# US 2020/0286707 A1 · Charged particle beam apparatus, and systems and methods for operating the apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0286707 A1 - Document ID: US20200286707A1 - Status: Published application - Kind: A1 - Application number: 16/824,499 - Filed: 2020-03-19 - Published: 2020-09-10 - Earliest claimed: 2017-09-19 - Assignees: ASML Netherlands B.V. - Applicants: ASML Netherlands B.V. - Inventors: Martinus Gerardus, Maria, Johannes MAASSEN; Peter Paul HEMPENIUS; Weiming REN; Zhongwei CHEN - Web page: https://patentgrep.com/patent/US20200286707A1 ## CPC - H01J 37/21: Means for adjusting the focus - H01J 37/222: {Image processing arrangements associated with the tube} - H01J 37/244: Detectors; Associated components or circuits therefor - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J 2237/0453: multiple apertures - H01J 2237/2817: Pattern inspection - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A charged particle beam apparatus includes a beamlet forming unit configured to form and scan an array of beamlets on a sample. A first portion of the array of beamlets is focused onto a focus plane, and a second portion of the array of beamlets has at least one beamlet with a defocusing level with respect to the focus plane. The charged particle beam apparatus also includes a detector configured to detect an image of the sample formed by the array of beamlets, and a processor configured to estimate a level of separation between the focus plane and the sample based on the detected image and then reduce the level of separation based on the estimated level. ## Claims ### Claim 1 A charged particle beam apparatus, comprising: a beamlet forming unit configured to form and scan an array of beamlets on a sample, a first portion of the array of beamlets being focused onto a focus plane, and a second portion of the array of beamlets having at least one beamlet with a defocusing level with respect to the focus plane; a detector configured to detect an image of the sample formed by the array of beamlets; and a processor configured to estimate a level of separation between the focus plane and the sample based on the detected image and then reduce the level of separation based on the estimated level. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the detector includes an array of detection elements that detect signals of the image formed by the array of beamlets respectively. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the processor is further configured to adjust a focusing power of a focusing element in the beamlet forming unit to reduce the level of separation. ### Claim 4 (depends on 1) The system of claim 1, wherein the processor is further configured to move the sample to reduce the level of separation. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein one beamlet of the second portion of the array of beamlets is focused on the focus plane. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the processor is further configured to: control the beamlet forming unit to perform a first scan of the sample using at least a first subset of beamlets in the array of beamlets to form an image of the sample; reduce a level of separation based on the image of the sample; and control the beamlet forming unit to perform a second scan of the sample using at least a second subset of beamlets in the array of beamlets. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein the first subset of beamlets includes a subset of beamlets in the second portion, wherein the first subset of beamlets includes the beamlets in the first portion and a subset of beamlets in the second portion, wherein the second subset of beamlets includes the beamlets in the first portion, or wherein the second subset of beamlets includes the beamlets in the first portion and a subset of beamlets in the second portion. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein a scanning condition of each beamlet of the second portion is different from a scanning condition of each beamlet of the first portion. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the scanning condition is scanning area. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the scanning area of each beamlet of the second portion is smaller than the scanning area of each beamlet of the first portion. ### Claim 11 (depends on 8) The apparatus of claim 8, wherein the scanning condition is scanning frequency. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the scanning frequency of each beamlet of the second portion is higher than the scanning frequency of each beamlet of the first portion. ### Claim 13 (depends on 8) The apparatus of claim 8, wherein the scanning condition is scanning direction. ### Claim 14 A method performed by a controller for controlling a charged particle beam system, comprising: estimating a level of separation between a focus plane and a sample based on an image of the sample formed by an array of beamlets, a first portion of the array of beamlets being focused onto the focus plane, and a second portion of the array of beamlets having at least one beamlet with a defocusing level with respect to the focus plane; and adjusting the level of separation based on the estimated level. ### Claim 15 A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor of a controller to cause the controller to perform a method for controlling a charged particle beam system, the method comprising: estimating a level of separation between a focus plane and a sample based on an image of the sample formed by an array of beamlets, a first portion of the array of beamlets being focused onto the focus plane, and a second portion of the array of beamlets having at least one beamlet with a defocusing level with respect to the focus plane; and adjusting the level of separation based on the estimated level.