U.S. patent application number 10/458629 was filed with the patent office on 2006-01-26 for ultraviolet polarization beam splitter with minimum apodization.
This patent application is currently assigned to ASML Holding N.V.. Invention is credited to Ronald A. Wilklow.
Application Number | 20060018011 10/458629 |
Document ID | / |
Family ID | 35744719 |
Filed Date | 2006-01-26 |
United States Patent
Application |
20060018011 |
Kind Code |
A9 |
Wilklow; Ronald A. |
January 26, 2006 |
Ultraviolet polarization beam splitter with minimum apodization
Abstract
A beamsplitter includes a first fluoride prism and a second
fluoride prism. A coating interface is between the first and second
fluoride prisms, wherein an overall R(s)*T(p) function of the
beamsplitter varies no more than .+-.2.74% in the range of 40-50
degrees of incidence.
Inventors: |
Wilklow; Ronald A.;
(Fairfield, CT) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX PLLC
1100 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
ASML Holding N.V.
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20040252369 A1 |
December 16, 2004 |
|
|
Family ID: |
35744719 |
Appl. No.: |
10/458629 |
Filed: |
June 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10264318 |
Oct 4, 2002 |
6680794 |
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10458629 |
Jun 11, 2003 |
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09538529 |
Mar 30, 2000 |
6480330 |
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10264318 |
Oct 4, 2002 |
|
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60184782 |
Feb 24, 2000 |
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Current U.S.
Class: |
359/359 ;
359/350; 359/352 |
Current CPC
Class: |
G02B 27/283 20130101;
G02B 5/3041 20130101 |
Class at
Publication: |
359/359 ;
359/350; 359/352 |
International
Class: |
G02B 5/08 20060101
G02B005/08 |
Claims
1. A beamsplitter comprising: a first fluoride prism; a second
fluoride prism; a coating interface between the first and second
fluoride prisms, wherein an overall R(s)*T(p) function of the
beamsplitter varies no more than .+-.2.74% in the range of 40-50
degrees of incidence.
2. The beamsplitter of claim 1, wherein the coating interface
includes alternating layers of MgF.sub.2 and LaF.sub.3.
3. The beamsplitter of claim 1, wherein the coating interface
includes at least 27 alternating layers of high and low refractive
index materials.
4. The beamsplitter of claim 1, wherein the coating interface
includes at least 27 alternating layers of high and low refractive
index materials.
5. The beamsplitter of claim 1, wherein the coating interface
includes alternating layers of NdF.sub.3 and AlF.sub.3.
6. The beamsplitter of claim 1, wherein the coating interface
includes at least 30 alternating layers of high and low refractive
index materials.
7. The beamsplitter of claim 1, wherein the coating interface
includes at least 32 alternating layers of high and low refractive
index materials.
8. The beamsplitter of claim 1, wherein the coating interface
includes at least 11 alternating layers of high and low refractive
index materials.
9. The beamsplitter of claim 1, wherein the coating interface
includes at least 21 alternating layers of high and low refractive
index materials.
10. The beamsplitter of claim 1, wherein the first and second
prisms include CaF.sub.2.
11. The beamsplitter of claim 1, wherein the first and second
prisms include fused silica.
12. The beamsplitter of claim 1, wherein the overall R(s)*T(p)
function of the beamsplitter varies no more than .+-.0.87% in the
range of 35-55 degrees of incidence.
13. The beamsplitter of claim 1, wherein the overall R(s)*T(p)
function of the beamsplitter varies no more than .+-.2.74% in the
range of 35-55 degrees of incidence.
14. The beamsplitter of claim 1, wherein the beamsplitter operates
at about 157.6 nm.
15. The beamsplitter of claim 1, wherein the beamsplitter operates
at about 193 nm.
16. A beamsplitter comprising: a first fluoride prism; a second
fluoride prism; a coating interface between the first and second
fluoride prisms, wherein an overall R(s)*T(p) function of the
beamsplitter varies no more than .+-.0.445% in the range of 40-50
degrees of incidence.
17. The beamsplitter of claim 16, wherein the coating interface
includes alternating layers of MgF.sub.2 and LaF.sub.3.
18. The beamsplitter of claim 16, wherein the coating interface
includes at least 27 alternating layers of high and low refractive
index materials.
19. The beamsplitter of claim 16, wherein the coating interface
includes at least 29 alternating layers of high and low refractive
index materials.
20. The beamsplitter of claim 16, wherein the coating interface
includes alternating layers of NdF.sub.3 and AlF.sub.3.
21. The beamsplitter of claim 16, wherein the coating interface
includes at least 30 alternating layers of high and low refractive
index materials.
22. The beamsplitter of claim 16 wherein the coating interface
includes at least 32 alternating layers of high and low refractive
index materials.
23. The beamsplitter of claim 16, wherein the coating interface
includes at least 11 alternating layers of high and low refractive
index materials.
24. The beamsplitter of claim 16, wherein the coating interface
includes at least 21 alternating layers of high and low refractive
index materials.
25. The beamsplitter of claim 16, wherein the first and second
prisms include CaF.sub.2.
26. The beamsplitter of claim 16, wherein the first and second
prisms include fused silica.
27. The beamsplitter of claim 16, wherein an overall R(s)*T(p)
function of the beamsplitter varies no more than 0.87% in the range
of 35-55 degrees of incidence in the ultraviolet range.
28. A beamsplitter comprising: a first fluoride prism; a second
fluoride prism; a coating interface between the first and second
fluoride prisms, wherein an apodization function of the
beamsplitter is relatively flat in the range of 40-50 degrees of
incidence.
29. A beamsplitter comprising: a first fluoride prism; a second
fluoride prism; a coating interface between the first and second
fluoride prisms, wherein an overall R(s)*T(p) function of the
beamsplitter varies no more than .+-.0.1% in the range of 44-60
degrees of incidence.
30. The beamsplitter of claim 29, wherein the overall R(s)*T(p)
function of the beamsplitter varies no more than .+-.0.064% in the
range of 44-60 degrees of incidence
31. The beamsplitter of claim 29, wherein the coating interface
includes at least 21 alternating layers of high and low refractive
index materials.
32. The beamsplitter of claim 29, wherein the first and second
prisms include CaF.sub.2.
33. A method of forming a beamsplitter comprising the steps of:
forming a coating on a first fluoride prism, wherein an apodization
function of the beamsplitter is relatively flat in the range of
40-50 degrees of incidence; and joining the first fluoride prism
with the second fluoride prism to form the beamsplitter.
34. The method of claim 33, wherein the step of forming the coating
includes the step of forming alternating layers of MgF.sub.2 and
LaF.sub.3.
35. The method of claim 29, wherein the step of forming alternating
layers of MgF.sub.2 and LaF.sub.3 forms at least 27 alternating
layers.
36. The method of claim 33, wherein the step of forming the coating
includes the step of forming alternating layers of NdF.sub.3 and
AlF.sub.3.
37. The method of claim 33, comprising providing the first and
second prisms as CaF.sub.2 prisms.
38. The method of claim 33, comprising providing the first and
second prisms as fused silica prisms.
39. The method of claim 33, comprising forming the coating so that
the overall R(s)*T(p) function of the beamsplitter varies no more
than .+-.0.87% in the range of 35-55 degrees of incidence.
40. The method of claim 33, comprising forming the coating so that
the overall R(s)*T(p) function of the beamsplitter varies no more
than .+-.2.74% in the range of 35-55 degrees of incidence.
41. The method of claim 33, comprising forming the coating so that
the beamsplitter operates at about 157.6 nm.
42. The method of claim 33, comprising forming the coating so that
the beamsplitter operates at about 193 nm.
43. The method of claim 33, comprising forming the coating so that
the apodization function of the beamsplitter varies no more than
.+-.0.87% in the range of 35-55 degrees of incidence.
44. The method of claim 33, comprising forming the coating so that
the apodization function of the beamsplitter varies no more than
.+-.2.74% in the range of 35-55 degrees of incidence.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to optics, and in particular,
to beam splitters used in microlithography.
[0003] 2. Related Art
[0004] Photolithography (also called microlithography) is a
semiconductor fabrication technology. Photolithography uses
ultraviolet or visible light to generate fine patterns in a
semiconductor device design. Many types of semiconductor devices,
such as, diodes, transistors, and integrated circuits, can be
fabricated using photolithographic techniques. Exposure systems or
tools are used to carryout photolithographic techniques, such as
etching, in semiconductor fabrication. An exposure system can
include a light source, reticle, optical reduction system, and a
wafer alignment stage. An image of a semiconductor pattern is
printed or fabricated on the reticle (also called a mask). A light
source illuminates the reticle to generate an image of the
particular reticle pattern. An optical reduction system is used to
pass a high-quality image of the reticle pattern to a wafer. See,
Nonogaki et al., Microlithography Fundamentals in Semiconductor
Devices and Fabrication Technology, Marcel Dekker, Inc., New York,
N.Y. (1998), incorporated in its entirety herein by reference.
[0005] Integrated circuit designs are becoming increasingly
complex. The number of components and integration density of
components in layouts is increasing. Demand for an ever-decreasing
minimum feature size is high. The minimum feature size (also called
line width) refers to the smallest dimension of a semiconductor
feature that can be fabricated within acceptable tolerances. As a
result, it is increasingly important that photolithographic systems
and techniques provide a higher resolution.
[0006] One approach to improve resolution is to shorten the
wavelength of light used in fabrication. Increasing the numerical
aperture (NA) of the optical reduction system also improves
resolution. Indeed, commercial exposure systems have been developed
with decreasing wavelengths of light and increasing NA.
[0007] Catadioptric optical reduction systems include a mirror that
reflects the imaging light after it passes through the reticle onto
a wafer. A beam splitter cube is used in the optical path of the
system. A conventional beam splitter cube, however, transmits about
50% of input light and reflects about 50% of the input light. Thus,
depending upon the particular configuration of optical paths,
significant light loss can occur at the beam splitter.
[0008] In UV photolithography, however, it is important to maintain
a high light transmissivity through an optical reduction system
with little or no loss. Exposure time and the overall semiconductor
fabrication time depends upon the intensity or magnitude of light
output onto the wafer. To reduce light loss at the beam splitter, a
polarizing beam splitter and quarter-wave plates are used.
[0009] Generally, polarizing beam splitters are designed for
maximum optical throughput, but without a particular attention to
the apodization they impose on the pupil of the projection optics.
In optical systems having low numerical apertures (i.e., on
numerical apertures corresponding to a lower range of operating
angles at the beam splitter coating), this is not a significant
problem, since the natural bandwidth of the coating is typically
large enough to cover the requirements. However, at higher
numerical apertures, the coating designs become more complex, and
result in an increase in undesirable performance fluctuations over
the angular range of operation.
[0010] Accordingly, what is needed is a beamsplitter with a
relatively flat apodization function over a wide angular range that
is usable in UV photolithography.
SUMMARY OF THE INVENTION
[0011] The present invention embodies a technique for providing a
beam splitter with a relatively flat apodization function.
[0012] In an embodiment of the present invention, a beam splitter
is provided whose product of the P transmittance and S
transmittance is relatively flat.
[0013] In another embodiment of the present invention, a beam
splitter is provided having the above characteristics that is
usable for ultraviolet and deep ultraviolet photo lithographic
applications.
[0014] In one aspect of the invention, there is provided a
beamsplitter including a first fluoride prism and a second fluoride
prism. A coating interface is between the first and second fluoride
prisms, wherein an overall R(s)*T(p) function of the beamsplitter
varies no more than .+-.2.74% in the range of 40-50 degrees of
incidence.
[0015] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0016] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, there is provided a
BRIEF DESCRIPTION OF THE FIGURES
[0017] The accompanying drawings, which are incorporated herein and
form a part of the specification, illustrate the present invention
and, together with the description, further serve to explain the
principles of the invention and to enable a person skilled in the
pertinent art to make and use the invention. In the drawings:
[0018] FIG. 1A is a perspective view of a conventional polarizing
beam splitter cube;
[0019] FIG. 1B is a diagram showing a cross-section of a
conventional coating interface for the polarizing beam splitter
cube of FIG. 1A;
[0020] FIG. 2A illustrates how the polarizing beam splitter cube of
FIG. 1A separates light into separate polarization states;
[0021] FIG. 2B illustrates how the polarizing beam splitter cube of
FIG. 1A can be used as part of a catadioptric optical reduction
system to improve transmission efficiency;
[0022] FIG. 3A is a perspective view of a UV polarizing beam
splitter cube according to one embodiment of the present
invention;
[0023] FIG. 3B is a diagram showing a cross-section of a coating
interface for the UV polarizing beam splitter cube of FIG. 3A;
and
[0024] FIGS. 4-8 illustrate exemplary beamsplitter transmission
performance according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The present invention will now be described with reference
to the accompanying drawings. In the drawings, like reference
numbers indicate identical or functionally similar elements.
Additionally, the left-most digit(s) of a reference number
identifies the drawing in which the reference number first
appears.
[0026] While the present invention is described herein with
reference to illustrative embodiments for particular applications,
it should be understood that the invention is not limited thereto.
Those skilled in the art with access to the teachings provided
herein will recognize additional modifications, applications, and
embodiments within the scope thereof and additional fields in which
the present invention would be of significant utility.
Terminology
[0027] The terms "beam splitter" or "cube" used with respect to the
present invention have a broad meaning that refers to a beam
splitter that includes, but is not limited to, a beam splitter
having an overall cubic shape, rectangular cubic shape, or
truncated cubic shape, or approximating an overall cubic shape,
rectangular cubic shape, or truncated cubic shape.
[0028] The term "long conjugate end" refers to a plane at the
object or reticle end of an optical reduction system.
[0029] The term "short conjugate end" refers to the plane at the
image or wafer end of an optical reduction system.
[0030] The term "wafer" refers to the base material in
semiconductor manufacturing, which goes through a series of
photomasking, etching and/or implementation steps.
[0031] The term "wave plate" refers to retardation plates or phase
shifters made from materials which exhibit birefringence.
[0032] FIGS. 1A and 1B illustrate an example conventional
polarizing beam splitter cube 100 used in a conventional
catadioptric optical reduction system. Polarizing beam splitter
cuber 100 includes two prisms 110, 150, and a coating interface
120. Prisms 120, 150 are made of fused silica and are transmissive
at wavelengths of 248 nm and 193 nm. Coating interface 120 is a
multi-layer stack. The multi-layer stack includes alternating thin
film layers. The alternating thin film layers are made of thin
films having relatively high and low indices of refraction (n.sub.1
and n.sub.2). The alternating thin film layers and their respective
indices of refraction are selected such that the MacNeille
condition (also called Brewster condition) is satisfied. In one
example, the high index of refraction thin film material is an
aluminum oxide. The low index of refraction material is aluminum
fluoride. A protective layer may be added during the fabrication of
the stack. Cement or glue is included to attach one of the
alternating layers to a prism 150 at face 152 or to attach the
protective layer to prism 110 at face 112.
[0033] As shown in FIG. 2A, the MacNeille condition (as described
in U.S. Pat. No. 2,403,731) is a condition at which light 200
incident upon the multi-layer stack is separated into two beams
260, 280 having different polarization states. For example, output
beam 260 is an S-polarized beam, and output beam 280 is a
P-polarized beam (or polarized at 90 degrees with respect to each
other). FIG. 2B shows the advantage of using a polarizing beam
splitter in a catadioptric optical reduction system to minimize
light loss. Incident light 200 (usually having S and P polarization
states) passes through a quarter-wave plate 210. Quarter wave plate
210 converts all of incident light 200 to a linearly polarized beam
in an S polarization state. Beam splitter cube 100 reflects all or
nearly all of the S polarization to quarter wave plate 220 and
mirror 225. Quarter wave plate 220 when doubled passed acts like a
half-waveplate. Quarter wave plate 220 converts the S polarization
light to circular polarization, and after reflection from mirror
225, converts light into P-polarized light. The P-polarized light
is transmitted by beam splitter cube 100 and output as a
P-polarized beam 290 toward the wafer. In this way, the polarizing
beam splitter 100 and quarter wave plates 210, 220 avoid light loss
in a catadioptric optical reduction system that includes a mirror
225. Note, as an alternative, mirror 225 and quarter wave plate 220
can be positioned at face B of cube 100, rather than at face A, and
still achieve the same complete or nearly complete light
transmission over a compact optical path length.
[0034] The invention, which will be further described below, can be
used in catadioptric photolithography systems. It can be used in
any polarizing beamsplitter system in which the beamsplitter is
used over a range of angles and in which the light passes through
the beamsplitter twice at orthogonal polarizations.
[0035] Typical polarizing beamsplitters, as described above with
reference to FIGS. 1A-2B, are designed for maximum optical
throughput but without particular attention to the apodization they
impose on the pupil of the projection optics. This is not a
significant problem in systems with low numerical apertures (i.e.,
a lower range of operating angles at the beamsplitter coating),
where the natural bandwidth of the coating was large enough to
cover the requirement. At higher numerical apertures, coating
designs become more complex, with a resultant increase in
undesirable performance fluctuations over the angular range of
operation.
[0036] In the beamsplitter of the present invention, light passes
through the beamsplitter twice, first in S polarization and then
again in P polarization. The two performance curves (S and P as
functions of angle) multiplied together determine the overall
apodization function that the coating introduces into the system
pupil. Previous efforts to design coatings with lower pupil
apodization focused on flattening the S and P performance curves
individually. In the design of the beamsplitter coating it is
relatively easy to effect changes in the performance for the S
polarization, and more difficult to effect changes in the P
polarization performance. If the beamsplitter is doubled-passed in
the system, P polarization performance variations can be
compensated for by a coating whose S polarization performance has
the opposite "signature." When the two functions R(s) and T(p) are
multiplied together, they produce an apodization function R(s)*T(p)
that is relatively flat.
[0037] To achieve a relatively flat R(s)*T(p) function, the present
invention provides a ultraviolet (UV) polarizing beam splitter. The
UV polarizing beam splitter is transmissive to light at wavelengths
equal to or less than 200 nm, for example, at 193 nm or 157 nm. The
UV polarizing beam splitter can image at high quality light
incident over a wide range of reflectance and transmittance angles.
The UV polarizing beam splitter can accommodate divergent light in
an optical reduction system having a numeric aperture at a wafer
plane greater than 0.6, and for example at 0.75. In different
embodiments, the UV polarizing beam splitter can have a cubic,
rectangular cubic, or truncated cubic shape, or approximates a
cubic, rectangular cubic, or truncated cubic shape.
[0038] In one embodiment, a UV polarizing beam splitter cube
comprises a pair of prisms and a coating interface. The prisms are
made of at least a fluoride material, such as, calcium fluoride
(CaF.sub.2) or barium fluoride (BaF.sub.2). The coating interface
has a plurality of layers of a thin film fluoride material. In one
example implementation, the coating interface includes a
multi-layer stack of alternating layers of thin film fluoride
materials. The alternating layers of thin film fluoride materials
comprise first and second fluoride materials. The first and second
fluoride materials have respective first and second refractive
indices. The first refractive index is greater than (or higher
than) the second refractive index. In one feature of the present
invention, the first and second refractive indices form a stack of
fluoride materials having relatively high and low refractive
indices of refraction such that the coating interface separates UV
light (including light at wavelengths less than 200 nm, for
example, at 193 nm or 157 nm) depending on two polarized
states.
[0039] In one example, to achieve a relatively flat R(s)*T(p)
function, the coating interface comprises a multi-layer design of
the form (H L).sup.n H or (H L).sup.n, where H indicates a layer of
a first fluoride material having a relatively high refractive
index. The first fluoride material can include, but is not limited
to, gadolinium tri-fluoride (GdF.sub.3), lanthanum tri-fluoride
(LaF.sub.3), samarium fluoride (SmF.sub.3), europium fluoride
(EuF.sub.3), terbium fluoride (TbF.sub.3), dysprosium fluoride
(DyF.sub.3), holmium fluoride (HoF.sub.3), erbium fluoride
(ErF.sub.3), thulium fluoride (TmF.sub.3), ytterbium fluoride
(YbF.sub.3), lutetium fluoride (LuF.sub.3), zirconium fluoride
(ZrF.sub.4), hafnium fluoride (HfF.sub.4), yttrium fluoride
(YF.sub.3), neodymium fluoride (NdF.sub.3), any of the other
lanthanide series tri-fluorides, metallic fluorides, or other high
index, ultraviolet transparent material. L indicates a layer of a
second fluoride material having a relatively low refractive index.
The second fluoride material can include, but is not limited to,
magnesium fluoride (MgF.sub.2), aluminum tri-fluoride (AlF.sub.3),
barium fluoride (BaF.sub.2), strontium fluoride (SrF.sub.2),
calcium fluoride (CaF.sub.2), lithium fluoride (LiF), and sodium
fluoride (NaF), or other low index, ultraviolet transparent
material. The value "n" indicates the basic (H L) group is repeated
n times in a multi-layer stack, where n is a whole number equal to
one or more.
[0040] According to a further feature, the prisms and coating
interface are joined by optical contact. No cement is needed,
although its use is not precluded.
[0041] Further multi-layer designs can be generated by computer
iterated design. Layers in a multi-layer stack can also be graded
across the hypotenuse face of a prism to adjust layer thicknesses
at any point so as to compensate for changes in the incidence angle
of the light.
[0042] The present invention provides a method for splitting an
incident light beam based on polarization state. The method
includes the step of orienting a coating interface having a
plurality of layers of a fluoride material at an angle relative to
the incident light such that the coating interface transmits
incident light in a first polarization state and reflects incident
light in a second polarization state. In one example, the method
further includes the step of selecting thicknesses of alternating
thin film layers and their respective indices of refraction such
that the coating interface transmits incident light at a wavelength
equal to or less than 200 nm in a first polarization state and
reflects incident light at a wavelength equal to or less than 200
nm in a second polarization state.
UV Polarizing Beam Splitter
[0043] FIG. 3A is a perspective view of a UV polarizing beam
splitter cube 300 according to one embodiment of the present
invention. UV polarizing beam splitter cube 300 has a pair of
prisms 310, 350 and a coating interface 320. Prisms 310,350 are
preferably made of a fluoride material. Coating interface 320 has a
plurality of layers of a thin film fluoride material.
[0044] In the example shown in FIG. 3A, prism 310 is a right angle
prism having five faces. These five faces consist of two side
faces, two end faces, and a hypotenuse face. The two side faces are
square (or approximately square) at their perimeter and share right
angle corners 314 and 316. One side face B is shown in FIG. 3A, the
other side face is not shown. The two end faces are both right
triangles. One end face A, shown in FIG. 3A, is a right triangle at
its perimeter formed by a ninety degree (or approximately ninety
degree) angle at corner 314 and two 45 degree (or approximately 45
degree) angles opposite corner 314. The other end face (not shown)
is the right triangle formed by a ninety degree (or approximately
ninety degree) angle at corner 316 and two 45 degree (or
approximately 45 degree) angles opposite corner 316. The hypotenuse
face is a planar face 312 which is on a hypotenuse side of right
angle prism 310 opposite right angle corners 314, 316.
[0045] Prism 350 is also a right angle prism having five faces.
These five faces consist of two side faces, two end faces, and a
hypotenuse face. The two side faces are square (or approximately
square) at their perimeter and share right angle corners 354 and
356. One side face D is shown in FIG. 3A, the other side face is
not shown. The two end faces are both right triangles. One end face
C, shown in FIG. 3A, is a right triangle at its perimeter formed by
a ninety degree (or approximately ninety degree) angle at corner
354 and two 45 degree (or approximately 45 degree) angles opposite
corner 354. The other end face (not shown) is the right triangle
formed by a ninety degree (or approximately ninety degree) angle at
corner 356 and two 45 degree (or approximately 45 degree) angles
opposite corner 356. The hypotenuse face is a planar face 352 which
is on a hypotenuse side of right angle prism 350 opposite right
angle corners 354, 356. Coating interface 320 lies between
hypotenuse faces 312 and 352.
[0046] UV polarizing beam splitter cube 300 has width, depth, and
height dimensions equal to values d.sub.1, d.sub.2, and d.sub.3
respectively, as shown in FIG. 3A. In one example implementation,
d.sub.1, d.sub.2, and d.sub.3 are equal (or approximately equal)
such that prisms 310 and 350 when coupled along their faces 312 and
352 have an overall cube or cube-like shape. In one example
implementation, prisms 310, 350 are made of calcium fluoride
(CaF.sub.2) material, barium fluoride (BaF.sub.2) material, or a
combination thereof.
Coating Interface
[0047] FIG. 3B is a diagram showing a cross-section of an example
coating interface 320, used to achieve a relatively flat R(s)*T(p)
function, in greater detail. Coating interface 320 includes a stack
of alternating layers of thin film fluoride materials (331-337,
341-346), and a protective layer 351. Anti-reflection (AR) coatings
(not shown) can also be included in coating interface 320.
Protective layer 351 and AR coatings are optional. Also, the
present invention in not limited to thirteen layers of alternating
layers of thin film fluoride materials. In general, larger and
smaller numbers of alternating layers of thin film fluoride
materials can be used as would be apparent to a person skilled in
the art given this description.
[0048] Further, FIG. 3B shows the coating interface 320 mounted on
face 352 of prism 350. The stack of alternating layers of thin film
fluoride materials (331-337, 341-346) and/or protective layer 351
are grown, etched, or fabricated on face 352 using conventional
thin film techniques. Prism 310 is then placed in optical contact
with the coating interface 320. In this way, prisms 310 and 350 are
coupled strongly through coating interface 320 resulting in a very
strong polarizing beam splitter cube. One further feature of the
present invention is that it applies this optical contact (where
optical components are joined so closely together that van der
Waal's forces couple the components to one another) in a complex
geometry involving angled surfaces, such as, the hypotenuse face of
prism 310.
[0049] The alternating layers of thin film fluoride materials
include two groups of layers. The first group of layers 331-337 has
a first index of refraction n.sub.1. The second group of layers
341-346 has a second index of refraction n.sub.2. According to one
feature of the present invention, the first and second refractive
indices n.sub.1 and n.sub.2 are different. In particular, the
second refractive index n.sub.2 is relatively low compared to the
first refractive index n.sub.1. In this way, coating interface 320
includes a stack of fluoride materials 331-337, 341-346 having
alternating relatively high and low refractive indices n.sub.1,
n.sub.2 such that the coating interface 320 separates incident UV
light based on two different polarization states, such as S and P
polarization states. According to the present invention, polarizing
beam splitter cube 300 can be used with light at wavelengths equal
to or less than 200 nm, and in particular, at 193 or 157.6 nm, for
example.
[0050] As noted above, to achieve a relatively flat R(s)*T(p)
function, the coating interface 320 comprises a multi-layer design
of the form (H L).sup.n H or (H L).sup.n, where H indicates a layer
of a first fluoride material having relatively high refractive
index. The first fluoride material can include, but is not limited
to, gadolinium tri-fluoride (GdF.sub.3), lanthanum tri-fluoride
(LaF.sub.3), samarium fluoride (SmF.sub.3), europium fluoride
(EuF.sub.3), terbium fluoride (TbF.sub.3), dysprosium fluoride
(DyF.sub.3), holmium fluoride (HoF.sub.3), erbium fluoride
(ErF.sub.3), thulium fluoride (TmF.sub.3), ytterbium fluoride
(YbF.sub.3), lutetium fluoride (LuF.sub.3), zirconium fluoride
(ZrF.sub.4), hafnium fluoride (HfF.sub.4), yttrium fluoride
(YF.sub.3), neodymium fluoride (NdF.sub.3), any of the other
lanthanide series tri-fluorides, metallic fluorides, or other high
index, ultraviolet-transparent material. L indicates a layer of a
second fluoride material having relatively low refractive index.
The second fluoride material can include, but is not limited to,
magnesium fluoride (MgF.sub.2), aluminum tri-fluoride (AlF.sub.3),
barium fluoride (BaF.sub.2), strontium fluoride (SrF.sub.2),
calcium fluoride (CaF.sub.2), lithium fluoride (LiF), and sodium
fluoride (NaF), or other low index, ultraviolet transparent
material. The superscript value "n" indicates the basic (H L) group
is repeated n times in a multi-layer stack, where n is a whole
number equal to one or more.
[0051] Other designs for a multi-layer coating interface 320, 520
can be generated through a computer iterated technique as would be
apparent to a person skilled in the art given this description.
[0052] The examples below are illustrative of how a flat overall
R(s)*T(p) function can be achieved using a number of alternating
coating layers.
BEAMSPLITTER EXAMPLE 1
[0053] The table below illustrates one example of a coating
interface 320 for 157.6 nm that satisfies the requirements of a
flat R(s)*T(p) apodization function using a total of 27 alternating
layers (n=13) of MgF.sub.2 and LaF.sub.3. This example provides a
relatively flat R(s)*T(p) function between 35 and 55 degrees
incident. In that range, the R(s)*T(p) function ranges from a
maximum of 70.85 to a minimum of 65.37, or a delta of 5.48%
(.+-.2.74%). TABLE-US-00001 TABLE 1 Mechanical Optical Thickness
Layer Thickness Layer Index (quarter-waves at Number Material (nm)
(at 157.6 nm) 157.6 nm) exit medium CaF.sub.2 massive 1 MgF.sub.2
37.14 1.465 1.381 2 LaF.sub.3 9.18 1.78 0.415 3 MgF.sub.2 36.58
1.465 1.360 4 LaF.sub.3 16.11 1.78 0.728 5 MgF.sub.2 45.68 1.465
1.699 6 LaF.sub.3 8.92 1.78 0.403 7 MgF.sub.2 42.92 1.465 1.596 8
LaF.sub.3 22.20 1.78 1.003 9 MgF.sub.2 32.03 1.465 1.191 10
LaF.sub.3 19.82 1.78 0.895 11 MgF.sub.2 30.10 1.465 1.119 12
LaF.sub.3 24.30 1.78 1.098 13 MgF.sub.2 31.56 1.465 1.173 14
LaF.sub.3 25.91 1.78 1.171 15 MgF.sub.2 30.78 1.465 1.144 16
LaF.sub.3 24.27 1.78 1.096 17 MgF.sub.2 28.51 1.465 1.060 18
LaF.sub.3 23.46 1.78 1.060 19 MgF.sub.2 31.52 1.465 1.172 20
LaF.sub.3 27.37 1.78 1.237 21 MgF.sub.2 35.97 1.465 1.337 22
LaF.sub.3 29.89 1.78 1.350 23 MgF.sub.2 39.21 1.465 1.458 24
LaF.sub.3 30.97 1.78 1.399 25 MgF.sub.2 42.48 1.465 1.580 26
LaF.sub.3 30.31 1.78 1.369 27 MgF.sub.2 31.33 1.465 1.165 entrance
CaF.sub.2 massive medium
[0054] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 4 in graphical form, and are illustrated in the Table 2
below in tabular form: TABLE-US-00002 TABLE 2 Wavelength 157.6 nm
Range 35-55 degrees Substrate CaF.sub.2 H LaF.sub.3 L MgF.sub.2
angle T(p) R(s) R(s) * T(p) 30.0 41.67 84.81 35.34 30.5 44.75 84.78
37.94 31.0 47.94 84.93 40.71 31.5 51.23 85.21 43.65 32.0 54.62
85.60 46.75 32.5 58.10 86.03 49.98 33.0 61.66 86.45 53.30 33.5
65.24 86.79 56.62 34.0 68.77 87.02 59.84 34.5 72.13 87.08 62.82
35.0 75.18 86.96 65.37 35.5 77.77 86.60 67.35 36.0 79.83 85.98
68.64 36.5 81.33 85.07 69.19 37.0 82.35 83.89 69.08 37.5 83.00
82.48 68.46 38.0 83.45 81.02 67.60 38.5 83.85 79.72 66.84 39.0
84.33 78.83 66.47 39.5 84.94 78.47 66.65 40.0 85.72 78.57 67.35
40.5 86.61 78.91 68.35 41.0 87.57 79.25 69.39 41.5 88.51 79.38
70.26 42.0 89.37 79.19 70.78 42.5 90.11 78.63 70.85 43.0 90.71
77.69 70.48 43.5 91.18 76.49 69.74 44.0 91.52 75.23 68.85 44.5
91.77 74.19 68.08 45.0 91.94 73.68 67.74 45.5 92.05 73.80 67.93
46.0 92.10 74.42 68.54 46.5 92.09 75.26 69.31 47.0 92.00 76.02
69.94 47.5 91.82 76.49 70.23 48.0 91.51 76.59 70.09 48.5 91.07
76.34 69.52 49.0 90.47 75.85 68.63 49.5 89.77 75.35 67.64 50.0
89.02 75.10 66.85 50.5 88.30 75.29 66.48 51.0 87.70 75.94 66.60
51.5 87.27 76.86 67.08 52.0 87.00 77.80 67.69 52.5 86.84 78.53
68.19 53.0 86.72 78.88 68.40 53.5 86.59 78.81 68.24 54.0 86.48
78.31 67.72 54.5 86.48 77.43 66.96 55.0 86.72 76.24 66.11 55.5
87.29 74.80 65.30 56.0 88.13 73.13 64.45 56.5 88.95 71.10 63.24
57.0 89.26 68.38 61.04 57.5 88.54 64.44 57.06 58.0 86.61 58.46
50.63 58.5 83.78 49.39 41.38 59.0 80.81 36.52 29.52 59.5 78.60
21.85 17.17 60.0 77.82 13.52 10.52 60.5 78.79 19.28 15.19 61.0
81.31 33.46 27.20 61.5 84.46 46.33 39.13 62.0 86.54 54.54 47.19
62.5 85.76 58.28 49.98 63.0 81.71 58.10 47.47 63.5 75.84 53.92
40.90 64.0 70.32 44.86 31.55 64.5 66.72 29.85 19.92 65.0 65.78
11.20 7.37
BEAMSPLITTER EXAMPLE 2
[0055] Table 3 below illustrates another example of a coating
interface 320 for 157.6 nm that satisfies the requirements of a
flat R(s)*T(p) apodization function using a total of 29 alternating
layers (n=14) of MgF.sub.2 and LaF.sub.3. This example provides a
relatively flat R(s)*T(p) function between 35 and 55 degrees
incident. In that range, the R(s)*T(p) function ranges from a
maximum of 67.9% to a minimum of 66.15%, or a delta of 1.74%
(.+-.0.87%). TABLE-US-00003 TABLE 3 Mechanical Optical Thickness
Layer Thickness Layer Index (quarter-waves at Number Material (nm)
(at 157.6 nm) 157.6 nm) exit medium CaF.sub.2 massive 1 MgF.sub.2
36.50 1.465 1.357 2 LaF.sub.3 7.94 1.78 0.359 3 MgF.sub.2 36.32
1.465 1.350 4 LaF.sub.3 16.76 1.78 0.757 5 MgF.sub.2 38.91 1.465
1.447 6 LaF3 14.25 1.78 0.644 7 MgF2 34.13 1.465 1.269 8 LaF3 22.09
1.78 0.998 9 MgF2 32.09 1.465 1.193 10 LaF3 23.17 1.78 1.047 11
MgF2 29.18 1.465 1.085 12 LaF3 22.79 1.78 1.030 13 MgF2 29.33 1.465
1.091 14 LaF3 24.78 1.78 1.120 15 MgF2 30.99 1.465 1.152 16 LaF3
25.57 1.78 1.155 17 MgF2 30.99 1.465 1.152 18 LaF3 23.80 1.78 1.075
19 MgF2 29.45 1.465 1.095 20 LaF3 21.68 1.78 0.979 21 MgF2 32.53
1.465 1.210 22 LaF3 25.53 1.78 1.153 23 MgF2 39.95 1.465 1.485 24
LaF3 29.40 1.78 1.328 25 MgF2 44.37 1.465 1.650 26 LaF3 28.78 1.78
1.300 27 MgF2 41.05 1.465 1.526 28 LaF3 25.76 1.78 1.164 29 MgF2
24.85 1.465 0.924 entrance CaF.sub.2 massive medium
[0056] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 5 in graphical form, and are illustrated in the Table 2
below in tabular form: TABLE-US-00004 TABLE 4 Wavelength 157.6 nm
Range 35-55 degrees Substrate CaF.sub.2 H LaF.sub.3 L MgF.sub.2
angle T(p) R(s) R(s) * T(p) 30.0 47.96 82.40 39.52 30.5 51.50 82.73
42.61 31.0 54.89 83.39 45.77 31.5 58.15 84.21 48.97 32.0 61.31
85.06 52.15 32.5 64.38 85.83 55.26 33.0 67.36 86.45 58.23 33.5
70.17 86.85 60.95 34.0 72.73 87.03 63.30 34.5 74.94 86.96 65.17
35.0 76.75 86.63 66.49 35.5 78.15 86.05 67.25 36.0 79.21 85.22
67.50 36.5 80.02 84.20 67.38 37.0 80.73 83.06 67.05 37.5 81.43
81.93 66.71 38.0 82.21 80.90 66.51 38.5 83.10 80.07 66.53 39.0
84.08 79.40 66.77 39.5 85.13 78.84 67.11 40.0 86.16 78.26 67.43
40.5 87.13 77.58 67.59 41.0 87.99 76.74 67.52 41.5 88.71 75.77
67.22 42.0 89.31 74.77 66.78 42.5 89.80 73.90 66.36 43.0 90.22
73.32 66.15 43.5 90.57 73.14 66.24 44.0 90.88 73.30 66.61 44.5
91.15 73.65 67.13 45.0 91.39 73.99 67.61 45.5 91.57 74.15 67.90
46.0 91.67 74.06 67.89 46.5 91.68 73.72 67.58 47.0 91.58 73.24
67.07 47.5 91.37 72.82 66.53 48.0 91.07 72.67 66.18 48.5 90.71
72.93 66.15 49.0 90.32 73.60 66.47 49.5 89.91 74.50 66.99 50.0
89.49 75.42 67.49 50.5 89.02 76.16 67.80 51.0 88.46 76.65 67.81
51.5 87.83 76.87 67.51 52.0 87.18 76.88 67.02 52.5 86.62 76.78
66.51 53.0 86.34 76.66 66.19 53.5 86.44 76.53 66.15 54.0 86.97
76.28 66.35 54.5 87.83 75.74 66.52 55.0 88.73 74.63 66.22 55.5
89.32 72.61 64.85 56.0 89.26 69.21 61.78 56.5 88.48 63.81 56.46
57.0 87.19 55.64 48.51 57.5 85.85 44.32 38.05 58.0 84.93 31.55
26.79 58.5 84.71 22.80 19.32 59.0 85.20 23.04 19.63 59.5 86.12
29.65 25.53 60.0 86.96 36.61 31.84 60.5 87.25 40.65 35.46 61.0
86.82 40.89 35.50 61.5 85.90 37.21 31.97 62.0 84.99 29.67 25.21
62.5 84.49 19.04 16.09 63.0 84.52 8.16 6.90 63.5 84.74 1.86 1.58
64.0 84.60 2.87 2.43 64.5 83.62 8.46 7.07 65.0 81.86 13.91
11.38
BEAMSPLITTER EXAMPLE 3
[0057] Table 5 below illustrates another example of a coating
interface 320 that satisfies the requirements of a flat R(s)*T(p)
apodization function using a total of 26 alternating layers (n=13)
of MgF.sub.2 and LaF.sub.3. This example provides a relatively flat
R(s)*T(p) function between 40 and 60 degrees incident. In that
range, the R(s)*T(p) function ranges from a maximum of 72.69% to a
minimum of 71.80% or a delta of 0.89% (.+-.0.445%). TABLE-US-00005
TABLE 5 Mechanical Optical Thickness Layer Thickness Layer Index
(quarter-waves at Number Material (nm) (at 157.6 nm) 157.6 nm) exit
medium CaF.sub.2 massive 1 MgF.sub.2 38.09 1.465 1.416 2 LaF.sub.3
8.56 1.78 0.387 3 MgF.sub.2 40.19 1.465 1.494 4 LaF.sub.3 25.39
1.78 1.147 5 MgF.sub.2 25.43 1.465 0.946 6 LaF.sub.3 20.00 1.78
0.904 7 MgF.sub.2 29.25 1.465 1.088 8 LaF.sub.3 27.49 1.78 1.242 9
MgF.sub.2 36.72 1.465 1.365 10 LaF.sub.3 16.23 1.78 0.733 11
MgF.sub.2 27.28 1.465 1.014 12 LaF.sub.3 29.49 1.78 1.332 13
MgF.sub.2 120.76 1.465 4.490 14 LaF.sub.3 30.60 1.78 1.382 15
MgF.sub.2 38.55 1.465 1.433 16 LaF.sub.3 30.80 1.78 1.391 17
MgF.sub.2 39.70 1.465 1.476 18 LaF.sub.3 31.34 1.78 1.416 19
MgF.sub.2 40.71 1.465 1.514 20 LaF.sub.3 30.44 1.78 1.375 21
MgF.sub.2 45.04 1.465 1.675 22 LaF.sub.3 21.30 1.78 0.962 23
MgF.sub.2 23.64 1.465 0.879 24 LaF.sub.3 8.82 1.78 0.398 25
MgF.sub.2 51.75 1.465 1.924 26 LaF.sub.3 25.88 1.78 1.169 entrance
CaF.sub.2 massive medium
[0058] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 6 in graphical form, and are illustrated in the Table 2
below in tabular form: TABLE-US-00006 TABLE 6 Wavelength 157.6 nm
Range 40-60 degrees Substrate CaF.sub.2 H LaF.sub.3 L MgF.sub.2
angle T(p) R(s) R(s) * T(p) 30.0 63.71 69.28 44.14 30.5 62.12 72.74
45.19 31.0 61.84 74.61 46.14 31.5 62.88 75.10 47.22 32.0 65.23
74.22 48.41 32.5 68.80 71.69 49.32 33.0 73.37 66.88 49.07 33.5
78.53 58.54 45.97 34.0 83.64 44.72 37.40 34.5 87.91 24.45 21.50
35.0 90.68 6.05 5.48 35.5 91.68 9.93 9.11 36.0 91.12 32.89 29.97
36.5 89.56 53.91 48.29 37.0 87.66 67.30 59.00 37.5 85.91 75.18
64.59 38.0 84.62 79.80 67.53 38.5 83.91 82.50 69.23 39.0 83.75
84.01 70.36 39.5 84.04 84.70 71.18 40.0 84.62 84.82 71.78 40.5
85.36 84.49 72.12 41.0 86.15 83.84 72.22 41.5 86.92 82.99 72.13
42.0 87.65 82.09 71.95 42.5 88.35 81.28 71.81 43.0 89.01 80.67
71.80 43.5 89.64 80.23 71.92 44.0 90.21 79.90 72.08 44.5 90.69
79.59 72.18 45.0 91.07 79.25 72.17 45.5 91.33 78.91 72.07 46.0
91.46 78.64 71.93 46.5 91.47 78.53 71.83 47.0 91.37 78.64 71.85
47.5 91.15 78.96 71.97 48.0 90.79 79.43 72.12 48.5 90.28 79.97
72.20 49.0 89.59 80.54 72.16 49.5 88.69 81.18 72.00 50.0 87.58
82.02 71.83 50.5 86.30 83.16 71.76 51.0 84.91 84.60 71.83 51.5
83.52 86.18 71.98 52.0 82.24 87.69 72.12 52.5 81.15 88.96 72.19
53.0 80.28 89.92 72.19 53.5 79.63 90.57 72.13 54.0 79.19 90.94
72.02 54.5 78.97 91.05 71.90 55.0 78.99 90.93 71.83 55.5 79.29
90.61 71.84 56.0 79.86 90.10 71.95 56.5 80.62 89.44 72.10 57.0
81.40 88.66 72.17 57.5 82.07 87.80 72.05 58.0 82.68 86.89 71.83
58.5 83.52 85.95 71.78 59.0 84.91 84.98 72.15 59.5 86.63 83.91
72.69 60.0 87.12 82.49 71.87 60.5 83.25 80.23 66.79 61.0 72.90
76.04 55.43 61.5 58.52 67.52 39.51 62.0 45.05 48.70 21.94 62.5
35.16 13.70 4.82 63.0 29.00 16.06 4.66 63.5 25.91 58.38 15.12 64.0
25.40 78.80 20.01 64.5 27.46 86.76 23.82 65.0 32.39 90.12 29.19
BEAMSPLITTER EXAMPLE 4
[0059] Table 7 below illustrates another example of a coating
interface 320 that satisfies the requirements of a flat R(s)*T(p)
apodization function using a total of 32 alternating layers (n=16)
of AlF.sub.3 and NdF.sub.3. This example provides a relatively flat
R(s)*T(p) function between 35 and 55 degrees incident. In that
range, the R(s)*T(p) function ranges from a maximum of 72.55% to a
minimum 71.24%, or a delta of 1.31% (.+-.0.655%). TABLE-US-00007
TABLE 7 Mechanical Optical Thickness Layer Thickness Layer Index
(quarter-waves at Number Material (nm) (at 157.6 nm) 193 nm) exit
medium CaF.sub.2 massive 1 NdF.sub.3 28.95 1.7 1.0200 2 AlF.sub.3
39.10 1.417 1.1483 3 NdF.sub.3 24.88 1.7 0.8766 4 AlF.sub.3 39.09
1.417 1.1480 5 NdF.sub.3 28.67 1.7 1.0101 6 AlF.sub.3 38.99 1.417
1.1451 7 NdF.sub.3 23.93 1.7 0.8431 8 AlF.sub.3 35.48 1.417 1.0420
9 NdF.sub.3 28.67 1.7 1.0101 10 AlF.sub.3 44.86 1.417 1.3174 11
NdF.sub.3 35.18 1.7 1.2395 12 AlF.sub.3 46.91 1.417 1.3776 13
NdF.sub.3 36.51 1.7 1.2864 14 AlF.sub.3 48.21 1.417 1.4158 15
NdF.sub.3 37.64 1.7 1.3262 16 AlF.sub.3 50.12 1.417 1.4719 17
NdF.sub.3 38.90 1.7 1.3706 18 AlF.sub.3 53.67 1.417 1.5762 19
NdF.sub.3 41.69 1.7 1.4689 20 AlF.sub.3 95.59 1.417 2.8073 21
NdF.sub.3 48.10 1.7 1.6947 22 AlF.sub.3 55.92 1.417 1.6423 23
NdF.sub.3 40.70 1.7 1.4340 24 AlF.sub.3 126.79 1.417 3.7236 25
NdF.sub.3 30.49 1.7 1.0743 26 AlF.sub.3 46.76 1.417 1.3732 27
NdF.sub.3 23.50 1.7 0.8280 28 AlF.sub.3 42.27 1.417 1.2414 29
NdF.sub.3 26.20 1.7 0.9231 30 AlF.sub.3 42.51 1.417 1.2484 31
NdF.sub.3 17.93 1.7 0.6317 32 AlF.sub.3 140.21 1.417 4.1177
entrance CaF.sub.2 massive medium
[0060] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 7 in graphical form, and are illustrated in the Table 8
below in tabular form: TABLE-US-00008 TABLE 8 Wavelength 193 nm
Range 35-55 degrees Substrate CaF.sub.2 H NdF.sub.3 L AlF.sub.3
angle T(p) R(s) R(s) * T(p) 30.0 44.49 89.57 39.85 30.5 45.29 89.66
40.60 31.0 48.52 88.81 43.08 31.5 54.32 86.62 47.06 32.0 62.78
81.91 51.42 32.5 73.33 71.24 52.24 33.0 84.11 44.86 37.73 33.5
92.02 2.27 2.09 34.0 94.70 29.38 27.83 34.5 92.54 66.24 61.30 35.0
88.02 81.04 71.33 35.5 83.48 87.12 72.73 36.0 80.13 89.90 72.03
36.5 78.27 91.18 71.37 37.0 77.73 91.65 71.24 37.5 78.13 91.58
71.55 38.0 79.05 91.09 72.01 38.5 80.17 90.26 72.36 39.0 81.30
89.15 72.48 39.5 82.43 87.88 72.44 40.0 83.58 86.58 72.36 40.5
84.81 85.34 72.37 41.0 86.13 84.13 72.46 41.5 87.50 82.90 72.54
42.0 88.87 81.61 72.53 42.5 90.17 80.34 72.44 43.0 91.35 79.22
72.37 43.5 92.37 78.38 72.39 44.0 93.21 77.78 72.50 44.5 93.88
77.28 72.55 45.0 94.38 76.71 72.41 45.5 94.71 76.07 72.04 46.0
94.87 75.51 71.63 46.5 94.85 75.30 71.43 47.0 94.70 75.56 71.56
47.5 94.47 76.13 71.91 48.0 94.21 76.70 72.26 48.5 93.98 77.05
72.41 49.0 93.76 77.10 72.30 49.5 93.52 77.01 72.02 50.0 93.17
77.01 71.75 50.5 92.62 77.32 71.61 51.0 91.80 78.01 71.61 51.5
90.64 79.04 71.63 52.0 89.16 80.32 71.61 52.5 87.49 81.80 71.56
53.0 85.80 83.39 71.55 53.5 84.26 84.97 71.60 54.0 82.90 86.48
71.69 54.5 81.61 87.87 71.71 55.0 80.20 89.14 71.49 55.5 78.33
90.27 70.71 56.0 75.36 91.20 68.73 56.5 70.40 91.87 64.68 57.0
63.00 92.21 58.10 57.5 54.11 92.16 49.87 58.0 45.72 91.74 41.94
58.5 39.42 91.35 36.01 59.0 35.88 91.88 32.96 59.5 35.19 93.20
32.79 60.0 37.40 94.28 35.26 60.5 42.56 94.80 40.35 61.0 50.07
94.83 47.49 61.5 57.74 94.41 54.52 62.0 62.06 93.47 58.01 62.5
60.65 91.77 55.66 63.0 53.77 88.93 47.82 63.5 44.08 84.65 37.31
64.0 35.18 79.69 28.03 64.5 29.30 76.59 22.44 65.0 26.97 78.20
21.09
BEAMSPLITTER EXAMPLE 5
[0061] Table 9 below illustrates another example of a coating
interface 320 for 193 nm that satisfies the requirements of a flat
R(s)*T(p) apodization function using a total of 30 alternating
layers (n=15) of AlF.sub.3 and NdF.sub.3. This example provides a
relatively flat R(s)*T(p) function between 35 and 55 degrees
incident. In that range, the R(s)*T(p) function ranges from a
maximum 74.60% to a minimum of 70.38%, or a delta of 4.33$
(.+-.2.11%). TABLE-US-00009 TABLE 9 Mechanical Optical Thickness
Layer Thickness Layer Index (quarter-waves at Number Material (nm)
(at 157.6 nm) 193 nm) exit fused silica massive medium 1 NdF.sub.3
26.46 1.7 0.9323 2 AlF.sub.3 23.86 1.417 0.7007 3 NdF.sub.3 33.23
1.7 1.1708 4 AlF.sub.3 44.51 1.417 1.3072 5 NdF.sub.3 27.74 1.7
0.9774 6 AlF.sub.3 27.66 1.417 0.8123 7 NdF.sub.3 31.81 1.7 1.1208
8 AlF.sub.3 58.21 1.417 1.7095 9 NdF.sub.3 4.19 1.7 0.1476 10
AlF.sub.3 49.37 1.417 1.4499 11 NdF.sub.3 39.27 1.7 1.3836 12
AlF.sub.3 43.00 1.417 1.2628 13 NdF.sub.3 40.45 1.7 1.4252 14
AlF.sub.3 43.96 1.417 1.2910 15 NdF.sub.3 41.24 1.7 1.4530 16
AlF.sub.3 44.88 1.417 1.3180 17 NdF.sub.3 41.57 1.7 1.4646 18
AlF.sub.3 45.85 1.417 1.3465 19 NdF.sub.3 42.57 1.7 1.4999 20
AlF.sub.3 65.98 1.417 1.9377 21 NdF.sub.3 70.52 1.7 2.4846 22
AlF.sub.3 60.70 1.417 1.7826 23 NdF.sub.3 41.06 1.7 1.4467 24
AlF.sub.3 122.77 1.417 3.6055 25 NdF.sub.3 51.95 1.7 1.8304 26
AlF.sub.3 40.83 1.417 1.1991 27 NdF.sub.3 7.85 1.7 0.2766 28
AlF.sub.3 61.42 1.417 1.8038 29 NdF.sub.3 96.34 1.7 3.3944 30
AlF.sub.3 123.13 1.417 3.6161 entrance fused silica massive
medium
[0062] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 8 in graphical form, and are illustrated in the Table 10
below in tabular form: TABLE-US-00010 TABLE 10 Wavelength 193 nm
Range 35-55 degrees Substrate fused silica H NdF.sub.3 L AlF.sub.3
angle T(p) R(s) R(s) * T(p) 30.0 63.31 77.30 48.94 30.5 64.24 76.82
49.35 31.0 67.59 73.70 49.81 31.5 73.17 66.26 48.48 32.0 80.32
50.57 40.62 32.5 87.57 22.59 19.79 33.0 92.81 8.04 7.46 33.5 94.47
37.85 35.76 34.0 92.68 64.77 60.03 34.5 89.04 77.91 69.37 35.0
85.31 84.09 71.74 35.5 82.57 87.09 71.91 36.0 81.16 88.44 71.77
36.5 80.96 88.78 71.88 37.0 81.63 88.39 72.15 37.5 82.76 87.41
72.34 38.0 84.03 86.00 72.27 38.5 85.31 84.40 72.00 39.0 86.56
82.95 71.80 39.5 87.83 81.82 71.87 40.0 89.14 80.89 72.11 40.5
90.43 79.93 72.28 41.0 91.62 78.83 72.23 41.5 92.63 77.71 71.98
42.0 93.40 76.84 71.76 42.5 93.94 76.42 71.79 43.0 94.27 76.41
72.03 43.5 94.44 76.50 72.25 44.0 94.50 76.45 72.24 44.5 94.43
76.26 72.01 45.0 94.23 76.15 71.75 45.5 93.85 76.40 71.71 46.0
93.32 77.04 71.90 46.5 92.70 77.83 72.15 47.0 92.09 78.45 72.24
47.5 91.52 78.78 72.10 48.0 91.00 78.92 71.81 48.5 90.38 79.25
71.63 49.0 89.48 80.19 71.75 49.5 88.11 81.82 72.09 50.0 86.26
83.77 72.27 50.5 84.28 85.50 72.06 51.0 82.80 86.62 71.72 51.5
82.57 86.88 71.73 52.0 83.99 86.04 72.26 52.5 86.74 83.77 72.66
53.0 89.69 80.03 71.78 53.5 91.59 76.84 70.38 54.0 92.04 78.08
71.86 54.5 90.69 82.25 74.60 55.0 84.32 85.21 71.85 55.5 68.51
85.56 58.62 56.0 47.66 83.36 39.73 56.5 31.16 84.45 26.31 57.0
21.39 91.43 19.56 57.5 16.45 94.99 15.63 58.0 14.61 96.15 14.04
58.5 15.24 96.33 14.68 59.0 18.89 95.92 18.12 59.5 27.56 94.84
26.13 60.0 43.58 92.61 40.36 60.5 59.39 88.45 52.53 61.0 54.07
83.58 45.19 61.5 29.58 84.97 25.13 62.0 11.69 90.40 10.57 62.5 4.76
93.82 4.47 63.0 2.36 94.86 2.24 63.5 1.49 95.34 1.42 64.0 1.21
97.88 1.19 64.5 1.35 98.57 1.33 65.0 2.33 98.89 2.30
BEAMSPLITTER EXAMPLE 6
[0063] Table 11 below illustrates another example of a coating
interface 320 for 157.6 nm that satisfies the requirements of a
flat R(s)*T(p) apodization function using a total of 21 alternating
layers of LaF.sub.3 and MgF.sub.2. This example provides a
relatively flat R(s)*T(p) function between 44 and 60 degrees
incident. In that range, the R(s)*T(p) function ranges from a
maximum 68.08% to a minimum of 67.95%, or a delta of 0.128%
(.+-.0.064%). TABLE-US-00011 TABLE 11 Index of refraction Thickness
Material (at 157.6) (nm) Exit medium CaF2 1.558 massive Layer 1
LaF3 1.78 6.58 Layer 2 MgF2 1.465 26.99 Layer 3 LaF3 1.78 26.67
Layer 4 MgF2 1.465 13.76 Layer 5 LaF3 1.78 43.26 Layer 6 MgF2 1.465
15.96 Layer 7 LaF3 1.78 26.76 Layer 8 MgF2 1.465 22.79 Layer 9 LaF3
1.78 30.06 Layer 10 MgF2 1.465 21.23 Layer 11 LaF3 1.78 41.81 Layer
12 MgF2 1.465 30.49 Layer 13 LaF3 1.78 39.32 Layer 14 MgF2 1.465
30.48 Layer 15 LaF3 1.78 40.11 Layer 16 MgF2 1.465 31.22 Layer 17
LaF3 1.78 47.42 Layer 18 MgF2 1.465 20.04 Layer 19 LaF3 1.78 28.12
Layer 20 MgF2 1.465 89.08 Layer 21 LaF3 1.78 45.99 Entrance medium
CaF2 1.558 massive
[0064] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 9 in graphical form, and are illustrated in the Table 12
below in tabular form: TABLE-US-00012 TABLE 12 Wavelength 157.6 nm
Range 44-60 degrees Substrate CaF.sub.2 H LaF.sub.3 L MgF.sub.2
Efficiency Angle R(s) T(p) (Rs * Tp) 30 58.9139 69.5322 40.96413078
30.5 59.2118 70.3769 41.67142927 31 58.9692 71.5766 42.20814841
31.5 58.1352 73.1124 42.50403996 32 56.6385 74.9485 42.44970617
32.5 54.387 77.0295 41.89403417 33 51.2722 79.278 40.64757472 33.5
47.1894 81.5955 38.50442688 34 42.0867 83.8674 35.29702104 34.5
36.0681 85.9728 31.00875548 35 29.5641 87.7991 25.95701372 35.5
23.5225 89.2587 20.99587771 36 19.4119 90.3033 17.52958629 36.5
18.7295 90.9307 17.03086546 37 22.0851 91.1835 20.13796716 37.5
28.6865 91.1384 26.14441712 38 36.8679 90.8907 33.50949239 38.5
45.0672 90.5386 40.80321194 39 52.3501 90.1693 47.20371872 39.5
58.3732 89.851 52.44890393 40 63.1419 89.6287 56.59326413 40.5
66.8075 89.5251 59.80948118 41 69.5546 89.5433 62.28148414 41.5
71.5537 89.6718 64.16349076 42 72.9471 89.8899 65.57207524 42.5
73.851 90.1731 66.59373608 43 74.3622 90.4966 67.29526269 43.5
74.5655 90.8379 67.73373432 44 74.5416 91.1777 67.96531642 44.5
74.3703 91.4985 68.04770895 45 74.1315 91.7828 68.03996638 45.5
73.9005 92.0117 67.99710636 46 73.7397 92.1631 67.96079345 46.5
73.6918 92.2131 67.95349323 47 73.7764 92.1366 67.97506656 47.5
73.9948 91.9112 68.00950862 48 74.3402 91.5192 68.03555632 48.5
74.8088 90.9504 68.03890284 49 75.4066 90.2031 68.0190908 49.5
76.1483 89.2848 67.98885736 50 77.0487 88.2121 67.96627629 50.5
78.1109 87.01 67.96429409 51 79.3161 85.712 67.98341563 51.5
80.6216 84.3595 68.01197865 52 81.9672 83.0007 68.03334977 52.5
83.2877 81.6874 68.03555665 53 84.5248 80.4707 68.01769823 53.5
85.6345 79.3955 67.98993945 54 86.5885 78.4947 67.96738331 54.5
87.3719 77.7853 67.96249453 55 87.9786 77.267 67.97842486 55.5
88.4071 76.9249 68.00707327 56 88.6567 76.7374 68.03284651 56.5
88.7245 76.6865 68.03971369 57 88.6036 76.7707 68.02160395 57.5
88.2817 77.0131 67.9884739 58 87.7394 77.4623 67.96495725 58.5
86.9495 78.1816 67.97851029 59 85.8754 79.2247 68.03452802 59.5
84.4685 80.5999 68.08152653 60 82.6643 82.2249 67.97063801 60.5
80.3745 83.8828 67.42038109 61 77.4752 85.2016 66.01011 61.5
73.7899 85.6985 63.23683745 62 69.0744 84.9216 58.65908567 62.5
63.0206 82.6559 52.09024412 63 55.3373 79.0697 43.7550371 63.5
46.0352 74.6757 34.37710785 64 36.0758 70.1277 25.2991288 64.5
28.1251 65.998 18.5620035 65 25.8553 62.6575 16.2002846 P-V
0.128033306 (44-60)
BEAMSPLITTER EXAMPLE 7
[0065] Table 13 below illustrates another example of a coating
interface 320 for 157.6 nm that satisfies the requirements of a
flat R(s)*T(p) apodization function using a total of 11 alternating
layers of LaF.sub.3 and MgF.sub.2. This example provides a
relatively flat R(s)*T(p) function between 44 and 60 degrees
incident. In that range, the R(s)*T(p) function ranges from a
maximum 63.11% to a minimum of 62.897%, or a delta of 0.21%
(.+-.0.1%). TABLE-US-00013 TABLE 13 Index of refraction Material
(at 157.6) (nm) Exit medium CaF2 1.558 massive Layer 1 LaF3 1.78
58.48 Layer 2 MgF2 1.465 60.07 Layer 3 LaF3 1.78 55.11 Layer 4 MgF2
1.465 47.98 Layer 5 LaF3 1.78 31.71 Layer 6 MgF2 1.465 40.26 Layer
7 LaF3 1.78 31 Layer 8 MgF2 1.465 38.79 Layer 9 LaF3 1.78 27.29
Layer 10 MgF2 1.465 37.73 Layer 11 LaF3 1.78 65.71 Entrance medium
CaF2 1.558 massive
[0066] The R(s), T(p) and the overall R(s)*T(p) functions are shown
in FIG. 10 in graphical form, and are illustrated in the Table 14
below in tabular form: TABLE-US-00014 TABLE 14 Wavelength 157.6 nm
Range 44-60 degrees Substrate CaF.sub.2 H LaF.sub.3 L MgF.sub.2
Efficiency Angle R(s) T(p) (Rs * Tp) 30 4.2925 94.1131 4.039804818
30.5 4.9315 94.151 4.643056565 31 6.2593 94.054 5.887122022 31.5
8.34 93.8199 7.82457966 32 11.1766 93.4551 10.44510271 32.5 14.7035
92.9743 13.6704762 33 18.7935 92.3995 17.36510003 33.5 23.2756
91.7586 21.3573647 34 27.9613 91.0837 25.46818661 34.5 32.6691
90.4083 29.53557794 35 37.2438 89.7656 33.43212053 35.5 41.5667
89.1865 37.0718849 36 45.5572 88.698 40.40832526 36.5 49.1694
88.3219 43.4273483 37 52.385 88.0741 46.13761729 37.5 55.2061
87.9641 48.56154901 38 57.6482 87.9947 50.72736065 38.5 59.7349
88.1623 52.66366174 39 61.4939 88.457 54.39565912 39.5 62.9544
88.8633 55.94335734 40 64.1456 89.3609 57.32108547 40.5 65.0956
89.9258 58.53773906 41 65.8314 90.5318 59.59835139 41.5 66.3789
91.1519 60.50562855 42 66.7633 91.76 61.26200408 42.5 67.0091
92.3328 61.87137828 43 67.1408 92.8507 62.34070279 43.5 67.1827
93.2989 62.68072009 44 67.1593 93.668 62.90677312 44.5 67.0943
93.9534 63.03737606 45 67.0105 94.1549 63.09366926 45.5 66.929
94.2753 63.09751554 46 66.8681 94.3193 63.06952384 46.5 66.8428
94.2921 63.02747982 47 66.8641 94.1984 62.98491237 47.5 66.9396
94.0412 62.95080312 48 67.0734 93.8216 62.92933705 48.5 67.2673
93.5386 62.92089068 49 67.522 93.1893 62.92327915 49.5 67.8382
92.769 62.93281976 50 68.218 92.2721 62.94618118 50.5 68.6649
91.6927 62.96070076 51 69.1845 91.0251 62.97526031 51.5 69.7837
90.2651 62.99032659 52 70.4695 89.4101 63.00685042 52.5 71.2471
88.4607 63.02568339 53 72.118 87.421 63.04627678 53.5 73.0774
86.3001 63.06586928 54 74.1132 85.1126 63.07967146 54.5 75.205
83.8797 63.08172839 55 76.3256 82.6292 63.06723268 55.5 77.4426
81.3954 63.03471404 56 78.5213 80.2182 62.98837348 56.5 79.5277
79.1413 62.93925564 57 80.4303 78.2084 62.90325075 57.5 81.2007
77.4598 62.89789982 58 81.8137 76.9248 62.9350251 58.5 82.2453
76.614 63.01141414 59 82.47 76.5069 63.09524043 59.5 82.4576
76.5366 63.11024348 60 82.168 76.572 62.91768096 60.5 81.5458
76.4036 62.30392685 61 80.5115 75.743 60.98182545 61.5 78.9521
74.2563 58.62690823 62 76.7092 71.6439 54.95746254 62.5 73.574
67.7567 49.85131446 63 69.3133 62.6944 43.45555756 63.5 63.7968
56.8124 36.2444932 64 57.3686 50.6164 29.03792005 64.5 51.5131
44.6044 22.97710918 65 49.0297 39.1471 19.19370569 P-V 0.212343663
(44-60)
[0067] While specific embodiments of the present invention have
been described above, it should be understood that they have been
presented by way of example only, and not limitation. It will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the invention as defined in the appended claims. Thus,
the breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims and
their equivalents.
* * * * *