FUJI ELECTRIC CO., LTD.

Patent Trials and Appeals Board

Sep 9, 2021

2021000385 (P.T.A.B. Sep. 9, 2021)

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.
15/796,890 10/30/2017 Naoyuki OHSE ASA-216 8143
23995 7590 09/09/2021
Rabin & Berdo, PC
2650 Park Tower Drive
Suite 800
Vienna, VA 22180
EXAMINER
DYKES, LAURA M
ART UNIT PAPER NUMBER
2892
NOTIFICATION DATE DELIVERY MODE
09/09/2021 ELECTRONIC
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.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
eofficeaction@appcoll.com
firm@rabinberdo.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
_________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
__________

Ex parte NAOYUKI OHSE,
MAKOTO UTSUMI,
and YASUHIKO OONISHI
__________

Appeal 2021-000385
Application 15/796,890
Technology Center 2800
___________

Before ADRIENE LEPIANE HANLON, BEVERLY A. FRANKLIN, and
GEORGE C. BEST, Administrative Patent Judges.

HANLON, Administrative Patent Judge.

DECISION ON APPEAL

A. STATEMENT OF THE CASE
The Appellant1 filed an appeal under 35 U.S.C. § 134(a) from an Examiner’s
decision finally rejecting claims 1, 2, 4–13, 15, and 16. We have jurisdiction under
35 U.S.C. § 6(b).
We REVERSE.

1 We use the word “Appellant” to refer to “applicant” as defined in 37 C.F.R.
§ 1.42. The Appellant identifies the real party in interest as FUJI ELECTRIC CO.,
LTD. Appeal Brief dated May 11, 2020 (“Appeal Br.”), at 3.
Appeal 2021-000385
Application 15/796,890

2

The claimed invention is directed to a silicon carbide semiconductor device
and a method of manufacturing the device. The semiconductor device comprises,
inter alia, an n-type semiconductor region that is a source region or an emitter
region and consists of a first portion that contains ion implanted arsenic and a
second portion that contains phosphorous.
Representative claim 1 is reproduced below from the Claims Appendix to
the Appeal Brief. The limitations at issue are italicized.
1. A silicon carbide semiconductor device, comprising:
an n-type silicon carbide substrate;
a p-type silicon carbide region provided on the n-type silicon
carbide substrate and having an impurity concentration equal to or
lower than 1.0×1018 cm-3; and
an n-type semiconductor region that is a source region or an
emitter region, that is disposed in at least a region of an upper portion
of the p-type silicon carbide region provided on the n-type silicon
carbide substrate, and that consists of a first portion that contains ion
implanted arsenic having an ion implanted arsenic concentration
ranging from 1.0×1019 cm-3 to 5.0×1020 cm-3, which is effective to
suppress leakage current, and a second portion that contains
phosphorous.
Appeal Br. 17.
Similarly, claim 12, the other independent claim on appeal, recites a method
of manufacturing a silicon carbide semiconductor device comprising, inter alia, the
step of “forming an n-type semiconductor region that is a source region or an
emitter region . . . , the n-type-semiconductor region consisting of a first portion
that contains ion implanted arsenic . . . and a second portion that contains
phosphorous.” Appeal Br. 19–20.
Appeal 2021-000385
Application 15/796,890

3

The Examiner maintains the following grounds of rejection on appeal:
(1) claims 1, 2, 4, 5, and 8–13 under 35 U.S.C. § 103 as unpatentable over
Suzuki 9102 in view of Suzuki 507;3 and
(2) claims 6, 7, 15, and 16 under 35 U.S.C. § 103 as unpatentable over
Suzuki 910 in view of Suzuki 507, further in view of Harada.4
B. DISCUSSION
The Examiner finds Suzuki 910 discloses a silicon carbide semiconductor
device as recited in claim 1 with the exception of an n-type semiconductor region
consisting of a first portion containing ion implanted arsenic and a second portion
containing phosphorous. Final Act. 3–4;5 see also id. at 10 (finding that Suzuki
910 does not disclose forming an n-type semiconductor region consisting of an ion
implanted arsenic first portion and a phosphorous-containing second portion as
recited in claim 12).
The Examiner finds Suzuki 507 discloses a semiconductor device
comprising an n-type semiconductor region consisting of first portion 22
containing an ion implanted n-type impurity and second portion 24 containing
phosphorous. Final Act. 4. The Examiner finds Suzuki 507 does not expressly
disclose that first portion 22 contains ion implanted arsenic as recited in the claims
on appeal. Final Act. 4. Rather, Suzuki 507 discloses that portion 22 contains
nitrogen as the n-type impurity. Suzuki 507, at ¶ 29.

2 US 2016/0247910 A1, to Suzuki et al., published August 25, 2016 (“Suzuki
910”). The Examiner and the Appellant refer to this reference as “Suzuki ’10.”
3 US 2017/0271507 A1, to Suzuki et al., published September 21, 2017 (“Suzuki
507”). The Examiner and the Appellant refer to this reference as “Suzuki ’07.”
4 US 2011/0175111 A1, to Harada et al., published July 21, 2011 (“Harada”).
5 Final Office Action dated December 9, 2019.
Appeal 2021-000385
Application 15/796,890

4

Nonetheless, the Examiner finds Suzuki 507 discloses that the n-type
impurity for first portion 22 and the n-type impurity for second portion 24 are
different and a choice for first portion 22 is ion-implanted arsenic. Final Act. 4
(citing Suzuki 507, at ¶¶ 30, 42). The Examiner also finds Suzuki 507 discloses
that the n-type impurity for portion 24 (corresponding to the claimed second
portion) preferably has a higher solid solubility and activity in silicon carbide than
the n-type impurity for portion 22 (corresponding to the claimed first portion), and
phosphorous has a higher solid solubility and activity in silicon carbide than
arsenic. Final Act. 4–5 (citing Suzuki 507, at ¶¶ 53, 54). Based on those findings,
the Examiner concludes that it would have been obvious to one of ordinary skill in
the art to substitute arsenic for the n-type impurity (nitrogen) in Suzuki 507’s first
portion 22 “since it has been held to be within the general skill of a worker in the
art to select a known material on the base [sic] of its suitability, for its intended use
involves only ordinary skill in the art.” Final Act. 5.
The Examiner relies on paragraph 42 of Suzuki 507 to show that ion-
implanted arsenic is a choice for first portion 22. Final Act. 4. Paragraph 42,
however, discloses that silicon carbide portion or region 22 is formed using ion
implantation of nitrogen and silicon carbide portion or region 24 is formed using
ion implantation of phosphorus or arsenic. Similarly, paragraph 30 of Suzuki 507,
which is also relied on by the Examiner, discloses that the n-type impurity
contained in silicon carbide region 22 is nitrogen and the n-type impurity contained
in silicon carbide region 24 is phosphorus or arsenic and may further contain
nitrogen. See also Suzuki 507, at ¶ 54 (disclosing that silicon carbide region 24
preferably contains phosphorus because “the solid solubility and activity of the
phosphorus to the silicon carbide is particularly higher than that of the arsenic”).
Appeal 2021-000385
Application 15/796,890

5

The Appellant argues that Suzuki 507 “read as a whole does not teach or
suggest using arsenic as the impurity in region 22.” Appeal Br. 11; see also Reply
Br. 46 (contending that Suzuki 507 “everywhere discloses ion implanted nitrogen
in . . . SiC region (22)”). Indeed, Suzuki 507 only discloses that nitrogen is ion
implanted in region 22. See Suzuki 507, at ¶¶ 29, 42, 53. According to Suzuki
507, nitrogen is used in region 22 because nitrogen causes less ion implantation
damage on the silicon carbide regions than phosphorus. Suzuki 507, at ¶ 53; see
also Reply Br. 4 (discussing paragraph 53 of Suzuki 507).
Based on the foregoing, we find Suzuki 507 does not teach that arsenic is a
suitable impurity for portion 22. The Examiner does not rely on Harada to cure
that deficiency in Suzuki 507. See Final Act. 13 (finding Harada teaches a n-type
semiconductor region on a threading screw dislocation). Thus, on this record,
there would have been no reason to modify Suzuki 910’s n-type semiconductor
region with a first portion containing ion implanted arsenic as recited in claims 1
and 12, absent the Appellant’s disclosure.
The obviousness rejections on appeal are not sustained.
C. CONCLUSION
The Examiner’s decision is reversed.
In summary:

6 Reply Brief dated October 20, 2020.
Appeal 2021-000385
Application 15/796,890

6

Claims
Rejected
35 U.S.C. § Reference(s)/Basis Affirmed Reversed
1, 2, 4, 5, 8–
13
103 Suzuki 910, Suzuki
507
1, 2, 4, 5, 8–
13
6, 7, 15, 16 103 Suzuki 910, Suzuki
507, Harada
6, 7, 15, 16
Overall
Outcome
1, 2, 4–13,
15, 16

REVERSED