of center-pole refracting surface
regions 52 and shield regions are provided corresponding to the
shield regions 53.
[0135] The deflecting surface regions for the center pole have a
planar shape perpendicular to the optical axis AX (and, therefore,
perpendicular to the Y-axis) as the third deflecting surface
regions 45f in the fifth modification example and the fifth
deflecting surface regions 46k in the sixth modification example,
and have a function to transmit rays incident through the
corresponding refracting surface regions 52 for the center pole and
in parallel with the optical axis AX, without change in their
traveling direction. Accordingly, nearly parallel beams guided
through the respective center-pole refracting surface regions 52 to
the respective corresponding center-pole deflecting surface regions
are not substantially subjected to deflection in the respective
center-pole deflecting surface regions, to form an accurate light
intensity distribution of a circular shape centered on the optical
axis AX on the illumination pupil plane, in a superimposed manner.
In this case, therefore, there is no need for limiting the beams by
the circular aperture of the center-pole aperture member 10a of the
aperture stop 10a shown in FIG. 15 (b).
[0136] It is also possible to adopt a configuration example
wherein, instead of the center-pole refracting surface regions 52
or in addition to the center-pole refracting surface regions 52, a
plurality of circular center-pole refracting surface regions 54
with various sizes are formed in a crescent region in contact with
a refracting surface region 51a located at an end and the rest
region is formed as a shield region 55. In this case, a plurality
of circular center-pole deflecting surface regions with various
sizes are also provided corresponding to the plurality of
center-pole refracting surface regions 54 and a shield region is
provided corresponding to the shield region 55, on the exit side
(mask side) of the micro fly's eye lens.
[0137] The refracting surface regions 54 for the center pole have a
spherical convex shape symmetric with respect to each center axis
parallel to the optical axis AX and the deflecting surface regions
for the center pole have a planar shape perpendicular to the
optical axis AX (and, therefore, perpendicular to the Y-axis).
However, each center-pole refracting surface region 54 is provided
with a refracting power according to the size of the contour
thereof so that beams having passed through the respective
center-pole refracting surface regions 54 are superimposed in a
circular region centered on the optical axis AX on the illumination
pupil plane. In this case, therefore, there is no need for limiting
the beams by the circular aperture of the center-pole aperture
member 10aa of the aperture stop 10a shown in FIG. 15 (b),
either.
[0138] Each of the above-described embodiment and modification
examples uses the micro fly's eye lens in which the refracting
surface regions are formed on the entrance side and in which the
deflecting surface regions are formed on the exit side, but it is
also possible to realize a micro fly's eye lens in which the
deflecting surface regions are formed on the entrance side and in
which the refracting surface regions are formed on the exit
side.
[0139] In each of the above-described embodiment and modification
examples the deflecting surface regions are formed in the planar
shape with no refracting power, but, without having to be limited
to this, it is also possible to form the deflecting surface regions
in a curved surface shape with a substantial refracting power,
e.g., a curved surface shape corresponding to a spherical surface
or aspherical surface of a convex shape, or a spherical surface or
an aspherical surface of a concave shape. This configuration
permits the deflecting surface regions to share the refracting
action of the refracting surface regions.
[0140] When the micro fly's eye lens (4; 41-46) is made by physical
processing, the light intensity distribution of the secondary light
source might not be a desired light intensity distribution because
of a processing error. In this case, for example, a correction
filter may be located on the illumination pupil plane. Such a
correction filter located on the illumination pupil plane is
disclosed, for example, in Japanese Patent Application Laid-open
No. 2004-247527. The teaching of Japanese Patent Application
Laid-open No. 2004-247527 is incorporated herein by reference.
[0141] In the above description, the micro fly's eye lens (4;
41-46) in each of the above embodiment and modification examples is
made of fluorite in order to ensure sufficient durability to light
in the ultraviolet region of short wavelengths, but, without having
to be limited to this, the micro fly's eye lens can also be made of
another fluoride crystal material, e.g., barium fluoride, lithium
fluoride, magnesium fluoride, sodium fluoride, or strontium
fluoride.
[0142] The micro fly's eye lens (4; 41-46) in each of the
above-described embodiment and modification examples can also be
made of an oxide crystal material, e.g., rock crystal (SiO.sub.2),
barium titanate (BaTiO.sub.3), titanium trioxide (TiO.sub.3),
magnesium oxide (MgO), or sapphire (Al.sub.2O.sub.3). Furthermore,
the micro fly's eye lens (4; 41-46) in each of the above-described
embodiment and modification examples can also be made of an
optically transparent amorphous material such as silica glass.
[0143] The micro fly's eye lens (4; 41-46) in each of the
above-described embodiment and modification examples can also be
made, for example, of an optical material with optical activity
(rotatory polarization characteristic) or an optical material with
retardation. This enables the following polarization setting: for
example, while forming a secondary light source localized in an
annular region, a beam passing through the secondary light source
is set in a linearly polarized state with a direction of
polarization along its circumferential direction (hereinafter
referred to as a "circumferential polarization state").
[0144] A micro fly's eye lens for quadrupole illumination with the
circumferential polarization state in the seventh modification
example will be described below with reference to FIGS. 19 to 22.
With reference to FIG. 19, the following refracting surface regions
are formed on the entrance side (light source side) of the micro
fly's eye lens 47 for quadrupole illumination with the
circumferential polarization state according to the seventh
modification example: a large number of first refracting surface
regions 47a of an arcuate shape with the center projecting in the
-X-direction; a large number of second refracting surface regions
47b of an arcuate shape with the center projecting in the
+X-direction; a large number of third refracting surface regions
47c of an arcuate shape with the center projecting in the
+Z-direction; a large number of fourth refracting surface regions
47d of an arcuate shape with the center projecting in the
-Z-direction.
[0145] The first to fourth refracting surface regions 47a-47d have
respective configurations corresponding to the first to fourth
refracting surface regions 44a-44d in the micro fly's eye lens 44
for quadrupole illumination shown in FIGS. 9 to 12. Regions 47e
hatched in the drawing are shield regions between the first and
second refracting surface regions 47a, 47b and the third and fourth
refracting surface regions 47c, 47d.
[0146] On the other hand, the following deflecting surface regions
are formed on the exit side (mask side) of the micro fly's eye lens
47 for quadrupole illumination with the circumferential
polarization state, as shown in FIG. 20: a large number of arcuate
first deflecting surface regions 47f densely arranged along the
X-direction corresponding to the large number of first refracting
surface regions 47a; a large number of arcuate second deflecting
surface regions 47g densely arranged along the X-direction
corresponding to the large number of second refracting surface
regions 47b; a large number of arcuate third deflecting surface
regions 47h densely arranged along the Z-direction corresponding to
the large number of third refracting surface regions 47c; a large
number of arcuate fourth deflecting surface regions 47i densely
arranged along the Z-direction corresponding to the large number of
fourth refracting surface regions 47d. Regions 47j hatched in the
drawing are shield regions between the first and second deflecting
surface regions 47f, 47g and the third and fourth deflecting
surface regions 47h, 47i. The exit-side shield regions 47j are
provided corresponding to the entrance-side shield regions 47e.
[0147] The first to fourth deflecting surface regions 47f-47i have
respective configurations corresponding to the first to fourth
deflecting surface regions 44f-44i in the micro fly's eye lens 44
for quadrupole illumination shown in FIGS. 9 to 12. The micro fly's
eye lens 47 in the seventh modification example is made of an
optical material with optical activity, e.g., rock crystal
(SiO.sub.2). In this case, the crystal optic axis of rock crystal
is approximately matched with the optical-axis direction (the
Y-axis direction in the drawing).
[0148] In the micro fly's eye lens 47 of the seventh modification
example, as shown in FIG. 21, the thickness d1 in the optical-axis
direction (Y-axis direction) of the regions corresponding to the
first and second refracting surface regions 47a, 47b (first and
second deflecting surface regions 47f, 47g) and the thickness d2 in
the optical-axis direction of the regions corresponding to the
third and fourth refracting surface regions 47c, 47d (third and
fourth deflecting surface regions 47h, 47i) are set so as to
satisfy d1.rho.=.theta.1 and d2.rho.=.theta.2.
[0149] It is, however, provided that p represents the optical
activity of the optical material (rock crystal), .theta.1 a
rotation angle of the polarization direction of linearly polarized
light having passed through the first and second refracting surface
regions 47a, 47b (first and second deflecting surface regions 47f,
47g), and .theta.2 a rotation angle of the polarization direction
of linearly polarized light having passed through the third and
fourth refracting surface regions 47c, 47d (third and fourth
deflecting surface regions 47h, 47i); and a relative difference
between the rotation angles .theta.1 and .theta.2 is
90.degree..
[0150] When linearly polarized light with the polarization
direction along the Z-direction is made incident into the micro
fly's eye lens 47 of the seventh modification example, as shown in
FIG. 22, the polarization directions in a pair of arcuate surface
illuminants 27a and 27b formed by light having passed through the
first and second refracting surface regions 47a, 47b (first and
second deflecting surface regions 47f, 47g) can be set in the
Z-direction in the drawing and the polarization directions in a
pair of arcuate surface illuminants 27c and 27d formed by light
having passed through the third and fourth refracting surface
regions 47c, 47d (third and fourth deflecting surface regions 47h,
47i) can be set in the X-direction in the drawing. Namely, the
secondary light source 27a-27d localized in the annular region can
be formed in the circumferential polarization state and, therefore,
quadrupole illumination can be implemented in a polarization state
of s-polarization for the wafer W.
[0151] The micro fly's eye lens 47 of the seventh modification
example can also be made of an optical material with retardation.
In this case, the micro fly's eye lens can be set so that a
difference between an optical path length corresponding to the
first and second refracting surface regions 47a, 47b (first and
second deflecting surface regions 47f, 47g) and an optical path
length corresponding to the third and fourth refracting surface
regions 47c, 47d (third and fourth deflecting surface regions 47h,
47i) is a half wavelength.
[0152] In the seventh modification example the secondary light
source is formed in the quadrupole shape with the circumferential
polarization state, but it is also possible to form a secondary
light source of a cross-shaped double quadrupole shape, a secondary
light source of an X-shaped double quadrupole shape, a secondary
light source of a tripole shape, or a secondary light source of a
pentapole shape, as in the aforementioned modification examples.
Furthermore, the shape of each pole is not limited to the arcuate
shape, but it is also possible to apply other appropriate arcuate
contours. Namely, in the seventh modification example various
modification examples can be contemplated as to the contours,
numbers, and arrangement of the respective refracting surface
regions, the contours, numbers, and arrangement of the respective
deflecting surface regions, and the optical path lengths between
the respective refracting surface regions and the respective
deflecting surface regions.
[0153] The below will describe an embodiment of a method for
manufacturing the micro fly's eye lens 4, 41-47 for modified
illumination according to each of the aforementioned embodiment and
modification examples, with reference to the flowchart of FIG.
23.
[0154] The first block 101 in FIG. 23 is to prepare a
plane-parallel plate made of a fluoride crystal material, e.g.,
fluorite as in the above-described embodiment. Where the micro
fly's eye lens to be manufactured is the one in the seventh
modification example, the plane-parallel plate to be prepared is an
optical material with optical activity or an optical material with
retardation.
[0155] The next block 102 is to measure the crystal plane
orientation of the plane-parallel plate of fluorite and to check
whether the crystal plane {111} of the plane-parallel plate of
fluorite is directed to the optical axis. In this block 102, the
measurement can be performed by applying a technique of carrying
out, for example, the Laue measurement to directly measure the
crystal plane orientation, or a technique of measuring
birefringence of the plane-parallel plate of fluorite and
determining the crystal axis orientation from the measured
birefringence, based on the known relationship between crystal axis
orientation and birefringence. When the micro fly's eye lens to be
manufactured is the one of the seventh modification example, it is
checked whether the crystal optic axis of rock crystal as an
optical material with optical activity is directed to the optical
axis.
[0156] Here the sentence "the crystal plane {111} is directed to
the optical axis," or "the crystal optic axis is directed to the
optical axis" means that a deviation angle between the optical axis
and the crystal axis direction is not more than a predetermined
tolerance. The measurement of the crystal plane orientation may be
carried out by performing the measurement at only a specific point
on the plane-parallel plate of fluorite or by performing the
measurement at a plurality of points on the plane-parallel plate of
fluorite. When a region with a heretical deviation of the crystal
plane orientation is locally present in the plane-parallel plate of
fluorite, the deviation of the crystal plane orientation can be
permitted as long as it is not more than the tolerance.
[0157] The subsequent block 103 is to physically process the
plane-parallel plate of fluorite (by micromachining, processing
with a die in a high temperature state, or the like) to create a
plurality of deflecting surfaces, a plurality of refracting
surfaces, or a plurality of refracting and deflecting surfaces on
the fluorite substrate or on the rock crystal substrate.
[0158] The subsequent block 104 is to examine the fluorite
substrate with the plurality of deflecting surfaces, the plurality
of refracting surfaces, or the plurality of refracting and
deflecting surfaces, i.e., the micro fly's eye lens for modified
illumination. In this examination of the micro fly's eye lens, it
is checked whether the contour and illuminance distribution of the
annular or multi-pole illumination field formed in the far field of
the micro fly's eye lens are within a predetermined tolerance. This
examination can be performed, for example, by using the technology
disclosed in U.S. Patent Publication No. 2006/0166142. The U.S.
Patent Publication No. 2006/0166142 is incorporated herein by
reference.
[0159] When they are off the predetermined tolerance, the micro
fly's eye lens will be used in combination with a correction filter
disposed on the illumination pupil plane as described above;
therefore, it is preferable to calculate a density distribution of
the correction filter for correcting the contour and illuminance
distribution of the annular or multi-pole illumination field to the
predetermined tolerance. It is preferable to provide the examined
micro fly's eye lens with information about this density
distribution of the correction filter. A method for providing the
micro fly's eye lens for modified illumination with the information
about the density distribution of the correction filter can be
selected from such techniques as a technique of impressing the
information in the substrate of the micro fly's eye lens for
modified illumination, a technique of attaching, for example, an RF
tag to a below-described holding member for holding the micro fly's
eye lens for modified illumination and storing the information in
the RF tag, and a technique of storing the information of the
correction filter for every manufacture number of the examined
micro fly's eye lens in the form of a correspondence table in a
computer for process management in a manufacturing factory of the
illumination optical apparatus or exposure apparatus incorporated
with the micro fly's eye lens.
[0160] The subsequent block 105 is to incorporate the examined
micro fly's eye lens into the holding member. According to the
aforementioned embodiment, the micro fly's eye lens can be
manufactured with light-quantity loss small at the aperture stop 10
in the modified illumination and with sufficient durability to
light in the ultraviolet region of short wavelengths.
[0161] The exposure apparatus according to the above-described
embodiment can manufacture micro devices (semiconductor devices,
imaging devices, liquid-crystal display devices, thin-film magnetic
heads, etc.) through a process of illuminating a mask (reticle) by
the illumination optical apparatus (illumination block) and
exposing a photosensitive substrate with a transfer pattern formed
in the mask, by the projection optical system (exposure block). An
example of a method for obtaining semiconductor devices as micro
devices by forming a predetermined circuit pattern in a wafer or
the like as a photosensitive substrate by means of the exposure
apparatus of the above embodiment will be described below with
reference to the flowchart of FIG. 24.
[0162] The first block 301 in FIG. 24 is to deposit a metal film on
each wafer in one lot. The next block 302 is to apply a photoresist
onto the metal film on each wafer in the lot. The subsequent block
303 is to use the exposure apparatus of the above embodiment to
sequentially transfer an image of a pattern on a mask into each
shot area on each wafer in the lot through the projection optical
system of the exposure apparatus. The subsequent block 304 is to
perform development of the photoresist on each wafer in the lot and
the next block 305 is to perform etching using the resist pattern
on each wafer in the lot as a mask, and thereby to form a circuit
pattern corresponding to the pattern on the mask, in each shot area
on each wafer. Thereafter, devices such as semiconductor devices
are manufactured through blocks including formation of circuit
patterns in upper layers. The above-described semiconductor device
manufacturing method permits us to obtain the semiconductor devices
with extremely fine circuit patterns at high throughput.
[0163] The exposure apparatus of the above embodiment can also
manufacture a liquid-crystal display device as a micro device by
forming predetermined patterns (circuit pattern, electrode pattern,
etc.) on plates (glass substrates). An example of a method in this
case will be described below with reference to the flowchart of
FIG. 25. In FIG. 25, a pattern forming block 401 is to execute the
so-called photolithography block of transferring a pattern of a
mask onto a photosensitive substrate (a glass substrate coated with
a resist or the like) by means of the exposure apparatus of the
above embodiment. This photolithography block results in forming a
predetermined pattern including a large number of electrodes and
others on the photosensitive substrate. Thereafter, the exposed
substrate is processed through each of blocks including a
development block, an etching block, a resist removing block, etc.
whereby the predetermined pattern is formed on the substrate,
followed by the next color filter forming block 402.
[0164] The next color filter forming block 402 is to form a color
filter in which a large number of sets of three dots corresponding
to R (Red), G (Green), and B (Blue) are arrayed in a matrix pattern
or in which sets of filters of three stripes of R, G, and B are
arrayed in the horizontal scan line direction. After the color
filter forming block 402, a cell assembling block 403 is executed.
The cell assembling block 403 is to assemble a liquid crystal panel
(liquid crystal cell) using the substrate with the predetermined
pattern obtained in the pattern forming block 401, the color filter
obtained in the color filter forming block 402, and others.
[0165] In the cell assembling block 403, the liquid crystal panel
(liquid crystal cell) is manufactured, for example, by pouring a
liquid crystal into between the substrate with the predetermined
pattern obtained in the pattern forming block 401 and the color
filter obtained in the color filter forming block 402. The
subsequent module assembling block 404 is to attach various
components such as electric circuits and backlights for display
operation of the assembled liquid crystal panel (liquid crystal
cell) to complete the liquid-crystal display device. The
above-described manufacturing method of the liquid-crystal display
device permits us to obtain the liquid-crystal display device with
extremely fine circuit patterns at high throughput.
[0166] The aforementioned embodiment used the ArF excimer laser
light (the wavelength: 193 nm) or the KrF excimer laser light (the
wavelength: 248 nm) as the exposure light, but the exposure light
does not have to be limited to these: the present invention can
also be applied to any other appropriate laser light source, e.g.,
an F.sub.2 laser light source for supplying the laser light at the
wavelength of 157 nm.
[0167] The foregoing embodiment was the application of the present
invention to the illumination optical apparatus for illuminating
the mask or the wafer in the exposure apparatus, but, without
having to be limited to this, the present invention can also be
applied to commonly-used illumination optical apparatus for
illuminating an illumination target surface except for the mask or
the wafer.
[0168] For example, when the optical integrator according to the
above embodiment is used in multipole illumination with an
illumination optical apparatus, a beam guided through each first
refracting surface region of the arcuate shape to each
corresponding first deflecting surface region and a beam guided
through each second refracting surface region of the arcuate shape
opposite to each first refracting surface region, to each
corresponding second deflecting surface region are subjected to
opposite deflection actions of the first deflecting surface region
and the second deflecting surface region to form a dipolar
secondary light source of a nearly desired shape consisting of two
substantial surface illuminants of an arcuate shape corresponding
to a part of an annular region. As a result, beams from the
secondary light source of the nearly desired shape are guided to an
illumination target surface, without any light-quantity loss or
with only a small light-quantity loss at the aperture of the
aperture stop.
[0169] Therefore, the illumination optical apparatus of the above
embodiment is able to illuminate the illumination target surface
under a desired illumination condition, using the optical
integrator capable of keeping down the light-quantity loss in the
modified illumination. The exposure apparatus of the above
embodiment is able to implement good exposure under a good
illumination condition, using the illumination optical apparatus
which illuminates a pattern under a desired illumination condition,
and, in turn, to manufacture good devices at high throughput.
[0170] The invention is not limited to the foregoing embodiments
but various changes and modifications of its components may be made
without departing from the scope of the present invention. Also,
the components disclosed in the embodiments may be assembled in any
combination for embodying the present invention. For example, some
of the components may be omitted from all components disclosed in
the embodiments. Further, components in different embodiments may
be appropriately combined.
* * * * *