The embodiments of the present disclosure provide various techniques for detecting backscatter charged particles, including accelerating charged particle sub-beams along sub-beam paths to a sample, repelling secondary charged particles from detector arrays, and providing devices and detectors which can switch between modes for primarily detecting charged particles and modes for primarily detecting secondary particles.

A multi-beam apparatus for observing a sample with high resolution and high throughput is proposed. In the apparatus, a source-conversion unit changes a single electron source into a virtual multi-source array, a primary projection imaging system projects the array to form plural probe spots on the sample, and a condenser lens adjusts the currents of the plural probe spots. In the source-conversion unit, the image-forming means is on the upstream of the beamlet-limit means, and thereby generating less scattered electrons. The image-forming means not only forms the virtual multi-source array, but also compensates the off-axis aberrations of the plurality of probe spots.

A charged particle multi-beam device includes a charged particle source, a collimator lens, a multi-light-source forming unit, and a reduction projection optical system. The multi-light-source forming unit has first to third porous electrodes disposed side by side in an optical axis direction. A plurality of holes for causing the multi-beams to pass is formed in each of the first to third porous electrodes. The first porous electrode and the third porous electrode have the same potential and the second porous electrode has potential different from the potential of the first porous electrode and the third porous electrode. A diameter of the holes on the second porous electrode is formed larger further away from an optical axis such that a surface on which the multi-light sources are located is formed in a shape convex to the charged particle source side.

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.

Arrangements involving objective lens array assemblies for charged-particle assessment tools are disclosed. In one arrangement, the assembly comprises an objective lens array and a control lens array. Each objective lens projects a respective sub-beam of a multi-beam onto a sample. The control lens array is associated with the objective lens array and positioned up-beam of the objective lens array. The control lenses pre-focus the sub-beams.

A multi-beam apparatus for observing a sample with oblique illumination is proposed. In the apparatus, a new source-conversion unit changes a single electron source into a slant virtual multi-source array, a primary projection imaging system projects the array to form plural probe spots on the sample with oblique illumination, and a condenser lens adjusts the currents of the plural probe spots. In the source-conversion unit, the image-forming means not only forms the slant virtual multi-source array, but also compensates the off-axis aberrations of the plurality of probe spots. The apparatus can provide dark-field images and/or bright-field images of the sample.

Systems, methods, and programming are described for inspecting a substrate having a pattern imaged thereon, including obtaining a plurality of selected target locations on the substrate, the selected target locations dependent on characteristics of the pattern, scanning the substrate with a plurality of electron beamlets, wherein the scanning includes individually addressing the beamlets to impinge on the selected target locations independently, detecting a reflected or a transmitted portion of the beamlets, and generating images of the selected target locations.

A charged particle beam system includes a charged particle source that generates a first charged particle beam and a multi beam generator that generates a plurality of charged particle beamlets from an incoming first charged particle beam. Each individual beamlet is spatially separated from other beamlets. The charged particle beam system also includes an objective lens that focuses incoming charged particle beamlets in a first plane so that a first region in which a first individual beamlet impinges in the first plane is spatially separated from a second region in which a second individual beamlet impinges in the first plane. The charged particle beam system also includes a projection system and a detector system including a plurality of individual detectors. The projection system images interaction products leaving the first region within the first plane due to impinging charged particles onto a first detector and images interaction products leaving the second region in the first plane onto a second detector.

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.