Appeal No. 95-1487
Application 07/813,387
for forming a phase shift mask and pattern. The invention
basically centers around use of MgO or a compound formed from MgO
and Al O as an etching stop layer for phase shift masks (main
2 3
brief, page 2). Claim 1 is illustrative of the subject matter on
appeal and is reproduced below:
1. An optical exposure mask for patterning an optical beam,
comprising:
an etching stop layer of a material containing MgO or a
compound formed from MgO and A1 O , said etching stop layer
2 3
having upper and lower major surfaces and said material being
substantially transparent to the optical beam used for the
exposure;
a transparent pattern of a material provided on one of said
upper and lower major surfaces of said etching stop layer, said
transparent pattern passing the optical beam freely; and
an opaque pattern provided on one of said upper and lower
major surfaces of said etching stop layer for patterning the
optical beam, said opaque pattern being defined be [sic, by] an
edge,
said etching stop layer having an etching rate substantially
smaller than an etching rate of the material that forms the
transparent pattern for any of dry and wet etching processes, and
said transparent pattern being provided along said edge of
said opaque pattern and having a thickness set to cancel a
diffraction of the optical beam at said edge of said opaque
pattern.
The references relied upon by the examiner as evidence of
obviousness are as follows:
Nakagawa et al. (Nakagawa) 61-278179 Dec. 9, 1986
(Japanese Kokai)
Kawabata et al. (Kawabata) 0 395 425 Oct. 31, 1990
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