Ex Parte Uehara et al

Board of Patent Appeals and Interferences

Jan 4, 2012

10960898 (B.P.A.I. Jan. 4, 2012)

UNITED STATES PATENT AND TRADEMARK OFFICE
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BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
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Ex parte ICHIRO UEHARA, KAZUHIRO TOSHIMA, and
SHUNPEI YAMAZAKI
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Appeal 2012-002623
Application 10/960,898
Technology Center 2800
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Before JOSEPH F. RUGGIERO, CARLA M. KRIVAK, and
BRADLEY W. BAUMEISTER, Administrative Patent Judges.

BAUMEISTER, Administrative Patent Judge.

DECISION ON APPEAL

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SUMMARY
Appellants appeal under 35 U.S.C. § 134(a) from the Examiner’s
rejection of claims 19-21. These claims stand rejected under 35 U.S.C.
§ 103(a) as obvious over Sung (US 5,174,857; issued Dec. 29, 1992) in view
of Kim (KR 10-1999-0004786; published June 30, 1997).
Claims 1-12 and 22-24 are allowed, and claims 13-18 have been
cancelled (Ans. 3).
We reverse.

STATEMENT OF THE CASE
The present application is a reissue application of Uehara (US
6,461,886 B1; issued Oct. 8, 2002). Appellants describe their invention as
an improvement to the process of patterning inverted stagger type thin film
transistors (TFTs) (Abstract).1 In the course of manufacturing such TFTs, a
positive photo resist is used as a mask in patterning various device features
that are present on an insulating substrate. To do so, a photo resist such as
diazo naphthoquinone (DNQ)-Novolac resin is coated onto the surface of an
intermediate device structure, such as a conductive wiring layer. The photo
resist is then (1) pre-baked at a first temperature; (2) masked and exposed to
light, such as with a reduction projection exposure apparatus; (3) optionally
post exposure baked (PEB) at a second temperature; (4) chemically

1 Citations to Appellants’ Specification refer to the format of the issued
Uehara patent.
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patterned; and (5) post-baked at a third temperature (col. 1, ll. 1 – col. 2- l.
40). The resultant, patterned photo resist possesses tapered sidewalls (col. 1,
ll. 55-67).
Appellants recognized that when using the conventional photo resist-
developing process, changes in photo resist’s pattern size and shape
sometimes cause variations in the taper angle of the photo resist’s sidewall
(id.). These taper angle variations can undesirably affect the size and shape
of the subsequently etched TFT device structures that the patterned photo
resist is used to mask. Appellants consider this variation in sidewall taper
angle “to be caused due to evacuation of residual solvent from the resist
pattern at the post-bake” step (id., col. 2, ll. 7-8). Appellants have
determined that the variation in the photo resist’s sidewall taper angle can be
prevented if “the difference between the pre-bake temperature and the post-
bake temperature must be 10° C. or less” (id., col. 4, ll. 59-61).
Claim 19 is the sole independent claim on appeal. It is directed to a
method of manufacturing a semiconductor device, which method includes
etching a conductive film that is coated with a patterned photo resist. Claim
19 recites, inter alia, steps of pre-baking the photo resist at a first
temperature and post-baking the developed photo resist at a second
temperature. Central to the present appeal is independent claim 19’s further
recitation “wherein the first temperature is within +10° C relative to the
second temperature.”

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CONTENTIONS
The Examiner finds that Sung discloses every step of the claimed
process for depositing and preparing a photo resist on a conductive layer that
coats an insulating substrate except for the requirement that “the first
temperature is within +10° C relative to the second temperature” (Ans. 5).
Instead, Sung discloses that the pre-bake is carried out at about 90° C, while
the post-bake is carried out at about 130° C to 150° C (Sung, col. 5, ll. 1-17).
The Examiner further finds that Kim teaches a method of preparing a
photoresist wherein the pre-bake and post-bake temperatures are the same:
120° C (Ans. 5) (citing Kim 10:1-15).2 3 The Examiner concludes that it
would have been obvious to employ Kim’s specific pre-bake temperature in
Sung’s process so as to “reduce deformations due by controlling reflow,” as
taught by Kim (Ans. 6). Specifically, the Examiner proposes that Sung’s
pre-bake be performed at Kim’s temperature of 120° C instead of 90° C, and

2 Citations to Kim refer to Appellants’ English translation, which was filed
Oct. 25, 2007.
3 The particular photo resist processing steps of Kim upon which the
Examiner relies are those steps Kim sets forth in relation to the photo resist
181, which is used to etch sacrificial phosphosilicate glass layer 180 (e.g.,
Kim, 24:2-9; Figs. 5b-5c). Photo resist 181 is not used in relation to etching
a conductive film. Kim does use additional photo resists as masks for
etching various conductive films such as conductive layer 165 (e.g., Kim,
20:20 – 21:8; Fig. 5b) and conductive layer 199 (e.g., Kim, 25:24-25; Figs.
5c-5d). However, the processing steps associated with these other photo
masks are not described, and Kim does not indicate whether the resulting
wirings are tapered upon etching. As such, the record does not contain
sufficient evidence to determine whether Kim anticipates claim 19.
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Sung’s post-bake be performed specifically at 130° C – the lowest
temperature of Sung’s disclosed range (130° C - 150° C) and the highest
temperature of Kim’s disclosed range (110° C - 130° C) (Ans. 7-8). The
Examiner reasons that such control would have been relevant to Sung
because Sung also indicates that photo resist deformation is to be avoided
(id).
Appellants assert that one of ordinary skill would not have modified
Sung so as to use Kim’s temperature parameters because Kim teaches that
the bake temperatures used should be low enough to avoid reflow of the
photo resist (App. Br. 7) (citing Kim 4:8-12, 23:17-21), while Sung indicates
that reflow is not only desirable (App. Br. 7) (citing Sung, col. 5, ll. 16-17),
but also important to provide the photoresist with tapered edges so that the
etched chromium layer 25 will have tapered edges (App. Br. 7) (citing Sung,
col. 5, ll. 50-57, col. 6, ll. 36-48). Appellants summarize that nothing in
Kim or Sung would have led one of ordinary skill in the art to conclude that
Kim’s approach to avoiding the reflow phenomenon actually results in a
reflow phenomenon (App. Br. 7).
Appellants further contend that one would have no reason to replace
Sung’s 90° C pre-bake temperature with Kim’s 120° C pre-bake temperature
because Kim does not indicate that any benefit would result
from the higher temperature. In addition, the Examiner has
provided no reason that one of ordinary skill in the art would
have had [sic] made this change. Instead, the Examiner merely
asserts that the higher temperature would have achieved the
same result of evaporating solvents (i.e., that the change could
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have been made), and then relies on an improper hindsight
reconstruction of the invention to change the temperature.
(Reply Br. 1).

ANALYSIS
We agree with the Examiner’s position that Sung and Kim together
teach that in order to volatize the solvent components, a photo resist may be
pre-baked at any temperatures within the range of at least 90° C to 120° C.
That is, since pre-baking at any temperature within this range would be
effective in evaporating the solvents, all temperatures within the range,
inclusive of 90° C and 120° C, were art-recognized equivalents for the
purpose of evaporating solvents.
However, Appellants’ invention is not merely to pre-bake the photo
resist at 120° C in order to evaporate the solvents. Appellants acknowledge
that pre-baking was generally known (Uehara, col. 2, ll. 1-2). Appellants’
invention, instead, goes beyond the general idea of evaporating solvents.
Appellants’ additionally discovered that the taper angle of the photo resist’s
sidewall can be better controlled by using pre-bake and post-bake
temperatures that have a specific relationship – temperatures that are within
+10° C of each other.
Restated, the Examiner has shown that a genus of baking parameters
was known for achieving one result (solvent evaporation), while Appellants’
invention is a sub-genus or species of these baking parameters within this
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genus, and this species of parameters achieves an additional result (taper
angle control). It is well settled, “[t]he fact that a claimed compound may be
encompassed by a disclosed generic formula does not by itself render that
compound obvious” (In re Baird, 16 F.3d 380, 382 (Fed. Cir. 1994)). This
reasoning, albeit arising in the context of compositions as opposed to the
context of baking parameters for forming a composition, applies to the
present situation. The Examiner has not shown that the cited prior art
further foresaw controlling the taper angle of the photo resist’s sidewall by
controlling the relationship between the pre-bake and post-bake
temperatures. That is, the Examiner has not established that the cited prior
art would have led one of ordinary skill to select from all possible
combinations of disclosed baking temperatures, the specific combination of
pre-bake and post-bake temperatures that would be required to control the
taper angle.
For the foregoing reasons, Appellants have persuaded us of error in
the Examiner’s obviousness rejection of independent claim 19.
Accordingly, we will not sustain the Examiner’s rejection of that claim or of
claims 20 and 21, which depend from claim 19.

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DECISION
The Examiner’s decision rejecting claims 19-21 is reversed.

REVERSED

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