Ex Parte Singh et al

Board of Patent Appeals and Interferences

Aug 31, 2010

11455671 (B.P.A.I. Aug. 31, 2010)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte HARMEET SINGH, DAVID COOPERBERG,
and VAHID VAHEDI
__________

Appeal 2009-009419
Application 11/455,671
Technology Center 1700
____________

Before MICHAEL P. COLAIANNI, BRADLEY R. GARRIS, and
BEVERLY A. FRANKLIN, Administrative Patent Judges.

COLAIANNI, Administrative Patent Judge.

DECISION ON APPEAL1
Appellants appeal under 35 U.S.C. § 134 the final rejection of claims
1-5 and 7-24. We have jurisdiction over the appeal pursuant to 35 U.S.C.
§ 6(b).

1 The two-month time period for filing an appeal or commencing a civil
action, as recited in 37 C.F.R. § 1.304, or for filing a request for rehearing,
as recited in 37 C.F.R. § 41.52, begins to run from the “MAIL DATE”
(paper delivery mode) or the “NOTIFICATION DATE” (electronic delivery
mode) shown on the PTOL-90A cover letter attached to this decision.
Appeal 2009-009419
Application 11/455,671

We AFFIRM-IN-PART.
Appellants disclose a method of etching a semiconductor substrate
with improved critical dimension uniformity (Spec. ¶ [0001]).
Claim 1 is illustrative:
1. A method of etching a semiconductor substrate with improved
critical dimension uniformity comprising:

supporting a semiconductor substrate on a substrate support in an
inductively coupled plasma etch chamber;

supplying a first etch gas comprising a silicon containing gas to a
central region over the semiconductor substrate;

supplying a second gas comprising at least one silicon containing gas
to a peripheral region over the semiconductor substrate surrounding the
central region, wherein a concentration of silicon in the second gas is greater
than a concentration of silicon in the first etch gas;

adjusting an amount of silicon in the first etch gas relative to an
amount of silicon in the second gas;

generating a plasma from the first etch gas and second gas by
inductively coupling radio frequency energy into the chamber; and

plasma etching an exposed surface of the semiconductor substrate
with the plasma.

Appellants appeal the following rejections:
1. Claims 1-5, 7-10, and 15 are rejected under 35 U.S.C. § 103(a) as
being unpatentable over Mui (US Patent 7,250,373 B2, issued July 31,
2007) in view of Mungekar (US 2004/0079728 A1, pub. Apr. 29,
2004).
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2. Claims 11-14 are rejected under 35 U.S.C. § 103(a) as being
unpatentable over Mui in view of Mungekar and Laermer (US Patent
7,166,536 B1, issued Jan. 23, 2007).
3. Claims 16-23 are rejected under 35 U.S.C. § 103(a) as being
unpatentable over Mui in view of Mungekar and Puppo (US
2004/0175950 A1, pub. Sep. 9, 2004).
4. Claim 24 is rejected under 35 U.S.C. § 103(a) as being unpatentable
over Mui in view of Mungekar and Verbeke (US 2003/0045131 A1,
pub. Mar. 6, 2003).
With regard to rejection (1), Appellants separately argue claims 1 and
7. With regard to rejection (2), Appellants argue claims 11 and 14 only.
With regard to rejection (3), Appellants argue claim 16 only. Appellants
further argue claim 24 under rejection (4).

Rejection (1): Claims 1 and 7
ISSUES
1. Did the Examiner err in concluding that it would have been obvious to
modify Mui’s process in view of Mungekar’s teachings to use SiF4, a
silicon containing etchant gas, as the etchant gas in the central region
of the apparatus as required by claim 1 so as to etch silicon oxide from
a substrate? We decide this issue in the negative.
2. Did the Examiner adequately explain how the process of Mui in view
of Mungekar would teach or suggest the subject matter of claim 7 so
as to satisfy the Examiner’s initial burden of establishing a prima facie
case of obviousness of that claim? We decide this issue in the
negative.
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Appeal 2009-009419
Application 11/455,671

FACTUAL FINDINGS & ANALYSIS
Issue (1)
Appellants argue that Mui teaches away from the claimed method
because Mui teaches etching polysilicon and because SiF4 is used as a
passivating gas not an etchant (App. Br. 4). Appellants further argue that
Mungekar’s teachings do not relate to polysilicon, but instead relate to
etching silicon oxide (App. Br. 5). Appellants contend that the Examiner
has not articulated any reasons why a person of ordinary skill in the art
would have taken Mungekar’s isolated teachings regarding etchants for
etching silicon oxide and used Mungekar’s etchants in Mui’s polysilicon
etch process (App. Br. 6). Appellants further contend that adding
Mungekar’s SiF4 etchant to the central area of the apparatus would render
Mui’s process inoperable because Mui teaches adding SiF4 as a passivating
gas to the periphery of the apparatus during polysilicon etching (App. Br. 7).
All of Appellants’ arguments however fail to address the Examiner’s
stated case, which is based on modifying Mui’s process to use Mungekar’s
SiF4 etchant in the central region of the apparatus during the etching of
Mui’s gate dielectric layer made of silicon oxide (i.e., layer 204 in Mui’s
Figure 2A) (Ans. 5, 9-10). Mui teaches that the gate dielectric layer is
etched during the processing of the semiconductor material (Mui, col. 6,
ll.64-67). The Examiner is not proposing to use the SiF4 as the etchant
during the polysilicon etch as argued by Appellants.
Therefore, we are unpersuaded by Appellants’ arguments and affirm
the Examiner’s rejection of claims 1-5, 8-10, and 15 over Mui in view of
Mungekar.
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Issue (2)
Appellants argue that the Examiner’s position that Mui teaches using
chlorine as the etchant gas and SiCl4 with argon as the passivating gas
conflicts with the Examiner’s position regarding how Mui would be
modified by Mungekar to satisfy the requirement of claim 1 to have a silicon
gas be part of the first etch gas (App. Br. 8-9). Appellants find the
Examiner’s position regarding claim 7 to be unclear (App. Br. 9). We agree.
The Examiner’s statement that Mui teaches using chlorine as the
etchant and SiCl4 with argon as the passivating gas fails to explain how that
teaching will be modified or combined with the teachings of Mungekar. As
correctly stated by Appellants, claim 7 depends from claim 1, so the
Examiner must explain how his position, regarding how Mui’s process
would have been modified by Mungekar to satisfy claim 1, comports with
his position regarding claim 7.
The Examiner appears to have attempted to provide some explanation
by indicating in his Response to Arguments section that the SiCl4 would
dissociate into chlorine atoms that would function as the etchant and silicon
atoms which would function as passivating material (Ans. 12). However,
the Examiner fails to provide any evidence or technical reasoning to support
that such a dissociation would necessarily occur in Mui’s process.
Accordingly, the Examiner’s inadequate explanation of how Mui in
view of Mungekar’s teachings are being applied to dependent claim 7 is
insufficient to establish a prima facie case of obviousness. We reverse the
Examiner’s § 103 rejection of claim 7 over Mui in view of Mungekar.

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REJECTION (2): Claims 11 and 14
ISSUES
1. Did the Examiner err in determining that one of ordinary skill would
have added etchant to the passivating gas (claim 11) in the periphery
of Mui’s apparatus in order to provide additional etching enhancement
to the periphery of the substrate when needed? We decide this issue
in the negative.
2. Did the Examiner err in determining that Laermer teaches adding O2
as a passivating gas such that it would have been obvious to add O2 to
Mui’s passivating gas as recited in claim 14? We decide this issue in
the negative.

FACTUAL FINDINGS & ANALYSIS
ISSUE (1): Claim 11
Appellants argue that Mui teaches separately adding the passivating
gas to the periphery of the substrate such that mixing an etch gas with Mui’s
passivating gas would go directly against Mui’s teachings (App. Br. 10).
Appellants contend that Laermer does not provide any suggestion to go
against Mui’s teachings to only supply passivating gas at the wafer’s edge
(App. Br. 9-10).
However, Appellants’ arguments do not specifically address the
Examiner’s reason for adding the etchant to the second gas: to provide
enhanced etching to the periphery when needed (Ans. 7). Indeed, the
Examiner relies on Laermer to teach that it is conventionally known to mix
etchants and passivating gases (Ans. 6). Accordingly, it appears that
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providing such a mixture of etchants and passivating gases to the periphery
region would have been within the skill of one of ordinary skill in the art.
Appellants’ teaching away arguments regarding Mui are premised on
Mui’s disclosure that “in one embodiment” the passivating and etchant gases
may be separately provided and Mui’s teaching to have a high concentration
of passivating gas in the periphery (App. Br. 8 and 10). However, we do not
view Mui’s “in one embodiment” language or having a high concentration of
passivating gas in the periphery teaching to discourage the mixing or use of
etchant with the passivating gas in the periphery. The plain meaning of “in
one embodiment” means that there are other embodiments, which may
reasonably include a mixing of the gases, which Laermer teaches to be
conventionally known. Moreover, Mui’s teaching to have a high
concentration of passivating gas does not preclude mixing an etchant with
the passivating gas as taught by Laermer such that the passivating gas is in a
higher concentration than the etchant.
For these reasons, we affirm the Examiner’s § 103 rejection of claims
11-13 over Mui in view of Mungekar and Laermer.

ISSUE (2): CLAIM 14
Appellants argue that the Examiner has not articulated a reason to
select N2 of Laermer’s etch gas and add it to Mui’s passivation gas (App. Br.
10). Appellants argue that Mui considers N2 a diluent gas for the center etch
gas and would not have added N2 to the passivating gas in light of such a
teaching (App. Br. 10).
However, the Examiner relies on Laermer’s teachings to add O2 with
SiF4 (used as a passivating gas) to form SiO2 (Ans. 6 and 12). In other
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words, the Examiner relies on adding O2 to Mui’s passivating gas based on
Laermer’s teaching as to what is conventionally known. Appellants’
arguments do not address the Examiner’s stated case. Accordingly, the
preponderance of the evidence weighs in favor of obviousness of the
claimed invention.
We affirm the Examiner’s § 103 rejection of claim 14 over Mui in
view of Mungekar and Laermer.

REJECTIONS (3) AND (4): CLAIMS 16 AND 24
ISSUES
1. Did the Examiner fully explain his position regarding how
Puppo’s strained silicon, etch single crystal silicon, or silicon
germanium would be combined with Mui so as to meet claim
16, which depends from claim 1, and thereby establish a prima
facie case of obviousness? We decide this issue in the negative.
2. Does the preponderance of the evidence presented by
Appellants and the Examiner weigh in favor of a conclusion
that the subject matter of claim 24 would have been obvious?
We decide this issue in the negative.

FACTUAL FINDING & ANALYSIS
ISSUE (1): CLAIM 16
Appellants argue that Puppo was cited for etching polysilicon, but no
reasons are provided in support of the rejection of claim 16 (App. Br. 11).
Appellants argue that the Examiner failed to cite to any portion of Puppo in
support of modifying the process of Mui to etch single crystal silicon,
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strained silicon or silicon germanium as required by claim 16 (App. Br. 11).
We agree.
The portions of Puppo cited by the Examiner (Puppo, p. 2 ¶¶ [12]-
[13]) fail to teach any of the silicon species of claim 16. The portions of
Puppo cited by the Examiner are drawn to polysilicon material as correctly
argued by Appellants. It is unclear how Puppo’s disclosure of polysilicon
would satisfy the requirements of claim 16.
For these reasons, we reverse the Examiner’s rejection of claim 16
over Mui in view of Mungekar and Puppo. We affirm the rejection of
claims 17-23 over Mui in view of Mungekar and Puppo because Appellants
do not specifically contest the Examiner’s rejection of those claims.

ISSUE (2): Claim 24
Appellants argue that the Examiner’s reliance on Verbeke’s etch gas,
which is designed for etching features in a metal-containing material, to
modify an etch gas designed for polysilicon demonstrates that the rejection
is improper (i.e., the Examiner has merely shown elements of the claims can
be found in the prior art without any apparent reason to combine them)
(App. Br. 11).
The Examiner reasons that one of ordinary skill would use Verbeke’s
gas mixture when Mui’s gate electrode is made of a metal silicide layer,
which are commonly used in new devices (Ans. 8). However, the Examiner
does not direct us to any evidence (either in Mui or otherwise) to
substantiate that metal silicide would have been used for Mui’s gate
electrode or that metal silicides are commonly used in new devices. Indeed,
the Examiner does not respond to Appellants’ argument. As such,
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Appellants’ persuasive argument remains unrefuted. Because the
preponderance of the evidence weighs most heavily in favor of non-
obviousness, we are constrained to reverse the Examiner’s § 103 rejection of
claim 24 over Mui in view of Mungekar and Verbeke.

DECISION
The Examiner’s decision is affirmed-in-part.
TIME PERIOD
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).

AFFIRMED-IN-PART

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