Multi-beam particle microscope operating with a wide range of landing energies

Abstract

This invention discloses a multi-beam particle microscope that reduces aberrations in the secondary particle optical beam path. This solution is applicable to a wide range of landing energies up to several keV. One measure to achieve this is to employ a structural approach that improves the overall projection path design, particularly improving the positioning of the first projection lens in the secondary particle optical beam path, where the first projection lens is a space-consuming magnetic lens. When operating a multi-beam particle microscope at a wide range of landing energies, the fill factor in the first projection lens is considered a major source of residual aberrations in the secondary particle optical beam path. Another measure is to improve the performance of the beam splitter configuration itself in the secondary particle optical beam path. This invention discloses several designs and design rules for beam splitter configurations to reduce aberrations when operating a multi-beam particle microscope at a wide range of landing energies.

Description

Multi-beam particle microscope with a wide range of landing energies This invention relates to a multi-beam particle microscope operating at a wide range of landing energies. The multi-beam particle microscope includes an improved projection system and / or an improved beam splitter configuration. The beam splitter configuration includes a magnet configuration for separating the primary particle optical beam path from the secondary particle optical beam path. As semiconductor components and other microstructures continue to shrink and become increasingly complex, there is a need to further develop and optimize planar fabrication technologies and detection systems for producing and detecting these small-sized microstructures. For example, the development and production of semiconductor components requires monitoring and testing wafer designs, while planar fabrication technologies need process optimization to achieve reliable production with high throughput. Furthermore, there is a growing need to analyze semiconductor wafers used for reverse engineering of semiconductor components and for customer-specific individual configurations. Therefore, there is a need for inspection components that can be used in high-volume production to inspect microstructures on wafers with high accuracy. Typical silicon wafers used to manufacture semiconductor components can reach diameters of up to 300 mm. Each wafer is divided into 30 to 60 repeating regions (dies), with dimensions up to 800 mm². Semiconductor devices comprise multiple semiconductor structures, which are layered on the wafer surface using planar integration technology. Due to the manufacturing process, semiconductor wafers typically have a flat surface. The structural dimensions of the integrated semiconductor structures in this case extend from a few µm to critical dimensions (CD) of 5 nm, and these dimensions are expected to become even smaller in the near future; in the future, the structural dimensions, or critical dimensions (CD), are projected to be less than 3 nm, for example, 2 nm, or even less than 1 nm. With these small structural dimensions, dimensional defects in critical dimensions must be identified rapidly over a very large area. For several applications, the specifications for the measurement accuracy provided by inspection equipment are even higher, for example, by a factor of two or one order of magnitude. For example, the width of a semiconductor feature must be measured with an accuracy of less than 1 nm, such as 0.3 nm or even smaller, and the relative positions of semiconductor structures must be determined with an overlap accuracy of less than 1 nm, such as 0.3 nm or even smaller. MSEM (Multi-beam Scanning Electron Microscopy) is a relatively new development in the field of charged particle systems (charged particle microscopes, CPMs). For example, a multi-beam scanning electron microscope is disclosed in patent documents US 7,244,949 B2 and US 2019 / 0355544 A1. In the case of a multi-beam electron microscope or MSEM, a sample is simultaneously irradiated using a plurality of individual electron beams arranged in a field or raster. For example, 4 to 10,000 individual electron beams can be provided as the main radiation, with each individual electron beam separated from an adjacent individual electron beam by a spacing of 1 to 200 micrometers. For example, an MSEM has approximately 100 individual electron beams ("small beams"), which are arranged, for example, in a hexagonal raster, with the individual electron beams separated by a spacing of approximately 10 μm. The plurality of charged individual particle beams (the main beam) are focused onto the surface of the sample to be examined by a common objective lens. For example, the sample may be a semiconductor wafer, fixed to a wafer holder mounted on a movable platform. During irradiation of the wafer surface with a beam of charged primary individual particles, interaction products, such as secondary electrons or backscattered electrons, are emitted from the wafer surface. Their origins correspond to the locations on the sample where the plurality of primary individual particle beams are focused in various cases. The number and energy of the interaction products depend on the material composition and the morphology of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are focused by a common objective lens and incident on a detector arranged in a detection plane by a projection imaging system of a multi-beam inspection system. The detector comprises a plurality of detection regions, each containing a plurality of detection pixels, and the detector captures an intensity distribution of each secondary individual particle beam. In this process, an image field of, for example, 100 µm × 100 µm is obtained. Conventional multibeam electron microscopes include a series of electrostatic and magnetic elements. At least some of these electrostatic and magnetic elements are adjustable to accommodate the focal positions and stigmation-free nature of a plurality of charged individual particle beams. Furthermore, conventional multibeam systems with charged particles include at least one intersecting plane of primary or secondary charged individual particle beams. Additionally, conventional systems include a detection system to facilitate adjustment. Conventional multibeam particle microscopes include at least one deflector (deflection scanner) for collectively scanning a region of the sample surface with a plurality of primary individual particle beams to obtain an image field of the sample surface. A beam splitter (or alternatively, a beam sepatator or beam divider) is used to separate the particle optical beam paths of the primary beam from those of the secondary beam. In this case, the separation is achieved by a special configuration of magnetic and / or electrostatic fields, such as by a Wien filter. Imaging aberrations are typically caused by the use of particle optics components. Aberrations also occur within the particle optics imaging range when using a beam splitter, and these need to be corrected as much as possible. Ideally, imaging aberrations of all individual particle beams should be avoided or corrected. Correction generally becomes increasingly important as the image field becomes wider within the particle optics imaging range. In the case of multi-beam particle microscopy (multi-image field, so-called mFOV) using multiple individual particle beams, the image field can be particularly extensive. To correct for aberrations caused by the beam splitter in a multi-beam particle microscope, EP 1 668 662 B1 discloses providing an additional magnetic field in the main path upstream of the actually separated magnetic field. Aberrations in the secondary path are corrected by up to three additional magnetic fields in the secondary path. US 9,153,413 B2 discloses another beam splitter for multi-beam particle microscopy, in which aberrations caused by the beam splitter are corrected. The beam splitter operates based on the principle of a Wien filter. To correct aberrations, the alignment or tilt of individual particle beams is corrected individually or separately by a multi-deflector array after passing through the beam splitter. DE 10 2022 120 496 A1 discloses a particle optics configuration, particularly a multi-beam particle microscope, having a magnetic configuration for separating primary and secondary particle optical beam paths. The magnetic configuration includes: a first magnetic field region through which both the primary and secondary particle optical beam paths pass, for separating the primary and secondary particle optical beam paths from each other; a second magnetic field region disposed within the primary particle optical beam path but not within the secondary particle optical beam path, the second magnetic field region being positioned upstream of the primary particle optical beam path relative to the first magnetic field region, and the first and second magnetic field regions substantially deflecting the primary particle optical beam path in different directions; and a third magnetic field region disposed within the primary particle optical beam path but not within the secondary particle optical beam path, the third magnetic field region being positioned upstream of the primary particle optical beam path relative to the second magnetic field region, and the first and third magnetic field regions substantially deflecting the primary particle optical beam in the same direction. The entry direction of the primary particle optical beam path into the third magnetic field region and the exit direction of the primary particle optical beam path leaving the first magnetic field region are parallel to each other and without offset. As the requirements for resolution in multi-beam particle microscopy increase, so too do the requirements for aberration correction. Therefore, comprehensive improvements are needed in correcting imaging aberrations caused by beam splitters. DE 10 2023 120 127 A1 (not published on the priority date of this patent application) discloses an improved beam splitter suitable for multi-beam particle microscopy, the entire disclosure of which is incorporated herein by reference. This application discloses the arrangement of two magnetic regions in the main beam path, wherein a so-called first magnetic region or split magnetic region for separating the main particle optical beam path and the secondary particle optical beam path has a specific orientation, through which the main particle optical beam path and the secondary particle optical beam path pass. More precisely, each magnetic region has an entrance region with an entrance tilt angle for the main particle optical beam path and an exit region with an exit tilt angle for the main particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the alignment of the entrance region deviates from the normal to the optical axis of the main particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the alignment of the exit region deviates from the normal to the optical axis of the main particle optical beam path. In DE 10 2023 120 127 A1, it is disclosed that the exit tilt angle is intentionally deviated from 0°. This measure helps to further and significantly reduce aberrations caused by the beamsplitter configuration in the primary particle optical beam path. Furthermore, it is revealed that after passing through the first magnetic region, the beamsplitter configuration in the secondary particle optical beam path has at least six additional magnetic field regions and / or quadrupole fields. These are configured to precisely couple the particle optical axes in the secondary beam path (whose path forms the secondary particle optical beam path) to subsequent projection optics in terms of offset and angle when the energy of the secondary particles changes, and also achieve paraxial astigmatism-free, paraxial distortion-free, and paraxial dispersion-free imaging. Further details of the beamsplitter configuration in the secondary particle optical beam path are not disclosed. Therefore, it is necessary to further reduce the aberrations caused by beam splitters in the secondary particle optical beam path. EP 1 668 662 B1 discloses a beamsplitter configuration in a secondary particle optical beam path. This beamsplitter configuration comprises four magnetic regions in the secondary particle optical beam path, followed by a quadrupole lens. For a given landing energy LE of the primary electrons on the object, the beamsplitter configuration in the secondary particle optical beam path has first-order astigmatism-free, first-order distortion-free, and first-order dispersion correction. A beamsplitter configuration is also needed that allows for corresponding corrections at more than one landing energy. EP 1 668 662 B1 reveals a typical range of landing energies for objects, from 0 eV to approximately 100 eV. However, because the optimal landing energy depends on the properties of the sample / object, the goal is to operate multi-beam particle microscopy with higher landing energies. However, if the landing energy is too high, the kinetic energy of secondary particles emitted from the object decreases, and aberrations in the secondary particle optical beam path are typically enhanced. Therefore, operating multi-beam particle microscopy with higher landing energies while still being able to correct aberrations well in the secondary particle optical beam path is a common task. The currently available landing energy range cited is insufficient for performing specific defect inspection and / or metrology tasks. For example, for physical defect inspection of EUV photoresist layers, lower landing energies in the 50 eV to 500 eV range are beneficial for improving contrast and reducing CD shrinkage. On the other hand, higher landing energies in the 3 keV to 30 keV range would be useful for overburden metrology or imaging of deep trenches and contact holes. The purpose of this invention is to provide an improved multi-beam particle microscope that can operate over a wide range of landing energies while still providing very good correction for aberrations in the secondary particle optical beam path. Another objective of this invention is to further reduce aberrations caused by beam splitters in the secondary particle optics beam path of multi-beam particle microscopes. This objective is achieved through the object of the independent item request. Advantageous specific embodiments of the invention are clearly visible from the appendix claims. This patent application claims priority to German patent application No. 10 2024 108 091.4, filed on March 21, 2024, the entire disclosure of which is incorporated herein by reference. The performance of the state-of-the-art projection systems in the aforementioned multi-beam particle microscopes hinders access to extended ranges of the described electron beams (LEs), particularly higher LEs, for several reasons, two of which are: - To avoid crosstalk between adjacent detectors, the blurring and distortion of the projected signal / secondary electron point must be sufficiently small, which is not currently the case at high landing energy LEs (the typical limitation on the blur point radius plus the maximum distortion is approximately 80% of the detector circle radius, attributed to the detection of each individual signal electron beam). - To limit contrast anisotropy, it is necessary to avoid excessive ellipticity of the beam crossing cross section on the plane of the contrast aperture (typically limited to 0.1 ellipticity). The inventors further investigated the above-mentioned problems and identified two solutions that sometimes conflict with each other. The first solution focuses on optimizing the performance of the entire projection system (architectural approach), while the second solution focuses on optimizing the performance of the internal beam splitters (component-based approach). The motivation for the first approach stems from the discovery that the performance of the projection system (especially at higher landing energies) is not necessarily primarily limited by the performance of the internal beamsplitter, but rather by the aberrations of one or more projection system lenses (PLs) positioned after the beamsplitter configuration relative to the secondary particle optical beam path, according to existing technology. The basic idea is that if the aberrations of the performance-limiting projection lens system can be significantly reduced in this way, then reducing the requirements for beamsplitter performance is beneficial. The motivation for the second method is based on the following fundamental principle: a well-calibrated beam splitter design firstly introduces only a small aberration into the entire projection system, and secondly, it transmits a small beam of signal electrons with very little aberration to the subsequent electron-optical components in the projection system, thereby helping to avoid corresponding errors. This invention covers solutions based on the two methods described above. According to the first method, it has been found that when operating at higher landing energies, the so-called fill factor of the first projection lens in the projection lens system has a decisive influence on aberrations. More specifically, to increase the landing energy, the energy of secondary particles / signal electrons becomes increasingly smaller, resulting in a larger focusing objective lens. Due to the optimal operation of the primary particle beam path, the focusing of the objective lens is fixed and cannot be changed for secondary particles. Therefore, the first intermediate image of the secondary particle / signal electron beam gets closer and closer to the sample / object. Consequently, for higher landing energies (LE), the multi-field-of-view (mFOV) radius within the first projection lens increases. This increases the fill factor within the first projection lens, leading to a larger accumulation of aberrations in the first projection lens and in subsequent particle optical paths. Recognizing the importance of the fill factor of the first projection lens for suppressing aberrations, according to a first aspect of the invention, the fill factor is reduced. More specifically, according to a first aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; and a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, wherein the second separate particle beam originates from... The second field includes the incident position; a magnetic and / or electrostatic objective lens system through which both the first and second individual particle beams pass; a beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first individual particle beam on the object; wherein the beam splitter configuration includes at least one first magnetic region configured to provide a uniform magnetic field through which the primary and secondary particle optical beam paths pass during use. The first magnetic region configuration is used to separate the primary particle optical beam path and the secondary particle optical beam path from each other; wherein each magnetic region has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region deviates from 0°; wherein the secondary particle optical beam path includes a first intersection of a second individual particle beam corresponding to the focal plane of the objective lens system, and A second crossover of a second individual particle beam, configured between a beam splitter configuration and a detection unit and configurable during use to be flush with a contrast aperture; wherein the second particle optical unit includes a projection lens system having a first projection lens, the first projection lens being a magnetic lens, the first projection lens being configured relative to the secondary particle optical beam path after the first crossover and before the second crossover, the projection lens system being configured to image the second individual particle beam onto a third field, and the first projection lens system being configured to focus a plurality of second individual particle beams onto the second crossover; wherein a controller configuration is configured to control the first projection lens to focus a plurality of second individual particle beams onto the second crossover according to the landing energy;The first projection lens is configured so close to the first intersection that the fill factor PL1 of the first projection lens is set to PL1 ≤ 15%, specifically PL1 ≤ 10% or PL1 ≤ 5%, where the fill factor PL1 is defined as the ratio between the maximum radius Rmax of all the plurality of second separate particle beams within the first projection lens and the inner radius Ri of an opening through which the second separate particle beams pass, therefore PL1 = Rmax / Ri. In other words, the first projection lens (which is a magnetic lens) typically has pole pieces, with a central bore of inner diameter Ri. The second individual particle beam must pass through this bore or opening and must maintain a certain distance from the inner wall to avoid excessive aberrations. The sum of the areas of the plurality of second individual particle beams corresponds to the field of view (FOV) within the first projection lens. However, in principle, the first projection lens of the projection lens system, as well as any other possible lenses, can also be electrostatic lenses. Landing energy can range from zero to several keV, such as 3 keV, 5 keV, 10 keV, 15 keV, 20 keV, 25 keV, or 30 keV. The magnetic regions themselves can be formed in known ways. In particular, they are designed to create a uniform magnetic field, the direction of which is orthogonal to the direction of motion of the individual particle beams. For example, each magnetic region can be formed from two spaced-apart plates of magnetizable material, each plate having a milled groove into which a current conductor or coil is inserted. However, other specific embodiments are also possible. The second cross is flush with the contrast aperture when using a multi-beam particle microscope. This contrast aperture allows filtering of a second, individual beam of particles emitted from the object relative to its initial angle relative to the object. The first individual charged particle beam can be, for example, electrons, positrons, muons, ions, or other charged particles. The second individual charged particle beam can be the mirror image of the first individual charged particle beam; these can be secondary electrons or backscattered electrons. Therefore, in principle, the particle optics configuration can be used flexibly. The terms "primary particle optical beam path" and "secondary particle optical beam path" are used as is customary in the art. However, it should be noted that, like the secondary particle optical beam path, the primary particle optical beam path describes the path of a plurality of first or second separate particle beams. However, for simplicity, depending on the context, the terms "primary particle optical beam path" and "secondary particle optical beam path" may naturally refer only to a single separate particle beam or central beam moving along the system's optical axis. According to a preferred embodiment, the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The second magnetic region is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting a second, separate particle beam. The beam splitter configuration further includes a third magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The third magnetic region is positioned downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field. A first projection lens is disposed between the first and second magnetic regions; and a controller is configured to control the second and third magnetic regions based on the landing energy. Using this radical approach, and with the first projection lens very close to the object / sample, the fill factor PL1 within the first projection lens can be reduced very effectively. The second and third magnetic regions can be used for further correction in the secondary particle optical beam path. According to a preferred embodiment, the controller is configured to control the second and third magnetic zones to adjust a tilt and a shift of the particle optical axis within the projection lens system. For example, the coupling to the second projection lens can be corrected for the tilt and shift. The second magnetic zone can be used to adjust the tilt, and the third magnetic zone can be used to adjust the shift, and vice versa. According to a preferred embodiment, the beam splitter configuration further includes: at least one multi-pole configuration disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the multi-pole configuration being disposed downstream of the first magnetic region relative to the secondary particle optical beam path. A first projection lens is disposed after the first magnetic region and before the multi-pole configuration along the direction of the secondary particle optical beam path. The controller is configured to control the multi-pole configuration according to the landing energy. According to a preferred embodiment, the controller is configured to control at least one multi-pole configuration to further achieve paraxial astigmatism-free, paraxial distortion-free, and / or paraxial chromatic aberration-free imaging on the detection plane. According to a preferred embodiment, the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path, but not in the primary particle optical beam path. The second magnetic region is disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting the second additional particle beam. The first projection lens is disposed immediately after the second magnetic region relative to the secondary particle optical beam path. The controller is configured to control the second magnetic region based on the landing energy. Controlling the second magnetic region and thereby adjusting its magnetic field provides an optimized parameter before the second additional particle beam enters the first projection lens. According to a preferred embodiment, the controller is configured to control the second magnetic region to adjust the tilt or offset of the secondary particle optical axis before a plurality of second additional particle beams enter the first projection lens. According to another specific embodiment, the beam splitter configuration includes: a final magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path, configured to provide a uniform magnetic field. This final magnetic region is configured relative to the secondary particle optical beam path as the last magnetic region of the beam splitter configuration prior to the first projection lens. The final magnetic region may be, for example, a third or fourth magnetic region. The beam splitter configuration further includes an isolation trench configured to decouple the magnetic field of the final magnetic region from the magnetic field of the first projection lens. An exit tilt angle of the final magnetic region is less than 15°, particularly less than 10° or 5°. This has the advantage of providing the isolation trench in a space-saving manner. This, in turn, allows the first projection lens to be positioned closer to the sample, thereby reducing its fill factor. Through this measure, the fill factor can be reduced to approximately 8%. According to a preferred embodiment, the isolation trench is substantially rectangular. Rectangular trenches require less installation space than triangular isolation trenches and can be used when the exit angle of the last magnetic zone is sufficiently small. According to a preferred embodiment, the secondary particle optical beam path further includes a collimating lens disposed relative to the secondary particle optical beam path after the first magnetic region and before the first projection lens. The controller is configured to control the collimating lens based on the landing energy. The provision of the collimating lens results in a reduction in the FOV radius within the first projection lens, thereby reducing its fill factor PL1. For example, the collimating lens may be turned on at high landing energies but remain closed at low landing energies. According to a preferred embodiment, the focal length f_col of the collimating lens is in the range of 20 mm ≤ f_col ≤ 500 mm, particularly 50 mm ≤ f_col ≤ 150 mm. According to a preferred embodiment, the collimating lens is an electrostatic lens. An electrostatic lens requires less mounting space than a magnetic lens, thus facilitating the positioning of the first projection lens quite close to the sample. According to a preferred embodiment, the strength of the magnetic field M1 in the first magnetic region is similar to, and in particular the same as, the strength of the magnetic field M2 in the second magnetic region, so 0.8 ≤ M1 / M2 ≤ 1.2. According to a preferred embodiment, the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The second magnetic region is disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field to further deflect the second secondary particle beam in the same direction as in the first magnetic region. A total deflection angle α in the secondary particle optical beam path deflected by the beam splitter configuration satisfies the following relationship: α ≥ 40°, particularly α ≥ 41° or α ≥ 42°. This large deflection angle α is a decisive parameter for creating mounting space in the secondary particle optical beam path. More mounting space allows for the installation of a larger first projection lens, i.e., a magnetic lens. If the first projection lens can be made larger, its aperture can be made larger, thereby reducing the fill factor PL1 and generating fewer aberrations within the first projection lens. According to a preferred embodiment, the strength of the magnetic field M1 in the first magnetic region is different from the strength of the magnetic field M2 in the second magnetic region, and satisfies one of the following relationships: (i) M1 / M2 ≥ 2.0, especially M1 / M2 ≥ 2.5 or M1 / M2 ≥ 3.0; or (ii) M2 / M1 ≥ 2.0, especially M2 / M1 ≥ 2.5 or M2 / M1 ≥ 3.0. Therefore, at least for a single magnetic region providing a relatively strong magnetic field, the increase in aberrations produced in the beam splitter configuration is acceptable. However, the reduction in aberrations produced by the first projection lens is sufficient to offset this effect. This is a fairly general finding that can be transferred to other specific embodiments and aspects of the invention, such as specific embodiments having more than two magnetic regions in the secondary particle optical beam path, and specific embodiments with two different magnetic region configurations to deflect the secondary particle beam substantially in different directions. According to a second aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from an incident position in the second field; and a magnetic and / or electrostatic objective lens system. The system includes a first and second individual particle beams, both passing through a magnetic and / or electrostatic objective lens system; a beam splitter configuration disposed in the primary particle optical beam path between the multibeam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multibeam microscope and control the landing energy of the first individual particle beam on an object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field through which the primary and secondary particle optical beam paths pass during use, and the first magnetic region configuration to separate the primary and secondary particle optical beam paths from each other; wherein each The magnetic region has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein the beam splitter configuration further includes up to five other components, one of which can be a separate magnetic region or multipole configuration, these other components providing up to five degrees of freedom for further adjustment of imaging in the secondary particle optical beam path; wherein the secondary particle optical beam path includes corresponding to the object The system comprises a first intersection of a second individual particle beam at the focal plane of a mirror lens system, and a second intersection of a second individual particle beam disposed between a beam splitter configuration and a detection unit and configurable during use to be flush with the contrast aperture; wherein the second particle optical unit includes a projection lens system having a first projection lens, the projection lens system being configured to image the second individual particle beam onto a third field, and the first projection lens being disposed after the first intersection and before the second intersection relative to the secondary particle optical beam path, and the first projection lens system being configured to focus a plurality of second individual particle beams onto the second intersection; wherein a controller configuration is used to control the first projection lens to focus a plurality of second individual particle beams onto the second intersection according to the landing energy;The controller is configured to control other components based on landing energy to at least adjust the axial fundamental ray height ratio xa / ya between the axial fundamental rays in the x and y directions within the first projection lens, such that (1-xa / ya) ≤ 15%, specifically (1-xa / ya) ≤ 10% or (1-xa / ya) ≤ 5%. Generally, reducing the FOV anisotropy within the first projection lens in the x and y directions reduces the ellipticity of the second cross. However, if fewer than five magnetic zones or multipoles are applied before the first projection lens as further correction components, the beamsplitter configuration cannot achieve perfectly astigmatic-free imaging for all landing energies; instead, only one or two aspects of the four beamsplitter astigmatic components can be corrected for all landing energies. Therefore, the question arises: which astigmatic component should receive the best compensation? To achieve a smaller cross ellipticity, it is advantageous to pursue a smaller FOV anisotropy within the first projection lens, for example, by targeting similar heights of the axial fundamental rays in the x and y directions within the first projection lens. According to a third aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; and a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, wherein the second separate particle beams are... From the incident position in the second field; a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass; a beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first separate particle beam on the object; wherein the beam splitter configuration includes: at least one first magnetic region configured to provide a uniform magnetic field, during use, separating the primary particle optical beam path and the secondary particle optical beam path A uniform magnetic field is used, and a first magnetic region configuration is employed to separate the primary particle optical beam path and the secondary particle optical beam path from each other; each magnetic region configured by the beam splitter has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein the beam splitter configuration includes secondary particle optical... A dispersion-free plane in the beam path, the z-position of which is fixed by a beam splitter configuration; wherein the secondary particle optical beam path includes a first intersection of a second individual particle beam corresponding to the focal plane of the objective lens system, the objective lens system further having an image plane of the objective lens system disposed relative to the secondary particle optical beam path after the first intersection; and wherein the second particle optical unit includes an adjustment member configured to adjust the z-position of the image plane of the objective lens system; wherein the controller is configured to control the adjustment member according to the landing energy, such that the adjusted z-position of the image plane of the objective lens system matches the fixed z-position of the dispersion-free plane of the beam splitter configuration. This solution, in contrast to known methods, assumes the z-position of the image plane of the objective lens system to be fixed and, for example, adjusts the magnetic region of the beam splitter configuration to adjust the dispersion-free plane so that it matches the image plane of the fixed objective lens system. The opposite method according to the invention can be implemented in several different ways. According to a preferred embodiment, the adjustment component includes an adjustment lens positioned after the first magnetic region relative to the secondary particle optical beam path. The adjustment lens acts only on the second secondary particle beam. Minimal landing energy / low landing energy requires the maximum refractive index of this adjustment lens. According to a preferred embodiment, the controller is configured to control the landing energy value between, and including, the minimum landing energy LEmin and the maximum landing energy LEmax; and the controller is configured to control the adjustment lens between, and including, zero and the maximum adjustment value. The controller is configured to control the adjustment lens with the maximum adjustment value when the minimum landing energy LEmin is set. According to a preferred embodiment, the lens configuration is adjusted to have a maximum refractive index RP of RP ≥ 20 / m. However, smaller or larger values ​​are also possible. According to another preferred embodiment, the objective lens system includes a two-part objective lens, and the adjustment mechanism is implemented by the two parts of the objective lens system. The two parts of the objective lens system are configured to be independently controllable. A controller is configured to control the two parts of the objective lens to maintain their image plane positions in the primary particle optical beam path, and the controller is also configured to control the two parts of the objective lens to adjust their image plane positions in the secondary particle optical beam path. In short, this effect of the two-part objective lens can be understood through the fact that the two parts of the objective lens are equivalent to a displacement lens configured in a variable position and having variable intensity. According to a fourth aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; and a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from a second... The field includes: an incident position; a magnetic and / or electrostatic objective system through which both the first and second individual particle beams pass; a beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first individual particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field, through which the primary and secondary particle optical beam paths pass during use, and the first magnetic region... A beam splitter configuration is used to separate the primary particle optical beam path and the secondary particle optical beam path from each other; a dispersion correction region is configured to provide a uniform magnetic field through which the secondary particle optical beam path passes during use, but the primary particle optical beam path does not; wherein the beam splitter configuration includes a dispersion-free plane in the secondary particle optical beam path, the position of which is adjusted by controlling the dispersion correction region; wherein each magnetic region of the beam splitter configuration has an entrance region with an entrance tilt angle for the secondary particle optical beam path and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the arrangement offset of the entrance region. The angle of the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle of the normal to the optical axis of the secondary particle optical beam path from which the arrangement of the exit region deviates; and wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein the secondary particle optical beam path includes a first intersection of a second individual particle beam corresponding to the focal plane of the objective lens system, the objective lens system further having an image plane of the objective lens system disposed after the first intersection relative to the secondary particle optical beam path; and wherein the controller is configured to control the dispersion correction region according to the landing energy, such that the position of the dispersion-free plane of the beam splitter is matched with the position of the image plane of the objective lens system. According to a fifth aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from an incident position in the second field; and a magnetic and / or electrostatic... An objective system, wherein both the first and second individual particle beams pass through a magnetic and / or electrostatic objective system; a beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first individual particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field through which the primary and secondary particle optical beam paths pass during use, and the first magnetic region configuration to separate the primary and secondary particle optical beam paths from each other; A second magnetic region, disposed within the secondary particle optical beam path but not within the primary particle optical beam path, is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting the second secondary particle beam. A third magnetic region, also disposed within the secondary particle optical beam path but not within the primary particle optical beam path, is positioned downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field. Each magnetic region configured in the beam splitter configuration has an entrance region with an entrance tilt angle for the secondary particle optical beam path and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is fixed. The angle at which the arrangement of the entrance region deviates from the normal to the optical axis of the secondary particle optical beam path is defined, and the exit tilt angle is defined as the angle at which the arrangement of the exit region deviates from the normal to the optical axis of the secondary particle optical beam path; and the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and the beam splitter configuration does not include a dispersion correction region or other dispersion correction component for controlling the position of a dispersion-free plane in the secondary particle optical beam path according to the landing energy LE; and the secondary particle optical beam path includes a first intersection of a second individual particle beam corresponding to a focal plane of the objective lens system, the objective lens system further having an image plane of the objective lens system disposed relative to the secondary particle optical beam path after the first intersection.The controller configuration is used to control the landing energy LE within the range of LEmin ≤ LE ≤ LEmax, and the beam splitter configuration is designed such that, for a landing energy LE_ave = (LEmax-LEmin) / 2, the z-position z1 of the dispersion-free plane of the beam splitter configuration matches the z-position z2 of the image plane of the objective lens system within a range of + / -5%, therefore 0.95 ≤ |(z1-z2) / z2| ≤ 1.05. The idea behind this solution is as follows: It has been found that for landing energies up to several keV, beam splitter aberrations are primarily dominated by first-order dispersion (Ck term). Therefore, focusing on reducing dispersion to decrease the total aberrations of the beam splitter is highly effective. This choice is optimal if a dedicated magnetic field is not available for dispersion correction at all landing energies, and dispersion correction can only be performed on a reference LE_ref by selecting a suitable beam splitter / magnet configuration design. Beam splitter aberrations are minimized at the minimum position on the dispersion curve. This minimum is achieved by each beam splitter design having a specific plane where dispersion vanishes, the so-called dispersion-free plane. The position of the image plane behind the objective lens and beam splitter varies considerably with landing energy. At lower landing energies, the image plane is located higher above the sample, where secondary particles / signal electrons have higher energies, while at higher landing energies, the image plane is closer to the sample, with the specific position depending on the refractive index of the corresponding objective lens and beam splitter. Now, there exists a landing energy at which the image plane behind the objective lens and beam splitter intersects the dispersion-free plane, and at this landing energy LE_ref, the minimum dispersion of the beam splitter occurs. Therefore, if the beam splitter is to be used within a specific landing energy range, the goal is to optimize the beam splitter design so that the dispersion-free plane is located approximately in the middle of the target LE range where the minimum dispersion occurs. In this case, the dispersion at the two edges of the LE range is the same, thus achieving the minimum maximum dispersion value that can occur throughout the entire landing energy range. According to a sixth aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optical beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optical beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from an incident position in the second field; and a magnetic and / or electrostatic objective lens system, the first... Both the first and second individual particle beams pass through a magnetic and / or electrostatic objective lens system; a beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first individual particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field M1 through which the primary and secondary particle optical beam paths pass during use, and the first magnetic region configuration is configured to separate the primary and secondary particle optical beam paths from each other; a second magnetic region disposed in the secondary particle... In the optical beam path, but not in the main particle optical beam path, a second magnetic region is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M2 for deflecting the second secondary particle beam; a third magnetic region is positioned in the secondary particle optical beam path but not in the main particle optical beam path, and is positioned downstream of the second magnetic region relative to the secondary particle optical beam path, configured to provide a uniform magnetic field M3; a fourth magnetic region is positioned in the secondary particle optical beam path but not in the main particle optical beam path, and is positioned downstream of the third magnetic region relative to the secondary particle optical beam path, configured to provide a uniform magnetic field M4; wherein the beam splitter is configured as follows: Each magnetic region has an entrance region with an entrance tilt angle for a secondary particle optical beam path, and an exit region with an exit tilt angle for a secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being substantially free of magnetic field; wherein the first magnetic region comprises two plates arranged parallel to each other and having a plate distance D1, wherein during use, the uniform magnetic field M1 is generated between the two plates;The entrance region of the first magnetic field is linear and contains a width W11, and the exit region of the first magnetic field is linear and contains a width W12. For a ratio R11 = W11 / D1, the following relationship is satisfied: R11 ≥ 2.0, specifically R11 ≥ 3.0 or R11 ≥ 3.5; and for a ratio R12 = W12 / D1, the following relationship is satisfied: R12 ≥ 2.0, specifically R12 ≥ 3.0 or R12 ≥ 3.5; and wherein the second magnetic region comprises two plates arranged parallel to each other and having a plate distance D2, wherein during use, a uniform magnetic field M2 is generated between the two plates; wherein the entrance region of the second magnetic region is linear and comprises a width W21, and wherein the exit region of the second magnetic region is linear and comprises a width W22, and wherein for a ratio R21 = W21 / D2, the following relationship is satisfied: R21 ≥ 2.0, particularly R21 ≥ 3.0 or R21 ≥ 3.5; and / or wherein for a ratio R22 = W22 / D2, the following relationship is satisfied: R22 ≥ 2.0, particularly R22 ≥ 3.0 or R22 ≥ 3.5. The aforementioned ratios R11, R12, R21, and R22 help to further reduce aberrations. This is particularly useful for field tilt and field astigmatism. The linear inlet / outlet region of the particle optical beam path lies between the two plates and is often referred to as a groove. Therefore, it is advantageous to make the widths of the grooves W11, W12, W21, and W22 as large as possible. However, if more magnetic regions of the primary particle optical beam path are to be configured, this is only structurally feasible or reasonable within a limited range. These may collide with the magnetic regions of the secondary particle optical beam path. Another option to achieve the above ratios is to make the distances D1 and D2 between the two plates as small as possible, for example, D1 ≤ 20 mm or D1 ≤ 15 mm or D1 ≤ 10 mm and / or D2 ≤ 20 mm or D2 ≤ 15 mm or D2 ≤ 10 mm. According to a preferred embodiment, the third magnetic region comprises two plates arranged parallel to each other and having a plate distance D3, wherein a uniform magnetic field M3 is generated between the two plates during use. The entrance region of the third magnetic region is linear and includes a width W31, and the exit region of the third magnetic region is linear and includes a width W32. Then, for a ratio R31 = W31 / D3, the following relationship is satisfied: R31 ≥ 2.0, particularly R31 ≥ 3.0 or R31 ≥ 3.5; and / or for a ratio R32 = W32 / D3, the following relationship is satisfied: R32 ≥ 2.0, particularly R32 ≥ 3.0 or R32 ≥ 3.5. According to a preferred embodiment, the fourth magnetic region comprises two plates arranged parallel to each other and having a plate distance D4, wherein a uniform magnetic field M4 is generated between the two plates during use. The entrance region of the fourth magnetic region is linear and includes a width W41, and the exit region of the fourth magnetic region is linear and includes a width W42. Then, for a ratio R41 = W41 / D4, the following relationship is satisfied: R41 ≥ 2.0, particularly R41 ≥ 3.0 or R41 ≥ 3.5; and / or for a ratio R42 = W42 / D4, the following relationship is satisfied: R42 ≥ 2.0, particularly R42 ≥ 3.0 or R42 ≥ 3.5. According to a preferred embodiment, the outlet tilt angle of the first magnetic zone is limited to η12 ≤ 35°, preferably η12 ≤ 25° or most preferably η ≤ 15°. According to a seventh aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, wherein the second separate particle beam originates from an incident position in the second field; and a magnetic and / or electrostatic objective lens system, comprising first and second... Each particle beam passes through a magnetic and / or electrostatic objective lens system; a beam splitter is configured in the primary particle optical beam path between the multi-beam generator and the objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field M1 through which the primary and secondary particle optical beam paths pass during use, and the first magnetic region is configured to separate the primary and secondary particle optical beam paths from each other; and a second magnetic region configured in the secondary particle optical beam path but not in the primary particle optical beam path. In the primary particle optical beam path, a second magnetic region is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M2 for deflecting the second secondary particle beam; a third magnetic region is positioned in the secondary particle optical beam path but not in the primary particle optical beam path, and is positioned downstream of the second magnetic region relative to the secondary particle optical beam path, configured to provide a uniform magnetic field M3; a fourth magnetic region is positioned in the secondary particle optical beam path but not in the primary particle optical beam path, and is positioned downstream of the third magnetic region relative to the secondary particle optical beam path, configured to provide a uniform magnetic field M4; wherein each magnetic region configured by the beam splitter has a specific feature for the secondary particle optical beam path. An entrance region with an entrance tilt angle and an exit region with an exit tilt angle for a secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being essentially free of magnetic field; wherein the second, third, and fourth magnetic regions are directly and continuously arranged, with no drift region between adjacent magnetic regions, therefore the exit region of the second magnetic region corresponds to the entrance region of the third magnetic region, and the exit region of the third magnetic region corresponds to the entrance region of the fourth magnetic region;The entrance regions of the second, third, and fourth magnetic regions, and the exit region of the fourth magnetic region are linear, and their theoretical extensions share a common intersection point or several intersection points within an intersecting circle with a minimum diameter d, wherein all intersection points between their extensions lie within this intersecting circle. The exit region of the second magnetic region is linear and has a width W22; and the diameter d and width WD22 have the following relationship: d ≤ WD22, specifically d ≤ 0.5*WD22. This specific embodiment describes a fairly fan-shaped design, and therefore the configuration of the second, third, and fourth magnetic regions is also described. This fan-shaped design helps to balance and equalize the widths of the linear entrance and exit regions. Very short entrance and / or exit regions are avoided. This measure, in turn, helps to reduce aberrations, especially rather strong field astigmatism. According to a preferred embodiment, the diameter d of the intersecting circles satisfies the following relationship: d ≤ 10 mm, preferably d ≤ 5 mm or d ≤ 3 mm. This is on the order of magnitude of the groove width. According to an eighth aspect of the invention, the invention relates to a multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics beam path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; and a second particle optics unit having a secondary particle optics beam path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from an incident position in the second field; A magnetic and / or electrostatic objective system, through which both first and second individual particle beams pass; a beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control the landing energy of the first individual particle beam on an object; wherein the beam splitter configuration includes a magnet configuration consisting of a first magnetic region, a second magnetic region, and a third magnetic region, the first magnetic region being configured to provide a uniform magnetic field M1 through which the primary and secondary particle optical beam paths pass during use. Furthermore, the first magnetic region is configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; the second magnetic region is configured within the secondary particle optical beam path but not within the primary particle optical beam path, and is positioned downstream of the first magnetic region relative to the secondary particle optical beam path, and is configured to provide a uniform magnetic field M2 to deflect the secondary particle beam; and the third magnetic region is configured within the secondary particle optical beam path but not within the primary particle optical beam path, and is positioned downstream of the second magnetic region relative to the secondary particle optical beam path, and is configured to provide a uniform magnetic field M3; wherein each magnetic region configured with the magnet has an entrance tilt angle for the secondary particle optical beam path. The system includes an entrance region and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance region deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit region deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being substantially free of magnetic field; wherein a second drift region is provided between the second magnetic region and the third magnetic region, the second drift region being substantially free of magnetic field; wherein the controller configuration is used to control the landing energy LE within the range of LEmin ≤ LE ≤ LEmax;The design system configuration of the second magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a low landing energy (LE_low), and the design system configuration of the third magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a high landing energy (LE_high); or the design system configuration of the second magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a high landing energy (LE_high), and the design system configuration of the third magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a low landing energy (LE_low), where LEmin < LE_low < LE_high < LEmax. For internal beamsplitter performance, choosing a beamsplitter / magnet configuration design with gaps between continuous magnetic regions is advantageous because it provides more geometric degrees of freedom (opposite to the sector design rule explained earlier). Consider a design consisting of three magnetic regions in the secondary particle optical beam path with drift regions between continuous magnetic regions; this provides sufficient degrees of freedom to achieve... Astigmatism and dispersion correction under two landing energies. For example, the geometry of the first magnetic region can be used to correct astigmatism and dispersion at low landing energies over a wide range of target landing energies, while the geometry of the second region can be used to compensate for astigmatism and dispersion at high landing energies. This results in a "W"-shaped landing energy dependence of internal beam splitter aberrations, thus having a smaller maximum aberration value compared to a "V"-shaped curve that corrects astigmatism and dispersion only at a single landing energy. According to a preferred embodiment, the controller is configured to shut down the second or third magnetic zone when the controller sets the landing energy LE to LE_high or LE_low. According to a preferred embodiment, the design parameters of the second magnetic region are geometric parameters, and include or consist of the following: the length of the first drift region, the inlet tilt angle, the outlet tilt angle, and the distance between the inlet and outlet regions. Conversely, the magnetic field strength in the magnetic region is not a geometric design parameter. According to a preferred embodiment, the design parameters of the third magnetic region are geometric parameters, and include or consist of the following: the length of the second drift region, the inlet tilt angle, the outlet tilt angle, and the distance between the inlet region and the outlet region. The various aspects and specific embodiments of the present invention described above can be combined completely or partially with each other, as long as there is no technical contradiction. Figure 1 schematically shows a multi-beam particle microscope 1. The multi-beam particle microscope 1 includes a beam generating device 300 with a particle source 301 (e.g., an electron source). A diverging particle beam 309 is collimated through a series of condenser lenses 303.1 and 303.2 and strikes a multi-aperture configuration 305. The multi-aperture configuration 305 includes a plurality of multi-aperture plates 306 and a field lens 308. The multi-aperture configuration generates a plurality of individual particle beams 3 or individual electron beams 3. The midpoints of the apertures in the multi-aperture plate configuration are arranged in a field, which is imaged onto another field formed by the beam points 5 in the object plane 101. The spacing between the midpoints of the apertures in the multi-aperture plates 306 can be, for example, 5 µm, 100 µm, and 200 µm. The diameter D of the aperture is smaller than the spacing between the midpoints of the apertures, with examples of diameters being 0.2, 0.4, and 0.8 times the spacing between the midpoints of the apertures. The multi-aperture configuration 305 and field lens 307 are configured to generate multiple focal points 323 of the main beam 3 in a grating arrangement on surface 325. Surface 325 does not need to be a planar surface, but can be a spherical curved surface to compensate for the field curvature of the subsequent particle optics system. The multi-beam particle microscope 1 further includes a system of electromagnetic lenses 103 and objective lenses 102, which images a reduced-size beam focal point 323 onto the object plane 101 from the intermediate image surface 325. During this process, the first individual particle beam 3 is deflected during operation by a beam splitter 400 and a beam deflection system 500, thereby scanning the image field. The first individual particle beams 3 incident on the object plane 101 form, for example, a substantially regular field, wherein the spacing between adjacent incident positions 5 can be, for example, 1 µm, 10 µm, or 40 µm. For example, the field formed by the incident positions 5 can have rectangular or hexagonal symmetry. The object 7 to be inspected can be of any desired type, such as a semiconductor wafer or a biological sample, and may contain configurations such as micro-components. The surface 15 of the object 7 is disposed in the object plane 101 of the objective lens 102. The objective lens 102 may include one or more electro-optical lenses. For example, this may be a magnetic objective lens and / or an electrostatic objective lens. The principal particles 3 incident on object 7 produce interaction products, such as secondary electrons, backscattered electrons, or principal particles that have undergone motion reversal for other reasons. These interaction products are emitted from the surface of object 7 or from the first plane 101 or the object plane 101. The interaction products emitted from the surface 15 of object 7 are shaped by objective lens 102 to form a secondary particle beam 9. In this process, the secondary particle beam 9 passes through beam splitter 400 after objective lens 102 and is provided to projection system 200. Projection system 200 includes imaging system 205 having a plurality of projection lenses (e.g., magnetic projection lenses 206, 208, and 210), a contrast aperture 214 located in second cross 212 that allows filtering of the secondary particle beam 9 according to the starting angle from object 7, a beam deflector (reverse scan) 222, and a multi-particle detector 209. The individual secondary particle beams 9 are incident on the detection area of ​​multi-particle detector 209 at a third field, with regular spacing between them. Example values ​​are 10 µm, 100 µm, and 200 µm. The multibeam particle microscope 1 further includes a computer system or control unit 10, which may consist of one or more parts and is designed to control the individual particle optical components of the multibeam particle microscope 1 and to evaluate and analyze the signals obtained by the multidetector 209 or the detection unit 209. There are also components for altering the landing energy LE, wherein the main particle beam 3 impacts the object 7 with the landing energy LE. This can be achieved, for example, by providing a corresponding voltage to the object 7 or its support 600, or by changing the deceleration voltage supplied to electrodes (not shown) disposed between the objective lens 102 and the object 7. The variation of the landing energy LE can be controlled by the controller 10. Further information regarding such a multi-beam particle system or multi-beam particle microscope 1 and its components (e.g., particle source, multi-aperture plate, and lens) is available in international patent applications WO 2005 / 024881 A2, WO 2007 / 028595 A2, WO 2007 / 028596 A1, WO 2011 / 124352 A1, WO 2007 / 060017 A2 and German patent applications DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1, the entire disclosure of which is incorporated herein by reference. Figure 2 schematically shows a cross-sectional view of a multi-beam particle microscope 1 with a beamsplitter configuration 400 according to the prior art. Specific aspects of the known beamsplitter configuration 400 are explained here. In the multi-beam particle microscope 1 shown in Figure 2, a particle beam emitted by a particle source 301 passes through a magneto-optical focusing lens system 303 and subsequently strikes a multi-aperture configuration 305. The multi-aperture configuration 305 acts as a multi-beam particle generator, from which individual particle beams 3 emitted subsequently pass through a magneto-optical field lens system 307 and then enter the magneto-optical beamsplitter configuration 400. The beamsplitter configuration 400 shown includes a beam tube configuration 490, which has a Y-shaped specific embodiment and, in the example shown, includes three branches 461, 462, and 463. Here, in addition to two flat, interconnected structures for holding magnetic or magnetic field regions 410 and 430, the beamsplitter 400 includes two magnetic or magnetic field regions 410 and 430 (which are contained in or fixed to this structure). After passing through beam splitter 400, before the primary particle beam 3 is incident on the surface 15 of object 7 (in this case, a semiconductor wafer with an HV structure), the first particle beam 3 passes through scanning deflector 500 and then through particle optics objective lens 102. In this case, the HV structure represents a semiconductor structure profile that is primarily horizontal or vertical. In this case, the semiconductor wafer 7 is positioned by a displacement stage 600 below objective lens 102. Due to the incident of the first secondary particle beam 3, secondary particles, or a second secondary particle beam 9, are released from object 7. After being emitted from object 7, the second secondary particle beam 9 first passes through particle optics objective lens 102, then through scanning deflector 500, and then through beam splitter configuration 400. From beam splitter configuration 400, the second secondary particle beam 9 is emitted from branch 462, passes through projection lens system 205 (shown in a very simplified manner), passes through electrostatic element 260 (so-called reverse scanning), and then strikes particle optics detection unit 209. The computer system 10 or control unit 10 used to control the particle optics components and other components of the multi-beam particle microscope 1 shown in Figure 2 is not shown in Figure 2 for the sake of simplicity. As can be clearly seen from the conventional beam splitter 400, the arrangement of the beam tube configuration 490 provides an advantage to the structure shown and to the necessary evacuation around the first and second particle optical beam paths 13 and 11 within the beam splitter 400. However, it is equally apparent that when the beam splitter 400 is in the closed state, the first particle optical beam path 13 cannot pass through the beam splitter 400 and instead impacts the wall of the beam tube configuration 490. This makes the adjustment of the multi-beam particle microscope 1 more difficult, as the effect of the beam splitter 400 on potential misalignment cannot be examined independently. Figure 3 schematically illustrates a beam splitter configuration 400 according to conventional techniques and the occurrence of field tilt. In the illustrated example, the magnet configuration 400 includes a first magnetic region 410 and a second magnetic region 430, whose magnetic field directions are opposite to each other, and the primary particle optical beam path 13 passes through these two magnetic regions. Furthermore, in the illustrated example, three additional magnetic regions 450, 460, and 470 are provided. The secondary particle optical beam path 11 extends through the first magnetic region 410 and through these additional magnetic regions 450, 460, and 470. The magnetic field in magnetic region 450 is in the same direction as the magnetic field in magnetic region 410; therefore, the curvature of the secondary particle optical beam path 11 does not change in these magnetic field regions 410 and 450. The beam splitter configuration 400 shown in Figure 3 is not an aligned optical axis type: instead, there is a tilt angle β between the optical axis Z and axis A of the first particle optical beam path 13, with axis A corresponding to the optical axis of the objective lens 102 or its extension. The lower edge of the first magnetic region 410 is set at a right angle to axis A, which is an intuitive configuration due to the symmetry between the first and second particle optical paths 13, 11. The angle γ is the so-called beam splitting angle, which provides a measure of the separation between the primary particle optical beam path 13 and the secondary particle optical beam path 11 within the magnetic region 410. This angle cannot be chosen too small, otherwise there may not be enough installation space to configure the magnetic regions 450, 460, and 470 in the secondary particle optical beam path 11. The imaging aberrations of the first particle optical beam path 13 can be largely corrected, and the imaging can essentially achieve first-order astigmatism-free and first-order distortion-free imaging. However, in the increasingly precise measurement tasks of the multi-beam particle microscope 1, the requirements for resolution are also increasing. As a result, it has been found that the field tilt ɗ of the beam splitter 400 shown in Figure 3 usually accounts for most of the remaining aberrations. In Figure 3, this field tilt ɗ is not drawn to scale. First, the first individual particle beam 3 strikes the object 7 or object plane 101 at slightly different heights, where the position of the smallest particle beam diameter is considered the focal point in this case. The focal point of the individual particle beam 3 located directly above the optical axis A is exactly on the object plane 101, the focal point of the first individual particle beam 3 positioned to its left is exactly in front of the object plane 101, and the focal point of the first individual particle beam 3 positioned to the right of axis A is slightly below the object plane 101. The concentration of the field tilt ɗ can be essentially explained by the slightly different path lengths traversed by the plurality of first individual particle beams 3 within the magnet configuration 400. Figure 4 schematically shows the improved beam splitter configuration 400. The main difference between this beam splitter configuration 400 and the beam splitter configuration shown in Figure 3 lies in the configuration of the first magnetic region 410: the orientation of its linear bottom region (corresponding to the exit region of the primary particle beam 3 and the entrance region of the secondary particle beam 9) is tilted relative to the normal to the optical axis Z. By deviating from the 0° exit tilt angle, the aberrations in the primary particle optical beam path 13 of the beam splitter configuration 400 can be significantly reduced. If the beam splitter configuration 400 is integrated as a beam switch 400 into the multi-beam particle microscope 1, this results in the extension of the particle optical axis A of the objective lens 102 not being orthogonal to the exit region of the first magnetic region of the magnet configuration. Therefore, surprisingly, with this geometric configuration, the aberrations generated in the beam splitter configuration 400 and thus the aberrations occurring in the multi-beam particle microscope 1 are significantly reduced. Specifically, compared to a beam splitter configuration where the exit tilt angle σ1 of the first magnetic region 410 is 0°, or compared to a multi-beam particle microscope 1 where the extension of the particle optical axis A of the objective lens 102 is orthogonal to the exit region of the first magnetic region 410, the image field tilt and astigmatism caused by beam switching can be reduced by approximately 6 times. For example, the image field tilt δ in the object plane 101 can be reduced to δ ≤ 0.05°, preferably δ ≤ 0.04° – without the need for or additional active correctors (e.g., multi-stigmator arrangement). Furthermore, an exit tilt angle σ1 = η11 ≠ 0 also significantly improves the resolution of the multi-beam particle microscope 1, by approximately 1.5 to 2 times. All other second-order or higher-order aberrations are also small or remain small overall. Further details are described in unpublished German patent application No. 10 2023 120 127.1, the full scope of which is incorporated herein by reference. Figure 5 is an enlarged view of the first magnetic region 410, showing its configuration geometry in more detail. According to the specific embodiment shown (not drawn to scale), the exit tilt angle η12 of the first magnetic region 410 is limited to η12 ≤ 35°, preferably η12 ≤ 25°, or most preferably η12 ≤ 15°. Furthermore, the entrance tilt angle η12 of the second magnetic region 450 (not shown) is limited to η21 ≤ 35°, preferably η21 ≤ 25°, or most preferably η21 ≤ 15°. This reduces aberrations. The terms primary particle optical beam path 13 and secondary particle optical beam path 11 are used according to technical terminology conventions. However, it should be noted that primary particle optical beam path 13 (similar to secondary particle optical beam path 11) describes the path of a plurality of first or second individual particle beams 3, 9. However, for simplicity, the terms primary particle optical beam path 13 or secondary particle optical beam path 11 may, depending on the context, be used only to refer to a single particle beam 3, 9 moving along the particle optical axis Z of the system or central beam. The central beam corresponds to the middle (i.e., the center) single particle beam 3, 9 in the bundle. The direction of the particle optical axis Z when entering or leaving the magnetic region is defined by the direction of the central beam, which is preferably the same as the central beam of all individual particle beams in the bundle. According to the example, the following relationship applies to the exit tilt angle σ1 of the first magnetic zone: |σ1| ≥ 0.5°, preferably |σ1| ≥ 1°, |σ1| ≥ 3°, or |σ1| ≥ 5°. Meanwhile, for the entrance tilt angle of the second particle optical beam path, maintain |η1| ≥ 0.5°, preferably |η11| ≥ 1°, |η11| ≥ 3°, or |η11| ≥ 5°. Therefore, the exit tilt angle σ1 / entrance tilt angle η11 is the "true" tilt, and any tilt greater than this is only due to inaccuracies in the adjustment process. The sign or direction of the tilt depends on the specific design of the magnet configuration and the charge of the primary particle beam used. According to another example, the following relationship applies to the exit tilt angle σ of the first magnetic region: 0° < |σ1| ≤ 10°, preferably 1° ≤ |σ1| ≤ 9°, or most preferably 3° ≤ |σ1| ≤ 7°. Limiting the exit slope σ of the primary particle optical beam path to its maximum value may be useful, as the geometry of the second particle optical beam path 11 must also be considered. A finite exit slope σ1 may help limit aberrations occurring in the secondary particle optical beam path 11 as it passes through the first magnetic region 410. However, this depends on the specific design of the secondary path 11. As mentioned above, when the corresponding multibeam particle microscope 1 is operated at a fixed landing energy LE, the existing beam splitter configuration 400 operates quite well with low aberrations. However, as mentioned above, changing the landing energy LE increases aberrations. This is especially true for large variations and very high landing energies. It has been found that when the landing energy increases significantly, the so-called fill factor of the first projection lens in the projection lens system has a decisive influence on aberrations. More specifically, to increase the landing energy, the energy of secondary particles / signal electrons becomes increasingly smaller, resulting in enhanced focusing effect produced by objective lens 102. The focusing of the objective lens cannot be freely changed, but is fixed in principle due to the optimal operation of the primary particle beam path. Therefore, the first intermediate image of the secondary particle / signal electron beam gets closer and closer to the sample / object 7. Consequently, for high landing energies LE, the multi-field-of-view (mFOV) radius within the first projection lens 205a increases. This increases the fill factor within the first projection lens 205a, leading to a larger accumulation of aberrations in the first projection lens 205a and thus in subsequent particle optical paths. Figure 6 schematically illustrates the problem of increased fill factor within the first projection lens 205a when the landing energy LE is varied over a wide range. The secondary particle beam paths 13 are plotted in a very simplified manner for different landing energies (50 eV, 500 eV, and 5 keV). The intermediate images indicated by asterisks in Figure 6 move closer to the objective lens 102 as the landing energy LE increases. Assuming the position of the first projection lens 205a is fixed after the beam splitter configuration 400, the height of the α-rays within the first projection lens 205a increases sharply, thus increasing the fill factor PL1 within the first projection lens 205a. Figure 7 shows the definition of the fill factor PL1: The fill factor PL1 is defined as the ratio between the maximum radius Rmax of all the complex number of second separate particle beams 9 within the first projection lens 205a and the inner radius Ri of the opening 213 of the first projection lens 205a through which the second separate particle beams 9 pass. Therefore, PL1 = Rmax / Ri. The maximum radius Rmax corresponds to the multiple field of view (mFOV) within the first projection lens 205a. The first projection lens 205a is a magnetic lens. Therefore, the opening 213 corresponds to the borehole of the magnetic lens 205a. Figure 8 schematically shows the position of the first projection lens 205a in the secondary particle optical beam path 11. A plurality of second individual particle beams 9 originate from an object 7 (not shown) and pass through its focusing objective lens 102. In Figure 8, two exemplary second individual particle beams 9a and 9c are illustrated. They intersect each other at a first intersection 215 in the secondary particle optical beam path 11. Subsequently, they pass through a beam splitter configuration 400 and then through the first projection lens 205a (which is a magnetic lens in the illustrated example). Lens 205a is positioned in front of a contrast aperture 214, which is positioned at a second intersection 212 in the secondary particle optical beam path 11. The first projection lens 205a focuses (or helps to focus) the second individual particle beams 9a, 9c onto the second intersection 212. If another magnetic projection lens (not shown in Figure 8) is positioned after the beam splitter configuration 400 but before the second intersection 212, the magnetic projection lens positioned closest to the objective lens 102 is the first projection lens according to the invention. In other words, the first magnetic lens of the projection system 205 through which the second particle beams 9a and 9c pass is the first projection lens according to the present invention. In the example shown in FIG8, two additional projection lenses 205b and 205c are provided, however, they are positioned after the second cross 212. In the example shown, projection lens 205b can be used to adjust the focal point on the detection system 209, and lens 205c can be used to adjust the magnification on the detection system 209. Therefore, the multi-beam particle microscope 1 according to the present invention includes a multi-beam particle generator 5 configured to generate a first field of a plurality of charged first individual particle beams 3. It further includes a first particle optics unit having a primary particle optics path 13 configured to image the generated first individual particle beams 3 onto an object plane 101, such that the first individual particle beams 3 strike an object 7 at an incident position 5, thereby forming a second field. The multi-beam particle microscope 1 includes: a detection unit 209 having a plurality of detection regions forming a third field; and a second particle optics unit having a secondary particle optics path 11 configured to image a second individual particle beam 9 emitted from an incident position 5 in the second field onto the third field of the detection region of the detection system 209. The multi-beam particle microscope 1 further includes: a magnetic and / or electrostatic objective lens system 102 through which first and second individual particle beams 3, 9 pass; and a beam splitter configuration 400 disposed in a primary particle optical beam path 13 between the multi-beam generator 5 and the objective lens 102, and disposed in a secondary particle optical beam path 11 between the objective lens system 102 and the detection unit 209. A controller 10 is configured to control the multi-beam particle microscope 1 and to control the landing energy LE of the first individual particle beam 3 on the object 7. The beam splitter configuration 400 includes at least a first magnetic region 410 in the secondary particle optical beam path 11, the first magnetic region 410 being configured to provide a uniform magnetic field through which the primary particle optical beam path 13 and the secondary particle optical beam path 11 pass during use. The first magnetic region 410 is configured to separate the primary particle optical beam path 13 and the secondary particle optical beam path 11 from each other. The entrance tilt angle η11 of the first magnetic region 410 deviates from 0°. The secondary particle optical beam path 11 includes a first cross 215 (see FIG. 8) of the second individual particle beam 9 corresponding to the focal plane of the objective lens system 102, and a second cross 212 of the second individual particle beam 9 disposed between the beam splitter configuration 400 and the detection unit 209. Preferably, a contrast aperture 214 is disposed at the second cross 212. The second particle optical unit includes a projection lens system 205 having a first projection lens 205a disposed relative to the secondary particle optical beam path 11 after the first cross 215 and before the second cross 212; the projection lens system 205 is configured to image the second individual particle beam 9 to a third field and the first projection lens 205a is configured to focus a plurality of the second individual particle beams onto the second cross 212. The controller 10 is configured to control the first projection lens 205a to focus a plurality of the second individual particle beams 9 onto the second cross 212 according to the landing energy LE. The first projection lens 205a is positioned so close to the first cross 215 that the fill factor PL1 of the first projection lens 205a can be set to PL1≤15%, and in particular PL1≤10% or PL1≤5%, wherein the fill factor PL1 is defined as described above. The corresponding landing energy LE of the first individual particle beam can be in the range from zero to several keV, such as 3 keV, 5 keV, 10 keV, 15 keV, 20 keV, 25 keV or 30 keV. Magnetic region 410 (and other magnetic regions, if present) can be formed in ways known per se. They are specifically designed to create a uniform magnetic field, the direction of which is orthogonal to the direction of motion of the individual particle beams. For example, each magnetic region can be formed from two spaced-apart plates of magnetizable material, each plate having a milled recess into which a current conductor or coil has been inserted. However, other specific embodiments are also possible. Figure 9 schematically shows a beam splitter configuration 400 according to the present invention. Beam splitter configuration 400 is compatible with the multi-beam particle microscope shown in Figure 1. According to Figure 9, beam splitter configuration 400 further includes a second magnetic region 450 disposed in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The second magnetic region 450 is disposed downstream of the first magnetic region 410 relative to the secondary particle optical beam path 11 and configured to provide a uniform magnetic field for deflecting a second, separate particle beam 9-. The beam splitter configuration further includes a third magnetic region 460 disposed in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The third magnetic region 460 is disposed downstream of the second magnetic region 450 relative to the secondary particle optical beam path and configured to provide a uniform magnetic field. A first projection lens 205a is disposed between the first magnetic region 410 and the second magnetic region 450; and a controller 10 is configured to control the second magnetic region 450 and the third magnetic region 460 according to landing energy. Using this radical approach, and with the first projection lens 205a very close to the object 7 / sample 7, the fill factor PL1 within the first projection lens 205a can be reduced very effectively. The second and third magnetic regions 450 and 460 can be used for further correction in the secondary particle optical beam path 11. According to a preferred embodiment, the controller 10 is configured to control the second magnetic region 450 and the third magnetic region 460 to adjust the tilt and offset of the particle optical axis Z within the projection lens system 205. For example, the tilt and offset can be corrected for the coupling with the second projection lens 205b. The second magnetic region 450 can be used to adjust the tilt, and the third magnetic region 460 can be used to adjust the offset, and vice versa. According to a preferred embodiment, the beam splitter configuration 400 further includes at least one multipole configuration (not shown in FIG. 9) configured in the secondary particle optical beam path 11 but not in the primary particle optical beam path, the multipole configuration being positioned downstream of the first magnetic region 410 relative to the secondary particle optical beam path. The first projection lens 205a is positioned after the first magnetic region 410 and before the multipole configuration along the direction of the secondary particle optical beam path 11. The controller 10 is configured to control the multipole configuration based on the landing energy. According to a preferred embodiment, the controller 10 is configured to control at least one multipole configuration to additionally achieve paraxial astigmatism-free, paraxial distortion-free, and / or paraxial chromatic aberration-free imaging on the detection plane. Figure 10 schematically illustrates a beam splitter configuration 400 according to the present invention. Beam splitter configuration 400 is also compatible with the multi-beam particle microscope shown in Figure 1. According to this specific embodiment, beam splitter configuration 400 further includes a second magnetic region 450 disposed in the secondary particle optical beam path 11, but not in the primary particle optical beam path 13. The second magnetic region 450 is disposed downstream of the first magnetic region 410 relative to the secondary particle optical beam path 11 and configured to provide a uniform magnetic field to deflect the second individual particle beam 9, in the illustrated example, in the same deflection direction as the first magnetic region 410. The first projection lens 205a is disposed directly after the second magnetic region 450 relative to the secondary particle optical beam path 11, indicating that no other particle optical elements are disposed in between. Controller 10 is configured to control the second magnetic region 450 according to the landing energy. Controlling the second magnetic region 450 and thus adjusting its magnetic field provides an optimized parameter before the second individual particle beam 9 enters the first projection lens 205a. According to a preferred embodiment, the controller 10 is configured to control the second magnetic zone 205a to adjust the tilt or offset of the secondary particle optical axis Z before the plurality of second individual particle beams 9 enter the first projection lens 205a. Figure 11 schematically shows an alternative specific embodiment. The beam splitter configuration 400 is also compatible with the multi-beam particle microscope shown in Figure 1. The beam splitter configuration 400 includes a final magnetic region 470, configured in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13, and configured to provide a uniform magnetic field. The final magnetic region 470 is configured relative to the secondary particle optical beam path 11 as the final magnetic region 470 of the beam splitter configuration 400 prior to the first projection lens 205a. The final magnetic region may be a fourth magnetic region, as shown in the illustrated specific embodiment, but this is not mandatory. The beam splitter configuration 400 further includes an isolation trench 480 configured to decouple the magnetic field of the final magnetic region 470 from the magnetic field of the first projection lens 205a. The exit tilt angle ηlast of the final magnetic region 470 is less than 15°, particularly less than 10° or 5°. This has the advantage of providing the isolation trench 480 in a space-saving manner. This, in turn, allows the first projection lens to be positioned closer to the sample, thereby reducing its fill factor. This measure can reduce the fill factor to approximately 8%. According to the specific embodiment shown, the isolation trench 480 is substantially rectangular. The rectangular isolation trench 480 requires less installation space than the triangular isolation trench (see Figure 4) and can accommodate the outlet angle η of the last magnetic zone 470. last Use when it is small enough. Figure 12 schematically shows a beam splitter configuration 400 according to the invention. Beam splitter configuration 400 is also compatible with the multi-beam particle microscope shown in Figure 1. According to the specific embodiment shown, the secondary particle optical beam path 11 further includes a collimating lens 204, which is disposed relative to the secondary particle optical beam path 11 after the first magnetic region 410 and before the first projection lens 205a. A controller 10 is configured to control the collimating lens 204 according to the landing energy. The provision of the collimating lens 204 helps to reduce the FOV radius within the first projection lens 205, thereby reducing its fill factor PL1. The collimating lens 204 can, for example, be turned on at high landing energies but remain closed at low landing energies. The collimating lens 204 is preferably an electrostatic lens. Electrostatic lenses require less mounting space than magnetic lenses, thus facilitating the positioning of the first projection lens 205a closer to the sample 7. According to one example, the focal length f_col of the collimating lens 204 ranges from 50 mm ≤ f_col ≤ 150 mm. According to a preferred embodiment, the strength of the magnetic field M1 in the first magnetic region 410 is similar to the strength of the magnetic field M2 in the second magnetic region 450, therefore 0.8 ≤ M1 / M2 ≤ 1.2. According to an alternative embodiment, the beam splitter configuration 400 further includes a second magnetic region 450, which is configured in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The second magnetic region 450 is configured downstream of the first magnetic region 410 relative to the secondary particle optical beam path 11 and is configured to provide a uniform magnetic field to further deflect a second, separate particle beam in the same direction as in the first magnetic region. The total deflection angle α in the secondary particle optical beam path 11 (deflected by the beam splitter configuration 400) is described by the following relationship: α ≥ 40°, particularly α ≥ 41° or α ≥ 42°. This large deflection angle can be a decisive parameter for establishing mounting space in the second particle optical beam path 11. More mounting space allows for the installation of a larger first projection lens 205a (preferably a magnetic lens), thus requiring a significant amount of space. If the first projection lens can be made larger, its opening / drill hole 213 can be made larger, thereby reducing the fill factor PL1 and producing fewer aberrations within the first projection lens 205a. According to the example, the strength of the magnetic field M1 in the first magnetic region 410 differs from the strength of the magnetic field M2 in the second magnetic region 450 and satisfies one of the following relationships: (i) M1 / M2 ≥ 2.0, preferably M1 / M2 ≥ 2.5 or M1 / M2 ≥ 3.0; or (ii) M2 / M1 ≥ 2.0, preferably M2 / M1 ≥ 2.5 or M2 / M1 ≥ 3.0. Therefore, at least for a magnetic region providing a relatively strong magnetic field, the increase in aberrations produced in the beam splitter configuration 400 is acceptable. However, this can be completely offset by the reduction in aberrations produced in the first projection lens 205a. According to an alternative embodiment of the invention, the beam splitter configuration 400 further includes up to five additional components, wherein the components may be configured for additional magnetic regions 450, 460, 470 or multipole configurations, these additional components providing up to five degrees of freedom for further adjustment of imaging in the secondary particle optical beam path. The controller 10 is configured to control the additional components based on the landing energy to at least adjust the axial fundamental ray height ratio xa / ya between the axial fundamental rays in the x and y directions within the first projection lens 205a, such that (1-xa / ya) ≤ 15%, particularly (1-xa / ya) ≤ 10% or (1-xa / ya) ≤ 5%. Generally, reducing the FOV anisotropy inherent in the first projection lens 205a in the x and y directions reduces the ellipticity of the second cross 212. However, if fewer than five magnetic zones or multipoles are applied as additional correction components before the first projection lens 205a, the imaging of the beam splitter configuration 400 cannot be perfectly astigmatic-free for all landing energies, but can only correct one or two aspects of the total four beam splitter astigmatic components for all landing energies. Therefore, the question arises of which astigmatic component should be best compensated. To achieve a smaller cross ellipticity, it is advantageous to pursue a smaller FOV anisotropy within the first projection lens 205a, for example, by targeting similar heights of the axial fundamental rays in the x and y directions within the first projection lens 205a. According to another specific embodiment, the beam splitter configuration 400 includes a dispersion-free plane in the secondary particle optical beam path 11, the z-position of which is fixed by the design of the beam splitter configuration 400. The second particle optical unit includes an adjustment member configured to adjust the z-position of the objective lens system image plane. The controller 10 is configured to control the adjustment member based on the landing energy, such that the adjusted z-position of the objective lens system image plane matches the fixed z-position of the dispersion-free plane of the beam splitter configuration. This solution, in contrast to known methods, interprets the z-position of the objective lens system image plane as fixed and adjusts, for example, the magnetic region of the beam splitter configuration 400 to adjust the dispersion-free plane so that it matches the fixed objective lens system image plane. The opposite method according to the invention can be implemented in several different ways: According to a preferred embodiment, the adjustment component includes an adjustment lens positioned after the first magnetic region relative to the secondary particle optical beam path. The adjustment lens acts only on the second individual particle beam. The maximum refractive index of this adjustment lens is required for minimum landing energy / small landing energy. The adjustment lens can be configured as a collimating lens as shown in Figure 12. Controller 10 can be configured, for example, to control the landing energy between a minimum landing energy LEmin and a maximum landing energy LEmax (inclusive); and controller 10 is configured to control the adjustment lens 204 between zero and a maximum adjustment value (inclusive). Controller 10 is configured to control the adjustment lens 204 with the maximum adjustment value when the controller sets the minimum landing energy LEmin. According to an example, the adjustment lens 204 is configured to have a maximum refractive index RP of RP ≥ 15 / m. However, smaller or larger values ​​are also possible, for example, RP ≥ 20 / m. According to an alternative embodiment, the objective lens system 102 includes two objective lenses, and the adjustment mechanism is implemented by the two objective lenses 102. The two parts of the objective lens system 102 are configured to be independently controllable. A controller configuration is used to control the two objective lenses to maintain their image planes in the primary particle optical beam path, and also to control the two objective lenses to adjust their image planes in the secondary particle optical beam path. In short, this effect of the two objective lenses 102 can be understood through the fact that the two objective lenses 102 are equivalent to a displacement lens configured in a variable position and having variable intensity. According to another specific embodiment, the beam splitter configuration 400 further includes a dispersion correction region configured to provide a uniform magnetic field through which the secondary particle optical beam path 11 passes during use, but the primary particle optical beam path 13 does not. The beam splitter configuration 400 includes a dispersion-free plane in the secondary particle optical beam path 11, the position of which can be adjusted by controlling the dispersion correction region. The entrance tilt angle of the first magnetic region 410 is intentionally deviated from 0°. The controller 10 is configured to control the dispersion correction region based on the landing energy so that the position of the dispersion-free plane in the beam splitter configuration matches the position of the image plane of the objective lens system. According to an alternative embodiment, beamsplitter configuration 400 does not include a dispersion correction region or other dispersion correction components for controlling the position of the dispersion-free plane in the secondary particle optical beam path 11 based on the landing energy LE. Controller 10 is configured to control the landing energy LE within the range of Lemin ≤ LE ≤ Lemax. Beamsplitter configuration 400 is designed such that, for a landing energy LE_ave = (LEmax - LEmin) / 2, the z-position z1 of the dispersion-free plane of the beamsplitter configuration matches the z-position z2 of the image plane of the objective lens system within a range of + / -5%, therefore 0.95 ≤ |(z1-z2) / z2| ≤ 1.05. The idea behind this solution is as follows: It has been found that for landing energies up to several keV, beamsplitter aberrations are primarily dominated by first-order dispersion (Ck term). Therefore, efforts to reduce dispersion to reduce total beamsplitter aberrations are effective. If a dedicated magnetic field is unavailable for dispersion correction at all landing energies, and dispersion correction for a reference LE_ref can only be performed by selecting a suitable beamsplitter 400 / magnet configuration design, then this choice is optimal. Beamsplitter aberrations are minimized at the location of the minimum on the dispersion curve. This minimum is achieved by each beamsplitter design having a specific plane where dispersion disappears, the so-called dispersion-free plane. The image plane position behind objective lens 102 and beamsplitter 400 varies considerably with the landing energy LE. At lower landing energies, the image plane is located higher above sample 7, where secondary particles / signal electrons have higher energy. At higher landing energies, the image plane is closer to sample 7, the specific position depending on the refractive index of the corresponding objective lens 102 and beamsplitter 400. Now, there exists a landing energy LEopt at which the image plane behind the objective lens and beamsplitter intersects the dispersion-free plane. At this landing energy LEopt, the minimum of beamsplitter dispersion occurs. Therefore, if the beam splitter 400 is to be used within a specific landing energy range, the goal is to optimize the beam splitter design so that the dispersion-free plane is located approximately in the middle of the target LE range, where the minimum dispersion occurs. In this case, the dispersion at the two edges of the LE range is the same, thus achieving the minimum maximum dispersion value that can occur throughout the entire landing energy range. Figure 13 illustrates the aforementioned adjustment scheme: Figure 13a schematically shows the aberrations depending on the landing energy LE according to the present invention without specific adjustments. The curve is generally V-shaped. However, this curve is not symmetrical with respect to the landing energy LEopt, where dispersion disappears. The aberrations are relatively low in the range LEmin ≤ LE ≤ LE1. However, the aberrations increase sharply in the range LE1 < LE ≤ LEmax. Therefore, the aberrations vary considerably throughout the entire range LEmin ≤ LE ≤ LEmax, ranging from 0 to a2 in the example shown. Figure 13b illustrates the following: the beam splitter design 400 is designed such that the dispersion-free plane is located approximately in the middle of the target LE range where the minimum dispersion occurs. In other words, minimum dispersion is achieved at the landing energy LEopt, which, according to the beam splitter 400 design, is approximately located between the minimum landing energy LEmin and the maximum landing energy LEmax. Therefore, aberration differences are small throughout the entire LEmin ≤ LE ≤ LEmax range, ranging from 0 to a1 or a1' in the illustrated example. Figures 14 to 17 show the parameters that affect the suppression of aberrations in the second particle optical beam path 11. More precisely, for magnetic regions 410, 450, 460, and 470, it has been found that the ratio between the width W of the linear inlet or outlet region and the distance D between the two plates forming the corresponding magnetic regions 410, 450, 460, and 470 has a decisive influence on the suppression of aberrations. Figure 14 schematically illustrates the geometry of the first magnetic region 410, which can serve as an independent control parameter to further help reduce aberrations: Figure 14a shows the entrance region of the first magnetic region 410, where the particle optical axis Z points to the paper plane in the example shown. The first magnetic region 410 has two mutually parallel plates 411, 412, with a distance D1 between them in the example shown. The spaced-apart plates 411, 412 can be made of a magnetizable material, and grooves can be milled into the plates 411, 412, into which current conductors or coils are inserted. However, other specific embodiments of the two mutually parallel plates 411, 412 are also possible. The entrance region of the first magnetic region 410 is linear and has a width of W11. Therefore, in principle, the entire entrance region or groove is linear, and the width W11 can be fully defined. It has now been found that the ratio of groove width W11 to plate spacing D1 is advantageous if the ratio R11 = W11 / D1 satisfies the following relationship: R11 ≥ 2.0, preferably R11 ≥ 3.0 or R11 ≥ 3.5. In this case, aberrations can be further reduced. The same applies to the ratio R12 = W12 / D1, where W12 represents the width of the exit region of the first magnetic zone 410, as shown in Figure 14b. Similarly, the following ratio also offers advantages in reducing aberrations: R12 ≥ 2.0, preferably R12 ≥ 3.0 or R12 ≥ 3.5. Figure 15 schematically illustrates the geometry of the second magnetic field region 450, which, as an independent control parameter, can further help reduce aberrations: Figure 15a shows the entrance region of the second magnetic region 450, where, in the example shown, the particle optical axis Z points towards the plane of the paper. The second magnetic region 450 has two mutually parallel plates 451, 452, with a distance D2 between them in the example shown. The spaced-apart plates 451, 452 can be made of a magnetizable material, and grooves can be milled into the plates 451, 452, into which current conductors or coils are inserted. However, other specific embodiments of the two mutually parallel plates 451, 452 are also possible. The entrance region of the second magnetic region 450 is linear and has a width W21. Therefore, in principle, the entire entrance region or groove is linear, and the width W21 can be fully defined. It has been found that the ratio of groove width W21 to plate spacing D2 is advantageous if the ratio R21 = W21 / D2 satisfies the following relationship: R21 ≥ 2.0, preferably R21 ≥ 3.0 or R21 ≥ 3.5. In this case, aberrations can be further reduced. The same applies to the ratio R22 = W22 / D2, where W22 represents the width of the exit region of the second magnetic zone 450, as shown in Figure 15b. Similarly, an advantage in reducing aberrations is also found if the following ratio is applied: R22 ≥ 2.0, preferably R22 ≥ 3.0 or R22 ≥ 3.5. Figure 16 schematically illustrates the geometry of the third magnetic region 460, which, as an independent control parameter, can further help reduce aberrations: Figure 16a shows the entrance region of the third magnetic region 460, where, in the example shown, the particle optical axis Z points towards the paper plane. The third magnetic region 460 has two mutually parallel plates 467, 468, with a distance D3 between them in the example shown. The spaced-apart plates 467, 468 can be made of a magnetizable material, and grooves can be milled into the plates 467, 468 into which current conductors or coils are inserted. However, other specific embodiments of the two mutually parallel plates 467, 468 are also possible. The entrance region of the third magnetic region 460 is linear and has a width W31. Therefore, in principle, the entire entrance region or groove is linear, and the width W31 can be fully defined. It has been found that the ratio of groove width W31 to plate spacing D3 is advantageous if the ratio R31 = W31 / D3 satisfies the following relationship: R31 ≥ 2.0, preferably R31 ≥ 3.0 or R31 ≥ 3.5. In this case, aberrations can be further reduced. The same applies to the ratio R32 = W32 / D3, where W32 represents the width of the exit region of the third magnetic zone 460, as shown in Figure 16b. Similarly, an advantage in reducing aberrations is also found if the following ratio is applied: R32 ≥ 2.0, preferably R32 ≥ 3.0 or R32 ≥ 3.5. Figure 17 schematically illustrates the geometry of the fourth magnetic region 470, which, as an independent control parameter, can further help reduce aberrations: Figure 17a shows the entrance region of the fourth magnetic region 470, where, in the example shown, the particle optical axis Z points towards the paper plane. The fourth magnetic region 470 has two mutually parallel plates 471, 472, with a distance D4 between them in the example shown. The spaced-apart plates 471, 472 can be made of a magnetizable material, and grooves can be milled into the plates 471, 472, into which current conductors or coils are inserted. However, other specific embodiments of the two mutually parallel plates 471, 472 are also possible. The entrance region of the fourth magnetic region 470 is linear and has a width W41. Therefore, in principle, the entire entrance region or groove is linear, and the width W41 can be fully defined. It has been found that the ratio of groove width W41 to plate spacing D4 is advantageous if the ratio R41 = W41 / D4 satisfies the following relationship: R41 ≥ 2.0, preferably R41 ≥ 3.0 or R41 ≥ 3.5. In this case, aberrations can be further reduced. The same applies to the ratio R42 = W42 / D4, where W42 represents the width of the exit region of the fourth magnetic zone 470, as shown in Figure 17b. Similarly, an advantage in reducing aberrations is also found if the following ratio is applied: R42 ≥ 2.0, preferably R42 ≥ 3.0 or R42 ≥ 3.5. Figure 18 illustrates another specific embodiment of the beam splitter configuration 400. This specific embodiment describes the fan-shaped design and configuration of the second, third, and fourth magnetic regions 450, 460, and 470. This fan-shaped design helps to balance and equalize the widths of the linear entry and exit regions, avoiding very short entry and / or exit regions. This measure, in turn, helps to reduce aberrations, especially relatively strong field astigmatism. More specifically, the beam splitter configuration 400 includes a first magnetic region 410 configured to provide a uniform magnetic field M1 through which the primary particle optical beam path 13 and the secondary particle optical beam path 11 pass during use, and is configured to separate the primary particle optical beam path 13 and the secondary particle optical beam path 11 from each other. The entrance tilt angle η11 of the first magnetic region 410 is intentionally deviated from 0°. Furthermore, the beam splitter configuration 400 includes a second magnetic region 450, which is disposed in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The second magnetic region 450 is disposed downstream of the first magnetic region 410 relative to the secondary particle optical beam path 13 and configured to provide a uniform magnetic field M2 for deflecting the second secondary particle beam 9. A first drift region with essentially no magnetic field is provided between the first magnetic region 410 and the second magnetic region 450. The beam splitter configuration 400 further includes a third magnetic region 460, which is disposed in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The third magnetic region 460 is disposed downstream of the second magnetic region 450 relative to the secondary particle optical beam path 11 and configured to provide a uniform magnetic field M3. The beam splitter configuration 400 further includes a fourth magnetic region 470, which is disposed in the secondary particle optical beam path 11 but not in the primary particle optical beam path 13. The fourth magnetic region 470 is disposed downstream of the third magnetic region 460 relative to the secondary particle optical beam path 11 and configured to provide a uniform magnetic field M4. The second, third, and fourth magnetic regions 450, 460, and 470 are directly and continuously arranged, with no drift region between adjacent regions. Therefore, the exit region of the second magnetic region 450 corresponds to the entrance region of the third magnetic region 460, and the exit region of the third magnetic region 460 corresponds to the entrance region of the fourth magnetic region 470. In the example shown, the entrance regions of the second, third, and fourth magnetic regions 450 and 470 are linear and have several intersection points within an intersecting circle 479 with a minimum diameter of d along their theoretical extensions. All intersections between the extensions are located within this intersecting circle. The two intersection points P1 and P2 are the intersection points with the largest distance between each pair of possible intersection points. Therefore, points P1 and P2 are arranged on the intersecting circle 479. The exit region W22 of the second magnetic region 460 is linear and has a width W22. For the diameter d and width WD22, the following relationship is satisfied: d ≤ WD22, and in particular d ≤ 0.5*WD22. According to the example, the diameter d of the intersecting circle 479 satisfies the following relationship: d ≤ 10 mm, preferably d ≤ 5 mm or d ≤ 3 mm. This is on the order of magnitude of the groove width, or smaller. Figure 19 schematically illustrates another specific embodiment of the invention, wherein the magnet configuration of the beam splitter configuration 400 consists of only three magnetic regions 410, 450, and 460. The first magnetic region 410 is configured to provide a uniform magnetic field M1, through which the primary particle optical beam path 13 and the secondary particle optical beam path 11 pass during use, and is configured to separate the primary particle optical beam path 13 and the secondary particle optical beam path 11 from each other. The second magnetic region 450 is disposed in the secondary particle optical beam path 11, but not in the primary particle optical beam path 13. The second magnetic region 450 is disposed downstream of the first magnetic region 410 relative to the secondary particle optical beam path 11 and configured to provide a uniform magnetic field M2 to deflect the second secondary particle beam 9. The third magnetic region 460 is configured in the secondary particle optical beam path 11, but not in the primary particle optical beam path 13. The third magnetic region 460 is configured downstream of the second magnetic region 450 relative to the secondary particle optical beam path 11 and is configured to provide a uniform magnetic field M3. The entrance inclination angle η11 of the first magnetic region 410 is intentionally deviated from 0°, and a first drift region 453 with essentially no magnetic field is provided between the first magnetic region 410 and the second magnetic region 450. In addition, a second drift region 473 with essentially no magnetic field is provided between the second magnetic region 450 and the third magnetic region 460. The controller 10 is configured to control the landing energy LE within the range of Lemin ≤ LE ≤ LEmax. According to this specific embodiment, the design system of the second magnetic region 450 is configured to achieve optimal astigmatism and chromatic aberration correction at low landing energy LE_low, while the design system of the third magnetic region 460 is configured to achieve optimal astigmatism and chromatic aberration correction at high landing energy LE_high, and vice versa, where LEmin < LE_low < LE_high < LEmax. According to a preferred embodiment, the controller 10 is configured to shut down the second magnetic zone 450 or the third magnetic zone 460 when the controller 10 sets the landing energy LE to LE_high or LE_low. For inherent beam splitter performance, choosing a beam splitter design / magnet configuration design 400 with gaps / drift regions 453, 463 between consecutive magnetic regions is advantageous because it provides more geometric degrees of freedom (opposite to the sector design rule explained earlier with respect to Figure 18). Consider a design consisting of three magnetic regions in the secondary particle optical beam path, with drift regions between consecutive magnetic regions, which provides sufficient degrees of freedom to achieve... Astigmatism and dispersion correction under two landing energies. For example, the geometry of the first magnetic region can be used to correct astigmatism and dispersion at low landing energies over a wide range of target landing energies, while the geometry of the second region can be used to compensate for astigmatism and dispersion at high landing energies, thus producing a "W"-shaped landing energy dependence of internal beam splitter aberrations. Therefore, it has a smaller maximum aberration value compared to the "V"-shaped curve for correcting astigmatism and dispersion only at a single landing energy. According to a preferred embodiment, the design parameters of the second magnetic region 450 are geometric parameters, and include or consist of the following: the length of the first drift region 453, the inlet tilt angle η21, the outlet tilt angle η22, and the distance between the inlet and outlet regions. Conversely, the magnetic field strength in the magnetic region is not a geometric design parameter. According to a preferred embodiment, the design parameters of the third magnetic region 460 are geometric parameters, and include or consist of the following: the length of the second drift region 463, the inlet tilt angle η31, the outlet tilt angle η32, and the distance between the inlet region and the outlet region. The above aspects and specific embodiments of the present invention can be combined with each other in whole or in part, as long as no technical contradictions arise. In many specific embodiments of the beam splitter configuration 400 in the above figures, details of the beam splitter configuration relative to the first particle optical beam path are also disclosed. However, it should be noted that the beam splitter configuration 400 described for the secondary particle optical beam path can also be used in conjunction with other beam splitter configurations in the primary particle optical beam path. The details of the primary particle optical beam path are shown only as illustrative examples. The disclosed specific embodiments can also be adapted to the following beam splitter configuration: the beam splitter configuration has a first magnetic region 410 disposed in the first and second particle optical beam paths 13, 11, wherein the lower groove G11 is orthogonal to the extension of the optical axis A of the objective lens system 102, and therefore η11=0. In addition, it should be noted that the diagrams presented are not drawn to scale and are for illustrative purposes only. This invention discloses a multi-beam particle microscope 1 with reduced aberrations in the secondary particle optical beam path 11. This solution is applicable to a wide range of landing energies (LE) up to several keV. One measure to achieve this is to employ a structural approach that improves the overall projection path design, particularly improving the positioning of the first projection lens 205a in the secondary particle optical beam path 11, where the first projection lens 205a is a space-consuming magnetic lens. When operating the multi-beam particle microscope 1 at a wide range of landing energies (LE), the fill factor in the first projection lens 205a is considered a major source of residual aberrations in the secondary particle optical beam path 11. Another measure is the performance improvement of the beam splitter configuration 400 itself in the secondary particle optical beam path 11. This invention discloses several designs and design rules for the beam splitter configuration 400 to reduce aberrations when operating the multi-beam particle microscope 1 at a wide range of landing energies (LE). 1: Multi-beam particle microscope; 3: Particle beam; 5: Beam point; 7: Object; 9: Secondary particle beam; 9a: Secondary particle beam; 9c: Secondary particle beam; 10: Computer system; 11: Secondary particle optical beam path; 13: Primary particle optical beam path; 15: Surface; 101: Object plane; 102: Objective lens; 103: Electromagnetic lens; 105: Center; 200: Projection system; 204: Collimating lens; 205: Imaging system; 205a: Projection lens; 205b: Projection lens; 205c: Projection lens; 206: Magnetic projection lens; 208: Magnetic projection lens; 209: Multi-particle detector; 210: Magnetic projection lens; 212: Cross; 213: Aperture; 214: Contrast aperture; 215: Cross point; 222: Beam deflector; 260: Electrostatic element; 300: Beam generation device; 301: Particle source; 303: Condensing lens system; 303.1: Condensing lens; 303.2: Condensing lens; 305: Multi-aperture. Configuration 306: Multi-aperture plate; 307: Field lens; 308: Field lens; 309: Diverging particle beam; 323: Beam focus; 325: Intermediate image surface; 400: Magnet configuration; 410: Magnetic region; 411: Plate; 412: Plate; 430: Magnetic region; 450: Magnetic region; 451: Plate; 452: Plate; 453: Drift region; 460: Magnetic region; 461: Branch; 462: Branch; 463: Branch; 467: Plate; 468: Plate; 470: Magnetic region; 471: Plate; 472: Plate 473: Drift Zone 479: Intersecting Circle 480: Isolation Groove 490: Beam Tube Configuration 500: Scanning Deflector 600: Displacement Stage β: Tilt Angle γ: Splitting Angle δ: Image Field Tilt Angle σ1: Exit Tilt Angle ηij: Exit Tilt Angle A: Axis D: Diameter D1, D2, D3, D4: Plate Spacing G11: Lower Groove G12: Upper Groove Ri: Inner Radius Rmax: Maximum Radius P1: Intersection Point P2: Intersection Point Wij: Width Z: Particle Axis The invention can be better understood with reference to the accompanying drawings, in which: Figure 1 schematically shows a multi-beam particle microscope; Figure 2 schematically shows a multi-beam particle microscope with a beam splitter or magnet configuration according to the prior art; Figure 3 schematically shows the beam splitter or magnet configuration; Figure 4 schematically shows the beam splitter configuration; Figure 5 schematically shows a segmented magnetic region and its configuration in the first and second particle optical beam paths; Figure 6 schematically illustrates the problem of increased fill factor inside the first projection lens when the landing energy LE varies over a wide range; Figure 7 schematically shows the definition of the fill factor PL1; Figure 8 schematically shows the position of the first projection lens in the path of the secondary particle optical beam; Figure 9 schematically shows a beam splitter configuration; Figure 10 schematically shows a beam splitter configuration; Figure 11 schematically shows a beam splitter configuration; Figure 12 schematically shows a beam splitter configuration; Figure 13 schematically illustrates the dependence of aberrations on landing energy; Figure 14 schematically shows the geometric relationship of the first magnetic region; Figure 15 schematically shows the geometric relationship of the second magnetic region; Figure 16 schematically shows the geometric relationship of the third magnetic region; Figure 17 schematically shows the geometric relationship of the fourth magnetic region; Figure 18 schematically shows the configuration of the fan-shaped beam splitter; and Figure 19 schematically shows a beam splitter configuration. 102: Objective lens 205a: Projection lens 400: Magnet Configuration

Claims

1. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes the following features: at least one first magnetic region configured to provide a uniform magnetic field through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration to separate the primary particle optical beam path and the secondary particle optical beam path from each other; wherein each magnetic region has an entrance region for the secondary particle optical beam path having an entrance tilt angle, and an exit region for the secondary particle optical beam path having an exit tilt angle, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance region deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit region deviates from the normal to the optical axis of the secondary particle optical beam path; The inlet tilt angle of the first magnetic region deviates from 0°; the secondary particle optical beam path includes a first intersection of the second separate particle beam corresponding to a focal plane of the objective lens system, and a second intersection of the second separate particle beam disposed between the beam splitter configuration and the detection unit and configurable during use to be flush with a contrast aperture; the second particle optical unit includes a projection lens system having a first projection lens, the first projection lens being a magnetic lens, the first projection lens being disposed relative to the secondary particle optical beam path after the first intersection and before the second intersection; the projection lens system is configured to image the second separate particle beam onto the third field, and the first projection lens system is configured to focus the plurality of second separate particle beams onto the second intersection; the controller is configured to control the first projection lens to focus the plurality of second separate particle beams onto the second intersection according to the landing energy.And the first projection lens is configured such close to the first intersection that a fill factor PL1 of the first projection lens is set to PL1 ≤ 15%, specifically PL1 ≤ 10% or PL1 ≤ 5%, wherein the fill factor PL1 is defined as the ratio between the maximum radius Rmax of all the plurality of second separate particle beams within the first projection lens and the inner radius Ri of an opening of the first projection lens through which the second separate particle beam passes, therefore PL1 = Rmax / Ri.

2. The multi-beam particle microscope as claimed in claim 1: wherein the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the second magnetic region being disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting the second secondary particle beam; and a third magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the third magnetic region being disposed downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field; and wherein the first projection lens is disposed between the first magnetic region and the second magnetic region; and wherein the controller is configured to control the second magnetic region and the third magnetic region according to the landing energy.

3. The multi-beam particle microscope as claimed in claim 2, wherein the controller is configured to control the second magnetic zone and the third magnetic zone to adjust a tilt and a shift of the particle optical axis within the projection lens system.

4. The multi-beam particle microscope as claimed in claim 3, wherein the beam splitter configuration further comprises: at least one multi-pole configuration disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the multi-pole configuration being disposed downstream of the first magnetic region relative to the secondary particle optical beam path; wherein the first projection lens is disposed after the first magnetic region and before the multi-pole configuration along the direction of the secondary particle optical beam path; and wherein the controller is configured to control the multi-pole configuration according to the landing energy.

5. The multi-beam particle microscope as claimed in claim 4, wherein the controller is configured to control the at least one multipole configuration to further achieve paraxial astigmatism-free, paraxial distortion-free, and / or paraxial chromatic aberration-free imaging in the detection plane.

6. The multi-beam particle microscope as claimed in claim 1, wherein the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the second magnetic region being disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting the second secondary particle beam, wherein the first projection lens is disposed immediately after the second magnetic region relative to the secondary particle optical beam path; and wherein the controller is configured to control the second magnetic region according to the landing energy.

7. The multi-beam particle microscope as claimed in claim 6, wherein the controller is configured to control the second magnetic zone to adjust a tilt or offset of the secondary particle optical axis defined by the plurality of second separate particle beams before entering the first projection lens.

8. The multi-beam particle microscope as claimed in claim 1, wherein the beam splitter configuration further comprises: a last magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path and configured to provide a uniform magnetic field, the last magnetic region being configured relative to the secondary particle optical beam path as the last magnetic region of the beam splitter configuration prior to the first projection lens; and an isolation trench configured to decouple the magnetic field of the last magnetic region from the magnetic field of the first projection lens, wherein an exit tilt angle ηlast of the last magnetic region is less than 15°, particularly less than 10° or 5°.

9. The multi-beam particle microscope as claimed in claim 8, wherein the isolation trench is substantially rectangular.

10. The multi-beam particle microscope as claimed in claim 1, wherein the secondary particle optical beam path further includes a collimating lens disposed relative to the secondary particle optical beam path after the first magnetic region and before the first projection lens, and wherein the controller is configured to control the collimating lens according to the landing energy.

11. The multi-beam particle microscope as claimed in claim 10, wherein a focal length f_col of the collimating lens is in the range of 20 mm ≤ f_col ≤ 500 mm, particularly 50 mm ≤ f_col ≤ 150 mm.

12. The multibeam particle microscope as claimed in claim 10 or 11, wherein the collimating lens is an electrostatic lens.

13. A multi-beam particle microscope as claimed in claim 2 or 6, wherein the intensity of the magnetic field M1 in the first magnetic region is similar to, in particular the same as, the intensity of the magnetic field M2 in the second magnetic region, and therefore 0.8 ≤ M1 / M2 ≤ 1.

2.

14. The multi-beam particle microscope as claimed in claim 1, wherein the beam splitter configuration further includes a second magnetic region disposed in the secondary particle optical beam path but not in the primary particle optical beam path, the second magnetic region being disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for further deflecting the second secondary particle beam in the same direction as in the first magnetic region, wherein... For the secondary particle optical beam path deflected by the beam splitter, a total deflection angle α in the secondary particle optical beam path satisfies the following relationship: α ≥ 40°, especially α ≥ 41° or α ≥ 42°.

15. A multi-beam particle microscope as claimed in claim 14, wherein the strength of the magnetic field M1 in the first magnetic region is different from the strength of the magnetic field M2 in the second magnetic region and satisfies one of the following relationships: (i) M1 / M2 ≥ 2.0, particularly M1 / M2 ≥ 2.5 or M1 / M2 ≥ 3.0; or (ii) M2 / M1 ≥ 2.0, particularly M2 / M1 ≥ 2.5 or M2 / M1 ≥ 3.

0.

16. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes the following features: a first magnetic region configured to provide a uniform magnetic field through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration to separate the primary particle optical beam path and the secondary particle optical beam path from each other; wherein each magnetic region has an entrance region for the secondary particle optical beam path having an entrance tilt angle, and an exit region for the secondary particle optical beam path having an exit tilt angle, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance region deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit region deviates from the normal to the optical axis of the secondary particle optical beam path; The entrance tilt angle of the first magnetic region is intentionally deviated from 0°; the beam splitter configuration further includes up to five other components, one of which may be an additional magnetic region or a multipole configuration, the other components providing up to five degrees of freedom for further adjusting the imaging in the secondary particle optical beam path; the secondary particle optical beam path includes a first intersection of the second separate particle beam corresponding to a focal plane of the objective lens system, and a second intersection of the second separate particle beam disposed between the beam splitter configuration and the detection unit and configurable during use to be flush with a contrast aperture; the second particle optical unit includes a projection lens system having a first projection lens configured to image the second separate particle beam onto the third field, and the first projection lens is disposed relative to the secondary particle optical beam path after the first intersection and before the second intersection, and the first projection lens is configured to focus the plurality of second separate particle beams onto the second intersection;The controller configuration controls the first projection lens to focus the plurality of second individual particle beams onto the second cross based on the landing energy; and the controller is configured to control other components based on the landing energy to at least adjust the axial fundamental ray height ratio xa / ya between the axial fundamental rays in the x and y directions within the first projection lens, such that the following relationship holds: (1-xa / ya) ≤ 15%, particularly (1-xa / ya) ≤ 10% or (1-xa / ya) ≤ 5%.

17. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and the objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes: at least one first magnetic region configured to provide a uniform magnetic field through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration is configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; wherein each magnetic region of the beam splitter configuration has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance region deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit region deviates from the normal to the optical axis of the secondary particle optical beam path; The inlet tilt angle of the first magnetic region is intentionally deviated from 0°; the beam splitter configuration includes a dispersion-free plane in the secondary particle optical beam path, the z-position of which is fixed by the design of the beam splitter configuration; the secondary particle optical beam path includes a first intersection of the second secondary particle beam corresponding to a focal plane of the objective lens system, the objective lens system further having an image plane of the objective lens system disposed relative to the secondary particle optical beam path after the first intersection; and the second particle optical unit includes an adjustment member configured to adjust a z-position of the image plane of the objective lens system; the controller configuration is configured to control the adjustment member according to the landing energy, such that the adjusted z-position of the image plane of the objective lens system matches the fixed z-position of the dispersion-free plane of the beam splitter configuration.

18. The multi-beam particle microscope as claimed in claim 17, wherein the adjustment member includes an adjustment lens disposed after the first magnetic region relative to the secondary particle optical beam path.

19. The multibeam particle microscope of claim 18, wherein the controller is configured to control the landing energy value between and including a minimum landing energy LEmin and a maximum landing energy LEmax; and wherein the controller is configured to control the adjustment lens between and including a maximum adjustment value; wherein the controller is configured to control the adjustment lens with the maximum adjustment value when the controller sets the minimum landing energy LEmin.

20. The multi-beam particle microscope as claimed in claim 18 or 19, wherein the adjustable lens configuration has a maximum refractive index RP having RP ≥ 15 / m.

21. The multi-beam particle microscope of claim 17, wherein the objective lens system comprises a two-part objective lens; wherein the adjustment device is implemented by the two-part objective lens, the two parts of the objective lens system being configured to be independently controllable; wherein the controller is configured to control the two-part objective lens to maintain the position of its image plane in the primary particle optical beam path; and wherein the controller is configured to control the two-part objective lens to adjust the position of its image plane in the secondary particle optical beam path.

22. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and an objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration is configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; a dispersion correction region configured to provide a uniform magnetic field through which the secondary particle optical beam path passes during use, but the primary particle optical beam path does not pass through the uniform magnetic field; wherein the beam splitter configuration includes a dispersion-free plane in the secondary particle optical beam path, the position of which is adjusted by controlling the dispersion correction region. Each magnetic region configured in the beam splitter has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein the secondary particle optical beam path includes a first intersection of the second secondary particle beam corresponding to a focal plane of the objective lens system, and the objective lens system further has an image plane of the objective lens system disposed relative to the secondary particle optical beam path after the first intersection; and wherein the controller is configured to control the dispersion correction region according to the landing energy, such that the position of the dispersion-free plane configured in the beam splitter matches the position of the image plane of the objective lens system.

23. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration disposed in the primary particle optical beam path between the multi-beam generator and an objective lens, and disposed in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration to separate the primary particle optical beam path and the secondary particle optical beam path from each other; A second magnetic region is disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The second magnetic region is disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field for deflecting the second secondary particle beam. A third magnetic region is disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The third magnetic region is disposed downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field. Each magnetic region of the beam splitter configuration has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and wherein the beam splitter configuration does not include a dispersion correction region or other dispersion correction member for controlling the position of a dispersion-free plane in the secondary particle optical beam path according to the landing energy LE;The secondary particle optical beam path includes a first intersection of the second secondary particle beam corresponding to a focal plane of the objective lens system, and the objective lens system further has an image plane of the objective lens system disposed after the first intersection relative to the secondary particle optical beam path; and the controller configuration is configured to control the landing energy LE within the range of LEmin ≤ LE ≤ LEmax, and the beam splitter configuration is designed such that, for a landing energy LE_ave = (LEmax-LEmin) / 2, the z-position z1 of the dispersion-free plane configured by the beam splitter matches the z-position z2 of the image plane of the objective lens system within a range of + / -5%, therefore 0.95 ≤ |(z1-z2) / z2| ≤ 1.

05.

24. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and an objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field M1, through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration is configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; A second magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M2 for deflecting the second secondary particle beam; a third magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M3; and a fourth magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the third magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M4. Each magnetic region configured in the beam splitter has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being substantially free of magnetic field;The first magnetic region comprises two plates arranged parallel to each other with a plate distance D1, wherein a uniform magnetic field M1 is generated between the two plates during use; wherein the entrance region of the first magnetic region is linear and comprises a width W11, and wherein the exit region of the first magnetic region is linear and comprises a width W12, and wherein for a ratio R11 = W11 / D1, the following relationship is satisfied: R11 ≥ 2.0, particularly R11 ≥ 3.0 or R11 ≥ 3.5; wherein for a ratio R12 = W12 / D1, the following relationship is satisfied: R12 ≥ 2.0, particularly R12 ≥ 3.0 or R12 ≥ 3.5; and wherein the second magnetic region comprises two plates arranged parallel to each other and having a plate distance D2, wherein during use, a uniform magnetic field M2 is generated between the two plates; wherein the entrance region of the second magnetic region is linear and comprises a width W21, and wherein the exit region of the second magnetic region is linear and comprises a width W22, and wherein for a ratio R21 = W21 / D2, the following relationship is satisfied: R21 ≥ 2.0, particularly R21 ≥ 3.0 or R21 ≥ 3.5; and / or wherein for a ratio R22 = W22 / D2, the following relationship is satisfied: R22 ≥ 2.0, particularly R22 ≥ 3.0 or R22 ≥ 3.

5.

25. A multi-beam particle microscope as claimed in claim 24, wherein the third magnetic region comprises two plates arranged parallel to each other and having a plate distance D3, wherein during use, a uniform magnetic field M3 is generated between the two plates; wherein the entrance region of the third magnetic region is linear and comprises a width W31, and wherein the exit region of the third magnetic region is linear and comprises a width W32, and wherein for a ratio R31 = W31 / D3, the following relationship is satisfied: R31 ≥ 2.0, particularly R31 ≥ 3.0 or R31 ≥ 3.5; and / or wherein for a ratio R32 = W32 / D3, the following relationship is satisfied: R32 ≥ 2.0, particularly R32 ≥ 3.0 or R32 ≥ 3.

5.

26. A multi-beam particle microscope as claimed in claim 24 or 25, wherein the fourth magnetic region comprises two plates arranged parallel to each other and having a plate distance D4, wherein during use, a uniform magnetic field M4 is generated between the two plates; wherein the entrance region of the fourth magnetic region is linear and comprises a width W41, and wherein the exit region of the fourth magnetic region is linear and comprises a width W42, and wherein for a ratio R41 = W41 / D4, the following relationship is satisfied: R41 ≥ 2.0, particularly R41 ≥ 3.0 or R41 ≥ 3.5; and / or wherein for a ratio R42 = W42 / D4, the following relationship is satisfied: R42 ≥ 2.0, particularly R42 ≥ 3.0 or R42 ≥ 3.

5.

27. The multi-beam particle microscope as claimed in claim 24 or 25, wherein the exit tilt angle of the first magnetic region is limited to η12 ≤ 35°, preferably η12 ≤ 25° or most preferably η ≤ 15°.

28. The multi-beam particle microscope as claimed in claim 24 or 25, wherein the inlet tilt angle of the second magnetic region is limited to η21 ≤ 35°, preferably η21 ≤ 25° or most preferably η21 ≤ 15°.

29. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and an objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes: a first magnetic region configured to provide a uniform magnetic field M1, through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region configuration is configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; A second magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M2 for deflecting the second secondary particle beam; a third magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M3; and a fourth magnetic region, disposed in the secondary particle optical beam path but not in the primary particle optical beam path, is positioned downstream of the third magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M4. Each magnetic region configured in the beam splitter has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; and wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being substantially free of magnetic field;The second, third, and fourth magnetic regions are directly and continuously arranged, with no drift region between adjacent regions. Therefore, the exit region of the second magnetic region corresponds to the entrance region of the third magnetic region, and the exit region of the third magnetic region corresponds to the entrance region of the fourth magnetic region. The entrance regions of the second, third, and fourth magnetic regions are linear, and their theoretical extensions have an intersection point or an intersecting circle with a minimum diameter d. All intersections between these extensions are within the intersecting circle. The exit region of the second magnetic region is linear and has a width W22. The diameter d and the width WD22 have the following relationship: d ≤ WD22, specifically d ≤ 0.5*WD22.

30. The multi-beam particle microscope as claimed in claim 29, wherein d ≤ 10 mm, particularly d ≤ 5 mm or d ≤ 3 mm.

31. A multi-beam particle microscope, comprising: a multi-beam particle generator configured to generate a first field of a plurality of charged first separate particle beams; a first particle optics unit having a primary particle optics path configured to image the generated first separate particle beams onto an object plane such that the first separate particle beams strike an object at an incident position, thereby forming a second field; a detection unit having a plurality of detection regions forming a third field; a second particle optics unit having a secondary particle optics path configured to image a second separate particle beam onto the third field of the detection region of the detection unit, the second separate particle beam originating from the incident position in the second field; and a magnetic and / or electrostatic objective lens system through which both the first and second separate particle beams pass. A beam splitter configuration is disposed in the primary particle optical beam path between the multi-beam generator and an objective lens, and in the secondary particle optical beam path between the objective lens system and the detection unit; and a controller configured to control the multi-beam particle microscope and control a landing energy of the primary particle beam on the object; wherein the beam splitter configuration includes a magnet configuration consisting of a first magnetic region, a second magnetic region, and a third magnetic region, the first magnetic region being configured to provide a uniform magnetic field M1, through which the primary particle optical beam path and the secondary particle optical beam path pass during use, and the first magnetic region being configured to separate the primary particle optical beam path and the secondary particle optical beam path from each other; The second magnetic region is disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The second magnetic region is disposed downstream of the first magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M2 to deflect the second secondary particle beam. The third magnetic region is disposed in the secondary particle optical beam path but not in the primary particle optical beam path. The third magnetic region is disposed downstream of the second magnetic region relative to the secondary particle optical beam path and configured to provide a uniform magnetic field M3. Each magnetic region configured in the magnet has an entrance region with an entrance tilt angle for the secondary particle optical beam path, and an exit region with an exit tilt angle for the secondary particle optical beam path, wherein the entrance tilt angle is defined as the angle by which the arrangement of the entrance regions deviates from the normal to the optical axis of the secondary particle optical beam path, and wherein the exit tilt angle is defined as the angle by which the arrangement of the exit regions deviates from the normal to the optical axis of the secondary particle optical beam path; wherein the entrance tilt angle of the first magnetic region is intentionally deviated from 0°; wherein a first drift region is provided between the first magnetic region and the second magnetic region, the first drift region being substantially free of magnetic field; wherein a second drift region is provided between the second magnetic region and the third magnetic region, the second drift region being substantially free of magnetic field;The controller configuration is used to control the landing energy LE within the range of LEmin ≤ LE ≤ LEmax; the design system configuration of the second magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a low landing energy LE_low, and the design system configuration of the third magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a high landing energy LE_high; or the design system configuration of the second magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a high landing energy LE_high, and the design system configuration of the third magnetic region is used to achieve optimal astigmatism and chromatic aberration correction at a low landing energy LE_low, where LEmin < LE_low < LE_high < LEmax.

32. The multi-beam particle microscope as claimed in claim 31, wherein the controller is configured to shut down the second magnetic zone or the third magnetic zone when the controller sets the landing energy LE to LE_high or LE_low.

33. The multi-beam particle microscope as claimed in claim 31 or 32, wherein the design parameters of the second magnetic region are geometric parameters and include or consist of the following: the length of the first drift region, the inlet tilt angle, the outlet tilt angle, and the distance between the inlet region and the outlet region.

34. The multi-beam particle microscope as claimed in claim 31 or 32, wherein the design parameters of the third magnetic region are geometric parameters and include or consist of the following: the length of the second drift region, the inlet tilt angle, the outlet tilt angle, and the distance between the inlet region and the outlet region.

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