# US 12,217,929 B2 · Systems and methods for chromatic aberration mitigation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,217,929 B2 - Document ID: US12217929B2 - Status: Granted - Kind: B2 - Application number: 17/785,886 - Filed: 2020-12-16 - Published: 2023-01-26 - Granted: 2025-02-04 - Earliest claimed: 2019-12-19 - Assignees: ASML Netherlands B.V. - Applicants: Asml Netherlands B.V. - Inventors: Yan Ren - Web page: https://patentgrep.com/patent/US12217929B2 ## CPC - H01J 37/153: Electron-optical or ion-optical arrangements for the correction of image defects, e.g. stigmators - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J 37/05: Electron or ion-optical arrangements for separating electrons or ions according to their energy {or mass}(particle separator tubes H01J49/00) - H01J 2237/1205: Microlenses - H01J 2237/1534: Aberrations - 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 method of reducing aberration comprises separating charged particles of a beam based on energy of the charged particles to form beamlets, each of the beamlets configured to include charged particles at a central energy level; and deflecting the beamlets so that beamlets having different central energy levels are deflected differently. An aberration corrector comprises a dispersive element configured to cause constituent parts of a beam (e.g. a charged particle beam) to spread apart based on energy; an aperture array configured to form beamlets from the spread apart beam; and a deflector array configured to deflect the beamlets differently based on central energy levels of particles that form the beamlets. ## Claims ### Claim 1 A method of reducing aberration, comprising: separating charged particles of a beam based on energy of the charged particles to form beamlets, each of the beamlets configured to include charged particles at a central energy level; and deflecting the beamlets so that beamlets having different central energy levels are deflected differently. ### Claim 2 An aberration corrector, comprising: a dispersive element configured to cause constituent parts of a beam to spread apart based on energy; an aperture array configured to form beamlets from the spread apart beam; and a deflector array configured to deflect the beamlets differently based on central energy levels of particles that form the beamlets. ### Claim 3 (depends on 2) The aberration corrector of claim 2, wherein the constituent parts include particles within a range around a central energy level of a beamlet. ### Claim 4 (depends on 3) The aberration corrector of claim 3, wherein the particles include electrons. ### Claim 5 (depends on 2) The aberration corrector of claim 2, wherein the dispersive element is configured to cause the constituent parts of the beam to spread apart based on energy by altering a trajectory of each of the constituent parts travelling through the dispersive element such that the constituent parts become spaced apart from one another. ### Claim 6 (depends on 2) The aberration corrector of claim 2, wherein the aperture array includes a plurality of openings and the deflector array includes a plurality of deflectors, each of the deflectors aligned with an opening of the aperture array. ### Claim 7 (depends on 2) The aberration corrector of claim 2, wherein the aperture array is configured to output the beamlets such that particles forming each beamlet are within a range around a central energy level, and to cut off particles included in the beam having energy at a periphery of the range. ### Claim 8 (depends on 2) The aberration corrector of claim 2, further comprising: a focusing lens, wherein the deflector array is configured to adjust beamlet entry positions and beamlet entry angles into the focusing lens so as to compensate for chromatic aberration of the lens. ### Claim 9 (depends on 2) The aberration corrector of claim 2, further comprising a lens array adjacent to the deflector array and configured to focus the beamlets differently so as to compensate for field curvature aberration. ### Claim 10 (depends on 9) The aberration corrector of claim 9, wherein the lens array includes a plurality of micro lenses that are configured so as to focus the beamlets differently based on a distance from a central axis of the lens array. ### Claim 11 (depends on 9) The aberration corrector of claim 9, wherein the lens array includes a first lens array configured to compensate for field curvature aberration and a second lens array configured to compensate for astigmatism aberration. ### Claim 12 (depends on 11) The aberration corrector of claim 11, wherein the second lens array includes an array of multipole micro lenses. ### Claim 13 (depends on 2) The aberration corrector of claim 2, wherein the dispersive element is configured to generate a magnetic field. ### Claim 14 (depends on 2) The aberration corrector of claim 2, wherein the dispersive element includes a component of a charged particle beam system. ### Claim 15 (depends on 14) The aberration corrector of claim 14, wherein the dispersive element includes a beam separator.