Ex Parte Schowalter et al

Patent Trial and Appeal Board

Apr 28, 2016

12020006 (P.T.A.B. Apr. 28, 2016)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE
12/020,006 01125/2008
23517 7590 05/02/2016
MORGAN, LEWIS & BOCKIUS LLP (BO)
1111 PENNSYLVANIA A VENUE, N.W.
WASHINGTON, DC 20004
FIRST NAMED INVENTOR
Leo J. Schowalter
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.
CIS-01117303632001 1050
EXAMINER
JACKSON JR, JEROME
ART UNIT PAPER NUMBER
2815
NOTIFICATION DATE DELIVERY MODE
05/02/2016 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):
kcatalano@morganlewis.com
patents@morganlewis.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte LEO J. SCHOW ALTER,
JOSEPH A. SMART, JAMES R. GRANDUSKY,
and SHIWEN LIU
Appeal2013-008996
Application 12/020,006
Technology Center 2800
Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and
JAMES C. HOUSEL, Administrative Patent Judges.
HANLON, Administrative Patent Judge.
DECISION ON APPEAL
A. STATEMENT OF THE CASE
The Appellants filed an appeal under 35 U.S.C. § 134 from a final rejection
of claims 1-8, 10-17, 19-21, and 23-31under35 U.S.C. § 103(a) as unpatentable
over Schowalter et al., 1 in view of Flynn et al.,2 and Bennett et al.3 We have
jurisdiction under 35 U.S.C. § 6(b).
1 US 2004/0033690 Al, published February 19, 2004 ("Schowalter").
2 US 2003/0213964 Al, published November 20, 2003 ("Flynn").
3 Brian R. Bennett & Jesus A. del Alamo, High Quality InGaAs/InP and
InAlAs/InP Heterostructures Beyond the Matthews-Blakeslee Critical Layer
Appeal2013-008996
Application 12/020,006
We REVERSE.
The subject matter on appeal is directed to a semiconductor heterostructure
comprising an aluminum nitride single-crystal substrate and at least one strained
layer epitaxially grown there over, wherein a thickness of the strained layer(s)
exceeds a predicted critical thickness associated therewith by at least a factor of 5
or 10 as calculated with the Matthews-Blakeslee theory.
According to the evidence of record:
If the lattice mismatch between the epilayer and substrate is
small and the layer is thin, the mismatch will be accommodated
entirely by strain in the layer. . . . If the layer is sufficiently thick and
mismatched, the formation of misfit dislocations at the
substrate/epilayer interface becomes energetically favorable. These
dislocations relieve strain, allowing the epilayer lattice to relax back
toward its natural cubic symmetry. The point at which misfit
dislocations begin to form is known as the critical layer thickness.
Bennett 650, col. 1.
The Appellants disclose that "[ u ]nexpectedly, we have found that it is
possible to grow pseudomorphic layers[4J with thicknesses much greater than the
predicted critical thickness." Spec. 5, 11. 15-17. According to the Appellants, the
ability to grow highly strained alloys of III-nitride on certain AlN substrates is
dependent on:
(i) substrate crystal quality, (ii) surface preparation, (iii) crystal
orientation of the substrate surface, (iv) alloy concentration, (v)
Thickness, 650-53. The copy of the Bennett article in the Official file of the
instant Application does not bear a publication date. The Appellants state that the
Bennett article is from "Proceedings of the Fourth International Conference on
Indium Phosphide and Related Materials" held on April 21-24, 1992. See Appeal
Brief dated February 5, 2013 ("App. Br."), at 7.
4 The Appellants define "pseudomorphic" as "epitaxial layers strained to at least
approximately 80% of a lattice parameter of an underlying substrate (i.e., less than
approximately 20% relaxed to its innate lattice parameter)." Spec. 5, 11. 24-27.
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Appeal2013-008996
Application 12/020,006
growth conditions including substrate temperature and V-III ratio
during growth, and/or (vi) rate of grading of the alloy concentration.
Spec. 7, 11. 3-6.
Representative claim 1 is reproduced below from the Claims Appendix of
the Appeal Brief. The limitations at issue are italicized.
1. A semiconductor heterostructure comprising:
an aluminum nitride single-crystal substrate; and
at least one strained layer epitaxially grown thereover, the
layer comprising at least one of AlN, GaN, InN, or any binary or
tertiary alloy combination thereof,
wherein a thickness of the strained layer exceeds a predicted
critical thickness associated therewith by at least a factor of 5, as
calculated with the Matthews-Blakeslee theory,
f} lt . ·1' "''""~' ("') I:•
f -'·-·· . ~ ........ l.t,x. "'·. r.1•.1i±~ -t-· ·.1 \, ·. ti-.-. :-::-::-:: \ .'t ' 1 { ~
8?rf' { i ·-'· v) cos >!. • h · ·· ·
where he is the predicted critical thickness, bis the magnitude
of the Burgers vector of a dislocation formed between the layer and
the substrate, f is the lattice mismatch between the layer and the
substrate, vis the Poisson's ratio of the layer, "A is the angle between
the slip direction of the layer and the direction in the plane of the layer
perpendicular to the line of intersection of the slip plane of the layer
and the interface between the layer and the substrate, and a is the
angle between the dislocation and the Burgers vector of the
dislocation.
App. Br. 19 (emphasis added).
B. DISCUSSION
The Examiner finds Schowalter discloses III-N layers, such as AlGaN,
epitaxially grown on an AlN substrate. Ans. 3--4.5 There is no dispute on this
record that Schowalter does not disclose the thickness of the AlGaN layers or
5 Examiner's Answer dated May 10, 2013.
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Appeal2013-008996
Application 12/020,006
disclose whether the AlGaN layers are strained layers. Nonetheless, the Examiner
finds that "the growth of AlGaN on AlN is inherently growth of a strained layer [in
Schowalter] because AlGaN does not have the same lattice constant as AlN." Ans.
4. The Examiner cites paragraphs 24 and 25 of Schowalter and page 5 line 12 to
page 6, line 1 of the Appellants' Specification for support. Ans. 4-7.
The Appellants argue the Examiner's finding of inherency is not supported
by the record. More specifically, the Appellants argue:
[A ]s those of skill in the art realize, the formation of a layer of
material on a substrate having a different lattice constant does not
necessarily result in that layer being strained. Indeed, that is the very
point of the critical-thickness criterion expressed in the instant claims
and illustrated in exemplary fashion in Figure 1 of the present
application - indicating when such layers should be strained and when
they should be lattice-relaxed (or simply "relaxed").
Reply Br. 4;6 see also Reply Br. 4 (contending that Appellants' description of Pig.
1 "demonstrates two regimes of AlGaN growth on AlN, strained-layer growth
below the critical thickness and relaxed-layer growth above the critical thickness").
The Appellants' argument is supported by the record. See In re Oelrich, 666
F.2d 578, 581 (CCPA 1981) ("Inherency ... may not be established by probabilities
or possibilities. The mere fact that a certain thing may result from a given set of
circumstances is not sufficient." (quoting Hansgirg v. Kemmer, 102 F.2d 212, 214
(CCPA 1939))).
As for the claimed thickness of the strained layer, the Examiner turns to
Bennett. The Examiner finds "Bennett discloses heterojunction layers of strained
III-V materials often have critical layer thicknesses 3-10 times larger than the
predicted critical layer thickness from the M[ atthews ]-B [lakeslee] formula." Ans.
6 Reply Brief dated July 10, 2013.
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Appeal2013-008996
Application 12/020,006
3--4. The Examiner concludes that "it would have been obvious for one of skill to
try to make epitaxial layers thicker than any predicted M[atthews]-B[lakeslee]
result, knowing the formula to be inexact and knowing that the thickest layers
possible were clearly desirable in the art. "7 Final 6 (emphasis added). 8
The Appellants argue:
In relying on Bennett to reject the instant claims, the Examiner
effectively equates two different classes of materials - cubic zinc-
blende crystals (such as InGaAs and InAlAs) and hexagonal crystals
(such as AlN, GaN, and InN) - that evidence on the record[9J clearly
indicates may not be equated, and he provides no reasoned
justification for doing so.
App. Br. 9.
Indeed, the disclosure of Bennett is limited to epitaxial layers of InGaAs and
InAlAs grown by molecular beam epitaxy on InP, 10 and, on appeal, the Examiner
fails to address the differences in the epitaxial layers and substrates disclosed in
Schowalter and Bennett. See Bennett 652, col. 2.
InKSR Int'! Co. v. Teleflex Inc., 550 U.S. 398, 421 (2007), the Supreme
Court explained "obvious to try" as follows:
When there is a design need or market pressure to solve a problem
and there are a finite number of identified, predictable solutions, 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 but of ordinary skill
and common sense. In that instance the fact that a combination was
7 The Examiner relies on Flynn to show that III-N based layers were known to be
used to form heterojunction transistors. Ans. 3.
8 Final Office Action dated August 3, 2012.
9 Declaration of Leo J. Schowalter, Ph.D., dated May 23, 2012, at ,-i,-i 6, 7.
10 In paragraph 24, relied on by the Examiner, Schowalter discloses that AlGaN
may be epitaxially grown on single crystal AlN substrates by, for example,
organometallic vapor phase epitaxy and other formation processes.
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Appeal2013-008996
Application 12/020,006
obvious to try might show that it was obvious under § 103. [Emphasis
added.]
In this case, the Examiner has failed to show that epitaxially growing a
strained AlGaN layer on an AlN substrate, wherein the strained AlGaN layer has a
thickness as claimed, was known to be a predictable solution, at the time of the
Appellants' invention, for increasing the thickness of Schowalter' s epitaxial layer.
The Examiner concludes that Schowalter enables the growth of a strained
epitaxial layer having the claimed thickness, citing the Appellants' statement on
page 12 of the Appeal Brief that "the instant specification ... recognizes the
suitability of Schowalter' s substrate preparation techniques in the context of
growth of strained layers beyond their critical thickness." Ans. 9. However,
enablement and obviousness are separate statutory requirements. The test for
obviousness, for example, "is what the combined teachings of the references would
have suggested to those of ordinary skill in the art." 11 In re Keller, 642 F.2d 413,
425 (CCPA 1981). As explained inin re McLaughlin, 443 F.2d 1392, 1313-14
(CCPA 1971):
Any judgment on obviousness is in a sense necessarily a
reconstruction based upon hindsight reasoning, but so long as it takes
into account only knowledge which was within the level of ordinary
skill at the time the claimed invention was made and does not include
knowledge gleaned only from applicant's disclosure, such a
reconstruction is proper. [Emphasis added.]
Suffice it to say that absent the Appellants' disclosure, there is no evidence
on this record showing that an AlGaN layer epitaxially grown on the AlN substrate
of Schowalter to the claimed thickness would have been expected to be strained
11 "[E]nablement requires that the specification teach those in the art to make and
use the invention without undue experimentation." In re Wands, 858 F.2d 731,
737 (Fed. Cir. 1988).
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Application 12/020,006
rather than relaxed. See Spec. 1, 11. 28-30 ("as the thickness of the epitaxial layer
is increased, the strain energy in the epitaxial layer will grow and, typically, the
layer will find some way to reduce the strain energy").
For the reasons set forth above, the § 103(a) rejection of claims 1-8, 10-17,
19-21, 23, 26-30 is not sustained.
Independent claim 24 recites, inter alia, "wherein a total thickness of the
plurality of strained layers exceeds a predicted critical thickness associated
therewith by at least a factor of 10, as calculated with the Matthews-Blakeslee
theory." App. Br. 23.
The Examiner states:
Flynn discloses devices with multiple stacked strained layers[12J •••
and together the references suggest that critical layer thickness of the
strained layers would be obvious beyond the M[atthews]-B[lakeslee]
predicted thickness because the [Schowalter] substrate is enabling for
such thickness critical layers.
Ans. 9.
As discussed above, the mere fact that the instant Application discloses that
the Schowalter substrate is suitable for epitaxially growing a strained layer having
the claimed thickness is not sufficient to demonstrate that the subject matter recited
in claim 24 would have been obvious to one of ordinary skill in the art at the time
of the Appellants' invention. For this reason, the§ 103(a) rejection of claims 24,
25, and 31 is not sustained.
C. DECISION
The decision of the Examiner is reversed.
12 Flynn discloses that "thin strained layers or superlattices can be employed with
layers having less than the critical thickness, to relieve strain in the epitaxial device
structure." Flynn ,-i 331.
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Application 12/020,006
REVERSED
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