# US 9,752,992 B2 · Variable image field curvature for object inspection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,992 B2 - Document ID: US9752992B2 - Status: Granted - Kind: B2 - Application number: 14/662,602 - Filed: 2015-03-19 - Published: 2015-10-01 - Granted: 2017-09-05 - Earliest claimed: 2014-03-25 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: Paul Horn - Web page: https://patentgrep.com/patent/US9752992B2 ## CPC - G01N 21/8851: {Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges (G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002)} - G01N 21/8806: {Specially adapted optical and illumination features} - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects} - G01N 2201/06113: Coherent sources; lasers - G01N 2201/105: Purely optical scan - 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) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 ## Abstract Field curvature of an optical system is modified based on topography of the surface of a wafer such that an image of each of the segments of the surface is in focus across the segment. The wafer may be non-planar. The optical system may be a multi-element lens system connected to a controller that modifies the field curvature by changing position of the lens elements. The wafer may be held by a chuck, such as an edge grip chuck. Multiple optical systems may be arranged across a dimension of the wafer. ## Claims ### Claim 1 An inspection system comprising: an optical system for capturing images of segments of a surface of a wafer, the optical system having lens elements, wherein a position of the lens elements can be changed to modify field curvature, wherein the lens elements include: a first lens element having a positive refractive power, the first lens element comprising one or more lenses; a second lens element having a negative refractory power, the second lens element being adjacent to an imaging side of the first lens element, and the second lens element comprising one or more lenses; and a third lens element having a positive refractory power, the third lens element being adjacent to an imaging side of the second lens element, and the third lens element comprising one or more lenses; and a controller configured to: receive topography data of the surface of the wafer; and change a position of at least one of the lens elements based on the topography data of the surface of the wafer such that the field curvature of the optical system is modified and an image of each of the segments is in focus across the segment. ### Claim 2 (depends on 1) The inspection system of claim 1, further comprising a mapping system for generating the topography data of the surface, wherein the mapping system includes a laser source configured to generate a laser beam and a detector configured to receive the laser beam, and wherein the mapping system is operatively connected to the controller. ### Claim 3 (depends on 2) The inspection system of claim 2, wherein the laser beam is configured to scan across the wafer. ### Claim 4 (depends on 1) The inspection system of claim 1, wherein the relative refractive powers of the first and second lens elements are such that optical ray traces from an object on the optical axis at infinity are approximately parallel with the optical axis in a space between the second and third lens elements, and the first and second lens elements are movable relative to the third lens element for changing the field curvature of the optical system without varying a back focal distance of the optical system. ### Claim 5 (depends on 1) The inspection system of claim 1, further comprising an actuator in communication with the controller, the actuator configured to change the position of the first lens element and/or the second lens element. ### Claim 6 (depends on 1) The inspection system of claim 1, further comprising additional optical systems arranged across a dimension of the wafer. ### Claim 7 (depends on 1) The inspection system of claim 1, further comprising a chuck configured to hold the wafer. ### Claim 8 (depends on 7) The inspection system of claim 7, wherein the chuck comprises an edge grip chuck. ### Claim 9 (depends on 1) The inspection system of claim 1, further comprising a scanning system configured to move one of the wafer or the optical system with respect to each other. ### Claim 10 A non-transitory computer-readable storage medium, comprising one or more programs for executing the following steps on one or more computing devices: receiving topography data of at least a segment of a surface of a wafer; and modifying field curvature of an optical system based on the topography data such that an image of each of a plurality of segments of the surface is in focus across the segment wherein the optical system comprises a first lens element having a positive refractive power, a second lens element having a negative refractory power, and a third lens element having a positive refractory power, wherein the first lens element comprises one or more lenses, wherein the second lens element is adjacent to an imaging side of the first lens element, wherein the second lens element comprises one or more lenses, wherein the third lens element is adjacent to an imaging side of the second lens element, and wherein the third lens element comprises one or more lenses. ### Claim 11 (depends on 10) The non-transitory computer-readable storage medium of claim 10, further comprising mapping the surface of a wafer to determine the topography data. ### Claim 12 (depends on 10) The non-transitory computer-readable storage medium of claim 10, further comprising moving one of the wafer or the optical system with respect to another of the wafer or the optical system. ### Claim 13 An inspection method comprising: receiving, at a controller, topography data of at least a segment of a surface of a wafer; modifying, based on the received topography data, field curvature of an optical system having a field of view corresponding to the segment, wherein the optical system comprises a first lens element having a positive refractive power, a second lens element having a negative refractory power, and a third lens element having a positive refractory power, wherein the first lens element comprises one or more lenses, wherein the second lens element is adjacent to an imaging side of the first lens element, wherein the second lens element comprises one or more lenses, wherein the third lens element is adjacent to an imaging side of the second lens element, and wherein the third lens element comprises one or more lenses; and capturing an image of the segment using the modified field curvature. ### Claim 14 (depends on 13) The inspection method of claim 13, further comprising mapping the surface of the wafer to determine the topography data by scanning at least one laser beam across the surface. ### Claim 15 (depends on 13) The inspection method of claim 13, wherein the field curvature of an imaging lens of the optical system is continually modified while the wafer is scanned. ### Claim 16 (depends on 13) The inspection method of claim 13, further comprising moving one of the wafer or the optical system with respect to each other. ### Claim 17 (depends on 13) The inspection method of claim 13, further comprising holding the wafer using a chuck. ### Claim 18 (depends on 17) The inspection method of claim 17, wherein the chuck is an edge grip chuck.