Method of operating a control circuitry of a multi-beam scanning particle imaging system, computer program product, control circuitry and multi-beam scanning particle imaging system

Abstract

A method is provided for operating a control circuit (800) of a multi-beam scanning particle imaging system (1). The multi-beam scanning particle imaging system (1) includes a micro-optical configuration (305) for splitting an incident converging particle beam (309) into a plurality of particle beams (3). The multi-beam scanning particle imaging system (1) is configured to co-scan at least one set of the plurality of particle beams across an object plane (101). The method includes: acquiring one or more sensor signals from one or more sensors positioned along a particle beam path of the multi-beam scanning particle imaging system (1); determining one or more characteristics of the converging particle beam (309) at the micro-optical configuration (305) based on the one or more sensor signals; and controlling one or more particle optics elements (302) of the multi-beam scanning particle imaging system (1) based on the one or more characteristics of the converging particle beam (309).

Description

Technical Field

[0001] The present invention generally relates to the field of multi-beam scanning particle imaging systems, and more particularly to a method for operating control circuitry of a multi-beam scanning particle imaging system for improving beam control. The invention further relates to a multi-beam scanning particle imaging system incorporating control circuitry that implements this method. Prior Technology

[0002] A scanning particle microscope (SPM) is an instrument used for imaging and analyzing sample surfaces at the nanometer scale. They use focused beams of particles (such as electrons or ions) to probe the sample surface. Scanning electron microscopes (SEMs) are widely used instruments. SPMs offer unique features and advantages in terms of resolution, contrast, and sample preparation. Key components of an SPM include a particle source, lenses, a sample chamber, a scanning system, and detectors. The particle source generates a particle beam for scanning the sample. SPMs can use a variety of particles as probes, including electrons, ions, and even neutral atoms or molecules. Electromagnetic or electrostatic lenses focus and guide the particle beam onto the sample surface, enabling high-resolution imaging and analysis. The sample chamber is maintained under vacuum to prevent particle scattering and ensure optimal imaging conditions. The scanning system includes electromagnetic coils or plates used to scan the particle beam across the sample surface in raster mode, enabling imaging and analysis. Different detectors capture signals generated by the interaction between the particle beam and the sample, providing information about surface morphology, composition, and other properties.

[0003] Multibeam particle microscopy represents an advancement in particle microscopy technology. These instruments simultaneously scan and analyze sample surfaces using multiple particle beams. By employing parallel imaging, multibeam particle microscopy offers significant improvements in imaging speed, throughput, and efficiency compared to single-beam instruments.

[0004] For example, US 7,244,949 B2 and US 2019 / 0355544 A1 disclose a multi-beam scanning electron microscope (MSEM). In an MSEM, a sample is simultaneously irradiated by multiple single-electron beams arranged in a field or grid. For example, tens or hundreds of single-electron beams can be provided as the main radiation, with the spacing between each single-electron beam and its adjacent single-electron beams ranging from 1 to 200 micrometers. For example, an MSEM may have approximately 100 independent single-electron beams ("small beams") arranged, for example, in a hexagonal grid, with the spacing between each small beam approximately 10 micrometers. Multiple charged single-particle beams (main small beams) are focused onto the surface of the sample to be examined through a common large-field optical system (including a common objective lens). For example, the sample may be a semiconductor wafer mounted on a wafer holder on a movable platform. When the charged main beam irradiates the wafer surface, interaction products (such as secondary electrons or backscattered electrons) are emitted from the wafer surface. Their respective starting points correspond to the focal points of multiple main particle beams on the sample. The number and energy of the interaction products depend on factors such as the material composition and morphology of the wafer surface. The interaction products form multiple sub-independent particle beams (sub-small W beams), which are collected by a common objective and incident on a detector arranged in the detection plane through the projection imaging system of the multi-beam detection system. The detector contains multiple detection regions, each containing multiple detection pixels, and the detector captures the intensity distribution of each sub-independent particle beam. An image field of, for example, 100 μm x 100 μm can be obtained.

[0005] Especially in multi-beam particle scanning microscopy, particle beam generation is crucial for accurate imaging. Factors to consider when generating a particle beam include beam intensity and the beam's position within the sample plane. The particle beam can change, for example, after changing the particle source or during microscope operation, such as due to particle source aging.

[0006] For example, DE 10 2021 118 561 B4 relates to a method for operating a multi-beam particle microscope. The beam current is measured. The beam current measurement includes measuring the current on a multi-aperture array at a selected location during image acquisition. The deviation between the measured beam current and the nominal beam current is determined. The determined deviation is decomposed into a drift component and a high-frequency component. The high-frequency component of the beam current is controlled by a first beam current control tool, and / or the influence of the high-frequency component on the image quality of the multi-beam particle microscope is compensated by a device other than the first beam current control tool. Optionally, the drift component of the beam current can be controlled by a second beam current control tool.

[0007] Similarly, WO 2023 / 001401 relates to a multi-beam particle microscope with improved beam stability. Figure 6 schematically shows a quadrant detector: a multi-aperture plate configured into five mutually isolated independent regions 351, 352, 353, 354, and 367 for measuring excess electrons. The inner region 367 contains all the openings in the multi-aperture array. Therefore, the inner region 367 is completely unaffected by any structure or separately positioned detector. This ensures that the generated single particle beam has very good beam quality. The outer region is subdivided into four quadrants 351, 352, 353, and 354. Quadrants 351 and 353 have the same area size. The same is true for the larger areas of regions 352 and 354. If the beam cone of the illuminating particle beam strikes the center of the multi-aperture array, the signals produced by measurements in regions 351 and 353 should have the same signal strength. The same is true for measurements in regions 352 and 354. In different scenarios, when the beam cone of the illumination particle beam shifts in one direction, the signals generated in each quadrant 351, 352, 353, and 354 will show changes, thus allowing the direction of the shift to be identified. Summary of the Invention

[0008] Therefore, there is a need for improved techniques for generating beams in multibeam particle microscopy. In particular, this technique can also be used on-site during the operation of this microscope, that is, during the analysis of samples.

[0009] The aforementioned requirements can be achieved through the technical features of the independent request. The features of the subsidiary request define many embodiments.

[0010] A method is provided for operating a control circuit of a multi-beam scanning particle imaging system. The multi-beam scanning particle imaging system includes a micro-optical configuration for splitting an incident co-current particle beam into multiple particle beams. Each of these multiple particle beams may also be referred to as a small beam. The multi-beam scanning particle imaging system is configured to co-scan at least one set of the multiple particle beams across an object plane. For example, the multi-beam scanning particle imaging system may be a multi-beam scanning electron microscope. The incident co-current particle beam may be a co-current electron beam, and the multiple particle beams may be multi-electron beams. At least one set of electron beams may be used to co-scan the object plane. In other examples, the particles may include ions, such as helium ions. According to this method, one or more sensor signals from one or more sensors are acquired. These one or more sensors are positioned along a particle beam path of the multi-beam scanning particle imaging system. Based on the one or more sensor signals, one or more characteristics of the co-current particle beam at the micro-optical configuration are determined. It is worth noting that although the sensor may not be located in the micro-optical configuration, the characteristics of the aggregated particle beam at the micro-optical configuration are determined based on the sensor signal. Based on one or more characteristics of this aggregated particle beam (309), one or more particle optics elements of the multi-beam scanning particle imaging system are controlled.

[0011] For example, one or more characteristics may represent the tilt angle of the aggregated particle beam about an optical axis of a beam-generating device in the multi-beam scanning particle imaging system at a reference position along the beam path. The reference position may be located at the incident point of the aggregated particle beam in the micro-optical configuration. In some examples, the reference position may be located at a short distance upstream of the micro-optical configuration. However, the characteristics determined for the aggregated particle beam may be closely related to the characteristics of the multiple particle beams generated by the aggregated particle beam at the micro-optical configuration.

[0012] For example, a collimated and telecentric cohesive particle beam can be assumed. This beam contains a large number of particles, such as electrons, each with its own trajectory. Each trajectory may have a tilt angle relative to the optical axis of the beam-generating device in a multi-beam scanning particle imaging system. The optical axis can be defined as the axis perpendicular to the central aperture of the multi-aperture plate in the micro-optical configuration. The cohesive particle beam can be considered a global beam. Global beam tilt can be defined as a comprehensive consideration of the particle trajectories of this global beam. For example, global beam tilt can be defined as the angle at which the midpoint of all or some particle trajectories deviates from the optical axis. If only some particle trajectories are considered, the considered particles should be uniformly selected across the cross-section of the cohesive particle beam. This one or more characteristics may include a global beam tilt along the beam path at a reference position.

[0013] Additionally or alternatively, a local beam can be defined as a combination of particles constituting a microparticle beam, or as a combination of particles spatially close to each other, at a distance approximately equal to the aperture size of a multi-aperture plate in a micro-optical configuration. For each such local beam, its local beam tilt can be defined as the combination of the trajectories of the particles in that local beam. For example, local beam tilt can be defined as the angle at which the midpoint of all or part of the particle trajectories deviates from the optical axis. If only partial particle trajectories are considered, the particles under consideration should be uniformly selected across the profile of the local beam. This one or more characteristics may include a corresponding local beam tilt for each local beam at a reference position along the beam path. This one or more characteristics may also include the angular deviation of the local beams relative to each other.

[0014] For example, multiple local beams can be considered. These local beams can include certain particles from multiple particle beams generated at a micro-optical configuration. For example, the micro-optical configuration can have 91 apertures in a hexagonal arrangement. For example, a sensor positioned downstream of the micro-optical configuration can analyze the six local beams generated by the outermost aperture and one local beam generated by the central aperture, and determine the corresponding local beam tilt. The global beam tilt can be determined based on the seven local beam tilts, for example, as an average tilt angle. One or more particle optics elements can be adjusted or controlled such that predetermined requirements regarding the global beam tilt, local beam tilts, and / or local beam angles relative to each other can be achieved or at least approximately achieved. For example, a requirement could be defined as a global beam tilt less than 10 mrad, each local beam tilt less than 10 mrad, and a maximum deviation between the local beam angles of adjacent local beams less than 5 mrad.

[0015] Although the examples above assume collimated and telecentric converging particle beams, the examples and embodiments discussed herein can also be applied to diverging or converging particle beams, which may also have moderate propagation angles, and the angle of each individual trajectory may be subject to corresponding constraints, such as the maximum deviation of the moderate propagation angle from the optical axis.

[0016] For example, one or more particle optics elements are positioned upstream of the micro-optical configuration along the particle beaming path. These one or more particle optics elements may include, for example, electric or magnetic lenses, such as condenser lens systems and / or deflection systems. Because the particle optics elements are located upstream of the micro-optical configuration, changes in these elements can directly affect the converged particle beam at the micro-optical configuration and can be detected by one or more sensors. Therefore, a direct feedback loop can be implemented.

[0017] In some examples, the micro-optical configuration may include one or more particle optics elements. For example, the one or more particle optics elements may be configured to selectively act on different particle beams among the plurality of particle beams, for example, through lenses and / or deflectors for each of the plurality of particle beams. In some examples, the micro-optical configuration may include lenses and / or deflectors acting on the entire plurality of particle beams. By using a suitable model that takes into account lenses and / or deflectors in each of the multiple particle beams or the entire plurality of particle beams, one or more characteristics of the converged particle beams at the micro-optical configuration may be determined based on sensor signals obtained by one or more sensors (particularly sensors downstream of the micro-optical configuration).

[0018] In various examples, a loading lock of the multi-beam scanning particle imaging system can be controlled to load a sample into a vacuum chamber of the system. One or more sensor signals can be acquired while the sample is being loaded into the vacuum chamber.

[0019] Furthermore, the multi-beam scanning particle imaging system can control a sample platform to place the sample on the object plane; and acquire one or more sensor signals while placing the sample on the object plane.

[0020] This means that, based on signals from one or more sensors, the characteristics of the aggregated particle beam and the control of the particle optics can be determined for a sample in a vacuum chamber (i.e., in the field).

[0021] According to various examples, the micro-optical configuration includes at least two multi-aperture plates arranged parallel and spaced apart along the particle beam path.

[0022] The one or more sensors may include: for each of the plurality of particle beams in another set, a designated particle detection sensor is positioned downstream of the micro-optical configuration along the path of the particle beam. For example, the other set of plurality of particle beams may include some of the outermost apertures of the micro-optical configuration, such as the six outermost apertures of a hexagonal micro-optical configuration. The other set of plurality of particle beams may include other apertures, such as the central aperture of the micro-optical configuration. To determine the one or more characteristics of the aggregated particle beam at the micro-optical configuration, a corresponding current may be determined for each of the plurality of particle beams in the other set, based on a sensor signal from the designated particle detection sensor, as these characteristics of the aggregated particle beam at the micro-optical configuration.

[0023] In some examples, controlling the one or more particle optics elements involves changing multiple control parameters of such particle optics elements to minimize the variation in the current.

[0024] In some examples, controlling the one or more particle optics elements involves changing multiple control parameters of such particle optics elements to maximize the current.

[0025] According to various examples, the aperture of one of the at least two porous plates is aligned with the aperture of the other of the at least two porous plates in a direction along the particle beam path.

[0026] For example, at least two aperture plates may include a first aperture plate and a second aperture plate. At least some or all of the apertures of the first aperture plate may be configured with the same pattern as some or all of the apertures of the second aperture plate. For example, the first and second aperture plates may be configured such that at least some of the apertures of the first aperture plate are aligned with the corresponding apertures of the second aperture plate. Therefore, the corresponding apertures of the first and second aperture plates are configured along an axis parallel to the optical axis of the beam generating device. A particle beam passing through the corresponding apertures of the first and second aperture plates may have maximum intensity when aligned with the optical axis and reduced intensity when misaligned. The control parameters of the particle optics can be varied to achieve the overall maximum intensity of the monitored particle beam (i.e., a particle beam in another set of multiple particle beams). In some examples, the control parameters of the particle optics can be varied to achieve uniform intensity of the monitored particle beam. The aforementioned optimization criteria (i.e., overall maximum intensity and intensity uniformity) can be used in combination, for example, by assigning a corresponding score to each optimization criterion and combining these scores through weighted averaging. Other criteria can also be considered, such as upper and lower limits of intensity for each monitored particle beam.

[0027] According to various examples, the position of the first porous plate of the at least two porous plates relative to the second porous plate of the at least two porous plates is changed in a direction perpendicular to the particle beam path. For example, the corresponding apertures of the first and second porous plates are misaligned. This misalignment may be only a small fraction of the aperture diameter. The distance between the first and second porous plates may be small, for example, less than the distance between two adjacent apertures in the plates. In this case, the particle beam generated by the first porous plate and aligned with the optical axis will be partially absorbed by the second porous plate. However, a particle beam misaligned with respect to the optical axis but aligned with the degree of misalignment of the first and second porous plates can pass through the corresponding apertures of the first and second porous plates without or without significant intensity loss. Because the misalignment between the first and second porous plates is intentionally induced, the direction and / or degree of misalignment of the monitored particle beam can be determined, and the particle optics can be adjusted accordingly.

[0028] In various examples, the position of one of the at least two porous plates (i.e., the first porous plate) relative to the other of the at least two porous plates (i.e., the second porous plate) is changed along one direction of the particle beam path. For example, the distance between the corresponding apertures of the first and second porous plates can be changed. Therefore, a particle beam generated by the first porous plate and not aligned with the optical axis will be partially absorbed by the second porous plate. The amount of absorption depends on the distance between the first and second porous plates. The greater the distance, the greater the absorption. However, a particle beam aligned with the optical axis can pass through the corresponding apertures of the first and second porous plates without significant intensity loss, regardless of the distance between the first and second porous plates. Example optical elements can be adjusted to minimize absorption.

[0029] Depending on the variety of examples, each of the one or more sensors includes at least one of a Faraday cup and a quadrant detector. For example, a corresponding sensor, such as a corresponding Faraday cup or a corresponding quadrant detector, can be provided for each beam in another set of multiple particle beams. In some examples, the corresponding sensor can be movable and can sequentially monitor another set of multiple particle beams. A quadrant detector can be considered as a particle current sensor similar to a Faraday cup, having a certain spatial resolution and a small coverage area assumed to cover the region where the particle microbeams are expected to reach when the particle optics change. The effect of the particle optics change on the direction of each particle microbeam can be determined and accounted for.

[0030] The one or more sensors may include multiple particle detection sensors in a detector system of the multi-beam scanning particle imaging system. The multi-beam scanning particle imaging system may be in a mirror mode to reflect at least the other set of multiple particle beams across the object plane. In the normal operating mode of the multi-beam scanning particle imaging system, a high voltage is applied to the sample or sample carrier, with a polarity opposite to that of the multiple particle beams. Therefore, particles from the particle beam generator (so-called primary particles, such as primary electrons) are decelerated and impact the sample. When the primary particle beams interact with the sample surface, ionization and excitation occur. Due to this interaction, some particles (such as electrons) in the sample are ejected. These ejected electrons, called secondary particles (such as secondary electrons), are accelerated by the high voltage and may be detected by the detector system of the multi-beam scanning particle imaging system. In mirror mode, the high voltage on the sample or sample carrier is increased so that the primary particles (such as primary electrons) do not reach the sample surface but are reflected back into the detector system of the multi-beam scanning particle imaging system. In the detector system, the position and intensity of each small beam in multiple particle beams can be detected, and the control parameters of the particle optics can be adjusted accordingly. It is important to note that, due to the use of mirror mode, the subparticles are not affected by the sample; therefore, when adjusting the control parameters of the particle optics, the stability of the sample can be maintained in the multi-beam scanning particle imaging system.

[0031] According to various examples, the other set of multiple particle beams are multiple adjustable beams. That is, the other set of multiple particle beams may not be used to scan the sample, but only for adjustment purposes. Each of the at least two multi-aperture plates may have multiple inner apertures and multiple outer apertures located around one of the inner apertures. The inner apertures split the incident polymeric particle beam into the multiple particle beams of the set, and the outer apertures split the incident polymeric particle beam into the other set of multiple particle beams. In other words, the inner apertures divide the incident polymeric particle beam into smaller beams for scanning the sample, and the outer apertures divide the incident polymeric particle beam into adjustable smaller beams. Therefore, the sensor can be configured to detect sensor signals based on the adjustable smaller beams without affecting the scanning smaller beams. Thus, the multi-beam scanning particle imaging system can perform continuous adjustment while scanning the sample. Variations in the multi-beam scanning particle imaging system, such as those due to particle source aging, can be compensated for in-situ.

[0032] In another example, at least one of the at least two aperture plates is located between a first and a second of the one or more particle optics elements. For example, in addition to the first and second aperture plates described above, a third aperture plate can be disposed between the first and second particle optics elements. For example, the first particle optics element may include a first lens and a first deflector, while the second particle optics element may include a second lens and a second deflector. The converging particle beam can be influenced by the first lens and the first deflector. The first lens can provide a first portion of focusing and / or collimation of the converging particle beam. The converging particle beam is then split into multiple smaller particle beams by the third aperture plate, which are subsequently focused and / or collimated by the second lens and optionally aligned by the second deflector. The multiple smaller particle beams can then be guided through the first and second aperture plates as described above. This configuration can enhance the effect by increasing the distance between the aperture plates. Furthermore, mounting space is more readily available between the particle optics elements. Depending on the time it takes for the converging particle beam to be split by the third aperture plate, the effects of Coulomb interaction can be reduced because the current can be decreased.

[0033] According to various examples, the one or more sensors include a diffraction element disposed in the beam path of at least one of the plurality of particle beams. The diffraction element may include, for example, a diffraction crystal, particularly a single crystal, or a diffraction grating. The one or more sensors may also include a designated two-dimensional particle detection sensor for each of the at least one of the plurality of particle beams, disposed downstream of the micro-optical configuration along the beam path. For determining one or more characteristics of the aggregated particle beam at the micro-optical configuration, a corresponding diffraction pattern is determined for each of the at least one of the plurality of particle beams based on a sensor signal from the designated two-dimensional particle detection sensor. The diffraction pattern can be used to characterize the aggregated particle beam at the micro-optical configuration. When the diffraction element is aligned with the optical axis, for example, the (principal) axis of the crystal structure is aligned with the optical axis, the symmetry of the diffraction pattern may depend on the incident angle of the particle beam. The symmetry of the particle beam can be determined based on information from the two-dimensional particle detection sensor. A two-dimensional particle detection sensor can be located between a micro-optical configuration and the object plane. As described above, adjustable small beams can be provided. For each adjustable small beam, a corresponding diffraction element and a two-dimensional particle detection sensor can be provided.

[0034] For example, controlling one or more particle optical elements includes changing multiple control parameters of the particle optical elements to maximize the symmetry of the diffraction pattern. In some examples, one or more particle optical elements can be controlled by changing the control parameters of the particle optical elements to achieve a predetermined diffraction pattern or a predetermined direction of the diffraction pattern.

[0035] According to some examples, the two-dimensional particle detection sensor includes multiple particle detection sensors in a detector system of the multi-beam scanning particle imaging system, wherein the multi-beam scanning particle imaging system is in a mirror mode to reflect at least one of the multiple particle beams across the object plane. One or more diffraction elements can be arranged in the beam path of one, more, or all of the small beams downstream of the micro-optics configuration. One or more diffraction elements can be moved into the beam path while the sample is already placed in the multi-beam scanning particle imaging system. After adjusting the particle optics, one or more diffraction elements can be removed from the beam path, and then the sample is scanned. The diffraction elements can include, for example, diffraction crystals (especially single crystals) or diffraction gratings.

[0036] In various examples, the micro-optical configuration includes a porous plate with one or more pyramidal elements on its upstream side. The one or more sensors include a current sensor for measuring a current generated by a plurality of particles of the polymeric particle beam absorbed by the porous plate. The porous plate and the pyramidal elements may be made of a conductive material and can measure the current caused by the focused and deflected polymeric particle beam. Based on the slope of the pyramidal elements, the positions of the tip and bottom of each pyramidal element can be determined. Determining the one or more characteristics of the polymeric particle beam at the micro-optical configuration includes focusing the polymeric particle beam on the plane of the porous plate and scanning the one or more pyramidal elements. For each of the one or more pyramidal elements, a corresponding offset of a tip of the pyramidal element with respect to a center of the bottom of the pyramidal element is determined as such characteristic of the polymeric particle beam at the micro-optical configuration. It can be assumed that focusing and deflection of the polymeric particle beam in a plane perpendicular to the optical axis do not change the tilt direction of the polymeric particle beam. Therefore, when the focused and deflected polymer particle beam detects that the apex of the pyramid-shaped element is located at the center of the bottom surface of the element, the optical axis of the beam generating device can be aligned with the propagation direction of the polymer particle beam.

[0037] Controlling the one or more particle optics elements may include changing multiple control parameters of these particle optics elements to minimize the one or more offsets, that is, to align the detection point at the tip of the pyramidal element with the center of the detection base of the pyramidal element. The pyramidal element may be positioned outside the aperture device on a multi-aperture plate of a micro-optical configuration so that the pyramidal element does not interfere with sample scanning. Sample scanning can be performed when the particle optics elements are configured for scanning, for example, when the polymeric particle beam is configured for collimation and telecentricity.

[0038] According to various examples, the micro-optical configuration includes at least one multi-aperture plate and a multi-beam multi-pole alignment element arranged parallel and spaced apart along the particle beam path. The multi-beam multi-pole alignment element may be located downstream of the multi-aperture plate along the particle beam path. The multi-beam multi-pole alignment element may include at least one pair of opposite poles for each of the plurality of particle beams (i.e., each sub-beam) in the other set. The multi-beam multi-pole alignment element may include four pairs of opposing poles arranged along the edge of an octagon for each sub-beam. By applying a voltage to each pole, the multi-beam multi-pole alignment element may be configured to act as a deflector, astigmatism corrector, or both on the respective sub-beam. An astigmatism corrector is a component that can reduce astigmatism in sub-beams.

[0039] The one or more sensors may include a designated particle detection sensor for each small beam, disposed downstream of the micro-optical configuration along the particle beam path. Determining the one or more characteristics of the aggregated particle beam at the micro-optical configuration may include: applying a first excitation mode to the at least one pair of opposite poles of each of the plurality of particle beams in the other group; applying a second excitation mode to the at least one pair of opposite poles of each of the plurality of particle beams in the other group. The second excitation mode may be different from the first excitation mode. For each small beam, an offset between an incident point of the particle beam at the designated particle detection sensor when the first excitation mode is applied and an incident point of the particle beam at the designated particle detection sensor when the second excitation mode is applied may be determined as such characteristics of the aggregated particle beam at the micro-optical configuration.

[0040] Assume a multi-beam multi-pole alignment element is aligned with a multi-aperture plate along the optical axis of the beam generating device. This means that each pair of poles of the multi-beam multi-pole alignment element is aligned with the corresponding aperture of the multi-aperture plate, i.e., the center of the aperture is aligned with the center between the two pairs of poles along the optical axis. Therefore, when the multi-beam multi-pole alignment element is used as an astigmatism corrector, the profile shape of the small beam generated by the aperture of the multi-aperture plate can be changed, for example, from a circle to an ellipse, or from one ellipse to another ellipse, but as long as the small beam is not tilted about the optical axis, its center will not move in a plane perpendicular to the optical axis. However, the situation changes when the small beam is tilted about the optical axis. When the multi-beam multi-pole alignment element is used as an astigmatism corrector, beam tilting causes additional beam offset because the small beam is slightly deflected when the beam passes obliquely through a pair of poles. Specifically, when using four pairs of poles, i.e., a so-called octet alignment element, tilting in any direction will cause the small beam to offset. By applying different excitation modes, different beam shifts will occur when the small beam is not perfectly aligned with the optical axis. However, when the small beam is aligned with the optical axis, no beam shift will occur regardless of the excitation mode (astigmatism corrector) applied.

[0041] Therefore, when no beam offset is detected when using different excitation modes at the multi-beam multi-pole alignment element, the optical axis of the beam generating device can be aligned with the beam propagation direction. That is, even if the excitation mode changes, there is no offset between the incident points of the small beams at the designated particle detection sensor.

[0042] For example, the multi-beam multi-pole alignment element may include at least two pairs of opposite poles for each of the plurality of particle beams in the other set. When the first excitation mode is applied, the same potential is applied to all poles. When the second excitation mode is applied, a first potential is applied to a first pair of opposite poles, and a second potential is applied to a second pair of opposite poles. The second potential is different from the first potential.

[0043] The particle detection sensor may include at least one of a Faraday cup and a quadrant detector. For example, a corresponding sensor, such as a corresponding Faraday cup or a corresponding quadrant detector, may be provided for each of the multiple particle beams in another set. In some examples, the corresponding sensor may be movable, for example via a linear translation device, and may sequentially monitor the multiple particle beams in another set.

[0044] In some examples, the particle detection sensor may include multiple particle detection sensors in a detector system of a multi-beam scanning particle imaging system. The multi-beam scanning particle imaging system may be in a mirror mode as described above.

[0045] Different examples of the method further include removing the micro-optical configuration from the particle beam path. Therefore, the converging particle beam does not split into multiple particle beams. A first edge element in a first plane perpendicular to the optical axis of one of the beam generating devices of one of the multi-beam scanning particle imaging systems is moved from a position radially outside the converging particle beam into the converging particle beam. The first plane is located between the particle optical elements and the object plane. Therefore, during the movement, an increased portion of the converging particle beam is absorbed by the first edge element. Simultaneously with the movement of the first edge element, a first path of current is detected by the one or more sensors for a portion of the converging particle beam not absorbed by the first edge element. The one or more sensors can be the sensors described above for acquiring sensor signals to determine the converging particle beam characteristics as described above, wherein the micro-optical configuration is in place. However, the one or more sensors can be different sensors specifically configured to detect the current in the portion of the converging particle beam not absorbed by the first edge element.

[0046] Next, the first edge element is removed from the particle beam, and a second edge element in a second plane perpendicular to the optical axis is moved from a position radially outward of the particle beam into the particle beam, thereby absorbing an increased portion of the particle beam. This second plane is different from the first plane and is located between the particle optical elements and the object plane. The direction of movement of the first edge in the first plane can be parallel to the direction of movement of the second edge in the second plane. Simultaneously with the movement of the second edge element, a second path of a current in a portion of the particle beam not absorbed by the second edge element is detected by one or more sensors. At least one of an offset value and a width difference is determined based on the first path and the second path. The offset value represents the amount of offset between a center of the particle beam at the first plane and a center of the particle beam at the second plane. The width difference represents the difference between the width of the particle beam at the first plane and the width of the particle beam at the second plane.

[0047] Multiple control parameters of these particle optical elements can be changed to minimize at least one of the offset value and the width difference.

[0048] For example, a first edge element (e.g., a sharp edge) is progressively pushed into the converging particle beam, and the unobstructed beamflow is measured at each step. A profile within this first plane can be extracted from the measured beamflow (e.g., as an integral signal using deconvolution). Specifically, the center position and width of the profile within this plane can be obtained. The beamflow path along the z-direction (i.e., the optical axis of the beam generating device) is extended to two different planes; the combination of the two center positions and two widths can be used to calculate the tilt of the beamflow. Furthermore, the opening angle of the converging particle beam, i.e., the collimation, can also be calculated. The tilt and collimation can then be adjusted (e.g., iteratively) through control parameters of one or more particle optics elements (e.g., including lenses and deflectors).

[0049] The one or more sensors may include a Faraday cup located between the first plane and the object plane, and between the second plane and the object plane.

[0050] The one or more sensors may include multiple particle detection sensors in a detector system of a multi-beam scanning particle imaging system, wherein the multi-beam scanning particle imaging system is in a mirror mode to reflect the portion of the polymeric electron beam that is not absorbed by the first edge element or the second edge element across the object plane.

[0051] In another example, the one or more sensors include a magnetic coil and a Faraday cup. The magnetic coil is located between the first plane and the object plane, and between the second plane and the object plane. The magnetic coil is configured to deflect the aggregated particle beam toward the Faraday cup, which is located outside the optical axis. This coil is electrically controllable and does not generate particles. No mechanical movement is required, especially the Faraday cup, which does not need to be mechanically moved to the particle beam.

[0052] According to various examples, this method further includes removing the micro-optical configuration from the particle beam path; and setting a single-aperture plate in a first plane perpendicular to an optical axis of a beam-generating device of the multi-beam scanning particle imaging system, the center of the single aperture being aligned with the optical axis. The size of the single aperture corresponds to the size of the cross-section of the polymeric particle beam in the first plane. Then, an edge element is moved in a second plane perpendicular to the optical axis to enter the polymeric particle beam passing through the single aperture. The second plane is located downstream of the first plane. Depending on the position of the edge element, a portion of the polymeric particle beam is absorbed at the edge element, and one or more sensors are disposed downstream of the edge element to determine the current generated by the portion of the polymeric particle beam not absorbed by the edge element. While moving the edge element, a path of a current of the portion of the polymeric particle beam not absorbed by the edge element is detected by the one or more sensors. Based on the path of the current, a width and / or a position of the polymeric particle beam in the second plane is determined. The width and position of a non-tilted and collimated particle beam on the second plane may correspond to the width and position of a single aperture on the first plane. The position of a tilted particle beam on the second plane may differ from its position on the first plane, and the width of a non-collimated particle beam on the second plane may differ from its position on the first plane.

[0053] Based on the determined current curve, the tilt and / or collimation of the polymer particle beam can be corrected by adjusting the control parameters of the particle optical element.

[0054] The one or more sensors may include a Faraday cup located between the second plane and the object plane.

[0055] According to various examples, the polymeric particle beam has a known non-uniform intensity distribution in a cross-section within a plane perpendicular to the optical axis of a beam-generating device of the multi-beam scanning particle imaging system. The following steps can be performed. The micro-optical configuration can be removed from the particle beam path. A single-aperture plate can be positioned in a first plane perpendicular to the optical axis, wherein the center of one aperture of the single-aperture plate is aligned with the optical axis. The first plane can substantially correspond to the plane in which the micro-optical configuration is located. The size of the single aperture is smaller than the size of the cross-section of the polymeric particle beam in the first plane. For example, the size of the single aperture can correspond to the outer diameter of the aperture configuration in the multi-aperture plate of the micro-optical configuration. Then, using a two-dimensional sensor positioned in a second plane perpendicular to the optical axis and downstream of the first plane, a two-dimensional intensity path of the current generated by a portion of the polymeric particle beam not absorbed by the single-aperture plate is determined. An offset between a desired location of the known non-uniform intensity profile and a location of a corresponding intensity determined in the two-dimensional intensity path can be determined.

[0056] Multiple control parameters of these particle optical elements can be changed to minimize the offset.

[0057] Furthermore, the difference between the size of the portion of the polymeric particle beam that is not absorbed by the single-aperture plate in the two-dimensional intensity path and the size of the single-aperture plate can be determined. Several control parameters of these particle optics elements can be varied to minimize this difference.

[0058] As in the previous example, the following example assumes that the aggregated particle beam has a known non-uniform intensity distribution on a cross-section within a plane perpendicular to the optical axis of a beam-generating device in the multi-beam scanning particle imaging system. However, a micro-optical configuration is not removed from the particle beam path, thus splitting the aggregated particle beam into multiple electron beams. A two-dimensional sensor positioned in a plane perpendicular to the optical axis and downstream of the micro-optical configuration is used to determine a two-dimensional intensity path of the current generated by the multiple particle beams. Based on this, an offset between a desired position of the known non-uniform intensity profile and a position of a corresponding intensity determined in the two-dimensional intensity path can be determined.

[0059] Several control parameters of these particle optical elements can be changed to minimize the offset.

[0060] Furthermore, the difference between the size of one particle beam in the multiple particle beams in the two-dimensional intensity path and the size of a corresponding aperture in the micro-optical configuration that generates the particle beam can be determined, and multiple control parameters of these particle optical elements can be changed to minimize the difference.

[0061] Another example involves removing the micro-optical configuration from the particle beam path and arranging a diffraction element in a first plane perpendicular to the optical axis of a beam-generating device in the multi-beam scanning particle imaging system. The diffraction element may, for example, comprise a diffraction crystal (particularly a single crystal) or a diffraction grating. For instance, the diffraction element can replace the micro-optical configuration in the beam path. A two-dimensional sensor, positioned in a second plane perpendicular to the optical axis and downstream of the first plane, determines a two-dimensional intensity path of the current generated by the polymeric particle beam passing through a diffraction pattern of the diffraction element. The diffraction element can be configured such that its axis (e.g., the principal axis of the single crystal) is aligned with the optical axis. The symmetry of the diffraction pattern may depend on the tilt angle of the polymeric particle beam. When the incident angle of the polymeric particle beam is parallel to the axis of the diffraction element, the diffraction pattern can be symmetrical about the center of the polymeric particle beam.

[0062] Multiple control parameters of these particle optical elements can be changed to maximize the symmetry of the diffraction pattern.

[0063] According to various paradigms, one or more sensors include particle detection sensors in the detector system of a multi-beam scanning particle imaging system. To determine one or more characteristics of the converged particle beams at the micro-optical configuration, for each of at least a plurality of particle beams, the distance between the incident point of that particle beam and the incident points of adjacent particle beams is determined in an object-planar image generated based on sensor signals from the particle detection sensors. Furthermore, variations in the distance are determined as characteristics of the converged particle beams at the micro-optical configuration. Control parameters of the particle optics elements can be varied to minimize these variations.

[0064] Another example relates to a computer program product containing code to perform the methods described above. For instance, the method steps described above could be executed by the control circuitry or processing device of a multi-beam scanning particle imaging system.

[0065] According to various examples, a control circuit for a multi-beam scanning particle imaging system is provided. The multi-beam scanning particle imaging system includes a micro-optical configuration for splitting an incident convergent particle beam into multiple particle beams. The multi-beam scanning particle imaging system is configured to co-scan at least one set of the multiple particle beams across an object plane. The control circuit may be configured to acquire one or more sensor signals from one or more sensors positioned along a particle beam path of the multi-beam scanning particle imaging system. Furthermore, the control circuit may be configured to determine one or more characteristics of the convergent particle beam at the micro-optical configuration based on the one or more sensor signals, and control one or more particle optics elements of the multi-beam scanning particle imaging system based on the one or more characteristics of the convergent particle beam.

[0066] The control circuit can be configured to perform the methods described in the examples above.

[0067] A system comprising: the aforementioned control circuit and a multi-beam scanning particle imaging system. Simple Explanation of the Diagram

[0068] Figure 1 schematically illustrates multibeam scanning particle imaging systems, such as multibeam scanning electron microscopes (MSEMs), according to different examples.

[0069] Figure 2 schematically illustrates the generation of small beams and beam paths according to different examples.

[0070] Figure 3 schematically illustrates global beam tilt and local beam tilt according to different examples.

[0071] Figure 4 schematically illustrates micro-optical configurations including uniformity sensors according to different examples.

[0072] Figure 5 schematically illustrates the details of the micro-optical configurations according to different examples.

[0073] Figure 6 schematically illustrates the viewpoint of the MSEM based on different examples.

[0074] Figure 7 schematically illustrates the configuration of two multi-aperture plates and their corresponding beam paths according to different examples.

[0075] Figure 8 schematically illustrates the configuration of two multi-aperture plates and their corresponding beam paths according to another example.

[0076] Figure 9 schematically illustrates the configuration of two multi-aperture plates and corresponding beam paths according to another example.

[0077] Figure 10 schematically illustrates the configuration of two multi-aperture plates and corresponding beam paths according to another example.

[0078] Figure 11 schematically illustrates the pore configuration in a multi-pore plate according to different examples.

[0079] Figure 12 schematically illustrates the configuration of apertures in a multi-aperture plate according to another example.

[0080] Figure 13 schematically illustrates the configuration of apertures in a multi-aperture plate according to another example.

[0081] Figure 14 schematically illustrates the configuration of two multi-aperture plates and their corresponding beam paths according to different examples.

[0082] Figure 15 schematically illustrates the configuration of two multi-aperture plates and corresponding beam paths according to another example.

[0083] Figure 16 schematically illustrates a multi-aperture plate positioned upstream of a micro-optical configuration, according to different examples.

[0084] Figure 17 schematically illustrates configurations of placing a multi-aperture plate upstream of a micro-optical configuration, according to different examples.

[0085] Figure 18 schematically illustrates techniques for controlling particle optical elements (including quadrant detectors) according to different examples.

[0086] Figure 19 schematically illustrates quadrant detectors based on different examples.

[0087] Figure 20 schematically illustrates images of small beams captured by a detector system in mirror mode, according to different examples.

[0088] Figure 21 schematically illustrates an image of a small beam captured by a detector system in mirror mode, according to another example.

[0089] Figure 22 schematically illustrates techniques for controlling particle optical elements (including diffraction elements) according to different examples.

[0090] Figure 23 schematically illustrates, according to different examples, a porous plate composed of pyramidal elements.

[0091] Figure 24 schematically shows a top view of a porous plate containing pyramidal elements according to different examples.

[0092] Figure 25 schematically illustrates particle beams incident on a pyramid-shaped element according to different examples.

[0093] Figure 26 schematically illustrates the use of non-tilted particle beams to detect pyramid-shaped elements according to different examples.

[0094] Figure 27 schematically illustrates the use of tilted particle beams to detect pyramid-shaped elements according to different examples.

[0095] Figure 28 schematically illustrates techniques for controlling particle optics (including multi-pole alignment elements) according to different examples.

[0096] Figure 29 schematically illustrates multi-pole alignment elements used as deflectors according to different examples.

[0097] Figure 30 schematically illustrates a multi-pole alignment element used as an astigmatism corrector for non-tilted small beams, according to different examples.

[0098] Figure 31 schematically illustrates a multi-pole alignment element used as an astigmatism corrector for a tilted small beam, according to different examples.

[0099] Figure 32 schematically illustrates techniques involving two movable edges for controlling particle optics elements, according to different examples.

[0100] Figure 33 schematically illustrates a beam generating device including two movable edges, according to different examples.

[0101] Figure 34 schematically illustrates the current signal profiles generated by two movable edges in evaluations of different examples.

[0102] Figure 35 schematically illustrates the resolution of the estimated tilt angle for different examples.

[0103] Figure 36 schematically illustrates the accuracy of the estimated collimation based on different examples.

[0104] Figure 37 schematically illustrates the implementation of edge technology according to different examples.

[0105] Figure 38 schematically illustrates an implementation of edge technology according to another example.

[0106] Figure 39 schematically illustrates techniques for controlling particle optics using known non-uniform intensity distributions of particle beams, based on different examples.

[0107] Figure 40 schematically illustrates, according to different examples, the technique of Figure 39 using coils to deflect multiple particle beams.

[0108] Figure 41 schematically illustrates the use of the technique in Figure 39 to determine two-dimensional intensity routes according to different examples.

[0109] Figure 42 schematically illustrates how the tilt and divergence of the particle beam are determined by the intensity distribution in different examples.

[0110] Figure 43 schematically illustrates techniques for controlling particle optics using known non-uniform intensity paths of particle beams, based on different examples, where a two-dimensional intensity path is determined.

[0111] Figure 44 schematically illustrates how the tilt and divergence of the particle beam are determined by the intensity distribution in different examples.

[0112] Figure 45 schematically illustrates calibration techniques based on diffraction elements according to different examples.

[0113] Figure 46 schematically illustrates the defined diffraction patterns according to different examples.

[0114] Figure 47 schematically illustrates the symmetrical diffraction patterns of non-tilted particle beams according to different examples.

[0115] Figure 48 schematically illustrates the asymmetric diffraction patterns of tilted particle beams according to different examples.

[0116] Figure 49 schematically illustrates diffraction patterns for non-tilted divergent particle beams according to different examples.

[0117] Figure 50 schematically illustrates diffraction patterns for non-tilted collimated particle beams according to different examples.

[0118] Figure 51 schematically illustrates diffraction patterns for non-tilted convergent particle beams according to different examples.

[0119] Figure 52 schematically illustrates the diffraction patterns of higher-order illumination points including non-tilted particle beams, according to different examples.

[0120] Figure 53 schematically illustrates the relationship between the diameter of the illumination spot and the collimation angle for diffraction patterns according to different examples.

[0121] Figure 54 shows a flowchart of the operation method of the control circuit of a multi-beam scanning particle imaging system according to different examples. Implementation

[0122] Some examples of the present invention typically provide multiple circuits or other electrical devices. All references to circuits and other electrical devices and the functions provided by each device are not intended to be limited to what is illustrated and described herein. While specific labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation of the circuits and other electrical devices. Such circuits and other electrical devices may be combined and / or separated from each other in any way based on the specific type of electrical implementation desired. It should be understood that any circuit or other electrical device disclosed herein may include any number of microcontrollers, graphics processing units (GPUs), integrated circuits, memory devices (e.g., flash memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations), and software that cooperates with each other to perform the operations disclosed herein. Additionally, any one or more electrical devices may be configured to execute code that may be embodied in a non-transitory computer-readable medium programmed to perform any number of the functions disclosed.

[0123] Hereinafter, several embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the embodiments should not be considered as limiting. The scope of the present invention is not intended to be limited to the embodiments or drawings described below, but is merely illustrative.

[0124] The diagrams should be considered schematic representations, and the elements shown are not necessarily to scale. Rather, those skilled in the art will understand the function and general purpose of the various elements. Any connection or coupling between functional blocks, devices, components, or other entities or functional units shown in the diagrams or described herein may also be implemented through indirect connections or couplings. Coupling between multiple components may also be established through wireless connections. Functional blocks can be implemented in hardware, firmware, software, or a combination thereof.

[0125] Some array elements, such as multiple primary charged particle microbeams, are identified by reference numbers. Depending on the context, the same reference number can also identify a single element within the array. For example, each primary charged particle microbeam 3.1, 3.2, 3.3 is one of multiple primary charged particle microbeams 3. In the various figures, the same reference number indicates similar or identical components.

[0126] The following section will disclose the techniques for operating and controlling a multi-beam charged particle grating scanning microscope (MSEM). Specifically, several techniques are explained for MSEM, but other types of multi-beam charged particle grating scanning microscopes can also be used.

[0127] In multi-beam charged particle scanning microscopy, multiple images can be captured simultaneously. That is, multiple charged particle beams are scanned synchronously and simultaneously, resulting in multiple images in multiple fields of view (FOV). Therefore, compared with single-beam charged particle scanning microscopy, the amount of image data captured per unit time is significantly increased.

[0128] In this specification, the terms "upstream" and "downstream" will be used as follows: In a multi-beam charged particle scanning microscope, a particle beam is generated at the particle source and guided to the sample, and then from the sample to the detector. This direction of the particle beam is called downstream. The opposite direction is called upstream. If two components are placed along the aforementioned particle beam path, and if the first component is closer to the particle source than the second component, then the first component is upstream of the second component. Therefore, in this case, the second component is downstream of the first component.

[0129] Figure 1 is a schematic diagram of MSEM 1. More information about this type of MSEM and the components used therein (such as particle sources, porous plates, and lenses) can be found in PCT patent applications WO 2005 / 024881, WO 2007 / 028595, WO 2007 / 028596, WO 2011 / 124352, WO 2007 / 060017, WO 2023 / 001401, WO 2023 / 001402, WO 2023 / 016678, WO 2023 / 247067, and WO 2024 / 008329, and publications DE 10 2013 016 113 A1, DE 10 2013 014 976 A1, and DE 10 2021 118 561. As may be known from German patent application B4, the entire disclosure of which is incorporated herein by reference.

[0130] MSEM 1 uses multiple charged particle beams (also known as small beams) to image sample 7 on sample platform 500. MSEM 1 generates multiple J main small beams 3.1, 3.2, and 3.3, which, upon impacting sample 7, produce interaction products, such as secondary electrons. These interaction products are emitted from sample 7, forming secondary small beams 9.1, 9.2, and 9.3, which are subsequently detected.

[0131] The primary and secondary small beams 3.1, 3.2, 3.3, 9.1, 9.2, and 9.3 are all formed and guided by the corresponding imaging subsystems of MSEM 1. Each imaging subsystem is associated with a corresponding field of view (FOV). The images captured by the respective imaging subsystems depict the corresponding FOV. Multiple FOVs are arranged in a spatial pattern, thus defining a composite FOV.

[0132] The main small beams 3.1, 3.2, and 3.3 are formed by electrons incident on the surface 25 of the sample 7 at multiple locations, and produce multiple main electron beam focal points 5.1, 5.2, and 5.3 that are spatially separated from each other.

[0133] The sample 7 to be inspected can be any desired type, such as a semiconductor wafer or semiconductor photomask, and can include a configuration of micro-components.

[0134] The surface 25 of the sample 7 is set in the sample plane 101 (also called the object plane 101) of the objective lens system 102 of the first particle optical unit 100 (also called the illumination system 100).

[0135] The diameter of the minimum beam points or focal points 5.1, 5.2, 5.3 formed in the sample plane 101 can be very small. An example value for this diameter is less than 4 nanometers, for example, 3 nanometers or less. Focusing of the primary small beams 3.1, 3.2, 3.3 used to form the focal points 5.1, 5.2, 5.3 is performed by the objective system 102. In this case, the objective system 102 may include a magnetically immersed lens. German Patent DE 102020125534 B3 describes further examples of focusing tools, the entire contents of which are incorporated herein by reference.

[0136] The number J (i.e. the number of FOVs) of the main small beams 3.1, 3.2 and 3.3 can be 5, 25, 90 to 100 or more (for simplicity, only three main small beams 3.1, 3.2 and 3.3 and their corresponding focal points 5.1, 5.2 and 5.3 are shown in Figure 1).

[0137] In practice, a significantly larger number of small beams J can be selected, thereby significantly increasing the number of fields of view, for example, J = 10 x 10, J = 20 x 30, or J = 100 x 100. Typical values ​​for the spacing between the incident position and the field of view are 1 micrometer, 10 micrometers, or larger, such as 40 micrometers.

[0138] For example, each field of view can be hexagonal. The number J (i.e., the number of fields of view) of the main small beams 3.1, 3.2, and 3.3 can be 91, and the composite field of view can also be hexagonal.

[0139] The number of primary and secondary beams J determines the number of fields of view (FOV). Each imaging subsystem has its own field of view (FOV). Each field of view (FOV) is defined by scanning the sample 7 within its respective field of view using corresponding pairs of primary and secondary beams (e.g., beams 3.1 and 9.1).

[0140] The primary small beams 3.1, 3.2, and 3.3 impacting sample 7 produce interaction products, such as secondary electrons, backscattered electrons (originating from the surface of sample 7), or primary particles whose motion has been reversed for other reasons. These interaction products emanating from surface 25 of sample 7 are shaped by objective system 102 to form secondary small beams 9.1, 9.2, and 9.3. The secondary electrons contained in these secondary small beams 9.1, 9.2, and 9.3 are used for imaging.

[0141] MSEM1 provides a detection beam path for guiding multiple sub-beams 9.1, 9.2, and 9.3 to the secondary electronic imaging system 200. The secondary electronic imaging system 200 includes multiple electro-optical lenses 205.1 to 205.5 for guiding the sub-beams 9.1, 9.2, and 9.3 to the spatial resolution detector system 600.

[0142] The secondary electron imaging system 200 exhibits extremely strong magnification, enabling the imaging of the main small beam pattern on the wafer surface, as well as the size and shape of the main small beam focal point, to be magnified. For example, with a scaling factor / magnification between 100x and 300x, an imaging size of 1 nanometer on the wafer surface is magnified to between 100 and 300 nanometers. In one example, the image field of a multi-beam device with a diameter of 100 micrometers is magnified to approximately 30 millimeters.

[0143] The main sub-beams 3.1, 3.2, and 3.3 are generated by beam generating device 300, which includes at least one particle source 301 (e.g., an electron source), at least one collimating lens 303, a micro-optical configuration 305, a first field lens 331, and a second field lens 333. The particle source 301 generates at least one diverging particle beam 309, which is at least substantially collimated by at least one collimating lens 303 and illuminates the micro-optical configuration 305. The micro-optical configuration 305 includes a first aperture plate 304 (also called a filter plate or aperture plate) having a plurality of J openings arranged in a first grating. Particles illuminating the particle beam 309 pass through the J apertures or openings of the first aperture plate 304, forming a plurality of J main sub-beams 3.1, 3.2, and 3.3. The particles of the illumination particle beam 309 that impact the first aperture plate 304 will be absorbed by the first aperture plate and will not participate in the formation of the main small beams 3.1, 3.2, and 3.3. The micro-optical configuration 305 typically has at least one other aperture plate 306, such as a lens array, an astigmatism corrector array, or a deflection element array.

[0144] The micro-optical configuration 305, together with the first field lens 331 and the second field lens 333, focuses each main small beam 3.1, 3.2, 3.3, so that its focal point is formed on the intermediate image surface 321. Alternatively, the beam focal point and the intermediate image surface 321 can be virtual. The intermediate image surface 321 can be curved to pre-compensate for the field curvature of the imaging system located downstream of the intermediate image surface 321.

[0145] At least one field lens 103 and objective lens system 102 constitute a first imaging particle optics unit for imaging the surface 321 formed by the beam focus onto the sample plane 101, thereby forming a second pattern thereof composed of the focal points 5.1, 5.2, and 5.3 of the main small beams 3.1, 3.2, and 3.3. Typically, the surface 25 of the sample 7 lies within the sample plane 101, and the focal points 5.1, 5.2, and 5.3 are correspondingly formed on the sample surface 25. The multiple main small beams 3.1, 3.2, and 3.3 form an intersection point 108, and a first deflection scanner 110 is positioned near this intersection point. The first deflection scanner 110 is used to simultaneously and synchronously deflect the multiple main small beams 3.1, 3.2, and 3.3, so that the multiple focal points 5.1, 5.2, and 5.3 move simultaneously on the surface 25 of the sample 7. A grating scan is performed to image the sample 7. The first deflector scanner 110 is driven by the scan control unit 860 to acquire multiple two-dimensional image data of the surface in operational inspection mode. Additionally, the MSEM1 may include other static deflectors for adjusting the positions of multiple main small beams 3.1, 3.2, and 3.3.

[0146] The objective lens system 102 and the projection lens 205 constitute the secondary electronic imaging system 200, used to image the sample plane 101 onto the imaging plane 225. Therefore, the objective lens system 102 is a lens or lens system that is part of both the first particle optical unit 100 and the secondary electronic imaging system 200; while the field lenses 103, 331, and 333 belong only to the first particle optical unit 100, and the projection lens 205 belongs only to the secondary electronic imaging system 200.

[0147] The beam splitter 400 is disposed in the beam path of the first particle optics unit 100, located between the field lens 103 and the objective lens system 102. The beam splitter 400 is also part of the secondary electronic imaging system 200, located in the beam path between the objective lens system 102 and the projection lens 205.

[0148] The first deflector 110 is configured in the primary electron beam path or the combined electron beam path. In the example shown in Figure 1, the secondary beams 9.1, 9.2, and 9.3 are transmitted in opposite directions during the use of the first deflector 110, and the scanning motion of the secondary beams 9.1, 9.2, and 9.3 is partially compensated. Secondary electrons typically have different kinetic energies than primary electrons. Therefore, the scanning motion of moving the irradiation position is only partially compensated. To fully compensate for the scanning motion of the secondary beams 9.1, 9.2, and 9.3, a beam deflector 222 is configured in the secondary electron beam path.

[0149] The secondary electronic imaging system 200 includes a second beam deflector 222, which is positioned near the intersection of the sub-beams 9.1, 9.2, and 9.3. The second beam deflector 222 operates synchronously with the first deflector scanner 110 and compensates for beam deflection of the sub-beams 9.1, 9.2, and 9.3 during use, keeping the center 15 of the sub-beams 9 in a constant position on the imaging plane 225. Therefore, each sub-beam 9 remains within the region of a set of detection elements assigned to it.

[0150] The secondary electronic imaging system 200 includes electro-optical lenses 205.1 to 205.5 for adjusting the focal planes of the secondary small beams 9.1, 9.2, and 9.3. Defocusing can be applied. Therefore, the electro-optical lenses 205.1 to 205.5 can realize correction elements to correct the focal planes. The electro-optical lenses 205.1 to 205.5 are illustrated as magneto-optical elements, but are not limited to magneto-optical elements, and may also include electrostatic lens elements or astigmatism correctors. Using the electro-optical lenses 205.1 to 205.5, the secondary small beams 9.1, 9.2, and 9.3 can be focused onto the imaging plane 225 of the secondary electronic imaging system 200.

[0151] The secondary electronic imaging system 200 may include at least one of multiple additional correction elements, such as a multi-aperture array element, a deflector, or a replaceable aperture stop. These lenses, together with the objective lens system 102, are used to focus the secondary beams 9.1, 9.2, 9.3 onto the spatial resolution detector system 600, and in the process correct or compensate for magnification and rotation of the patterns of the secondary beams 9.1, 9.2, 9.3 on the imaging plane 225. This allows for the stabilization of the patterns of the multiple secondary beams 9.1, 9.2, 9.3. For example, the first and second magnetic lenses 205.4 and 205.5 (as a further example of correction elements) are designed in opposite order and have magnetic fields in opposite directions. Larmor rotation of the secondary beams 9.1, 9.2, 9.3 can be compensated by appropriately applying control signals to (driving) the magnetic lenses 205.4 and 205.5.

[0152] In addition, MSEM1 is connected to a processing unit 800 (also called a control circuit), which is used both to control the individual particle optics of the multiple particle beam systems and to evaluate and analyze the signals acquired by the detector system 600. The processing unit 800 can be separate from or part of MSEM1. For example, the processing unit 800 can be configured to acquire pairs of test images and then evaluate these test images to determine the values ​​of one or more imaging parameters. In this case, the control or processing unit 800 can consist of multiple independent computers or electronic components. For example, the processing unit 800 includes a control processor 880, a control module 840 for controlling the electro-optical elements of the secondary electron imaging system 200, and a control module 830 for controlling the electro-optical elements of the main small beam generation unit. The processing unit 800 is also connected to a control module 503 for providing a voltage to the sample 7, also called the extraction voltage. Therefore, during use, an extraction field is generated between the objective system 102 and the surface 25 of the sample 7. During use, the extraction field decelerates the main charged particles of the main small beams 3.1, 3.2, and 3.3 before they reach the object surface 25, and produces an additional focusing effect on the multiple main small beams 3.1, 3.2, and 3.3. In use, the extraction field is also used to accelerate secondary particles away from the surface 25 of the sample 7.

[0153] Additionally, the processing device 800 includes a scanning control unit 860 for raster scanning.

[0154] The detector system 600 includes multiple sets of detection elements, with each sub-beam 9 corresponding to one set of detection elements. In use, each set of detection elements is configured to record the intensity signal of the assigned sub-beam 9. Multiple intensity signals from multiple sub-beams 9.1, 9.2, and 9.3 are transmitted to the image data acquisition unit 810, where the image data is processed and stored in memory 890. Therefore, each imaging subsystem acquires multiple images. These multiple images (or aggregated images determined based on individual image sequences) can be combined into a composite image with a composite field of view (FOV).

[0155] Accurate generation of the main small beam 3.1, 3.2, and 3.3 is an important factor in obtaining accurate images. For example, the small beam generated by the micro-optical configuration 305 may need to be equidistant, parallel, collimated, and / or telecentric, that is, multiple small beams should respectively illuminate the sample 7 at equidistant grating positions, telecentric positions, and positions perpendicular to the sample surface 25 and the sample plane 101.

[0156] The study found that the illumination conditions of the illumination particle beam 309 affect the accuracy of the smaller beams 3.1, 3.2, and 3.3. The illumination uniformity and telecentricity at the micro-optical configuration 305 have a significant impact on the accuracy of the smaller beams 3.1, 3.2, and 3.3.

[0157] Figure 2 schematically illustrates the process of generating a small beam 3 at a micro-optical configuration 305. A particle source 301 generates a diverging particle beam 309, which is collimated and selectively deflected by a particle optics element 302. The particle optics element 302 may include, for example, one or more collimating lenses 303 and / or one or more alignment deflectors 313. The collimated beam 309 strikes the micro-optical configuration 305. The micro-optical configuration 305 generates the small beam 3, which is then projected onto the sample surface 25 through field lenses 103, 331, 333 and the objective lens system 102. The collimated beam 309 includes particles, such as electrons, that form the small beam 3. Therefore, the collimated beam 309 can be considered as an incident converging particle beam, characterized by its direct influence on the properties of the small beam 3. Electrons in the collimated beam 309 that do not form the small beam 3 are absorbed at the micro-optical configuration 305.

[0158] Precise adjustment of the collimating beam 309 may be required. However, the illumination conditions of the illuminating particle beam 309 may change due to modifications to the particle source 301 and operational aging. Influencing parameters include the position of the particle source 301 relative to the optical axis of the beam generating device 300 (dashed line in Figure 2), the axis and tilt of the collimating lens system 303, and the optional astigmatism corrector located upstream of the micro-optics configuration 305.

[0159] Furthermore, the study found that in a collimated particle beam, the trajectory of a single particle may differ from the overall direction of the collimated particle beam. Figure 3 illustrates this. The overall macroscopic direction of the collimated (converged) particle beam 309 is indicated by arrow 310. However, the trajectory 311 of a single particle may have a slightly different direction. Therefore, optimizing the characteristics of the collimated beam 309 impacting the micro-optical configuration 305 may have different objectives. One objective might be to optimize the collimated convergent particle beam 309 so that it impacts the micro-optical configuration 305 perpendicularly, i.e., at a 90° angle with respect to the surface of the porous plate 304, and with a minimal tilt angle (e.g., less than 10 milliradians). Another objective might be to optimize the individual particle trajectories 311 so that each impacts the micro-optical configuration 305 perpendicularly, i.e., at an angle of 90° with respect to the surface of the porous plate 304, and with a minimal tilt angle, e.g., less than 10 milliradians, more preferably less than 5 milliradians or 1 milliradian. The reference for the tilt angle can be the optical axis perpendicular to the surface of the multi-aperture plate 304, passing through its central aperture.

[0160] The intensity uniformity of the aggregated particle beam 309 can affect the intensity of the smaller beams 3. For the uniform beam current intensity of each smaller beam 3, the emission characteristics of the particle source 301 may be important, more specifically, the uniformity of the emission characteristics over the entire range of emission angles used. When using relatively large emission angles, the emission characteristics of the particle source 301 (e.g., a thermal field emission source) are not uniform across the entire range. Therefore, the irradiance at the first aperture plate 304 is no longer uniform, and the current intensity variations between different smaller beams 3 are relatively large. However, in a multi-beam scanning particle imaging system, the system may require very small current intensity variations between the smaller beams, typically less than a few percent or even less than one percent, so that all individual image fields in the multi-image field are scanned using the same number of particles or electrons. For example, this is a prerequisite for obtaining images with approximately the same brightness. The achievable resolution of a single image may also depend on the smaller beam current.

[0161] Figure 4 illustrates a micro-optical configuration 305 including uniformity sensors. A particle beam 309 is generated by a particle source 301 (e.g., an electron source) and collimated by a collimating lens 303. An alignment deflector 313 may be configured downstream of the collimating lens 303. Thus, the collimated particle beam 309 impacts a first aperture plate 304. The aperture plate 304 may have multiple apertures 85 that form small beams 3 with cross-sections corresponding to the apertures 85. Following the aperture plate 304 is another aperture plate 306, which has a lens array, i.e., apertures with electrodes 81. The apertures of the other aperture plate 306 are aligned with the apertures 85 of the aperture plate 304. Multiple uniformity sensors 160 may be disposed on the surface of the aperture plate 304 facing the particle source 301. The uniformity sensors 160 may be disposed between and outside the apertures 85. Uniformity sensor 160 measures the uniformity of the incident collimated particle beam 309. Uniformity sensor 160 may be coupled to control unit 830 to adjust the intensity, for example, by adjusting collimating lens 303.

[0162] The incident angle j on the first aperture plate 304 is expected to be 90°, meaning the particle trajectory should be parallel to the z-axis perpendicular to the surface of the aperture plate 304 in the x / y plane. As described above in conjunction with Figure 3, the average trajectory 310 and the individual particle trajectory 311 should have a small tilt angle about the z-axis at each lateral position of the aperture plate 304. If the incident angle j on the aperture plate 304 deviates from 90°, the small beam 3 will be off-axis about the local lens axis (z, z', z'') when passing through the electrostatic lens field in another aperture plate 306, causing the small beam 3 to deflect, which will result in a deviation from the ideal grating position. This effect can be partially compensated for by components downstream of the micro-optical configuration 305.

[0163] According to Figure 5, an exemplary micro-optical configuration 305 includes a sequence of five porous plates 304 and 306.1 to 306.4 and a spherical focusing lens 308 in the z-direction of particle propagation. Each porous plate 304 and 306.1 to 306.4 contains a plurality of apertures 85, which are spaced apart on each plate with the same lateral spacing P1, and each plate is aligned to generate and shape a plurality of main charged particle beams 3. The plurality of porous plates 304 and 306.1 to 306.4 and the spherical lens electrode 308 are separated by spacers 83.1 to 83.5. The micro-optical configuration 305 is shown in cross-section (x, z), where only four apertures 85 in each porous plate are shown.

[0164] On the entrance side, each aperture 85 is circular. A portion of the collimated incident electron beam 309 passes through the aperture 85, forming multiple main charged particle beams 3. A first multi-aperture plate 304 is covered with a metal layer 99 for blocking and absorbing the incident electron beams 309 around the multiple apertures 85. The metal layer 99 is made of, for example, aluminum or gold and is connected to a large capacitor, such as ground (0V). In use, most of the incident electrons from the electron beams 309 are absorbed by the absorption layer 99, generating a current corresponding to the number of absorbed electrons.

[0165] The body material of the aperture plate 304 is made of a conductive material, such as silicon doped, and is connected to ground.

[0166] The multi-aperture plate 306.1 includes, for example, four or eight electrostatic elements for each of the plurality of apertures 85, such as electrodes 81, to individually deflect each of the plurality of small beams 3.

[0167] The multi-aperture plate 306.2 may have the function of a microlens array, which includes multiple annular electrodes 81, each of which is set to a separately defined potential, so that the focal position of multiple main small beams 3 can be independently adjusted in the intermediate image surface 321.

[0168] The porous plate 306.3 is a ground electrode plate. The porous plate 306.3 is made of a conductive material, such as doped silicon, and is connected to the ground potential (0V).

[0169] The multi-aperture plate 306.4 can serve as a terminal multi-aperture plate, comprising a plurality of annular electrodes 81 arranged around each or more terminal apertures 94 of the multi-aperture plate 306.4. Each annular electrode 81 is individually connected to a control module 830, which is configured to provide multiple independent voltages to the annular electrode 81 during use to individually and independently control the depth of electrostatic field penetration from the annular electrode 82 of the electrostatic focusing lens 308 to the terminal aperture 94.

[0170] The tilt of the small beam 3 can be measured through beam position distortion and adjusted at a specific reference working point. As shown in Figure 6, in the sample plane 101, each small beam 3 can be configured to scan a corresponding field of view (FoV) 610. The field of view can be configured with a spacing 620, for example, the spacing 620 corresponding to the distance from the center of one FoV 610 to the center of another adjacent FoV 610. A scanning reference object with pre-calibrated reference mark positions can be placed in the sample plane 101, and the position of the small beams can be measured. The spacing variation on the reference object can be determined.

[0171] The adjustment objective could be to achieve minimal pitch variation, such as by adjusting the tilt of the condenser illumination. However, this adjustment objective itself does not include minimum tilt and parallel illumination. Tilt errors can be compensated for by other alignment errors and may introduce errors, such as small beam aberrations, leading to resolution loss or changes in beam resolution.

[0172] Therefore, the following embodiments aim to adjust and optimize the aggregated particle beam at the micro-optical configuration, and in particular optimize the tilt and collimation of the aggregated particle beam at the micro-optical configuration.

[0173] In principle, one or more sensor signals can be acquired from one or more sensors positioned along the particle beam path of the multi-beam scanning particle imaging system, and one or more characteristics of the converging particle beam at the micro-optical configuration can be determined based on these sensor signals. Based on these characteristics, one or more particle optics 302 of the multi-beam scanning particle imaging system can be controlled. In other words, sensor information indicating the tilt and / or collimation deviation of the converging particle beam 309 upon impact with the micro-optical configuration 305 is obtained. For example, the characteristics of the converging particle beam 309 may include global beam tilt, such as the tilt of the average trajectory 310 of the converging particle beam 309 at a reference position (e.g., at the first aperture plate 304) along the beam path. Furthermore, or alternatively, the characteristics of the converging particle beam 309 may include local beam tilt, such as the tilt of a single particle trajectory 311 at a reference position (e.g., at the first aperture plate 304) along the beam path.

[0174] These deviations can be compensated by controlling the particle optics element 302. The particle optics element 302 can be located upstream of the micro-optics configuration 305 along the particle beam path, such as a collimating lens 303. The particle optics element 302 can be contained within the micro-optics configuration 305, such as the condenser lens 308 discussed above in conjunction with Figure 5, or a collimating lens disposed between the components of the micro-optics configuration, which will be described in more detail in conjunction with Figure 17.

[0175] The particle optics element 302 can act as a whole on the converging particle beam 309, such as the collimating lens 303 and / or the alignment deflector 313. Alternatively, the particle optics element 302 can selectively act on different particle beams among multiple particle beams, such as the condensing lens 308 connected to the annular electrode 81 disposed in the multi-aperture plate 306.4.

[0176] It is worth noting that the techniques described herein can be performed in-situ, i.e., during MSEM operation (e.g., while scanning a sample), or at least when the MSEM is ready to scan a sample. For example, the loading lock of the MSEM can be controlled to load the sample 7 into the vacuum chamber of the MSEM1, for example, by controlling the sample platform 500 to place the sample 7 on the sample plane 101. Sensor signals can be acquired while the sample 7 is loaded into the vacuum chamber (i.e., the sample is placed on the sample plane 101).

[0177] For example, the micro-optical configuration 305 includes an additional multi-aperture plate. As shown in Figure 7, in addition to the first multi-aperture plate 304, an additional multi-aperture plate 350 is provided, which is parallel to and downstream of the first multi-aperture plate 304. The additional multi-aperture plate 350 can be offset relative to the first multi-aperture plate 304. This offset can be along the x-direction and / or the y-direction, i.e., perpendicular to the z-direction. This offset amount can be less than the diameter of the aperture 85, for example, 10% to 30% of the diameter of the aperture 85. However, when viewed from the z-direction, the apertures of the first multi-aperture plate 304 and the apertures of the additional multi-aperture plate 350 partially overlap. The aperture arrangement of the additional multi-aperture plate 350 is substantially the same as that of the first multi-aperture plate 304, i.e., the aperture spacing and size are substantially the same.

[0178] As further shown in Figure 7, due to the offset between the first porous plate 304 and the additional porous plate 350, the intensity of the small beam 3 decreases when the particles of each small beam 3 are collimated and strike the first porous plate 304 in a non-tilted manner, i.e., when the small beam is incident at a right angle with respect to the surface of the first porous plate 304. However, as shown in Figure 8, the tilted small beam 3.3 can pass through the corresponding apertures in the first porous plate 304 and the additional porous plate 350, and its intensity loss is smaller or non-attentional compared to the non-tilted small beam 3.1.

[0179] The intensity of at least a portion of the small beams generated by the first aperture plate 304 and the additional aperture plate 350 is monitored. Sensors for monitoring the intensity of the small beams can be positioned downstream of the micro-optical configuration 305. These sensors can determine the current of each monitored small beam. The monitoring of the small beams and the corresponding sensors will be discussed below with reference to Figures 16 to 18.

[0180] The characteristics of the polymer particle beam 309 can be determined by monitoring the small beam 3. As shown in Figure 3, the polymer particle beam 309 may have local beam tilt, resulting in tilted small beams, such as small beam 3.3. To compensate for local beam tilt, the particle optics element 302 can be modified to minimize the current variation of the monitored small beam.

[0181] Figures 9 and 10 illustrate another exemplary embodiment of the additional aperture plate 350 in the micro-optical configuration 305. In addition to the first aperture plate 304, the additional aperture plate 350 is disposed parallel to and downstream of the first aperture plate 304. The aperture arrangement of the additional aperture plate 350 substantially corresponds to the aperture arrangement of the first aperture plate 304. The additional aperture plate 350 may be aligned with the first aperture plate 304, i.e., the aperture center of the additional aperture plate 350 is aligned along the optical axis with the aperture center of the first aperture plate 304.

[0182] As shown in Figure 9, due to the alignment of the first porous plate 304 and the additional porous plate 350, the small beam generated at the first porous plate 304 and propagating parallel to the optical axis (i.e., the untilted small beam) is essentially unaffected by the additional porous plate 350. However, when the polymer particle beam 309 has a global or local tilt, all or part of the small beams are tilted about the optical axis, and therefore are affected by the additional porous plate 350, as shown in Figure 10. Compared to the untilted small beam, the intensity of the tilted small beam is reduced, which can be seen from the width of the small beam 3 in Figures 9 and 10.

[0183] The intensity of at least a portion of the small beams generated by the first aperture plate 304 and the additional aperture plate 350 is monitored. Sensors for monitoring the intensity of the small beams can be positioned downstream of the micro-optical configuration 305. These sensors can determine the current of each monitored small beam. The monitoring of the small beams and the corresponding sensors will be discussed below with reference to Figures 16 to 18.

[0184] The characteristics of the aggregated particle beam 309 can be determined based on the monitoring of the small beam. To compensate for global and / or local beam tilt, the particle optics 302 can be modified to maximize the current of the monitored small beam.

[0185] The techniques described above in conjunction with Figures 7 and 8 can be combined with those described in conjunction with Figures 9 and 10. For example, the additional aperture plate 350 can be moved under the control of the control module 830, allowing its position relative to the first aperture plate 304 to vary in a direction perpendicular to the optical axis. Therefore, the offset between the first aperture plate 304 and the additional aperture plate 350 can be configured as shown in Figures 7 and 8, and subsequently, the alignment between the first aperture plate 304 and the additional aperture plate 350 can be configured as shown in Figures 9 and 10. The particle optics element 302 can be modified to minimize variations in the measurement current and maximize the measurement current. A trade-off between these two adjustment objectives can be considered. Optimization can be iteratively performed by repeatedly applying the above configuration.

[0186] In some examples, only a portion of the small beam can be used to determine the characteristics of the polymerizing particle beam 309 and to adjust the particle optics 302. Hereinafter, these small beams will be referred to as the adjusting small beams, while the beam used to scan the sample 7 will be referred to as the scanning beam. For example, the adjusting beam can be located on the periphery outside the scanning beam. Figure 11 shows an exemplary arrangement of the apertures in the first porous plate 304, and Figure 12 shows an exemplary arrangement of the apertures in the additional porous plate 350.

[0187] The first multi-aperture plate 304 provides seven apertures 1101-1107 for generating scanning small beams and twelve apertures 1110-1121 for generating adjusting small beams. It should be noted that the apertures used to generate adjusting small beams can also be used to generate scanning small beams, for example, after the particle optics element 302 has been adjusted. The number of apertures used for generating scanning and adjusting small beams is merely an example and can be selected according to actual needs.

[0188] The additional multi-aperture plate 350 provides a corresponding aperture arrangement. As shown in Figure 12, the additional multi-aperture plate 350 provides seven apertures 1201-1207 for passing through the scanning small beam and twelve apertures 1210-1221 for passing through the adjustment small beam. The diameter of the apertures 1201-1207 for passing through the scanning small beam is larger than the corresponding apertures 1101-1107, so even if the scanning small beam is not perfectly aligned with the optical axis and / or is not collimated, the scanning small beam will not be affected by the additional multi-aperture plate 350. However, the diameter of the apertures 1210-1221 for passing through the adjustment small beam is substantially the same as the diameter of the apertures 1110-1121 for generating the adjustment small beam.

[0189] Typically, although not shown in Figures 11 and 12, in order to achieve higher sensitivity for the adjustable small beam, the diameter of the adjustable small beam can be smaller than the diameter of the scanning small beam, that is, the diameters of apertures 1110-1121 and 1210-1221 can be smaller than the diameters of apertures 1101-1107.

[0190] In another example, as shown in Figure 13, the first multi-aperture plate 304 can provide 91 apertures (without reference numerals) for generating scanning small beams and 6 apertures 1301-1306 for generating adjusting small beams. Apertures 1301-1306 can be located in the outer peripheral region of the scanning small beam apertures. As shown, apertures 1301-1306 can be positioned along the long axis of the hexagonal arrangement of the scanning small beam apertures. When the intensity of the adjusting small beam is scanned using the detector system 600 (as described in more detail below), the detector system 600 can provide corresponding detectors for the adjusting small beam at these designated locations.

[0191] Figures 14 and 15 illustrate the effect of collimation quality on the alignment of the first porous plate 304 and the additional porous plate 350. In Figure 14, the polymeric particle beam 309 is perfectly collimated without any local tilt. Therefore, the small beam 3 generated at the first porous plate 304 can pass through the aperture of the additional porous plate 350 unaffected. The small beam 3 has the same intensity and a high value. In contrast, in Figure 15, the polymeric particle beam 309 is not perfectly collimated. Therefore, at least a portion of the small beam 3 generated at the first porous plate 304 is partially blocked by the additional porous plate 350. Specifically, the intensity of the outer peripheral small beams 3.1 and 3.6 may be significantly reduced. Small beams 3.1 and 3.6 can be configured to adjust the small beams, as described above in conjunction with Figures 11 to 13.

[0192] The intensity of the small beam, especially the intensity of the small beam, can be obtained through various sensors.

[0193] For example, the detector system 600 can be used to detect the intensity of a small beam. Referring to Figure 1, when scanning the sample 7, a high voltage can typically be applied to the sample 7 or the sample platform 500, causing particles (e.g., primary electrons) to decelerate before reaching the sample surface 25, while secondary particles are accelerated.

[0194] The voltage applied to sample 7 or sample platform 500 can be increased so that electrons no longer reach sample surface 25, but are reflected into beam splitter 400 and guided to secondary electron imaging system 200, and finally to detector system 600. This increased voltage configuration is called mirror mode. In mirror mode, the intensity of the small beam is not affected by sample 7, so detector system 600 can directly provide reliable intensity information.

[0195] Therefore, in the above-described technology, the intensity of the small beam can be obtained in mirror mode by using the detector system 600 as an intensity sensor. As described above, the detector system 600 can provide a detector for receiving and measuring the modulated small beam, particularly the surrounding modulated small beam generated by apertures 1110-1121 in FIG. 11 and apertures 1301-1306 in FIG. 13.

[0196] Alternatively, a Faraday cup can be used to determine the intensity of the small beam (specifically, to adjust the small beam). The Faraday cup can be fixedly set for adjusting the small beam, or it can be moved within the first particle optics unit 100 to be placed into the small beam path and removed from the small beam path after adjustment. The Faraday cup can be located downstream of the micro-optics configuration 305 and upstream of the field lens 103, or upstream of the second field lens 333.

[0197] Alternatively, quadrant detectors can be used to determine the intensity of the small beam (especially the adjusting small beam). Quadrant detectors can also provide positional information of the small beam. Quadrant detectors can be fixedly set for adjusting the small beam, or they can be moved within the first particle optics unit 100 so that they can be moved into the small beam path and removed from the small beam path after adjustment. Quadrant detectors can be located downstream of the micro-optics configuration 305 and upstream of the field lens 103, or upstream of the second field lens 333. Quadrant detectors can be integrated into the micro-optics configuration, for example, downstream of the global focusing lens 308.

[0198] In the above example, the additional aperture plate 350 is located downstream of the first aperture plate 304. However, in various examples, the additional aperture plate may be located upstream of the first aperture plate 304. Figure 16 shows an additional aperture plate 371 located upstream of the micro-optical configuration 305. The additional aperture plate 371 provides a peripheral aperture for generating the adjustable small beams 3.1 and 3.7, and a central aperture for generating the scanning small beams 3.2 to 3.6. The aperture diameter for generating the adjustable small beams may be smaller than the aperture diameter for generating the scanning small beams. In practice, the scanning small beams 3.2 to 3.6 are formed at the first aperture plate 304.

[0199] Faraday cups 1601 and 1602 function as sensors for measuring the intensities I1 and I2 of the adjustable small beams 3.1 and 3.7. As described above, the particle optics 302 (e.g., collimating lens 303 and alignment deflector 313) can be adjusted to maximize the intensity and uniformity of the adjustable small beams 3.1 and 3.7. Alternatively, a quadrant detector can be configured as a sensor to measure the intensities of the adjustable small beams 3.1 and 3.7. The quadrant detector can also provide positional information of the adjustable small beams 3.1 and 3.7. Alternatively, the intensities of the adjustable small beams 3.1 and 3.7 can also be measured in mirror mode via the detector system 600.

[0200] Figure 17 illustrates another exemplary configuration in which an additional aperture plate 371 is located upstream of the micro-optics configuration 305. In this example, the additional aperture plate 371 is disposed within the particle optics element 302. The particle optics element 302 may include collimating lenses 303.1 to 303.4 and alignment deflectors 313.1 and 313.2. The additional aperture plate 371 may be located downstream of collimating lenses 303.1 and 303.2 and upstream of collimating lenses 303.3 and 303.4. Therefore, in the illustrated configuration, the additional aperture plate 371 may be located downstream of alignment detector 313.1 and upstream of alignment detector 313.2.

[0201] An additional multi-aperture plate 371 provides a peripheral aperture for generating the adjustable small beams 3.1 and 3.4, and a central aperture for generating the scanning small beams 3.2 and 3.3. The aperture diameter for generating the adjustable small beams can be smaller than the aperture diameter for generating the scanning small beams. The resulting adjustable and scanning small beams are further collimated and deflected by collimating lenses 303.3 and 303.4 and alignment deflector 313.2. In practice, the scanning small beams 3.2 and 3.3 are formed on the first multi-aperture plate of the micro-optical configuration 305.

[0202] As described above in conjunction with Figure 16, the Faraday cup can be used as a sensor to measure the intensity of the adjustable small beams 3.1 and 3.4. The particle optics element 302 (i.e., the collimating lens 303 and the alignment deflector 313) can be adjusted to maximize the intensity and uniformity of the adjustable small beams 3.1 and 3.4. Alternatively, a quadrant detector can be used as a sensor to measure the intensity of the adjustable small beams 3.1 and 3.4. The quadrant detector can also provide positional information for the adjustable small beams 3.1 and 3.4. Alternatively, the detector system 600 can measure the intensity of the adjustable small beams 3.1 and 3.4 in mirror mode.

[0203] Figure 18 illustrates another exemplary technique for controlling particle optics element 302. Micro-optical configuration 305 may include apertures for generating scanning mini-beams 3.2 to 3.5, and additional apertures for generating modulating mini-beams 3.1 and 3.6. The modulating mini-beams may be configured outside the scanning mini-beam configuration; that is, modulating mini-beams 3.1 and 3.6 are peripheral mini-beams relative to scanning mini-beams 3.2 to 3.5. More than the two modulating mini-beams 3.1 and 3.6 illustrated may be provided in micro-optical configuration 305; for example, as shown in Figure 13, six modulating mini-beams may be provided. For example, apertures may be provided in a first multi-aperture plate 304, and corresponding apertures may be provided in another multi-aperture plate 306 and a condenser lens plate 307. Each modulating mini-beam may be equipped with corresponding quadrant detectors 1801 and 1802.

[0204] Figure 19 shows the quadrant detector 1802 in more detail. The following details about the quadrant detector 1802 also apply to quadrant detectors associated with other adjustable small beams. The quadrant detector 1802 may have four detector fields, each providing a corresponding intensity signal based on the amount of electrons incident on the detector field. Depending on the position of the adjustable small beam 3.6 incident on the quadrant detector 1802, one detector field may show a greater intensity than another. When the center of the quadrant detector 1802 is aligned with the aperture center of the adjustable small beam 3.6 in the micro-optical configuration 305, the deviation of the small beam 3.6 from the center of the quadrant detector 1802 in a plane perpendicular to the optical axis can be determined. This deviation indicates that the small beam 3.6 is tilted due to the overall or partial tilt of the aggregated particle beam 309. The particle optics element 302 can be controlled to minimize the deviation determined by the quadrant detector.

[0205] In various examples, the distance between the micro-optical configuration 305 and the particle optical element 302 can be varied; that is, the micro-optical configuration 305 can be moved along the optical axis, for example, through an adjustment device. The center of the small beam can be detected at two different positions of the micro-optical configuration 305 along the optical axis. If the particle beam 309 is not tilted, the centers of the two configurations should be substantially in the same position. If the centers deviate, the degree of tilt can be determined by the geometry of the array, and / or the particle optical element can be controlled to minimize the deviation of the center.

[0206] Specifically, by using additional aperture plates 350 and 371 aligned with the first aperture plate 304 as described above, even minute clipping of the tilted small beam can be detected on the detector system 600. Here, clipping refers to a portion of the small beam being truncated (i.e., absorbed) at the additional aperture plates 350 and 371. For example, in mirror mode, the diameter of the small beam detectable on the detector system 600 is 30 µm. Using the additional aperture plates 350 and 371 located in the beam path, the tilt of the small beam causes the image of the small beam on the detector system 600 to be clipped. Clipping of 1 µm or less can be detected on the detector system 600.

[0207] Furthermore, the tilt of the small beam at the micro-optical configuration 305 may cause image drift of the small beam at the detector system 600. Figure 20 shows the image of small beam 3 captured by the detector system 600 in mirror mode with an illumination current of 570 pA. Figure 21 shows the image of small beam 3 captured by the detector system 600 in mirror mode with an illumination current of 50 pA. As shown, the corresponding small beam exhibits image position drift; for example, there is a drift between the image positions of small beam 3.1 in Figure 20 and small beam 3.1 in Figure 21. This may indicate that small beam 3.1 is tilted at the micro-optical configuration 305. The particle optics element 302 can be controlled to minimize the drift of all or at least part of the image of small beam 3 at the detector system 600.

[0208] Referring to Figure 22, another exemplary technique for controlling particle optics element 302 is illustrated. In micro-optical configuration 305, a diffraction element (transmission) is provided in at least a portion of the small beam path. This diffraction element may include, for example, a diffraction crystal (particularly a single crystal) or a diffraction grating. For example, additional adjustable small beams may be provided as described above, and a corresponding diffraction element may be provided in each small beam path of the adjustable small beam. The diffraction element may be located in a separate plate or integrated into one of the plates of the micro-optical configuration, such as condenser lens plate 307. For each particle beam equipped with a diffraction element, a two-dimensional particle detection sensor 2201 and 2202 are associated and located downstream of micro-optical configuration 302 along the particle beam path. As the particle beam passes through the diffraction element, corresponding diffraction patterns 2203 and 2204 are generated. Diffraction patterns 2203 and 2204 are detected by the associated two-dimensional particle detection sensors 2201 and 2202. Depending on the type of diffraction element, the diffraction pattern may include a central illumination point (zero-order diffraction) and multiple surrounding illumination points (higher-order diffraction), see Figures 47 to 52. The symmetry of the surrounding illumination points may depend on the tilt angle of the small beam with respect to the structure of the diffraction element. The structure of the diffraction element can be aligned with the optical axis of the illumination system 100 of MSEM 1. Any tilt of the small beam will result in asymmetry in the spot intensity of the diffraction pattern. The diffraction pattern can be scanned using two-dimensional particle detection sensors 2201, 2202. The control parameters of the particle optics 302 can be controlled to maximize the symmetry of the spot intensity of the diffraction pattern.

[0209] Another exemplary technique for controlling the particle optical element 302 will be described below with reference to Figures 23 to 27.

[0210] Figure 23 illustrates a micro-optical configuration 305 incorporating pyramidal elements. The micro-optical configuration 305 includes a multi-aperture plate containing one or more pyramidal elements 2301 on its upstream side. For example, the pyramidal elements 2301 may be disposed on the upper side of a first aperture plate 304. As shown in more detail in Figure 24, four pyramidal elements 2301 are disposed on the surface of the first aperture plate 304, surrounding an aperture 85.

[0211] As shown in Figure 23, the particle optics element 302 (particularly the collimating lens 303 and the alignment deflector 313) is controlled such that the polymeric particle beam 309 is focused onto the plane of the first aperture plate 304 and scans at least one or more pyramidal elements 2301. For example, a current sensor can be placed on the first aperture plate 304 to measure the current generated by the particles of the polymeric particle beam 309 absorbed by the aperture plate 304. The current pattern determined during the scan can correspond to the surface morphology of the first aperture plate 304 and the pyramidal elements 2301 scanned by the focused particle beam 309. Based on this scan, for each pyramidal element 2301, a corresponding offset of the tip of the pyramidal element 2301 with respect to the center of the bottom of the pyramidal element 2301 (as seen by the scanning beam) is determined. This offset characterizes the overall tilt of the polymeric particle beam at the micro-optical configuration, particularly the polymeric particle beam 309.

[0212] More specifically, as shown in Figure 25, the non-tilted polymeric particle beam 309 can scan the pyramidal element 2301 as indicated by the solid arrow. The scanning pattern can identify the tip 2501 of the pyramidal element 2301 and the corners of the base 2502 of the pyramidal element 2301. As shown in Figure 26, in the projection of the non-tilted particle beam 309 scan, the tip 2501 is located at the center of the base 2502. However, when the polymeric particle beam 309 is tilted, the pyramidal element 2301 will be scanned as indicated by the dashed arrow in Figure 25. Therefore, the tip 2501 identified by the scanning pattern is located outside the center of the base 2502, as shown in Figure 27.

[0213] The control parameters of the particle optics element 302 can be changed to minimize the offset between the tip 2501 and the base 2502 of each pyramidal element 2301. After scanning the pyramidal element 2301 and adjusting the control parameters of the particle optics element 302, the collimating lens 303 defocuses so that the converging particle beam 309 is not focused on the surface of the first aperture plate 304, but provides a collimated beam.

[0214] Figures 28 to 31 illustrate another exemplary technique for controlling the parameters of particle optics element 302. As shown in Figure 28, the micro-optics configuration 305 includes at least a first aperture plate 304 and another aperture plate 306.1 containing a multi-pole alignment element, i.e., the other aperture plate 306.1 contains a multi-pole alignment element 2801 in at least a portion of its aperture. The multi-pole alignment element 2801 may be an octagonal alignment element, which can be used as an astigmatism corrector and / or deflector. The eight components of the alignment element 2801 may be arranged in an octagon as shown in Figure 29, and two components on each side of the octagon may be applied with a specific potential, which is represented by a signed number in Figures 29 to 31. Positive numbers represent positive potentials, and negative numbers represent negative potentials. The number indicates the magnitude of the potential.

[0215] Figure 29 illustrates the function of alignment element 2801 as a deflector. As shown in Figure 29, after a potential is applied, a beam that enters alignment element 2801 from the center position 2901 and is not tilted as shown by arrow 2802 in Figure 28 will be deflected to the left and then leave alignment element 2801 from the off-center position 2902.

[0216] Figure 30 illustrates the function of alignment element 2801 as an astigmatism corrector. By applying the potential shown in Figure 30, the astigmatism of a small beam entering alignment element 2801 from the center position 2901 and not tilted as indicated by arrow 2802 in Figure 28 about axis 3001 can be corrected. The small beam does not deflect, so its center position when leaving alignment element 2801 is the same as when it enters, as shown by the intersection with the dashed axis.

[0217] Figure 31 illustrates the function of the alignment element 2801 as an astigmatism corrector when used in conjunction with the tilted small beam. By applying the potential shown in Figure 31, the astigmatism of the small beam, which enters the alignment element 2801 from the center position 2901 and is tilted as shown by arrow 2804 in Figure 28, about axis 3101 can be corrected. However, the small beam will also deflect, causing it to leave the alignment element 2801 at an off-center position, as shown at the intersection with the dashed axis.

[0218] This can be used to detect and compensate for tilted illumination at the first aperture plate 304. For example, when astigmatic excitation changes in mirror mode, the deflection of each or a portion of the small beams generated by the first aperture plate 304 can be determined at the detector system 600. The corresponding tilt indication of each or at least a portion of the small beams generated by the first aperture plate 304 can be determined. The characteristics of the converging particle beam 309 can be determined based on the tilt indication. The particle optics 302 can be controlled to minimize the overall tilt indication or to keep the tilt indication within predetermined limits.

[0219] For example, a first excitation mode can be applied to each octet alignment element 2801 of each sub-beam to act as an astigmatism corrector. For instance, the same potential can be applied to each opposite pole pair of the octet alignment element, but different potentials can be applied to different pole pairs. At the detector system 600, the incident position of each sub-beam is determined. Then, a second excitation mode can be applied to each octet alignment element 2801 of each sub-beam to act as an astigmatism corrector. However, the second excitation mode differs from the first excitation mode. The second excitation mode can also be a zero-excitation mode, i.e., no potential is applied to the poles in the second excitation mode. Again, at the system detector 600, the incident position of each sub-beam is determined. For each sub-beam, the offset between the incident position when the first excitation mode is applied and the incident position when the second excitation mode is applied is determined. These offsets can characterize the aggregation particle beam 309 at the micro-optical configuration 305, particularly the local and global tilt. Minimizing the offset can be used as an objective function to control the particle optics element 302.

[0220] In various examples, a Faraday cup or quadrant detector located downstream of the micro-optical configuration 305 can be used to determine the incident position.

[0221] The aforementioned techniques may require or benefit from routine calibration, such as the routine alignment of the particle beam 309 along the optical axis. Such calibration may not be possible in the field. For example, specific adjustment devices may be inserted into the illumination system 100, and / or the micro-optical configuration 305 may be removed from the illumination system 100.

[0222] The so-called blade-edge technique can be used to measure the profile of the particle beam 309. For example, a sharp edge can be progressively pushed into the particle beam 309 in the x / y plane, and the unobstructed beam flow at each step can be measured. The profile of the plane can be extracted from the measured beam flow, for example, through integration or deconvolution, particularly the center position and width of the plane profile.

[0223] These techniques can be extended to two planes at different z-axis positions, and the tilt and / or opening angle, i.e., collimation, of the beam can be calculated by combining two center positions and widths. Subsequently, the tilt and collimation can be iteratively adjusted using particle optics 302, particularly collimating lens 303 and / or alignment deflector 313.

[0224] The principle is shown in Figure 32. After the micro-optical configuration 305 is removed from the path of the particle beam 309, the first edge element 3202 moves from a position radially outside the particle beam 309 into the particle beam 309 in a first plane perpendicular to the optical axis 3204 of the beam generating device 300. Therefore, the increased portion of the particle beam 309 is absorbed by the first edge element 3202. The first plane is located between the particle optical element 302 and the object plane 101. As the first edge element 3202 moves, the first course 3206 of the current in the particle beam 309 that is not absorbed by the first edge element 3202 is detected by the detector 3208. After obtaining the first course 3206, the first edge element 3202 is removed from the particle beam 309. Next, the second edge element 3210 is moved from a position radially outside the particle beam 309 into the particle beam 309 in a second plane perpendicular to the optical axis 3204. Therefore, as the second edge element 3210 advances, the increased portion of the particle beam 309 is absorbed by the second edge element 3210. The second plane is located between the first plane and the detector 3208. As the second edge element 3210 moves, a second path 3212 detects the current of the portion of the aggregated particle beam that is not absorbed by the second edge element 3210. Based on the first path 3206 and the second path 3212, an offset value indicating the offset between the center of the aggregated particle beam at the first plane and the center of the aggregated particle beam at the second plane can be calculated. This offset value is related to the average tilt angle 3214 of the particle beam 309 about the optical axis 3204. Alternatively, a width difference can be determined based on the first path 3206 and the second path 3212. The width difference represents the difference between the width of the particle beam 309 in the first plane and the width of the particle beam 309 in the second plane. The width difference is related to the collimation 3216 of the particle beam 309. A smaller width difference or no width difference indicates perfect or near-perfect collimation. Based on the offset value and width difference, the particle optical element 302 can be adjusted to reduce tilt and optimize collimation.

[0225] Figure 33 illustrates exemplary implementation details of the blade edge technology. A single-aperture plate (not shown) can be used to limit the cross-sectional area of ​​the particle beam 309. A first linear translation device 3302 can be used to drive the first edge 3202. A second linear translation device 3304 can be used to drive the second edge 3210. Another linear translation device 3306 can be used to drive the detector 3208. The detector 3208 can be a Faraday cup that provides an integral current signal. As shown, the micro-optical configuration 305 has been removed from the path of the particle beam 309.

[0226] In a further example, detector 3208 in Figure 32 can be implemented by detector system 600. MSEM 1 can operate in mirror mode, reflecting the portion of particle beam 309 that is not absorbed by the first or second edges 3202, 3210 through sample plane 101 to detector system 600.

[0227] Figure 34 shows the current profile (integrated current signal 3402) determined when the first edge 3202 is moved into the particle beam 309, and the current profile (integrated current signal 3404) determined when the second edge 3202 is moved into the particle beam 309. By deconvolving the integrated current signals 3402 and 3404, extracted profiles 3406 and 3408 can be obtained, respectively. The extracted profiles 3406 and 3408 indicate the width and position of the particle beam 309 in the first and second planes along the directions of movement of the first and second edges, respectively. Based on the extracted profiles 3406 and 3408, the final alignment of the particle beam 309 about the optical axis can be determined. As shown on the right side of Figure 34, the tilt and collimation of the particle beam 309 can be determined.

[0228] The aforementioned blade edge measurements can be performed in different lateral dimensions (e.g., the x and y directions) to obtain the complete profile of the particle beam 309. Generally, the measurement accuracy may depend on the step size of the linear translater, the measurement accuracy of the current detector 3208, and the evaluation software.

[0229] The accuracy of tilt and collimation measurements can be estimated as follows. The mechanical error at the first and second edge positions can be assumed to be at most 1 µm. The distance d between the first and second planes can be 20 cm. The positioning accuracy of the corresponding encoder for the first and second translations can be assumed to be 1 nm. The measurement resolution (maximum) of the contour fitted by the convolution curve can reach 100 nm.

[0230] Therefore, for the tilt angle, we can assume that the positioning error dt for each contour is 1.1 µm. As shown in Figure 35, based on the distance d = 20 cm and twice the positioning error 2 x dt = 1.1 µm, the tilt angle resolution can be calculated to be 0.011 mrad.

[0231] Similarly, for collimation, we can assume the total error of the full width at half maximum (FWHM) is dc = 2 x 100 nm. Based on the distance d = 20 cm and the FWHM error dc, the opening resolution can be calculated to be 0.001 mrad, as shown in Figure 36.

[0232] Figure 37 illustrates another exemplary implementation of the blade edge technology. Similar to Figure 33, a first linear translation 3302 can be used to drive the first edge 3202, and a second linear translation 3304 can be used to drive the second edge 3210. However, in this exemplary embodiment, the detector is not positioned along the optical axis of the beam generating device 300, but rather a coil 3702 is used to deflect the particle beam 309 to the sidewall of the beam generating device 300. The deflection angle is approximately 90°. The detector 3704 can be positioned on the sidewall of the beam generating device 300. The detector 3704 can be a Faraday cup or any other suitable detector, such as a quadrant detector. For clarity, the particle optics element 302 is omitted in Figure 37. However, even in this embodiment, the micro-optics configuration 305 can be removed from the path of the particle beam 309.

[0233] Typically, in order to deflect the particle beam to the sidewall of the beam generating device 300, not only the aforementioned coils can be used, but also mirrors. The mirror can be positioned at an angle of 45° to the optical axis of the beam generating device 300. The mirror can be a conductive plate with a reverse electric field. The velocity of the particles (e.g., electrons) slows down, and their motion is reversed in a direction perpendicular to the plate surface. Therefore, the reflection angle equals the incident angle. This can lengthen the measurement path, thereby improving sensitivity.

[0234] Figure 38 illustrates another exemplary implementation of the edge-edge technology. The micro-optical configuration is removed from the particle beam path, for example, by replacing it with a single-aperture plate 3802, which is positioned in a first plane perpendicular to the optical axis of the beam generating device 300. This first plane can substantially correspond to the plane before the micro-optical configuration is removed. The center of the single aperture of the single-aperture plate 3802 is aligned with the optical axis. The size of the single aperture corresponds to the cross-sectional size of the polymeric particle beam 309 in the first plane. An edge element 3804 is movably disposed in a second plane perpendicular to the optical axis, such that the edge element 3804 can move into the polymeric particle beam 309 until it completely blocks the polymeric particle beam 309. The second plane differs from the first plane and is located downstream of the first plane. The edge element 3804 can move continuously or incrementally within the second plane, entering the polymeric particle beam 309 from outside its path, thereby absorbing any additional portion of the polymeric particle beam 309 at the edge element 3804. When the edge element 3804 is moved (e.g., along the x-direction), the detector 3806 detects the current I(x) curve of the portion of the polymer particle beam not absorbed by the edge element 3804. The width of the polymer particle beam 309 in the second plane is determined based on the current curve. When the polymer particle beam 309 is not tilted about the optical axis, the width of the polymer particle beam 309 in the second plane (determined by the movement of the edge element 3804) substantially corresponds to the size of the single aperture. As shown in Figure 38, when the polymer particle beam 309 is tilted, the width of the polymer particle beam 309 in the second plane is smaller.

[0235] The control parameters of the particle optical element 302 can be changed to make the determined width consistent with the size of the single aperture.

[0236] The detector 3806 may include a Faraday cup located between the second plane and the object plane.

[0237] Depending on the specific example, the polymeric particle beam 309 may have a known non-uniform intensity distribution in its cross-section within a plane perpendicular to the optical axis of the beam generating device 300. For instance, the intensity distribution of the polymeric particle beam 309 may resemble a normal or Gaussian distribution, with its maximum intensity located at the center of the beam cross-section.

[0238] For example, as shown in Figure 39, a porous plate 3902 can be positioned in the path of the particle beam 309. The porous plate 3902 can be one of the porous plates in the micro-optical configuration 305, which is also used to scan samples during MSEM 1 operations. In some examples, the micro-optical configuration 305 can be removed. The porous plate 3902 can be a porous plate or grating specifically designed for calibrating the beam generation device 300, i.e., having a known aperture size and aperture spacing. A specially designed porous plate can have fewer but larger apertures than the porous plate in the micro-optical array 305. When the micro-optical configuration 305 is used as the porous plate 3904, the optical lenses and deflectors in the micro-optical configuration 305 can be deactivated (i.e., turned off). When the porous plate 3902 is irradiated by the particle beam 309, multiple small particle beams 3906 are generated in the downstream direction. The irradiated porous plate 3902 may need to be conductive and grounded.

[0239] The two-dimensional detector 3904 is positioned in a plane perpendicular to the optical axis, downstream of the aperture plate 3902, at a predetermined distance (e.g., 20 cm). Both the aperture plate 3902 and the detector 3904 can be aligned with the optical axis. Specifically, the aperture plate 3902 and the detector 3904 may not be tilted about the optical axis.

[0240] When a known object (e.g., a porous plate 3902) is irradiated by a particle beam 309 with a known profile and imaged on a spatial resolution detector 3904, the collimation can be determined based on the width of the projected shadow, and the tilt can be determined based on the offset of the known profile position.

[0241] Figure 40 illustrates another exemplary embodiment of the above-described technology. Similar to that shown in Figure 39, the multi-aperture plate 3902 can be positioned along the path of the particle beam 309. However, in this exemplary embodiment, the detector is not positioned along the optical axis of the beam generating device 300. Instead, a coil 4002 is provided to deflect multiple small particle beams 3906 toward the sidewall of the beam generating device 300. The deflection angle is approximately 90°. A two-dimensional detector 3904 can be positioned on the sidewall of the beam generating device 300.

[0242] As shown in Figure 41, the two-dimensional detector 3904 can be used to determine the two-dimensional intensity path 4102 of the current generated by multiple particle beams 3906.

[0243] The tilt and divergence of the particle beam 309 can be determined based on the current curve 4102, as shown in Figure 42.

[0244] Figure 42 schematically illustrates the paths of the particle beam 309 and its multiple sub-beams 3906 on the left, as well as the intensity distribution 4202 of the particle beam 309 at the multi-aperture plate 3902. The central portion of Figure 42 shows the intensity 4204 measured by the two-dimensional detector 3904. The intensity in the shaded area is essentially zero. Based on intensity 4204, the beam position at the two-dimensional detector 3904 can be reconstructed. Specifically, the deviation (offset) of the maximum value from the center of the multi-aperture plate 3902 determines the tilt 4206 of the particle beam 309 about the optical axis 4208. By comparing the measured profile width (corresponding to the diameter or size of the sub-beams at the two-dimensional detector 3904) with the known aperture diameter, the divergence of the sub-beams can be determined. The emissivity of the sub-beams can also be determined using a grating.

[0245] The control parameters of the particle optics system 302 can be changed to minimize the deviation (offset) between the determined position of the maximum beam intensity at the two-dimensional detector 3904 and the center of the multi-aperture plate 3902 and / or minimize beam divergence.

[0246] The measurement accuracy for tilt and collimation can be estimated as follows. Assuming the aperture center is located on the optical axis with an accuracy of 1 µm, and the aperture diameter determination accuracy is 1 µm, the position accuracy of the two-dimensional detector is 1 µm, and the accuracy of the maximum position in the profile is 1 µm. Therefore, the total possible deviation is 3 µm. When the distance between the two planes is d = 20 cm, the accuracy of the tilt resolution is 0.011 mrad, and the accuracy of the opening angle resolution is 0.02 mrad.

[0247] Figures 43 and 44 illustrate another example where it is assumed that the polymeric particle beam 309 has a known non-uniform intensity distribution. The micro-optical configuration can be removed from the particle beam path, and a single-aperture plate 4302 can be positioned in the path of the particle beam 309. The single-aperture plate 4302 can be positioned in a first plane perpendicular to the optical axis 4304, with the center of the single aperture of the single-aperture plate 4302 aligned with the optical axis 4304 of the beam generating device 300. The size of this single aperture is smaller than the cross-sectional size of the polymeric particle beam 309 in the first plane. Therefore, the single-aperture plate 4302 generates a truncated particle beam 4308 based on the particle beam 309. The single-aperture plate 4302 may need to be conductive and grounded.

[0248] The two-dimensional detector 4310 is positioned in a second plane perpendicular to the optical axis 4304 and located at a predetermined distance downstream of the single aperture plate 4302, for example, 20 cm. Both the single aperture plate 4302 and the detector 4310 can be aligned with the optical axis 4304. Specifically, both the single aperture plate 4302 and the detector 4310 are not tilted about the optical axis 4304.

[0249] When a known object (e.g., a single-aperture plate 4302) is illuminated by a particle beam 309 with a known profile and imaged on a spatial resolution detector 4310, collimation can be determined based on the width of the projected shadow, and tilt can be determined based on the positional offset of the known profile.

[0250] As further shown in Figure 43, the two-dimensional intensity path 4306 of the current generated by the cut particle beam 4308 can be determined using the two-dimensional detector 4304.

[0251] The tilt and divergence of the particle beam 309 can be determined based on the current curve 4306, as shown in Figure 44.

[0252] Figure 44 schematically illustrates the path of particle beam 309 and the generated clipped particle beam 4308 on the left, also showing the intensity distribution 4402 of particle beam 309 at the single-aperture plate 4302. The center of Figure 44 shows the intensity 4404 measured by the two-dimensional detector 4310. In the shaded (clipped) region, the intensity is essentially zero. Based on intensity 4404, the beam position at the two-dimensional detector 4310 can be reconstructed. Specifically, the maximum deviation (offset) of the center of the single-aperture plate 4302 provides the tilt 4406 of particle beam 309 about the optical axis 4304. The measured profile width (corresponding to the diameter or size of the clipped particle beam 4308 at the two-dimensional detector 4310) provides the divergence of particle beam 309 compared to the known single-aperture diameter.

[0253] The control parameters of the particle optics system 302 can be changed to minimize the deviation (offset) between the determined position of the maximum beam intensity at the two-dimensional detector 4310 and the center of the single aperture plate 4302 and / or minimize beam divergence.

[0254] Further exemplary calibration techniques can be based on diffraction elements. As shown in Figure 45, the micro-optical configuration can be removed from the beam generating device 300, and the diffraction element 4502 can be positioned in a first plane perpendicular to the optical axis of the beam generating device 300. The diffraction element 4502 can include, for example, a diffraction crystal (particularly a single crystal) or a diffraction grating. The first plane can substantially correspond to the plane in which the micro-optical configuration was located before removal. The diffraction element 4502 can be inserted into the beam generating device 300 via a linear translation device 4504. A two-dimensional detector 4506 can be positioned in a second plane perpendicular to the optical axis of the beam generating device 300. The second plane can be located downstream of the first plane, for example, at a distance of approximately 30 cm. The two-dimensional detector 4506 can be configured to determine the two-dimensional intensity path generated at the two-dimensional detector 4506 by the diffraction pattern of the aggregate particle beam passing through the diffraction element 4502.

[0255] The transmission diffraction of the diffraction element 4502 can directly control the tilt and collimation of the particle beam 309. The intensity symmetry of the diffraction pattern spot is extremely sensitive to the angle of incidence. The important factor is not the exact pattern, but the intensity symmetry. When the tilt disappears, the intensity of the same diffraction order is the same. Furthermore, the sharpness of the diffracted spot may directly depend on the collimation of the particle beam. The diameter of the diffracted spot is smallest when the beam is parallel. The control parameters of the particle optical element 302 can be changed to optimize the symmetry of the diffraction pattern and / or the sharpness and size of the diffracted spot.

[0256] The diffraction pattern may include a central illumination point 4508 (zero-order diffraction) and multiple peripheral illumination points 4510 (high-order diffraction) surrounding the central illumination point.

[0257] Figure 46 schematically illustrates the diffraction of the tilted particle beam 309 on the diffraction crystal 4502.

[0258] Figures 47 to 51 show the diffraction patterns produced when the particle beam 309 passes through the diffraction crystal.

[0259] Figure 47 shows the diffraction pattern of a perfectly aligned particle beam 309 (i.e., an untilted particle beam 309). Higher-order illumination spots 4510 are symmetrically arranged around the zero-order illumination spot 4508.

[0260] Figure 48 shows the diffraction pattern of the tilted particle beam 309. Some higher-order illumination spots 4510, i.e., the illumination spots on the left, are significantly larger than the illumination spots on the right.

[0261] Figures 49 to 51 show the diffraction pattern of the non-tilted particle beam 309. Higher-order illumination spots 4510 are symmetrically arranged around the zero-order illumination spot 4508. However, compared to the diffraction pattern shown in Figure 50 (where higher-order illumination spots 4510 are also symmetrically arranged around the zero-order illumination spot 4508), the diameters of the extinction spots in Figures 49 and 51 are larger than those in Figure 50. The larger diameter is because the particle beam 309 either diverges as in Figure 49 or converges as in Figure 51. In contrast, the particle beam 309 in Figure 50 is collimated. The diffraction pattern shown in Figure 50 can be achieved by adjusting the control parameters of the particle optics element 302.

[0262] The examples above consider zero-order and first-order diffraction points. However, higher-order diffraction points can also be considered. First-order diffraction points with Miller indices of (1, + / -1, + / -1) and (1, + / -3, + / -3) should have high intensity. At a detector distance of 30 cm, these are located at radii of 3.4 mm and 8.5 mm, respectively (see Figure 52). The example values ​​above may be applicable to, for example, diffraction crystals made of silicon. Other values ​​may be applicable to other materials. The two-dimensional detector 4506 should at least reach this size.

[0263] The relationship between collimation accuracy and spot size can be estimated as follows: The diameter of the diffracted spot at 0.1° defocus is approximately 500 µm. The sharpest diffracted spot depends on crystal quality, detector resolution, and light source emissivity. Assuming the sharpest diffracted spot diameter is 50 µm (detector resolution is 5 µm), the collimation accuracy is approximately 0.01°. Figure 53 shows the relationship between the spot diameter and collimation angle on detector 4506 at a distance of 30 cm.

[0264] Figure 54 is a flowchart of method 5400 according to various paradigms. The method of Figure 54 is applicable to processing apparatuses associated with MSEM (e.g., MSEM 1 shown in Figure 1). For example, the method of Figure 54 can be executed by processing apparatus 800 shown in Figure 1. The method of Figure 54 can be executed using parallel processing distributed among multiple computing units. In Figure 54, optional method steps are indicated by dashed boxes.

[0265] Before scanning the sample, the MSEM 1, particularly the beam generating device 300, can be selectively calibrated routinely. In step 5402 of the selected method, the micro-optical configuration 305 can be removed from the path of the particle beam 309, and in step 5404, calibration as described above in conjunction with Figures 32 and 53 can be performed. After calibration, the micro-optical configuration 305 can be moved back into the path of the particle beam 309 in step 5406.

[0266] To scan the sample, the prepared sample can be loaded into MSEM 1. In step 5408, the loading lock of MSEM 1 is controlled to load sample 7 into the vacuum chamber of MSEM 1. In step 5410, the sample platform 500 can be controlled to place sample 7 on the object plane 101.

[0267] In step 5412, one or more sensor signals are acquired from one or more sensors located along the path of the particle beam 309. Based on the one or more sensor signals, in step 5414, one or more characteristics of the converging particle beam 309 at the micro-optical configuration 305 are determined. Based on the one or more characteristics of the converging particle beam 309, one or more particle optics elements 302 are controlled in step 5416.

[0268] Acquiring sensor signals, determining the characteristics of the aggregated particle beam 309, and controlling the particle optics 302 can be performed as described above in conjunction with Figures 1 to 31.

[0269] It should be noted that steps 5412 to 5416 can be performed while sample 7 is placed on the sample stage 500 within the micro-scanning electron microscope 1. Furthermore, at least a portion of steps 5412 to 5416 can be performed in parallel with scanning sample 7 to allow for on-site adjustment of the particle optics element 302. Specifically, steps 5412 to 5416 can be repeated, for example, while scanning the sample, to ensure adjustment of the particle optics element 302, i.e., improving the tilt, collimation, and / or telecentricity of the converging particle beam 309 at the micro-optical configuration 305.

[0270] 1: Multibeam Scanning Electron Microscopy 3: Main small beam 3.1: Main small beam 3.2: Main small beam 3.3: Main Small Beam 3.4: Main small beam 3.5: Main small beam 3.6: Main small beam 3.7: Main small beam 5.1: Beam Focus 5.2: Beam Focus 5.3: Beam Focus 7: Sample 9.1: Sub-small beam 9.2: Sub-small beam 9.3: Sub-small beam 25: Sample surface 81: Ring electrode 82: Condenser lens ring electrode 83.1: Spacers 83.2: Spacers 83.3: Spacers 83.4: Spacers 83.5: Spacers 85: Aperture 94: Terminal aperture 99: Metal layer 100: First Particle Optical Unit / Illumination System 101: Sample plane / Object plane 102: Objective lens system 103: Field Lens 108: Intersection 110: First deflection scanner 160: Uniformity sensor 200: Secondary Electron Imaging System 205.1: Electro-optical lenses 205.2: Electro-optical lens 205.3: Electro-optical lenses 205.4: Electro-optical lens 205.5: Electro-optical lens 222: Converging Beam Deflector 225: Imaging plane 300: Beam generating equipment 301: Particle Source 302: Particle optical element 302.1: Particle Optical Elements 302.2: Particle Optical Elements 303: Collimating Lens 303.1: Collimating Lens 303.2: Collimating Lens 303.3: Collimating Lens 303.4: Collimating Lens 304: The first multi-aperture plate 305: Micro-optical configuration 306: Another multi-pore plate 306.1: Multi-aperture plate 306.2: Multi-aperture plate 306.3: Multi-aperture plate 306.4: Multi-aperture plate 307: Condensing Lens Plate 308: Spherical lens electrode / spherical condenser lens 309: Polymer Particle Beam 313: Alignment deflector 313.1: Alignment Deflector 313.2: Alignment Deflector 321: Intermediate image surface 331: First Field Lens 333: Second Field Lens 350: Additional multi-aperture plate 371: Additional multi-aperture plate 400: Beam splitter 500: Sample Platform 503: Control Module (Voltage Extraction) 600: Detector System 610: Field of View (FoV) 620: Spacing 800: Processing unit / control circuit 810: Image Data Acquisition Unit 830: Control Module 840: Control Module 860: Scanning Control Unit 880: Control Processor 890: Memory 1101: Aperture 1102: Aperture 1103: Aperture 1104: Aperture 1105: Aperture 1106: Aperture 1107: Aperture 1110: Aperture 1111: Aperture 1112: Aperture 1113: Aperture 1114: Aperture 1115: Aperture 1116: Aperture 1117: Aperture 1118: Aperture 1119: Aperture 1120: Aperture 1121: Aperture 1201: Aperture 1202: Aperture 1203: Aperture 1204: Aperture 1205: Aperture 1206: Aperture 1207: Aperture 1210: Aperture 1211: Aperture 1212: Aperture 1213: Aperture 1214: Aperture 1215: Aperture 1216: Aperture 1217: Aperture 1218: Aperture 1219: Aperture 1220: Aperture 1221: Aperture 1301: Aperture 1302: Aperture 1303: Aperture 1304: Aperture 1305: Aperture 1306: Aperture 1601: Faraday Cup 1602: Faraday Cup 1801: Quadrant Sensor 1802: Quadrant Sensor 2201: Two-dimensional particle detector 2202: Two-dimensional particle detector 2203: Diffraction Pattern 2204: Diffraction Pattern 2301: Pyramid-shaped component 2501: Advanced 2502: Base 2801: Multi-pole alignment element 2802: Arrow 2804: Arrow 2901: Central position 2902: Off-center position 3001: Shaft 3101: Shaft 3202: First edge element 3204: Optical Axis 3206: First Current Profile / First Path 3208: Detector 3210: Second edge element 3212: Second Current Profile / Second Path 3214: Tilt Angle 3216:Collimation 3302: First Linear Translator 3304: Second Linear Translator 3402: Integrating Current Signal 3404: Integrating Current Signal 3406: Outline 3408: Outline 3702: Coil 3704: Detector 3802: Single-aperture plate 3804: Edge element 3806: Detector 3902:Multi-aperture plate 3904: Two-dimensional detector 3906: Particle Microbeam 4002: Coil 4102: Two-dimensional intensity route 4302: Single-aperture plate 4304: Optical Axis 4306: Two-dimensional intensity route 4308: Trimmed Particle Beam 4310: Two-dimensional detector 4402: Intensity Route 4404: Strength 4406: Inclination 4502: Diffraction element / Diffraction crystal 4504: Linear Translator 4506: Two-dimensional detector 4508: Center illumination point / zero-level illumination spot 4510: Peripheral Illumination Point / Higher-Order Illumination Point 5400: Method 5402: Steps 5404: Steps 5406: Steps 5408: Steps 5410: Steps 5412: Steps 5414: Steps 5416: Steps d: distance dc: Collimation deviation dt: tilt deviation I1: Strength I2: Intensity P1: Spacing z'': Local lens axis z: Local lens axis z': Local lens axis

Claims

1. A method of operating a control circuit (800) of a multi-beam scanning particle imaging system (1), the multi-beam scanning particle imaging system (1) comprising a micro-optical configuration (305) for splitting an incident cohesive particle beam (309) into a plurality of particle beams (3), the multi-beam scanning particle imaging system (1) being configured to co-scan at least one set of the plurality of particle beams across an object plane (101), wherein the method comprises: - Obtain one or more sensor signals from one or more sensors positioned along a particle beam path of the multi-beam scanning particle imaging system (1); - Based on the one or more sensor signals, determine one or more characteristics of the aggregated particle beam (309) at the micro-optical configuration (305), wherein the one or more characteristics include a tilt angle of the aggregated particle beam (309) about an optical axis of a beam generating device (300) of the multi-beam scanning particle imaging system (1) at a reference position on the particle beam path; - Based on the one or more characteristics of the aggregated particle beam (309), control one or more particle optical elements (302) of the multi-beam scanning particle imaging system (1), wherein the one or more particle optical elements (302) are positioned upstream of the micro-optical configuration (305) along the particle beam path.

2. The method as described in claim 1, further comprising: - Control a loading lock of the multi-beam scanning particle imaging system (1) to load a sample (7) into a vacuum chamber of the multi-beam scanning particle imaging system (1), wherein one or more sensor signals are acquired when the sample (7) is loaded into the vacuum chamber.

3. The method as described in claim 2 further includes: - Control a sample platform (500) of the multi-beam scanning particle imaging system (1) to place the sample (7) on the object plane (101), wherein one or more sensor signals are acquired when the sample (7) is placed on the object plane (101).

4. The method of any one of claims 1 to 3, wherein the micro-optical configuration (305) includes the one or more particle optical elements (302).

5. The method of any one of claims 1 to 3, wherein the one or more particle optics elements (302) are configured to selectively act on different particle beams in the plurality of particle beams (3).

6. The method of any one of claims 1 to 3, wherein the one or more features include an overall beam tilt at a reference position along the beam path.

7. The method of any one of claims 1 to 3, wherein the one or more features include a partial beam tilt at a reference position along the beam path.

8. The method of any one of claims 1 to 3, wherein the micro-optical configuration (305) comprises at least two aperture plates (304, 350) arranged parallel to and spaced apart along the particle beam path; wherein the one or more sensors comprise: For each of the plurality of particle beams (3) in another group, a designated particle detection sensor is set downstream of the micro-optical configuration (305) along the path of the particle beam; wherein determining the one or more characteristics of the aggregated particle beam at the micro-optical configuration (305) includes: - determining a corresponding current for each of the plurality of particle beams (3) in the other group as the characteristics of the aggregated particle beam (309) at the micro-optical configuration (305) based on a sensor signal from the designated particle detection sensor.

9. The method of claim 8, wherein controlling the one or more particle optical elements (302) includes changing a plurality of control parameters of the particle optical elements (302) to minimize the variation in the current.

10. The method of claim 8, wherein controlling the one or more particle optics (302) includes changing a plurality of control parameters of the particle optics (302) to maximize the current.

11. The method of claim 8, wherein the apertures of one (304) of the at least two porous plates (304, 350) are aligned with the apertures of the other (350) of the at least two porous plates (304, 350) in a direction along the particle beam path.

12. The method as described in claim 8, further comprising: Change the position of one of the at least two porous plates (304, 350) with respect to the other porous plate (350) in a direction perpendicular to the path of the particle beam.

13. The method as described in claim 8, further comprising: Change the position of one of the at least two porous plates (304, 350) with respect to the other porous plate (350) in one direction along the particle beam path.

14. The method of claim 8, wherein each of the one or more sensors comprises at least one of a Faraday cup and a quadrant detector.

15. The method of claim 8, wherein the one or more sensors include a plurality of particle detection sensors in a detector system (600) of the multi-beam scanning particle imaging system (1), wherein the multi-beam scanning particle imaging system (1) is in a mirror mode to reflect at least the other set of the plurality of particle beams (3) across the object plane (101).

16. The method of claim 8, wherein the plurality of particle beams of the other group are a plurality of modulated beams (3), wherein each of the at least two multi-aperture plates (304, 350) has a plurality of inner apertures and a plurality of outer apertures located outside one of the inner apertures, wherein the inner apertures split the incident polymeric particle beams into the plurality of particle beams of the group, and the outer apertures split the incident polymeric particle beams into the plurality of particle beams of the other group.

17. The method of claim 8, wherein at least one (371) of the at least two aperture plates (304, 371) is located between a first of the one or more particle optical elements (302) and a second of the one or more particle optical elements (302).

18. The method of any one of claims 1 to 3, wherein the one or more sensors include a diffraction element disposed in a particle beam path of at least one of the plurality of particle beams, and for each particle beam of at least one of the plurality of particle beams, a designated two-dimensional particle detection sensor (2201, 2202) is disposed downstream of the micro-optical configuration (305) along the particle beam path, wherein determining the one or more characteristics of the converging particle beam (309) at the micro-optical configuration (305) includes: - Based on a sensor signal from the designated two-dimensional particle detection sensor (2201, 2202), a corresponding diffraction pattern (2203, 2204) is determined for each of the at least one of the plurality of particle beams, as such characteristics of the aggregated particle beam (309) at the micro-optical configuration (305).

19. The method of claim 18, wherein controlling the one or more particle optical elements (302) includes changing a plurality of control parameters of the particle optical elements (302) to maximize the symmetry of the diffraction pattern (2203, 2204).

20. The method of claim 18, wherein the two-dimensional particle detection sensor (2201, 2202) is located between the micro-optical configuration (305) and the object plane (101).

21. The method of claim 18, wherein the two-dimensional particle detection sensor includes a plurality of particle detection sensors in a detector system (600) of the multi-beam scanning particle imaging system (1), wherein the multi-beam scanning particle imaging system (1) is in a mirror mode to reflect at least one of the plurality of particle beams over the object plane (101).

22. The method of any one of claims 1 to 3, wherein the micro-optical configuration (305) includes a porous plate (304), and one or more pyramidal elements (2301) are included on the upstream side of the porous plate; wherein the one or more sensors include a current sensor for measuring a current generated by a plurality of particles of the polymeric particle beam (309) absorbed by the porous plate (304); wherein determining the one or more characteristics of the polymeric particle beam (309) at the micro-optical configuration (305) includes: - Focus the polymeric particle beam (309) on the plane of the porous plate (304) and scan the one or more pyramidal elements (2301); - For each of the one or more pyramidal elements (2301), determine a corresponding offset of a tip (2501) of the pyramidal element (2301) with respect to a center of the bottom (2502) of the pyramidal element (2301), as such characteristics (309) of the polymeric particle beam located at the micro-optical configuration (305).

23. The method of claim 22, wherein controlling the one or more particle optics (302) includes changing a plurality of control parameters of the particle optics (302) to minimize the one or more offsets.

24. The method of any one of claims 1 to 3, wherein the micro-optical configuration (305) includes at least one aperture plate (304) and a multi-beam multi-pole alignment element (2801) arranged parallel and spaced apart along the particle beam path, wherein the multi-beam multi-pole alignment element (2801) is located downstream of the aperture plate (304) along the particle beam path, wherein the multi-beam multi-pole alignment element (2801) includes at least one pair of opposite poles for each of the plurality of particle beams in the other set, wherein the one or more sensors include a designated particle detection sensor for each of the plurality of particle beams in the other set, which is arranged downstream of the micro-optical configuration (305) along the particle beam path, wherein determining the one or more characteristics of the converging particle beam (309) at the micro-optical configuration (305) includes: - Apply a first excitation mode to the at least one pair of opposite poles of each of the plurality of particle beams in the other group, - Apply a second excitation mode to the at least one pair of opposite poles of each of the plurality of particle beams in the other group, the second excitation mode being different from the first excitation mode, - For each of the plurality of particle beams in the other group, determine an offset between an incident point of the particle beam at a designated particle detection sensor when the first excitation mode is applied and an incident point of the particle beam at a designated particle detection sensor when the second excitation mode is applied, as such characteristics of the aggregated particle beam (309) at the micro-optical configuration (305).

25. The method of claim 24, wherein controlling the one or more particle optics elements (302) includes changing a plurality of control parameters of the particle optics elements (302) to minimize the offset.

26. The method of claim 24, wherein the multi-beam multi-pole alignment element (2801) includes at least two pairs of opposite poles for each of the plurality of particle beams in the other set, wherein applying the first excitation mode is applying the same potential to all poles; and wherein applying the second excitation mode is applying a first potential to a first pair of opposite poles of the at least two pairs of opposite poles and applying a second potential to a second pair of opposite poles of the at least two pairs of opposite poles, the second potential being different from the first potential.

27. The method of claim 24, wherein the particle detection sensor comprises at least one of a Faraday cup and a quadrant detector.

28. The method of claim 24, wherein the particle detection sensor comprises a plurality of particle detection sensors in a detector system (600) of a multi-beam scanning particle imaging system (1), wherein the multi-beam scanning particle imaging system (1) is in a mirror mode to reflect at least the other set of the plurality of particle beams (3) across the object plane (101).

29. The method of any one of claims 1 to 3 further comprises: - Remove the micro-optical configuration (305) from the particle beam path; - Move a first edge element (3202) in a first plane perpendicular to the optical axis of one of the beam generating devices (300) of the multi-beam scanning particle imaging system (1) from a position radially outside the aggregated particle beam (309) into the aggregated particle beam (309), thereby absorbing an increased portion of the aggregated particle beam (309) in the first edge element (3202), the first plane being located between the particle optical elements (302) and the object plane (101); - While moving the first edge element (3202), detect a first path (3206) of a current of a portion of the aggregated particle beam (309) not absorbed by the first edge element (3202) with one or more sensors; - Remove the first edge element (3202) from the aggregated particle beam (309); - A second edge element (3210) in a second plane perpendicular to the optical axis is moved from a position radially outside the aggregated particle beam (309) into the aggregated particle beam (309), thereby absorbing an increased portion of the aggregated particle beam (309) in the second edge element (3210). The second plane is different from the first plane and is located between the particle optical element (302) and the object plane (101); - While moving the second edge element (3210), a second path (3212) of a current of a portion of the aggregated particle beam (309) not absorbed by the second edge element (3210) is detected by the one or more sensors; - Based on the first path (3206) and the second path (3212), at least one of the following is determined: An offset value, representing an offset between a center of the aggregated particle beam (309) at the first plane and a center of the aggregated particle beam (309) at the second plane; and a width difference value, representing the difference between a width of the aggregated particle beam (309) at the first plane and a width of the aggregated particle beam (309) at the second plane.

30. The method as described in claim 29, further comprising: - Change a number of control parameters of the particle optical element (302) to minimize at least one of the offset value and the width difference.

31. The method of claim 29, wherein the one or more sensors include a Faraday cup located between the first plane and the object plane (101), and between the second plane and the object plane (101).

32. The method of claim 29, wherein the one or more sensors comprise a plurality of particle detection sensors in a detector system (600) of a multi-beam scanning particle imaging system (1), wherein the multi-beam scanning particle imaging system (1) is in a mirror mode to reflect portions of the aggregated particle beam (309) that are not absorbed by the first edge element (3202) or the second edge element (3210) across the object plane (101).

33. The method of claim 29, wherein the one or more sensors include a magnetic coil (3702) and a Faraday cup (3704), wherein the magnetic coil (3702) is located between the first plane and the object plane (101) and between the second plane and the object plane (101), wherein the magnetic coil (3702) is configured to deflect the polymer particle beam (309) to the Faraday cup (3704) located outside the optical axis.

34. The method of any one of claims 1 to 3 further comprises: - Remove the micro-optical configuration (302) from the particle beam path; - A single-aperture plate (3802) is disposed in a first plane perpendicular to the optical axis of a beam generating device (300) of the multi-beam scanning particle imaging system (1), the center of the single aperture being aligned with the optical axis, wherein the size of the single aperture corresponds to the size of the cross-section of the aggregated particle beam (309) on the first plane; - An edge element (3804) is moved in a second plane perpendicular to the optical axis, thereby absorbing an increased portion of the aggregated particle beam (309) at the edge element (3804), the second plane being different from the first plane and located downstream of the first plane; - While moving the edge element (3804), a current path of a portion of the aggregated particle beam (309) not absorbed by the edge element (3804) is detected by one or more sensors; - Based on the current path, a width of the aggregated particle beam (309) at the second plane is determined.

35. The method as described in claim 34, further comprising: - Change several control parameters of the particle optical element (302) to align the determined width with the size of the single aperture.

36. The method of claim 34, wherein the one or more sensors include a Faraday cup located between the second plane and the object plane.

37. The method of any one of claims 1 to 3, wherein the polymeric particle beam (309) has a known non-uniform intensity distribution on a cross-section in a plane perpendicular to an optical axis of a beam generating device (300) of the multi-beam scanning particle imaging system (1), the method further comprising: - Remove the micro-optical configuration (302) from the particle beam path; - Set a single-aperture plate (4302) in a first plane perpendicular to the optical axis, wherein the center of one aperture of the single-aperture plate is aligned with the optical axis, wherein the size of the single aperture is smaller than the size of the cross-section of the polymeric particle beam (309) in the first plane; - Determine a two-dimensional intensity path (4306) of the current generated by a portion of the polymeric particle beam (309) not absorbed by the single-aperture plate (4302) using a two-dimensional sensor (4310) disposed in a second plane perpendicular to the optical axis and downstream of the first plane; - Determine an offset between a known non-uniform intensity profile and a position of a corresponding intensity determined in the two-dimensional intensity path (4306).

38. The method as described in claim 37 further includes: - Change several control parameters of the particle optical element (302) to minimize the offset.

39. The method as described in claim 37 further includes: - Determine the difference between the size of a portion of the polymeric particle beam (309) in the two-dimensional intensity path (4306) that is not absorbed by the single aperture plate (4302) and the size of the single aperture plate (4302), - Change multiple control parameters of the particle optical element (302) to minimize the difference.

40. The method of any one of claims 1 to 3, wherein the polymeric particle beam (309) has a known non-uniform intensity distribution on a cross-section in a plane perpendicular to an optical axis of a beam generating device (300) of the multi-beam scanning particle imaging system (1), the method further comprising: - Using a two-dimensional sensor (3904) positioned in a plane perpendicular to the optical axis and downstream of the micro-optical configuration (302), a two-dimensional intensity path (4102) of the current generated by the plurality of particle beams is determined; - An offset is determined between a desired position of a known non-uniform intensity profile and a position of a corresponding intensity determined in the two-dimensional intensity path (4102).

41. The method as described in claim 40, further comprising: The offset is minimized by changing several control parameters of the particle optical element (302).

42. The method as described in claim 41 further includes: - Determine the difference between the size of one of the multiple particle beams in the two-dimensional intensity path (4102) and the size of a corresponding aperture in the micro-optical configuration (302) that generates the particle beam, - Change multiple control parameters of the particle optical elements (302) to minimize the difference.

43. The method of any one of claims 1 to 3, further comprising: - Remove the micro-optical configuration (302) from the particle beam path; - A diffraction element (4502) is disposed in a first plane perpendicular to the optical axis of a beam generating device (300) of the multi-beam scanning particle imaging system (1). - A two-dimensional sensor (4506) disposed in a second plane perpendicular to the optical axis and downstream of the first plane is used to determine a two-dimensional intensity path of the current generated by the aggregated particle beam (309) passing through a diffraction pattern of the diffraction element (4502).

44. The method as described in claim 43 further includes: Multiple control parameters of the particle optical element (302) are changed to maximize the symmetry of the diffraction pattern.

45. A computer program product comprising program code to perform the method as described in any one of claims 1 to 44.

46. ​​A control circuit (800) for a multi-beam scanning particle imaging system (1), the multi-beam scanning particle imaging system (1) comprising a micro-optical configuration (305) for splitting an incident aggregated particle beam (309) into a plurality of particle beams (3), the multi-beam scanning particle imaging system (1) being configured to co-scan at least one set of the plurality of particle beams (3) across an object plane (101), wherein the control circuit (800) is configured to: - acquire one or more sensor signals from one or more sensors positioned along a particle beam path of the multi-beam scanning particle imaging system (1); - determine one or more characteristics of the aggregated particle beam (309) at the micro-optical configuration (305) based on the one or more sensor signals; and - Based on one or more characteristics of the aggregated particle beam (309), one or more particle optical elements (302) of the multi-beam scanning particle imaging system (1) are controlled, wherein the one or more particle optical elements (302) are configured upstream of the micro-optical configuration (305) along the particle beam path.

47. The control circuit as claimed in claim 46, wherein the control circuit (800) is configured to perform the method as claimed in any one of claims 1 to 44.

48. A multi-beam scanning particle imaging system (1), comprising: - Control circuit (800) as described in request item 46 or 47.

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