Ex Parte O et al

Patent Trial and Appeal Board

Sep 7, 2017

11745817 (P.T.A.B. Sep. 7, 2017)

United States Patent and Trademark Office
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
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APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
11/745,817 05/08/2007 Michael John O'Loughlin 5308-395DV 1483
65106 7590
MYERS BIGEL, P.A.
P.O. BOX 37428
RALEIGH, NC 27627
09/11/2017 EXAMINER
DUCLAIR, STEPHANIE P.
ART UNIT PAPER NUMBER
1713
NOTIFICATION DATE DELIVERY MODE
09/11/2017 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):
u spto @ my ersbigel. com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte MICHAEL JOHN O’LOUGHLIN
and JOSEPH JOHN SUMAKERIS
Appeal 2015-005769
Application 11/745,817
Technology Center 1700
Before ADRIENE LEPIANE HANLON, KAREN M. HASTINGS, and
MICHAEL G. McMANUS, 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 an Examiner’s
decision finally rejecting claims 1—3, 6—17, 19, 20, 31, 32, and 34. We have
jurisdiction under 35 U.S.C. § 6(b).
We REVERSE.
Claim 1 is reproduced below from the Claims Appendix of the Appeal Brief
dated October 24, 2014 (“App. Br.”). The limitation at issue is italicized.
1. A method of manufacturing a single crystal silicon carbide
epitaxial layer on an off-axis silicon carbide substrate comprising:
Appeal 2015-005769
Application 11/745,817
flowing a source gas and a carrier gas into a reaction chamber
for growing a first layer of epitaxial silicon carbide on the substrate
wherein the source gas is flowed at a first flow rate;
reducing, but not halting, the flow of the source gas from the
first flow rate to a reduced flow rate while maintaining a flow of the
carrier gas;
etching the first layer of epitaxial silicon carbide with at least
the carrier gas and at least partially due to the reduction in flow of the
source gas from the first flow rate to the reduced flow rate without
halting the flow of the source gas to reduce the thickness of the first
layer and maintaining a reduced flow of the source gases into the
reaction chamber while etching the first layer of epitaxial silicon
carbide with at least the carrier; and
growing a second layer of epitaxial silicon carbide on the
etched first layer of epitaxial silicon carbide.
App. Br. 16.
The claims on appeal stand rejected as follows:
(1) claims 1—3, 6, 8—17, 32, and 34 under 35 U.S.C. § 103(a) as
unpatentable over Futatsuyama1 in view of Ellison et al.,2 Okada et al.,3 and Chu;4
(2) claim 7 under 35 U.S.C. § 103(a) as unpatentable over Futatsuyama in
view of Ellison, Okada, and Chu, and further in view of Neyret et al.;5
1 JP 2004-043211 A, published February 12, 2004 (“Futatsuyama”).
2 A. Ellison et al., Epitaxial growth of SiC in a chimney CVD reactor, 236 J.
Crystal Growth 225-238 (2002) (“Ellison”).
3 Tatsuya Okada et al., Correspondence between Surface Morphological Faults
and Crystallographic Defects in 4H-SiC Homoepitaxial Film, 41 Jpn. J. Appl.
Phys. 6320-6326 (2002) (“Okada”).
4 US 3,501,356, issued March 17, 1970 (“Chu”).
5 E. Neyret et al., Deposition, evaluation and control of 4H and 6H SiC epitaxial
layers for device applications, B80 Materials Sci. & Eng’g 332—336 (2001)
(“Neyret”).
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Appeal 2015-005769
Application 11/745,817
(3) claim 19 under 35 U.S.C. § 103(a) as unpatentable over Futatsuyama,
in view of Ellison, Okada, and Chu, and further in view of Kondo et al.;6 and
(4) claims 20 and 31 under 35 U.S.C. § 103(a) as unpatentable over
Futatsuyama in view of Ellison, Okada, and Chu, and further in view of Di Cioccio
et al.7
B. DISCUSSION
1. Claim 1
The Examiner finds Futatsuyama discloses a method of manufacturing a
single crystal silicon carbide epitaxial layer on a silicon carbide substrate
comprising the steps of (1) flowing a source gas and a carrier gas into a reaction
chamber for growing a first layer of epitaxial silicon carbide on the substrate; (2)
suspending or halting the flow of the source gas; (3) flowing an etching gas and
etching the first layer of epitaxial silicon carbide, and (4) reflowing the source gas
to grow a second layer of epitaxial silicon carbide on the etched first layer of
epitaxial silicon carbide. Final Act. 2—3.8
The Examiner finds Futatsuyama does not disclose:
reducing the source gas to a first flow rate wherein the first flow
rate ... is reduced [but] not halted and etching the first layer of
epitaxial silicon carbide with at least the carrier gas and at least
partially due to the reduction in the flow of the source gas from the
first flow rate to the reduced flow rate without halting the flow of the
source gas.
Id. at 3 (emphasis added).9
6 JP 2000-053498 A, published February 22, 2000 (“Kondo”).
7 US 2006/0125057 Al, published June 15, 2006 (“Di Cioccio”).
8 Final Office Action (“Final Act.”) dated April 23, 2014.
9 The Examiner also finds Futatsuyama does not disclose forming epitaxial silicon
carbide layers on an off axis silicon carbide substrate as recited in claim 1. The
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Appeal 2015-005769
Application 11/745,817
The Examiner finds Chu discloses a method of manufacturing a single
crystal silicon carbide epitaxial layer on a silicon carbide substrate including the
step of introducing a source gas and a carrier gas to grow the silicon carbide layer.
Final Act. 4. The Examiner finds Chu discloses that “the growth rate of the silicon
carbide is dependent on the concentration of the source gas and the carrier gas
wherein the layer is being simultaneously grown and etched wherein the net result
is dependent on the gas mixture.” Id. (citing Chu, col. 6,11. 47—62).
The Examiner concludes that it would have been obvious to one of ordinary
skill in the art to modify Futatsuyama’s method “to include the reduced but not
halting flow rate of CHU because one of ordinary skill in the art at the time of the
invention would have had a reasonable expectation of predictably achieving the
desired etching result using the reduced flow rate of CHU.” Id. at 5.
The Appellants argue that Chu describes a constant flow rate of 2.5 liters per
minute of hydrogen with variations in the concentration of silicon tetrachloride and
carbon tetrachloride (i.e., source gases) rather than a “reduction in flow of the
source gas from the first flow rate to the reduced flow rate’ '' as recited in claim 1.
App. Br. 9 (emphasis added).
The Appellants’ argument is supported by the record. Chu discloses that
“[a]t a given flow rate, the concentrations of silicon tetrachloride and carbon
tetrachloride in the reactant gas mixture can be adjusted to yield the desired growth
rate.” Chu, col. 6,11. 51—53. More specifically, Chu discloses:
At a flow rate of 2.5 liters per minute of hydrogen at a
brightness temperature of 1700° C., if the concentrations of both
silicon tetrachloride and carbon tetrachloride are each only of the
order of 0.055 mole percent, the epitaxial growth of silicon carbide on
Examiner, however, finds Ellison and Okada teach that limitation. Final Act. 3.
The Appellants do not direct us to any error in the Examiner’s findings.
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Application 11/745,817
the substrate occurs but the net result of the growth process is the
chemical etching of the substrates. When the concentration of both
the silicon tetrachloride and the carbon tetrachloride exceeds 0.055
mole percent, the rate of epitaxial growth of silicon carbide exceeds
the chemical etching rate of the hydrogen and a net growth of
epitaxial silicon carbide is achieved.
Chu, col. 6,11. 63—74 (emphasis added).
The record on appeal supports a finding that Chu adjusts the concentration
of reactants relative to hydrogen to control the etching rate of hydrogen. See Ans.
9 (finding that the cited prior art teaches that “growing and etching can be adjusted
by changing the proportions of the source gas and hydrogen gas”).10 The
Examiner, however, does not direct us to any portion of Chu disclosing that the
flow rate of the source gas is adjusted to control the etching rate. In that regard,
the Examiner does not make any finding that correlates concentration to flow rate
in Chu’s method. Thus, on this record, Chu, at best, teaches maintaining a constant
flow rate of the source gas in Futatsuyama’s method but reducing its concentration
during etching.
The § 103(a) rejection of independent claim 1 and dependent claims 2, 3, 6,
and 8—17 based on Futatsuyama in view of Ellison, Okada, and Chu is not
sustained.
The Examiner does not rely on the remaining prior art of record to cure the
deficiencies in the § 103(a) rejection of claim 1. Therefore, the § 103(a) rejections
of claims 7, 19, 20, and 31 are also not sustained.
2. Claim 32
Claim 32, the other independent claim on appeal, is also directed to “[a]
method of manufacturing a single crystal silicon carbide epitaxial layer on an off-
10 Examiner’s Answer dated March 12, 2015.
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Application 11/745,817
axis silicon carbide substrate.” App. Br. 19. However, in contrast to claim 1,
claim 32 recites that the total flow rate of the combined process gas (i.e., a source
gas and a carrier gas) is reduced from a first flow rate to a reduced flow rate
without halting the flow of the combined process gas.11 Id.
The Appellants argue that the Examiner does not address the limitations of
claim 32, including the limitation of “reducing a total flow rate of the combined
process gas from the first flow rate to a reduced flow rate without halting the flow
of the combined process gas,” but simply repeats the statements made in the
rejection of claim 1. App. Br. 13 (emphasis added). The Appellants’ argument is
supported by the record. See Final Act. 11 (concluding that “based on the
teachings of CHU it would have been obvious to one of ordinary skill in the art. . .
that the source gas may be reduced but not halted during the etching of the
epitaxial layer” (emphasis added)); see also Ans. 10 (stating that “[t]he Examiner
maintains the rejection for claim 32 for those reasons in claim 1.”). Therefore, the
§ 103(a) rejection of independent claim 32 and dependent claim 3412 is not
sustained. See In re Oetiker, 977 F.2d 1443, 1445 (Fed. Cir. 1992) (the examiner
bears the initial burden of presenting a prima facie case of unpatentability).
C. DECISION
The Examiner’s decision is reversed.
REVERSED
11 Claim 1 recites that the flow rate of the source gas is reduced from a first flow
rate to a reduced flow rate while maintaining a flow of the carrier gas. App. Br.
16.
12 We note that claim 34 is dependent on cancelled claim 33. See App. Br. 19. In
the event of further prosecution, the Examiner and the Appellants should consider
amending the dependency of claim 34.
6