# US 11,309,202 B2 · Overlay metrology on bonded wafers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,202 B2 - Document ID: US11309202B2 - Status: Granted - Kind: B2 - Application number: 17/028,878 - Filed: 2020-09-22 - Published: 2021-08-05 - Granted: 2022-04-19 - Earliest claimed: 2020-01-30 - Assignees: KLA Corporation - Applicants: KLA Corporation - Inventors: Shankar Krishnan; David Y. Wang; Johannes D. de Veer - Web page: https://patentgrep.com/patent/US11309202B2 ## CPC - 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} - H10P 72/53: {using optical controlling means} - G01B 11/06: for measuring thickness {; e.g. of sheet material (thickness measurement by thermal means G01B21/085)} - G01N 21/211: {Ellipsometry (optical thickness measurement G01B11/06)} - G01N 21/27: using photo-electric detection (G01N21/31 takes precedence){; circuits for computing concentration (logarithmic circuits G06G7/24; photometric circuits in general G01J)} - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G01B 2210/56: Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth - H10W 80/00: Direct bonding of chips, wafers or substrates - H10W 80/163: {using active alignment, e.g. detecting marks and correcting position} - 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) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - 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) - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract A metrology system for characterizing a sample formed from a first wafer and a second wafer bonded at an interface with a metrology target near the interface may include a metrology tool and a controller. The metrology tool may include one or more illumination sources and an illumination sub-system to direct illumination from the one or more illumination sources to the metrology target, a detector, and a collection sub-system to collect light from the sample. The light collected from the sample may include light from the metrology target and light from a top surface of the first wafer, and the collection sub-system is may direct the light from the metrology target to the detector. The controller may execute program instructions causing the one or more processors to generate estimates of one or more parameters associated with the sample based on data received from the detector. ## Claims ### Claim 1 A metrology system comprising: a metrology tool comprising: one or more illumination sources; one or more illumination optics configured to direct illumination from the one or more illumination sources to a metrology target on a sample at one or more selected incidence angles, wherein the sample is formed from a first wafer and a second wafer bonded to the first wafer at an interface, wherein the metrology target is located at the interface, wherein the illumination from the one or more illumination sources propagates through the first wafer to reach the metrology target; a detector; one or more collection optics configured to collect light from the sample, wherein the light collected from the sample includes light from the metrology target and light from a top surface of the first wafer, wherein the one or more collection optics is configured to direct the light from the metrology target to the detector; and a controller communicatively coupled to the detector, wherein the controller includes one or more processors configured to execute program instructions causing the one or more processors to generate estimates of one or more parameters associated with the sample based on data received from the detector. ### Claim 2 (depends on 1) The metrology system of claim 1, wherein the one or more illumination optics are further configured to direct the illumination from the illumination source to the metrology target at one or more selected azimuth angles. ### Claim 3 (depends on 2) The metrology system of claim 2, wherein the one or more selected azimuth angles include azimuth angles ranging from 0 degrees to 360 degrees. ### Claim 4 (depends on 1) The metrology system of claim 1, wherein generating estimates of one or more parameters associated with the sample based on the data received from the detector comprises: generating an estimate of an overlay error indicative of alignment of the first wafer with respect to the second wafer based on the reflected light from the metrology target. ### Claim 5 (depends on 4) The metrology system of claim 4, wherein the generating an estimate of an overlay error indicative of alignment of the first wafer with respect to the second wafer based on the reflected light from the metrology target comprises: generating an estimate of an overlay error indicative of alignment of the first wafer with respect to the second wafer based on the reflected light from the metrology target using a rigorous coupled-wave analysis technique based on the reflected light from the metrology target. ### Claim 6 (depends on 4) The metrology system of claim 4, wherein the generating an estimate of an overlay error indicative of alignment of the first wafer with respect to the second wafer based on the reflected light from the metrology target comprises: generating an estimate of an overlay error indicative of alignment of the first wafer with respect to the second wafer based on the reflected light from the metrology target using a machine learning technique based on the reflected light from the metrology target. ### Claim 7 (depends on 1) The metrology system of claim 1, wherein the illumination from at least one of the one or more illumination sources comprises: wavelengths ranging from 750 nanometers to 2,800 nanometers. ### Claim 8 (depends on 1) The metrology system of claim 1, wherein the illumination from at least one of the one or more illumination sources comprises: wavelengths ranging from 150 nanometers to 300 nanometers. ### Claim 9 (depends on 1) The metrology system of claim 1, wherein the illumination from at least one of the one or more illumination sources comprises: wavelengths ranging from 190 nanometers to 900 nanometers. ### Claim 10 (depends on 1) The metrology system of claim 1, wherein the metrology tool comprises: a spectroscopic ellipsometer. ### Claim 11 (depends on 10) The metrology system of claim 10, wherein the one or more selected incidence angles are greater than 35 degrees. ### Claim 12 (depends on 1) The metrology system of claim 1, wherein the metrology tool comprises: a spectroscopic reflectometer. ### Claim 13 (depends on 12) The metrology system of claim 12, wherein the one or more selected incidence angles are in a range of 5 degrees to 40 degrees. ### Claim 14 (depends on 12) The metrology system of claim 12, further comprising: an objective lens, wherein the one or more illumination optics direct the illumination from the one or more illumination sources to the metrology target through the objective lens, wherein the one or more collection optics collect the light from the sample through the objective lens. ### Claim 15 (depends on 1) The metrology system of claim 1, wherein the one or more collection optics include one or more elements to isolate the light from the metrology target from the light reflected from the top surface of the first wafer. ### Claim 16 (depends on 15) The metrology system of claim 15, wherein the one or more collection optics include at least one of a field stop or a beam block to block the light from the top surface of the first wafer and pass the light from the metrology target. ### Claim 17 (depends on 15) The metrology system of claim 15, wherein the one or more collection optics include at least one optical element having a non-zero optical power to selectively direct the light reflected from the metrology target to the detector. ### Claim 18 (depends on 1) The metrology system of claim 1, wherein the one or more processors are further configured to execute program instructions causing the one or more processors to isolate the light from the metrology target from the light from the top surface of the first wafer based on one or more known characteristics of at least one of the light from the metrology target or the light from the top surface of the first wafer. ### Claim 19 (depends on 18) The metrology system of claim 18, wherein the one or more known characteristics of at least one of the light from the metrology target or the light from the top surface of the first wafer are based on at least one of a wavelength of the illumination from the one or more illumination sources, an incident angle of the illumination from the one or more illumination sources on the metrology target, an azimuth angle of the illumination from the one or more illumination sources on the metrology target, a transmissivity of the first wafer, or a thickness of the first wafer, or a design of the metrology target. ### Claim 20 (depends on 1) The metrology system of claim 1, wherein the one or more illumination sources comprise: one or more lasers providing one or more narrow-band spectra. ### Claim 21 (depends on 20) The metrology system of claim 20, wherein the one or more illumination optics and the one or more collection optics form at least one of a narrow-band ellipsometer or a narrow-band reflectometer. ### Claim 22 (depends on 1) The metrology system of claim 1, wherein the illumination from the one or more illumination sources includes a broad-band spectrum. ### Claim 23 (depends on 22) The metrology system of claim 22, wherein the one or more collection optics include a dispersive element to provide a selected spatial distribution of wavelengths of the broad-band spectrum across the detector, wherein the detector includes one or more sensors oriented along the spatial distribution of wavelengths, wherein each of the one or more sensors has a selected sensitivity to a range of incident wavelengths based on the selected spatial distribution of wavelengths. ### Claim 24 (depends on 23) The metrology system of claim 23, wherein the detector includes a single sensor having calibrated sensitivity across the selected spatial distribution of wavelengths. ### Claim 25 (depends on 23) The metrology system of claim 23, wherein the detector includes two or more sensors having calibrated sensitivities across the selected spatial distribution of wavelengths. ### Claim 26 A metrology method comprising: illuminating a metrology target on a sample with illumination from one or more illumination sources at one or more selected incidence angles, wherein the sample is formed from a first wafer and a second wafer bonded to the first wafer at an interface, wherein the metrology target is located at the interface, wherein the illumination from the one or more illumination sources propagates through the first wafer to reach the metrology target; collecting light from the sample in response to the illumination from the one or more illumination sources, wherein the light collected from the sample includes light from the metrology target and light from a top surface of the first wafer, wherein the light from the metrology target is directed to a detector; and generating, with one or more processors, estimates of one or more parameters associated with the sample based on data received from the detector. ### Claim 27 (depends on 26) The metrology method of claim 26, further comprising: illuminating the metrology target on the sample with the illumination from the one or more illumination sources at one or more selected azimuth angles. ### Claim 28 (depends on 26) The metrology method of claim 26, wherein the one or more parameters associated with the sample include an overlay error between the first wafer and the second wafer. ### Claim 29 (depends on 26) The metrology method of claim 26, further comprising: isolating the light from the metrology target from the light from the top surface of the first wafer. ### Claim 30 (depends on 29) The metrology method of claim 29, wherein isolating the light from the metrology target from light reflected from the top surface of the first wafer comprises: selectively directing the light reflected from the metrology target to the detector using at least one of a cylindrical optical element or an aspherical optical element. ### Claim 31 (depends on 29) The metrology method of claim 29, wherein isolating the light from the metrology target from the light reflected from the top surface of the first wafer comprises: blocking the light from the top surface of the first wafer and passing the light from the metrology target. ### Claim 32 (depends on 29) The metrology method of claim 29, wherein isolating the light from the metrology target from the light reflected from the top surface of the first wafer comprises: isolating, with the one or more processors, the light from the metrology target from the light from the top surface of the first wafer based on one or more known characteristics of at least one of the light from the metrology target or the light from the top surface of the first wafer. ### Claim 33 (depends on 32) The metrology method of claim 32, wherein the one or more known characteristics of at least one of the light from the metrology target or the light from the top surface of the first wafer are based on at least one of a wavelength of the illumination from the one or more illumination sources, an incident of the illumination from the one or more illumination sources on the metrology target, a transmissivity of the first wafer, or a thickness of the first wafer, or a design of the metrology target. ### Claim 34 A metrology system comprising: one or more illumination sources; one or more detectors; an ellipsometer configured to direct, with one or more ellipsometer illumination optics, illumination from the one or more illumination sources to a metrology target on a sample at a first set of one or more selected incidence angles, wherein the sample is formed from a first wafer and a second wafer bonded to the first wafer at an interface, wherein the metrology target is located at the interface, wherein the illumination from the one or more illumination sources propagates through the first wafer to reach the metrology target, wherein the ellipsometer is further configured to direct, with one or more ellipsometer collection optics, light reflected from the metrology target to at least one of the one or more detectors to generate ellipsometry signals; a reflectometer configured to direct, with one or more reflectometer illumination optics, the illumination from the one or more illumination sources to the metrology target at a second set of one or more selected incidence angles, the reflectometer further configured to direct, with one or more reflectometer collection optics, the light reflected from the metrology target to at least one of the one or more detectors to generate reflectometry signals; and a controller communicatively coupled to the ellipsometer and the reflectometer, the controller including one or more processors configured to execute program instructions causing the one or more processors to generate estimates of one or more parameters associated with the sample based on the ellipsometry signals and the reflectometry signals. ### Claim 35 (depends on 34) The metrology system of claim 34, wherein the ellipsometry signals and the reflectometry signals are collected simultaneously. ### Claim 36 (depends on 34) The metrology system of claim 34, wherein the ellipsometry signals and the reflectometry signals are collected sequentially. ### Claim 37 (depends on 34) The metrology system of claim 34, wherein the ellipsometer and the reflectometer direct the illumination from the one or more illumination sources to collocated portions of the sample. ### Claim 38 (depends on 34) The metrology system of claim 34, wherein the ellipsometer and the reflectometer direct the illumination from the one or more illumination sources to different portions of the sample. ### Claim 39 (depends on 34) The metrology system of claim 34, wherein the one or more parameters associated with the sample include an overlay error between the first wafer and the second wafer.