# US 12,117,734 B2 · Metrology method and device for determining a complex-valued field > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,117,734 B2 - Document ID: US12117734B2 - Status: Granted - Kind: B2 - Application number: 17/638,975 - Filed: 2020-07-31 - Published: 2022-09-22 - Granted: 2024-10-15 - Earliest claimed: 2019-09-02 - Assignees: ASML Netherlands B.V. - Applicants: ASML Netherlands B.V. - Inventors: Nitesh Pandey; Alexander Prasetya Konijnenberg - Web page: https://patentgrep.com/patent/US12117734B2 ## CPC - G03F 7/705: {Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions} - G03F 7/70633: {Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching} - G01N 21/4738: {Diffuse reflection (precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration), e.g. also for testing fluids, fibrous materials} - 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) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Disclosed is a method of measuring a structure, and associated metrology device and computer program. The method comprises obtaining an amplitude profile of scattered radiation relating to a measurement of a first structure on a first substrate and obtaining a reference phase profile relating to a reference measurement of at least one reference structure on a reference substrate. The at least one reference structure is not the same structure as said first structure but is nominally identical in terms of at least a plurality of key parameters. The method further comprises determining a complex-valued field to describe the first structure from the amplitude profile and reference phase profile. ## Claims ### Claim 1 A method comprising: obtaining an amplitude profile of scattered radiation relating to a measurement of a structure on a substrate; obtaining a reference phase profile relating to a reference measurement of at least one reference structure on a reference substrate, the at least one reference structure being a different structure than the structure, and the at least one reference structure and the structure being nominally identical in terms of at least a plurality of key parameters; and determining a complex-valued field to describe the structure from the amplitude profile and the reference phase profile. ### Claim 2 (depends on 1) The method of claim 1, wherein the measurement and the reference measurement are performed under same measurement conditions. ### Claim 3 (depends on 1) The method of claim 1, wherein the at least one reference structure was measured at a time preceding the measurement to determine the reference phase profile. ### Claim 4 (depends on 3) The method of claim 3, wherein the reference measurement is performed in a reference phase and the reference phase profile obtained therefrom is used in a plurality of subsequent measurements of a plurality of structures in addition to the structure, to determine a complex-valued field for each of the plurality of structures, the plurality of structures being nominally identical to the at least one reference structure in terms of at least the plurality of key parameters. ### Claim 5 (depends on 1) The method of claim 1, wherein: the structure comprises a periodic grating structure, and the key parameters include grating pitch, grating size, and grating orientation. ### Claim 6 (depends on 1) The method of claim 1, wherein: the reference phase profile is obtained from a reference measurement of a plurality of reference structures, and phase profiles are determined for each of the reference structures and are averaged to determine the reference phase profile. ### Claim 7 (depends on 1) The method of claim 1, comprising: aligning the amplitude profile with a reference amplitude profile relating to the reference measurement of the at least one reference structure, to obtain a registered amplitude template; and applying the reference profile to the registered amplitude template to determine the complex-valued field. ### Claim 8 (depends on 1) The method of claim 1, comprising: performing an adjustment for an overlay induced global phase offset, wherein the performing an adjustment for the overlay induced global phase offset comprises optimizing, in terms of the overlay induced global phase offset, an image quality described by the complex-valued field. ### Claim 9 (depends on 1) The method of claim 1, wherein: the determining the complex-valued field comprises performing a correction to the complex-valued field to correct for aberrations in sensor optics used to obtain the amplitude profile, and the performing the correction to the complex-valued field comprises: Fourier transforming the complex-valued field to obtain a Fourier transformed complex-valued field; obtaining a conjugated lens aberration phase profile related to the aberrations in the sensor optics; and multiplying the conjugated lens aberration phase profile with the Fourier transformed complex-valued field. ### Claim 10 (depends on 1) The method of claim 1, comprising performing the measurement of the structure by: illuminating the structure with measurement radiation; capturing scattered radiation therefrom on a detector operable to detect an intensity profile of the scattered radiation, the capturing comprising capturing a single diffraction order; and determining the amplitude profile from the intensity profile. ### Claim 11 (depends on 1) The method of claim 1, comprising: measuring the at least one reference structure; and performing a phase retrieval to obtain the reference phase profile. ### Claim 12 (depends on 11) The method of claim 11, wherein the measuring the at least one reference structure comprises performing repeated captures with at least one parameter varied to provide sufficient information for the phase retrieval. ### Claim 13 (depends on 1) A metrology device being operable to perform the method of claim 1. ### Claim 14 A computer program comprising program instructions operable to perform operations comprising: obtaining an amplitude profile of scattered radiation relating to a measurement of a structure on a substrate; obtaining a reference phase profile relating to a reference measurement of at least one reference structure on a reference substrate, the at least one reference structure being a different structure than the structure, and the at least one reference structure and the structure being nominally identical in terms of at least a plurality of key parameters; and determining a complex-valued field to describe the structure from the amplitude profile and the reference phase profile. ### Claim 15 A lithographic cell comprising: a metrology device operable to perform measurements from which corrections are determined for a lithographic process and operable to perform the measurements and the corrections by: obtaining an amplitude profile of scattered radiation relating to a measurement of a structure on a substrate; obtaining a reference phase profile relating to a reference measurement of at least one reference structure on a reference substrate, the at least one reference structure being a different structure than the structure, and the at least one reference structure and the structure being nominally identical in terms of at least a plurality of key parameters; and determining a complex-valued field to describe the structure from the amplitude profile and the reference phase profile; and a lithographic apparatus operable to perform the lithographic process in accordance with the corrections.