Ex Parte HARLEY et al

Patent Trial and Appeal Board

Sep 10, 2018

14793356 (P.T.A.B. Sep. 10, 2018)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR
14/793,356 07/07/2015 Gabriel HARLEY
74254 7590 09/10/2018
Okamoto & Benedicto LLP
P.O. Box 641330
San Jose, CA 95164-1330
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.
10031.009113 2742
EXAMINER
NGUYEN, KHIEM D
ART UNIT PAPER NUMBER
2823
MAIL DATE DELIVERY MODE
09/10/2018 PAPER
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.
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte GABRIEL HARLEY, 1
David D. Smith, and Peter John Cousins
Appeal2018-000791
Application 14/793,356
Technology Center 2800
Before MARK NAGUMO, DONNA M. PRAISS, and JANEE. INGLESE,
Administrative Patent Judges.
NAGUMO, Administrative Patent Judge.
DECISION ON APPEAL
SunPower Corporation ("Harley") timely appeals under
35 U.S.C. § 134(a) from the Final Rejection2 of all pending claims 1, 2, 4,
6-18, and 20. We have jurisdiction. 35 U.S.C. § 6(b).
We reverse.
1 The applicant under 3 7 C.F .R. § 1.46, and hence the appellant under
35 U.S.C. § 134, is the real party in interest, identified as SunPower
Corporation. (Appeal Brief, filed 24 May 2017 ("Br."), 1.)
2 Office Action mailed 10 February 2017 ("Final Rejection"; cited as "FR").
Appeal2018-000791
Application 14/793,356
A. Introduction 3
OPINION
The subject matter on appeal relates to making electrical contacts to
semiconductor devices, especially to the back-side of back-contact solar
cells. According to the '356 Specification, "[m]ost contact formation to
electrically active areas in semi-conductor and solar industries often involves
a removal of dielectric materials ... [and] may require several process
operations, such as deposition of a mask layer, selective etching of dielectric
layer( s ), and removal of a mask, or laser with subsequent etch or anneal."
(Spec. 1 [0004].) Harley seeks patent protection for a process for "the
formation of single-step damage free solar cell contact openings using a
laser." (Spec. 1 [0003].)
According to an embodiment of the claimed process, as shown in
Figure 2B', reproduced on the following page, a single crystal of silicon
substrate 2004 (Spec. 5 [0022], 11. 10-11) is provided with a dielectric
film 201 of silicon dioxide, which in a specific embodiment may have a
thickness of 1-2 nm. (Id. at 11. 15-17.) "In a particular environment," the
Specification teaches, "dielectric film 201 is a tunnel oxide barrier film."
3 Application 14/793,356, Solar cell contact formation using laser ablation,
filed 7 July 2015 as a continuation of 14/334,401, filed 17 July 2014, now
U.S. Patent No. 9,087,939, which is a continuation of 13/669,147, filed
5 November 2012, now U.S. Patent No. 8,785,236, which is a continuation
of 12/895,437, filed 30 September 2010, now U.S. Patent No. 8,324,015,
which claims benefit of a provisional application filed 1 December 2009.
We refer to the "'356 Specification," which we cite as "Spec."
4 Throughout this Opinion, for clarity, labels to elements are presented in
bold font, regardless of their presentation in the original document.
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Application 14/793,356
(Id. at 11. 17-18.) The '356 Specification does not appear to describe the
function of this dielectric film, but prior art of record teaches that "[t]he
presence of the thin interfacial tunnel oxide layer ... mitigates any high
interface recombination at the single crystal surface of [the] substrate ... "
Swanson '279 5 1 [0013], 4th sentence.)
{Figure 2B' is shown below}
2038 ·
{Figure 2B' shows a diagram of a cross section of the back-side of a solar
cell prior to contact hole formation; annotations added}
The Specification teaches that a layer 202 of polycrystalline material 6
may be formed on dielectric film 201. (Id. at 11. 6-7; 11. 8-11.) As shown in
Figure 2B', an absorption layer 203B, of silicon nitride (SiN), is provided as
dielectric stack7 204 (not labelled in Fig. 2B'; see Figs. 2A-D) directly on
5 Full cite at 6 n.13, infra.
6 The Specification instructs that the term "polycrystalline layer, when
referring to a polycrystalline silicon layer, is intended to also cover material
that can be described as amorphous- or a-silicon." (Spec. 9 [0034]. 1st
sentence.)
7 In disclosed embodiments not within the scope of the appealed claims, a
layer 203A of Si02 may be present between polycrystalline silicon layer 202
and absorbing SiN layer 203B. Layers 203A and 203B together form
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Application 14/793,356
the polycrystalline silicon layer. (Id. at 6 [0023], last sentence.) A plurality
of contact holes 208 are then prepared by exposing the structure to laser
radiation having a wavelength of approximately 1064 nm or less, ablating
material from dielectric material stack 204 and exposing a portion of poly-
crystalline material layer 202. (Id. at 6 [0024].) Conductive contacts 210
are then formed in the plurality of contacts holes 208. 8 (Id. at [0025].)
In embodiments, "both N-type and P-type doped regions 202A
and 202B, respectively," can be formed 9 "in the layer of polycrystalline
silicon." (Id. at 11. 11-13.) The Specification teaches that, with these
embodiments in a laser processing method, "any damage or melt is received
and accommodated by the poly-crystalline layer instead of by the single
crystal substrate." (Id. at 3 [0017], 11. 8-9.) Moreover, the polysilicon layer
is said to reduce or even essentially eliminate the formation of
recombination sites in the single crystal substrate. (Id. at 11. 10-12.)
The Specification teaches further that, "[i]n an embodiment, formation
of a dielectric or passivation layer in combination with a poly-crystalline
material layer is tuned in a way to accommodate commercially available
"dielectric stack" layer 204, which can be adjusted to tune sensitivity to the
ablating laser wavelength. (Spec. 4 [0019}-[0020].)
8 Figures 2C and 2D (not reproduced here) illustrate these steps for a
variation that includes a silicon dioxide layer 203A between polycrystalline
layer 202 and absorbing layer 203B; and Figure 3B (not reproduced here)
illustrates a final product that includes "recast polysignature 320" (not
described in any further detail in the Specification) under contact 310.
9 The Specification teaches that "instead of or in addition to forming N-type
and P-type doped regions in the polycrystalline layer, such regions can
instead be formed directly in a single crystalline layer." (Spec. 9 [0034],
2d sentence.)
4
Appeal2018-000791
Application 14/793,356
lasers which confine any laser damage to the poly-crystalline material layer
or to the dielectric or passivation layer." (Id. at 4 [0020], 11. 1--4.) In a
particular embodiment, the Specification reveals that "with the addition of
an absorbing layer, such as a silicon nitride layer with the composition
SixNy, total thermal and optical damage is confined within a poly-crystalline
material layer so that high-efficiencies are achieved in a solar cell without
the need for post-laser etching processes, or selective emitter formation."
(Id. at 11. 9-12.)
No detailed descriptions or working examples are provided for any of
the steps of fabrication. We therefore presume that all of these fabrication
steps are well-known to persons having ordinary skill in the art.
Claim 1 is representative and reads:
A method of fabricating a solar cell, the method comprising:
forming a first dielectric layer [201] over a silicon
substrate [200];
forming a poly-crystalline layer [202] over the first dielectric
layer [201 ];
forming an absorbing layer [203B] directly on the poly-
crystalline layer [202];
before forming any other layer on the absorbing
layer [203B] forming, by laser processing,
a plurality of contact holes [208] through the absorbing
layer [203B]; and
forming conductive contacts [210] in the plurality of
contact holes [208].
(Claims App., Br. 1 O; some indentation, paragraphing, emphasis, and
bracketed labels to Figures 2B', 2C, and 2D added.)
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Appeal2018-000791
Application 14/793,356
The Examiner maintains the following grounds of rejection 1°, 11 :
A. Claims 1, 2, 4, 6-10, 16-18, and 20 stand rejected under
35 U.S.C. § I03(a) in view of the combined teachings of
Luan, 12 Swanson '279, 13 and either Yamazaki 14 or Xu. 15
Al. Claims 11-13 and 15 stand rejected under 35 U.S.C. § I03(a)
in view of the combined teachings of Luan and either
Yamazaki or Xu.
A2. Claim 14 stands rejected under 35 U.S.C. § I03(a) in view of
the combined teachings of Luan, Swanson '279, and either
Yamazaki or Xu.
10 Examiner's Answer mailed 19 September 2017 ("Ans.").
11 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.
12 Hsin-Chiao Luan and Denis De Ceuster, Anti-reflective coating with high
optical absorption layer for backside contact solar cells, U.S. Patent
Application Publication 2009/0151784 Al (18 June 2009), based on an
application filed 1 December 2008.
13 Richard M. Swanson, Solar cell having silicon nano-particle emitter, U.S.
Patent Application Publication 2008/0121279 Al (2008), now abandoned
(assigned to SunPower Corporation, the present real party in interest).
14 Shunpei Yamazaki and Mai Akiba, Semiconductor device, U.S. Patent
Application Publication 2007/0176845 Al (2007).
15 Baomin Xu and David K. Fork, Metallization contact structures and
methods for forming multiple-layer electrode structures for silicon solar
cells, U.S. Patent Application Publication 2009/0162872 Al (25 June 2009),
based on an application filed 21 December 2007.
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Appeal2018-000791
Application 14/793,356
B. Discussion
The Board's findings of fact throughout this Opinion are supported by
a preponderance of the evidence of record.
Harley argues for the patentability of the rejected claims based on
limitations recited in claim 1, with additional arguments based on further
limitations recited in claim 4, which depends from claim 1. Accordingly, we
focus our attention on claim 1.
The Examiner finds that Luan discloses, in Figure 1, below, and in
(120
to7
. ~..,..,.l031 110
.· -12~~
paragraphs [0007]-[0009], a method for fabrication of a solar cell meeting
all the requirements of claim 1, including a substrate 102, a polycrystalline
layer 105, an absorbing layer 107, and a plurality of contact holes through
the absorbing layer filled with conductive contacts 109 and 110. (FR, para.
16 Luan 1 [0013].
7
Appeal2018-000791
Application 14/793,356
bridging 2-3.) The Examiner finds that Luan does not describe: (a) forming
a first dielectric layer over a silicon substrate (id. at 3, 11. 5-6); and
(b) forming a plurality of contact holes through absorbing layer 107 by laser
processing (id. at 4, 11. 3--4).
The Examiner finds that Swanson '279 describes a process of making
a solar cell in which a first dielectric layer 14 is formed over silicon layer 10
to reduce high interface recombination at the substrate surface. (Id. at 3,
11. 7-10.) The Examiner reasons that it would have been obvious to provide
such a layer in the process taught by Luan to obtain the same benefits.
(Id. at 11. 11--4, 1. 2.) The Examiner also finds that Yamazaki and Xu
disclose methods of making contact holes in semiconductor devices and
solar cells, respectively. (Id. at 11. 5-10.) The Examiner concludes that it
would have been obvious to form contact holes through absorber 107,
disclosed by Luan, using the laser processing methods disclosed by
Yamazaki and by Xu, to take advantage of the high precision of laser
processing and the avoidance of the larger number of steps necessary in
chemical etching. (Id. at 11. 11-16.)
As Harley points out (Br. 4, 11. 3-5), Luan describes a layered solar
cell structure, but does not describe in paragraphs [0007]-[0009], how and in
which step layer 107 (the "absorbing layer") is formed. At most, Harley
emphasizes (id. at 11. 6-7), Luan indicates that "diffusion regions 105
and 106 may be formed by diffusion of appropriate dopants from the
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Appeal2018-000791
Application 14/793,356
backside" (Luan 1 [0008]. 2d sentence). In this regard, Harley cites prior art
of record, namely Swanson '485 17, Figure 12, shown below, and
84A
--""""""r-..,.---"'N...,+ _+-t-......:.----,+-...t_ . t 04
I
84B 84A 1 .. 04 \·. '01
106
84B
t06
{Figure 12 shows the structure of a wafer that is heated to diffuse dopants
into p- and n-type layers 84A and 84B, respectively}
as evidence that, in some embodiments, multiple layers must be formed on
the polycrystalline layer of a nascent solar cell before the contact holes are
formed.
In particular, Swanson '485 teaches that, after formation of
polycrystalline silicon layer 84, p-type dopant source layer 104, n-type
dopant source layer 501, and undoped silicon dioxide layers 106 and 502 are
deposited. Wafer 102 is then heated "to diffuse dopants into polysilicon
layer[] 84 ... using a conventional annealing process, including rapid
thermal annealing (RTP)." (Swanson '485, col. 6, 11. 34--37 .) Swanson '485
then teaches that conventional solar cell back end processes may be
17 Richard M. Swanson, Back side contact solar cell with doped polysilicon
regions, U.S. Patent No. 7,468,485 Bl (23 December 2008) (assigned to
Sunpower Corporation, the present real party in interest.
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Appeal2018-000791
Application 14/793,356
employed to form metal contacts to the p-type regions 84A and then-type
regions 84B. (Id. at 11. 38--46.)
Steps such as the formation of the diffusion sources 104 and 501,
which appear to correspond to the remarks of Luan, quoted supra, that
diffusion regions 105 and 106 may be formed by diffusion of dopants from
the backside, are problematic as the basis for rendering processes covered by
the appealed claims obvious because they appear to be in conflict with the
requirement that the "absorbing layer" be deposited directly on the
polycrystalline layer. Moreover, according to the claimed method, before a
contact hole is formed, layers other than an absorbing layer may not be
deposited on the polycrystalline layer. In this regard, as noted supra, Harley
emphasizes that Luan does not indicate when the contact holes are formed
through absorption layers 107. (Br. 4, 11. 9--10.)
The Examiner responds that, "based on the above teaching of Luan,
there are no other layers formed between the step of forming the conductive
contacts 109, 110, and the step of forming the absorbing layer 107."
( Ans. 11, 11. 1-3.) The "above teachings" cited by the Examiner are
paragraphs [0008] and [0009], and Figure 1, of Luan. Luan [0008] describes
the backside structure, alluding only to the diffusion process of forming the
diffusion regions 105 and 106 described supra. Luan [0009] describes the
front side of the solar cell and is not directly relevant to processing steps for
the back side.
We conclude that no credible substantial evidence supports the
Examiner's findings that Luan describes a process of fabricating solar cells
that includes the step of forming an absorption layer directly on a
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Appeal2018-000791
Application 14/793,356
polycrystalline layer. Put another way, the Examiner has, at best, inferred
tacitly from the '356 Specification disclosure, that all of the process steps
were known in the prior art and inherent in, or suggested by, the backside
solar cell structure described by Luan. The inherency prong of this
argument has been rebutted by the evidence from Swanson '485 that other
methods of making back-contact solar cells are known, if not standard. The
inference of suggestion by the structure lacks credible prior art evidentiary
support, particularly regarding the formation and composition of electrical
isolation layers 107, that these layers would have been expected to function
as an absorbing layer for the proposed laser-ablation steps described by
Yamazaki or Xu.
The Examiner makes no findings regarding the supplementary
references that cure these defects of Luan.
We therefore reverse the rejections of record.
C. Order
It is ORDERED that the rejections of claims 1, 2, 4, 6-18, and 20 are
reversed.
REVERSED
11