Ex Parte Akram et al

Board of Patent Appeals and Interferences

Mar 10, 2008

10173936 (B.P.A.I. Mar. 10, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte SALMAN AKRAM and Y. JEFF HU
____________

Appeal 2007-3477
Application 10/173,936
Technology Center 2800
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Decided: March 10, 2008
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Before KENNETH W. HAIRSTON, JOSEPH F. RUGGIERO,
and MAHSHID D. SAADAT, Administrative Patent Judges.

SAADAT, Administrative Patent Judge.

DECISION ON APPEAL
STATEMENT OF CASE
Appellants appeal under 35 U.S.C. § 134(a) from a Final Rejection of
claims 1-5, which are all of the claims pending in this application. We have
jurisdiction under 35 U.S.C. § 6(b).

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Appellants’ invention relates to a method of forming silicide
interfaces wherein a porous dielectric layer is disposed between a silicon-
containing substrate and a silicidable material (Spec. 5). During the anneal
process for forming the silicide, silicide material may also form in
imperfections or voids within the porous dielectric, which can cause shorting
and current leakage (id.). According to Appellants, application of a barrier
layer between the dielectric material and the silicidable material prevents
formation of silicide material through the voids and passages in the dielectric
layer (id.).
Claim 1, which is representative of the claims on appeal, reads as
follows:
1. A semiconductor device structure, comprising:

a substrate comprising a semiconductor material and including
at least one active-device region;

a layer comprising dielectric material located over the substrate;

at least one contact opening formed through the layer, the at
least one contact opening exposing at least a portion of the at least one
active device region;

a metal silicide within the at least one contact opening and in
contact with the portion of the at least one active device region, voids
and imperfections continuous with an upper major surface of the layer
being substantially free of metal silicide and silicidable material.

The prior art applied in rejecting the claims on appeal is:
Havemann US 5,661,344 Aug. 26, 1997
Kuo US 6,169,025 B1 Jan. 2, 2001
(filed Jun. 10, 1998)

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The Examiner rejected claims 1-5 under 35 U.S.C. § 103(a) based
upon the teachings of Kuo and Havemann.
We affirm.

ISSUE
Under 35 U.S.C § 103(a), with respect to the appealed claims 1-5,
would the ordinarily skilled artisan have found it obvious to modify Kuo
with Havemann to render the claimed invention unpatentable?1

PRINCIPLES OF LAW
To reach a conclusion of obviousness under section 103, the Examiner
bears the burden of producing factual basis supported by teaching in a prior
art reference or shown to be common knowledge of unquestionable
demonstration. Our reviewing court requires this evidence in order to
establish a prima facie case. In re Piasecki, 745 F.2d 1468, 1471-72 (Fed.
Cir. 1984).
Furthermore, the test for obviousness is what the combined teachings
of the references would have suggested to one of ordinary skill in the art.
See In re Kahn, 441 F.3d 977, 987-988 (Fed. Cir. 2006), In re Young, 927
F.2d 588, 591 (Fed. Cir. 1991) and In re Keller, 642 F.2d 413, 425 (CCPA
1981).
“Section 103 forbids issuance of a patent when ‘the differences
between the subject matter sought to be patented and the prior art are such

1 The Examiner has withdrawn the rejection of claims 1-5 under the first
and the second paragraphs of 35 U.S.C. § 112 (Ans. 2-3), which leaves the
35 U.S.C. § 103(a) rejection of the claims as the only issue before this panel.
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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 combination of familiar elements according to known methods
is likely to be obvious when it does no more than yield predictable results.”
Leapfrog Enter., Inc. v. Fisher-Price, Inc., 485 F.3d 1157, 1161 (Fed. Cir.
2007) (quoting KSR, 127 S. Ct. at 1739-40). “One of the ways in which a
patent's subject matter can be proved obvious is by noting that there existed
at the time of invention a known problem for which there was an obvious
solution encompassed by the patent’s claims.” KSR, 127 S. Ct. at 1742.

ANALYSIS
Appellants do not dispute the teachings of Kuo with respect to the
claimed elements such as the substrate, dielectric layer, contact opening, and
the metal silicide within the contact opening. However, Appellants’
contentions focus on whether the combination of Kuo and Havemann
teaches the claim limitation of voids and imperfections in a layer that
comprises dielectric material are “‘substantially free of metal silicide and
silicidable material’” and whether such combination would have been
obvious to one of ordinary skill in the art (App. Br. 10-11).
Appellants specifically contend that Havemann’s insulating cap layer
is formed of material that inherently includes voids and imperfections that
would likely allow for formation of metal silicide within voids of the
underlying porous layer (App. Br. 11). The Examiner responds (Ans. 6-7)
that Havemann identifies the problem of formation of filaments of
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conductive material in the porous dielectric layer (col. 2, ll. 55-64) and
solves the problem by using a cap layer 24 of silicon oxide or silicon nitride
between the porous dielectric layer 22 and the metallic conductor 38 (col. 5,
ll. 59- 63).
We agree with the Examiner’s line of reasoning and find that
Havemann clearly solves the problem of filament formation in the porous
dielectric layer by using a cap layer. In fact, contrary to Appellants’
argument (Reply Br. 4), whether the cap layer is porous or substantially
solid is not relevant to the claimed features of claim 1 which merely recite
the condition and the characteristics of the dielectric layer without reciting a
barrier or cap layer. As such, while Havemann’s cap layer may not be
inherently void free, its effect on the underlying porous dielectric layer is
explicitly taught to be preventing the conductive material from filling the
voids and imperfections in the dielectric layer and forming filaments (col. 2,
ll. 55-64), independently of how porous the dielectric is.
Additionally, Appellants contend that the combination of Kuo and
Havemann would not have been obvious to one of ordinary skill in the art
since the insulating cap of Havemann is formed of the same type of
materials used for the dielectric layer (Br. 11). Appellants further argue that
while both references teach processes in which a silicide layer is formed,
neither one discusses preventing the introduction of a silicidable material or
silicide into the voids or imperfections that are continuous with a surface of
the respective dielectric layer and insulating cap thereof (id.).
In response, the Examiner points out that the cap layer 24 prevents the
metal from seeping or migrating into the voids and imperfections of the
porous dielectric layer 22 (Ans. 7-8). The Examiner concludes that the
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protected dielectric layer 22 meets the claimed limitation of “‘voids and
imperfections continuous with an upper major surface of the layer being
substantially free of metal silicide and silicidable material’” (Ans. 8).
Again, we disagree with Appellants that the type of the material used
in the cap layer of Havemann or whether it is another dielectric precludes its
combination with Kou for protecting the dielectric layer from filament
formation. As discussed above, Havemann suggests protecting the dielectric
layer from the conducting layer by forming a cap layer in between which
prevents formation of filaments in the porous dielectric layer (col. 2, ll. 55-
64). In other words, we disagree with Appellants’ assertion (App. Br. 11)
implying that the voids and imperfections that are continuous with a surface
of both the dielectric layer and the cap layer are to be free of metal silicide
or silicidable material. Therefore, using silicon oxide or silicon nitride as
the cap layer 24 (col. 5, ll. 59-63), as long as the filament formation at least
in the dielectric layer 22 is prevented, satisfies the claimed requirement of
voids and imperfections continuous with the upper surface of the dielectric
layer being substantially free of metal silicide or silicidable materials.
For all of the previously discussed reasons, we simply find no error in
the Examiner’s position that using a cap layer to prevent formation of
filaments in the underlying dielectric, as taught by Havemann, would be
recognized by the skilled artisan as an obvious enhancement to the silicide
formation of Kou. According to Leapfrog, when combination of familiar
elements according to methods known to the skilled artisan, such as
preventing the conducting material from forming filaments in the voids in
dielectric layer, achieves a predictable result, it is likely to be obvious.

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CONCLUSION OF LAW
Because Appellants have failed to point to any error in the Examiner’s
position, we sustain the 35 U.S.C. § 103 rejection with respect to claim 1
and also with respect to claims 2-5, which are not argued separately (App.
Br. 12).

DECISION
The decision of the Examiner rejecting claims 1-5 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

KIS

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