Ex parte Baum et al.

Board of Patent Appeals and Interferences

Aug 25, 1999

08168569 (B.P.A.I. Aug. 25, 1999)

Application for patent filed December 16, 1993.1
1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered
today (1) was not written for publication in a law
journal and (2) is not binding precedent of the
Board.
Paper No. 12
UNITED STATES PATENT AND TRADEMARK OFFICE
________________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
________________
Ex parte THOMAS H. BAUM, PAUL B. COMITA
and FRANKLIN M. SCHELLENBERG
________________
Appeal No. 96-0294
Application 08/168,5691
________________
ON BRIEF
________________
Before METZ, GARRIS and OWENS, Administrative Patent Judges.
METZ, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134 from the
examiner's refusal to allow claims 1 through 9, all the claims
in this application.
Appeal No. 96-0294
Application No. 08/168,569
2
THE INVENTION
The appealed subject matter is directed to a method for
repairing a defect in the light transmissive, non-printing
region of a phase-shifting mask. Phase-shifting masks are
useful in the production of integrated circuits. Appellants
describe phase-shifting masks as generally comprising "a
plurality of individual transmissive phase-shifting layers
disposed in a pattern on a transmissive substrate." (page 1,
lines 14 through 16 of the specification).
Claim 1 is believed to be adequately representative of
the appealed subject matter and is reproduced below for a more
facile understanding of the claimed subject matter.
1. A method for repairing a defect in the
transmissive nonprinting region of a phase-shifting
mask comprising the step of depositing an opaque
material on the defect from a gaseous precursor by
beam-induced deposition.
The references of record which are being relied on by the
examiner as evidence of obviousness are:
Kellogg et al. (Kellogg) 4,698,236 Oct.
Appeal No. 96-0294
Application No. 08/168,569
3
6, 1987
Drozdowicz et al. (Drozdowicz) 4,778,693 Oct. 18,
1988
Harriott et al. (Harriott) 5,273,849 Dec. 28,
1993
Claims 1 through 9 stand rejected under 35 U.S.C. § 103
as unpatentable from the disclosure of Drozdowicz. Claims 1
through 9 stand further rejected under 35 U.S.C. § 103 as
being unpatentable from the disclosure of Harriott considered
with Kellogg. Because we are of the opinion that the examiner
has failed to establish that the subject claimed by appellants
would have been prima facie obvious at the time appellants'
invention was made, we shall reverse the examiner's rejection
for reasons set forth below.
OPINION
We agree with the examiner's conclusion that the art on
which he has relied to reject the appealed claims establishes
that at the time appellants' invention was made it was well-
known in the art to repair defects in lithographic masks. We
also agree with the examiner that the art relied on shows that
such repair is effected by laying down opaque solid materials
from gaseous precursors on lithographic masks. However, in
each of the references relied on by the examiner, the mask
repaired included opaque patterns. The masks were designed to
Appeal No. 96-0294
Application No. 08/168,569
4
exclude light from reaching the substrate (photoresist)
beneath the mask and the defect was a transparency (hole) in
the opaque patterns. See for example column 1, lines 17
through 19 of Kellogg ("alteration of a precisely localized
site on a substrate such as a transparent defect site in a
photolithographic mask."); column 3, lines 11 through 14 of
Drozdowicz ("The metal film deposits produced by this method,
when extended over adjacent clear (missing chrome) defect
areas, make these clear areas opaque, thus effecting the
repair."); and column 6, line 11 of Harriott ("repairing a
transparent defect in said pattern").
Here, the claimed subject matter requires that the mask
being repaired be a particular type of mask, a phase-shifting
mask, which is not shown by any of the references on which the
examiner has relied and is designed to permit light through
the mask to be shifted for the purpose of causing coherent
destructive interference. The defect in appellants' mask is
not a transparency (hole) in an opaque pattern.
We have not overlooked pages 5 and 6 of the Examiner's
Answer wherein the examiner opines:
it is not all that surprising that a relatively
small area of the transmissive region which is
rendered opaque does not adversely affect
Appeal No. 96-0294
Application No. 08/168,569
5
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.
Appeal No. 96-0294
Application No. 08/168,569
6
Accordingly, we shall reverse the examiner's rejection of
claims 1 through 9.
SUMMARY
The decision of the examiner is reversed.
REVERSED
ANDREW H. METZ )
Administrative Patent Judge )
)
)
)
)
BRADLEY R. GARRIS )BOARD OF
PATENT
Administrative Patent Judge ) APPEALS AND
)INTERFERENCES
)
)
)
TERRY J. OWENS )
Administrative Patent Judge )
AHM/gjh
Robert B. Martin
IBM Corporation
Dept. K02/802
650 Harry Road
Appeal No. 96-0294
Application No. 08/168,569
7
San Jose, CA 95120-6099