The beamlets in a multi-beam microscopy system are aligned based on coefficients of a fitted aberration model. In particular, an illuminator for directing the beamlets towards the sample is adjusted based on the coefficients to correct the aberrations. The coefficients are obtained based on measured beamlets' positions in the sample plane.

Disclosed herein is an inspection tool and a method for identifying defects in a sample. The method includes steps of scanning a first area of a sample with a first detector-beam and scanning a second area of the sample with a second detector-beam, then receiving first and second signals that are derived from the first and second detector-beams. The first and second signals are compared to determine whether a defect is present in the sample.

Objective lens array assemblies and associated methods are disclosed. In one arrangement, the objective lens array assembly focuses a multi-beam of sub-beams on a sample. Planar elements define a plurality of apertures aligned along sub-beam paths. An objective lens array projects the multi-beam towards a sample. Apertures of one or more of the planar elements compensate for off-axis aberrations in the multi-beam.

A multi-beam apparatus for observing a sample with high resolution and high throughput is proposed. In the apparatus, a source-conversion unit forms plural and parallel images of one single electron source by deflecting plural beamlets of a parallel primary-electron beam therefrom, and one objective lens focuses the plural deflected beamlets onto a sample surface and forms plural probe spots thereon. A movable condenser lens is used to collimate the primary-electron beam and vary the currents of the plural probe spots, a pre-beamlet-forming means weakens the Coulomb effect of the primary-electron beam, and the source-conversion unit minimizes the sizes of the plural probe spots by minimizing and compensating the off-axis aberrations of the objective lens and condenser lens.

A Wien filter and a charged particle beam imaging apparatus are provided. The Wien filter Wien filter, including a Wien filter body which includes: an electrostatic deflector, including at least one pair of electrodes, respective two electrodes in each pair of which are opposite to each other, each electrode including an electrode body constructed in an arc-shaped form, and respective electrode bodies of respective two electrodes in each pair of the at least one pair of electrodes being arranged concentrically with and opposite to each other in a diameter direction, and the at least one pair of electrodes being configured to generate respective electric fields by cooperation of the respective two electrodes in each pair of the at least one pair of electrodes, in the condition of respective bias voltages applied individually thereon; and a magnetic deflector, including at least one pair of magnetic poles, respective two magnetic poles in each pair of which are opposite to each other, each magnetic pole including a magnetic pole body constructed in an arc-shaped form, and respective magnetic pole bodies of respective two magnetic poles in each pair of the at least one pair of magnetic poles being arranged concentrically with and opposite to each other in the diameter direction, and the magnetic pole bodies of the at least one pair of magnetic poles in the magnetic deflector and the electrode bodies of the at least one pair of electrodes in the electrostatic deflector being arranged concentrically and spaced apart from each other in a circumferential direction, and the at least one pair of magnetic poles being configured to generate respective magnetic fields by cooperation of respective two magnetic poles in each pair of the at least one pair of magnetic poles; a resultant electric field formed collectively by all of the respective electric fields is perpendicular to a resultant magnetic field formed collectively by all of the respective magnetic fields; and each electrode is also provided with a respective first protrusion extending radially inwards from a radial inner side of the respective electrode body thereof, and each magnetic pole is also provided with a second protrusion extending radially inwards from a radial inner side of the respective magnetic pole body thereof.

A method of determining aberrations of a charged particle beam (11) focused by a focusing lens (120) with a given numerical aperture (NA) toward a sample (10) in a charged particle beam system is described. The method includes: (a.) simulating, based at least on the given numerical aperture (NA), one or more beam cross sections at one or more first defocus settings for each of two or more different values of a first beam aberration coefficient (C.sub.1) of a set of beam aberration coefficients (C.sub.1 . . . n), to provide a plurality of first simulated beam cross sections; (b.) extracting two or more values of a first aberration characteristic (.sup.˜C.sub.1) that is related to the first beam aberration coefficient (C.sub.1) from the plurality of first simulated beam cross sections; (c.) determining a first dependency between the first beam aberration coefficient (C.sub.1) and the first aberration characteristic (.sup.˜C.sub.1); (d.) taking one or more images of the sample at the one or more first defocus settings or at one or more second defocus settings, to provide one or more taken images, and retrieving one or more retrieved beam cross sections from the one or more taken images; (e.) extracting a retrieved value of the first aberration characteristic from the one or more retrieved beam cross sections; and (f.) determining an actual value of the first beam aberration coefficient based on the first dependency and based on the retrieved value of the first aberration characteristic.

A method for electron microscopy comprises: adjusting at least one of an electron beam and an image beam in such a way that off-axial aberrations inflicted on at least one of the electron beam and the image beam are minimized, the adjusting performed by using a beam adjusting component to obtain at least one modified image beam, wherein the adjusting comprises applying both shifting and tilting to at least one of the electron beam and the image beam and wherein the amount of tilting of at least one of the electron beam and the image beam depends on the amount of shifting of at least one of the electron beam and the image beam respectively and wherein the amount of tilting is computed based on at least one of coma and astigmatism introduced as a consequence of the shift.

As a device for correcting positive spherical aberration of an electromagnetic lens for a charged particle beam, a spherical aberration correction device combining a hole electrode and a ring electrode is known. In this spherical aberration correction device, when a voltage is applied between the hole electrode and the ring electrode, the focus of the charged particle beam device changes due to the convex lens effect generated in the hole electrode. Therefore, in a charged particle beam device including a charged particle beam source which generates a charged particle beam, a charged particle beam aperture having a ring shape, and a charged particle beam aperture power supply which applies a voltage to the charged particle beam aperture, the charged particle beam aperture power supply is configured to apply, to the charged particle beam aperture, a voltage having a polarity opposite to a polarity of charges of the charged particle beam.

An electron optical module for providing an off-axial electron beam with a tunable coma, according to the present disclosure includes a structure positioned downstream of an electron source and an electron lens assembly positioned between the structure and the electron source. The structure generates a decelerating electric field, and is positioned to prevent the passage of electrons along the optical axis of the electron lens assembly. The electron optical module further includes a micro-lens that is not positioned on the optical axis of the electron lens assembly and is configured to apply a lensing effect to an off-axial election beam. Aberrations applied to the off-axial electron beam by the micro-lens and the electron lens assembly combine so that a coma of the off-axial beam has a desired value in a downstream plane.

Systems for reducing the generation of thermal magnetic field noise in optical elements of microscope systems, are disclosed. Example microscopy optical elements having reduced Johnson noise generation according to the present disclosure comprises an inner core composed of an electrically isolating material, and an outer coating composed of an electrically conductive material. The product of the thickness of the outer coating and the electrical conductivity is less than 0.01Ω.sup.−1. The outer coating causes a reduction in Johnson noise generated by the optical element of greater than 2×, 3×, or an order of magnitude or greater. In a specific example embodiment, the optical element is a corrector system having reduced Johnson noise generation. Such a corrector system comprises an outer magnetic multipole, and an inner electrostatic multipole. The inner electrostatic multipole comprises an inner core composed of an electrically isolating material and an outer coating composed of an electrically conductive material.