# US 12,601,984 B2 · Metrology method and apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,601,984 B2 - Document ID: US12601984B2 - Status: Granted - Kind: B2 - Application number: 18/413,910 - Filed: 2024-01-16 - Published: 2024-07-11 - Granted: 2026-04-14 - Earliest claimed: 2021-07-16 - Assignees: ASML Netherlands B.V. - Applicants: ASML Netherlands B.V. - Inventors: Arjan Johannes Anton Beukman; Omar El Gawhary; Ilse Van Weperen; Pieter Joseph Marie Wöltgens - Web page: https://patentgrep.com/patent/US12601984B2 ## CPC - G03F 9/7076: {Mark details, e.g. phase grating mark, temporary mark} - G03F 9/7088: {Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection} - G03F 9/7046: {Strategy, e.g. mark, sensor or wavelength selection} - G03F 9/7092: {Signal processing} - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) ## Abstract Disclosed is a method for measuring alignment on an alignment mark, and associated apparatuses. The method comprises illuminating the alignment mark with illumination comprising at least one wavelength; capturing the scattered radiation scattered from the alignment mark as a result of said illumination step, and determining at least one position value for said alignment mark from an angularly resolved representation of said scattered radiation, wherein said alignment mark, or a feature thereof, is smaller than said at least one wavelength in at least one dimension of a substrate plane. ## Claims ### Claim 1 A method for measuring alignment on an alignment mark, the method comprising: illuminating the alignment mark with illumination comprising at least one wavelength, wherein the illumination comprises coherent illumination; capturing scattered radiation scattered from the alignment mark as a result of the illumination, wherein the scattered radiation, includes a zeroth order component and is directed to a balanced detector or differential detector; and determining at least one position value for the alignment mark from an angle-resolved scatterometry measurement using the scattered radiation; wherein the alignment mark, or a feature thereof, is smaller than the at least one wavelength in at least one dimension of a substrate plane. ### Claim 2 (depends on 1) The method as claimed in claim 1, wherein the determining at least one position value comprises determining the at least one position value from measurement of balance or symmetry in the angle-resolved scatterometry measurement. ### Claim 3 (depends on 1) The method as of claim 1, further comprising: scanning the illumination over the alignment mark, and determining the at least one position value from a zero crossing of an alignment signal determined from the angle-resolved scatterometry measurement. ### Claim 4 (depends on 1) The method of claim 1, wherein the determining at least one position value comprises determining a first position value for a first dimension of the substrate plane and a second position value for a second dimension of the substrate plane. ### Claim 5 (depends on 4) The method of claim 4, further comprising: scanning the illumination obliquely over the alignment mark; determining the first position value from a zero crossing of a first alignment signal determined from the angle-resolved scatterometry measurement; and determining the second position value from a zero crossing of a second alignment signal determined from the angle-resolved scatterometry measurement. ### Claim 6 (depends on 5) The method of claim 5, wherein the first alignment signal is determined from a first combination of quadrants of the angle-resolved scatterometry measurement and the second alignment signal is determined from a second combination of quadrants of the angle-resolved scatterometry measurement. ### Claim 7 (depends on 1) The method of claim 1, wherein the alignment mark is a functional product structure. ### Claim 8 (depends on 1) The method of claim 1, wherein the alignment mark is surrounded by a contrasting region, the contrasting region optically contrasting the alignment mark. ### Claim 9 (depends on 8) The method of claim 8, wherein the alignment mark comprises a structure. ### Claim 10 (depends on 9) The method of claim 9, wherein the contrasting region is an empty region. ### Claim 11 (depends on 8) The method of claim 8, wherein the alignment mark is an empty region. ### Claim 12 (depends on 11) The method of claim 11, wherein the contrasting region comprises exposed dummy structure. ### Claim 13 (depends on 1) The method of claim 1, wherein the alignment mark is partially or completely surrounded by auxiliary features. ### Claim 14 (depends on 1) The method of claim 1, wherein a target is smaller than the wavelength in both dimensions of the substrate plane. ### Claim 15 (depends on 1) The method of claim 1, wherein the alignment mark comprises a line, or a pair of orthogonal lines. ### Claim 16 (depends on 1) The method of claim 1, wherein the alignment mark comprises a periodic alignment mark comprising repetitions of features, wherein each feature is smaller than the wavelength in at least one dimension of the substrate plane. ### Claim 17 (depends on 16) The method of claim 16, wherein one or more features of the alignment mark comprise broken features having one or more gaps. ### Claim 18 (depends on 16) The method of claim 16, wherein the alignment mark mimics actual product structure. ### Claim 19 (depends on 1) The method of claim 1, wherein the alignment mark is symmetrical in at least one dimension of the substrate plane. ### Claim 20 (depends on 1) The method of claim 1, wherein the alignment mark is located within-die. ### Claim 21 (depends on 1) The method of claim 1, wherein the at least one dimension of the alignment mark is no more than two orders of magnitude different to a critical dimension of product structure on a same substrate as the alignment mark. ### Claim 22 (depends on 1) The method of claim 1, wherein the at least one dimension of the alignment mark is of the same order of magnitude as a critical dimension of product structure on a same substrate as the alignment mark. ### Claim 23 (depends on 1) The method of claim 1, further comprising measuring a plurality of the alignment marks simultaneously. ### Claim 24 (depends on 23) The method of claim 23, further comprising illuminating each of the alignment marks with a respective beam of the illumination; and capturing and processing respective scattered radiation from each alignment mark to determine a respective position value. ### Claim 25 (depends on 1) A coherent Fourier scatterometer being operable to perform the method of claim 1. ### Claim 26 (depends on 1) An alignment sensor configured to perform the method of claim 1. ### Claim 27 (depends on 26) A lithographic apparatus comprising the alignment sensor of claim 26.