U.S. patent application number 11/920332 was filed with the patent office on 2009-02-19 for projection optical system, exposure apparatus, and exposure method.
Invention is credited to Hiroyuki Nagasaka, Takaya Okada, Yasuhiro Omura.
Application Number | 20090046268 11/920332 |
Document ID | / |
Family ID | 37396518 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090046268 |
Kind Code |
A1 |
Omura; Yasuhiro ; et
al. |
February 19, 2009 |
Projection optical system, exposure apparatus, and exposure
method
Abstract
An immersion projection optical system having, for example, a
catadioptric and off-axis structure, reduces the portion of an
image space filled with liquid (immersion liquid). The projection
optical system, which projects a reduced image of a first plane
onto a second plane through the liquid, includes a refractive
optical element (Lp) arranged nearest to the second plane. The
refractive optical element includes a light emitting surface (Lpb)
shaped to be substantially symmetric with respect to two axial
directions (XY-axes) perpendicular to each other on the second
plane. The light emitting surface has a central axis (Lpba) that
substantially coincides with a central axis (40a) of a circle (40)
corresponding to a circumference of a light entering surface (Lpa)
of the refractive optical element. The central axis of the light
emitting surface is decentered in one of the two axial directions
(Y-axis) from an optical axis (AX).
Inventors: |
Omura; Yasuhiro;
(Saitama-ken, JP) ; Okada; Takaya; (Saitama-ken,
JP) ; Nagasaka; Hiroyuki; (Saitama-ken, JP) |
Correspondence
Address: |
KLARQUIST SPARKMAN, LLP
121 SW SALMON STREET, SUITE 1600
PORTLAND
OR
97204
US
|
Family ID: |
37396518 |
Appl. No.: |
11/920332 |
Filed: |
May 8, 2006 |
PCT Filed: |
May 8, 2006 |
PCT NO: |
PCT/JP2006/309254 |
371 Date: |
November 9, 2007 |
Current U.S.
Class: |
355/67 |
Current CPC
Class: |
G02B 21/33 20130101;
G03F 7/70225 20130101; G02B 17/08 20130101; G02B 17/0892 20130101;
G02B 1/06 20130101; G03F 7/702 20130101; G03F 7/70341 20130101;
G03F 7/70725 20130101 |
Class at
Publication: |
355/67 |
International
Class: |
G03B 27/54 20060101
G03B027/54 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2005 |
JP |
2005-139344 |
Claims
1. A projection optical system for projecting an image of a first
plane onto a second plane through a liquid, the projection optical
system comprising: a refractive optical element arranged nearest to
the second plane; wherein the refractive optical element includes a
light emitting surface shaped to be rotationally asymmetric with
respect to an optical axis of the projection optical system in
accordance with the shape of an effective projection region formed
on the second plane.
2. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element is
one-fold rotationally symmetric with respect to the optical axis of
the projection optical system.
3. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, the light emitting
surface has a central axis that substantially coincides with a
central axis of a circle corresponding to a circumference of a
light entering surface of the refractive optical element, and the
central axis of the light emitting surface is decentered in one of
the two axial directions from the optical axis.
4. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element is shaped
to be substantially symmetric with respect to one of two axial
directions perpendicular to each other on the second plane and
asymmetric with respect to the other one of the axial directions, a
central axis of a circle corresponding to a circumference of a
light entering surface of the refractive optical element
substantially coincide with the optical axis, and the light
emitting surface has a central axis decentered in the one of the
axial directions.
5. The projection optical system according claim 1, wherein the
light emitting surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, a central axis of
a circle corresponding to a circumference of a light entering
surface of the refractive optical element substantially coincide
with the optical axis, and the light emitting surface has a central
axis decentered in one of the two axial directions from the optical
axis.
6. The projection optical system according to claim 3, wherein a
central axis of the effective projection region substantially
coincides with the central axis of the light emitting surface.
7. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element is
two-fold rotationally symmetric with respect to the optical axis of
the projection optical system.
8. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, and the light
emitting surface has a central axis that substantially coincides
with the optical axis and a central axis of a circle corresponding
to a circumference of a light entering surface of the refractive
optical element.
9. The projection optical system according to claim 8, wherein the
effective projection region has a central axis decentered in one of
the two axial directions from the central axis of the light
emitting surface.
10. The projection optical system according to claim 1, wherein the
refractive optical element is an interface lens of which first
plane side comes in contact with gas and second plane side comes in
contact with the liquid.
11. The projection optical system according to claim 1, wherein the
refractive optical element is an optical member that has
substantially no refractive power and arranged in an optical path
formed between the second plane and an interface lens of which
first plane side comes in contact with the gas and second plane
side comes in contact with the liquid.
12. The projection optical system according to claim 1, wherein a
reduced image of the first plane is projected onto the second plane
through the liquid.
13. The projection optical system according to claim 1, wherein a
center of an effective projection region on the second plane is
decentered from the optical axis of the projection optical
system.
14. The projection optical system according to claim 1, further
comprising: at least one concave reflective mirror and a plurality
of refractive optical elements, wherein an effective field of view
region on the first plane and the effective projection region on
the second plane excludes the optical axis.
15. The projection optical system according to claim 14, further
comprising: a refractive first imaging optical system for forming a
first intermediate image based on light from the first plane; a
second imaging optical system including the at least one concave
reflective mirror, for forming a second intermediate image based on
light from the first intermediate image; and a refractive third
imaging optical system for forming the image on the second plane
based on light from the second intermediate image.
16. The projection optical system according to claim 15, further
comprising: a first deflection mirror arranged in an optical path
between the first imaging optical system and the second imaging
optical system; and a second deflection mirror arranged in an
optical path between the second imaging optical system and the
third imaging optical system.
17.-25. (canceled)
26. A projection optical system for projecting an image of a first
plane onto a second plane through a liquid, the projection optical
system comprising: a refractive optical element arranged nearest to
the second plane, wherein when two axial directions perpendicular
to each other are set on the second plane, a light emitting surface
of the refractive optical element has a length in one of the axial
directions and a length in the other one of the axial directions
that differ from each other.
27. The projection optical system according to claim 26, wherein
the refractive optical element includes a light entering surface
having lengths in the two axial directions that are substantially
equal to each other.
28. The projection optical system according to claim 26, wherein:
the projection optical system is used in an exposure apparatus that
projects a pattern while changing a positional relationship of the
image and a substrate arranged on the second plane in a scanning
direction; the length of the light emitting surface in the one of
the axial directions is set to be shorter than the length of the
light emitting surface in the other one of the axial directions;
and the one of the axial directions coincides with the scanning
direction.
29. The projection optical system according to claim 26 wherein the
light emitting surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, the light emitting
surface has a central axis that substantially coincides with a
central axis of a circle corresponding to a circumference of a
light entering surface of the refractive optical element, and the
central axis of the light emitting surface is decentered in one of
the two axial directions from the optical axis.
30. The projection optical system according to claim 26, wherein
the light emitting surface of the refractive optical element is
shaped to be substantially symmetric with respect to two axial
directions perpendicular to each other on the second plane, and the
light emitting surface has a central axis that substantially
coincides with the optical axis and a central axis of a circle
corresponding to a circumference of a light entering surface of the
refractive optical element.
31. The projection optical system according to claim 30, wherein
the effective projection region has a central axis decentered in
one of the two axial directions from the central axis of the light
emitting surface.
32. The projection optical system according to claim 26, wherein
the light emitting surface of the refractive optical element is
shaped to be substantially symmetric with respect to one of two
axial directions perpendicular to each other and asymmetric with
respect to the other one of the axial directions on the second
plane, a central axis of a circle corresponding to a circumference
of a light entering surface of the refractive optical element
substantially coincides with the optical axis, and the light
emitting surface has a central axis decentered in the one of the
axial directions from the optical axis.
33. The projection optical system according to claim 26 wherein the
refractive optical element includes a light emitting surface shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other, a central axis of a circle
corresponding to a circumference of the light emitting surface of
the refractive optical element substantially coincides with the
optical axis, and the light emitting surface has a central axis
decentered in one of the two axial directions from the optical
axis.
34. The projection optical system according to claim 29, wherein
the effective projection region has a central axis that coincides
with the central axis of the light emitting surface.
35. The projection optical system according to claim 26, wherein a
reduced image of the first plane is projected onto the second plane
through the liquid.
36. The projection optical system according to claim 26, wherein
when two axial directions perpendicular to each other are set on
the second plane, a region on which the image is formed has a
length in one of the axial directions and a length in the other one
of the axial directions that differ from each other.
37. The projection optical system according to claim 1, wherein the
light emitting surface of the refractive optical element includes a
planar surface.
38. The projection optical system according to claim 1, wherein the
refractive optical element includes a light entering surface having
a planar surface.
39. An exposure apparatus comprising: the projection optical system
according to claim 1 for projecting an image of a predetermined
pattern onto a photosensitive substrate that is set on the second
plane based on illumination light from the pattern set on the first
plane.
40. The exposure apparatus according to claim 39, wherein the
pattern is projected while changing a positional relationship of
the image of the pattern and the photosensitive substrate in a
scanning direction.
41. The exposure apparatus according to claim 39, further
comprising: a supply and discharge mechanism for supplying and
discharging the liquid.
42.-43. (canceled)
44. A device manufacturing method comprising: an exposure step of
projecting and exposing an image of a pattern set on the first
plane onto a photosensitive substrate set on the second plane with
the projection optical system according to claim 1; and a
development step of developing the photosensitive substrate that
has undergone the exposure step.
45. The device manufacturing method according to claim 44, wherein
in the exposure step include projecting the pattern while changing
a positional relationship of the image of the pattern and the
photosensitive substrate in a scanning direction.
46. A refractive optical element for use in an immersion objective
optical system that forms an image of a first plane onto an
effective projection region on a second plane, wherein one optical
surface comes in contact with a liquid, the refractive optical
element wherein: the one optical surface of the refractive optical
element is shaped to be rotationally asymmetric with respect to an
optical axis of the immersion objective optical system in
accordance with a shape of the effective projection region on the
second plane.
47. The refractive optical element according to claim 46, wherein
the one optical surface of the refractive optical element is shaped
to be one-fold rotationally symmetric with respect to the optical
axis of the immersion objective optical system.
48. The refractive optical element according to claim 46, wherein
the one optical surface of the refractive optical element is shaped
to be substantially symmetric with respect to one of two axial
directions perpendicular to each other and asymmetric with respect
to the other one of the axial directions on the second plane, a
central axis of a circle corresponding to a circumference of
another optical surface of the refractive optical element
substantially coincides with the optical axis, and the one optical
surface has a central axis that is decentered in the one of the
axial directions from the optical axis.
49. The refractive optical element according to claim 46, wherein
the one optical surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, a central axis of
a circle corresponding to a circumference of another optical
surface of the refractive optical element substantially coincides
with the optical axis, and the one optical surface has a central
axis decentered in one of the two axial directions from the optical
axis.
50. The refractive optical element according to claim 47, wherein
the effective projection region has a central axis that
substantially coincides with a central axis of the one optical
surface.
51. The refractive optical element according to claim 46, wherein
the one optical surface of the refractive optical element is shaped
to be two-fold rotationally symmetric with respect to the optical
axis of the immersion objective optical system.
52. The refractive optical element according to claim 46, wherein
the one optical surface of the refractive optical element is shaped
to be substantially symmetric with respect to two axial directions
perpendicular to each other on the second plane, and the one
optical surface has a central axis that substantially coincides
with a central axis of a circle corresponding to a circumference of
another optical surface of the refractive optical element.
53. The refractive optical element according to claim 52, wherein
the effective projection region has a central axis decentered in
one of the two axial directions from the central axis of the one
optical surface.
54. A refractive optical element for use in an immersion objective
optical system that forms an image of a first plane on a second
plane, wherein one optical surface comes in contact with a liquid,
wherein: when two axial directions perpendicular to each other are
set on the second plane, the one optical surface of the refractive
optical element has a length in one of the axial directions and a
length in the other one of the axial directions that differ from
each other.
55. The refractive optical element according to claim 54, wherein
another optical surface of the refractive optical element has
substantially equal lengths in the first axial direction and the
second axial direction.
56. The refractive optical element according to claim 54, wherein
the refractive optical element is an optical member that has
substantially no refractive power and is arranged in an optical
path between the second plane and an interface lens of which first
plane side comes in contact with gas and second plane side comes in
contact with the liquid.
57. The refractive optical element according to claim 54,
comprising: another optical surface having a flat plane.
58. The refractive optical element according to claim 54, wherein
the refractive optical element is an interface lens of which first
plane side comes in contact with gas and second plane side comes in
contact with the liquid.
59. The refractive optical element according to claim 54, wherein
the one optical surface of the refractive optical element has a
planar surface.
60. The refractive optical element according to claim 54, wherein
when two axial directions perpendicular to each other are set on
the second plane, an effective projection region on the second
plane has a length in one of the axial directions and a length in
the other one of the axial directions that differ from each
other.
61.-100. (canceled)
101. An immersion objective optical system for forming an image of
a first plane on a second plane, the immersion objective optical
system comprising: a reflective surface forming a two-way optical
path; a two-way optical element arranged in the two-way optical
path; a one-way optical element arranged in a one-way optical path
that differs from the two-way optical path; and an aspherical
surface formed on an optical surface of the two-way optical
element; wherein an aspherical surface is not formed on every
optical surface of the two-way optical element.
102. The immersion objective optical system according to claim 101,
wherein the reflective surface is a concave reflective surface.
103. The immersion objective optical system according to claim 101,
wherein the two-way optical element is formed by an amorphous
material.
104. An exposure apparatus comprising: the immersion objective
optical system according to claim 101 for projecting an image of a
predetermined pattern onto a photosensitive substrate that is set
on the second plane based on illumination light from the pattern
set on the first plane.
105. The exposure apparatus according to claim 104, wherein the
pattern is projected while changing a positional relationship of
the image of the pattern and the photosensitive substrate in a
scanning direction.
106. The exposure apparatus according to claim 104, further
comprising: a supply and discharge mechanism for supplying and
discharging the liquid.
107.-108. (canceled)
109. A device manufacturing method comprising: an exposure step of
projecting and exposing an image of a pattern set on the first
plane onto a photosensitive substrate set on the second plane with
the immersion objective optical system according to claim 101; and
a development step of developing the photosensitive substrate that
has undergone the exposure step.
110. The device manufacturing method according to claim 109,
wherein the exposure step includes projecting the pattern while
changing a positional relationship of the image of the pattern and
the photosensitive substrate in a scanning direction.
111.-118. (canceled)
119. An exposure optical system for use in an exposure apparatus
for forming a pattern on an immersion region defined on part of a
substrate by exposing the substrate, the exposure optical system
comprising: an optical member including one optical surface that is
contactable with the liquid; wherein when two axial directions
perpendicular to each other are set on the substrate, the one
optical surface of the optical member has a length in one of the
axial directions and a length in the other one of the axial
directions that differ from each other.
120. The exposure optical system according to claim 119, wherein
the one optical surface of the optical member has lengths in the
two axial directions that are substantially equal to each
other.
121. The exposure optical system according to claim 119, wherein
the optical member has substantially no refractive power and is
arranged in an optical path between the substrate and an interface
lens with which another optical surface side comes in contact with
gas and the one optical surface side comes in contact with the
liquid.
122. The exposure optical system according to claim 119, being
characterized by comprising: the optical member including another
optical surface having a flat plane.
123. The exposure optical system according to claim 119, wherein
the optical member is an interface lens with which another optical
surface side comes in contact with gas and the one optical surface
side comes in contact with the liquid.
124. The exposure optical system according to claim 123, wherein
the one optical surface of the optical member has a planar
surface.
125. The exposure optical system according to claim 119, wherein
when two axial directions perpendicular to each other are set on
the substrate, a pattern formation region in which a pattern is
formed on the substrate has a length in one of the axial directions
and a length in the other one of the axial directions that differ
from each other.
126. The exposure optical system according to claim 119, wherein
the substrate is exposed while changing a positional relationship
of the pattern and the substrate in a scanning direction.
127.-128. (canceled)
129. A device manufacturing method comprising: an exposure step of
forming a pattern set on a substrate through a liquid that forms an
immersion region on part of the substrate with the exposure optical
system according to claim 119; and a development step of developing
the photosensitive substrate.
130. The device manufacturing method according to claim 129,
wherein the exposure step includes exposing the substrate while
changing a positional relationship of the pattern and the substrate
in a scanning direction.
131. An exposure apparatus for exposing substrate based on exposure
light through a liquid that forms an immersion region on part of
the substrate, the exposure apparatus comprising: a supply and
discharge mechanism for supplying and discharging the liquid; and
an optical member for transmitting the exposure light; wherein the
optical member includes a means for narrowing the immersion
region.
132. The exposure apparatus according to claim 131, wherein the
substrate is exposed while changing a positional relationship of
the exposure light and the substrate in a scanning direction.
133. The exposure apparatus according to claim 132, wherein the
means narrows the immersion region in the scanning direction.
134. The exposure apparatus according to claim 131, wherein: the
means is provided on a light emitting surface of the optical
member, wherein the light emitting surface is contactable with the
liquid.
135. A device manufacturing method comprising: projecting and
exposing a pattern on the substrate using the exposure apparatus
according to claim 131.
136. The projection optical system according to claim 32, wherein
the effective projection region has a central axis that coincides
with the central axis of the light emitting surface.
137. The projection optical system according to claim 33, wherein
the effective projection region has a central axis that coincides
with the central axis of the light emitting surface.
138. The refractive optical element according to claim 46, wherein
the refractive optical element is an interface lens of which first
plane side comes in contact with gas and second plane side comes in
contact with the liquid.
139. The refractive optical element according to claim 46, wherein
the refractive optical element is an optical member that has
substantially no refractive power and is arranged in an optical
path between the second plane and an interface lens of which first
plane side comes in contact with gas and second plane side comes in
contact with the liquid.
140. The refractive optical element according to claim 46, wherein
when two axial directions perpendicular to each other are set on
the second plane, an effective projection region on the second
plane has a length in one of the axial directions and a length in
the other one of the axial directions that differ from each other.
Description
TECHNICAL FIELD
[0001] The present invention relates to a projection optical
system, an exposure apparatus, and an exposure method, and more
particularly, to a projection optical system optimal for an
exposure apparatus used to manufacture microdevices, such as
semiconductor devices and liquid crystal display devices, through a
photolithography process.
BACKGROUND ART
[0002] An exposure apparatus projects and exposes an image of a
pattern of a mask (or a reticle) on a photosensitive substrate
(e.g., wafer or a glass plate coated by a photoresist). More
specifically, the exposure apparatus uses a projection optical
system to project and expose the image in a photolithography
process, in which semiconductor devices or the like are
manufactured. The projection optical system is required to have a
higher resolution due to the increasing level of integration of
semiconductor devices or the like manufactured with the exposure
apparatus.
[0003] To improve the resolution of the projection optical system,
the projection optical system needs to shorten the wavelength
.lamda. of its illumination light (exposure light) and increase the
numerical aperture NA at its image side. The resolution of the
projection optical system is written as k*.lamda./NA (where k is a
process coefficient). The image-side numerical aperture NA is
written as n*sin .theta., where n is the refractive index of a
medium (usually gas, such as air) that arranged between the
projection optical system and the photosensitive substrate, and
.theta. is the maximum incident angle at which light enters the
photosensitive substrate.
[0004] When the maximum angle .theta. is set larger in an effort to
increase the image-side numerical aperture, the angle at which
light is emitted from the projection optical system and the angle
at which the light enters the photosensitive substrate increase.
This increases reflection loss occurring at an optical surface. As
a result, the projection optical system cannot obtain a large
effective numerical aperture at its image side. One conventional
technique for increasing the image-side numerical aperture is an
immersion technique (refer to, for example, Patent Document 1),
with which an optical path formed between a projection optical
system and a photosensitive substrate is filled with a medium such
as a liquid having a high refractive index.
[0005] Patent Document 1: International Patent Publication No.
WO2004/019128
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] As described above, the conventional technique of filling an
image space with a liquid medium having a higher refractive index
than a gas medium enables the projection optical system to have an
image-side numerical aperture that is greater than 1 and improves
the resolution of the projection optical system, which is used in
an exposure apparatus. However, microlithography, through which
micropatterns are formed, always needs to consider chip costs. To
reduce chip costs, the predominant immersion lithography system is
a local immersion lithography system, which uses a mechanism for
supplying and discharging liquid to and from only a limited portion
of an image space of a projection optical system. To prevent
enlargement of a substrate stage (wafer stage) of the projection
optical system and improve the accuracy of an alignment optical
system, the local immersion system is required to minimize the
portion of the image space in the projection optical system that is
filled with the liquid (immersion liquid).
[0007] An immersion projection optical system may have, for
example, an image-side numerical aperture that is greater than 1.2.
An immersion projection optical system with such an image-side
numerical aperture preferably employs a catadioptric projection
optical system structure to satisfy Petzval's condition and ensure
the flatness of an image. A immersion projection optical system
with such an image-side numerical aperture also preferably employs
an off-axis optical system structure, in which an effective field
of view region and an effective projection region do not extend on
an optical axis of the projection optical system (the regions are
"off" the optical axis), to increase the variety of patterns of
images that can be formed. When a catadioptric and off-axis
immersion projection optical system is employed, images can be
produced with a greater maximum height than a conventional
refractive projection optical system. However, if a refractive
optical element arranged nearest to an imaging position in the
projection optical system is formed to have a light emitting
surface that is rotationally symmetric with respect to the optical
axis in accordance with the conventional technique, a large portion
of an image space of the projection optical system will be filled
with the liquid. As a result, the substrate stage may be enlarged
or the accuracy of the alignment optical system may be lowered.
[0008] The present invention has been made to solve the above
problems. It is an object of the present invention to provide an
immersion projection optical system with, for example, a
catadioptric and off-axis structure that reduces the portion of an
image space filled with liquid (immersion liquid). It is another
object of the present invention to provide an exposure apparatus
and an exposure method that use a high-resolution immersion
projection optical system, which reduces the portion of an image
space filled with liquid, and enable a micropattern to be projected
and exposed with a high accuracy without enlarging a substrate
stage of the projection optical system or lowering the accuracy of
an alignment optical system of the projection optical system.
Means of Solving the Problems
[0009] To achieve the above object, a first aspect of the present
invention provides a projection optical system for projecting an
image of a first plane onto a second plane through a liquid. The
projection optical system includes a refractive optical element
arranged nearest to the second plane. The refractive optical
element includes a light emitting surface shaped to be rotationally
asymmetric with respect to an optical axis of the projection
optical system in accordance with the shape of an effective
projection region formed on the second plane. The phrase "shaped to
be rotationally asymmetric" refers to a state having "a shape other
than an infinitely symmetric rotation".
[0010] A second aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be two-fold rotationally symmetric with
respect to an optical axis of the projection optical system.
[0011] A third aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be substantially symmetric with respect
to two axial directions perpendicular to each other on the second
plane, and the light emitting surface has a central axis that
substantially coincides with an optical axis and a central axis of
a circle corresponding to a circumference of a light entering
surface of the refractive optical element.
[0012] A fourth aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be one-fold rotationally symmetric with
respect to an optical axis of the projection optical system.
[0013] A fifth aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be substantially symmetric with respect
to two axial directions perpendicular to each other on the second
plane. The light emitting surface has a central axis that
substantially coincides with a central axis of a circle
corresponding to a circumference of a light entering surface of the
refractive optical element, and the central axis of the light
emitting surface is decentered in one of the two axial directions
from the optical axis.
[0014] A sixth aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be substantially symmetric with respect
to one of two axial directions perpendicular to each other and
asymmetric with respect to the other one of the axial directions on
the second plane, a central axis of a circle corresponding to a
circumference of a light entering surface of the refractive optical
element substantially coincides with the optical axis, and the
light emitting surface has a central axis decentered in one of the
two axial directions from the optical axis.
[0015] A seventh aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. The refractive optical element includes a light
emitting surface shaped to be substantially symmetric with respect
to two axial directions perpendicular to each other on the second
plane, a central axis of a circle corresponding to a circumference
of a light entering surface of the refractive optical element
substantially coincides with the optical axis, and the light
emitting surface has a central axis decentered in one of the axial
directions from the optical axis.
[0016] An eighth aspect of the present invention provides a
projection optical system for projecting an image of a first plane
onto a second plane through a liquid. The projection optical system
includes a refractive optical element arranged nearest to the
second plane. When two axial directions perpendicular to each other
are set on the second plane, a light emitting surface of the
refractive optical element has a length in one of the axial
directions and a length in the other one of the axial directions
that differ from each other.
[0017] A ninth aspect of the present invention provides an exposure
apparatus including the projection optical system according to any
one of the first to eighth aspects for projecting an image of a
predetermined pattern onto a photosensitive substrate that is set
on the second plane based on illumination light from the pattern
set on the first plane.
[0018] A tenth aspect of the present invention provides an exposure
method including a setting step of setting a predetermined pattern
on the first plane, and an exposure step of projecting and exposing
an image of the pattern onto a photosensitive substrate that is set
on the second plane with the projection optical system according to
any one of claims 1 to 35 based on illumination light from the
predetermined pattern.
[0019] An eleventh aspect of the present invention provides a
device manufacturing method including an exposure step of
projecting and exposing an image of a pattern set on the first
plane onto a photosensitive substrate set on the second plane with
the projection optical system according to any one of the first to
eighth aspects, and a development step of developing the
photosensitive substrate that has undergone the exposure step.
[0020] A twelfth aspect of the present invention provides a
refractive optical element for use in an immersion objective
optical system that forms an image of a first plane onto an
effective projection region on a second plane. One optical surface
comes in contact with a liquid. The one optical surface of the
refractive optical element is shaped to be rotationally asymmetric
with respect to an optical axis of the immersion objective optical
system in accordance with a shape of the effective projection
region on the second plane.
[0021] A thirteenth aspect of the present invention provides a
refractive optical element for use in an immersion objective
optical system that forms an image of a first plane on a second
plane. One optical surface comes in contact with a liquid. When two
axial directions perpendicular to each other are set on the second
plane, the one optical surface of the refractive optical element
has a length in one of the axial directions and a length in the
other one of the axial directions that differ from each other.
EFFECT OF THE INVENTION
[0022] The immersion projection optical system according to a
typical aspect of the present invention has, for example, a
catadioptric and off-axis structure, in which a light emitting
surface of a refractive optical element that is arranged nearest to
an imaging position is rotationally-asymmetric with respect to an
optical axis of the projection optical system according to the
shape of an effective projection region formed on an image surface.
More specifically, the light emitting surface of the refractive
optical element is substantially symmetric with respect to two
axial directions that are perpendicular to each other on the image
surface. A central axis of the light emitting surface and a central
axis of a circle corresponding to a circumference of a light
entering surface of the refractive optical element substantially
coincide with each other. The central axis of the light emitting
surface is decentered along one of the two axial directions with
respect to the optical axis.
[0023] As a result, the light emitting surface of the refractive
optical element that is arranged nearest to the imaging position in
the projection optical system of the present invention is
rotationally-asymmetric in accordance with the shape of the
effective projection region. The projection optical system of the
present invention reduces the portion of an image space filled with
liquid (immersion liquid). Further, the exposure apparatus and the
exposure method of the present invention use a high-resolution
immersion projection optical system, which reduces a portion of an
image space filled with liquid, and enable a micropattern to be
projected and exposed with a high accuracy without enlarging a
substrate stage of the projection optical system or lowering the
accuracy of an alignment optical system of the projection optical
system. Consequently, this produces a satisfactory microdevice with
high accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic diagram showing the structure of an
exposure apparatus according to a present embodiment of the present
invention;
[0025] FIG. 2 shows the positional relationship between a
rectangular stationary exposure region formed on a wafer and a
reference optical axis in the present embodiment of the present
invention;
[0026] FIG. 3 is a schematic diagram showing the structure of an
interface lens and a wafer in examples of the present
invention;
[0027] FIG. 4 shows a lens structure of a projection optical system
in a first example of the present invention;
[0028] FIG. 5 shows lateral aberration occurring in the projection
optical system in the first example of the present invention;
[0029] FIG. 6 shows a lens structure of a projection optical system
in a second example of the present invention;
[0030] FIG. 7 shows lateral aberration occurring in the projection
optical system in the second example of the present invention;
[0031] FIG. 8 is a diagram illustrating problems occurring when a
light emitting surface of a refractive optical element arranged
nearest to an imaging position is formed rotationally symmetric in
the prior art;
[0032] FIG. 9 is a schematic diagram showing the structure of an
immersed plane parallel plate in each example of the present
invention;
[0033] FIG. 10 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a first modification of
the present embodiment;
[0034] FIG. 11 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a second modification of
the present embodiment;
[0035] FIG. 12 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a third modification of
the present embodiment;
[0036] FIG. 13 is a flowchart showing a method for forming a
microdevice, which serves as a semiconductor device; and
[0037] FIG. 14 is a flowchart showing a method for forming a
microdevice, which serves as a liquid crystal display device.
TABLE-US-00001 DESCRIPTION OF REFERENCE NUMERALS R reticle RST
reticle stage PL projection optical system Lp interface lens Lp
immersed plane parallel plate Lm1, Lm2 pure water (liquid) W wafer
1 illumination optical system 9 Z-stage 10 XY-stage 12 movable
mirror 13 wafer laser interferometer 14 main control system 15
wafer stage drive system 21 first supply and discharge mechanism 22
second supply and discharge mechanism
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] An embodiment of the present invention will now be described
with reference to the drawings. FIG. 1 is a schematic diagram
showing the structure of an exposure apparatus of the present
embodiment of the present invention. In FIG. 1, X-axis and Y-axis
are directions parallel to a wafer W, whereas Z-axis is a direction
perpendicular to the wafer W. More specifically, the XY surface is
parallel to the horizontal surface, and +Z-axis is oriented upward
in the vertical direction.
[0039] The exposure apparatus of the present embodiment includes an
ArF excimer laser light source, which functions for example as an
exposure light source, and an illumination optical system 1 as
shown in FIG. 1. The illumination optical system 1 includes an
optical integrator (homogenizer), a field stop, and a condenser
lens. Exposure light (an exposure beam) IL, which is ultraviolet
pulsed light having a wavelength of 193 nm, is emitted from the
light source, passes through the illumination optical system 1, and
illuminates a reticle (mask) R. The reticle R has a pattern that is
to be transferred. The entire pattern region on the reticle R
includes a rectangular (slit) pattern region of which long sides
extend in X-axis direction and of which short sides extend in the
Y-axis direction. The exposure beam IL illuminates the rectangular
pattern region on the reticle R.
[0040] Light that has passed through the reticle R enters an
immersion projection optical system PL. The projection optical
system PL projects the reticle pattern with a predetermined
reduction ratio onto the wafer (photosensitive substrate) W that is
coated with a photoresist. The projection optical system PL forms
an image of the reticle pattern on the wafer W. More specifically,
the projection optical system PL forms the pattern image on a
rectangular stationary exposure region (effective exposure region)
of which long sides extend in the X-axis direction and of which
short sides extend in the Y-axis direction on the wafer W, which
optically corresponds to the rectangular illumination region formed
on the reticle R.
[0041] FIG. 2 shows the positional relationship between the
rectangular stationary exposure region (effective exposure region)
that is formed on the wafer and a reference optical axis in the
present embodiment. In the present embodiment, as shown in FIG. 2,
the rectangular effective exposure region ER having a predetermined
size is defined at a position distant from the reference optical
axis AX in the Y-axis direction by an off-axis amount A within a
circular region (image circle) IF. The center of the image circle
IF coincides with the reference optical axis AX. The image circle
IF has a radius B.
[0042] The effective exposure region ER has a length LX in the
X-axis direction and a length LY in the Y-axis direction. Although
not shown in the drawing, the rectangular illumination region
(effective illumination region) corresponding to the rectangular
effective exposure region ER is formed on the reticle R. More
specifically, a rectangular illumination region having a size and
shape corresponding to the effective exposure region ER is formed
on the reticle R at a position distant from the reference optical
axis AX in the Y-axis direction by the off-axis amount A.
[0043] A reticle stage RST supports the reticle R in such a manner
that the reticle R is parallel to the XY surface. The reticle stage
RST incorporates a mechanism for slightly moving the reticle R in
the X-axis direction, the Y-axis direction, and a rotation
direction. The positions of the reticle stage RST in the X-axis
direction, the Y-axis direction, and the rotation direction are
measured and controlled in real time by a reticle laser
interferometer (not shown). A wafer holder (not shown) fixes the
wafer W to a Z-stage 9 in a manner that the wafer W is parallel to
the XY surface.
[0044] The Z-stage 9 is fixed to an XY-stage 10. The XY-stage 10
moves along the XY surface, which is substantially parallel to an
image surface of the projection optical system PL. The Z-stage 9
controls the focus position (Z-axis position) and the tilt angle of
the wafer W. The positions of the Z-stage 9 in the X-axis
direction, the Y-axis direction, and the rotation direction are
measured and controlled in real time by a wafer laser
interferometer 13. The wafer laser interferometer 13 uses a movable
mirror 12, which is arranged on the Z-stage 9.
[0045] The XY-stage 10 is mounted on a base 11. The XY-stage 10
controls the positions of the wafer W in the X-axis direction, the
Y-axis direction, and the rotation direction. A main control system
14, which is mounted on the exposure apparatus of the present
embodiment, adjusts the positions of the reticle R in the X-axis
direction, the Y-axis direction, and the rotation direction based
on the values measured by the reticle laser interferometer. More
specifically, the main control system 14 transmits a control signal
to mechanisms incorporated in the reticle stage RST, and positions
the reticle R by slightly moving the reticle stage RST.
[0046] The main control system 14 adjusts the focus position
(Z-axis position) and the tilt angle of the wafer W to align the
surface of the wafer W to the image surface of the projection
optical system PL through autofocusing and automatic leveling. More
specifically, the main control system 14 transmits a control signal
to a wafer stage drive system 15 and drives the Z-stage 9 using the
wafer stage drive system 15 to adjust the focus position and the
tilt angle of the wafer W.
[0047] The main control system 14 further adjusts the positions of
the wafer W in the X-axis direction, the Y-axis direction, and the
rotation direction based on the values measured by the wafer laser
interferometer 13. More specifically, the main control system 14
transmits a control signal to the wafer stage drive system 15, and
adjusts the positions of the wafer W in the X-axis direction, the
Y-axis direction, and the rotation direction by driving the XY
stage 10 using the wafer stage drive system 15.
[0048] During exposure, the main control system 14 transmits a
control signal to mechanisms incorporated in the reticle stage RST
and also transmits a control signal to the wafer stage drive system
15. This drives the reticle stage RST and the XY-stage 10 at a
speed ratio determined by the projection magnitude of the
projection optical system PL, while the pattern image of the
reticle R is projected and exposed within a predetermined shot
region formed on the wafer W. Afterwards, the main control system
14 transmits a control signal to the wafer stage drive system 15,
and drives the XY-stage 10 using the wafer stage drive system 15 to
cause a step movement of the exposure position to another shot
region formed on the wafer W.
[0049] The pattern image of the reticle R is repeatedly scanned and
exposed on the wafer W with the step-and-scan method as described
above. More specifically, the reticle stage RST and the XY-stage 10
and consequently the reticle R and the wafer W are moved (scanned)
in synchronization in the short-side direction of the rectangular
stationary exposure region and the stationary illumination region,
or the Y-axis direction, while the positions of the reticle R and
the wafer W are adjusted using the wafer stage drive system 15 and
the wafer laser interferometer 13 or the like. Through this
operation, the reticle pattern is scanned and exposed in the region
on the wafer W that has the same length as the length of the long
side LX of the stationary exposure region and has the same width as
the width corresponding to the scanning amount (moving amount) of
the wafer W.
[0050] FIG. 3 is a schematic diagram showing the structure of an
interface lens and a wafer in examples of the present embodiment.
As shown in FIG. 3, an immersed plane parallel plate Lp is arranged
nearest to the wafer W in the projection optical system PL in each
example of the present embodiment. One surface of the immersed
plane parallel plate Lp nearer to the reticle R (object side
surface) is in contact with a second liquid Lm2, and another
surface of the immersed plane parallel plate Lp nearer to the wafer
W (image side surface) is in contact with a first liquid Lm1. An
interface lens Lb is arranged adjacent to the immersed plane
parallel plate Lp. One surface of the interface lens Lb nearer to
the retile R (reticle side surface) is in contact with gas, and
another surface of the interface lens Lb nearer to the wafer W
(wafer side surface) is in contact with the second liquid Lm2.
[0051] The projection optical system PL of each example of the
present invention uses, for example, pure water (deionized water)
as the first liquid Lm1 and the second liquid Lm2, which have a
reflective index greater than 1.1. Pure water is easily obtained in
large amounts at, for example, a semiconductor manufacturing
factory. The projection optical system PL of each example uses, as
the interface lens Lb, a positive lens that has a convex surface at
the reticle side and a planar surface as the wafer side. The
interface lens Lb and the immersed plane parallel plate Lp are both
made of silica. Silica is selected as the material for the
interface lens Lb and the immersed plane parallel plate Lp because
the projection optical system PL may fail to maintain stable
imaging performance when, for example, the interface lens Lb and/or
the immersed plane parallel plate Lp are made of fluorite, which is
soluble in water.
[0052] Further, the internal refractive index distribution of
fluorite is known to contain a high-frequency element. The uneven
refractive indexes of fluorite including the high-frequency element
may cause flares. This may easily lower the imaging performance of
the projection optical system. Moreover, fluorite is known to have
natural birefringence. The natural birefringence effect of fluorite
needs to be corrected to achieve high imaging performance of the
projection optical system. The solubility, high-frequency element
in the refractive index distribution, and natural birefringence
make fluorite unsuitable for the material for the interface lens Lb
and the immersed plane parallel plate Lp. It is preferable that the
interface lens Lb and the immersed plane parallel plate Lp be made
of silica.
[0053] The exposure apparatus that performs scanning and exposure
while moving the wafer W relative to the projection optical system
PL with the step-and-scan method needs to continuously fill the
optical path between the interface lens Lb and the wafer W of the
projection optical system PL with the liquid (Lm1 and Lm2) from the
start to the end of the scanning and exposure process. To enable
this, the exposure apparatus may use a technique described for
example in International Patent Publication No. WO99/49504 or a
technique described for example in Japanese Laid-Open Patent
Publication No. 10-303114.
[0054] According to the technique described in International Patent
Publication No. WO99/49504, a liquid supply apparatus supplies
liquid, which has been adjusted to a predetermined temperature, to
fill the optical path between the interface lens Lb and the wafer W
through a supply pipe and an ejection nozzle, and then recovers the
liquid on the wafer W through a recovery pipe and a suction nozzle.
According to the technique described in Japanese Laid-Open Patent
Publication No. 10-303114, a wafer holder table functions as a
container for accommodating liquid. The wafer W is positioned and
supported at the center of an inner bottom surface of the wafer
holder table (immersed in the liquid) by vacuum contact. A distal
end of a barrel of the projection optical system PL is immersed in
the liquid. A wafer-side optical surface of the interface lens Lb
is immersed in the liquid.
[0055] As shown in FIG. 1, the projection optical system PL of the
present embodiment uses a first supply and discharge mechanism 21
to circulate pure water, which functions as the first liquid Lm1,
in the optical path between the immersed plane parallel plate Lp
and the wafer W. The projection optical system PL also uses a
second supply and discharge mechanism 22 to circulate pure water,
which functions as the second liquid Lm2, in the optical path
between the interface lens Lb and the immersed plane parallel plate
Lp. In this manner, the projection optical system PL circulates a
small amount of pure water as the immersion liquid to prevent
corrosion or fungal deterioration of the liquid.
[0056] In the examples of the present invention, an aspherical
surface can be written as expression (a) shown below. In expression
(a), y represents the height in the direction vertical to the
optical axis, z represents the distance (sag amount) between a
contact planar surface at the vertex of the aspherical surface and
the position at the height y on the aspherical surface, r
represents the curvature radius of the vertex, k represents the
coefficient of the cone, and C.sub.n represents the n-th degree
aspherical coefficient. In tables 1 and 2, which are shown below,
the surface number of each aspherical lens surface is marked with
*.
z=(y.sup.2/r)/[1+{1-(1+k)*y.sup.2/r.sup.2}.sup.1/2]+C.sub.4*y.sup.4+C.su-
b.6*y.sup.6+C.sub.8*y.sup.8+C.sub.10*y.sup.10+C.sub.12*y.sup.12+C.sub.14*y-
.sup.14+ Expression (a)
[0057] The projection optical system PL of each example of the
present embodiment includes a first imaging optical system G1, a
second imaging optical system G2, and a third imaging optical
system G3. The first imaging optical system G1 forms a first
intermediate image of a pattern of the reticle R, which is arranged
on an object plane (first plane) of the projection optical system
PL. The second imaging optical system G2 forms a second
intermediate image (which is an image of the first intermediate
image as well as a secondary image of the reticle pattern) of the
reticle pattern based on the light from the first intermediate
image. The third imaging optical system G3 forms a final image
(which is a reduced image of the reticle pattern) on the wafer W,
which is arranged on an image plane (second plane) of the
projection optical system PL, based on light from the second
intermediate image. The first imaging optical system G1 and the
third imaging optical system G3 are both refractive optical
systems. The second imaging optical system G2 is a catadioptric
optical system that includes a concave reflective mirror CM.
[0058] A first planar reflective mirror (first folding mirror) M1
is arranged in an optical path formed between the first imaging
optical system G1 and the second imaging optical system G2. A
second planar reflective mirror (second folding mirror) M2 is
arranged in an optical path formed between the second imaging
optical system G2 and the third imaging optical system G3. In the
projection optical system PL of each example of the present
invention, light from the reticle R passes through the first
imaging optical system G1 and forms a first intermediate image of
the reticle pattern in the vicinity of the first planar reflective
mirror M1. Light from the first intermediate image then passes
through the second imaging optical system G2 and forms a second
intermediate image of the reticle pattern in the vicinity of the
second planar reflective mirror M2. Finally, light from the second
intermediate image passes through the third imaging optical system
G3, and forms a final image of the reticle pattern on the wafer
W.
[0059] In the projection optical system PL of each example of the
present invention, the first imaging optical system G1 has an
optical axis AX1 and the third imaging optical system G3 has an
optical axis AX3. The optical axes AX1 and AX3 extend linearly in
the vertical direction. The optical axes AX1 and AX3 coincide with
the reference optical axis AX. The second imaging optical system G2
has an optical axis AX2 that extends linearly along the horizontal
direction (vertical to the reference optical axis AX). The reticle
R, the wafer W, all the optical members forming the first imaging
optical system G1, and all the optical members forming the third
imaging optical system G3 are arranged parallel to one another
along planes perpendicular to the direction of gravitational force,
that is, along horizontal planes. Further, the first planar
reflective mirror M1 and the second planar reflective mirror M2
have reflective surfaces that each form an angle of 45 degrees with
the reticle surface. The first planar reflective mirror M1 and the
second planar reflective mirror M2 are formed integrally as a
single optical member. Further, the projection optical system PL of
each example of the present invention is formed to be substantially
telecentric at both of the object side and the image side.
FIRST EXAMPLE
[0060] FIG. 4 shows a lens structure of a projection optical system
according to a first example of the present embodiment. As shown in
FIG. 4, the first imaging optical system G1 included in the
projection optical system PL of the first example includes a plane
parallel plate P1, a biconvex lens L11, a positive meniscus lens
L12 having a convex surface at its reticle side, a biconvex lens
L13, a biconcave lens L14 having an aspherical concave surface at
its reticle side, a positive meniscus lens L15 having a convex
surface at its reticle side, a positive meniscus lens L16 having a
concave surface at its reticle side, a negative meniscus lens L17
having a concave surface at its reticle side, a positive meniscus
lens L18 having an aspherical concave surface at its reticle side,
a positive meniscus lens L19 having a concave surface at its
reticle side, a biconvex lens L110, and a positive meniscus lens
L111 having an aspherical concave surface at its wafer side, which
are arranged sequentially in this order from the reticle side.
[0061] The second imaging optical system G2 includes a negative
meniscus lens L21 having a concave surface at its reticle side, a
negative meniscus lens L22 having a concave surface at its reticle
side, and a concave reflective mirror CM having a concave surface
at its reticle side, which are arranged sequentially in this order
along the traveling path of the incoming light from the reticle
side (light entering side) of the projection optical system PL. The
third imaging optical system G3 includes a positive meniscus lens
L31 having a concave surface at its reticle side, a biconvex lens
L32, a positive meniscus lens L33 having a convex surface at its
reticle side, a positive meniscus lens L34 having a spherical
concave surface at its wafer side, a biconcave lens L35, a
biconcave lens L36 having an aspherical concave surface at its
wafer side, a positive meniscus lens L37 having an aspherical
concave surface at its reticle side, a positive meniscus lens L38
having an aspherical concave surface at its wafer side, a negative
meniscus lens L39 having an aspherical concave surface at its wafer
side, a positive meniscus lens L310 having an aspherical concave
surface at its reticle side, a biconvex lens L311, an aperture stop
AS, a plano-convex lens L312 having a planar surface at its wafer
side, a positive meniscus lens L313 having an aspherical concave
surface at its wafer side, a positive meniscus lens S314 having an
aspherical concave surface at its wafer side, a plano-convex lens
L315 (interface lens Lb) having a planar surface at its wafer side,
and a plane parallel plate Lp, which are arranged sequentially in
this order from the reticle side (light entering side).
[0062] In the projection optical system PL of the first example, an
optical path between the interface lens Lb and the plane parallel
plate (immersed plane parallel plate) Lp and an optical path
between the plane parallel plate Lp and the wafer W are filled with
pure water (Lm1 and Lm2) having a refractive index of 1.435876 for
an ArF excimer laser beam (having a central wavelength .lamda. of
193.306 nm), which is the used light (exposure beam). All the light
transmitting members including the interface lens Lb and the plane
parallel plate Lp are made of silica (SiO.sub.2), which has a
refractive index of 1.5603261 relative to the central wavelength of
the used light.
[0063] Table 1 below shows the specifications of the projection
optical system PL in the first example. In Table 1, .lamda.
represents the central wavelength of the exposure beam, .beta.
represents the projection magnification (imaging ratio of the
entire system), NA represents the numerical aperture at the image
side (wafer side) of the system, B represents the radius of the
image circle IF on the wafer W, A represents the off-axis amount of
the effective exposure region ER, LX represents the size of the
effective exposure region ER in the X-axis direction (the long-side
dimension of the effective exposure region ER), and LY represents
the dimension of the effective exposure region ER in the Y-axis
direction (the short-side dimension of the effective exposure
region ER).
[0064] In the table, the surface number represents the order of
each surface on the path of the light traveling from the reticle
surface, which is the object surface (first plane), to the wafer
surface, which is the image surface (second plane), r represents
the curvature radius of each surface (the curvature radius (mm) of
the vertex in the case of an aspherical surface), d represents the
axial interval of each surface or the surface interval (mm), and n
represents the refractive index about the central wavelength of the
exposure beam. The sign of the surface interval d is inverted
whenever the light is reflected. Accordingly, the surface interval
d has a negative sign for the optical path from the reflective
surface of the first planar reflective mirror M1 to the concave
reflective mirror CM and for the optical path from the second
planar reflective mirror M2 to the image surface, whereas the
surface interval d has a positive sign for other optical paths.
[0065] In the first imaging optical system G1, the curvature radius
is positive for convex surfaces facing toward the reticle side, and
the curvature radius is negative for concave surfaces facing toward
the reticle side. In the second imaging optical system G2, the
curvature radius is positive for concave surfaces facing toward the
light entering side (reticle side) of the incoming light, and the
curvature radius is negative for convex surfaces facing toward the
light entering side. The notations used in Table 1 are used in
Table 2, which will be described later.
TABLE-US-00002 TABLE 1 (Main Specifications) .lamda. = 193.306 nm
.beta. = 1/4 NA = 1.32 B = 15.3 mm A = 2.8 mm LX = 26 mm LY = 5 mm
(Specifications of Optical Members) Surface Optical No. r d n
Member (Reticle Surface) 113.7542 1 .infin. 8.0000 1.5603261 (P1) 2
.infin. 6.0000 3 961.49971 52.0000 1.5603261 (L11) 4 -260.97642
1.0000 5 165.65618 35.7731 1.5603261 (L12) 6 329.41285 15.7479 7
144.73700 56.4880 1.5603261 (L13) 8 -651.17229 4.1450 9* -678.61021
18.2979 1.5603261 (L14) 10 173.73534 1.0000 11 82.85141 28.4319
1.5603261 (L15) 12 122.17403 24.6508 13 -632.23083 15.8135
1.5603261 (L16) 14 -283.76586 22.9854 15 -95.83749 44.8780
1.5603261 (L17) 16 -480.25701 49.9532 17* -327.24655 37.6724
1.5603261 (L18) 18 -152.74838 1.0000 19 -645.51205 47.0083
1.5603261 (L19) 20 -172.70890 1.0000 21 1482.42136 32.7478
1.5603261 (L110) 22 -361.68453 1.0000 23 185.06735 36.2895
1.5603261 (L111) 24* 1499.92500 72.0000 25 .infin. -204.3065 (M1)
26 115.50235 -15.0000 1.5603261 (L21) 27 181.35110 -28.1819 28
107.57500 -18.0000 1.5603261 (L22) 29 327.79447 -34.9832 30
165.18700 34.9832 (CM) 31 327.79446 18.0000 1.5603261 (L22) 32
107.57500 28.1819 33 181.35110 15.0000 1.5603261 (L21) 34 115.50235
204.3065 35 .infin. -72.0000 (M2) 36 552.89298 -24.4934 1.5603261
(L31) 37 211.40931 -1.0000 38 -964.15750 -27.5799 1.5603261 (L32)
39 451.41200 -1.0000 40 -239.74429 -35.7714 1.5603261 (L33) 41
-171769.23040 -1.0000 42 -206.94777 -50.0000 1.5603261 (L34) 43*
-698.47035 -43.1987 44 560.33453 -10.0000 1.5603261 (L35) 45
-116.92245 -46.5360 46 209.32811 -10.0000 1.5603261 (L36) 47*
-189.99848 -23.6644 48* 1878.63986 -31.5066 1.5603261 (L37) 49
211.85278 -1.0000 50 -322.20466 -33.1856 1.5603261 (L38) 51*
-1160.22740 -10.0172 52 -2715.10365 -22.0000 1.5603261 (L39) 53*
-959.87714 -42.0799 54* 727.37853 -62.0255 1.5603261 (L310) 55
240.59248 -1.0000 56 -16276.86134 -62.1328 1.5603261 (L311) 57
333.64919 -1.0000 58 .infin. -1.0000 (AS) 59 -303.09919 -68.2244
1.5603261 (L312) 60 .infin. -1.0000 61 -182.25869 -77.6122
1.5603261 (L313) 62* -472.72383 -1.0000 63 -131.14200 -49.9999
1.5603261 (L314) 64* -414.78286 -1.0000 65 -75.90800 -43.3351
1.5603261 (L315: Lb) 66 .infin. -1.0000 1.435876 (Lm2) 67 .infin.
-13.0000 1.5603261 (Lp) 68 .infin. -2.9999 1.435876 (Lm1) (Wafer
Surface) (Aspherical Surface Data) 9th surface K = 0 C.sub.4 =
-7.9031 * 10.sup.-8 C.sub.6 = 8.6709 * 10.sup.-12 C.sub.8 = -6.5472
* 10.sup.-16 C.sub.10 = 1.5504 * 10.sup.-20 C.sub.12 = 2.6800 *
10.sup.-24 C.sub.14 = -2.6032 * 10.sup.-28 C.sub.16 = 7.3308 *
10.sup.-33 C.sub.18 = 0 17th surface K = 0 C.sub.4 = 4.7672 *
10.sup.-9 C.sub.6 = -8.7145 * 10.sup.-13 C.sub.8 = -2.8591 *
10.sup.-17 C.sub.10 = 3.9981 * 10.sup.-21 C.sub.12 = -1.9927 *
10.sup.-25 C.sub.14 = 2.8410 * 10.sup.-30 C.sub.16 = 6.5538 *
10.sup.-35 C.sub.18 = 0 24th surface K = 0 C.sub.4 = 2.7118 *
10.sup.-8 C.sub.6 = -4.0362 * 10.sup.-13 C.sub.8 = 8.5346 *
10.sup.-18 C.sub.10 = -1.7653 * 10.sup.-22 C.sub.12 = -1.1856 *
10.sup.-27 C.sub.14 = 5.2597 * 10.sup.-31 C.sub.16 = -2.0897 *
10.sup.-35 C.sub.18 = 0 43th surface K = 0 C.sub.4 = -1.8839 *
10.sup.-8 C.sub.6 = 5.6009 * 10.sup.-13 C.sub.8 = -1.8306 *
10.sup.-17 C.sub.10 = 2.2177 * 10.sup.-21 C.sub.12 = -2.3512 *
10.sup.-25 C.sub.14 = 1.7766 * 10.sup.-29 C.sub.16 = -6.5390 *
10.sup.-34 C.sub.18 = 0 47th surface K = 0 C.sub.4 = 9.0773 *
10.sup.-8 C.sub.6 = -5.4651 * 10.sup.-12 C.sub.8 = 4.4000 *
10.sup.-16 C.sub.10 = -2.7426 * 10.sup.-20 C.sub.12 = 3.2149 *
10.sup.-25 C.sub.14 = 2.3641 * 10.sup.-28 C.sub.16 = -1.3953 *
10.sup.-32 C.sub.18 = 0 48th surface K = 0 C.sub.4 = 3.0443 *
10.sup.-8 C.sub.6 = -1.6528 * 10.sup.-12 C.sub.8 = 2.3949 *
10.sup.-17 C.sub.10 = -4.4953 * 10.sup.-21 C.sub.12 = 3.0165 *
10.sup.-25 C.sub.14 = -1.2463 * 10.sup.-28 C.sub.16 = 1.0783 *
10.sup.-32 C.sub.18 = 0 51th surface K = 0 C.sub.4 = 1.8357 *
10.sup.-8 C.sub.6 = -4.3103 * 10.sup.-13 C.sub.8 = -9.4499 *
10.sup.-17 C.sub.10 = 4.3247 * 10.sup.-21 C.sub.12 = -1.6979 *
10.sup.-25 C.sub.14 = 8.6892 * 10.sup.-30 C.sub.16 = -1.5935 *
10.sup.-34 C.sub.18 = 0 53th surface K = 0 C.sub.4 = -3.9000 *
10.sup.-8 C.sub.6 = -7.2737 * 10.sup.-13 C.sub.8 = 1.1921 *
10.sup.-16 C.sub.10 = -2.6393 * 10.sup.-21 C.sub.12 = -3.1544 *
10.sup.-26 C.sub.14 = 1.8774 * 10.sup.-30 C.sub.16 = -2.3545 *
10.sup.-35 C.sub.18 = 0 54th surface K = 0 C.sub.4 = 1.9116 *
10.sup.-8 C.sub.6 = -6.7783 * 10.sup.-13 C.sub.8 = 1.5688 *
10.sup.-17 C.sub.10 = -6.0850 * 10.sup.-22 C.sub.12 = 1.8575 *
10.sup.-26 C.sub.14 = -4.2147 * 10.sup.-31 C.sub.16 = 7.3240 *
10.sup.-36 C.sub.18 = 0 62th surface K = 0 C.sub.4 = 3.0649 *
10.sup.-8 C.sub.6 = -2.3613 * 10.sup.-12 C.sub.8 = 1.5604 *
10.sup.-16 C.sub.10 = -7.3591 * 10.sup.-21 C.sub.12 = 2.1593 *
10.sup.-25 C.sub.14 = -3.5918 * 10.sup.-30 C.sub.16 = 2.5879 *
10.sup.-35 C.sub.18 = 0 64th surface K = 0 C.sub.4 = -6.0849 *
10.sup.-8 C.sub.6 = -8.7021 * 10.sup.-13 C.sub.8 = -1.5623 *
10.sup.-16 C.sub.10 = 1.5681 * 10.sup.-20 C.sub.12 = -1.6989 *
10.sup.-24 C.sub.14 = 7.9711 * 10.sup.-29 C.sub.16 = -2.7075 *
10.sup.-33 C.sub.18 = 0
[0066] FIG. 5 shows lateral aberrations in the projection optical
system PL of the first example. In the aberration charts, Y
represents the image height, the solid line represents lateral
aberration occurring when the exposure beam has a central
wavelength of 193.3060 nm, the broken line represents lateral
aberration occurring when the exposure beam has a central
wavelength of 193.306 nm+0.2 pm=193.3062 nm, the single-dash line
represents lateral aberration occurring when the exposure beam has
a central wavelength of 193.306 nm -0.2 pm=193.3058 nm. The
notations used in FIG. 5 are used in FIG. 7, which will be
described later. As apparent from FIG. 5, the aberration is
corrected in a satisfactory manner for the exposure beams with a
wavelength width of 193.306 nm.+-.0.2 pm although the projection
optical system PL has an extremely large image-side numerical
aperture (NA=1.32) and a relatively large effective exposure region
ER (26 mm by 5 mm).
SECOND EXAMPLE
[0067] FIG. 6 shows a lens structure for a projection optical
system according to a second example of the present embodiment. As
shown in FIG. 6, the first imaging optical system G1 in the
projection optical system PL of the second example includes a plane
parallel plate P1, a biconvex lens L11, a positive meniscus lens
L12 having a convex surface at its reticle side, a positive
meniscus lens L13 having a convex surface at its reticle side, a
biconcave lens L14 having an aspherical concave surface at its
reticle side, a positive meniscus lens L15 having a convex surface
at its reticle side, a positive meniscus lens L16 having a concave
surface at its reticle side, a negative meniscus lens L17 having a
concave surface at its reticle side, a positive meniscus lens L18
having an aspherical concave surface at its reticle side, a
positive meniscus lens L19 having a concave surface at its reticle
side, a biconcave lens L110, and a positive meniscus lens L111
having an aspherical concave surface at its wafer side, which are
arranged sequentially in this order from the reticle side.
[0068] The second imaging optical system G2 includes a negative
meniscus lens L21 having a concave surface at its reticle side, a
negative meniscus lens L22 having a concave surface at its reticle
side, and a concave reflective mirror CM having a concave surface
at its reticle side, which are arranged sequentially in this order
along a traveling path of the incoming light from the reticle side
(light entering side) of the projection optical system PL. A third
imaging optical system G3 includes a positive meniscus lens L31
having a concave surface at its reticle side, a biconvex lens L32,
a positive meniscus lens L33 having a convex surface at its reticle
side, a positive meniscus lens L34 having an aspherical concave
surface at its wafer side, a biconcave lens L35, a biconcave lens
L36 having a aspherical concave surface at its wafer side, a
positive meniscus lens L37 having an aspherical concave surface at
its reticle side, a positive meniscus lens L38 having an aspherical
concave surface at its wafer side, a plano-concave lens L39 having
an aspherical concave surface at its wafer side, a positive
meniscus lens L310 having an aspherical concave surface at its
reticle side, a positive meniscus lens L311 having a concave
surface at its reticle side, an aperture stop AS, a plano-convex
lens L312 having a planar surface at its wafer side, a positive
meniscus lens L313 having an aspherical concave surface at its
wafer side, a positive meniscus lens S314 having an aspherical
concave surface at its wafer side, a plano-convex lens L315
(interface lens Lb) having a planar surface at its wafer side, and
a plane parallel plate Lp, which are arranged sequentially in this
order from the reticle side (light entering side).
[0069] In the same manner as in the first example, in the second
example, an optical path between the interface lens Lb and the
plane parallel plate (immersed plane parallel plate) Lp and an
optical path between the plane parallel plate Lp and the wafer W
are filled with pure water (Lm1 and Lm2) having a refractive index
of 1.435876 relative to an ArF excimer laser beam (having a central
wavelength .lamda. of 193.306 nm), which is the used laser beam
(exposure beam). All the light transmitting members including the
interface lens Lb and the plane parallel plate Lp are made of
silica (SiO.sub.2), which has a refractive index of 1.5603261
relative to the central wavelength of the used light. Table 2 below
shows the specifications of the projection optical system PL
according to the second example.
TABLE-US-00003 TABLE 2 (Main Specifications) .lamda. = 193.306 nm
.beta. = 1/4 NA = 1.3 B = 15.4 mm A = 3 mm LX = 26 mm LY = 5 mm
(Specifications of Optical Members) Surface Optical No. r d n
Member (Reticle Surface) 128.0298 1 .infin. 8.0000 1.5603261 (P1) 2
.infin. 3.0000 3 708.58305 50.0000 1.5603261 (L11) 4 -240.96139
1.0000 5 159.28256 55.0000 1.5603261 (L12) 6 1030.42583 15.3309 7
175.91680 33.4262 1.5603261 (L13) 8 1901.42936 13.4484 9*
-313.76486 11.8818 1.5603261 (L14) 10 235.56199 1.0000 11 90.40801
53.3442 1.5603261 (L15) 12 109.36394 12.8872 13 -1337.13410 20.2385
1.5603261 (L16) 14 -314.47144 10.2263 15 -106.13528 42.5002
1.5603261 (L17) 16 -334.97792 56.0608 17* -1619.43320 46.3634
1.5603261 (L18) 18 -167.00000 1.0000 19 -568.04127 48.4966
1.5603261 (L19) 20 -172.67366 1.0000 21 637.03167 27.8478 1.5603261
(L110) 22 -838.93167 1.0000 23 264.56403 30.7549 1.5603261 (L111)
24* 3443.52617 72.0000 25 .infin. -237.1956 (M1) 26 134.07939
-15.0000 1.5603261 (L21) 27 218.66017 -33.2263 28 111.51192
-18.0000 1.5603261 (L22) 29 334.92606 -28.5215 30 170.92067 28.5215
(CM) 31 334.92606 18.0000 1.5603261 (L22) 32 111.51192 33.2263 33
218.66017 15.0000 1.5603261 (L21) 34 134.07939 237.1956 35 .infin.
-72.0000 (M2) 36 1133.17643 -25.2553 1.5603261 (L31) 37 247.47802
-1.0000 38 -480.60890 -29.6988 1.5603261 (L32) 39 626.43077 -1.0000
40 -208.29831 -36.2604 1.5603261 (L33) 41 -2556.24930 -1.0000 42
-173.46230 -50.0000 1.5603261 (L34) 43* -294.18687 -26.4318 44
699.54032 -11.5000 1.5603261 (L35) 45 -106.38847 -47.9520 46
158.19938 -11.5000 1.5603261 (L36) 47* -189.99848 -27.6024 48*
487.32943 -34.3282 1.5603261 (L37) 49 153.21216 -1.0000 50
-280.33475 -39.4036 1.5603261 (L38) 51* -1666.66667 -17.3862 52
.infin. -22.0000 1.5603261 (L39) 53* -1511.71580 -40.3150 54*
655.86673 -62.2198 1.5603261 (L310) 55 242.88510 -1.0000 56
843.73059 -49.2538 1.5603261 (L311) 57 280.00000 -1.0000 58 .infin.
-1.0000 (AS) 59 -291.92686 -61.1038 1.5603261 (L312) 60 .infin.
-1.0000 61 -179.32463 -67.4474 1.5603261 (L313) 62* -438.34656
-1.0000 63 -128.42402 -52.4156 1.5603261 (L314) 64* -401.88080
-1.0000 65 -75.86112 -41.5893 1.5603261 (L315: Lb) 66 .infin.
-1.0000 1.435876 (Lm2) 67 .infin. -16.5000 1.5603261 (Lp) 68
.infin. -3.0000 1.435876 (Lm1) (Wafer Surface) (Aspherical Surface
Data) 9th surface K = 0 C.sub.4 = -3.1753 * 10.sup.-8 C.sub.6 =
9.0461 * 10.sup.-12 C.sub.8 = -1.0355 * 10.sup.-15 C.sub.10 =
1.2398 * 10.sup.-19 C.sub.12 = -1.1221 * 10.sup.-23 C.sub.14 =
5.7476 * 10.sup.-28 C.sub.16 = -1.1800 * 10.sup.-32 C.sub.18 = 0
17th surface K = 0 C.sub.4 = -2.8399 * 10.sup.-8 C.sub.6 = -3.0401
* 10.sup.-13 C.sub.8 = 1.1462 * 10.sup.-17 C.sub.10 = 4.0639 *
10.sup.-22 C.sub.12 = -8.6125 * 10.sup.-26 C.sub.14 = 4.4202 *
10.sup.-30 C.sub.16 = -9.9158 * 10.sup.-35 C.sub.18 = 0 24th
surface K = 0 C.sub.4 = 2.1499 * 10.sup.-8 C.sub.6 = -3.8861 *
10.sup.-13 C.sub.8 = 5.4812 * 10.sup.-18 C.sub.10 = -2.1623 *
10.sup.-23 C.sub.12 = -2.5636 * 10.sup.-26 C.sub.14 = 2.1879 *
10.sup.-30 C.sub.16 = -6.5039 * 10.sup.-35 C.sub.18 = 0 43th
surface K = 0 C.sub.4 = -2.0533 * 10.sup.-8 C.sub.6 = 7.8051 *
10.sup.-13 C.sub.8 = 9.4002 * 10.sup.-18 C.sub.10 = -2.1043 *
10.sup.-21 C.sub.12 = 7.8182 * 10.sup.-25 C.sub.14 = -9.2007 *
10.sup.-29 C.sub.16 = 3.6742 * 10.sup.-33 C.sub.18 = 0 47th surface
K = 0 C.sub.4 = 9.8639 * 10.sup.-8 C.sub.6 = -6.7359 * 10.sup.-12
C.sub.8 = 6.8579 * 10.sup.-16 C.sub.10 = -6.1604 * 10.sup.-20
C.sub.12 = 5.1722 * 10.sup.-24 C.sub.14 = -2.9412 * 10.sup.-28
C.sub.16 = 8.6688 * 10.sup.-33 C.sub.18 = 0 48th surface K = 0
C.sub.4 = 4.3101 * 10.sup.-8 C.sub.6 = -3.2805 * 10.sup.-12 C.sub.8
= 5.6432 * 10.sup.-17 C.sub.10 = -9.2345 * 10.sup.-22 C.sub.12 =
1.0713 * 10.sup.-25 C.sub.14 = -9.9944 * 10.sup.-30 C.sub.16 =
1.8148 * 10.sup.-33 C.sub.18 = 0 51th surface K = 0 C.sub.4 =
2.5839 * 10.sup.-8 C.sub.6 = -1.8848 * 10.sup.-12 C.sub.8 = -4.9271
* 10.sup.-17 C.sub.10 = 4.4946 * 10.sup.-21 C.sub.12 = -7.2550 *
10.sup.-26 C.sub.14 = 4.9237 * 10.sup.-31 C.sub.16 = -2.4260 *
10.sup.-35 C.sub.18 = 6.2565 * 10.sup.-40 53th surface K = 0
C.sub.4 = -4.7449 * 10.sup.-8 C.sub.6 = -2.3075 * 10.sup.-13
C.sub.8 = 1.0475 * 10.sup.-16 C.sub.10 = -2.1805 * 10.sup.-21
C.sub.12 = -9.0530 * 10.sup.-26 C.sub.14 = 4.6274 * 10.sup.-30
C.sub.16 = -6.4961 * 10.sup.-35 C.sub.18 = 3.4402 * 10.sup.-41 54th
surface K = 0 C.sub.4 = 2.0328 * 10.sup.-8 C.sub.6 = -7.7439 *
10.sup.-13 C.sub.8 = 1.6217 * 10.sup.-17 C.sub.10 = -3.5531 *
10.sup.-22 C.sub.12 = 8.2634 * 10.sup.-27 C.sub.14 = 2.6232 *
10.sup.-31 C.sub.16 = -2.0989 * 10.sup.-35 C.sub.18 = 4.0888 *
10.sup.-40 62th surface K = 0 C.sub.4 = 2.5121 * 10.sup.-8 C.sub.6
= -2.0342 * 10.sup.-12 C.sub.8 = 1.2906 * 10.sup.-16 C.sub.10 =
-5.4455 * 10.sup.-21 C.sub.12 = 1.2885 * 10.sup.-25 C.sub.14 =
-1.4600 * 10.sup.-30 C.sub.16 = 3.2850 * 10.sup.-36 C.sub.18 = 0
64th surface k = 0 C.sub.4 = -2.8098 * 10.sup.-8 C.sub.6 = -3.9565
* 10.sup.-12 C.sub.8 = 3.1966 * 10.sup.-16 C.sub.10 = -2.7246 *
10.sup.-20 C.sub.12 = 1.8266 * 10.sup.-24 C.sub.14 = -8.6244 *
10.sup.-29 C.sub.16 = 2.1570 * 10.sup.-33 C.sub.18 = 0
[0070] FIG. 7 shows lateral aberrations occurring in the projection
optical system PL of the second example. As apparent from FIG. 7,
the aberration is corrected in an satisfactory manner for the
exposure beams having a wavelength width of 193.306 nm.+-.0.2 pm
even though the projection optical system PL of the second example
has an extremely large image-side numerical aperture (NA=1.3) and a
relatively large effective exposure region ER (26 mm by 5 mm) in
the same manner as in the projection optical system PL of the first
example.
[0071] In this manner, the optical path formed between the
interface lens Lb and the wafer W is filled with pure water (Lm1
and Lm2) having a large refractive index in the projection optical
system PL of the present embodiment. This enables the projection
optical system PL to have a relatively large effective imaging
region while achieving a large effective image-side numerical
aperture. The projection optical system PL of each example of the
present invention has a rectangular effective exposure region
(stationary exposure region) ER having the dimensions of 26 mm by 5
mm while achieving a high image-side numerical aperture of about
1.3 for an ArF excimer laser beam having a central wavelength of
193.306 nm. This enables the projection optical system PL of each
example to scan and expose a circuit pattern within a rectangular
exposure region of, for example, 26 mm by 33 mm with a high
accuracy.
[0072] A shape error on any lens surface of the two-way optical
elements (L21 and L22) in a catadioptric optical system affects
local flares twice as much as a normal lens surface. Thus, in each
of the above examples, aspherical surfaces are excluded from a
two-way optical path in which twice as much local flares may occur
with a single lens surface. That is, all of the two-way optical
elements do not include optical surfaces with an aspherical shape.
In each of the above examples, local flares are further reduced by
eliminating crystalline material from the two-way optical path
portions, through which light passes twice, that is, by using an
amorphous material (silica in the present embodiment) to form all
the two-way optical elements (L21 and L22) in the second imaging
optical system G2. Further, a shape error occurring on the
reflective surface of the concave reflection mirror in the second
imaging optical system G2 also affects local flares twice as much
as a shape error occurring on a lens surface on a one-way optical
element. Thus, in each of the above examples, local flares are
reduced by forming the concave reflection mirror CM to have a
spherical reflective surface.
[0073] The immersion projection optical system PL of the present
embodiment employs a catadioptric optical system structure. Thus,
the projection optical system PL substantially satisfies Petzval's
condition and ensures the flatness of an image although the
projection optical system PL has a large image-side numerical
aperture. The projection optical system PL also employs an off-axis
optical system structure, in which an effective field of view
region (effective illumination region) and an effective projection
region (effective exposure region ER) do not extend on an optical
axis of the projection optical system (the regions are "off" the
optical axis). This projection optical system PL eliminates a light
shielding portion in its lens aperture (pupil), and increases the
variety of patterns of images that can be formed. However, the
catadioptric and off-axis immersion projection optical system PL of
the present embodiment will have problems when the light emitting
surface of the immersed plane parallel plate Lp, which is a
refractive optical element arranged nearest to the imaging position
(to the wafer W), is formed rotationally symmetric with respect to
the optical axis AX3 (or the reference optical axis AX) according
to a conventional technique.
[0074] FIG. 8 is a diagram describing problems occurring when the
light emitting surface of the refractive optical element arranged
nearest to the imaging position is formed rotationally symmetric
according to a conventional technique. As shown in FIG. 8, the
light entering surface of the immersed plane parallel plate Lp,
which is the refractive optical element arranged nearest to the
imaging position (to the wafer W) in the immersion projection
optical system PL, has a circumference corresponding to a circle 30
of which center coincides with the optical axis AX. In other words,
the light entering surface of the immersed plane parallel plate Lp
has substantially equal lengths in the two axial directions that
are perpendicular to each other. The circumference of the light
entering surface of the immersed plane parallel plate Lp may
actually include a cutaway portion such as an orientation flat, the
circumference of the light entering surface may actually have a
polygonal shape, and the circumference of the light entering
surface may actually have a holding tab that is flush with the
light entering surface. In any case, the central axis of the circle
30 corresponding to the outer circumference of the light entering
surface of the immersed plane parallel plate Lp coincides with the
optical axis AX.
[0075] The effective light emitting region 31 is defined on the
light emitting surface of the immersed plane parallel plate Lp as a
region through which an effective imaging light beam passes. The
effective light emitting region 31 corresponds to the rectangular
effective exposure region (stationary exposure region) ER that is
formed on the wafer W and that does not include the optical axis
AX. The effective light emitting region 31 is decentered in one
direction (Y-axis) with respect to the optical axis AX and has a
rectangular shape with round corners. In the conventional
technique, the light emitting surface of the immersed plane
parallel plate Lp is rotationally symmetric (infinite-fold
rotationally symmetric) with respect to the optical axis AX
irrespective of the rotation asymmetry of the effective light
emitting region 31. In other words, the light emitting surface of
the immersion parallel plate Lp has substantially equal lengths in
the two axial directions that are perpendicular to each other.
Thus, the light emitting surface of the immersed plane parallel
plate Lp has a circumference of which center coincides with the
optical axis AX and corresponds to a large circle 32 that contains
the effective light emitting region 31. As a result, the structure
of the conventional technique enlarges the portion of the image
space in the projection optical system PL that is filled with the
liquid Lm1. This consequently enlarges the substrate stage (9 to
11) and lowers the accuracy of the alignment optical system (not
shown).
[0076] FIG. 9 is a schematic diagram showing the structure of an
immersed plane parallel plate in each example of the present
embodiment. FIG. 9(a) is a bottom view of the immersed plane
parallel plate Lp, and FIGS. 9(b) and 9(c) are side views of the
immersed plane parallel plate Lp. As shown in FIG. 9, a light
entering surface Lpa of the immersed plane parallel plate Lp in
each example of the present embodiment has a circumference
corresponding to a circle 40. The circle 40, which corresponds to
the circumference of the light entering surface Lpa, has a center
40a that is decentered in the Y-axis direction with respect to the
optical axis AX (AX3). A reference circle indicated by a broken
line 41 is a circle of which center coincides with the optical axis
AX and that is inscribed in the circle 40. In other words, the
light entering surface Lpa of the immersed plane parallel plate Lp
has substantially equal lengths in the two axial directions
(XY-axes directions) that are perpendicular to each other.
[0077] An effective light emitting region 42 formed on the light
emitting surface Lpb of the immersed plane parallel plate Lp is
substantially symmetric with respect to X-axis and Y-axis
directions and has a rectangular shape with round corners. The
effective light emitting region 42 has a center 42a that coincides
with the center 40a of the circle 40 corresponding to the
circumference of the light entering surface Lpa. The light emitting
surface Lpb of the immersed plane parallel plate Lp is
substantially symmetric with respect to the X-axis and Y-axis
directions and contains the effective light emitting region 42 with
a small marginal region formed around the effective light emitting
region 42. The light emitting surface Lpb has a center Lpba that
coincides with the center 42a of the effective light emitting
region 42 and the center 40a of the circle 40 corresponding to the
outer circumference of the light entering surface Lpa. From another
point of view, the light emitting surface Lpb of the immersed plane
parallel plate Lp is one-fold rotationally symmetric with respect
to the optical axis AX. In FIG. 9(a), a hatched portion Lpc
surrounding the light emitting surface Lpb shows a tilted surface
that extends from the outer circumference of the light emitting
surface Lpb toward the light entering side.
[0078] More specifically, in each example of the present invention,
the light emitting surface Lpb of the immersed plane parallel plate
Lp is substantially symmetric with respect to the two axial
directions that are perpendicular to each other on the wafer W,
that is, with respect to the X-axis and Y-axis directions. Further,
the central axis Lpba of the light emitting surface Lpb and the
central axis 40a of the circle 40 corresponding to the outer
circumference of the light entering surface Lpa coincide with each
other. The central axis Lpba of the light emitting surface Lpb is
decentered in the Y-axis direction with respect to the optical axis
AX. The central axis (barycenter axis) of the effective exposure
region ER formed on the wafer W (the effective projection region of
the projection optical system PL) substantially coincides with the
central axis Lpba of the light emitting surface Lpb. In other
words, the length of the light emitting surface Lpb in one axial
direction (Y-axis) differs from the length of the light emitting
surface Lpb in the other axial direction (X-axis).
[0079] As described above, the present embodiment differs from the
prior art in that the portion of the image space in the projection
optical system PL filled with liquid (immersion liquid) Lm1 can be
reduced. In the conventional technique, the light emitting surface
of the immersed plane parallel plate Lp is formed rotationally
symmetric relative to the optical axis AX irrespective of the
effective light emitting region 42 being rotationally asymmetric
relative to the optical axis AX. In the present embodiment, the
light emitting surface Lpb of the immersed plane parallel plate Lp
is formed to be asymmetric relative to the optical axis AX in
accordance with the shape of the effective exposure region ER (or
the effective projection region of the projection optical system
PL) that excludes the optical axis AX (i.e., formed so that the
light emitting surface Lpb has different lengths in two axial
directions (XY-axes directions) that are perpendicular to each
other) on the wafer W. In the exposure apparatus of the preferred
embodiment, the projection optical system PL of the present
embodiment reduces the portion of the image space of the projection
optical system PL filled with the liquid (immersion liquid) Lm1.
The exposure apparatus of the present embodiment employs the
high-resolution immersed projection optical system PL that reduces
the portion of the image space in the projection optical system PL
filled with liquid (immersion liquid) Lm1. Thus, a micropattern can
be projected and exposed with high accuracy without enlarging the
substrate stages (9 to 11) or lowering the accuracy of the
alignment optical system.
[0080] FIG. 10 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a first modification of
the present embodiment. FIG. 10(a) is a bottom view of the immersed
plane parallel plate Lp, and FIGS. 10(b) and 10(c) are side views
of the immersed plane parallel plate Lp. As shown in FIG. 10, a
light entering surface Lpa of the immersed plane parallel plate Lp
according to the first modification has an outer circumference
corresponding to a circle 50 of which center coincides with an
optical axis AX (AX3). In other words, the light entering surface
Lpa of the immersed plane parallel plate Lp has substantially equal
lengths in the two axial directions (XY-axis directions) that are
perpendicular to each other. An effective light emitting region 51
formed on a light emitting surface Lpb of the immersed plane
parallel plate Lp is substantially symmetric in the X-axis and
Y-axis directions and has a rectangular shape with round corners.
The effective light emitting region 51 has a center 51a decentered
in the Y-axis direction from the optical axis AX.
[0081] The light emitting surface Lpb of the immersed plane
parallel plate Lp is substantially symmetric with respect to X-axis
and Y-axis directions and contains the effective light emitting
region 51 with a small marginal region formed at one long side and
the two short sides of the effective light emitting region 51 and a
relatively large marginal region formed at the other long side of
the effective light emitting region 51. In FIG. 10(a), a hatched
portion Lpc surrounding the light emitting surface Lpb shows a
tilted surface that extends from the circumference of the light
emitting surface Lpb toward the light entering side.
[0082] More specifically, the light emitting surface Lpb of the
immersed plane parallel plate Lp according to the first
modification is substantially symmetric with respect to the X-axis
and Y-axis directions. From another point of view, the light
emitting surface Lpb of the immersed plane parallel plate Lp is
two-fold rotationally symmetric with respect to the optical axis
AX. Further, the central axis Lpba (not shown in FIG. 10) of the
light emitting surface Lpb and the central axis 50a (not shown in
FIG. 10) of the circle 50 corresponding to the circumference of the
light entering surface Lpa coincide with the optical axis AX. The
central axis (barycenter axis) of an effective exposure region ER
(an effective projection region of the projection optical system
PL) formed on the wafer W is decentered in the Y-axis direction
from the central axis Lpba (the optical axis AX). In other words,
the length of the light emitting surface Lpb in one axial direction
(Y-axis) differs from the length of the light emitting surface Lpb
in the other axial direction (X-axis).
[0083] In the same manner as the embodiment shown in FIG. 9, in the
first modification shown in FIG. 10, the portion of the image space
in the projection optical system PL filled with liquid (immersion
liquid) Lm1 can be reduced. This is because the light emitting
surface Lpb of the immersed plane parallel plate Lp is formed to be
asymmetric relative to the optical axis AX in accordance with the
shape of the effective exposure region ER (or the effective
projection region of the projection optical system PL) that
excludes the optical axis AX (i.e., formed so that the light
emitting surface Lpb has different lengths in two axial directions
(XY-axes directions) that are perpendicular to each other) on the
wafer W.
[0084] FIG. 11 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a second modification of
the present embodiment. FIG. 11(a) is a bottom view of the immersed
plane parallel plate Lp, and FIGS. 11(b) and 11(c) are side views
of the immersed plane parallel plate Lp. As shown in FIG. 11, a
light entering surface Lpa of the immersed plane parallel plate Lp
according to the second modification has a circumference
corresponding to a circle 60 of which center coincides with an
optical axis AX (AX3). An effective light emitting region 61 of a
light emitting surface Lpb of the immersed plane parallel plate Lp
is substantially symmetric with respect to X-axis and Y-axis and
has a rectangular shape with round corners. The effective light
emitting region 61 has a center 61a of decentered in the Y-axis
direction from the optical axis AX. In other words, the length of
the light emitting surface Lpb in one axial direction (Y-axis)
differs from the length of the light emitting surface Lpb in
another axial direction (X-axis).
[0085] The light emitting surface Lpb of the immersed plane
parallel plate Lp is substantially symmetric with respect to the
Y-axis direction and asymmetric with respect to the X-axis and
contains the effective light emitting region 61 with a small
marginal region formed around the effective light emitting region
61. A center (barycenter axis) Lpba of the light emitting surface
Lpb (not shown in FIG. 11) is in the vicinity (vicinity in the
Y-axis direction) of the center 61a of the effective light emitting
region 61. In FIG. 11(a), a hatched portion Lpc surrounding the
light emitting surface Lpb shows a tilted surface that extends from
the circumference of the light emitting surface Lpb toward the
light entering side.
[0086] More specifically, the light emitting surface Lpb of the
immersed plane parallel plate Lp according to the second
modification is substantially symmetric with respect to the Y-axis
direction and asymmetric with respect to X-axis. In other words,
the length of the light emitting surface Lpb in one axial direction
(Y-axis direction) differs from the length of the light emitting
surface Lpb in the other axial direction (X-axis direction).
Further, the circle 60, which corresponds to the circumference of
the light entering surface Lpa, has a central axis 60a (not shown
in FIG. 11) that coincides with the optical axis AX coincide with
each other, and the central axis (barycenter axis) Lpba of the
light emitting surface Lpb is decentered in the Y-axis direction
from the optical axis AX. The central axis (barycenter axis) of an
effective exposure region ER (an effective projection region of the
projection optical system PL) formed on the wafer W substantially
coincides with the central axis (barycenter axis) Lpba of the light
emitting surface Lpb. From another point of view, the light
emitting surface Lpb of the immersed plane parallel plate Lp of the
second modification is one-fold rotationally symmetric with respect
to the optical axis AX.
[0087] In the same manner as the embodiment shown in FIG. 9, in the
second modification shown in FIG. 11, the portion of the image
space in the projection optical system PL filled with liquid
(immersion liquid) Lm1 can be reduced. This is because the light
emitting surface Lpb of the immersed plane parallel plate Lp is
formed to be asymmetric relative to the optical axis AX in
accordance with the shape of the effective exposure region ER (or
the effective projection region of the projection optical system
PL) that excludes the optical axis AX (i.e., formed so that the
light emitting surface Lpb has different lengths in two axial
directions (XY-axes directions) that are perpendicular to each
other) on the wafer W.
[0088] FIG. 12 is a schematic diagram showing the structure of an
immersed plane parallel plate according to a third modification of
the present embodiment. FIG. 12(a) is a bottom view of the immersed
plane parallel plate Lp, and FIGS. 12(b) and 12(c) are side views
of the immersed plane parallel plate Lp. As shown in FIG. 12, a
light entering surface Lpa of the immersed plane parallel plate Lp
according to the third modification has a circumference
corresponding to a circle 70 of which center coincides with an
optical axis AX (AX3). In other words, the light entering surface
Lpa of the immersed plane parallel plate Lp has substantially equal
lengths in the two axial directions (XY-axes directions) that are
perpendicular to each other. An effective light emitting region 71
of a light emitting surface Lpb of the immersed plane parallel
plate Lp is substantially symmetric with respect to X-axis and
Y-axis directions and has a rectangular shape with round corners.
The effective light emitting region 71 has a center 71a decentered
in the Y-axis direction from the optical axis AX.
[0089] The light emitting surface Lpb of the immersed plane
parallel plate Lp is substantially symmetric with respect to the
X-axis and Y-axis directions and contains the effective light
emitting region 71 with a small marginal region formed around the
effective light emitting region 71. The light emitting surface Lpb
has a center Lpba that coincides with the center 71a of the
effective light emitting region 71. In FIG. 12(a), a hatched
portion Lpc surrounding the light emitting surface Lpb shows a
tilted surface that extends from the circumference of the light
emitting surface Lpb toward the light entering side.
[0090] More specifically, the light emitting surface Lpb of the
immersed plane parallel plate Lp according to the third
modification is substantially symmetric with respect to the X-axis
and Y-axis directions. In other words, the length of the light
emitting surface Lpb in one axial direction (Y-axis) differs from
the length of the light emitting surface Lpb in the other axial
direction (X-axis). Further, the central axis 70a (not shown in
FIG. 12) of the circle 70 corresponding to the circumference of the
light entering surface Lpa coincides with the optical axis AX, and
the central axis Lpba of the light emitting surface Lpb is
decentered in the Y-axis direction from the optical axis AX. The
central axis (barycenter axis) of an effective exposure region ER
(an effective projection region of the projection optical system
PL) on the wafer W substantially coincides with the central axis
Lpba of the light emitting surface Lpb. From another point of view,
the light emitting surface Lpb of the immersed plane parallel plate
Lp of the third modification is one-fold rotationally symmetric
with respect to the optical axis AX.
[0091] In the same manner as the embodiment shown in FIG. 9, in the
third modification shown in FIG. 12, the portion of the image space
in the projection optical system PL filled with liquid (immersion
liquid) Lm1 can be reduced. This is because the light emitting
surface Lpb of the immersed plane parallel plate Lp is formed to be
asymmetric relative to the optical axis AX in accordance with the
shape of the effective exposure region ER (or the effective
projection region of the projection optical system PL) that
excludes the optical axis AX (i.e., formed so that the light
emitting surface Lpb has different lengths in two axial directions
(XY-axes directions) that are perpendicular to each other) on the
wafer W. The structures of the first to third modifications are
only examples, and the structures of the light entering surface and
the light emitting surface of the immersed plane parallel plate Lp
may be modified in various manners within the scope of the present
invention.
[0092] In the above embodiment, the plane parallel plate (optical
member that typically has substantially no refractive power) Lp is
arranged in the optical path formed between the interface lens Lb
and the wafer W. Thus, even when pure water, which is used as the
immersion liquid, is contaminated with gases generated from
photoresist coated on the wafer W, the plane parallel plate Lp
arranged between the interface lens Lp and the wafer W effectively
prevents the image-side optical surface of the interface lens Lb
from being contaminated with such contaminated pure water. Further,
the refractive index of the liquid (pure water Lm1 and Lm2) and the
refractive index of the plane parallel plate Lp only slightly
differ from each other. This significantly reduces requirements on
the posture and the positional accuracy of the plane parallel plate
Lp. The contaminated plane parallel plate Lp can easily be replaced
when necessary. Thus, the optical performance of the projection
optical system PL can easily be restored.
[0093] Further, the immersed plane parallel plate Lp functions to
reduce pressure fluctuations during scanning and exposure performed
with the liquid Lm2 that comes in contact with the interface lens
Lp or reduce pressure fluctuations during a step movement. In this
case, liquid is accommodated in a relatively small space. However,
the above embodiment is not limited to the described structure. For
example, the plane parallel plate Lp may be eliminated. In this
case, the present invention may be applied to the interface lens
Lb, which is the refractive optical element arranged nearest to the
imaging position (to the wafer W). More specifically, the structure
of the first modification shown in FIG. 10, the structure of the
second modification shown in FIG. 11, or the structure of the third
modification shown in FIG. 12 may be applied to the light entering
surface and the light emitting surface of the interface lens Lb. In
such cases, the interface lens Lb has the same advantages as
described in the above embodiment of the present invention. The
structure of the embodiment shown in FIG. 9, in which the center of
the circle corresponding to the circumference of the light entering
surface is decentered from the optical axis AX, is not applicable
to the light entering surface of the interface lens Lb.
[0094] In the above embodiment, the present invention is applied to
an off-axis catadioptric optical system of which the effective
field of view excludes the optical axis. However, the application
of the present invention is not limited in such a manner. The
present invention is applicable to other typical immersion
projection optical systems. As described above, the application of
the present invention to the catadioptric and off-axis optical
system ensures the flatness of an image and increases the variety
of patterns of images that can be formed. In the catadioptric and
off-axis optical system according to each example that forms an
image through an imaging operation performed three times, the
effective exposure region ER is formed nearer to the optical axis
AX. This reduces the rotational asymmetry of the refractive optical
element (the plane parallel plate Lp or the interface lens Lb)
arranged nearest to the imaging position (to the wafer W). This
projection optical system is easy to manufacture, and the structure
of the apparatus using this projection optical system can be
simplified.
[0095] In the above embodiment, the pure water (Lm1 and Lm2) is
used as the liquid filled in the optical path between the interface
lens Lb and the wafer W. A liquid having a refractive index higher
than the pure water (e.g., a liquid having a refractive index of
1.6 or more) may be used instead. Examples of such high-refractive
index liquids include glycenol (concentrated glycerin/fructose)
(CH.sub.2[OH]CH[OH]CH.sub.2[OH]) and heptane (C.sub.7H.sub.16).
Other examples include water containing H.sup.+, Cs.sup.-, K.sup.+,
Cl.sup.-, SO.sub.4.sup.2-, or PO.sub.4.sup.2-, water containing
particles of oxide of aluminum, isopropanol, hexane, heptane,
decane, Delphi (cyclic hydrocarbon compound) manufactured by Mitusi
Chemicals, Inc., HIF-001 manufactured by JSR Corporation, and
IF131, IF132, and IF175 manufactured by E. I. du Pont de Nemours
and Company.
[0096] When such a high-refractive index liquid is used, it is
preferable that some of the lenses in the projection optical system
PL, in particular, lenses near the image surface (to the wafer W),
be formed from a material having a high refractive index. In this
case, the size of the projection optical system PL or particularly
the diameter dimension of the projection optical system PL is
reduced. It is preferable that a crystalline material, such as
calcium oxide, magnesium oxide, barium fluoride, strontium oxide,
barium oxide, barium fluoride, barium lithium fluoride
(BaLiF.sub.3), lutetium aluminum garnet (LuAG), or crystalline
magnesium aluminum spinel (MgAl.sub.2O.sub.4), or mixed crystal
mainly composed of such a crystalline material be used as the
high-refractive index material.
[0097] This realizes a high numerical aperture with a feasible
size. When, for example, an ArF excimer laser (having a wavelength
of 193 nm) is used, the projection optical system PL achieves a
high numerical aperture of about 1.5 or more. When an F.sub.2 laser
having a wavelength of 157 nm is used as the exposure beam IL, it
is preferable to use a liquid enabling transmission of an F.sub.2
laser beam, specifically, a fluorinated fluid, such as
perfluoropolyalkyether (PFPE), or fluorinated oil as the liquid
that fills the image space portion.
[0098] The exposure apparatus of the above embodiment illuminates
the reticle (mask) using an illumination apparatus (an illumination
process) and exposes a transfer pattern in the mask onto the
photosensitive substrate using the projection optical system (an
exposure process). Through the illumination and exposure processes,
the exposure apparatus manufactures microdevices (semiconductor
devices, imaging devices, liquid crystal display devices, or
thin-film magnetic heads). A method for manufacturing a microdevice
or specifically a semiconductor device through formation of a
predetermined circuit pattern on a wafer or the like as a
photosensitive substrate using the exposure apparatus of the
present embodiment will now be described with reference to a
flowchart shown in FIG. 13.
[0099] In step S301 in FIG. 13, a metal film is first formed on
wafers of a single lot through vapor deposition. In step S302,
photoresist is applied to a metal film formed on each wafer of the
single lot. In step S303, the exposure apparatus of the present
invention is used to sequentially expose and transfer an image of a
pattern in a mask onto shot-regions of each wafer in the single lot
with the projection optical system. Then, in step S304, the
photoresist formed on each wafer of the single lot is developed. In
step S305, each wafer of the single lot is etched using the resist
pattern formed on the wafer as a mask. This forms a circuit pattern
corresponding to the mask pattern in the shot-regions of each
wafer.
[0100] Afterwards, circuit patterns corresponding to upper layers
are formed to complete the semiconductor device or the like. With
the semiconductor device manufacturing method described above, a
semiconductor device with an extremely fine circuit pattern is
produced with high throughput. In steps S301 to S305, metal is
deposited on the wafer through vapor deposition, resist is coated
on the metal film, and then processes in which the resist is
exposed, developed, and etched are performed. Prior to these
processes, a silicon oxide film may first be formed on the wafer,
and the resist may be coated on the silicon oxide film. Then, the
processes in which the resist is exposed, developed, and etched may
be performed.
[0101] The exposure apparatus of the present embodiment may also be
used to produce a liquid crystal display device serving as a
microdevice by forming a predetermined pattern (a circuit pattern
or an electrode pattern) on a plate (glass substrate). One example
method for manufacturing a liquid crystal display device will now
be described with reference to a flowchart shown in FIG. 14. In
FIG. 14, a pattern formation process is performed in step S401. In
step S401, a mask pattern is transferred and exposed onto a
photosensitive substrate (e.g., a glass substrate coated with
resist) using the exposure apparatus of the present embodiment. In
other words, a photolithography process is performed. Through the
photolithography process, a predetermined pattern including, for
example, a large number of electrodes is formed on the
photosensitive substrate. Afterwards, a predetermined pattern is
formed on the substrate through processes including a developing
process, an etching process, and a resist removing process. Then, a
color filter formation process is performed in step S402.
[0102] In step S402, a color filter is formed by, for example,
arranging plural sets of R (red), G (green), and B (blue) dots in a
matrix, or arranging plural of sets of filters formed by R, G, and
B stripes in horizontal scanning line directions. After the color
filter formation process is performed in step S402, a cell assembly
process is performed in step S403. In step S403, the substrate
having a predetermined pattern obtained through the pattern
formation process performed in step S401 and the color filter or
the like obtained through the color filter formation process
performed in step S402 are assembled together to form the liquid
crystal panel (liquid crystal cell).
[0103] In S403, for example, a liquid crystal is injected between
the substrate having the predetermined pattern obtained through the
pattern formation process performed in S401 and the color filter
obtained through the color filter formation process performed in
S402 to form the liquid crystal panel (liquid crystal cell). In a
module assembly process performed subsequently in step S404, an
electric circuit for enabling the assembled liquid crystal panel
(liquid crystal cell) to perform a display operation and other
components including a backlight are mounted. This completes the
liquid crystal display device. The liquid crystal display device
manufacturing method described above enables a liquid crystal
device having an extremely fine circuit pattern to be produced with
high throughput.
[0104] Although the ArF excimer laser light source is used in the
above embodiment, other appropriate light sources, such as an
F.sub.2 laser light source, may be used. When an F.sub.2 laser beam
is used as the exposure beam, a fluorinated liquid enabling
transmission of an F.sub.2 laser beam, such as fluorinated oil or
perfluoropolyalkyether (PFPE), is used as the liquid that fills the
image space portion.
[0105] The present invention is applied to an immersion projection
optical system that is mounted on the exposure apparatus in the
above embodiment. However, the application of the present invention
is not limited to such an optical system. The present invention is
applicable to other typical immersion projection optical systems.
The present invention is also applicable to an immersion objective
optical system that uses a refractive optical element of which
optical surface comes in contact with liquid.
[0106] Although the interface lens Lp and the immersed plane
parallel plate Lp are formed from silica, which is an amorphous
material, in the above embodiment, the interface lens Lb and the
immersed plane parallel plate Lp do not have to be made of silica.
For example, the interface lens Lb and the immersed plane parallel
plate Lp may be formed from a crystalline material, such as
magnesium oxide, calcium oxide, strontium oxide, or barium
oxide.
[0107] Although pure water is used as the first liquid and the
second liquid in the above embodiment, the first and second liquids
should not be limited to pure water. For example, water containing
H.sup.+, Cs.sup.+, K.sup.+, Cl.sup.-, SO.sub.4.sup.2-, or
PO.sub.4.sup.2-, or isopropanol, glycerol, hexane, heptane, or
decane may be used as the first and second liquids.
* * * * *