STC.UNM v. Intel Corporation

Filing 133

MARKMAN RESPONSE BRIEF re 110 Brief filed by STC. UNM. (Attachments: # 1 Exhibit 3 - IEDM Article, # 2 Exhibit 4 - Semiconductor International Article, # 3 Exhibit 5 - 998 Response and Amendment 01141999, # 4 Exhibit 6 - 998 Response and Amendment 05181999, # 5 Exhibit 7 - Declaration of Dr. Chris Mack)(Pedersen, Steven)

Exhibit 6 
Response and Amendment, May 18, 1999 

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IN THE UNITED STATES PATENT AND
TRADEMARK OFFICE

Applicants:

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08/932,428

1752

Filing Date:
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28516.1100

Serial No.:
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Steven R.J. Brueck et a

September 17, 1997

Jill Hackathorn

TITLE~n\\p~~.1IMETHOD AND APPARATUS FOR EXTENDING SPATIAL

REGIE» '(J bl!,JlFREQUENCIES IN PHOTOLITHOGRAPHY IMAGES

MAY 25 1998
RESPONSE AND AMENDMENT

Assistant Commissioner of Patents
Box: Non-Fee Amendment
Washington, D.C. 20231
Dear Assistant Commissioner:
In response to the Final Office Action mailed March 18, 1999, of which this Response is

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within the shortened statutory three month response period, please amend the above reference
application as follows:

IN THE SPECIFICATION:

-_page 17, line 23 at the end, insert:

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() with a preferred embodiment of the present invention.

Figure 11 D shows an exemplary narrow line having superior vertical sidewalls which

"~~ ~ was produced by very high spatial frequencies achieved from the nonlinearities in accordance

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Figure liE shows a concept drawing of an exemplary two color separation for a typical

~ SRAM circuit pattern demonstrating the possibilities for using spatial frequency doubling to
enhance the pattern density. --.

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Page 26, line 27, at the end, insert:

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Iscussed above, nonlinearities allow the extension of optics beyond the linear
systems limit. As such, higher spatial frequencies can be accessed by taking advantage of
nonlinearities in processing. In other words, the linear systems constraints apply to pattern
frequencies, not to linewidths. This is dramatically illustrated by the micrograph in Fig. 11 D that
shows a 50-nm CD line on a 2-llm pitch, a line:space ratio of 1:20. The very high spatial
frequencies corresponding to this narrow line are the result of photoresist process nonlinearities,
the exposure aerial image was a 2-llm period sine wave. Importantly, the process latitude for
printing this fine line was much greater than that for printing the 150-nm dense line:space
pattern. This is a superior result in that it is always more difficult to print 1: 1 patterns since these
occur very near the threshold dose for developing all the way through the resist. Larger
line:space ratios are closer to saturation where the process is very forgiving of small dose
variations and the nonlinearities (vertical sidewalls) are larger. Thus, it is easier (greater process
latitude) to print smaller CD structures at a fixed pitch.
Fig. 11 E shows,! concept drawing of how the aforementioned frequency doubling
technique might be applied to a circuit pattern, in this case a typical SRAM pattern. The two
colors indicate the patterns written in each exposure. No two features of the same color approach
each other by less than 1.5CD. The spacing is less than 2 CD because of the staggered features
in the SRAM pattern, so changing the design to a CD grid would allow a straightforward
doubling of the pattern density.

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IN THE CLAIMS:

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Please amend the claims as follows:
1. (Twice Amended) A method for obtaining a patter1)LcQRotainiag high spatial
frequencies by combining nonlinear functions of intensity of ~ 'least two exposures combined

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with [an] at least one nonlinear processing step intermediate between the two exposures to form
three dimensional patterns comprising the steps of:
coating a substrate with a first photoresist layer;

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exposing said first photoresist layer with a first exposure;
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developing said first photoresist layer to fonn a first [image] pattern in said first

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photoresist layer, said first [image] pattern containing spatial frequencies greater than those in

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[an aerial image] a two dimensional optical intensity image imposed onto said photoresist layer
in said first exposure as a result of a nonlinear response of said first photoresist layer;

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coating said substrate with a second photoresist layer;

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exposing said second photoresist layer with a second exposure;

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developing said second photoresist layer to fonn a second [image] pattern in said second

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photoresist layer, said second [image] pattern containing spatial frequencies greater than those in

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[an aerial image] a two dimensional optical intensity image imposed onto said photoresist layer

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in said second exposure as a result of a nonlinear response of said second photoresist layer;
combining said [images] patterns to provide a final [image] pattern.

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6. (Twice Amended) A method for obtaining a patter~~lItaiIliIig high spatial
frequencies by combining nonlinear functions of intensity of at least two exposures combined
with [an] at least one nonlinear processing step intermediate between the two exposures to form
three dimensional patterns comprising the steps of:

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coating a substrate with a first mask material and a first photoresist layer;

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exposing said first photoresist layer with a first exposure

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developing said photoresist to form a first [image] pattern in said first photoresist layer,

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said first [image] pattern containing spatial frequencies greater than those in [aerial image] a two

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dimensional optical intensity image imposed onto said photoresist layer in said first exposure as
a result of a nonlinear response of said first photoresist layer;

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transferring said first [image] pattern into said first mask material, said first mask material

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comprising at least one of Si0 2, Si3N 4, a metal, a polysilicon and a polymer;

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coating said substrate with a second photoresist;

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exposing said second photoresist with a second exposure

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developing said second photoresist layer to fonn a second [image] pattern in said second
photoresist layer, said second [image] pattern containing spatial frequencies greater than those in

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[aerial image] a two dimensional optical intensitv image imposed onto said photoresist layer in

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said second exposure as a result of a nonlinear response of said second photoresist layer.;
transferring said first [image] pattern and said second [image] pattern into said substrate

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using a combined mask including parts of said first mask layer and said second photoresist;
removing said first mask material and said second photoresist.

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(Amended) A method for increasing spatial frequencYA.,,0f lithographic patterns

comprising the steps of:

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depositing a material;

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depositing a photoresist on said material;

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exposing a periodic [pattern] image in said photoresist, said periodic [pattern] image

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having a pitch Pmi" and a linewidth less than Pmi,/2;

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developing said periodic [pattern] image to form a periodic pattern in said photoresist;

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transferring said periodic pattern to said material;

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depositing a second photoresist layer on said material;

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offsetting said periodic pattern by Pmj2;

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repeating said exposing, developing and transferring steps, thereby interpolating new said

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pattern midway between said pattern.

(Amended)

The method of claim 1, wherein a minimum of said spatial

frequencies along at least one direction in said first or second [image] pattern is smaller than 2/)...

REMARKS

Applicant responds to the Office Action mailed March 18, 1999, of which this Response
is within the shortened statutory three month response period. Claims 1,4-7, 15-23,25-40,48
and 49 are pending in the present Application and the Examiner rejects all of the aforementioned
claims.

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The Examiner objects to the disclosure due to the blank lines on page 1. Applicant
thanks the Examiner for the reminder to provide this information before issuance. The Examiner
next objects to Claims 1 and 6 due to a typographical error. As suggested by the Examiner,
Applicant amends Claims 1 and 6 by changing "an least" to "at least".
The Examiner next rejects Claims 1 and 4-7 under 35 U.S.C. § 112 because the Examiner
asserts that the Claims include subject matter not in the present specification. Applicant
respectfully traverses this rejection. Application asserts that the term "aerial image" is
commonly used in the art to refer to the two-dimensional optical intensity image incident on the
photoresist layer. The disclosure of an optical intensity image incident on a photoresist layer is
adequately supported in the spec, inter alia, page 10, lines 16- 30; page 14, lines 7- 12; page 18,
lines 10- 25; and, page 23, lines 1- 3. However, to further clarify the Claim language,.Applicant
deletes the phrase "aerial image" and inserts the phrase "two-dimensional optical intensity image
imposed onto said photoresist layer" in Claims 1 and 6. Moreover, to help clarify the Claim
language, Applicant amends the Claims to use the term "pattern" to refer to the result of the
expose/develop step and the term "image" to refer to the aerial image input of the
photolithography step.
The Examiner next rejects Claims 1 and 4-7 under 35 U.S.C. § 112 because certain terms
are unclear. The Examiner asserts that it is unclear how a pattern can "contain" spatial
frequencies. Applicant respectfully traverses this rejection. A primary goal of the present
invention is to achieve a desired pattern. It is well known in the art that any pattern can be
equivalently described by specifying the amplitudes and phases of the spatial frequencies in the
pattern's Fourier transform. Thus, the present application discloses a method for producing a
desired pattern which contains a desired spatial frequency content comprising the amplitudes and
phases of the spatial frequencies in the pattern's Fourier transform.
The Examiner next ,asserts that "nonlinear processing step" is unclear. As discussed
above, the present invention discloses a method for producing a desired pattern. Because of the
bandpass constraints of an optical system, the spatial frequencies in the aerial image are restricted
(due to the diffraction limits) to be at spatial frequencies less than 2 NA/A, wherein NA is the
numerical aperture of the optical system (imaging lens) and A is the optical wavelength. In
28516, I 100/662153

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interferometric lithography, an imaging lens is not required and the maximum spatial frequency
in the aerial image is 2/1... Thus, a preferred embodiment of the present invention specifies a
process for producing patterns with spatial frequencies larger than the aforementioned
limitations.
Particularly, a "linear process" reproduces only the spatial frequencies in the previous
step (not necessarily with fidelity in amplitude and phase), wherein the previous step is the aerial
image. Therefore, a linear development step would result in a photoresist profile whose Fourier
transform contains only those frequencies present in the aerial image. For example, in the simple
case of a two beam interferometric lithography exposure, as described in Figure 5 of the
specification, the aerial image contains only 3 spatial frequencies at 0, +2k sin8 and -2ksin8,
wherein k=1/A and 28 is the angle between the incident beams because a linear photoresist
development process yields a sinusoidal photoresist profile. In other words, a linear process is
one in which the Fourier transform of the output (e.g., developed photoresist pattern for a
photolithography expose/develop sequence) contains only those spatial frequencies that were
present in the Fourier transform of the input (aerial image for the photolithography step).
1Ii contrast, a "nonlinear process" is a process in

~hich

the Fourier transform of the

output contains spatial frequencies that were not present in the Fourier transform of the input.
For example, the higher harmonics of the frequencies in the aerial image are present in the output
but not in the original aerial image. By obtaining the higher spatial frequencies using the
nonlinear process, the presently claimed invention can create smaller features because the higher
spatial frequencies correspond to the smaller features. As is best shown in Figure 5 of the
present application, the nonlinearity associated with the photoresist exposure and development
process produces higher harmonics (multiples) of the fundamental frequency in the aerial image.
As is known in the art, the higher harmonics allows the sharpening of the sidewalls.
The Examiner asserts that it is unclear how the first or second images can have spatial
frequencies greater than those in the aerial images. For clarification, the nonlinearity does not
produce a pattern with more lines; rather, the number of lines is fixed by the spatial frequency of
the optical exposure (aerial image). However, Applicant asserts that changing the line-to-space

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ratio of the photoresist pattern by changing the exposure parameters, changes the relative
intensities of the spatial frequency components in the Fourier transform.
Moreover, to respond the Examiner's questions about the procedure and to clarify the
explanation of the nonlinearity process, Applicant adds text and Figure examples of applying
nonlinearities to structures. Particularly, the text and Figures describe the use of nonlinearities
for producing high frequencies thereby achieving, for example, a narrow line with superior
vertical walls, as shown

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Figure 110 (the micrograph was produced before the filing ofthe

present patent application), and a typical SRAM circuit pattern with enhanced pattern density, as
shown in the concept drawing of Figure lIE. Because the text and Figures simply provide
further examples to clarify the previously disclosed frequency multiplying techniques, no new
matter is added by the text or Figure amendments.
The Examiner next asserts that Claims 1, 6, 15 and 27 are rejected under the judicially
created doctrine of double patenting over Claim 1 of U.S. Patent No. 5,705,321. Applicant
respectfully traverses this rejection. Applicant asserts that the use of frequency doubling to
obtain a denser pattern and the redistribution of Fourier intensities to obtain square two
dimensional holes at the resolution limit with square profiles, as disclosed in the presently
claimed invention, is not disclosed in the '321 Patent. However, in order to expedite prosecution
of this case, Applicant submits with this Response a Terminal Disclaimer in compliance with 37
CFR 1.32l(c).
The Examiner next rejects Claims 1,4-7,15,17-20,23,25-27,29-32,35-37 and 39 under
35 U.S.c. § 102(e) as being anticipated by Brueck, et al. (U.S. Patent No. 5,705,321). Applicant
respectfully traverses this rejection. As set forth above, Applicant submits a Terminal
Disclaimer with respect to the '321 Patent; therefore, the Examiner's rejection with respect to the
'321 Patent is now moot.
The Examiner next rejects Claims 16,28,40,48 and 49 under 35 U.S.C. § 103(a) as
being unpatentable over Brueck (U.S. Patent No.5,705,321) as applied to the aforementioned
Claims, and further in view of Gardner, et al. (U.S. Patent No. 5,801,075). Applicant
respectfully traverses this rejection. As set forth above, Applicant files a Terminal Disclaimer
with this response; therefore, this rejection is now moot. Moreover, while the '321 Patent
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discloses the results of a first exposure and develop step (e.g., line width much less than p/2), the
presently claimed invention obtains fine lines which are closer to each other. The disclosure of
the' 321 Patent uses additional exposures to isolate areas or otherwise incorporate lower
frequency information. In contrast, the presently claimed invention repeats the exposure with a
phase shift.
The Examiner next rejects Claims 21 and 33 under 35 U.S.c. § 103(a) as being
unpatentable over Brueck and further in view of Ausschnitt (U.S. Patent No. 5,790,254).
Applicant respectfully traverses this rejection. As set forth above, Applicant submits with this
response a Terminal Disclaimer; therefore, the rejection is now moot.
The Examiner next rejects Claims 22 and 34 under 35 U.S.C. § 103(a) as being
unpatentable over Brueck and further in view of Hosono, et al. (U.S. Patent No. 5,486,449).
Applicant respectfully traverses this rejection. As set forth above, Applicant submits with this
response a Terminal Disclaimer with respect to the Brueck reference; therefore, the rejection is
now moot.
The Examiner next rejects Claim 38 under 35 U.S.c. § 103(a) as being unpatentable over
Brueck and further in view of Dalton, et al. (U.S. Patent No. 5,116,718). As set forth above,
Applicant submits with this response a Terminal Disclaimer with respect to the Brueck reference;
therefore, the rejection is now moot.
Upon entry of the foregoing amendments, Applicant asserts that the present patent
application is now in condition for allowance and respectfully requests a Notice of Allowance.
No new matter is added by the foregoing amendments.
this Response or the Patent Application, please do ot

Dated: May 18. 1999
SNELL & WILMER L.L.P.
One Arizona Center
400 E. Van Buren
Phoenix, AZ 85004-0001
602-382-6228
28516.1100/662153

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the Examiner has questions related to

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of the full statutory tenn as defined in 35 U.S.C. 154 to 156 and 173 of the prior patent, as
presently shortened by any Tenninal Disclaimer, in the event that it later expires for failure to
pay a maintenance fee, is held unenforceable, is found invalid by a court of competent
jurisdiction, is statutorily disclaimed in whole or tenninally disclaimed under 37 C.F.R. 1.321,
has all claims canceled by a reexamination certificate, is reissued, or is in any' manner tenninated
prior to the expiration of its full statutory term as presently shortened by any Terminal
Disclaimer.
The undersigned is an attorney of record. The fee set forth in § 1.20(d) accompanies this
Tenninal Disclaimer.

Dated: May 18 1999
Howard 1. Sobelman, Reg. No. 39,038

SNELL & WILMER L.L.P.
One Arizona Center
400 E. Van Buren
Phoenix, AZ 85004-0001
[phone]