Multipole array and multi-beam charged particle beam system for manipulating multiple primary charged particle beamlets

Abstract

This invention provides an improvement to the multi-pole array of a multi-beam system. At least one of the following improvements—better vacuum extraction, absence of contamination risk, and greater maneuverability—is achieved by at least one improved component comprising a plurality of circular edges within a vacuum gap, a plurality of deep recesses formed in a conductive material, and a plurality of electrodes within the vacuum gap for generating repulsive or attractive forces on charged particles.

Description

Multi-beam generating unit with enhanced focusing power The present invention relates to a multi-beam array element for individually manipulating a plurality of charged particle beamlets and a multi-beam charged particle beam system having the multi-beam array element. Document WO 2005 / 024881 A2 discloses an electron microscope system that utilizes multiple electron beamlets for parallel scanning of an object to be inspected using a cluster of electron beamlets. The cluster of electron beamlets is generated by directing a primary electron beam onto a porous plate having a plurality of openings. A portion of the electrons in the electron beam are incident on the porous plate and absorbed, while another portion of the electrons in the electron beam are emitted through the openings of the porous plate, thereby forming an electron beamlet in the beam path downstream of each opening, the cross section of which is defined by the cross section of the opening. A porous plate having a plurality of openings is also provided, wherein at least one electrode is provided at each opening. This allows each of the plurality of charged particle beamlets to be individually influenced, for example, by focusing or deflecting. For example, a lens array is provided using a single electrode at each opening. A deflector array or an astigmatism corrector array is provided using, for example, four or eight electrodes. The focus of the electron beamlet is formed on the surface of the object or sample to be inspected using a lens array and a plurality of additional electromagnetic lenses. A primary electron beamlet triggers the emission of secondary electrons or backscattered electrons from the object as secondary electron beamlets, which are focused and imaged onto a detector. Each of these secondary beamlets is incident on a separate detector element, so that the detected secondary electron intensity provides information about the sample at the location where the corresponding primary beamlet impinges on the sample. The cluster of primary beamlets is systematically scanned over the sample surface, generating an electron microscope image of the sample in the manner commonly used in scanning electron microscopy. The resolution of a scanning electron microscope is limited by the focal diameter of the primary beamlets incident on the object. Therefore, in a multibeam electron system, all beamlets should form the same small focal spot on the object. Multibeam deflectors or astigmatism arrays with at least two electrodes per aperture are widely used in the prior art. These are fabricated, for example, using MEMS technology. The electrodes are separated by an insulating material. Because scattered electrons can adhere to the surface of the insulating material and form localized surface electrons, it is well known from multipole elements in single-beam electron optical systems to form a vacuum gap between the electrodes and reduce the probability of electrons reaching the insulating material surface. For example, various shapes of vacuum gaps between the individual electrodes have been proposed. For example, US Patent No. 5,245,194 shows a T-shaped vacuum gap between eight multipole electrodes, wherein the portion of the insulating material surface hidden behind the electrodes extends only relative to the corresponding electron beamlet. US Patent No. 5,401,974 or US Patent No. 6,977,377 B2 show an L-shaped vacuum gap with an insulating surface region hidden behind the electrodes. Other vacuum gap shapes that reduce the likelihood of electrons reaching the insulating surface segments are known from US Patent Nos. 5,041,731, 6,055,719, and 7,554,095 B2. These shapes include T- or L-shaped vacuum gaps, angled vacuum gaps, curved vacuum gaps, or labyrinthine vacuum gaps, where the insulating region is at least partially hidden behind the electrodes of the multipole, preventing electrons from directly reaching the insulating surface segments.Furthermore, for example, US Pat. No. 7,554,095 B2 provides a charge-absorbing electrode in the vacuum gap in the line of sight of the electron beam through the apertures in the multiple electrodes. Thus, electrons that accidentally penetrate the vacuum gap are collected by the charge-absorbing electrode connected to a ground potential. In US Pat. No. 7,276,707 B2, this type of single-beam solution has been transferred to array elements for multi-beam charged-particle beam systems. Array elements for multi-beam charged-particle beam systems are typically produced using MEMS technology, which allows for easy fabrication of vacuum gaps and electrodes of arbitrary shapes. However, these multipole arrays have proven to have lifetime and reliability issues. These issues are particularly critical for wafer inspection, where high system reliability and high uptime are crucial. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a multipole array element for a multi-beam charged particle beam system having higher reliability and increased lifetime. It has been proven that contamination is a challenge for multipole array elements. Therefore, the work of the present invention is to provide a multipole array element for multiple charged particle beam systems that is less sensitive to contamination. One of the reasons for contamination is that it is difficult to evacuate the multipole array element with a plurality of apertures. Therefore, the work of the present invention is to provide a multipole array element for multiple charged particle beam systems that is suitable for improving high vacuum operation. Patent documents DE 10 2018 124 219 A1, US 2017 / 0125205 A1, US 2016 / 0336147 A1, DE 10 2014 008 083 A1 and DE 689 18 144 T2 provide technical background information related to the patents applied in this patent. IL Berry et al., "Programmable Aperture Plate for Maskless High-Throughput Nanolithography," Journal of Vacuum Science and Technology B: Microelectronics and Nanostructure Processing, Measurements and Phenomena 15 (1997), pp. 2382–2386, also provide technical background information for this patent application. This patent application claims priority from German patent application No. 10 2023 209 409.6, filed on September 26, 2023, the disclosure of which is incorporated herein by reference in its entirety. An improvement in a multipole array for manipulating a plurality of primary charged particle beamlets is provided. A multipole array comprises a plurality of first apertures, each first aperture being used to emit a charged particle beamlet from a plurality of primary charged particle beamlets. A multipole array comprises a plurality of multipole elements, each multipole element comprising at least two individual electrodes for manipulating a single beamlet of charged particles. Each of the multipole elements is arranged at an aperture. The improvement comprises an improvement in a vacuum gap for separating and isolating at least two electrodes of a multipole element. A multipole array for manipulating a plurality of primary charged particle beamlets is manufactured using MEMS technology and is made of doped silicon or polysilicon as a conductive material, and, for example, silicon dioxide as an isolation material. A multipole array may further comprise a metal coating, for example containing gold, aluminum, copper or tungsten. At least one first electrode and one second electrode are disposed at each aperture of a multipole array. Each electrode is individually connected to a control unit for individually controlling each primary charged particle beamlet. The beamlets can be deflected using at least two electrodes. The multipole array can include more electrodes at each aperture, such as six, eight, twelve, or even more electrodes. This allows shaping of each beamlet, for example, to compensate for astigmatism or to achieve linear power focusing. Each electrode has a radial thickness T1 and an inner surface within the aperture. Between the apertures, a multipole array includes a conductive material that acts as a shield for the electrostatic field and reduces crosstalk between different multipole elements at different apertures. These structures or structures formed of conductive material are also referred to as shielding electrodes. The plurality of electrodes of the multipole element include at least two electrodes at each aperture and are connected to the multipole array via an insulating material, such as a conductive material forming a shielding electrode. For example, at least a first electrode and a second electrode are isolated from the conductive material or shielding electrode by a ring of insulating material between the plurality of electrodes and a shielding electrode. A vacuum gap having two side surfaces is formed between the first electrode and the second electrode, with a width W and a depth T3. The depth T3 is greater than the radial thickness T1 of the electrodes and the depth T3. In one embodiment, the two side surfaces are parallel to each other. In a first embodiment, depth T3 is at least equal to or greater than depth T2 of the insulating material ring segment, where T3 ≥ T2. This allows the open surface of the insulating material to lie within the side surface of the vacuum gap, reducing the profile of the open surface of the insulating material relative to the scattered charged particles. In one embodiment, depth T3 exceeds depth T2, forming a recess within the conductive material of the shield electrode. Consequently, contaminant particles accumulate within the recess in the conductive material and do not cause electrons to adhere to the open surface of the insulating material. In one example, the width W is less than 4 μm, such as 2 μm or less, such as 1.6 μm, and the aspect ratio AR = T1 / W is greater than 8:1, such as 10:1. In this way, any parasitic fields generated by electrons deep within the vacuum gap (e.g., by electrons sticking to open surfaces of insulating materials) do not interfere with the electrostatic fields generated by the electrodes of the multipole element within the hole. In one embodiment, the tangent line of the side surface of the vacuum gap is tilted at an angle J greater than 15° (e.g., 20°, 30°, or even 45°) relative to the radius vector of the center of the corresponding hole. This reduces the likelihood of scattered charged particles reaching the open surface of the insulating material. In one embodiment, the intersection between the inner surface of the first electrode having an aperture and the side surface of the vacuum gap forms a cylindrical edge segment at the intersection. This avoids sharp edges or large field gradients at the intersection of the two surfaces, and also prevents large field gradients. Large field gradients can attract charged contaminant particles, which can adhere to sharp edges and create areas where sparks may form. By using a cylindrical edge segment with a radius R exceeding 1 μm (e.g., R = 2 μm or R = 3 μm), large field gradients at sharp edges can be avoided, reducing the risk of contaminant growth and sparks. In one embodiment, one side surface of the vacuum gap includes a rounded surface segment to avoid large field gradients at sharp edges within the vacuum gap. For example, a vacuum gap may have an "s"-shaped, rounded V-shaped, or "c"-shaped cross-section. The "s" or "c" shape reduces the likelihood of scattered charged particles reaching the open surface of the insulating material. In one embodiment, the multipole array further includes a voltage source for applying a voltage Ub to the conductive material, such as the shield electrodes. This voltage can be applied to the shield electrodes, for example, and can attract charged particles into the vacuum gap or repel charged particles from entering the vacuum gap. For example, charged particles can be attracted to recesses formed in the shield electrodes. In one embodiment, an improved multipole array includes a plurality of additional electrodes made of a conductive material, arranged within the vacuum gap in the direction of the line of sight (LoW) through which charged particles propagate through the corresponding apertures, for example, in the direction of the line of sight (LoW) from the center of the corresponding apertures. These electrodes can serve as lightning conductors, concentrating the current that generates sparks within the vacuum gap. These electrodes can, in turn, be connected to a voltage source for providing a voltage Ub and can function as either attracting or repelling electrodes. For example, the additional electrodes can have a negative voltage to prevent scattered electrons from penetrating deep into the vacuum gap. This attracts positively charged contaminant particles to the additional electrodes and prevents them from adhering to other surface segments of the vacuum gap. This reduces the likelihood of scattered charged particles reaching the open surfaces of the insulating material. For example, the voltage Ub can also be applied during evacuation, and can be a pulsed or alternating voltage. This improves the removal of residual gases and contaminant particles. In one embodiment, the additional electrodes are formed from a thin wire or a wire grid. In one embodiment, a multipole array includes a conductive covering on a first side of the incident path of a plurality of primary charged particles. The conductive covering includes a plurality of apertures and an intervening extension at each aperture extending into the aperture in a propagation direction. Thus, at each aperture, an annular first radial vacuum gap is formed between the intervening extension of the conductive covering and each electrode of the aperture. Thus, an insulating material isolating the electrodes from the conductive covering is shielded by the intervening extension, reducing the likelihood of scattered charged particles reaching the open surface of the insulating material. In one embodiment, each of the electrodes further includes an inserted extension extending in the propagation direction of the emitted beamlets. The inserted extension of the electrode and a bottom layer formed of a conductive material downstream of the electrode form a second radial vacuum gap. The inserted extension of the electrode is covered with an insulating material that isolates the electrode from the conductive material downstream of the electrode. Thus, the electrode is embedded within a conductive covering layer and a conductive bottom layer along the propagation direction of the transmitted charged particles. In one embodiment, at least one circular ring segment is disposed at the first or second radial vacuum gap to prevent large field gradients at the sharp edges of the radial vacuum gap. In one embodiment, a multipole array includes a plurality of second holes or vacuum holes. Each of the vacuum holes is connected to a vacuum gap from the rear end. Thereby, the evacuation of a narrow vacuum gap is improved. In one embodiment, an improved multipole array for manipulating a plurality of primary charged particle beamlets includes a plurality of first holes, each hole is used to emit one of the plurality of primary charged particle beamlets and at least a first electrode and a second electrode arranged at each hole. Each of the electrodes is connected to a control unit for individually controlling each of the plurality of charged particle beamlets. Each of the first and second electrodes has an inner surface located within the hole and includes an insulating material layer on the side opposite to the inner surface, the insulating material layer being covered by a conductive material connected to a voltage source to provide a voltage Ub or a ground potential. The conductive material covering thereby forms a shielding electrode. A vacuum gap having multiple side surfaces is formed between at least the first electrode and the second electrode. The improved multipole array includes a first outer layer covering the electrodes from the direction of incident primary beamlets, including the plurality of first apertures, and further including a plurality of second apertures or vacuum apertures for improving evaporation of the vacuum space between the plurality of electrodes at different apertures. In one embodiment, the voltage source is configured to provide a pulsed voltage Ub to the shield electrode during evacuation to improve evacuation of the vacuum gap. By improving the multipole array or a combination of multipole array improvements, vacuum separation of electrodes of a multipole element with improved lifetime and increased operating range is provided. With the improvement of the small vacuum gap width below a few μm, limited to the small size of the multipole array aperture of about 40 μm to 80 μm, at least one of several effects is achieved, including: reducing large field gradients at sharp edges, thereby reducing the risk of contaminant growth and sparking; improving the evacuation of the narrow vacuum gap; focusing charged particles, including contaminant particles, in recesses of the conductive material; reducing the impact of parasitic fields generated by charged particles in the narrow vacuum gap on the multipole field generated in the aperture; reducing the profile relative to the open surface of the isolation material from which the charged particles are scattered; and reducing the risk of the profile of the open surface of the isolation material from which the scattered charged particles impinge. Examples and embodiments according to the present invention may be applied to any multipole array, such as a multipole array within a primary beamlet generating unit, a corrector for telecentricity, or a multipole array within a secondary electron beam path. It should be understood that the present invention is not limited to the embodiments and examples, but also includes combinations and variations of the embodiments and examples. In the exemplary embodiments of the present invention described below, components with similar functions and structures are indicated by similar or identical reference numerals as much as possible. The multi-beam grating unit of the example is described in an illumination beam path in which charged particles propagate in the positive z-direction and the z-direction is downward. However, the multi-beam grating unit can also be applied in an imaging beam path in which secondary charged particle beamlets propagate in the negative z-direction in the coordinate system of Figure 1. Moreover, the sequence of multi-aperture plates is arranged in sequence along the propagation direction of the emitted charged particle beam or beamlet. With the beam entry side or upper side being understood as the first surface or side of the element in the direction of the emitted charged particle beam or beamlet, the bottom side or beam exit side is understood as the last surface or side of the element in the direction of the emitted charged particle beam or beamlet. Reference numerals identify array elements, such as a plurality of primary charged particle beamlets. According to the text, the same reference numerals may also identify a single element or array element. Each primary charged particle beamlet (3.1, 3.2, 3.3, 3.4) is one of a plurality of primary charged particle beamlets (3). It is clear from the text whether a single element of an array of elements is being referred to. FIG1 is a schematic diagram illustrating the basic features and functionality of a multi-beam charged particle system 1 according to an embodiment of the present invention. It should be noted that the symbols used in the figure have been selected to symbolize their relative functionality. The system shown is a multi-beam scanning electron microscope (MSEM or multi-SEM) that uses a plurality of primary electron beamlets 3 to generate a plurality of primary charged particle beam spots 5 on a surface 25 of an object 7, such as a wafer whose top surface 25 is located in an object plane 101 of an objective lens 102. For simplicity, only five primary charged particle beamlets 3 and five primary charged particle beam spots 5 are shown. The features and functionality of the multi-beam charged particle system 1 can be implemented using electrons or other types of primary charged particles, such as ions, and in particular helium ions. Further details of the microscope system 1 are provided in WO 2022 262970 A1, which is incorporated herein by reference in its entirety. The system 1 includes an object irradiation unit 100, a detection unit 200, and a beam splitter unit 400 for separating a secondary charged particle beam path 11 from a primary charged particle beam path 13. The object irradiation unit 100 includes a charged particle multi-beam generator 300 for generating a plurality of primary charged particle beamlets 3 and is adapted to focus the plurality of primary charged particle beamlets 3 in an object plane 101, wherein the surface 25 of the wafer 7 is positioned by a sample platform 500. The primary beam generator 300 generates a plurality of primary charged particle beamlet spots 311 in an intermediate image surface 321, which is typically a spherically curved surface. According to an embodiment of the present invention, the intermediate image plane 321 is further tilted to compensate for the tilt caused by the off-axis symmetry of the object irradiation unit 100. The positions of the plurality of focal points (311) of the plurality of primary charged particle beamlets (3) in the intermediate image surface (321) are adjusted by a multi-beam generation unit (305) to pre-compensate for the field curvature and image plane tilt of the optical elements of the object irradiation unit (100) downstream of the multi-beam generation unit 305. The image plane tilt orientation and field curvature of the intermediate image surface 321 are adjusted according to the driving parameters of the object irradiation unit 100, such as the focusing power of the objective lens 102 or the electrostatic field generated between the objective lens 102 and the wafer surface 25 by the voltage provided by the sample voltage source (503), both of which are the main sources of field curvature and tilted image plane rotation. Further details regarding the curvature and tilt of the intermediate image plane are described in German patent DE 10 2021 200 799 B3, which is incorporated herein by reference. The primary beamlet generator 300 includes a primary charged particle source 301, such as electrons. The primary charged particle source 301 emits a diverging primary charged particle beam, which is collimated by at least one collimating lens 303 to form a collimated or parallel primary charged particle beam 309. The collimating lens 303 is typically composed of one or more electrostatic lenses or magnetic lenses, or a combination of electrostatic and magnetic lenses. The primary beamlet generator 300 further includes a deflector 302 for adjusting the angle of the collimated or parallel primary charged particle beam 309. The collimated primary charged particle beam 309 is incident on a primary multi-beam forming unit 305. The multi-beam forming unit 305 basically includes a first porous plate or filter plate 304 irradiated by the collimated primary charged particle beam 309. The first porous plate or filter plate 304 comprises a plurality of apertures in a grating configuration for generating a plurality of primary charged particle beamlets 3 by transmitting a collimated primary charged particle beam 309 through the plurality of apertures. The multi-beam forming unit 305 comprises at least two further porous plates 306.1 and 306.2, which are located downstream of the first porous plate or filter plate 304 relative to the direction of movement of electrons in the primary charged particle beam 309. For example, the second porous plate 306.1 functions as a microlens array comprising a plurality of ring electrodes, each set to a defined potential, such that the focal position of the plurality of primary beamlets 3 is independently adjusted in the intermediate image surface 321. The third porous plate 306.2 comprises, for example, four or eight electrostatic elements for each of the plurality of apertures, for example, to individually deflect each of the plurality of beamlets. The third porous plate 306.2 thus forms a multipole array element. In one embodiment, the multi-beam forming unit 305 is configured with an additional multi-aperture plate (306.3), which can be configured as an additional multipole array element. The plurality of primary charged particle beamlets 3 are focused together with the field lens 308 onto or near the intermediate image surface 321. In or near the intermediate image surface 321, a beam control porous plate 390 can be configured with a plurality of holes with electrostatic elements, for example, multipole elements, such as deflectors, to individually steer the propagation direction of each of the plurality of charged particle beamlets 3. The holes of the beam control porous plate 390 are configured with a large diameter to allow the plurality of primary charged particle beamlets 3 to pass through, even when the focal point 311 of the primary charged particle beamlet 3 is located on the curved intermediate image surface 321. The primary charged particle source 301, each of the active porous plates 306.1, 306.2, 306.3, and the beam control porous plate 390 are controlled by a primary beamlet control module 830 connected to the control unit 800. The plurality of foci of the primary charged particle beamlets 3 passing through the intermediate image surface 321 are imaged by the field lens set 103 and the objective lens 102 into the image or object plane 101, in which the surface 25 of the wafer 7 is located. A voltage is applied to the wafer via a sample voltage source (503), generating a decelerating electrostatic field between the objective lens 102 and the wafer surface. The object illumination system 100 further includes a focusing multi-beam raster scanner 110 located near the first beam intersection point 108, whereby the plurality of charged particle beamlets 3 can be deflected in a direction perpendicular to the propagation direction of the charged particle beamlets. The propagation direction of the primary beamlets in this embodiment is the positive z-direction, which is aligned with the optical axis 105 at the object plane 101. The objective lens 102 and the focusing multi-beam raster scanner 110 are centered on the optical axis 105 of the multi-beam charged particle system 1, which is perpendicular to the wafer surface 25. A plurality of primary charged particle beamlets 3 forming a plurality of beam spots 5 arranged in a grating configuration are synchronously scanned on the wafer surface 25. In one embodiment, the grating configuration of the focus 5 of the plurality of N primary charged particles 3 is a hexagonal grating of about one hundred or more primary charged particle beamlets 3, for example, N = 91, N = 100, or N about 300 or more beamlets. The distance between the primary beam spots 5 is about 6 μm to 15 μm, and the diameter is less than 5 nm, for example, 3 nm, 2 nm, or even smaller. In one embodiment, the beam spot size is about 2.5 nm, and the distance between two adjacent beam spots is 8 μm. At each scanning position of each of the plurality of main beam spots 5, a plurality of secondary electrons are generated to form a plurality of secondary electron beamlets 9 in the same grating configuration as the main beam spot 5. The intensity of the secondary charged particle beamlet 9 generated at each beam spot 5 depends on the intensity of the impinging primary charged particle beamlet 3 irradiating the corresponding beam spot 5, the material composition and layout of the object 7 under the beam spot 5, and the charging condition of the sample at the beam spot 5. The secondary charged particle beamlet 9 is accelerated by the electrostatic field generated by the sample charging unit 503 between the sample 7 and the objective lens 102. The plurality of secondary charged particle beamlets 9 are accelerated by the electrostatic field between the objective lens 102 and the wafer surface 25, and are focused by the objective lens 102 and pass through the first focusing multi-beam raster scanner 110 in a direction relative to the primary beamlet 3. The plurality of secondary beamlets 9 are deflected and scanned by the first focusing multi-beam raster scanner 110. Then, the plurality of secondary charged particle beamlets 9 are guided by the beam splitter unit 400 to follow the secondary beam path 11 of the detection unit 200. The plurality of secondary electron beamlets 9 travel in a direction relative to the primary charged particle beamlet 3, and the beam splitting unit 400 is configured to separate the secondary beam path 11 from the primary beam path 13, typically using a magnetic field or a combination of a magnetic field and an electrostatic field. Optionally, an additional magnetic correction element 420 is present in the primary beam path or the secondary beam path. The detection unit 200 images the secondary electron beamlets 9 onto the image sensor 207, forming a plurality of secondary charged particle image spots 15 on the image sensor. The detector or image sensor 207 comprises a plurality of detector pixels or individual detectors. The intensity of each of the plurality of secondary charged particle beam spots 15 is detected separately, and the material composition of the wafer surface 25 is determined with high resolution, enabling high-throughput detection of large image blocks of the wafer. For example, for a 10×10 beamlet raster with an 8 μm pitch, a single imaging scan by the multi-beam raster scanner 110 generates an image block of approximately 88 μm × 88 μm, with an image resolution of, for example, 2 nm or less. The image block is sampled using half the beam spot size, resulting in 8,000 pixels per image line per beamlet, resulting in an image block generated by 100 beamlets containing 6.4 billion pixels. The digital image data is aggregated by the control unit 800. Details of digital image data capture and processing using, for example, parallel processing are described in International Patent Application WO 20201 / 51904 A2 and U.S. Patent No. 9,536,702, which are hereby incorporated by reference herein. The projection system 205 of the detection unit 200 further comprises at least one second focusing raster scanner 222, which is connected to the scanning image control unit 820. The control unit 800 and the imaging control unit 820 are configured to compensate for residual differences in the positioning of the plurality of focal spots 15 of the plurality of secondary electron beamlets 9, so that the positioning of the plurality of secondary electron focal spots 15 remains constant at the image sensor 207. The projection system 205 of the detection unit 200 further includes electrostatic or magnetic lenses 208, 209, 210 and a second intersection 212 of the plurality of secondary electron beamlets 9, in which an aperture filter 214 is located. The imaging control unit 820 is further connected to at least one electrostatic lens 206 and a third deflection unit 218. The projection system 205 may further include at least one first multi-aperture corrector 220 having a plurality of apertures and electrodes for individually influencing each of the plurality of secondary electron beamlets 9 and an optional additional active element 216 connected to the control unit 800 or the imaging control unit 820. The image sensor 207 is configured with an array of sensing areas whose pattern corresponds to the grating configuration of the secondary electron beamlets 9 focused onto the image sensor 207 by the projection lens 205. This allows each individual secondary electron beamlet to be detected independently of the other secondary electron beamlets incident on the image sensor 207. The image sensor 207 shown in FIG1 may be an electron-sensitive detector array, such as a CMOS or CCD sensor. This electron-sensitive detector array may include an electron-to-photon conversion unit, such as a scintillator element or an array of scintillator elements. In another embodiment, the image sensor 207 may be configured as an electron-to-photon conversion unit or a scintillator plate disposed in the focal plane of a plurality of secondary electron particle image spots 15. In this embodiment, the image sensor 207 may further include a relay optical system for imaging and directing photons generated by the electron-to-photon conversion unit onto the secondary charged particle image spots 15 on dedicated photon detection elements, such as a plurality of photomultiplier tubes or avalanche photodiodes (not shown). Such an image sensor is disclosed in US Pat. No. 9,536,702, which is incorporated herein by reference in its entirety. In one embodiment, the relay optical system further comprises a beam splitting element for splitting and directing light to a first slow light detector and a second fast light detector. The second fast light detector is, for example, configured by an array of photodiodes, such as avalanche photodiodes, which is fast enough to resolve image signals of the plurality of secondary electron beamlets 9 according to the scanning speed of the plurality of primary charged particle beamlets 3. The first slow light detector is preferably a CMOS or CCD sensor that provides a high-resolution sensor data signal for monitoring the focus 15 or the plurality of secondary electron beamlets 9 and for controlling the operation of the multi-beam charged particle microscope 1. While acquiring image blocks by scanning the plurality of primary charged particle beamlets 3, the stage 500 preferably does not move. After acquiring an image block, the stage 500 moves to the next image block to be acquired. In an alternative embodiment, the stage 500 continuously moves in the second direction while simultaneously acquiring images by scanning the plurality of primary charged particle beamlets 3 in the first direction using a focused multi-beam raster scanner 110. Stage movement and stage positioning are monitored and controlled by sensors known in the art, such as laser interferometers, grating interferometers, and confocal microlens arrays. According to one embodiment of the present invention, a plurality of electrical signals are created and converted into digital image data and processed by the control unit 800. During an image scan, the control unit 800 is configured to trigger the image sensor 207 to detect a plurality of real-time resolved intensity signals from the plurality of secondary electron beamlets 9 at predetermined time intervals, and digital images of image blocks are accumulated and stitched together from all scan positions of the plurality of primary charged particle beamlets 3. A multi-beam generating unit 305 is described, for example, in US 2019 / 0259575 and US 10,741,355 B1, both of which are incorporated herein by reference. Further details of the multi-beam generating unit 305, which is insensitive to manufacturing errors and scattering, are disclosed in WO 2021 / 180365 A1, which is incorporated herein by reference. FIG2 illustrates another example of an embodiment of the present invention. The same reference numerals as in FIG1 are used, and reference is also made to FIG1. ​​The example of FIG2 includes a first aperture plate 316 and a first filter plate 304.1, through which the primary charged particle beam 309 is filtered. The pre-filtered electron beam is collimated by a condenser 303 and incident on a second filter plate 304.2, where it is ultimately formed into a primary beamlet. The first filter plate 304.1 helps reduce the electron current absorbed by the second filter plate 304.2. FIG2 further illustrates an example of a tilt angle 109 introduced by a beam splitter 400 within the primary beam path 11. Due to the tilt angle 109, the axis z' upstream of the beam splitter is tilted relative to the z-axis corresponding to the wafer-level optical axis 105 by the tilt angle 109. To achieve identical imaging characteristics, each primary electron beamlet must be circular and identical. Identical means that the pupil distribution 117 of each electron beamlet 3 in the pupil or intersection plane 108 must also be identical. For each beamlet 3, this corresponds to an equal far-field distribution 113 in a plane 111 parallel to the image plane 101 (see FIG1 ). To achieve an equal and circular far-field distribution 113 or an equal and circular pupil distribution 117, respectively, the beamforming apertures in the filter plate 304 are configured to pre-compensate for the geometric effects of the beam tilt angle 109. FIG3 illustrates an example of a reduction in the number of primary charged particle beamlets 3. Each beamforming aperture 85.0 to 85.ij of the filter plate 304 or 304.2 exhibits a slightly different ellipse. For the different sizes and different ellipse shapes, field curvature, image plane tilt, and the geometric effects due to the tilt angle 109 are pre-compensated. FIG4 shows a cross-section of an example of a multi-beam generating unit 305. The example of FIG4 includes an inner region 335 of a thin film having porous plates 304 and 306 of the multi-beam generating unit 305. The stack of porous plates further includes a support region 333 to support the thin film region and provide mechanical stability. The multi-beam generating unit 305 includes a series of five porous plates 304 and 306.1 to 306.4 in the z-direction of propagating electrons and a global condenser 308. Each porous plate 304 and 306.1 to 306.4 includes a plurality of holes 85, which are spaced apart at the same lateral distance P1 of about 70 μm to 100 μm in each plate and each plate is aligned so that a plurality of primary charged particle beamlets 3 are generated and shaped. In the example of FIG4 , a plurality of porous plates 304 and 306.1-306.4 and a global field lens 308 with an electrode 82 are separated by spacers 83.1-83.4 and spacer 83.5. However, other configurations (e.g., without spacers 83.1 or 83.4) are also possible. The multi-beam generating unit 305 is shown in cross-section (x, z) with only four holes 85 in each porous plate in the inner thin film region 335. As described above, the number of beamlets 3 and the corresponding number of holes 85 can be much larger. The multi-beam generating unit 305 includes two multipole or multi-astigmat arrays 306.1 and 306.4. The multipole or multi-astigmat array is further designated by reference numeral 316. For example, the multipole array 306.4 functions as a multi-deflector array for adjusting the beam spacing in the intermediate image plane 321 (see FIG. 2 ). Each of the multipole arrays 306.1 and 306.4 includes four or more electrodes 81, for example, eight electrodes, for each of the plurality of apertures 85. During use, a different voltage, for example, in the range of -20 V to +20 V, can be applied individually to each of the plurality of electrodes 81, thereby individually influencing each of the beamlets 3.1 to 3.4. For example, using antisymmetric voltage differences, each beamlet 3.1 to 3.4 can be deflected in a direction to adjust the spacing or pre-compensate for distortion aberrations of the illumination unit 100. By means of an optional further global field lens 308, attached to the stack of porous plates 306 by means of a gasket 86, each of the plurality of primary charged particle beamlets 3 comprising beamlets 3.1 to 3.4 is focused during use onto a curved and tilted intermediate image plane 321 to form a focal astigmatism corrected spot. A multipole charged particle beam system 1 thus includes at least one multipole array element (306.1, 306.2, 306.3, or 306.4; 316). FIG. 5 schematically illustrates a top view of a multipole array 316 having eight electrodes 81 per aperture 85. For better illustration, only seven apertures 85 are shown. The eight electrodes 81 at each aperture form a multipole element 79, with seven multipole elements 79.1 to 79.7 shown. The configuration of FIG. 5 illustrates hexagonal symmetry, but other shapes (such as a Cartesian grating) are also possible. The multiple electrodes 81 at each aperture are isolated from each other. Each of the plurality of multipole electrodes 81 is connected to a control unit 830 via a wiring interconnect 86, which is configured to individually influence each primary beamlet during use. In use, a plurality of low voltages in the range of -20V to 20V are applied to the plurality of electrodes. FIG6 a shows a multipole electrode 81 having electrode rings 81.1 to 81.8 of a multipole element 79 of a multipole array 316 according to the prior art. Electrode rings 81.1 to 81.8, located in the circumference of a corresponding aperture 85, typically have a radial extent of between 2 μm and 10 μm. An isolating vacuum gap or recess 173.1 is formed between each electrode 81.1 to 81.8. Electrodes 81.1 to 81.8 are further embedded in insulating material 191. The electrodes are in turn connected to a control unit 830 (not shown) via electrical interconnects. Vacuum gap 173.1 extends radially from the center 89 of aperture 85. A problem with this solution is the open surface area 73 of insulating material 191 within the vacuum gap. Scattered electrons can reach surface area 73 and adhere to insulating material 191, causing undesirable effects on the electrostatic field generated by multipole array 316 during use. A first attempt to address this issue was to introduce a maze-shaped vacuum gap 173.2, as shown in FIG6 b. By utilizing the labyrinthine vacuum gap 173.2, the open surface 73 of the isolation material can be effectively shielded by the conductive electrodes 81.1 to 81.8, and the likelihood of scattered electrons reaching the surface 73 of the isolation material 191 is reduced. FIG6 c shows another multipole element 79 according to the prior art, which has a T-shaped vacuum gap 173.3 between the electrodes 81.1 to 81.8 embedded in a ring segment of the isolation material 191 and is completely embedded in the conductive material 95. The conductive material 95 can be grounded. The conductive material has the property of shielding the electric field generated by the electrodes 81.1 to 81.8 of each multipole element 79 of the multipole array 316 and is generally used to suppress crosstalk between the individual multipole elements of the multipole array 316. Each hole 85 typically has a diameter D of about 40 μm ≤ D ≤ 70 μm; therefore, the width W of each vacuum gap is only a few μm, such as 5 μm, 4 μm, or 3 μm, or even smaller. Those narrow, maze-like vacuum gaps 173.2 or T-shaped vacuum gaps 173.3 with corners or edges 181 (see Figures 6b and 6c) are more difficult to evacuate and more difficult to achieve the high vacuum requirements of charged particle beam systems. Narrow vacuum gaps 173.2 or 173.3 with multiple corners or edges 181 typically take longer to reach low vacuum pressure or 10E. -6 Torr or lower, if this is possible at the vacuum gap 173. According to a first embodiment of the improved multipole array 316, a vacuum gap 173.4 is advantageously used that lacks corners or edges 181 within the vacuum gap 173. FIG. 7 a illustrates an example of a solution using a deep vacuum gap 173.4. Multipole electrodes 81.1 to 81.8 are positioned at aperture 85 of the multipole array element 316 and embedded in a ring segment of isolation material 191, which in turn is embedded in a conductive material 95, such as doped silicon or polysilicon. Thus, the conductive material 95 forms a shielding electrode. A deep vacuum gap or trench 173.4 of depth T3 is formed, extending beyond depth T2 of the isolation material 191 and into the conductive material 95, which functions as a shielding electrode. The open surface area 73 of the isolation material 191 is located at the sidewalls 75 of the vacuum gap 173.4 and thus has a reduced cross-section as the line of sight of the electron beamlet 3 passes through the aperture 85. This reduces the likelihood of scattered electrons reaching the open surface area 73 of the isolation material 191. In one embodiment, the thickness T1 of the electrode ring is further increased and is approximately 10 μm, 15 μm, or 20 μm. Generally, a greater thickness of the electrode in the radial direction increases the volume and thus the capacity of each electrode. The greater capacity provides greater stability against fluctuating electrons or electron diffusion. As the depth of trench 173.4 increases, and width W is approximately 3 μm or less, such as 2 μm or 1.6 μm, the aspect ratio AR of depth T1 to diameter W can reach AR = 8:1 or AR = 10:1 or greater. This further reduces the likelihood of scattered electrons reaching the open surface region 73 of isolation material 191. For such deep trenches 173.4, with aspect ratios AR = T1:W and AR ≥ 8:1, a positive voltage Ub, for example, can be applied to conductive material 95 without disrupting the multipole field generated by multipole electrodes 81.1 to 81.8 within aperture 85. Furthermore, conductive material 95 still forms a shielding electrode between the electrodes of different multipole elements 79 of multipole array 316. Consequently, any negatively charged electrons or charged particles reaching the depth between T2 and T1 are accelerated to conductive material 95, further reducing the likelihood of scattered electrons reaching the open surface region 73 of isolation material 191. Furthermore, deep trenches 173.4 extending into conductive material 95 include recesses 197 within conductive material 95, which act as concentrators for contaminant particles. By concentrating contaminant particles within recesses 197, the lifespan of multipole array element 316 is increased. On the other hand, contaminant particles, such as those charged with positrons, are repelled by the positive voltage Ub applied to conductive material 95 and do not penetrate deep into trenches 173.4. They are therefore more easily expelled through apertures 85. For example, during evacuation, a voltage pulse can be applied to conductive material 95 to push charged contaminant particles out of trenches 173.4. According to another example, the deep vacuum gap or trench can also be configured with an inclination angle J between a tangent to the side surface 75 of the deep trench 173.5 and a radial vector 187 from the hole center 89. Such an example is illustrated in FIG7b. Using the inclination angle J, the likelihood of scattered electrons reaching the open surface section 73 of the isolation material 191 is even further reduced. The inclination angle J can be selected to exceed 15°, 20°, 30°, or even greater, such as 45°. When the inclination angle J exceeds 30°, the likelihood of scattered electrons reaching the open surface section 73 of the isolation material 191 is even further reduced. Although the inclination angles J are shown to be equal and have the same direction in FIG7b, this is not necessarily the case. Different inclination angles J between adjacent electrodes 81.1 to 81.8 are also possible, as well as different orientations of the vacuum gaps 173.5, with each vacuum gap 173.5 having a different positive or negative angle J. It should be noted that the multipolar array element 316 according to any embodiment is generally not limited to only eight electrodes 81.1 to 81.8 at each aperture 85, but the number of electrodes 81 can be any number greater than 1, such that at least two adjacent electrodes 81.1 and 81.2 are separated from each other by an isolation gap 173. Another problem to be solved with narrow vacuum gaps is the large field gradient within the narrow vacuum gap 173. Typically, the large field gradient limits the voltage range applied to the multipole element 79. For example, the typical maximum voltage difference allowed between adjacent electrodes is in the range of less than 20V, and at higher voltages, sparks can be generated. A particular cause of sparks is residual air pressure after evacuation or contaminant particles in the vacuum. Sparks have been shown to be particularly prone to occurring at corners or edges of the vacuum gap. Figure 8a provides a simplified illustration of the effect. Charged contaminant particles or residual gas particles 167.1 are attracted and accelerated along path 169 by the large field gradients 177.1, 177.2 generated between edge 179.1 of electrode 81.7 and edge 179.2 of electrode 81.6. Edge 179 is formed at the intersection of side surface 75 of vacuum gap 173 and inner surface 77 of electrode 81 leading to aperture 85. During use, large field gradients 177.1, 177.2 at edge 179 are generated based on the voltage difference U2-U1 applied to electrodes 81.6 and 81.7. Large field gradients 177.1, 177.2 are shown in simplified form. Contaminant particles 167.1 may adhere to edge 179.1. When multiple particles 167.2 adhere to edge 179.1, the gap width W is effectively reduced, and sparks may be generated during use. A similar effect is expected for the inner edge 181 within a T-shaped or labyrinthine vacuum gap 173 (see FIG8 b ). Contaminant particles 167.3 within the vacuum gap 173 are accelerated by the high local field gradient at the inner edge 181 and can form an accumulation area for contaminant particles 167.4, which can adhere to the electrodes 81.6 or 81.7 at the inner edge or corner 181. Consequently, sparks or even short circuits may occur during use. According to one embodiment, multipole array element 316 includes a plurality of electrodes at each aperture having a vacuum gap 173.6 but no edges 181 or 179. For example, the intersections between surface segments 75 on either side of vacuum gap 173 and inner surface 77 of electrode 81 are rounded, with a radius R ≥ 1 μm, such as R = 2 μm, R = 3 μm, or R = 4 μm. This prevents the large field gradient 177 shown in FIG8 . A first example is shown in FIG9a . The same reference numerals as in FIG7 are used and referenced above. The inclined deep vacuum gap 173.6 reduces the likelihood of electrons reaching isolated surface region 73. Furthermore, the intersection of the surfaces forming the electrodes at vacuum gap 173.6 is rounded to form rounded cylindrical edge segments 183, 183.1, and 183.2. Rounded edge segment 183 extends in the direction of propagation of the electron beamlet of transmission aperture 85 (the z' direction is perpendicular to the x' and y' directions in the figure). Thereby, the risk of contaminants adhering to the intersection of the surface 75 of the vacuum gap 173.6 and the inner surface 77 of the hole 85 is reduced, and the generation of sparks during use is reduced. Thereby, the voltage range for driving the multipole element can be increased, for example by more than 30%, for example by increasing to more than 26V difference between adjacent electrodes 81 or even more, for example 30V, and a larger operating range is implemented without the risk of sparks. FIG9 b shows another example of a multipolar array element 316 having a plurality of electrodes 81.1 to 81.8 with vacuum gaps 173.7 and no sharp edges 181 or 179. Here, each vacuum gap 173.7 comprises a circular profile or S-shape with circular inner surface segments 185.1 and 185.2, in addition to circular edge segments 183.1 and 183.2 at the inner surface of aperture 85. This reduces the risk of contaminants adhering to vacuum gaps 173.7 and further reduces the likelihood of electrons reaching isolated surface region 73. In the example shown in FIG9 c , circular surface segments 185 and circular edges 183 are provided at the entrance to and within vacuum gap 173.8. This example further illustrates electrodes with increased volume, achieving a greater depth T1 than the solutions shown in FIG9 a or FIG9 b . Electrodes 81.1 to 81.8 can partially reach behind one another, and isolation surface 73 can be hidden behind adjacent electrodes 81.1 to 81.8 (relative to the electron beam passing through aperture 85). 9d shows a vacuum gap 173.9 having a "c"-shaped V-shape with rounded edges 185 within the vacuum gap 173.9 and rounded edges 183 at the intersection of the vacuum gap 173.9 with the inner surface 77 of the hole 85. Compared to a T-shaped, S-shaped, or J-shaped vacuum gap, the evacuation of the vacuum gap 173.9 having a rounded V-shape or C-shape is improved, and the likelihood of electrons reaching the surface 75 of the isolation material 191 is reduced. FIG10 a shows another variation of the multipole electrode arrangement of the multipole array element 316 with an improved vacuum gap. Furthermore, the circular surface segments 183 and the rounded edges 185 avoid sharp edges. Here, an additional electrode 195 is embedded in the isolation material 191, and a vacuum gap 173.10 is formed between the adjacent electrodes 81.1 to 81.8 and the additional electrode 195. The open surface segments 73 of the isolation material 191 are hidden behind the electrodes 81.1 to 81.8 (for the emission of electron beamlets 3 (not shown) through the aperture 85). Within the vacuum gap 137.10 along the line of sight vector LoS, an isolation electrode 195 is provided, facing the line of sight vector LoS within the vacuum gap 173.9. Each of these electrodes 195 can be supplied with a separate voltage Ub, thereby pushing contaminants or any charged particles out of the vacuum gap 173.9 or attracting them to the additional electrode 195. FIG10 b shows another example of a multipolar array element 316 having a plurality of electrodes 81.1 to 81.8 having a T-shaped vacuum gap 173.11 and no edges 181 or 179, but having circular surface segments 183 and 185. Here, the electrodes 81.1 to 81.8 are isolated by an isolation material 191 embedded within the conductive material 95. In both examples, the electrodes 81.1 to 81.8 can have a larger volume, where the outer electronic radius R2 of the electrodes exceeds the inner radius R3 of the conductive material 95. FIG10c shows another example of an improved multipolar array element 316. A thin electrode 195 is disposed within the vacuum gap 173 between two adjacent surfaces 73 of the insulating material. Electrode 195 is connected to a power source. Electrode 195 is disposed within the vacuum gap 173 and can attract or repel charged particles, such as scattered electrons, that enter the vacuum gap 173. This eliminates the need for surface electrons on the open surface 73 or the insulating material 191. Alternatively, a metal wire or wire grid can be provided on top of the open surface 73 of the insulating material 191, rather than thin electrode 195. This avoids surface electrons, and scattered charged particles within the vacuum gap 173 are collected and directed, for example, to a positive voltage source Ub or a ground potential. In the example of FIG10 , the width W of the vacuum gap can typically be increased to approximately 4 μm or greater, and evacuation of the vacuum gap 173 can be improved. The vacuum gap 173 separating adjacent electrodes 81 or multipole elements extends in the axial or z-direction, parallel to the direction of propagation of the emission beamlets 3. Alongside the axial vacuum gap 173, the electrodes are also separated from the conductive material of the counter-electrode upstream or downstream in the direction of propagation of the emission beamlets 3 by radial vacuum gaps. Figure 11 shows a cross-section of the multipole array element 316 along the xz direction at one of the plurality of apertures 85. A cross-section through electrode 81.1 is shown. Electrode 81.1 is isolated from conductive material (e.g., doped silicon or polysilicon) 95 by an isolation material 191 (e.g., silicon dioxide). Upstream of electrode 81.1 in the direction of emission of electron beamlet 3, a conductive cover layer 299 is provided, configured to absorb incident electrons. The conductive layer 299 has an inset extension 295.1 in the direction of propagation of the electron beamlets 3. Electrode 81.1 is provided with an extension or yoke 287 of a larger radius R3 on the incident side of the electron beamlet 3. A radial vacuum gap 273.1 with a radius R3 is formed between the insertion extension 295.1 and the yoke 287 of the electrode 81.1. This radial vacuum gap 273.1 includes an open surface section 73 of the insulating material 191. This open surface section 73 is hidden behind the insertion extension 295.1 in the cover layer 299. This reduces the likelihood that electrons will reach the open surface section 73 of the insulating material 191. Furthermore, the insertion extension 295.1 includes a circular surface ring section 283.1 with a radius R, thereby reducing large local field gradients at the vacuum gap 273.1. The upper inner edge of the electrode 81.1 (as viewed in FIG. 11 ) also includes a circular annular surface section 283.2 with a radius R of approximately R = 2 μm or 3 μm, thereby reducing large local field gradients. A second vacuum gap 273.2 downstream of the electrode 81.1 is configured similarly. Here, the insertion extension 295.2 is provided at the electrode 81.1. In general, the inserted extensions 295.1 and 295.2 for covering the open surfaces 73.1 and 73.2 of the insulating material 191 are arranged in the direction of the emission beamlet 3, always at the conductive element upstream of the radial vacuum gap 273. The edges of the inner surface 77 with the plurality of holes 85 are again rounded and form circular ring segments 283.3 and 283.3, so that large local field gradients are reduced. FIG12 a shows another example of an improved multipolar array element 316. The same reference numerals as in FIG11 are used, and reference is also made to the description of FIG11 . Here, a plurality of electrodes 81 are embedded between a first outer layer 151.1 and a second outer layer 151.2. In addition to apertures 85, a plurality of additional vacuum apertures 155 are provided. The electrodes 81 ( 81.1 in FIG12 a ) are isolated from the outer layers 151.1 and 151.2 through an isolation material 191 and embedded in a conductive material 95. A shielding electrode layer 157 is formed behind each electrode 81. In FIG12 a , a shielding layer 157.1 is formed behind electrode 81.1, separated by isolation material 191. Vacuum spaces 159 provide isolation between each electrode segment. The additional vacuum apertures 155 provided in the outer layers 151.1 and 151.2 improve vacuum generation within the vacuum gap 173 between adjacent electrodes 81. FIG12b shows a simplified perspective view of a lower or second outer layer 151.2 and a plurality of electrodes at each of the apertures 85 for the electron beamlets and additional vacuum apertures 155. The first outer layer 151.1 on the electron beamlet entrance side is not shown but contains the same apertures 85 and 155. Through the apertures 155, a vacuum space 159 between the electrodes is evacuated. The vacuum space 159 communicates with the vacuum gap 173 and improves evacuation of the narrow vacuum gap 173. According to this example, the plurality of electrodes 81 are connected to at least one of the first or second outer or cover layers 151.1 or 151.2 and are isolated from the first or second outer or cover layers 151.1 or 151.2 by an insulating material 191. Between the first and second layers 151.1, 151.2, each electrode 81 is completely surrounded by a vacuum formed by the vacuum gap 173, the vacuum 85 within the apertures, and the vacuum space 159 behind each electrode 81. Each electrode 81 may in turn have a shielding electrode layer 157. The shielding electrode layer 157 may be connected to the first outer layer 151.1 and the second outer layer 151.2 or both. According to one embodiment, a method for attracting or repelling charged particles in or from a narrow vacuum gap 173, 273 between a plurality of adjacent electrodes 81 of a multipole element is provided. For example, during evacuation or during use of the multi-beam charged particle beam system 1, a voltage Ub is applied to electrodes disposed within the vacuum gap 173, 273, thereby generating an attractive or repulsive force on the charged particles within the vacuum gap 173, 273. This allows charged particles, such as contaminants, to be removed from the narrow vacuum gap or accelerated deep into the narrow vacuum gap and accumulated at electrodes or recesses within the vacuum gap. This improves evacuation and reduces the risk of sparks during use. Improvements to multipole arrays of multi-beam systems are provided. At least one of better vacuuming, no risk of contamination, and a greater range of manipulation is achieved by at least one improved component comprising a plurality of rounded edges within a vacuum gap, a plurality of deep recesses formed in a conductive material, and a plurality of electrodes within the vacuum gap for generating a repulsive or attractive force on charged particles. The present invention and various embodiments of the invention are described by way of the following examples. Example 1: A multipole array (316) for manipulating a plurality of primary charged particle beamlets (3), comprising: - a plurality of first apertures (85), wherein each aperture is used to transmit one of the plurality of primary charged particle beamlets (3); - at least one first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8), which are arranged at each aperture (85) to form a multipole element (79) and are connected to a control unit (830) for individually controlling the primary charged particle beamlets (3), each electrode (81) having a radial thickness (T1), the first and second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) having an inner surface (77) in the hole (85), and at least a first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) are embedded in the conductive material (95) and isolated from the conductive material (95) by a ring segment of the isolation material (191) between the electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) and the conductive material (95); - a vacuum gap (173) having a plurality of side surfaces (75) formed between the first and second electrodes, having a width W and a depth T3 and an aspect ratio AR = T1 / W, the depth T3 being greater than the depth T2 of the isolation material (191), thereby forming a recess (197) in the conductive material (95). Example 2: The multipolar array (316) as described in Example 1, wherein the width W is less than 3 μm, such as 2 μm or 1.6 μm, and the aspect ratio AR = T1 / W is greater than 8:1, such as 10:1. Example 3: A multipolar array (316) as described in Example 1 or 2, wherein the tangent of the side surface (75) of the vacuum gap (173) is inclined at an angle J relative to the radius vector (187) of the center of the corresponding first hole (85), wherein J is greater than 15°, for example 20° or 30° or even 45°. Example 4: A multipolar array (316) as described in any one of Examples 1 to 3, wherein the intersection between the inner surface (77) of the first electrode (81) and the side surface (75) of the vacuum gap (173) forms a rounded cylindrical edge segment (183) with a radius R greater than 1 μm at the intersection, for example, R = 2 μm or R = 3 μm, thereby avoiding large field gradients (177). Example 5: The multipole array (316) of any one of Examples 1 to 4, wherein the vacuum gap (173) comprises a plurality of planar side surfaces (75). Example 6: A multipole array (316) as described in any one of Examples 1 to 4, wherein the side surface (75) of the vacuum gap (173) includes a circular surface segment (185) to avoid large field gradients (177) within the vacuum gap (173). Example 7: The multipolar array (316) as described in Example 6, wherein the cross-section of the dry vacuum gap (173) is "s"-shaped, circular V-shaped, or "c"-shaped. Example 8: The multipolar array (316) as described in any one of Examples 1 to 7 further comprises a voltage source for providing a voltage Ub to the conductive material (95). Example 9: A multipole array (316) for manipulating a plurality of primary charged particle beamlets (3), comprising: - a plurality of first apertures (85), wherein each aperture transmits one of the plurality of primary charged particle beamlets (3); - at least one first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) arranged in each hole (85) and connected to a control unit (830) for individually controlling a primary charged particle beamlet (3), the first and second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) having an inner surface (77) within the hole (85), and the at least first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) being embedded in an insulating material (191); a vacuum gap (173) having a side surface (75) formed between the first and second electrodes; An additional electrode (195) is arranged in the vacuum gap (173) along the line of sight (LoS) direction, and has a primary charged particle beam (3) that transmits a first aperture (85). The additional electrode (195) is connected to a voltage source for providing a voltage Ub to generate a repulsive or attractive force on the charged particles entering the vacuum gap (173). Example 10: The multipolar array (316) of Example 9, wherein the additional electrode (195) is formed by thin wires or a wire grid. Example 11: A multipole array (316) as described in any one of Examples 1 to 10, further comprising a conductive covering layer (299) located on the first side of the incidence of the plurality of primary charged particles (3), the conductive covering layer (299) comprising an inserted extension (295.1) extending along the propagation direction and covering the isolation material (191) and forming a first radial vacuum gap (273.1) having each electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8). Example 12: A multipolar array (316) as described in any one of Examples 1 to 11, wherein each electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) includes an inserted extension (295.2) extending along the propagation direction and covering the isolation material (191), and a second radial vacuum gap (273.2) having a conductive material (95) is formed downstream of the electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8). Example 13: A multipole array (316) as described in any one of Examples 11 or 12, wherein at least one circular ring segment (283) is provided at the first or second radial vacuum gap (273.2) to avoid large field gradients within the vacuum gap (273.1, 273.2). Example 14: A multipole array (316) as described in any one of Examples 1 to 13, further comprising a plurality of second or vacuum holes (155), each of the vacuum holes (155) being connected to a vacuum gap (173) from a rear end opposite to the inner surface (77) of the first hole (85). Example 15: A multipole array (316) for manipulating a plurality of primary charged particle beamlets (3), comprising: - a plurality of first apertures (85), wherein each aperture is used to transmit one of the plurality of primary charged particle beamlets (3); - at least a first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8), which are arranged in each aperture (85) and connected to a control unit (830) for individually controlling the primary charged particle beamlets (3), the first and second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) having apertures ( 85), and the at least first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) include a layer of insulating material (191) on a side opposite to the inner surface (77), the insulating material (191) layer being covered by a conductive material (95) connected to a voltage source for providing a voltage Ub or a ground potential; - a vacuum gap (173) having a side surface (75) formed between the first and second electrodes; - a first outer layer (151.1) covering the electrode (81) from the direction of the plurality of primary charged particle beamlets (3) and comprising the plurality of first holes (85) and further comprising a plurality of second or vacuum holes (155) for improving evaporation of the vacuum space (159) between the plurality of electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) of different holes (85, 85.1 to 85.11). Example 16: The multipolar array (316) of any one of Examples 8 to 15, wherein the voltage source is configured to provide a pulsed voltage Ub during evacuation to enhance evacuation of the vacuum gap (173). Example 17: The multipolar array (316) of any one of Examples 8 to 16, wherein the voltage source is configured to provide a voltage Ub during operation of the multipolar array (316). Example 18: A multi-beam charged particle beam system (1), comprising at least one first multipole array (316, 306, 390) as described in any one of Examples 1 to 17. Example 19: A multi-beam charged particle beam system (1) as described in Example 18, wherein the first multipole array (316, 306) is configured in a multi-beam forming unit (305), which is configured for individual deflection, focusing or shaping during use of at least one of the plurality of primary charged particle beamlets (3). Example 20: The multi-beam charged particle beam system (1) as described in Example 18, wherein the first multipole array (316, 306) is configured adjacent to the intermediate image surface (321) for individual deflection during use of at least one of the plurality of primary charged particle beamlets (3). Example 21: The multi-beam charged particle beam system (1) as described in Example 19 or 20, further comprising a second multipole array (316, 306, 390). Example 22: A multi-beam charged particle beam system (1) as described in Example 21, wherein the first and second multipole arrays (316, 306) are configured for at least two functions, which are selected from the functions of individual deflection, individual focusing and individual shaping during the use of at least one of a plurality of primary charged particle beamlets (3). Example 23: A multi-beam charged particle beam system (1) as described in Example 18, wherein the first and second multipole arrays (316, 306) are configured for at least one first deflection to adjust the position of a charged particle beamlet (3) at an image plane (101); and configured for at least one second deflection to adjust the angle (101) of the charged particle beamlet (3) at the image plane. Example 24: A multi-beam charged particle beam system (1) as described in any one of Examples 18 to 23, further comprising a filter plate (304, 304.2) having a plurality of holes (85) located upstream of the multipole array (316, 306, 390) and configured to generate a plurality of primary charged particle beamlets (3) from an incident charged particle beam (309) during use. Example 25: The multi-beam charged particle beam system (1) as described in Example 24, wherein each of the plurality of holes (85, 85.0, 85.11, 85.12, 85.22) of the filter plate (304, 304.2) has a cross-section of different size, shape or orientation. However, the present invention is not limited to the examples described, and it should be understood that various combinations and modifications are possible. 1: Multi-beam charged particle system 3: Primary charged particle beamlet 3.1: Beamlet 3.2: Beamlet 3.3: Beamlet 3.4: Beamlet 5: Primary charged particle beam spot 7: Object; Wafer 9: Secondary electron beamlet 11: Secondary charged particle beam path; Secondary beam path 13: Primary beam path 15: Secondary charged particle image point; Focus 25: Surface 73: Open surface area; Open surface; Open surface segment; Adjacent surface 75: Sidewall; Side surface; Side surface segment; Surface 77: Inner surface; Inner surface 79: Multipole element Component 79.1: Multipole element 79.2: Multipole element 79.3: Multipole element 79.4: Multipole element 79.5: Multipole element 79.6: Multipole element 79.7: Multipole element 81: Electrode 81.1: Electrode 81.2: Electrode 81.3: Electrode 81.4: Electrode 81.5: Electrode 81.6: Electrode 81.7: Electrode 81.8: Electrode 82: Electrode 83.1: Gasket 83.2: Gasket 83.3: Gasket 83.4: Gasket 83.5: Gasket 85: Aperture 85.0 ~ 85.ij: beam-forming aperture 86: spacer; interconnect 89: center 95: conductive material 100: object illumination unit; object illumination system 101: object plane; image plane 102: objective lens 103: field lens assembly 105: optical axis 108: first beam intersection; pupil or intersection plane 109: tilt angle 110: focusing multi-beam raster scanner 111: plane 113: far-field distribution 117: pupil distribution 151.1: first outer layer / first layer 151.2: second outer layer / second layer 155: aperture 157: shielding electrode layer 157.1: shielding layer 159: vacuum space 167.1: charged contamination particle or residual gas particle 167.2: particle 167.3: contamination particle 167.4: contamination particle 173: vacuum gap 173 .1: Isolating vacuum gap or recess 173.2: Labyrinthine vacuum gap 173.3: T-shaped vacuum gap 173.4: Solutions using deep vacuum gaps; deep vacuum gaps or grooves 173.5: Deep grooves; vacuum gaps 173.6: Vacuum gaps 173.7: Vacuum gaps 173.8: Vacuum gaps 173.9: Vacuum gaps 173.10: Vacuum gaps 173.11: T-shaped vacuum gaps 177: Large field of view gradient 177.1: Large field of view gradient 177.2: Large field of view gradient 179: Edge 179.1: Edge 179.2: Edge 181: Corner / edge; Inner edge 183: Edge segment 183.1: Edge segment 183.2: Edge segment 185: Edge; Surface segment 185.1: Surface segment 185.2: Surface segment 191: Isolation material 195: Electrode 197: Recess 200: Detection unit 205: Projection system; Projection lens 206: Electrostatic lens 207: Image sensor 208: Electrostatic or magnetic lens 209: Electrostatic or magnetic lens 210: Electrostatic or magnetic lens 212: Second intersection 214: Aperture filter 216: Active element 218: Deflection device 220: Multi-aperture corrector 222: Focusing raster scanner 273: Vacuum gap 273.1: Vacuum gap 273.2: Vacuum gap 283: Ring segment 283. 1: surface ring segment 283.2: surface segment 283.3: ring segment 287: yoke 295.1: insertion extension 295.2: insertion extension 299: conductive covering layer; conductive layer; covering layer 300: charged particle multi-beam generator; primary beam generator; primary beamlet generator 301: source; primary charged particle source 302: deflector 303: collimating lens 304: filter plate; porous plate 304.1: filter plate 304.2: filter plate 305: multi-beam forming unit; multi-beam generating unit 306: porous plate 306.1: multipole Array; porous plate; multipole or multi-astigmat array; multipole array element 306.2: multipole array; porous plate; multipole array element 306.3: multipole array; porous plate; multipole array element 306.4: multipole array; porous plate; multipole or multi-astigmat array; multipole array element 308: field lens; global condenser; global field lens 309: primary charged particle beam; incident charged particle beam; primary electron beam 311: primary charged particle beamlet; focus 316: first aperture plate; multipole array; multipole array element 321: intermediate image table Surface; intermediate image plane 333; support region 335; inner region; inner membrane region 390: beam control porous plate; multipole array 400: beam splitter unit; beam splitter 420: magnetic correction element 500: stage 503: sample voltage source; sample charging unit 800: control unit 820: imaging control unit 830: control unit D: diameter J: tilt angle LoS: line of sight vector R: radius R2: outer electron radius R3: inner radius T1: radial thickness T2: depth T3: depth U1: voltage U2: voltage Ub: voltage W: width. Several embodiments of the present invention will be described in more detail below with reference to the accompanying drawings, wherein: FIG1 is a schematic cross-sectional view of a multi-beam charged particle system 1; FIG2 shows parts of another example of a multi-beam charged particle system 1 ; FIG3 shows an example of a filter plate 304 or 304.2; FIG4 shows an example of a multi-beam forming unit 305; FIG5 shows an example of a multipole array 316; Figures 6a, 6b, and 6c show some examples of multipole arrays 316 of the prior art; FIG7a and FIG7b show a first example of improvement of the multipole array 316; 8a and 8b illustrate a failure mechanism of a multipolar array 316 of the prior art; FIG9a, FIG9b, FIG9c, and FIG9d show a second example of improvement of the multipole array 316; FIG10a, FIG10b, FIG10c show further examples of improvements of the multipole array 316; FIG11 shows a cross-section of the improved multipole array 316; and 12a and 12b show further examples of improvements to the multipole array 316. 73: open surface area; open surface; open surface segment; adjacent surface 75: side wall; side surface; side surface segment; surface 77: inner surface; inner surface 79: Multipole components 81.1: Electrodes 81.2: Electrodes 81.3: Electrodes 81.4: Electrodes 81.5: Electrodes 81.6: Electrodes 81.7: Electrodes 81.8: Electrodes 85: Aperture 95: Conductive material 173.6: Vacuum gap 183:Edge segment 183.1: Marginal segment 183.2: Marginal segment 191: Isolation material 197: concave part 316: first aperture plate; multipole array; multipole array element R: Radius T1: radial thickness T2: Depth T3: Depth Ub: voltage W: width

Claims

1. A multipole array (316) for manipulating a plurality of primary charged particle beams (3), comprising: a plurality of first apertures (85), each first aperture (85) for conveying one of the plurality of primary charged particle beams (3); at least one first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8), disposed at each first aperture (85) to form a multipole element (79) and connected to a control unit (830) for individually controlling the primary charged particle beams (3), each electrode (81) having a radial thickness (T1), the first and the second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, ... 81.8) has an inner surface (77) in the first hole (85), and the at least first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) are embedded in the conductive material (95) and are isolated from the conductive material (95) by an annular segment of the insulating material (191) between the electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) and the conductive material (95); a vacuum gap (173) having a plurality of side surfaces (75) formed between the first and second electrodes, having a width W and a depth T3 and an aspect ratio AR = T1 / W, the depth T3 being greater than the depth T2 of the insulating material (191), thereby forming a recess (197) in the conductive material (95).

2. The multipole array (316) as described in claim 1, wherein the width W is less than 3 μm and the aspect ratio AR = T1 / W is greater than 8:

1.

3. The multipole array (316) as described in claim 1 or 2, wherein the tangent system of the side surface (75) of the vacuum gap (173) is tilted at an angle J relative to the radius vector (187) corresponding to the center of the first hole (85), wherein J is greater than 15°.

4. The multi-pole array (316) as described in claim 1 or 2, wherein the intersection between the inner surface (77) of the first electrode (81) and the side surface (75) of a vacuum gap (173) forms a rounded cylindrical edge segment (183) with a radius R exceeding 1 μm at the intersection, thereby avoiding large field gradients (177).

5. The multipole array (316) as described in claim 1 or 2, wherein the vacuum gap (173) comprises a plurality of planar side surfaces (75).

6. The multipole array (316) as described in claim 1 or 2, wherein the side surface (75) of the vacuum gap (173) includes a circular surface segment (185) for avoiding large field gradients (177) within the vacuum gap (173).

7. The multipole array (316) as described in claim 6, wherein the cross-section of the vacuum gap (173) is "S"-shaped, circular V-shaped, or "C"-shaped.

8. The multipole array (316) as described in claim 1 or 2 further includes a voltage source for supplying voltage Ub to the conductive material (95).

9. A multipole array (316) for manipulating a plurality of primary charged particle beams (3), comprising: a plurality of first apertures (85), each first aperture (85) for transmitting one of the plurality of primary charged particle beams (3); At least one first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) are disposed in each of the first holes (85) and connected to a control unit (830) for individual control of a primary charged particle beam (3). The first and second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) have an inner surface (77) within the first hole (85), and the at least one first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) are embedded in the insulating material (191); a vacuum gap (173) has a plurality of side surfaces (75) formed between the first and second electrodes; An additional electrode (195) is disposed within the vacuum gap (173) along the line of sight (LoS) direction and has a primary beam (3) of charged particles that transmits through the first hole (85). The additional electrode (195) is connected to a voltage source to provide a voltage Ub to generate a repulsive or attractive force on the charged particles entering the vacuum gap (173).

10. The multi-pole array (316) as described in claim 9, wherein the additional electrode (195) is formed by a thin wire or a wire grid.

11. The multipole array (316) as described in claim 1 or 9 further includes a conductive cover layer (299) located on the first side of the incident of the plurality of primary charged particles (3), the conductive cover layer (299) including an insertion extension (295.1) extending in the propagation direction and covering the insulating material (191), and forming a first radial vacuum gap (273.1) with each electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8).

12. The multipole array (316) as claimed in claim 1 or 9, wherein each electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) includes an insertion extension (295.2) extending in the propagation direction and covering the insulating material (191), and forms a second radial vacuum gap (273.2) with the conductive material (95) downstream of the electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8).

13. The multipole array (316) as claimed in claim 11, wherein at least one circular ring segment (283) is provided at the first or the second radial vacuum gap (273.2) to avoid large field gradients within the vacuum gap (273.1, 273.2).

14. The multipole array (316) as described in claim 1 or 9 further includes a plurality of second or vacuum holes (155), each of which is connected from a rear end opposite the inner surface (77) of the first hole (85) to a vacuum gap (173).

15. A multipole array (316) for manipulating a plurality of primary charged particle beams (3), comprising: a plurality of first apertures (85), each first aperture (85) for transmitting one of the plurality of primary charged particle beams (3); at least one first electrode and one second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8), disposed in each first aperture (85) and connected to a control unit (830) for individually controlling the primary charged particle beams (3), the first and second electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) having The first hole (85) has an inner surface (77), and the at least first electrode and a second electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) include an insulating material (191) layer on one side opposite to the inner surface (77), the insulating material (191) layer being covered by a conductive material (95) connected to a voltage source for providing a voltage Ub or a grounding level; A vacuum gap (173) having a plurality of side surfaces (75) formed between the first and second electrodes; a first outer layer (151.1) covering the electrode (81) from the direction of the plurality of primary charged particle bundles (3), comprising the plurality of first holes (85), and further comprising a plurality of second or vacuum holes (155) for improving evaporation of the vacuum space (159) between the electrodes (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) of different first holes (85, 85.1 to 85.11).

16. The multipole array (316) as described in claim 15, wherein the voltage source is configured to provide a pulse voltage Ub during evacuation to enhance the evacuation of a vacuum gap (173).

17. The multipole array (316) as described in claim 15 or 16, wherein the voltage source is configured to provide a voltage Ub during operation of the multipole array (316).

18. A multi-beam charged particle beam system (1) comprising at least one first multipole array (316, 306, 390) as described in claims 1, 9 or 15.

19. The multi-beam charged particle beam system (1) as claimed in claim 18, wherein the first multipole array (316, 306) is disposed within a multi-beam forming unit (305) configured to be used for individual deflection, focusing or shaping during the use of at least one of a plurality of primary charged particle beams (3).

20. The multi-beam charged particle beam system (1) as claimed in claim 18, wherein the first multipole array (316, 306) is configured adjacent to the intermediate image surface (321) for individual deflection during the use of at least one of a plurality of primary charged particle beams (3).

21. The multi-beam charged particle beam system (1) as described in claim 19 further includes a second multipole array (316, 306, 390).

22. The multi-beam charged particle beam system (1) as claimed in claim 21, wherein the first and second multipole arrays (316, 306) are configured for at least two functions selected from the functions of individual deflection, individual focusing and individual shaping during at least one of a plurality of primary charged particle beams (3).

23. The multi-beam charged particle beam system (1) as claimed in claim 21, wherein the first and second multipole arrays (316, 306) are configured for at least one first deflection to adjust the position of a primary charged particle beam (3) at an image plane (101) and are configured for at least one second deflection to adjust the angle (101) of the primary charged particle beam (3) at the image plane.

24. The multi-beam charged particle system (1) as described in claim 18 further includes a filter plate (304, 304.2) having a plurality of the first apertures (85) located upstream of the multipole array (316, 306, 390) and configured to generate a plurality of primary charged particle sub-beams (3) from the incident charged particle beam (309) during use.

25. The multi-beam charged particle beam system (1) as described in claim 24, wherein the plurality of first holes (85, 86, 87, 88, 89) of the filter plate (304, 304.2) Each of 85.0, 85.11, 85.12, and 85.22 has a cross section of different size, shape, or orientation.

Images