U.S. patent application number 10/808360 was filed with the patent office on 2004-09-16 for optical cube.
This patent application is currently assigned to ASML US, Inc.. Invention is credited to Edlou, Samad M., Peterson, David H..
Application Number | 20040179260 10/808360 |
Document ID | / |
Family ID | 31993528 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040179260 |
Kind Code |
A1 |
Edlou, Samad M. ; et
al. |
September 16, 2004 |
Optical cube
Abstract
A cube used to perform optical functions in a system, such as
beam splitting or polarizing, or both, is manufactured by optically
contacting a coated prism with an uncoated prism. The coated prism
includes a dielectric stack having alternating layers of high and
low index of refraction materials. To ensure secure optical
contacting between the coated prism and uncoated prism, low
interface reflection, and good throughput, a contacting layer is
deposited on the dielectric stack. The contacting layer can be
fused silica or SiO.sub.2, which has natural compatibility with the
CaF.sub.2 materials that make up the uncoated prism and the coating
layers.
Inventors: |
Edlou, Samad M.; (Danbury,
CT) ; Peterson, David H.; (Milford, CT) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX PLLC
1100 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
ASML US, Inc.
|
Family ID: |
31993528 |
Appl. No.: |
10/808360 |
Filed: |
March 25, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10808360 |
Mar 25, 2004 |
|
|
|
10260308 |
Oct 1, 2002 |
|
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Current U.S.
Class: |
359/349 ;
359/237 |
Current CPC
Class: |
G02B 27/283 20130101;
G02B 27/142 20130101 |
Class at
Publication: |
359/349 ;
359/237 |
International
Class: |
G02B 026/00 |
Claims
What is claimed is:
1. A cube comprising: an uncoated prism; a coated prism coupled to
said uncoated prism, the coated prism including, a first coating
section having a multi-layered coating, and a second coating
section formed on top of said first coating section, said second
coating section having a contact layer coating.
2. The cube of claim 1, wherein said contact layer coating is a
SiO.sub.2 coating.
3. The cube of claim 1, wherein said contact layer coating is a
fused silica coating.
4. The cube of claim 1, wherein the cube is a polarizing cube.
5. The cube of claim 1, wherein the cube is a beam splitter.
6. An optical device comprising: an uncoated optical element; a
coated optical element coupled to a surface of said uncoated
optical element, the coated optical element including, a
multi-layered coating formed on said surface, and a contact layer
coating formed on said multi-layered coating.
7. The device of claim 6, wherein said contact layer coating is a
SiO.sub.2 coating.
8. The device of claim 6, wherein said contact layer coating is a
fused silica coating.
9. The device of claim 6, wherein said uncoated and said coated
optical elements are prisms.
10. The device of claim 6, wherein said uncoated optical element
and said coated optical element are coupled together to form a
polarizing cube.
11. The device of claim 6, wherein said uncoated optical element
and said coated optical element are coupled together to form a beam
splitter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. Ser. No. 10/260,308
to Edlou et al., entitled "Cube and Method of Making Same," filed
Oct. 1, 2002, which is incorporated by reference herein in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a cube and method of making
same.
[0004] 2. Background Art
[0005] Generally, to make a polarizing cube or a beam splitting
cube a prism with a coating (e.g., a dielectric stack) is optically
contacted (e.g., bonded) to an uncoated prism. Many parameters must
be taken into consideration when optically contacting the prisms to
ensure they remain bonded and that they have a certain amount of
optical compatibility. Being compatible ensures the lowest amount
of reflection occurs when light travels between the bonded
surfaces. Problems with adherence and reflection are more common
with cubes manufactured for systems using shorter wavelengths of
light (e.g., vacuum ultra violet (VUV) and deep ultra violet (DUV)
light). In the case of cubes used in VUV and DUV systems, the
materials available to manufacture the cubes are very limited for
performance reasons, and are typically not conductive to optical
contacting. To compound the problem, there are strict environmental
parameters that must be maintained for DUV applications that are
contrary to current contacting techniques. To overcome these
problems, different types of contacting processes have been
developed. However, these processes have produced other problems,
such as low throughput that can dramatically reduce the
effectiveness of the system. For example, in a lithography system
the output light is too weak to write patterns on a substrate.
[0006] Therefore, what is needed is a process of making a cube that
can be used with any wavelength of light in which the bonded prisms
are securely optically contacted and optically compatible, which
substantially eliminates any reflectivity between bonded surfaces
and increases throughput of light in a system using the cube.
BRIEF SUMMARY OF THE INVENTION
[0007] An embodiment of the present invention provides a method of
making a cube. The method includes the steps of performing a
multi-layer coating process to form a multi-layer coating on a
prism, performing a contact layer coating process to form a contact
layer coating on top of the multi-layer coating, and coupling the
prism to an uncoated prism. The contacting layer coating process
includes the step of forming a silicon dioxide (SiO.sub.2) or fused
silica layer as the contact layer.
[0008] Another embodiment of the present invention provides a cube
including an uncoated prism and a coated prism coupled to the
uncoated prism. The coated prism includes a first coating section
having a multi-layered coating and a second coating section formed
on top of the first coating section. The second coating section has
a contact layer coating, which can be a SiO.sub.2 or fused silica
coating.
[0009] An advantage of the cube made by the process according to
embodiments of the present invention is that it allows for secure
bonding between an uncoated and coated prism though use of the
contact layer, while still providing high throughput and low
reflection between bonded surfaces.
[0010] Further embodiments, features, and advantages of the present
inventions, as well as the structure and operation of the various
embodiments of the present invention, are described in detail below
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0011] 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.
[0012] FIG. 1 shows an exemplary environment in which a cube
according to embodiments of the present invention is used.
[0013] FIG. 2 shows a perspective view of an exemplary cube formed
by two prisms according to embodiments of the present
invention.
[0014] FIG. 3 is an exploded view showing the two prisms used to
form the cube of FIG. 2.
[0015] FIG. 4 is a cross-section of a portion of one of the two
prisms in FIGS. 2-3.
[0016] FIG. 5 shows an exemplary vacuum chamber used during part of
a process that forms a cube according to embodiments of the present
invention.
[0017] FIG. 6 shows a flow chart depicting method steps for a
process used to form a cube according to embodiments of the present
invention.
[0018] FIG. 7 shows a more detailed flow chart depicting method
steps used during the process of FIG. 6.
[0019] 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.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Embodiments of the present invention provide a cube used to
perform optical functions in a system, such as beam splitting or
polarizing, or both, that is manufactured by optically contacting a
coated prism with an uncoated prism. The coated prism includes a
dielectric stack having alternating layers of high and low index of
refraction materials. To ensure secure optical contacting between
the coated prism and uncoated prism, low interface reflection, and
good throughput, a contacting layer is deposited on the dielectric
stack. The contacting layer can be fused silica or silicon dioxide
(SiO.sub.2), which have natural compatibility with the calcium
fluoride (CaF.sub.2) materials that make up the uncoated prism.
[0021] A system 100 utilizing a cube 102 manufactured according to
embodiments of the present invention is shown in FIG. 1. The system
100 includes a laser 104 that emits light through a beam
conditioner 106, a reticle 108, and projection optics 110. After
passing through the projection optics 110, the light is reflected
by a portion of the cube 102 towards a reflector 112. The reflector
112 reflects the light back through the cube 102 and through wafer
group optics 114 onto a wafer 116 to write a pattern on the wafer
116. Although shown in a lithography environment, any system
requiring the cube 102 to perform various optical functions (e.g.,
polarization, beam splitting, etc.) falls within the scope of the
embodiments of the present invention.
[0022] As seen in FIGS. 2-3, the cube 102 is formed by coupling a
coated optical element 200A to an uncoated optical element 200B
according to an embodiment of the present invention. As best
illustrated in FIG. 3, a surface 300 of prism 200A and a surface
302 of prism 200B are coupled together during an optical contacting
process, which is discussed in more detail below. It is to be
appreciated that in some embodiments optical element 200A can be
uncoated and optical element 200B can be coated. In an embodiment,
the optical elements 200 are prisms made from CaF.sub.2 with
similar dimensions, although other embodiments utilize prisms 200
of different dimensions and compositions. In one embodiment, the
prisms 200 have about .alpha.1=.alpha.2=45.degree. and
.alpha.3=90.degree., while in another embodiment the prisms 200
have about .alpha.1=.alpha.2=52.degree. and
.alpha.3=76.degree..
[0023] As seen in FIG. 4, one of the prisms 200A has a dielectric
stack 400 deposited onto a main body 402 of the prism 200A. The
dielectric stack 400 includes multiple and alternating layers of
high 404 and low 406 index of refraction materials. These layers
404 and 406 are deposited onto the main body 402 of the prism 200
during a multi-layer coating process 604, discussed in more detail
below. The dielectric stack 400 can contain a plurality (e.g.,
20-50) of layers having with each layer being 500 mm-2 micron
thick, depending on the environment in which the cube 102 is used.
In some embodiments utilizing light having a wavelength of 157 nm,
the high index of refraction material is gadolinium fluoride
(GdF.sub.3) or lanthium fluoride (LaF.sub.3) and the low index of
refraction material is magnesium fluoride (MgF.sub.3). In other
embodiments utilizing light having a wavelength of 193 nm, the high
index of refraction material is neodymium fluoride (NdF.sub.3) and
the low index of refraction material is aluminum fluoride
(AlF.sub.3). In alternative embodiments, other materials with the
same properties as those described above can be used.
[0024] With continuing reference to FIG. 4, a contact layer 408 is
deposited on top of the dielectric stack 400 during a contact layer
depositing process 606, discussed in more detail below. The contact
layer 408 can be a fused silica or SiO.sub.2 layer. The contact
layer 408 is a naturally compatible material with the CaF.sub.2
material of the uncoated prism 200B. This allows for secure
glass-to-glass bonding between the two prisms 200, while ensuring
there is little to no interface reflection.
[0025] Now turning to FIG. 5, a vacuum chamber 500 according to an
embodiment of the present invention is shown. The vacuum chamber
500 includes a coating nest 502 that holds the prism 200 during
deposition operations. In various embodiments, either a sputter
device 504 (e.g., sputter gun) or a electron beam device 506 (e.g.,
electron beam gun), or both can be used to deposit materials that
form the dielectric stack 400 and the contacting layer 408 on the
coated prism 200A. It is to be appreciated, other deposition
devices can be used to form the cube 102.
[0026] FIG. 6 shows a method 600 for forming the cube 102 according
to embodiments of the present invention. At step 602, the prisms
200A-B, which are received from a manufacturer in raw material
form, are processed. At step 604, a multi-layer coating process is
performed to build the dielectric stack 400 on the main body 402 of
the coated prism 200A. At step 606, a contact layer coating process
is performed that deposits a contact layer 408 on the dielectric
stack 400. At step 608, an optical contacting process is performed
that couples the coated prism 200A to the uncoated prism 200B. The
method 600 ends at step 610.
[0027] FIG. 7 shows more detailed method steps for method 600
according to embodiments of the present invention. During the
processing step 602, the prisms 200A-B are receive in as raw
material at step 700. At step 702, the prisms 200A-B are polished
until they conform to end-user specified parameters (e.g.,
wavelength, dimensions, etc.). The prisms 200A-B are cleaned at
step 704 and inspected at step 706 to ensure they meet the end-user
specifications.
[0028] During the multi-layer coating process 604, the prism 200A
that will become a coated prism is placed in the vacuum chamber 500
at step 708. A multi-layer coating process is performed at step
710. During this process alternating deposition of a layer of high
index of refraction material 404 and a layer of low index of
refraction material 406 forms the dielectric stack 400. The
deposition process can be performed by electron beam evaporation,
ion beam sputtering, resistance source evaporation, or any other
known deposition method. The coated prism 200A is cooled at step
721 and inspected at step 714.
[0029] During the contact layer forming process 606, the coated
prism 200A is again placed in the vacuum chamber 500 at step 716. A
contacting layer 408 (e.g., a fused silica or SiO.sub.2 layer) is
deposited at step 718. The specific process used to deposit the
contacting layer 408 is chosen based on the end use of the cube
102. In embodiments when an end-user's system will be using light
in the 157 nm range, the contact layer 408 is deposited with a
magnetron sputtering process or an ion beam sputtering process.
This ensures there will be high throughput of 157 nm light through
the cube 102, (i.e., there will be very little absorption of 157 nm
light through the cube 102). If throughput is not a concern for the
end-user, then other deposition methods (e.g., electron beam
evaporation or resistive source evaporation) can be used. In
embodiments when an end-user's system will be using light in the
193 nm range, the contact layer 408 will be deposited with an
electron beam evaporation process for good throughput of 193 nm
light. Again, where throughput is not a concern, any deposition
process can be used. The coated prism 200A is cooled at step 720
and inspected at step 722.
[0030] In alternative embodiments, coated prism 200A can remain in
vacuum chamber 500 after multi-layer coating process 604. In these
embodiments, contact layer forming process 606 can be immediately
performed without any intervening steps.
[0031] During the contacting process 608, the prisms 200A-B are
prepared (e.g., cleaned and positioned) at step 724. At step 726,
the prisms 200A-B are optically contacted to securely bond surfaces
300 and 302 together. In some embodiments this is accomplished
through glass-to-glass bonding. In other embodiments, other bonding
techniques can be used.
CONCLUSION
[0032] While various 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
apparent to persons skilled in the relevant art that various
changes in form and detail can be made therein without departing
from the spirit and scope of the invention. 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.
* * * * *