Ex Parte Kammler et al

Board of Patent Appeals and Interferences

Sep 5, 2007

10859552 (B.P.A.I. Sep. 5, 2007)

The opinion in support of the decision being entered today
is not binding precedent of the Board.

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte THORSTEN KAMMLER, KARSTEN WIECZOREK,
and AUSTIN FRENKEL
____________

Appeal 2007-2101
Application 10/859,552
Technology Center 2800
____________

Decided: September 5, 2007
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Before BRADLEY R. GARRIS, CHUNG K. PAK, and
CHARLES F. WARREN, Administrative Patent Judges.

GARRIS, Administrative Patent Judge.

DECISION ON APPEAL
Appellants appeal under 35 U.S.C. § 134 the final rejection of claims
18-22. We have jurisdiction over the appeal pursuant to 35 U.S.C. § 6(b).
We AFFIRM.

INTRODUCTION
Appellants claim a method of forming a field effect transistor that
comprises, in relevant part, the following steps: (1) patterning a layer stack
Appeal 2007-2101
Application 10/859,552

comprising a gate insulation layer, a polysilicon layer and a cap layer to
form a gate electrode having a cap layer, (2) forming silicide regions
comprising a first metal in said drain and source regions, and (3) exposing
the top of the gate electrode (i.e., removing the cap layer), and forming a
nickel silicide/cobalt silicide layer stack region in said gate electrode (claim
18).
Claim 18 is illustrative:
18. A method of forming a field effect transistor, the method comprising:

forming a layer stack including at least a gate insulation layer, a polysilicon
layer and a cap layer above a silicon region formed on a substrate;

patterning said layer stack to form a gate electrode having a top surface
covered by at least said cap layer;

forming a drain and a source region adjacent to said gate electrode;

forming silicide regions comprising a first metal in said drain and source
regions;

exposing said top surface of said gate electrode; and

forming a nickel silicide/cobalt silicide layer stack region in said gate
electrode.

The Examiner relies on the following prior art references as evidence
of unpatentability:
Yu US 6,376,320 B1 Apr. 23, 2002
Maex US 2002/01581170 A1 Oct. 17, 2002
Wieczorek US 6,620,718 B1 Sep. 16, 2003

The rejection as presented by the Examiner is as follows:
1. Claims 18-22 are rejected under 35 U.S.C. § 103(a) as being
unpatentable over Maex in view of Yu or Wieczorek.
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Appellants argue claim 18 only. Accordingly, claims 19-22, which
directly or ultimately depend from claim 18, stand or fall with claim 18.

OPINION
Appellants argue that claim 18 requires that the metal used to form
“silicide regions comprising a first metal in said drain and source regions” is
different than the nickel and cobalt metals used to form the “nickel
silicide/cobalt silicide layer stack region” formed on the gate electrode (Br. 4
and 5). Appellants further argue that the Examiner used hindsight in
modifying Maex’s method of forming a gate electrode on a semiconductor to
arrive at the claimed invention (Br. 5 and 6).
We have considered all of Appellants’ arguments and are unpersuaded
for the reasons below.
The Examiner states that the claims do not require that the “first
metal” is different than the nickel and cobalt metals used to form the “nickel
silicide/cobalt silicide formed on the gate electrode (Answer 5). We agree.
During examination, “claims … are to be given their broadest
reasonable interpretation consistent with the specification, and … claim
language should be read in light of the specification as it would be
interpreted by one of ordinary skill in the art.” In re Am. Acad. of Sci. Tech.
Ctr., 367 F.3d 1359, 1364, 70 USPQ2d 1827, 1830 (Fed. Cir. 2004).
““Reading a claim in light of the specification,” to thereby interpret
limitations explicitly recited in the claim, is a quite different thing from
“reading limitations of the specification into a claim,” to thereby narrow the
scope of the claim by implicitly adding disclosed limitations which have no
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Application 10/859,552

express basis in the claim.” In re Prater, 415 F.2d 1393, 1404, 162 USPQ
541, 550 (CCPA 1969).
Applying the broadest reasonable interpretation standard to claim 18,
the Examiner properly construes the claim features, “forming silicide
regions comprising a first metal in said drain and source regions” and
“forming a nickel silicide/cobalt silicide layer stack region in said gate
electrode,” as not requiring different metals to form the silicides (Answer 5).
Plainly, Appellants’ claims do not require that the “first metal” used to form
the silicide regions on the drain and source regions is different than the metal
used to form the “nickel silicide/cobalt silicide layer stack region.”
Appellants argue that the Specification at page 9, lines 9-16 and page
14, lines 5-12 indicate that different metals are used to form the silicide
regions in the source and drain regions and the silicide in the gate electrode
such that the argued claim features should be construed as requiring different
metals (Br. 4 and 5). However, Appellants’ claim construction would have
us improperly read limitations into the claim that have no express basis in
the claim. Prater, 415 F.2d at 1404-05, 162 USPQ at 550-51.
Additionally, as the Examiner noted both Yu and Wieczorek disclose
that it is known in the art to use different metals to form the silicide layer in
the drain and source regions and in the gate electrode (Answer 5; Yu, col. 7,
ll. 45-47; Wieczorek, col. 6, ll. 51-54; col. 7, ll. 1-5). Therefore, even if the
claim is construed as argued by Appellants, the Yu or Wieczorek disclosures
would render obvious a claim construction that requires the “first metal”
used to form the silicide material in the source and drain regions to be
different than the nickel and cobalt used to form the silicide region in the
gate electrode.
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Regarding Appellants’ argument that the Examiner has not identified
any source of motivation for modifying the disclosure of Maex to arrive at
Appellants’ claimed invention (Br. 5 and 6), the Examiner has provided
motivation directly from the references. Specifically, the Examiner stated
that it would have been obvious to use a cap layer as taught by either Yu or
Wieczorek in Maex’s siliciding process “to independently optimize the
silicide thicknesses of the gate and source/drain regions” (Answer 4). The
Examiner further states that Yu and Wieczorek provide motivation for using
a cap layer and separate siliciding steps in the gate electrode and in the
source and drain regions to produce a relatively thick gate silicide having a
lower gate resistance, and an increased switching speed, while also
producing a relatively shallow source/drain silicide that minimizes unwanted
short channel effects (Answer 4).
The Examiner’s motivation for the combination of Yu’s or
Wieczorek’s cap and separate siliciding steps with Maex’s method of
forming a nickel/cobalt silicide layers on transistor gates is taken directly
from the Wieczorek and Yu disclosures (Wieczorek, col. 7, ll. 16-27; Yu,
col. 8, ll. 19-22, 44-61). In re Rouffet, 149 F.3d 1350, 1357-58, 47 USPQ2d
1453, 1458 (Fed. Cir. 1998). Appellants have not rebutted the Examiner’s
motivation for the combination of Maex in view of Yu or Wieczorek.
Accordingly, Appellants’ argument regarding lack of motivation for the
combination of Maex in view of Yu or Wieczorek is not persuasive.
For the above reasons, we affirm the Examiner’s § 103(a) rejection of
claims 18-22 over Maex in view Yu or Wieczorek.

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DECISION
The Examiner’s decision 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).
AFFIRMED

clj

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