Appeal No. 96-0294
Application No. 08/168,569
destructive interference which occurs at the
boundary between phase shifting and transparent
regions.
We understand the examiner's explanation, found under the
heading "Response to Argument", to mean that so long as the
defect is small, rendering said small defective region opaque
would not have been expected to adversely effect the phase-
shifting properties of the remainder of the region of the mask
which is not defective. Neither have we overlooked the fact
that appellants did not respond to the above-noted reasoning.
Nevertheless, we still cannot find in this record any
suggestion to use the well-known prior art methods for
repairing transmissive non-printing regions of a phase-
shifting mask as claimed in appellants' method.
There is simply no evidence in the record which
establishes that a phase-shifting mask having an opaque
material-covered defect would have been expected to retain its
phase-shifting properties. Further, absent any suggestion in
the prior art to apply to the particular substrate claimed the
technique shown in the patents on which the examiner has
relied as evidence of obviousness, we cannot agree with the
examiner's conclusion that the claimed subject matter would
have been obvious at the time appellants' invention was made.
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