DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claim(s) 1, 3, 5-7, 10, 12-14, 18, 19 and 21 are rejected under 35 U.S.C. 103 as being unpatentable over Kusunose et al. (U.S. PGPub No. 2015/0204729 A1) in view of Lee et al. (U.S. PGPub No. 2010/0001199 A1) further in view of Fu et al. (U.S. PGPub No. 2016/0299121 A1).
As to claim 1, Kusunose discloses and shows in figure 4, a mask characterization apparatus comprising:
a light source (10) arranged to illuminate a reflective (17, reflective as shown in figure 4) or transmissive mask with light whereby mask-reflected or mask-transmitted light is generated ([0070], ll. 1-3; [0074], ll. 11-14);
an optical grating (19) arranged to convert the mask-reflected or mask-transmitted light into an interference pattern ([0077], ll. 20-45); and
an optical detector array (23) arranged to generate an interference signal by measuring the interference pattern ([0077], ll. 35-49).
Kusunose does not explicitly disclose where the quality metric is determined based on comparing strength and regularity of interference fringes of the measured pattern with strength and regularity of the interference fringes of a reference interference pattern.
However, Lee does disclose in ([0049]) the basic concept of using a reference interference fringe pattern in EUV phase mask analysis for comparison with a measurement interference fringe pattern. The examiner further notes that fringe regularity/pitch and strength/intensity/amplitude are the two fundamental and well-known metrics by which one can compare a measured pattern with a reference pattern. This is further evidenced as being obvious as Fu discloses in ([0032]) that inter-fringe spacing (i.e. regularity) is used in a reference vs measured interference comparison approach. Further Ehm also provides evidence in ([0022]) that comparing a measured to reference interference pattern is commonly done via taking into account amplitude (i.e. strength).
It would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify Kusunose where the quality metric is determined based on comparing strength and regularity of interference fringes of the measured pattern with strength and regularity of the interference fringes of a reference interference pattern in order to provide the advantage of expected results and increased accuracy/efficiency as obviously using the common concept of comparing a measured to a reference value (via strength and spacing) provides an efficient and rapid manner with which to characterize the quality of a phase mask ([0004] from Lee).
As to claim 18, Kusunose discloses and shows in figure 4, a mask characterization apparatus comprising:
a light source (10) arranged to illuminate a reflective (17, reflective as shown in figure 4) or transmissive mask with light whereby mask-reflected or mask-transmitted light is generated ([0070], ll. 1-3; [0074], ll. 11-14);
an optical grating (19) arranged to convert the mask-reflected or mask-transmitted light into an interference pattern ([0077], ll. 20-45); and
an optical detector array (23) arranged to generate an interference signal by measuring the interference pattern ([0077], ll. 35-49); and
an electronic processor (24) programmed to determine a quality metric (phase shift amount which as explicitly disclosed when incorrect reduces resolution, as such phase shift is clearly a quality metric of the printed mask) for the reflective or transmissive mask based on the measured interference pattern ([0004], ll. 24-34; [0078]).
wherein the mask characterization apparatus includes a single optical grating consisting of the optical grating arranged to convert the mask-reflected or mask- transmitted light into the interference pattern (19) ([0077], ll. 20-45; the examiner notes that the transitional phrase used in claim 18 is “comprising” which is an open ended transitional phrase as such the prior art need only have at least “a single optical grating”, which Kusunose explicitly does).
As to claims 3 and 19, Kusunose does disclose in ([0078]; [0096], ll. 22-28) the use/measurement of reference data and using phase shift to determine a quality metric.
Kusunose does not explicitly disclose wherein the reference interference pattern is for a reference reflective or transmissive mask measured using the light source, the optical grating, and the optical detector array.
However, Lee does disclose in ([0049]) the basic concept of using a reference interference fringe pattern in EUV phase mask analysis for comparison with a measurement interference fringe pattern to determine a phase shift amount.
It would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify Kusunose wherein the reference interference pattern is for a reference reflective or transmissive mask measured using the light source, the optical grating, and the optical detector array in order to provide the advantage of increased accuracy and efficiency as using a common comparison between a reference value and a measurement value allowed for an efficient and rapid means by which one can characterize the quality of a phase mask ([0004] from Lee).
As to claim 5, Kusunose discloses a mask characterization apparatus wherein the light source comprises a coherent light source having spatial coherence effective for the interference pattern to have interference fringes at least in a central region of the interference pattern ([0076], this is implied by the use of the fringe scan method of Kusunose).
As to claim 6, Kusunose discloses a mask characterization apparatus wherein:
the reflective or transmissive mask is a reflective mask (explicitly shown in figure 4) ([0077], ll. 18-20);
the light source comprises an extreme ultraviolet (EUV) light source arranged to illuminate the reflective mask with EUV light whereby mask-reflected EUV light is generated ([0070], [0077], ll. 18-20);
the optical grating (19) is arranged to convert the mask-reflected EUV light into the interference pattern ([0077], ll. 20-45); and
the optical detector (23) is an EUV-sensitive optical detector array arranged to measure the interference pattern [0077], ll. 35-49, as explicitly disclosed the detector 23 responds and has sensitivity to EUV light).
As to claim 7, Kusunose discloses a mask characterization apparatus wherein the EUV light source does not comprise a synchrotron ([0070], where the examiner notes that Kusunose explicitly discloses that a “synchrotron can be used”, as such it is not required and therefore the source can explicitly not comprise one as claimed).
As to claim 10, Kusunose discloses a mask characterization apparatus wherein the EUV light source comprises a laser-produced plasma (LPP) EUV light source ([0047]; where an Sn+ plasma source is a laser-produced plasma).
As to claim 12, Kusunose discloses a mask characterization apparatus wherein the light source is arranged to illuminate a reflective or transmissive mask with a single light beam (e.g. the beam is singular between optics 11 and 14; further the claim is constructed with the transitional phrase “comprising” as such explicitly the prior art includes at least a single light beam) whereby mask-reflected or mask-transmitted light is generated ([0070], ll. 1-3; [0077], ll. 20-45).
As to claims 13 and 14, Kusunose discloses a mask characterization apparatus wherein the mask characterization apparatus includes only a single optical grating consisting of the optical grating (19, where again the claim is constructed with the transitional phrase “comprising” as such explicitly the prior art includes at least a single grating 19) arranged to convert the mask-reflected or mask-transmitted light into the interference pattern ([0070], ll. 1-3; [0077], ll. 20-45; the examiner notes that the only grating after the light is reflected from the mask (i.e. mask-reflected as claimed) is grating 19, as such the limitation is still met by the prior art of record).
As to claim 21, Kusunose does not explicitly disclose where the quality metric is determined based on comparing strength and regularity of interference fringes of the measured pattern with strength and regularity of the interference fringes of a reference interference pattern.
However, Lee does disclose in ([0049]) the basic concept of using a reference interference fringe pattern in EUV phase mask analysis for comparison with a measurement interference fringe pattern. The examiner further notes that fringe regularity/pitch and strength/intensity/amplitude are the two fundamental and well-known metrics by which one can compare a measured pattern with a reference pattern. This is further evidenced as being obvious as Fu discloses in ([0032]) that inter-fringe spacing (i.e. regularity) is used in a reference vs measured interference comparison approach. Further Ehm also provides evidence in ([0022]) that comparing a measured to reference interference pattern is commonly done via taking into account amplitude (i.e. strength).
It would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify Kusunose where the quality metric is determined based on comparing strength and regularity of interference fringes of the measured pattern with strength and regularity of the interference fringes of a reference interference pattern in order to provide the advantage of expected results and increased accuracy/efficiency as obviously using the common concept of comparing a measured to a reference value (via strength and spacing) provides an efficient and rapid manner with which to characterize the quality of a phase mask ([0004] from Lee).
Claim(s) 20 are rejected under 35 U.S.C. 103 as being unpatentable over Kusunose et al. in view of Lee et al in view of Fu et al. further in view of Ando et al. (U.S. PGPub No. 2016/0123810 A1).
As to claims 20, Kusunose in view of Lee further in view of Fu does not explicitly disclose a mask characterization apparatus wherein the electronic processor is programmed to compare the interference signal with the reference interference signal by computing a mean squared error (MSE) between the measured interference signal and the reference interference signal.
However, Ando does disclose in ([0118]) the use of the common MSE two
dimensional image based equation (EQ5) relative to image signals. It would have been obvious to apply a known mathematical image analysis technique to interference patterns (as disclosed MSE is commonly used to compare a known (i.e. example) to a reference (i.e. comparative example)) of Kusunose in a predictable manner in order to allow efficient image analysis.
It would have been obvious to one having ordinary skill in the art before the
effective filing date of the claimed invention to modify Kusunose in view of Lee further in view of Fu with a mask characterization apparatus wherein the electronic processor is programmed to compare the interference signal with the reference interference signal by computing a mean squared error (MSE) between the measured interference signal and the reference interference signal in order to provide the advantage of increased accuracy in using a common technique one can compare images to get a more correct answer on the differences between the two images as disclosed in Ando.
Claim(s) 8-9 are rejected under 35 U.S.C. 103 as being unpatentable over Kusunose et al. in view of Lee in view of Fu further in view of Boonzajer Flaes et al. (U.S. PGPub No. 2017/0269482 A1).
As to claims 8-9, Kusunose in view of Lee further in view of Fu does not explicitly disclose a mask characterization apparatus wherein the EUV light source comprises a free electron laser (FEL) source or wherein the EUV light source comprises a high harmonic generation (HHG) EUV source which outputs spatially coherent light.
However, Boonzajer Fales does disclose in ([0070], ll. 1-11) the use of both HHG and FEL sources in place of plasma sources as each being a known alternative in EUV materials under inspection.
It would have been obvious to one having ordinary skill in the art before the effective filing date of the claimed invention to modify Kusunose in view of Lee further in view of Fu with a mask characterization apparatus wherein the EUV light source comprises a free electron laser (FEL) source or wherein the EUV light source comprises a high harmonic generation (HHG) EUV source which outputs spatially coherent light in order to provide the advantage of increased efficiency and expected results in using common and predictable alternative sources one can account for differing materials/layers of the sample under test and measure all based on specific needs as explicitly taught by Boonzajer Fales.
Claim(s) 11 is rejected under 35 U.S.C. 103 as being unpatentable over Kusunose et al. in view of Park et al. (U.S. Patent No. 11,635,371 B2).
As to claim 11, Kusunose in view of Lee further in view of Fu does not explicitly disclose a mask characterization apparatus wherein the EUV light source further a spatial filter arranged to increase spatial coherence of the EUV light.
However, Park does disclose and show in figure 1 and in (col. 3, II. 18-24; col. 3,
I. 38-62) the basic concept of using a plasma based EUV laser light source (100) that is
filtered with a spatial filter (200, and sub-part 210) in order to output as explicitly
disclosed an improved coherent of light.
It would have been obvious to one having ordinary skill in the art before the
effective filing date of the claimed invention to modify Kusunose in view of Lee further in view of Fu a mask characterization apparatus wherein the EUV light source further a spatial filter arranged to increase spatial coherence of the EUV light in order to provide the advantage of
expected results in using a common EUV configuration to provide a more spatially
coherent light to the sample under test resulting in higher quality interference fringes for
measurement.
Allowable Subject Matter
Claims 15-17 are allowed.
Claim 22 is objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
The following is an examiner’s statement of reasons for allowance:
As to claims 15 and 22 the prior art taken alone or in combination fails to teach or disclose a mask characterization apparatus wherein: the electronic processor, is programmed to determine the quality metric for the reflective or transmissive mask by: computing a mean value µ(ST) for the target interference signal ST; computing a mean value µ(SR) for a reference interference signal µ(SR) obtained by measuring a reference reflective EUV (or not EUV specifically in the case of claim 22) mask using the EUV light source, the reflection EUV grating, and the optical detector array; and calculating the quality metric as a difference metric via the equation claimed in combination with the entirety of elements of instant claims 15 and 22.
Any comments considered necessary by applicant must be submitted no later than the payment of the issue fee and, to avoid processing delays, should preferably accompany the issue fee. Such submissions should be clearly labeled “Comments on Statement of Reasons for Allowance.”
Response to Arguments
Applicant’s arguments with respect to claim(s) 1, 3, 5-12 have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument.
Applicant's arguments filed 04/21/2026 have been fully considered but they are not persuasive.
As to claims 13, 14 and 18, and the prior art failing to teach or disclose the use of only a single optical grating arranged to convert the mask-reflected or mask-transmitted light into an interference patter, the examiner respectfully disagrees. Applicant seems to be interpreting the claim fair more narrowly than the broadest reasonable interpretation of the instant claim language. The language is currently “wherein the mask characterization apparatus includes only a single optical grating consisting of the optical grating arranged to convert the mask-reflected or mask-transmitted light into the interference pattern.” At the most reasonably narrow interpretation the claim limitation requires merely that there is a grating in place for converting light optically downstream (i.e. mask-reflected or mask-transmitted as explicitly claimed) from the mask to produce the interference pattern. As noted by applicant this grating 19 explicitly exists at this position and is the only downstream grating from mask transmitted or reflected light. For this reason the rejection has been maintained. The arguments about Kusunose being a two-beam interferometer are not relevant to the limitation in question in a manner that would distinguish from the prior art.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to MICHAEL P LAPAGE whose telephone number is (571)270-3833. The examiner can normally be reached Monday-Friday 8-5:30.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Tarifur Chowdhury can be reached at 571-272-2287. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/Michael P LaPage/Primary Examiner, Art Unit 2877
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