Aperture assembly, beam manipulator unit, method of manipulating a charged particle beam, and charged particle projection apparatus

Abstract

The present disclosure relates to apparatuses and methods for manipulating a charged particle beam. In one arrangement, an aperture assembly is provided, the aperture assembly comprising a first aperture body and a second aperture body. Apertures in the first aperture body are aligned with apertures in the second aperture body. The alignment allows a charged particle beam to pass through the aperture assembly. The first aperture body comprises a first electrode system for applying an electric potential to an aperture peripheral surface of each aperture in the first aperture body. The first electrode system comprises a plurality of electrodes. Each electrode is electrically isolated from one another and is simultaneously electrically connected to an aperture peripheral surface of a different aperture in a plurality of aperture groups in the first aperture body.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to EP application 20168281.2, filed on April 6, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments provided herein generally relate to apparatus and methods for manipulating charged particle beams, particularly in the context of charged particle beam tools for examining samples. Background Technology

[0004] When manufacturing semiconductor integrated circuit (IC) chips, undesirable pattern defects inevitably occur on the substrate (i.e., wafer) or mask during the manufacturing process, as a result of optical effects and incident particles, thereby reducing yield. Therefore, monitoring the extent of these undesirable pattern defects is a critical step in IC chip manufacturing. More generally, the inspection and / or measurement of the surface of the substrate or other objects / materials are important steps during and / or after their manufacturing process.

[0005] Pattern inspection tools with charged particle beams have been used to inspect objects, for example, to detect pattern defects. These tools typically employ electron microscopy techniques, such as scanning electron microscopy (SEM). In SEM, a primary electron beam, containing electrons at relatively high energies, targets a final deceleration step, thus landing on the sample at a relatively low landing energy. The electron beam is focused onto the sample as a probe point. The interaction between the material structure at the probe point and the landing electrons from the electron beam causes electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons. The generated secondary electrons can be emitted from the material structure of the sample. By scanning the primary electron beam, acting as a probe point, over the sample surface, secondary electrons can be emitted across the sample surface. By collecting these emitted secondary electrons from the sample surface, an image representing the material structure of the sample surface can be obtained.

[0006] There is usually a need to improve the throughput and other characteristics of inspection tools and methods using charged particle beams. Summary of the Invention

[0007] According to one aspect of the invention, an aperture assembly for a beam manipulator unit of a charged particle projection device is provided, the aperture assembly comprising: a first aperture body and a second aperture body, wherein: a plurality of apertures in the first aperture body are aligned with corresponding plurality of apertures in the second aperture body, the alignment such that the path of each of the corresponding plurality of charged particle beams passes through the aperture assembly through the corresponding apertures in the first aperture body and the second aperture body; the first aperture body includes a first electrode system for applying a potential to the aperture peripheral surface of each aperture in the first aperture body; the second aperture body includes a second electrode system for applying a potential to the aperture peripheral surface of each aperture in the second aperture body; and the first electrode system includes a plurality of electrodes, each electrode being electrically isolated from each other and simultaneously electrically connected to the aperture peripheral surface of a different aperture in a plurality of aperture groups in the first aperture body.

[0008] According to one aspect of the invention, an aperture assembly for a beam manipulator unit of a charged particle projection device is provided, the aperture assembly comprising: a first aperture body and a second aperture body, wherein: a plurality of apertures in the first aperture body are aligned with corresponding plurality of apertures in the second aperture body, the alignment such that the path of each of the corresponding plurality of charged particle beams passes through the aperture assembly through the corresponding apertures in the first and second aperture bodies; each aperture in at least a subset of the apertures in the first aperture body is formed by an elongated slit; and each corresponding aperture in the second aperture body is formed by an opening smaller than the elongated slit at least in a direction parallel to the longest axis of the elongated slit.

[0009] According to one aspect of the invention, a method for manipulating a beam of charged particles is provided, the method comprising: guiding a plurality of charged particle beams onto a sample via an aperture assembly; and electrostatically manipulating the charged particle beams by applying a potential to electrodes in the aperture assembly, wherein: the aperture assembly includes a first aperture body and a second aperture body; a plurality of apertures in the first aperture body are aligned with corresponding plurality of apertures in the second aperture body such that each charged particle beam passes through the aperture assembly through a corresponding aperture in the first aperture body and the second aperture body; and applying the potential comprises applying the potential to a plurality of electrodes, each of the plurality of electrodes being electrically isolated from each other and simultaneously electrically connected to the aperture peripheral surface of a different aperture in a plurality of aperture groups of the first aperture body.

[0010] According to one aspect of the invention, a method for manipulating a beam of charged particles is provided, the method comprising: guiding a plurality of charged particle beams onto a sample via an aperture assembly; and electrostatically manipulating the charged particle beams by applying a potential to electrodes in the aperture assembly, wherein: the aperture assembly includes a first aperture body and a second aperture body; a plurality of apertures in the first aperture body are aligned with corresponding plurality of apertures in the second aperture body such that each charged particle beam passes through the aperture assembly through a corresponding aperture in the first aperture body and the second aperture body; applying the potential comprises applying a potential difference between the apertures in the first aperture body and the corresponding apertures in the second aperture body; each aperture in at least a subset of the apertures in the first aperture body is composed of an elongated slit; and each corresponding aperture in the second aperture body is composed of an opening smaller than the elongated slit at least in a direction parallel to the longest axis of the elongated slit.

[0011] According to one aspect of the invention, an aperture assembly for a manipulator unit of a charged particle multi-beam projection system is provided, the aperture assembly comprising: a first aperture body in which a first aperture array is defined; and a second aperture body in which a corresponding aperture array aligned with the first aperture array is defined to define paths of corresponding charged particle beams of a plurality of beams through the aperture assembly; a first electrode system associated with the first aperture body configured to apply a potential to a peripheral surface of each aperture of the first aperture body; and a second electrode system associated with the second aperture body configured to apply a potential to a peripheral surface of each aperture of the second aperture body, wherein the first electrode system comprises a plurality of electrodes, each electrode electrically isolated from each other and simultaneously electrically connected to a peripheral surface of a different aperture of a plurality of aperture groups of the first aperture body.

[0012] According to one aspect of the invention, an aperture assembly is provided for a beam manipulator unit of a charged particle multi-beam projection device, the aperture assembly comprising: a first aperture body in which a first plurality of apertures are defined; and a second aperture body in which corresponding plurality of apertures positioned relative to the first plurality of apertures are defined to define the paths of corresponding charged particle beams of the plurality of beams through the aperture assembly, wherein: each aperture in at least a subset of the apertures in the first aperture body is an elongated slit; and each of the plurality of apertures corresponding to the elongated slit is an opening with an aspect ratio smaller than that of the elongated slit.

[0013] According to one aspect of the invention, a beam manipulator unit for a charged particle multi-beam projection system is provided. The manipulator unit includes a lens comprising: an up-beam lens aperture array having an associated up-beam perturbation electrode array; and a down-beam lens aperture array having an associated down-beam perturbation electrode array, wherein: the up-beam lens aperture array, the down-beam lens aperture array, and the perturbation array are positioned relative to each other such that the aperture in each array defines the path of a corresponding charged particle beam in a plurality of beams through the manipulator unit; and the up-beam and down-beam perturbation electrodes are controllable to apply a perturbation field to the field generated by the lens during operation.

[0014] According to one aspect of the invention, a method for manipulating a charged particle beam is provided, the method comprising: providing a lens including an up-beam lens aperture array and a down-beam lens aperture array, the up-beam lens aperture array having an associated up-beam perturbation electrode array and the down-beam lens aperture array having an associated down-beam perturbation electrode array; causing a plurality of charged particle beams to pass through a corresponding aperture in each of the up-beam lens aperture array and the down-beam lens aperture array; and controlling the up-beam and down-beam perturbation electrodes to apply a perturbation field to a field generated by the lens. Attached Figure Description

[0015] The above and other aspects of this disclosure will become more apparent from the description of exemplary embodiments in conjunction with the accompanying drawings.

[0016] Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus.

[0017] Figure 2 It is illustrated as Figure 1 A schematic diagram of an exemplary charged particle beam tool, representing a portion of an exemplary charged particle beam inspection apparatus.

[0018] Figure 3 This is a schematic diagram of a charged particle beam tool, in which the sub-beams travel in a straight line between a focusing lens and an objective lens.

[0019] Figure 4 This is a schematic diagram of a charged particle beam tool, in which a collimator is provided between the focusing lens and the objective lens.

[0020] Figure 5 This is a schematic diagram of a beam manipulator unit including an aperture assembly.

[0021] Figure 6 yes Figure 4 A schematic diagram of a beam manipulator unit of the type shown, wherein the aperture assembly is integrated with the lens of the charged particle projection device.

[0022] Figure 7It is a schematic top view of an example first electrode system or second electrode system including relatively wide, elongated conductive strips aligned along a first direction.

[0023] Figure 8 It is a schematic top view of an example second electrode system or a first electrode system having relatively wide, elongated conductive strips aligned along a second direction.

[0024] Figure 9 It is a schematic top view of an example first electrode system or second electrode system having relatively narrow, elongated conductive strips aligned along a first direction.

[0025] Figure 10 It is a schematic top view of an example second electrode system or a first electrode system having relatively narrow, elongated conductive strips aligned along a second direction.

[0026] Figure 11 This is a schematic top view of an example first or second electrode system with a checkerboard-like conductive element having a low aspect ratio.

[0027] Figure 12 This is a schematic top view of an example first or second electrode system having conductive elements including concentric rings.

[0028] Figure 13 It is a schematic top view of a first electrode system or a second electrode system, including a single electrode electrically connected to the circumferential surface of all apertures of the corresponding aperture body.

[0029] Figure 14 It is a schematic top view of a first electrode system or a second electrode system, wherein each electrode is electrically isolated from each other and electrically connected to the aperture peripheral surface of a different aperture in the aperture body.

[0030] Figure 15 This is a schematic top view of the aperture assembly, where the uppermost aperture body includes an elongated slit.

[0031] Figure 16 It is along Figure 15 A schematic side section view of the element line X-X.

[0032] Figure 17 It is along Figure 15 A schematic side section view of the Y-Y line of the element.

[0033] Figure 18 In the case where the lowest aperture body includes locally integrated electronics for applying a potential, along Figure 15 A schematic side section view of line X-X for a unit of the type shown.

[0034] Figure 19In the case where the lowest aperture body includes locally integrated electronics for applying a potential, along Figure 15 A schematic side section view of the Y-Y line of the element.

[0035] Figure 20 This is a schematic top view of an example first or second electrode system with radially aligned elongated slits.

[0036] Figure 21 This is a schematic top view of an example first or second electrode system having a narrow slit aligned perpendicularly to the radial direction.

[0037] Figure 22 It is a schematic top view of an example first electrode system or second electrode system having parallel elongated slits aligned with a first direction.

[0038] Figure 23 This is a schematic top view of an example second electrode system or first electrode system having parallel elongated slits aligned with the second direction.

[0039] Figure 24 This is a schematic top view of an example third electrode system with an elongated slit aligned at a 45-degree angle to the elongated slits in the electrode system with different aperture bodies.

[0040] Figure 25 It is observed along a narrow slit perpendicular to the third electrode system, and has the following characteristics: Figure 24 A schematic side cross-sectional view of a portion of the aperture assembly of the third electrode system and the fourth electrode system with circular openings, as shown.

[0041] Figure 26 It is observed along a direction parallel to the narrow slit of the third electrode system. Figure 25 A schematic side section view of the arrangement.

[0042] Figure 27 This is an example of an electronic inspection device integrated with a three-electrode objective.

[0043] Figure 28 This is an example of an electronic inspection device integrated with a dual-electrode objective.

[0044] Figure 29 yes Figure 27 or Figure 28 A bottom view of a detector module of the type shown.

[0045] Figure 30 This is a top view of the alternative detector module, where the beam aperture is a hexagonal close-packed array.

[0046] Figure 31A portion of the detector module is depicted in cross-section. Detailed Implementation

[0047] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise stated, the same reference numerals in different drawings denote the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with the aspects of the invention as described in the appended claims.

[0048] The enhanced computing power of electronic devices (which reduces the physical size of the devices) can be achieved by significantly increasing the packaging density of circuit components (such as transistors, capacitors, diodes, etc.) on IC chips. This can be achieved by increasing resolution, making it possible to manufacture smaller structures. For example, the IC chip for a smartphone can include more than 2 billion transistors, each smaller than 1 / 1000th the size of a human hair, and the IC chip itself is the size of a thumbnail and was available in 2019 or earlier. Therefore, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. Even an error in one step can significantly affect the functionality of the final product. Only one “fatal defect” will cause the device to fail. The goal of a manufacturing process is to improve the overall process yield. For example, for a 50-step process (where steps can indicate the number of layers formed on the wafer), to achieve a 75% yield, each individual step must have a yield greater than 99.4%. If the yield of an individual step is 95%, the overall process yield will be as low as 7%.

[0049] While high process yields are required in IC chip manufacturing facilities, maintaining high substrate (i.e., wafer) yields (defined as the number of substrates processed per hour) is also essential. The presence of defects can negatively impact both high process yields and high substrate yields. This is especially true when operator intervention is required to inspect for defects. Therefore, high-volume detection and identification of micron- and nanometer-scale defects using inspection tools such as scanning electron microscopy (“SEM”) is necessary to maintain both high yields and low costs.

[0050] SEM comprises scanning equipment and detector devices. The scanning equipment includes an illumination device and a projection device. The illumination device includes an electron source for generating primary electrons, and the projection device is used to scan a sample, such as a substrate, using one or more focused beams of primary electrons. At least the illumination device or system and the projection device or system can be collectively referred to as an electron optical system or apparatus. Primary electrons interact with the sample and generate secondary electrons. As the sample is scanned, the detector captures these secondary electrons from the sample, allowing the SEM to create an image of the scanned area of ​​the sample. For high-throughput inspection, some inspection devices use multiple focused beams, i.e., multiple beams of primary electrons. The component beams of these multiple beams can be referred to as sub-beams or wavelets. Multiple beams can scan different portions of the sample simultaneously. Multi-beam inspection devices can therefore inspect samples at much higher speeds than single-beam inspection devices.

[0051] The following figures are schematic. Therefore, for clarity, the relative dimensions of the components in the figures are enlarged. In the following description of the figures, the same or similar reference numerals refer to the same or similar components or entities, and only differences with respect to the various embodiments are described. Although the description and figures are directed to an electro-optical device, it should be understood that these embodiments are not intended to limit this disclosure to specific charged particles. Therefore, references to electrons in this document should be considered as a general reference to charged particles, which are not necessarily electrons.

[0052] Now for reference Figure 1 , Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus 100. Figure 1 The charged particle beam inspection device 100 includes a main chamber 10, a load locking chamber 20, a charged particle beam tool 40 (which may be referred to as an electron beam tool, wherein electrons are used as charged particles), an equipment front-end module (EFEM) 30, and a controller 50. The charged particle beam tool 40 is located within the main chamber 10.

[0053] EFEM 30 includes a first loading port 30a and a second loading port 30b. EFEM 30 may include additional loading ports. The first loading port 30a and the second loading port 30b may receive a front-opening substrate collection box (FOUP) containing, for example, a substrate to be inspected (e.g., a semiconductor substrate or a substrate made of other materials) or a sample (substrate, wafer, and sample are collectively referred to below as "sample"). One or more robotic arms (not shown) in EFEM 30 transport the sample to the load-locking chamber 20.

[0054] A load-locked chamber 20 is used to remove gas surrounding the sample. This creates a vacuum with a local gas pressure lower than the ambient pressure. The load-locked chamber 20 can be connected to a load-locked vacuum pump system (not shown), which removes gas particles from the load-locked chamber 20. Operation of the load-locked vacuum pump system allows the load-locked chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the sample from the load-locked chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles from the main chamber 10, causing the pressure around the sample to reach a second pressure below the first pressure. After reaching the second pressure, the sample is transported to a charged particle beam tool 40, through which it can be examined. The charged particle beam tool 40 may include a multi-beam electron optics device.

[0055] The controller 50 is electrically connected to the charged particle beam tool 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle beam inspection device 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is... Figure 1 The controller 50 is shown outside the structure comprising the main chamber 10, the load locking chamber 20, and the EFEM 30; however, it should be understood that the controller 50 may be part of this structure. The controller 50 may be located in one of the component elements of the charged particle beam inspection apparatus 100, or it may be distributed across at least two component elements. While this disclosure provides an example of a main chamber 10 for housing an electron beam inspection tool, it should be noted that aspects of this disclosure are not limited, in their broadest sense, to chambers housing electron beam inspection tools. Rather, it should be understood that the above principles can also be applied to other arrangements of other tools and apparatuses operating under a second pressure.

[0056] Now for reference Figure 2 , Figure 2 It is illustrated as Figure 1 This is a schematic diagram of an exemplary charged particle beam tool 40, a portion of an exemplary charged particle beam inspection apparatus 100. The charged particle beam tool 40 (also referred to herein as apparatus 40) may include a charged particle source 201 (e.g., an electron source), a projection device 230, a motorized stage 209, and a sample holder 207. The charged particle source 201 and the projection device 230 may be collectively referred to as an electron-optical apparatus. The sample holder 207 is supported by the motorized stage 209 to hold a sample 208 (e.g., a substrate or mask) for inspection. The charged particle beam tool 40 may also include an electronic detection device 240.

[0057] The charged particle source 201 may include a cathode (not shown) and an extractor or anode (not shown). The charged particle source 201 may be configured to emit electrons as primary electrons from the cathode. The primary electrons are extracted or accelerated by the extractor and / or anode to form a charged particle beam 202 comprising the primary electrons.

[0058] The projection device 230 is configured to convert the charged particle beam 202 into multiple sub-beams 211, 212, and 213, and to direct each sub-beam onto the sample 208. Although three sub-beams are illustrated for simplicity, there can be tens, hundreds, or thousands of sub-beams. Sub-beams may be referred to as wavelets.

[0059] Controller 50 can be connected to Figure 1 The charged particle beam inspection apparatus 100 comprises various components, such as the charged particle source 201, the electronic inspection device 240, the projection device 230, and the motorized stage 209. The controller 50 can perform various image and signal processing functions. The controller 50 can also generate various control signals to manage the operation of the charged particle beam inspection apparatus 100 (including the charged particle beam tool 40).

[0060] Projection device 230 can be configured to focus sub-beams 211, 212, and 213 onto sample 208 for inspection, and can form three probe points 221, 222, and 223 on the surface of sample 208. Projection device 230 can be configured to deflect primary sub-beams 211, 212, and 213 to scan probe points 221, 222, and 223 on various scanning areas within a portion of the surface of sample 208. In response to the incident primary sub-beams 211, 212, and 213 on probe points 221, 222, and 223 on sample 208, electrons can be generated from sample 208, and these electrons may include secondary electrons and backscattered electrons. Secondary electrons typically have electron energies of ≤~50 eV. Backscattered electrons typically have electron energies between 50 eV and the landing energies of primary sub-beams 211, 212, and 213.

[0061] The electron detection device 240 can be configured to detect secondary electrons and / or backscattered electrons and generate corresponding signals that are sent to the controller 50 or a signal processing system (not shown), for example, to construct an image of a corresponding scanned area of ​​the sample 208. The electron detection device 240 can be incorporated into the projection device 230 or can be separate from the projection device 230, with a secondary optical column provided to guide secondary electrons and / or backscattered electrons to the electron detection device 240.

[0062] The controller 50 may include an image processing system, which includes an image acquirer (not shown) and a storage device (not shown). For example, the controller 50 may include a processor, computer, server, mainframe, terminal, personal computer, any type of mobile computing device, or combinations thereof. The image acquirer may include at least a portion of the controller's processing capabilities. Therefore, the image acquirer may include at least one or more processors. The image acquirer may be communicatively coupled to the electronic detection device 240 of the charged particle beam tool 40 to allow signal communication, such as electrical conductors, fiber optic cables, portable storage media, IR, Bluetooth, the Internet, wireless networks, radio, or combinations thereof. The image acquirer may receive signals from the electronic detection device 240, process the data included in the signals, and construct an image from them. The image acquirer can thus acquire an image of sample 208. The image acquirer may also perform various post-processing functions, such as generating contours, overlaying indicators on the acquired image, etc. The image acquirer may be configured to perform adjustments such as brightness and contrast of the acquired image. The storage device may be a storage medium such as a hard disk, flash memory drive, cloud storage device, random access memory (RAM), or other types of computer-readable storage. The storage device can be coupled to the image acquirer and can be used to save scanned raw image data as the original image and to save the post-processed image.

[0063] The image acquirer can acquire one or more images of a sample based on imaging signals received from the electronic detection device 240. The imaging signals may correspond to a scanning operation used for imaging charged particles. The acquired image may be a single image comprising multiple imaging regions. The single image may be stored in a storage device. The single image may be an original image that can be divided into multiple regions. Each region may include an imaging region containing features of sample 208. The acquired images may include multiple images of a single imaging region of sample 208 sampled multiple times within a time period. Multiple images may be stored in a storage device. The controller 50 may be configured to perform image processing steps using multiple images of the same location on sample 208.

[0064] The controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of the detected charged particles (e.g., secondary electrons). The charged particle (e.g., electron) distribution data collected during the detection time window can be combined with corresponding scan path data of each of the primary sub-beams 211, 212, and 213 incident on the sample surface to reconstruct an image of the examined sample structure. The reconstructed image can be used to reveal various features of the internal or external structure of sample 208. Therefore, the reconstructed image can be used to reveal any defects that may be present in the sample.

[0065] The controller 50 can control the movement of the motorized stage 209 during sample inspection 208. At least during sample inspection, the controller 50 can cause the motorized stage 209 to move the sample 208 in a preferably continuous direction, for example, at a constant speed. The controller 50 can control the movement of the motorized stage 209 such that it varies the speed of the sample 208 according to various parameters. For example, the controller 50 can control the speed (including its direction) based on the characteristics of the inspection steps in the scanning process.

[0066] A multi-beam electron beam tool can be provided, comprising a primary projection device, a motorized stage, and a sample holder. The primary projection device may include an illumination device. It may include one or more of the following components: an electron source, an electron gun aperture plate, a focusing lens, an aperture array, a beam manipulator (which may include a MEMS structure), an objective lens, and a beam splitter (e.g., a Wien filter). The sample holder is supported by the motorized stage. The sample holder is arranged to hold a sample (e.g., a substrate or mask) for examination.

[0067] Multi-beam electron beam tools may also include secondary projection devices and associated electronic detection equipment. The electronic detection equipment may include multiple electronic detection elements.

[0068] A primary projection device is configured to irradiate the sample. In response to the primary sub-beam or probe point incident on the sample, electrons are generated from the sample, including secondary electrons and backscattered electrons. The secondary electrons propagate in multiple secondary electron beams. These secondary electron beams typically consist of secondary electrons (with electron energies ≤ eV) and may also include at least some backscattered electrons (with electron energies between 50 eV and the landing energy of the primary sub-beam). A beam splitter in the primary projection device can be arranged such that the path of the secondary electron beams is deflected toward the secondary projection device. The secondary projection device then focuses the path of the secondary electron beams onto multiple elements of an electron detection device. The detection elements generate corresponding signals, which can be sent to a controller or signal processing system, for example, to construct an image of the corresponding scanned area of ​​the sample.

[0069] Figure 3 and Figure 4 These are schematic diagrams illustrating one embodiment of a charged particle beam tool 40. The charged particle beam tool 40 includes a projection device 230. The charged particle beam tool 40 can be used as part of the charged particle beam inspection device 100 as described above. The projection device 230 can be incorporated into other types of charged particle beam tools (such as the multi-beam electron beam tool described above) 40.

[0070] The projection device 230 includes a focusing lens array. The focusing lens array divides the charged particle beam 112 into a plurality of sub-beams 114. In one embodiment, the focusing lens array focuses each sub-beam 114 to a corresponding intermediate focal point 115.

[0071] In the illustrated embodiment, the focusing lens array includes a plurality of beam apertures 110. The beam apertures 110 may be formed, for example, by openings in a generally planar beam aperture body 111. The beam apertures 110 divide the charged particle beam 112 into corresponding plurality of sub-beams 114. In some embodiments, the charged particles include or consist of electrons. The charged particles are provided by a charged particle source 201. The charged particle source 201 may or may not form part of the charged particle beam tool 40. The charged particle source 201 may be referenced above. Figure 2 The charged particle source 201 may therefore include a cathode (not shown) and an extractor or anode (not shown). The charged particle source 201 may include a high-brightness thermal field emitter with an ideal balance between luminance and total emission current.

[0072] In the illustrated embodiment, the focusing lens array includes a plurality of focusing lenses 116. The plurality of focusing lenses 116 can be considered as a focusing lens array and can be in a common plane. Each focusing lens 116 can be associated with a corresponding beam aperture 110. Each focusing lens 116 can, for example, be formed within a beam aperture 110, positioned directly adjacent to the beam aperture 110, and / or integrated with a beam aperture body 111 (e.g., the beam aperture body 111 forms one of the electrodes of the focusing lens 116). Therefore, a plate or array of electrodes forming the focusing lens array can also be used as a beam aperture. The object forming the plate or array can be referred to as an aperture body.

[0073] The focusing lens 116 may include a multi-electrode lens. The lens array may take the form of at least two plates serving as electrodes, with apertures in each plate aligned with each other and corresponding to the position of the sub-beam. During operation, at least two plates are maintained at different potentials to achieve the desired lensing effect. In one arrangement, the focusing lens array is formed by an array of three plates, where charged particles have the same energy as when they enter and exit each lens; this arrangement may be referred to as a single lens. Single lenses (e.g., including those that can be used in a focusing lens array) may also typically have electrodes (e.g., plate arrays) arranged symmetrically relative to each other, such as inlet and outlet electrodes equidistant from the electrodes between them. The inlet and outlet electrodes are also typically maintained at the same potential. In other arrangements, the focusing lens is formed by four or more electrodes (e.g., plate arrays), where charged particles have the same energy as when they enter and exit each lens. Such arrangements may again have inlet and outlet electrodes and / or symmetrical arrangements of electrodes maintained at the same potential, but because there are more than three electrodes, these arrangements cannot be strictly considered as single lenses. Arranging lenses (whether or not strictly single lenses) such that charged particles have the same energy when entering and leaving each lens means that dispersion occurs only within each lens (between the inlet and outlet electrodes), thus limiting off-axis chromatic aberration. When the thickness of the focusing lens is very small (e.g., a few millimeters), such aberrations have a small or negligible effect.

[0074] Each focusing lens 116 focuses one of the sub-beams 114 (e.g., a correspondingly different sub-beam) onto a corresponding intermediate focal point 115. The intermediate focal points 115 of the multiple focusing lenses 116 may lie substantially in a common plane, which may be referred to as the intermediate image plane 120.

[0075] The projection device 230 also includes a plurality of objectives 118. The objectives 118 are located downstream of the intermediate focal point (and intermediate image plane 120). The plurality of objectives 118 can be considered as an array of objectives and can be in a common plane. Each objective 118 projects one of the sub-beams 114 (from the corresponding condenser lens 116) onto the sample 208 to be evaluated. Therefore, a one-to-one correspondence can exist between the condenser lens 116 and the objectives 118, where each sub-beam 114 propagates between a unique pair of condenser lenses 116 and objectives 118 for that sub-beam. A one-to-one correspondence can also exist between the beam aperture 110 of the condenser lens array and the objectives 118.

[0076] like Figure 3As shown, the projection system 230 can be configured such that each sub-beam 114 (e.g., the path 122 of the main ray of sub-beam 114, corresponding to the beam axis of sub-beam 114) is essentially a straight line from each focusing lens 116 to the corresponding objective lens 118 (i.e., to the objective lens 118 corresponding to that focusing lens 116). The straight path can further extend to the sample 208. Alternatively, as... Figure 4 As exemplified, collimator 524 can be provided between the condenser lens 116 and the objective lens 118, for example, in the intermediate image plane 120. Collimator 524 collimates the sub-beam. Collimation of the sub-beam reduces the field curvature effect at the objective lens 118, thereby reducing errors caused by field curvature, such as astigmatism and focusing errors.

[0077] In some embodiments, such as Figure 3 and Figure 4 As exemplified, the projection device 230 also includes one or more aberration correctors 124, 125, and 126 that reduce one or more aberrations in the sub-beams 114. In one embodiment, each of at least a subset of the aberration correctors 124 is positioned in or directly adjacent to one of the intermediate focal points 115 (e.g., in or near the intermediate image plane 120). The sub-beams 114 have a minimal cross-sectional area in or near a focal plane such as the intermediate image plane 120. This provides the aberration correctors 124 with more space than elsewhere (i.e., the ascending or descending beams of the intermediate image plane 120, or compared to the space available in alternative arrangements without the intermediate image plane 120). In one embodiment, an aberration corrector 124 located in or directly adjacent to the intermediate focal point 115 (or intermediate image plane 120) includes a deflector for correcting source 201 which appears at different locations for different beams. Corrector 124 can be used to correct macroscopic aberrations generated by source 201 that prevent proper alignment between each sub-beam 114 and its corresponding objective lens 118. Aberration corrector 124 can correct aberrations that interfere with proper column alignment. Such aberrations can also cause misalignment between sub-beams 114 and corrector 124. For this purpose, it may be desirable to additionally or alternatively position aberration correctors 125 at or near condenser lenses 116 (e.g., each such aberration corrector 125 is integrated with or directly adjacent to one or more condenser lenses 116). This is desirable because at or near the focusing lens 116, aberrations do not cause a shift in the corresponding sub-beams 114, since the focusing lens 116 is perpendicularly close to or coincides with the beam aperture 110. However, the challenge in positioning the corrector 125 at or near the focusing lens 116 is that each sub-beam 114 has a relatively large cross-sectional area and a relatively small spacing at that location compared to a more downstream position.

[0078] In some embodiments, such as Figure 3 and Figure 4 As exemplified, each of at least a subset of aberration correctors 126 is integrated with or directly adjacent to one or more of the objectives 118. In one embodiment, these aberration correctors 126 reduce one or more of the following: field curvature; focusing error; and astigmatism. Additionally or alternatively, one or more scan deflectors (not shown) may be integrated with or directly adjacent to one or more objectives 118 for scanning sub-beams 114 over sample 208. Such an arrangement can be implemented, for example, as described in EP 2425444A1, which is incorporated herein by reference specifically in the disclosure of using aperture arrays as scan deflectors.

[0079] Aberration correctors 124 and 125 may be CMOS-based individual programmable deflectors as disclosed in EP 2702595A1, or multi-pole deflector arrays as disclosed in EP 2715768A2, the descriptions of sub-beam manipulators in these two documents are incorporated herein by reference.

[0080] In one embodiment, an aberration corrector, such as aberration corrector 126 associated with objective lens 118, includes a field curvature corrector that reduces field curvature. Reducing field curvature reduces errors caused by field curvature, such as astigmatism and focusing errors. Figure 3 As exemplified, due to the resulting angle of incidence on objective 118, in an embodiment where the sub-beam 114 propagates along a straight path between the focusing lens 116 and objective 118 without correction, a significant field curvature aberration effect is expected at objective 118.

[0081] In one embodiment, the field curvature corrector is integrated with or directly adjacent to one or more objectives 118. In one embodiment, the field curvature corrector includes a passive corrector. A passive corrector can be implemented, for example, by changing the diameter and / or ellipticity of the aperture of the objective 118. A passive corrector can be implemented, for example, as described in EP 2575143A1, which is incorporated herein by reference specifically to the disclosed use of aperture patterns to correct astigmatism. The passive nature of the passive corrector is desirable because it means that no control voltage is required. In embodiments where the passive corrector is implemented by changing the diameter and / or ellipticity of the aperture of the objective 118, the passive corrector provides the further desirable characteristic of not requiring any additional elements, such as additional lens elements. The challenge with passive correctors is that they are fixed, thus requiring careful pre-calculation of the desired correction. Additionally or alternatively, in one embodiment, the field curvature corrector includes an active corrector. An active corrector can provide correction by controllably correcting charged particles. The correction applied by each active corrector can be controlled by controlling the potential of each of one or more electrodes of the active corrector. In one embodiment, the passive corrector applies a coarse correction, while the active corrector applies a finer and / or adjustable correction.

[0082] The following describes an example of a beam manipulator unit 300. The beam manipulator unit 300 includes an aperture assembly 370. The beam manipulator unit 300 can be provided as part of any configuration of the projection device 230 described above. The beam manipulator unit 300 exerts an effect on the charged particle beam passing through it. This effect can include correcting aberrations, multipole errors, or focusing errors associated with the charged particle beam. The beam manipulator unit 300 can be used to implement one or more of the aberration correctors 124, 125, and 126 described above. The beam manipulator unit 300 can therefore be positioned in or directly adjacent to a corresponding intermediate focus 115. Alternatively or additionally, the beam manipulator unit 300 can be integrated with or directly adjacent to one or more objectives 118. Alternatively or additionally, the beam manipulator unit 300 can be integrated with or directly adjacent to one or more focusing lenses 116.

[0083] like Figure 5 and Figure 6As exemplified, the aperture assembly 370 may include a first aperture body 301 and a second aperture body 302. The first aperture body 301 may be an uplink beam in the beam path of the second aperture body 302, but this is not mandatory. A plurality of apertures 304 in the first aperture body 301 are aligned with corresponding plurality of apertures 306 in the second aperture body 302. This alignment provides a charged particle path for each of the corresponding plurality of charged particle beams. Following the charged particle path, each charged particle beam can pass through the aperture assembly 370 through the corresponding aperture in the first aperture body 301 and the second aperture body 302. In the case where the charged particle beam is incident obliquely onto the aperture assembly 370, the aperture 306 in the second aperture body 302 may be laterally displaced relative to the corresponding aperture 304 in the first aperture body 301 (i.e., not aligned in the vertical direction). This lateral displacement in this case achieves the necessary alignment with the path of the charged particle beam to allow the charged particle beam to pass through the aperture assembly 370. When a charged particle beam is orthogonally incident on the aperture assembly 370, the aperture 306 in the second aperture body 302 can be directly positioned below the corresponding aperture 304 in the first aperture body 301 (i.e., aligned in the vertical direction). An example path of the charged particle beam is shown in... Figure 5 and Figure 6 The aperture 304 in the first aperture body 301 may have the same size and / or shape as the aperture 306 in the second aperture body 302. Alternatively, the aperture 304 in the first aperture body 301 may have a different size and / or shape than the aperture 306 in the second aperture body 302. In some arrangements, all apertures 304 and 306 have curved edge shapes, such as circular, elliptical, or oval, but other shapes are also possible. The first aperture body 301 and the second aperture body 302 may be substantially planar. Typically, the maximum in-plane dimension (e.g., diameter) of each aperture 304 in the first aperture body 301 is smaller than the interval between the first aperture body 301 and the second aperture body 302. However, in some embodiments, the maximum in-plane dimension (e.g., diameter) of each aperture 304 in the first aperture body 301 may be equal to or greater than the interval between the first aperture body 301 and the second aperture body 302 (e.g., where the first aperture body 301 and the second aperture body 302 form part of a single lens).

[0084] An electric drive unit 320 is provided for applying a potential to at least the peripheral surfaces of apertures 304 and 306 defining the first aperture body 301 and the second aperture body 302. The drive unit may be connected to one or both of the first aperture body 301 and the second aperture body 302 via a voltage source connector (not shown). Thus, during operation, multiple charged particle beams are guided through the aperture assembly to the sample 208. The electric drive unit 320 may be provided, for example, as part of a charged particle projection system 230 including a manipulator unit 300 and / or a beam tool 40, or as part of the manipulator unit 300. The charged particle beam tool 40 may be used as part of the charged particle beam inspection apparatus 100 as described above. As described above, the electric drive unit 320 may be provided as part of a charged particle beam tool 40 referred to as an electro-optical system or apparatus.

[0085] This document generally illustrates an embodiment in which the first aperture body 301 is the uplink beam of the second aperture body 302. However, the first aperture body 301 and the second aperture body 302 may be provided in an opposite configuration, such that the second aperture body 302 is the uplink beam of the first aperture body 301.

[0086] The aperture assembly 370 is used to manipulate a charged particle beam by controlling the electric field in the region through which the charged particle beam passes. This is achieved by applying an appropriate potential to the electrodes of the aperture assembly 370.

[0087] In some embodiments, the first aperture body 301 includes a first electrode system 311. The first electrode system 311 can be formed in various ways. Figure 5 As schematically shown, the first electrode system 311 can be provided as an integral part of the first aperture body 301. Alternatively, as Figure 6 As schematically depicted, the first electrode system 311 can be provided as such Figure 6 A conductive layer or structure on the first support structure 361 is shown. In one method, the first electrode system 311 can be formed using a silicon-on-insulator process. The first electrode system 311 can be provided as a conductive layer or structure on a silicon oxide insulating layer. The first electrode system 311 may include a metallization layer and / or a conductive semiconductor such as silicon or doped silicon. The first electrode system 311 may include a metal such as molybdenum or aluminum. Examples of the first electrode system 311 are shown in... Figure 7 - Figure 12The following describes and discusses a first electrode system 311 configured to apply a potential to the aperture peripheral surface of each aperture 304 of a first aperture body 301. The first electrode system 311 may include multiple electrodes. Each electrode may include a conductive element and / or a conductive track. Each electrode is electrically isolated from each other and simultaneously electrically connected to the aperture peripheral surface of a different aperture in a plurality of aperture 304 groups of the first aperture body 301. Each group contains multiple apertures 304. Each electrode is therefore able to simultaneously apply a potential to multiple apertures 304 independently of the potentials applied to the other apertures 304 in the first aperture body 301. Therefore, fewer electrodes are required compared to the case where each electrode is connected to only one aperture. Fewer electrodes facilitate electrode wiring, thereby facilitating manufacturing and optionally enabling the formation of denser aperture patterns within the electrodes. Independently controlling the potential applied to the groups of apertures 304 provides a greater level of control than if all apertures were electrically connected together (such as when apertures are formed in a monolithic metal sheet). Therefore, an improved balance is achieved between the ease of manufacturing the beam manipulator unit and the controllability of beam manipulation.

[0088] In some embodiments, the second aperture body 302 includes a second electrode system 312. The second electrode system 312 applies a potential to the aperture peripheral surface of each aperture 306 of the second aperture body 302. The second electrode system 312 can be configured in any of the manner described above for the first electrode system 311. The second electrode system 312 can therefore include a plurality of electrodes formed on the second support structure 362. Each electrode can be electrically isolated from each other and simultaneously electrically connected to the aperture peripheral surface of a different aperture in the plurality of apertures 306 of the second aperture body 302. Alternatively, the second electrode system 312 can include electrodes electrically connected to all aperture peripheral surfaces of the second aperture body 302. The second electrode system 312 can therefore be implemented as a single integral conductive plate, such that the second aperture body 302 and the second electrode system 312 are provided by the same element (i.e., such that the second aperture body is composed of the second electrode system 312).

[0089] In some embodiments, such as Figure 7 - Figure 12 As exemplified, the same number of apertures 304 are provided in each of the at least two aperture groups 304 in the first aperture body 301. Alternatively or additionally, the same number of apertures 306 may be provided in each of the at least two aperture groups 306 in the second aperture body 302.

[0090] In some embodiments, such as Figure 7 - Figure 10As exemplified, each electrode of the first electrode system 311 includes an elongated conductive strip 322, a conductive strip 324, and / or each electrode of the second electrode system 312 includes an elongated conductive strip 322, a conductive strip 324. The respective elongated conductive strips in each electrode system can be implemented as opposing parallel plates. The conductive strips 322, 324 of each respective electrode system are preferably parallel to each other and / or substantially linear. Arranging the electrodes in the conductive strips 322, 324 of the respective electrode systems simplifies wiring because electrical connections to the conductive strips 322, 324 can be made at the ends of the conductive strips 322, 324. In some arrangements, such as... Figure 7 - Figure 10 As schematically shown, conductive strips 322 and 324 are arranged to extend to the peripheral edge of the first electrode system 311 or the second electrode system 312. Extending the conductive strips 322 and 324 to the peripheral edge means that electrical connections to the conductive strips 322 and 324 can be made at the peripheral edge. The peripheral edge of the electrode system shown in the figure is schematic. The shape and relative dimensions of the peripheral surface may differ in actual arrangements. For example, the dimensions of the peripheral surface may be designed to include more apertures 304 and 306 than shown in the figure.

[0091] In some embodiments, the apertures 304 in the first aperture body 301 and / or the apertures 306 in the second aperture body 302 are each arranged in a regular array. The regular array has repeating unit cells. For example, the regular array may include a square array, a rectangular array, or a hexagonal array. The apertures 304 or 306 may alternatively be arranged in an irregular arrangement comprising a plurality of apertures 304 or 306, which may be referred to as an irregular array. In an arrangement with a regular array, the conductive strips 322 and 324 may be parallel to each other and perpendicular to the main axis of the array. Figure 7 - Figure 10 In the example shown, apertures 304 and 306 are arranged in a square array. A regular array can have one main axis horizontal in the page plane and another main axis vertical in the page plane. Figure 7 and Figure 9 The conductive strips 322 in the middle are therefore parallel to each other and perpendicular to the horizontal principal axis. Figure 8 and Figure 10 The conductive strips 324 are parallel to each other and perpendicular to the vertical main axis.

[0092] Conductive strip 322 and conductive strip 324 can each have a short axis and a long axis. Figure 7 and Figure 9 In the example, each minor axis is horizontal, and each major axis is vertical. Figure 8 and Figure 10In the example, each minor axis is vertical, and each major axis is horizontal. The spacing of the conductive strips 322 and 324 parallel to the minor axis can be greater than the spacing of the array parallel to the minor axis. Each vertical conductive strip can therefore include multiple columns of apertures 304 or 306 and / or each horizontal strip can therefore include multiple rows of apertures 304 or 306. This method provides a good balance between controllability and ease of manufacture. Alternatively, the spacing of the conductive strips 322 and 324 parallel to the minor axis can be equal to the spacing of the array parallel to the minor axis, which provides finer spatial control of the electric field.

[0093] In one embodiment, the conductive strips 322 of the first electrode system 311 are not parallel to, for example, perpendicular to, the conductive strips 324 of the second electrode system 322. This arrangement may be particularly preferred, for example, when the conductive strips 322 of the first electrode system 311 are parallel to each other and the conductive strips 324 of the second electrode system 312 are parallel to each other. For example, the first electrode system 311 may include, for example, Figure 7 or Figure 9 The conductive strip 322 shown, and the second electrode system 312 may include, for example, the ... Figure 8 or Figure 10 The conductive strip 324 shown is the same as the one shown. Without making wiring to the corresponding conductive strips 322 and 324 more difficult, this method provides a wide range of possible combinations of potential differences between corresponding apertures 304 and 306 in the first aperture body 301 and the second aperture body 302, spanning the conductive strips 322 and 324 in different electrode systems 311 and 312.

[0094] In another arrangement, such as Figure 11 As illustrated, the multiple electrodes comprise multiple conductive elements 326 that are interlocked with each other. In the example shown, the conductive elements 326 are square. Other interlocking shapes may be used. (Refer to the above reference...) Figure 7 - Figure 10 Compared to the arrangement of conductive strips discussed, this method offers more degrees of freedom to manipulate charged particles, but routing electrical signals to individual electrodes can be more complex.

[0095] In another arrangement, such as Figure 12 As exemplified, the multiple electrodes include multiple conductive elements 328, each comprising at least partially concentric rings, such as circular rings. This method can allow for efficient correction of aberrations having the same or similar symmetry as the concentric rings. However, routing electrical signals to the individual electrodes may be more efficient than using the references described above. Figure 7 - Figure 10 The arrangement of the conductive strips is more complex.

[0096] In some embodiments, the first electrode system 311 includes a plurality of electrodes, each electrode being connected to the reference above. Figure 7 - Figure 12 The aperture peripheral surface assembly, and the second electrode system 312 include as follows Figure 13 A single electrode 319 is shown. The single electrode 319 is electrically connected to all the aperture circumferential surfaces of the second aperture body 302. The aperture circumferential surfaces of the second aperture body 302 are thus maintained at the same potential. Alternatively, the first electrode system 311 includes multiple electrodes, each electrode being connected to as shown in the reference above. Figure 7 - Figure 12 The aforementioned aperture peripheral surface assembly, and as Figure 14 As exemplified, the second electrode system 312 includes a plurality of electrodes, each electrically isolated from each other and electrically connected to the aperture peripheral surface of a different corresponding aperture in the aperture body 302.

[0097] In some embodiments, the aperture assembly 370 is used in conjunction with the charged particle projection device 230. The charged particle projection device 230 may be part of a charged particle beam tool 40. The charged particle beam tool 40 may include any type of tool that uses a charged particle beam. The charged particle beam tool 40 and / or the projection device 230 include multiple lenses. Each lens projects a corresponding charged particle sub-beam. Figure 3 or Figure 4 In the charged particle beam tool 40 of the type shown, the multiple lenses may include multiple focusing lenses 116 or multiple objective lenses 118 of the projection device 230. In other charged particle beam tools 40, other multiple lenses may be provided.

[0098] In such an embodiment, the aperture assembly 370 may be integrated with or directly adjacent to multiple lenses. In one embodiment, each lens includes a multi-electrode lens. In this case, the first aperture body 301 may include the first electrode of the multi-electrode lens. Figure 6 In the schematic structure shown, the first electrode of the multi-electrode lens can be the first support structure 361 of the first aperture body 301. The multiple electrodes of the first electrode system 311 are electrically isolated from the first electrode of the multi-electrode lens. This can be achieved by... Figure 6 An electrically insulating layer is provided between the first electrode system 311 and the first support structure 361 (which acts as an electrode of the multi-electrode lens). In one embodiment, the second aperture body 302 includes a second electrode of the multi-electrode lens. Figure 6In the schematic structure shown, the second electrode of the multi-electrode lens can be the second support structure 362 of the second aperture body 302. The multiple electrodes of the second electrode system 312 are electrically isolated from the second electrode of the multi-electrode lens. The first electrode system 311, the second electrode system 312, or both can have a voltage source connector. The voltage source connector can be configured to apply a potential difference to the peripheral surface of the aperture of at least one of the aperture bodies 301 and 302.

[0099] Multiple lenses integrated with or directly adjacent to the aperture assembly 370 may include multiple objectives 118. Objectives 118 may be referenced above. Figure 3 and Figure 4 Any configuration as described. Alternatively or additionally, the aperture assembly 370 may include, or be directly adjacent to, multiple lenses integrated with or directly adjacent to it, a plurality of focusing lenses 116. Alternatively or additionally, the aperture assembly 370 may be provided in or directly adjacent to an intermediate image plane 120 containing an intermediate focal point 115 of a sub-beam focused by the focusing lenses 116. The focusing lenses 116 may be referenced above. Figure 3 and Figure 4 Configure it in any of the ways described.

[0100] The first electrode system 311 and the second electrode system 312 can be configured to provide a perturbation (which may be referred to as a perturbation field) to the global focusing field provided by the first and second electrodes of each multi-element lens (and any other electrodes of the multi-element lens). The first electrode system 311 and the second electrode system 312 can, for example, apply local corrections for focusing. Regarding embodiments of this type, the first electrode system 311 and the second electrode 312 can therefore be referred to as a perturbation electrode system, a perturbation electrode array, or a local focus correction electrode. The local focus correction can vary between different sub-beams passing through the manipulator unit. The local focus correction can involve potential differences between different electrodes of the first electrode system 311 or between different electrodes of the second electrode system 312, which are small compared to the average total potential difference between the first and second electrodes of the multi-element lens. The electric drive unit 320 can be configured to control the potentials of the electrodes of the first electrode system 311 and / or the second electrode system 312 to achieve this. The electric drive unit 320 can be connected to a voltage source connector. Control can be made such that the potential difference between the highest and lowest potential electrodes of the first electrode system 311 is less than (optionally less than 50%, optional less than 10%, optional less than 5%, optional less than 1%, optional less than 0.1%) the difference between the average potential of the electrodes of the first electrode system 311 and the average potential of the electrodes of the second electrode system 312. In a particular implementation, for example, the first electrode of the multi-electrode lens (having a potential equal to or close to the average potential of the electrodes of the first electrode system 311) is provided at 30 kV, the second electrode of the multi-electrode lens (having a potential equal to or close to the average potential of the electrodes of the second electrode system 312) is provided at 2.5 kV, and deviations from these potentials by an order of 100 V are provided by the electrodes of the first electrode system 311 and / or the second electrode system 312. Based on known formulas Given the focal length, where It is the local energy of a beam of charged particles and This is the local electric field strength. It can be expected that, for a typical configuration including electrons as charged particles, this deviation in potential can impose a focal length change of approximately 1 micrometer. This method can therefore be used to provide macroscopic focusing and / or leveling correction. The correction can, for example, be used to correct focal plane deviation caused by any one or more of the following:

[0101] - Limited manufacturing tolerances: for example, control over the flatness (or curvature) of objective lens 118 and / or the spacing between electrodes.

[0102] - Mechanical mounting tolerances and deformations caused by the mechanical mounting of objective lens 118.

[0103] - Deformation caused by the force of an electrostatic field.

[0104] - For embodiments without collimator 525: due to the field curvature caused by the non-telecentric channel of objective lens 118, and

[0105] - Field curvature of focusing lens 116 (because the beam is not collimated when passing through focusing lens 116).

[0106] The integration of the beam manipulator unit 300 can be particularly effectively achieved using a first electrode system 311 and a second electrode system 312 comprising the cross conductive strips 322 and 324 as described above. In the case of a dual-electrode multi-electrode lens, the conductive strip 324 aligned along the X direction can be formed on the first electrode, while the conductive strip 322 aligned along the Y direction can be formed on the second electrode. The focal plane can then be corrected according to the following function: ,in and This represents a focus correction that can be applied as a function of X and Y, respectively. Typically, focus correction can be applied by providing a relatively increasing potential variation from one conductive band to the next, such that any potential difference between adjacent conductive bands remains relatively low, while still providing a relatively large potential variation over longer length scales. Possible corrections that can be applied with the example geometries described above include any tilt plane corrections as well as higher-order corrections (such as curved surfaces aligned with the X or Y axes) or corrections with R... 2 Correlation rotational symmetry correction (where This method can also be used with a multi-electrode lens configured to operate as a single lens.

[0107] In one type of embodiment, such as Figure 15 - Figure 17 As illustrated, each aperture in at least a subset of apertures 304 in the first aperture body 301 comprises an elongated slit. Each elongated slit may be substantially linear. The elongated slit may have an aspect ratio of less than 0.5. Figure 15As shown, the ratio of the width 341 of the elongated slit to the length 342 of the elongated slit is therefore less than 0.5. Additionally, each corresponding aperture 306 in the second aperture body 302 includes an opening smaller than the elongated slit at least in a direction parallel to the longest axis of the elongated slit. The first aperture body 301 can be an up-beam in the beam path of the second aperture body 302. The shape of the corresponding aperture 306 in the second aperture body can be different from the shape of the opening of the elongated slit in the first aperture body 301. Each opening in at least a subset of these openings can have a shape with substantially curved edges, such as one of the following shapes: circular, oval, or elliptical. When the elongated slit is rectangular, the longest axis of the elongated slit will be the length of the elongated slit, or when the elongated slit is oval or elliptical, the longest axis of the elongated slit will be the principal axis of the elongated slit. The opening can, for example, have an aspect ratio between 0.5 and 1.0, optionally between 0.9 and 1.0, optionally substantially equal to 1.0. Therefore, the elongated slit in the first aperture body 301 can be aligned with a smaller elongated (i.e., having a smaller aspect ratio in the sense that the aspect ratio is close to 1.0) or non-elongated (e.g., a circular, oval, or elliptical opening with an aspect ratio close to 1.0) opening in the second aperture body 302. Alternatively, the opening in the second aperture body 302 can be elongated but not parallel to the elongated slit in the first aperture 301. This approach may be less ideal than having an opening with an aspect ratio close to 1, as it may unnecessarily complicate the wiring in the second aperture body 302 by making the available space for wiring smaller. The first aperture body 301, the second aperture body 302, or both may have a voltage source connection. The voltage source connection can be configured to have a potential difference applied to the aperture peripheral surface of at least one of the aperture bodies in the first and second aperture bodies 302.

[0108] The effect of the aperture 304, shaped as an elongated slit in the first aperture body 301, contributes to the lensing effect through the asymmetry of the aperture 304. This contribution is negligible in the direction parallel to the elongated slit and is enhanced in the direction perpendicular to the slit (relative to a circular opening). The effect of the corresponding opening in the second aperture body 302 (e.g., having a different shape than the opening in the corresponding aperture 304 in the first aperture body 301) is to contribute a stronger lensing effect (relative to the elongated slit) in the direction parallel to the elongated slit with opposite polarity, while contributing a weaker or negligible lensing effect (relative to the elongated slit) in the direction perpendicular to the elongated slit. As described above, the opening in the second aperture body 302 is generally circular or nearly circular. However, the effect becomes stronger when the opening in the second aperture body 302 is elongated and not parallel (e.g., perpendicular) to the elongated slit in the first aperture body 301. In the vertical case, for example, when the opening in the second aperture body 302 is circular, the contribution of the opening in the second aperture body 302 to the lens effect is twice as strong in the direction parallel to the elongated slit in the first aperture body 301, and negligible in the direction perpendicular to the elongated slit in the first aperture body 301.

[0109] In one embodiment, the length 342 of each elongated slit in the first aperture body 301 is sufficiently large relative to the spacing between the first aperture body 301 and the second aperture body 302, such that the ends of the elongated slits are shielded by the second aperture body 302 (i.e., effectively making the ends non-existent for charged particles passing through the aperture assembly 370). The length of the elongated slits may, for example, typically be at least twice as large as, and optionally at least three times as large as, the spacing between the first aperture body 301 and the second aperture body 302.

[0110] The spacing between the first aperture body 301 and the second aperture body 302 is ideally larger than (optionally at least twice as large, optional at least three times as large) the width of each elongated slit. This provides a sufficient distance from the elongated slits such that the field becomes nearly uniform before reaching the second aperture body 302, regardless of any perturbation of the field by the elongated slits in the width direction of the elongated slits.

[0111] The spacing between the first aperture body 301 and the second aperture body 302 is also ideally larger than (optionally at least twice as large, optional at least three times as large) the maximum in-plane dimension (e.g., the diameter of a circular opening) of each aperture 306 in the second aperture body 302. This, in turn, provides a sufficient distance from the apertures 306 such that the field becomes nearly uniform before reaching the first aperture body 301.

[0112] The maximum in-plane dimension of each aperture 306 in the second aperture body 302 can be substantially equal to the minimum in-plane dimension (i.e., width) of the corresponding elongated slit in the first aperture body 301. This can be achieved by the apertures 306 in the second aperture body 302 having a different shape than the corresponding elongated slits in the first aperture body 301. This allows the apertures 306 to perform their function efficiently while minimizing wiring interruptions in the second aperture body 302. Due to the increased space available for wiring in the second aperture body 302, it is desirable to provide more wiring in the second aperture body 302 than in the first aperture body 301 (as discussed further below).

[0113] As described above, the elongation of the elongated slit produces a lensing effect caused by the slit, which is smaller along its length parallel to the slit and larger in the vertical direction. This allows for the creation of a quadrupole effect. The quadrupole effect allows the manipulator unit 300 to operate as an astigmatism corrector to correct astigmatism. The size and polarity of the quadrupole effect are determined by the potential difference between the effect apertures 304 and 306. The orientation of the quadrupole effect is determined by the orientation of the elongated slit. Therefore, height control of the astigmatism effect applied to a single beam provides the minimum independent electrical connection required for the area where the astigmatism effect is applied. For the case where the opening in the second aperture body 302 is circular, in Figure 16 and Figure 17 The effect was qualitatively described in the text.

[0114] Figure 16 This is a side cross-sectional view along the X direction (i.e., parallel to the width of the narrow slit). Figure 16 Above the dashed area, the potential difference (in the Z direction) between the first aperture body 301 and the second aperture body 302 causes a relatively strong positive lensing effect in the X direction (parallel to the width 341 of the elongated slit) near the aperture 304 in the first aperture body 301. This relatively strong positive lensing effect is due to the elongated shape. The focal length of the infinitely elongated lens (sometimes called a slit lens) is determined by... The negative lensing effect in the X direction occurs near the corresponding aperture 306 in the second aperture body 302. However, the negative lensing effect is smaller because aperture 306 is less elongated (or less slender). The focal length of an ideal circular negative lens (sometimes called an aperture lens) is... The end result is a residual positive lensing effect in the X direction. This residual positive lensing effect can be quantified by referencing the corresponding focal length; if the slit is sufficiently long, the focal length will be approximately equal to... Here, It is the local energy of a beam of charged particles and It refers to the local electric field strength.

[0115] Figure 17This is a side cross-sectional view along the Y direction (i.e., parallel to the length of the elongated slit). In this orientation, a much smaller (or negligible) positive lensing effect exists near each aperture 304 in the first aperture body 301 along the Y direction (parallel to the length 342 of the elongated slit). A negative lensing effect in the Y direction appears near aperture 306 in the second aperture body 302. Figure 16 As shown, the intensity of the negative lensing effect in the Y direction is the same as or similar to the intensity of the negative lensing effect in the X direction at aperture 306. The negative lensing effect in the Y direction is greater than the positive lensing effect in the Y direction starting from the corresponding aperture 304 in the first aperture body 301. The final result is a residual negative lensing effect in the Y direction, where the corresponding focal length is approximately equal to... .

[0116] In the alternative scenario where each opening in the second aperture body 302 is elongated and perpendicular to the corresponding elongated slit in the first aperture body 301, the contribution of each opening in the second aperture body 302 to the lens effect is twice as strong in the direction perpendicular to the elongation of the opening, and negligible in the direction parallel to the elongation of the opening. The end result is that the astigmatic effect is twice as strong. In a configuration with... A residual positive lensing effect is provided in the X direction for approximately equal corresponding focal lengths. In a configuration with... A residual negative lensing effect is provided in the Y direction for approximately equal corresponding focal lengths.

[0117] Therefore, a residual positive lensing effect is provided in the X direction, while a residual negative lensing effect is provided in the Y direction, thus constituting the aforementioned quadrupole effect.

[0118] The potential difference between aperture 304 and aperture 306 can be referenced above. Figure 5 - Figure 14Either the first electrode system 311 or the second electrode system 312 described herein may be provided. The corresponding first electrode system 311 or second electrode system 312 of the first aperture body 301 or the second aperture body 302, or both, may be electrically connected via a voltage source connector. This includes the use of electrode systems that are not necessarily limited to providing a potential to an electrode assembly. Embodiments using elongated slits may use electrode systems that allow individual control of the potential difference for each elongated slit or a corresponding opening facing the elongated slit. For example, in one arrangement, the first aperture body 301 includes a first electrode system 311 for applying a potential to the aperture peripheral surface of each aperture 304 of the first aperture body 304. The first electrode system 311 includes a plurality of electrodes. Each electrode is electrically isolated from each other electrode of the first electrode system 311 and is electrically connected to the aperture peripheral surface of a different corresponding aperture 304 of the aperture body 301. Alternatively or additionally, the second aperture body 302 may include a second electrode system 312 for applying a potential to the circumferential surface of each aperture 306 of the second aperture body 302. The second electrode system 312 may include a plurality of electrodes. Each electrode may be electrically isolated from each other electrode of the second electrode system 312 and is electrically connected to the circumferential surface of a different corresponding aperture of one of the apertures 306 of the second aperture body 302. Therefore, one or both of the first aperture body 301 and the second aperture body 302 may include… Figure 14 The electrode system is of the type shown. However, typically, only one of the two aperture bodies 301 and 302 includes... Figure 14 The electrode system shown is designed to avoid unnecessary and complex electrical wiring requirements. For example, Figure 14 An electrode system of the type shown can be provided in one of two aperture bodies 301 and 302 that do not include the elongated slit. This arrangement may be advantageous because the aperture body without the elongated slit may have a less elongated opening. A less elongated opening can provide more space for wiring of electrical connections. However, as mentioned above, any other combination of the disclosed first electrode system 311 and second electrode system 312 can be used. For example, such as Figure 12 The second electrode system 312 shown is as follows Figure 20 or Figure 21 The combination of the first aperture system 311 shown may be particularly effective.

[0119] As an alternative or addition to the example implementations of the first electrode system 311 and the second electrode system 312 described above, the potential difference between apertures 304 and 306 can be provided using locally integrated electronics. For example, the locally integrated electronics can be implemented using CMOS technology. Figure 18 and Figure 19An example of a method using CMOS technology is depicted. In this example, the second aperture body 302 includes locally integrated electronics for each aperture 306 of the second aperture body 302. The locally integrated electronics are configured to apply a potential to the aperture peripheral surface of the aperture 306. Alternatively or additionally, the first aperture body 301 may include locally integrated electronics for each aperture 304 of the first aperture body 301, wherein the locally integrated electronics are configured to apply a potential to the aperture peripheral surface of the aperture 304. The locally integrated electronics of the first aperture body 301 or the second aperture body 302, or both, are connected via voltage source connections. Alternatively or additionally, the potential difference between apertures 304 and 306 can be provided using integrated passive circuitry. The integrated passive circuitry may include a resistor network. The resistor network allows different potentials to be applied to the aperture peripheral surfaces of at least a subset of the apertures of the first aperture body through potential distribution. The resistor network may include resistors connected in series. The series resistors can be selected to achieve a desired series of steps of potential at the node between the resistors (as achieved in a voltage divider). The potential at the node is used to provide a potential difference of a desired range between apertures 304 and 306. The resistor network can be integrated into one or both aperture bodies 301 and 302. The resistor network in the first aperture body 301 or the second aperture body 302 or both is connected via a voltage source connector. Using locally integrated electronics and / or integrated passive circuitry to provide the desired potential difference provides a high level of control and reduces wiring difficulties. However, the construction of the corresponding first or second aperture body is more complex. Additionally, the range of potential differences that can be applied by such integrated electronics and / or integrated passive circuitry can be narrower than the range of potential differences that can be applied using externally driven electrodes (e.g., using electrode systems such as those described herein).

[0120] The orientation of the quadrupole effect is determined by the orientation of the elongated slit. The orientation of the elongated slit can therefore vary according to the expected symmetry of the aberration to be corrected.

[0121] In one embodiment, such as Figure 20 As exemplified, at least most of the elongated slits (labeled aperture 304) are radially aligned relative to a common axis perpendicular to the plane passing through the first aperture body 311. Figure 20 In the orientation, the common axis can be perpendicular to the plane of the page. The first aperture body 311 of the plate can be a plane having multiple apertures 304. In one arrangement, the aperture defined in the first aperture body 311 is an elongated slit. The slit can have a major axis and a minor axis, and can be rectangular or elliptical. A rectangular slit can have a long side aligned with the major axis of the slit. Therefore, the sides of the rectangular slit are aligned with the direction of each slit toward the common axis. The first aperture body 311 can have a... Figure 20 The axis corresponding to the center of the first aperture body shown. This axis can be referred to, for example, as a common axis with respect to slit aperture 304. At least most (if not all) of the slit apertures can be oriented relative to the common axis, such that the major axis of the slit aperture is aligned with the direction from the slit aperture to the common axis. Slit apertures located on the reflection axis of the pattern of slit apertures defined in the first aperture body 311 are angularly similar along the reflection axis and are displaced only in position within the pattern. Such axes are the x-axis and y-axis, and are, for example, between 45 degrees. All other slit apertures are angularly displaced relative to each other and in position, but aligned with the direction of the common axis in the plane of the first aperture body 311.

[0122] In one embodiment, such as Figure 21 As exemplified, at least most of the elongated slits (labeled aperture 304) are substantially azimuthally aligned with respect to the common axis, i.e., substantially perpendicular to the radial direction with respect to the common axis. The arrangement of aperture 304 in the first aperture body 311 is similar to... Figure 20 The patterns shown are identical with key differences. The alignment directions of the major and minor axes of each aperture are interchanged, such that the minor axis of each aperture is aligned with the direction toward the common axis of the first aperture body 311, and the major axis is orthogonally aligned with the direction toward the common axis of the aperture patterns in the first aperture body 311. Apertures equidistant from the common axis in the first aperture body 311 are aligned tangentially with respect to their respective common radial displacements with respect to the common axis. Therefore, for a rectangular slit, the side of the slit aligned with the major axis of the slit is orthogonal to the direction from the slit toward the common axis.

[0123] In one embodiment, such as Figure 22 and Figure 23 As exemplified, at least most of the elongated slits are parallel to each other. The elongated slits may additionally be aligned in rows across the first aperture body, preferably extending between the edges of the first aperture body 301. In the first aperture body 311, the rows may be linear, such as transverse or longitudinal or vertical or horizontal. The rows may be parallel to each other. The rows may or may not be parallel to the edges of the first aperture body 301.

[0124] To provide more comprehensive control over astigmatism, including control over the magnitude and direction of astigmatism, an additional quadrupole effect with independently controllable and tilt-aligned properties can be provided through a separate aperture body. Figure 24 - Figure 26 An example of such an arrangement is depicted, in which the elongated slit is relative to... Figure 15 - Figure 17The arrangement is rotated by 45 degrees. In this type of embodiment, a third aperture body 351 and a fourth aperture body 352 are provided. The third aperture body 351 can be configured in any of the ways described above for the first aperture body 301. The fourth aperture body 352 can be configured in any of the ways described above for the second aperture body 302. The potential difference between the third aperture body 351 and the fourth aperture body 352 can be controlled in any of the ways described above for the first aperture body 301 and the second aperture body 302 to control additional quadrupole effects. A plurality of apertures 354 in the third aperture body 351 are aligned with corresponding plurality of apertures 304, 306, and 356 in the first aperture body 301, the second aperture body 302, and the fourth aperture body 352. This alignment allows each of the respective plurality of charged particle beams to pass through an aperture assembly via corresponding apertures 304, 306, 354, and 356 in four corresponding bodies (e.g., first aperture body 301, second aperture body 302, third aperture body 351, and fourth aperture body 352). Each aperture in at least a subset of apertures 354 in the third aperture body 351 includes an elongated slit. Each corresponding aperture 356 in the fourth aperture body 352 includes an opening smaller than the elongated slit, at least in a direction parallel to the longest axis of the elongated slit. The elongated slit in the third aperture body 351 can be configured in any of the manner described above for the elongated slit in the first aperture body 301. The opening in the fourth aperture body 352 can be configured in any of the manner described above for the opening in the second aperture body 302. (For example, the opening in the fourth aperture body 352 can have a different shape than the corresponding elongated slit in the third aperture body 351). The elongated slits in the first aperture body 301 and the third aperture body 351 are aligned such that each beam of charged particles passes through the elongated slits in the first aperture body 301 and the third aperture body 351, the elongated slits being tilted relative to each other when viewed along the path of the charged particle beams. In the specific example shown, the elongated slits are aligned at 45 degrees, but other tilt angles can also be selected. By controlling the quadrupole effect provided by the first aperture body 301 and the second aperture body 302, and the quadrupole effect of the tilted alignment provided by the third aperture body 351 and the fourth aperture body 352, the amplitude and direction of the total quadrupole effect applied to each sub-beam of charged particles can be controlled. Thus, a high degree of control is provided without requiring numerous independent electrical connections.

[0125] In one embodiment, the charged particle beam tool 40 includes an electron detection device 240 that detects one or both of secondary electrons and backscattered electrons from the sample. Figure 3 and Figure 4In the example shown, the electron detection device 240 is integrated with the objective lens 118. The electron detection device 240 may, for example, include a CMOS chip detector integrated with the bottom electrodes of one or more objectives lens 118. Alternatively, a secondary optical column may be provided to guide secondary electrons and / or backscattered electrons to the electron detection device 240 located elsewhere. As described above, the electron detection device 240 can generate signals sent to the electron detection device 240 as referenced above. Figure 1 and Figure 2 The signals from the controller 50 or signal processing system are used, for example, to construct an image of a region of the sample 208 scanned by the charged particle beam tool 40 or to perform other post-processing.

[0126] In one embodiment, as discussed below Figure 27 - Figure 31 As exemplified, the objective lens includes a multi-electrode lens, wherein the bottom electrode of the multi-electrode lens is integrated with a CMOS chip detector array. The multi-electrode lens may include, for example... Figure 27 The three electrodes in the example, such as Figure 28 The examples illustrate two electrodes or different numbers of electrodes. Integrating the detector array into the objective lens replaces the need for secondary pillars for detecting secondary electrons and backscattered electrons. The CMOS chip is preferably oriented towards the sample (because the distance between the wafer and the bottom of the electron optics system is small (e.g., 100 μm)). In one embodiment, electrodes for capturing secondary electron signals are formed in the top metal layer of the CMOS device. Electrodes can be formed in other layers. The CMOS power and control signals can be connected to the CMOS via through-silicon vias (TSVs). For robustness, the bottom electrode preferably consists of two elements: the CMOS chip and a passive silicon (Si) plate with vias. The plate shields the CMOS from high electric fields.

[0127] To maximize detection efficiency, it is desirable to make the electrode surface as large as possible, such that the electrodes occupy virtually all the area of ​​the array objective (except for the aperture), and each electrode has a diameter substantially equal to the array spacing. In one embodiment, the outer shape of the electrodes is circular, but this can be made square to maximize the detection area. The diameter of the aperture through the substrate can also be minimized. The typical size of the electron beam is approximately 5–15 micrometers.

[0128] In one embodiment, a single electrode surrounds each aperture. In another embodiment, multiple electrode elements are provided around each aperture. Electrons captured by the electrode elements surrounding an aperture can be combined into a single signal or used to generate independent signals. The electrode elements can be divided radially (i.e., to form multiple concentric rings), angularly (i.e., to form multiple fan-shaped plates), radially and angularly, or in any other convenient manner.

[0129] However, a larger electrode surface area results in a larger parasitic capacitance, thus leading to a lower bandwidth. Therefore, limiting the outer diameter of the electrode may be desirable, especially when a larger electrode provides only a slightly higher detection efficiency but a significantly larger capacitance. Circular (ring-shaped) electrodes offer a good trade-off between collection efficiency and parasitic capacitance.

[0130] A larger outer diameter of the electrode can also lead to greater crosstalk (sensitivity to signals from adjacent apertures). This may also be a reason to reduce the outer diameter of the electrode, especially when a larger electrode only provides slightly higher detection efficiency but significantly greater crosstalk.

[0131] The backscattered and / or secondary electron currents collected by the electrodes are amplified by a transimpedance amplifier.

[0132] exist Figure 27 and Figure 28 An exemplary embodiment of the multibeam objective lens 401 is illustrated in schematic cross-section. A detector module 402 is provided on the output side of the objective lens 401, i.e., the side facing the sample 403. Figure 29 This is a bottom view of detector module 402, which includes a substrate 404 on which a plurality of capture electrodes 405 are provided, each capture electrode 405 surrounding a beam aperture 406. The beam aperture 406 is formed by etching through the substrate 404. Figure 29 In the arrangement shown, the beam apertures 406 are represented in a rectangular array. The beam apertures 406 can also be arranged differently, for example, as... Figure 30 The hexagonal close-packed array shown.

[0133] Figure 31 A cross-section of a portion of detector module 402 is depicted at a larger scale. The capture electrode 405 forms the bottommost part of detector module 402, i.e., the surface closest to the sample. A logic layer 407 is provided between the capture electrode 405 and the body of silicon substrate 404. Logic layer 407 may include amplifiers (e.g., transimpedance amplifiers), analog-to-digital converters, and readout logic. In one embodiment, each capture electrode 405 has one amplifier and one analog-to-digital converter. Logic layer 407 and capture electrode 405 can be fabricated using a CMOS process, where capture electrode 405 forms the final metallization layer.

[0134] Wiring layer 408 is provided on the back side of substrate 404 and connected to logic layer 407 via through-silicon vias 409. The number of through-silicon vias 409 need not be the same as the number of beam apertures 406. Specifically, if the electrode signals are digitized in logic layer 407, only a small number of through-silicon vias may be needed to provide the data bus. Wiring layer 408 may include control lines, data lines, and power lines. It should be noted that despite the beam apertures 406, there is sufficient space for all necessary connections. Detection module 402 may also be fabricated using bipolar or other manufacturing techniques. Printed circuit boards and / or other semiconductor chips may be provided on the back side of detector module 402.

[0135] In embodiments where the aperture assembly 370 is integrated with multiple objectives, the aperture assembly 370 can be integrated with... Figure 27 or Figure 28 The multi-beam objective lens 401 is integrated. In this case, the first aperture body 301 will include... Figure 27 or Figure 28 One electrode of the multi-beam objective lens, and the second aperture body 302 will include a different electrode of the multi-beam objective lens 401.

[0136] Embodiments of this disclosure may be provided in the form of a method, which may use any of the above arrangements or other arrangements.

[0137] In one embodiment, a method for manipulating charged particles is provided, optionally an inspection method, which includes guiding a plurality of charged particle beams onto a sample 208 through an aperture assembly 370. The charged particle beams are electrostatically manipulated by applying a potential to electrodes in the aperture assembly. The aperture assembly 370 can take any of the forms described above. The aperture assembly 370 may therefore include a first aperture body 301 and a second aperture body 302. A plurality of apertures 304 in the first aperture body 301 are aligned with a corresponding plurality of apertures 306 in the second aperture body 302, such that each charged particle beam passes through the aperture assembly 370 through a corresponding aperture 304 or aperture 306 in the first aperture body 301 and the second aperture body 302. Applying the potential includes applying the potential to a plurality of electrodes, each electrode being electrically isolated from each other and simultaneously electrically connected to the circumferential surface of a different aperture in a plurality of aperture groups of the first aperture body 301.

[0138] In another embodiment, a method for manipulating charged particles is provided, optionally including the method of guiding a plurality of charged particle beams onto a sample 208 via an aperture assembly. The charged particle beams are electrostatically manipulated by applying a potential to electrodes in the aperture assembly. The aperture assembly can take any of the forms described above. The aperture assembly may therefore include a first aperture body 301 and a second aperture body 302. A plurality of apertures 304 in the first aperture body 301 are aligned with corresponding plurality of apertures 306 in the second aperture body 302 such that each charged particle beam passes through the aperture assembly through the corresponding aperture 304 or aperture 306 in the first aperture body 301 and the second aperture body 302. The shape of the aperture in the second aperture body may differ from the shape of the aperture in the first aperture body; the aperture may be elongated. Applying the potential includes applying a potential difference between the apertures 304 in the first aperture body 301 and the corresponding apertures 306 in the second aperture body 302. Each aperture in at least a subset of apertures 304 in the first aperture body 301 includes an elongated slit. Each corresponding aperture 306 in the second aperture body 302 includes an opening smaller than the elongated slit, at least in a direction parallel to the longest axis of the elongated slit. An electric potential can be applied to reduce astigmatism in the charged particle beam.

[0139] Adjacent electro-optical elements along the beam path can be structurally connected to each other, for example, using electrically insulating elements such as spacers. The insulating elements can be made of electrically insulating materials such as ceramics or glass.

[0140] Reference to a component or component system or element controllable to manipulate a charged particle beam in a certain manner includes: configuring a controller or control system or control unit to control the component to manipulate the charged particle beam in said manner, and optionally using other controllers (such as controller 50) or devices (e.g., voltage sources and / or current sources) to control the component to manipulate the charged particle beam in that manner. For example, under the control of a controller or control system or control unit, a voltage source, or “drive unit” herein, may be electrically connected to one or more components to apply a potential to the components, such as objective array 118, focusing lens 231, correctors 124, 125 and 126, and collimator element array 524, as listed in the non-limiting list. Actuable components (such as stages) may be controlled to be actuated and thus moved relative to another component (such as a beam path) using one or more controllers, control systems or control units, thereby controlling the actuation of the components.

[0141] The embodiments described herein can take the form of a series of aperture arrays or electro-optical elements arranged in an array along a beam or multi-beam path. Such electro-optical elements can be electrostatic. In one embodiment, all electro-optical elements, such as the last electro-optical element in the sub-beam path from the beam-limiting aperture array to the sample, can be electrostatic and / or can be in the form of an aperture array or a plate array. In some arrangements, one or more electro-optical elements are fabricated as microelectromechanical systems (MEMS) (i.e., using MEMS fabrication techniques).

[0142] References to upper and lower, ascending and descending, above and below should be understood to refer to directions parallel (generally, but not always vertical) to the directions of the ascending and descending beams of the electron beam or multiple beams impacting sample 208. Therefore, references to the ascending and descending beams are intended to refer to directions about the beam path, independent of any existing gravitational field.

[0143] The embodiments may be further described using the following terms:

[0144] 1. An aperture assembly for a beam manipulator unit of a charged particle projection device, the aperture assembly comprising:

[0145] First aperture body and second aperture body, wherein:

[0146] Multiple apertures in the first aperture body are aligned with corresponding multiple apertures in the second aperture body, such that the alignment allows the path of each of the corresponding multiple charged particle beams to pass through the aperture assembly by passing through the corresponding apertures in the first aperture body and the second aperture body.

[0147] The first aperture body includes a first electrode system for applying a potential to the peripheral surface of each aperture in the first aperture body;

[0148] The second aperture body includes a second electrode system for applying a potential to the peripheral surface of each aperture in the second aperture body; and

[0149] The first electrode system includes multiple electrodes, each of which is electrically isolated from each other and simultaneously electrically connected to the circumferential surface of a different aperture of a plurality of aperture groups in the first aperture body.

[0150] 2. The component according to Clause 1, wherein at least two aperture groups in the aperture group comprise the same number of apertures.

[0151] 3. The component according to Clause 1 or 2, wherein each electrode of the first electrode system comprises an elongated conductive strip.

[0152] 4. The component according to Clause 3, wherein the apertures in the first aperture body are arranged in an array, preferably a regular array.

[0153] 5. The component according to Clause 4, wherein the conductive strips are parallel to each other and perpendicular to the main axis of the array.

[0154] 6. The component according to Clause 5, wherein the pitch of the conductive strip parallel to the short axis of the conductive strip is greater than the pitch of the array parallel to the short axis.

[0155] 7. The component according to Clause 5, wherein the pitch of the conductive strip parallel to the short axis of the conductive strip is equal to the pitch of the array parallel to the short axis.

[0156] 8. The component according to any one of the preceding clauses, wherein the plurality of electrodes comprises a plurality of conductive elements configured to interlock with each other.

[0157] 9. The component according to Clause 1 or 2, wherein the plurality of electrodes include a plurality of conductive elements, the plurality of conductive elements including at least a portion of a concentric ring.

[0158] 10. The component according to any one of the preceding clauses, wherein the second electrode system includes electrodes electrically connected to all aperture peripheral surfaces of the second aperture body.

[0159] 11. The component according to any one of clauses 1 to 9, wherein the second electrode system comprises a plurality of electrodes, each electrode being electrically isolated from each other and simultaneously electrically connected to the circumferential surface of a different aperture of a plurality of aperture groups of the second electrode system.

[0160] 12. The component as described in Clause 11, wherein:

[0161] Each electrode in the first electrode system includes a thin, elongated conductive strip;

[0162] Each electrode of the second electrode system includes a thin, elongated conductive strip; and

[0163] The conductive bands of the first electrode system are not parallel to the conductive bands of the second electrode system.

[0164] 13. The component according to Clause 12, wherein the conductive strips of the first electrode system are parallel to each other, the conductive strips of the second electrode system are parallel to each other, and the conductive strips of the first electrode system are perpendicular to the conductive strips of the second electrode system.

[0165] 14. The component according to any one of the preceding clauses, wherein the aperture in the first aperture body and / or the aperture in the second aperture body has a shape with curved edges, preferably circular, elliptical or oval.

[0166] 15. The component according to any one of the foregoing clauses, wherein:

[0167] Each aperture in at least one subset of the apertures in the first aperture body consists of elongated slits; and

[0168] Each corresponding aperture in the second aperture body includes an opening smaller than the elongated slit in at least a direction parallel to the longest axis of the elongated slit.

[0169] 16. An aperture assembly for a beam manipulator unit of a charged particle projection device, comprising:

[0170] First aperture body and second aperture body, wherein:

[0171] Multiple apertures in the first aperture body are aligned with corresponding multiple apertures in the second aperture body, such that the alignment allows the path of each of the corresponding multiple charged particle beams to pass through the aperture assembly by passing through the corresponding apertures in the first aperture body and the second aperture body.

[0172] Each aperture in at least one subset of the apertures in the first aperture body consists of elongated slits; and

[0173] Each corresponding aperture in the second aperture body includes an opening smaller than the elongated slit in at least a direction parallel to the longest axis of the elongated slit.

[0174] 16a. The aperture assembly according to Clause 16, including a voltage source connector configured to apply a potential difference to the peripheral surface of the aperture of at least one of the first and second aperture bodies.

[0175] 16b. The aperture assembly according to clause 16 or 16a, wherein each corresponding aperture in the second aperture body consists of an opening having a shape different from the corresponding elongated slit.

[0176] 16c. An aperture assembly for an aberration corrector of a beam manipulator unit for a charged particle projection device, comprising: a first aperture body; a second aperture body, the first aperture body being configured as an upward beam along the path of a charged particle, a plurality of apertures in the first aperture body being aligned with corresponding plurality of apertures in the second aperture body, the alignment being such that the path of each of the corresponding plurality of charged particle beams is allowed to pass through the aperture assembly through the corresponding apertures in the first and second aperture bodies; each aperture in at least a subset of the apertures in the first aperture body being composed of an elongated slit; and each corresponding aperture in the second aperture body being composed of an opening having a different shape from the corresponding elongated slit and being smaller than the corresponding elongated slit at least in a direction parallel to the longest axis of the elongated slit; and a voltage source connector configured to apply a potential difference to the aperture peripheral surface of the aperture of at least one of the first and second aperture bodies.

[0177] 17. The component according to any one of clauses 16 to 16c, wherein:

[0178] The first aperture body includes a first electrode system for applying a potential to the circumferential surface of each aperture of the first aperture body. The first electrode system is preferably associated with and electrically connected to a voltage source connector. The first electrode system includes a plurality of electrodes, each electrode being electrically isolated from each other electrode of the first electrode system and electrically connected to the circumferential surface of a different corresponding aperture in the aperture body; and / or

[0179] The second aperture body includes a second electrode system for applying a potential to the aperture peripheral surface of each aperture of the second aperture body. The second electrode system is preferably associated with and electrically connected to a voltage source connector. The second electrode system includes a plurality of electrodes, each of which is electrically isolated from each other electrode of the second electrode system and electrically connected to the aperture peripheral surface of a different corresponding aperture in the aperture body.

[0180] 18. The component according to any one of clauses 16 to 16c, wherein:

[0181] The first aperture body includes locally integrated electronics for each aperture of the first aperture body, the locally integrated electronics being configured to apply a potential to the aperture peripheral surface of the aperture, and the locally integrated electronics being preferably associated with and electrically connected to a voltage source connector; and / or

[0182] The second aperture body includes locally integrated electronics for each aperture of the second aperture body, the locally integrated electronics being configured to apply a potential to the aperture peripheral surface of the aperture, and the locally integrated electronics being preferably associated with and electrically connected to a voltage source connector.

[0183] 19. The component according to any one of clauses 16 to 16c or 18, wherein:

[0184] The first aperture body includes an integrated passive circuit, which includes a resistor network configured to allow different potentials to be applied to the aperture periphery of at least a subset of the aperture of the first aperture body by potential distribution of the resistor network. The resistor network is preferably associated with and electrically connected to a voltage source connector; and / or

[0185] The second aperture body includes an integrated passive circuit, which includes a resistor network configured to allow different potentials to be applied to the aperture peripheral surface of at least a subset of the aperture of the second aperture body by potential distribution of the resistor network. The resistor network is preferably associated with and electrically connected to a voltage source connector.

[0186] 20. The component according to any one of clauses 15 to 19, wherein each elongated slit in at least a subset of the elongated slits is a substantially linear slit.

[0187] 21. The component according to any one of clauses 15 to 20, wherein each opening in at least a subset of the openings has a shape with curved edges, preferably substantially one of the following shapes: circular, oval, elliptical.

[0188] 22. The component according to any one of Clauses 15 to 21, wherein at least a majority of the elongated slit is radially aligned with respect to a common axis perpendicular to a plane passing through the first aperture body.

[0189] 23. The component according to any one of Clauses 15 to 22, wherein at least a majority of the elongated slit is aligned radially relative to a common axis of a plane perpendicular to the first aperture body.

[0190] 24. The component according to any one of clauses 15 to 23, wherein at least a majority of the elongated slits are parallel to each other.

[0191] 25. The component according to any one of clauses 15 to 24, wherein the maximum in-plane dimension of each opening in the first aperture body is substantially equal to the minimum in-plane dimension of the corresponding elongated slit in the second aperture body.

[0192] 25a. The component according to any one of clauses 15 to 24, wherein the maximum in-plane dimension of each opening in the second aperture body is substantially equal to the minimum in-plane dimension of the corresponding elongated slit in the first aperture body.

[0193] 26. The component according to any one of clauses 15 to 25a, wherein:

[0194] The aperture assembly also includes a third aperture body and a fourth aperture body; a plurality of apertures in the third aperture body are aligned with corresponding plurality of apertures in the first aperture body, the second aperture body and the fourth aperture body, such that the alignment allows the path of each of the respective plurality of charged particle beams to pass through the aperture assembly by passing through the corresponding apertures in the first aperture body, the second aperture body, the third aperture body and the fourth aperture body;

[0195] Each aperture in at least one subset of the apertures in the third aperture body consists of elongated slits;

[0196] Each corresponding aperture in the fourth aperture body consists of an opening smaller than the elongated slit, at least in the direction parallel to the longest axis of the elongated slit; and

[0197] The elongated slits in the first and third aperture bodies are aligned such that each beam of charged particles passes through the elongated slits in the first and third aperture bodies, and the elongated slits are aligned at an angle relative to each other when observed along the path of the charged particle beams.

[0198] 27. A beam manipulator unit for a charged particle projection device, comprising:

[0199] The aperture assembly according to any one of the foregoing clauses; and

[0200] An electrically driven unit, preferably configured by being connected to a voltage source connector, applies a potential to the circumferential surface of the apertures in a first aperture body and / or a second aperture body when multiple charged particle beams are guided toward a sample through an aperture assembly.

[0201] 28. A charged particle projection device, comprising:

[0202] The beam manipulator unit as described in Clause 27; and

[0203] Multiple lenses, each configured to project a corresponding sub-beam of charged particles.

[0204] 29. The apparatus according to Clause 28, wherein the aperture assembly is integrated with or directly adjacent to a plurality of lenses, preferably directly adjacent to a direct upward or downward beam comprising a plurality of lenses.

[0205] 30. The apparatus according to clause 29, wherein:

[0206] Each lens includes a multi-electrode lens;

[0207] The first aperture body includes the first electrode of the multi-electrode lens; and

[0208] The first aperture body includes a first electrode system, which includes multiple electrodes electrically isolated from the first electrode of the multi-electrode lens.

[0209] 31. The apparatus according to clause 30, wherein:

[0210] The second aperture body includes the second electrode of the multi-electrode lens; and

[0211] The second aperture body includes a second electrode system, which comprises multiple electrodes electrically isolated from the second electrode of the multi-electrode lens.

[0212] 32. The apparatus according to clause 30 or 31, wherein the electric drive unit is configured to control the potential of the electrodes of the first electrode system such that the potential difference between the highest potential electrode and the lowest potential electrode of the first electrode system is less than the difference between the average potential of the electrodes of the first electrode system and the average potential of the electrodes of the second electrode system.

[0213] 33. The apparatus according to any one of clauses 28 to 32, wherein the plurality of lenses include a plurality of objectives configured to project respective sub-beams onto the sample.

[0214] 34. The apparatus according to any one of clauses 28 to 32, wherein the plurality of lenses include a plurality of focusing lenses configured to focus respective sub-beams onto an upward beam from an intermediate focal point of a plurality of objectives, the plurality of objectives being configured to project the sub-beams onto a sample.

[0215] 35. The apparatus according to any one of clauses 28 to 32, wherein:

[0216] The device includes multiple focusing lenses configured to focus respective sub-beams onto a central focal point in the intermediate image plane; and

[0217] The aperture assembly is provided in or directly adjacent to the intermediate image plane, preferably directly adjacent to a direct up-beam or a direct down-beam or both of which include the intermediate image plane.

[0218] 36. A charged particle beam tool, comprising:

[0219] The charged particle projection device according to any one of clauses 28 to 35; and

[0220] An electronic detection device configured to detect either or both of secondary electrons and backscattered electrons from a sample.

[0221] 37. A method for manipulating a beam of charged particles, comprising:

[0222] Multiple beams of charged particles are guided onto the sample using an aperture assembly; and

[0223] A beam of charged particles is electrostatically manipulated by applying a potential to electrodes in the aperture assembly, wherein:

[0224] The aperture assembly includes a first aperture body and a second aperture body;

[0225] Multiple apertures in the first aperture body are aligned with corresponding multiple apertures in the second aperture body, such that each charged particle beam in the charged particle beam passes through the aperture assembly by passing through the corresponding apertures in the first and second aperture bodies; and

[0226] Applying a potential involves applying a potential to a plurality of electrodes, each electrically isolated from each other and simultaneously electrically connected to the circumferential surface of a different aperture in a plurality of aperture groups of a first aperture body.

[0227] 38. A method for manipulating a beam of charged particles, comprising:

[0228] Multiple beams of charged particles are guided onto the sample using an aperture assembly; and

[0229] A beam of charged particles is electrostatically manipulated by applying a potential to electrodes in the aperture assembly, wherein:

[0230] The aperture assembly includes a first aperture body and a second aperture body;

[0231] Multiple apertures in the first aperture body are aligned with corresponding multiple apertures in the second aperture body, such that each charged particle beam in the charged particle beam passes through the aperture assembly by passing through the corresponding apertures in the first aperture body and the second aperture body.

[0232] Applying an electric potential involves applying a potential difference between the apertures in the first aperture body and the corresponding apertures in the second aperture body.

[0233] Each aperture in at least one subset of the apertures in the first aperture body consists of elongated slits; and

[0234] Each corresponding aperture in the second aperture body includes an opening smaller than the elongated slit in at least a direction parallel to the longest axis of the elongated slit.

[0235] 39. The method according to Clause 38, wherein an electric potential is applied to reduce astigmatism in the charged particle beam.

[0236] 40. An aperture assembly for a manipulator unit of a charged particle multi-beam projection device, the aperture assembly comprising:

[0237] A first aperture body, a first aperture array being confined within the first aperture body; and

[0238] The second aperture body, in which the corresponding aperture array is confined, is aligned with the first aperture array to define the path of multiple charged particle beams through the aperture assembly.

[0239] A first electrode system associated with the first aperture body, the first electrode system being configured to apply a potential to the peripheral surface of each aperture of the first aperture body;

[0240] A second electrode system associated with the second aperture body, the second electrode system being configured to apply a potential to the peripheral surface of each aperture of the second aperture body.

[0241] The first electrode system includes multiple electrodes, each of which is electrically isolated from each other and simultaneously electrically connected to the peripheral surface of a different aperture in a plurality of aperture groups of the first aperture body.

[0242] 41. An aperture assembly for a beam manipulator unit of a charged particle multi-beam projection device, comprising:

[0243] A first aperture body, and a first plurality of apertures being confined within the first aperture body; and

[0244] The second aperture body, in which multiple apertures are defined, and the multiple apertures are positioned relative to the first multiple apertures to define the path of the corresponding multiple charged particle beams through the aperture assembly;

[0245] Each aperture in at least a subset of the apertures in the first aperture body is an elongated slit; and

[0246] Each of the multiple apertures corresponding to the elongated slit is an opening with an aspect ratio smaller than that of the elongated slit.

[0247] 42. A beam manipulator unit for a charged particle multi-beam projection device, the manipulator unit comprising a lens, the lens comprising:

[0248] An uplink lens aperture array having an associated uplink beam perturbation electrode array; and

[0249] A down-beam lens aperture array having an associated down-beam perturbation electrode array, wherein the up-beam lens aperture array, the down-beam lens aperture array, and the perturbation array are positioned relative to each other such that the aperture in each array defines the path of a corresponding multi-beam charged particle beam through the manipulator unit; and

[0250] The up-beam and down-beam perturbation electrodes are controllable to apply a perturbation field to the field generated by the lens during operation.

[0251] 43. A method for manipulating a beam of charged particles, comprising:

[0252] A lens is provided, comprising an up-beam lens aperture array having an associated up-beam perturbation electrode array; and a down-beam lens aperture array having an associated down-beam perturbation electrode array;

[0253] This allows multiple charged particle beams to pass through the corresponding apertures in each of the upward and downward beam lens aperture arrays; and

[0254] The up-beam and down-beam perturbation electrodes are controlled to apply a perturbation field to the field generated by the lens.

[0255] Any charged particle beam tool 40 discussed herein can be an evaluation tool. An evaluation tool according to one embodiment of this disclosure can be a tool for qualitative evaluation of a sample (e.g., pass / fail), a tool for quantitative measurement of a sample (e.g., dimension of features), or a tool for generating an image of a map of the sample. Examples of evaluation tools are inspection tools (e.g., for identifying defects), review tools (e.g., for classifying defects), and metrology tools, or any combination of tools capable of performing evaluation functions associated with inspection tools, review tools, or metrology tools (e.g., metrology-inspection tools). Electron optical column 40 can be a component of an evaluation tool; such as an inspection tool or metrology-inspection tool, or part of an electron beam lithography tool. Any reference to tools herein is intended to cover devices, apparatus, or systems, and tools include various components that may or may not be coupled and may even be located in separate rooms, particularly components such as those used for data processing elements.

[0256] The terms “sub-beam” and “wavelet” are used interchangeably herein and are understood to encompass any beam of radiation obtained from the parent beam by dividing or splitting the parent beam. The term “manipulator” is used to encompass any element that affects the path of a sub-beam or wavelet, such as a lens or deflector.

[0257] While the invention has been described in conjunction with various embodiments, other embodiments of the invention will be apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

[0258] The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications as described can be made without departing from the scope of the claims set forth below.

Claims

1. An aperture assembly of an aberration corrector of a beam manipulator unit of a charged particle projection apparatus, comprising: a first aperture body; a second aperture body, the first aperture body being configured to be an upstream beam of the second aperture body along a path of the charged particles, a plurality of apertures in the first aperture body being aligned with a corresponding plurality of apertures in the second aperture body, the alignment being such that a path of each of a respective plurality of charged particle beams is allowed to pass through the aperture assembly by passing through a respective aperture in the first aperture body and the second aperture body; each aperture of at least a subset of the apertures in the first aperture body consisting of an elongated slit; and each corresponding aperture in the second aperture body consisting of an opening having a different shape than the elongated slit and being smaller than the elongated slit at least in a direction parallel to a longest axis of the elongated slit; and a voltage source connection configured to apply a potential difference to an aperture periphery surface of the apertures of at least one of the first aperture body and the second aperture body.

2. The assembly according to claim 1, wherein: the first aperture body comprises a first electrode system associated with and electrically connected to the voltage source connection for applying a potential to an aperture periphery surface of each aperture of the first aperture body, the first electrode system comprising a plurality of electrodes, each electrode being electrically isolated from each other electrode of the first electrode system and electrically connected to the aperture periphery surface of a different respective one of the apertures of the first aperture body; and / or the second aperture body comprises a second electrode system associated with and electrically connected to the voltage source connection for applying a potential to an aperture periphery surface of each aperture of the second aperture body, the second electrode system comprising a plurality of electrodes, each electrode being electrically isolated from each other electrode of the second electrode system and electrically connected to the aperture periphery surface of a different respective one of the apertures of the second aperture body.

3. The assembly according to claim 1, wherein: the first aperture body comprises a local integrated electronics for each aperture of the first aperture body, the local integrated electronics being associated with and electrically connected to the voltage source connection and being configured to apply a potential to the aperture periphery surface of the aperture; and / or the second aperture body comprises a local integrated electronics for each aperture of the second aperture body, the local integrated electronics being associated with and electrically connected to the voltage source connection and being configured to apply a potential to the aperture periphery surface of the aperture.

4. The assembly according to claim 1 or 3, wherein: ​ ​ The first aperture body comprises integrated passive circuitry comprising a resistor network associated with and electrically connected to the voltage source connection and configured to allow different potentials to be applied to the peristaltic surface of at least a subset of the apertures of the first aperture body by potential distribution; and / or The second aperture body comprises integrated passive circuitry comprising a resistor network associated with and electrically connected to the voltage source connection and configured to allow different potentials to be applied to the peristaltic surface of at least a subset of the apertures of the second aperture body by potential distribution.

5. The assembly of any one of claims 1 to 3, wherein each of the at least a subset of the elongated slits is a substantially linear slit.

6. The assembly of any one of claims 1 to 3, wherein each of the at least a subset of the openings has substantially one of the following shapes: circular, oval, elliptical.

7. The assembly of any one of claims 1 to 3, wherein at least a majority of the elongated slits are radially aligned with respect to a common axis normal to a plane passing through the first aperture body.

8. The assembly of any one of claims 1 to 3, wherein at least a majority of the elongated slits are aligned normal to a radial direction with respect to a common axis normal to a plane passing through the first aperture body.

9. The assembly of any one of claims 1 to 3, wherein at least a majority of the elongated slits are parallel to each other.

10. The assembly of any one of claims 1 to 3, wherein a maximum in-plane dimension of each opening in the second aperture body is substantially equal to a minimum in-plane dimension of the corresponding elongated slit in the first aperture body.

11. The assembly of any one of claims 1 to 3, wherein: the aperture assembly further comprises a third aperture body and a fourth aperture body; a plurality of apertures in the third aperture body are aligned with corresponding pluralities of apertures in the first aperture body, the second aperture body and the fourth aperture body, the alignment allowing a path of each of a corresponding plurality of charged particle beams to pass through the aperture assembly by passing through corresponding apertures in the first aperture body, the second aperture body, the third aperture body and the fourth aperture body; each of the apertures in at least a subset of the apertures in the third aperture body consists of an elongated slit; each corresponding aperture in the fourth aperture body consists of an opening that is smaller than the elongated slit at least in a direction parallel to a longest axis of the elongated slit; and the elongated slits in the first aperture body and the third aperture body are aligned such that each charged particle beam passes through elongated slits in the first aperture body and the third aperture body that are obliquely aligned with respect to each other when viewed along the path of the charged particle beam. ​ 12. An aperture assembly for a beam manipulator unit of a charged particle projection apparatus, the aperture assembly comprising: a first aperture body and a second aperture body, wherein: a plurality of apertures in the first aperture body are aligned with a corresponding plurality of apertures in the second aperture body, the alignment allowing a path of each of a respective plurality of charged particle beams through the aperture assembly by passing through a respective aperture in the first aperture body and the second aperture body; the first aperture body comprises a first electrode system for applying electric potentials to aperture periphery surfaces of each aperture in the first aperture body; the second aperture body comprises a second electrode system for applying electric potentials to aperture periphery surfaces of each aperture in the second aperture body; and the first electrode system comprises a plurality of electrodes, each electrode being electrically isolated from one another and being simultaneously electrically connected to the aperture periphery surfaces of a different one of a plurality of aperture groups in the first aperture body.

13. The assembly of claim 12, wherein at least two of the aperture groups comprise a same number of apertures.

14. The assembly of claim 12 or 13, wherein each electrode of the first electrode system comprises an elongated electrically conductive strip.

15. The assembly of claim 14, wherein the apertures in the first aperture body are arranged in an array.

16. The assembly of claim 15, wherein the array is a regular array.

17. The assembly of claim 15, wherein the electrically conductive strips are parallel to one another and perpendicular to a principal axis of the array.

18. The assembly of claim 17, wherein a pitch of the electrically conductive strips parallel to a minor axis of the electrically conductive strips is greater than a pitch of the array parallel to the minor axis.

19. The assembly of claim 17, wherein a pitch of the electrically conductive strips parallel to a minor axis of the electrically conductive strips is equal to a pitch of the array parallel to the minor axis.

20. The assembly of any one of claims 12, 13, and 15-19, wherein the plurality of electrodes comprises a plurality of electrically conductive elements configured to interlock with one another.

21. The assembly of claim 12 or 13, wherein the plurality of electrodes comprises a plurality of electrically conductive elements comprising at least a portion of a concentric ring.

22. The assembly of any one of claims 12, 13, and 15-19, wherein the second electrode system comprises an electrode electrically connected to all of the aperture periphery surfaces of the second aperture body.

23. The assembly of any one of claims 12, 13, and 15-19, wherein the second electrode system comprises a plurality of electrodes, each electrode being electrically isolated from one another and being simultaneously electrically connected to the aperture periphery surfaces of a different one of a plurality of aperture groups of the second electrode system.

24. The assembly of claim 23, wherein: each electrode of the first electrode system comprises an elongated electrically conductive strip; each electrode of the second electrode system comprises an elongated electrically conductive strip; and the electrically conductive strips of the first electrode system are not parallel to the electrically conductive strips of the second electrode system.

25. The assembly of claim 24, wherein the electrically conductive strips of the first electrode system are parallel to each other, the electrically conductive strips of the second electrode system are parallel to each other, and the electrically conductive strips of the first electrode system are perpendicular to the electrically conductive strips of the second electrode system.

26. The assembly of any one of claims 12, 13, 15-19, 24, and 25, wherein the aperture in the first aperture body and / or the aperture in the second aperture body has a shape with curved edges.

27. The assembly of claim 26, wherein the shape is circular, elliptical, or oval.

28. A beam manipulator unit for a charged particle projection device, comprising: an aperture assembly according to any one of claims 1-11; and an electrical drive unit configured to be connected to the voltage source connection to apply an electric potential to the aperture perimeter surface of an aperture in the first aperture body and / or second aperture body when a plurality of charged particle beams is directed through the aperture assembly towards a sample.

29. A charged particle projection device, comprising: a beam manipulator unit according to claim 28; and a plurality of lenses, each lens configured to project a respective beamlet of charged particles.

30. The device of claim 29, wherein the aperture assembly is integrated with the plurality of lenses, or directly adjacent to the plurality of lenses.

31. The device of claim 30, wherein: each lens comprises a multi-electrode lens; the first aperture body comprises a first electrode of the multi-electrode lens; and the first aperture body comprises a first electrode system comprising a plurality of electrodes electrically isolated from the first electrode of the multi-electrode lens.

32. The device of claim 31, wherein: the second aperture body comprises a second electrode of the multi-electrode lens; and the second aperture body comprises a second electrode system comprising a plurality of electrodes electrically isolated from the second electrode of the multi-electrode lens.

33. The device of claim 32, wherein the electrical drive unit is configured to control the electric potentials of the electrodes of the first electrode system such that the potential difference between the highest potential electrode and the lowest potential electrode of the first electrode system is less than the difference between the average electric potential of the electrodes of the first electrode system and the average electric potential of the electrodes of the second electrode system.

34. The device of any one of claims 29-32, wherein the plurality of lenses comprises a plurality of objective lenses configured to project respective beamlets onto a sample, and / or wherein the plurality of lenses comprises a plurality of condenser lenses configured to focus respective beamlets to an intermediate focus on-beam from a plurality of objective lenses configured to project the beamlets onto a sample.

35. The device of any one of claims 29-32, wherein: the device comprises a plurality of condenser lenses configured to focus respective beamlets to an intermediate focus in an intermediate image plane; and the device comprises a plurality of objective lenses configured to project respective beamlets onto a sample. The aperture assembly is provided in or directly adjacent to the intermediate image plane.

36. A method of steering a plurality of charged particle beams, comprising: directing the plurality of charged particle beams onto a sample by an aperture assembly; and electrostatically steering the charged particle beams by applying electric potentials to electrodes in the aperture assembly, wherein: the aperture assembly comprises a first aperture body and a second aperture body; a plurality of apertures in the first aperture body are aligned with a corresponding plurality of apertures in the second aperture body such that each of the charged particle beams passes through the aperture assembly by passing through respective apertures in the first aperture body and the second aperture body; applying electric potentials comprises applying a potential difference between apertures in the first aperture body and corresponding apertures in the second aperture body; each aperture in at least a subset of the apertures in the first aperture body consists of an elongated slit; and each corresponding aperture in the second aperture body comprises an opening that is smaller than the elongated slit at least in a direction parallel to a longest axis of the elongated slit.

37. The method of claim 36, wherein the electric potentials are applied such that astigmatism in the charged particle beams is reduced.

38. An aperture assembly for a manipulator unit of a charged particle multi-beamlet projection apparatus, the aperture assembly comprising: a first aperture body in which a first aperture array is defined; and a second aperture body in which a corresponding aperture array is defined, the corresponding aperture array being aligned with the first aperture array to define a path for respective charged particle beams of the multi-beamlet to pass through the aperture assembly; a first electrode system associated with the first aperture body, the first electrode system being configured to apply electric potentials to a peripheral surface of each aperture of the first aperture body; a second electrode system associated with the second aperture body, the second electrode system being configured to apply electric potentials to a peripheral surface of each aperture of the second aperture body, wherein the first electrode system comprises a plurality of electrodes, each electrode being electrically isolated from one another and being simultaneously electrically connected to the peripheral surface of a different group of apertures of a plurality of aperture groups of the first aperture body.

39. A method of steering a plurality of charged particle beams, comprising: directing the plurality of charged particle beams onto a sample by an aperture assembly; and electrostatically steering the charged particle beams by applying electric potentials to electrodes in the aperture assembly, wherein: the aperture assembly comprises a first aperture body and a second aperture body; a plurality of apertures in the first aperture body are aligned with a corresponding plurality of apertures in the second aperture body such that each of the charged particle beams passes through the aperture assembly by passing through respective apertures in the first aperture body and the second aperture body; applying electric potentials comprises applying electric potentials to a plurality of electrodes, each electrode of the plurality of electrodes being electrically isolated from one another and being simultaneously electrically connected to the aperture peripheral surface of a different group of apertures of a plurality of aperture groups in the first aperture body.

40. An aperture assembly for a beam manipulator unit of a charged particle multi-beamlet projection apparatus, comprising: a first aperture body, a first plurality of apertures being defined in the first aperture body; and a second aperture body, a corresponding plurality of apertures being defined in the second aperture body, the corresponding plurality of apertures being positioned relative to the first plurality of apertures to define a path for passing respective charged particle beamlets of the multi-beamlet through the aperture assembly, wherein each aperture of at least a subset of the apertures in the first aperture body is an elongated slit; and each corresponding aperture of the plurality of apertures corresponding to the elongated slit is an opening having an aspect ratio less than the elongated slit. ​

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