Ex parte Yagura et al.

Board of Patent Appeals and Interferences

Jun 18, 1998

08121794 (B.P.A.I. Jun. 18, 1998)

Attorney docket no. 25417-20001001
Counsel waived a scheduled hearing. (Paper 19.)2
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
This opinion (1) was not written for publication and
(2) is not binding precedent of the Board.
Paper No. 20
UNITED STATES PATENT AND TRADEMARK OFFICE
____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
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Ex parte MOTOJI YAGURA,
MASANORI KOMINAMI, TOSHIAKI KINOSADA,
KOKEN YOSHIKAWA, and JOHN K. TWYNAM
____________
Appeal No. 95-5148
Application No. 08/121,7941
____________
ON BRIEF2
____________
Before KRASS, LEE, and TORCZON, Administrative Patent Judges.
TORCZON, Administrative Patent Judge.
DECISION ON APPEAL
BACKGROUND
This is an appeal under 35 U.S.C. § 134 from the final
rejection of claims 1-5. We reverse and enter a new ground of
rejection under 37 CFR § 1.196(b).
The application is entitled "Ohmic electrode structure".
The subject matter of the invention is illustrated in
Appeal No. 95-5148 Page 2
Application 08/121,794
We rely on a translation (attached) for our3
understanding of this reference.
Figures 3 and 4 and is broadly represented by claim 1, the
sole independent claim:
An ohmic electrode structure having a layered
structure comprising:
a compound semiconductor;
an In Ga As layer (0 < x # 1) on said compoundx 1-x
semiconductor;
a metal layer including at least one metal
sublayer; and
a barrier layer between said metal layer and
said In Ga As layer for prevention of the diffusionx 1-x
of metallic components between said metal layer and
said In Ga As layer;x 1-x
said barrier layer being composed of a metallic
nitride having a high melting point and providing an
ohmic interface with said In Ga As layer.x 1-x
The examiner rejected all of the claims on appeal as
unpatentable in view of the admitted prior art (Paper 1 at 1-
3; Figs. 1 & 2) and the following Japanese k«kai:3
Yamagishi 62-213158 pub'd. 19 Sept. 1987
In the answer, the examiner also relied heavily on
Marc Wittmer, "Barrier layers: Principles and applications in
microelectronics", 2 J. Vac. Technol. 273-80 (Apr.-June 1984)
(Wittmer)
but the examiner never positively recited Wittmer as part of
the rejection. We, therefore, do not rely on Wittmer in
Appeal No. 95-5148 Page 3
Application 08/121,794
Wittmer indicates, however, that the barrier height4
of Schottky junctions is "a very sensitive indicator of
interfacial changes" at the metal/semiconductor interface.
(p. 276.)
reviewing the rejection as stated. In re Hoch, 428 F.2d 1341,
1342 n.3, 166 USPQ 406, 407 n.3 (CCPA 1970).
The admitted prior art teaches all of the essential claim
limitations in the claimed relationships except a barrier
layer "composed of a" high melting point metallic nitride
(claim 1, emphasis added) "with an amorphous structure"
(claim 5). According to the specification, "metallic nitrides
having high melting points assume amorphous structures"
(Paper 1 at 4:15-16), so the only remaining question is
whether Yamagishi teaches or suggests adding or substituting a
barrier layer composed of a metallic nitride having a high
melting point.
Yamagishi is directed to a Schottky junction (p. 3), not
an ohmic contact. Although the fields of endeavor are related
(metal/semiconductor junctions), they are distinct. 4
Yamagishi notes that both silicides and nitrides have been
used to form gate electrodes for self-matching field-effect
transistors (FETs). (p. 3.) His refinement is to use two
nitrides--tungsten nitride (WN) and tantalum nitride (TaN)--as
a laminate to form the gate. (p. 4-5; Fig. 2(b).)
Appeal No. 95-5148 Page 4
Application 08/121,794
DISCUSSION
We are unpersuaded, based on the record before us, that
the combination of the admitted prior art and Yamagishi would
have rendered the subject matter of the claims obvious.
Yamagishi's suggestion to use a WN/TaN laminate is an
empirical solution to a specific problem. The examiner has
not convincingly explained why a person having ordinary skill
in the art would have been motivated to try a single nitride,
e.g., WN (not TaN or WN/TaN), as a barrier layer in the
admitted prior art. The analysis the examiner presented
appears to be impermissible hindsight.
NEW GROUND OF REJECTION
Although the examiner never makes a rejection based on
Wittmer, the combination of Wittmer and the admitted prior art
strongly suggests the claimed invention. Wittmer teaches that
at high temperatures the metallic layer (in his case, aluminum
(Al)) decomposes, and forms compounds with, silicides.
(p. 276.) For this reason, he reports that "transition metal
silicides cannot be used as barrier material." (p. 279,
emphasis added.) In contrast, Wittmer teaches that "[t]he
performance of [another material] is only surpassed by
refractory metal nitride barriers, such as TiN and ZrN."
(Id., emphasis added.) TiN (titanium nitride) is in
Appeal No. 95-5148 Page 5
Application 08/121,794
Appellants' claimed Markush group of nitrides (claim 2), but
the teaching is broad enough to cover all refractory metal
nitrides, of which Wittmer considers TiN representative
(p. 278). Wittmer identifies the other members of the claimed
Markush group, tungsten (W) and molybdenum (Mo), as refractory
metals (e.g., p. 277, Table II). A person having ordinary
skill in the art contemplating the combination of the admitted
prior art and Wittmer would have been inexorably drawn to the
claimed subject matter.
DECISION
The examiner's rejection of all claims on appeal is
reversed. We enter a new ground of rejection for claims 1-5
as unpatentable under section 103 in view of the admitted
Appeal No. 95-5148 Page 6
Application 08/121,794
prior art and Wittmer. Appellant should note that a new
ground of rejection is not final for purposes of judicial
review.
WITHIN TWO MONTHS FROM THE DATE OF THIS DECISION,
Appellants must either:
1) submit an appropriate amendment of the claims
so rejected or a showing of facts relating to the
claims so rejected, or both, and have the matter
reconsidered by the examiner, in which event the
application will be remanded to the examiner; or
2) request a rehearing on the same record.
See 37 CFR §§ 1.196(b) & 1.197(b). No time period for taking
any subsequent action in connection with this appeal may be
extended under 37 CFR § 1.136(a). 37 CFR § 1.136(b).
REVERSED; 37 CFR § 1.196(b)
ERROL A. KRASS )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
JAMESON LEE ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
Appeal No. 95-5148 Page 7
Application 08/121,794
)
)
)
RICHARD TORCZON )
Administrative Patent Judge )
Appeal No. 95-5148 Page 8
Application 08/121,794
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