Ex Parte Mantz et al

Board of Patent Appeals and Interferences

Oct 30, 2009

10960327 (B.P.A.I. Oct. 30, 2009)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte ULRICH MANTZ, PETER WEIDNER,
RALPH WIENHOLD, and PIERRE-YVES GUITTET
____________

Appeal 2009-003539
Application 10/960,327
Technology Center 2800
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Decided: October 30, 2009
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Before HOWARD B. BLANKENSHIP, JEAN R. HOMERE, and
STEPHEN C. SIU, Administrative Patent Judges.

BLANKENSHIP, Administrative Patent Judge.

DECISION ON APPEAL
STATEMENT OF THE CASE
This is an appeal under 35 U.S.C. § 134(a) from the Examiner’s final
rejection of claims 1, 3-6, and 8-14, which are all the claims remaining in the
application. We have jurisdiction under 35 U.S.C. § 6(b).
We affirm.
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Invention
Appellants’ invention relates to a method for determining or
inspecting a lateral dimension or a volume of a recess in a layer at a surface
of a substrate or a property of a material arranged in the recess. The layer
having the recess is irradiated with an electromagnetic scanning radiation
having a wavelength that is greater than a lateral dimension of the recess,
and an electromagnetic response radiation that emerges from an interaction
of the scanning radiation with the layer having the recess is received.
Characterization data, which characterize the interaction between the layer
having the recess and the scanning radiation, are ascertained from the
received electromagnetic response radiation, the characterization data
mapping the lateral dimension or the volume of the recess or the property of
the material arranged in the recess. The lateral dimension or the volume of
the recess or the property of the material arranged in the recess is determined
or inspected on the basis of the characterization data. Abstract.

Representative Claim
1. A method for inspecting a recess in a layer at a surface of a
substrate, comprising:
irradiating the layer having the recess with an electromagnetic
scanning radiation having a wavelength greater than a lateral
dimension of the recess, wherein the scanning radiation is linearly
polarized;
receiving an electromagnetic response radiation resulting from
an interaction between the scanning radiation and the layer having the
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recess, wherein the step of receiving the electromagnetic response
radiation comprises ascertaining the polarization of the response
radiation;
ascertaining characterization data, from the received
electromagnetic response radiation, wherein the characterization data
characterize the interaction between the layer having the recess and
the scanning radiation and maps at least one of a lateral dimension of
the recess, a volume of the recess and a property of a material
disposed in the recess;
postulating a model structure comprising one or more model
layers with one or ore free parameters;
calculating model characterization data that characterize an
interaction of the model structure with the scanning radiation, the
model characterization data being dependent on the free parameter;
ascertaining one or more values of the one or more free
parameters for which the model characterization data and the
characterization data are substantially similar; and
determining at least one of the lateral dimension of the recess,
the volume of the recess and the property of the material disposed in
the recess based on the ascertained one or more values of the one or
more free parameters.

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Prior Art
Michaelis 6,031,614 Feb. 29, 2000
Halle EP 1 018 632 A2 Jul. 12, 2000

Shoaib Zaidi, et al., FTIR-based Non-destructive Method for
Metrology of Depths in Poly Silicon Filled Trenches, Metrology, Inspection
and Process Control for Microlithography XVII, Proceedings of SPIE, Vol.
5038, pages 185-190 (May 2003) (“Zaidi”).

Examiner’s Rejections
Claims 1, 3-6, and 8-14 stand rejected under 35 U.S.C. § 112, second
paragraph, as being indefinite for failing to particularly point out and
distinctly claim the subject matter which Appellants regard as the invention.
Claims 1, 3, 5, 6, 8, and 10-14 stand rejected under 35 U.S.C. § 103(a)
as being unpatentable over Zaidi and Michaelis.
Claims 4 and 9 stand rejected under 35 U.S.C. § 103(a) as being
unpatentable over Zaidi, Michaelis, and Halle.

Claim Groupings
Based on Appellants’ arguments in the Appeal Brief, we will decide
the appeal with respect to the rejections over the prior art on the basis of
claim 1. See 37 C.F.R. § 41.37(c)(1)(vii).

ISSUES
(1) Have Appellants shown that the Examiner erred in concluding
that claims 1, 3-6, and 8-14 are indefinite under 35 U.S.C. § 112, second
paragraph, for failing to particularly point out and distinctly claim the
subject matter which Appellants regard as the invention?
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(2) Have Appellants shown that using polarized light as disclosed
by Michaelis in the ellipsometric measurement method as disclosed by Zaidi
does anything more than yield the predictable result of determining sizes of
features on a semiconductor device as taught by Michaelis?

FINDINGS OF FACT
Zaidi
1. Zaidi discloses a method that uses Fourier Transform Infrared
(FTIR) Reflectance spectroscopy to determine the recess depths of poly
silicon filled trenches. The method is non-contact and non-destructive. A
large number of points per wafer can be measured to determine etch
uniformity. Unlike cross section SEM based metrology, the wafer does not
need to be cleaved, and thereby destroyed for metrology. The technique is
thus suited for in-line metrology of product wafers. The FTIR method was
found to be very robust, and provided an excellent correlation with SEMs for
110 nm trenches. The method is a viable manufacturing solution for in-line,
non-destructive, rapid metrology on product wafers. Abstract.
2. Optical, IR-based metrology has been successfully applied to
trench recess measurements. The FTIR technique allows rapid feedback of
etch chamber performance, since measurements are fast (of the order of
seconds) and are taken on actual product wafers. All the wafers from the lot
can then be immediately processed, thus avoiding variations introduced by
changes in etch chamber conditions. The FTIR technique has also shown
good performance in determining etch depths across multiple sites on a
wafer. The sampling density can be easily increased without requiring
significant increases in time or other resources. Thus, additional data points
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can be acquired inexpensively. The use of smaller ground rules is not a
problem for FTIR measurements, because the IR light will still be sensitive
to trench effects independently of their width. Finally, another advantage is
that the IR light actually probes a region of trenches, not individual ones as
with SEM. Section 1.2.
3. The measurement principle is outlined in Figure 2, where the
incoming infrared beam (shown at two wavelengths, displaced laterally for
clarity) is shown reflecting off the trench surfaces. Section 2.1.
4. The reflectance from multiple layered films is well understood
and can be accurately simulated by using Fresnel’s reflection equations.
Such modeling is very commonly used in ellipsometric measurements for
thin film thickness and composition determination. The reflectance analysis
method involves fitting a simulated reflectance spectrum (calculated using a
multilayered film stack model) to the measured data. Each layer is defined
by its thickness and optical properties (spectral n and k). During the fit,
parameters such as the recess depth and other parameters of interest are
iteratively varied to fit the measured spectrum. To accurately model the
optical properties of vertical transistor structures, “effective medium”
approximations have been used to calculate the “effective” index of
refraction of non-homogeneous structures or films (such as a trench/silicon
“film”). Section 2.2.
Michaelis
5. Michaelis discloses a measurement system and method for
measuring critical dimensions using ellipsometry. Title.
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6. The system and method measures sub-quarter micron
dimensions in semiconductor devices, which are known as critical
dimensions. Col. 1, ll. 6-10.
7. The system includes a radiation source for providing radiation
incident on a surface having surface features. A radiation detecting device is
provided for measuring characteristics of the incident radiation after being
reflected from the surface features. A rotating stage rotates the surface such
that incident light is directed at different angles due to the rotation of the
rotating stage. A processor is included for processing the measured
characteristics of the reflected light and correlating the characteristics to
measure the surface features. Col. 1, l. 66 to col. 2, l. 10.
8. In alternate embodiments of the system, the measured
characteristics of the reflected light may be correlated to surface features by
a formula relation between a complex index of refraction of the light and
dimensional feature size. The surface features may include features
extending substantially parallel to the surface and/or thicknesses extending
substantially perpendicular to the surface. The incident radiation may
include linearly polarized light. The reflected radiation may include
elliptically polarized light. The radiation source and detecting device
preferably includes a conventional ellipsometer. The measured
characteristics of the reflected light may be correlated to surface features by
an empirical calibrated relationship between the characteristics of the
reflected light and dimensional feature sizes. The surface features below a
length of about 250 nanometers are preferably measurable. Col. 2, ll. 11-25.

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PRINCIPLES OF LAW
Indefiniteness
The function of claims is (1) to point out what the invention is in such
a way as to distinguish it from the prior art; and (2) to define the scope of
protection afforded by the patent. In re Vamco Machine & Tool, Inc., 752
F.2d 1564, 1577 n.5 (Fed. Cir. 1985). The legal standard for definiteness is
whether a claim reasonably apprises those of skill in the art of its scope. In
re Warmerdam, 33 F.3d 1354, 1361 (Fed. Cir. 1994). The inquiry is merely
to determine whether the claims do, in fact, set out and circumscribe a
particular area with a reasonable degree of precision and particularity. In re
Moore, 439 F.2d 1232, 1235 (CCPA 1971). The definiteness of the
language employed must be analyzed -- not in a vacuum, but in light of the
teachings of the prior art and of the particular application disclosure as it
would be interpreted by one possessing the ordinary level of skill in the
pertinent art. Id.

Obviousness
The question of obviousness is resolved on the basis of underlying
factual determinations including (1) the scope and content of the prior art,
(2) any differences between the claimed subject matter and the prior art, and
(3) the level of skill in the art. Graham v. John Deere Co., 383 U.S. 1, 17
(1966). “The combination of familiar elements according to known methods
is likely to be obvious when it does no more than yield predictable results.”
KSR Int’l Co. v. Teleflex, Inc., 550 U.S. 398, 416 (2007).

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ANALYSIS
Section 112 rejection
The Examiner finds that the recitation “a wavelength greater than a
lateral dimension of the recess” renders claim 1 indefinite because the
relationship of parts is based on the lateral dimension of an unspecified
recess (Ans. 3, 8-10). The Examiner makes a similar finding for the
recitation of “a thickness of the layer having the recess is less than the
wavelength of the electromagnetic scanning radiation” in claim 8 (Ans. 3).
Appellants contend that the Specification provides a sufficient standard for
understanding the relationship between the wavelength and a lateral
dimension of the recess (App. Br. 10-11).
The claim 1 recitation in controversy appears, on its face, to be
simple. The claim covers irradiating the layer having the recess with an
electromagnetic scanning radiation having a wavelength greater than a
lateral dimension of the recess. The claim does not cover irradiating the
layer having the recess with an electromagnetic scanning radiation having a
wavelength less than or equal to a lateral dimension of the recess.
While it is true that claim 1 does not provide a specific measurement
or quantity for the lateral dimension of the recess, the relationship between
the unspecified “dimension” and the scanning radiation wavelength appears
to be precisely set forth, such that the relationship is sufficiently defined by
any lateral dimension of the recess that is practical and supported by the
instant disclosure. Similarly, for claim 8, the thickness of the layer having
the recess is less than -- not equal to, not more than -- the wavelength of the
electromagnetic scanning radiation.
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We thus agree with Appellants to the extent that the claims reasonably
apprise those of skill in the art of their scope, and therefore pass muster
under § 112, second paragraph.

Section 103 rejection
Appellants contend that there is no suggestion or reason to combine
the teachings of Zaidi and Michaelis, because the method in Zaidi uses light
that is not polarized and the method in Michaelis uses light that is polarized
(App. Br. 13). However, the Zaidi reference does not mention whether the
light is polarized or not polarized. Appellants have provided no evidence to
support the allegation that the “FTIR method in Zaidi uses infrared light that
is not polarized.”
Zaidi discloses a method that reflects light waves from a
semiconductor device (FF 1-3). This reflectance is used to measure
dimensions of the semiconductor device using ellipsometry (FF 4).
Michaelis teaches a method of measuring dimensions of a
semiconductor device using ellipsometry (FF 5-7). This ellipsometry
measures characteristics of elliptically polarized light reflected from the
semiconductor device and correlates the measured characteristics to
dimensional sizes of the device (FF 8). The Examiner has therefore
provided evidence from the teachings of Michaelis to show that the
ellipsometry method disclosed by Zaidi can, and in all probability does, use
linearly polarized light when measuring the dimensions of features of a
semiconductor device.
Appellants have provided no evidence to show that the method of
Zaidi, or any other method for that matter, can perform ellipsometric
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measurements using light that is not polarized. Appellants simply assume
without evidence that the method of Zaidi measures characteristics of
unpolarized light, then conclude that a person of ordinary skill in the art at
the time of invention would not have used polarized light when performing
the ellipsometric measurements disclosed by Zaidi.
We find that using polarized light as disclosed by Michaelis in the
ellipsometric measurement method as disclosed by Zaidi is, at most, the
combination of familiar elements according to known methods that does no
more than yield the predictable result of determining sizes of features on a
semiconductor device as taught by Michaelis. See KSR, 550 U.S. at 416.
Appellants have provided no evidence to show that using polarized light as
disclosed by Michaelis in the ellipsometric measurement method as
disclosed by Zaidi “was uniquely challenging or difficult for one of ordinary
skill in the art.” See Leapfrog Enters., Inc. v. Fisher-Price, Inc., 485 F.3d
1157, 1162 (Fed. Cir. 2007) (citing KSR, 550 U.S. at 418-19).
We are therefore not persuaded that the claims have been rejected in
error under 35 U.S.C. § 103(a) over the applied prior art.

CONCLUSIONS OF LAW
(1) Appellants have shown that the Examiner erred in concluding
that claims 1, 3-6, and 8-14 are indefinite under 35 U.S.C. § 112, second
paragraph, for failing to particularly point out and distinctly claim the
subject matter which Appellants regard as the invention.
(2) Appellants have not shown that using polarized light as
disclosed by Michaelis in the ellipsometric measurement method as
disclosed by Zaidi does anything more than yield the predictable result of
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determining sizes of features on a semiconductor device as taught by
Michaelis.

DECISION
The rejection of claims 1, 3-6, and 8-14 under 35 U.S.C. § 112,
second paragraph is reversed.
The rejection of claims 1, 3, 5, 6, 8, and 10-14 under 35 U.S.C.
§ 103(a) as being unpatentable over Zaidi and Michaelis is affirmed.
The rejection of claims 4 and 9 under 35 U.S.C. § 103(a) as being
unpatentable over Zaidi, Michaelis, and Halle is affirmed.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a). See 37 C.F.R.
§ 41.50(f).

AFFIRMED

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