Ex Parte Wang et al

Board of Patent Appeals and Interferences

Apr 10, 2008

10424800 (B.P.A.I. Apr. 10, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte FUCHAO WANG and MING FANG

____________

Appeal 2007-4448
Application 10/424,800
Technology Center 2800
____________

Decided: April 10, 2008
____________

Before BRADLEY R. GARRIS, THOMAS A. WALTZ, and
KAREN M. HASTINGS, Administrative Patent Judges.

HASTINGS, Administrative Patent Judge.

DECISION ON APPEAL
Appellants appeal under 35 U.S.C. § 134(a) from the Examiner’s
final rejection of claims 15-19. We have jurisdiction under 35 U.S.C. § 6(b).
We AFFIRM.

Appeal 2007-4448
Application 10/424,800

BACKGROUND
The invention relates to a transistor gate structure within an integrated
circuit. Claim 15 is illustrative:
15. An improved transistor gate structure within an integrated
circuit, comprising:

a gate oxide over a substrate; and

a gate electrode over the gate oxide, the gate electrode
comprising:
a polysilicon layer; and

a silicide layer on the polysilicon layer, the silicide layer
including a first region at an interface between the silicide layer
and the polysilicon layer and having a first silicon/metal ratio, a
second region on the first region having a second silicon/metal
ratio less than the first silicon/metal ratio, and a third region on
the second region having a third silicon/metal ratio greater than
the second silicon/metal ratio.

The Examiner relies upon the following prior art references in
the rejections of the appealed claims:
Hu 5,863,393 Jan. 26, 1999
Pan 6,087,254 Jul. 11, 2000
Kizilayalli 6,103,607 Aug. 15, 2008

The Examiner rejected claims 15-18 under 35 U.S.C. § 103(a) as
being unpatentable over Kizilayalli in view of Pan. To reject claim 19, the
Examiner added Hu.
Appellants do not separately argue with any reasonable specificity the
individual dependent claims in the grouping of claims 15-18 rejected under
35 U.S.C. § 103 (App. Br. 5-8; Reply Br. 2-6). Therefore, we select the
2
Appeal 2007-4448
Application 10/424,800

broadest independent claim 15 to decide the issue in the first ground of
rejection on appeal. 37 C.F.R. § 41.37(c)(1)(vii)(2006). Appellants do
separately argue dependent claim 19 (App. Br. 8; Reply Br. 6-7). Thus, we
will likewise separately address dependent claim 19.

ISSUES ON APPEAL
The issues on appeal arising from the contentions of Appellants and
the Examiner are whether the Appellants have shown that the Examiner
reversibly erred in rejecting the claims because:
(a) the “tungsten silicide nitride” layer of Kizilayalli is not a second
region of a silicide layer as claimed in claim 15;
(b) there is no suggestion or teaching for the second region of
Kizilayalli having a silicon/metal ratio less than the silicon/metal ratio of the
first and third regions as claimed in claim 15; and
(c) there is no suggestion or teaching for “stepped changes in
silicon/metal ratio across a thickness of the silicide layer” as set forth in
dependent claim 19.

PRINCIPLES OF LAW
“Section 103 forbids issuance of a patent when ‘the differences
between the subject matter sought to be patented and the prior art are such
that the subject matter as a whole would have been obvious at the time the
invention was made to a person having ordinary skill in the art to which said
subject matter pertains.’” KSR Int'l Co. v. Teleflex Inc., 127 S.Ct. 1727,
1734 (2007). The legal question of obviousness is resolved on the basis of
underlying factual determinations including (1) the scope and content of the
3
Appeal 2007-4448
Application 10/424,800

prior art, (2) any differences between the claimed subject matter and the
prior art, (3) the level of skill in the art, and (4) secondary considerations, if
any. Graham v. John Deere Co., 383 U.S. 1, 17-18 (1966). See also KSR,
127 S. Ct. at 1734.
During examination of a patent application, a claim is given its
broadest reasonable construction “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 (Fed. Cir. 2004). Although claims are to be
interpreted in light of the specification, limitations from the specification are
not to be read into the claims. See In re Van Geuns, 988 F.2d 1181, 1184
(Fed. Cir. 1993).
OPINION
The § 103 Rejection Based on Kizilayalli
We agree with the Examiner’s findings of facts and legal conclusions
of obviousness as set out in the Answer. We add the following primarily for
emphasis.
Appellants do not dispute the Examiner’s findings of facts and
conclusion of obviousness with respect to the secondary reference Pan as
combined with Kizilayalli. Appellants’ disagreement with the Examiner’s
rejection focuses solely on the alleged deficiencies of Kizilayalli discussed
below.
Implicit in our review of the Examiner’s obviousness analysis is that
the claim must first have been correctly construed to define the scope and
meaning of each contested limitation. See Gechter v. Davidson, 116 F.3d
1454, 1457, 1460 n.3 (Fed. Cir. 1997). In particular, the Appellants and the
Examiner disagree on the interpretation of the limitation, “a silicide layer…”
4
Appeal 2007-4448
Application 10/424,800

recited in claim 1. Appellants argue that the “tungsten silicide nitride” layer
of Kizilayalli is not a silicide layer, and that the claim term “silicide” should
be limited to a binary compound consisting only of silicon and one other
element (App. Br. 6-7; Reply Br. 2-4). The Examiner argues for a broader
reading to include the “tungsten silicide nitride” layer of Kizilayalli, and
provides numerous additional references as evidence in support thereof
(Ans. 6-8). We agree with the Examiner.
It is axiomatic that claims are given their broadest reasonable
interpretation in light of the specification and as they would be interpreted
by one of ordinary skill in the art. Am. Acad. of Sci., 367 F.3d at 1364.
Appellants provide a dictionary definition and urge us to consider that
“silicide” can only be a binary compound, and that Kizilayalli does not teach
or suggest such a silicide for the middle region/layer (Reply Br. 2-3).
We find no basis in the claim language or in the disclosure in the
Specification on which to read “silicide” in the narrow chemical sense
urged by Appellants as a limitation into claim 1. See, e.g., In re Zletz, 893
F.2d 319, 321-22 (Fed. Cir. 1989). The Specification contains no explicit
definition of “silicide”; to the contrary, the Specification merely states that
“any metal silicide, including titanium silicide, tantalum silicide, or cobalt
silicide” may be used (Spec. 10: 13-15; emphasis provided).
Furthermore, the Examiner has provided evidence showing how one
of skill in the art uses the phrase “silicide”. This evidence includes the
repeated use of the phrases “tungsten silicide nitride”, “silicide-nitride” and
“silicide/nitride” to describe the central layer in the primary reference
Kizilayalli (i.e., 6,103,607) as well as similar phrases used in numerous
other references (see Ans. 6-8). In particular, we rely upon Kizilayalli
5
Appeal 2007-4448
Application 10/424,800

6,331,460 as evidence for our interpretation of the both the claim language
and the language used in the primary reference Kizilayalli.
Kizilayalli ‘460 states:
The present invention provides a method of forming a
metal oxide metal (MOM) capacitor over a semiconductor
wafer. The method may include forming a first metal layer
over the semiconductor wafer, forming a metal silicide layer,
such as a tungsten silicide, silicide nitride or a refractory metal
silicide, over the first metal layer and forming an oxide layer
over the metal silicide layer. The metal silicide layer, which in
an advantageous embodiment may be tungsten silicide
nitride,….
….

Turning now to FIG. 4, there is illustrated a partial
sectional view of the device of FIG. 3 following the deposition
of a metal silicide layer 410. In advantageous embodiments, the
metal silicide layer 410 is a silicide nitride and more
specifically is a tungsten silicide nitride, which is formed using
conventional physical vapor deposition (PVD) or chemical
vapor deposition (CVD) methods. One who is skilled in the art
will recognize that in alternative embodiments, other metal
silicide compounds may be employed in place of the tungsten
silicide nitride.…

(Kizilayalli ‘460, abstract; col. 4, ll. 21-31; emphasis provided).

Therefore, Kizilayalli ‘460 is evidence that one of skill in this art
would interpret the term “silicide” as inclusive of “tungsten silicide nitride”
and “tungsten silicide”. Appellants’ argument also fails to appreciate the
scope of Appellants’ claim. Claim 15 uses open claim language (i.e.,
“comprising” and “including”). The transitional term “comprising” is
“inclusive or open-ended and does not exclude additional, unrecited
6
Appeal 2007-4448
Application 10/424,800

elements or method steps.” Georgia-Pacific Corp. v. United States Gypsum
Co., 195 F.3d 1322, 1327 (Fed. Cir. 1999). Therefore, Appellants’ use of
the terms “comprising” and “including” permits the presence of additional
elements, such as the nitride of the metal silicide nitride layer of Kizilayalli.
While Appellants’ Specification does provide examples of silicides
which include binary compounds (Spec. 10:14-15), we find no basis in the
claim language or in the disclosure in the Specification on which to read
these illustrative embodiments as limitations on “silicide” into claim 15,
especially in view of the evidence discussed above. See, e.g., In re Zletz,
893 F.2d at 321-22.
Appellants also contend that Kizilayalli discloses a “stack” (of three
layers) instead of “a layer with three silicide regions” as claimed (App. Br.
6). We fully agree with the Examiner’s analysis of this issue; we see no
distinction between Appellants’ three regions 110a, 110b, 100c (e.g., Spec.,
Figs. 2, 4A) and Kizilayalli’s layers 43, 44, 45 (see Ans. 8). Indeed,
Appellants describe Fig. 4A as an embodiment formed by “distinct layers”
of silicides (Spec. 10:8-10).
Thus, one of ordinary skill in the art would readily recognize that the
tungsten silicide nitride layer of Kizilayalli is indeed a second region of a
silicide layer (i.e., a central silicide layer) as claimed.
Appellants also contend that Kizilayalli does not suggest that the
central layer has a lower silicon/metal ratio than the first and third layers
(App. Br. 7; Reply Br. 4-6). We do not agree.
Kizilayalli describes that the silicon to metal ratio of both the first and
third layers (i.e., the first and third regions) are >2, preferably >2.5, and the
most effective range is 2.5 to 2.9; whereas the composition of the central
7
Appeal 2007-4448
Application 10/424,800

layer (i.e., the second region) is such that its silicon/metal ratio may lie
between .8 and 60 (Kizilayalli, col. 3., ll. 16-40; App. Br. 7). Appellants
contend that these disclosed ranges “lack sufficient specificity to anticipate
the claims”, since “only upon careful selection from the ranges disclosed in
Kizilayalli can the claim limitation be satisfied…” (Reply Br. 4). However,
the issue is one of obviousness, not anticipation. Here, as Appellants admit,
the ranges described in Kizilayalli for the silicon/metal ratio of each
layer/region are such that a portion of the respective ranges would satisfy the
claimed limitation. Our reviewing court has repeatedly found that where the
claimed ranges overlap or lie inside ranges disclosed in the prior art, a prima
facie case of obviousness exists. See, e.g., In re Peterson, 315 F.3d 1325,
1330 (Fed. Cir. 2003); also In re Woodruff, 919 F.2d 1575 (Fed. Cir. 1990).
“The law is replete with cases in which the difference between the claimed
invention and the prior art is some range or other variable within the
claims…These cases have consistently held that in such a situation, the
applicant must show that the particular range is critical, generally by
showing that the claimed range achieves unexpected results relative to the
prior art range.” Id at 1578. Appellants have made no such showing in the
present case.
Thus, it would have been obvious to one of ordinary skill in the art to
have used a silicon/metal ratio for each layer of Kizilayalli such that the
second (central) silicide layer had a silicon/metal ratio less than the first and
third layers.
Appellants also argue that Kizilayalli’s description of forming all
three layers from a single sputtering target and turning the nitrogen on and
off to create the second layer means the ratio of silicon/metal will remain the
8
Appeal 2007-4448
Application 10/424,800

same in all three layers (Reply Br. 5-6). We disagree, since Kizilayalli
describes that the central layer is formed by controlling the nitrogen flow to
the reactor, and explicitly states that the composition of this layer may be
controlled (e.g., such that the silicon/metal ratio is less than the silicon/metal
ratio of the other two layers) (col. 3, ll. 26-40). It appears most likely that
the nitrogen would replace some of the silicon as the tungsten reacts with the
nitrogen. Therefore, the silicon/metal ratio would likely decrease in the
central layer relative to its adjoining layers, in order to account for the
addition of the nitrogen to this central layer
We also note that claims 7 and 8 of Kizilayalli specify the ratio of
silicon to tungsten metal in the first and third layers is “greater than 2.5”, or
“in the range of 2.5-2.9”, whereas claim 6 recites ranges for the relative
amounts of nitrogen, silicon and tungsten in the second layer. This is further
evidence that the second (central) layer has a different silicon/metal ratio
that may be lower than the first and third layers.
Appellants’ remarks regarding the alleged limited enabling disclosure
of Kizilayalli (Reply Br. 6) are not well taken. It is well established that a
prior art patent is presumed to be enabling, and that the burden is upon
Appellants to provide facts rebutting this presumption. See In re Sasse, 629
F.2d 675 (CCPA 1980). Appellants have proffered no such evidence.
Therefore, for the foregoing reasons and those stated in the Answer,
we agree with the Examiner’s findings in support of obviousness for claims
15-18 based on the combined teachings of Kizilayalli and Pan.

9
Appeal 2007-4448
Application 10/424,800

Dependent claim 19
Dependent claim 19 adds the limitation “…wherein the silicide layer
has stepped changes in silicon/metal ratio across a thickness of the silicide
layer.” Appellants contend that Hu, applied by the Examiner to illustrate
that stepped changes in stoichiometry of a metal silicide layer are known,
instead only teaches or suggests that a continuous variation is known (Reply
Br. 6-7)1. We disagree with the Appellants’ interpretation of Hu.
Hu describes a “graded” stoichiometry of a silicide layer such that
each layer, e.g., of a deposited or resputtered material, may have a
stoichiometry (i.e., a different silicon/metal ratio) different from each other
layer (Hu, abstract; col. 3, ll. 35-60; col. col. 9, l. 55 to col. 10, l. 5). We
determine that this “graded” stoichiometry described in Hu is more akin to
“stepped” changes than to a “continuous variation” since each layer of Hu
may have a different silicon/metal ratio, similar to the embodiment described
in Appellants’ Specification wherein each silicide layer (i.e., region) has a
different silicon/metal ratio (Spec. 10:8-11; Fig. 4). Furthermore, the
primary reference Kizilayalli suggests that each silicide layer may have a
different metal/silicon ratio as discussed previously.
The Supreme Court noted in KSR that although the teaching,
suggestion, motivation test “captured a helpful insight,” an obviousness

1 If Appellants are correct that Hu describes a continuous variation of
silicon/metal ratio in a silicide layer, it appears that the indication of
allowability of claims 20-27 should be reconsidered. The Examiner’s
statement of reasons for the indication of allowable subject matter was that
the prior art “neither teaches nor suggests the gradual (claim 20) nor the
continuous (claim 21) change of the silicon/metal ratio…” (See, Non-final
Action mailed Nov. 17, 2003, p. 5).
10
Appeal 2007-4448
Application 10/424,800

analysis “need not seek out precise teachings directed to the specific subject
matter of the challenged claim, for a court can take account of the inferences
and creative steps that a person of ordinary skill in the art would employ.”
KSR, 127 S. Ct. at 1741. The knowledge that having different layers with
different stoichiometry (i.e., different silicon/metal ratios) was desirable
would have been within the skill in the art, as evidenced by Hu.
Furthermore, one of ordinary skill in the art is also a person of ordinary
creativity, not an automaton. KSR, 127 S. Ct. at 1742.
Therefore, in view of the reference evidence, we determine that
having stepped changes in the silicon/metal ratio of the three layers of
Kizilayalli would have been within the ordinary level of skill in the art.
For the foregoing reasons and those stated in the Answer, we agree
with the Examiner’s findings and conclusion in support of obviousness for
claim 19 based on the combined teachings of Kizilayalli, Pan and Hu.

CONCLUSION
Accordingly, based on our consideration of the totality of the record
before us, we have weighed the evidence of obviousness found in the
combined teachings of the applied references, with Appellants’
countervailing evidence and arguments for nonobviousness and conclude
that the claimed invention encompassed by appealed claims 15-19 would
have been obvious as a matter of law under 35 U.S.C. § 103(a).
The Primary Examiner’s decision is affirmed.

11
Appeal 2007-4448
Application 10/424,800

No time period for taking any subsequent action in connection with
this appeal maybe extended under 37 C.F.R. § 1.136(a)(1)(iv).

AFFIRMED

tc

LISA JORGENSEN, ESQ.
STMICROELECTRONICS, INC.
1310 ELECTRONICS DRIVE
CARROLLTON, TX 75006-5039

12