Ex Parte Kordina et al

Board of Patent Appeals and Interferences

Oct 27, 2009

10949577 (B.P.A.I. Oct. 27, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
_______________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_______________

Ex parte OLLE CLAES ERIK KORDINA
and MICHAEL JAMES PAISLEY
______________

Appeal 2009-007334
Application 10/949,577
Technology Center 1700
_______________

Decided: October 27, 2009
_______________

Before CHUNG K. PAK, CHARLES F. WARREN, and
PETER F. KRATZ, Administrative Patent Judges.

WARREN, Administrative Patent Judge.

DECISION ON APPEAL
Applicants appeal to the Board from the decision of the Primary
Examiner finally rejecting claims 1, 3-7, 9-12, 14-18, 20, and 22-30 in the
Office Action mailed August 30, 2007. The Examiner subsequently refused
to allow appealed claims 1, 3-7, 9-12, 14-18, 20, and 22-30 as amended in the
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the Amendment filed November 19, 2007, which was entered in the Office
Action mailed December 10, 2007. 35 U.S.C. §§ 6 and 134(a) (2002);
37 C.F.R. § 41.31(a) (2007).
An oral hearing was held October 14, 2009.
We affirm the decision of the Primary Examiner.
Claim 1 illustrates Appellants’ invention of a seed silicon carbide (SiC)
crystal growth system, and is representative of the claims on appeal:
1. A seed SiC crystal growth system for high temperature SiC crystal
growth, comprising:
a container for receiving a silicon carbide seed crystal, said container
comprising:
a first inlet to the interior of the container;
a second inlet to the interior of the container;
a graphite core; and
a refractory metal coating on said graphite core selected from the group
consisting of tantalum carbide, hafnium carbide, niobium carbide, titanium
carbide, zirconium carbide, tungsten carbide, vanadium carbide, tantalum
nitride, hafnium nitride, niobium nitride, titanium nitride, zirconium nitride,
tungsten nitride, vanadium nitride and mixtures thereof, said coating being
characterized by a melting point above the sublimation temperature of SiC,
chemical inertness with respect to silicon and hydrogen at the sublimation
temperature of SiC, and a coefficient of thermal expansion sufficiently similar
to said graphite core to prevent cracking between said graphite core and said
coating during heating and cooling of said container to and from the
sublimation temperature of SiC.
The Examiner relies upon the evidence in these references:
Sugiyama US 5,964,944 Oct. 12, 1999
Maeda EP 0 554 047 A1 Aug. 4, 1993
Balakrishna WO 99/29934 A1 Jun. 17, 1999
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Appellants request review of the ground of rejection under 35 U.S.C. §
103(a) advanced on appeal by the Examiner: appealed claims 1, 3-7, 9-12, 14-
18, 20, and 22-30 over Maeda in view of Balakrishna and Sugiyama. App.
Br. 5; Ans. 3.1
Appellants submit argument based on the claims as a group. Thus, we
decide this appeal based on independent claims 1, 7, and 18. App. Br.
5 and 9. 37 C.F.R. § 41.37(c)(1)(vii) (2007).
Issue
The issues in this appeal is whether Appellants have shown that the
evidence in Maeda, Balakrishna, and Sugiyama would have taught away from
using graphite crucibles and from using a silane source in the formation of a
SiC single crystal, thus leading one of ordinary skill in this art away from
combining these references and thence to the claimed seed SiC crystal growth
system encompassed by claims 1, 7, and 18.
Findings of Fact
We find Maeda would have evinced it was known in the art that in
conventional sublimation processes which form a SiC single crystal by
depositing SiC gas on a SiC seed crystal in a graphite crucible or container,
SiC gas is formed not only from evaporated SiC material but also from the
reaction of certain gaseous components of the evaporated SiC material and
the carbon in the wall of the graphite crucible. Maeda 2:6-27. Maeda further
evinces that “[d]uring the reactions with [the carbon of] the crucible, the

1 We considered the Appeal Brief filed May 6, 2008; the Examiner’s Answer
mailed July 31, 2008; and the Reply Brief filed September 30, 2008.
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the impurity elements in the crucible are evaporated at the same time and
introduced into the growing single crystal,” wherein the “crucible
changes its structure and its wall thickness,” such that the “resulting crystal
has poor homogeneity and less reliable quality.” Maeda 2:27-32. In this
respect, Maeda discloses that “[t]he crucible to be used in these methods must
be made of high-grade graphite to avoid the resultant SiC single crystal from
being contaminated with inclusions,” and even high purity graphite material
can contain impurities which, if included in the SiC single crystal, can “cause
various problems such as poor performance characteristics and even
malfunction, when the single crystal is used to make a semiconductor
device.” Maeda 2:16-21.
We find Maeda would have disclosed to one of ordinary skill in this
art, as illustrated by the Figure, an apparatus in which a silane gas and a
hydrocarbon gas are introduced via a carrier gas into reactor tube 24 of
reaction zone 20. The SiC material thus formed is evaporated in sublimation
part 36 of sublimation zone 30 and deposited onto a SiC seed crystal (not
shown) to form SiC single crystal 43 in crystal growth zone 40 of sublimation
zone 30 . Maeda, e.g., 2:44 to 3:56. Maeda discloses that “the crystal growth
is done without using a graphite crucible” to obtain a SiC single crystal of
high purity with “less opportunity of including impurities.” Maeda 2:40-43
and 3:1-5.
We find Balakrishna would have evinced it was known in the art that
growing a SiC single crystal in a furnace using “silane gas . . . requires an
extensive investment in safety equipment since silane is highly toxic and
explosive.” Balakrishna 1:30 to 2:2.
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We find Balakrishna would have disclosed to one of ordinary skill in
this art, as illustrated by Figure 2, physical vapor transport growth furnace 30
in which silicon 36 contained within, among other things, graphite receptacle
38 surrounded by graphite susceptor 40 is vaporized and reacted with a
hydrocarbon gas to form SiC gas. The SiC gas is deposited on SiC seed
crystal 50 in interior growth cavity 58 to form a SiC single crystal, wherein
growth cavity 58 has porous graphite wall 54 surrounded by graphite
susceptor 56. Balakrishna 5:5-30. Balakrishna discloses that “[i]n order to
reduce the radial migration of potential impurities into the growth cavity from
the [graphite] wall 54 or [graphite] susceptor 56, a protective coating 60, of a
high purity material such as [SiC] or tantalum carbide, may be incorporated.”
Balakrishna 5:30-35.
We find Sugiyama would have evinced it was known in the art that a
SiC single crystal can be grown with a sublimation recrystallization method
in which SiC material is sublimated in a graphite crucible with precise control
of the temperature of the SiC material and SiC seed crystal, and of the
atmosphere in the graphite crucible to obtain a high quality SiC single crystal.
Sugiyama col. 1, ll. 11-27. Sugiyama further evinces that the sublimation of
the SiC material “makes it difficult to stably supply [SiC] vapor (source
material gas).” Sugiyama col. 1, ll. 28-42; see also col. 1,
l. 43 to col. 2, l. 10, and col. 2, ll. 25-37. Sugiyama also evinces that a
technical document reports “a bulk single crystal of [SiC] is obtained by
carrying out a reaction represented by the following formula: SiH4 + C3H8 →
SiC.” Sugiyama col. 2, ll. 18-24. In this respect, Sugiyama discloses that this
reported method “is not suitable to mass production of bulk single crystals
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crystals because the method employs expensive silane (SiH4) gas as a source
material” and “the growth rate of the crystal may decrease because silane
contains hydrogen.” Sugiyama col. 2, ll. 45-49.
We find Sugiyama would have disclosed to one of ordinary skill in this
art, as illustrated in Figure 1, an apparatus in which silicon powder 13 is
heated at the bottom of graphite growth chamber 1, the silicon vapor reacted
with hydrocarbon gas therein, and the resulting SiC gas deposited on SiC
seed crystal 12 adhered to graphite lid 2 to grow SiC single crystal 15 which
“was an extremely highly pure crystal.” Sugiyama col. 3, l. 66 to col. 5,
l. 11. Sugiyama discloses that materials suitable for growth chamber 1
“include graphite, SiC coated graphite, a metal with a high melting point,
such as, [tantalum] and [tungsten], and a carbide of the metal with a high
melting point, which are stable at high or elevated temperatures.” Sugiyama
col. 3, ll. 55-60.
We find Appellants acknowledge in the Specification that a technical
document reports that a SiC single crystal can be prepared from a silane gas
and a hydrocarbon gas, such as propane (C3H8) wherein “most of the carbon
utilized in this technique actually comes from the graphite walls of the
crucible,” destroying the graphite crucible. Spec. ¶ 0024. “Silicon reacts
with the graphite containers utilized in most sublimation processes and, as
noted above, is encouraged to do so in some applications,” which pits the
walls of the graphite container and forms carbon dust which contaminates the
crystal. Spec. ¶ 0025. We further find Appellants do not acknowledge any
problem with the use of silane gas. Spec. ¶ 0025.
Opinion
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We considered the totality of the record in light of Appellants’
arguments with respect to claims 1, 7, and 18 and the ground of rejection
advanced on Appeal. See, e.g., In re Kahn, 441 F.3d 977, 985-86 (Fed. Cir.
2006) (“‘On appeal to the Board, an applicant can overcome a rejection by
showing insufficient evidence of prima facie obviousness or by rebutting the
prima facie case with evidence of secondary indicia of nonobviousness.’”)
(quoting In re Rouffet, 149 F.3d 1350, 1355 (Fed. Cir. 1998)); In re Oetiker,
977 F.2d 1443, 1445 (Fed. Cir. 1992) (“After evidence or argument is
submitted by the applicant in response, patentability is determined on the
totality of the record, by a preponderance of evidence with due consideration
to persuasiveness of argument.”) (citing, inter alia, In re Spada, 911 F.2d
705, 707 n.3 (Fed. Cir. 1990)).
We are of the opinion Appellants have not established that the evidence
in Maeda, Balakrishna, and Sugiyama would have taught away from using
graphite crucibles and from using a silane source in the formation of a SiC
single crystal, thus leading one of ordinary skill in this art away from
combining these references and thence to the claimed seed SiC crystal growth
system encompassed by claims 1, 7, and 18.
We disagree with Appellants’ position that Maeda’s teaching to avoid
graphite crucibles in sublimation processes to form a SiC single crystal is “an
explicit antagonism” teaching away from using graphite crucibles, which
Appellants contend is “a claim element,” for two reasons. App. Br. 7. First,
the claimed graphite core (claim 1), graphite enclosure (claim 7), and graphite
crucible (claim 18) are not graphite per se but graphite coated with a
refractory metal which can be, among other things, tantalum carbide that is
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disclosed for the same purposes in both Balakrishna and Sugiyama. Claims
1, 7, and 18; see above pp. 5 and 6.
Second, on this record, we do not find that Maeda’s disclosure that
sublimation processes are deleterious to graphite containers would have led
one of ordinary skill in the art away from using coated graphite containers.
Indeed, graphite per se containers continued to be used in sublimation
processes to form a SiC single crystal subsequent to Maeda’s cautionary
disclosure as evinced by Sugiyama’s “highly pure crystal” results, and
acknowledged by Appellants. See above p. 6. Thus, Maeda, Balakrishna,
and Sugiyama evince and Appellants acknowledge that problems using
graphite per se container in sublimation processes were known to one of
ordinary skill in this art, and Maeda, Balakrishna, and Sugiyama further
evince that this person would have had a reasonable expecting of achieving a
desired SiC single crystal by modifying process steps and apparatus
components to overcome the graphite per se problem. See above pp. 3-6. Cf.,
e.g., In re Gurley, 27 F.3d 551, 552-53 (Fed. Cir. 1994). (“We share Gurley’s
view that a person seeking to improve the art of flexible circuit boards, on
learning from Yamaguchi that epoxy was inferior to polyester-imide resins,
might well be led to search beyond epoxy for improved products. However,
Yamaguchi also teaches that epoxy is usable and has been used for Gurley’s
purpose.”).
Indeed, as the Examiner points out, the record provides no basis for us
to ignore the use of the refractory metal tantalum carbide to coat graphite
container as a solution to the graphite per se container problem taught by
Balakrishna and Sugiyama. Thus, contrary to Appellants’ position, the
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teachings of Balakrishna and Sugiyama would have led one of ordinary skill
in this art to combine these references with Maeda, leading to a seeded SiC
crystal growth system having a tantalum carbide coated graphite container
falling within the appealed claims. Ans. 5-6. See, e.g., In re ICON Health
and Fitness, Inc., 496 F.3d 1374, 1385-86 (Fed. Cir. 2007).
For similar reasons, we are also not persuaded by Appellants’ position
that the disclosures of Balakrishna and Sugiyama with respect to the
characteristics of silane would have led one of ordinary skill in this art from
combining other disclosures of these references which do not involve silane
with Maeda’s disclosure which teaches the use of silane. App. Br. 8. On this
record, we find one of ordinary skill in this art would have known that the use
of silane gas is a matter of expense, because of necessary safety equipment
and cost of the gas, and may influence crystal growth rate as evinced by the
disclosures of Balakrishna and Sugiyama. See above
pp. 4 and 5. Indeed, this person would have reasonably chosen to use silane
gas in spite of these cautionary disclosures with a reasonable expectation of
successfully obtaining a SiC .single crystal. See, e.g., Gurley, 27 F.3d at 552-
53. In this respect, Appellants admit that these disclosures are independent of
the crucible material and the reactor material taught in Balakrishna and
Sugiyama, respectively. App. Br. 8. Thus, Appellants have not established
that the Examiner improperly combined the teachings of t Balakrishna and
Sugiyama with Maeda. Ans. 5.
Appellants’ further arguments “[g]oing beyond the explicit disclosures
of these references” are unsupported and thus entitled to little weight. App.
Br. 9. See, e.g., In re De Blauwe, 36 F.2d 699, 705 (Fed. Cir. 1984); In re
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1984); In re Payne, 606 F.2d 303, 315 (CCPA 1979); In re Lindner,
457 F.2d 506, 508 (CCPA 1972).
Conclusion
Accordingly, based on our consideration of the totality of the record
before us, we have weighed the evidence of obviousness found in the
combined teachings of Maeda, Balakrishna, and Sugiyama with Appellants’
countervailing evidence of and argument for nonobviousness and conclude,
by a preponderance of the evidence and weight of argument, that the claimed
invention encompassed by appealed claims 1, 3-7, 9-12, 14-18, 20, and 22-30
would have been obvious as a matter of law under 35 U.S.C.
§ 103(a).
The Primary Examiner’s decision 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)(a)(iv).
AFFIRMED

PL Initial:
sld

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