Ex parte YU

Board of Patent Appeals and Interferences

Jul 31, 2000

08498357 (B.P.A.I. Jul. 31, 2000)

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(2) is not binding precedent of the Board.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. 16
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte CHEN-HUA D. YU
_____________
Appeal No. 1997-3635
Application No. 08/498,357
______________
ON BRIEF
_______________
Before FLEMING, BARRETT, and BARRY, Administrative Patent
Judges.
FLEMING, Administrative Patent Judge.
This is a decision on appeal from the rejection of claims
1 through 5, 8 through 12, 14 through 16, and 19. Claim 13
has been canceled. The rejection of claims 6, 7, 17, 18, and
20 is not appealed.
Appellant’s invention is generally directed to a method
for forming a barrier metallization with low contact
resistance and in particular, to the protection of a barrier
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metallization layer from oxidation. As disclosed on pages 8
and 9 of the specification, the surface of a barrier
metallization layer is coated in-situ with a thin silicon
layer prior to its removal from the reaction chamber.
Additionally, the silicon layer may be sintered with the
barrier layer to form a metal silicide which serves as a
passivation layer as well as providing a low contact
resistance to the underlying barrier layer. The disclosure on
pages 16 through 18 teaches that any one of the Chemical Vapor
Deposition (CVD) methods: Plasma Enhanced Chemical Vapor
Deposition (PECVD) methods, and Physical Vapor Deposition
(PVD) sputtering methods may be used for forming the barrier
metallization and the silicon layers.
Representative independent claim 1 is reproduced as
follows:
1. A method for forming a barrier metallization
layer upon a semiconductor substrate comprising:
providing a semiconductor substrate;
forming upon the semiconductor substrate a barrier
metallization layer; and
forming in-situ upon the barrier metallization layer
a silicon layer, the silicon layer being formed without
exposing the barrier metallization layer to oxygen, the
silicon layer having a thickness such that the contact
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resistance of the barrier metallization layer is not
substantially increased.
The Examiner relies on the following references:
Wong et al. (Wong) 4,873,204 Oct. 10, 1989
Yu et al. (Yu) 4,977,098 Dec.
11, 1990
Zhang 5,236,850 Aug. 17,
1993
Whitten et al. (Whitten) 5,451,811
Sep. 19, 1995
Sato (Japan '414) 04-63414 Feb. 28, 1992
(published Japanese Patent Application)
Claims 1, 2, 4, 5, 9, 10, 12, 14, and 19 stand rejected
under 35 U.S.C. § 102 as being anticipated by Wong. Claims 3,
8, 15, and 16 stand rejected under 35 U.S.C. § 103 over Wong.
Claims 1 through 3, 5, 8, 9, 11, 12, 14, 16, and 19 stand
rejected under 35 U.S.C. § 103 over Yu and Japan '414. Claims
11 and 20 stand rejected under 35 U.S.C. § 103 over Wong and
Yu. Claim 6 stands rejected under 35 U.S.C. § 103 over Wong
and Whitten. Claim 17 stands rejected under 35 U.S.C. § 103
over Wong, Yu, and Whitten. Claim 7 stands rejected under 35
U.S.C. § 103 over Wong and Zhang. Claim 18 stands rejected
under 35 U.S.C. § 103 over Wong, Yu, and Zhang.
Appeal No. 1997-3635
Application No. 08/498,357
Appellant filed an appeal brief on August 5, 1996. 1
Appellant also filed a reply brief on May 3, 2000, which
included a correct copy of the claims.
The Examiner mailed a supplemental answer on 2
April 11, 2000, requiring a correct copy of the claims.
4
Rather than repeat the arguments of Appellant and the
Examiner, we make reference to the brief and the answer for1 2
the details thereof.
OPINION
After careful review of the evidence before us, we agree
with the Examiner that claims 1, 2, 4, 5, 9, 10, 12, 14, and
19 are properly rejected as anticipated under 35 U.S.C. § 102.
However, we reach the opposite conclusion with regard to the
obviousness rejection of claims 1 through 3, 5, 8, 9, 11, 12,
14 through 16, and 19 under 35 U.S.C. § 103.
We note that Appellant does not respond in the brief to
the Examiner’s rejections of claims 6, 7, 11, 17, 18, and 20
under
35 U.S.C. § 103. In particular, the rejections are as follow:
claims 11 and 20 are rejected under 35 U.S.C. § 103 over Wong
and Yu; claim 6 is rejected under 35 U.S.C. § 103 over Wong
and Whitten; claim 17 is rejected under 35 U.S.C. § 103 over
Appeal No. 1997-3635
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Wong, Yu, and Whitten; claim 7 is rejected under 35 U.S.C. §
103 over Wong and Zhang; claim 18 is rejected under 35 U.S.C.
§ 103 over Wong, Yu, and Zhang. 37 CFR § 1.192(a) (July 1,
1996) as amended at 60 Fed. Reg. 14518 (March 17, 1995), which
was controlling at the time of Appellant’s filing the brief,
states:
Appellant must, within two months from the date of
the notice of appeal under § 1.191 or within the
time allowed for reply to the action from which
the appeal was taken, if such time is later,
file a brief in triplicate. The brief must be
accompanied by the fee set forth in § 1.17(c)
and must set forth the authorities and arguments
on which appellant will rely to maintain the appeal.
Any arguments or authorities not included in the
brief will be refused consideration by the Board
of Patent Appeals and Interferences, unless good
cause is shown [emphasis added].
Appellant did not include in the brief any arguments with
regard to the above mentioned claims. We therefore, dismiss
the appeal for rejection of claims 6, 7, 11, 17, 18, and 20
under 35 U.S.C. § 103.
Turning to the rejection of claims 1, 2, 4, 5, 9, 10, 12,
14, and 19 under 35 U.S.C. § 102(b) as anticipated by Wong, we
note that Appellant on page 6 of the brief points out the
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groupings of the claims. 37 C.F.R. § 1.192(c)(7) (July 1,
1996) states:
For each ground of rejection which appellant
contests and which applies to a group of two
or more claims, the Board shall select a single
claim from the group and shall decide the appeal
as to the ground of rejection on the basis of
that claim alone unless a statement is included
that the claims of the group do not stand or
fall together and, in the argument under paragraph
(c)(8) of this section, appellant explains why the
claims of the group are believed to be separately
patentable. Merely pointing out differences in
what the claims cover is not an argument as to
why the claims are separately patentable.
Although Appellant has provided a statement regarding the
grouping of the claims, Appellant has not in the arguments
section of the brief provided separate arguments for the
independent claims 1 and 14. We will, thereby, consider
Appellant’s claims 1, 2, 4, 5, 9, 10, 12, 14, and 19 as
standing or falling together as a group and we will treat
claim 1 as the representative claim of that group.
Appellant on page 7 of the brief argues that Wong does
not preclude successive pump down cycles employing a single
sputtering system or separate sputtering systems. Appellant
adds that Wong therefore does not inherently disclose the
claimed exclusion of oxygen and its effect on the resistance
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of the metal layer. Additionally, Appellant on page 8 of the
brief argues that Wong teaches a low resistivity silicide but
is silent with regard to the particular silicon layer
thickness such that the contact resistance of the metal layer
is not substantially increased.
The Examiner on page 6 of the answer responds to
Appellant’s arguments by stating that Wong’s single pump down
cycle precludes the presence of oxygen or other gases. The
Examiner further states that other disclosed embodiments that
may include more than one pump down cycle do not contradict
the exclusion of oxygen in the single pump down cycle.
Additionally, the Examiner points out that the claimed
invention does not preclude an increase in the contact
resistance but “only that the contact resistance is not
substantially increased [emphasis is original].” The Examiner
concludes that Wong’s silicon film does not substantially
increase the resistance of the metallization layer.
As pointed out by our reviewing court, we must first
determine the scope of the claim. “[T]he name of the game is
the claim.” In re Hiniker Co., 150 F.3d 1362, 1369, 47 USPQ2d
1523, 1529 (Fed. Cir. 1998). Claims will be given their
Appeal No. 1997-3635
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broadest reasonable interpretation consistent with the
specification, and limitation appearing in the specification
are not to be read into the claims. In re Etter, 756 F.2d
852, 858, 225 USPQ 1, 5 (Fed. Cir. 1985).
We note that Appellant’s claim 1 recites
. . . forming upon the semiconductor substrate
a barrier metallization layer; and
forming in-situ upon the barrier metallization
layer a silicon layer, the silicon layer being formed
without exposing the barrier metallization layer
to oxygen, the silicon layer having a thickness such
that the contact resistance of the barrier
metallization layer is not substantially increased
[emphasis added].
Appellant’s claim 1, in addition to providing a
semiconductor substrate, recites forming a barrier
metallization layer and forming a silicon layer under specific
conditions. These conditions include in-situ formation of the
layers such that the barrier metallization layer is not
exposed to oxygen. Additionally, the claim requires the
silicon layer to have such a thickness that does not
substantially increase the contact resistance of the barrier
metallization layer. Therefore, we do not find that the claim
precludes some increase in the contact resistance.
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A rejection for anticipation under section 102 requires
that each and every limitation of the claimed invention be
disclosed in a single prior art reference. In re Paulsen, 30
F.3d 1475, 1478-79, 31 USPQ2d 1671, 1673 (Fed. Cir. 1994),
citing In re Spada, 911 F.2d 705, 708, 15 USPQ2d 1655, 1657
(Fed. Cir. 1990).
We find that Wong teaches a method of forming low
resistance interconnects and contacts by sputter depositing an
amorphous silicon layer over a refractory metal layer upon a
semiconductor substrate. Wong in col. 3, lines 44 through 48,
specifically discloses that:
The deposition of first the metal 26 and then
the silicon 25 can be accomplished during a
single pump down cycle in a sputtering system by
providing both a metal target and a silicon target
within the sputtering machine [emphasis added].

Therefore, Wong’s sputtering system is pumped down once and
uses the silicon and the metal targets within the machine to
sequentially deposit the metal and silicon layers without
breaking the vacuum. We find that such arrangement results in
deposition of silicon over the barrier metallization layer
without exposing the metal layer to ambient oxygen, as recited
in Appellant’s claim 1. Wong in col. 3, lines 58 through 66,
Appeal No. 1997-3635
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Wolf, Stanley, “Silicon Processing for the VLSI Era, 3
Volume 2: Process Integration,” 164-165 (Sunset Beach, CA,
Lattice Press, 1990).
10
further discloses thermal annealing to convert the composite
metal and silicon layer to low resistivity silicide.
Additionally, Wong teaches in col. 6, lines 14 through 16
(patent claim 2), that the thickness of amorphous silicon is
such that it is fully consumed in the reaction with the
refractory metal. Therefore, Wong’s silicon layer has a
thickness which is small enough so that it does not
substantially increase the contact resistance of the metal
layer. We further point out the teachings of Wolf to3
buttress our findings with regard to Wong’s single pump down
cycle. Wolf on page 164 discloses a sequential sputter-
deposition of refractory metal and amorphous silicon layers in
one pump down, identical to Wong’s process, to minimize the
formation of an oxide on the metal layer. Wolf also limits
the thickness of silicon layer such that the silicon reacts
fully with the underlying metal layer. Therefore, Wolf
supports our finding that Wong’s single pump down sputtering
forms the silicon layer without exposing the metal layer to
oxygen, as recited in Appellant’s claim 1. Additionally, we
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find that Wong’s silicon layer has a thickness such that the
contact resistance of the barrier layer is not substantially
increased as the silicon layer is fully consumed by reacting
with the metal.
In view of the analysis above, we find that the Examiner
has met the burden of providing a prima facie case of
anticipation. We find that Wong teaches the formation of
silicon and metal layers over a semiconductor substrate as
recited in Appellant’s independent claim 1. Accordingly, we
affirm the rejection of claims 1, 2, 4, 5, 9, 10, 12, 14, and
19 under 35 U.S.C.
§ 102 over Wong.
Turning to the rejection of claims 3, 8, 15, and 16 under
35 U.S.C. § 103 over Wong, Appellant on pages 8 and 9 of the
brief argues that the claimed thickness of metal and silicon
layers have particular significance. Additionally, Appellant
refers to different parts of the specification and points out
the thickness of various layers in relation to the claimed
thickness as specified for the metal and the silicon layers.
In response, the Examiner argues on page 7 of the answer that
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Appellant has not provided any indication that the disclosed
metal and silicon thicknesses are not conventional.
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The Examiner has failed to set forth a prima facie case.
It is the burden of the Examiner to establish why one having
ordinary skill in the art would have been led to the claimed
invention by the express teachings or suggestions found in the
prior art, or by implications contained in such teachings or
suggestions. In re Sernaker, 702 F.2d 989, 995, 217 USPQ 1,
6 (Fed. Cir. 1983). “Additionally, when determining
obviousness, the claimed invention should be considered as a
whole; there is no legally recognizable ‘heart’ of the
invention.” Para-Ordnance Mfg., Inc. v. SGS Importers Int'l,
Inc., 73 F.3d 1085, 1087,
37 USPQ2d 1237, 1239 (Fed. Cir. 1995), cert. denied, 117 S.
Ct. 80 (1996) citing W.L. Gore & Assocs., Inc. v. Garlock,
Inc.,
721 F.2d 1540, 1548, 220 USPQ 303, 309 (Fed. Cir. 1983), cert.
denied, 469 U.S. 851 (1984).
We are not inclined to dispense with proof by evidence
when the proposition at issue is not supported by a teaching
in a prior art reference or shown to be common knowledge of
unquestionable demonstration. Our reviewing court requires
this evidence in order to establish a prima facie case. In re
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Piasecki, 745 F.2d 1468, 1471-72, 223 USPQ 785, 787-88 (Fed.
Cir. 1984); In re Knapp-Monarch Co., 296 F.2d 230, 232, 132
USPQ 6,
8 (CCPA 1961); In re Cofer, 354 F.2d 664, 668, 148 USPQ 268,
271-72 (CCPA 1966). Furthermore, our reviewing court states
in Piasecki, 745 F.2d at 1472, 223 USPQ at 788 (Fed. Cir.
1984) the following:
The Supreme Court in Graham v. John Deere Co.,
383 U.S. 1, 148 USPQ 459 (1966), focused on the
procedural and evidentiary processes in reaching
a conclusion under section 103. As adapted to
ex parte procedure, Graham is interpreted as
continuing to place the "burden of proof on the
Patent Office which requires it to produce the
factual basis for its rejection of an application
under section 102 and 103" [citing In re Warner,
379 F.2d 1011, 1016, 154 USPQ 173, 177 (CCPA 1967)]
[emphasis added].
After a review of Wong’s disclosure, we fail to find any
teachings related to the thickness of the metal and the
silicon layers. We do not agree with the Examiner that the
claimed thicknesses are conventional and obtained by merely
changing the dimensions disclosed in the prior art. In this
case, the prior art teaches the relative thicknesses but is
silent with regard to the actual thickness of barrier
metallization and the amorphous silicon. Therefore, Wong
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fails to provide any teachings related to different layer
thicknesses such that one of ordinary skill in the art would
have modified them in order to form the metal and the silicon
layers having thicknesses as claimed by Appellant.
Accordingly, we reverse the rejection of claims 3, 8, 15, and
16 under 35 U.S.C. § 103 over Wong.
With regard to the rejection of claims 1 through 3, 5, 8,
9, 11, 12, 14, 16, and 19 under 35 U.S.C. § 103 over Yu and
Japan '414, Appellant argues on pages 11 and 12 of the brief
that neither reference suggests the combination. Appellant
further points out that Japan '414 teaches a method for
preventing surface oxidation whereas Yu discloses the
formation of undesired native oxide layer during diffusion of
impurities. Appellant concludes that Yu’s diffusion step and
the method disclosed by Japan '414 cannot be combined since
they are related to oxide layers formed at different stages of
processing. Appellant further argues that the combination of
references does not teach a method for in-situ forming of a
composite silicon and metal layer having low resistivity.
The Examiner responds to Appellant’s arguments on page 7
of the answer by stating that the motivation for combining the
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references is derived from the need for avoiding native oxide
formation and its removal in order to reduce the number of
processing steps. The Examiner further argues that since
Japan '414 teaches the benefits associated with absence of
oxygen during process steps, one of ordinary skill in the art
would have combined the references to avoid exposure to oxygen
in Yu’s process. Additionally, the Examiner asserts that,
similar to arguments made with regard to Wong, the resistance
of the metallization layer of Yu would not be increased by
depositing the silicon layer.
The Federal Circuit states that “[t]he mere fact that the
prior art may be modified in the manner suggested by the
Examiner does not make the modification obvious unless the
prior art suggested the desirability of the modification.” In
re Fritch, 972 F.2d 1260, 1266 n.14, 23 USPQ2d 1780, 1783-84
n.14 (Fed. Cir. 1992), citing In re Gordon, 733 F.2d 900, 902,
221 USPQ 1125, 1127 (Fed. Cir. 1984). The Federal Circuit
reasons in Para-Ordnance Mfg. Inc. v. SGS Importers Int’l
Inc., 73 F.3d 1085, 1088-89, 37 USPQ2d 1237, 1239-40 (Fed.
Cir. 1995), cert. denied, 519 U.S. 822 (1996), that for the
determination of obviousness, the court must answer whether
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one of ordinary skill in the art who sets out to solve the
problem and who had before him in his workshop the prior art,
would have been reasonably expected to use the solution that
is claimed by the Appellants.
We find that Yu teaches a process for forming multiple
layers as the emitter diffusion source and the associated
contact structure. Specifically, Yu in col. 4, line 52
through col. 5, line 6, discloses steps of forming titanium
layer 120 and amorphous silicon layer 121 through amorphous
silicon layer
116 upon a semiconductor substrate. Yu is concerned with
removal of the undesired native oxide, formed over silicon
layer 116 during the anneal and diffusion step, prior to the
formation of titanium layer 120. However, we fail to find any
particular teachings in Yu requiring particular conditions for
depositing the silicon layer over the titanium layer to avoid
oxidation of the metal layer.
Analyzing Japan '414, we find that a method and a device
for processing semiconductor devices in a continuous state of
reduced pressure are disclosed. Japan '414 specifically
teaches a series of chambers with reduced pressure for
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performing different steps of processing. Therefore, we find
that Japan '414 is generally concerned with preventing
unwanted surface oxidation which eliminates the need for
additional cleaning steps. However, we do not find any
teachings or suggestions to prevent exposure of a
metallization layer to oxygen, and in particular, in-situ
deposition of a silicon layer over a metal layer.
We do not find any reason or suggestion to combine Yu and
Japan '414 to form the silicon overlayer without exposing the
barrier metallization layer to oxygen as recited in
Appellant’s claim 1. Although Japan '414 teaches process
steps that prevent surface oxidation, Yu is silent with regard
to the need for protecting the metallization layer from oxygen
during the formation of amorphous silicon layer. Therefore,
we do not agree with the Examiner that one of ordinary skill
in the art would have combined Japan '414 teachings to avoid
exposure of the metallization layer to oxygen.
We do not find that the Examiner has provided sufficient
reason to combine Yu and Japan '414 to form the silicon layer
without oxidizing the metal layer and substantially reducing
its resistivity. We note that the other independent claim
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14 similarly recites the steps of forming the barrier
metallization layer and in-situ forming a silicon layer
without exposing the barrier layer to oxygen. Accordingly, we
reverse the Examiner’s rejection of claims 1 through 3, 5, 8,
9, 11, 12, 14, 16, and 19 under 35 U.S.C. § 103 over Yu and
Japan '414.
In view of the forgoing, the decision of the Examiner
rejecting claims 1, 2, 4, 5, 9, 10, 12, 14, and 19 under
35 U.S.C. § 102 is affirmed. The decision of the Examiner
rejecting claims 1 through 3, 5, 8, 9, 11, 12, 14 through 16,
and 19 under 35 U.S.C. § 103 is reversed. The appeal for
rejection of claims 6, 7, 11, 17, 18, and 20 under 35 U.S.C.
§ 103 is dismissed. Accordingly, we affirm-in-part.
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No time period for taking any subsequent action in
connection with this appeal may be extended under 37 CFR
§ 1.136(a).
DISMISSED-IN-PART
AFFIRMED-IN-PART

LEE E. BARRETT )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
MICHAEL R. FLEMING )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
LANCE LEONARD BARRY )
Administrative Patent Judge )
MRF:hh
Appeal No. 1997-3635
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George O. Saile
20 McIntosh Drive
Poughkeepsie, NY 12603