Ex parte Johnson

Board of Patent Appeals and Interferences

Jul 7, 1998

07877253 (B.P.A.I. Jul. 7, 1998)

Application for patent filed April 28, 1992. According1
to appellant, this application is a continuation of Application
07/621,268, filed December 3, 1990, now abandoned; which is a
division of Application 07/331,250, filed March 29, 1989, now
abandoned.
1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered today (1)
was not written for publication in a law journal and (2) is not
binding precedent of the Board.
Paper No. 31
UNITED STATES PATENT AND TRADEMARK OFFICE
__________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________
Ex parte DAVID A. JOHNSON
__________
Appeal No. 95-0326
Application No. 07/877,2531
__________
ON BRIEF
__________
Before JOHN D. SMITH, GARRIS and WEIFFENBACH, Administrative
Patent Judges.
GARRIS, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on an appeal from the final rejection of
claims 9 through 12, 14 through 19, 21, 22, 24 through 26, 28
through 31, 33 through 36, 38, 39 and 43. The only other claims
Appeal No. 95-0326
Application No. 07/877,253
2
remaining in the application have been indicated by the examiner
as being either allowed or allowable.
The subject matter on appeal relates to a process for
forming a thermally stable, low resistance ohmic contact on a
major surface of a III-V semiconductor substrate comprising the
steps of (a) doping to form an active region to which the ohmic
contact is to be made, (b) introducing a Group VI element onto
the surface of the active region to form treated portions
comprising a thin film at most a few monolayers thick, (c)
forming a metal contact on the treated portions and (d) heating
the metal contact to form said low resistance ohmic contact.
This appealed subject matter is adequately illustrated by
independent claim 28 which reads as follows:
28. A process for forming a thermally stable, low
resistance ohmic contact on a major surface of a III-V
semiconductor substrate, comprising:
(a) doping at least one region in said major surface of
said III-V semiconductor substrate with a dopant to form an
active region to which said ohmic contact is to be made;
(b) introducing a Group VI element onto the surface of said
at least one active region to form treated portions of said III-V
surface of said at least one active region, said treated portions
comprising a thin film at most a few monolayers thick;
(c) forming a metal contact, capable of forming an ohmic
contact to said III-V semiconductor, on said treated portions of
said III-V surface to form a metal contact thereto; and
Appeal No. 95-0326
Application No. 07/877,253
3
(d) heating said metal contact and said III-V semiconductor
to form said low resistance ohmic contact.
The references relied upon by the examiner as evidence of
obviousness are:
Anderson et al. (Anderson), “Ohmic Contacts To GaAs For High-
Temperature Device Applications,” Conference Paper at “Ohmic
Contacts” (March 25-27, 1981) pp. 39-42.
Japanese patent (Nagaoka ‘191) 60-161191 Jan. 30, 1987
Japanese patent (Nagaoka ‘192) 60-161192 Jan. 30, 1987
European patent (Cunningham) 252,300 Jan. 13, 1988
Claims 28 through 31, 33 through 36, 38, 39 and 43 stand
rejected under 35 U.S.C. § 103 as being unpatentable over
Anderson taken with Cunningham, and claims 9 through 12, 14
through 19, 21, 22 and 24 through 26 stand correspondingly
rejected over these references and further in view of either of
the Nagaoka references.
We refer to the Briefs and the Answer for a complete
exposition of the opposing viewpoints expressed by the appellant
and the examiner concerning the above noted rejections.
OPINION
For the reasons set forth below, none of the rejections
advanced by the examiner can be sustained.
Appeal No. 95-0326
Application No. 07/877,253
4
We fully agree with the appellant’s conclusion expressed in
the Briefs that the applied references and in particular
Cunningham would not have suggested providing Anderson’s process
with the step of introducing a Group VI element onto the surface
of an active (i.e., doped) region as required by step (b) of the
independent claims on appeal. This is because Cunningham, rather
than introducing such an element onto the surface of a doped
region, fabricates delta-doped layers of a Group VI element at a
distance from the metal-semiconductor junction (which corresponds
to the here claimed surface); e.g., see the paragraph bridging
columns 1 and 2 on page 2. We do not perceive and the examiner
does not explain how Cunningham’s step of fabricating delta-doped
layers at a distance from his metal-semiconductor junction would
have suggested (or inherently practiced) the here claimed step of
introducing a Group VI element onto the surface of the active
(i.e., doped) region whereat the appellant’s metal-semiconductor
junction is to be formed.
In light of the foregoing, we cannot sustain the examiner’s
§ 103 rejection of claims 28 through 31, 33 through 36, 38, 39
and 43 as being unpatentable over Anderson taken with Cunningham.
Moreover, since the above discussed deficiencies are not supplied
by the Nagaoka references, we also cannot sustain the § 103
Appeal No. 95-0326
Application No. 07/877,253
5
rejection of claims 9 through 12, 14 through 19, 21, 22 and 24
through 26 as being unpatentable over Anderson taken with
Cunningham and further in view of either of the Nagaoka
references.
The decision of the examiner is reversed.
REVERSED
JOHN D. SMITH )
Administrative Patent Judge)
)
)
)
BRADLEY R. GARRIS ) BOARD OF PATENT
Administrative Patent Judge) APPEALS AND
) INTERFERENCES
)
)
CAMERON WEIFFENBACH )
Administrative Patent Judge)
Appeal No. 95-0326
Application No. 07/877,253
6
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