U.S. patent number RE40,743 [Application Number 10/916,650] was granted by the patent office on 2009-06-16 for projection exposure system having a reflective reticle.
This patent grant is currently assigned to Carl Zeiss SMT AG. Invention is credited to Gerhard Fuerter, Uwe Goedecke, Henriette Mueller, Christian Wagner.
United States Patent |
RE40,743 |
Fuerter , et al. |
June 16, 2009 |
Projection exposure system having a reflective reticle
Abstract
A projection exposure system for microlithography includes an
illuminating system (2), a reflective reticle (5) and reduction
objectives (71, 72). In the reduction objective (71, 72), a first
beam splitter cube (3) is provided which superposes the
illuminating beam path (100) and the imaging beam path (200). In
order to obtain an almost telecentric entry at the reticle, optical
elements (71) are provided between beam splitter cube (3) and the
reflective reticle (5). Advantageously, the reduction objective is
a catadioptric objective having a beam splitter cube (3) whose
fourth unused side can be used for coupling in light. The
illuminating beam path (100) can also be coupled in with a
non-parallel beam splitter plate. The illuminating beam path is
refractively corrected in passthrough to compensate for aberrations
via the special configuration of the rear side of the beam splitter
plate. Advantageously, a beam splitter plate of this kind is used
within a reduction objective in lieu of a deflecting mirror and
only refractive components are introduced between the beam splitter
plate and the reflective reticle.
Inventors: |
Fuerter; Gerhard (Ellwangen,
DE), Wagner; Christian (Eersel, NL),
Goedecke; Uwe (Abtsgmuend, DE), Mueller;
Henriette (Aalen, DE) |
Assignee: |
Carl Zeiss SMT AG (Oberkochen,
DE)
|
Family
ID: |
7630003 |
Appl.
No.: |
10/916,650 |
Filed: |
August 11, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
09773519 |
Feb 2, 2001 |
06590718 |
Jul 8, 2003 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Feb 5, 2000 [DE] |
|
|
100 05 189 |
|
Current U.S.
Class: |
359/732; 359/649;
359/726 |
Current CPC
Class: |
G03F
7/70066 (20130101); G03F 7/70225 (20130101); G03F
7/70283 (20130101) |
Current International
Class: |
G02B
17/00 (20060101) |
Field of
Search: |
;359/649-651 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1 191 378 |
|
Mar 2002 |
|
EP |
|
61053646 |
|
Mar 1986 |
|
JP |
|
6110213 |
|
Apr 1994 |
|
JP |
|
06215997 |
|
Aug 1994 |
|
JP |
|
09017719 |
|
Jan 1997 |
|
JP |
|
WO-93/09469 |
|
May 1993 |
|
WO |
|
WO-97/34171 |
|
Sep 1997 |
|
WO |
|
WO-01/04682 |
|
Jan 2001 |
|
WO |
|
WO-03/036361 |
|
May 2003 |
|
WO |
|
Other References
"Lithography for 0.25 .mu.m and below using simple high-performance
optics" by Pease et al., IEEE Symp. VLSI Technology (1992), pp. 116
and 117. cited by other .
" 1/8 .mu.m optical lithography" Owen et al., J. Vac. Sci. B 10
(1992), pp. 3032 to 3036. cited by other .
"Optical projection system for gigabit dynamic random acess
memories" by Jeong et al. J. Vac Sci. B 11 (1993), pp. 2675 to
2679. cited by other.
|
Primary Examiner: Schwartz; Jordan M.
Attorney, Agent or Firm: Darby & Darby P.C.
Claims
What is claimed is:
1. A projection exposure system for microlithography, the
projection exposure system comprising: a light source; an
illuminating system mounted downstream of said light source for
transmitting light from said light source as an illuminating beam
along an illuminating beam path; a reflective reticle; a reduction
objective defining an imaging beam path and being configured for
imaging said reticle onto an object; a beam splitter cube mounted
in said imaging beam path for mutually superposing said
illuminating beam path and said imaging beam path; optical elements
mounted on said imaging beam path between said reflective reticle
and said beam splitter cube; and, said illuminating light beam
having chief rays which impinge on said reflective reticle at an
angle of incidence having a value up to |15| mrad.
2. The projection exposure system of claim 1, wherein said angle of
incidence is up to |5| mrad.
3. The projection exposure system of claim 1, wherein said angle of
incidence is up to |1.0| mrad.
4. The projection exposure system of claim 1, wherein said
illuminating light beam has centroidal rays which, after being
reflected at said reflective reticle, deviate from said chief rays
by a maximum of |2.5| mrad.
5. A projection exposure system for microlithography, the
projection exposure system comprising: a light source; an
illuminating system mounted downstream of said light source for
transmitting light from said light source as an illuminating beam
along an illuminating beam path; a reflective reticle; a reduction
objective defining an imaging beam path and being configured for
imaging said reticle onto an object; a beam splitter cube mounted
in said imaging beam path for mutually superposing said
illuminating beam path and said imaging beam path; said beam
splitter cube being a polarization beam splitter cube having a beam
splitter surface; and, the light of said illuminating light beam,
before entering said polarized beam splitter cube, being linearly
polarized to more than 95% perpendicular to said beam splitter
surface when said illuminating beam is not to be reflected at said
beam splitter surface or being linearly polarized to more than 95%
parallel to said beam splitter surface when the illuminating beam
path is to be reflected at said beam splitter surface.
6. The projection exposure system of claim 5, wherein said
reduction objective is a catadioptric objective.
7. The projection exposure system of claim 6, wherein said beam
splitter cube is a first beam splitter cube; said reduction
objective includes a concave mirror and a second beam splitter cube
which separates the beam path to and from said concave mirror.
8. The projection exposure system of claim 6, wherein said first
beam splitter cube defines a deflecting surface in the beam path of
said reduction objective.
9. The projection exposure system of claim 8, wherein said
reduction objective is configured to be free of an intermediate
image.
10. The projection exposure system of claim 8, wherein said
reduction objective is configured to have an intermediate
image.
11. A projection exposure system for microlithography, the
projection exposure system comprising: a light source; an
illuminating system mounted downstream of said light source for
transmitting light from said light source as an illuminating beam
along an illuminating beam path; a reflective reticle; a reduction
objective defining an imaging beam path and being configured for
imaging said reticle onto an object; a beam splitter cube mounted
in said imaging beam path for mutually superposing said
illuminating beam path and said imaging beam path; said reduction
objective including a first objective incorporating said beam
splitter, an intermediate image; and, a second objective; and, said
first objective having an imaging scale of -1.0.+-.0.25 and said
second objective having an intermediate imaging scale of
-0.25.+-.0.15.
12. The projection exposure system of claim 11, wherein said first
objective and said second objective are configured to be purely
refractive.
13. The projection exposure system of claim 11, wherein said first
objective is configured to be purely refractive; and, said second
objective is configured to be catadioptric.
14. A projection exposure system for microlithography, the
projection exposure system comprising: a light source; an
illuminating system mounted downstream of said light source for
transmitting light from said light source as an illuminating beam
along an illuminating beam path; a reflective reticle; a reduction
objective defining an imaging beam path and being configured for
imaging said reticle onto an object; a beam splitter plate for
mutually superposing said illuminating beam path and said imaging
beam path; said beam splitter plate having a first surface on which
said imaging beam path is reflected in air and said beam splitter
plate having a second surface; and, said first surface being a
planar surface and said second surface being a corrective surface
deviating from said planar surface.
15. The projection exposure system of claim 14, wherein said beam
splitter plate is wedge shaped.
16. The projection exposure system of claim 14, wherein said
illuminating beam is refractively corrected in passing through said
beam splitter plate.
17. The projection exposure system of claim 16, wherein said beam
splitter plate defines a deflecting surface in the beam path of
said reduction objective.
18. The projection exposure system of claim 15, wherein only
refractive elements and a .lamda./4 platelet are provided between
said beam splitter plate and said reflective reticle.
19. The projection exposure system of claim 15, wherein said beam
splitter plate is accommodated in a catadioptric reduction
objective.
20. The projection exposure system of claim 19, wherein said
catadioptric reduction objective is configured to be free of an
intermediate image.
21. A method for making a microstructured object with a projection
exposure system for microlithography which includes: a light
source; a reflective reticle defining a reticle plane; an
illuminating system mounted downstream of said light source for
transmitting light from said light source along an illuminating
beam path as an illuminating light beam having chief rays which
impinge on said reflective reticle at an angle of incidence having
a value up to |15| mrad; a reduction objective defining an imaging
beam path and an imaging plane and being configured for imaging
said reticle onto the object; and, a beam splitter cube mounted in
said imaging beam path for mutually superposing said illuminating
beam path and said imaging beam path; and, the method comprising
the steps of: placing an object in the form of a substrate having a
light-sensitive layer in said imaging plane; inserting a mask
containing a pattern thereon into said illuminating beam path at
said reticle plane; imaging said pattern onto said
.[.lightsensitive.]. .Iadd.light-sensitive .Iaddend.layer of said
substrate utilizing said projection exposure system; and, exposing
said light-sensitive layer by passing the light of said light
source along said illuminating beam path thereby structuring said
substrate.
22. A method for making a mcirostructured object with a projection
exposure system for microlithography which includes: a light
source; an illuminating system mounted downstream of said light
source for transmitting light from said light source as an
illuminating beam along an illuminating beam path; a reflective
reticle defining a reticle plane; a reduction objective defining an
imaging beam path and an imaging plane and being configured for
imaging said reticle onto an object; a beam splitter plate for
mutually superposing said illuminating beam path and said imaging
beam path; said beam splitter plate having a first surface on which
said imaging beam path is reflected in air and said beam splitter
plate having a second surface; and, said first surface being a
planar surface and said second surface being a corrective surface
deviating from said planar surface; and, the method comprising the
steps of: placing an object in the form of a substrate having a
light-sensitive layer in said imaging plane; inserting a mask
containing a pattern thereon into said illuminating beam path at
said reticle plane; imaging said pattern onto said light-sensitive
layer of said substrate utilizing said projection exposure system;
and, exposing said light-sensitive layer by passing the light of
said light source along said illuminating beam path thereby
structuring said substrate.
23. A projection exposure system for microlithography, the
projection exposure system comprising: a light source; an
illuminating system mounted downstream of said light source for
transmitting light from said light source as an illuminating beam
along an illuminating beam path; a reflective reticle; a reduction
objective defining an imaging beam path and being configured for
imaging said reticle onto an object; a beam splitter cube mounted
in said imaging beam path for mutually superposing said
illuminating beam path and said imaging beam path; said reduction
objective being a catadioptric objective; said beam splitter cube
being a first beam splitter cube; and, said reduction objective
including a concave mirror and a second beam splitter cube which
separates the beam path to and from said concave mirror.
.Iadd.24. A microlithographic projection exposure system
comprising: a light source; an illuminating system; a reticle; and
a reduction objective being configured for imaging said reticle
onto an object, wherein said reduction objective includes: a first
objective; an intermediate image; a second objective comprising a
concave mirror; a second intermediate image; a third objective in
sequence; and a deflecting mirror with two deflecting surfaces.
.Iaddend.
.Iadd.25. The system of claim 24, wherein said first objective has
an imaging scale of one of the group consisting of -1.0.+-.0.25 and
-0.5.+-.0.2. .Iaddend.
.Iadd.26. A microlithographic projection exposure system
comprising: a light source; an illuminating system; a reticle; and
a reduction objective being configured for imaging said reticle
onto an object, wherein said reduction objective includes: a first
objective; an intermediate image; a second objective comprising a
concave mirror; a second intermediate image; a third objective in
sequence; and a deflecting mirror with two deflecting surfaces;
wherein the reduction objective has an image end numerical aperture
of a value of more than 0.8. .Iaddend.
.Iadd.27. A projection exposure system for microlithography for
imaging a reticle to a wafer plane with two intermediate image
planes comprising: a first intermediate imaging system for imaging
of a reticle to a first intermediate image; and a catadioptric
intermediate imaging system having an object field; wherein the
object field of the catadioptric intermediate imaging system is
decentered with respect to the optical axis, and having a
deflecting mirror with two deflecting surfaces. .Iaddend.
.Iadd.28. A system according to claim 27, wherein said catadioptric
intermediate imaging system is arranged offset to the first
intermediate imaging system. .Iaddend.
.Iadd.29. A system according to claim 27, wherein said first
intermediate imaging system has an imaging scale of one of the
group consisting of -1.0.+-.0.25 and -0.5.+-.0.2. .Iaddend.
.Iadd.30. A system according to claim 27, wherein said catadioptric
intermediate imaging system comprises a concave mirror.
.Iaddend.
.Iadd.31. A system of claim 27, wherein the reduction objective has
an image end numerical aperture of a value of more than 0.8.
.Iaddend.
.Iadd.32. A microlithographic projection exposure system
comprising: a light source; an illuminating system; a reticle; and
a reduction objective being configured for imaging said reticle
onto an object; wherein said reduction objective includes: a first
objective providing an intermediate image; a catadioptric objective
comprising a concave mirror; a second intermediate image; a purely
refractive objective; and a wafer plane parallel to said reticle.
.Iaddend.
.Iadd.33. The system of claim 32, wherein said first objective has
an imaging scale of one of the group consisting of -1.0.+-.0.25 and
-0.5.+-.0.2. .Iaddend.
.Iadd.34. A system of claim 32, wherein the reduction objective has
an image end numerical aperture of a value of more than 0.8.
.Iaddend.
.Iadd.35. A projection exposure system for microlithography for
imaging a reticle to a wafer plane with two intermediate image
planes comprising: a first intermediate imaging system for imaging
of the reticle to a first intermediate image; a catadioptric
intermediate imaging system for imaging the first intermediate
image to a second intermediate image; wherein the object field of
the catadioptric intermediate imaging system is not centered with
respect to the optical axis, said wafer plane being parallel to
said reticle. .Iaddend.
.Iadd.36. A system according to claim 35, wherein said catadioptric
intermediate imaging system is arranged offset to the first
intermediate imaging system. .Iaddend.
.Iadd.37. A system according to claim 35, wherein said first
intermediate imaging system has an imaging scale of one of the
group consisting of -1.0.+-.0.25 and -0.5.+-.0.2. .Iaddend.
.Iadd.38. A system according to claim 35, wherein said catadioptric
intermediate imaging system comprises a concave mirror and a
deflecting mirror with two deflecting surfaces. .Iaddend.
.Iadd.39. A system according to claim 32, further comprising a
deflecting mirror with two deflecting surfaces. .Iaddend.
.Iadd.40. The system of claim 26, wherein said first objective has
an imaging scale of one of the group consisting of -1.0.+-.0.25 and
-0.5.+-.0.2. .Iaddend.
Description
FIELD OF THE INVENTION
The invention relates to a projection exposure system having a
reticle which operates in reflection.
BACKGROUND OF THE INVENTION
Projection exposure systems having a reflective reticle have been
used in the past, inter alia, together with 1:1 Dyson objectives.
These projection exposure systems are described in the following
publications: a) Owen et al, "1/8 .mu.m optical lithography" J.
Vac. Sci. B 10 (1992), pages 3032 to 3036, especially Parts B and
C; b) Pease et al, "Lithography for 0.25 .mu.m and below . . . "
IEEE Symp. VLSI Technology (1992), pages 116 and 117; c) Jeong et
al, "Optical projection system . . . " J. Vac. Sci. B 11 (1993),
pages 2675 to 2679; and, d) U.S. Pat. No. 4,964,705.
The incoupling of the illumination takes place via a partially
transmitting mirror as shown, for example, in U.S. Pat. No.
4,964,705 (FIGS. 3A and 3B). Beam splitter cubes or beam splitter
plates are not provided in these designs.
Reflective reticles are used exclusively in the area of lithography
utilizing soft X-rays (EUVL). The beam splitting of illuminating
and imaging beam paths is realized by an inclined incidence of the
illumination. Beam splitter cubes or beam splitter plates are not
used. The objectives are pure mirror objectives having a non-axial
symmetrical beam path. The inclined incidence of the illuminating
light on the reflective reticle has the disadvantage that the
raised mask struts lead to vignetting.
Japanese patent publication 9-017719 discloses a wafer projection
exposure system having a reflex LCD as a special reticle. According
to FIG. 1 of this publication, a planar beam splitter plate is used
to separate the illuminating and imaging beam paths. Illuminating
system and projection objective are operated with a field
symmetrical to the optical axis. The incoupling of the illuminating
light via a beam splitter plate directly ahead of the reticle as
shown in Japanese patent publication 9-017719 requires, on the one
hand, the corresponding entry intersection distance, and, on the
other hand, the passthrough through the planar plate leads to the
astigmatic deformation of the illuminating light between which
disturbs the required clean pupil imaging.
U.S. Pat. No. 5,956,174 discloses a catadioptric microscope
objective wherein the illuminating light is coupled in via a beam
splitter cube between the microscope objective and the tube lens.
This type of illumination is conventional in reflected light
microscopes. The illuminating field sizes are only in the order of
magnitude of 0.5 mm.
Catadioptric systems for wavelengths of 193 nm and 157 nm are
known. Catadioptric projection objectives having beam splitter
cubes without an intermediate image are shown, for example, in U.S.
Pat. Nos. 5,742,436 and 5,880,891 incorporated herein by
reference.
Catadioptric projection objectives having a beam splitter cube and
an intermediate image are disclosed in U.S. Pat. No.
.[.06/424,471.]. .Iadd.6,424,471.Iaddend..
Illuminating devices for microlithography are disclosed in U.S.
Pat. No. 5,675,401 and U.S. Pat. No. 6,285,443. So-called REMA
objectives for imaging a reticle masking device (REMA) into the
plane of the reticle are disclosed in U.S. Pat. No. 5,982,558 and
U.S. Pat. No. 6,366,410, also incorporated herein by reference.
With these objectives, inter alia, the entry pupil of the
downstream projection objective is illuminated.
The production of transmission reticles (that is, masks operated in
transmission for microlithography) is difficult for deep
ultraviolet wavelengths, especially 157 nm, inter alia, because of
suitable transmitting carrier materials. The materials CaF.sub.2 or
MgF.sub.2 can be considered. However, reticles made of CaF.sub.2 or
MgF.sub.2 are difficult to process and are therefore very
expensive. Furthermore, a reduction of the minimal structural size
which can be applied to a semiconductor chip results because of
absorption and the thermal expansion of the reticle resulting
therefrom when there are multiple illuminations. When possible,
materials such as MgF.sub.2 are avoided because they are also
double refracting.
The alternative are reflective reticles. To reduce the requirements
imposed on the reticle, it is advantageous when the projection
objective is configured as a reduction objective and the reticle is
imaged so as to be demagnified. The reticle can then be provided
with larger structures.
In conventional reduction objectives, the use of reflective
reticles is not easily possible. The typical entry intersection
distance of, for example, 30 mm reduces the illumination at
suitable angles of incidence.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a projection exposure
system having a reduction objective which functions without problem
with reflective reticles.
The projection exposure system of the invention is for
microlithography and includes: a light source; an illuminating
system mounted downstream of the light source for transmitting
light from the light source as an illuminating beam along an
illuminating beam path; a reflective reticle; a reduction objective
defining an imaging beam path and being configured for imaging the
reticle onto an object; and, a beam splitter cube mounted in the
imaging beam path for mutually superposing the illuminating beam
path and the imaging beam path.
According to a feature of the invention, a beam splitter cube
functions to superpose the illuminating and imaging beam paths. In
this way, numerous objective design concepts for reflective
reticles can be adapted as will be shown in the following examples.
Erroneous entries by the beam splitter plate are avoided by
utilizing a beam splitter cube in lieu of a planar parallel beam
splitter plate. The beam splitter plate is operated in passthrough
and mounted at 45.degree..
According to another feature of the invention, optical elements are
provided between the beam splitter cube and the reticle. With these
optic elements, it is possible to reduce the angle of incidence of
the main beams of the reduction objective on the reticle in such a
manner that the incident angle has values between -15 mrad and +15
mrad.
According to still another feature of the invention, the
illuminating system is so configured that the illuminating beam
path passes over into the imaging beam path with deviations of less
than .+-.2.5 mrad. This deviation can be measured in that the
angles with respect to the reticle plane are determined for the
centroidal rays after the reflection and the deviation to the
angles of the corresponding chief rays is computed. The angles of
the centroidal rays are dependent upon the emission characteristics
of the light source and the design of illuminating system and the
angles of the chief ray are exclusively dependent upon the design
of the reduction objective.
According to another feature of the invention, a polarization beam
splitter cube is used in order to reduce transmission losses at the
beam splitter cube and so that no scattering light is deflected
onto the wafer. For an optimal operation, the illuminating light
should be linearly polarized to more than 95%. The polarization
direction is dependent upon whether the illuminating beam path is
intended to be reflected or not at the beam splitter layer. In the
case of a reflection, the illuminating light has to be polarized
parallel to the beam splitter surface and, in the case of the
transmission, the illuminating light has to be polarized
perpendicularly to the beam splitter surface.
In other embodiments of the invention, the beam splitter cube
functions exclusively for incoupling the illuminating beam path. To
be able to more easily integrate the beam splitter cube into the
design of the reduction objective, it is advantageous to subdivide
the reduction objective into two component objectives with a first
intermediate image having an imaging scale of -1.0.+-.0.25 and a
second image having an imaging scale of -0.25.+-.0.15. The beam
splitter cube is integrated into the first intermediate image. The
second image can be configured to be strictly refractive or
catadioptric.
The coupling in of the illuminating beam path with a beam splitter
cube is especially advantageous when the beam splitter cube is
already a part of the reduction objective. Then, the fourth unused
face of the beam splitter cube can be used to couple in the
illuminating beam path.
If the design of the catadioptric objective includes a deflecting
mirror, then the deflecting mirror can be replaced by a beam
splitter cube via which the illuminating light is coupled in.
The design of the catadioptric objective can be configured with or
without an intermediate image.
In another embodiment of the invention, a special beam splitter
plate is provided in the projection exposure system. This beam
splitter plate is operated in pass through in the illuminating beam
path and is operated reflectively in the imaging beam path. Here,
reflection in air is provided, that is, in the optically thinner
medium which can also be a vacuum or a special gas mixture or a gas
such as nitrogen or helium. The beam splitter plate is so
configured that astigmatic errors because of the plate mounted at
an angle can be refractively corrected.
The common inventive concept is that the imaging beam path is held
free of disturbances by the beam splitter arrangement and the
illuminating beam path is corrected with less requirements directly
via the beam splitter arrangement. For a beam splitter cube, only
rotationally-symmetrical imaging errors are introduced which can be
corrected within the illuminating system via
rotationally-symmetrical optical elements such as spherical lenses.
In the beam splitter plate according to a feature of the invention,
the correction of the illuminating beam path is provided by the
special configuration of the side of the beam splitter plate facing
toward the illuminating system.
According to still another feature of the invention, the beam
splitter plate is provided with a non-planar corrective surface. By
mounting the beam splitter plate at an angle, the corrective
surface exhibits no rotational symmetry, rather, a simple symmetry
with respect to the meridian plane.
The beam splitter plate is configured to have a wedge shape in
accordance with another embodiment of the invention for correcting
the astigmatism of the lowest order. The use of a beam splitter
plate is especially advantageous when it is used in lieu of a
deflecting mirror provided in the design of the reduction
objective.
The superposition of the illuminating optics and the projection
optics make possible the use of reflective reticles especially at
operating wavelengths in the range from 100 to 200 nm. In this way,
the difficulties are avoided which occur in the manufacture of
transmission reticles because of machining of the materials
transparent at these wavelengths.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be explained with reference to the drawings
wherein:
FIG. 1 is a schematic of a reduction objective having a reflective
reticle and a beam splitter cube for coupling in the illumination
light;
FIG. 2 shows a reduction objective with an intermediate imaging
optic disposed ahead of the reduction objective and with a beam
splitter cube being integrated for coupling in illumination;
FIG. 3 shows a catadioptric reduction objective having an
intermediate imaging optic disposed forward thereof into which the
beam splitter cube is integrated for coupling in illumination;
FIG. 4 shows a catadioptric reduction objective without an
intermediate imaging optic wherein the illuminating beam path is
coupled in via the beam splitter cube of the catadioptric reduction
objective;
FIG. 5 shows a catadioptric reduction objective without an
intermediate imaging optic where the illumination is coupled in via
a beam splitter plate at the location of the deflection;
FIG. 6 shows a catadioptric reduction objective without an
intermediate imaging optic wherein the illumination is coupled in
via a beam splitter cube at the location of the deflection;
FIG. 7 shows a catadioptric reduction objective having an
intermediate imaging optic wherein the illumination is coupled in
via the beam splitter cube of the catadioptric reduction objective;
and,
FIG. 8 shows an embodiment for a catadioptric reduction objective
having a beam splitter cube and an intermediate imaging optic.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1 shows a typical configuration of a projection exposure
system for microlithography in accordance with an embodiment of the
invention. The reflective reticle 5 is imaged via demagnifying
imaging optics onto the wafer 6 at a typical imaging scale .beta.
of -0.25.+-.0.15. The illuminated field on the wafer 6 has a
diameter of at least 10 mm. Rectangular fields having an x-y aspect
ratio of 1:1 to 1:4 are typical. The image end numerical aperture
is greater than 0.5. The imaging takes place via the optical
elements 71 and 72. A beam splitter cube 3 is integrated into the
imaging beam path 200 of the reduction objective between reflective
reticle 5 and wafer 6 for illuminating the reflective reticle 5.
The beam splitter cube can, for example, be a polarization beam
splitter cube wherein a layer system is located between the prism
surfaces. This layer system almost completely reflects polarized
light parallel to the beam splitter surface 30; however, the beam
splitter surface 30 is light transmissive for polarized light
perpendicular to the beam splitter surface 30.
A condition precedent for the arrangement of FIG. 1 is therefore
that the illuminating light is polarized in parallel to the
incidence plane of the beam splitter surface 30 mounted at an angle
of 45.degree.. Polarized light of this kind is reflected at the
beam splitter surface 30 and is deflected in the direction of
reflective reticle 5. A .lamda./4 plate 4 is mounted between the
beam splitter cube 3 and the reflective reticle 5 and this plate 4
is run through a total of two times. The first time is in the
illuminating beam path 100 so that the linearly polarized light is
polarized circularly. After the reflection at the reticle 5, the
circularly polarized light in the imaging beam path 200 runs the
second time through the .lamda./4 platelet 4 and is now again
linearly polarized. The polarization direction now, however, is
aligned perpendicular to the beam splitter surface 30 of the beam
splitter cube 3 so that the beam splitter cube 3 is passed through
without reflection. In this way, a separation of the illuminating
light beam path 100 and of the imaging beam path 200 is provided in
the combination of the following: polarization beam splitter cube
3, two-time passthrough of the .lamda./4 platelet 4 and the
reflective reticle 5. A plane-parallel beam splitter plate would
have the disadvantage compared to the polarization beam splitter
cube 3 that rotationally-symmetrical imaging errors would not be
introduced by the beam splitter plate of finite thickness
positioned at an angle of 45.degree..
The polarization beam splitter cube 3 should be mounted within the
imaging beam path 200 at a location at which the rays impinging on
the beam splitter surface 30 exhibit a slight divergence. This is
the case when the polarization beam splitter cube 3 is disposed at
a location having an almost collimated beam path. For this reason,
optical elements 71 having an overall positive refractive power are
to be provided between reflective reticle 5 and the polarization
beam splitter cube 3. The optical elements 71 essentially collimate
the diverging beam coming from the reticle. The optical elements 72
can, in accordance with the type of design, be configured
differently but also likewise have a positive refractive power in
order to achieve imaging on a possible intermediate image plane or
on the wafer plane 6.
One can view the optical elements 71 and 72 taken together as a
refractive reduction objective having a typical imaging scale
.beta. of -0.25.+-.0.15. In the design of the refractive objective,
the .lamda./4 platelet 4 and the beam splitter cube 3 are to be
provided between the optical elements 71 and the optical elements
72.
The reflective reticle 5 is illuminated with the aid of the
illuminating system 2. In the design of the illuminating system 2,
the beam splitter cube 3, the .lamda./4 platelet 4 and the optical
elements 71 need be considered. The interface between the
illuminating system 2 and the imaging optic is therefore not the
reticle 5 as would be the case in a transmission reticle or when
there is an inclined illumination of the reticle; instead, the
interface is the input of the beam splitter cube 3 facing toward
the illuminating system 2.
In order to simplify the optical configuration of the illuminating
optics 2, it is advantageous when the chief ray angles are less
than .+-.15 mrad with reference to the reticle plane, that is, the
reticle 5 is virtually telecentrically illuminated. The chief rays
are so defined in the reduction objective that they intersect the
optical axis at the location of the system diaphragm. For larger
chief ray angles, the design of the illuminating optics 2 is
thereby made more difficult because the centroidal rays of the
illuminating beam path 100 have to pass in the reticle plane 5 into
the chief rays of the imaging beam path 200. Because of the
reflection at the reticle, the incident angles of the centroidal
rays have to exhibit the reverse sign from the incident angles of
the chief rays. In this way, the illuminating beam path 100 is
different from the imaging beam path 200 within the optical
components 71. The distribution of the chief ray angles over the
illuminated field has to be overcompensated by the illuminating
system 2. The chief ray angle distribution at the reticle 5 is
determined primarily by the optical elements 71 and these optical
elements 71 are fixedly pregiven for the design of the illuminating
system 2. For these reasons, optical components have to be provided
in the illuminating system 2, such as a sequence of converging and
diverging lenses, which operate on the centroidal ray angle on the
reticle 5.
The optical components in the illuminating system 2 are so
configured that the centroidal rays of the illuminating beam path
100, after the reflection at the reflective reticle 5, are
coincident with the chief rays up to a maximum angle deviation of
.+-.2.5 mrad depending upon field height. The chief rays are
pregiven by the design of the reduction objective. Otherwise, the
usually required telecentricity in the wafer plane 6 is
deteriorated.
The illuminating system 2 has to have a unit for changing the
polarization state of the illuminating light. In linearly polarized
light of the source 1, the polarization direction has to be
rotated, as required, for example, via double refracting crystals
or double refracting foils. For unpolarized light of the source 1,
polarizers are used for generating light which is polarized
perpendicularly or parallely to the beam splitter surface 30.
Preferably, these components for influencing the state of
polarization are introduced directly forward of the polarization
beam splitter cube 3. The polarization direction is dependent upon
whether or not the illuminating beam path 100 should be reflected
at the beam splitter layer 30. In the case of a reflection, for
example, the illuminating light has to be polarized parallel to the
beam splitter surface 30.
Conventionally, the illuminating system 2 includes integrators for
homogeneously illuminating the reticle plane 5. The integrators
are, for example, honeycomb condensers, hollow conductors or glass
rods. For varying the illumination mode, the illuminating system
can include: two zoom optics, axicon elements, filter plates in the
pupillary planes and/or masking devices in the pupillary field
planes or in the intermediate field planes.
The operation of these elements is disclosed, for example, in U.S.
Pat. No. 6,285,443, and incorporated herein by reference.
Objectives within the illuminating system 2 for adapting the
centroidal ray angles of the illuminating beam path 100 to the
chief ray angles of the reduction objective are known as REMA
objectives for the correct illumination of the entry pupil of the
reduction objective from U.S. Pat. No. 6,366,410 and from U.S. Pat.
No. 5,982,558, both incorporated herein by reference.
As a light source, a DUV laser or VUV laser can be used, for
example, an ArF laser at 193 nm, a F.sub.2 laser at 157 nm, an
Ar.sub.2 laser at 126 nm and a NeF laser at 109 nm.
FIG. 2 shows a further embodiment of the projection exposure system
of the invention for microlithography. Components in FIG. 2 which
correspond to those in FIG. 1 are identified with the same
reference numerals. The imaging system (7, 8) in FIG. 2 includes an
intermediate image plate 103. The intermediate imaging system 7
includes the optical elements 101, the .lamda./4 platelet 4, the
polarization beam splitter cube 3 and the optical elements 102. The
intermediate imaging system 7 then provides an intermediate imaging
of the reflective reticle 5 onto the intermediate image plane 103.
The imaging scale .beta..sub.1 of this intermediate imaging can,
for example, be .beta..sub.1=-1.0.+-.0.2. Also possible is a
reduction imaging at an imaging scale, .beta..sub.1=-0.5.+-.0.2 if
thereby the design of the downstream optical system 8 is
simplified. In this case, the incoupling of the illuminating light
takes place via the polarization beam splitter cube 3 with the
downstream .lamda./4 platelet 4 within the intermediate imaging
optics 7. The optical elements 101 and 102 each have a positive
refractive power. The polarization beam splitter cube 3 is disposed
in a region having an almost collimated beam path. Optical elements
104 follow the intermediate image plane 103 and image the
intermediate image plane 103 onto the wafer plane 6 at an imaging
scale of B.sub.2=-0.25.+-.0.15 or .beta..sub.2=0.5.+-.0.15. In this
embodiment, the reduction objective is subdivided into the
intermediate imaging system 7 and the reduction system 8. This
affords the advantage that, in the intermediate imaging system 7,
adequate space is provided for the polarization beam splitter cube
3. Also in this configuration, the optical elements 101, the
.lamda./4 platelet 4 and the beam splitter cube 3 are included in
the design of the illuminating system 2. It is advantageous when
the intermediate imaging optics 7 are so configured that the
reflective reticle 5 is almost entirely telecentrically
illuminated. The angles of incidence of the chief rays on the
reflective reticle 5 should then be less than 15 mrad.
FIG. 3 shows an additional embodiment of the projection exposure
system of the invention for microlithography. The imaging between
reflective reticle 5 and wafer plane 6 takes place with two
intermediate image planes 113 and 118. The intermediate imaging
system 9 of reflecting reticle 5 to intermediate image plane 113 is
configured similarly to the intermediate imaging system 7 of FIG.
2. The imaging of intermediate image plane 113 on the wafer 6 takes
place first with the aid of the catadioptric intermediate imaging
system 10 and a downstream refractive reduction system 11. The
catadioptric intermediate imaging system 10 comprises the optical
elements 114, a deflecting mirror 115, the optical elements 116 and
the concave mirror 117. The object field of the intermediate
imaging system 10 is not centered with respect to the optical axis
because of the reflective deflecting mirror 115; instead, the
object field is outside of the optical axis. This means in this
case that the component systems 10 and 11 must be arranged offset
to the component system 9. For these projection objectives, the
image end numerical aperture can have values in the range from 0.65
to 0.8 or more. Field sizes in the wafer plane 6 in the range from
20 mm.times.7 mm to 30 mm.times.10 mm are possible. Objectives of
this kind are disclosed in U.S. Pat. No. 6,496,306, and
incorporated herein by reference.
The incoupling of the illuminating beam path 100 into the imaging
beam path 200 can be done in an especially advantageous manner when
a beam splitter cube is already provided in the imaging beam path
200 as is the case in some catadioptric objective types.
Catadioptric objective types having beam splitter cubes are known
in various configurations.
FIG. 4 shows a possible catadioptric projection objective having a
beam splitter cube 31 which is assembled without an intermediate
image. Objectives of this kind comprise, starting with the reticle
5: a first lens group 121, a deflecting mirror 122, a second lens
group 123, the beam splitter cube 31, a third lens group 124, a
concave mirror 125, a fourth lens group 126 and a diaphragm which
is arranged between the elements 123 and 126. For these objectives,
the following can be considered: an imaging scale .beta. of
-0.25.+-.0.15; an image end numeric aperture of >0.5; and, an
image field diameter >10 mm, preferably >20 mm.
The first lens group 121 and the second lens group 123 can be so
arranged that the divergence of the rays on the beam splitter
surface 310 of the polarization beam splitter cube 31 is minimized.
If one views a peripheral ray which originates from an object point
on the optical axis, then the sine of the angle of this ray with
respect to the optical axis can be reduced up to 40% by the first
and second lens groups 121 and 123. The lens group 124 must have a
negative refractive power in order to obtain an adequate color
correction together with the concave mirror 125. The lens group 126
generates the image in the wafer plane 6 and therefore exhibits a
positive refractive power. The reduction objective 12, which is
shown in FIG. 4, comprises the optical elements 121, 122, 123, 124,
125, 126 and the beam splitter cube 31. This reduction objective 12
is taken from U.S. Pat. No. 5,880,891 incorporated herein by
reference.
If one now uses this objective type with a reflective reticle 5,
then the illuminating light can be coupled in via the polarization
beam splitter cube 31. Advantageously, the fourth unused face of
the polarization beam splitter cube 31 is used for this purpose. It
is absolutely necessary that the illuminating light is polarized
more than 95% perpendicularly to the beam splitter surface 310 so
that no illuminating light is reflected at the beam splitter
surface 310 in the direction of wafer 6 so that thereby contrast
and resolution are not reduced. For this reason, it is advantageous
to build in a polarization filter between illuminating system 2 and
polarization beam splitter cube 31. The polarization filter has a
transmissive polarization direction which is orientated
perpendicular to the beam splitter surface 310.
A first .lamda./4 platelet 41 follows the polarization beam
splitter cube 31. The light beams of the illuminating beam path 100
are circularly polarized with the aid of this first .lamda./4
platelet 41. The light beams of the imaging beam path 200 run from
the reflective reticle 5 to the wafer 6 and are, in turn, linearly
polarized by the .lamda./4 platelet 41 but parallel to the beam
splitter surface 310 and are reflected at the beam splitter surface
310 to the concave mirror 125. Before the light beams impinge on
the concave mirror 125, the beams are circularly polarized by a
second .lamda./4 platelet 42 and, after the reflection at the
concave mirror 125 with the second passthrough, are linearly
polarized by the second .lamda./4 platelet 42 again parallel to the
beam splitter layer 310 so that the light beams pass through the
polarization beam splitter cube 31 in the direction of wafer 6.
Except for the first .lamda./4 platelet 41 between polarization
beam splitter cube 31 and reticle 5, a conventional catadioptric
reduction objective 12 having a polarization beam splitter cube 31
can be used unchanged with the reflective reticle 5. What is
decisive is that, in the design of the illuminating system 2, the
optical elements of the projection objective, which are likewise
passed through by the illuminating light, also have to be
considered.
The light of the light source 1 is so configured in the
illuminating unit 2 that it illuminates the reflective reticle 5 in
correspondence to the lithographic requirements after passing
through the following: the polarization beam splitter cube 31, the
first .lamda./4 platelet 41, the second lens group 123, the
deflecting mirror 122 and the first lens group 121. The homogeneity
of the illumination and the illuminating mode is made available by
corresponding components in the illuminating system 2. The
illuminating mode includes coherent, incoherent, annular or
quadrupole illumination. In order to correctly illuminate the entry
pupil of the reduction objective 12, the polarization beam splitter
cube 31 and the optical elements 121 to 123 are considered as fixed
components of the illuminating beam path 100 and their effect is to
be considered in the design of the illuminating system 2.
In the configuration of the reduction objective 12 of FIG. 4, it is
also possible to couple in the illumination light 100 via the
deflection mirror 122 as shown in FIGS. 5 and 6.
In FIG. 5, the deflecting mirror 122 of FIG. 4 is replaced by a
polarization beam splitter plate 32. The illuminating light 100
should be so polarized that it passes through the polarization beam
splitter plate 32. A .lamda./4 platelet 43 is disposed between
polarization beam splitter plate 32 and the reticle 5 and leads to
the circular polarization of the illuminating light 100. After the
reflection at reticle 5, the light beams of the imaging beam path
200 are polarized when passing through the .lamda./4 platelet 43
parallel to the beam splitter surface 321 so that the beam is
reflected in the direction of polarization beam splitter cube 33.
The use of a known planes parallel beam splitter plate, which is
positioned in the beam path 200 at an angle of 45.degree., would
lead within the illuminating beam path 100 to non-rotationally
symmetrical imaging errors such as astigmatism and coma in the
axis. For this reason, the beam splitter plate 32 of the invention
is utilized. This plate is configured as a wedge plate such that
the astigmatism of lowest order can be completely eliminated by an
optimized wedge angle. The wedge angle is so configured that the
thicker end of the wedge is directed toward the illuminating system
2 and the thinner end is directed toward the reticle 5.
The remaining imaging errors of higher order can be compensated by
a targeted aspherization of the surface 322 facing toward the
illuminating system 2. The aspherization can, for example, be
undertaken by an ion beam or a robotic refinement. The aspheric
shape is then, as a rule, not rotationally symmetric; instead, the
aspheric form has a simple symmetry. The symmetry plane is the
meridian plane. A correction of this kind via the wedge plate and
the aspherized surface 322 is adequate within the illuminating beam
path 100 in order to achieve the required specification for the
correct illumination of the reticle 5. In contrast, within the
imaging beam path 200, the use of a polarization beam splitter
plate 32 in transmission would not be possible because of the
introduced imaging errors. In a configuration of FIG. 5, no adverse
effect on the imaging beam path 200 occurs because, in the imaging
beam path 200, only the planar surface 321 of the beam splitter
plate 32 is used in reflection so that the light rays of the
imaging beam path 200 are reflected by air. With air, a medium
having a refractive index of almost 1.0 is understood. In this
connection, consideration can be given also to gas fillings, for
example, with nitrogen, helium or partially evacuated air
spaces.
The deflection mirror 122 in FIG. 4 or the beam splitter plate 31
in FIG. 5 can also be replaced by a polarization beam splitter cube
34 as shown in FIG. 6. A polarization beam splitter cube 34 has the
advantage compared to a beam splitter plate 32 that only
rotationally symmetrical imaging errors are introduced which can be
easily corrected. In comparison to the beam splitter plate 32, a
beam splitter cube 34 has the advantage that the additional glass
path through the glass prisms leads to transmission losses which
are disturbing especially at low wavelengths.
Coupling in the illuminating light via a polarization beam splitter
cube 36 can also be done in another class of objective designs as
shown in FIG. 7. The reduction objective includes the following: a
catadioptric component objective 15 having a polarization beam
splitter cube 36, an intermediate image 95 and a refractive
reduction objective 16. The catadioptric component objective 15 can
be disposed after the reticle 5 as shown in FIG. 7 as well as
forward of the wafer 6. In the catadioptric component objective 15,
a polarization beam splitter cube 36 is already provided having a
fourth and still unused face. Via this face, the illuminating light
100 can be coupled in.
The light coming from the illuminating unit 2 has to be very well
polarized, advantageously to more than 95%, perpendicularly to the
beam splitter surface 360. In this way, one avoids an unwanted
reflection in the direction of wafer 6 whereby contrast and
resolution of the projection objective would have been reduced.
A first .lamda./4 platelet 47 has to be mounted between
polarization beam splitter cube 36 and reticle 5 so that the light
rays of the imaging beam path 200 are polarized after passing
through the .lamda./4 platelet 47 so that they are reflected at the
polarization beam splitter cube 36 in the direction of concave
mirror 93.
Optical elements 91, which overall have a positive refractive
power, are disposed between reticle 5 and polarization beam
splitter cube 36 so that the beam splitter surface 360 is passed
through in the almost entirely collimated beam path.
A second .lamda./4 platelet 48 has to be introduced between
polarization beam splitter cube 36 and concave mirror 93 so that
the light rays of the imaging beam path 200 can, after the
deflection at concave mirror 93, pass through the polarization beam
splitter cube 36 undeflected in the direction of the intermediate
image 95.
The optical elements 92 having an overall negative refractive power
are disposed between the polarization beam splitter cube 36 and the
concave mirror 93. The elements 92 are passed through by the light
beam in two passthroughs and lead to a chromatic overcorrection.
The concave mirror 93 affords the advantage that it introduces no
chromatic aberrations and has an adequately positive refractive
power so that the catadioptric component objective 15 overall has a
positive refractive power.
If the polarization beam splitter cube 3 is passed through in the
almost collimated beam path, then further optical elements 94
having overall positive refractive power are required ahead of the
intermediate image 95 in order to generate the intermediate
image.
One can omit optical elements 94 if the intermediate image 95 is
already generated by the action of the concave mirror 93 and the
optical elements 92 and if the collimated beam path within the
polarization beam splitter cube 93 is omitted.
Usually, the object is imaged onto the intermediate image with an
imaging scale of .beta..sub.1=-1.0.+-.0.25.
A refractive reduction imaging having an imaging scale of, for
example, .beta..sub.2=0.25.+-.0.15 follows the intermediate image
95. In FIG. 7, the component objective between intermediate image
95 and wafer 6 comprises the optical elements (96, 98) and the
deflecting mirror 97.
It is also possible to arrange the deflecting mirror 97 forward of
the optical components 96.
The diameter of the illuminated field in the wafer plane 6 is, in
this class of objectives, greater than 10 mm for an image end
numerical aperture greater than 0.5.
For the embodiment shown in FIG. 7 with beam splitter cube and
intermediate image, FIG. 8 shows a specific embodiment for an image
scale .beta.=-0.25, for an image field having a diameter of 14.3 mm
and for an image end numerical aperture of 0.7. The reference
numerals in FIG. 8 correspond to the reference numerals in FIG. 7.
The optical data are set forth in Table 1.
The embodiment of FIG. 8 is taken from U.S. patent application Ser.
No. 09/711,256, filed Nov. 10, 2000 (now U.S. Pat. No. 6,424,471),
incorporated herein by reference.
In Table 1, the surface 7 is assigned to the beam splitter surface
360 for the first contact and the surface 19 is assigned to the
concave mirror 93. The surface 31 is assigned to the beam splitter
surface 360 for the second contact and the surface 36 is assigned
to the deflecting mirror 97. The surface 38 is assigned to the
intermediate image 95. SiO.sub.2 identifies quartz glass and
CaF.sub.2 identifies calcium fluoride monocrystals.
The optical elements 91 in this case comprise two converging lenses
131 and 132. The converging lens 132 is mounted close to the
polarization beam splitter cube 3 and reduces the divergence of the
peripheral rays. In this way, the substantially collimated beam
path is produced within the polarization beam splitter cube 3. An
almost telecentric chief ray trace is achieved at the reticle 5
with the converging lens 131 close to the reticle 5.
Table 2 provides the chief ray angles with respect to the surface
normal in mrad for seven object heights in the reticle plane 5. The
chief ray angles are positive when the chief rays run convergent to
the optical axis after reflection at reticle 5. The maximum chief
ray angle in this embodiment is only 0.5 mrad. The entry at the
reticle is thereby almost perfectly telecentric.
The adaptation of the centroid ray angles of the illuminating beam
path 100 in the illuminating system 2 to the chief ray angle of the
projection objective is, in this case, especially simple because
the illuminating beam path 100 and the imaging beam path 200
substantially overlap within the common components 91 between beam
splitter cube 3 and reticle 5.
The polarization beam splitter cube 3 and the two converging lenses
131 and 132 are to be included in the design of the illuminating
system 2. If the last component of the illuminating system 2
forward of the reticle is a REMA objective as disclosed in U.S.
Pat. No. 5,982,558 or in U.S. Pat. No. 6,366,410, then the REMA
objective can be so modified without great difficulty that a
refractive cube is integrated for the polarization beam splitter
cube 3 and a refractive planar plate is integrated for the
.lamda./4 platelet 47 and the two converging lenses 131 and 132 are
integrated into the field lens of the REMA objective.
An incoupling of the illuminating light 100 via the deflecting
mirror 97 is in this case not possible. The incoupling of
illuminating light via a polarization beam splitter cube or a
polarization beam splitter plate is only possible when the light
does not impinge on a further beam splitter surface after passing
through this first beam splitter surface but is reflected after
passthrough by possibly further optical elements. However, in the
configuration of FIG. 8, if the illuminating light would be coupled
in via the deflecting mirror 97, no reflecting surface would follow
but a further polarization beam splitter surface 360 of the beam
splitter cube 3. An incoupling would, in this case, be conceivable
only via a geometric beam splitter plate or a geometric beam
splitter cube. This, however, would lead to high transmission
losses.
It is understood that the foregoing description is that of the
preferred embodiments of the invention and that various changes and
modifications may be made thereto without departing from the spirit
and scope of the invention as defined in the appended claims.
TABLE-US-00001 TABLE 1 Surface No. Radius Thickness Mirror Material
Reticle .infin. 35.000 1 .infin. 0.000 2 .infin. 10.000 SiO2 3
-356.062 157.474 4 152.317 20.000 SiO2 5 -207.509 15.494 6 .infin.
46.000 SiO2 7 .infin. -46.000 S SiO2 8 .infin. -11.450 9 714.294
-10.000 SiO2 10 -233.153 -14.054 11 11257.823 -7.320 SiO2 12
5681.927 -0.268 13 -294.458 -29.996 SiO2 14 2624.912 -21.086 15
118.550 -6.001 SiO2 16 372.661 -9.646 17 89.532 -6.000 SiO2 18
220.679 -3.804 19 134.415 3.804 S 20 220.679 6.000 SiO2 21 89.532
9.646 22 372.661 6.001 SiO2 23 118.550 21.086 24 2624.912 29.996
SiO2 25 -294.458 0.268 26 5681.927 7.320 SiO2 27 11257.823 14.054
28 -233.153 10.000 SiO2 29 714.294 11.450 30 .infin. 46.000 SiO2 31
.infin. 46.000 SiO2 32 .infin. 0.000 33 .infin. 11.000 34 -6197.721
20.000 SiO2 35 -220.469 289.683 36 .infin. -35.000 S 37 -283.115
-27.145 SiO2 38 291.549 -0.100 39 -169.090 -12.856 SiO2 40
-2565.582 -24.512 41 380.926 -6.000 SiO2 42 3955.807 -18.476 43
360.725 -6.000 SiO2 44 890.059 -2.724 45 -179.574 -11.560 SiO2 46
-339.907 -16.696 47 -147.863 -16.313 SiO2 48 -65.738 -18.352 49
103.683 -7.718 SiO2 50 197.447 -2.785 51 111.947 -15.000 SiO2 52
106.337 -38.908 53 -152.812 -22.411 SiO2 54 194.070 -0.375 55
-199.667 -7.318 SiO2 56 -93.343 -30.485 57 89.838 -7.125 SiO2 58
197.820 -35.859 59 -713.001 -13.228 SiO2 60 274.158 -0.375 61
-106.260 -6.375 SiO2 62 -76.991 -18.206 63 -207.243 -16.125 SiO2 64
265.977 -0.375 65 -105.982 -6.938 SiO2 66 -70.150 -5.070 67
-110.355 -11.250 SiO2 68 -337.355 -1.500 69 .infin. 0.000 70
-83.054 -13.500 SiO2 71 -64.019 -0.100 72 -60.890 -13.500 SiO2 73
-102.440 -0.101 74 -65.466 -8.393 SiO2 75 -75.287 -0.523 76 -74.115
-10.249 SiO2 77 -48.411 -4.972 78 -70.661 -26.250 SiO2 79 135.365
-0.038 80 -38.281 -23.828 CaF2 81 -41.066 -0.038 82 -46.927 -9.292
CaF2 83 187.500 -5.625 Wafer .infin. 0.000
TABLE-US-00002 TABLE 2 Object Height at Reticle Chief Ray Angle at
Reticle (mm) (mrad) 28.7 +0.29 26.8 +0.36 24.9 +0.41 20.3 +0.49
14.4 +0.47 10.1 +0.38 0.0 +0.00
* * * * *