Ex parte Stephani et al.

Board of Patent Appeals and Interferences

Feb 14, 2002

08702074 (B.P.A.I. Feb. 14, 2002)

The opinion in support of the decision being entered today was not
written for publication and is not binding precedent of the Board.
Paper No. 16
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte DIETRICH STEPHANI
and
HEINZ MITLEHNER
_____________
Appeal No. 1999-0887
Application No. 08/702,074
______________
ON BRIEF
_______________
Before THOMAS, HAIRSTON, and RUGGIERO, Administrative Patent
Judges.
RUGGIERO, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on the appeal from the final rejection
of claims 1, 4, 5, and 9-36. Claims 2, 3, and 6-8 have been
indicated by the Examiner to be allowable subject to being
rewritten in independent form to include all of the
limitations of the base and intervening claims.
The claimed invention relates to a barrier junction
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termination structure for a silicon-based semiconductor
component. The semiconductor component has a semiconductor
region which forms a depletion region in the active area of
the semiconductor component. The junction termination, which
surrounds the active area on or in a surface of the
semiconductor region, is formed with silicon with a doping
opposite to that of the semiconductor region, the dopant
having an impurity level of at least 0.1 eV in silicon.
Claim 1 is illustrative of the invention and reads as
follows:
1. A semiconductor component comprising:
at least one silicon semiconductor region with
n-type conduction, the semiconductor region forming a
depletion region in an active area of the semiconductor
region when an off-state voltage is applied to the active
area; and
a junction termination for the active area, the
junction termination being disposed around the active
area at or in a surface of the semiconductor region, the
junction termination comprising silicon with p-type
conduction, the silicon with p-type conduction of the
junction termination being doped with at least one dopant
having an acceptor level of at least approximately 0.1 eV
in silicon.
The Examiner relies on the following prior art:
Jenny 2,809,165 Oct. 08,
1957
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Bemski 2,827,436 Mar. 18,
1958
Temple 4,242,690 Dec. 30,
1980
Jaecklin 4,742,382 May 03,
1988
Okabe et al. (Okabe) 5,510,634 Apr. 23,
1996
(filed Oct. 18,
1994)
Appeal No. 1999-0887
Application No. 08/702,074
The Appeal Brief was filed May 26, 1998 (Paper No. 10). In response1
to the Examiner’s Answer dated August 4, 1998 (Paper No. 12), a Reply Brief
was filed October 13, 1998 (Paper No. 13), which was acknowledged and entered
by the Examiner as indicated in the communication dated October 23, 1998
(Paper No. 14).
4
J. S. Moore et al. (Moore), “Energy Levels in Cobalt
Compensated Silicon,” 41 Journal of Applied Physics, No. 13,
5282-85 (December 1970).
Claims 1, 4, 5, and 9-36 stand finally rejected under
35 U.S.C. § 103(a). As evidence of obviousness, the Examiner
offers Temple in view of Moore with respect to claims 1, 5, 9,
10, 14, 16-21, 25, 26, 30, and 32-36, adds Jaecklin to the
basic combination with respect to claims 11-13, and 27-29, and
adds Okabe to the basic combination with respect to claims 15
and 31. In separate rejections under 35 U.S.C. § 103(a),
claims 21-23 are rejected as being unpatentable over Temple in
view of Jenny, and claims 1, 4, and 5 are rejected as being
unpatentable over Temple in view of Bemski.
Rather than reiterate the arguments of Appellants and the
Examiner, reference is made to the Briefs and Answer for the1
respective details.
OPINION
It is our view, after consideration of the record before
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5
us, that the collective evidence relied upon and the level of
skill in the particular art would not have suggested to one of
ordinary skill in the art the obviousness of the invention as
set forth in claims 1, 4, 5, and 9-36. Accordingly, we
reverse.
With respect to independent claims 1 and 21, the
Examiner, as the initial basis for an obviousness rejection,
proposes to modify the semiconductor device of Temple which
describes a high breakdown voltage device having a junction
extension region adjacent to a p-n junction termination.
According to the Examiner, Temple discloses the claimed
invention except that the reference “ . . . does not teach the
dopant in the junction region to have an acceptor or donor
level greater than 0.1 eV in silicon.” (Final Office action,
page 3). To address this deficiency, the Examiner turns to
Moore which discloses the doping of silicon with cobalt which
exhibits an energy level greater than 0.1 eV in silicon. In
the Examiner’s analysis, “[i]t would have been obvious to a
person of ordinary skill in the art at the time of invention
to use cobalt as either a donor or acceptor dopant as taught
by Moore et al. in the device of Temple to increase said
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6
device’s breakdown voltage.” (Id.)
In response, Appellants assert that the Examiner has
failed to set forth a prima facie case of obviousness since
proper motivation for one of ordinary skill to make the
Examiner’s proposed combination has not been established.
Upon careful review of the applied prior art, we are in
agreement with Appellants’ stated position in the Briefs. The
mere fact that
the prior art may be modified in the manner suggested by the
Examiner does not make the modification obvious unless the
prior art suggested the desirability of the modification. In
re Fritch, 972 F.2d 1260, 1266 n.14, 23 USPQ2d 1780, 1783-84
n.14
(Fed. Cir. 1992).
It is our view that, while a showing of proper motivation
does not require that a combination of prior art teachings be
made for the same reason as Appellants to achieve the claimed
invention, we can find no motivation for the skilled artisan
to apply the cobalt doped silicon teachings of Moore to the
semiconductor device of Temple. As pointed out by Appellants
(Brief, page 8), Moore is directed to the measurement of
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certain characteristics such as resistivity and Hall effect on
laboratory samples of cobalt doped silicon. We fail to see
how the laboratory sample measurement disclosure of Moore
would have any relevance to the semiconductor device structure
of Temple,
let alone the specific claimed doping of the device junction
termination region. There is nothing in the disclosure of
Temple to indicate that the regulation of the electrical
characteristics measured in Moore was ever a concern. It is
our opinion that
the only basis for applying the teachings of Moore to the
semiconductor device structure of Temple comes from an
improper attempt to reconstruct Appellants’ invention in
hindsight. Accordingly, since the Examiner has not
established a prima facie case of obviousness, the rejection
of independent claims 1 and 21, and claims 4, 5, 9-20, and 22-
36 dependent thereon, over the combination of Temple and Moore
is not sustained.
Turning to a consideration of the Examiner’s separate
35 U.S.C. § 103(a) rejection of independent claim 1, and
dependent claims 4 and 5, based on the combination of Temple
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and Bemski, we do not sustain this rejection as well. As the
basis for this rejection, the Examiner proposes to add
Bemski’s disclosure of cobalt or nickel doped silicon, and its
described advantages in increasing minority carrier lifetime,
to the teachings of Temple. In the Examiner’s view, “[i]t
would have been obvious to a person of ordinary skill in the
art at the time of invention to use cobalt or nickel as an
acceptor dopant as taught by Bemski in the device of Temple to
improve the minority carrier lifetime.” (Final Office action,
page 5).
In response, Appellants’ arguments mirror those made
supra with respect to the Moore reference, arguments with
which we agree for essentially the same reasons as discussed
previously. The disclosure of Bemski is directed to the heat
treatment of a single crystal silicon body in the presence of
nickel or cobalt to improve minority carrier lifetime. We
find nothing in the disclosure of Bemski, however, which would
indicate any practical application of the disclosure to
semiconductor component devices or components, let alone to
the specific claimed junction termination region of such
devices. As particularly set forth at column 7, lines 32-34
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of Bemski, “ . . . the practical application of this invention
is restricted to single crystal silicon.” In view of the
above, we are left to speculate why the skilled artisan would
employ the single crystal silicon body teachings of Bemski in
the semiconductor device of Temple. The only reason we can
discern is improper hindsight reconstruction of Appellants’
claimed invention. In order for us to sustain the Examiner’s
rejection under 35 U.S.C. § 103, we would need to resort to
speculation or unfounded assumptions or rationales to supply
deficiencies in the factual basis of the rejection before us.
In re Warner, 379 F.2d 1011, 1017, 154 USPQ 173, 178 (CCPA
1967), cert. denied, 389 U.S. 1057 (1968), reh’g denied, 390
U.S. 1000 (1968).
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Lastly, with the above discussion in mind, we also do not
sustain the Examiner’s separate obviousness rejection of
claims 21-23 based on the combination of Temple and Jenny.
Although Jenny provides a disclosure of the doping of silicon
with sulfur or selenium, dopants which have a donor energy
level greater than 0.1 eV in silicon, there is nothing which
would indicate the suitability of such a material for a
junction termination. We agree with Appellants (Brief, page
15) that, at best, Jenny provides a teaching of utilizing
sulfur and selenium doped silicon in the active region of a
semiconductor device. Such a teaching, however, falls well
short of providing motivation to the skilled artisan to
utilize such material in the junction termination region of a
semiconductor device, particularly in the manner specifically
set forth in the appealed claims.
We have also reviewed the Jaecklin and Okabe references
applied by the Examiner to address the stacked layers and
field ring structure, respectively, of several dependent
claims. We find nothing in either of these references,
however, that would overcome the innate deficiencies of the
Temple, Moore, Bemski, and Jenny references discussed
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previously.
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In conclusion, we have not sustained the Examiner’s
35 U.S.C. § 103 rejections of any of the claims on appeal.
Accordingly, the decision of the Examiner rejecting claims
1, 4, 5, and 9-36 is reversed.

REVERSED
JAMES D. THOMAS )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
KENNETH W. HAIRSTON ) APPEALS AND
Administrative Patent Judge ) INTERFERENCES
)
)
)
)
JOSEPH F. RUGGIERO )
Administrative Patent Judge )
JFR:hh
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