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.

The invention relates to charged particle beam generator comprising a charged particle source for generating a charged particle beam, a collimator system comprising a collimator structure with a plurality of collimator electrodes for collimating the charged particle beam, a beam source vacuum chamber comprising the charged particle source, and a generator vacuum chamber comprising the collimator structure and the beam source vacuum chamber within a vacuum, wherein the collimator system is positioned outside the beam source vacuum chamber. Each of the beam source vacuum chamber and the generator vacuum chamber may be provided with a vacuum pump.

An electrostatic lens for transporting charged particles in an axial direction includes a first group of first electrodes configured to receive a first DC potential from a DC voltage source, and a second group of second electrodes configured to receive a second DC potential from the DC voltage source different from the first DC potential. The first electrodes are interdigitated with the second electrodes. The first group and/or the second group has a geometric feature that progressively varies along the axial direction. The lens generates an axial potential profile that progressively changes along the axial direction, and thereby reduces geometrical aberrations. The lens may be part of a charged particle processing apparatus such as, for example, a mass spectrometer or an electron microscope.

The invention relates to a charged particle beam device for inspection of a specimen with a plurality of charged particle beamlets. The charged particle beam device comprises a specimen holder for holding a specimen; a source for producing a beam of charged particles; and an illuminator for converting said beam of charged particles into a plurality of charged particle beamlets and directing said plurality of charged particle beamlets onto said specimen. According to the disclosure, the illuminator comprises a multi-aperture lens plate having a plurality of apertures for defining the corresponding plurality of charged particle beamlets; as well as at least a first electrode for generating an electrical field at a surface of the multi-aperture lens plate. The apertures in said multi-aperture lens plate have a noncircular cross-sectional shape to correct for neighbouring aperture induced aberrations. This allows for decreased spot size, and with this imaging resolution of the device is increased.

The invention relates to charged particle beam generator comprising a charged particle source for generating a charged particle beam, a collimator system comprising a collimator structure with a plurality of collimator electrodes for collimating the charged particle beam, a beam source vacuum chamber comprising the charged particle source, and a generator vacuum chamber comprising the collimator structure and the beam source vacuum chamber within a vacuum, wherein the collimator system is positioned outside the beam source vacuum chamber. Each of the beam source vacuum chamber and the generator vacuum chamber may be provided with a vacuum pump.

A multi-beam generation unit for a multi-beam system has larger individual focusing power for each of a plurality of primary charged particle beamlets. The multi-beam generation unit comprises an active terminating multi-aperture plate. The terminating multi-aperture plate can be used for a larger focusing range for an individual stigmatic focus spot adjustment of each beamlet of a plurality of primary charged particle beamlets.

A method includes operating a multiple particle beam system at different working points. The numerical aperture can be set for each of the working points in such a way that the resolution of the multiple particle beam system is optimal. In the process, the beam pitch between adjacent individual particle beams on the sample to be scanned is kept constant as a boundary condition. There are no mechanical reconfigurations of the system whatsoever for the purposes of varying the numerical aperture.

A method includes operating a multiple particle beam system at different working points. The numerical aperture can be set for each of the working points in such a way that the resolution of the multiple particle beam system is optimal. In the process, the beam pitch between adjacent individual particle beams on the sample to be scanned is kept constant as a boundary condition. There are no mechanical reconfigurations of the system whatsoever for the purposes of varying the numerical aperture.

The invention relates to a collimator electrode stack (70), comprising: at least three collimator electrodes (71-80) for collimating a charged particle beam along an optical axis (A), wherein each collimator electrode comprises an electrode body with an electrode aperture for allowing passage to the charged particle beam, wherein the electrode bodies are spaced along an axial direction (Z) which is substantially parallel with the optical axis, and wherein the electrode apertures are coaxially aligned along the optical axis; and a plurality of spacing structures (89) provided between each pair of adjacent collimator electrodes and made of an electrically insulating material, for positioning the collimator electrodes at predetermined distances along the axial direction. Each of the collimator electrodes (71-80) is electrically connected to a separate voltage output (151-160). The invention further relates to a method of operating a charged particle beam generator.

An electron beam apparatus (100) is described, including an electron source (105) configured to generate a primary electron beam propagating along an optical axis (A), a sample stage (108) configured to support a sample, an objective lens (120) configured to focus the primary electron beam on the sample for causing an emission of a signal electron beam and a foil or grid lens (300, 400) for influencing the signal electron beam. The foil or grid lens includes an electrode (340) that surrounds the optical axis; and a first foil or grid (320) adjacent to the electrode and perpendicular to the optical axis, the first foil or grid being substantially transparent to electrons, wherein a central opening (325) configured to allow the primary electron beam to pass through the central opening is provided in the first foil or grid.