Appeal No. 1998-1578
Application No. 08/543,827
titanium is incorporated into the sputtered film.
Also, the bombardment of the plasma onto the target
can generate chemical reactions. The plasma can
strip the nitrogen and titanium atoms from one
another with a TiN molecule. Anytime sputtering is
used to deposit the TiN barrier layer, both TiN and
titanium will be incorporated into the sputtered
film. Within the sputtered TiN film, there will be
titanium-rich areas. Compared to TiN, titanium is
more reactive with the substrate and etchants. The
titanium is more likely to form unwanted compounds
(such as titanium silicide, TiAl , TiAlSi, etc.) or
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to be etched away more readily than the TiN.
[Underlining added; col. 1, l. 54 to col. 2, l. 29.]
Further, Ho teaches that when a metal is sputtered on top
of
TiN during the same evacuation cycle, the integrity of the
barrier layer is “unacceptable,” causing “spike formation or
metal diffusion into the substrate.” (Column 2, lines 30-41.)
To avoid these problems, Ho describes an “atmospheric
furnace” process in which a sputtered TiN barrier layer is
annealed prior to subsequent metal deposition. (Column 3,
lines 52-68.) Specifically, this “atmospheric furnace”
process applies to “any device where a TiN barrier will be
used between a layer or layers of metal and underlying
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