The invention and the meaning of "phase grating mask"
10. In our decision on preliminary motions, we made a
finding that "phase mask" or, "phase grating mask ,5 as recited in
the count, is a transparent mask having varying thickness across
the surface of the mask (Paper 208 at 17).
11. Specifically as we discussed in that decision,
Shirasakil shows in Fig. 6 a phase grating mask as shown below.
Fig. 6
V
tj
140,57ý-f 4-- 7-14 '-14
24
12. The description of Shirasaki Fig. 6 is as follows:
The illustrated mask is in the form of plate 11
which consists of a material transparent to the
exposure radiations such as quartz glass, the
plate having selectively formed on a major surface
thereof rectangular parallelopiped-shaped
projections 24 which also consist of a material
transparent to the exposure radiations such as
silicon dioxide (S'02) (Shirasaki, column 9,
lines 59-65).
5 We use the term "phase mask" and "phase grating mask"
interchangeably, as do the parties in their respective briefs.
6 Shirasaki et al. (Shirasaki), U.S. Patent 4,806,422, granted February 21,
1989, based on application 06/841,801, filed March 20, 1986.
4
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