Ex Parte Kuchiyama et al

Patent Trial and Appeal Board

Apr 5, 2018

13816216 (P.T.A.B. Apr. 5, 2018)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE
13/816,216 02/08/2013
145327 7590 04/09/2018
Alleman Hall Creasman & Tuttle LLP
900 SW 5th A venue
Suite 2300
Portland, OR 97204
FIRST NAMED INVENTOR
Takashi Kuchiyama
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.
IZN12304PCTUS 7119
EXAMINER
MEKHLIN, ELIS
ART UNIT PAPER NUMBER
1721
NOTIFICATION DATE DELIVERY MODE
04/09/2018 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):
patentdocket@allemanhall.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE
THE PATENT TRIAL AND APPEAL BOARD
Ex parte T AKASHI KUCHIY AMA, 1
Kenji Yamamoto, and Masashi Y oshimi
Appeal2016-004570
Application 13/816,216
Technology Center 1700
Before ROMULO H. DELMENDO, MARK NAGUMO, and
WESLEY B. DERRICK, Administrative Patent Judges.
NAGUMO, Administrative Patent Judge.
DECISION ON APPEAL
Takashi Kuchiyama, Kenji Yamamoto, and Masashi Y oshimi
("Kuchiyama") timely appeal under 35 U.S.C. § 134(a) from the Final
Rejection2 of all pending claims 1--4 and 8. We have jurisdiction.
35 U.S.C. § 6(b)(l). We affirm.
1 The real party in interest is identified as Kaneka Corporation. (Appeal
Brief, filed 9 October 2015 ("Br."), 3.)
2 Office Action mailed 9 March 2015 ("Final Rejection"; cited as "FR"), as
modified by the Advisory Action (27 May 2015, "Adv."), entering
amendments filed after the Final Rejection under 3 7 C.F .R. § 1.116
on 11 May 2015 ("AAF").
Appeal 2016-004570
Application 13/816,216
A. Introduction 3
OPINION
The subject matter on appeal relates to heterojunction solar cells,
which, according to the '216 Specification, are solar cells that have a
conductive amorphous silicon-based thin film having a band gap different
from the band gap of the [conductive] crystalline silicon substrate to form a
diffusion potential. (Spec. 1 [0002].) A cross-sectional diagram of an
inventive solar cell is shown in the Figure, reproduced below.
-~·"··
·.·.·.·.·.·.···.·············--·······--· ti -~
{The Figure shows a cross section of a solar cell}
3 Application 13/816,216, Crystalline silicon-based solar cell, 8 February
2013 as the national stage under 35 U.S.C. § 371 of PCT/JP2011/067783,
filed 3 August 2011, claiming the benefit of an application filed in Japan
on 9 August 2010. We refer to the "'216 Specification," which we cite as
"Spec."
2
Appeal 2016-004570
Application 13/816,216
The solar cell comprises conductive crystalline silicon substrate 14, with, on
the external, light-facing side, silicon-based thin film 41 of a first
conductivity type (typically amorphous p-type silicon (id. at 5---6 [0019])),
transparent electrode 61, and collecting electrode 71. (Id. at 5 [0018].) On
the opposite (base) side of substrate 1 are silicon-based thin film 42 of the
opposite conductivity type, transparent electrode 62, and collecting
electrode 72. (Id.) The Specification teaches that it is known to provide
intrinsic 5 amorphous silicon thin films 21, 22, between substrate 1 and
conductive amorphous silicon thin films 41, 42, in order to terminate
dangling bonds on conductive substrate 1 with hydrogen, thereby reducing
the generation of new defect levels as well have preventing impurity
diffusion through the overlying layers during their formation.
(Id. at [0003].) The Specification teaches further that the transparent
electrodes are critical to the extraction of photoinduced carriers, and
improvements are said to require improving the electrical junction between
the silicon-based thin-film and the transparent electrode layer. (Id. at 2-
3 [0007].) Merely decreasing the resistance of the transparent electrode is
said to be insufficient. (Id. at 2 [0005].)
More specifically, the Specification discloses an improvement in
which the "first transparent electrode"-i.e., electrode 61, facing the light
4 Throughout this Opinion, for clarity, labels to elements are presented in
bold font, regardless of their presentation in the original document.
5 We understand the term "intrinsic," in this context, to refer to a "pure'
material that contains, at most, a slight amount of n- or p-type impurity, such
that "the silicon-based thin-film can function as an intrinsic layer (i-type
layer)." (Spec. 8 [0028].)
3
Appeal 2016-004570
Application 13/816,216
source---comprises a two-layer structure in which both layers are amorphous
transparent conductors, wherein substrate-side layer 61A has a higher carrier
density than surface-side layer 61B. (Id. at 3 [0009]-[0010].) The thickness
of first transparent electrode layer 61A is 50 to 120 nm, to optimize
transparency as well as to provide adequate conductivity to transport carriers
to the collecting electrode 71. (Id. at 12 [0040].) Too high a conductivity in
surface-side transparent electroconductive layer 61B is said to reduce the
transparency and thereby lower the light capture efficiency of the solar cell.
(Id. at 14 [0046].) The higher carrier concentration at substrate side
transparent electroconductive layer 61A, however, is said to provide a good
electrical junction with the conductive silicon-based thin film 41. (Id.)
The Specification reveals further that when the thickness of
conductive single-crystal silicon substrate 1 is 250 nm or less, warpage may
occur upon formation of the transparent electrodes 61, 62, of differing
thicknesses on the light-incident side (which is optimized for transmitting
light into the cell) and the back surface side (which is optimized for
electricity extraction efficiency). (Id. at 18 [0056]-[0057].) A film of
crystalline indium oxide doped with tin oxide ("ITO"), for example, is said
to generally have residual compressive stress. (Id. at 19 [0059].) An
amorphous ITO film, however, is said to have less or no compressive stress
(id.), and is therefore preferred as both the first (light-incident side) and
second (back-side) transparent electroconductive layer. (Id. at [0060].) The
Specification teaches that such layers may be prepared by decreasing the
power density during deposition or by increasing the deposition pressure.
(Id. at 21 [0066].)
4
Appeal 2016-004570
Application 13/816,216
Sole independent claim 1 is representative and reads:
A crystalline silicon-based solar cell comprising
a silicon based thin-film of a first conductivity type [ 41] and
a first transparent electrode layer [61], in this order,
on one surface of a conductive single-crystal silicon
substrate [1] of the first conductivity type or an opposite
conductivity type; and
a silicon-based thin-film of the opposite conductivity type [ 42]
and a second transparent electrode layer [62], in this order,
on another surface of the conductive single-crystal silicon
substrate [1 ], wherein
the first transparent electrode layer [ 61] and the second
transparent electrode layer [ 62] are each formed of a
transparent conductive metal oxide,
the first transparent electrode layer [ 61] satisfies
requirements (i) to (iii):
(i) at least two layers, including a substrate-side
electroconductive layer [ 61A] and a surface-side
electroconductive layer [61B], are provided in the first
transparent electrode layer [61 ],
and the substrate-side electroconductive layer [ 61A] and
the surface-side electroconductive layer [61B] are
amorphous layers;
(ii) a total thickness of the first transparent electrode
layer [ 61] is 50 to 120 nm; and
(iii) a carrier density of the substrate-side
electroconductive layer [61A] is higher than a carrier
density of the surface-side electroconductive
layer [61B], and the carrier density of the surface-side
electro conductive layer [61B] is 1 to 4 x 1020 cm-3,
and
a thickness of the conductive single-crystal silicon
substrate [1] is 250 µm or less.
(Claims App., Br. 21; some indentation, paragraphing, emphasis, and
bracket labels to the Figure added.)
5
Appeal 2016-004570
Application 13/816,216
It may be noted that claim 1 requires the first and second transparent
electrode layers 61, 62, to be transparent conductive metal oxides, but only
first transparent electrode layer 61 is required to have the recited dual-
amorphous layer structure.
The Examiner maintains the following grounds of rejection6' 7, 8 :
A. Claims 1--4 and 8 stand rejected under 35 U.S.C. § 103(a) in
view of the combined teachings ofNakashima, 9 Wada, 10
Nishioka, 11 Kariya, 12 and Sun. 13
B. Claims 1--4 and 8 stand rejected under 35 U.S.C. § 103(a) in
view of the combined teachings of Nakashima, Nakano, 14
Nishioka, Kariya, and Sun.
6 Examiner's Answer mailed 28 January 2016 ("Ans.").
7 Because this application was filed before the 16 March 2013, effective
date of the America Invents Act, we refer to the pre-AIA version of the
statute.
8 Claim 7 was canceled and incorporated into claim 1 as the final limitation
(AAF 2-3), rendering the separate rejections of claim 7 moot, but requiring
that the additional reference Sun be applied in the rejections of claim 1.
9 Takeshi Nakashima and Eiji Maruyama, Photovoltaic device, U.S. Patent
Application Publication 2005/0150543 Al (2005).
1° Katsuhito Wada, Photovoltaic element and its manufacturing method,
JP 2002-208715 Al (2002) (JPO translation).
11 Yukiya Nishioka et al., Method for forming a transparent conductive ITO
film, U.S. Patent No. 5,538,905 (1996).
12 Toshimitsu Kariya et al., Photovoltaic element, U.S. Patent Application
Publication 2002/0002992 Al (2002).
13 Hai-Lin Sun et al., Solar cell, U.S. Patent Application Publication
2009/0250113 Al (2009).
14 Kengo Nakano et al., Photoelectric conversion device, JP1205474 A
(1989) (USPTO translation).
6
Appeal 2016-004570
Application 13/816,216
B. Discussion
The Board's findings of fact throughout this Opinion are supported by
a preponderance of the evidence of record.
Initially, we find that Kuchiyama bases all arguments for patentability
on limitations recited in claim 1. We therefore focus on that claim, with
which all remaining claims stand or fall. 37 C.F.R. § 41.37(c)(l)(iv) (2014).
The Examiner finds, and Kuchiyama does not dispute, that Nakashima
describes a crystalline silicon-based solar cell comprising layers
corresponding to those recited in claim 1, but for (first) the two-layer
structure required of first transparent electrode layer 61. (Adv., para.
bridging 3--4 and first full para. at 4.) The Examiner finds that Wada
discloses two-layer ITO transparent electrodes. (Id. at 4, 2d full para.) The
Examiner finds further that Wada discloses that the substrate-side ITO
layer 106 has a lower oxygen density than the surface-side ITO layer 107.
The Examiner determines that the lower oxygen density results in a higher
conductivity at the interface with the doped silicon layer, allowing for
decreased contact resistance. (Id.) Moreover, the Examiner finds that the
higher oxygen density at the surface-side ITO layer "maintains the light
transmittance of the film." (Id.) The Examiner finds that these references
are silent as to the amorphous state of the first transparent electrode (id. at 6,
last para.), but finds (id. at 7, 1st para.), that Kariya discloses that ("[t] he
transparent conductive layers employed in the present invention are
comprised of indium tin oxide (ITO) and may be in a polycrystalline,
microcrystalline, or amorphous state" (Kariya 5 [0058], emphasis added).
The Examiner reasons that a person having ordinary skill in the art would
7
Appeal 2016-004570
Application 13/816,216
have had a reasonable expectation of successfully combining these teachings
to obtain a useful solar cell, and that the teachings of Wada and Nishioka 15
provide sufficient basis to conclude that the carrier concentration was
recognized as a result effective variable, such that routine optimization
would have resulted in arriving at the recited carrier concentrations. (Adv.,
para. bridging 5---6.) Finally, the Examiner finds that Sun teaches that
conductive single crystal silicon substrates are useful in solar cell
applications at a thickness of 200 to 300 µm (id. para. bridging 7-8, citing
Sun [0022]). The Examiner concludes that a solar cell having required
thickness of the silicon crystal substrate would have been obvious. (Id. at 8,
1st full para.)
Kuchiyama urges that the teachings of Kari ya must be considered in
context, and that Kariya teaches a dual-layer ITO transparent electrode with
a lower tin content on the substrate side than the surface-side. "Thus,"
Kuchiyama concludes, "it is inherent in Kariya's disclosure that, in Kariya's
solar cell, the carrier density of the substrate-side layer is less than the
surface-side layer, since the higher the tin content in ITO, the higher the
carrier density." (Br. 13, 2d para.) In response to the Examiner's reasoning
that Kariya's disclosure of a multi-layer transparent electrode is independent
of the tin concentration variation of the layers, Kuchiyama argues that
"amorphousness and carrier density gradient (tin concentration relationship)
are both related to the features of the multi-layer transparent electrode layer,
15 The Examiner cites Nishioka, column 2, lines 1-3 ("[t]he carrier density
of the thus formed ITO film is reduced as the oxygen partial pressure of the
ITO film is increased, or the oxygen deficiency of the ITO film is lowered.")
as further support. (Id. at 5, 1st full para.)
8
Appeal 2016-004570
Application 13/816,216
and thus these features are not independent." The opposite carrier density
gradients of Wada and Kariya are incompatible, Kuchiyama urges, and the
person of ordinary skill in the art would therefore not have been motivated to
combine the teachings of the references. (Id. at 14.)
We do not find these arguments persuasive of harmful error. As the
Examiner finds, Kariya states unequivocally that the transparent conductive
layers may be polycrystalline, microcrystalline, or amorphous. While there
is no dispute that Kariya prefers the crystalline state, Kuchiyama has not
directed our attention to any teaching in the record indicating that the
amorphous state of the ITO transparent electrode would have been
considered inoperable. Nor, perhaps equivalently, has Kuchiyama
demonstrated that the functions of the preferred crystalline ITO layer are so
tightly related to the presence of the tin gradient in that layer that a person
having ordinary skill in the art would have disregarded Kariya's clear
statement that any of the three states would be suitable, and concluded that
only the crystalline layer would be suitable. We are thus not persuaded that
the Examiner erred harmfully in concluding that the subject matter of
claim 1 would have been prima facie obvious in view of the combined
teaching of the references cited in Rejection A.
The reasoning and arguments regarding the teachings of Nakano
(Adv. 10-13; Br. 16-20) are essentially parallel to those regarding the
teachings of Wada, and we are accordingly not persuaded of harmful error in
the prima facie case of obviousness in Rejection B.
9
Appeal 2016-004570
Application 13/816,216
Kuchiyama does not raise any other arguments for patentability in the
principal Brief on Appeal. The citation in the Reply 16 of new evidence,
namely, the translation of the Japanese priority document underlying Kari ya,
is belated under the rules governing appeals 17 and we decline to consider it
in the absence of a showing of good cause why that evidence was not
presented earlier, i.e., in the amendment-after-Final-Rejection
filed 11May2015, under 37 C.F.R. § 1.116. In any event, it is not
unreasonable to interpret the allegedly critical passage in the record copy of
Kariya, paragraph [0058], namely, "it is necessary to optimize the forming
temperature for the concerned layers in order to obtain even a little higher
conversion efficiency," as elaborating why the crystalline state of the
transparent electrode is preferred, as Kuchiyama urges in the Reply. But, as
we explained supra, such a preference does not amount to a teaching away
from less preferred, but still operable, embodiments. See, e.g., In re Mouttet,
686 F.3d 1322, 1334 (Fed. Cir. 2012) ('just because better alternatives exist
in the prior art does not mean that an inferior combination is inapt for
obviousness purposes.")
Similarly, the argument regarding unexpected results (Reply 5-7) is
belated and there is no plausible showing of good cause why that argument
was not presented in the principal Brief on appeal. Our principal role is
review. Such an inquiry would involve a fact-intensive analysis of the
evidence of record, which we decline to undertake de novo, without the
16 Reply Brief filed 28 March 2016 ("Reply").
17 37 C.F.R. § 41.41(b )(2) (2015) ("A reply brief shall not include ... any
new or non-admitted affidavit or other Evidence."); see also 37 C.F.R.
§ 1.116(e).
10
Appeal 2016-004570
Application 13/816,216
evaluation of that evidence in the first instance by the Examiner, who, by
dint of experience in this and related fields, is better positioned to make such
findings.
We therefore are not persuaded of harmful error in the Examiner's
legal conclusion of obviousness, which we affirm.
C. Order
It is ORDERED that the rejection of claims 1--4, 7, and 8 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).
AFFIRMED
11