Appeal No. 1999-2347
Application 08/892,560
conductor layers, each over a metal plug to a lower metal
conductor. We conclude that it would have been obvious to
deposit the metal pad in Appellants' claim 21 over a metal plug
based on general knowledge in the art and on Wolf.
Another difference is that Woo's claim 1 recites that the
via created by the two etching steps is filled with a metal to
form a filled opening, whereas Appellants' claim 21 does not
recite a sixth step of filling the via (although it is manifestly
intended to be filled with a metal plug). We find that it was
well known in the semiconductor art that vias were formed to be
filled with a metal plug. Also, Fig. 4-59(d) of Wolf shows the
via to a first metal layer filled with a metal plug. We conclude
that it would have been obvious to fill the via of Appellants'
claim 21 with a metal plug based on general knowledge in the art
and on Wolf.
Another difference is that Woo's claim 1 recites repeating
the first five steps a second time, whereas Appellants' claim 21
does not. We find that it was well known in the semiconductor
art to repeat the same process steps used to connect a conductive
layer with an underlying conductive layer to provide a second (or
higher level) of interconnections. Wolf shows the use of the
identical structure for a two level interconnect structure. We
conclude that it would have been obvious to repeat the five steps
of Appellants' claim 21 a second time after filling the via with
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