Appeal No. 1997-3635
Application No. 08/498,357
further discloses thermal annealing to convert the composite
metal and silicon layer to low resistivity silicide.
Additionally, Wong teaches in col. 6, lines 14 through 16
(patent claim 2), that the thickness of amorphous silicon is
such that it is fully consumed in the reaction with the
refractory metal. Therefore, Wong’s silicon layer has a
thickness which is small enough so that it does not
substantially increase the contact resistance of the metal
layer. We further point out the teachings of Wolf to 3
buttress our findings with regard to Wong’s single pump down
cycle. Wolf on page 164 discloses a sequential sputter-
deposition of refractory metal and amorphous silicon layers in
one pump down, identical to Wong’s process, to minimize the
formation of an oxide on the metal layer. Wolf also limits
the thickness of silicon layer such that the silicon reacts
fully with the underlying metal layer. Therefore, Wolf
supports our finding that Wong’s single pump down sputtering
forms the silicon layer without exposing the metal layer to
oxygen, as recited in Appellant’s claim 1. Additionally, we
3Wolf, Stanley, “Silicon Processing for the VLSI Era,
Volume 2: Process Integration,” 164-165 (Sunset Beach, CA,
Lattice Press, 1990).
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