Ex Parte Shannon et al

Board of Patent Appeals and Interferences

Apr 20, 2010

10823364 (B.P.A.I. Apr. 20, 2010)

UNITED STATES PATENT AND TRADEMARK OFFICE
________________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
________________

Ex parte STEVEN C. SHANNON, DENNIS S. GRIMARD,
THEODOROS PANAGOPOULOS, DANIEL J. HOFFMAN,
MICHAEL G. CHAFIN, TROY S. DETRICK, ALEXANDER
PATERSON, JINGBAO LIU, TAEHO SHIN, and
BRYAN Y. PU
________________

Appeal 2009-009785
Application 10/823,364
Technology Center 1700
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Decided: April 20, 2010
________________

Before CHUNG K. PAK, CHARLES F. WARREN, and
TERRY J. OWENS, Administrative Patent Judges.

OWENS, Administrative Patent Judge.

DECISION ON APPEAL
STATEMENT OF THE CASE
The Appellants appeal under 35 U.S.C. § 134(a) from the Examiner’s
rejection of claims 1-14 and 33-46, which are all of the pending claims. We
have jurisdiction under 35 U.S.C. § 6(b).
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The Invention
The Appellants claim a method for using a dual frequency radio
frequency (RF) source to control plasma characteristics in a semiconductor
substrate etch processing chamber. Claim 1 is illustrative:
1. A method of controlling characteristics of a plasma in
a semiconductor substrate etch processing chamber using a dual frequency
RF source, comprising:

supplying a first RF signal to a first electrode disposed in an etch
chamber; and

supplying a second RF signal to the first electrode, wherein an
interaction between the first and second RF signals is used to control at least
one characteristic of a plasma formed in the etch chamber.

The References
Demaray 2003/0127319 A1 Jul. 10, 2003
Dhindsa 2003/0148611 A1 Aug. 7, 2003

M.A. Lieberman et al., “Standing wave and skin effects in large-area,
high-frequency capacitive discharges”, 11 Plasma Sources Sci. Tech, 283-93
(2002) (hereafter Lieberman).

V. Georgieva et al., “Numerical study of Ar/CF4/N2 discharges in single-
and dual-frequency capacitively coupled plasma reactors”, 94 J. Appl. Phys.,
3748-56 (Sep. 15, 2003) (hereafter Georgieva).

The Rejections
The claims stand rejected under 35 U.S.C. § 103 as follows: claims 1-
3 and 10 over Demaray; claims 40-42 over Demaray in view of Dhindsa;
claims 4-9, 11 and 12 over Demaray in view of Georgieva; claims 13 and 33
over Demaray in view of Georgieva and Lieberman; claim 14 over Demaray
in view of Georgieva and Dhindsa; claims 34, 35, 37-39 and 43-46 over
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Dhindsa in view of Lieberman and Demaray;1 and claim 36 over Dhindsa in
view of Lieberman, Demaray and Georgieva.
OPINION
The rejections are affirmed as to claims 1-12, 33-37 and 39, and
reversed as to claims 13, 38 and 40-46.
Rejections of claims 1-12, 14, 33-37 and 39
Issue
Have the Appellants indicated reversible error in the Examiner’s
determination that the applied prior art would have rendered prima facie
obvious, to one of ordinary skill in the art, supplying first and second RF
signals to the same electrode in an etch chamber such that an interaction
between the signals controls at least one characteristic of a plasma in the
etch chamber?
Findings of Fact
Demaray discloses a bias sputtering process which simultaneously
deposits and etches a film (¶ 0048). The sputtering process can be a dual
frequency RF sputtering process in which both high frequency RF power,
typically 13.56 MHz, and low frequency power, typically about 100-
400 kHz, are applied to a sputtering target which acts as a cathode (¶¶ 0011,
0024, 0043). Typically the high frequency RF power is about 500-
5000 watts and the low frequency RF power is about 500-2500 watts, with
the low frequency RF power being about 1/10 to about 3/4 of the high

1 The Examiner omits Demaray from the statement of the rejection, but
includes Demaray in the discussion of the rejection (Ans. 12), and in the
Reply Brief the Appellants presume that this rejection is over Dhindsa,
Lieberman and Demaray (Reply Br. 11-12). Hence, we include Demaray in
this rejection.
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frequency RF power (¶ 0043). The high frequency RF power is chiefly
responsible for sputtering the target material and the low frequency RF
power causes plasma ions to bombard the film being deposited on a
substrate, resulting in sputtering and densification of the film. See id.
Substrate bias is provided by RF power applied to the substrate (¶ 0046).
The substrate bias RF power can be similar to the 13.56 MHz high
frequency power or can be in the low frequency RF range. See id. “When
power is applied to the substrate, a so-called plasma sheath is formed”
(¶ 0047). “The effects of adding substrate bias are akin to, but more
dramatic than, the effects of adding the low frequency RF component to the
sputter source.” See id.
Dhindsa discloses a plasma etching process wherein dual RF
frequencies, for example 2 MHz and 27 MHz, are simultaneously applied to
a substrate holder (chuck 202, 302) during etching (¶¶ 0023, 0029).
Georgieva discloses RF plasma etching simulations which compare
single (13.56 MHz) and dual (2 + 27 MHz) frequencies (abstract).
Liebermann discloses mathematical model results which show plasma
electric field directions and contours as a function of plasma sheath edge and
radial edge at frequencies of 13.56 MHz and 40.7 MHz (Figs. 8 and 10).
Analysis
The Appellants argue with respect to claim 1 that Demaray merely
discloses (¶ 0043) RF signals applied to the target to provide independent
control of different plasma characteristics and that Demaray is silent as to
any interaction between the RF signals (Br. 4-6; Reply Br. 5-6). The
Appellants argue that Demaray does not teach or suggest either an effect on
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the plasma caused by an interaction between the two RF signals or control of
that effect via control over the interaction (Br. 6-7).
The Appellants’ RF frequencies also provide independent control of
different plasma characteristics. “For example, high frequencies effect
ionization and dissociation, while lower frequencies effect sheath
modulation” (Spec. ¶ 0039). As indicated by the Appellants’ Figure 3 the
interaction is an inherent result of the RF high and low frequencies being
applied to the same electrode. Because Demaray’s RF high and low
frequencies also are applied to the same electrode (¶ 0043), it appears that
like the Appellants’ high and low frequencies, they necessarily interact.
Hence, the burden has shifted to the Appellants to show that there is no
interaction, and the Appellants have not carried that burden. See In re Best,
562 F.2d 1252, 1255 (CCPA 1977):
Where, as here, the claimed and prior art products are identical or
substantially identical, or are produced by identical or substantially
identical processes, the PTO can require an applicant to prove that the
prior art products do not necessarily or inherently possess the
characteristics of his claimed product. [citation omitted] Whether the
rejection is based on “inherency” under 35 USC 102, on “prima facie
obviousness” under 35 USC 103, jointly or alternatively, the burden
of proof is the same, and its fairness is evidenced by the PTO’s
inability to manufacture products or to obtain and compare prior art
products.

As for the Appellants’ argument that Demaray does not disclose control of
an effect on a plasma by control over the interaction (Br. 7), the Appellants
exert control over the interaction by controlling the ratio between the high
and low frequency RF power sources; as stated in the Appellants’
Specification, “[a]djusting the ratio between the source 122 and 123 controls
the characteristics of the plasma” (Spec. ¶ 0019). Demaray likewise adjusts
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the ratio of the high frequency and low frequency RF power (¶ 0043, “the
low frequency power is from about a tenth to about three quarters of the high
frequency power”). Hence, it appears that like the Appellants, Demaray
controls plasma characteristics via an interaction between the high and low
frequency RF signals. The Appellants, therefore, have the burden of
providing evidence to the contrary, and the Appellants have not carried that
burden. See Best, 562 F.2d at 1255.
Regarding claim 2 which requires that “the plasma characteristic is at
least sheath modulation” the Appellants argue that Demaray discloses that a
separate bias signal is used to create a plasma sheath about the substrate
(¶ 0047), and that Demaray does not teach or suggest using an interaction
between two RF signals to control plasma sheath modulation (Br. 8; Reply
Br. 6-7).
Demaray discloses that substrate bias power can be either at the
13.56 MHz high frequency or in the range of the low frequency RF, and that
“[w]hen power is applied to the substrate, a so-called plasma sheath is
formed” (¶¶ 0046-47). That disclosure combined with Demaray’s disclosure
that “[t]he effects of adding substrate bias are akin to, but more dramatic
than, the effects of adding the low frequency RF component to the sputter
source” (¶ 0047) indicates that the low frequency RF power applied to the
sputter source (¶ 0043) contributes to the formation of a plasma sheath. The
Appellants disclose that “RF sources 122, 123 provide bias power that both
self-biases the substrate and modulates the plasma sheath” (Spec. ¶ 0019).
The Appellants disclose that “RF sources 122[low frequency source], 123
[high frequency source] provide up to about 10,000 Watts of total RF power
in a predetermined power ratio from the source 122 to the source 123
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between 1:0 and 0:1.” See id. Similarly, Demaray’s low frequency and high
frequency power sources provide up to 7,500 Watts at a low frequency to
high frequency ratio between about 0.1 and about 0.75. See id. Thus, it
appears that like the Appellants’ high frequency and low frequency RF
power sources, Demaray’s low frequency and high frequency RF power
sources modulate a plasma sheath. Consequently, the burden has shifted to
the Appellants to provide evidence to the contrary, and the Appellants have
not carried that burden. See Best, 562 F.2d at 1255.
The Appellants argue that Demaray fails to teach or suggest the
claim 10 requirement that “the plasma characteristic is at least a power
distribution within the plasma” (Br. 8-9; Reply Br. 7-8).
The Appellants disclose that their RF power sources 122 and 123
provide up to about 10,000 Watts of total RF power and that adjusting the
ratio between sources 122 and 123 controls the characteristics of the plasma
(Spec. ¶ 0019). Demaray’ low frequency and high frequency power sources
provide, respectively, about 500 to 2,500 Watts and about 500 to
5,000 Watts, and the low frequency to high frequency power ratio is
adjusted between about 0.1 and about 0.75 (¶ 0043). Therefore, it appears
that like the Appellants’ adjustment of their low frequency to high frequency
RF power source ratio, Demaray’s adjustment of the low frequency to high
frequency RF power source ratio provides an interaction which controls
power distribution within the plasma. Thus, the burden has shifted to the
Appellants to provide evidence to the contrary, and the Appellants have not
carried that burden. See Best, 562 F.2d at 1255.
Regarding claim 4 which requires that “the first RF signal provides a
broad ion energy distribution and the second RF signal provides a peaked,
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well defined ion energy distribution” the Appellants argue that Georgieva
fails to teach or suggest that an interaction between frequencies can be used
to control plasma properties (Br. 10-11; Reply Br. 9).
As discussed above, Demaray’s low and high frequencies appear to
have such an interaction. The Appellants’ Figure 3 indicates that the broad
and peaked ion energy distributions required by claim 4 are an inherent
result of low and high frequency RF being applied to the same electrode.
One such electrode is the backing plate (25) of Demaray’s sputtering target
(Fig. 1a).
With respect to claim 9 which requires “supplying a third RF signal to
a second electrode to form the plasma” the Appellants argue that Demaray
does not teach or suggest that claim requirement (Br. 12).
Demaray’s disclosures that the bias power to the substrate can be
similar to the high frequency RF power applied to the sputtering target and
that the high frequency RF power applied to the sputtering target is chiefly
responsible for sputtering material off the target (via the plasma which is
formed) (¶¶ 0043, 0046) indicate that like the high frequency RF power
applied to the sputtering target, the high frequency RF power applied to the
substrate contributes to the formation of the plasma.
Regarding claim 11 which requires that “the first and second RF
signals provide similar plasma excitation properties and different spatial
uniformity profiles” the Appellants argue that Georgieva’s Figures 2 and 3
fail to teach or suggest a modification of Demaray that would result in
spatial distributions that vary as a function of frequency (Br. 12).
Because, like the Appellants (Spec. ¶ 0019), Demaray uses low and
high RF frequencies (¶ 0043), it appears that like the Appellants’ low and
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high RF frequencies Demaray’s low and high frequencies provide different
spatial uniformity profiles.
The Appellants argue regarding claim 12 which requires that “the
interaction between the first and second RF signals is a varying effect on the
power distribution in the plasma”, that Georgieva fails to teach or suggest a
modification to Demaray that results in that claim requirement (Br. 13).
Because, like the Appellants (Spec. ¶ 0019), Demaray can vary the
ratio of low frequency RF power to high frequency RF power (¶ 0043), it
appears that like the Appellants’ interaction Demaray’s interaction between
the low and high frequency RF signals discussed above can have a varying
effect on the power distribution in the plasma.
Regarding claim 14 which requires that “the interaction between the
first and second RF signals is used to control the uniformity of a plasma
enhanced etch process” the Appellants argue that Demaray discloses a
different method (¶¶ 0029-30) for controlling uniformity (Br. 16-17).
The Appellants’ claim 14 does not require that only the interaction
between the first and second RF signals is used to control the plasma
uniformity. Demaray’s disclosure that the application of the RF power to
the target periphery is uniform (¶ 0040) indicates that Demaray’s application
of low frequency and high frequency RF power and their apparent inherent
interaction as discussed above contribute to plasma uniformity.
With respect to claim 33 which requires that “the first RF signal has a
frequency of about 2 MHz and the second RF signal has a frequency of
about 13.56 MHz” the Appellants argue that none of the references teach or
suggest that frequency is a result effective variable (Br. 15).
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Demaray’s teaching that the RF power low frequency of about 100 to
400 kHz is typical (¶ 0043) would have led one of ordinary skill in the art,
through no more than ordinary creativity, to use other low frequencies which
are known in the art in dual frequency devices for forming plasmas, such as
the 2 MHz disclosed by Georgieva (abstract). See KSR Int’l. Co. v. Teleflex
Inc., 550 U.S. 398, 418 (2007) (In making an obviousness determination one
“can take account of the inferences and creative steps that a person of
ordinary skill in the art would employ”).
The Appellants’ arguments concerning claims 34, 36 and 37 are
similar to those set forth with respect to claims 1, 10 and 33 (Br. 17-19), and
are not persuasive for the reasons given above regarding those claims.
Conclusion of Law
The Appellants have not indicated reversible error in the Examiner’s
determination that the applied prior art would have rendered prima facie
obvious, to one of ordinary skill in the art, supplying first and second RF
signals to the same electrode in an etch chamber such that an interaction
between the signals controls at least one characteristic of a plasma in the
etch chamber.
Rejections of claims 13, 38 and 40-46
Issue
Have the Appellants indicated reversible error in the Examiner’s
determination that the applied prior art would have rendered prima facie
obvious, to one of ordinary skill in the art, 1) a combined effect of first and
second RF signals that produces a substantially flat power distribution
(claims 13 and 38), or 2) positioning beneath a substrate support surface an
electrode to which first and second RF signals are applied (claims 40-46).
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Analysis
Regarding claims 13 and 38 the Examiner argues that “Lieberman
teaches how spatial power distribution (page 287) depends on frequency”
(Ans. 9) and that “Lieberman teaches radial plasma electric field distribution
for different frequencies (see Figs. 8 and 10)” (Ans. 16). The Examiner
argues that “[o]ne of ordinary skill in the art would be motivated [to] modify
the method of Demaray to include the teachings of Lieberman in order to
obtain a highly uniform process area which is desirable for plasma
processing in general by combining two frequencies with complementing
energy or power distributions” (Ans. 9-10).
The Appellants argue that Lieberman in no way teaches or suggests
that the 13.56 MHz frequency in Figure 8, the 40.7 MHz frequency in
Figure 10, or any combinations of frequencies may be complementary or
may be combined to form a net power distribution that is substantially
uniform (Br. 14).
Lieberman’s Figures 8 and 10 relied upon by the Examiner disclose
mathematical model results which show plasma electric field directions and
contours as a function of plasma sheath edge and radial edge at frequencies
of 13.56 MHz and 40.7 MHz. The Examiner has not explained how that
disclosure would have led one of ordinary skill in the art to apply combined
RF frequencies to the same electrode such that a substantially flat power
distribution is obtained as required by claims 13 and 38.
With respect to the requirement of claims 40-46 that the first electrode
is positioned beneath a substrate support surface in the etch chamber the
Examiner relies upon Dhindsa workpiece holder (chuck 202) to which dual
frequency RF is applied (¶¶ 0024, 0029; Fig. 2), and argues that “it would
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have been obvious to one of ordinary skill in the art at the time the invention
was made to select the position of first electrode below the substrate surface
in the etch chamber because Dhindsa illustrates that positioning of the
substrate would improve process uniformity across the entire wafer surface
(paragraph 0026)” (Ans. 5).
The Appellants argue that modifying Demaray’s apparatus as
proposed by the Examiner would impermissibly change its principle of
operation and make it unsuitable for its intended purpose (Br. 9).
Dhindsa discloses in paragraph 0026 relied upon by the Examiner that
“[d]ue to the geometry of the upper electrode 208 and the chuck 202, the
field lines may not be uniform across the wafer surface and may vary
significantly at the edge of the wafer 204.” Dhindsa obtains plasma
uniformity by use of a focus ring (218) (¶ 0026). The Examiner has not
pointed out where Dhindsa would have indicated to one of ordinary skill in
the art that the position below the wafer of the chuck (202) to which dual
frequency RF is applied provides plasma uniformity. Also, the Examiner
has not explained why one of ordinary skill in the art would have used the
location of the substrate holder (chuck 202) in Dhindsa’s etching apparatus
as the location of Demaray’s sputtering apparatus’s sputter target’s backing
plate (25) to which dual frequency RF is applied (Fig. 1a).
Conclusion of Law
The Appellants have indicated reversible error in the Examiner’s
determination that the applied prior art would have rendered prima facie
obvious, to one of ordinary skill in the art, 1) a combined effect of first and
second RF signals that produces a substantially flat power distribution
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(claims 13 and 38), or 2) positioning beneath a substrate support surface the
electrode to which first and second RF signals are applied (claims 40-46).
DECISION/ORDER
The rejections under 35 U.S.C. § 103 of claims 1-3 and 10 over
Demaray, claims 4-9, 11 and 12 over Demaray in view of Georgieva,
claim 14 over Demaray in view of Georgieva and Dhindsa, and claim 36
over Dhindsa in view of Lieberman, Demaray and Georgieva are affirmed.
The rejection under 35 U.S.C. § 103 of claims 13 and 33 over Demaray in
view of Georgieva and Lieberman is reversed as to claim 13 and affirmed as
to claim 33. The rejection under 35 U.S.C. § 103 of claims 34, 35, 37-39
and 43-46 over Dhindsa in view of Lieberman and Demaray is affirmed as to
claims 34, 35, 37 and 39 and reversed as to claims 38 and 43-46. The
rejection of claims 40-42 over Demaray in view of Dhindsa is reversed.
It is ordered that the Examiner’s decision is affirmed-in-part.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a).

AFFIRMED-IN-PART

kmm

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