# US 10,312,052 B2 · Multi electron beam inspection apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,312,052 B2 - Document ID: US10312052B2 - Status: Granted - Kind: B2 - Application number: 15/507,661 - Filed: 2015-09-03 - Published: 2017-08-24 - Granted: 2019-06-04 - Earliest claimed: 2014-09-04 - Assignees: Technische Universiteit Delft - Applicants: Technische Universiteit Delft - Inventors: Pieter Kruit - Web page: https://patentgrep.com/patent/US10312052B2 ## CPC - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J 37/12: electrostatic - H01J 2237/24592: Inspection and quality control of devices - H01J 2237/2817: Pattern inspection - H01J 2237/31774: Multi-beam - H01J 2237/31798: detecting pattern defects - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract Provided is an assembly for inspecting the surface of a sample. The assembly includes two or more multi-beam electron column units. Each unit has: a single thermal field emitter for emitting a diverging electron beam towards a beam splitter; wherein the beam splitter includes a first multi-aperture plate having multiple apertures for creating multiple primary electron beams; a collimator lens for collimating the diverging electron beam from the emitter; an objective lens unit for focusing said multiple primary electron beams on said sample; and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample. The two or more multi-beam electron column units are arranged adjacent to each other for inspecting different parts of the surface of the sample at the same time. ## Claims ### Claim 1 An assembly for inspecting the surface of a sample, wherein the assembly comprises two or more multi-beam electron column units, each multi-beam electron column unit comprising: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter, wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample, wherein the objective lens unit comprises a second electrostatic lens array for focusing said multiple primary electron beams on the surface of the sample, wherein the second electrostatic lens array comprises at least a second multi-aperture plate, wherein substantially each aperture of said second multi-aperture plate in use comprises an electrostatic lens, and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, wherein said two or more multi-beam electron column units are arranged adjacent to each other, and are arranged to focus their multiple primary electron beams onto the surface of the sample for inspecting different parts of the surface of the sample at the same time. ### Claim 2 (depends on 1) The assembly according to claim 1, wherein at least one of the two or more multi-beam electron column units comprises a single signal processing unit which is connected to the multi-sensor detector system of said one of the two or more multi-beam electron column units. ### Claim 3 (depends on 2) The assembly according to claim 2, wherein said one of the two or more multi-beam electron column units is connected to a central signal processing unit of the assembly via a single signal line. ### Claim 4 (depends on 1) The assembly according to claim 1, wherein the beam splitter comprises a first electrode which together with the first multi-aperture plate provides a first electrostatic lens array, wherein substantially each aperture of said first multi-aperture plate in use comprises an electrostatic lens, and wherein the electrostatic lenses of the first electrostatic lens array are arranged to focus the multiple primary electron beams in a first focus plane. ### Claim 5 (depends on 4) The assembly according to claim 4, wherein the first focus plane is arranged in or near the collimator lens unit. ### Claim 6 (depends on 1) The assembly according to claim 1, wherein said second electrostatic lens array comprises a second electrode at a distance from the second multi-aperture plate, wherein said second electrode comprises a single hole for passing said multiple primary electron beams there through. ### Claim 7 (depends on 1) The assembly according to claim 1, wherein said second multi-aperture plate, in use, is set at a different voltage from the surface of the sample in order to provide an electrostatic deceleration field for the primary electrons between the second multi-aperture plate and the surface of the sample, which is smaller than an electrostatic deceleration field between the second electrode and the second multi-aperture plate. ### Claim 8 (depends on 1) The assembly according to claim 1, wherein each multi-beam electron column unit further comprising an electro-magnetic deflection unit for aligning the multiple primary electron beams from said beam splitter onto the centers of the lenses in said second electrostatic lens array. ### Claim 9 (depends on 8) The assembly according to claim 8, wherein the electro-magnetic deflection unit is arranged for providing a substantial equal deflection for all primary electron beams of said multiple primary electron beams. ### Claim 10 (depends on 1) The assembly according to claim 1, wherein the collimator lens is a combined magnetic and electrostatic collimator lens for adjusting the pitch and rotation of the multiple primary electron beams created by said beam splitter to the pitch and rotation position of the centers of the lenses in said second electrostatic lens array. ### Claim 11 (depends on 1) The assembly according to claim 1, wherein said multi-beam electron columns comprise an array of individually adjustable deflection elements for steering the multiple primary electron beams from said beam splitter onto the centers of the lenses in said second electrostatic lens array. ### Claim 12 (depends on 1) The assembly according to claim 1, wherein at least in use each lens of the second electrostatic lens array is arranged to focus the secondary electrons from the sample on to the multi-sensor detector with one additional cross-over as compared to a primary electron beam. ### Claim 13 (depends on 1) The assembly according to claim 1, wherein each of said multi-beam electron column units comprise an electro-magnetic deflection system between said collimator lens and said objective lens unit for deflecting the secondary electron beams towards said multi-sensor detector system. ### Claim 14 (depends on 13) The assembly according to claim 13, wherein the electro-magnetic deflection system is arranged for deflecting said secondary electron beams over an angle between 1 and 20 degrees, preferably over an angle of approximately 3 degrees. ### Claim 15 (depends on 1) The assembly according to claim 1, wherein said multi-sensor detector system comprises: a fluorescent plate which is arranged for receiving the secondary electron beams and for generating a substantially separate light emitting spot for each one of said secondary electron beams, and a mirror for imaging the light emitting spots on a multi-sensor detector. ### Claim 16 (depends on 1) The assembly according to claim 1, wherein said multi-sensor detector system comprises: a fluorescent plate or layer which is arranged for receiving the secondary electron beams and for generating a substantially separate light emitting spot for each one of said secondary electron beams, an array of optical fibers, wherein said fluorescent plate or layer is arranged adjacent or is attached to a first end of said array of optical fibers for coupling light from said substantially separate light emitting spots into the optical fibers, and a multi-sensor detector which is coupled to a second end of said array of optical fibers, opposite to said first end. ### Claim 17 (depends on 15) The assembly according to claim 15, wherein the multi-sensor detector comprises a multi-pixel light detector. ### Claim 18 (depends on 1) The assembly according to claim 1, wherein said multi-sensor detector comprises a direct multi-pixel electron detector. ### Claim 19 (depends on 1) The assembly according to claim 1, wherein each multi-beam electron column unit comprises a third multi-aperture plate arranged at or near the first focus plane, wherein said third multi-aperture plate comprises multiple apertures which are arranged for passing the focused electron beams there through, one focused electron beam per aperture of said third multiple apertures. ### Claim 20 (depends on 19) The assembly according to claim 19, wherein each multi-beam electron column unit comprises a chamber, wherein said single thermal field emission source and said beam splitter are arranged inside said chamber, and wherein said second multi-aperture plate provides a wall of said chamber. ### Claim 21 (depends on 20) The assembly according to claim 20, wherein said chamber is connected to or comprises a vacuum pump, wherein said vacuum pump preferably comprises an ion pump. ### Claim 22 (depends on 1) The assembly according to claim 1, wherein each multi-beam electron column unit comprises a deflector at or near the single thermal field emission source. ### Claim 23 (depends on 1) The assembly according to claim 1, wherein said multi-beam electron columns occupy a surface area above the surface of said sample in a range of 20×20 mm2 to 60×60 mm2, preferably approximately 26×32 mm2. ### Claim 24 (depends on 1) The assembly according to claim 1, wherein a pitch of said focused multiple primary electron beams on the surface of the sample is in a range from 50 to 500 μm, preferably approximately 150 μm. ### Claim 25 A multi-beam electron column unit for inspecting the surface of a sample, wherein the multi-beam electron column unit comprises: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter, wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, wherein the beam splitter comprises a first electrode which together with the first multi-aperture plate provides a first electrostatic lens array, wherein substantially each aperture of said first multi-aperture plate in use comprises an electrostatic lens, and wherein the electrostatic lenses of the first electrostatic lens array are arranged to focus the multiple primary electron beams in a first focus plane, a further multi-aperture plate arranged at or near the first focus plane, wherein said further multi-aperture plate comprises multiple apertures which are arranged for passing the focused primary electron beams there through, one focused electron beam per aperture of said third multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample, and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, wherein the multi-beam electron column unit comprises a chamber, wherein said single thermal field emission source and said beam splitter are arranged inside said chamber, and wherein said further multi-aperture plate provides a wall of said chamber. ### Claim 26 (depends on 25) The multi-beam electron column unit according to claim 25, wherein said chamber is connected to or comprises a vacuum pump. ### Claim 27 A multi-beam electron column unit for inspecting the surface of a sample, wherein the multi-beam electron column unit comprises: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter, wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample, and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, wherein said multi-beam electron column unit comprises a deflector at or near the single thermal field emission source, wherein said deflector is arranged for correcting a drift of said emission source. ### Claim 28 A method for inspecting the surface of a sample comprising the steps of: (A) providing an assembly which comprises two or more multi-beam electron column units, each of said two or more multi-beam electron column units comprising: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter, wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample, wherein the objective lens unit comprises a second electrostatic lens array for focusing said multiple primary electron beams on the surface of the sample, wherein the second electrostatic lens array comprises at least a second multi-aperture plate, wherein substantially each aperture of said second multi-aperture plate in use comprises an electrostatic lens, and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, and wherein said two or more multi-beam electron column units are arranged adjacent to each other, and are arranged to focus their multiple primary electron beams onto the surface of the sample for inspecting different parts of the surface of the sample at the same time; (B) emitting a diverging electron beam towards the beam splitter using the single thermal field emission source; (C) creating multiple primary electron beams using the beam splitter; (D) collimating the diverging electron beam from the emitter using the collimator lens; (E) focusing said multiple primary electron beams on said sample using the objective lens unit; and (F) separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample using the multi-sensor detector system. ### Claim 29 A method for inspecting the surface of a sample comprising the steps of: (A) providing a multi-beam electron column unit, wherein the multi-beam electron column unit comprises: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter, wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, wherein the beam splitter comprises a first electrode which together with the first multi-aperture plate provides a first electrostatic lens array, wherein substantially each aperture of said first multi-aperture plate in use comprises an electrostatic lens, and wherein the electrostatic lenses of the first electrostatic lens array are arranged to focus the multiple primary electron beams in a first focus plane, a further multi-aperture plate arranged at or near the first focus plane, wherein said further multi-aperture plate comprises multiple apertures which are arranged for passing the focused primary electron beams there through, one focused electron beam per aperture of said third multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample, and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, wherein the multi-beam electron column unit comprises a chamber, wherein said single thermal field emission source and said beam splitter are arranged inside said chamber, and wherein said further multi-aperture plate provides a wall of said chamber; (B) emitting a diverging electron beam towards the beam splitter using the single thermal field emission source; (C) creating multiple primary electron beams using the beam splitter and focusing the multiple primary electron beams in the first focus plane; (D) passing the focused primary electron beams through the further multi-aperture plate arranged at or near the first focus plane; (E) collimating the diverging electron beam from the emitter using the collimator lens; (F) focusing said multiple primary electron beams on said sample using the objective lens unit; and (G) separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample using the multi-sensor detector system. ### Claim 30 (depends on 16) The assembly according to claim 16, wherein the multi-sensor detector comprises a multi-pixel light detector. ### Claim 31 A method for inspecting the surface of a sample comprising the steps of: (A) providing a multi-beam electron column unit, comprising: a single thermal field emission source for emitting a diverging electron beam towards a beam splitter; wherein the beam splitter comprises a first multi-aperture plate comprising multiple apertures which are arranged for creating multiple primary electron beams, one primary electron beam per aperture of said first multiple apertures, a collimator lens for substantially collimating the diverging electron beam from the emitter, an objective lens unit for focusing said multiple primary electron beams on said sample; and a multi-sensor detector system for separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample, wherein said multi-beam electron column unit comprises a deflector at or near the single thermal field emission source, wherein said deflector is arranged for correcting a drift of said emission source; (B) emitting a diverging electron beam towards the beam splitter using the single thermal field emission source; (C) creating multiple primary electron beams using the beam splitter; (D) collimating the diverging electron beam from the emitter using the collimator lens; (E) focusing said multiple primary electron beams on said sample using the objective lens unit; (F) separately detecting the intensity of secondary electron beams created by each one of said focused primary electron beams on said sample using the multi-sensor detector system; and (G) correcting a drift of said emission source of said multi-beam electron column unit using the deflector at or near the single thermal field emission source.