Ex Parte Figura

Board of Patent Appeals and Interferences

Nov 21, 2002

09257899 (B.P.A.I. Nov. 21, 2002)

1
The opinion in support of the decision being entered today was
not written for publication and is not binding precedent of the
Board.
Paper No. 34
UNITED STATES PATENT AND TRADEMARK OFFICE
__________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________
Ex parte THOMAS A. FIGURA
__________
Appeal No. 2002-0677
Application 09/257,899
___________
ON BRIEF
___________
Before GARRIS, OWENS and DELMENDO, Administrative Patent Judges.
OWENS, Administrative Patent Judge.
DECISION ON APPEAL
This appeal is from the final rejection of claims 18-25, 28,
32 and 46-50, which are all of the claims remaining in the
application.
THE INVENTION
The appellant’s claimed invention is directed toward a
method for forming a roughened surface on a polysilicon layer of
a capacitor. Claim 18 is illustrative:
Appeal No. 2002-0677
Application 09/257,899
1 In the answer (page 5) the examiner relies upon
U.S. patent 5,256,587 to Jun et al. Because this reference is
not included in the statement of the rejection, it is not
properly before us. See In re Hoch, 428 F.2d 1341, 1342 n.3, 166
USPQ 406, 407 n.3 (CCPA 1970). Accordingly, we do not further
discuss this reference.
2
18. A method for forming a roughened polysilicon surface on
a substrate, comprising:
forming a first polysilicon layer on the substrate;
subsequent to forming the first polysilicon layer, forming a
second polysilicon layer at a temperature and a pressure selected
to form a hemispherical grained surface supported by the first
polysilicon layer, wherein the hemispherical grained surface has
a plurality of grains; and
removing a portion of the second polysilicon layer, thereby
decreasing a size of the grains and increasing a distance between
adjacent grains while maintaining continuity of the first
polysilicon layer.
THE REFERENCES
Fazan et al. (Fazan) 5,130,885 Jul. 14, 1992
Ko et al. (Ko) 5,350,707 Sep. 27, 1994
Hirota et al. (Hirota) 5,372,962 Dec. 13, 1994
THE REJECTION
The claims stand rejected under 35 U.S.C. § 103 as being
obvious over the combination of Hirota, Ko, Fazan and the
appellant’s admitted prior art.1
OPINION
We reverse the aforementioned rejection.
Hirota discloses a method for increasing capacitance by
Appeal No. 2002-0677
Application 09/257,899
3
roughening the surface of the lower electrode of a capacitor,
thereby increasing the surface area of the lower electrode
(abstract). The disclosed roughening techniques include anodic
oxidation, wet etching and dry etching. See id. Hirota also
discloses that the inventors in that patent have proposed two
methods for making a lower capacitor electrode having a surface
of hemispherical grains (col. 2, line 58 - col. 3, line 27). In
the first method dense hemispherical silicon grains are formed
using low pressure chemical vapor deposition and are patterned
using dry etching (col. 2, line 58 - col. 3, line 7). In the
second method a smooth amorphous silicon layer is deposited on a
substrate, patterned using lithography and etching, and heated to
form a crystallized, rough surface (col. 3, lines 8-27).
The portion of Fazan relied upon by the examiner discloses a
lower capacitor electrode formed by depositing a polycrystalline
silicon-germanium alloy (SixGe1-x) coating on a conformal
polysilicon layer by rapid thermal chemical vapor deposition
using SiH2Cl2 and GeH4 as precursor gases and H2 as a carrier gas
under conditions that favor macroscopic islanding of the
deposited alloy crystals (col. 4, line 46 - col. 5, line 5).
Appeal No. 2002-0677
Application 09/257,899
4
The portion of Ko relied upon by the examiner pertains to
the appellant’s claim 32 which recites treating an amorphous
silicon layer overlying a polysilicon layer to form a polysilicon
surface having grains thereon. The relied-upon portion of Ko
discloses making a capacitor layer of materials which can be
amorphous silicon (col. 3, lines 58-64).
The admitted prior art relied upon by the examiner is a
disclosure that it was known in the art to form hemispherical
grain polysilicon at a critical temperature and pressure at which
an anomalous nucleation occurs, and that the grains are so close
together that a dielectric layer deposited over them bridges
between the grains (specification, page 4, line 21 - page 5,
line 10).
The appellant’s independent claims require 1) deposition of
a silicon or polysilicon layer on a substrate before deposition
of the layer from which the hemispherical grains are formed, and
2) etching or removing part of the hemispherical grain-containing
layer to decrease the size of the grains or increase the surface
area. The examiner argues that the appellant’s admitted prior
art and Hirota show that forming hemispherical grains was known
Appeal No. 2002-0677
Application 09/257,899
2 In support of this argument the examiner relies upon the
above-discussed portion of Hirota and also Hirota’s fourth,
fifth, thirteenth and fourteenth embodiments (answer, page 4).
In the fourth embodiment a doped polysilicon film is annealed and
then etched with phosphoric acid to form microrecesses in the
film (col. 11, lines 18-48). In the fifth embodiment a method
similar to that in the fourth embodiment is disclosed, and a
method is disclosed wherein an amorphous silicon film is annealed
to form silicon crystal grains and the film is then etched with
phosphoric acid to produce microrecesses therein (col. 11,
line 50 - col. 12, line 11). In the thirteenth embodiment a
porous silicon is annealed to recrystallize the silicon and
thereby form grains which, compared to the original grains, have
larger sizes and larger microrecesses between them (col. 17,
lines 5-24). In the fourteenth embodiment an amorphous silicon
film which has been formed partially on a single crystal silicon
substrate and partially on a silicon oxide film is annealed to
form hemispherical grains and is then etched with phosphoric acid
to decrease the microrecess size and increase the surface area
(col. 17, line 26 - col. 18, line 9).
5
in the art,2 and relies upon Fazan for a teaching of forming
hemispherical grains on a polysilicon layer (answer, page 4).
Fazan, however, teaches that his polycrystalline silicon-
germanium alloy grains are deposited as macroscopic islands
having diameters which are sufficiently large relative to a
subsequently-applied dielectric layer that the dielectric layer
does not bridge the gaps between the islands (col. 4, line 46 -
col. 5, line 5). Fazan does not disclose etching the macroscopic
islands.
Appeal No. 2002-0677
Application 09/257,899
6
To arrive at the appellant’s claimed methods by combining
the applied references as proposed by the examiner, one of
ordinary skill in the art would have had to substitute Fazan’s
polycrystalline silicon-germanium alloy macroscopic island
layer/polysilicon layer combination for Hirota’s polysilicon
hemispherical grain layer, and then apply Hirota’s etching step
to Fazan’s macroscopic islands. The examiner has not provided
the required explanation as to why the applied prior art itself
would have provided one of ordinary skill in the art with a
motivation to make this substitution and a reasonable expectation
of success in doing so. See In re Vaeck, 947 F.2d 488, 493, 20
USPQ2d 1438, 1442 (Fed. Cir. 1991); In re O’Farrell, 853 F.2d
894, 902, 7 USPQ2d 1673, 1680 (Fed. Cir. 1988). The examiner’s
argument that “the motivation is found in the knowledge generally
available to one of ordinary skill in the art” (answer, page 6)
is not sufficient for carrying this burden; nor is the examiner’s
argument that one of ordinary skill in the art would have made
the proposed substitution “with an anticipation of an expected
result” (answer, pages 4 and 5).
Appeal No. 2002-0677
Application 09/257,899
3 Ko and the appellant’s admitted prior art are not relied
upon by the examiner for a teaching which remedies the above-
discussed deficiency in Hirota and Fazan.
7
The examiner, therefore, has not carried the burden of
establishing a prima facie case of obviousness of the method
recited in any of the appellant’s claims.3 Accordingly, we
reverse the examiner’s rejection.
DECISION
The rejection under 35 U.S.C. § 103 as being obvious over
the combination of Hirota, Ko, Fazan and the appellant’s admitted
prior art is reversed.
REVERSED
)
BRADLEY R. GARRIS )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
TERRY J. OWENS )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
ROMULO H. DELMENDO )
Administrative Patent Judge )
Appeal No. 2002-0677
Application 09/257,899
8
SCHWEGMAN, LUNDBERG,
WOESSNER & KLUTH, P.A.
P. O. BOX 2938
MINNEAPOLIS, MN 55402
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