Ex Parte Kraus et al

Board of Patent Appeals and Interferences

Mar 27, 2012

10588766 (B.P.A.I. Mar. 27, 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 HARALD KRAUS and MARTINE CLAES
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Appeal 2010-007916
Application 10/588,766
Technology Center 1700
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Before ROMULO H. DELMENDO, MICHAEL P. COLAIANNI, and
GEORGE C. BEST, Administrative Patent Judges.

BEST, Administrative Patent Judge.

DECISION ON APPEAL
Pursuant to 35 U.S.C. § 134, Appellants seek reversal of the
Examiner’s final rejection of claims 3-5, 8, 11-15, and 17 of Application
10/588,766. We have jurisdiction under 35 U.S.C. § 6(b).
For the reasons set forth below, we AFFIRM.
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Issue
Did the Examiner reversibly err by rejecting claims 3-5, 8, 11-15, and
17 as obvious over the combination of published U.S. Patent Application
2003/0235985 (“Christenson,” Dec. 25, 2003) in view of U.S. Patent No.
5,032,217 (“Tanaka,” issued July 16, 1991) further in view of published U.S.
Patent Application 2003/0230549 (“Buchanan,” Dec. 18, 2003).
We answer this question in the negative.
Background
The ’766 application discloses and seeks to claim a method for
etching materials with a high dielectric constant (“high-k materials”)
selectively in the presence of SiO2.
High-k materials can be used in complementary metal oxide
semiconductor (“CMOS”) technology to reduce quantum tunneling effects
in transistor gates compared to SiO2 as a gate material. Christenson, ¶¶ 2-3.
Hafnium oxide, HfO2, and zirconium oxide, ZrO2, are examples of high-k
materials which would enable higher transistor operation speeds at lower
voltages. Id. at ¶¶ 2-3, 22.
In a manufacturing process, the high-k material is deposited as a layer
over a substrate. Spec. ¶ 4. To be useful in CMOS chips, therefore, the chip
manufacturer must be able to selectively remove the high-k material from
those portions of the chip where it is unwanted in the presence of other
materials, such as SiO2. Id. at ¶¶ 4-7, 39.
The ’766 application discloses an etching process that can achieve
high degrees of selectivity for the materials HfO2 and ZrO2. According to the
’766 application, the necessary selectivity can be achieved by first subjecting
the metal oxide to ion bombardment, id. at ¶ 6, and then using an etchant
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comprising dilute hydrofluoric acid in an organic solvent such as an alcohol
wherein the pH is adjusted to less than 3, id. at ¶ 7. The etchant is dispersed
in a continuous stream at a rate that is sufficient to generate a mean etchant
flow velocity parallel to the substrate’s surface of at least 0.1 m/s. Id. at ¶¶
10-12.
Claim 17, the only independent claim at issue, is representative.
17. A method of selective etching comprising:
providing a first material on a substrate, wherein said first
material is HfO2 or ZrO2, and said first material is pretreated
with an energetic particle bombardment;
providing a second material on the substrate; and
selectively etching said first material with a selectivity of at
least 2:1 towards said second material by dispensing a liquid
etchant onto the substrate surface and generating a flow having
a mean velocity v parallel to the surface of the substrate of at
least 0.1 m/s,
wherein said liquid etchant is dispensed in a continuous flow as
a free beam or as a liquid stream onto the substrate and spreads
over the surface of the substrate.
(emphasis added).
Discussion
Appellants argue that there are two defects with the Examiner’s
rejection: (1) Christenson does not teach that the flow velocity parallel to the
substrate surface is a result effective variable that can be optimized, and
(2) Christenson teaches away from using HfO2 or ZrO2. Br. 3.
Although we will address these arguments individually, they suffer
from a common defect. Both arguments are premised on the notion that one
can attack an obviousness determination that uses a combination of
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references by attacking one reference individually. This is incorrect.
“Nonobviousness cannot be established by attacking references individually
where the rejection is based upon the teachings of a combination of
references.” In re Merck & Co., 800 F.2d 1091, 1097 (Fed. Cir. 1986); see
also In re Keller, 642 F.2d 413, 425-26 (CCPA 1981).
I. The prior art taken as a whole teaches the velocity limitation
Appellants argue that the prior art does not teach any method of
dispensing the etchant that results in the claim 17 requirement of “a flow
having a mean velocity v parallel to the surface of the substrate of at least
0.1 m/s.” Br. 3-6. First, Appellants argue that Christenson does not suggest
that etchant flow velocity parallel to the substrate surface is a variable that
could be optimized. Br. 4-5. Second, Appellants argue that Christenson does
not teach a continuous flow of etchant parallel to the substrate surface. Br. 5-
6.
Neither of Appellants’ arguments is sufficient to overcome the
Examiner’s rejections. While Christenson does not specify a particular flow
rate across the substrate surface, it does teach that etchant flow rates need to
be optimized for the particular type of processor that is being used. As
Appellants point out, in some of its examples Christenson uses a static bath
of etchant solution. Br. 5 (citing Christenson ¶ 43). Other examples in
Christenson use a centrifugal spray processor with high cross wafer flow
rates. Christenson ¶ 55-62. From the similar results obtained in these
disparate examples, Christenson draws the conclusion that etchant flow rate
is not critical. Id. at ¶ 43. The rejection, however, is based upon the
combination of Christenson, Buchanan, and Tanaka. Christenson teaches
that etchant flow rates will have to be “selected based upon factors including
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the type(s) of equipment being used.” Id. Tanaka teaches the use of a single
wafer centrifugal processor which supplies the etchant as a continuous
stream onto a spinning wafer. Ans. 6. In such an apparatus, the etchant flows
across the surface of the substrate, Tanaka Fig. 6; col. 4, l. 63-col. 5, l. 43,
and necessarily has a velocity that is parallel to the substrate surface. In the
experiments described in Tanaka, etchant was supplied with a flow velocity
of 0.1 m/s. Ans. 6-7.
The prior art, therefore, taken as a whole, teaches the provision of a
continuous stream of etchant with a velocity parallel to the substrate surface
of at least 0.1 m/s.
II. The prior art taken as a whole teaches the use of HfO2 and ZrO2
Appellants argue that Christenson teaches away from the use of HfO2
or ZrO2. Br. 6-8. Christenson does state that “a material comprising only one
elemental constituent other than oxygen (e.g., HfO2 and ZrO2), are [sic]
highly resistant to dilute etchants.” Christenson ¶ 22.
This argument, however, is based on the flawed premise that the
obviousness rejection can be overcome by attacking Christenson rather than
considering the teachings of all the references. Rather, the Christenson
reference must be read for what it fairly teaches in combination with the
prior art as a whole. Merck, 800 F.2d at 1097.
Read together and as a whole, the prior art teaches that HfO2 and ZrO2
are useful high-k materials. Christenson speculates that the reason that
compounds like Hf0.6Si0.4O2 can be etched by dilute HF solutions is that the
inclusion of the silicon atoms disrupts the crystal lattice. Christenson ¶ 22.
Buchanan teaches that bombardment of high-k materials renders them
susceptible to etching with dilute HF. Buchanan ¶ 10. Indeed, Buchanan
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notes that HfO2 and ZrO2 are preferred materials for use in its process. Id. at
¶ 30. Buchanan further suggests that the reason the bombardment renders
the material susceptible to etching is that it disrupts the crystal lattice. Id. at
¶ 24. Thus it would have been obvious to supplement the etching process
taught in Christenson with Buchanan’s ion bombardment techniques in order
to etch HfO2 or ZrO2 materials on the substrate.
Appellants’ argument, therefore, is not sufficient to overcome the
Examiner’s rejections.
Conclusion
We have considered Appellants’ arguments and do not find them
convincing. We therefore sustain the Examiner’s rejections of the claims
under 35 U.S.C. § 103(a).

No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv) (2011).

AFFIRMED.

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