# US 10,504,802 B2 · Target location in semiconductor manufacturing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,504,802 B2 - Document ID: US10504802B2 - Status: Granted - Kind: B2 - Application number: 15/576,811 - Filed: 2017-10-24 - Published: 2018-10-18 - Granted: 2019-12-10 - Earliest claimed: 2016-11-09 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: Naomi Ittah; Nadav Gutman; Eran Amit; Vincent Immer; Einat Peled - Web page: https://patentgrep.com/patent/US10504802B2 ## CPC - H10P 74/23: {characterised by multiple measurements, corrections, marking or sorting processes} - G01B 11/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) - G01B 11/26: for measuring angles or tapers; for testing the alignment of axes - H10P 72/0604: {Process monitoring, e.g. flow or thickness monitoring} - H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects} - 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 ## Abstract A method of overlay control in silicon wafer manufacturing comprises firstly locating a target comprising a diffraction grating on a wafer layer; and then measuring the alignment of patterns in successive layers of the wafer. The location of the target may be done by the pupil camera rather than a vision camera by scanning the target to obtain pupil images at different locations along a first axis. The pupil images may comprise a first order diffraction pattern for each location. A measurement of signal intensity in the first order diffraction pattern is then obtained for each location. The variation of signal intensity with location along each axis is then analyzed to calculate the location of a feature in the target. ## Claims ### Claim 1 A method of target location in a semiconductor manufacturing process, wherein a target comprises a diffraction grating, the method comprising: acquiring the target based on a coarse location of a feature; scanning the target to capture pupil images at different locations along a first axis and a second axis, wherein the pupil images comprise a first order diffraction pattern for each of the different locations, and wherein the second axis is perpendicular to the first axis; obtaining a measurement of signal intensity in the first order diffraction pattern for each of the different locations; analyzing a variation of signal intensity with location along the first axis and the second axis to calculate a position vector of the feature of the target along the first axis and the second axis; and calculating a shift between the coarse location and the calculated position vector by an image analysis unit. ### Claim 2 (depends on 1) The method of claim 1 wherein the first order diffraction pattern comprises positive and negative first order diffraction patterns. ### Claim 3 (depends on 2) The method of claim 2 wherein obtaining a measurement of signal intensity comprises calculating an average signal intensity or a total signal intensity of the positive and negative first order diffraction patterns. ### Claim 4 (depends on 2) The method of claim 2 wherein the feature is a center of the target. ### Claim 5 (depends on 1) The method of claim 1 wherein the feature is a center of the target. ### Claim 6 (depends on 1) The method of claim 1 wherein said target comprises a plurality of cells, said scanning comprises scanning a single cell, and said feature comprises a center of said single cell or an edge of said single cell. ### Claim 7 (depends on 1) The method of claim 1 wherein said target comprises a plurality of cells, said scanning comprises scanning more than one cell along an axis continuing from one cell to another, and said feature comprises a boundary between two cells, an edge of a cell, or a center of a cell. ### Claim 8 (depends on 1) A computer readable medium comprising instructions which when implemented in a processor of a semiconductor metrology system cause the system to operate according to the method of claim 1. ### Claim 9 (depends on 1) The method of claim 1, further comprising moving the target an amount along the first axis and the second axis that corresponds to the position vector. ### Claim 10 A method of overlay control in silicon wafer manufacturing comprising: acquiring a target based on a coarse location of a feature; locating the target comprising a diffraction grating on a wafer layer; measuring an overlay in successive layers of the wafer; wherein locating the target comprises: scanning the target to capture pupil images at different locations along a first axis and a second axis, wherein the pupil images comprise a first order diffraction pattern for each of the different locations, and wherein the second axis is perpendicular to the first axis; obtaining a measurement of signal intensity in the first order diffraction pattern for each of the different locations; and analyzing a variation of signal intensity with location along the first axis and the second axis to calculate a position vector of the feature in the target along the first axis and the second axis; and calculating a shift between the coarse location and the calculated position vector by an image analysis unit. ### Claim 11 (depends on 10) The method of claim 10 comprising moving the wafer by an amount corresponding to the shift. ### Claim 12 (depends on 10) The method of claim 10 wherein the same camera is used to locate the target and measure the overlay. ### Claim 13 (depends on 12) The method of claim 12 wherein the same measurement settings for a pupil camera are used for locating the target and for measuring alignment. ### Claim 14 (depends on 10) The method claim 10 wherein signal intensity data used to determine the location of said feature is used to measure alignment of patterns in successive layers of the wafer. ### Claim 15 (depends on 10) The method claim 10 wherein signal intensity data used to determine the location of said feature is used to measure alignment of patterns in successive layers of the wafer. ### Claim 16 A semiconductor metrology system comprising: an imaging system comprising an illumination source for illuminating a target based on a coarse location of a feature on a wafer and a pupil camera for capturing light returned from said target; a controller configured to control the imaging system to scan the target to capture pupil images at different locations along a first axis and a second axis, wherein the pupil images comprise a first order diffraction pattern for each of the different locations along the first axis and the second axis, and wherein the second axis is perpendicular to the first axis; and an image analysis unit configured to obtain a measurement of signal intensity in the first order diffraction pattern for each of the different locations along said first axis and the second axis, analyze variation of signal intensity with location along the first axis and the second axis to calculate a position vector of a feature in the target along the first axis and the second axis, and calculate a shift between the coarse location and the calculated position vector. ### Claim 17 (depends on 16) The system of claim 16 further configured to measure alignment of patterns in successive layers of the wafer using data from said pupil images. ### Claim 18 (depends on 17) The system of claim 17 comprising a movable stage for supporting the wafer in which the controller is configured to control movement of the stage according to the calculated location of the feature. ### Claim 19 (depends on 16) The system of claim 16 comprising a movable stage for supporting the wafer in which the controller is configured to control movement of the stage according to the calculated location of the feature. ### Claim 20 (depends on 16) The system of claim 16, wherein: the imaging system further comprises: a beam splitter; a collimator disposed between the beam splitter and the illumination source along a first optical axis, wherein the first optical axis passes through the beam splitter and the illumination source; an apodizer disposed between the beam splitter and the collimator along the first optical axis; a movable stage for supporting the wafer in which the controller is configured to control movement of the stage according to the calculated location of the feature; an objective disposed between the beam splitter and the wafer along a second optical axis, wherein the second optical axis passes through the beam splitter and the movable stage; a focus lens disposed between the beam splitter and the pupil camera disposed along a third optical axis, wherein the third optical axis passes through the beam splitter and the pupil camera; and a field stop disposed between the focus lens and the pupil camera along the third optical axis; and the controller is configured to receive electronic input from the image analysis unit.