Ex Parte Herman

Board of Patent Appeals and Interferences

Apr 28, 2005

09723655 (B.P.A.I. Apr. 28, 2005)

1
The opinion in support of the decision being entered today
was not written for publication and
is not binding precedent of the Board.

UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte THOMAS HERMAN
_____________
Appeal No. 2005-0328
Application No. 09/723,655
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ON BRIEF
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Before HAIRSTON, RUGGIERO and NAPPI, Administrative Patent Judges.
NAPPI, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on appeal under 35 U.S.C. § 134 of the final rejection of
claims 9 through 14, 21 and 22
Invention
The invention relates to a method of making a MOS gated device. The
method makes use of polysilicon stripes to define a mask for the formation of
three sequential regions, the first being a base diffusion, the second being a
source diffusion and the third being a higher concentration base region which
underlies the first base and does not invade the invertible channel formed by the
first base and source. See page 4 of appellant’s specification.
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Application No. 09/723,655
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Claim 9 is representative of the invention.
9. A process of manufacture of a MOSgated device comprising:
forming a gate oxide layer atop a silicon surface of one conductivity
type;
forming a layer of polysilicon atop said gate oxide layer; etching said
polysilicon layer and said underlying gate oxide layer into a plurality of
stripes of oxide and polysilicon spaced 1 to 4 microns and overlying said
silicon surface; implanting and diffusing a plurality of spaced first base
diffusion stripes of the other conductivity type into said silicon surface,
using said stripes of oxide and polysilicon as a mask; implanting and
diffusing a plurality of source diffusions into said first base diffusion
stripes, using said stripes of oxide and polysilicon as a mask, and leaving
invertible channel regions along the outer edges of said first base diffusion
stripes; implanting and diffusing second base diffusion stripes into said
silicon surface using said stripes of oxide and polysilicon as a mask, to a
depth below that of said source diffusions and extending to between the
opposite edges of adjacent pairs of said polysilicon stripes; wherein said
stripes of oxide and polysilicon do not include sidewall spacers during
implanting and diffusing of said first base diffusion stripes, said source
diffusions, and said second base diffusions.
References
The references relied upon by the examiner are as follows:
Davies 5,155,052 Oct. 13, 1992
Ajit et al. (Ajit) 5,474,946 Dec. 12, 1995
Rejection at Issue
Claims 9 through 14, 21 and 22 are rejected under 35 U.S.C. § 103 as
being unpatentable over Davies and Ajit as set forth on pages 5 through 7 of the
answer. Throughout the opinion we make reference to the briefs and the answer
for the respective details thereof.
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Application No. 09/723,655
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Opinion
We have carefully considered the subject matter on appeal, the rejection
advanced by the examiner and the evidence of obviousness relied upon by the
examiner as support for the rejection. We have, likewise, reviewed and taken
into consideration, in reaching our decision, the appellant’s arguments set forth in
the briefs along with the examiner’s rationale in support of the rejection and
arguments in rebuttal set forth in the examiner’s answer.
With full consideration being given to the subject matter on appeal, the
examiner’s rejection and the arguments of appellant and examiner, for the
reasons stated infra we reverse the examiner’s rejection of claims 9 through 14,
21 and 22 under 35 U.S.C. § 103.
Appellant argues on pages 4 and 5 of the brief:
Davies does not teach using the oxide and polysilicon stripes in
forming the second base diffusions. Indeed, Davies teaches the opposite.
Davies teaches forming sidewall spacers 18 before forming low
resistivity regions 17. That is, sidewall spacers 18 are used for positioning
low resistivity regions. Col. 4, lines 12-14. As a result, contrary to the
results achieved by the present invention, the low resistively regions 17 do
not extend laterally as far as possible.
Further, on pages 5 and 6 of the brief, appellant argues, citing Davies column 4,
lines 25-43, that the sidewall spacers are critical to Davies device and as such
Davis teaches away from the claimed feature of using the oxide and polysilicon
stripes which do not have sidewall spacers as a mask for forming the second
base diffusions.
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Application No. 09/723,655
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In response, the examiner states, on pages 7 and 8 of the answer:
With regard to the appellant’s arguments that “Davies teaches
forming sidewall spacers 18 before forming low resistivity regions 17,” it
should be noted that Davies, in column 4, lines 38-43, specifically recites
the situation where sidewall spacers are not used in implanting the low
resistivity regions 17 which correspond to the claimed second base
diffusion. Thus Davies teaches in figures 1-4 and column 4, lines 38-43
the limitation wherein the stripes of oxide and polysilicon do not include
sidewall spacers during implanting and diffusion of the second base
diffusion. Therefore, the arguments are not persuasive, and the rejection
is proper.
With regard to the appellant’s argument that “Davies actually
teaches away from using the oxide and polysilicon stripes as a mask in
forming the second base regions (low resistivity regions 17),” it should be
noted Davies never states that the claimed situation cannot produce a
working device. While Davies suggests in column 4, lines 25-43 “it has
been found that if a thin oxide, analogous to oxide 15 [which is a misprint
and should be ‘oxide 16’] shown in Fig.1, is used rather than a sidewall
spacer 18, insufficient separation between base 12 and low resistively
region 17 is provided, and correspondingly low yield result,” (emphasis
added [by examiner]) it is clear that insufficient separation does not make
the device inoperable. Low yields, whether good or bad, do not make
Davies teach away from the subject matter. On the contrary, the low
yields cited by Davies when sidewall spacers are not used prove that this
method is disclosed and does produce a working device. Therefore,
appellant’s arguments are not persuasive, and the rejection is proper.
We disagree with the examiner’s rationale. Claim 9 includes the limitation
“wherein said stripes of oxide and polysilicon do not include sidewall spacers
during implanting and diffusing of said first base diffusion stripes, said source
diffusions, and said second base diffusions.” We concur with the appellant that
Davies teaches away from this limitation.
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Our reviewing court has said “[A] reference may be said to teach away
when a person of ordinary skill, upon reading the reference, would be
discouraged from following the path set out in the reference, or would be lead in
a direction divergent from the path that was taken by the applicant. The degree
of teaching away will of course depend on the particular facts; in general, a
reference will teach away if it suggests that the line of development flowing from
the reference’s disclosure is unlikely to be productive of the result sought by the
applicant.” In re Gurley, 27 F.3d 551, 553, 31 USPQ2d 1130, 1131 (Fed. Cir.
1994) (citing United States V. Adams, 383 U.S. 39, 52, 148 USPQ 479, 484
(1966)(“known disadvantages in old devices which would naturally discourage
the search for new inventions may be taken into account in determining
obviousness”). However, a reference that “teaches away” does not per se
preclude a prima facie case of obviousness, but rather the “teaching away” of
the reference is a factor to be considered in determining unobviousness. Id 27
F.3d at 552, 31 USPQ 2d at 1132. A reference that neither teaches a limitation
nor warns against using the limitation does not require a finding that the
reference “teaches away” rather the teaching of the reference must be
considered alongside the teachings of the secondary reference. ParaOrdnance
Manufacturing Inc. V. SGS Importers Int. Inc., 73 F.3d 1085, 1090, 37
USPQ2d 1237, 1241 (Fed. Cir. 1995).
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Application No. 09/723,655
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Davies states “Width of the sidewall spacer 18 is a critical feature of the
present invention” (column 4, lines 25-26) “[i]f this spacing is too small, or varies
widely due to the process control of forming the spacer 18, low resistivity region
17 will extend into channel 26, destroying the device. For example, it has been
found that if a thin oxide, analogous to oxide 15 [sic, 16] shown in Fig. 1, is used
rather than a sidewall spacer 18, insufficient separation between base 12 and
low resistivity region 17 is provided, and correspondingly low yields result”
(column 4, lines 35-43). We find that one of ordinary skill in the art reading these
sections of Davies would be discouraged from pursuing the path of
manufacturing the device without the use of sidewall spacers. The examiner has
presented no other evidence to show that one of ordinary skill in the art would be
motivated to not include sidewall spacers during implanting and diffusing of said
base diffusion stripes, said source diffusions and said second base diffusions.
Accordingly, we find that the examiner has not established a prima facie of
obviousness and we will not sustain the examiner’s rejection of independent
claim 9 or dependent claims 10 through 14, 21 and 22.
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Application No. 09/723,655
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In view of the forgoing, we will not sustain the examiner’s rejection of
claims 9 through 14, 21 and 22 under 35 USC § 103.
REVERSED
KENNETH W. HAIRSTON )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
JOSEPH F. RUGGIERO ) APPEALS AND
Administrative Patent Judge ) INTERFERENCES
)
)
)
ROBERT E. NAPPI )
Administrative Patent Judge )
RN/RWK
Appeal No. 2005-0328
Application No. 09/723,655
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