Ex Parte Piner et al

Patent Trial and Appeal Board

May 21, 2018

12023480 (P.T.A.B. May. 21, 2018)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR
12/023,480 01/31/2008 Edwin L. Piner
57579 7590 05/23/2018
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.
1012-1419/2004P80148
US02
7457
EXAMINER
TRAN,TONY
ART UNIT PAPER NUMBER
2894
NOTIFICATION DATE DELIVERY MODE
05/23/2018 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 EDWIN L. PINER, JOHN C. ROBERTS, and
PRADEEP RAJAGOP AL
Appeal2017-005909
Application 12/023 ,480
Technology Center 2800
Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and
JAMES C. HOUSEL, Administrative Patent Judges.
HOUSEL, Administrative Patent Judge.
DECISION ON APPEAL 1
Appellants2 appeal under 35 U.S.C. § 134 from the Examiner's
decision finally rejecting claims 1 and 4--20 under 35 U.S.C. § 103(a) as
unpatentable over Frayssinet3 and Sakai, 4 in view ofTemkin. 5 We have
jurisdiction over the appeal under 35 U.S.C. § 6(b ).
We REVERSE..
1 Our decision refers to the Specification (Spec.) filed January 31, 2008, the
Examiner's Final Office Action (Final Act.) dated May 4, 2016, Appellants'
Brief (Br.) filed October 28, 2016, and the Examiner's Answer (Ans.) dated
January 9, 2017.
2 Appellants identify the real party in interest in this appeal as International
Rectifier Corporation. App. Br. 2.
3 US 2004/0137732 Al, published July 15, 2004.
4 US 6,475,882 Bl, issued November 5, 2002
5 US 6,391,748 Bl, issued May 21, 2002.
Appeal2017-005909
Application 12/023,480
STATEMENT OF THE CASE
The invention relates to a method of forming a semiconductor
structure including a nitride material region and an amorphous strain-
absorbing layer. Spec. 2:5-11. In particular, Appellants disclose the strain-
absorbing layer covers substantially the entire top surface of the
semiconductor substrate, and a nitride-based material layer is formed
directly on the strain-absorbing layer, with a misfit dislocation density in the
nitride-based material layer that is less than about 1010 defects/cm2. Id. at
2: 17-27. The overlying nitride-based material layer is disclosed to be
formed in a vertical growth process, i.e., in a vertical direction with respect
to the strain-absorbing layer. Id. at 18:5-9.
Claim 1, reproduced below from the Claims Appendix to the Appeal
Brief, is illustrative of the subject matter on appeal:
1. A method of forming a semiconductor structure comprising:
forming an amorphous strain-absorbing layer on an entire
top surface of a non-nitride material of a semiconductor
substrate by nitridating the entire top surface, wherein said
amorphous strain-absorbing layer does not include gallium;
forming a nitride-based material layer using a vertical
growth process, wherein the amorphous strain-absorbing
layer separates the semiconductor substrate and the nitride-
based material layer at all points with the amorphous strain-
absorbing layer being directly on the non-nitride material of
the semiconductor substrate and the nitride-based material
layer being directly on the strain-absorbing layer, wherein
said semiconductor substrate is a non-nitride material-based
substrate, wherein the misfit dislocation density in the
nitride-based material layer is less than about 1010
defects/ cm2.
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Appeal2017-005909
Application 12/023,480
ANALYSIS
The Examiner has the initial burden of establishing a prima facie case
of obviousness. See In re Piasecki, 745 F.2d 1468, 1472 (Fed. Cir. 1984); In
re Rinehart, 531 F.2d 1048, 1051 (CCPA 1976). Meeting that burden requires
establishing that the applied prior art would have provided one of ordinary
skill in the art with an apparent reason to modify the prior art to arrive at the
claimed invention. See KSR Int 'l Co. v. Teleflex Inc., 550 U.S. 398, 418
(2007).
The Examiner finds that Frayssinet teaches a method of forming a
semiconductor structure comprising forming an amorphous strain-absorbing
SiN layer directly on a semiconductor non-nitride sapphire substrate, and
forming a nitride-based GaN material layer directly on the strain-absorbing
layer using a vertical growth process, wherein the misfit dislocation density
in the nitride-based material layer is in the mid 107 defects/cm2 range, i.e.,
less than about 1010 defects/cm2 . Final Act. 2-3. The Examiner
acknowledges that Frayssinet fails to teach nitridating the entire top surface
of the substrate such that the amorphous strain-absorbing layer covers the
entire top surface of the substrate and separates the substrate from the
nitride-based material layer at all points. Id. at 3.
The Examiner further finds that Sakai teaches nitridating an entire top
surface of a non-nitride semiconductor sapphire substrate 10 to form an
amorphous strain-absorbing layer ( GaN semiconductor layer 40 and SiN
buffer body 42) directly on the substrate, and forming a nitride-based GaN
material layer 44 using a vertical growth process directly on the amorphous
strain-absorbing layer such that the amorphous strain-absorbing layer
separates the nitride-based material layer from the substrate. Final Act. 3-5.
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Application 12/023,480
The Examiner acknowledges Sakai fails to teach a reduction in the misfit
dislocation density in the nitride-based material layer of less than about 1010
defects/ cm2. Id. at 5.
The Examiner concludes that it would have been obvious to include
forming the nitride-based material layer directly on Frayssinet's amorphous
strain-absorbing layer for the purpose of reducing the dislocation density of
this nitride-based material layer as taught by Sakai, with a reasonable
expectation of success. Final Act. 4. In combining Frayssinet and Sakai, the
Examiner determines that the resulting amorphous strain-absorbing layer
would separate the nitride-based material layer and the substrate at all
points. Id. Alternatively, the Examiner concludes that it would have been
obvious to include Frayssinet's teaching regarding reduction of the misfit
dislocation density down to the mid 107 defects/cm2 range into Sakai's
process. Id. at 5.
Recognizing that neither Frayssinet nor Sakai teach an amorphous
strain-absorbing layer that does not include gallium, the Examiner finds that
Temkin teaches an amorphous AlN strain-absorbing layer 28,30 not
including gallium. Final Act. 6. The Examiner concludes that it would have
been obvious to include Temkin's teaching regarding the use of an
amorphous AlN strain-absorbing layer for the purpose of reducing defect
density. Id.
Appellants argue, inter alia, that Temkin purposely teaches away
from forming an amorphous SiN layer on which GaN can be grown. Br. 9.
In particular, Appellants contend that Temkin intentionally avoids the
formation of an amorphous SiN layer. Id., citing Temkin, Abstract; 4:3-17;
5:3-8; 5:49---6:9; 6:11-12. Appellants further contend that Temkin's nitride-
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Appeal2017-005909
Application 12/023,480
based material layer growth process is primarily vertical and requires a
continuous non-amorphous SiN layer, whereas the nitride-based material
layer growth process of both Frayssinet and Sakai relies on both lateral and
vertical growth over a patterned or discontinuous amorphous SiN layer. Id.,
citing Temkin, 7:1-38.
Appellants' argument is persuasive of reversible error in the
Examiner's obviousness rejection of claim 1. Although the Examiner finds
that Temkin specifically teaches a "process [that] minimizes the formation
of amorphous silicon nitride, SiN.sub.x, compounds on the surface of the
substrate and that "[a] surface free of amorphous silicon nitride is necessary
for formation of high quality AlN," the Examiner nonetheless maintains that
the process of claim 1 would have been obvious based on a combination of
Temkin's teaching of a buffer of high quality nitride layers 28,30 between
the substrate and a GaN layer at all points. Ans. 6. In other words, even
though Temkin teaches away from the use of an amorphous strain-absorbing
layer underlying the AlN layer, the Examiner ignores this teaching to
conclude that it would have been obvious to do so.
It has been held that "[ w ]hat the prior art teaches and whether it
teaches toward or away from the claimed invention ... is a determination of
fact." Para-Ordnance Mfg., Inc. v. SGS Importers Int'!, Inc., 73 F.3d 1085,
1088 (Fed. Cir. 1995). When the prior art teaches away from a combination,
that combination is more likely to be nonobvious, KSR Int'!. Co. v. Teleflex
Inc., 550 U.S. 398, 417 (2007), but to teach away, a reference must
discourage one of ordinary skill in the art from following the path set out in
the reference, or lead that person in a direction divergent from the path that
was taken by the applicant. In re Gurley, 27 F.3d 551, 553 (Fed. Cir. 1994).
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Application 12/023,480
Here, as Appellants argue and the Examiner acknowledges, Temkin
specifically discourages the use of an amorphous strain-absorbing layer
when using the non-gallium nitride-based AlN material layer. Because
Frayssinet and Sakia both teach the use of an amorphous strain-absorbing
layer between the nitride-based GaN material layer and the substrate,
Temkin clearly teaches away from the substitution of AlN in Frayssinet and
Sakia absent the use of a non-amorphous layer separating the AlN layer
from the substrate.
Appellants further argue that Sakai fails to teach an amorphous strain-
absorbing layer not including gallium that covers and is directly on the entire
top surface of the substrate and separating the nitride-based layer from the
substrate at all points. Br. 7. Appellants contend that Sakai includes GaN
layer 40 directly on substrate 10 and SiN layer 42 is not directly on substrate
IO. Id. In addition, Appellants contend that Sakai's SiN layer 12 as shown
in Figure 1 contains intentional pores or gaps and, therefore, does not cover
the entire top surface of the underlying substrate nor separate the overlying
nitride-based GaN material layer from the substrate at all points. Id. at 8.
This argument is also persuasive of reversible error. As the Examiner
finds, Sakai's Figure 1 is substantially similar to Frayssinet's Figure 3. Ans.
4. However, although the Examiner relies on the fact that Sakai teaches
Figure 12 as a different embodiment which appears to show continuous SiN
layer 42, this layer is not formed directly on non-nitride based
semiconductor substrate 10 as required by claim 1. Moreover, we note
Sakai discloses that SiN buffer body layer 42 of Figure 12 is formed in the
same process as SiN buffer body layer 12 of Figure 1, a process which
produces a layer with pores or gaps. Sakai, 4:15-21. As such, Sakai's SiN
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Application 12/023,480
buffer body 42 is neither directly formed on the substrate nor separates the
substrate from nitride-based material layer 44 at all points. Therefore, Sakai
fails to teach an amorphous strain-absorbing layer not including gallium that
covers and is directly on the entire top surface of the substrate and separating
the nitride-based layer from the substrate at all points.
Finally, Appellants assert that Frayssinet specifically teaches use of a
discontinuous SiN layer in order to enable epitaxial lateral overgrowth
(ELO) of the GaN layer thereby reducing defect density as compared to a
GaN layer vertically grown on the substrate. Br. 6. Appellants, therefore,
argue that modifying Frayssinet's SiN layer to be continuous would have
been expected to increase defect density of the GaN layer. Id. As such,
Appellants contend the Examiner's proposed modification of Frayssinet
would change Frayssinet's principle of operation by increasing, rather than
decreasing, defect density. Id.
This argument is also persuasive of reversible error. As Appellants
urge, Frayssinet's principle of operation is the inclusion of a discontinuous
amorphous SiN layer over the substrate so as to enable the growth of the
GaN layer by ELO without the requirement of making a mask. Frayssinet
,r 11. Frayssinet's amorphous SiN layer has islands that function as a micro-
mask during subsequent GaN ELO growth, which Frayssinet attributes to a
significant reduction in defect density. Id. ,r 12. Therefore, modifying
Frayssinet's SiN layer to cover the entire top surface of the substrate would
effectively prevent Frayssinet from operating as disclosed.
Accordingly, the Examiner has not carried the burden of establishing,
by a preponderance of the evidence, the factual basis for the conclusion that
the claimed invention would have been obvious. Under these circumstances,
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Application 12/023,480
we cannot conclude that the Examiner has met the minimum threshold of
establishing obviousness under 35 U.S.C. § 103(a) of claim 1 and dependent
claims 4--20. See In re Oetiker, 977 F.2d 1443, 1445 (Fed. Cir. 1992); KSR
Int'! Co. v. Teleflex, Inc., 550 U.S. 398,418 (2007) (quoting In re Kahn, 441
F.3d 977, 988 (Fed. Cir. 2006)).
DECISION
Upon consideration of the record, and for the reasons given above and
in the Appeal Brief, the decision of the Examiner rejecting claims 1 and 4--
20 under 35 U.S.C. § 103(a) as being unpatentable over Frayssinet and
Sakai, in view of Temkin, is reversed.
REVERSED
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