Charged particle beam device and method of operating a charged particle beam device

Abstract

The charged particle beam device includes a charged particle source and a beamlet forming porous plate. The device also includes: a precompensator, the precompensator is used to reduce the aberration of the beamlet at the target; a scanner, the scanner is used to scan each beamlet in the beamlet; the objective lens, the objective lens is used to focus each beamlet on the target; and a controller, the controller is configured to synchronize with the precompensator and the scanner. The precompensator includes: at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; and at least one "Cartesian variable" porous electrode, wherein the diameter of each hole of the at least one "Cartesian variable" porous electrode scales with the x component of the position of the hole.

Description

Technical Field

[0001] Embodiments described herein relate to charged particle beam devices, such as scanning electron microscopes, which can be configured to inspect samples such as wafers or other substrates, for example to detect pattern defects. More specifically, embodiments described herein relate to charged particle beam devices configured to utilize multiple charged particle beams (e.g., multiple beamlets). Charged particle beamlets can be used for inspection and / or testing of high resolution, lithography, and surface imaging. Embodiments described herein further relate to correction of aberrations (such as field curvature), and to methods of operating charged particle beam devices. Background Art

[0002] Modern semiconductor technology places high demands on structuring and probing samples with high resolution, reaching nanometer or even sub-nanometer resolution. Process control, inspection and structuring at the micrometer and nanometer scale are usually performed with charged particle beams (e.g., electron beams generated, shaped, deflected and focused in charged particle beam devices such as electron microscopes). Charged particle beams can provide fine spatial resolution.

[0003] Devices using charged particle beams, such as scanning electron microscopes (SEMs), have many applications, especially in integrated circuit technology. In charged particle beam systems, fine probes with variable current density, such as high current density, can be used. For example, in the case of a SEM, a primary electron beam can generate signal charged particles, such as secondary electrons (SE) and / or backscattered electrons (BSE), which can be used to image and analyze samples.

[0004] The use of multiple beams (referred to herein as beamlets) in a single column may be useful in many applications. Guiding, scanning, deflecting, shaping, correcting and / or focusing the individual beamlets of a multi-beam system may be challenging, for example, when sample structures are to be rapidly scanned and inspected at nanometer-scale resolution with high throughput.

[0005] Correcting aberrations (such as field curvature) of multiple beams in a single column can also be challenging. It is desirable to reduce aberrations.

[0006] Hence, it would be beneficial to provide a charged particle beam apparatus configured as a multi-beam system which provides high throughput and good field quality for examining sample structures.In particular, it would be beneficial to provide a charged particle beam apparatus configured for multi-beam operation with reduced aberrations. Summary of the invention

[0007] A charged particle beam apparatus and a method of operating a charged particle beam apparatus are disclosed herein. Further aspects, advantages and features of embodiments are apparent from the dependent claims, the description and the accompanying drawings.

[0008] A charged particle beam device is disclosed herein. The charged particle beam device includes a charged particle source and a beamlet forming porous plate centered on an optical axis z. The beamlet forming porous plate includes a plurality of holes, each hole is used to allow a beamlet to pass through, and the beamlet forming porous plate forms a plurality of beamlets of charged particles. The device also includes: a precompensator, the precompensator is used to reduce the aberration of the beamlet at the target; a scanner, the scanner is used to scan each beamlet in the beamlet; an objective lens, the objective lens is used to focus each beamlet on the target; and a controller, the controller is configured to communicate with the precompensator and the scanner. The precompensator includes: at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; and at least one "Cartesian variable" porous electrode, wherein the diameter of each hole of the at least one "Cartesian variable" porous electrode scales with the x component of the position of the hole, x being perpendicular to z.

[0009] Disclosed herein is a method for operating a charged particle beam device, comprising the steps of forming a charged particle beam and forming a plurality of beamlets from the charged particle beam. The beamlets are centered on the optical axis z of the device, such that a majority of the beamlets in the plurality of beamlets are offset from the optical axis after passing through a beamlet forming porous plate. The method further comprises pre-compensating each beamlet by passing each of the beamlets through a pre-compensator, the pre-compensator reducing the aberration of the beamlet at a target. The pre-compensator comprises a plurality of porous electrodes, the plurality of porous electrodes comprising: at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; and at least one "Cartesian variable" porous electrode, wherein the diameter of each hole of the at least one "Cartesian variable" porous electrode scales with the x component of the position of the hole, x being perpendicular to z. The method further comprises scanning each of the beamlets in a direction perpendicular to z; and focusing each of the beamlets in the beamlets onto a target with an objective lens to form a plurality of focal points.

[0010] The present invention discloses a precompensator for a charged particle device, comprising: at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; and at least one "Cartesian variable" porous electrode, wherein the diameter of each hole of the at least one "Cartesian variable" porous electrode scales with the x component of the position of the hole, x being perpendicular to z.

[0011] It is advantageous to consider the decomposition of the aberration into a radially related part and a Cartesian related part. The precompensator as described herein takes advantage of this decomposition of the aberration. Furthermore, it may be convenient to consider that each of the radial and Cartesian parts of the aberration may be further decomposed into contributions scaled according to a coordinate such as x, y, or r (radial distance from the optical axis). The scaling may be according to parts or terms of different orders (M=1, 2, 3... and N=1, 2, 3... for the radial and Cartesian parts, respectively).

[0012] The embodiments disclosed herein are directed to apparatuses for performing the disclosed methods, and include device components for performing the various method actions. The methods may be performed by hardware elements, computers programmed by appropriate software, by any combination of the two, or in any other manner. In addition, the embodiments are also directed to methods of operating the described devices.

[0013] Further advantages, features, aspects and details which can be combined with the embodiments described herein are apparent from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more particular description of the embodiments briefly summarized above may be obtained by reference to further embodiments. The accompanying drawings relate to one or more embodiments and are described below.

[0015] Figure 1 is a schematic cross-sectional view of a charged particle beam apparatus according to embodiments described herein;

[0016] Figure 2 is a schematic cross-sectional view of a charged particle beam apparatus according to embodiments described herein;

[0017] Figure 3 shows a "radially variable" porous electrode according to an embodiment;

[0018] Figure 4 shows a "Cartesian variable" porous electrode according to an embodiment;

[0019] Figure 5 is a schematic cross-sectional view of a precompensator according to embodiments described herein; and

[0020] Figure 6 is a flow chart illustrating a method of operating a charged particle beam apparatus according to embodiments described herein.

[0021] Figure 7 A porous electrode according to embodiments described herein is shown. DETAILED DESCRIPTION

[0022] Reference will now be made in detail to various embodiments, one or more examples of which are shown in the accompanying drawings. In the following description of the drawings, the same reference numerals refer to the same parts. Generally, only the differences with respect to the various embodiments are described. Each example is provided by way of explanation and is not meant to be limiting. In addition, features shown or described as part of one embodiment may be used in other embodiments or used in conjunction with other embodiments to produce yet further embodiments. The description is intended to include such modifications and variations.

[0023] Semiconductor technology relies on precise control of various processes used during the production of integrated circuits. For example, substrates such as wafers and masks must be repeatedly inspected in order to locate problems or defects. In order to ensure that the mask accurately defines the predetermined pattern, the mask or reticle must be inspected during substrate processing before actual use. Defect inspection of samples such as substrates, wafers or masks typically involves inspecting a large surface area in a relatively short time. In order to avoid reducing the yield due to the inspection process, a high inspection speed may be required.

[0024] A surface of a target (e.g., a sample) can be scanned using a charged particle beam (e.g., an electron beam), which can be focused on the surface of the sample. When the charged particle beam hits the target, secondary charged particles (e.g., secondary electrons) are generated and detected. By comparing the intensity signal of the secondary charged particles with, for example, a reference signal corresponding to the same position of the target, pattern defects at the location of the target can be detected. When only one charged particle beam is used for scanning, the scanning may take a lot of time and only a limited yield can be obtained.

[0025] Throughput can be increased by providing a charged particle beam apparatus configured as a multi-beam system. In a multi-beam system, multiple beamlets of charged particles are generated that propagate adjacent to each other in a column so that two or more points on a target can be examined simultaneously. However, controlling, shaping and correcting multiple beamlets can be challenging.

[0026] In this context, the coordinates and / or directions x, y and z are perpendicular to each other, wherein z corresponds to the optical axis of the device.

[0027] In this document, "optional" features and steps can be combined with any embodiment of the charged particle device and / or its operating method disclosed herein. Optional features can be combined with each other. For example, optional components and / or configurations of components of the precompensator can be combined.

[0028] In this article, it is implied or stated that each diameter of the plurality of holes of the porous electrode is "scaled", "increased" and / or "decreased" with parameters (such as r, x and / or y) may mean that each diameter has an offset value so that each hole in the plurality of holes has a positive diameter. Similarly, the ratio Q of the major axis / minor axis of the plurality of holes of the porous electrode is "scaled", "increased" and / or "decreased" with parameters (such as r, x and / or y) may mean that each ratio Q has an offset value so that each hole has a plurality of ratios Q.

[0029] Figure 1 is a schematic cross-sectional view of a charged particle beam device 100 according to embodiments described herein.

[0030] The charged particle beam device 100 includes a charged particle source 105, which is configured to generate a charged particle beam 101 that propagates along an optical axis z. The charged particle source 105 can be an electron source configured to generate an electron beam. Alternatively, the charged particle source can be an ion source configured to generate an ion beam. The charged particle beam 101 can propagate from the charged particle source 105 along the optical axis z through the column toward the target.

[0031] In some embodiments, the charged particle source 105 may include at least one of the following in order to increase the yield: a cold field emitter (CFE), a Schottky emitter, a thermal field emitter (TFE), or another high current electron beam source. High current is considered to be 10μA or higher in 100 milliradians, for example up to 5mA, for example 30μA in 100 milliradians to 1mA in 100 milliradians. According to a typical implementation, the current is substantially uniformly distributed, for example with a deviation of + / -10%. According to some embodiments that can be combined with other embodiments described herein, the charged particle source can have a typical emission half angle of 5 milliradians or higher, for example 50 milliradians to 200 milliradians. In some embodiments, the charged particle source can have a virtual source size of 2nm or more and / or 60nm or less. For example, if the charged particle source is a milli-Schottky emitter, the source can have a virtual source size from 10nm to 60nm. For example, if the charged particle source is a cold field emitter (CFE), the source may have a virtual source size from 2 nm to 20 nm.

[0032] According to an embodiment that can be combined with other embodiments described herein, a TFE or another high reduced brightness source capable of providing a large beam current is a source whose brightness does not drop by more than 20% of the maximum value when the emission angle is increased to provide a maximum of 10 μA-100 μA. For example, a Schottky or TFE emitter currently available has a measured reduced brightness of 5·10 7 Am -2 (SR) -1 V -1, while the CFE emitter has a measured reduction in brightness of up to 5·10 9 Am -2 (SR) -1 V -1 For example, a product having at least 5·10 7 Am -2 (SR) -1 V -1 The bundle is beneficial.

[0033] A plurality of optical elements may be arranged along the beam path between the charged particle source and the target. For example, a collimating lens 108 may be arranged downstream of the charged particle source 105 to collimate the charged particle beam 101 .

[0034] The charged particle beam device 100 may include a beamlet forming porous plate 110 having a plurality of holes, the plurality of holes being configured to generate a plurality of beamlets 102 of charged particles from a charged particle beam 101. For example, the beamlet forming porous plate 110 may have three, five, ten or more holes, which are configured to generate three, five, ten or more beamlets. In particular, the beamlet forming porous plate 110 may have fifty or more holes for generating fifty or more beamlets. Each hole of the beamlet forming porous plate 110 may be configured to generate a beamlet of charged particles from the charged particle beam.

[0035] The beamlet forming porous plate 110 may include a plate in which holes are formed as beam limiting holes. When the charged particle beam 101 strikes the plate having holes formed therein, the charged particles may propagate through the holes in the plate to form a plurality of beamlets, and the remainder of the charged particle beam 101 may be blocked by the plate. In some embodiments, at least one surface of the beamlet forming porous plate 110 (e.g., the surface of the beamlet forming porous plate 110 pointing to the charged particle source 105) may be a conductor or semiconductor surface to reduce or avoid charge accumulation. The beamlet forming porous plate 110 may be centered on the optical axis z.

[0036] It should be noted that Figure 1 The porous plate 110 shown in FIG. 1 is upstream of the precompensator 120. It is also possible that a plurality of beamlets 102 may be formed from the charged particle beam 101 by the porous plate of the precompensator 120. In other words, in some embodiments, the beamlet forming porous plate and the precompensator may be integrally formed.

[0037] According to embodiments described herein, the charged particle beam apparatus 100 comprises a precompensator 120. The precompensator 120 reduces aberrations of the beamlets, such as those due to field curvature. It is desirable to reduce aberrations at the target.

[0038] The precompensator may include a plurality of porous electrodes, which may be centered on the optical axis. Each porous electrode may be a plate having a plurality of holes, wherein the potential of at least a portion of the plate is adjustable. The plate may include a conductive layer or membrane that may be addressed by a voltage source and / or controller 132. Each of the porous electrodes of the device 100 may be configured as a plate-like element in which a plurality of holes through which a plurality of beamlets may propagate are provided.

[0039] The Precompensator 120 may include at least one "radially variable" porous electrode 121, which may be centered on the optical axis. The Precompensator 120 may include at least one "cartesianally variable" porous electrode 122, which may be centered on the optical axis.

[0040] The porous electrodes 121, 122 of the precompensator 120 each have a plurality of openings for a plurality of beamlets. The plurality of openings of each porous electrode 121, 122 of the precompensator 120 may be aligned with each other and with the holes of the beamlet forming porous plate 110, for example, so that the plurality of beamlets propagate through each porous plate 121, 122 and the corresponding holes of the beamlet forming porous plate 110.

[0041] According to the embodiments described herein, (multiple) "radially variable" porous electrodes 121 may provide a focusing effect on the plurality of sub-beams 102. The strength of the focusing effect on each sub-beam may depend on the distance of the corresponding sub-beam from the optical axis z. The focusing effect may also depend on the (multiple) voltages applied to the (multiple) "radially variable" porous electrodes. The focusing effect provided by the (multiple) "radially variable" porous electrodes 121 on the sub-beams may vary with the distance from the optical axis z, so that the sub-beams far from the optical axis are focused differently from the sub-beams close to the optical axis.

[0042] In an embodiment, the focusing effect of each porous electrode of Precompensator 120 may be influenced / controlled by a respective voltage applied to the respective porous electrode, such as from controller 132 .

[0043] For example, the diameter of each hole of each "radially variable" porous electrode 121 scales with the distance of the hole from the optical axis z. Figure 1 , the distance from the optical axis z can be along the radial direction r.

[0044] like Figure 1As shown, the diameter of the holes of the "radially variable" porous electrode 121 may increase with increasing radial distance r from the optical axis z. Alternatively / additionally, the diameter of the holes of the "radially variable" porous electrode may decrease with increasing radial distance r from the optical axis z. The precompensator 120 may have, for example, a "radially variable" porous electrode in which the diameter of its holes increases with the distance from the optical axis z, and another "radially variable" porous electrode in which the diameter of the holes decreases with the distance from the optical axis.

[0045] The "Cartesian variable" porous electrode(s) 122 of the precompensator 120 may be understood similarly compared to the "radially variable" porous electrode(s) 121. The diameter of each hole of the "Cartesian variable" porous electrode(s) 122 may scale with the x-component (x is perpendicular to z) of the position of the hole.

[0046] As described herein, the porous electrodes 121, 122 of the precompensator 120 can be used to reduce aberrations of the beamlet 102, such as aberrations of the beamlet that are typically present at the target 103, particularly aberrations due to field curvature. As described in more detail herein, the precompensation can be adjusted and / or regulated by operation of the device. It may be beneficial to provide a precompensator 120 that can be adjusted so that an appropriate amount of aberration correction is provided on the beamlet, which can depend on the position and / or path of the beamlet through the device. It is particularly contemplated that the precompensator 120 can dynamically precompensate for aberrations that are dynamically generated (such as during scanning of the beamlet). This may be useful for correcting aberrations that may depend on changes in the optical path of the beamlet, which may change during operation of the device 100.

[0047] For example, it is useful to consider field curvature aberrations. The beamlets 102 may experience aberrations in the form of field curvature, which may result in a focus shift Δz in the z direction that scales with the radial distance r of the beamlet from the optical axis z. The sources of optical aberrations are not necessarily limited to field curvature. Other sources of aberrations may exist.

[0048] Figure 2 is a schematic cross-sectional view of a charged particle beam device 100 according to embodiments described herein. The charged particle beam device 100 may be a scanning electron microscope. The charged particle beam device 100 comprises a charged particle source 105, for example, an electron source configured to generate a charged particle beam 101 propagating along an optical axis z, and a precompensator 120 according to any embodiment described herein. The precompensator 120 may be an adjustable precompensator 120, such that the aberration correction provided by the precompensator 120 may be adjusted, such as by providing (multiple) variable voltages to (multiple) porous electrodes of the precompensator.

[0049] The apparatus 100 may include a scanner 205 that may scan the beamlets along an x ​​and / or y direction perpendicular to the optical axis z. The scanner 205 may be operable to induce variable aberrations in the beamlets 102. The variable aberrations may depend on at least one of the phase and amplitude of the scan, and the position of the beamlets (such as along r, x, and / or y relative to the optical axis). The porous electrodes of the precompensator 120 may reduce and / or precompensate for the aberrations.

[0050] The operation of the precompensator 120 may be synchronized with the scanning of the beamlets 120 by the scanner 205. The scanner 205 may be controlled by a controller 132, which may also control the precompensator 120. The apparatus 100 may include a controller 132, which may, for example, control the voltages Ur, Uc (see Figure 1 ).

[0051] The charged particle beam device 100 may include optical elements such as a collimating lens, a transfer lens, an objective lens, electrodes, a multipole device, a deflector, and / or a scanning deflector.

[0052] like Figure 2 Schematically depicted, the charged particle beam device 100 may include an objective lens 109 that may focus the plurality of beamlets 102 onto a target 103. A plurality of focal points may be formed by focusing each of the beamlets 102.

[0053] Optionally, the apparatus 100 comprises a detector 201 configured to detect signal particles emitted from the target 103. The detector 201 may comprise a plurality of detector segments configured to detect signal particles generated when the plurality of beamlets impinge on the target. Figure 2 Schematically depicting a first detector segment 202 and a second detector segment 203, wherein the first detector segment 202 is arranged to detect signal particles generated at the focus of a first beamlet in a plurality of beamlets, and the second detector segment 703 is arranged to detect signal particles generated by the focus of a second beamlet in a plurality of beamlets. A spatially resolved image can be generated, and / or the inspection speed can be increased by parallel inspection. The detector 201 can be a segmented detector.

[0054] The objective lens 109 may include a magneto-electrostatic objective lens having a combination of a magnetic lens portion and an electrostatic lens portion. In some embodiments, a delayed field device configured to reduce the landing energy of charged particles on the target may be provided. For example, a delayed field electrode may be arranged upstream of the target.

[0055] In an embodiment, in a projection in the xz plane at the target, each beamlet 102 is angled relative to the optical axis z, and each beamlet 102 is parallel to the xz plane. In such an embodiment, the Precompensator 120 may include at least one "Cartesian variable" porous electrode 122, which is oriented so that variable focusing can occur depending on the x-component of the position of each beamlet at the target.

[0056] According to embodiments that can be combined with other embodiments described herein, the charged particle source 105 is an electron source, the charged particle beam is an electron beam, and the charged particle beam device 100 is a scanning electron microscope (SEM). According to other embodiments, the charged particle beam device is an ion beam device, the charged particle source is an ion source, and the charged particle beam is an ion beam.

[0057] like Figure 2 As shown, the charged particle beam device may include an electrostatic multipole device 250. In some embodiments, the multipole unit of the electrostatic multipole device 250 may be selected from the group consisting of an electrostatic dipole, a quadrupole, a hexapole and an octupole. For example, at least one electrostatic octupole may be provided for each of the plurality of beamlets so that each beamlet can be individually affected, such as deflected or corrected. In some embodiments, higher order electrostatic multipole elements may be provided, such as a multipole having 12, 14 or 20 poles.

[0058] In some embodiments that may be combined with other embodiments described herein, a multipole device 250 may be provided to affect a charged particle beam propagating along an optical axis, for example downstream or upstream of a precompensator. The multipole device 250 may include an electrostatic corrector having four or more corrector electrodes, in particular eight or more corrector electrodes, more particularly 12 or more corrector electrodes, or even 20 or more corrector electrodes. High-order aberrations may be corrected or compensated. The corrector electrodes of the electrostatic corrector may be arranged in a plane substantially perpendicular to the optical axis of the charged particle beam device, for example on top of one of the porous electrodes of the precompensator.

[0059] In some embodiments, the multipole device 250 may further include an electrostatic deflector having at least two deflector electrodes for deflecting the charged particle beam by a deflection angle. For example, the deflector electrode may extend along the optical axis over a first length, and / or the corrector electrode of the electrostatic corrector may extend along the optical axis over a second length less than the first length.

[0060] Figure 3 A "radially variable" porous electrode of a precompensator according to an embodiment is shown. The precompensator may include at least one "radially variable" porous electrode 332, and Figure 3Two "radially variable" porous electrodes are shown. The upper "radially variable" porous electrode 301 has holes with diameters that increase with increasing distance r from the optical axis, which is referred to herein as the "forward" configuration. Figure 3 The "radially variable" porous electrode 302 below has holes with diameters that decrease with increasing distance r from the optical axis, which is referred to herein as an "inverted" configuration.

[0061] In an embodiment, each of the at least one "radially variable" porous electrode 332 of the precompensator 120 includes a plurality of holes whose diameters scale with the Mth power of the distance r of the corresponding hole from the optical axis (M is a positive integer). The "radially variable" porous electrode 332 may include a first-order "radially variable" porous electrode, in which the diameter of its holes increases with the first power of the distance r. Alternatively / additionally, there may be a second-order "radially variable" porous electrode, in which the diameter of the holes increases with the second power of the distance r from the optical axis. Alternatively / additionally, there may be a third-order "radially variable" porous electrode, in which the diameter of the holes increases with the third power of the distance r from the optical axis.

[0062] The focusing power of each hole of each "radially variable" porous electrode 332 of the precompensator 120 can vary with the diameter of the hole. The focusing power of the beamlets applied to the holes passing through the porous electrode can be scaled with the hole size. In addition, the potential or voltage of each porous electrode can be controllable / adjustable (such as by the controller 132). The focusing power of each hole of the "radially variable" porous electrode can be scaled with the voltage (in some embodiments, advantageously, the corresponding voltage applied to each corresponding porous electrode) and the diameter of the hole. The diameter of each hole of the porous electrode can further vary, for example, according to the Mth power of the distance r of the hole from the optical axis z.

[0063] Each porous electrode may be addressable by controller 132 , which may independently and / or dynamically control each voltage (eg, Ur1f, Ur1r) of each porous electrode.

[0064] The radial part of the aberration can be reduced by passing each of the beamlets through the corresponding aperture of each "radially variable" porous electrode. The pre-compensation of the beamlets can be accomplished by adjusting each "term" of the polynomial sequence expansion (of aperture size) by controlling the voltage of each of the plurality of "radially variable" porous electrodes; wherein each "radially variable" porous electrode has a pore size distribution that is scaled according to an integer power (M = 1, 2, 3, ...) of the distance r of the pores from the optical axis.

[0065] In an embodiment, each of the at least one "radially variable" porous electrode comprises a respective plurality of holes whose diameters scale with the distance r of the respective hole from the optical axis to the Mth power (M being selected from a set of positive integers).

[0066] For convenience, in this article, the porous electrode can be a "forward" porous electrode with holes that increase along a coordinate such as r, x, or y; or the porous electrode can be a "reverse" porous electrode that has holes that decrease along a coordinate such as r, x, or y. There are conceivable embodiments in which for each M-order "forward" porous electrode 301, there is a corresponding M-order "reverse" porous electrode 302.

[0067] The precompensator 120 may include both forward and reverse "radially variable" porous electrodes, which may correspond to an aberration correction that is the sum of the corrections of each "radially variable" porous plate, for example, a possible piecewise correction (M=1, 2, 3...) from a polynomial sequence of adjustable terms, each term coming from a porous electrode that can provide a positive correction (forward configuration of an M-order "radially variable" porous electrode) or a negative correction (reverse configuration of the same M-order "radially variable" porous electrode).

[0068] The precompensator may include each forward "radially variable" porous electrode of M order and lower order with M = 2, 3, 4, 5, 6, 7 or 8, and may also optionally include each reverse M order and lower order "radially variable" porous electrode.

[0069] According to an embodiment, Figure 3 A forward "radially variable" porous electrode 301 and a reverse "radially variable" porous electrode 302 are shown.

[0070] The (multiple) “radially variable” porous electrodes 121 may focus or perform optical operations on each of the plurality of beamlets in a manner that varies with the distance r from the optical axis z. The optical axis z may be defined by the central opening of the precompensator 120. In other words, by each “radially variable” porous electrode 121, beamlets propagating close to the optical axis z may be focused differently (e.g., have different focal lengths) than beamlets propagating away from the optical axis z.

[0071] Apply to Figure 3 The voltage applied to the upper radially variable porous electrode 301 is labeled Ur1f. The universal symbol for voltage U, labeled r1f, indicates that the voltage is applied to a radially variable porous (r) electrode that is first order (1) in the scaling of the pores with the distance from the optical axis, and the porous electrode is in the forward configuration (f). Figure 3The voltage of the lower "radially variable" porous electrode 301 is marked as Ur1r; the mark r1r indicates that the voltage is applied to the radially variable porous (r) electrode, which is first order (1) in the scaling of the pores with the distance from the optical axis, and the porous electrode is in the reverse configuration (r).

[0072] By way of illustration and not limitation, significant aberrations may exist due to field curvature in a multi-beam arrangement having beamlets located at different distances from the optical axis. Aberrations of the beamlets, particularly those resulting from field curvature, may scale to a large extent as a function of the second power of the distance r of the aperture and / or beamlet from the optical axis z. Field curvature aberrations are known to cause a shift in focus that may scale with the square of the distance of the beamlet from the optical axis. Beamlets that are far from the optical axis z (along coordinate r) may be focused farther in the z direction than those that are closer to z (at relatively low r). In view of the above, a precompensator 120 is particularly contemplated that includes a second order "radially variable" porous electrode among the "radially variable" porous electrodes, the second order "radially variable" porous electrode having apertures that scale with the second power of the distance from the optical axis.

[0073] Figure 4 A "Cartesian variable" porous electrode 432 of a precompensator 120 according to an embodiment is shown. The precompensator may include at least one "Cartesian variable" porous electrode 432, and Figure 4 Two "Cartesian variable" porous electrodes are shown. The upper "Cartesian variable" porous electrode 401 has holes with a diameter that increases along the coordinate x. Figure 4 The lower "Cartesian variable" porous electrode 402 has holes with diameters that decrease with the x-component of the position of the holes. The upper "Cartesian variable" porous electrode 401 can be considered as a forward porous electrode, while the lower 402 can be considered as a reverse porous electrode.

[0074] Similarly, as explained for the “radially variable” porous electrode of the precompensator, each of the “Cartesian variable” porous electrodes 432 may have a corresponding plurality of holes whose diameters scale with the Nth power (N being a positive integer) of the x-component of the position of the corresponding hole.

[0075] The precompensator may include each forward "Cartesian variable" porous electrode of N order and lower order with N = 2, 3, 4, 5, 6, 7 or 8, and may also optionally include each reverse M order and lower order "Cartesian variable" porous electrode. Alternatively / additionally, the precompensator 120 may include a set of similar porous electrodes with pore sizes that vary along the y direction.

[0076] In an embodiment, which may be combined with any other embodiment described herein, the forward "Cartesian variable" porous electrode of the Precompensator comprises first and second order (N=1 and 2) porous electrodes.

[0077] In an embodiment that may be combined with any other embodiment described herein, the reverse "Cartesian variable" porous electrode(s) comprise electrodes of the same order as the forward configuration, but arranged so that the diameter decreases along x rather than increases (as in the pores of the forward porous electrode(s)). In a specific example, there are first and second order forward and reverse "Cartesian variable" porous electrodes.

[0078] In an embodiment that may be combined with any other embodiment described herein, a radial or Cartesian variable type "inverse" porous electrode has a diameter that scales with the inverse power of the coordinate (r, x, or y as appropriate) (e.g., according to 1 / M and 1 / N). In other words, each inverse "Cartesian variable" porous electrode may have a diameter that scales with x for a positive integer N. -N scaled pore diameter; alternatively / additionally, each inversely "radially variable" porous electrode may have a positive integer M with increasing r -M The direction or coordinate x may be the direction in which the beamlets are scanned by the scanner 205. Alternatively / additionally, the x direction may be the x direction of a rotated coordinate system such that the x direction at each "Cartesian variable" porous electrode 432 of the Precompensator 120 matches the x direction at the scanner 205 and the target 103.

[0079] Alternatively / additionally, the precompensator 120 may include at least one "Cartesian variable" porous electrode in which the diameter of each hole scales with the y-component of the position of the hole. The scanner 205 may deflect the beamlet 102 along the y-direction, and the precompensation may include passing the beamlet through (multiple) "Cartesian variable" porous electrodes with variable holes that scale with the y-component of the position and may operate similarly to that described for the previously described "Cartesian variable" porous electrode 432 with holes that vary with the x-component of the position.

[0080] The controller 132 can control each corresponding voltage of each "Cartesian variable" porous electrode of the precompensator 120 having holes that vary along the x-direction, such as Ux1f, Ux2f, Ux3f... (and optionally Ux1r, Ux2r, Ux3r...); and the controller 132 can control each corresponding voltage of each "Cartesian variable" porous electrode of the precompensator 120 having holes that vary along the y-direction, such as Uy1f, Uy2f, Uy3f... (and optionally Uy1r, Uy2r, Uy3r...).

[0081] In an embodiment, the controller 132 is configured to dynamically adjust the respective voltage of each at least one "Cartesian variable" porous electrode in synchronization with the scanning of each of the beamlets by the scanner. Alternatively / additionally, the controller 132 may adjust the respective voltage of each at least one "Cartesian variable" porous electrode based on the deflection of the beamlet(s) by the scanner.

[0082] In some embodiments, a beamlet forming porous plate 110 having a plurality of holes forms a plurality of beamlets, and the beamlet forming porous plate 110 is arranged upstream of the precompensator 120 (see Figure 1 ). In other embodiments, multiple beamlets are produced by the precompensator 120 (eg, by one of the porous electrodes of the precompensator).

[0083] In some embodiments, a beam splitter 206 is provided (see Figure 2 ) for separating the signal electrons emitted from the target 103 from the electrons of the charged particle beam 101 propagating towards the target. The beam separator can be, for example, a magnetic beam separator or a Vienna filter. The device can detect the signal charged particles scattered by the target 103. The signal charged particles generated by each of the sub-beams 102 can be detected individually via the detector device 201.

[0084] The strength of aberration precompensation (e.g., field curvature correction provided by precompensator 120) can be adjusted as follows. Precompensator 120 may be connected to controller 132, which is configured to adjust at least one voltage Ur of (multiple) "radially variable" porous electrode 121 and at least one voltage of (multiple) "Cartesian variable" porous electrode 122 (see Figure 1 ).

[0085] The (multiple) "Cartesian variable" porous electrode 122 may be arranged upstream or downstream of the (multiple) "radially variable" porous electrode 121. For example, the distance between the (multiple) "radially variable" porous electrode 121 and the (multiple) Cartesian variable porous electrode 122 along the optical axis z may be 1 cm or less, or 5 mm or less. In particular, the controller 132 may include a variable voltage power supply connected to each of the porous electrodes of the precompensator 120.

[0086] It should be remembered that considering a possible series of "radially variable" porous electrodes 121 (such as first-order, second-order, third-order... electrodes with M=1,2,3...), the controller can control the voltage of each electrode of the series (multiple) "radially variable" porous electrodes 121.

[0087] Furthermore, it should be remembered that it is possible to have a variable control of the pre-compensation of each beamlet, taking into account also the forward and reverse porous electrodes (possibly for each order of porous electrodes M=1,2,3...). It may also be advantageous that each "radially variable" porous electrode 121 can be controlled by adjusting the corresponding voltage (Ur1f, Ur2f, Ur3f, Ur1r, Ur2r, Ur3r...).

[0088] In one embodiment, at least one "radially variable" porous electrode 121 is selectable from a group of "series" of forward and reverse configurations of M stages (M=1, 2, 3...) of radially variable porous electrodes.

[0089] The voltage of the electrode can be set to a value that substantially and / or significantly compensates / corrects aberrations (such as those caused by the optical elements of the charged particle beam device). For example, aberrations due to field curvature may come from the optical elements. Correcting the aberrations can improve the resolution of each beamlet.

[0090] In some embodiments, the diameter of the pores of the porous electrode of Precompensator 120 may span from approximately tens of microns to hundreds of microns, such as from 10 microns to 200 microns.

[0091] It is specifically contemplated that controller 132 may independently regulate and / or control the voltage of each porous electrode of precompensator 122 .

[0092] It should be noted that in some embodiments, the porous electrode of the Precompensator has a focusing effect on the multiple beamlets and produces an actual beam crossing downstream of the Precompensator. In other embodiments, the porous electrode of the Precompensator can provide multiple virtual foci. For example, the multiple beamlets can have a virtual focus upstream or downstream of the target to be inspected.

[0093] According to embodiments described herein, a precompensator 120 is provided that allows the amount of aberration correction, such as that due to field curvature, to be controlled. By varying the voltage of the porous electrode of the precompensator, it is possible to keep the focal length of the central beamlet substantially constant or within a certain range. Similarly, the focal length of the radially outer beamlets and / or any beamlet at a given distance from the optical axis may be kept substantially constant.

[0094] Each aperture of each porous electrode of Precompensator 120 may be aligned with a corresponding aperture of each other porous electrode of Precompensator 120. Each beamlet 102 may pass through exactly one aperture of each porous electrode of the Precompensator.

[0095] Precompensator 120 may also be configurable so that a user may select which porous electrodes to place in the path of a beamlet. For example, it may be desirable to configure Precompensator 120 so that it has M=2 "radially variable" porous electrodes and N=2 "Cartesian variable" forward porous electrodes, and optionally N=2 "Cartesian variable" reverse porous electrodes; another configuration would also add M=3 "radially variable" porous electrodes.

[0096] Each porous electrode of the Precompensator can be selectable, such that each porous electrode can be placed in the optical path or removed from the optical path and stored for selection in another configuration of the Precompensator. The selected porous electrode can be placed in the optical path (e.g., in a slot of the Precompensator in the optical path of a beamlet) to operate on the beamlet. For example, each beamlet passes through a corresponding hole of each selected porous electrode of the Precompensator.

[0097] The precompensator may have a porous electrode of "radially variable" and / or "Cartesian variable" type for each of the 0th order to the Mth order (M is a positive integer). The porous electrodes of the precompensator may also include a matching pair of "forward" and "reverse" electrodes for each of the 0th order to the Mth order porous electrodes of "radially variable" and / or "Cartesian variable" type, with the 0th order porous electrode having pores of constant diameter. The optional inlet and / or outlet porous electrodes may be considered as 0th order porous electrodes.

[0098] In an embodiment that may be combined with any other embodiment described herein, each non-zero-order porous electrode of the precompensator may be accompanied by at least one zero-order porous electrode, respectively. For example, each 1, 2, 3, 4 or higher order porous electrode is adjacent to a zero-order porous electrode. For example, each first-order or higher order porous electrode has an accompanying zero-order porous electrode directly before it in the optical path and another zero-order porous electrode directly after it in the optical path. (Multiple) zero-order porous electrodes can help reduce aberrations, such as field curvature.

[0099] In an embodiment that may be combined with any other embodiment described herein, the precompensator may include a "macro-lens" and / or a "macro-electrode" having a large hole through which all beamlets pass. The macro-electrode may generate a field that extends to each porous electrode of the precompensator and can be modified / adjusted by each porous electrode of the precompensator. Alternatively / additionally, the precompensator may include an electrostatic lens that operates on all beamlets passing through the precompensator; the field generated by the electrostatic lens may extend to each porous electrode of the precompensator and can be modified / adjusted by each porous electrode of the precompensator. Alternatively / additionally, the precompensator may include an electromagnetic lens that operates on all beamlets passing through the precompensator; the field generated by the electromagnetic lens may extend to each porous electrode of the precompensator and can be modified / adjusted by each porous electrode of the precompensator. The optional electrostatic and / or electromagnetic lens may be considered a kind of "macro-lens". The macro lens may be positioned close to or adjacent to the Precompensator such that the field of the macro lens extends to and may be modified / adjusted by the porous electrodes of the Precompensator; alternatively / additionally, the macro lens may be considered part of the Precompensator.

[0100] In an embodiment that may be combined with any other embodiment described herein, each beamlet passes through a corresponding hole of each porous electrode of the precompensator. This may allow, for example, sensitive control of optical operations on the beamlets, such as for aberration correction. In other embodiments, there may be a porous electrode with holes, each hole passing more than one beamlet. This may, for example, simplify alignment.

[0101] In an embodiment, which may be combined with any other embodiment described herein, the distance between the porous electrodes of the precompensator is non-constant. The distance may be adjustable. The distance may be determined to provide aberration correction and / or to provide flexibility in aberration correction, in particular field curvature.

[0102] In an embodiment, the arrangement of the holes is such that there is optical alignment between the corresponding holes of each porous electrode. The optical alignment may be such that each beamlet passes through the center of the corresponding hole of each porous electrode. Alternatively / additionally, there may be porous electrodes with slightly offset holes, which may allow correction of aberrations such as distortion.

[0103] Aberrations that may be corrected by a precompensator may include distortions such as pincushion and / or barrel distortion.

[0104] In an embodiment that may be combined with any other embodiment described herein, the porous electrodes of the precompensator may be aligned with the optical axis. In another embodiment that may be combined with other embodiments described herein, the porous electrodes of the precompensator are at least nominally aligned with (e.g., centered on) the optical axis z, except for at least one "shifted" porous electrode that is displaced from the optical axis in x and / or y. The at least one shifted porous electrode may help reduce aberrations, such as distortion.

[0105] In another embodiment that may be combined with other embodiments described herein, the precompensator comprises at least one "shift-variable" porous electrode, wherein the array formed by each hole of the at least one "shift-variable" porous electrode is offset from a nominal center, e.g., the optical axis z. Each "shift-variable" porous electrode can optionally be moved in x, y and / or z.

[0106] Another embodiment of the precompensator 120, which may be combined with any other embodiment described herein, has M=2 "radially variable" multi-aperture electrodes and N=1 "Cartesian variable" forward multi-aperture electrode, and optionally N=1 "Cartesian variable" reverse multi-aperture electrode.

[0107] The aberration introduced into the beamlet 102 may depend on the amount of deflection, in particular the amount of deflection by the scanner 205. The beamlet 102 may be dynamically deflected and / or offset by the scanner 205. The controller 132 may dynamically and / or statically set and / or adjust the corresponding voltage of any (or each) of the "Cartesian variable" porous electrodes 122, which may be synchronized with the scanning of each of the plurality of beamlets. Alternatively / additionally, the controller 132 may dynamically adjust the corresponding voltage of any (or each) of the porous electrodes 121, 122 of the precompensator 120. Alternatively / additionally, the controller 132 may dynamically adjust the corresponding voltage of any (or each) of the "radially variable" porous electrodes 121, which may be synchronized with the scanning of each of the plurality of beamlets. Alternatively / additionally, the controller 132 may set the corresponding voltage of any (or each) of the (multiple) "Cartesian variable" porous electrodes according to the deflection amplitude of each of the plurality of beamlets by the scanner 205. Alternatively / additionally, the controller 132 may set a respective voltage of any (or each) of the porous electrode(s) based on the deflection of each of the plurality of beamlets by the scanner 205 (which may include deflection direction and amplitude).

[0108] The precompensator 120 may include a set of "radially variable" porous electrodes 121 (a set is at least one). Precompensation of the beamlets may include passing each of the plurality of beamlets through the (multiple) "radially variable" porous electrodes 121 and reducing the radial portion of the aberration. The precompensator 120 may include a set of "Cartesian variable" porous electrodes 122. Precompensation may include passing each of the plurality of beamlets through the (multiple) "Cartesian variable" porous electrodes 122 and reducing the Cartesian portion of the aberration.

[0109] Advantageously, possible aberrations of the beamlets are considered, which can be precompensated to be decomposable into a radial contribution and a Cartesian contribution. The precompensator as described herein exploits this possible decomposition. Furthermore, it can be convenient to consider that each of the radial and Cartesian parts of the aberration can be further decomposed into contributions of different orders (M=1,2,3... and N=1,2,3... for the radial and Cartesian parts, respectively).

[0110] In an embodiment, reducing the radial portion of the aberration includes passing each beamlet through each corresponding aperture of each of the “radially variable” porous electrodes of the Precompensator 120. The voltage of each “radially variable” porous electrode is controlled by the controller 132.

[0111] In an embodiment, reducing the Cartesian portion (x and / or y) of the aberration comprises passing each beamlet through each corresponding aperture of each of the "Cartesian variable" porous electrodes.

[0112] The precompensator may optionally include an entrance porous electrode and / or an exit porous electrode. (Multiple) "radially variable" porous electrodes and at least one "Cartesian variable" porous electrode may be between the entrance and exit porous electrodes. The beamlets passing through the precompensator may each first pass through the entrance porous electrode and finally pass through the exit porous electrode. Precompensating each of the beamlets may include passing each of the beamlets through the entrance and exit electrodes in sequence, and passing each of the beamlets through (multiple) "radially variable" porous electrodes and (multiple) "Cartesian variable" porous electrodes after passing each of the beamlets through the entrance porous electrode and before passing through the exit porous electrode. The entrance porous electrode and / or the exit porous electrode may each have multiple holes of the same corresponding diameter (for example, the holes of the entrance porous electrode are d1, and the holes of the exit porous electrode are d2).

[0113] Figure 5 is a schematic cross-sectional view of a precompensator 120 according to embodiments described herein. Figure 5 The precompensator 120 may have Figure 1 For some or all features of the precompensator, reference may be made to the above description and will not be repeated here.

[0114] Figure 5 The precompensator 120 includes a "radially variable" porous electrode 121 having a first plurality of openings providing a variable focal length for a plurality of beamlets; a "Cartesian variable" porous electrode 122 having a second plurality of openings aligned with the first plurality of openings; and a controller 132 configured to adjust at least one of the voltages Ur and Uc of the radially variable and Cartesian variable porous electrodes 121, 122.

[0115] In some embodiments, which may be combined with other embodiments described herein, the Precompensator 120 may further include an exit porous electrode 123 having a third plurality of openings downstream of the radially variable porous electrode 121 and the Cartesian variable porous electrode 122. Alternatively or additionally, the Precompensator 120 may further include an inlet porous electrode 124 having a fourth plurality of openings upstream of the radially variable porous electrode 121 and the Cartesian variable porous electrode 122.

[0116] The inlet and outlet porous electrodes may have holes with constant diameters relative to coordinates r, x and / or y. In some embodiments, the inlet and / or outlet porous electrodes 123, 124 may be grounded, such as Figure 5 In particular, in some embodiments, the grounded inlet porous electrode 124 may be arranged upstream of the “radially variable” porous electrode 121 , and the grounded outlet porous electrode 123 may be arranged downstream of the “Cartesian variable” porous electrode 122 .

[0117] When the entrance porous electrode 124 and the exit porous electrode 123 are grounded, the precompensator 120 can substantially and / or essentially have the effect of an array of einzel lenses that focus multiple beamlets without changing the energy of the beamlets. Therefore, the charged particles leaving the precompensator 120 can have substantially and / or essentially the same energy as the charged particles entering the precompensator 120.

[0118] Conventionally, the ion focusing mirror may consist of three or more electrodes connected in series with a cylindrical opening along the optical axis. The electrostatic potential in the ion focusing mirror is symmetrical so that the charged particles regain their initial energy when leaving the ion focusing mirror. In particular, the entrance and exit electrodes of the ion focusing mirror may be grounded or may be set at the same potential. In the ion focusing mirror, the radial velocity of radially outer charged particles may be changed by at least one central electrode so that the outer charged particles converge toward the optical axis.

[0119] In an embodiment, the electrostatic multipole device 250 may be disposed at the beam entrance surface of the precompensator 120 pointing in the upstream direction. For example, the multipole unit of the electrostatic multipole device 250 may be integrally formed at the surface of the entrance porous electrode 124 pointing to the charged particle source. Alternatively or additionally, the multipole unit of the electrostatic multipole device 250 may be disposed at the beam exit surface of the precompensator 120 pointing in the downstream direction. For example, the multipole unit may be integrally formed at the surface of the exit porous electrode 123 pointing to the target.

[0120] Figure 6 A method of operating a charged particle device according to embodiments described herein is shown. The method includes forming beamlets 610, passing each beamlet through at least one "radially variable" porous electrode 620, passing each beamlet through at least one "Cartesian variable" porous electrode 630, scanning each beamlet in the beamlets 640, and focusing each beamlet on a target 650.

[0121] Figure 7 A porous electrode of a precompensator according to an embodiment is shown.The precompensator may include at least one porous electrode 732 having an elliptical aperture with unequal major and minor axes. Figure 7 Two "elliptical" porous electrodes are shown. The upper "elliptical" porous electrode 701 has a hole with a major axis along x, while Figure 7 The lower "elliptical" porous electrode 702 has a hole with a long axis along y. Each beamlet can pass through a corresponding hole in each "elliptical" porous electrode. The controller 132 can communicate with each "elliptical" porous electrode and apply variable voltages Uex, Uey to it. The elliptical holes can allow variably adjusting astigmatism.

[0122] As can be understood from the foregoing description, the precompensator may include a porous electrode of terms of a series of simulation polynomials. For example, each term of equation 1 may represent each "radially variable" porous electrode of order 0, 1, 2... and M. In the following sequence 1, each term represents a porous electrode having a pore size distribution given by each corresponding term. Each corresponding pore diameter is scaled according to a power of r ("radially variable" porous electrode). In sequence 2, the pore diameter is scaled according to a power of x ("Cartesian variable" porous electrode). A sequence similar to sequence 2, in which x is replaced by y, can represent a "Cartesian variable" porous electrode whose diameter scales along y instead of x.

[0123] (Sequence 1)

[0124] (Sequence 2)

[0125] Similarly, according to an embodiment that can be combined with any other embodiment, the precompensator may include a porous electrode with variable ellipticity. In each "variable elliptic" porous electrode, the ratio Q of the major / minor axis of the pores is scaled along r, x or y. Referring again to Sequence 1 and Sequence 2, each of its terms may correspond to a variable ratio Q (ratio of the major axis to the minor axis) instead of a variable pore diameter. The precompensator may include any "variable elliptic" porous electrode inferred from Sequence 1 and Sequence 2 and combinations thereof.

[0126] In an embodiment that may be combined with any other embodiment described herein, the arrangement of the holes of the porous electrode varies along x, y or r. For example, the holes are misaligned so that each beamlet is centered in a hole. The misalignment of the holes (in x, y or radial, respectively) of each hole of the porous electrode relative to the position where the beamlet is centered is scaled according to an item of sequence 1 or sequence 2. For example, such an arrangement is useful in providing flexible correction for coma.

[0127] Each configuration and / or type of porous electrodes described herein may optionally be in a precompensator.While the foregoing is directed to particular embodiments, other and further embodiments may be envisioned without departing from the basic scope thereof, and the scope of which is defined by the following claims.

Claims

1. A method of operating a charged particle beam device, comprising the following steps: Forming a charged particle beam; forming a plurality of beamlets from the charged particle beam, the beamlets being centered on an optical axis z of the charged particle beam device such that a majority of the beamlets in the plurality of beamlets are offset from the optical axis after passing through a beamlet forming porous plate; precompensating each of the beamlets by passing each of the beamlets through a precompensator that reduces aberrations of the beamlets at a target, the precompensator comprising a plurality of porous electrodes, including at least one "radially variable" porous electrode, wherein a diameter of each hole of the at least one "radially variable" porous electrode scales with a distance of the hole from the optical axis z; as well as at least one "Cartesian variable" porous electrode having a plurality of pores that scale in diameter with the x-component of the position of the respective pore to the Nth power, x being perpendicular to z and N being selected from the set of positive integers; scanning each of the beamlets in a direction perpendicular to z; as well as Each of the beamlets is focused onto the target using an objective lens to form a plurality of focal points.

2. The method of claim 1, wherein The pre-compensation includes passing each of said beamlets through said at least one "radially variable" porous electrode and reducing the radial portion of said aberration, and Each of the beamlets is passed through the at least one "Cartesian variable" porous electrode and the Cartesian part of the aberration is reduced.

3. The method of claim 1, wherein: At the target, a projection of each of the beamlets forms an angle in the xz plane relative to the optical axis z; and Each beamlet is parallel to the xz plane.

4. The method of claim 1, wherein Each of the at least one "radially variable" porous electrode comprises a corresponding plurality of holes, the corresponding plurality of holes being scaled in diameter as the distance of the corresponding holes from the optical axis to the Mth power; and wherein, For each “radially variable” porous electrode of the at least one “radially variable” porous electrode, M is selected from a set of positive integers.

5. The method according to any one of claims 1 to 4, wherein the at least one "Cartesian variable" porous electrode comprises a plurality of "Cartesian variable" porous electrodes, each "Cartesian variable" porous electrode comprising a corresponding plurality of holes that are scaled in diameter as the x-component of the position of the corresponding holes to the Nth power; and wherein, For each of the at least one “Cartesian variable” porous electrode, N is selected from a set of positive integers.

6. The method according to any one of claims 1 to 4, wherein The at least one "Cartesian variable" porous electrode comprises at least one "forward" porous electrode, wherein The diameter of the pores of each "forward" porous electrode increases with the x-component of the position of the pores, and For each "forward" porous electrode, The at least one "Cartesian variable" porous electrode further comprises a "counter" porous electrode, wherein The diameter of the pores of each "counter" porous electrode decreases with the x-component of the position of the pores.

7. The method of claim 4, wherein The at least one "radially variable" porous electrode comprises a “radially variable” porous electrode with M=2, wherein the “radially variable” porous electrode with M=2 is a second-order “radially variable” porous electrode, wherein the second-order “radially variable” porous electrode comprises a plurality of holes whose diameters scale with the second power of the distance of the holes from the optical axis; and The at least one "Cartesian variable" porous electrode comprises an N=2 “Cartesian variable” forward porous electrode, the N=2 “Cartesian variable” forward porous electrode being a second-order “Cartesian variable” porous electrode comprising a plurality of pores that scale in diameter with the second power of the x-component of the position of the pores, Wherein the at least one "Cartesian variable" porous electrode further comprises an N=2 "Cartesian variable" reverse porous electrode, wherein the N=2 "Cartesian variable" reverse porous electrode comprises a plurality of pores whose diameters decrease with the 2nd power of the x-component of the position of the pores.

8. The method according to any one of claims 1 to 4, further comprising the steps of: A corresponding voltage of a plurality of voltages is set on each porous electrode of the plurality of porous electrodes.

9. The method of claim 8, further comprising the steps of: dynamically adjusting the respective voltage of each of the at least one Cartesian variable porous electrode, wherein the dynamic adjustment is synchronized with scanning each of the beamlets, and / or The corresponding voltage of each of the at least one radially variable porous electrode is dynamically adjusted, wherein the dynamic adjustment is synchronized with scanning each of the beamlets.

10. The method of claim 9, further comprising the steps of: Depending on the magnitude of the deflection of each of the beamlets by the scanner, the respective voltage is set to the at least one "Cartesian variable" porous electrode.

11. The method of claim 2, wherein The at least one "radially variable" porous electrode is centered on the optical axis; and The radial portion for reducing the aberration comprises each beamlet is passed through each corresponding hole of each of the at least one "radially variable" porous electrodes; and wherein The at least one "Cartesian variable" porous electrode is centered on the optical axis; and The Cartesian portion that reduces the aberration includes Each beamlet is passed through each corresponding aperture of each of the at least one "Cartesian variable" porous electrodes.

12. The method of any one of claims 1 to 4, wherein Pre-compensating each of the beamlets further comprises sequentially passing each of the sub-beams through an entrance porous electrode and an exit porous electrode, and Each of the beamlets is passed through the at least one "radially variable" porous electrode and the at least one "Cartesian variable" porous electrode after passing through the entrance porous electrode and before passing through the exit porous electrode.

13. The method according to any one of claims 1 to 4, further comprising the steps of: Deflect each of the beamlets along a direction y, wherein y is perpendicular to x and z; and The pre-compensation further comprises At least one orthogonal "Cartesian variable" porous electrode, wherein the diameter of each hole of the at least one orthogonal "Cartesian variable" porous electrode scales with the y-component of the position of the hole.

14. The method according to any one of claims 1 to 4, further comprising the steps of: Signal charged particles scattered by the target are detected, wherein the signal charged particles generated by each of the beamlets are individually detected via a detector arrangement.

15. A charged particle beam device comprising: a charged particle source and a beamlet-forming porous plate centered on an optical axis z, wherein the beamlet-forming porous plate comprises a plurality of holes, each hole being used for passing a beamlet, and the beamlet-forming porous plate forms a plurality of beamlets of charged particles; A precompensator, the precompensator being used to reduce the aberration of the sub-beam at the target; a scanner, the scanner being used to scan each of the sub-beams; an objective lens, the objective lens being used to focus each beamlet onto the target; as well as a controller configured to communicate with the precompensator and the scanner; in The precompensator comprises: at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; as well as At least one "Cartesian variable" porous electrode, the at least one "Cartesian variable" porous electrode having a plurality of holes that scale in diameter with the Nth power of the x component of the position of the corresponding hole, x being perpendicular to z, and N being selected from a set of positive integers.

16. The charged particle beam apparatus according to claim 15, wherein The controller is configured to control each of a plurality of voltages of the at least one "Cartesian variable" porous electrode; and The controller is configured to control each of a plurality of voltages of the at least one “radially variable” porous electrode.

17. The charged particle beam apparatus according to claim 15 or 16, wherein Each of the at least one "radially variable" porous electrode comprises a corresponding plurality of holes, the corresponding plurality of holes being scaled in diameter as the distance of the corresponding holes from the optical axis to the Mth power; wherein For each of the at least one “radially variable” porous electrode, M is selected from the set of positive integers; and wherein: Each of the at least one "Cartesian variable" porous electrodes comprises: a corresponding plurality of holes that are scaled in diameter as the x-component of the position of the corresponding holes to the Nth power; and wherein, For each of the at least one "Cartesian variable" porous electrode, N is selected from the set of positive integers; where The at least one "radially variable" porous electrode comprises a "radially variable" porous electrode with M=2, wherein the "radially variable" porous electrode with M=2 is a second-order "radially variable" porous electrode, wherein the second-order "radially variable" porous electrode comprises a plurality of holes, wherein the plurality of holes scale in diameter with the second power of the distance of the holes from the optical axis; and The at least one "Cartesian variable" porous electrode comprises N=2 "Cartesian variable" forward porous electrodes, said N=2 "Cartesian variable" forward porous electrodes being second-order "Cartesian variable" porous electrodes, said second-order "Cartesian variable" porous electrodes comprising a plurality of pores that increase in diameter as a function of the second power of said x-component of said position of said pores; and wherein The controller is configured to dynamically adjust the respective voltage of each of the at least one Cartesian variable porous electrode.

18. A precompensator for a charged particle device, comprising at least one "radially variable" porous electrode, wherein the diameter of each hole of the at least one "radially variable" porous electrode scales with the distance of the hole from the optical axis z; and At least one "Cartesian variable" porous electrode, the at least one "Cartesian variable" porous electrode having a plurality of holes, the plurality of holes scaling in diameter with the Nth power of the x-component of the position of the corresponding hole, x being perpendicular to z, and N being selected from a set of positive integers.

19. A precompensator for a charged particle device, comprising At least one "variable ellipse" porous electrode, the at least one "variable ellipse" porous electrode having a plurality of pores, the major axis / minor axis ratio Q of the plurality of pores being as the distance of the corresponding aperture in the radial direction r from the optical axis z of the precompensator raised to the power M, M being selected from the set of positive integers, or Scaled as the x-component of the position of the corresponding hole to the power of N, x being perpendicular to z, N being selected from the set of positive integers.

20. A precompensator for a charged particle device, comprising at least one "variable offset" porous electrode, wherein the center of each hole of the at least one "variable offset" porous electrode is variably offset from the center configured to cause a beamlet to pass through the hole, the offset amount as the distance of the corresponding aperture in the radial direction r from the optical axis z of the precompensator raised to the power M, M being selected from the set of positive integers, or Scaled as the x-component of the position of the corresponding hole to the power of N, x being perpendicular to z, N being selected from the set of positive integers.

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