Appeal No. 1999-2683
Application 08/754,564
must teach the invention. Since there is no evidence that one
of ordinary skill in the art was aware that the layer 24
should function as an etch stop layer, it cannot be said that
the prior art enables those of ordinary skill in the art to
make a semiconductor device with an etch stop layer.
Second, we find no motivation for one of ordinary skill
in the art to modify Tsu to have a silicon nitride etch stop
layer as taught in Kalnitsky. Lack of motivation may preclude
a prima facie case of obviousness. The Examiner modifies the
material of layer 24 based on an etch stop property that is
not known, but that the Examiner considers inherent. This
modification based on an unknown, but inherent property
(assuming it were so) is not proper. See In re Spormann,
363 F.2d 444, 448, 150 USPQ 449, 452 (CCPA 1966) ("That which
may be inherent is not necessarily known. Obviousness cannot
be predicated on what is unknown."). If one skilled in the
art did not recognize that the layer 24 in Tsu should be an
etch stop layer, he or she would not have been motivated to
substitute a real etch stop layer, such as the silicon nitride
layer of Kalnitsky. As to the Examiner's finding that one of
ordinary skill in the art would have been motivated to arrive
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