Ex Parte LAI

Board of Patent Appeals and Interferences

Jul 29, 2008

10250228 (B.P.A.I. Jul. 29, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
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BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
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Ex parte JUN-CHENG LAI
____________

Appeal 2008-3545
Application 10/250,228
Technology Center 1700
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Decided: July 29, 2008
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Before EDWARD C. KIMLIN, TERRY J. OWENS, and
MICHAEL P. COLAIANNI, Administrative Patent Judges.

OWENS, Administrative Patent Judge.

DECISION ON APPEAL
The Appellant appeals from a rejection of claims 8-16, which are all
of the pending claims.
THE INVENTION
The Appellant claims a method for patterning a material layer using a
photomask. Claim 8 is illustrative:
Appeal 2008-3545
Application 10/250,228

8. A method of using a half-tone phase shift mask to form a strip
pattern having two thicker ends and a narrower mid section, comprising the
steps of:

providing a substrate;

forming a material layer over the substrate;

forming a photoresist layer on the material layer;

patterning the photoresist layer using the half-tone phase shift mask,
wherein the half-tone phase shift mask comprises:

a mask substrate;

two sheltering layer formed as first strips on the mask substrate
with a space therebetween;

a half-tone phase shift layer formed as a second strip and
disposed at least in the space between the first strips, wherein the
second strip is thinner than the first strips; and

patterning the material layer using the patterned photoresist
layer as an etching masks to form the strip.[ ]1

1 The Appellant’s Specification states:
In this invention, the half-tone phase shift layer and the sheltering
layer together form the non-exposed pattern area of the half-tone
phase shift mask and there is a 180° phase angle difference between
the half-tone phase shift layer and the sheltering layer. Hence, any
diffraction along the edge of the sheltering layer is canceled out and
the sheltering area is more solidly covered so that a higher
photolithographic resolution and contrast is obtained through the mask
[¶ 0035].
* * *
In addition, the half-tone phase shift layer and the sheltering layer are
formed on the surface of the same mask (a binary pattern layer) in this
invention. Without using a double exposure operation using two
2
Appeal 2008-3545
Application 10/250,228

THE REFERENCES
Tanaka (Tanaka ‘692) US 2002/0039692 A1 Apr. 4, 2002
Tanaka (Tanaka ‘050) US 2002/0177050 A1 Nov. 28, 2002

THE REJECTIONS
Claims 8-16 stand rejected under 35 U.S.C. § 103 over Tanaka ‘692
or Tanaka ‘050.
OPINION
We reverse the Examiner’s rejections. We need to address only the
sole independent claim, i.e., claim 8. That claim requires “two sheltering
layers formed as first strips on the mask substrate with a space
therebetween”, and “a half-tone phase shift layer formed as a second strip
and disposed at least in the space between the first strips, wherein the second
strip is thinner than the first strips”.
Tanaka ‘692 discloses a photomask having a half-tone strip (12)
between two hole regions (11a, 11b) and, surrounding the half-tone strip and
the hole regions, a light blocking film (103) (¶ 0055; figs. 2(A), 2(B)).
Tanaka ‘050 discloses a phase shift mask (40) having two translucent
regions (41a, 41b), a light shield region (44) surrounding each translucent
region, a half-tone strip (42) between the light shield regions, an auxiliary
pattern (43) surrounding the light shield regions and the half-tone strip, and a
light shield region (44) surrounding the auxiliary pattern (¶¶ 0152, 0163;
figs. 9A, 9B, 10A, 10B).
separate masks, the errors due to a mask misalignment is prevented
and the cost for producing the mask is reduced [¶ 0040].
3
Appeal 2008-3545
Application 10/250,228

The Examiner argues that “Tanaka ‘692 Figs. 1 and 2A show this
geometric pattern arrangement of a strip pattern having two thicker ends and
a narrower mid section” (Ans. 7).
The Examiner has not pointed out where Tanaka ‘692 discloses a
sheltering layer in the form of a strip. In the Tanaka ‘692 figures 1 and 2A,
at each end of the half-tone strip there is a hole pattern (1a, 1b, 11a, 11b),
and in figure 2A the half-tone strip and the hole pattern are surrounded by a
light blocking film (103). There is no light blocking film in the form of a
strip, which is “a long narrow piece of material”.2
The Examiner argues that “Tanaka ‘692 Fig. 2A, and Tanaka ‘050,
Figs. 9 and 10, show the same profile and pattern arrangement as applicant’s
Figs. 3 and 4” (Ans. 7).
The Appellant’s figure 3 shows a sheltering layer (306) in the form of
a strip, and such a strip is not shown in the Tanaka figures relied upon by the
Examiner. 3
The Examiner argues that “it would have been obvious to one having
ordinary skill in the art to take the teachings of the cited prior art and adjust
the pattern to give the desired optical transmission in order to make the
claimed invention because it is typical when using a mask comprising
halftone regions, to adjust the amount of transmission adjacent the halftone
regions in order to give the necessary destructive interference to produce the
desired pattern” (Ans. 5).

2 Webster’s New Collegiate Dictionary 1153 (G. & C. Merriam 1973).
3 The Appellant’s figure 4A shows a patterned photoresist (404), and
figure 4B shows a patterned material layer (402a) (Spec. ¶ 0034).
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Appeal 2008-3545
Application 10/250,228

Even if the Examiner is correct that it was known in the art to adjust
the transmission adjacent a halftone region to provide the necessary
destructive interference, the Examiner has not established that one of
ordinary skill in the art would have been led by the applied prior art to do so
by using sheltering layers in the form of strips. Thus, the record indicates
that the reason relied upon by the Examiner for modifying the Tanaka
photomasks to use sheltering layers in the form of strips comes from the
Appellant’s disclosure rather than coming from the applied prior art. The
record, therefore, indicates that the Examiner used impermissible hindsight
in rejecting the Appellant’s claims. See W.L. Gore & Associates v. Garlock,
Inc., 721 F.2d 1540, 1553 (Fed. Cir. 1983), cert. denied, 469 U.S. 851
(1984); In re Rothermel, 276 F.2d 393, 396 (CCPA 1960).
For the above reasons we conclude that the Examiner has not
established a prima facie case of obviousness of the Appellant’s claimed
invention over Tanaka ‘692 or Tanaka ‘050.
DECISION
The rejections of claims 8-16 under 35 U.S.C. § 103 over Tanaka ‘692
and over Tanaka ‘050 are reversed.
REVERSED

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Appeal 2008-3545
Application 10/250,228

PL initials:
sld

JIANQ CHYUN INTELLECTUAL PROPERTY OFFICE
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