Multi electron beam inspection apparatus

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.

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.

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.

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.

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.