Ex Parte Staals et al

Patent Trial and Appeal Board

Jun 19, 2014

11797505 (P.T.A.B. Jun. 19, 2014)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
11/797,505 05/03/2007 Frank Staals 1857.6100000 9334
26111 7590 06/23/2014
STERNE, KESSLER, GOLDSTEIN & FOX P.L.L.C.
1100 NEW YORK AVENUE, N.W.
WASHINGTON, DC 20005
EXAMINER
PURINTON, BROOKE J
ART UNIT PAPER NUMBER
2881
MAIL DATE DELIVERY MODE
06/23/2014 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)

UNITED STATES PATENT AND TRADEMARK OFFICE
________________

BEFORE
THE PATENT TRIAL AND APPEAL BOARD
________________

Ex parte FRANK STAALS,1
Joeri Lof, Erik Roelof Loopstra, Wim Tjibbo Tel,
and Bearrach Moest
________________

Appeal 2012-004067
Application 11/797,505
Technology Center 2800
________________

Before CHUNG K. PAK, BEVERLY A. FRANKLIN, and
MARK NAGUMO, Administrative Patent Judges.

NAGUMO, Administrative Patent Judge.

DECISION ON APPEAL
Frank Staals, Joeri Lof, Erik Roelof Loopstra, Wim Tjibbo Tel, and
Bearrach Moest (“Staals”) timely appeal under 35 U.S.C. § 134(a) from the
final rejection2 of claims 1-29, which are all of the pending claims. We have
jurisdiction. 35 U.S.C. § 6. We reverse.

1 The real party in interest is listed as ASML Netherlands B.V. (Appeal
Brief, filed 27 July 2011 (“Br.”), 3.)
2 Office action mailed 9 July 2010 (“Final Rejection,” cited as “FR”). .
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OPINION
A. Introduction3
The disclosed invention relates to high resolution lithographic devices
capable of achieving an overlay error budget of 10 nm or less.
(Spec. 1 [0003].) The claimed lithographic apparatus projects an image of a
circuit pattern onto a substrate held in a substrate holder. The image
includes an alignment mark that has dimensions comparable to a critical
dimension of the circuit pattern. According to the 505 Specification,
because the alignment mark is much smaller—e.g., “1 × 1 microns at
substrate level”—than prior art alignment marks (said to be, typically,
“64 × 40 microns at substrate level” (id. at 13 [0062]), the inventive
alignment marks can be within the exposure area of the mask rather than on
the periphery of the mask exposure area (id. at [0064]). The lithographic
apparatus further incorporates a transmission image sensor (“TIS”) in the
substrate holder. In the words of the Specification, “[a] TIS is a sensor that
is used to measure at substrate level the position of a projected aerial image
of a mark pattern at mask (reticle) level.” (Id. at 2 [0004].) The
Specification explains that because the optical transmission path for the
small alignment marks is the same as for the circuit pattern, the alignment
marks will not encounter different aberrations, so deformations leading to
overlay and focus errors will be avoided. (Id. at [0005].)

3 Application 11/797,505, Image sensor, lithographic apparatus comprising
an image sensor and use of an image sensor in a lithographic apparatus,
filed 3 May 2007. We refer to the specification as the “505 Specification
and cite it as “Spec.”
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An embodiment of a lithographic apparatus of the invention is
illustrated in Figures 1 and 3, reproduced below.
{Figure 1 is shown below}
Figure 1, right,
shows a lithographic
apparatus having a light
source SO, that
illuminates patterning
device or mask MA, a
projection system PS that
projects the image of the
pattern on illuminated
mask MA onto a substrate W
or an image sensor positioned
within substrate holder WT.

{Fig. 1 shows a lithographic apparatus}
{Figure 3 is shown below}
Figure 3, right, shows final
element FE of projection
system PS immersed in liquid 3,
which is in contact with substrate
holder WT. Substrate holder WT
contains an image sensor
{Fig. 3 shows a detail of an image sensor}
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comprising lens 5 and image detector 6. The image of mask MA is
projected through lens 5 onto the surface of image detector 6, e.g., a charge-
couple detector (“CCD”).
Staals presents a claim 15, for a method of transmission image
detection, as well as claims for a lithographic projection apparatus and
associated method claims, of which independent claim 1 is representative.
These claims are presented in full infra.
The Examiner maintains the following grounds of rejection:4
A. Claim 15 stands rejected under 35 U.S.C. § 102(b) in view of
Grodnensky.5
B. Claims 1-4, 9, and 20 stand rejected under 35 U.S.C. § 103(a)
in view of the combined teachings of Taniguchi6 and
Grodnensky.
The remaining claims are rejected as obvious in nine separately stated
rejections in view of the teachings of Taniguchi, Grodnensky, and additional
references. (Ans. 8-17.) As will become apparent, we need not consider
these rejections in detail.

4 Examiner’s Answer mailed 7 November 2011 (“Ans.”).
5 Ilya Grodnensky and Steve Slonaker, Method and apparatus for position
measurement of a pattern formed by a lithographic exposure tool, U.S.
Patent Application Publication 2003/0215965 A1 (2003).
6 Tetsuo Taniguchi, Exposure apparatus and method that use mark patterns
to determine image formation characteristics of the apparatus prior to
exposure, U.S. Patent 5,841,520 (1998).
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B. Discussion
Findings of fact throughout this Opinion are supported by a
preponderance of the evidence of record.
Claim 15
Method claim 15 reads:
A method for transmission image detection of an aerial image
formed in a lithographic projection apparatus by radiation of
a predetermined wavelength comprising:
providing a structure with an object mark having
comparable dimensions to critical dimension features of a
circuit pattern;
providing an image sensor;
providing a projection system between said structure and
said image sensor;
forming an object mark pattern upon illumination of said
object mark by said radiation with a predetermined
wavelength;
forming an object mark aerial image of said object mark
by said projection system at an image side of said
projection system; and
detecting said aerial image with said image sensor,
wherein said image sensor comprises:
an image detector; and
a lens arranged to project at least part of the aerial
image onto an image detector.
(Claims App., Br. 24-25; some indentation and emphasis added.)
Staals urges that the Examiner erred harmfully in finding that
Grodnensky describes, in Figures 8A and 8C, reproduced on the following
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page, a process in which a projection system is provided “between said
structure and said image sensor” as required by claim 15. (Br. 13-15.)
{Grodnensky Figures 8A (left) and 8C (right) are shown below}

{Fig. 8A (right) shows a lithographic exposure apparatus}
{Fig. 8C (left) shows a Critical Dimension [CD] measurement apparatus}
The Examiner explains, apparently for the first time in the Response
to Argument section of the Examiner’s Answer, that because Fig. 8C shows
Structure C (i.e., projection system 92) “between” Structure A (i.e.,
wafer 88, which bears marks 87 that have an object mark having comparable
dimensions to critical dimension features of a circuit pattern) and
Structure B (i.e., lens 21 and detector 20), the structure required by the
[method] claim is fully met. (Ans. 18.)
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As Staals points out, however, there is no credible evidence that
Figure 8C is drawn to scale. (Reply 3.)7 Indeed, as Staals explains (id.),
Grodnensky states that Figures 8A and 8C are merely “schematic”
illustrations. Moreover, the relative size of the wafer, the CCD, and the
energy source shown in the diagram indicate that Figure 8C is not to scale.
(Id. at para. bridging 3-4.) We conclude that Staals has demonstrated the
absence of a credible basis for the Examiner’s finding that projection
device 92 can be said to be “between” the structure with an object mark and
the image sensor.8 Accordingly we reverse the anticipation rejection of
claim 15.
Claim 1
Representative apparatus claim 1 reads:
A lithographic projection apparatus for exposing a pattern
onto a substrate held in a substrate plane by a substrate
holder, comprising;
an image sensor comprising:
an image detector; and
a lens arranged to project at least part of an aerial image
of an alignment mark onto said image detector;
wherein said image sensor is positioned within said
substrate holder such that said lens is positioned proximate
said substrate plane; and

7 Reply Brief filed 9 January 2012 (“Reply”).
8 We also note the Examiner has not explained how “projection system 92”
can be said to form an object mark aerial image “at an image side of said
projection system,” as required by claim 15.
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a patterning device comprising the pattern, wherein the
pattern includes the alignment mark that is of comparable
dimensions to critical dimension features of the pattern.
(Claims App., Br. 22; some indentation and emphasis added.)
Staals urges that the Examiner erred in finding that Grodnensky
describes an aerial image of an alignment mark, and a patterning device that
includes the alignment mark, thereby curing the deficient disclosure of
Taniguchi. (Br. 17-18.)
These arguments are not persuasive due to the breadth of the terms
“aerial image” and “patterning device.” Although not defined in
the 505 Specification, the term “aerial image” in photolithography refers to
the intensity distribution of light at a plane in space, as opposed to the actual
image produced in a photoresist.9 In the words of the 505 Specification,
“[t]he term ‘patterning device’ used herein should be broadly interpreted as
referring to any device that can be used to impart a radiation beam with a
pattern in its cross-section such as to create a pattern in a target portion of
the substrate.” (Spec. 6 [0035].) Given these definitions, we have no
difficulty determining that wafer 88 with metrology patterns 87 constitutes a
“patterning device,” and that an “aerial image”—a distribution of light

9 See, e.g., Chris A. Mack, The Death of the Aerial Image, in
Microlithography World, (August 2005), available on-line at
http://www.lithoguru.com/scientist/tutor.html, Tutor 50, page 1, 1st para.).
(“The aerial image is, quite literally, the image in air. In the world of
semiconductor lithography, it is the image of a photomask projected onto the
plane of the wafer but assuming that only air occupies this space rather than
the resist coated wafer.”)
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intensity corresponding to metrology patterns 87—is projected by lens 21
onto image detector 20. (Cf. FR 3; Ans. 5.)
The Examiner holds that it would have been obvious to “align[] the
apparatus of Taniguchi using the CD features as taught by Grodnensky,
using the sensor within the substrate holder, instead of the one to the side.”
(Id.)
The difficulty with this analysis is, as Staals points out (Br. 18, last
para.), that Taniguchi describes a lithographic apparatus that is “provided
with a mechanism capable of accurately detecting a position or a positional
discrepancy of a mark pattern on a mask or a projected image thereof before
actual exposure” (Taniguchi, col. 6, ll. 21-25.) In contrast, the alignment
marks provided by Grodnensky are created by a double-exposure process in
which two thin lines having a width comparable to a critical dimension of
the circuit are overlapped at a small angle α, resulting in a rhombus-shaped
mark at the intersection of the exposures. (Grodnensky 3 [0033].) Not only
is this mark created after an actual exposure, but the mark does not exist as
part of a mark pattern on a mask, as required by Taniguchi. Thus, the
approaches of these two references to solving the problems associated with
overlay in photo-lithographic processes are very different indeed. The
Examiner’s rejection of claim 1 fails because the record lacks support for the
final limitation of a patterning device that “includes the alignment mark that
is of comparable dimensions to critical dimension features of the pattern.”
The Examiner’s findings regarding the other references do not cure
the deficiencies of Taniguchi and Grodnensky.
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C. Order
We reverse the rejection of claims 1-29.
REVERSED
tc