Multi-beam particle microscope with improved beam current control

Abstract

A multi-beam particle microscope with improved beam current control is disclosed. Excess electrons discharged from one or only a few regions of an absorber layer provided on a multi-aperture array are measured using an ammeter. The measured current is used as a controlled variable in a closed-loop control. The measurement is large-area and low-noise. The multi-aperture array can be specially structured to also provide direction-sensitive detection, for example using a quadrant or tripartite detector.

Description

Technical Field

[0001] Generally, the present invention relates to a multi-beam particle microscope that operates using a plurality of individual particle beams. Specifically, the present invention relates to a multi-beam particle microscope with improved beam current control.

Background Art

[0002] With the continuous progress of miniaturized and complex microstructures such as semiconductor components, there is a need to develop and optimize planar manufacturing technologies for manufacturing microstructures and inspection systems for inspecting micro dimensions. For example, the development and manufacturing of semiconductor components require monitoring the design of test wafers, and planar manufacturing technologies require process optimization for reliable manufacturing with high throughput. In addition, there is a recent need for the analysis of semiconductor wafers for reverse engineering and for customer-specific individual configurations of semiconductor components. Therefore, there is a need for inspection means that can be used with high throughput to examine microstructures on wafers with high accuracy.

[0003] Typical silicon wafers used in the manufacture of semiconductor components have a maximum diameter of 300 mm. Each wafer has a maximum of 800 mm 2It is subdivided into 30 to 60 repetitive regions (“dies”) of the size. The semiconductor device includes a plurality of semiconductor structures, which are manufactured by forming layers on the surface of the wafer by planar integration technology. The semiconductor wafer typically has a flat surface due to the manufacturing process. In this case, the structure size of the integrated semiconductor structure ranges from several μm to 5 nm, which is the critical dimension (CD), but the structure size will be further miniaturized in the near future. In the future, it is expected that the structure size or the critical dimension (CD) will be less than 3 nm, for example 2 nm, or even less than 1 nm. In the case of the above micro-structure size, defects of the size of the critical dimension need to be quickly identified over a very wide area. In some applications, the specification requirements for the measurement accuracy provided by the inspection device are, for example, two digits or one digit higher. For example, the width of the semiconductor feature needs to be measured with an accuracy of less than 1 nm, for example 0.3 nm or even finer, and the relative position of the semiconductor structure needs to be determined with an overlay accuracy of less than 1 nm, for example 0.3 nm or even finer.

[0004] The MSEM, i.e., the multi-beam scanning electron microscope, is the result of a relatively new advancement in the field of charged particle systems (charged particle microscopes (CPMs)). For example, the multi-beam scanning electron microscope is disclosed in U.S. Patent No. 7,244,949 B2 and U.S. Patent Application Publication No. 2019 / 0355544. In the case of a multi-beam electron microscope or MSEM, a plurality of individual electron beams arranged in a field of view or raster are simultaneously irradiated onto a sample. For example, 4 to 10,000 individual electron beams can be provided as a primary irradiation, and each individual electron beam is separated from an adjacent individual electron beam by a pitch of 1 to 200 micrometers. For example, the MSEM has approximately 100 separated individual electron beams (“beamlets”), which are arranged, for example, in a hexagonal raster, and the individual electron beams are separated by a distance of approximately 10 μm. A plurality of charged individual particle beams (primary beams) are individually focused onto the surface of the sample to be inspected each time using a common wide-field optical system, particularly a common objective lens. For example, the sample can be a semiconductor wafer fixed to a wafer holder assembled on a movable stage. During the irradiation of the wafer surface by the charged primary individual particle beams, interaction products, such as secondary electrons or backscattered electrons, are emitted from the surface of the wafer. Each of their starting points corresponds each time to a location on the sample where a plurality of primary individual particle beams are focused. The amount and energy of the interaction products depend in particular on the material composition and topography of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are collected by a common objective lens and incident on a detector arranged on a detection surface as a result of the projection imaging system of the multi-beam inspection system. The detector includes a plurality of detection regions each including a plurality of detection pixels, and the detector captures the intensity distribution of each of the secondary individual particle beams. An image field of, for example, 100 μm × 100 μm is obtained in this process.

[0005] Conventional multi-beam electron microscopes include a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjusted to adapt the focal positions and spherical aberrations of the plurality of charged individual particle beams. Conventional charged particle multi-beam systems further include at least one crossover plane of the primary or secondary charged individual particle beams. The conventional system also includes a detection system to facilitate adjustment. Conventional multi-beam particle microscopes include at least one beam deflector ("deflection scanner") for collectively scanning a region of the sample surface using a plurality of primary individual beams to acquire an image field of the sample surface. Further details regarding multi-beam electron microscopes and methods of operating them are described in the German patent application with application number 102020206739.2 filed on May 28, 2020, the disclosure of which is hereby incorporated by reference in its entirety into this patent application.

[0006] As the requirements for imaging quality increase, so do the requirements for multi-beam particle microscopes used for imaging. Stable operating parameters are extremely important for high-quality recording. One of these is the beam current intensity of the individual particle beams used to scan the sample surface.

[0007] For a uniform beam current intensity of an individual particle beam, the radiation characteristics of the particle beam source, more precisely the uniformity of the radiation characteristics over the entire radiation angle used, are important. When using a relatively large radiation angle, the radiation characteristics of the particle source, such as a thermionic field emission (TFE) source, become non-uniform over the whole. Consequently, the irradiance in the first multi-aperture plate in the corresponding particle beam system also becomes non-uniform over the whole, and there is a relatively large variation in the current density in different individual beams. However, in the case of a multi-particle inspection system, it is a system requirement that there is only a slight variation in the current intensity between different individual beams, typically less than a few percent, and even less than 1 percent, so that all individual image fields of the multi-image field are scanned with an equal number of particles or electrons. For example, this is a prerequisite for obtaining individual images with approximately the same brightness. The achievable resolution of the individual images also depends on the individual beam current.

[0008] There are multiple options for individually adjusting the beam current of an individual particle beam. One option in this regard is disclosed in German Patent Application Publication No. 102018007652A1, the disclosure of which is hereby incorporated by reference in its entirety into this patent application.

[0009] The radiation characteristics of the particle source also gradually change over time and may exhibit a drift behavior as a whole. The particle source or the tip may deteriorate over time, for example, the brightness may decrease. The brightness of the image is further correlated with the brightness or luminance of the particle source. If the brightness of the particle source decreases, this also applies to the brightness of the image. Also, for example, the particle beam initially emitted from the particle source may change its direction. Therefore, when scanning a sample with a plurality of individual charged particle beams or beamlets, it is desirable to take means that enable providing a more stable and uniform beam current.

[0010] This is particularly true when the requirements for a stable beam current are even higher. Usually, the beam current stability of a multi-beam particle microscope has been regarded as sufficiently stable when the relative variation of the beam current with respect to the reference beam current is ≤ 10% or ≤ 5% over 1 hour. In future measurement operations, such stability is no longer considered sufficient. Higher requirements need to be met, and the relative beam current variation with respect to the reference beam current of a multi-beam charged particle microscope needs to be ≤ 1% for at least 1 month.

[0011] The state of the art discloses several principles for measuring or monitoring the beam current and for controlling the beam current respectively. However, with regard to the higher requirements for beam current stability, it has been found that the existing solutions are not sufficient and need to be improved.

[0012] U.S. Patent Application Publication No. 2020 / 0312619 discloses a system and method for measuring beam current in a multi-beam device that can be a multi-beam particle microscope. This multi-beam particle microscope includes a charged particle beam source configured to generate a primary charged particle beam and a multi-aperture array. The multi-aperture array includes a plurality of apertures configured to form a plurality of beamlets from the primary charged particle beam and a detector including a circuit for detecting at least a portion of the current of the primary charged particle beam irradiating the multi-aperture array. More specifically, a plurality of micro-detectors having circuits are provided in tiny additional holes provided above the multi-aperture array. These holes are associated with specific apertures, and thus are tiny and provided in the vicinity of the specific apertures. These holes are provided within the aperture array, directly at the boundary of the array, and in contact with the theoretical circumferential region of the array. Examples of detectors with circuits are Faraday cups, diodes, arrays of diodes, scintillators, or photomultiplier tubes. The detector with a circuit is used to monitor the current incident on the detector, and the total current can be determined from the measurement. Also, it is possible to detect changes in current, such as beam position, beam diameter, the beam current itself, beam current density, and uniformity of beam current density. These changes can be corrected by controlling the extraction voltage, accelerating voltage, beam deflection voltage, etc.

[0013] U.S. Patent Application Publication No. 2020 / 0312619 has several drawbacks. That is, the overall sensitivity of beam current detection is limited due to the narrow area used for a single detection. Assuming that the surface area of the detector is comparable to the area of the aperture that generates the beamlets, the beam current measured by the detector is on the same order as a single beam current passing through the associated aperture. Typically, this single beam current is on the order of several hundred picoamperes, which is a rather low order. Therefore, it is even more difficult to detect variations significantly smaller than 1%, and the signal-to-noise ratio of a detector with such a tiny entrance surface is relatively high. Also, the boundaries of the detector incorporated within the holes of the multi-aperture plate can cause problems due to cumulative changes that can adversely affect the beam direction and beam quality of the beamlets. Furthermore, the manufacture of the micro-detector is complex. Thus, overall, the detection system according to U.S. Patent Application Publication No. 2020 / 0312619 is not suitable for measurement operations that require beam current stability better than 1% over a period of one month or even longer.

[0014] U.S. Patent No. 6,969,862 B2 discloses a beam current detector for a lithography system. This patent discloses a multi-beam device including a charged particle source configured to generate a primary charged particle beam and an aperture array. The aperture array includes a plurality of apertures configured to form a plurality of beamlets from the primary charged particle beam, and a detector coupled to a circuit and configured to detect at least a part of the current of the primary charged particle beam irradiating the aperture array. The detector is disposed on the beam exit side of the aperture array with respect to the primary charged particle beam. Therefore, the multi-beam device according to U.S. Patent No. 6,969,862 B2 is very similar to the multi-beam device according to U.S. Patent Application Publication No. 2020 / 0312619 cited above. The difference between these two published documents is that the detector is located on the beam entrance side according to U.S. Patent Application Publication No. 2020 / 0312619, but is located on the beam exit side according to U.S. Patent No. 6,969,862 B2. However, since the detected beam current enters a hole specifically provided on the beam entrance side of the multi-aperture array in both cases and is then directly detected by a detector equipped with a circuit, the measurement principle is the same in both cases. Therefore, the detection system according to U.S. Patent No. 6,969,862 B2 is also not suitable for measurement operations that require a beam current stability better than 1% over a period of one month or even longer.

[0015] U.S. Patent No. 7,388,214 B2 discloses a charged particle beam exposure apparatus that divides a charged particle beam from a charged particle beam source into a plurality of charged particle beams by a plurality of apertures formed in an aperture array shape for exposing a wafer using a plurality of charged particle beams. This apparatus includes a stage for loading a wafer irradiated with a plurality of charged particle beams that have passed through the apertures of the aperture array, and a plurality of detection electrodes for detecting the intensities of the plurality of charged particle beams that pass through the plurality of apertures of the aperture array to expose the wafer, the detection electrodes being formed on the charged particle beam source side of the light-shielding peripheral regions of the plurality of apertures of the aperture array, and a grid array (including grid electrodes) for adjusting the intensities of the plurality of charged particle beams based on the detection results obtained by the plurality of detection electrodes. The detection system according to U.S. Patent No. 7,388,214 B2 is also not suitable for measurement operations that require beam current stability better than 1% over a period of one month or longer. Since each detection electrode provided on the electrode pad is preferably assigned to one aperture, in this case too, the detection area is extremely small, and thus the signal-to-noise ratio of the beam current measurement is relatively small. The assignment of several detection electrodes to one pad is also disclosed, and it is taught that this will improve the detection accuracy. However, on the other hand, this assignment has the disadvantage that the same control voltage is applied to the grid electrodes as a result of the common wiring of the pads, so the accuracy of a specific control using the grid electrodes is reduced. Therefore, the area used for detection has to remain small overall as a trade-off. Also, there is a risk that any active influence on the beamlets using the charge on the multi-aperture array will further affect the beamlet quality. From a manufacturing perspective, U.S. Patent No. 7,388,214 B2 is also quite complex.

[0016] U.S. Patent No. 9,607,806 B2 discloses a multi-beam lithography system having a detector for beam control provided at a specific position above a multi-aperture array. The detector can measure the beam current when the beam is deflected or blanked.

[0017] U.S. Patent No. 6,617,587 B2 discloses a multi-beam lithography system. It has a tip adjustment circuit with a current collection region on a single aperture plate, which is part of the electron gun itself and is provided separately for each of the plurality of beams.

[0018] U.S. Patent No. 5,111,053 A discloses the control of a liquid metal ion source by analog feedback and digital CPU control. This document relates to a single-beam system. A monitoring electrode is applied to measure the beam current, and the extraction voltage of the particle source is adjusted.

[0019] U.S. Patent No. 7,091,486 B1 first describes the prior art for correcting beam current fluctuations in a single-beam system. The prior art for correcting the described beam current fluctuations uses a circuit connected to a beam aperture to measure the current from the aperture. This current is due to electrons being absorbed by the aperture. From the measured current, the beam current can be estimated. The change in the measured current is used to estimate the change in the beam current. This prior art is taught to be suitable for detecting fluctuations only within a limited frequency bandwidth. In particular, it is said to have problems detecting high-frequency (e.g., above a few kilohertz) fluctuations. This bandwidth limitation is said to be due to the low current levels and high stray capacitances in this prior art. Therefore, U.S. Patent No. 7,091,486 B1 teaches using a fast detector mounted above the aperture to collect and measure secondary and / or backscattered electrons. Secondary and / or backscattered electrons are emitted due to the collision of a part (the blocked part) of the primary beam with the aperture. Fast electron detectors include, for example, Everhart-Thornley detectors, PIN diode-based detectors, and microchannel plate detectors. SUMMARY OF THE INVENTION

[0020] Accordingly, an object of the present invention is to provide a multi-beam particle microscope having improved beam current stability, which will be suitable for measurement operations requiring beam current stability better than 1% over a period of one month or even longer. The mechanism for implementing each feedback control is easy to manufacture and implement.

[0021] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention will become apparent from the dependent claims.

[0022] This patent application claims the priority of German Patent Application No. 102021118561.0 filed on July 19, 2021, the entire disclosure of which is incorporated herein by reference.

[0023] According to a first aspect of the present invention, the present invention is a multi-beam particle microscope, including a particle source, an extractor electrode, and an anode, and a beam generating system configured to generate a first charged particle beam, a multi-beam generator having a multi-aperture array, configured to generate a first field of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array including an absorption layer for absorbing charged particles on its upper side, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the multi-beam generator, a first beam current measuring means configured to at least measure discharged excess electrons generated by charged particles colliding with the multi-aperture array over a wide area in an outer region surrounding all of the openings in the multi-aperture array, A condenser lens system disposed between the beam generation system and the multi-beam generator, A first particle optical unit having a first particle optical beam path configured to direct a first individual particle beam toward a sample such that the generated first individual particle beam impinges on the sample at incidence locations that form a second field of view, A detection system, A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from an incidence location within the second field of view onto the detection system, A particle optical objective lens through which both the first and second individual particle beams pass, A beam switch disposed in the first particle optical beam path between the multi-beam generator and the objective lens and in the second particle optical beam path between the objective lens and the detection system, Including a beam generation system, a condenser lens system, a particle optical objective lens, a first particle optical unit, a second particle optical unit, and a controller configured to control the beam generation system, the condenser lens system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system, The controller is configured to control the beam generation system based on measurements using a first beam current measuring means and / or The controller is configured to control the condenser lens system based on measurements using a first beam current measuring means, relating to a multi-beam particle microscope.

[0024] The individual charged particle beam can be, for example, an electron, a positron, a muon or an ion, or other charged particles.

[0025] The multi-aperture array is preferably downstream of the condenser lens system in the particle optical beam path of the multi-beam particle microscope InitialIt is an array arranged as a multi-aperture array. This multi-aperture array is preferably an array that divides a first charged particle beam into a plurality of individual charged particle beams. In this case, the multi-aperture array is preferably a component of what is called a micro-optical system, which preferably consists of or includes a series of a plurality of multi-aperture plates or multi-aperture arrays (these two expressions are used as synonyms within this patent application). In this context, for good image quality, the first charged particle beam emitted from the particle source or tip needs to be incident on the multi-aperture array uniformly, particularly as perpendicularly as possible, and it is also necessary to irradiate the multi-aperture array so as to be located as uniformly or centered as possible. In that case, it is possible to ensure that the beam current of the individual particle beams passing through the multi-aperture array is sufficiently uniform in the individual particle beams. Uniform irradiation is achievable not only in the case of telecentric incidence of the first charged particle beam on the multi-aperture array, but also in the case of divergent incidence or convergent incidence, and in any case where the central beam axis is aligned perpendicular to the surface of the multi-aperture array. Here, the apertures in the multi-aperture array are preferably circular, but may have other shapes. Preferably, the apertures in the multi-aperture array have a regular arrangement, such as a rectangular, square or hexagonal arrangement. In the case of a hexagonal arrangement, preferably 3n(n - 1)+1 apertures are provided, where n is any natural number.

[0026] The multi-aperture array or multi-aperture plate includes, on its upper side, an absorption layer capable of absorbing electrons. Preferably, the absorption layer is provided on substantially the entire surface of the multi-aperture array (naturally excluding the apertures), and thus is provided not only in the inner region including the apertures, but also in the outer region around all the apertures within the multi-aperture array. Also, such an absorption layer is provided in existing multi-beam particle microscopes of the current state of the art. This ensures that no charge that would significantly degrade the beam quality of the first individual particle beam accumulates on the surface of the multi-aperture array.

[0027] This measurement system can be calibrated based on an individual particle beam that is measured using, for example, a movable stage and, for example, a Faraday cup thereon. Other embodiments, variations, and calibration methods are also conceivable.

[0028] According to the present invention, there is provided first beam current measuring means configured to measure at least discharge excess electrons generated by charged particles colliding with a multi-aperture array in an outer region surrounding all of the apertures in the multi-aperture array over a wide area. Different from the prior art directed to multi-beam particle devices, the measurement is performed over a wide area and not within the narrow area typically used when separate detectors are arranged on the multi-aperture array. By expanding the area, the signal-to-noise ratio at the time of detection is significantly improved. Also, surprisingly, in the measurements of the present inventors, it has been found that any variation in the signal obtained by measuring over a wide area in the outer region surrounding all of the apertures in the multi-aperture array reflects the beam current variation of the individual particle beam. Therefore, the measurement over a wide area is not an averaging that covers the larger fluctuations of the beam current of the individual charged particle beam. This discovery is extremely important and represents a conceptual change with respect to the prior art where the main focus is placed on measuring the beam current as precisely as possible separately for each individual particle beam. Surprisingly, such separate measurements for each individual particle beam are unnecessary.

[0029] Furthermore, the first beam current measuring means according to the present invention does not require a separate detection device that needs to be incorporated on the multi-aperture array, and thus there is no need to provide a specific circuit. Therefore, the solution according to the present invention is extremely simple and thus makes the manufacture of the multi-aperture array extremely easy. Any detection device, typically an ammeter, especially a picoammeter, can be provided at a distance from the multi-aperture array. There is no need to provide an ammeter inside the vacuum provided within the multi-beam particle microscope, and the ammeter can be provided outside the vacuum.

[0030] Also, the measurement principle is different from the measurement principle applied to multi-beam devices according to the state of the art. According to the state of the art, the particles measured by detectors separately provided on the multi-aperture array are the particles that collide with the multi-aperture array, or more precisely, the particles that collide with the positions where the detectors are provided. In contrast, according to the present invention, the excess electrons measured are at least not directly the collision charged electrons, and they can be transported and "converted", and nevertheless these electrons serve as a measure of the collision charged particles. This becomes clear when the multi-beam particle microscope operates using ions and does not operate using electrons. Ions are too large to be absorbed by the absorption layer but do adhere to the surface of the absorption layer. Ions emit electrons, and these electrons can be transported and discharged, or an equal number of existing electrons can be discharged.

[0031] According to the present invention, at least the discharge excess electrons generated by charged particles colliding with the multi-aperture array are measured over a larger area in the outer region around the entire periphery of the apertures in the multi-aperture array. The entire outer region around the apertures provides such a large area. A part of the outer region can also provide a large area, and thus an improved signal-to-noise ratio for detection can be achieved. Also, the measurement based on the colliding particles in the outer region can indicate the position shift of the entire beam cone of the first charged particle beam.

[0032] According to one embodiment, the first beam current measuring means is configured to also measure the discharge excess electrons generated by the charged particles colliding with the multi-aperture array in the inner region including the apertures in the multi-aperture array. The measurement of the excess electrons emitted from the inner region and the outer region can be performed as an overall excess electron measurement by one ammeter. In this case, the interaction region for the measurement is maximized and the signal-to-noise ratio is optimal. However, in this case, the position deviation of the entire first charged particle beam cannot be detected separately. However, this embodiment is the easiest to implement in an existing system.

[0033] The first beam current measuring means according to the present invention can, in principle, be implemented as a control loop already known from the state of the art in this case. The controller can be configured to control the beam generation system, for example, based on the measurement using the first beam current measuring means. In addition to or instead of this, the controller can be configured to control the condenser lens system based on the measurement using the first beam current measuring means. Other types of control embodiments are also possible. The beam current measuring means can be calibrated, for example, based on the individual particle beam measured using a movable stage and, for example, a Faraday cup thereon. Other embodiment variations and calibration methods are also conceivable.

[0034] According to one embodiment, the absorption layer on the multi-aperture array is structured into exactly two separate regions that are separated from each other and each region is connected to ground, with the first region being the inner region that includes the apertures of the multi-aperture array and the second region being the outer region surrounding all of the apertures in the multi-aperture array, and the first beam current measuring means is configured to measure only the excess electrons discharged from the outer region. Preferably, the inner region and the outer region are complementary regions on the multi-aperture array. In other words, the entire surface of the multi-aperture array consists of the inner region and the outer region. Measuring the excess electrons discharged from the outer region is sufficient to measure and thus control the fluctuations in the beam current of the individual charged particle beam. The inner region is not inhibited at all by any measurement or any structuring of the absorption layer, and thus the beam quality of the individual particle beam can be maintained in its best state.

[0035] According to one embodiment, the absorption layer on the multi-aperture array is structured into at least two separate regions that are separated from each other and each region is connected to ground, and the first beam current measuring means is configured to measure the excess electrons discharged separately from each region over a wide area. Thus, the structuring of the absorption layer is limited to segments such that sufficiently wide separate regions are still created. This is necessary to ensure a good signal-to-noise ratio for the measurement. According to a preferred embodiment, the entire structuring divides the absorption layer into a maximum of five or six separate regions.

[0036] According to one embodiment, the absorption layer is structured into an inner region including the openings of the multi-aperture array and an outer region surrounding all of the openings in the multi-aperture array. The outer region is further structured into four separate regions arranged to form a direction indicating quadrant detector, and the first beam current measuring means is configured to measure excess electrons discharged separately from each quadrant over a wide area. Preferably, the inner region is not structured at all and is left completely as it is. Excess electrons discharged from the inner region can be optionally measured. The term quadrant detector refers to the entire mechanism consisting of separate regions suitable for indicating the direction of movement of the beam cone impinging on the multi-aperture array. The size of each quadrant is preferably selected to be approximately the same, but depending on the specific arrangement of the openings in the multi-aperture plate that gives rise to a particular geometry of the envelope around the openings, certain deviations may be advantageous. This envelope can define the boundary between the inner region and the outer region and can be used for structuring and separation.

[0037] According to another embodiment, the absorption layer is structured into an inner region and an outer region, and the outer region is further structured into three separate regions arranged to form a direction indicating tertial detector, and the first beam current measuring means is configured to measure excess electrons discharged separately from each tertial region. The arrangement of the three separate regions of the tertial detector is derived from the triangular arrangement of the separate detection regions. After the calibration process, if there is a deviation detected using one of the three separate regions, it may well indicate a positional deviation and, in principle, enables the analysis of the type of positional deviation. The use of the direction indicating tertial detector is advantageous in that the number of region structures / separations is further limited, thus further minimizing the influence of the accumulated charge on the multi-aperture array surface on the beam current quality. The inner region is preferably not structured at all and is left completely as it is. Excess electrons discharged from the inner region can be optionally measured.

[0038] According to a preferred embodiment of the present invention, the multi-beam particle microscope further includes a double deflector in the region of the condenser lens system, and the controller of the multi-beam particle microscope is further configured to control the double deflector based on measurements using beam current measuring means. The double deflector is preferably an electrostatic double deflector that can be operated at high speed compared to a magnetic double deflector. However, a magnetic double deflector is also feasible. The double deflector can shift the entire first charged particle beam in parallel, and thus can correct the positional deviation of the beam cone colliding with the multi-aperture array.

[0039] In principle, the first beam current measuring means can include one or more components. According to a very clear and simple embodiment, the first beam current measuring means includes only one component. In the case of several components, it is preferable that they are the same, but they may be different from each other.

[0040] According to a preferred embodiment, the first beam current measuring means includes at least one ammeter, particularly a picoammeter. The picoammeter is extremely sensitive and can also detect even very small fluctuations in the provided excess electrons, which are a measure of the beam current.

[0041] According to a preferred embodiment, at least 60% of the beam current reaching the multi-aperture array is used for beam current measurement. Thereby, since measurement over a wide area is performed, a good signal-to-noise ratio can be ensured.

[0042] According to a preferred embodiment, at least 90%, preferably at least 95%, of the beam current reaching the multi-aperture array is used for beam current measurement. The above values are typically achieved when an absorption layer is provided on the entire surface of the multi-aperture array and all excess electrons that are discharged and transported to the ground electrode are measured. This can be done using one measurement device such as a picoammeter, or using several measurement devices, for example several picoammeters.

[0043] According to one embodiment, the active beam measurement surface of the absorption layer that absorbs charged particles and discharges electrons therefrom for beam current measurement is at least 60% of the entire surface of the multi-aperture array. Preferably, the active beam measurement surface is at least 90%, more preferably 95%, of the entire surface of the multi-aperture array. There is a difference between referring to the active beam measurement surface and referring to the beam current reaching the multi-aperture array. The active beam measurement surface is fixed by design, for example, by providing an absorption layer and a connection to ground via, for example, a current meter. In contrast, the ratio of the beam current reaching the multi-aperture array depends on the operating settings of the multi-beam particle microscope, for example, on the set beam diameter of the first charged particle beam. In either case, the above preferred embodiment ensures that the measurement using the first beam current measurement means is performed over a wide area, thus ensuring a good signal-to-noise ratio.

[0044] According to a preferred embodiment, the average single beam current of the plurality of first individual particle beams is 1 / 100 or less of the total beam current measured by the first beam current measuring means, preferably, the average single beam current of the plurality of first individual particle beams is 1 / 500 or less of the total beam current measured by the first beam current measuring means, and even more preferably 1 / 1000 or less. Therefore, the generated signal is much larger than the single beam current, which contributes to an extremely good signal-to-noise ratio as required. By way of example, a typical single beam current is on the order of several hundred picoamperes, for example 500 or 600 or 700 picoamperes. The total beam current measured using excess charge is in the range of, for example, 500, 600 or 700 nanoamperes. However, the single beam current and the total current generated by the measured excess electrons can be either larger or smaller, for example, in the case of a single beam current, it can be only several tens of picoamperes, and in the case of excess electrons, it can be only several tens of nanoamperes. However, a larger single beam current of up to several nanoamperes is also possible, and a beam current of several microamperes measured using excess electrons is also possible.

[0045] According to one embodiment, the absorption layer is an absorbent coating and / or the absorption layer comprises or consists of any one of gold, silver, titanium, and platinum. These are excellent conductors and are not easily oxidized. In principle, noble metals are preferred.

[0046] According to one embodiment, the multi-aperture array is arranged as the multi-aperture array downstream of the condenser lens system Initial and is an array that divides the first charged particle beam into a plurality of first charged particle beams. Alternatively, the multi-aperture array is not arranged as the multi-aperture array downstream of the condenser lens system Initial This variation can typically occur when a series of aperture plates, particularly a series of multi-aperture arrays, are provided.

[0047] According to one embodiment, the controller is configured to control the beam generation device by setting the voltage supplied to the extractor electrode. This type of control is already known in principle from the art.

[0048] According to one embodiment, the controller is configured to control the beam generation device by setting the temperature of the particle source, in particular by setting the heating current or heating voltage. This type of control is slightly slower than, for example, setting the voltage supplied to the extractor electrode, but this type of control is sufficient and it has also been found to be easy to reliably implement during the switch-on and off procedures.

[0049] According to a second aspect of the invention, the invention is a multi-beam particle microscope, a beam generation system including a particle source, an extractor electrode, and an anode, configured to generate a first charged particle beam, a multi-beam generator having a pre-aperture plate and a multi-aperture array, configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array being disposed downstream of and in the vicinity of the pre-aperture plate, the multi-aperture array including an absorption layer on its upper side for absorbing charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the pre-aperture plate including a pre-aperture plate absorption layer on its upper side for absorbing charged particles, the pre-aperture plate absorption layer being connected to at least one ground electrode for discharging excess electrons, first beam current measuring means configured to at least measure the discharge excess electrons generated by the charged particles colliding with the pre-aperture plate, a condenser lens system disposed between the beam generation system and the multi-beam generator, A first particle optical unit having a first particle optical beam path configured to direct a first individual particle beam toward a sample such that the generated first individual particle beam strikes the sample at an incident position forming a second field of view; A detection system; A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from an incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and in the second particle optical beam path between the objective lens and the detection system; A controller configured to control the beam generation system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system, comprising: The controller is configured to drive the beam generation system based on measurements using first beam current measuring means and / or; The controller is configured to control the condenser lens system based on measurements using first beam current measuring means, relating to a multi-beam particle microscope.

[0050] As already mentioned above, the multi-beam generator can include a series of aperture plates and multi-aperture plates, which can be part of a so-called micro-optical system. One feature of the invention according to the first aspect is that the excess electrons generated by the colliding particles in the outer region of the multi-aperture array are used for beam current measurement. Of course, it is also possible to arrange a pre-aperture plate, which means a plate having only a single central opening directly above / upstream of the outer region of the multi-aperture array, and it is possible to perform measurements based on the excess electrons discharged from this pre-aperture plate. The embodiment variations described for the first aspect of the invention can be transferred to the embodiment variations according to the second aspect of the invention. In particular, the absorption layer provided on the pre-aperture plate can be structured into a region that enables measurements over a wide area as detailed for the first aspect of the invention. Of course, it is also possible to additionally perform measurements of the excess electrons generated by the charged particles colliding with the multi-aperture array. Usually, this will coincide with the measurements in the inner region of the multi-aperture array as described above for the first aspect of the invention. Unless a technical contradiction occurs, the embodiments of the invention according to the first aspect and the embodiments of the invention according to the second aspect can be combined in whole or in part with each other.

[0051] In this context, the invention will be better understood with reference to the accompanying drawings.

Brief Description of the Drawings

[0052]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0053] FIG. 1 is a schematic diagram of a particle beam system 1 in the form of a multi-beam particle microscope 1 using a plurality of particle beams. The particle beam system 1 generates a plurality of particle beams that strike an object to be inspected in order to generate interaction products, such as secondary electrons, that are emitted from the object and then detected. The particle beam system 1 is of a scanning electron microscope (SEM) type that uses a plurality of primary particle beams 3 that are incident on the surface of an object 7 at a plurality of positions 5 and generate a plurality of electron beam spots, or spots, that are spatially separated from each other there. The object 7 to be inspected can be of any desired type, such as a semiconductor wafer or a biological sample, and can include an arrangement such as microelements. The surface of the object 7 is disposed on the first surface 101 (objective surface) of the objective lens 102 of the objective lens system 100.

[0054] FIG. 1 shows an enlarged excerpt I1 of FIG. 1, which is a plan view of an objective surface 101 having a square field of view 103 at an incident position 5 formed on a first surface 101. In FIG. 1, the number of incident positions is 25, which forms a 5×5 field of view 103. The number 25 of incident positions is a number selected for the sake of a simplified figure. In reality, the number of beams, and thus the number of incident positions, can be selected to be a much larger number, such as 20×30, 100×100, etc.

[0055] In the illustrated embodiment, the field of view 103 at the incident position 5 is substantially square with a constant pitch P1 between adjacent incident positions. Examples of values of the pitch P1 are 1 micrometer, 10 micrometers, and 40 micrometers. However, for example, the field of view 103 can also have other symmetric shapes, such as hexagonal symmetry.

[0056] The diameter of the beam spot formed within the first surface 101 can be made very small. Examples of values of this diameter are 1 nanometer, 5 nanometers, 10 nanometers, 100 nanometers, and 200 nanometers. The focusing of the particle beam 3 for forming the beam spot 5 is performed by the objective lens system 100.

[0057] The primary particles hitting the object generate interaction products, such as secondary electrons, backscattered electrons, or primary particles whose movement is reversed for other reasons, emitted from the surface of the object 7 or from the first surface 101. The interaction products emitted from the surface of the object 7 are shaped by the objective lens 102 to form a secondary particle beam 9. The particle beam system 1 provides a particle beam path 11 for guiding a plurality of secondary particle beams 9 to the detector system 200. The detector system 200 includes a particle optical unit having a projection lens 205 for directing the secondary particle beam 9 towards the particle multi-detector 209.

[0058] FIG. 1 shows a plan view of a plane 211 in which an individual detection region of a particle multi-detector 209 where a secondary particle beam 9 is incident on a position 213 is located in an extract view I2. The incident position 213 is within a field of view 217 having a regular pitch P2 from each other. Examples of values of the pitch P2 are 10 micrometers, 100 micrometers, and 200 micrometers.

[0059] The primary particle beam 3 is generated by a beam generator 300 including at least one particle source 301 (e.g., an electron source), at least one collimation lens 303, a multi-aperture array 305, and a field lens 307. The particle source 301 generates a divergent particle beam 309, which is collimated or at least substantially collimated by the collimation lens 303 to form a beam 311 that irradiates the multi-aperture array 305.

[0060] FIG. 1 shows a plan view of the multi-aperture array 305 in an extract view I3. The multi-aperture array 305 includes a multi-aperture plate 313 having a plurality of openings or apertures 315 formed therein. The midpoints 317 of the apertures 315 are arranged within a field of view 319 that is imaged onto a field of view 103 formed by the beam spot 5 on the objective plane 101. The pitch P3 between the midpoints 318 of the apertures 315 can have examples of values of 5 micrometers, 100 micrometers, and 200 micrometers. The diameter D of the aperture 315 is smaller than the pitch P3 between the midpoints of the apertures. Examples of values of the diameter D are 0.2×P3, 0.4×P3, and 0.8×P3.

[0061] The particles of the irradiated particle beam 311 pass through the apertures 315 to form the particle beam 3. The particles of the irradiated beam 311 that hit the plate 313 are absorbed by the plate 313 and do not contribute to the formation of the particle beam 3.

[0062] The multi-aperture array 305 focuses each of the particle beams 3 by means of an inca electrostatic field so that a beam focus 323 is formed within the plane 325. Alternatively, the beam focus 323 can be virtual. The diameter of the beam focus 323 can be, for example, 10 nanometers, 100 nanometers, and 1 micrometer.

[0063] The field lens 307 and the objective lens 102 provide a first imaging particle optical unit for imaging the plane 325 in which the beam focus 323 is formed onto the first surface 101 such that the incident position 5 or the field of view 103 of the beam spot occurs there. When the surface of the object 7 is disposed on the first surface, the beam spot is correspondingly formed on the objective surface.

[0064] The objective lens 102 and the projection lens array 205 provide a second imaging particle optical unit for imaging the first surface 101 onto the detection surface 211. Thus, the objective lens 102 is a lens that is part of both the first and second particle optical units, while the field lens 307 belongs only to the first particle optical unit and the projection lens 205 belongs only to the second particle optical unit.

[0065] A beam switch 400 is disposed between the multi-aperture array 305 and the objective lens system 100 in the beam path of the first particle optical unit. The beam switch 400 is also part of the second optical unit in the beam path between the objective lens system 100 and the detector system 200.

[0066] Further information regarding such multi-beam particle beam systems and components used therein, such as particle sources, multi-aperture plates and lenses, can be obtained from international patent applications WO2005 / 024881A2, WO2007 / 028595A2, WO2007 / 028596A1, WO2011 / 124352A1 as well as WO2007 / 060017A2, and German patent application publications No. 102013016113 and No. 102013014976, the disclosures of which are incorporated herein by reference in their entireties.

[0067] Figure 2 schematically shows the beam current measurement. The multi-aperture array 304 is shown in cross-section. The multi-aperture array 304 includes, on its upper side, an absorption layer 341 capable of absorbing charged particles. In the illustrated embodiment, the entire upper side of the multi-aperture array 304 is covered by the absorption layer 341. In this embodiment, the multi-aperture plate is downstream of a condenser lens system (not shown in FIG. 2) InitialIt is arranged as a multi-aperture array. The illumination particle beam 311 is incident on the multi-aperture array 304. Most of the incident particles of the illumination particle beam 311 collide with the absorption layer 304a, and a small portion of all the particles pass through the apertures 304a, thus generating a plurality of first individual charged particle beams 3. A part of the illumination particle beam 311 collides with the outer region 366 of the multi-aperture array 304. As an example, in FIG. 2, the particle beam 311Bb is shown. Another part of the illumination particle beam 311 collides with the multi-aperture array 304 in the inner region 367. A part of these particles is shown as an example by reference numeral 311a in FIG. 2. In this embodiment, the multi-aperture array 304 is not structured. Therefore, all the particles that collide with the absorption layer 341 are discharged from the absorption layer 341 to generate excess electrons that are measured by the first beam current measuring means 370 realized as a picoammeter in this example. The measured value is transmitted to the controller 10 and is used, for example, to control the voltage applied to the extractor electrode of a beam generation system or for control by setting the temperature of the particle source. Other control loops are also possible.

[0068] In the illustrated embodiment, only one picoammeter positioned between the connection to the absorption layer 341 and the ground electrode is applied. Therefore, the entire area of the absorption layer 341 contributes to the measured value, which includes the measurement of the discharge excess electrons generated by the charged particles that collide with the multi-aperture array 304 in the outer region 366 and the inner region 367. The illustrated measurement principle is a measurement over a wide area that ensures a very good signal-to-noise ratio. In the illustrated embodiment, the average single beam current of the plurality of first individual particle beams 3 is 1 / 1000 or less of the total beam current measured by the first current measuring means 370. It should be noted that the dimensions in FIG. 2 are not to scale.

[0069] Figure 3 schematically shows a multi-aperture array 304 having an absorption layer 341 on the upper side. In FIG. 3a, the multi-aperture array 304 already illustrated in FIG. 2 is shown in a top view. It should be noted that the absorption layer 341 is not structured, and the entire surface of the absorption layer 341 can be used for the measurement of excess electrons.

[0070] In contrast, FIG. 3b shows a multi-aperture plate 304 structured in two separate regions separated from each other. The first region is the same as the outer region 366 defined as the region around all of the openings 304a in the multi-aperture array 304. The second region is the inner region 367 including all of the openings 304a in the multi-aperture array 304. In the illustrated embodiment, a plurality of apertures 304a are arranged in a hexagonal shape. Therefore, the structuring 368 or separation 368 is also provided in a hexagonal shape. Of course, even when the overall arrangement of the apertures 304a is selected as hexagonal, other shapes of separation can also be selected. For example, it is possible to select a circular shape or, for example, a rectangular shape. Also in FIG. 3b, it should be noted that an absorption layer 341 is provided on the entire surface of the multi-aperture array 304, reference numeral 341a indicates the absorption layer in the outer region 366, and reference numeral 341b indicates the absorption layer in the inner region 367. The absorption layers in the inner region 367 and the outer region 366 can be selected to be made of the same material, but the materials can also be selected to be different. According to one embodiment, the absorption layer can include or consist of any one of gold, silver, titanium, and platinum. In principle, noble metals having excellent conductivity are preferred.

[0071] According to the embodiment shown in FIG. 3b, both absorption layers 341a and 341b can be connected to the ground electrode respectively. The excess electrons discharged from the absorption layer 341a are measured by the ammeter 370 in any case. On the other hand, the measurement of the excess electrons discharged from the absorption layer 341b by another ammeter is optional. Note that there is no further structuring in the inner region 367 of the multi-aperture array 304. Therefore, the formation of the plurality of first individual particle beams 3 is not hindered at all by the presence of any structuring or electrodes on the multi-aperture array 304.

[0072] In FIG. 4, the single beam current is compared with the current generated by the excess electrons discharged from the absorption layer 341 of the multi-aperture array 304. The curve indicated by reference numeral C1 shows the current measured by the first current measuring means 370. Reference numeral C2 indicates the single beam current (shifted in the graph), measured, for example, by a second beam current measuring means using a Faraday cup temporarily placed on the stage, for example, during the calibration of the entire multi-beam particle microscope. The important result of this comparison is that the fluctuations and variations occurring in the single beam current (curve C2) are reflected in curve C1 as well, and thus in measurements that are not at all aimed at measuring the single beam current and are in principle ensemble measurements. This result is a decisive basis enabling a change in the measurement principle according to the present invention. It is no longer the purpose to separately measure as many single beam currents as possible by additional detectors provided separately in the vicinity of each aperture in the multi-aperture array 304. Instead, the goal is to achieve a measurement with an extremely good signal-to-noise ratio, which is achievable by ensemble measurements, more precisely by measurements over a large area on the multi-aperture array 304. As an incidental finding, it should be noted that the necessary proportional relationship between the single beam current and the measured overall "coating" current cannot be automatically found by the large area measurements performed at other apertures within the system. Ensemble measurements performed at the extractor aperture or at the aperture of the anode of the particle source did not show the necessary proportional relationship between these two parameters.

[0073] Figure 5 schematically shows another beam current measurement according to another embodiment of the present invention. In this embodiment, the multi-beam generator includes a pre-aperture plate 380 and a multi-aperture array 304. Similar to the above, the entire surface of the multi-aperture array 304 is covered by an absorption layer 341 connected to ground. However, a pre-aperture plate 380 is provided immediately upstream of the aperture array 304. Basically, this pre-aperture plate 380 covers or blocks the outer region 366 of the multi-aperture array 304, creating its own "outer region" 366a. Particles that collide with the pre-aperture plate 380 are absorbed by the absorption layer 341a and converted into excess electrons, which are discharged from the layer 341a and transported to the ground electrode. Within this line to ground, a first beam current measuring means 370 is provided as a single picoammeter. The measured value is transmitted to the controller 10. Also in this case, based on this measurement result, the controller 10 is configured, for example, to drive the beam generation system or to control the condenser lens system. Although not shown in Figure 5, optionally, additional components of the first beam current measuring means 370 can be arranged along the line from the absorption layer 341 to ground, and thus, basically, it is also possible to measure the excess electrons generated by the particles colliding with the multi-aperture array 304 in the inner region 367.

[0074] FIG. 6 schematically shows a quadrant detector. According to the illustrated embodiment, the multi-aperture plate 304 is structured into five separate regions 351, 352, 353, 354 and 367 that are separated from each other. Each of the regions 351, 352, 353, 354 and 367 is connected to ground. The first beam current measuring means 370 includes five components 370a, 370b, 370c, 370d and 370e in the illustrated example. In each case, excess electrons are measured and the measurement results are transmitted to the controller 10. It should be noted that the inner region 367 includes all the apertures in the multi-aperture array 304. Thus, the inner region 367 is not inhibited at all by any structuring or by separately provided detectors. This ensures very good beam current quality of the generated individual particle beam 3. The outer region 366 is subdivided into four quadrants 351, 352, 353 and 354. Quadrants 351 and 353 have the same area. The same applies to the larger areas of regions 352 and 342. When the beam cone of the illumination particle beam 311 is centered on the multi-aperture array 304 and collides, the signals generated by the measurements in regions 351 and 353 should exhibit the same signal intensity. The same applies to the signals generated by the measurements in regions 352 and 354. In different scenarios when the beam cone of the illumination particle beam 311 is shifted in one direction, the signals generated by each of the quadrants 351, 352, 353 and 354 exhibit variations that make it possible to identify the direction of this shift. This shift can be corrected, for example, by controlling a deflector in the area of the condenser lens system that allows a parallel shift of the entire illumination beam cone 311.

[0075] Of course, the quadrant detector shown in FIG. 6 can in principle be implemented in different ways. The shape of the quadrants can be changed, and thus the arrangement of the apertures themselves, which are illustrated as hexagonal in this example, can also be changed.

[0076] In principle, the directional variation of the entire illumination beam cone 311 can already be specified by a detector that includes only three outer regions. One example is a direction display three-segment detector in which the outer region 366 is preferably subdivided into three different regions, preferably over an angle of approximately 120 degrees of the outer region.

[0077] Of course, it is also possible to further structure the outer region 366 into more than four separate regions. However, it must be noted that any structuring or separation provided on the multi-aperture array 304 bears the potential risk of deterioration of the beam quality of a plurality of first individual particle beams 3 that needs to be avoided. Also, the larger the area for measurement, the better the achievable signal-to-noise ratio for this type of measurement. Preferably, the total number of separate regions on the multi-aperture array 304 does not exceed six regions, and it is preferably only exactly four or five separate and separated regions.

[0078] In FIG. 6, the excess electrons emitted from the inner region 367 are measured by the first beam current measuring means 370e. However, this measurement is merely optional, and in any case, it is not necessary to provide the first beam current measuring means 370e. Instead, the central region 367 can be connected only to the ground electrode without inserting any further measurements.

[0079] FIG. 7 schematically shows another quadrant detector having regions 355, 356, 357, and 358. Also in this case, an absorption layer 341 is provided over the entire surface of the multi-aperture plate 304. However, the embodiment shown in FIG. 7 has the disadvantage that there is also structuring / separation within the inner region of the multi-aperture array 304 that bears the risk of an undesirable deterioration of the beam quality of the individual charged particle beam 3. Therefore, the embodiment of the figure is not very advantageous, even if it meets the requirement of measuring over a large area.

[0080] FIG. 8 shows a schematic diagram of the adjustment of the beam cone of the irradiation beam 311 when it is incident on the multi-aperture array 313. By adjusting the beam cone, the beam current for each individual particle beam 3 can be adjusted. First, a particle or a divergent particle beam 309 is emitted by the source 301. The divergent particle beam 309 passes through a collimation lens system or a condenser lens system 303 including two condenser lenses 303.1 and 303.2 in this embodiment. FIG. 8 shows two different settings of the condenser lens system 303 here. In the first setting, the condenser lens 303.1 is activated and the condenser lens 303.2 is deactivated. As a result, the particles of the divergent particle beam 309 are collimated in the condenser lens 303.1 and hit the multi-aperture array 313 as an irradiation particle beam 311.1 having a diameter d1. In the second case, the condenser lens 303.1 is deactivated and the condenser lens 303.2 is activated. Therefore, the divergent particle beam 309 spreads further and is collimated only in the second condenser lens 303.1 so that an irradiation particle beam 311.2 having a diameter d2 is incident on the multi-aperture plate 313. The number of particles incident on the multi-aperture array 313 is the same in both cases, but the density is different. Therefore, when the multi-aperture array 313 having an aperture 315 (not shown) is traversed, individual particle beams 3 having different beam current intensities depending on the diameter of the irradiation spot are formed.

[0081] In the illustrated embodiment, the condenser lenses 303.1 and 303.2 are magnetic lenses in each case. However, it is also possible to replace one or both of the magnetic lenses with electrostatic condenser lenses. Further, it is possible to change the number of condenser lenses in the entire condenser lens system 303, i.e., to provide only one lens, or to provide three or more lenses. Also, one or more deflectors can be provided for adjusting the irradiation beam 311. These adjustment means and the type of condenser lens affect how quickly the irradiation spot can be adjusted. This will be described in detail below within the scope of this patent application. First, what is illustrated here is how different beam currents of the individual particle beams are generated when different irradiation spots are used.

[0082] Figure 9 shows further design options for the closed-loop beam current control means. Figure 9 shows the radiation of a divergent particle beam 309 that moves along the optical axis 105 and is generated using the beam generation system 301. This radiation passes through a condenser lens system 33 having a first condenser lens 303.1 and a second condenser lens 303.2. In the illustrated embodiment, each condenser lens is a magnetic lens. An electrostatic double deflector having components 345 and 346 is arranged in the region of the condenser lens system 303. In the illustrated embodiment, with respect to the particle optical beam path, component 345 is downstream of the first condenser lens 303.1, and component 346 is downstream of the second condenser lens 303.2. However, other arrangements of the double deflector in the region of the condenser lens system 303 are also possible, for example, both components 345 and 346 can be arranged downstream of the second condenser lens 303.2 with respect to the particle optical beam path.

[0083] The beam 311 can be offset in parallel using a double deflector. When it is incident on the multi-aperture array 313, the beam 311 is relatively offset by the vector V with respect to the optical axis 105. In this case, the electrostatic double deflectors 345, 346 can be driven rapidly and are suitable for high-frequency correction of the offset when the multi-aperture array 313 is irradiated. Further, the double deflectors 345, 346 can be driven based on the current value measured using the first beam current measuring means, for example, measured using the sensor 370 on the surface of the multi-aperture plate 313. This feedback loop can also be used for high-speed closed-loop current control during the image recording procedure.

[0084] Also, one of the condenser lenses 303 can be formed as an electrostatic condenser lens 303. This electrostatic condenser lens 303 can also be driven rapidly and quasi-instantaneously in order to vary the diameter d of the irradiation spot upon incidence on the multi-aperture plate 313. Also in this case, the driving can be implemented in the form of a feedback loop based on current measurement, which is determined, for example, using the sensor 370 above the multi-aperture array 313.

[0085] FIG. 10 schematically shows a multi-beam particle microscope 1 having a closed-loop beam current control means and a compensator driven using a controller 10. The controller 10 can be formed in one part or multiple parts, and the entire multi-beam particle microscope 1 can in principle be controlled using the controller 10. In particular, the controller 10 controls the beam generation system 301, the components of the first particle optical unit, the second particle optical unit and the detection system 200, and further components of the multi-beam particle microscope 1 which may or may not be explicitly illustrated. In the schematic diagram of FIG. 10, only the most important control elements and aspects in the context of the present invention are represented by the connecting lines to the selected particle optical components.

[0086] First, the beam current is measured using various beam current measuring means, and the measured value is transmitted to the controller 10. In the illustrated embodiment, a first beam current measuring means configured to at least measure discharge excess electrons generated by charged particles colliding with the multi-aperture array in the outer regions surrounding all of the apertures within the multi-aperture array can be connected to the micro-optical system 306 including the multi-aperture array 313. In this case, this can be a detection mechanism as shown, for example, in FIGS. 2, 3, 5, 6 or 7. Further, in the illustrated embodiment, the total beam current is measured using a sensor system disposed on or associated with the beam stop 111. In this case, a multi-beam deflector 390 disposed at the same height as the crossover plane upstream of the objective lens 102 in the first particle optical beam path is used to steer the individual particle beam 3 onto the beam stop 111. In particular, the controller 10 can be configured to direct the first individual particle beam 3 into the beam stop 111 during a line jump or an image jump when scanning over the sample surface. Thus, the total beam current can be measured during the image recording procedure. Alternatively or in addition thereto, the beam current of the individual particle beam can be measured using a Faraday cup or an array of Faraday cups provided on the sample stage 503 for the calibration process.

[0087] The components of the multi-beam particle microscope 1 are driven in a manner known per se. This includes the adjustment of the extractor voltage in the beam generation system 301 and the driving of the condenser lens system 303. The deflector 330 additionally illustrated in FIG. 10 serves to perform a static adjustment of the illumination beam 311 upon incidence on the micro-optical system 306. However, the multi-beam particle microscope 1 can include further components and control elements for low-frequency or high-frequency driving for the purpose of controlling the beam current.

[0088] In addition to, or instead of, the above, the condenser lens of the condenser lens system 303 can be designed as a high-speed electrostatic condenser lens and can be driven equally rapidly. As a result, the diameter of the beam incident on the micro-optical system 306 can be corrected rapidly.

[0089] For the high-speed correction of the lateral offset of the illumination spot, one or more electrostatic deflectors, in particular, an electrostatic double deflector as shown, for example, in FIG. 8, may be provided in addition to or as an alternative to the condenser lens system 303. These deflectors can also be driven using a feedback signal based on the current value measured using the first beam current measuring means.

[0090] FIG. 11 shows details regarding beam current control. More specifically, details of the particle source control loop are shown. A current monitoring processor 840 is configured for the control loop. The input signal of the control loop is the measurement made by the first beam current measuring means configured to at least measure the discharge excess electrons generated by the charged particles colliding with the multi-aperture array 304 in the outer regions all around the apertures in the multi-aperture array 304. The first beam current measuring means, realizable by a current meter, in particular a picoammeter, is not shown in FIG. 11. However, an absorption layer 341 provided above the multi-aperture array 304 is schematically shown. The multi-aperture array 304 is part of the multi-aperture arrangement 305, and the multi-aperture arrangement 305 further includes a second multi-aperture 306 plate that can include, for example, a lens array, a deflector array, and / or an astigmatism correction device array, and the final multi-aperture plate 310. Other configurations are possible.

[0091] The current monitoring processor 840 is part of the overall controller 10 of the multi-beam particle microscope 1. The current monitoring processor 840 is configured to control the beam generation system 301 and / or the condenser lens system 303 based on measurements using the first beam current measuring means 370. Other particle optical components can also be controlled.

[0092] The beam generation system 301 includes several parts. In the illustrated embodiment, the beam generation system 301 includes a particle source tip 301.1, a suppressor electrode 301.2, and an extractor electrode 301.3. The current monitoring processor 840 can be configured to control the beam generation device 301, for example, by setting the voltage supplied to the extractor electrode 301.3. In addition to this, or alternatively, the controller 840 can be configured to control the beam generation device 301 by setting the temperature of the particle source 301.1, particularly by setting the heating current or heating voltage. In addition to this, or instead of this, the voltage supplied to the suppressor electrode 301.2 can be set.

[0093] In addition to or instead of the above, the controller 840 can, in this case, control the condenser lens system 303 including three condenser lenses 303.a, 303.b, and 303.c. These are also controllable for setting the focal length and for setting the diameter of the illuminating particle beam 311 that impinges on the multi-aperture array 304, more precisely the first multi-aperture array 304 in the illustrated embodiment.

[0094] In the illustrated embodiment, a double deflector 303.d, particularly an electrostatic double deflector 303.d, is provided in the region of the condenser lens system 303. The controller 840 is configured to control the double deflector 303.d based on measurements using the first beam current measuring means 370.

[0095] Optionally, the controller 840 can also control the electrode 307.1 that generates the immersion field in the first multi-aperture array 304. Optionally, a controlled multipole electrode for tilt correction can also be provided and can be controlled by the controller 840.

[0096] According to the above-described embodiments, the controlled variable in each case is the current generated by the discharge excess electrons, and the discharge excess electrons are generated by charged particles that collide with the multi-aperture array 304 in the outer region 366 surrounding all of the openings in the multi-aperture array 304. However, it is also possible to use another controlled variable that is not the current generated by the discharge excess electrons, and according to an alternative solution, the controlled variable is X-ray detection.

[0097] FIG. 12 schematically shows details of another beam current control based on the measurement of X-rays 900. In the illustrated embodiment, an X-ray detector 950 is provided instead of the ammeter that measures the discharge excess electrons. The X-rays 900 are generated by charged particles that collide with the absorption layer 341 above the multi-aperture array 304. Experiments conducted by the present inventors have shown that the amount of X-rays or the number of X-ray photons measured by the X-ray detector 950 is proportional to the beam current of the first individual particle beam that hits the sample at the incident position. In this case, the X-ray detector 950 is provided as a ring-shaped scintillator element on the outer periphery of the multi-aperture array 304. With this configuration, a good signal-to-noise ratio can be achieved. The controller 840 is configured to control the beam generation system 301 based on the measurement using the X-ray detector 950 in this case. The remaining elements of the current control by X-ray detection are the same as the elements already illustrated and described in detail in FIG. 11, and the same reference numerals indicate the same elements. For the sake of avoiding unnecessary repetition, refer to FIG. 11 for further explanation.

[0098] FIG. 13 schematically shows another implementation of the beam current measuring means using X-rays 900 that are converted into NIR (near-infrared) radiation. In the illustrated example, the multi-aperture array 304 includes a crystal plate 905 coated with an absorption layer 341. Instead of the crystal plate 905, other plates made of a transparent material such as PMMA can be used. The crystal plate is doped with a fluorescent agent that serves as a scintillator. Charged particles such as electrons that collide with the absorption layer 341 are first converted into X-rays 900. Inside the crystal plate 905, the X-rays 900 are converted into photons or near-infrared radiation 901. The photons 901 are guided by total internal reflection within the crystal plate 905 and are finally detected by one or more photodetectors 910 arranged on the outer periphery of the crystal plate 905. As an example, the point T where total internal reflection of the photons 901 occurs is illustrated in FIG. 13. The signal measured by the one or more photodetectors 910 is transmitted to the controller 10 (or for example its component 840) and is used to control the beam generation system 301 and / or the condenser lens system 303. Other types of control schematically shown in FIG. 12 can also be performed. Refer also to FIG. 12 and further to FIG. 11 in this regard.

[0099] Also, according to this embodiment, the required proportional relationship between the beam current of the individual particle beam hitting the sample and the near-infrared radiation detected using the photodetector 910 exhibits the required proportional relationship.

[0100] A multi-beam particle microscope with improved beam current control is disclosed. Excess electrons discharged from one region or only a few regions of the absorption layer provided on the multi-aperture array are measured using an ammeter. The measured current is used as a controlled variable in closed-loop control. The measurement is wide-area and low-noise. The multi-aperture array can be specially structured to also achieve direction-sensitive detection using, for example, a quadrant detector or a triple-segment detector.

[0101] (Example 1) A multi-beam particle microscope, A beam generation system including a particle source, an extractor electrode, and an anode, configured to generate a first charged particle beam, A multi-beam generator having a multi-aperture array, configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array including an absorption layer on its upper side for absorbing charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the multi-beam generator, An X-ray detector configured to detect X-rays generated by charged particles colliding with the absorption layer of the multi-aperture array, A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward a sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view, A detection system, A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from an incident position within the second field of view onto the detection system, A particle optical objective lens through which both the first and second individual particle beams pass, A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and disposed in the second particle optical beam path between the objective lens and the detection system, Including a beam generation system, a particle optical objective lens, a first particle optical unit, a second particle optical unit, and a controller configured to control the detection system, The controller is configured to drive the beam generation system based on measurements using the X-ray detector and / or, The controller is configured to control a condenser lens system based on measurements using the X-ray detector, a multi-beam particle microscope.

[0102] (Example 2) The multi-beam particle microscope according to Example 1, wherein the X-ray detector is provided as a ring-shaped scintillator element upstream of the multi-aperture array and on the outer periphery of the multi-aperture array.

[0103] (Example 3) A beam generation system including a particle source, an extractor electrode, and an anode, configured to generate a first charged particle beam; A multi-beam generator having a multi-aperture array, configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array including an absorption layer on its upper side that absorbs charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons; X-ray conversion means for converting X-rays generated by charged particles colliding with the absorption layer of the multi-aperture array into NIR radiation; A light guide for guiding the NIR radiation to a photodetector; A photodetector configured to detect the NIR radiation; A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward a sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view; A detection system; A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from an incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and in the second particle optical beam path between the objective lens and the detection system; A controller configured to control the beam generation system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system. A controller is configured to drive a beam generation system based on measurements using a photodetector, and / or A multi-beam particle microscope, wherein the controller is configured to control a condenser lens system based on measurements using a photodetector.

[0104] (Example 4) The light guide includes a crystalline glass plate doped with a scintillating material for converting X-rays into NIR radiation, The multi-beam particle microscope according to Example 3, wherein the photodetector is disposed around the crystalline glass plate.

Description of the reference numerals

[0105] 1 Multi-beam particle microscope 3 Primary particle beam (individual particle beam) 5 Beam spot, incident position 7 Object 9 Secondary particle beam 10 Computer system, controller 11 Secondary particle beam path 13 Primary particle beam path 25 Sample surface, wafer surface 100 Objective lens system 101 Object plane 102 Objective lens 103 Field of view 105 Optical axis of the multi-beam particle microscope 108 Crossover 110 Batch scanning deflector 111 Beam stop with a second current measuring means 200 Detector system 205 Projection lens 207 Detection region 208 Deflector for adjustment 209 Particle multi-detector 211 Detection surface 212 Crossover 213 Incident position 214 Aperture filter 215 Detection region 216 Active element 217 Field of view 218 Deflector system 220 Multi-aperture corrector, individual deflector array 222 Batch deflection system, anti-scan 300 Beam generation device 301 Particle source, beam generation system 303 Collimation lens system 304 Multi-aperture array 304a Aperture 305 Multi-aperture array 306 Micro-optical system 307 Field-of-view lens 308 Field-of-view lens 309 Diverging particle beam 311 Irradiating particle beam 313 Multi-aperture plate, multi-aperture array 315 Aperture of multi-aperture plate 316 Hexagon 317 Midpoint of aperture 319 Field of view 323 Beam focus 325 Intermediate image plane 326 Field-of-view lens system 330 Deflector 340 Tip 341 Absorbing layer 342 Extractor electrode 343 Anode 345 Deflector 346 Deflector 351 Region 352 Region 353 Region 354 Region 360 Beam current intensity diagram 366 Outer region 367 Inner region 368 Structuring, separation 370 First beam current measurement means, ammeter, picoammeter 380 Pre-aperture plate 390 Multi-beam deflector 400 Beam switch 420 Magnetic element 500 Sample stage 503 Voltage source for sample 900 X-ray 901 Photon, NIR emission 905 Quartz plate 910 Photodetector 950 X-ray detector d1 Beam cone diameter d2 Beam cone diameter V Displacement between the midpoint of the beam cone and the midpoint of the multi-aperture array T Total reflection point

Claims

1. A multi-beam particle microscope, comprising: a beam generation system including a particle source, an extractor electrode, and an anode, configured to generate a first charged particle beam; a multi-beam generator having a multi-aperture array, the multi-beam generator being configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array including, on its upper side, an absorption layer for absorbing charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the multi-beam generator; first beam current measuring means configured to at least measure discharge excess electrons generated by charged particles colliding with the multi-aperture array in an outer region surrounding all of the apertures in the multi-aperture array; a condenser lens system disposed between the beam generation system and the multi-beam generator; a first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward a sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view; a detection system; a second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from the incident position within the second field of view onto the detection system; a particle optical objective lens through which both the first and the second individual particle beams pass; a beam switch disposed in the first particle optical beam path between the multi-beam generator and the objective lens and disposed in the second particle optical beam path between the objective lens and the detection system; a controller configured to control the beam generation system, the condenser lens system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system; and the controller is configured to control the beam generation system based on a measurement using the first beam current measuring means, and / or the controller is configured to control the condenser lens system based on a measurement using the first beam current measuring means. The absorption layer is structured into an inner region including the openings of the multi-aperture array and an outer region surrounding all of the openings in the multi-aperture array, The outer region is further structured into four separate regions arranged to form a direction indication quadrant detector, The inner region and the four separate regions of the outer region are separated from each other and connected to ground, The first beam current measuring means is configured to measure the excess electrons discharged separately from each quadrant over a wide area. Multi-beam particle microscope. **Claim 2**: A multi-beam particle microscope, A beam generation system including a particle source, an extractor electrode, and an anode, and configured to generate a first charged particle beam, A multi-beam generator having a multi-aperture array, the multi-beam generator being configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array including, on its upper side, an absorption layer that absorbs charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, a multi-beam generator, First beam current measuring means configured to at least measure discharge excess electrons generated by charged particles colliding with the multi-aperture array in an outer region surrounding all of the openings in the multi-aperture array, A condenser lens system disposed between the beam generation system and the multi-beam generator, A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beams toward the sample such that the generated first individual particle beams strike the sample at an incident position where a second field of view is formed, A detection system, A second particle optical unit having a second particle optical beam path configured to image second individual particle beams emitted from the incident position within the second field of view onto the detection system, A particle optical objective lens through which both the first and the second individual particle beams pass, A beam switch disposed in the first particle optical beam path between the multi-beam generator and the objective lens and disposed in the second particle optical beam path between the objective lens and the detection system, The beam generation system, the condenser lens system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and a controller configured to control the detection system. The controller is configured to control the beam generation system based on measurements using the first beam current measuring means, and / or The controller is configured to control the condenser lens system based on measurements using the first beam current measuring means. The absorption layer is structured into the inner region and the outer region. The outer region is further structured into three separate regions arranged to form a direction indicating triple detector. The inner region and the three separate regions of the outer region are separated from each other and connected to ground. The first beam current measuring means is configured to measure the excess electrons discharged separately from each triple region. Multi-beam particle microscope.

3. The multi-beam particle microscope according to claim 1 or 2, wherein the first beam current measuring means is further configured to measure the discharge excess electrons generated by charged particles colliding with the multi-aperture array in an inner region including the apertures in the multi-aperture array.

4. The condenser lens system further includes a double deflector within the region. The multi-beam particle microscope according to claim 1 or 2, wherein the controller is further configured to control the double deflector based on measurements using the first beam current measuring means.

5. The multi-beam particle microscope according to claim 1 or 2, wherein the first beam current measuring means includes at least one ammeter, particularly a picoammeter.

6. The multi-beam particle microscope according to claim 1 or 2, wherein at least 60% of the beam current reaching the multi-aperture array is used for the beam current measurement.

7. The multi-beam particle microscope according to claim 1 or 2, wherein at least 90%, particularly at least 95% of the beam current reaching the multi-aperture array is used for the beam current measurement.

8. The active beam measurement surface of the absorption layer that absorbs charged particles and emits electrons therefrom for the beam current measurement is at least 60% of the total surface of the multi-aperture array, the multi-beam particle microscope according to claim 1 or 2.

9. The active beam measurement surface of the absorption layer that absorbs charged particles and emits electrons therefrom for the beam current measurement is at least 90%, particularly 95% of the total surface of the multi-aperture array, the multi-beam particle microscope according to claim 1 or 2.

10. The average single beam current of the plurality of first individual particle beams is at least 1 / 100 or less, particularly 1 / 500 or 1 / 1000 or less of the total beam current measured by the first beam current measurement means, the multi-beam particle microscope according to claim 1 or 2.

11. The absorption layer is an absorbent coating, and / or The absorption layer contains any one of gold, silver, titanium, platinum or consists of any one of these, the multi-beam particle microscope according to claim 1 or 2.

12. The multi-aperture array is arranged as the first multi-aperture array downstream of the condenser lens system, and is the array that divides the first charged particle beam into the plurality of first individual particle beams, the multi-beam particle microscope according to claim 1 or 2.

13. The multi-aperture array is not arranged as the first multi-aperture array downstream of the condenser lens system, the multi-beam particle microscope according to claim 1 or 2.

14. The controller is configured to control the beam generation device by setting the voltage supplied to the extractor electrode, the multi-beam particle microscope according to claim 1 or 2.

15. The controller is configured to control the beam generation device by setting the temperature of the particle source, particularly by setting the heating current or heating voltage, the multi-beam particle microscope according to claim 1 or 2.

16. A multi-beam particle microscope, A beam generation system including a particle source, an extractor electrode and an anode, and configured to generate a first charged particle beam, A multi-beam generator having a multi-aperture array, wherein the multi-beam generator is configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, and the multi-aperture array includes, on its upper side, an absorption layer for absorbing charged particles, and the absorption layer is connected to at least one ground electrode for discharging excess electrons, a multi-beam generator, First beam current measuring means configured to at least measure discharge excess electrons generated by charged particles colliding with the multi-aperture array in an outer region around all of the apertures in the multi-aperture array; A condenser lens system disposed between the beam generation system and the multi-beam generator; A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward the sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view; A detection system; A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from the incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam generator and the objective lens and in the second particle optical beam path between the objective lens and the detection system; Including a controller configured to control the beam generation system, the condenser lens system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system; The controller is configured to control the beam generation system based on measurements using the first beam current measuring means, and / or The controller is configured to control the condenser lens system based on measurements using the first beam current measuring means; The absorption layer on the multi-aperture array is structured into exactly two separate regions separated from each other, and each region is connected to ground. The first region is an inner region including the apertures of the multi-aperture array, and the second region is the outer region around all of the apertures in the multi-aperture array. The first beam current measuring means is configured to measure only the excess charged particles discharged from the outer region. Multi-beam particle microscope.

17. Further including a double deflector within the region of the condenser lens system. The controller is further configured to control the double deflector based on the measurement using the first beam current measuring means. The multi-beam particle microscope according to claim 16.

18. At least 90%, particularly at least 95% of the beam current reaching the multi-aperture array is used for the beam current measurement. The multi-beam particle microscope according to claim 16.

19. The average single beam current of the plurality of first individual particle beams is at most 1 / 100, particularly 1 / 500 or 1 / 1000 or less of the total beam current measured by the first beam current measuring means. The multi-beam particle microscope according to claim 16.

20. A multi-beam particle microscope, A beam generation system including a particle source, an extractor electrode, and an anode, and configured to generate a first charged particle beam, A multi-beam generator having a pre-aperture plate and a multi-aperture array, the multi-beam generator being configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array being disposed downstream and in the vicinity of the pre-aperture plate, the multi-aperture array including, on its upper side, an absorption layer for absorbing charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the pre-aperture plate including, on its upper side, a pre-aperture plate absorption layer for absorbing charged particles, the pre-aperture plate absorption layer being connected to at least one ground electrode for discharging excess electrons. A multi-beam generator, First beam current measuring means configured to at least measure the discharge excess electrons generated by the charged particles colliding with the pre-aperture plate, A condenser lens system disposed between the beam generation system and the multi-beam generator, A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward the sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view; A detection system; A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from the incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and the second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and disposed in the second particle optical beam path between the objective lens and the detection system; A controller configured to control the beam generation system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system; The controller is configured to drive the beam generation system based on measurements using the first beam current measuring means and / or; The controller is configured to control the condenser lens system based on measurements using the first beam current measuring means; The first beam current measuring means is configured to measure only the excess charged particles discharged from the pre-aperture plate; A multi-beam particle microscope. **Claim 21**: A multi-beam particle microscope, comprising: A beam generation system including a particle source, an extractor electrode, and an anode, and configured to generate a first charged particle beam; A multi-beam generator having a pre-aperture plate and a multi-aperture array, wherein the multi-beam generator is configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array is disposed downstream and in the vicinity of the pre-aperture plate, the multi-aperture array includes an absorption layer for absorbing charged particles on its upper side, the absorption layer is connected to at least one ground electrode for discharging excess electrons, the pre-aperture plate includes a pre-aperture plate absorption layer for absorbing charged particles on its upper side, and the pre-aperture plate absorption layer is connected to at least one ground electrode for discharging excess electrons, a multi-beam generator; First beam current measuring means configured to at least measure discharge excess electrons generated by charged particles colliding with the pre-aperture plate; A condenser lens system disposed between the beam generation system and the multi-beam generator; A first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam toward the sample such that the generated first individual particle beam hits the sample at an incident position forming a second field of view; A detection system; A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from the incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and in the second particle optical beam path between the objective lens and the detection system; Including a controller configured to control the beam generation system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and the detection system; The controller is configured to drive the beam generation system based on measurements using the first beam current measuring means, and / or The controller is configured to control the condenser lens system based on measurements using the first beam current measuring means. The pre-aperture plate is further structured into four separate regions arranged to form a direction display quadrant detector, the four separate regions of the pre-aperture plate are separated from each other and connected to ground, the first beam current measuring means is configured to measure the excess electrons discharged separately from each quadrant over a large area, Multi-beam particle microscope.

22. further comprising a double deflector within the region of the condenser lens system, the controller is further configured to control the double deflector based on measurements using the first beam current measuring means, the multi-beam particle microscope according to claim 20 or 21.

23. A multi-beam particle microscope, comprising a beam generation system configured to generate a first charged particle beam including a particle source, an extractor electrode, and an anode, a multi-beam generator having a pre-aperture plate and a multi-aperture array, the multi-beam generator being configured to generate a first field of view of a plurality of first individual charged particle beams from the first charged particle beam, the multi-aperture array being disposed downstream and in proximity to the pre-aperture plate, the multi-aperture array including, on its upper side, an absorption layer that absorbs charged particles, the absorption layer being connected to at least one ground electrode for discharging excess electrons, the pre-aperture plate including, on its upper side, a pre-aperture plate absorption layer that absorbs charged particles, the pre-aperture plate absorption layer being connected to at least one ground electrode for discharging excess electrons, a multi-beam generator, first beam current measuring means configured to at least measure the discharge excess electrons generated by the charged particles impinging on the pre-aperture plate, a condenser lens system disposed between the beam generation system and the multi-beam generator, a first particle optical unit having a first particle optical beam path configured to direct the first individual particle beam towards the sample such that the generated first individual particle beam strikes the sample at an incident position forming a second field of view, a detection system, A second particle optical unit having a second particle optical beam path configured to image a second individual particle beam emitted from the incident position within the second field of view onto the detection system; A particle optical objective lens through which both the first and second individual particle beams pass; A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and in the second particle optical beam path between the objective lens and the detection system; Including the beam generation system, the particle optical objective lens, the first particle optical unit, the second particle optical unit, and a controller configured to control the detection system; The controller is configured to drive the beam generation system based on measurements using the first beam current measurement means, and / or; The controller is configured to control the condenser lens system based on measurements using the first beam current measurement means; The pre-aperture plate is further structured into three separate regions arranged to form a direction display quadrant detector; The three separate regions of the pre-aperture plate are separated from each other and connected to ground; The first beam current measurement means is configured to measure the excess electrons discharged separately from each of the three divided regions; Multi-beam particle microscope. **Claim 24** Further comprising a double deflector within the region of the condenser lens system; The multi-beam particle microscope according to claim 23, wherein the controller is further configured to control the double deflector based on measurements using the first beam current measurement means.

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