Ex Parte Blanchard

Board of Patent Appeals and Interferences

May 21, 2012

11342484 (B.P.A.I. May. 21, 2012)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
11/342,484 01/30/2006 Richard A. Blanchard GS 129C2 3942
27774 7590 05/21/2012
MAYER & WILLIAMS PC
251 NORTH AVENUE WEST
Suite 201
WESTFIELD, NJ 07090
EXAMINER
DICKEY, THOMAS L
ART UNIT PAPER NUMBER
2826
MAIL DATE DELIVERY MODE
05/21/2012 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte RICHARD A. BLANCHARD
____________

Appeal 2010-003212
Application 11/342,484
Technology Center 2800
____________

Before MARC S. HOFF, CARLA M. KRIVAK, and
ELENI MANTIS MERCADER, Administrative Patent Judges.

KRIVAK, Administrative Patent Judge.

DECISION ON APPEAL
Appellant appeals under 35 U.S.C. § 134(a) from a final rejection of
claims 1, 2, 5, 8, and 9. We have jurisdiction under 35 U.S.C. § 6(b).
We reverse

Appeal 2010-003212
Application 11/342,484
2

STATEMENT OF THE CASE
Appellant’s claimed invention is directed to a power MOSFET.
Independent claim 1, reproduced below, is illustrative.
1. A power MOSFET, comprising:

a substrate of a first conductivity type;

an epitaxial layer on the substrate, said epitaxial layer
having a first conductivity type;

first and second body regions located in the epitaxial
layer defining a drift region therebetween, said body regions
having a second conductivity type;

first and second source regions of the first conductivity
type respectively located in the first and second body regions;
and

a plurality of trenches located below said body regions in
said drift region of the epitaxial layer, said trenches being filled
with a material having a dopant of the second conductivity type,
said trenches extending toward the substrate from the first and
second body regions, said dopant being introduced into
sidewalls of the trenches by diffusion, and, being diffused from
said trenches into portions of the epitaxial layer adjacent the
trenches.

REFERENCES and REJECTIONS
The Examiner rejected claims 1, 2, 5, 8, and 9 under 35 U.S.C. § 103
based upon the teachings of Tihanyi (US Patent No. 6,184,555 B1, February
6, 2001), Becker (US Patent No. 4,782,036, November 1, 1988), and So (US
Patent No. 5,895,951, April 20, 1999).

Appeal 2010-003212
Application 11/342,484
3
ANALYSIS
The Examiner finds Tihanyi teaches all the features of Appellant’s
claimed invention except Tihanyi teaches trenches that are filled with
insulating material such as SiO2 or weakly doped polysilicon (Tihanyi, Fig.
3 and col. 6, ll. 17-21; Ans. 7). The Examiner then finds Becker teaches a
trench filled with a borosilicate glass, which is a p-type dopant capable of
being diffused from the trench into portions of an adjacent epitaxial layer
(Ans. 8). Thus, the Examiner finds it would therefore be obvious to a skilled
artisan to substitute Becker’s boron silicate glass for Tihanyi’s insulating
material (Ans. 10).
Appellant contends, inter alia, combining Becker’s material to fill
Tihanyi’s trench is not a matter of simple substitution as alleged by the
Examiner (App. Br. 11). Rather, Becker’s highly doped trench filled with a
single conductivity type material is not suitable for use in Tihanyi’s
trenches, which are filled with an insulating material. Appellant asserts
Tihanyi’s trenches are surrounded by depletion and complementary doped
depletion zones for proper balance and “to reduce the forward resistance of
the device at a given reverse voltage”; whereas, the boron silicate glass
deposited in Becker’s trench is highly doped and the boron atoms diffuse out
of the trench to form a capacitive storage cell (App. Br. 6, 10-11).
The Examiner has provided no rebuttal evidence except to cite case
law and state it would be an obvious substitution without providing reasons
why it would be so. Thus, we find Appellant’s argument persuasive with
respect to the rejection of claims 1, 2, 5, 8, and 9 (see App. Br. 8-12).

DECISION
The Examiner’s decision rejecting claims 1, 2, 5, 8, and 9 is reversed.
Appeal 2010-003212
Application 11/342,484
4

REVERSED

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