# US 9,040,212 B2 · Endpoint detection for photolithography mask repair > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,040,212 B2 - Document ID: US9040212B2 - Status: Granted - Kind: B2 - Application number: 13/789,876 - Filed: 2013-03-08 - Published: 2014-09-11 - Granted: 2015-05-26 - Earliest claimed: 2013-03-08 - Assignees: Taiwan Semiconductor Manufacturing Company, Ltd. - Applicants: Taiwan Semiconductor Manufacturing Company, Ltd. - Inventors: Chien-Lin Chen; Chih-Wei Wen; Chung-Hung Lin - Web page: https://patentgrep.com/patent/US9040212B2 ## CPC - H01J 37/304: Controlling tubes by information coming from the objects {or from the beam}, e.g. correction signals - G03F 1/74: by charged particle beam [CPB], e.g. focused ion beam - H01J 37/3056: {for microworking, e. g. etching of gratings or trimming of electrical components} - H01J 37/3174: {Particle-beam lithography, e.g. electron beam lithography} - H01J 2237/063: Electron sources - H01J 2237/30466: Detecting endpoint of process - H01J 2237/31744: introducing gas in vicinity of workpiece - H01J 2237/3175: Lithography - Y10S 430/143: Electron beam - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - 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) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A method includes scanning a lithography mask with a repair process, and measuring back-scattered electron signals of back-scattered electrons generated from the scanning. An endpoint is determined from the back-scattered electron signals. A stop point is calculated from the endpoint. The step of scanning is stopped when the calculated stop point is reached. ## Claims ### Claim 1 A method comprising: scanning a lithography mask using an electron beam to repair the lithography mask, wherein the scanning is performed in an environment comprising a process gas, and wherein the process gas reacts with the lithography mask when stimulated by the electron beam; measuring back-scattered electron signals of back-scattered electrons generated from the scanning; determining an endpoint from the back-scattered electron signals; calculating a stop point from the endpoint; and stopping the step of scanning when the stop point is reached. ### Claim 2 (depends on 1) The method of claim 1, wherein the step of determining the endpoint is performed using global back-scattered electron signals, and wherein the global back-scattered electron signals are generated from the back-scattered electron signals, with each of the global back-scattered electron signals generated from one loop of the scanning. ### Claim 3 (depends on 2) The method of claim 2 further comprising smoothing the global back-scattered electron signals to generate smoothed global back-scattered electron signals, wherein the endpoint is determined from the smoothed global back-scattered electron signals. ### Claim 4 (depends on 3) The method of claim 3, wherein the step of determining the endpoint comprises: calculating slopes of the smoothed global back-scattered electron signals in real time; and after slopes of a consecutive number of global back-scattered electron signals are smaller than a pre-selected threshold slope, a respective loop of the scanning corresponding to a last one of the consecutive number is determined as the endpoint. ### Claim 5 (depends on 1) The method of claim 1 further comprising, before the step of determining the endpoint is performed, performing a plurality of pre-loops of the scanning. ### Claim 6 (depends on 1) The method of claim 1, wherein during a period of time between the endpoint has been determined and the scanning is stopped, the back-scattered electron signals are stopped from being measured. ### Claim 7 (depends on 1) The method of claim 1, wherein the stop point is calculated by multiplying a first number of loops of scanning corresponding to the endpoint by a pre-selected value to generate a product, and adding a pre-selected number of post loops to the product. ### Claim 8 A method comprising: scanning a lithography mask using an electron beam to repair the lithography mask, wherein the scanning is performed in an environment comprising a process gas, and wherein the process gas reacts with the lithography mask when stimulated by the electron beam; measuring global back-scattered electron signals of back-scattered electrons from the lithography mask; smoothing the global back-scattered electron signals to generate smoothed global back-scattered electron signals; calculating slopes of the smoothed global back-scattered electron signals in real time; comparing the slopes with a pre-selected threshold slope to determine an endpoint, wherein at the endpoint, a first number of loops of scanning have been executed; calculating a second number of loops of scanning, wherein the step of calculating the second number comprises multiplying the first number by a constant ratio greater than one to generate a product; and stopping the step of scanning when the second number of loops of scanning is reached. ### Claim 9 (depends on 8) The method of claim 8, wherein the process gas comprises Xeon di-fluoride (XeF2), and wherein scanned portions of the lithography mask react with the XeF2. ### Claim 10 (depends on 8) The method of claim 8, wherein process gas reacts with the lithography mask to generate a gaseous product. ### Claim 11 (depends on 8) The method of claim 8, wherein the second number of loops of scanning is equal to a sum of the product and a pre-selected number of post-loops, and wherein the pre-selected number of post-loops is greater than one. ### Claim 12 (depends on 8) The method of claim 8, wherein the step of smoothing the global back-scattered electron signals, the step of calculating the slopes, the step of comparing the slopes, the step of calculating the second number of loops, and the stopping the scanning are performed automatically. ### Claim 13 (depends on 8) The method of claim 8, wherein after the second number of loops is calculated, the global back-scattered electron signals are stopped from being measured. ### Claim 14 (depends on 8) The method of claim 8 further comprising, injecting XeF2 to assist removing portions of the lithography mask. ### Claim 15 A method comprising: scanning a lithography mask using an electron beam to repair the lithography mask, wherein the scanning is performed in an environment comprising a process gas, and wherein the process gas reacts with the lithography mask when stimulated by the electron beam; determining an endpoint from back-scattered electron signals of back-scattered electrons generated during the scanning; performing a first plurality of loops of scanning after the endpoint is reached; and upon the plurality of loops of scanning is performed, stopping the scanning. ### Claim 16 (depends on 15) The method of claim 15 further comprising calculating a count of the first plurality of loops, wherein the calculating comprises multiplying a count of a second plurality of loops of scanning by a pre-selected value to generate a product, with the second plurality of loops of scanning performed before the endpoint is reached. ### Claim 17 (depends on 16) The method of claim 16, wherein the calculating further comprises adding a pre-selected number of post loops to the product. ### Claim 18 (depends on 15) The method of claim 15, wherein the determining the endpoint is performed using global back-scattered electron signals, and wherein the global back-scattered electron signals are generated from the back-scattered electron signals, with each of the global back-scattered electron signals generated from one loop of the scanning. ### Claim 19 (depends on 18) The method of claim 18 further comprising smoothing the global back-scattered electron signals to generate smoothed global back-scattered electron signals, wherein the endpoint is determined from the smoothed global back-scattered electron signals. ### Claim 20 (depends on 15) The method of claim 15, wherein during a period of time between the endpoint has been determined and the scanning is stopped, the back-scattered electron signals are stopped from being measured.