Ex Parte Liu et al

Patent Trial and Appeal Board

Feb 14, 2014

11854937 (P.T.A.B. Feb. 14, 2014)

UNITED STATES PATENT AND TRADEMARK OFFICE
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BEFORE THE PATENT TRIAL AND APPEAL BOARD
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Ex parte JUNJUN LIU, DOREL L. TOMA, and ERIC M. LEE
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Appeal 2011-013196
Application 11/854,937
Technology Center 2800
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Before PETER F. KRATZ, JAMES C. HOUSEL, and DONNA M. PRAISS,
Administrative Patent Judges.

PRAISS, Administrative Patent Judge.

DECISION ON APPEAL
This is a decision on an appeal under 35 U.S.C. § 134 from the
Examiner’s final rejection of claims 1-3, 5-16, and 18-22. We have
jurisdiction pursuant to 35 U.S.C. § 6.

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STATEMENT OF THE CASE
Appellants’ claimed invention is directed to “a method of curing a low
dielectric constant (low-k) dielectric film and thermally treating the low-k
dielectric film.” Spec. ¶ 0002.
According to Appellants,
Low dielectric constant (low k) materials are conventionally
thermally cured at a temperature in the range of 300 °C to 400
°C for CVD films. . . . However, when processing porous
dielectric films (such as ultra low-k films) with a high level of
porosity, the degree of cross-linking achievable with thermal
treatment (or thermal curing) is no longer sufficient to produce
films of adequate strength for a robust interconnect structure.
Id. at ¶ 0007.
Only a small amount of thermal energy can actually be
absorbed in the low-k films to be cured due to the thermal
energy lost in the coupling of heat to the substrate and the heat
loss in the ambient environment.
Id. at ¶ 0008.

Claim 1 is illustrative and reproduced below:
1. A method of curing a low dielectric constant (low-k) dielectric
film on a substrate, comprising:
disposing a substrate having a low-k dielectric film in a
curing system;
exposing said low-k dielectric film to ultraviolet (UV)
radiation in said curing system to cause bond dissociation and
generation of cross-link initiators, and to cause partial
crosslinking within said low-k dielectric film;
during said UV exposure, heating said low-k dielectric
film by elevating the temperature of a substrate holder in
contact with said substrate to a cure temperature ranging from
approximately 200 degrees C to approximately 600 degrees C;
and
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following said UV exposure, exposing said low-k
dielectric film to infrared (IR) radiation, said IR radiation being
substantially monochromatic electromagnetic (EM) radiation
having a narrow band of wavelengths,
wherein the dielectric constant of said low-k dielectric
film is less than a value of approximately 4.
The Examiner relies on the following prior art references as evidence
in rejecting the appealed claims:1
Hwang US 5,705,232 Jan. 6, 1998
Sharangpani US 6,303,524 B1 Oct. 16, 2001
Shimizu US 2004/0253839 A1 Dec. 16, 2004
Reid US 2005/0064726 Mar. 24, 2005
Yoo US 2005/0085094 A1 Apr. 25, 2005

The Examiner maintains the following grounds of rejection.
Claims 1-3, 5, 7-14, 16, 18-20, and 22 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over the combination of Reid, Sharangpani,
and Shimizu. Claims 6 and 15 stand rejected under 35 U.S.C. § 103(a) as
being unpatentable over Reid, Sharangpani, Shimizu, and Yoo. Claim 21
stands rejected under 35 U.S.C. § 103(a) as being unpatentable over Reid,
Sharangpani, Shimizu, and Hwang.
We affirm the stated rejections. Our reasons follow.
Concerning the obviousness rejection of claim 1, the Examiner relies
on Reid for teaching the claimed subject matter except for “during said UV
exposure, heating said low-K dielectric film by elevating the temperature of

1 The Examiner omits listing Yoo and Hwang under the Evidence Relied
Upon section of the Answer. Ans. 2-3. We find the Examiner’s failure to
list these references relied upon in the rejections to be harmless error
because Appellants neither object to the omission nor address the teachings
of Yoo and Hwang relied upon by the Examiner. See App. Br. 14.
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a substrate holder in contact with said substrate to a cure temperature
ranging from approximate[ly] 200 degrees C to approximate[ly] 600 degrees
C” for which Sharangpani is relied upon, and “said IR radiation being
substantially monochromatic electromagnetic (EM) radiation having a
narrow band of wavelengths” for which Shimizu is relied upon. Ans. 4-5.
The Examiner’s rationale for combining the teaching of Sharangpani is “to
form thinner barrier metals to prevent copper diffusion in devices[.]” Id. at 5
(citing Sharangpani Abstr.). The Examiner’s rationale for combining the
teaching of Shimizu is “to selectively alter the properties of low-k dielectric
films.” Id. (citing Shimizu ¶ 0090).
Appellants contend that the Examiner’s obviousness rejections are
flawed because they “are based on speculation and are absent of articulated
reasoning with rational underpinning to support a legal conclusion of
obviousness.” App. Br. 9. Appellants distinguish Reid on the basis that
“[t]he UV exposure of Reid et al. is designed to anneal the low-k dielectric
film, and it is not designed to cause bond dissociation and generation of
cross-link initiators.” Id. at 10; see also id. at 13 (regarding claims 8 and 9).
Appellants concede that Reid discloses IR radiation, albeit broadband IR
radiation sources. Id.
Appellants contend that neither Reid nor Shimizu “suggest that IR
laser radiation selectively alters the properties of low-k dielectric films.” Id.
at 11. Appellants argue that Shimizu “simply suggests that dielectric films
may be selectively heated on a very short time scale, i.e., of order micro-
seconds” (id.) however “the process time would be excessively long” (id. at
12) if the laser IR radiation of Shimizu is substituted for the lamp radiation
of Reid. Appellants further argue that “Sharangpani et al. is silent about
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heating the low-k dielectric film by elevating the temperature of a
substrate holder in contact with the substrate to a cure temperature
ranging from approximately 200 degrees C to approximately 600 degrees
C.” Id. Appellants reiterate that the combination of all three references is
silent as to this point with respect to claims 2 and 3. Id.
The Examiner responds that the process of Reid “is specifically
designed to partially cross-link a low-k dielectric material (e.g.[,] siloxane-
based dielectrics; ¶¶ [0037]-[0038]).” Ans. 15. The Examiner further
reasons that
since the materials of Reid et al[.] are substantially identical to
the claimed materials and are formed by substantially identical
processes, it is expected that the materials behave similarly.
That is, it would be expected that the UV exposure of Reid et
al[.] would result in bond dissociation and generation of cross-
link initiators, and to cause partial cross-linking within the low-
k dielectric film on the substrate.
Id. Regarding Shimizu, the Examiner cites paragraph 0097 regarding the IR
laser irradiation altering the material properties of the low-k film. Id. at 16.
Shimizu states that “modification of a material can be performed so as to
provide a reduction in a dielectric constant or an improvement in a
mechanical strength of a low-dielectric film (low-k film)[.]” Shimizu ¶
0097.
On this record, the Examiner has established that claim 1
encompasses the combination of the thermal curing process with UV and IR
radiation of Reid that produces a low-k dielectric film with a dielectric
constant less than a value of approximately 4 with Sharangpani’s heating
temperatures during UV radiation and Shimizu’s narrow band of
wavelengths in the IR spectrum. Appellants do not direct us to evidence in
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this record to show that the UV radiation used to yield a cross-linked
siloxane structure in Reid’s process is not substantially identical to the
claimed materials and process such that the materials behave similarly. See
Ans. 15; see generally App. Br.; see generally Reply Br. In the Reply Brief,
Appellants argue that “an IR lamp and an IR laser are not functionally
equivalent.” Reply Br. 3. This argument is not persuasive because
Appellants’ Specification describes IR lamps and IR lasers as
interchangeable. Spec. ¶ 0032 (“The exposure of the dielectric film to IR
radiation may include exposing the dielectric film to IR radiation from one
or more IR lamps, one or more IR LEDs (light emitting diodes), or one or
more IR lasers, or a combination of two or more thereof.”) Accordingly, we
affirm the obviousness rejection of claim 1 over the combination of Reid,
Sharangpani, and Shimizu.
As for the separate obviousness rejections of dependent claims 6, 15,
and 21, the Appellants limit their obviousness challenges to the same
deficiencies said to be present in the combination of Reid, Sharangpani, and
Shimizu as applied against claim 1 (App. Br. 14). It follows that we shall
likewise affirm these latter rejections, which rely upon the unpersuasive
argument presented with regard to the affirmed obviousness rejection of
claim 1.

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Application 11/854,937

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The Examiner’s decision to reject the appealed claims is affirmed.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a). See 37 C.F.R.
§ 1.136(a)(1)(iv).

AFFIRMED

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