Ex Parte Doan et al

Patent Trial and Appeal Board

Aug 17, 2016

11840299 (P.T.A.B. Aug. 17, 2016)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR
111840,299 08/17/2007 HungQ. Doan
62294 7590 08/19/2016
BSTZ-OVT
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
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EXAMINER
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ART UNIT PAPER NUMBER
2891
NOTIFICATION DATE DELIVERY MODE
08/19/2016 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.
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PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte HUNG Q. DOAN and ERIC G. STEVENS
Appeal2014-003172
Application 11/840,299 1
Technology Center 2800
Before ADRIENE LEPIANE HANLON, CATHERINE Q. TIMM, and
JAMES C. HOUSEL, Administrative Patent Judges.
HOUSEL, Administrative Patent Judge.
DECISION ON APPEAL 2
Pursuant to 35 U.S.C. § 134(a), Appellants appeal from the
Examiner's decision finally rejecting claims 1-8 and 10-19 under 35 U.S.C.
§ 103(a). We have jurisdiction over the appeal under 35 U.S.C. § 6(b).
We AFFIRM.
1 According to Appellants, the real party in interest is OmniVision
Technologies, Inc. Appeal Br. 2.
2 Our decision refers to the Specification filed August 17, 2007, the Final
Office Action (Final Act.) mailed November 23, 2012, Appellants' Appeal
Brief (Appeal Br.) filed March 7, 2013, the Examiner's Answer (Ans.)
mailed September 16, 2013, and Appellants' Reply Brief (Reply Br.) filed
November 15, 2013.
Appeal2014-003172
Application 11/840,299
STATEMENT OF THE CASE
The invention relates to a method of fabricating a shallow trench
isolation (STI) in a semiconductor substrate for isolating devices formed in
the substrate, where the STI has an implant formed at the comer. According
to Appellants, such comer implants have the advantage of reducing
undesirable surface dark current in image sensors by preventing silicon pits
in the STI comers. Spec. 3:6-8.
Claim 1, reproduced from the Claims Appendix to the Appeal Brief, is
illustrative of the subject matter on appeal. The limitation at issue is
italicized.
1. A method for forming an isolation region in a semiconductor
substrate to isolate devices formed in the substrate, comprising:
forming a shallow implant in a portion of the
semiconductor substrate near an upper surface of the
semiconductor substrate by implanting a first P-type dopant
through an opening in a first hard mask layer;
forming a second hard mask layer over the portion of the
semiconductor substrate and the first hard mask layer;
etching the second hard mask layer to form sidewall
spacers along the sides of the first hard mask layer, wherein each
sidewall spacer overlies a perimeter portion of the shallow
implant in the semiconductor substrate; and
etching into the semiconductor substrate and through the
shallow implant between the sidewall spacers to form an
isolation trench in the semiconductor substrate and comer
implants at only the comers of the isolation trench near the upper
surface of the semiconductor substrate.
The Rejections
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Application 11/840,299
The following grounds of rejection under 35 U.S.C. § 103(a) are
before us on appeal:
A. Claims 1, 2, 7, and 18 as unpatentable over Lin in view of
Mehrad;
B. Claim 6 as unpatentable over Lin and Mehrad, further in view
of Jin;
C. Claims 3-5, 8, 10-15, and 19 as unpatentable over Lin and
Mehrad, further in view of Wu;
D. Claim 16 as unpatentable over Lin and Mehrad, further in view
of Wu and Fulford; and
E. Claim 17 as unpatentable over Lin and Mehrad, further in view
of Wu and Jin.
ANALYSIS
Rejection A
il1ppellants do not argue the claims covered under this rejection
separately, but instead focus their arguments on the P-type dopant limitation
ofclaim 1. Claims 2, 7, and 18 stand or fall with claim 1. 37 C.F.R.
§ 41.37(c)(iv)(2013).
The dispositive issue before us in the appeal of this rejection is
whether Appellants have identified reversible error in the Examiner's
determination that it would have been obvious to use a P-type dopant in Lin
for the benefit of providing a compensating dopant to alter threshold voltage
as taught by Mehrad.
After review of the opposing positions articulated by Appellants and
the Examiner and the evidence of obviousness adduced by the Examiner in
light of the countervailing evidence proffered by Appellants, we determine
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Application 11/840,299
that the Appellants' arguments and evidence are insufficient to outweigh the
evidence of obviousness marshalled by the Examiner. Thus, Appellants
have not identified reversible error in the Examiner's obviousness rejection.
In re Jung, 637 F.3d 1356, 1365 (Fed. Cir. 2011). The following comments
are added for emphasis.
The Examiner finds, without dispute, that Lin discloses a method as
recited in claim 1 except for the use of a P-type dopant as the first dopant.
Final Act. 3. The Examiner further finds Mehrad teaches a first dopant is a
P-type dopant which serves to adjust the threshold voltages in a direction
opposite to that of an N-type dopant, i.e., threshold voltage is decreased in a
PMOS and increased in an NMOS. Id.; Mehrad, i-fi-19 and 45. The Examiner
concludes it would have been obvious to have used a P-type dopant in Lin's
method to alter threshold voltage in an opposite direction as taught by
Mehrad. Final Act. 3.
Appellants present two arguments against the Examiner; s obviousness
rejection: 1) that the proposed modification to Lin's method would render
Lin ineffectual for its intended purpose (Appeal Br. 11 ); and 2) that the
Examiner's proposed combination of Lin and Mehrad involves
impermissible hindsight (id. at 14).
With regard to the first argument, Appellants assert that Lin teaches a
method of implanting an N-type dopant at the upper comers of a shallow
trench and oxidizing the doped structure. Id. at 11. Appellants further assert
that the N-doped comers oxidize at a higher rate thereby forming rounded
comers which reduce the "kink" effect in transistors. Id. According to
Appellants, replacing Lin's N-type dopant with a P-type dopant would
destroy Lin's stated purpose of forming rounded comers. Id.
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In support of this contention, Appellants cite two references, in
particular relying on teachings from Leaming Activity 43 which teaches that
high concentrations of dopants present in silicon tend to increase the oxide
growth rate. Id. at 12.4 Appellants further assert that Leaming Activity 4
teaches that oxidation occurs in two stages, a linear stage at the beginning of
oxidation in which the presence ofN-type dopants can increase oxide
growth rate, and a parabolic stage after oxide builds up in which the
presence of P-type dopants increase the oxide growth rate. Id. at 12-13.
Appellants also assert that the parabolic stage is the slow second portion of
the oxidation cycle. Id. at 13. Appellants argue that one of ordinary skill in
the art would understand that the linear stage is most at play in Lin, where
N-type dopants increase oxidation rate. Id. Appellants contend that if P-
type dopants are used in Lin, the comers would fail to round because by the
time sufficient oxide builds up for the P-type dopant to accelerate oxidation,
the comer would still be square. Id.
3 "Leaming Activity 4: Factors that affect oxidation and inspection
techniques," Maricopa Advanced Technology Education Center,
http://matec.org/ps/library3/secure/modules/033/LA4/M033LA4.html,
Appellants accessed January 12, 2012 (hereinafter, "Leaming Activity 4").
4 We note Appellants cite Razak, Dr. Khairunisak Abdul, "EBB 323
Semiconductor Fabrication Technology- Oxidation," University Sains
Malaysia, updated August 13, 2007,
http:// material. eng. usm. my I stafuome/khairunisak/nota. html, Appellants
accessed January 12, 2012 (hereinafter, "Razak"). However, Appellants
merely indicate that Razak, along with Leaming Activity 4, make clear that
there exists two oxidation rates for crystalline silicon, a linear stage at the
beginning of oxidation, and a parabolic stage when oxide builds up on the
surface. Appellants do not further discuss Razak, nor direct our attention to
any particular teaching in Razak.
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We do not find Appellants' arguments persuasive of reversible error
in the Examiner's obviousness rejection. The Examiner notes Lin merely
states that N-type dopants are preferred, and thus do not exclude P-type
dopants. Ans. 5. Indeed, Lin also teaches broadly that "adding dopants into
the substrate, the rate of oxidation of the substrate in a thermal oxidation
operation increases." Lin 3: 66-4: 1. Further, Leaming Activity 4 clearly
teaches that dopants tend to increase the oxidation growth rate, albeit that P-
type dopants tend to increase the oxidation growth rate during the parabolic
stage. Appellants do not direct our attention to any evidentiary support for
the assertion that this parabolic stage is slow relative to the linear stage, or
that one of ordinary skill in the art would recognize that, if P-type dopants
were used in Lin, the comers of the trench would fail to round. "Attorney's
argument in a brief cannot take the place of evidence." In re Pearson, 494
F.2d 1399, 1405 (CCPA 1974).5 Therefore, Appellants have not shown by
either persuasive technical reasoning or evidence that use of P-type dopants
in Lin would render Lin's process inoperable for the stated purpose of
forming rounded comers.
With regard to Appellants' second argument that the Examiner's
rejection relies on impermissible hindsight, Appellants contend that the
Examiner's proposed combination of Lin and Mehrad "contorts both
5 We note the Examiner, in response, directs attention to the newly cited
reference to Loo, US 2005/0079732, published April 14, 2005. Ans. 6-7.
Because Appellants' arguments and evidence fail to persuasively identify
reversible error in the Examiner's rejection, we need not address the
Examiner's and Appellants' discussion regarding this reference. Likewise,
we need not address the Examiner's newly cited reference to Liu, US
6,974,998, issued December 13, 2005. See Ans. 8.
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references without resulting in a workable combination." Appeal Br. 14. In
particular, Appellants assert that the rejection "suggests replacing the
implant region 212 of Lin with the implant region 318 of Mehrad, which
would not result in the rounded upper comers specified by Lin, rendering
Lin unsatisfactory for its intended purpose and significantly changing its
principle of operation." Id. Appellants argue that such a combination can
only be achieved through reliance on Appellants' Specification-the very
definition of impermissible hindsight. Id.
We disagree. "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."
In re McLaughlin, 443 F.2d 1392, 1395, 170 USPQ 209, 212 (CCPA 1971).
To begin, we note that to the extent Appellants are relying on their first
argument that using P-type dopants in Lin would not result in rounded
comers, rendering Lin unsatisfactory for its intended purpose and
significantly changing its principle of operation, we are not persuaded of
reversible error for the reasons explained supra. Moreover, we note that
Appellants misapprehend the Examiner's obviousness conclusion. The
Examiner's rejection proposes that it would have been obvious to have used
P-type dopants in Lin's method in view of Mehrad's teaching. The rejection
is not replacing Lin's doped regions 212 with Mehrad's doped regions 318.
Finally, we note the Examiner articulates a reason for combining the
teachings of Lin and Mehrad-to alter threshold voltage. Final Act. 3.
Appellants do not dispute, nor otherwise address, the Examiner's articulated
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reason. Accordingly, we are not persuaded that the Examiner's obviousness
rejection relies on impermissible hindsight.
Rejection B
Appellants do not raise substantively different arguments against the
Examiner's rejection of claim 6, but instead argue that Jin does not cure the
deficiencies of Lin and Mehrad. Appeal Br. 15. For the reasons given
above, there are no deficiencies in the Examiner's proposed combination of
Lin and Mehrad. Accordingly, we will sustain this rejection for the same
reasons supra.
Rejection C
Appellants raise the same two arguments against this rejection as
raised against Rejection A which we did not find persuasive as explained
above. Accordingly, we will sustain this rejection for the same reasons
supra.
Rejections D and E
Appellants do not raise substantively different arguments against the
Examiner's rejections of either of claims 17 and 18, but instead argue that
Jin and Fulford do not cure the deficiencies of Lin and Mehrad. Appeal Br.
20. For the reasons given above, there are no deficiencies in the Examiner's
proposed combination of Lin and Mehrad. Accordingly, we will sustain this
rejection for the same reasons supra.
DECISION
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Appeal2014-003172
Application 11/840,299
Upon consideration of the record, and for the reasons given above and
in the Final Office Action and Answer, the decision of the Examiner
rejecting claims 1-8 and 10-19 under 35 U.S.C. § 103(a) as unpatentable
over the combination of Lin and Mehrad, alone or further in view of Jin,
Wu, and/or Fulford 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)(l).
AFFIRMED
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