# US 8,772,731 B2 · Apparatus and method for synchronizing sample stage motion with a time delay integration charge-couple device in a semiconductor inspection tool > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,772,731 B2 - Document ID: US8772731B2 - Status: Granted - Kind: B2 - Application number: 13/862,148 - Filed: 2013-04-12 - Published: 2013-10-17 - Granted: 2014-07-08 - Earliest claimed: 2012-04-15 - Assignees: KLA-Tencor Corporation - Applicants: KLA-Tencor Corporation - Inventors: Pradeep Subrahmanyan; Daniel Wack; Michael Wright; David Alles - Web page: https://patentgrep.com/patent/US8772731B2 ## CPC - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G01N 21/956: Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G01N 2021/95676: {Masks, reticles, shadow masks} - 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 A method for synchronizing sample stage motion with a time delay integration (TDI) charge-couple device (CCD) in a semiconductor inspection tool, including: measuring a lateral position of a stage holding a sample being inspected; measuring a vertical position of the stage; determining a corrected lateral position of an imaged pixel of the sample based on the measured lateral and vertical positions; and synchronizing charge transfer of the TDI CCD with the corrected lateral position of the imaged pixel. ## Claims ### Claim 1 A method for synchronizing sample stage motion with a time delay integration (TDI) charge-couple device (CCD) in a semiconductor inspection tool, comprising: measuring a lateral position of a stage holding a sample being inspected; measuring a vertical position of the stage; determining a corrected lateral position of an imaged pixel of the sample based on the measured lateral and vertical positions; and synchronizing, using the corrected lateral position of the imaged pixel, charge transfer of the CCD. ### Claim 2 (depends on 1) The method of claim 1, further comprising: measuring a lateral velocity of the stage; measuring a vertical velocity of the stage; and, modifying the vertical velocity, wherein determining a corrected lateral position includes using the modified vertical velocity. ### Claim 3 (depends on 1) The method of claim 1, further comprising: measuring a lateral velocity of the stage; and, measuring a vertical velocity of the stage, wherein: the lateral and vertical velocities are coupled; the coupling distorts an actual lateral position of the imaged pixel; and, determining the corrected lateral position includes compensating for the distortion. ### Claim 4 (depends on 3) The method of claim 3, wherein: light used to charge the CCD is reflected from a surface of the sample at an acute angle; the reference signal generator is arranged generate, according to the acute angle, a reference signal; and, synchronizing the charge transfer includes using the reference signal to correct a difference between an apparent lateral position of the imaged pixel and the actual lateral position. ### Claim 5 (depends on 4) The method of claim 4, wherein: the acute angle is with respect to a line orthogonal to the surface; and, generating the reference signal includes generating the reference signal using a trigonometric function of the acute angle. ### Claim 6 (depends on 4) The method of claim 4, further comprising: inputting the reference signal to a phase lock loop; generating, using the phase lock loop, a control signal; generating, using the control signal, a pixel clock; and, synchronizing, using the pixel clock, the charge transfer. ### Claim 7 (depends on 4) The method of claim 4, further comprising: inputting the reference signal to a phase lock loop; generating, using the phase lock loop, a control signal; generating a pixel clock by modifying the control signal according to a contour, in the vertical direction, of the sample; and synchronizing, using the pixel clock, the charge transfer. ### Claim 8 (depends on 1) The method of claim 1, wherein synchronizing charge transfer includes using a phase lock loop. ### Claim 9 (depends on 1) The method of claim 1, wherein the sample is a reticle or a wafer. ### Claim 10 (depends on 1) The method of claim 1, wherein measuring the lateral and vertical positions includes using a six-axis laser interferometer. ### Claim 11 (depends on 1) The method of claim 1, further comprising: generating a pixel clock in a phase accumulator circuit using respective corrections from stage mirrors, at least one sample height map, and at least one sample surface map; and, synchronizing, using the pixel clock, the charge transfer. ### Claim 12 An apparatus for controlling charge transfer for a time delay integration (TDI) charge-coupled device (CCD) for a semiconductor inspection system, comprising: a phase and frequency controller arranged to generate a reference signal based on measured vertical and lateral positions of a stage holding a sample being inspected; and, a control system arranged to generate, using the reference signal, a pixel clock to control charge transfer of the CCD for an imaged pixel of the sample in a corrected lateral position. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein generating the reference signal includes modifying a vertical velocity of the stage. ### Claim 14 (depends on 12) The apparatus of claim 12, wherein: lateral and vertical velocities of the stage are coupled; the coupling distorts an actual lateral position of the imaged pixel; and, generating the pixel clock includes compensating for the distortion. ### Claim 15 (depends on 12) The apparatus of claim 12, wherein: light used to charge the CCD is reflected from a surface of the sample at an acute angle; and, the reference signal generator is arranged generate, according to the acute angle, the reference signal. ### Claim 16 (depends on 12) The apparatus of claim 12, wherein: the control system includes a phase lock loop; the phase lock loop is arranged to generate a control signal based on the reference signal; and the control system is arranged to generate the pixel clock using the control signal. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the control system is arranged to modify the control signal according to a contour, in the z direction, of the surface. ### Claim 18 An apparatus for controlling charge transfer for a time delay integration (TDI) charge-coupled device (CCD) for a semiconductor inspection system, comprising: a phase and frequency controller arranged to generate a reference signal based on measured vertical and lateral positions of a stage holding a sample being inspected; and, a control system: including a phase lock loop arranged to generate a control signal based on the reference signal; and, arranged to generate, using the control signal, a pixel clock to control charge transfer of the CCD and to correct a difference between an apparent lateral position of an imaged pixel of the sample and an actual lateral position of the imaged pixel, wherein: light used to charge the CCD is reflected from a surface of the sample at an acute angle; and, the reference signal generator is arranged to generate the reference signal based on the acute angle. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the control system is arranged to modify the control signal, according to a contour of the surface in the vertical direction, to generate the pixel clock.