Ex Parte Ku et al

Board of Patent Appeals and Interferences

Mar 6, 2010

10726638 - (D) (B.P.A.I. Mar. 6, 2010)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte JA-HUM KU, KWAN-JONG ROH, MIN-CHUL SUN, and
MIN-JOO KIM
____________

Appeal 2009-014245
Application 10/726,6381
Technology Center 2800
____________

Decided: March 8, 2010
____________

Before MAHSHID D. SAADAT, SCOTT R. BOALICK, and
THOMAS S. HAHN, Administrative Patent Judges.

BOALICK, Administrative Patent Judge.

DECISION ON APPEAL

1 Application filed December 4, 2003. Application 10/726,638 claims the
benefit under 35 U.S.C. § 119 of Korean Patent Application
No. 2003-42838, filed June 27, 2003. The real party in interest is Samsung
Electronics Co., Ltd.
Appeal 2009-014245
Application 10/726,638

2
This is an appeal under 35 U.S.C. § 134(a) from the final rejection of
claims 1-34. Claims 35-37 have been cancelled. We have jurisdiction under
35 U.S.C. § 6(b).
We reverse.

STATEMENT OF THE CASE
Appellants’ invention relates to methods for forming a nickel silicide
layer on semiconductor devices. (Spec. Abstract.) The nickel silicide layer
is formed from a nickel alloy that includes an alloying metal, such as
tantalum. (Spec. Abstract.) The nickel silicide layer includes a lower layer
formed primarily of nickel and silicon and an upper layer incorporating the
majority of the alloying metal. (Spec. Abstract.)
Claim 1 is exemplary:
1. A method of forming a nickel silicide layer on an exposed
silicon surface comprising:

depositing a nickel alloy layer on the exposed silicon surface, the
nickel alloy including nickel and an alloying metal that constitutes no more
than about 10 atomic percent of the nickel alloy;

reacting the nickel alloy layer with the exposed silicon surface to form
a nickel silicide layer having an upper layer and a lower layer, wherein the
alloying metal is preferentially segregated in the upper layer.

The prior art relied upon by the Examiner in rejecting the claims on
appeal is:
Chittipeddi 6,498,080 B1 Dec. 24, 2002
Amos 6,846,734 B2 Jan. 25, 2005
(filed Nov. 20, 2002)

Appeal 2009-014245
Application 10/726,638

3
Cabral 2005/0176247 A1 Aug. 11, 2005
(filed Mar. 8, 2005,
divisional of U.S.
Patent No. 6,905,560,
filed Dec. 31, 2002)

Claims 1-4, 7-9, 15-18, 26, 28, 29, and 31-34 stand rejected under 35
U.S.C. § 102(e) as being anticipated by Cabral.
Claim 30 stands rejected under 35 U.S.C. § 103(a) as being obvious
over Cabral.
Claims 5, 6, 10-14, 19, 20, and 27 stand rejected under 35 U.S.C.
§ 103(a) as being obvious over Cabral and Amos.
Claims 21-25 stand rejected under 35 U.S.C. § 103(a) as being
obvious over Cabral and Chittipeddi.

ISSUE
With respect to independent claims 1 and 15, Appellants argue that
Cabral does not teach the limitation “reacting the nickel alloy layer with the
exposed silicon surface to form a nickel silicide layer having an upper layer
and a lower layer, wherein the alloying metal is preferentially segregated in
the upper layer.” (App. Br. 10-12; see also Reply Br. 4-6.) In particular,
Appellants argue that “the Examiner does not provide the required objective
evidence or cogent technical reasoning to support his conclusion of
inherency” (App. Br. 11; Reply Br. 4) and “Cabral actually discloses that the
nickel alloy layer is a single layer, rather than a nickel silicide layer having
an upper and lower layer as recited in independent claim 1” (App. Br. 12).
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Application 10/726,638

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Appellants’ arguments present the following issue:
Does Cabral teach “reacting the nickel alloy layer with the exposed
silicon surface to form a nickel silicide layer having an upper layer and a
lower layer, wherein the alloying metal is preferentially segregated in the
upper layer”?

FINDINGS OF FACT
The record supports the following findings of fact (FF) by a
preponderance of the evidence.

Specification
1. Appellants describe “forming a nickel silicide layer by the reaction
between a nickel alloy and an exposed silicon surface.” (¶ [0007].)
For example, the nickel silicide layer can be used as conductors for
the gate, source and drain regions for metal oxide semiconductor
(MOS) devices. (¶ [0003].) Tantalum is added to the nickel alloy at
levels of “up to at least about 10 atomic percent, with levels in the
range of between about 0.1 atomic percent and about 5 atomic
percent, and particularly about 3.5 atomic percent exhibiting
acceptable performance.” (¶ [0011].)

2. The nickel silicide is formed by “heating the nickel alloy in contact
with a silicon surface to a temperature above about 200 °C. and below
about 700 °C., more typically between about 250 °C. and about
500 °C., for a period of at least about 10 seconds and possibly 30
minutes or longer.” (¶ [0016].) “The particular time and temperature
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combination selected should be sufficient to produce the two-layered
nickel silicide structure.” (¶ [0016].)

3. In one embodiment, as illustrated in Figure 2C, a nickel alloy layer 30
is deposited over an active region of a silicon substrate and annealed
“for a time period sufficient” to form a silicide. (¶ [0035].) This
reaction is performed using a rapid thermal anneal (RTP) process at a
temperature “typically above 450 °C.” (¶ [0035].)

4. In another embodiment, a series of 130 Å-thick (i.e., 13 nm-thick)
nickel silicides were formed. (¶ [0052].) These nickel silicides were
processed by sputtering nickel alloys containing tantalum (3.5, 5.0 and
10.0 atomic %) on silicon substrates, followed by annealing at 450 °C
for thirty seconds. (¶ [0052].) Upon completion of the annealing
step, a tantalum-rich upper layer and a NiSi lower layer were formed.
(¶ [0053]; Table 2.)

Cabral
5. Cabral relates to “a method of fabricating a low resistance
non-agglomerated Ni monosilicide contact” for semiconductor
devices (¶ [0001]), such as contacts for CMOS devices (¶ [0009]).
Tantalum is added as an alloying element to a Ni monosilicide phase
to retard agglomeration. (¶ [0036].)

6. To form CMOS contacts (¶ [0009]), a Ni alloy layer is formed over a
portion of a Si-containing material (¶ [0011]). Preferably, the Ta
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alloying element (¶ [0036]) is present in the Ni alloy layer in an
amount from 0.5 atomic % to 10 atomic % (¶ [0039]). The Ni alloy
layer can be deposited by sputtering to a thickness of 30 nm or less.
(¶ [0038].) The “Ni alloy layer [is annealed] at a temperature which is
effective in converting a portion of said Ni alloy layer into either a Ni
alloy monosilicide layer or a metal rich Ni silicide layer.” (¶ [0012].)
The metal-rich silicide phases can include Ni3Si2, Ni2Si, Ni31Si12 and
Ni3Si. (¶ [0047].)

7. The annealing step is performed by rapid thermal anneal (RTA) at
about 650 °C for thirty minutes. (¶ [0045].) Other annealing
temperatures include from about 250 to 600 °C, preferably 400 °C to
550 °C. (¶ [0045].) Low temperature annealing (i.e., below 500 °C or
preferably below 350 °C) results in the formation of metal-rich
silicide phases. (¶ [0047].) If this metal-rich silicide is formed during
annealing, a second anneal is required to form a low resistivity Ni
monosilicide. (¶ [0020].) Cabral is silent regarding the
microstructure of the Ni monosilicide layer and the metal-rich Ni
silicide layer during annealing.

PRINCIPLES OF LAW
Anticipation is established when a single prior art reference discloses,
expressly or under the principles of inherency, each and every limitation of
the claimed invention. Atlas Powder Co. v. IRECO, Inc., 190 F.3d 1342,
1347 (Fed. Cir. 1999); In re Paulsen, 30 F.3d 1475, 1478-79
(Fed. Cir. 1994). Inherency may not be established by probabilities or
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Application 10/726,638

7
possibilities, and “[t]he mere fact that a certain thing may result from a given
set of circumstances is not sufficient.” Continental Can Co. v. Monsanto
Co., 948 F.2d 1264, 1268 (Fed. Cir. 1991).

ANALYSIS
We conclude that the Examiner erred in rejecting claims 1-4, 7-9, 15-
18, 26, 28, 29 and 31-34 under 35 U.S.C. § 102(e) and claims 5, 6, 10-14,
19-25, 27 and 30 under 35 U.S.C. § 103(a).

Claims 1-4, 7-9, 15-18, 26, 28, 29 and 31-34
Appellants’ argument (App. Br. 10-12; see also Reply Br. 4-6) that
Cabral does not teach the limitation “reacting the nickel alloy layer with the
exposed silicon surface to form a nickel silicide layer having an upper layer
and a lower layer, wherein the alloying metal is preferentially segregated in
the upper layer,” as recited in independent claim 1, is persuasive.
The Examiner found that Cabral teaches all the features of
independent claim 1. (Ans. 3-4, 7.) In particular, the Examiner found that
Cabral inherently teaches the limitation “reacting the nickel alloy layer with
the exposed silicon surface to form a nickel silicide layer having an upper
layer and a lower layer, wherein the alloying metal is preferentially
segregated in the upper layer.” (Ans. 3-4.) In reaching this conclusion, the
Examiner reasoned that
Cabral . . . discloses embodiments including the claimed
alloying elements in the claimed compositions and therefore it
would be expected that a similar result would be achieved with
the reacting process step, particularly since the temperature
range of the reacting step of 250-600 Celsius . . . is substantially
the same or at the very least is contained within the temperature
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range of 200-700 Celsius in the reacting step of the instant
application.

(Ans. 7.) We do not agree.
Appellants’ Specification discloses forming a nickel silicide layer for
semiconductor device conductors by annealing a nickel alloy layer
containing up to 10 atomic % tantalum formed over a silicon substrate.
(FF 1-4.) Appellants’ Specification further discloses that a two-layered
nickel silicide structure can be formed by annealing the nickel alloy layer at
a temperature between 200 °C and 700 °C for ten seconds to thirty minutes
(FF 2) by rapid thermal annealing (FF 3-4). Cabral relates to Ni
monosilicide contacts for CMOS devices. (FF 5.) Cabral teaches that a Ni
alloy layer containing 0.5 atomic % to 10 atomic % tantalum is deposited
over a Si-containing material and annealed (FF 6) at a temperature of 250 to
600 °C for thirty minutes (FF 7).
Although the nickel alloy layer composition and the processing
conditions (i.e., range of annealing temperatures and times) disclosed in
Appellants’ Specification (see FF 1-4) are similar to those taught by Cabral
(see FF 5-7), they do not necessarily produce similar results. Appellants’
Specification discloses that a two-layered nickel silicide structure can be
formed by annealing the nickel alloy layer at a temperature below 500 °C for
thirty minutes. (See FF 2.) However, Cabral teaches that annealing the Ni
alloy layer at below 500 °C for thirty minutes results in the formation of a
metal-rich silicide phase (FF 7), rather than a two-layered nickel silicide
structure. Cabral teaches that a second anneal is required to transform this
metal-rich silicide phase to a Ni monosilicide layer. (FF 7.) However,
Cabral is silent regarding the microstructure of the Ni monosilicide layer and
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Application 10/726,638

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the metal-rich Ni silicide silicide layer during annealing. (FF 7.) Thus, the
Examiner has not established that the limitation of “reacting the nickel alloy
layer with the exposed silicon surface to form a nickel silicide layer having
an upper layer and a lower layer, wherein the alloying metal is preferentially
segregated in the upper layer” is necessarily present in Cabral. Accordingly,
the Examiner has erred in finding via inherency that Cabral teaches the
limitation “reacting the nickel alloy layer with the exposed silicon surface to
form a nickel silicide layer having an upper layer and a lower layer, wherein
the alloying metal is preferentially segregated in the upper layer,” as recited
in claim 1.
Thus, we conclude that the Examiner has erred in rejecting claim 1
under 35 U.S.C. § 102(e). Claims 2-4 and 7-9 depend from independent
claim 1, and we conclude that the Examiner has erred in rejecting these
claims for the reasons discussed with respect to independent claim 1.
Independent claim 15 recites limitations similar to those discussed with
respect to independent claim 1, and we further conclude that the Examiner
has erred in rejecting this claim, as well as claims 16-18, 26, 28, 29 and
31-34 which depend from claim 15, for the reasons discussed with respect to
claim 1.

Claim 30
Claim 30 depends from independent claim 15 and the Examiner has
erred in rejecting claim 15 for the reasons previously discussed.

Appeal 2009-014245
Application 10/726,638

10
Claims 5, 6, 10-14, 19, 20 and 27
Claims 5, 6, 10-14, 19, 20 and 27 depend from independent claims 1
and 15, and the Examiner has erred in rejecting claims 1 and 15 for the
reasons previously discussed. Amos does not cure the above-noted
deficiencies of Cabral.

Claims 21-25
Claims 21-25 depend from independent claim 15 and the Examiner
has erred in rejecting claim 15 for the reasons previously discussed.
Chittipeddi does not cure the above-noted deficiencies of Cabral.

CONCLUSION
Based on the findings of fact and analysis above, we conclude that the
Examiner has erred in rejecting claims 1-34.

DECISION
The rejection of claims 1-34 is reversed.

REVERSED

bim

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