Appeal No. 1998-0723
Application 08/570,851
of using a computer aided design (CAD) system for generating
phase shifted mask designs for very large scale integrated
(VLSI) chips. Spence is cited for teaching the use of a
design checker to determine design conflicts of critical
features of the circuit design. The examiner states that the
design checker is the “key of the invention.” The examiner
concludes that “it would have been obvious . . . to recognize
that, the design conflicts are characterized as those critical
features that either have a phase region (180 degrees phase)
on both sides or have no adjacent phase region at all”
[Answer, pages 5-6].
Appellant argues that even though Liebmann and Spence
teach the requirement to verify that every critical dimension
feature has a 180 degree phase shift on one side and not on
the other, neither reference teaches how to achieve this
verification. More particularly, appellant argues that the
specific steps for performing design checking in claims 1 and
5 are not taught or suggested by the broad design checker of
Spence or recognition of the problem in Liebmann [Brief, pages
9-14].
6
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