Appeal No. 1997-3489
Application No. 08/430,467
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
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