Appeal 2007-1312
Application 10/997,715
which are defined by upper elements 28 and 38. The gaps are defined by
more than just wiring 24.
Moreover, even if Liu were interpreted as completely filling the gaps
with the HDPCVD process, we completely agree with the Examiner that it
would have been a matter of obviousness for one of ordinary skill in the art
to use the HDPCVD process to only partially fill the gaps and use the
PECVD process to complete the deposition of the uppercladding layer. As
explained by the Examiner, Liu discloses that the PECVD process affords a
higher speed of deposition than is typical of HDPCVD processes. As a
result, one of ordinary skill in the art would have understood that a balance
can be effected between the benefits achieved by the slower HDPCVD
process and the faster PECVD process. Liu discloses that the HDPCVD
process deposits “a dielectric layer having superior density, moisture
resistance and planarization properties as compared to conventional CVD
dielectric layers” (sentence bridging col. 4-5), while also producing a void-
free gap filling. Liu also discloses that “[a]nother advantage of the use of
HDPCVD to deposit intermetal dielectrics is that it is generally not
necessary to perform subsequent high temperature densification steps to
densify the deposited dielectric material, which may sometimes be required
to densify oxide layers deposited using conventional CVD and other
techniques” (col. 6, ll. 5-10). Manifestly, it would have been obvious for
one of ordinary skill in the art to perform a cost-benefit analysis in
determining the amount of uppercladding layer to be deposited by the
6
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