Appeal No. 2005-0123
Application No. 10/114,759
particular, appellant argues (Brief, page 6) that Xu's reason for
forming the third sublayer with a top surface of pure titanium is
for promoting aluminum reflow into narrow plugs and is limited to
applications where aluminum is sputtered. Appellant asserts
(Brief, pages 6-7) that "the use of copper electroplating negates
the need for the pure titanium layer in the barrier deposition of
Xu because of the dependence between the aluminum sputtering and
the pure titanium layer." We agree with appellant that the
teachings of Xu and Simpson alone do not support a prima facie
case of obviousness.
Xu discloses (column 8, lines 21-23) that the third sublayer
of pure titanium "performs two functions. Its formation cleans
the sputter target for the next wafer, and its refractory-metal
surface promotes reflow in narrow apertures." Xu further
explains (column 13, lines 52-60) that the titanium provides
strong wetting at the interface with the aluminum, allowing the
aluminum to flow along the walls of the contact hole "at
reasonably low temperatures over reasonably short times." Thus,
"the metal [aluminum] layer 156 can be deposited by traditional
PVD processes" (column 14, lines 16-17). Accordingly, it is
clear from Xu that the top sublayer of pure titanium is
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