Abstract: A charged particle beam focusing apparatus includes a charged particle beam generator configured to project simultaneously at least one non-astigmatic charged particle beam and at least one astigmatic charged particle beam onto locations on a surface of a specimen, thereby causing released electrons to be emitted from the locations. The apparatus also includes an imaging detector configured to receive the released electrons from the locations and to form images of the locations from the released electrons. A processor analyzes the image produced by the at least one non-astigmatic charged particle beam and in response thereto adjusts a focus of the at least one non-astigmatic charged particle beam.

Abstract: The present invention relates to a charged particle system comprising: a charged particle source; a first multi aperture plate; a second multi aperture plate disposed downstream of the first multi aperture plate, the second multi aperture plate; a controller configured to selectively apply at least first and second voltage differences between the first and second multi aperture plates; wherein the charged particle source and the first and second multi aperture plates are arranged such that each of a plurality of charged particle beamlets traverses an aperture pair, said aperture pair comprising one aperture of the first multi aperture plate and one aperture of the second multi aperture plate, wherein plural aperture pairs are arranged such that a center of the aperture of the first multi aperture plate is, when seen in a direction of incidence of the charged particle beamlet traversing the aperture of the first multi aperture plate, displaced relative to a center of the aperture of the second multi aperture p

Abstract: An objective lens arrangement includes a first, second and third pole pieces, each being substantially rotationally symmetric. The first, second and third pole pieces are disposed on a same side of an object plane. An end of the first pole piece is separated from an end of the second pole piece to form a first gap, and an end of the third pole piece is separated from an end of the second pole piece to form a second gap. A first excitation coil generates a focusing magnetic field in the first gap, and a second excitation coil generates a compensating magnetic field in the second gap. First and second power supplies supply current to the first and second excitation coils, respectively. A magnetic flux generated in the second pole piece is oriented in a same direction as a magnetic flux generated in the second pole piece.