Ex parte WUU et al.

Board of Patent Appeals and Interferences

Oct 16, 2000

08630111 (B.P.A.I. Oct. 16, 2000)

The opinion in support of the decision being entered today was not written
for publication and is not binding precedent of the Board.
Paper No. 15
UNITED STATES PATENT AND TRADEMARK OFFICE
____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________
Ex parte SHOU-GWO WUU, MONG-SONG LIANG,
CHUNG-HUI SU, and CHEN-JANG WANG
____________
Appeal No. 1998-2887
Application No. 08/630,111
____________
ON BRIEF
____________
Before HAIRSTON, FLEMING, and BLANKENSHIP, Administrative
Patent Judges.
HAIRSTON, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal from the final rejection of claims
14 through 18.
The disclosed invention relates to a plug structure for
stacked contacts and metal contacts on a Static Random Access
Memory (SRAM) cell having thin film transistors.
Appeal No. 1998-2887
Application No. 08/630,111
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Claim 14 is the only independent claim on appeal, and it
reads as follows:
14. A novel plug structure for stacked contacts and metal
contacts on a Static Random Access Memory (SRAM) cell having
thin film transistors, on a partially completed semiconductor
substrate having device areas and field oxide areas and
further having field effect transistors (FETs) and word lines
formed from a first polysilicon layer and Vss ground plate
formed from a second polysilicon layer comprising of:
a first insulating layer on said substrate;
a patterned N doped third polysilicon layer on said first+
insulating layer forming first and second gate electrodes for
a first and second thin film transistor;
a second insulating layer forming a gate oxide on said
first and second gate electrodes;
a patterned N type amorphous silicon layer on said second
insulating layer with P doped areas over said first and+
second gate electrodes and with undoped P type areas for+
channel regions on said first and second thin film
transistors; and
said channel regions contiguous with said P-doped areas
and said P-doped areas extending over areas of the other said
gate electrode and on said second insulating layer;
said patterned N type amorphous silicon layer having
openings in said P-doped areas of said amorphous polysilicon
layer over said other gate electrode area and to said second
insulating layer;
a third insulating layer over said patterned N type
amorphous silicon layer having openings aligned over and
larger in size than said openings in said P doped portions of
said amorphous silicon layer,
Appeal No. 1998-2887
Application No. 08/630,111
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said third insulating layer openings extending to said
amorphous layer and further to said third polysilicon layer,
and said third insulating layer having other openings to
device areas elsewhere on said substrate;
conducting plugs in said third insulating layer openings
and thereby having low resistance ohmic stacked contacts for
said thin film transistors and other conducting plugs in said
other openings elsewhere to device areas on said substrate;
a patterned first metal layer forming electrical
interconnections, and thereby having said novel plug structure
on said SRAM cell.
The references relied on by the examiner are:
Krishna 4,639,274 Jan. 27,
1987
Kobayashi et al. (Koyabashi) 0 603 622 Jun. 29,
1994
(European Patent Application)
Claims 14 through 18 stand rejected under 35 U.S.C. § 103
as being unpatentable over the admitted prior art Figures 1
through 5 in view of Kobayashi and Krishna.
Reference is made to the final rejection, the brief and
the answer for the respective positions of the appellants and
the examiner.
OPINION
The obviousness rejection of claims 14 through 18 is
reversed.
Appeal No. 1998-2887
Application No. 08/630,111
4
The examiner acknowledges (Final rejection, page 3) that
“the admitted Prior Art Figures 1-5 fail to teach an amorphous
silicon layer and a gate conducting plug.” According to the
examiner (Answer, page 5):
Kobayashi et al was used to show that the level of
ordinary skill in the art includes knowledge of
forming a contact through an aperture in an
amorphous silicon layer (16). . . . Krishna was
used to show that the level of ordinary skill in the
art includes knowledge of forming a contact to a
polysilicon layer (20) through an aperture in an
insulating layer. Hence, the two missing features
in Applicants’ Admitted Prior Art Figures are
provided by the two references.
The examiner concludes (Answer, page 5) that “it would
have been obvious to use a contact to a polysilicon layer
through an opening in an insulating layer and an amorphous
silicon layer in view of the teachings of Kobayashi et al and
Krishna.”
Appellants argue (Brief, pages 7 and 8) that the applied
references do not teach applicants’ plug structure, namely,
the larger contact opening aligned over the other opening so
that “[w]hen the metal plug 24 (Fig. 8) is formed in the
opening 6 (and 4), the exposed P amorphous layer 18 in+
opening 6 and the exposed N polysilicon layer 14 in opening 4+
Appeal No. 1998-2887
Application No. 08/630,111
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electrically short the P layer 18 to the N layer 14 to form a+ +
low-resistance ohmic contact (Fig. 9).”
Although element 21 in Kobayashi may appear to be a
“contact through an aperture in an amorphous silicon layer
(16)” (Answer, page 5), it is really a silicon nitride
passivation layer (column 8, lines 4 through 19). We agree
with the examiner (Answer, page 5) that Krishna forms “a
contact to a polysilicon layer (20) through an aperture in an
insulating layer.” The polysilicon layer 20 in Krishna is,
however, one of two polysilicon plates 16 and 20 that are
separated from each other by an oxide layer 18 to form a
capacitor 12. The metal contact 22 is a contact for the
capacitor 12.
Based upon the foregoing, we agree with appellants that
neither Krishna nor Kobayashi teaches or would have suggested
the claimed low resistance ohmic stacked contact located in
the two differently sized openings (i.e., the stacked contact
24 extending through the smaller opening 4 in the amorphous
silicon layer 18 to make contact with the third polysilicon
layer 14).
Appeal No. 1998-2887
Application No. 08/630,111
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DECISION
The decision of the examiner rejecting claims 14 through
18 under 35 U.S.C. § 103 is reversed.
REVERSED
KENNETH W. HAIRSTON )
Administrative Patent Judge )
)
)
)
) BOARD OF PATENT
MICHAEL R. FLEMING ) APPEALS
Administrative Patent Judge ) AND
) INTERFERENCES
Appeal No. 1998-2887
Application No. 08/630,111
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)
)
)
HOWARD B. BLANKENSHIP )
Administrative Patent Judge )
lp
Appeal No. 1998-2887
Application No. 08/630,111
8
GEORGE O. SAILE
20 MCINTOSH DRIVE
POUGHKEEPSIE NY 12603
Leticia
Appeal No. 1998-2887
Application No. 08/630,111
APJ HAIRSTON
APJ FLEMING
APJ BLANKENSHIP
DECISION: REVERSED
Send Reference(s): Yes No
or Translation (s)
Panel Change: Yes No
Index Sheet-2901 Rejection(s):
Prepared: June 8, 2001
Draft Final
3 MEM. CONF. Y N
OB/HD GAU
PALM / ACTS 2 / BOOK
DISK (FOIA) / REPORT