# US 2022/0034820 A1 · Adaptive Focusing System for a Scanning Metrology Tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0034820 A1 - Document ID: US20220034820A1 - Status: Published application - Kind: A1 - Application number: 17/053,746 - Filed: 2020-10-08 - Published: 2022-02-03 - Earliest claimed: 2020-07-30 - Applicants: Kla Corporation - Inventors: Gilad Laredo - Web page: https://patentgrep.com/patent/US20220034820A1 ## CPC - G01N 21/8806: {Specially adapted optical and illumination features} - G01B 11/0608: {Height gauges} - G01B 11/24: for measuring contours or curvatures - G01J 1/0242: {Control or determination of height or angle information of sensors or receivers; Goniophotometry} - G01J 1/0448: {Adjustable, e.g. focussing} - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G03F 7/70616: {Monitoring the printed patterns} - G01B 2210/56: Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth - G01N 21/8422: {Investigating thin films, e.g. matrix isolation method} - H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects} - 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) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - 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 ## Abstract An adaptive focusing system including an optics module, an optics module height positioner (OMHP), a position sensor operative to generate a position output indicating a height of the optics module, a predictive height estimator operative to generate an estimated height value of a sample at each site of a plurality of sites, and generate a desired optics module height output for each of the sites, a regulator operative to generate, at least partially based on the desired optics module height output and a known height of the optics module, a sequence of optics module height control instructions for the plurality of sites, a driver operative to provide a sequence of control outputs to the OMHP and a model predictive controller (MPC) operative to monitor differences between a reported height of the optics module and an MPC-expected height of the optics module, thereby to generate system amelioration values. ## Claims ### Claim 1 An adaptive focusing system for a scanning metrology tool, the adaptive focusing system comprising: an optics module comprising at least one optical component; an optics module height positioner (OMHP); a position sensor operative to generate a position output indicating a height of said optics module; a predictive height estimator (PHE) operative to: generate an estimated height value of a sample at each site of a plurality of sites, said plurality of sites being located along a path defined by a movement of said optics module relative to said sample; and generate a desired optics module height output for each of said sites, said desired optics module height output being based at least partially on said estimated height value at said site; a regulator operative to generate, at least partially based on said desired optics module height output and a known height of said optics module, a sequence of optics module height control instructions for said plurality of sites; a driver operative to provide a sequence of control outputs to said OMHP, said sequence of control outputs being based on said sequence of optics module height control instructions; and a model predictive controller (MPC) operative to monitor differences between a reported height of said optics module, said reported height being at least partially based on said position output generated by said position sensor, and an MPC-expected height of said optics module, said MPC-expected height of said optics module being at least partially based on said optics module height control instructions, thereby to generate system amelioration values. ### Claim 2 (depends on 1) The adaptive focusing system according to claim 1, further comprising a filter operative to generate an ameliorated optics module height feedback value. ### Claim 3 (depends on 2) The adaptive focusing system according to claim 2, wherein said ameliorated optics module height feedback value is a function of at least said position output of said position sensor and a filter-expected height of said optics module. ### Claim 4 (depends on 3) The adaptive focusing system according to claim 3, wherein said filter-expected height of said optics module is a function of at least one of said optics module height control instructions of said regulator or said control outputs of said driver. ### Claim 5 (depends on 2) The adaptive focusing system according to claim 2, wherein said reported height of said optics module comprises said ameliorated optics module height feedback value generated by said filter. ### Claim 6 (depends on 2) The adaptive focusing system according to claim 2, wherein said filter is operative to communicate said ameliorated optics module height feedback value feedback to at least one of: said PHE; said regulator; or said MPC. ### Claim 7 (depends on 2) The adaptive focusing system according to claim 2, and wherein said system amelioration values comprise parameters of a set of equations, said set of equations describing a relationship between at least two of: said optics module; said OMHP; said position sensor; said PHE; said regulator; said driver; or said filter. ### Claim 8 (depends on 2) The adaptive focusing system according to claim 2, and wherein said MPC is operative to communicate said system amelioration values to at least one of: said PHE; said regulator; or said filter. ### Claim 9 (depends on 1) The adaptive focusing system according to claim 1, further comprising an estimated height database (EHD), and wherein said PHE is operative to access and modify said EHD. ### Claim 10 (depends on 1) The adaptive focusing system according to claim 1, wherein said PHE updates said estimated height values during at least one of: a measurement of said measurement site; or a movement of said optics module relative to said sample. ### Claim 11 (depends on 1) The adaptive focusing system according to claim 1, wherein said estimated height value comprises a surface height of a semiconductor device wafer at said site, and wherein said PHE generates said estimated height value at least partially based on at least one of: a chuck signature; an output from a patterned wafer geometry tool; at least one fabrication surface height output by a fabrication tool which fabricated at least a portion of said wafer; or a reported height of at least one additional site intended to be identical to a height of said site. ### Claim 12 (depends on 11) The adaptive focusing system according to claim 11, wherein said estimated height value is at least partially based on at least said reported height of at least one additional site, wherein said additional site comprises at least one site located on at least one of: one or more previously measured scribe lines on said wafer; one or more previously measured fields on said wafer; one or more previously measured scribe lines on an additional wafer; and or one or more previously measured fields on an additional wafer. ### Claim 13 (depends on 11) The adaptive focusing system according to claim 11, wherein said estimated height value is at least partially based on at least said reported height of at least one additional site, wherein a value of said height of said at least one additional site is generated at least partially based on a measurement of said wafer prior to the formation of a current layer on said wafer. ### Claim 14 (depends on 1) The adaptive focusing system according to claim 1, wherein said PHE comprises a linear estimation model, and wherein said linear estimation model comprises a minimum mean square estimation (MMSE) model. ### Claim 15 (canceled) ### Claim 16 (depends on 1) The adaptive focusing system according to claim 1, wherein said PHE comprises a non-linear estimation model, and wherein said non-linear estimation model comprises a neural network. ### Claim 17 (canceled) ### Claim 18 (depends on 1) The adaptive focusing system according to claim 1, wherein said optics module height control instructions are further based on a required magnitude of said control outputs. ### Claim 19 (depends on 1) The adaptive focusing system according to claim 1, wherein said regulator comprises one of: a linear quadratic regulator (LQR); and or a linear quadratic gaussian (LQG) regulator. ### Claim 20 (depends on 1) The adaptive focusing system according to claim 1, wherein said system amelioration values comprise at least one of: a mass; a damping constant; a spring constant; a power coefficient; an electro-magnetic force; a resistivity; an inductance; or a capacitance. ### Claim 21 (depends on 1) The adaptive focusing system according to claim 1, wherein said MPC-expected height is at least partially based on said control outputs. ### Claim 22 (depends on 1) The adaptive focusing system according to claim 1, wherein a difference between an actual optics module height at a site and said desired optics module height output at said site is less than 25 nm. ### Claim 23 (depends on 1) The adaptive focusing system according to claim 1, wherein: said optics module has a first focused operative orientation at a first measurement site; said optics module has a second focused operative orientation at a second measurement site; and said optics module is operative to move between said first focused operative orientation and said second focused operative orientation in a time of less than 2 milliseconds. ### Claim 24 (depends on 1) The adaptive focusing system according to claim 1, and wherein said OMHP draws an average power of less than 0.1 W and a maximum power of less than 2 W. ### Claim 25 A scanning metrology system comprising: a scanning metrology tool comprising an adaptive focusing system, the adaptive focusing system comprising: an optics module comprising at least one optical component; an optics module height positioner (OMHP); a position sensor operative to generate a position output indicating a height of said optics module; a predictive height estimator (PHE) operative to: generate an estimated height value of a sample at each site of a plurality of sites, said plurality of sites being located along a path defined by a movement of said optics module relative to said sample; and generate a desired optics module height output for each of said sites, said desired optics module height output being based at least partially on said estimated height value at said site; a regulator operative to generate, at least partially based on said desired optics module height output and a known height of said optics module, a sequence of optics module height control instructions for said plurality of sites; a driver operative to provide a sequence of control outputs to said OMHP, said sequence of control outputs being based on said sequence of optics module height control instructions; and a model predictive controller (MPC) operative to monitor differences between a reported height of said optics module, said reported height being at least partially based on said position output generated by said position sensor, and an MPC-expected height of said optics module, said MPC-expected height of said optics module being at least partially based on said optics module height control instructions, thereby to generate system amelioration values. ### Claim 26 (depends on 25) The scanning metrology system according to claim 25, wherein said scanning metrology tool comprises one of: a misregistration metrology tool; a critical dimension and shape metrology tool; a thin film metrology tool; or a defect inspection metrology tool.