Appeal No. 95-5148 Page 4
Application 08/121,794
DISCUSSION
We are unpersuaded, based on the record before us, that
the combination of the admitted prior art and Yamagishi would
have rendered the subject matter of the claims obvious.
Yamagishi's suggestion to use a WN/TaN laminate is an
empirical solution to a specific problem. The examiner has
not convincingly explained why a person having ordinary skill
in the art would have been motivated to try a single nitride,
e.g., WN (not TaN or WN/TaN), as a barrier layer in the
admitted prior art. The analysis the examiner presented
appears to be impermissible hindsight.
NEW GROUND OF REJECTION
Although the examiner never makes a rejection based on
Wittmer, the combination of Wittmer and the admitted prior art
strongly suggests the claimed invention. Wittmer teaches that
at high temperatures the metallic layer (in his case, aluminum
(Al)) decomposes, and forms compounds with, silicides.
(p. 276.) For this reason, he reports that "transition metal
silicides cannot be used as barrier material." (p. 279,
emphasis added.) In contrast, Wittmer teaches that "[t]he
performance of [another material] is only surpassed by
refractory metal nitride barriers, such as TiN and ZrN."
(Id., emphasis added.) TiN (titanium nitride) is in
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