Ex Parte Nallan et al

Board of Patent Appeals and Interferences

Apr 12, 2010

10338250 (B.P.A.I. Apr. 12, 2010)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte PADMAPANI C. NALLAN, GUANGXIANG JIN,
and AJAY KUMAR
____________

Appeal 2009-015431
Application 10/338,250
Technology Center 1700
____________

Decided: April 12, 2010
____________

Before EDWARD C. KIMLIN, PETER F. KRATZ, and
MARK NAGUMO, Administrative Patent Judges.

KIMLIN, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal from the final rejection of claims 1-5 and 22-28. We
have jurisdiction under 35 U.S.C. § 6(b). Claims 6 has been indicated as
allowable and claim 29 has been withdrawn from consideration.
Claim 1 is illustrative:

Appeal 2009-015431
Application 10/338,250

1. A method of etching a dielectric layer having a dielectric
constant that is greater than 4.0 on a semiconductor substrate, comprising:

providing a substrate having the dielectric layer to be selectively
etched disposed thereon; and

selectively plasma etching the dielectric layer by applying one or
more processing cycles to the substrate, wherein each cycle comprises a
period of etching the dielectric layer without substrate bias and a period of
etching the dielectric layer with substrate bias.

The Examiner relies upon the following references as evidence of
obviousness (Ans. 2-3):
O’Neill 5,683,538 Nov. 04, 1997
Ji 2004/0014327 A1 Jan. 22, 2004
Arghavani 2004/0033677 A1 Feb. 19, 2004

Appellants’ claimed invention is directed to a method of etching a
dielectric layer having a dielectric constant greater than 4.0. The method
entails applying one or more processing cycles to the substrate wherein each
cycle comprises a period of etching the dielectric layer without substrate
bias, and a period of etching the dielectric layer with substrate bias.
Appealed claims 1-3 and 22-28 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over O’Neill in view of Arghavani.
Appealed claims 4-5 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over the stated combination of references further in view of Ji.
Appellants do not present separate arguments for the two groups of
claims separately rejected by the Examiner. Accordingly, these groups of
claims stand or fall together.
We have thoroughly reviewed each of Appellants’ arguments for
patentability. However, we are in complete agreement with the Examiner
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Application 10/338,250

that the claimed subject matter would have been obvious to one of ordinary
skill in the art within the meaning of § 103 in view of the applied prior art.
Accordingly, we will sustain the Examiner’s rejections for essentially those
reasons expressed in the Answer, and we add the following primarily for
emphasis.
There is no dispute that O’Neill, like Appellants, discloses a method
of etching a dielectric layer on a semiconductor substrate that comprises
selectively plasma etching the dielectric layer by applying one or more
processing cycles to the substrate, wherein each cycle comprises a period of
etching the dielectric layer without substrate bias and a period of etching the
dielectric layer with substrate bias. As recognized by the Examiner, O’Neill
does not specify that the dielectric layer is one whose dielectric constant is
greater than 4.0, as presently claimed. However, Arghavani provides clear
evidence that it was known in the art at the time of filing the present
application that dielectric materials having a high dielectric constant have an
advantage over low dielectric constant materials in transistor devices. In
discussing the state of the prior art, Arghavani discloses:
Consequently, a more conventional practice has been to
replace the low-k dielectric with a high-k dielectric. A high-
k dielectric can provide dielectric qualities at a lower
thickness than low-k dielectrics.

([0003]). Arghavani also teaches that “[t]he term ‘high-k’ is a relative term
that refers to a material with a dielectric constant(k) substantially higher than
that of silicon dioxide (SiO2), or in other words substantially higher k = 3.9”
([0016]). Consequently, based on the collective teachings of O’Neill and
Arghavani, we are in complete agreement with the Examiner that it would
have been obvious for one of ordinary skill in the art to select the presently
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Application 10/338,250

claimed high dielectric constant material in the process of O’Neill in order to
achieve greater dielectric qualities at a lower thickness.
The principal argument advanced by Appellants is that O’Neill and
Arghavani disclose different etchant materials for removing the dielectric
layer and, therefore, it would not have been obvious to use the etchant
composition of O’Neill, which comprises two etchants, on the high dielectric
material of Arghavani. Appellants’ argument, however, is grounded on the
erroneous premise that O’Neill teaches that the dielectric material used in
the process is limited to the low dielectric material exemplified, and that
Arghavani teaches that the etchant material used to remove the high
dielectric material is limited to HF which is taught as exemplary. The focus
of O’Neill’s invention is that different radicals, such as CF, CF2 and CF3
have different lifetimes in a plasma environment such that in situ and real
time determination of etch selectivity can be monitored and controlled.
O’Neill provides a general teaching that the etchant composition comprising
different compounds can be used to selectively etch different materials in
making a semiconductor device, with silicon dioxide and polysilicon being
only examples of such different materials. Appellants have offered no
reason for why one of ordinary skill in the art would not have reasonably
expected the high dielectric materials of Arghavani to be suitable for the
selective etching method of O’Neill.
Similarly, Arghavani provides no teaching that a suitable etchant for
the high dielectric material is limited to the particular HF exemplified. In
relevant part, Arghavani discloses:
The etch chemistry should be such that the oxygen-
permeable dielectric layer 304 is etched but neither the
substrate 300, the gate electrode 318, nor the isolation
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Appeal 2009-015431
Application 10/338,250

regions 302 are etched. . . . . Because of the highly diffusible
nature of oxygen-permeable gate dielectric 319, the etching
of the oxygen-permeable dielectric layer 304 should be
careful not to introduce oxygen, whether directly as part of
the process since the oxygen-permeable gate dielectric 319
will be exposed and the oxygen would diffuse laterally into
the oxygen-permeable gate dielectric 319.

([0022]). Hence, we find that it would have been a matter of obviousness
for one of ordinary skill in the art to resort to routine optimization to
determine the particular etchant compositions that are suitable for etching a
high dielectric material.
In the present case, the appealed claims do not define any particular
etchant material for etching the dielectric layer having a high dielectric
constant. Accordingly, we concur with the Examiner that it would have
been obvious for one of ordinary skill in the art to employ routine
experimentation to reveal the most effective etchant compositions for high
dielectric materials in the selective etchant process of O’Neill. In our view,
the appealed claims encompass a selective etching process that is clearly
suggested by O’Neill in light of the state of the art at the time of filing the
present application.
Appellants have not presented a separate, substantive argument
against the rejection of claims 4 and 5, but rely upon the asserted deficiency
of the combined teachings of O’Neill and Arghavani.
As a final point, we note that Appellants base no argument upon
objective evidence of non-obviousness, such as unexpected results.
In conclusion, based on the foregoing and the reasons well stated by
the Examiner, the Examiner’s decision rejecting the appealed claims is
affirmed.
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Application 10/338,250

No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a) (2008).

AFFIRMED

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