Texas Instruments Incorporated

Patent Trials and Appeals Board

May 7, 2021

2020003827 (P.T.A.B. May. 7, 2021)

UNITED STATES PATENT AND TRADEMARK OFFICE
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
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
15/348,459 11/10/2016 BINGHUA HU TI-77213 1051
23494 7590 05/07/2021
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, MS 3999
DALLAS, TX 75265
EXAMINER
BRASFIELD, QUINTON A
ART UNIT PAPER NUMBER
2814
NOTIFICATION DATE DELIVERY MODE
05/07/2021 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@ti.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________

Ex parte BINGHUA HU, ABBAS ALI, SOPA CHEVACHAROENKUL,
and JARVIS BENJAMIN JACOBS1
____________

Appeal 2020-003827
Application 15/348,459
Technology Center 2800
____________

Before N. WHITNEY WILSON, CHRISTOPHER C. KENNEDY, and
SHELDON M. MCGEE, Administrative Patent Judges.

KENNEDY, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134(a) from the Examiner’s
decision rejecting claims 1–10 and 18–27. We have jurisdiction under
35 U.S.C. § 6(b). We REVERSE.
BACKGROUND
The subject matter on appeal relates to methods for forming trench
capacitors in semiconductors. E.g., Spec. ¶ 2; Claim 1. Claim 1 is
reproduced below from page 7 (Claims Appendix) of the Appeal Brief:

1 We use the word “Appellant” to refer to “applicant” as defined in
37 C.F.R. § 1.42. The Appellant identifies the real party in interest as Texas
Instruments Incorporated. Appeal Br. 3.
Appeal 2020-003827
Application 15/348,459

2
1. A method for forming trench capacitors in a semiconductor
surface of an integrated circuit (IC), comprising:
forming a silicon nitride layer over a first region of said
semiconductor surface that has a doping of a first type and over
a second region having a doping of a second type;
forming a patterned photoresist layer directly on said silicon
nitride layer;
etching within said first region to form a plurality of deep
trenches (DTs);
forming a liner oxide that lines said DTs;
after forming the plurality of deep trenches and forming the liner
oxide, wet etching said silicon nitride layer, wherein after said
wet etching, an opening through said silicon nitride layer is at
least as large in area as an area of an opening in said
semiconductor surface of said DT below said silicon nitride
layer;
removing said liner oxide;
forming at least one dielectric layer on a surface of said DTs;
depositing a top plate material layer on said dielectric layer to fill
said DTs, and
removing said top plate material layer beyond said DTs to form
a top plate.
REJECTIONS ON APPEAL
The claims stand rejected under 35 U.S.C. § 103 as follows:
1. Claims 1–9 and 18–26 as unpatentable over Cheng
(US 2006/0202249 A1, published Sept. 14, 2006), Rennie
(US 2006/0084222 A1, published Apr. 20, 2006), and Ho (US 6,693,006 B2,
issued Feb. 17, 2004). Final Act. 2.
Appeal 2020-003827
Application 15/348,459

3
2. Claims 3, 4, 10, 20, 21, and 27 as unpatentable over Cheng,
Rennie, Ho, and Claeys (US 2013/0069198 A1, published Mar. 21, 2013).
Final Act. 10.
ANALYSIS
Claims 1 and 18 are the only independent claims at issue in this
appeal. Both of those claims recite, inter alia, a step of “wet etching” the
silicon nitride layer after the deep trenches are formed in order to increase
the size of the openings in the silicon nitride layer to be at least as “large”
(claim 1) or “wide” (claim 18) as the deep trench. See Appeal Br. 7, 9
(Claims Appendix).
The Examiner finds that neither Cheng nor Rennie teaches a wet
etching step that corresponds to the wet etching step of claims 1 and 18.
Final Act. 3, 4, 7, 8. The Examiner finds, however, that Ho teaches a wet
etching step in which wet etching is used to increase the size of an opening
in a surface layer of silicon nitride so that the opening is at least as
large/wide as the trench. Id. at 4, 8. The Examiner determines that it would
have been obvious to incorporate Ho’s wet etching step into the method of
Cheng as modified by Rennie “to form a deeper recess within the substrate”
and to achieve an opening in the silicon nitride layer that is at least as
large/wide as the deep trench below the silicon nitride layer. Id. at 5, 8, 9.
The Appellant argues that Ho’s wet etching step is specific to features
of Ho (i.e., additional silicon nitride layers 50 and 80, see Ho. Fig. 1K
through 1N, 2:40–44) and that, because neither Cheng nor Rennie possesses
the unique features of Ho that Ho’s wet etching step is used to remove, there
is no reason to add Ho’s wet etching step to the method of Cheng as
modified by Rennie. Appeal Br. 4–5.
Appeal 2020-003827
Application 15/348,459

4
“[A] patent composed of several elements is not proved obvious
merely by demonstrating that each of its elements was, independently,
known in the prior art. . . . [I]t can be important to identify a reason that
would have prompted a person of ordinary skill in the relevant field to
combine the elements in the way the claimed new invention does.” KSR
Int’l Co. v. Teleflex Inc., 550 U.S. 398, 418 (2007).
In this case, the Examiner has not adequately established a reason to
combine the references as proposed. As an initial matter, we observe that
the Examiner’s analysis does not appear to identify a reason or motivation
for making the proposed modification. See Final Act. 4–5. The Examiner’s
analysis appears to simply state the result that would be achieved if the
modification were made (i.e., wet etching to form an opening that is at least
as large/wide as the deep trench) without explaining why a person of
ordinary skill in the art would have made the modification. Id.; see also
Ans. 6.
Beyond that, and consistent with the Appellant’s argument, Ho’s wet
etching step is included in Ho’s method to remove specific features. See Ho
at 2:40–44 (describing wet etching to etch “second nitride layer 50 and the
third nitride layer 80”). Given that the Examiner does not find that Cheng
and Rennie include features corresponding to the features that Ho’s wet
etching step is intended to remove (i.e., “second nitride layer 50 and the
third nitride layer 80,” Ho at 2:40–44), the Examiner has not adequately
established why a person of ordinary skill in the art would have incorporated
Ho’s wet etching step into the method of Cheng as modified by Rennie. The
Examiner has not meaningfully addressed the Appellant’s argument. Nor
Appeal 2020-003827
Application 15/348,459

5
does the Examiner rely on any disclosures in Cheng or Rennie concerning
wet etching.
On this record, we reverse the Examiner’s rejection of claims 1
and 18. Because all other claims on appeal depend from claim 1 or from
claim 18, and the Examiner’s discussion of those claims does not remedy the
error identified above, we likewise reverse the Examiner’s rejections of
those claims.
CONCLUSION
In summary:
Claim(s)
Rejected
35
U.S.C. § Reference(s)/Basis Affirmed Reversed
1–9, 18–26 103 Cheng, Rennie, Ho 1–9, 18–26
3, 4, 10, 20,
21, 27 103
Cheng, Rennie,
Ho, Claeys
3, 4, 10, 20,
21, 27
Overall
Outcome 1–10, 18–27

REVERSED