Ex Parte Hu et al

Patent Trial and Appeal Board

Jul 18, 2018

14688387 (P.T.A.B. Jul. 18, 2018)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR
14/688,387 04/16/2015 Yushi Hu
73115 7590 07/20/2018
SCHWEGMAN LUNDBERG & WOESSNER/MICRON
P.O. BOX 2938
MINNEAPOLIS, MN 55402
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.
303.F38US1 3781
EXAMINER
WARD,ERICA
ART UNIT PAPER NUMBER
2891
NOTIFICATION DATE DELIVERY MODE
07/20/2018 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):
uspto@slwip.com
SLW@blackhillsip.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte YUSHI HU, JOHN MARK MELDRIM, ERIC BLOMILEY,
EVERETT ALLEN MCTEER, and MATTHEW J. KING
Appeal2017-009866
Application 14/688,387
Technology Center 2800
Before ADRIENE LEPIANE HANLON, TERRY J. OWENS, and
MERRELL C. CASHION, JR., Administrative Patent Judges.
CASHION, Administrative Patent Judge.
DECISION ON APPEAL
STATEMENT OF THE CASE
This is an appeal under 35 U.S.C. § 134 from a final rejection of
claims 1-32. We have jurisdiction under 35 U.S.C. § 6.
We reverse.
Appeal2017-009866
Application 14/688,387
The invention is principally directed to a gate stack including a
tungsten silicide (WSix) material and a tungsten silicon nitride (WSiN)
material over the WSix material, where the WSiN material functions as both
a stress stabilization layer and a crack propagation barrier to limit crack
formation and propagation. Spec. ,r,r 14--15 and Figures 1 (A, B}-2. This
hybrid WSix/WSiN stack structure may mitigate possible cracking of the
WSix material that may affect gate functional reliability. Id. ,r,r 1, 15. Claim
1 is illustrative of the subject matter on appeal and is reproduced below:
1. A gate stack, comprising:
a gate horizontally between shallow trench isolations
(STis) and directly contacting the STis, a height of the gate
being different from a height of the STis;
a tungsten silicide (WSix) material on a top surface of the
gate and top surfaces of the STis; and
a tungsten silicon nitride (WSiN) material on a top
surface of the WSix material.
Appellant1 requests review of the following rejections from the
Examiner's Final Action (see generally Appeal Brief):
I. Claims 1, 2, 4--8, 12-14, 18, and 27-32 rejected under AIA 35
U.S.C. § 103 as unpatentable over Ramkumar (US 6,773,975 Bl, issued
August 10, 2004) and Hayashi (US 6,774,442 B2, issued August 10, 2004).
1 Appellant is the Applicant Micron Technology, Inc., also identified as the
real party in interest. App. Br. 2.
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Application 14/688,387
II. Claims 9, 11, 15-17, 19, 21-23, 25, and 26 rejected under AIA
35 U.S.C. §103 as unpatentable over Ramkumar, Hayashi, and Kizilyalli
(US 6,339,246 Bl, issued January 15, 2002).
III. Claim 3 rejected under AIA 35 U.S.C. § 103 as unpatentable
over Ramkumar, Hayashi, and Tseng (US 2002/0072209 Al, published June
13, 2002).
IV. Claim IO rejected under AIA 35 U.S.C. §103 as unpatentable
over Ramkumar, Hayashi, Kizilyalli, and Tseng.
V. Claim 20 rejected under AIA 35 U.S.C. § 103 as unpatentable
over Ramkumar, Hayashi, and Capellani (US 2001/0046765 Al, published
November 29, 2001).
VI. Claim 24 rejected under AIA 35 U.S.C. § 103 as unpatentable
over Ramkumar, Hayashi, Kizilyalli, and Capellani.
Claim 12
OPINION
Prior Art Rejections
After review of the respective positions provided by Appellant and the
Examiner, we reverse the Examiner's prior art rejections of claims 1-32
under 35 U.S.C. § I03(a) for the reasons presented by the Appellant and add
the following for emphasis.
The Examiner finds Ramkumar discloses a gate stack between STis
having a tungsten containing material on a top surface of the gate and top
2 Independent claims 1, 9, 12, and 21 are either directed to a gate stack or a
method of making a gate stack where the gate stack includes a tungsten
silicide (WSix) material and a tungsten silicon nitride (WSiN) material over
the WSix material. We also note that tungsten falls within the scope of
metals of independent claim 2 7.
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Appeal2017-009866
Application 14/688,387
surfaces of the STis but does not teach the tungsten containing material is
tungsten silicide (WSix) material and additionally a tungsten silicon nitride
(WSiN) material on a top surface of the WSix material. Final Act. 3;
Ramkumar Figures l(q), 2(a), 2(b), col. 3, 11. 62---63, col. 4, 11. 38-56. As
noted in the Answer, Ramkumar teaches the tungsten material to be tungsten
nitride and tungsten. Ans. 4; see Ramkumar col. 3, 11. 62---65. The Examiner
finds Hayashi teaches a gate stack comprising a tungsten silicide material
and additionally a tungsten silicon nitride (WSiN) material on top of the
WSix. Final Act. 3; Hayashi Abstract. Hayashi teaches that the
WSix/WSiN tungsten material structure in a gate electrode prevents
formation of a silicide layer at the interface between metal and conductive
silicon and also exhibits low resistance property and ohmic property.
Hayashi col. 5, 1. 65---col. 6, 1. 6. The Examiner determines that it would
have been obvious to one having ordinary skill in the art to have modified
Ramkumar's gate stack/ST! structure by replacing Ramkumar's tungsten
nitride (WN) with Hayashi's hybrid WSix/WSiN structure for the reasons
taught by Hayashi. Final Act. 3--4; Ans. 5; Hayashi col. 1, 11. 22-29, col. 2, 1.
44---col. 3, 1. 25.
Appellant argues that replacing Ramkumar's stack ofWN (130) and
W (131) with Hayashi's WSix and WSiN structure would be expected to
render Ramkumar inoperative for its ordinary function. App. Br. 10.
Appellant contends that Ramkumar uses the barrier layer WN 130 in one
embodiment to prevent cross-diffusion of dopants from one gate polysilicon
layer bounded by one trench structure to a gate polysilicon layer bounded by
another trench structure. App. Br. 10; Ramkumar col. 3, 1. 62- col. 4, 1. 5.
According to Appellant, replacing Ramkumar' s WN/W stack with Hayashi' s
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Appeal2017-009866
Application 14/688,387
WSi/WSiN stack would not permit the silicide WSi film to function as a
barrier layer preventing the undesired cross-diffusion disclosed by
Ramkumar because Hayashi teaches the silicide layer as relaxing the high
resistance property of the barrier film. App. Br. 1 O; Hayashi col. 6, 11. 26-
30. That is, Appellant argues that there is no reason to modify Ramkumar,
as proposed by the Examiner, in light of Hayashi's teachings.
We agree. The Examiner acknowledges Hayashi' s disclosure that the
silicide layer suffers from cross-diffusion of dopants. Ans. 8; see Hayashi
col. 10, 11. 17-37. Given this acknowledgment and the fact that Ramkumar
discloses using the WN layer as a barrier to prevent cross-diffusion of
dopants (App. Br. 10; Ramkumar col. 3, 1. 62---col. 4, 1. 5), the Examiner has
not provided an adequate technical explanation of why one skilled in the art
would have expected Hayashi's silicide layer to be suitable for Ramkumar's
gate structure. Therefore, the Examiner's articulated reason for combining
the references lacks rational underpinning. While the Examiner asserts that
Hayashi's solution of discontinuous islands of silicide to control the
diffusion would not render Ramkumar's gate inoperative (Ans. 8; see
Hayashi col. 9, 11. 63-67; col. 10, 1. 62---col. 11, 1. 4), this assertion is
speculatory in nature and also does not explain why one skilled in the art
would have expected Hayashi's silicide layer to be suitable for Ramkumar's
gate structure.
Accordingly, we will not sustain the Examiner's prior art rejections of
claims 1-32 under 35 U.S.C. § 103(a) for the reasons presented by Appellant
and given above.
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Appeal2017-009866
Application 14/688,387
DECISION
The Examiner's prior art rejections of claims 1-32 under 35 U.S.C. §
103(a) are reversed.
REVERSED
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