Ex Parte Cao

Board of Patent Appeals and Interferences

Jun 29, 2012

11142034 (B.P.A.I. Jun. 29, 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.
11/142,034 06/01/2005 Jianjun Cao 0400218 6131
25700 7590 06/29/2012
FARJAMI & FARJAMI LLP
26522 LA ALAMEDA AVENUE, SUITE 360
MISSION VIEJO, CA 92691
EXAMINER
RODELA, EDUARDO A
ART UNIT PAPER NUMBER
2893
MAIL DATE DELIVERY MODE
06/29/2012 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 JIANJUN CAO
________________

Appeal 2010-003886
Application 11/142,034
Technology Center 2800
________________

Before BRADLEY W. BAUMEISTER, ERIC B. CHEN, and
JEREMY J. CURCURI, Administrative Patent Judges.

CURCURI, Administrative Patent Judge.

DECISION ON APPEAL

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SUMMARY
Appellant appeals under 35 U.S.C. § 134(a) from the Examiner’s final
rejection of claims 1-8. Claims 9-13 have been cancelled.
Claims 1-8 stand rejected under 35 U.S.C. § 103(a) as obvious over
Omura (US 7,067,870 B2; issued June 27, 2006; filed Feb. 3, 2004) in view
of Peake (WO 03/103056 A2; published Dec. 11, 2003; filed May 21, 2003)
and Baliga (US 6,649,975 B2; issued Nov. 18, 2003; filed Nov. 5, 2001).
We affirm.

STATEMENT OF CASE
Appellant’s invention relates to “a trench type power semiconductor
device which includes a buried electrode that is electrically connected to an
electrode that can be biased to reach a voltage other than any of the other
power electrodes.” (Abstract.)
Claim 1, which is representative of the appealed claims,
1
is
reproduced below with disputed limitations in italics:
1. A power semiconductor device comprising:
a substrate having a first major surface and an opposing
second major surface;
a drift region of one conductivity formed on said first
major surface of said substrate;
a base region of another conductivity adjacent said drift
region;
at least one trench extending through said base region
and terminating at a depth below said base region;

1
Appellant argues claims 1-8 together as a group. See App. Br. 8-12.
Accordingly, we select independent claim 1 as representative. See 37 C.F.R.
§ 41.37(c)(1)(vii)(2010).
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a buried electrode disposed within said trench below said
base region;
an insulation body interposed between said buried
electrode and said trench walls;
an insulated gate electrode disposed in said trench and
over said buried electrode in said trench and spanning the entire
thickness of said base region;
at least one conductive region of said one conductivity
formed in said base region;
a first power electrode over said first major surface and
electrically connected to said at least one conductive region;
a second power electrode electrically connected to said
second major surface of said substrate;
a control electrode over said first major surface and
electrically connected to said gate electrode; and
a buried contact over said first major surface and
electrically connected to said buried electrode, said buried
contact being capable of biasing said buried electrode
independently of a voltage of the first and second power
electrodes, wherein said first power electrode includes an edge
opposite a first edge of said control electrode and a first edge of
said buried contact, and wherein said control electrode
includes a second edge transverse to said first edge thereof and
opposite a second edge of said buried contact that is transverse
to said first edge of said buried contact.

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The disputed limitations are exemplified in Figure 4 of Appellant’s
patent application. Figure 4 is reproduced below:

Figure 4 depicts a plan view of a device surface including a gate contact 37,
a buried contact 38, and a source contact 30.

We note for clarity that the claimed “first power electrode”
corresponds to the depicted source contact 30, the claimed “control
electrode” corresponds to the depicted gate contact 37, and the claimed
“buried contact” corresponds to the depicted contact 38, which is for buried
electrode 36 (App. Br. 4).

CONTENTIONS
The Examiner finds that Omura describes a power semiconductor
device comprising a substrate, a drift region, a base region, at least one
trench, a buried electrode, an insulation body, an insulated gate electrode, at
least one conductive region, a first power electrode, a second power
electrode, and a control electrode, as recited in claim 1. (Ans. 3-4). The
Examiner further finds that Omura describes biasing said buried electrode
independently of a voltage of the first and second power electrodes. (Ans. 4-
5).
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The Examiner finds that Peake describes, as further recited in claim 1,
“a buried contact over said first major surface and electrically connected to
said buried electrode.” The Examiner concludes it would have been
obvious:
to have a buried contact over said first major surface and
electrically connected to said buried electrode in the invention
of Omura as shown by Peake, for the purpose of providing a
practical means to provide an electrical contact / connection to
the buried electrode for the proper functioning of the device.
(Ans. 5).
The Examiner finds that Omura and Peake do not describe the
remaining limitation in claim 1, specifically,
said first power electrode includes an edge opposite a first edge
of said control electrode and a first edge of said buried contact,
and wherein said control electrode includes a second edge
transverse to said first edge thereof and opposite a second edge
of said buried contact that is transverse to said first edge of said
buried contact.
(Ans. 5).
The Examiner further finds, though, that Baliga in Figure 6 describes:
a particular electrode layout wherein said first power electrode
[204, source] includes an edge opposite [right most vertical
edge of 204] a first edge [left most vertical edge] of said control
electrode [202, gate electrode], and wherein said control
electrode [202] includes a second edge [lower edge] transverse
[shown] to said first edge thereof [right most vertical edge of
204].
(Ans. 6 (citing Baliga, Figure 6)).
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Figure 6 of Baliga is reproduced below:

Figure 6 depicts a plan view of a device including a gate contact 202, and a
source contact 204.

The Examiner finds that Baliga still does not describe said first power
electrode (Baliga’s source contact 204) includes an edge opposite a first
edge of said buried contact; wherein said control electrode (Baliga’s gate
contact 202) includes a second edge opposite a second edge of said buried
contact that is transverse to said first edge of said buried contact. (Ans. 6).
Restated, the plan view of the device shown in Baliga (in Figure 6) does not
show the claimed orientation for a buried electrode contact.
However, the Examiner concludes that it would have been obvious to
use the claimed layout including the additional limitations not described in
Baliga for the purpose of providing electricity to the buried electrode to
allow for proper device function. (Ans. 6-7).
The Examiner reasons:
[T]he system of Omura/Peake requires that the buried
electrode has a surface contact electrode, therefore it would
have been entirely obvious to have oriented a first power
electrode [sic: that] includes an edge opposite a first edge of
said buried contact; wherein said control electrode includes a
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second edge opposite a second edge of said buried contact that
is transverse to said first edge of said buried contact, since this
would be satisfied by placing the buried electrode contact either
below or above the gate contact [202] in Figure 6 of Baliga.
(Ans. 6).
Appellant does not dispute that the cited art either teaches or renders
obvious a power semiconductor device having all of the claimed
components, including the provision of a gate contact, a buried contact, and
a source contact on the surface of the semiconductor substrate. (App. Br. 8-
13). Appellant only challenges whether the cited prior art teaches or
suggests arranging the three surface contacts in the specific orientation
recited in the amended claims. (Id.).
Specifically, Appellant argues that Peake is the sole reference that is
pertinent to placement of a buried electrode, that Peake is explicit in
describing the layout of the contacts situated on the first major surface, that
Peake teaches a contact layout distinctly different from that recited in the
claims, and that Baliga teaches a structure from which a buried electrode
contact is entirely absent. (App. Br. 10-11).

ISSUE
It is undisputed that the cited prior art teaches or suggests all of the
claimed elements, including the provision of the three claimed surface
contacts. It is further undisputed that the cited prior art does not expressly
teach the three surface contacts being provided in the claimed orientation
such that:
said first power electrode includes an edge opposite a first edge
of said control electrode and a first edge of said buried contact,
and wherein said control electrode includes a second edge
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transverse to said first edge thereof and opposite a second edge
of said buried contact that is transverse to said first edge of
said buried contact.
(claim 1).
The issue before us, then, is has Appellant demonstrated that the
Examiner erred in concluding that the difference between the claimed
contact orientation and the prior art’s teachings constitutes an obvious
difference?

PRINCIPLES OF LAW
A claimed invention is unpatentable if the differences between it and
the prior art “are such that the subject matter as a whole would have been
obvious at the time the invention was made to a person having ordinary skill
in the art.” 35 U.S.C. § 103.
Altering a position of a component in a device does not render the
device patentable when operation of the device would not thereby be
modified. See In re Japikse, 181 F.2d 1019, 1023 (CCPA 1950) (specific
positioning of a starting switch of a hydraulic power press held unpatentable
because shifting the position of the starting switch would not have modified
the operation of the device); In re Kuhle, 526 F.2d 553, 555 (CCPA 1975)
(holding that the particular placement of a contact in a conductivity
measuring device was an obvious matter of design choice within the skill in
the art).
The rationale to support a conclusion that a claim would have been
obvious may be that:
a person of ordinary skill has good reason to pursue the
known options within his or her technical grasp. If this leads to
the anticipated success, it is likely the product not of innovation
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but of ordinary skill and common sense. In that instance the
fact that a combination was obvious to try might show that it
was obvious under § 103.
KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398, 421 (2007).

ANALYSIS
We are unpersuaded that the difference between the contact
orientation of claim 1 and the cited prior art’s teachings is sufficient to
render claim 1 patentable.
I.
Appellant has not presented any persuasive arguments or evidence
that the difference between the claimed surface contact orientation and that
of the prior art provides any additional functionality (App. Br. 3-12).
Likewise, Appellant’s Specification does not indicate that the difference in
layout orientation provides any additional functionality (Spec. 3-6).
Appellant’s Specification does mention the gate electrodes spanning the
entire thickness of the base region, and it also mentions the buried electrodes
being biased to be positive with respect to the source contact (Spec.,
¶¶ [0016]-[0017]). However, with regard to the specific contact layout,
itself, which is indicated as being merely exemplary (Spec., ¶ [0021] ),
Appellant’s Specification only provides a single paragraph description,
which we reproduce here:
Referring now to Figure 4, a device according to the
present invention includes gate contact 37, which is electrically
connected to gate electrodes 22 and buried contact 38 which is
electrically connected to buried electrodes 36. Preferably,
buried electrodes 36 are biased to be positive with respect to
source contact 30 when a device according to the present
invention is operated. As a result, the Qgd of the device and
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thus its switching characteristics are improved. In addition, the
breakdown voltage (BVdss) is higher than the prior art shown
in Figure 1, where the buried electrode is connected to the
source.
(Spec., ¶¶ [0019]).
Accordingly, we find the disputed claim limitations relating to the
contact layout to be directed to an arrangement that is achieved by routine
design choice without providing any additional functionality. Put another
way, the claimed contact orientation is a routine arrangement or
rearrangement of the prior art’s contacts, well within the grasp of one of
ordinary skill in the art. Such routine rearrangement, without any associated
functionality is merely a matter of obvious design choice. See In re Japikse,
181 F.2d at 1023; In re Kuhle, 526 F.2d at 555.
II.
Even if we were to assume, solely for the sake of argument, that the
claimed contact orientation does provide some further functionality, there is
still no showing that the orientation provides any criticality to the device’s
operation, any unexpected results, or any reason to doubt that such an
arrangement would be successful. Appellant has not presented any
persuasive arguments or evidence that the differences between the claimed
surface contact orientation and that of the prior art provides any additional
criticality to the device’s operation, any unexpected results, or any reason to
doubt that such an arrangement would be successful (App. Br. 3-12).
Likewise, Appellant’s Specification does not indicate that the difference
between the claimed surface contact orientation and that of the prior art
provides any additional criticality to the device’s operation, any unexpected
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results, or any reason to doubt that such an arrangement would be successful
(Spec. 3-6).
Given that the prior art’s provision of three surface contacts is
undisputed, there exists only a finite number of possible arrangements by
which these contacts could be provided. Necessarily, a first edge of the prior
art’s first power contact may only be provided so as to be opposite a first
edge of either none, one, or both of the control contact and the buried
electrode contact. Similarly, and for each of these three possible
arrangements, a second edge of the control contact must necessarily be
opposite either a second edge of the buried electrode contact, or not be
opposite.
We therefore, conclude that it would have been obvious to a person
having ordinary skill in the art to have designed a specific arrangement of
contacts meeting the argued claim limitations. Such a design layout would
have been merely a product of ordinary skill and common sense. This is
because when faced with the design need of locating the claimed transistor’s
three surface contacts, one of ordinary skill in the art would have found it
obvious to try orienting the contacts in the claimed arrangement from the
finite set of identified layout arrangements and because the claimed
arrangement produces a predictable solution that is within the grasp of one
of ordinary skill. See KSR, 550 U.S. at 421. For the foregoing reasons,
Appellant has not persuaded us of error in the Examiner’s obviousness
rejection of representative claim 1. We therefore, sustain the Examiner’s
rejection of claim 1, as well as claims 2-8, which are not separately argued.

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DECISION
The Examiner’s decision rejecting claims 1-8 is affirmed.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1). See 37 C.F.R.
§ 1.136(a)(1)(iv) (2010).

AFFIRMED

kis