U.S. patent application number 11/319057 was filed with the patent office on 2006-07-20 for beam transforming element, illumination optical apparatus, exposure apparatus, and exposure method.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Mitsunori Toyoda.
Application Number | 20060158624 11/319057 |
Document ID | / |
Family ID | 34616350 |
Filed Date | 2006-07-20 |
United States Patent
Application |
20060158624 |
Kind Code |
A1 |
Toyoda; Mitsunori |
July 20, 2006 |
Beam transforming element, illumination optical apparatus, exposure
apparatus, and exposure method
Abstract
There is disclosed a beam transforming element for forming a
predetermined light intensity distribution on a predetermined
surface on the basis of an incident beam, comprising: a first basic
element made of an optical material with optical activity, for
forming a first region distribution of the predetermined light
intensity distribution on the basis of the incident beam; and a
second basic element made of an optical material with optical
activity, for forming a second region distribution of the
predetermined light intensity distribution on the basis of the
incident beam, wherein the first basic element and the second basic
element have their respective thicknesses different from each other
along a direction of transmission of light.
Inventors: |
Toyoda; Mitsunori; (Sendai,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
34616350 |
Appl. No.: |
11/319057 |
Filed: |
December 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP04/16247 |
Nov 2, 2004 |
|
|
|
11319057 |
Dec 28, 2005 |
|
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Current U.S.
Class: |
355/18 |
Current CPC
Class: |
G02B 27/4261 20130101;
G03F 7/70091 20130101; G02B 27/0944 20130101; G02B 27/4233
20130101; G03F 7/70566 20130101; G02B 5/3025 20130101; G03F 7/70108
20130101; G02B 27/0927 20130101; G02B 27/28 20130101; G03F 7/70158
20130101 |
Class at
Publication: |
355/018 |
International
Class: |
G03B 27/00 20060101
G03B027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2003 |
JP |
P2003-390674 |
Claims
1. A beam transforming element for forming a predetermined light
intensity distribution on a predetermined surface on the basis of
an incident beam, comprising: a first basic element made of an
optical material with optical activity, for forming a first region
distribution of the predetermined light intensity distribution on
the basis of the incident beam; and a second basic element made of
an optical material with optical activity, for forming a second
region distribution of the predetermined light intensity
distribution on the basis of the incident beam, wherein the first
basic element and the second basic element have their respective
thicknesses different from each other along a direction of
transmission of light.
2. The beam transforming element according to claim 1, wherein the
thickness of the first basic element and the thickness of the
second basic element are so set that with incidence of linearly
polarized light a direction of polarization of linearly polarized
light forming the first region distribution is different from a
direction of polarization of linearly polarized light forming the
second region distribution.
3. The beam transforming element according to claim 2, wherein the
first region distribution and the second region distribution are
positioned in at least a part of a predetermined annular region,
which is a predetermined annular region centered around a
predetermined point on the predetermined surface, and wherein beams
passing through the first region distribution and through the
second region distribution have a polarization state in which a
principal component is linearly polarized light having a direction
of polarization along a circumferential direction of the
predetermined annular region.
4. The beam transforming element according to claim 3, wherein the
predetermined light intensity distribution has a contour of a shape
substantially identical with the predetermined annular region,
wherein the polarization state of the beam passing through the
first region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the first region distribution,
and wherein the polarization state of the beam passing through the
second region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the second region
distribution.
5. The beam transforming element according to claim 3, wherein the
predetermined light intensity distribution is a distribution of a
multipole shape in the predetermined annular region, wherein the
polarization state of the beam passing through the first region
distribution has a linear polarization component substantially
coincident with a tangential direction to a circle centered around
the predetermined point, at a central position along a
circumferential direction of the first region distribution, and
wherein the polarization state of the beam passing through the
second region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the second region
distribution.
6. The beam transforming element according to claim 3, the beam
transforming element including substantially the same number of
said first basic elements and said second elementary elements.
7. The beam transforming element according to claim 6, further
comprising: a third basic element made of an optical material with
optical activity, for forming a third region distribution of the
predetermined light intensity distribution on the basis of the
incident beam; and a fourth basic element made of an optical
material with optical activity, for forming a fourth region
distribution of the predetermined light intensity distribution on
the basis of the incident beam.
8. The beam transforming element according to claim 3, wherein the
first basic element and the second basic element have diffracting
action or refracting action.
9. The beam transforming element according to claim 8, wherein the
first basic element forms at least two said first region
distributions on the predetermined surface on the basis of the
incident beam, and wherein the second basic element forms at least
two said second region distributions on the predetermined surface
on the basis of the incident beam.
10. The beam transforming element according to claim 3, wherein the
first basic element and the second basic element are integrally
formed.
11. The beam transforming element according to claim 3, the beam
transforming element being used in an illumination optical
apparatus for illuminating a surface to be illuminated, based on a
beam from a light source, wherein an illumination pupil
distribution is formed on or near an illumination pupil of the
illumination optical apparatus.
12. The beam transforming element according to claim 1, wherein the
first basic element and the second basic element are made of an
optical material with an optical rotatory power of not less than
100.degree./mm for light of a wavelength used.
13. The beam transforming element according to claim 12, wherein
the first basic element and the second basic element are made of
crystalline quartz.
14. The beam transforming element according to claim 1, wherein the
first basic element and the second basic element are integrally
formed.
15. The beam transforming element according to claim 14, the beam
transforming element being used in an illumination optical
apparatus for illuminating a surface to be illuminated, based on a
beam from a light source, wherein an illumination pupil
distribution is formed on or near an illumination pupil of the
illumination optical apparatus.
16. A beam transforming element for, based on an incident beam,
forming a predetermined light intensity distribution of a shape
different from a sectional shape of the incident beam, on a
predetermined surface, comprising: a diffracting surface or a
refracting surface for forming the predetermined light intensity
distribution on the predetermined surface, wherein the
predetermined light intensity distribution is a distribution in at
least a part of a predetermined annular region, which is a
predetermined annular region centered around a predetermined point
on the predetermined surface, and wherein a beam from the beam
transforming element passing through the predetermined annular
region has a polarization state in which a principal component is
linearly polarized light having a direction of polarization along a
circumferential direction of the predetermined annular region.
17. The beam transforming element according to claim 16, wherein
the predetermined light intensity distribution has a contour of a
multipole shape or an annular shape.
18. The beam transforming element according to claim 17, the beam
transforming element being made of an optical material with optical
activity.
19. The beam transforming element according to claim 18,
comprising: a first basic element made of an optical material with
optical activity, for forming a first region distribution of the
predetermined light intensity distribution on the basis of the
incident beam; and a second basic element made of an optical
material with optical activity, for forming a second region
distribution of the predetermined light intensity distribution on
the basis of the incident beam, wherein the first basic element and
the second basic element have their respective thicknesses
different from each other along a direction of transmission of
light.
20. The beam transforming element according to claim 19, wherein
the thickness of the first basic element and the thickness of the
second basic element are so set that with incidence of linearly
polarized light a direction of polarization of linearly polarized
light forming the first region distribution is different from a
direction of polarization of linearly polarized light forming the
second region distribution.
21. The beam transforming element according to claim 20, wherein
the first region distribution and the second region distribution
are positioned in at least a part of a predetermined annular
region, which is a predetermined annular region centered around a
predetermined point on the predetermined surface, and wherein beams
passing through the first region distribution and through the
second region distribution have a polarization state in which a
principal component is linearly polarized light having a direction
of polarization along a circumferential direction of the
predetermined annular region.
22. The beam transforming element according to claim 21, wherein
the predetermined light intensity distribution has a contour of a
shape substantially identical with the predetermined annular
region, wherein the polarization state of the beam passing through
the first region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the first region distribution,
and wherein the polarization state of the beam passing through the
second region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the second region
distribution.
23. The beam transforming element according to claim 21, wherein
the predetermined light intensity distribution is a distribution of
a multipole shape in the predetermined annular region, wherein the
polarization state of the beam passing through the first region
distribution has a linear polarization component substantially
coincident with a tangential direction to a circle centered around
the predetermined point, at a central position along a
circumferential direction of the first region distribution, and
wherein the polarization state of the beam passing through the
second region distribution has a linear polarization component
substantially coincident with a tangential direction to a circle
centered around the predetermined point, at a central position
along a circumferential direction of the second region
distribution.
24. The beam transforming element according to claim 19, the beam
transforming element including substantially the same number of
said first basic elements and said second basic elements.
25. The beam transforming element according to claim 19, wherein
the first basic element and the second basic element have
diffracting action or refracting action.
26. The beam transforming element according to claim 19, wherein
the first basic element forms at least two said first region
distributions on the predetermined surface on the basis of the
incident beam, and wherein the second basic element forms at least
two said second region distributions on the predetermined surface
on the basis of the incident beam.
27. The beam transforming element according to claim 19, further
comprising: a third basic element made of an optical material with
optical activity, for forming a third region distribution of the
predetermined light intensity distribution on the basis of the
incident beam; and a fourth basic element made of an optical
material with optical activity, for forming a fourth region
distribution of the predetermined light intensity distribution on
the basis of the incident beam.
28. The beam transforming element according to claim 19, wherein
the first basic element and the second basic element are integrally
formed.
29. The beam transforming element according to claim 17, the beam
transforming element being used in an illumination optical
apparatus for illuminating a surface to be illuminated, based on a
beam from a light source, wherein an illumination pupil
distribution is formed on or near an illumination pupil of the
illumination optical apparatus.
30. The beam transforming element according to claim 16, the beam
transforming element being used in an illumination optical
apparatus for illuminating a surface to be illuminated, based on a
beam from a light source, wherein an illumination pupil
distribution is formed on or near an illumination pupil of the
illumination optical apparatus.
31. An illumination optical apparatus for illuminating a surface to
be illuminated, based on a beam from a light source, comprising:
the beam transforming element as defined in claim 1, for
transforming the beam from the light source in order to form an
illumination pupil distribution on or near an illumination pupil of
the illumination optical apparatus.
32. The illumination optical apparatus according to claim 31,
wherein the beam transforming element is arranged to be replaceable
with another beam transforming element having a different
characteristic.
33. The illumination optical apparatus according to claim 32,
further comprising: a wavefront splitting optical integrator
disposed in an optical path between the beam transforming element
and the surface to be illuminated, wherein the beam transforming
element forms the predetermined light intensity distribution on an
entrance surface of the optical integrator on the basis of the
incident beam.
34. The illumination optical apparatus according to claim 33,
wherein at least one of the light intensity distribution on the
predetermined surface, and the polarization state of the beam from
the beam transforming element passing through the predetermined
annular region is set in consideration of influence of an optical
member disposed in an optical path between the light source and the
surface to be illuminated.
35. The illumination optical apparatus according to claim 31,
wherein the polarization state of the beam from the beam
transforming element is so set that light illuminating the surface
to be illuminated is in a polarization state in which a principal
component is s-polarized light.
36. An exposure apparatus comprising the illumination optical
apparatus as defined in claim 31, for illuminating a predetermined
pattern, wherein a predetermined pattern is projected onto a
photosensitive substrate.
37. The exposure apparatus according to claim 36, wherein at least
one of the light intensity distribution on the predetermined
surface, and the polarization state of the beam from the beam
transforming element passing through the predetermined annular
region is set in consideration of influence of an optical member
disposed in an optical path between the light source and the
photosensitive substrate.
38. The exposure apparatus according to claim 37, wherein the
polarization state of the beam from the beam transforming element
is so set that light illuminating the photosensitive substrate is
in a polarization state in which a principal component is
s-polarized light.
39. An exposure method comprising an illumination step of
illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 31, and an exposure step of
projecting a pattern of the predetermined pattern onto a
photosensitive substrate.
40. The exposure method according to claim 39, wherein at least one
of the light intensity distribution on the predetermined surface,
and the polarization state of the beam from the beam transforming
element passing through the predetermined annular region is set in
consideration of influence of an optical member disposed in an
optical path between the light source and the photosensitive
substrate.
41. The exposure method according to claim 39, wherein the
polarization state of the beam from the beam transforming element
is so set that light illuminating the photosensitive substrate is
in a polarization state in which a principal component is
s-polarized light.
42. A device manufacturing method comprising an illumination step
of illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 31, an exposure step of
projecting the pattern onto a photosensitive substrate, and
developing step for developing the photosensitive substrate.
43. The device manufacturing method according to claim 42, wherein
the polarization state of the beam from the beam transforming
element is so set that light illuminating the photosensitive
substrate is in a polarization state in which a principal component
is s-polarized light.
44. An illumination optical apparatus for illuminating a surface to
be illuminated, based on a beam from a light source, comprising:
the beam transforming element as defined in claim 16, for
transforming the beam from the light source in order to form an
illumination pupil distribution on or near an illumination pupil of
the illumination optical apparatus.
45. The illumination optical apparatus according to claim 44,
wherein the beam transforming element is arranged to be replaceable
with another beam transforming element having a different
characteristic.
46. The illumination optical apparatus according to claim 44,
further comprising: a wavefront splitting optical integrator
disposed in an optical path between the beam transforming element
and the surface to be illuminated, wherein the beam transforming
element forms the predetermined light intensity distribution on an
entrance surface of the optical integrator on the basis of the
incident beam.
47. The illumination optical apparatus according to claim 44,
wherein at least one of the light intensity distribution on the
predetermined surface, and the polarization state of the beam from
the beam transforming element passing through the predetermined
annular region is set in consideration of influence of an optical
member disposed in an optical path between the light source and the
surface to be illuminated.
48. The illumination optical apparatus according to claim 44,
wherein the polarization state of the beam from the beam
transforming element is so set that light illuminating the surface
to be illuminated is in a polarization state in which a principal
component is s-polarized light.
49. An exposure apparatus comprising the illumination optical
apparatus as defined in claim 44, for illuminating a predetermined
pattern, wherein the predetermined pattern is projected onto a
photosensitive substrate.
50. The exposure apparatus according to claim 49, wherein at least
one of the light intensity distribution on the predetermined
surface, and the polarization state of the beam from the beam
transforming element passing through the predetermined annular
region is set in consideration of influence of an optical member
disposed in an optical path between the light source and the
photosensitive substrate.
51. The exposure apparatus according to claim 49, wherein the
polarization state of the beam from the beam transforming element
is so set that light illuminating the photosensitive substrate is
in a polarization state in which a principal component is
s-polarized light.
52. An exposure method comprising an illumination step of
illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 44, and an exposure step of
projecting a pattern of the predetermined pattern onto a
photosensitive substrate.
53. The exposure method according to claim 52, wherein at least one
of the light intensity distribution on the predetermined surface,
and the polarization state of the beam from the beam transforming
element passing through the predetermined annular region is set in
consideration of influence of an optical member disposed in an
optical path between the light source and the photosensitive
substrate.
54. The exposure method according to claim 52, wherein the
polarization state of the beam from the beam transforming element
is so set that light illuminating the photosensitive substrate is
in a polarization state in which a principal component is
s-polarized light.
55. A device manufacturing method comprising an illumination step
of illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 44, an exposure step of
projecting the pattern onto a photosensitive substrate, and
developing step for developing the photosensitive substrate.
56. The device manufacturing method according to claim 55, wherein
the polarization state of the beam from the beam transforming
element is so set that light illuminating the photosensitive
substrate is in a polarization state in which a principal component
is s-polarized light.
57. A diffraction optical element used in an illumination optical
apparatus for illuminating an object to be illuminated, based on a
beam from a light source, comprising: an optical member of an
uneven shape for forming a predetermined light intensity
distribution on a predetermined surface being an illumination pupil
plane of the illumination optical apparatus or a plane near the
illumination pupil plane, wherein the optical member comprises
portions with different thicknesses for providing the predetermined
light intensity distribution with a predetermined polarization
state.
58. The diffraction optical element according to claim 57, wherein
the object to be illuminated is a mask on which a predetermined
pattern is formed.
59. The diffraction optical element according to claim 57, the
diffraction optical element being one disposed in an optical path
between the light source and the object to be illuminated.
60. An illumination optical apparatus for illuminating a
predetermined pattern, comprising: the diffraction optical element
as defined in claim 57.
61. An exposure apparatus comprising the illumination optical
apparatus as defined in claim 60, the exposure apparatus projecting
the pattern onto a photosensitive substrate.
62. An exposure method comprising an illumination step of
illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 60, and an exposure step of
projecting the pattern onto a photosensitive substrate.
63. A device manufacturing method comprising an illumination step
of illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 60, an exposure step of
projecting the pattern onto a photosensitive substrate, and
developing step for developing the photosensitive substrate.
64. A diffraction optical element used in an illumination optical
apparatus for illuminating a predetermined pattern on the basis of
a beam from a light source, comprising: an optical member of an
uneven shape for forming a predetermined light intensity
distribution on a predetermined surface, wherein the optical member
comprises portions with different thicknesses for providing the
predetermined light intensity distribution with a predetermined
polarization state.
65. The diffraction optical element according to claim 64, wherein
the predetermined surface is an illumination pupil plane of the
illumination optical apparatus or a plane near the illumination
pupil plane.
66. The diffraction optical element according to claim 65, the
diffraction optical element being one disposed in an optical path
between the light source and the predetermined pattern.
67. The diffraction optical element according to claim 66, wherein
the predetermined polarization state has a polarization state in
which a principal component is linearly polarized light having a
direction of polarization along a circumferential direction of a
predetermined annular region, which is a predetermined annular
region centered around a predetermined point on the predetermined
surface.
68. The diffraction optical element according to claim 67, wherein
the predetermined light intensity distribution is of an annular
shape or a multipole shape positioned in the predetermined annular
region.
69. The diffraction optical element according to claim 66, wherein
the predetermined light intensity distribution is of an annular
shape or a multipole shape.
70. The diffraction optical element according to claim 66, wherein
the optical member of the uneven shape is made of crystalline
quartz.
71. The diffraction optical element according to claim 66, wherein
the optical member of the uneven shape is made of an optical
material with optical activity.
72. An illumination optical apparatus for illuminating a
predetermined pattern, comprising: the diffraction optical element
as defined in claim 64.
73. An exposure apparatus comprising the illumination optical
apparatus as defined in claim 72, the exposure apparatus projecting
the pattern onto a photosensitive substrate.
74. An exposure method comprising an illumination step of
illuminating the predetermined pattern by use of the illumination
optical apparatus as defined in claim 72, and an exposure step of
projecting the pattern onto a photosensitive substrate.
75. A device manufacturing method comprising an illumination step
of illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 72, an exposure step of
projecting the pattern onto a photosensitive substrate, and
developing step for developing the photosensitive substrate.
76. A polarization transforming element used in an illumination
optical apparatus for illuminating a predetermined pattern on the
basis of a beam from a light source, comprising: a plurality of
optical members with different thicknesses, wherein each of the
plurality of optical member provides a predetermined polarization
state on a predetermined surface according to the thickness of the
optical member.
77. The polarization transforming element according to claim 76,
wherein the predetermined surface is an illumination pupil plane of
the illumination optical apparatus or a plane near the illumination
pupil plane.
78. The polarization transforming element according to claim 77,
wherein a predetermined light intensity distribution of an annular
shape or a multipole shape positioned in a predetermined annular
region formed on the predetermined surface, and wherein the
predetermined annular region is centered around a predetermined
point on the predetermined surface.
79. The polarization transforming element according to claim 77,
wherein the diffraction optical element being one disposed in an
optical path between the light source and the predetermined
pattern.
80. The polarization transforming element according to claim 77,
wherein the predetermined polarization state has a polarization
state in which a principal component is linearly polarized light
having a direction of polarization along a circumferential
direction of a predetermined annular region, which is a
predetermined annular region centered around a predetermined point
on the predetermined surface.
81. The polarization transforming element according to claim 80,
wherein a predetermined light intensity distribution of an annular
shape or a multipole shape positioned in the predetermined annular
region formed on the predetermined surface.
82. The polarization transforming element according to claim 80,
wherein the optical members are made of crystalline quartz.
83. The polarization transforming element according to claim 82,
wherein an optical axis of the crystalline quartz is aligned along
a traveling direction of the beam.
84. The polarization transforming element according to claim 76,
wherein the optical members are made of an optical material with
optical activity.
85. An illumination optical apparatus for illuminating a surface to
be illuminated, based on a beam from a light source, comprising:
the polarization transforming element as defined in claim 76, for
transforming the beam from the light source in order to form a
predetermined polarization distribution on or near an illumination
pupil of the illumination optical apparatus.
86. The illumination optical apparatus according to claim 85,
wherein the polarization transforming element is arranged to be
replaceable with another polarization transforming element having a
different characteristic.
87. The illumination optical apparatus according to claim 85,
further comprising: a wavefront splitting optical integrator
disposed in an optical path between the polarization transforming
element and the surface to be illuminated, wherein the polarization
transforming element forms the predetermined polarization
distribution on an entrance surface of the optical integrator on
the basis of the incident beam.
88. The illumination optical apparatus according to claim 85,
wherein the polarization state of the beam from the polarization
transforming element is so set that light illuminating the surface
to be illuminated is in a polarization state in which a principal
component is s-polarized light.
89. An exposure apparatus comprising the illumination optical
apparatus as defined in claim 76, for illuminating a predetermined
pattern, wherein a predeterminined pattern is projected onto a
photosensitive substrate.
90. The exposure apparatus according to claim 89, wherein the
polarization state of the beam from the polarization transforming
element is so set that light illuminating the photosensitive
substrate is in a polarization state in which a principal component
is s-polarized light.
91. An exposure method comprising an illumination step of
illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 76, and an exposure step of
projecting the predetermined pattern onto a photosensitive
substrate.
92. The exposure method according to claim 91, wherein the
polarization state of the beam from the beam transforming element
is so set that light illuminating the photosensitive substrate is
in a polarization state in which a principal component is
s-polarized light.
93. A device manufacturing method comprising an illumination step
of illuminating a predetermined pattern by use of the illumination
optical apparatus as defined in claim 76, an exposure step of
projecting the pattern onto a photosensitive substrate, and
developing step for developing the photosensitive substrate.
94. The device manufacturing method according to claim 93, wherein
the polarization state of the beam from the polarization
transforming element is so set that light illuminating the
photosensitive substrate is in a polarization state in which a
principal component is s-polarized light.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part application of application
serial no. PCT/JP2004/016247 filed on Nov. 2, 2004, now pending,
and incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a beam transforming
element, illumination optical apparatus, exposure apparatus, and
exposure method and, more particularly, to an illumination optical
apparatus suitably applicable to exposure apparatus used in
production of microdevices such as semiconductor elements, image
pickup elements, liquid crystal display elements, and thin-film
magnetic heads by lithography.
[0004] 2. Related Background Art
[0005] In the typical exposure apparatus of this type, a beam
emitted from a light source travels through a fly's eye lens as an
optical integrator to form a secondary light source as a
substantial surface illuminant consisting of a number of light
sources. Beams from the secondary light source (generally, an
illumination pupil distribution formed on or near an illumination
pupil of the illumination optical apparatus) are limited through an
aperture stop disposed near the rear focal plane of the fly's eye
lens and then enter a condenser lens.
[0006] The beams condensed by the condenser lens superposedly
illuminate a mask on which a predetermined pattern is formed. The
light passing through the pattern of the mask is focused on a wafer
through a projection optical system. In this manner, the mask
pattern is projected for exposure (or transcribed) onto the wafer.
The pattern formed on the mask is a highly integrated pattern, and,
in order to accurately transcribe this microscopic pattern onto the
wafer, it is indispensable to obtain a uniform illuminance
distribution on the wafer.
[0007] For example, Japanese Patent No. 3246615 owned by the same
Applicant of the present application discloses the following
technology for realizing the illumination condition suitable for
faithful transcription of the microscopic pattern in arbitrary
directions: the secondary light source is formed in an annular
shape on the rear focal plane of the fly's eye lens and the beams
passing the secondary light source of the annular shape are set to
be in a linearly polarized state with a direction of polarization
along the circumferential direction thereof (hereinafter referred
to as a "azimuthal polarization state").
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to form an
illumination pupil distribution of an annular shape in a azimuthal
polarization state while well suppressing the loss of light
quantity. Another object of the present invention is to transcribe
a microscopic pattern in an arbitrary direction under an
appropriate illumination condition faithfully and with high
throughput, by forming an illumination pupil distribution of an
annular shape in a azimuthal polarization state while well
suppressing the loss of light quantity.
[0009] In order to achieve the above objects, a first aspect of the
present embodiment is to provide a beam transforming element for
forming a predetermined light intensity distribution on a
predetermined surface on the basis of an incident beam,
comprising:
[0010] a first basic element made of an optical material with
optical activity, for forming a first region distribution of the
predetermined light intensity distribution on the basis of the
incident beam; and
[0011] a second basic element made of an optical material with
optical activity, for forming a second region distribution of the
predetermined light intensity distribution on the basis of the
incident beam,
[0012] wherein the first basic element and the second basic element
have their respective thicknesses different from each other along a
direction of transmission of light.
[0013] A second aspect of the present embodiment is to provide a
beam transforming element for, based on an incident beam, forming a
predetermined light intensity distribution of a shape different
from a sectional shape of the incident beam, on a predetermined
surface, comprising:
[0014] a diffracting surface or a refracting surface for forming
the predetermined light intensity distribution on the predetermined
surface,
[0015] wherein the predetermined light intensity distribution is a
distribution in at least a part of a predetermined annular region,
which is a predetermined annular region centered around a
predetermined point on the predetermined surface, and
[0016] wherein a beam from the beam transforming element passing
through the predetermined annular region has a polarization state
in which a principal component is linearly polarized light having a
direction of polarization along a circumferential direction
(azymuthally direction) of the predetermined annular region.
[0017] A third aspect of the present invention is to provide an
illumination optical apparatus for illuminating a surface to be
illuminated, based on a beam from a light source, comprising:
[0018] the beam transforming element of the first aspect or the
second aspect for transforming the beam from the light source in
order to form an illumination pupil distribution on or near an
illumination pupil of the illumination optical apparatus.
[0019] A fourth aspect of the present embodiment is to provide an
exposure apparatus comprising the illumination optical apparatus of
the third aspect for illuminating a pattern,
[0020] the exposure apparatus being arranged to project the pattern
onto a photosensitive substrate.
[0021] A fifth aspect of the present embodiment is to provide an
exposure method comprising: an illumination step of illuminating a
pattern by use of the illumination optical apparatus of the third
aspect; and an exposure step of projecting the pattern onto a
photosensitive substrate.
[0022] The illumination optical apparatus of the present
embodiment, different from the conventional technology giving rise
to the large loss of light quantity at the aperture stop, is able
to form the illumination pupil distribution of the annular shape in
the azimuthal polarization state, with no substantial loss of light
quantity, by diffraction and optical rotating action of the
diffractive optical element as the beam transforming element.
Namely, the illumination optical apparatus of the present invention
is able to form the illumination pupil distribution of the annular
shape in the azimuthal polarization state while well suppressing
the loss of light quantity.
[0023] Since the exposure apparatus and exposure method using the
illumination optical apparatus of the present embodiment are
arranged to use the illumination optical apparatus capable of
forming the illumination pupil distribution of the annular shape in
the azimuthal polarization state while well suppressing the loss of
light quantity, they are able to transcribe a microscopic pattern
in an arbitrary direction under an appropriate illumination
condition faithfully and with high throughput and, in turn, to
produce good devices with high throughput.
[0024] The present invention will be more fully understood from the
detailed description given hereinbelow and the accompanying
drawings, which are given by way of illustration only and are not
to be considered as limiting the embodiment.
[0025] Further scope of applicability of the embodiment will become
apparent from the detailed description given hereinafter. However,
it should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will be
apparent to those skilled in the art from this detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is an illustration schematically showing a
configuration of an exposure apparatus with an illumination optical
apparatus according to an embodiment of the present invention.
[0027] FIG. 2 is an illustration showing a secondary light source
of an annular shape formed in annular illumination.
[0028] FIG. 3 is an illustration schematically showing a
configuration of a conical axicon system disposed in an optical
path between a front lens unit and a rear lens unit of an afocal
lens in FIG. 1.
[0029] FIG. 4 is an illustration to illustrate the action of the
conical axicon system on the secondary light source of the annular
shape.
[0030] FIG. 5 is an illustration to illustrate the action of a zoom
lens on the secondary light source of the annular shape.
[0031] FIG. 6 is an illustration schematically showing a first
cylindrical lens pair and a second cylindrical lens pair disposed
in an optical path between the front lens unit and the rear lens
unit of the afocal lens in FIG. 1.
[0032] FIG. 7 is a first drawing to illustrate the action of the
first cylindrical lens pair and the second cylindrical lens pair on
the secondary light source of the annular shape.
[0033] FIG. 8 is a second drawing to illustrate the action of the
first cylindrical lens pair and the second cylindrical lens pair on
the secondary light source of the annular shape.
[0034] FIG. 9 is a third drawing to illustrate the action of the
first cylindrical lens pair and the second cylindrical lens pair on
the secondary light source of the annular shape.
[0035] FIG. 10 is a perspective view schematically showing an
internal configuration of a polarization monitor in FIG. 1.
[0036] FIG. 11 is an illustration schematically showing a
configuration of a diffractive optical element for azimuthally
polarized annular illumination according to an embodiment of the
present invention.
[0037] FIG. 12 is an illustration schematically showing a secondary
light source of an annular shape set in the azimuthal polarization
state.
[0038] FIG. 13 is an illustration to illustrate the action of a
first basic element.
[0039] FIG. 14 is an illustration to illustrate the action of a
second basic element.
[0040] FIG. 15 is an illustration to illustrate the action of a
third basic element.
[0041] FIG. 16 is an illustration to illustrate the action of a
fourth basic element.
[0042] FIG. 17 is an illustration to illustrate the optical
activity of crystalline quartz.
[0043] FIGS. 18A and 18B are illustrations showing octapole
secondary light sources in the azimuthal polarization state
consisting of eight arc regions spaced from each other along the
circumferential direction and a quadrupole secondary light source
in the azimuthal polarization state consisting of four arc regions
spaced from each other along the circumferential direction.
[0044] FIG. 19 is an illustration showing a secondary light source
of an annular shape in the azimuthal polarization state consisting
of eight arc regions overlapping with each other along the
circumferential direction.
[0045] FIGS. 20A and 20B are illustrations showing hexapole
secondary light sources in the azimuthal polarization state
consisting of six arc regions spaced from each other along the
circumferential direction and a secondary light source in the
azimuthal polarization state having a plurality of regions spaced
from each other along the circumferential direction and a region on
the optical axis.
[0046] FIG. 21 is an illustration showing an example in which an
entrance-side surface of a diffractive optical element for
azimuthally polarized annular illumination is planar.
[0047] FIG. 22 is a flowchart of a procedure of obtaining
semiconductor devices as microdevices.
[0048] FIG. 23 is a flowchart of a procedure of obtaining a liquid
crystal display element as a microdevice.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Embodiments of the present invention will be described based
on the accompanying drawings.
[0050] FIG. 1 is an illustration schematically showing a
configuration of an exposure apparatus with an illumination optical
apparatus according to an embodiment of the present invention. In
FIG. 1, the Z-axis is defined 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 the plane of the wafer
W, and the X-axis along a direction of a normal to the plane of
FIG. 1 in the plane of wafer W. The exposure apparatus of the
present embodiment is provided with a light source 1 for supplying
exposure light (illumination light).
[0051] The light source 1 can be, for example, a KrF excimer laser
light source for supplying light with the wavelength of 248 nm, an
ArF excimer laser light source for supplying light with the
wavelength of 193 nm, or the like. A nearly parallel beam emitted
along the Z-direction from the light source 1 has a cross section
of a rectangular shape elongated along the X-direction, and is
incident to a beam expander 2 consisting of a pair of lenses 2a and
2b. The lenses 2a and 2b have a negative refracting power and a
positive refracting power, respectively, in the plane of FIG. 1 (or
in the YZ plane). Therefore, the beam incident to the beam expander
2 is enlarged in the plane of FIG. 1 and shaped into a beam having
a cross section of a predetermined rectangular shape.
[0052] The nearly parallel beam passing through the beam expander 2
as a beam shaping optical system is deflected into the Y-direction
by a bending mirror 3, and then travels through a quarter wave
plate 4a, a half wave plate 4b, a depolarizer (depolarizing
element) 4c, and a diffractive optical element 5 for annular
illumination to enter an afocal lens 6. Here the quarter wave plate
4a, half wave plate 4b, and depolarizer 4c constitute a
polarization state converter 4, as described later. The afocal lens
6 is an afocal system (afocal optic) set so that the front focal
position thereof approximately coincides with the position of the
diffractive optical element 5 and so that the rear focal position
thereof approximately coincides with the position of a
predetermined plane 7 indicated by a dashed line in the
drawing.
[0053] In general, a diffractive optical element is constructed by
forming level differences with the pitch of approximately the
wavelength of exposure light (illumination light) in a substrate
and has the action of diffracting an incident beam at desired
angles. Specifically, the diffractive optical element 5 for annular
illumination has the following function: when a parallel beam
having a rectangular cross section is incident thereto, it forms a
light intensity distribution of an annular shape in its far field
(or Fraunhofer diffraction region). Therefore, the nearly parallel
beam incident to the diffractive optical element 5 as a beam
transforming element forms a light intensity distribution of an
annular shape on the pupil plane of the afocal lens 6 and then
emerges as a nearly parallel beam from the afocal lens 6.
[0054] In an optical path between front lens unit 6a and rear lens
unit 6b of the afocal lens 6 there are a conical axicon system 8, a
first cylindrical lens pair 9, and a second cylindrical lens pair
10 arranged in order from the light source side on or near the
pupil plane of the afocal lens, and the detailed configuration and
action thereof will be described later. For easier description, the
fundamental configuration and action will be described below, in
disregard of the action of the conical axicon system 8, first
cylindrical lens pair 9, and second cylindrical lens pair 10.
[0055] The beam through the afocal lens 6 travels through a zoom
lens 11 for variation of .sigma.-value and then enters a micro
fly's eye lens (or fly's eye lens) 12 as an optical integrator. The
micro fly's eye lens 12 is an optical element consisting of a
number of micro lenses with a positive refracting power arranged
lengthwise and breadthwise and densely. In general, a micro fly's
eye lens is constructed, for example, by forming a micro lens group
by etching of a plane-parallel plate.
[0056] Here each micro lens forming the micro fly's eye lens is
much smaller than each lens element forming a fly's eye lens. The
micro fly's eye lens is different from the fly's eye lens
consisting of lens elements spaced from each other, in that a
number of micro lenses (micro refracting surfaces) are integrally
formed without being separated from each other. In the sense that
lens elements with a positive refracting power are arranged
lengthwise and breadthwise, however, the micro fly's eye lens is a
wavefront splitting optical integrator of the same type as the
fly's eye lens. Detailed explanation concerning the micro fly's eye
lens capable of being used in the present invention is disclosed,
for example, in U.S. Pat. No. 6,913,373(B2) which is incorporated
herein by reference in its entirety.
[0057] The position of the predetermined plane 7 is arranged near
the front focal position of the zoom lens 11, and the entrance
surface of the micro fly's eye lens 12 is arranged near the rear
focal position of the zoom lens 11. In other words, the zoom lens
11 arranges the predetermined plane 7 and the entrance surface of
the micro fly's eye lens 12 substantially in the relation of
Fourier transform and eventually arranges the pupil plane of the
afocal lens 6 and the entrance surface of the micro fly's eye lens
12 approximately optically conjugate with each other.
[0058] Accordingly, for example, an illumination field of an
annular shape centered around the optical axis AX is formed on the
entrance surface of the micro fly's eye lens 12, as on the pupil
plane of the afocal lens 6. The entire shape of this annular
illumination field similarly varies depending upon the focal length
of the zoom lens 11. Each micro lens forming the micro fly's eye
lens 12 has a rectangular cross section similar to a shape of an
illumination field to be formed on a mask M (eventually, a shape of
an exposure region to be formed on a wafer W).
[0059] The beam incident to the micro fly's eye lens 12 is
two-dimensionally split by a number of micro lenses to form on its
rear focal plane (eventually on the illumination pupil) a secondary
light source having much the same light intensity distribution as
the illumination field formed by the incident beam, i.e., a
secondary light source consisting of a substantial surface
illuminant of an annular shape centered around the optical axis AX,
as shown in FIG. 2. Beams from the secondary light source formed on
the rear focal plane of the micro fly's eye lens 12 (in general, an
illumination pupil distribution formed on or near the pupil plane
of the illumination optical apparatus) travel through beam splitter
13a and condenser optical system 14 to superposedly illuminate a
mask blind 15.
[0060] In this manner, an illumination field of a rectangular shape
according to the shape and focal length of each micro lens forming
the micro fly's eye lens 12 is formed on the mask blind 15 as an
illumination field stop. The internal configuration and action of
polarization monitor 13 incorporating a beam splitter 13a will be
described later. Beam through a rectangular aperture (light
transmitting portion) of the mask blind 15 are subject to light
condensing action of imaging optical system 16 and thereafter
superposedly illuminate the mask M on which a predetermined pattern
is formed.
[0061] Namely, the imaging optical system 16 forms an image of the
rectangular aperture of the mask blind 15 on the mask M. A beam
passing through the pattern of mask M travels through a projection
optical system PL to form an image of the mask pattern on the wafer
W being a photosensitive substrate. In this manner, the pattern of
the mask M is sequentially printed in each exposure area on the
wafer W through full-wafer exposure or scan exposure with
two-dimensional drive control of the wafer W in the plane (XY
plane) perpendicular to the optical axis AX of the projection
optical system PL.
[0062] In the polarization state converter 4, the quarter wave
plate 4a is arranged so that its crystallographic axis is rotatable
around the optical axis AX, and it transforms incident light of
elliptical polarization into light of linear polarization. The half
wave plate 4b is arranged so that its crystallographic axis is
rotatable around the optical axis AX, and it changes the plane of
polarization of linearly polarized light incident thereto. The
depolarizer 4c is composed of a wedge-shaped crystalline quartz
prism (not shown) and a wedge-shaped fused sillica prism (not
shown) having complementary shapes. The crystalline quartz prism
and the fussed sillica prism are constructed as an integral prism
assembly so as to be set into and away from the illumination
optical path.
[0063] Where the light source 1 is the KrF excimer laser light
source or the ArF excimer laser light source, light emitted from
these light sources typically has the degree of polarization of 95%
or more and light of almost linear polarization is incident to the
quarter wave plate 4a. However, if a right-angle prism as a
back-surface reflector is interposed in the optical path between
the light source 1 and the polarization state converter 4, the
linearly polarized light will be changed into elliptically
polarized light by virtue of total reflection in the right-angle
prism unless the plane of polarization of the incident, linearly
polarized light agrees with the P-polarization plane or
S-polarization plane.
[0064] In the case of the polarization state converter 4, for
example, even if light of elliptical polarization is incident
thereto because of the total reflection in the right-angle prism,
light of linear polarization transformed by the action of the
quarter wave plate 4a will be incident to the half wave plate 4b.
Where the crystallographic axis of the half wave plate 4b is set at
an angle of 0.degree. or 90.degree. relative to the plane of
polarization of the incident, linearly polarized light, the light
of linear polarization incident to the half wave plate 4b will pass
as it is, without change in the plane of polarization.
[0065] Where the crystallographic axis of the half wave plate 4b is
set at an angle of 45.degree. relative to the plane of polarization
of the incident, linearly polarized light, the light of linear
polarization incident to the half wave plate 4b will be transformed
into light of linear polarization with change of polarization plane
of 90.degree.. Furthermore, where the crystallographic axis of the
crystalline quartz prism in the depolarizer 4c is set at an angle
of 45.degree. relative to the polarization plane of the incident,
linearly polarized light, the light of linear polarization incident
to the crystalline quartz prism will be transformed (or
depolarized) into light in an unpolarized state.
[0066] The polarization state converter 4 is arranged as follows:
when the depolarizer 4c is positioned in the illumination optical
path, the crystallographic axis of the crystalline quartz prism
makes the angle of 45.degree. relative to the polarization plane of
the incident, linearly polarized light. Incidentally, where the
crystallographic axis of the crystalline quartz prism is set at the
angle of 0.degree. or 90.degree. relative to the polarization plane
of the incident, linearly polarized light, the light of linear
polarization incident to the crystalline quartz prism will pass as
it is, without change of the polarization plane. Where the
crystallographic axis of the half wave plate 4b is set at an angle
of 22.5.degree. relative to the polarization plane of incident,
linearly polarized light, the light of linear polarization incident
to the half wave plate 4b will be transformed into light in an
unpolarized state including a linear polarization component
directly passing without change of the polarization plane and a
linear polarization component with the polarization plane rotated
by 90.degree..
[0067] The polarization state converter 4 is arranged so that light
of linear polarization is incident to the half wave plate 4b, as
described above, and, for easier description hereinafter, it is
assumed that light of linear polarization having the direction of
polarization (direction of the electric field) along the Z-axis in
FIG. 1 (hereinafter referred to as "Z-directionally polarized
light") is incident to the half wave plate 4b. When the depolarizer
4c is positioned in the illumination optical path and when the
crystallographic axis of the half wave plate 4b is set at the angle
of 0.degree. or 90.degree. relative to the polarization plane
(direction of polarization) of the Z-directionally polarized light
incident thereto, the light of Z-directional polarization incident
to the half wave plate 4b passes as kept as Z-directionally
polarized light without change of the polarization plane and enters
the crystalline quartz prism in the depolarizer 4c. Since the
crystallographic axis of the crystalline quartz prism is set at the
angle of 45.degree. relative to the polarization plane of the
Z-directionally polarized light incident thereto, the light of
Z-directional polarization incident to the crystalline quartz prism
is transformed into light in an unpolarized state.
[0068] The light depolarized through the crystalline quartz prism
travels through the quartz prism as a compensator for compensating
the traveling direction of the light and is incident into the
diffractive optical element 5 while being in the depolarized state.
On the other hand, if the crystallographic axis of the half wave
plate 4b is set at the angle of 45.degree. relative to the
polarization plane of the Z-directionally polarized light incident
thereto, the light of Z-directional polarization incident to the
half wave plate 4b will be rotated in the polarization plane by
90.degree. and transformed into light of linear polarization having
the polarization direction (direction of the electric field) along
the X-direction in FIG. 1 (hereinafter referred to as
"X-directionally polarized light") and the X-directionally
polarized light will be incident to the crystalline quartz prism in
the depolarizer 4c. Since the crystallographic axis of the
crystalline quartz prism is set at the angle of 45.degree. relative
to the polarization plane of the incident, X-directionally
polarized light as well, the light of X-directional polarization
incident to the crystalline quartz prism is transformed into light
in the depolarized state, and the light travels through the quartz
prism to be incident in the depolarized state into the diffractive
optical element 5.
[0069] In contrast, when the depolarizer 4c is set away from the
illumination optical path, if the crystallographic axis of the half
wave plate 4b is set at the angle of 0.degree. or 90.degree.
relative to the polarization plane of the Z-directionally polarized
light incident thereto, the light of Z-directional polarization
incident to the half wave plate 4b will pass as kept as
Z-directionally polarized light without change of the polarization
plane, and will be incident in the Z-directionally polarized state
into the diffractive optical element 5. If the crystallographic
axis of the half wave plate 4b is set at the angle of 45.degree.
relative to the polarization plane of the Z-directionally polarized
light incident thereto on the other hand, the light of
Z-directional polarization incident to the half wave plate 4b will
be transformed into light of X-directional polarization with the
polarization plane rotated by 90.degree., and will be incident in
the X-directionally polarized state into the diffractive optical
element 5.
[0070] In the polarization state converter 4, as described above,
the light in the depolarized state can be made incident to the
diffractive optical element 5 when the depolarizer 4c is set and
positioned in the illumination optical path. When the depolarizer
4c is set away from the illumination optical path and when the
crystallographic axis of the half wave plate 4b is set at the angle
of 0.degree. or 90.degree. relative to the polarization plane of
the Z-directionally polarized light incident thereto, the light in
the Z-directionally polarized state can be made incident to the
diffractive optical element 5. Furthermore, when the depolarizer 4c
is set away from the illumination optical path and when the
crystallographic axis of the half wave plate 4b is set at the angle
of 45.degree. relative to the polarization plane of the
Z-directionally polarized light incident thereto, the light in the
X-directionally polarized state can be made incident to the
diffractive optical element 5.
[0071] In other words, the polarization state converter 4 is able
to switch the polarization state of the incident light into the
diffractive optical element 5 (a state of polarization of light to
illuminate the mask M and wafer W in use of an ordinary diffractive
optical element except for the diffractive optical element for
azimuthally polarized annular illumination according to the present
invention as will be described later) between the linearly
polarized state and the unpolarized state through the action of the
polarization state converter consisting of the quarter wave plate
4a, half wave plate 4b, and depolarizer 4c, and, in the case of the
linearly polarized state, it is able to switch between mutually
orthogonal polarization states (between the Z-directional
polarization and the X-directional polarization).
[0072] FIG. 3 is an illustration schematically showing the
configuration of the conical axicon system disposed in the optical
path between the front lens unit and the rear lens unit of the
afocal lens in FIG. 1. The conical axicon system 8 is composed of a
first prism member 8a whose plane is kept toward the light source
and whose refracting surface of a concave conical shape is kept
toward the mask, and a second prism member 8b whose plane is kept
toward the mask and whose refracting surface of a convex conical
shape is kept toward the light source, in order from the light
source side.
[0073] The refracting surface of the concave conical shape of the
first prism member 8a and the refracting surface of the convex
conical shape of the second prism member 8b are formed in a
complementary manner so as to be able to be brought into contact
with each other. At least one of the first prism member 8a and the
second prism member 8b is arranged movable along the optical axis
AX, so that the spacing can be varied between the refracting
surface of the concave conical shape of the first prism member 8a
and the refracting surface of the convex conical shape of the
second prism member 8b.
[0074] In a state in which the refracting surface of the concave
conical shape of the first prism member 8a and the refracting
surface of the convex conical shape of the second prism member 8b
are in contact with each other, the conical axicon system 8
functions as a plane-parallel plate and has no effect on the
secondary light source of the annular shape formed. However, when
the refracting surface of the concave conical shape of the first
prism member 8a and the refracting surface of the convex conical
shape of the second prism member 8b are spaced from each other, the
conical axicon system 8 functions a so-called beam expander.
Therefore, the angle of the incident beam to the predetermined
plane 7 varies according to change in the spacing of the conical
axicon system 8.
[0075] FIG. 4 is an illustration to illustrate the action of the
conical axicon system on the secondary light source of the annular
shape. With reference to FIG. 4, the secondary light source 30a of
the minimum annular shape formed in a state where the spacing of
the conical axicon system 8 is zero and where the focal length of
the zoom lens 11 is set at the minimum (this state will be referred
to hereinafter as a "standard state") is changed into secondary
light source 30b of an annular shape with the outside diameter and
inside diameter both enlarged and without change in the width (half
of the difference between the inside diameter and the outside
diameter: indicated by arrows in the drawing) when the spacing of
the conical axicon system 8 is increased from zero to a
predetermined value. In other words, an annular ratio (inside
diameter/outside diameter) and size (outside diameter) both vary
through the action of the conical axicon system 8, without change
in the width of the secondary light source of the annular
shape.
[0076] FIG. 5 is an illustration to illustrate the action of the
zoom lens on the secondary light source of the annular shape. With
reference to FIG. 5, the secondary light source 30a of the annular
shape formed in the standard state is changed into secondary light
source 30c of an annular shape whose entire shape is similarly
enlarged by increasing the focal length of the zoom lens 11 from
the minimum to a predetermined value. In other words, the width and
size (outside diameter) both vary through the action of zoom lens
11, without change in the annular ratio of the secondary light
source of the annular shape.
[0077] FIG. 6 is an illustration schematically showing the
configuration of the first cylindrical lens pair and the second
cylindrical lens pair disposed in the optical path between the
front lens unit and the rear lens unit of the afocal lens in FIG.
1. In FIG. 6, the first cylindrical lens pair 9 and the second
cylindrical lens pair 10 are arranged in order from the light
source side. The first cylindrical lens pair 9 is composed, for
example, of a first cylindrical negative lens 9a with a negative
refracting power in the YZ plane and with no refracting power in
the XY plane, and a first cylindrical positive lens 9b with a
positive refracting power in the YZ plane and with no refracting
power in the XY plane, which are arranged in order from the light
source side.
[0078] On the other hand, the second cylindrical lens pair 10 is
composed, for example, of a second cylindrical negative lens 10a
with a negative refracting power in the XY plane and with no
refracting power in the YZ plane, and a second cylindrical positive
lens 10b with a positive refracting power in the XY plane and with
no refracting power in the YZ plane, which are arranged in order
from the light source side. The first cylindrical negative lens 9a
and the first cylindrical positive lens 9b are arranged so as to
integrally rotate around the optical axis AX. Similarly, the second
cylindrical negative lens 10a and the second cylindrical positive
lens 10b are arranged so as to integrally rotate around the optical
axis AX.
[0079] In the state shown in FIG. 6, the first cylindrical lens
pair 9 functions as a beam expander having a power in the
Z-direction, and the second cylindrical lens pair 10 as a beam
expander having a power in the X-direction. The power of the first
cylindrical lens pair 9 and the power of the second cylindrical
lens pair 10 are set to be equal to each other.
[0080] FIGS. 7 to 9 are illustrations to illustrate the action of
the first cylindrical lens pair and the second cylindrical lens
pair on the secondary light source of the annular shape. FIG. 7
shows such a setting that the direction of the power of the first
cylindrical lens pair 9 makes the angle of +45.degree. around the
optical axis AX relative to the Z-axis and that the direction of
the power of the second cylindrical lens pair 10 makes the angle of
-45.degree. around the optical axis AX relative to the Z-axis.
[0081] Therefore, the direction of the power of the first
cylindrical lens pair 9 is perpendicular to the direction of the
power of the second cylindrical lens pair 10, and the composite
system of the first cylindrical lens pair 9 and the second
cylindrical lens pair 10 has the Z-directional power and the
X-directional power identical to each other. As a result, in a
perfect circle state shown in FIG. 7, a beam passing through the
composite system of the first cylindrical lens pair 9 and the
second cylindrical lens pair 10 is subject to enlargement at the
same power in the Z-direction and in the X-direction to form the
secondary light source of a perfect-circle annular shape on the
illumination pupil.
[0082] In contrast to it, FIG. 8 shows such a setting that the
direction of the power of the first cylindrical lens pair 9 makes,
for example, the angle of +80.degree. around the optical axis AX
relative to the Z-axis and that the direction of the power of the
second cylindrical lens pair 10 makes, for example, the angle of
-80.degree. around the optical axis AX relative to the Z-axis.
Therefore, the power in the X-direction is greater than the power
in the Z-direction in the composite system of the first cylindrical
lens pair 9 and the second cylindrical lens pair 10. As a result,
in a horizontally elliptic state shown in FIG. 8, the beam passing
through the composite system of the first cylindrical lens pair 9
and the second cylindrical lens pair 10 is subject to enlargement
at the power greater in the X-direction than in the Z-direction,
whereby the secondary light source of a horizontally long annular
shape elongated in the X-direction is formed on the illumination
pupil.
[0083] On the other hand, FIG. 9 shows such a setting that the
direction of the power of the first cylindrical lens pair 9 makes,
for example, the angle of +10.degree. around the optical axis AX
relative to the Z-axis and that the direction of the power of the
second cylindrical lens pair 10 makes, for example, the angle of
-10.degree. around the optical axis AX relative to the Z-axis.
Therefore, the power in the Z-direction is greater than the power
in the X-direction in the composite system of the first cylindrical
lens pair 9 and the second cylindrical lens pair 10. As a result,
in a vertically elliptical state shown in FIG. 9, the beam passing
through the composite system of the first cylindrical lens pair 9
and the second cylindrical lens pair 10 is subject to enlargement
at the power greater in the Z-direction than in the X-direction,
whereby the secondary light source of a vertically long annular
shape elongated in the Z-direction is formed on the illumination
pupil.
[0084] Furthermore, by setting the first cylindrical lens pair 9
and the second cylindrical lens pair 10 in an arbitrary state
between the perfect circle state shown in FIG. 7 and the
horizontally elliptical state shown in FIG. 8, the secondary light
source can be formed in a horizontally long annular shape according
to any one of various aspect ratios. By setting the first
cylindrical lens pair 9 and the second cylindrical lens pair 10 in
an arbitrary state between the perfect circle state shown in FIG. 7
and the vertically elliptical state shown in FIG. 9, the secondary
light source can be formed in a vertically long annular shape
according to any one of various aspect ratios.
[0085] FIG. 10 is a perspective view schematically showing the
internal configuration of the polarization monitor shown in FIG. 1.
With reference to FIG. 10, the polarization monitor 10 is provided
with a first beam splitter 13a disposed in the optical path between
the micro fly's eye lens 12 and the condenser optical system 14.
The first beam splitter 13a has, for example, the form of a
non-coated plane-parallel plate made of quartz glass (i.e., raw
glass), and has a function of taking reflected light in a
polarization state different from a polarization state of incident
light, out of the optical path.
[0086] The light taken out of the optical path by the first beam
splitter 13a is incident to a second beam splitter 13b. The second
beam splitter 13b has, for example, the form of a non-coated
plane-parallel plate made of quartz glass as the first beam
splitter 13a does, and has a function of generating reflected light
in a polarization state different from the polarization state of
incident light. The polarization monitor is so set that the
P-polarized light for the first beam splitter 13a becomes the
S-polarized light for the second beam splitter 13b and that the
S-polarized light for the first beam splitter 13a becomes the
P-polarized light for the second beam splitter 13b.
[0087] Light transmitted by the second beam splitter 13b is
detected by first light intensity detector 13c, while light
reflected by the second beam splitter 13b is detected by second
light intensity detector 13d. Outputs from the first light
intensity detector 13c and from the second light intensity detector
13d are supplied each to a controller (not shown). The controller
drives the quarter wave plate 4a, half wave plate 4b, and
depolarizer 4c constituting the polarization state converter 4,
according to need.
[0088] As described above, the reflectance for the P-polarized
light and the reflectance for the S-polarized light are
substantially different in the first beam splitter 13a and in the
second beam splitter 13b. In the polarization monitor 13,
therefore, the reflected light from the first beam splitter 13a
includes the S-polarization component (i.e., the S-polarization
component for the first beam splitter 13a and P-polarization
component for the second beam splitter 13b), for example, which is
approximately 10% of the incident light to the first beam splitter
13a, and the P-polarization component (i.e., the P-polarization
component for the first beam splitter 13a and S-polarization
component for the second beam splitter 13b), for example, which is
approximately 1% of the incident light to the first beam splitter
13a.
[0089] The reflected light from the second beam splitter 13b
includes the P-polarization component (i.e., the P-polarization
component for the first beam splitter 13a and S-polarization
component for the second beam splitter 13b), for example, which is
approximately 10%.times.1%=0.1% of the incident light to the first
beam splitter 13a, and the S-polarization component (i.e., the
S-polarization component for the first beam splitter 13a and
P-polarization component for the second beam splitter 13b), for
example, which is approximately 1%.times.10%=0.1% of the incident
light to the first beam splitter 13a.
[0090] In the polarization monitor 13, as described above, the
first beam splitter 13a has the function of extracting the
reflected light in the polarization state different from the
polarization state of the incident light out of the optical path in
accordance with its reflection characteristic. As a result, though
there is slight influence of variation of polarization due to the
polarization characteristic of the second beam splitter 13b, it is
feasible to detect the polarization state (degree of polarization)
of the incident light to the first beam splitter 13a and,
therefore, the polarization state of the illumination light to the
mask M, based on the output from the first light intensity detector
13c (information about the intensity of transmitted light from the
second beam splitter 13b, i.e., information about the intensity of
light virtually in the same polarization state as that of the
reflected light from the first beam splitter 13a).
[0091] The polarization monitor 13 is so set that the P-polarized
light for the first beam splitter 13a becomes the S-polarized light
for the second beam splitter 13b and that the S-polarized light for
the first beam splitter 13a becomes the P-polarized light for the
second beam splitter 13b. As a result, it is feasible to detect the
light quantity (intensity) of the incident light to the first beam
splitter 13a and, therefore, the light quantity of the illumination
light to the mask M, with no substantial effect of change in the
polarization state of the incident light to the first beam splitter
13a, based on the output from the second light intensity detector
13d (information about the intensity of light successively
reflected by the first beam splitter 13a and the second beam
splitter 13b).
[0092] In this manner, it is feasible to detect the polarization
state of the incident light to the first beam splitter 13a and,
therefore, to determine whether the illumination light to the mask
M is in the desired unpolarized state or linearly polarized state,
using the polarization monitor 13. When the controller determines
that the illumination light to the mask M (eventually, to the wafer
W) is not in the desired unpolarized state or linearly polarized
state, based on the detection result of the polarization monitor
13, it drives and adjusts the quarter wave plate 4a, half wave
plate 4b, and depolarizer 4c constituting the polarization state
converter 4 so that the state of the illumination light to the mask
M can be adjusted into the desired unpolarized state or linearly
polarized state.
[0093] Quadrupole illumination can be implemented by setting a
diffractive optical element for quadrupole illumination (not shown)
in the illumination optical path, instead of the diffractive
optical element 5 for annular illumination. The diffractive optical
element for quadrupole illumination has such a function that when a
parallel beam having a rectangular cross section is incident
thereto, it forms a light intensity distribution of a quadrupole
shape in the far field thereof. Therefore, the beam passing through
the diffractive optical element for quadrupole illumination forms
an illumination field of a quadrupole shape consisting of four
circular illumination fields centered around the optical axis AX,
for example, on the entrance surface of the micro fly's eye lens
12. As a result, the secondary light source of the same quadrupole
shape as the illumination field formed on the entrance surface is
also formed on the rear focal plane of the micro fly's eye lens
12.
[0094] In addition, ordinary circular illumination can be
implemented by setting a diffractive optical element for circular
illumination (not shown) in the illumination optical path, instead
of the diffractive optical element 5 for annular illumination. The
diffractive optical element for circular illumination has such a
function that when a parallel beam having a rectangular cross
section is incident thereto, it forms a light intensity
distribution of a circular shape in the far field. Therefore, a
beam passing through the diffraction optical element for circular
illumination forms a circular illumination field centered around
the optical axis AX, for example, on the entrance plane of the
micro fly's eye lens 12. As a result, the secondary light source of
the same circular shape as the illumination field formed on the
entrance surface is also formed on the rear focal plane of the
micro fly's eye lens 12.
[0095] Furthermore, a variety of multipole illuminations (dipole
illumination, octapole illumination, etc.) can be implemented by
setting other diffractive optical elements for multipole
illuminations (not shown), instead of the diffractive optical
element 5 for annular illumination. Likewise, modified
illuminations in various forms can be implemented by setting
diffractive optical elements with appropriate characteristics (not
shown) in the illumination optical path, instead of the diffractive
optical element 5 for annular illumination.
[0096] In the present embodiment, a diffractive optical element 50
for so-called azimuthally polarized annular illumination can be
set, instead of the diffractive optical element 5 for annular
illumination, in the illumination optical path, so as to implement
the modified illumination in which the beam passing through the
secondary light source of the annular shape is set in the azimuthal
polarization state, i.e., the azimuthally polarized annular
illumination. FIG. 11 is an illustration schematically showing the
configuration of the diffractive optical element for azimuthally
polarized annular illumination according to the present embodiment.
FIG. 12 is an illustration schematically showing the secondary
light source of the annular shape set in the azimuthal polarization
state.
[0097] With reference to FIGS. 11 and 12, the diffractive optical
element 50 for azimuthally polarized annular illumination according
to the present embodiment is constructed in such an arrangement
that four types of basic elements 50A-50D having the same cross
section of a rectangular shape and having their respective
thicknesses different from each other along the direction of
transmission of light (Y-direction) (i.e., lengths in the direction
of the optical axis) are arranged lengthwise and breadthwise and
densely. The thicknesses are set as follows: the thickness of the
first basic elements 50A is the largest, the thickness of the
fourth basic elements 50D the smallest, and the thickness of the
second basic elements 50B is greater than the thickness of the
third basic elements 50C.
[0098] The diffractive optical element 50 includes an approximately
equal number of first basic elements 50A, second basic elements
50B, third basic elements 50C, and fourth basic elements 50D, and
the four types of basic elements 50A-50D are arranged substantially
at random. Furthermore, a diffracting surface (indicated by
hatching in the drawing) is formed on the mask side of each basic
element 50A-50D, and the diffracting surfaces of the respective
basic elements 50A-50D are arrayed along one plane perpendicular to
the optical axis AX (not shown in FIG. 11). As a result, the
mask-side surface of the diffractive optical element 50 is planar,
while the light-source-side surface of the diffractive optical
element 50 is uneven due to the differences among the thicknesses
of the respective basic elements 50A-50D.
[0099] The diffracting surface of each first basic element 50A is
arranged to form a pair of arc regions (bow shape) 31A symmetric
with respect to an axis line of the Z-direction passing the optical
axis AX, in the secondary light source 31 of the annular shape
shown in FIG. 12. Namely, as shown in FIG. 13, each first basic
element 50A has a function of forming a pair of arc (bow shape)
light intensity distributions 32A symmetric with respect to the
axis line of the Z-direction passing the optical axis AX
(corresponding to a pair of arc regions 31A) in the far field 50E
of the diffractive optical element 50 (i.e., in the far field of
each basic element 50A-50D).
[0100] The diffracting surface of each second basic element 50B is
arranged so as to form a pair of arc (bow shape) regions 31B
symmetric with respect to an axis line obtained by rotating the
axis line of the Z-direction passing the optical axis AX, by
-45.degree. around the Y-axis (or obtained by rotating it by
45.degree. counterclockwise in FIG. 12). Namely, as shown in FIG.
14, each second basic element 50B has a function of forming a pair
of arc (bow shape) light intensity distributions 32B symmetric with
respect to the axis line resulting from the -45.degree. rotation
around the Y-axis, of the axis line of the Z-direction passing the
optical axis AX (corresponding to a pair of arc regions 31B), in
the far field 50E.
[0101] The diffracting surface of each third basic element 50C is
arranged to form a pair of arc (bow shape) regions 31C symmetric
with respect to an axis line of the X-direction passing the optical
axis AX. Namely, as shown in FIG. 15, each third basic element 50C
has a function of forming a pair of arc (bow shape) light intensity
distributions 32C symmetric with respect to the axis line of the
X-direction passing the optical axis AX (corresponding to a pair of
arc regions 31C), in the far field 50E.
[0102] The diffracting surface of each fourth basic element 50D is
arranged so as to form a pair of arc (bow shape) regions 31D
symmetric with respect to an axis line obtained by rotating the
axis of the Z-direction passing the optical axis AX by +45.degree.
around the Y-axis (i.e., obtained by rotating it by 45.degree.
clockwise in FIG. 12). Namely, as shown in FIG. 16, each fourth
basic element 50D has a function of forming a pair of arc (bow
shape) light intensity distributions 32D symmetric with respect to
the axis line resulting from the +45.degree. rotation around the
Y-axis, of the axis line of the Z-direction passing the optical
axis AX (corresponding to a pair of arc regions 31D), in the far
field 50E. The sizes of the respective arc regions 31A-31D are
approximately equal to each other, and they form the secondary
light source 31 of the annular shape centered around the optical
axis AX, while the eight arc regions 31A-31D are not overlapping
with each other and not spaced from each other.
[0103] In the present embodiment, each basic element 50A-50D is
made of crystalline quartz being an optical material with optical
activity, and the crystallographic axis of each basic element
50A-50D is set approximately to coincide with the optical axis AX.
The optical activity of crystalline quartz will be briefly
described below with reference to FIG. 17. With reference to FIG.
17, an optical member 35 of a plane-parallel plate shape made of
crystalline quartz and in a thickness d is arranged so that its
crystallographic axis coincides with the optical axis AX. In this
case, by virtue of the optical activity of the optical member 35,
incident, linearly polarized light emerges in a state in which
its-polarization direction is rotated by .theta. around the optical
axis AX.
[0104] At this time, the angle .theta. of rotation of the
polarization direction due to the optical activity of the optical
member 35 is represented by Eq (1) below, using the thickness d of
the optical member 35 and the rotatory power .rho. of crystalline
quartz. .theta.=d.rho. (1)
[0105] In general, the rotatory power .rho. of crystalline quartz
tends to increase with decrease in the wavelength of used light
and, according to the description on page 167 in "Applied Optics
II," the rotatory power .rho. of crystalline quartz for light
having the wavelength of 250.3 nm is 153.9.degree./mm.
[0106] In the present embodiment the first basic elements 50A are
designed in such a thickness dA that when light of linear
polarization having the direction of polarization along the
Z-direction is incident thereto, they output light of linear
polarization having the polarization direction along a direction
resulting from +180.degree. rotation of the Z-direction around the
Y-axis, i.e., along the Z-direction, as shown in FIG. 13. As a
result, the polarization direction of beams passing through a pair
of arc light intensity distributions 32A formed in the far field
50E is also the Z-direction, and the polarization direction of
beams passing through a pair of arc regions 31A shown in FIG. 12 is
also the Z-direction.
[0107] The second basic elements 50B are designed in such a
thickness dB that when light of linear polarization having the
polarization direction along the Z-direction is incident thereto,
they output light of linear polarization having the polarization
direction along a direction resulting from +135.degree. rotation of
the Z-direction around the Y-axis, i.e., along a direction
resulting from -45.degree. rotation of the Z-direction around the
Y-axis, as shown in FIG. 14. As a result, the polarization
direction of beams passing through a pair of arc light intensity
distributions 32B formed in the far field 50E is also the direction
obtained by rotating the Z-direction by -45.degree. around the
Y-axis, and the polarization direction of beams passing through a
pair of arc regions 31A shown in FIG. 12 is also the direction
obtained by rotating the Z-direction by -45.degree. around the
Y-axis.
[0108] The third basic elements 50C are designed in such a
thickness dC that when light of linear polarization having the
polarization direction along the Z-direction is incident thereto,
they output light of linear polarization having the polarization
direction along a direction resulting from +90.degree. rotation of
the Z-direction around the Y-axis, i.e., along the X-direction, as
shown in FIG. 15. As a result, the polarization direction of beams
passing through a pair of arc light intensity distributions 32C
formed in the far field 50E is also the X-direction, and the
polarization direction of beams passing through a pair of arc
regions 31C shown in FIG. 12 is also the X-direction.
[0109] The fourth basic elements 50D are designed in such a
thickness dD that when light of linear polarization having the
polarization direction along the Z-direction is incident thereto,
they output light of linear polarization having the polarization
direction along a direction resulting from +45.degree. rotation of
the Z-direction around the Y-axis, as shown in FIG. 16. As a
result, the polarization direction of beams passing through a pair
of arc light intensity distributions 32D formed in the far field
50E is also the direction obtained by rotating the Z-direction by
+45.degree. around the Y-axis, and the polarization direction of
beams passing through a pair of arc regions 31D shown in FIG. 12 is
also the direction obtained by rotating the Z-direction by
+45.degree. around the Y-axis.
[0110] In the present embodiment, the diffractive optical element
50 for azimuthally polarized annular illumination is set in the
illumination optical system on the occasion of effecting the
azimuthally polarized annular illumination, whereby the light of
linear polarization having the polarization direction along the
Z-direction is made incident to the diffractive optical element 50.
As a result, the secondary light source of the annular shape
(illumination pupil distribution of annular shape) 31 is formed on
the rear focal plane of the micro fly's eye lens 12 (i.e., on or
near the illumination pupil), as shown in FIG. 12, and the beams
passing through the secondary light source 31 of the annular shape
are set in the azimuthal polarization state.
[0111] In the azimuthal polarization state, the beams passing
through the respective arc regions 31A-31D constituting the
secondary light source 31 of the annular shape turn into the
linearly polarized state having the polarization direction
substantially coincident with a tangent line to a circle centered
around the optical axis AX, at the central position along the
circumferential direction of each arc region 31A-31D.
[0112] In the present embodiment, as described above, the beam
transforming element 50 for forming the predetermined light
intensity distribution on the predetermined surface on the basis of
the incident beam comprises the first basic element 50A made of the
optical material with optical activity, for forming the first
region distribution 32A of the predetermined light intensity
distribution on the basis of the incident beam; and the second
basic element 50B made of the optical material with optical
activity, for forming the second region distribution 32B of the
predetermined light intensity distribution on the basis of the
incident beam, and the first basic element 50A and the second basic
element 50B have their respective thicknesses different from each
other along the direction of transmission of light.
[0113] Thanks to this configuration, the present embodiment is able
to form the secondary light source 31 of the annular shape in the
azimuthal polarization state, with no substantial loss of light
quantity, through the diffracting action and optical rotating
action of the diffractive optical element 50 as the beam
transforming element, different from the conventional technology
giving rise to the large loss of light quantity at the aperture
stop.
[0114] In a preferred form of the present embodiment, the thickness
of the first basic element 50A and the thickness of the second
basic element 50B are so set that with incidence of linearly
polarized light the polarization direction of the linearly
polarized light forming the first region distribution 32A is
different from the polarization direction of the linearly polarized
light forming the second region distribution 32B. Preferably, the
first region distribution 32A and the second region distribution
32B are positioned in at least a part of a predetermined annular
region, which is a predetermined annular region centered around a
predetermined point on the predetermined surface, and the beams
passing through the first region distribution 32A and through the
second region distribution 32B have a polarization state in which a
principal component is linearly polarized light having the
polarization direction along the circumferential direction of the
predetermined annular region.
[0115] In this case, preferably, the predetermined light intensity
distribution has a contour of virtually the same shape as the
predetermined annular region, the polarization state of the beam
passing through the first region distribution 32A has a linear
polarization component substantially coincident with a tangential
direction to a circle centered around a predetermined point at the
central position along the circumferential direction of the first
region distribution 32A, and the polarization state of the beam
passing through the second region distribution 32B has a linear
polarization component substantially coincident with a tangential
direction to a circle centered around a predetermined point at the
central position along the circumferential direction of the second
region distribution 32B. In another preferred configuration, the
predetermined light intensity distribution is a distribution of a
multipole shape in the predetermined annular region, the
polarization state of the beam passing through the first region
distribution has a linear polarization component substantially
coincident with a tangential direction to a circle centered around
a predetermined point at the central position along the
circumferential direction of the first region distribution, and the
polarization state of the beam passing through the second region
distribution has a linear polarization component substantially
coincident with a tangential direction to a circle centered around
a predetermined point at the central position along the
circumferential direction of the second region distribution.
[0116] In a preferred form of the present embodiment, the first
basic element and the second basic element are made of an optical
material with an optical rotatory power of not less than
100.degree./mm for light of a wavelength used. Preferably, the
first basic element and the second basic element are made of
crystalline quartz. The beam transforming element preferably
includes virtually the same number of first basic elements and
second basic elements. The first basic element and the second basic
element preferably have diffracting action or refracting
action.
[0117] In another preferred form of the present embodiment,
preferably, the first basic element forms at least two first region
distributions on the predetermined surface on the basis of the
incident beam, and the second basic element forms at least two
second region distributions on the predetermined surface on the
basis of the incident beam. In addition, preferably, the beam
transforming element further comprises the third basic element 50C
made of the optical material with optical activity, for forming the
third region distribution 32C of the predetermined light intensity
distribution on the basis of the incident beam, and the fourth
basic element 50D made of the optical material with optical
activity, for forming the fourth region distribution 32D of the
predetermined light intensity distribution on the basis of the
incident beam.
[0118] In the present embodiment, the beam transforming element 50
for forming the predetermined light intensity distribution of the
shape different from the sectional shape of the incident beam, on
the predetermined surface, has the diffracting surface or
refracting surface for forming the predetermined light intensity
distribution on the predetermined surface, the predetermined light
intensity distribution is a distribution in at least a part of a
predetermined annular region, which is a predetermined annular
region centered around a predetermined point on the predetermined
surface, and the beam from the beam transforming element passing
through the predetermined annular region has a polarization state
in which a principal component is linearly polarized light having
the direction of polarization along the circumferential direction
of the predetermined annular region.
[0119] In the configuration as described above, the present
embodiment, different from the conventional technology giving rise
to the large loss of light quantity at the aperture stop, is able
to form the secondary light source 31 of the annular shape in the
azimuthal polarization state, with no substantial loss of light
quantity, through the diffracting action and optical rotating
action of the diffractive optical element 50 as the beam
transforming element.
[0120] In a preferred form of the present embodiment, the
predetermined light intensity distribution has a contour of a
multipole shape or annular shape. The beam transforming element is
preferably made of an optical material with optical activity.
[0121] The illumination optical apparatus of the present embodiment
is the illumination optical apparatus for illuminating the surface
to be illuminated, based on the beam from the light source, and
comprises the above-described beam transforming element for
transforming the beam from the light source in order to form the
illumination pupil distribution on or near the illumination pupil
of the illumination optical apparatus. In this configuration, the
illumination optical apparatus of the present embodiment is able to
form the illumination pupil distribution of the annular shape in
the azimuthal polarization state while well suppressing the loss of
light quantity.
[0122] Here the beam transforming element is preferably arranged to
be replaceable with another beam transforming element having a
different characteristic. Preferably, the apparatus further
comprises the wavefront splitting optical integrator disposed in
the optical path between the beam transforming element and the
surface to be illuminated, and the beam transforming element forms
the predetermined light intensity distribution on the entrance
surface of the optical integrator on the basis of the incident
beam.
[0123] In a preferred form of the illumination optical apparatus of
the present embodiment, at least one of the light intensity
distribution on the predetermined surface and the polarization
state of the beam from the beam transforming element passing
through the predetermined annular region is set in consideration of
the influence of an optical member disposed in the optical path
between the light source and the surface to be illuminated.
Preferably, the polarization state of the beam from the beam
transforming element is so set that the light illuminating the
surface to be illuminated is in a polarization state in which a
principal component is S-polarized light.
[0124] The exposure apparatus of the present embodiment comprises
the above-described illumination optical apparatus for illuminating
the mask, and projects the pattern of the mask onto the
photosensitive substrate. Preferably, at least one of the light
intensity distribution on the predetermined surface and the
polarization state of the beam from the beam transforming element
passing through the predetermined annular region is set in
consideration of the influence of an optical member disposed in the
optical path between the light source and the photosensitive
substrate. Preferably, the polarization state of the beam from the
beam transforming element is so set that the light illuminating the
photosensitive substrate is in a polarization state in which a
principal component is S-polarized light.
[0125] The exposure method of the present embodiment comprises the
illumination step of illuminating the mask by use of the
above-described illumination optical apparatus, and the exposure
step of projecting the pattern of the mask onto the photosensitive
substrate. Preferably, at least one of the light intensity
distribution on the predetermined surface and the polarization
state of the beam from the beam transforming element passing
through the predetermined annular region is set in consideration of
the influence of an optical member disposed in the optical path
between the light source and the photosensitive substrate.
Preferably, the polarization state of the beam from the beam
transforming element is so set that the light illuminating the
photosensitive substrate is in a polarization state in which a
principal component is S-polarized light.
[0126] In other words, the illumination optical apparatus of the
present embodiment is able to form the illumination pupil
distribution of the annular shape in the azimuthal polarization
state while well suppressing the loss of light quantity. As a
result, the exposure apparatus of the present embodiment is able to
transcribe the microscopic pattern in an arbitrary direction under
an appropriate illumination condition faithfully and with high
throughput because it uses the illumination optical apparatus
capable of forming the illumination pupil distribution of the
annular shape in the azimuthal polarization state while well
suppressing the loss of light quantity.
[0127] In the azimuthally polarized annular illumination based on
the illumination pupil distribution of the annular shape in the
azimuthal polarization state, the light illuminating the wafer W as
a surface to be illuminated is in the polarization state in which
the principal component is the S-polarized light. Here the
S-polarized light is linearly polarized light having the direction
of polarization along a direction normal to a plane of incidence
(i.e., polarized light with the electric vector oscillating in the
direction normal to the plane of incidence). The plane of incidence
herein is defined as the following plane: when light arrives at a
boundary surface of a medium (a surface to be illuminated: surface
of wafer W), the plane includes the normal to the boundary plane at
the arrival point and the direction of incidence of light.
[0128] In the above-described embodiment, the diffractive optical
element 50 for azimuthally polarized annular illumination is
constructed by randomly arranging virtually the same number of four
types of basic elements 50A-50D with the same rectangular cross
section lengthwise and breadthwise and densely. However, without
having to be limited to this, a variety of modification examples
can be contemplated as to the number of basic elements of each
type, the sectional shape, the number of types, the arrangement,
and so on.
[0129] In the above-described embodiment, the secondary light
source 31 of the annular shape centered around the optical axis AX
is composed of the eight arc regions 31A-31D arrayed without
overlapping with each other and without being spaced from each
other, using the diffractive optical element 50 consisting of the
four types of basic elements 50A-50D. However, without having to be
limited to this, a variety of modification examples can be
contemplated as to the number of regions forming the secondary
light source of the annular shape, the shape, the arrangement, and
so on.
[0130] Specifically, as shown in FIG. 18A, it is also possible to
form a secondary light source 33a of an octapole shape in the
azimuthal polarization state consisting of eight arc (bow shape)
regions spaced from each other along the circumferential direction,
for example, using the diffractive optical element consisting of
four types of basic elements. In addition, as shown in FIG. 18B, it
is also possible to form a secondary light source 33b of a
quadrupole shape in the azimuthal polarization state consisting of
four arc (bow shape) regions spaced from each other along the
circumferential direction, for example, using the diffractive
optical element consisting of four types of basic elements. In the
secondary light source of the octapole shape or the secondary light
source of the quadrupole shape, the shape of each region is not
limited to the arc shape, but it may be, for example, circular,
elliptical, or sectorial. Furthermore, as shown in FIG. 19, it is
also possible to form a secondary light source 33c of an annular
shape in the azimuthal polarization state consisting of eight arc
regions overlapping with each other along the circumferential
direction, for example, using the diffractive optical element
consisting of four types of basic elements.
[0131] In addition to the quadrupole or octapole secondary light
source in the azimuthal polarization state consisting of the four
or eight regions spaced from each other along the circumferential
direction, the secondary light source may be formed in a hexapole
shape in the azimuthal polarization state and of six regions spaced
from each other along the circumferential direction, as shown in
FIG. 20A. In addition, as shown in FIG. 20B, the secondary light
source may be formed as one having secondary light source of a
multipole shape in the azimuthal polarization state consisting of a
plurality of regions spaced from each other along the
circumferential direction, and a secondary light source on the
center pole in the unpolarized state or linearly polarized state
consisting of a region on the optical axis. Furthermore, the
secondary light source may also be formed in a dipole shape in the
azimuthal polarization state and of two regions spaced from each
other along the circumferential direction.
[0132] In the aforementioned embodiment, as shown in FIG. 11, the
four types of basic elements 50A-50D are individually formed, and
the diffractive optical element 50 is constructed by combining
these elements. However, without having to be limited to this, the
diffractive optical element 50 can also be integrally constructed
in such a manner that a crystalline quartz substrate is subjected,
for example, to etching to form the exit-side diffracting surfaces
and the entrance-side uneven surfaces of the respective basic
elements 50A-50D.
[0133] In the aforementioned embodiment each basic element 50A-50D
(therefore, the diffractive optical element 50) is made of
crystalline quartz. However, without having to be limited to this,
each basic element can also be made of another appropriate optical
material with optical activity. In this case, it is preferable to
use an optical material with an optical rotatory power of not less
than 100.degree./mm for light of a wavelength used. Specifically,
use of an optical material with a low rotatory power is undesirable
because the thickness necessary for achieving the required rotation
angle of the polarization direction becomes too large, so as to
cause the loss of light quantity.
[0134] The aforementioned embodiment is arranged to form the
illumination pupil distribution of the annular shape (secondary
light source), but, without having to be limited to this, the
illumination pupil distribution of a circular shape can also be
formed on or near the illumination pupil. In addition to the
illumination pupil distribution of the annular shape and the
illumination pupil distribution of the multipole shape, it is also
possible to implement a so-called annular illumination with the
center pole and a multipole illumination with the center pole, for
example, by forming a center region distribution including the
optical axis.
[0135] In the aforementioned embodiment, the illumination pupil
distribution in the azimuthal polarization state is formed on or
near the illumination pupil. However, the polarization direction
can vary because of polarization aberration (retardation) of an
optical system (the illumination optical system or the projection
optical system) closer to the wafer than the diffractive optical
element as the beam transforming element. In this case, it is
necessary to properly set the polarization state of the beam
passing through the illumination pupil distribution formed on or
near the illumination pupil, with consideration to the influence of
polarization aberration of these optical systems.
[0136] In connection with the foregoing polarization aberration,
reflected light can have a phase difference in each polarization
direction because of a polarization characteristic of a reflecting
member disposed in the optical system (the illumination optical
system or the projection optical system) closer to the wafer than
the beam transforming element. In this case, it is also necessary
to properly set the polarization state of the beam passing through
the illumination pupil distribution formed on or near the
illumination pupil, with consideration to the influence of the
phase difference due to the polarization characteristic of the
reflecting member.
[0137] The reflectance in the reflecting member can vary depending
upon the polarization direction, because of a polarization
characteristic of a reflecting member disposed in the optical
system (the illumination optical system or the projection optical
system) closer to the wafer than the beam transforming element. In
this case, it is desirable to provide offsets on the light
intensity distribution formed on or near the illumination pupil,
i.e. to provide a distribution of numbers of respective basic
elements, in consideration of the reflectance in each polarization
direction. The same technique can also be similarly applied to
cases where the transmittance in the optical system closer to the
wafer than the beam transforming element varies depending upon the
polarization direction.
[0138] In the foregoing embodiment, the light-source-side surface
of the diffractive optical element 50 is of the uneven shape with
level differences according to the differences among the
thicknesses of respective basic elements 50A-50D. Then the surface
on the light source side (entrance side) of the diffractive optical
element 50 can also be formed in a planar shape, as shown in FIG.
21, by adding a compensation member 36 on the entrance side of the
basic elements except for the first basic elements 50A with the
largest thickness, i.e., on the entrance side of the second basic
elements 50B, third basic elements 50C, and fourth basic elements
50D. In this case, the compensation member 36 is made of an optical
material without optical activity.
[0139] The aforementioned embodiment shows the example wherein the
beam passing through the illumination pupil distribution formed on
or near the illumination pupil has only the linear polarization
component along the circumferential direction. However, without
having to be limited to this, the expected effect of the present
invention can be achieved as long as the polarization state of the
beam passing through the illumination pupil distribution is a state
in which the principal component is linearly polarized light having
the polarization direction along the circumferential direction.
[0140] The foregoing embodiment uses the diffractive optical
element consisting of the plural types of basic elements having the
diffracting action, as the beam transforming element for forming
the light intensity distribution of the shape different from the
sectional shape of the incident beam, on the predetermined plane,
based on the incident beam. However, without having to be limited
to this, it is also possible to use as the beam transforming
element a refracting optical element, for example, consisting of
plural types of basic elements having refracting surfaces virtually
optically equivalent to the diffracting surfaces of the respective
basic elements, i.e., consisting of plural types of basic elements
having the refracting action.
[0141] The exposure apparatus according to the foregoing embodiment
is able to produce microdevices (semiconductor elements, image
pickup elements, liquid crystal display elements, thin-film
magnetic heads, etc.) by illuminating a mask (reticle) by the
illumination optical apparatus (illumination step) and projecting a
pattern for transcription formed on the mask, onto a photosensitive
substrate by use of the projection optical system (exposure step).
The following will describe an example of a procedure of producing
semiconductor devices as microdevices by forming a predetermined
circuit pattern on a wafer or the like as a photosensitive
substrate by means of the exposure apparatus of the foregoing
embodiment, with reference to the flowchart of FIG. 22.
[0142] The first step 301 in FIG. 22 is to deposit a metal film on
each of wafers in one lot. The next step 302 is to apply a
photoresist onto the metal film on each wafer in the lot.
Thereafter, step 303 is to sequentially transcribe an image of a
pattern on a mask into each shot area on each wafer in the lot,
through the projection optical system by use of the exposure
apparatus of the foregoing embodiment. Subsequently, step 304 is to
perform development of the photoresist on each wafer in the lot,
and step 305 thereafter is to perform etching with the resist
pattern as a mask on each wafer in the lot, thereby forming a
circuit pattern corresponding to the pattern on the mask, in each
shot area on each wafer. Thereafter, devices such as semiconductor
elements are produced through execution of formation of circuit
patterns in upper layers and others. The semiconductor device
production method as described above permits us to produce the
semiconductor devices with extremely fine circuit patterns at high
throughput.
[0143] The exposure apparatus of the foregoing embodiment can also
be applied to production of a liquid crystal display element as a
microdevice in such a manner that predetermined patterns (a circuit
pattern, an electrode pattern, etc.) are formed on a plate (glass
substrate). An example of a procedure of this production will be
described below with reference to the flowchart of FIG. 23. In FIG.
23, pattern forming step 401 is to execute a so-called
photolithography step of transcribing a pattern on a mask onto a
photosensitive substrate (a glass substrate coated with a resist or
the like) by use of the exposure apparatus of the foregoing
embodiment. In this photolithography step, the predetermined
patterns including a number of electrodes and others are formed on
the photosensitive substrate. Thereafter, the exposed substrate is
subjected to steps such as a development step, an etching step, a
resist removing step, etc., to form the predetermined patterns on
the substrate, followed by next color filter forming step 402.
[0144] The next color filter forming step 402 is to form a color
filter in which a number of sets of three dots corresponding to R
(Red), G (Green), and B (Blue) are arrayed in a matrix, or in which
a plurality of sets of filters of three stripes of R, G, and B are
arrayed in the direction of horizontal scan lines. After the color
filter forming step 402, cell assembly step 403 is carried out. The
cell assembly step 403 is to assemble a liquid crystal panel
(liquid crystal cell), using the substrate with the predetermined
patterns obtained in the pattern forming step 401, the color filter
obtained in the color filter forming step 402, and so on.
[0145] In the cell assembly step 403, for example, a liquid crystal
is poured into the space between the substrate with the
predetermined patterns obtained in the pattern forming step 401 and
the color filter obtained in the color filter forming step 402 to
produce the liquid crystal panel (liquid crystal cell). Thereafter,
module assembly step 404 is carried out to attach such components
as an electric circuit, a backlight, and so on for implementing the
display operation of the assembled liquid crystal panel (liquid
crystal cell), to complete the liquid crystal display element. The
production method of the liquid crystal display element described
above permits us to produce the liquid crystal display elements
with extremely fine circuit patterns at high throughput.
[0146] The foregoing embodiment is arranged to use the KrF excimer
laser light (wavelength: 248 nm) or the ArF excimer laser light
(wavelength: 193 nm) as the exposure light, but, without having to
be limited to this, the present invention can also be applied to
other appropriate laser light sources, e.g., an F.sub.2 laser light
source for supplying laser light of the wavelength of 157 nm.
Furthermore, the foregoing embodiment described the present
invention, using the exposure apparatus with the illumination
optical apparatus as an example, but it is apparent that the
present invention can be applied to ordinary illumination optical
apparatus for illuminating the surface to be illuminated, except
for the mask and wafer.
[0147] In the foregoing embodiment, it is also possible to apply
the so-called liquid immersion method, which is a technique of
filling a medium (typically, a liquid) with a refractive index
larger than 1.1 in the optical path between the projection optical
system and the photosensitive substrate. In this case, the
technique of filling the liquid in the optical path between the
projection optical system and the photosensitive substrate can be
selected from the technique of locally filling the liquid as
disclosed in PCT International Publication No. WO99/49504, the
technique of moving a stage holding a substrate as an exposure
target in a liquid bath as disclosed in Japanese Patent Application
Laid-Open No. 6-124873, the technique of forming a liquid bath in a
predetermined depth on a stage and holding the substrate therein as
disclosed in Japanese Patent Application Laid-Open No. 10-303114,
and so on. The PCT International Publication No. WO99/49504,
Japanese Patent Application Laid-Open No. 6-124873, and Japanese
Patent Application Laid-Open No. 10-303114 are incorporated herein
by reference.
[0148] The liquid is preferably one that is transparent to the
exposure light, that has the refractive index as high as possible,
and that is stable against the projection optical system and the
photoresist applied to the surface of the substrate; for example,
where the exposure light is the KrF excimer laser light or the ArF
excimer laser light, pure water or deionized water can be used as
the liquid. Where the F.sub.2 laser light is used as the exposure
light, the liquid can be a fluorinated liquid capable of
transmitting the F.sub.2 laser light, e.g., fluorinated oil or
perfluoropolyether (PFPE).
[0149] From the invention thus described, it will be obvious that
the invention may be varied in many ways. Such variations are not
to be regarded as a departure from the spirit and scope of the
invention, and all such modifications as would be obvious to one
skilled in the art are intended for inclusion within the scope of
the following claims.
* * * * *