Ex Parte Benjamin et al

Patent Trial and Appeal Board

Sep 18, 2014

12436443 (P.T.A.B. Sep. 18, 2014)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________

Ex parte NEIL BENJAMIN
and
ROBERT STEGER
____________

Appeal 2012-000774
Application 12/436,443
Technology Center 3700
____________

Before JAMES T. MOORE, CHARLES N. GREENHUT, and
JILL D. HILL, Administrative Patent Judges.

MOORE, Administrative Patent Judge.
DECISION ON APPEAL

The Appellants1 have appealed from the final rejection of claims 24–
37 and 40–47 under 35 U.S.C. §6(b).
We have jurisdiction pursuant to 35 U.S.C. § 134.
For the reasons stated hereinafter, we affirm-in-part the rejections of
record.
BACKGROUND
The present invention relates to a chuck which holds a semiconductor
wafer for processing in a plasma processor. Plasma processing generates

1 The real party in interest is Lam Research Corporation. Br. 1.
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00774
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Appeal 2012-000774
Application 12/436,443

3

24. A method for controlling the spatial temperature
across a semiconductor wafer during a multistep plasma etching
process wherein wafer temperature is changed for the particular
layer being etched comprising:
maintaining a base at a constant temperature, said
constant temperature being below the temperature of the
substrate, said base having a layer of thermal insulation material
mounted on top of said base;
electrostatically clamping the substrate against a top face
of a flat support having a plurality of spatial regions, said flat
support mounted on top of said layer of thermal insulation
material;
plasma etching a layer on the wafer under conditions
such that local concentration of reactants varies across the
wafer;
independently heating each spatial region of said flat
support with a plurality of heaters mounted to an underside of
said flat support so as to induce a radial temperature gradient
which compensates for the local reactant concentration; and
changing the temperature of at least one spatial region of
said flat support during the multistep etching process at a rate of
at least 1 °C per second.

THE REJECTIONS
Claims 24–37, 40–43, 46 and 47 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over Arami.2
Claims 44 and 45 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over Arami in view of Kuibira.3

2 U.S. 5,591,269, issued January 7, 1997.
3 U.S. 6,365,879 B1, issued April 2, 2002.
Appeal 2012-000774
Application 12/436,443

4

DISCUSSION
I. The Rejection of Claims 24–37, 40–43, 46 and 47 under 35
U.S.C. § 103(a) as being unpatentable over Arami
The Examiner has found that Arami describes plasma etching of a
semiconductor wafer. Ans. 4.
More specifically, the Examiner has made a finding that Arami
describes controlling of the temperature across the wafer by changing the
temperature with a base for maintaining a temperature below the
temperature of the wafer. The Examiner has found that the base of Arami
includes cooling water and a thermal layer mounted on the top of the base
providing a thermal impedance break. Id.
The Examiner also found that Arami describes flat supports including
electrodes to electrostatically clamp or chuck the wafer on the flat support.
Id.
The Examiner also has found that Arami describes a plurality of
independent heaters in specific spatial regions inducing a radial temperature
gradient by changing the temperatures in their respective heating spatial
regions. Ans. 4–5. The Examiner finds that Arami describes that the heater
elements are provided on the underside of the flat support, or alternatively
embedded within the flat support. Ans. 5.
The Examiner admits that Arami does not explicitly describe an
etching process with a spatial region having a temperature change rate of at
least 1° Celsius per second. Id.
The Examiner finds that Arami describes a controller which controls
the heaters to set desired temperatures when temperature sensors in the
respective regions sense and input signals to the controller to effect
temperature changes. By turning the heaters on and off, the flat support is
Appeal 2012-000774
Application 12/436,443

5

independently heated in respective regions to desired temperatures to control
the heat transfer medium. Id.
As such, the Examiner concludes that it would have been obvious to
one of ordinary skill in the art at the time the invention was made to adapt
the controller of Arami to provide the etching process at the recited
temperature change rate (or any other rate to provide the desired etching or
heating process). The Examiner finds that this would have been a matter of
a routine experimentation and lacks criticality. Id.
The Examiner also concludes that it would have been obvious to one
of ordinary skill at the time the invention was made to utilize the process for
a subsequent etching process of multistep etching process to perform etching
applications as desired by a user as a matter of a routine application. Id.
With respect to the heat flux impinging on the wafer, the Examiner
finds that heat flux would necessarily be present in the process of Arami, as
in normal and usual operation plasma is generated. Ans. 5–6.
Finally, the Examiner finds that the base of Arami is maintained at the
recited range below the temperature of the substrate, as Arami describes a
controller which controls the base by supplying cooling water to provide a
cooling temperature that further maintains a desired temperature to the
substrate. Ans. 6.
The Examiner concludes that it would have been obvious to one of
ordinary skill in the art at the time the invention was made to adapt the
cooling temperature within the recited range (or any other suitable range that
would further enhance the rate of cooling of the heated substrate to maintain
the desired heating temperature). Id.
Figure 18 of Arami is reproduced below:
App
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00774
/436,443
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Appeal 2012-000774
Application 12/436,443

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plasma etching a layer on a wafer under conditions such that
local concentration of reactants varies across the wafer (Claim
24).
Applicants discovered that the local concentration of
reactants can be compensated for by altering the wafer support
zone temperatures to induce a radial temperature gradient
(specification at paragraph [0031]. Arami seeks to achieve
uniform temperature and thus cannot suggest the claimed step
of independently heating each spatial region so as to induce a
radial temperature gradient which compensates for local
concentration of reactants varies across the wafer (Claims 24
and 31).
App. Br. 12.
These arguments are unpersuasive of error.
We note that the very outset of the Arami specification states that the
Arami process “relates to a vacuum processing apparatus for performing a
process such as film formation, etching, or the like with respect to a target
object in a vacuum.” Arami 1:6–9. While it is true that Arami does not
describe plasma etching in great detail, a patent specification need not
describe in detail that which is already well known to those of ordinary skill
in the art. We do not find error with the Examiner applying the Arami
apparatus to a plasma etching process generally.
As regards the argument that Arami seeks uniform temperature, we
find that the Appellants are reading the disclosure of Arami far too narrowly.
Arami teaches precise control of spatial regions utilizing both cooling and
heating with multiple heaters to customize a “plurality of desired regions on
the surface of the mounting table that can be independently heated and
insulated at desired temperatures.” Arami 16:65–67, see also 16:38–65.
Appeal 2012-000774
Application 12/436,443

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Moreover, the Examiner has correctly pointed out another instance of
thermal gradient based upon a concentration boundary layer of gas. Arami
17:11–22 and 23–30.
Finally, as acknowledged by the Appellants, Arami specifically sets
up a gradient on a wafer to be treated. Id. at 18:3–12 (500, 450, and 400
degrees Celsius). The Appellants are correct that that specifically cited
embodiment does not use plasma, but we read the specification as
instructing one of ordinary skill in the art that etching is a viable use of the
apparatus as well.
The Appellants raise the argument that identification of the problem
being solved must be taken into account. They assert that the problem—
local concentration of reactants—can be compensated for by the solution—
altering the wafer support zone temperatures to induce a radial temperature
gradient. App. Br. 12.
We do agree that sometimes identification of the problem to be solved
can provide the basis of a patentable invention. However, the Arami
reference in this instance recognizes the problems of thermal control in
wafer processing, and effectively solves them. Arami uses a gradient for
differing gas concentrations, a similar concept. Arami also suggests etching
as a use for their apparatus. In this instance, we find the balance of evidence
favors the Examiner’s conclusion that the claimed subject matter is
unpatentable.
Claims 30 and 37 are argued separately by the Appellants. Each
requires changing temperature in one or more of the spatial regions by less
than 10oC.

Appeal 2012-000774
Application 12/436,443

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The Final Rejection notes that it:
would have been obvious to one of ordinary skill in the art to
adapt the controller of Arami that can also provide the etching
process at the recited rate or any other rates to adequately and
sufficiently provide the desired etching or heating process as a
matter of a routine experimentation and lacking criticality.
Fin. Rej. 3 (emphasis added).
The Appellants argue that the Final Rejection fails to address claims
30 and 37, and the Arami reference only discusses 50 degree intervals. As a
consequence, they urge reversal is warranted. App. Br. 15.
We disagree. While the Final Rejection did not discuss claims
separately, the Examiner did conclude that any other rates would have been
an obvious adaptation of the controller. Appellants have placed no
persuasive argument or evidence in the record as to why the Examiner’s
conclusion is in error.
Claims 40 and 41 are argued separately by the Appellants as well.
The claims each recite that heat flux impinging on the wafer from the plasma
is “less than 2 W/cm2.”
The Examiner made a finding that
[w]ith respect to the heat flux impinging on the wafer, it
is noted that such heat flux would also necessarily be performed
in Arami as the Arami device is substantially [the] same as that
of the applicant's described device in the specification and is
carried out in the normal and usual operation as plasma is
generated. Also see 2112.02.
Fin. Rej. 3.
According to the Appellants, Arami does not disclose processing a
wafer wherein heat flux from the plasma is less than 2 W/cm2. It is urged
Appeal 2012-000774
Application 12/436,443

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that Arami is directed at heating a wafer to at least 400°C to perform CVD
in a non-plasma environment.
On the record before us, we are constrained to reverse this rejection
for lack of evidence. The Examiner seems to be indicating that Arami’s
apparatus, when used in a plasma etch, would inherently have this limitation
of less than 2 W/cm2, but only because it is the same as the Appellants’
apparatus.
However, we can not find in the record that this limitation was either
admitted to be known in the art (e.g. in the Appellants’ Specification) or
within the normal flux impingement from plasma (established by a reference
or other evidence). We have only an assumption it would be the same as the
Appellants’ method, without sufficient evidence to support that assumption.
As a consequence, no prima facie case of unpatentability exists.
Accordingly, the rejection of claims 40 and 41 is reversed.
Claims 46 and 47 are also argued separately. Each recites that the
base is maintained at a temperature that is 10 to 50°C below the wafer
temperature.
The Final Rejection has this to say about the base temperature:
With respect to the base that is maintained at the recited
range below the temperature of the substrate, Arami teaches
that a controller (119) which controls the base which supplies a
cooling water to provide a cooling temperature that further
maintains a desired temperature to the substrate, and it would
have been obvious to one of ordinary skill in the art to adapt the
cooling temperature within the recited range or any other
suitable range that would further enhance the rate of cooling
effects to the heated substrate to maintain the desired heating
temperature.
Fin. Rej. 4 (emphasis added).
Appeal 2012-000774
Application 12/436,443

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The Appellants urge that Arami heats the wafer to a temperature of
800°C (column 10, line 34) or at least 400°C (column 18, lines 3–12), thus
teaching away from the method recited in claims 46 and 47. Additionally,
they urge that the Final Rejection fails to specifically address claims 46 and
47.
We again must disagree. While the Final Rejection did not discuss
claims separately, the Examiner did make a finding that any other cooling
temperature would have been an obvious adaptation of the controller of
Arami. Appellants have placed no persuasive argument or evidence in the
record as to why the Examiner’s conclusion is in error.
II. The Rejection of Claims 44 and 45 under 35 U.S.C. § 103(a)
as being unpatentable over Arami and Kuibira
Claims 44 and 45 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over Arami and Kuibira.
The Examiner has found that Arami shows the method claimed except
for the layer of thermal insulation having a thermal conductivity of .05 to .20
W. The Examiner relies upon the description in Kuibira to show a heater
having a thermal insulator having a thermal conductivity of 10W/mk or less.
The Examiner then concludes that it would have been obvious to one
of ordinary skill in the art at the time the invention was made to provide
Arami with a thermal insulator having the claimed thermal conductivity to
improve the thermal insulation while preventing undesired heat loss. Fin.
Rej. 4.
The Appellants urge that
Kuibira describes a wafer holder having a layer of ceramic [4]
bonded to an ESC electrode 3, plasma generating electrode 2
and heater 1 such that the ceramic layer below the heater
Appeal 2012-000774
Application 12/436,443

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prevents “heat from escaping toward the portion under the
heater (backside) and thus efficiently heat a wafer located on
the wafer holding surface”
App. Br. 16 (citing Kuibira 2:29–39, 48–56; 9:11–14).
The Appellants urge that Kuibira’s wafer holder does not include a
base maintained at a constant temperature, but instead seeks to prevent heat
flow below the heater so that the wafer can be rapidly heated to temperatures
of 700°C. Id. (citing Kuibira 3:4; 7:51–52; 8:18–19,41–42; 9:1–2).
The Appellants conclude that that the addition of the heat insulator of
Kuibira to Arami would prevent heat flow and thus lead away from the
claimed “thermal impedance break” between the base and the flat support as
recited in claims 43 and 44.
The Examiner disagrees, finding that Kuibira shows substantially the
same structure—having a thermal insulation between the base and the flat
support (citing Kuibira Figures 1 and 2). Ans. 8.
It appears to us that the evidence supports the Examiner’s position.
The insulation layer in Figures 1 and 2 of Kuibira would have the same
function in both Kuibira’s heater as well as the instantly claimed process.
The Appellants have not provided persuasive evidence otherwise.
Accordingly, we affirm this rejection.

Appeal 2012-000774
Application 12/436,443

13

CONCLUSION
Accordingly, we are persuaded of error on the Examiner’s part
as regards claims 40 and 41. However, we are unpersuaded on all
other grounds, and conclude that a preponderance of evidence in the
record supports the rejections.
DECISION
The rejection of claims 24–37, 42, 43, 46 and 47 under 35 U.S.C.
§ 103(a) as being unpatentable over Arami is affirmed.
The rejection of claims 40 and 41under 35 U.S.C. § 103(a) as being
unpatentable over Arami is reversed.
The rejection of claims 44 and 45 under 35 U.S.C. § 103(a) as being
unpatentable over Arami in view of Kuibira is affirmed.

AFFIRMED-IN-PART

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