Ex parte Lee

Board of Patent Appeals and Interferences

Apr 21, 2000

08430467 (B.P.A.I. Apr. 21, 2000)

1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered today
(1) was not written for publication in a law journal and
(2) is not binding precedent of the Board.
Paper No. 16
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte CHING-YING LEE
_____________
Appeal No. 1997-3489
Application 08/430,467
______________
ON BRIEF
_______________
Before HAIRSTON, SMITH, JERRY and LALL, Administrative Patent
Judges.
HAIRSTON, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal from the final rejection of claims
1 through 15.
The disclosed invention relates to a method for
inspecting a silicon substrate of a semiconductor device for
aluminum spiking.
Appeal No. 1997-3489
Application No. 08/430,467
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Claim 1 is illustrative of the claimed invention, and it
reads as follows:
1. A method for inspecting a silicon substrate for
aluminum spiking comprising:
providing a silicon substrate having an aluminum
containing metallization layer formed on a
surface of the silicon substrate;
etching the aluminum containing metallization
layer completely from the surface of the silicon
substrate;
etching the surface of the silicon substrate
through contacting the surface of the silicon
substrate with
a buffered aqueous etchant solution comprising
about 1.5 to about 2 parts by volume 10:1 buffered
oxide etchant and about 1 part by volume 98%
acetic acid;
the etching of the surface of the silicon substrate
being undertaken until the surface of the silicon
substrate is gray in color; and
inspecting the surface of the silicon
substrate.
The references relied on by the examiner are:
Payne et al. (Payne) 4,120,744 Oct. 17,
1978
Lowrey et al (Lowrey) 4,999,160 Mar. 12,
1991
Wolf et al. (Wolf), “Silicon Processing for the VLSI Era,
Volume 1: Process Technology,” Lattice Press, 1986, pages 532,
589 and 590 (hereinafter Wolf ‘86).
Appeal No. 1997-3489
Application No. 08/430,467
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Wolf, “Silicon Processing for the VLSI Era, Volume 2: Process
Integration,” Lattice Press, 1990, pages 101 and 102
(hereinafter Wolf ‘90).
Appeal No. 1997-3489
Application No. 08/430,467
We assume that the obviousness rejections of claims 2,1
3, 7, 8, 11 and 13 have been withdrawn because the rejections
set forth in the final rejection have not been repeated in the
answer, and the references to Wei and Hauck are not listed in
the answer.
5
Claims 1, 4 through 6, 9, 10, 12, 14 and 15 stand
rejected under 35 U.S.C. § 103 as being unpatentable over the
admitted prior art in view of the Wolf publications, Lowrey
and Payne.1
Reference is made to the briefs and the answer for the
respective positions of the appellant and the examiner.
OPINION
The obviousness rejection of claims 1, 4 through 6, 9,
10, 12, 14 and 15 is reversed.
We agree with the examiner (Answer, page 4) that Wolf ‘90
“teaches . . . forming a silicon dioxide layer with a contact
hole between the metallization and silicon,” but this teaching
is merely redundant to the well-known conventional device
described on pages 1 through 6 of appellant’s specification.
Stated differently, appellant is claiming a method of etching
the layers from an already constructed device to inspect for
aluminum spiking, and is not claiming the device.
Appeal No. 1997-3489
Application No. 08/430,467
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Although Lowrey also recognizes the problem of aluminum
spiking, and the use of a barrier layer to prevent aluminum
migration (column 1, lines 50 through 55), Lowrey is only
concerned with the use of an acid bath etch of a device to
inspect for silicon precipitate from an aluminum-silicon alloy
used in the device (column 1, lines 31 through 49; column 2,
lines 56 through 68).
We agree with the examiner (Answer, page 5) that Payne
uses hydrofluoric acid (HF) and acetic acid to selectively
etch both silicon dioxide and silicon (column 3, line 67
through column 4, line 13). We likewise agree with the
examiner (Answer, page 5) that Wolf ‘86 discloses (page 532)
wet etching of silicon dioxide with HF at 25 degrees
centigrade.
Appellant argues (Brief, page 10) that there is no
motivation to combine the references, and that any combination
of the teachings of the references would lack a teaching that
“an etchant composition comprising a buffered oxide etchant
(ie: ammonium fluoride and hydrofluoric acid) and acetic acid
will etch a silicon substrate, in particular there is no
teaching that the silicon substrate is etched to provide a
Appeal No. 1997-3489
Application No. 08/430,467
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surface having adequate contrast to view . . . the protruding
ends of aluminum spikes from an aluminum containing
metallization layer which has spiked into the silicon
substrate.”
Notwithstanding our agreement with the examiner
concerning the individual teachings of the references, we,
nevertheless, agree with appellant’s arguments concerning the
lack of motivation to combine the teachings of the references,
and the lack of a teaching in the references to etch the
surface of the silicon substrate until the surface turns gray
in color to thereby observe aluminum spiking. There is no
evidence in the record to support the examiner’s conclusion
(Answer, page 6) that “[u]pon removal of the silicon dioxide
layer it would have been inherent that the color of the
substrate turned gray when the oxide was removed since silicon
is gray.”
In summary, the obviousness rejection of claims 1, 4
through 6, 9, 10, 12, 14 and 15 is reversed because the
examiner has not demonstrated the prima facie obviousness of
the claimed invention.
Appeal No. 1997-3489
Application No. 08/430,467
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DECISION
The decision of the examiner rejecting claims 1, 4
through 6, 9, 10, 12, 14 and 15 under 35 U.S.C. § 103 is
reversed.
REVERSED
)
KENNETH W. HAIRSTON )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
JERRY SMITH )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
PARSHOTAM S. LALL )
Administrative Patent Judge )
KWH:hh
Appeal No. 1997-3489
Application No. 08/430,467
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GEORGE O. SAILE
20 MCINTOSH DRIVE
POUGHKEEPSIE, NY 12603