Ex Parte Mani et al

Patent Trial and Appeal Board

Apr 4, 2013

11736562 (P.T.A.B. Apr. 4, 2013)

UNITED STATES PATENT AND TRADEMARK OFFICE
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BEFORE THE PATENT TRIAL AND APPEAL BOARD
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Ex parte RADHIKA MANI, NICOLAS GANI, WEI LIU,
MEIHUA SHEN, and SHASHANK C. DESHMUKH
____________________

Appeal 2010-009183
Application 11/736,562
Technology Center 2800
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Before MAHSHID D. SAADAT, KRISTEN L. DROESCH, and
JUSTIN BUSCH, Administrative Patent Judges.

BUSCH, Administrative Patent Judge.

DECISION ON APPEAL

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Application 11/736,562

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Appellants appeal under 35 U.S.C. § 134(a) from a rejection of claims
1-7. We have jurisdiction under 35 U.S.C. § 6(b).
We AFFIRM.

Introduction
According to Appellants, the invention relates to the manufacturing of
semiconductor devices and, more particularly, to methods for etching SiO2
with high selectivity to Si3N4 and etching metal oxides with high selectivity
to SiO2 at elevated temperatures, using BCl3-based etch chemistries. See
Spec. ¶¶ [0002] and [0010].

STATEMENT OF THE CASE

Exemplary Claim
Claim 1, reproduced below, is illustrative of the claimed subject
matter:
1. A method for fabricating a semiconductor device
comprising:
providing a wafer into a plasma etch processing chamber,
wherein said wafer comprises a high K dielectric layer and an oxide or
nitride containing layer;
applying a source power to generate an inductively coupled
plasma;
introducing into said chamber a gas comprising BCl3;
setting the temperature of said wafer to be between 100 °C and
350 °C; and
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etching said wafer with a selectivity of high K dielectric to
oxide or nitride greater than 10:1.

Reference
Lin US 2005/0081781 A1 Apr. 21, 2005

Rejection
Claims 1-7 stand rejected under 35 U.S.C. § 103(a) as being obvious
in view of Lin. Ans. 4-6.
1

ISSUE
Appellants argue the temperature range and gas mixture recited in
their claims is patentably distinct over Lin. App. Br. 3-4. Appellants also
assert Lin does not inherently result in etching a wafer with a “selectivity of
high K dielectric to oxide or nitride greater than 10:1.” App. Br. 4. Appellant
argues it would not have been obvious to modify Lin to come up with the
claimed method. App. Br. 5.
Issue: Does Lin teach “introducing into said chamber a gas
comprising BCl3; setting the temperature of said wafer to be between 100 °C
and 350 °C; and etching said wafer with a selectivity of high K dielectric to
oxide or nitride greater than 10:1,” as recited in independent claim 1?

1
All references to the Examiner’s Answer in this opinion refer to the
Supplemental Examiner’s Answer, mailed on March 9, 2010.
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ANALYSIS
We have reviewed the Examiner’s rejections in light of Appellants’
arguments that the Examiner has erred. We disagree with Appellants’
contentions. We adopt the Examiner’s findings and conclusions and
highlight specific issues as follows.
Appellants acknowledge the “gas comprising BCl3,” recited in claim
1, uses open-ended language but allege the recited limitation “etching said
wafer with a selectivity of high K dielectric to oxide or nitride greater than
10:1” “places restrictions on the gas composition,” further limiting the
claim. App. Br. 6.
This argument is directed to features or limitations not claimed by
Appellants. See Ans. 7. We must give the claims their broadest reasonable
interpretation consistent with Appellants’ Specification. Appellants’ have
not provided sufficient evidence or argument to persuade us that the claimed
etch selectivity further limits the gas composition. Lin uses “‘BCl3’ as ‘the
main etchant.’” Ans. 7. Therefore, Lin teaches or suggests “introducing into
said chamber a gas comprising BCl3,” as recited in claim 1.
Appellants also argue Lin does not teach or suggest “setting the
temperature of said wafer to be between 100 °C and 350 °C,” as recited in
claim 1. App. Br. 7-10. Appellants argue “[c]hanging the gas chemistry and
the temperature range is much more than simple routine optimization,” and
“the claimed temperature range does not merely enhance the selectivity of
the etching process so that the etching process is selective of high K
dielectric to oxide or nitride, but also results in residue free etching.” App.
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Br. 8-9. Appellants contend the resultant residue free etching is an
unexpected result. App. Br. 9 (citing Spec. 13:20-15:12).
First, as discussed above, we find that Lin does teach or suggest using
the gas claimed as an etchant. Additionally, we agree with the Examiner that
adjustable process parameters such as time, temperature, pressure, gases, and
relative gas flows are merely variables that one of ordinary skill in the art
may change and optimize by simple routine optimization. Ans. 8. We find
nothing recited in Appellants’ claim 1 that would require a residue free
etching. Nor have Appellants, as pointed out by the Examiner (Ans. 8),
provided sufficient argument or objective evidence to persuade us that
residue free etching is an unexpected result. Therefore, we are not persuaded
of error in the Examiner’s findings and conclusion of obviousness.
Appellants further argue that Lin is directed to an etching process with
an etch selectivity to polysilicon, not an etch selectivity to oxide (or nitride)
and Lin stops the etching process “before, or as soon as, the shallow trench
isolation (STI) features which lie below the dielectric layer 22 are exposed
to the etching process.” App. Br. 10. However, we agree with the
Examiner’s finding that the process conditions taught by Lin are the same as
what is claimed by Appellants and the process is applied to similar materials
as those claimed by Appellants, producing the same results. Ans. 9.
While Appellants acknowledge Lin “teaches that the etching process
does not cause an oxide loss in the STI features,” they assert this disclosure
does not teach or suggest “a selectivity of high K dielectric to oxide or
nitride greater than 10:1,” as recited in claim 1 because “Lin’s etching
process does not cause oxide loss because Lin stops the etching process
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before the STI features, which contain oxide, are exposed to the etching the
[sic] process.” App. Br. 12.
The Examiner points out that the end point detection discussed in Lin
is a well-known technique for controlling over-etching and is not indicative
of etch rates or etch selectivity and that Lin identifies precautions to
“avoid[] damage to the substrate 20 and the STI features 21.” Ans. 10
(citing Lin [0034]). Moreover, a second embodiment of Lin teaches a nitride
or oxide spacer. Therefore, both the STI features and the spacer are formed
of oxides that are exposed to the etching process for the entire etching
period. Ans. 9-11.
We find Appellants have not provided any persuasive argument or
sufficient evidence to convince us using BCl3 etchant in Lin does not result
in the claimed step of “etching said wafer with a selectivity of high K
dielectric to oxide or nitride greater than 10:1,” or any other limitation of
independent claim 1. That is, to the extent described in Appellants’
Specification, the recited selectivity greater than 10:1 is a result of merely
using BCl3 etchant. Spec. ¶¶ [0074] – [0076]. Appellants do not provide
separate arguments regarding dependent claims 2-7, allowing these claims to
fall with independent claim 1.

DECISION
For the above reasons, the Examiner’s rejection of claims 1-7 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)(1)(iv).
Appeal 2010-009183
Application 11/736,562

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AFFIRMED

ELD