Ex Parte Herman

Patent Trials and Appeals Board

Jan 31, 2019

15191863 - (D) (P.T.A.B. Jan. 31, 2019)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR
15/191,863 06/24/2016 Thomas Herman
57579 7590 02/04/2019
MURPHY, BILAK & HOMILLER/INFINEON TECHNOLOGIES
1255 Crescent Green
Suite 200
CARY, NC 27518
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
ATTORNEY DOCKET NO. CONFIRMATION NO.
1012-1690 / 2008P80058 6905
us
EXAMINER
TRAN,TONY
ART UNIT PAPER NUMBER
2894
NOTIFICATION DATE DELIVERY MODE
02/04/2019 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):
official@mbhiplaw.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte THOMAS HERMAN
Appeal2018-004797
Application 15/191,863 1
Technology Center 2800
Before KAREN M. HASTINGS, JAMES C. HOUSEL, and
JEFFREY R. SNAY, Administrative Patent Judges.
SNAY, Administrative Patent Judge.
DECISION ON APPEAL
Appellant filed an appeal under 35 U.S.C. § 134(a) from the
Examiner's decision rejecting claims 44--47 and 49---67. We have
jurisdiction under 35 U.S.C. § 6(b). 2
We REVERSE.
1 Appellant is the Applicant, INFINEON TECHNOLOGIES AMERICAS
CORP., which, according to the Appeal Brief, is the real party in interest.
Appeal Brief (Appeal Br. 2) filed Dec. 18, 2017.
2 Our Decision additionally refers to the Specification filed June 24, 2016
("Spec."), the Final Office Action dated July 5, 2017 ("Final Act."), the
Examiner's Answer dated Feb. 12, 2018 ("Ans."), and the Reply Brief dated
Apr. 4, 2018 ("Reply Br.").
Appeal2018-004797
Application 15/191,863
BACKGROUND
The subject matter on appeal relates to power semiconductor devices
(see, e.g., claim 44). The Inventor discloses that a high electric field build-
up near the gate arrangement of conventional III-nitride power
semiconductor devices results in gate breakdown and that such conventional
devices also exhibit low drain-source breakdown voltage and time dependent
degradation of device parameters due to hot carriers and charge trapping.
Spec. ,r,r 3, 7. In view of this, the Inventor discloses a device in which the
mobile charge concentration is reduced in a region under the gate to keep a
parasitic-source-drain series resistance at a low value. Id. ,r 14. According
to the Inventor, this is accomplished in one embodiment via a reduced
charge region that is less conductive than adjacent regions of a two-
dimensional electron gas (2DEG) of a device when the 2DEG is in a
conductive state, which results in weaker electric fields near the edges of a
gate arrangement above the reduced charge region in comparison to prior
devices. Id. ,r 28.
Independent claim 44 is illustrative and is reproduced below from the
Claims Appendix of the Appeal Brief. Limitations at issue are italicized.
44. A power semiconductor device, comprising:
a III-nitride heterojunction body that includes a first III-
nitride body and a second III-nitride body having a different
band gap than that of said first III-nitride body;
a first power electrode comprising a conductive material
coupled to said second III-nitride body;
a second power electrode comprising said conductive
material coupled to said second III-nitride body;
a gate arrangement including a gate electrode disposed
between said first and said second power electrodes;
a conductive channel that includes a two-dimensional
electron gas (2DEG) that in a conductive state includes a
2
Appeal2018-004797
Application 15/191,863
reduced charge region produced by an implanted region in said
second III-nitride body under said gate electrode, wherein said
reduced charge region is less conductive than regions of said
2DEG adjacent each side of said reduced charge region;
said implanted region having implanted charge in said
second III-nitride body, said implanted charge configured to
repel electrons in said 2DEG under and beyond edges of said
gate electrode;
said reduced charge region extending beyond at least
one of said edges of said gate electrode and comprising
negative charge which repels negative carriers in a region
below said gate arrangement, said conductive channel being
devoid of said negative charge in said regions of said 2DEG
adjacent each side of said reduced charge region.
REJECTIONS ON APPEAL
I. claims 44, 47, 49--52, 56-61, and 64---67 3 under 35 U.S.C.
§ 102(b) as being anticipated by Kasahara; 4
II. claims 45, 46, and 55 as being unpatentable under 35
U.S.C. § I03(a) over Kasahara in view of Kinzer; 5
III. claims 53 and 54 as being unpatentable under 35 U.S.C.
§ I03(a) over Kasahara in view of Saxler; 6
3 The Examiner includes claim 48 in the statement of the rejection (Final
Act. 4) and sets forth a rejection for claim 48 (id. at 6) but claim 48 was
canceled via an amendment filed May 4, 2017. Therefore, claims 44--47 and
49--67 are before us on appeal.
4 Kasahara et al., US 2002/0017648 Al, published Feb. 14, 2002
("Kasahara").
5 Kinzer et al., US 2005/0189561 Al, published Sept. 1, 2005 ("Kinzer").
6 Saxler et al., US 7,612,390 B2, issued Nov. 3, 2009 ("Saxler").
3
Appeal2018-004797
Application 15/191,863
IV. claims 62 and 63 as being unpatentable under 35 U.S.C.
§ 103 over Kasahara in view of Parikh; 7 and
V. claims 44--47 and 49---67 on the ground of nonstatutory
double patenting over claims 22, 24, 25, 31, 32, and 34--
43 of U.S. Patent Application No. 12/162,749 in view of
Kasahara.
DISCUSSION
Rejection I
Claims 44, 47, 49-52, 56-61, and 64--67 are rejected under 35 U.S.C.
§ 102(b) as being anticipated by Kasahara.
The Examiner finds Kasahara discloses a power semiconductor device
comprising, among other things, a conductive channel including a reduced
charge region that is less conductive, wherein the reduced charge region
comprises a negative charge that repels negative carriers in a region below a
gate arrangement and wherein the conductive region is devoid of the
negative charge in regions of a 2DEG of the conductive channel adjacent
each side of the reduced charge region, citing the n- region depicted in
Kasahara's Figure 13 as a reduced charge region. Final Act. 4--6; Ans. 3-5.
Appellant contends Kasahara does not disclose a conductive channel
including a reduced charge region so that the conductive channel is devoid
of a negative charge in regions of the channel's 2DEG adjacent each side of
the reduced charge region, as recited in claim 44, because Kasahara
discloses n+ regions of the 2DEG having a higher negative charge (i.e.,
7 Parikh et al., US 7,501,669 B2, issued Mar. 10, 2009 ("Parikh").
4
Appeal2018-004797
Application 15/191,863
higher electron density) on each side of then- region in Figure 13, where the
2DEG has a lower electron density. Appeal Br. 4, 8-9; Reply Br. 4.
Appellant's arguments are persuasive. Kasahara discloses a
semiconductor device comprising an active layer, an electron supply layer,
and a 2DEG produced at an interface between the layers. Kasahara ,r 2. The
device has a first area having a relatively low two-dimensional electron
concentration (i.e., channel concentration) formed under a gate electrode and
a second area having a relatively high two-dimensional electron
concentration formed under a source electrode and under a gate electrode.
Id. ,r,r 8, 11. In one embodiment, Kasahara achieves the areas of different
electron concentrations by providing different portions of an AlGaN
material, which functions as an electron supply layer, with different
aluminum contents. Id. ,r,r 13-14, 17, 30, 33. Kasahara discloses that
channel portions under high aluminum content areas have high electron
concentrations and channel portions under low aluminum content areas have
low electron concentrations. Id. ,r 29.
According to another embodiment, the aluminum content for the
AlGaN electron supply layer is varied with distance from the active layer,
which produces a distribution of induced charge that provides two-
dimensional electron concentrations. Id. ,r 15. For instance, in the case of
the embodiment depicted in Figure 13, Kasahara discloses the electron
supply layer 10 is an AlGaN layer having an Al content that increases during
formation. Id. ,r,r 67---68. As explained by Kasahara in paragraph 24, such a
configuration results in a two dimensional electron concentration. As noted
above, Kasahara explains that such an arrangement results in a reduced
5
Appeal2018-004797
Application 15/191,863
channel concentration (i.e., electron concentration) under the gate and an
increased channel concentration for the source and drain areas. Id. ,r 8, 11.
As argued by Appellant (Appeal Br. 7, 9), the arrangement of claim
44 can be achieved by introducing extraneous charges into the region of the
conductive channel ( e.g., via ion implantation), thus providing excess charge
that repels negative carriers. See Spec. ,r 31. As noted above, Kasahara's
structure, such as the configuration depicted in Figure 13, results in a two-
dimensional concentration arrangement in which a relatively low electron
concentration area beneath the gate is between two areas of relatively high
electron concentration, not an area under the gate of high charge relative to
its neighboring regions.
In view of this, the Examiner has not sufficiently explained how
Kasahara's structure anticipates a conductive channel that includes a reduced
charge region that comprises a negative charge that repels negative carriers
in a region below a gate arrangement, wherein the conductive channel is
devoid of the negative charge in regions of a 2DEG adjacent each side of the
reduced charge region, as recited in claim 44.
Claims 47, 49-52, 56-61, and 64---67 depend from claim 44. For these
reasons, we do not sustain the Examiner's§ 102 rejection of claims 44, 47-
52, 56-61, and 64---67 over Kasahara.
Re} ections II-IV
Claims 45, 46, and 55 are rejected as being unpatentable under 35
U.S.C. § 103(a) over Kasahara in view of Kinzer.
Claims 53 and 54 are rejected as being unpatentable under 35 U.S.C.
§ 103(a) over Kasahara in view of Saxler.
6
Appeal2018-004797
Application 15/191,863
Claims 62 and 63 are rejected as being unpatentable under 35 U.S.C.
§ 103 over Kasahara in view of Parikh.
The Examiner does not rely on Kinzer, Saxler, or Parikh to remedy
the deficiencies discussed above with regard to the § 102 rejection of claim
44 over Kasahara. Therefore, we do not sustain the § 103 rejections of
claims 45, 46, 53-55, 62, and 63.
Rejection V
Claims 44--47 and 49---67 are rejected on the ground of nonstatutory
double patenting over claims 22, 24, 25, 31, 32, and 34--43 of U.S. Patent
Application No. 12/162,749 in view of Kasahara.
Appellant has not presented arguments for this rejection. U.S. Patent
Application No. 12/162,749 issued as US 9,391,185 on July 12, 2016. In
view of the issuance of US 9,391,185 and the unspecified reliance on
Kasahara8 in this rejection, we leave it to the Examiner to assess whether
any obviousness type patenting rejection should be made based on the
claims issued in US 9,391,185.
As a result, we do not reach the double patenting rejection of claims
44--47 and 49---67.
8 Because the rejection consists of the statement "[a]though the claims at
issue are not identical, they are not patentably distinct from each other"
(Final Act. 3), the record is unclear as to what extent Kasahara is relied upon
in the double patenting rejection.
7
Appeal2018-004797
Application 15/191,863
DECISION
On the record before us and for the reasons given in Appellant's
Appeal Brief and above, we reverse the Examiner's rejections under 35
U.S.C. §§ 102 and 103. We do not reach the Examiner's double patenting
rejection over U.S. Patent Application No. 12/162,749.
REVERSED
8