# US 8,786,842 B2 · Grazing and normal incidence interferometer having common reference surface > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,842 B2 - Document ID: US8786842B2 - Status: Granted - Kind: B2 - Application number: 11/702,876 - Filed: 2007-02-05 - Published: 2008-11-13 - Granted: 2014-07-22 - Earliest claimed: 1999-06-18 - Assignees: KLA-Tencor Corporation - Applicants: Dieter Muller; Daniel Kavaldjiev; Rainer Schierle - Inventors: Dieter Muller; Daniel Kavaldjiev; Rainer Schierle - Web page: https://patentgrep.com/patent/US8786842B2 ## CPC - G01B 11/06: for measuring thickness {; e.g. of sheet material (thickness measurement by thermal means G01B21/085)} - G01B 9/02021: {contacting different faces of object, e.g. opposite faces} - G01B 9/02072: {by calibration or testing of interferometer} - G01B 9/0209: Low-coherence interferometers - G01B 11/0675: {using interferometry} - 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 - G01B 2290/30: Grating as beam-splitter - 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) ## Abstract A system for inspecting specimens such as semiconductor wafers is provided. The system provides scanning of dual-sided specimens using a diffraction grating that widens and passes nth order (n>0) wave fronts to the specimen surface and a reflective surface for each channel of the light beam. Two channels and two reflective surfaces are preferably employed, and the wavefronts are combined using a second diffraction grating and passed to a camera system having a desired aspect ratio. The system preferably comprises a damping arrangement which filters unwanted acoustic and seismic vibration, including an optics arrangement which scans a first portion of the specimen and a translation or rotation arrangement for translating or rotating the specimen to a position where the optics arrangement can scan the remaining portion(s) of the specimen. The system further includes-means for stitching scans together, providing for smaller and less expensive optical elements. ## Claims ### Claim 1 A method for measuring specimen thickness variations in a specimen having at least two sides, the method comprising: transmitting variable coherence light energy; receiving the variable coherence light energy, forming diffracted light energy, and passing the diffracted light energy toward two sides of said specimen and toward a plurality of reflective surfaces spaced apart from said specimen, the plurality of reflective surfaces comprising a semi-transparent reflective surface transparent through a first side and less than 90 percent reflective on a second side; sensing light energy from the specimen and the plurality of reflective surfaces; and performing an interferometric normal incidence inspection through the semi-transparent reflective surface. ### Claim 2 (depends on 1) The method of claim 1, wherein forming diffracted light energy comprises diffracting coherence light energy such that the passing the diffracted light energy passes diffracted nonzero order light energy. ### Claim 3 (depends on 2) The method of claim 2, further comprising blocking passage of diffracted zero order light energy. ### Claim 4 (depends on 1) The method of claim 1, further comprising receiving light energy from said plurality of reflective surfaces at a diffraction grating before said sensing. ### Claim 5 (depends on 1) The method of claim 1, wherein the sensing comprises receiving light energy from the plurality of reflective surfaces and the specimen at a sensor. ### Claim 6 (depends on 1) The method of claim 1, wherein the sensing employs a sensor comprising at least one camera, wherein each camera converts an elliptical image of at least one side of said specimen into an image having an aspect ratio closer to 1:1. ### Claim 7 (depends on 4) The method of claim 4, further comprising collimating variable coherence light energy and further collimating light energy received from said diffraction grating. ### Claim 8 (depends on 1) The method of claim 1, wherein said receiving comprises: passing nonzero order light energy toward at least one reflective surface and said specimen; and simultaneously blocking zero order light energy. ### Claim 9 (depends on 1) The method of claim 1, wherein the interferometric normal incidence inspection employs a collimator. ### Claim 10 (depends on 9) The method of claim 9, wherein said interferometric normal incidence inspection comprises emitting light toward a beamsplitter and the collimator. ### Claim 11 (depends on 1) The method of claim 1, further comprising optimizing diffracting for zero intensity of a zero order. ### Claim 12 A method for measuring thickness variations of a specimen comprising a plurality of sides, the method comprising: diffracting variable coherence light energy into multiple channels of light energy; directing said multiple channels of light energy toward two sides of said specimen and toward multiple reflecting surfaces, the multiple reflecting surfaces comprising a semi-transparent reflecting surface transparent through a first side and less than 90 per cent reflective on a second side; sensing light energy received from the two sides of the specimen; and performing an interferometric normal incidence inspection of the specimen through the semi-transparent reflecting surface. ### Claim 13 (depends on 12) The method of claim 12, wherein said diffracting comprises diffracting for zero intensity of the zero order of the multiple channels of light energy received. ### Claim 14 (depends on 12) The method of claim 12, further comprising performing an initial calibration. ### Claim 15 (depends on 12) The method of claim 12, wherein performing the interferometric normal incidence inspection on the specimen occurs prior to said diffracting. ### Claim 16 (depends on 12) The method of claim 12, wherein performing the interferometric normal incidence inspection of the specimen occurs after said sensing. ### Claim 17 (depends on 12) The method of claim 12, wherein said light energy received from the two sides of the specimen forms an image, and said directing step comprises altering the image aspect ratio. ### Claim 18 A specimen thickness measurement method, comprising: diffracting variable coherence light energy toward a specimen having a plurality of sides; receiving light energy from said diffracting at a plurality of reflecting surfaces and at two sides of said specimen, the plurality of reflecting surfaces comprising a semi-transparent reflecting surface transparent through a first side and less than 90 percent reflective on a second side; and performing an interferometric normal incidence inspection of the specimen through the semi-transparent surface; wherein said diffracting directs energy simultaneously toward one reflecting surface and one side of the specimen. ### Claim 19 (depends on 18) The method of claim 18, further comprising sensing light energy received from the plurality of reflecting surfaces and said specimen to determine thickness variations in said specimen. ### Claim 20 (depends on 18) The method of claim 18, further comprising blocking zero order light energy received from said diffracting.