Electron optical assembly

Abstract

A charged particle optical assembly configured to direct a plurality of charged particle beams as a beam grid towards a sample position, the charged particle optical assembly comprising: a planar charged particle optical element configured to act on the charged particle beams of the beam grid with a voltage, the planar charged particle optical element comprising a plurality of apertures for the paths of different beams of the beam grid; a conductive body electrically connected to the charged particle optical element, a recess being defined within the conductive body, the conductive body being configured to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power source via an electrical coupling; and an electrical insulator covering at least a part of the surface of the conductive body, the surface facing away from the charged particle optical element.

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims the priority of European Patent Application No. 22184926.8, filed on July 14, 2022, which is incorporated herein by reference in its entirety.

[0002]

[0002] Embodiments provided herein generally relate to charged - particle optical assemblies, charged - particle optical devices, charged - particle optical apparatuses, and methods for providing electrical connections and methods for electrically insulating a conductive body of a charged - particle optical assembly.

Background Art

[0003]

[0003] When manufacturing a semiconductor integrated circuit (IC) chip, unwanted pattern defects may occur on a substrate (e.g., a wafer) or a mask during the manufacturing process, thereby reducing the yield. Defects can occur, for example, as a result of optical effects and attendant particles or other processing steps such as etching, deposition of chemical - mechanical polishing. Therefore, monitoring the degree of unwanted pattern defects is an important process in the manufacture of IC chips. More generally, inspection and / or measurement of the surface of a substrate or other object / material is an important process during and / or after its manufacture.

[0004]

[0004] Pattern inspection tools using a charged particle beam have been used to inspect an object, for example, to detect pattern defects. These tools generally use electron microscopy techniques such as a scanning electron microscope (SEM). In an SEM, a primary electron beam of relatively high-energy electrons is targeted at a target in a final deceleration step so that it lands on the target with a relatively low landing energy. The electron beam is focused as a probing spot on the target. Due to the interaction between the material structure at the probe spot and the landing electrons from the electron beam, electrons such as secondary electrons, backscattered electrons, or Auger electrons, which may be collectively called signal electrons or more generally signal particles, are emitted from the surface. The generated secondary electrons may be emitted from the material structure of the target.

[0005]

[0005] By scanning the surface of the target as a probe spot with the primary electron beam, secondary electrons can be emitted over the surface of the target. By collecting these secondary electrons emitted from the target surface, a pattern inspection tool (or apparatus) can acquire an image-like signal representing the characteristics of the material structure of the target surface. In such an inspection, the collected secondary electrons are detected by a detector in the apparatus. The detector generates a signal in response to the accompanying particles. When an area of the sample is inspected, the signal contains data that is processed to generate an inspection image corresponding to that inspected area of the sample. The image may include pixels. Each pixel may correspond to a portion of the inspected area. Typically, an electron beam inspection apparatus has a single beam and may be called a single beam SEM. Attempts have been made to introduce multi-electron beam inspection into an apparatus (or "multi-beam tool") that may be called a multi-beam SEM (MBSEM).

[0006]

[0006] Another use of an electron optical device (or device or column) is lithography. The charged particle beam reacts with a resist layer on the surface of a substrate. By controlling the position on the resist layer at which the charged particle beam is directed, a desired pattern can be generated in the resist.

[0007]

[0007] An electro-optical device can be a device for generating, irradiating, projecting, and / or detecting one or more beams of charged particles. The path of the charged particle beam is controlled by electromagnetic fields (i.e., electrostatic and magnetic fields). A floating electromagnetic field can undesirably deflect the direction of the beam.

[0008]

[0008] In some electro-optical devices, typically, an electrostatic field is generated between two electrodes. It is necessary to apply a high voltage to those electrodes. For example, unwanted electron creep may occur between high-voltage connectors and / or between a high-voltage connector and the electro-optical assembly of the electro-optical device, resulting in an unwanted discharge.

SUMMARY OF THE INVENTION

[0009]

[0009] The present invention provides a suitable architecture for enabling a desired high-voltage connection while reducing the risk of electron creep. According to a first aspect of the present invention, a charged particle optical assembly configured to direct a charged particle beam along a beam path towards a sample position, the charged particle optical assembly comprising a planar charged particle optical element configured to act on the charged particle beam traveling along the beam path towards the sample position, the planar charged particle optical element comprising an aperture for the beam path, and a conductive body electrically connected to the charged particle optical element, the conductive body having a recess defined therein and configured to provide an electric-field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power source via an electrical coupling. The charged particle optical assembly is provided, wherein the conductive body is spaced apart from the planar charged particle optical element and comprises an electrical insulator providing at least a part of the surface of the conductive body.

[0010]

[0010] According to a second aspect of the present invention, there is provided a charged particle optical assembly configured to direct a plurality of charged particle beams along a beam path towards a sample position, the charged particle optical assembly comprising a planar charged particle optical element configured to act on a charged particle beam travelling along the beam path towards the sample position, the planar charged particle optical element comprising an aperture for the beam path, and a conductive body electrically connected to the charged particle optical element, the conductive body having a recess defined therein and being configured to provide an electric field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling, an electrical insulator covering at least a part of the surface of the conductive body, the surface facing away from the charged particle optical element.

[0011]

[0011] According to a third aspect of the present invention, there is provided a method of electrically insulating a conductive body of a charged particle optical assembly configured to direct a charged particle beam towards a sample position, the method comprising covering at least a part of the surface of the conductive body with one or more electrical insulators, the surface facing away from a planar charged particle optical element to which the conductive body is electrically connected, the charged particle optical element being configured to act on a charged particle beam travelling along the beam path, the charged particle optical element comprising an aperture for the beam path, the conductive body having a recess defined therein and being configured to provide an electric field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling.

[0012] According to a fourth aspect of the present invention, there is provided a method of electrically insulating a conductive body of a charged particle optical assembly configured to direct a charged particle beam along a beam path towards a sample position, the charged particle optical assembly comprising a planar charged particle optical element for acting on the charged particle beam, the method comprising: having a conductive body having a conductive concave surface of a recess of the conductive body, the conductive body comprising an electrical insulator spaced apart from the planar charged particle optical element, the planar charged particle optical element being electrically connected to the conductive body, a recess being formed in the conductive body to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling between the conductive body and the high voltage cable.

[0013] According to a fifth aspect of the present invention, there is provided a charged particle optical assembly configured to direct a plurality of charged particle beams along a beam path towards a sample position, the charged particle optical assembly comprising: a planar charged particle optical element configured to act on a charged particle beam traveling towards the sample position along the beam path with a voltage, the planar charged particle optical element comprising an aperture for the beam path; and a conductive body electrically connected to the charged particle optical element, the conductive body having a recess defined therein and configured to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling, the conductive body comprising an electrical insulator, the electrical insulator comprising at least an end face of the conductive body and an extending surface extending from the end face into the recess.

[0014] The advantages of the present invention will become apparent by reading the following description in conjunction with the accompanying drawings, which illustrate and exemplify specific embodiments of the invention.

[0015] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016]

Figure 1

Figure 2

[0017] FIG. 17 is a schematic diagram showing an exemplary multi-beam electron optical device that is part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 3

[0018] FIG. 18 is a schematic diagram of an exemplary electron optical device including a collimator element array and a scanning deflector array that is part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 4

[0019] FIG. 19 is a schematic diagram of an exemplary electron optical device array including the electron optical device of FIG. 3.

Figure 5

[0020] FIG. 20 is a schematic diagram of an alternative exemplary electron optical device that is part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 6

[0021] FIG. 21 is a schematic diagram of an exemplary electron optical assembly that is part of the electron optical devices of FIGS. 3, 4, and 5.

Figure 7

[0022] FIG. 22 is a schematic diagram of an electron optical element electrically connected to a cable.

Figure 8

[0023] FIG. 23 is a schematic diagram of an electron optical element electrically connected to a cable.

Figure 9

[0024] FIG. 24 is a plan view of an electron optical assembly.

Figure 10

[0025] FIG. 25 is a plan view of an electron optical assembly.

Figure 11

[0026] FIG. 26 is a plan view of an electron optical assembly. DETAILED DESCRIPTION OF THE INVENTION

[0017]

[0027] Here, reference is made in detail to exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, and unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following description of the exemplary embodiments do not represent all implementations that are consistent with the present invention. Instead, those implementations are merely examples of devices and methods that are consistent with aspects related to the present invention, as described in the appended claims.

[0018] Brief Description of the Drawings

[0028] By significantly increasing the mounting density of circuit components such as transistors, capacitors, and diodes on an IC chip, it is possible to reduce the physical size of the device and improve the computing power of the electronic device. This is made possible by the improvement in resolution, enabling the fabrication of even smaller structures. Semiconductor IC manufacturing is a complex and time-consuming process involving hundreds of individual steps. If an error occurs in any step of the process of manufacturing an IC chip, it may have an adverse effect on the function of the final product. Even a single defect can cause the device to malfunction. It is desirable to improve the overall yield of the process. For example, for a 50-step process (where the steps may indicate the number of layers formed on a wafer), to achieve a 75% yield, each individual step must have a yield higher than 99.4%. If the yield of an individual step is 95%, the overall process yield drops to as low as 7-8%.

[0019]

[0029] It is also desirable to maintain a high substrate (i.e., wafer) throughput, defined as the number of substrates processed per hour. High process yield and high substrate throughput can be affected by the presence of defects. This is particularly true when operator intervention is required to examine the defects. It is desirable to detect and identify micro- and nano-scale defects at high throughput by an inspection system (such as a scanning electron microscope ("SEM")) in order to maintain a high yield and low cost of IC chips.

[0020]

[0030] A scanning electron microscope includes a scanning device and a detector device. The scanning device includes an illumination device including an electron source for generating primary electrons, and a projection device for scanning a target such as a substrate with one or a plurality of focused beams of primary electrons. The primary electrons interact with the target to generate interaction products such as signal particles such as secondary electrons and / or backscattered electrons. The secondary electrons may be considered to have an energy of up to 50 eV. The backscattered electrons have an energy range from substantially zero to the maximum energy of the charged particle device, but are conventionally set to electrons (or signal electrons) having an energy exceeding 50 eV. The detection device captures signal particles (e.g., secondary electrons and / or backscattered electrons) from the target as the target is scanned so that the scanning electron microscope can generate an image of the scanned area of the target. The design of the electron optical device embodying these scanning electron microscope functions may have a single beam. In order to increase the throughput such as inspection, in the design of some devices, a plurality of focused beams of primary electrons, i.e., multi-beams, are used. The constituent beams of the multi-beam may be called sub-beams or beamlets. The multi-beam can scan different portions of the target simultaneously. Therefore, a multi-beam inspection device can inspect the target much more quickly than a single-beam inspection device, for example, by moving the target at a higher speed.

[0021]

[0031] In a multi-beam inspection apparatus, the paths of some of the primary electron beams are displaced from the central axis of the scanning device, i.e., the central point of the primary electron optical axis (also referred to herein as the charged particle axis). In order to ensure that all electron beams reach the sample surface at substantially the same angle of incidence, the sub-beam paths with a larger radial distance from the central axis need to be operated to move through a larger angle than the sub-beam paths with a path closer to the central axis. This more intense operation causes aberrations, which can result in the resulting image being blurred and out of focus. One example is spherical aberration, which brings the focus of each sub-beam path to a different focal plane. In particular, for sub-beam paths not on the central axis, the change in the focal plane of the sub-beam becomes larger due to the radial displacement from the central axis. The effects of such aberrations and defocus can remain associated with the signal particles (e.g., secondary electrons) from the target when the secondary electrons are detected. For example, the shape and size of the spot formed by the sub-beam on the target will be affected. Therefore, such aberrations degrade the quality of the resulting image generated during the inspection.

[0022]

[0032] The implementation of a known multi-beam inspection apparatus will be described below.

[0023]

[0033] The figures are schematic diagrams. Therefore, in the drawings, the relative dimensions of the components are enlarged for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the individual embodiments are described. The description and the drawings are directed to electron optical devices, but it is understood that the embodiments are not used to limit the present disclosure to specific charged particles. Therefore, throughout this specification, references to electrons and items related to electrons can be considered more generally as references to charged particles and items related to charged particles, and the charged particles are not necessarily electrons.

[0024]

[0034] Referring now to FIG. 1, FIG. 1 is a schematic diagram showing an exemplary electron beam evaluation apparatus, or inspection apparatus 100. The inspection apparatus 100 of FIG. 1 includes a vacuum chamber 10, a load lock chamber 20, an electron optical device, an EFEM (equipment front end module) 30, and a controller 50. The electron optical device 40 may be within the vacuum chamber 10. The electron optical apparatus may include an electron optical device 40 (also known as an electron optical device, an electron beam device, or an electron beam device) and a motorized or actuated stage.

[0025]

[0035] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include one or more additional loading ports. The first loading port 30a and the second loading port 30b can receive, for example, a substrate front opening unified pod (FOUP) that houses a substrate (e.g., a semiconductor substrate or a substrate made of other materials) or a target to be inspected (hereinafter, substrates, wafers, and samples are collectively referred to as "targets"). One or more robot arms (not shown) within the EFEM 30 carry the target to the load lock chamber 20.

[0026]

[0036] The load lock chamber 20 is used to remove the gas around the target. The load lock chamber 20 can be connected to a load lock vacuum pump system (not shown), and the load lock vacuum pump system removes gas particles within the load lock chamber 20. By operating the load lock vacuum pump system, the load lock chamber can reach a first pressure below atmospheric pressure. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas molecules within the main chamber 10 so that the pressure around the target reaches a second pressure below the first pressure. After reaching the second pressure, the target can be inspected by an electron beam tool using the electron optical device 40. The electron optical device 40 can include either a single beam or a multi-beam electron optical apparatus.

[0027]

[0037] The controller 50 is electronically connected to the electron optical device 40. The controller 50 can be a processor (such as a computer) configured to control the charged particle beam inspection apparatus 100. The controller 50 can also include a processing circuit configured to execute various signal and image processing functions. In FIG. 1, the controller 50 is shown as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, but it is understood that the controller 50 can be part of the structure. The controller 50 can be located inside one of the component elements of the charged particle beam inspection apparatus, or the controller 50 can be distributed among at least two of the component elements. Although the present disclosure provides an example of the main chamber 10 that houses the electron beam inspection apparatus, it should be noted that aspects of the present disclosure are not limited, in a broad sense, to chambers that house electron optical devices. Rather, it is understood that the foregoing principles are also applicable to other devices and other arrangements of devices operating under a second pressure.

[0028]

[0038] Here, refer to FIG. 2. FIG. 2 is a schematic diagram of a multi-beam electron optical device 40 of an exemplary evaluation device such as the evaluation device 100 of FIG. 1. In an alternative embodiment, the inspection device 100 is a single-beam inspection device. The electron optical device 40 may include an electron source 201, a beam former array 372 (also known as a gun aperture plate, a Coulomb aperture array, or a presubbeam forming aperture array), a condenser lens 310, a radiation source converter (or a micro-optical array) 320, an objective lens 331, and a target 308. In one embodiment, the condenser lens 310 is magnetic. (A single-beam evaluation device may have the same features as a multi-beam evaluation device, except that the electron optical components having the array apertures 372, 320 may have a single aperture. The radiation source converter 320 may be replaced by a plurality of electron optical components along the beam path.) The target 308 may be supported by a support on a stage. The stage may be motorized. The stage moves so that the target 308 is scanned by accompanying electrons. The electron source 201, the beam former array 372, and the condenser lens 310 may be components of an illumination device included by the electron optical device 40. The radiation source converter 320 (also known as a radiation source conversion unit), which will be described in more detail below, and the objective lens 331 may be components of a projection device included by the electron optical device 40.

[0029]

[0039] The electron source 201, the beam former array 372, the condenser lens 310, the radiation source converter 320, and the objective lens 331 are aligned with the primary electron optical axis 304 of the electron optical device 40. The electron source 201 can generally generate a primary beam 302 along the electron optical axis 304 and with an (imaginary or real) radiation source crossover 301S. During operation, the electron source 201 is configured to emit electrons. The electrons are extracted or accelerated by an extractor and / or an anode to form the primary beam 302.

[0030]

[0040] The beam former array 372 cuts off the electrons at the edge of the primary electron beam 302 to reduce the resulting Coulomb effect. The primary electron beam 302 can be trimmed by the beam former array 372 into a specified number of sub-beams, such as three sub-beams 311, 312, and 313. It should be understood that this description is intended to apply to an electron optical device 40 having any number of sub-beams, such as one, two, or four or more. The beam former array 372 is configured to block the edge electrons during operation to reduce the Coulomb effect. Due to the Coulomb effect, the size of each of the probe spots 391, 392, 393 can be enlarged, and thus the inspection resolution can be reduced. The beam former array 372 reduces the aberration resulting from the Coulomb interaction between a plurality of electrons projected into the beam. The beam former array 372 may include a plurality of apertures for generating a plurality of primary sub-beams even in front of the radiation source converter 320.

[0031]

[0041] The radiation source converter 320 is configured to convert the beam (including sub-beams if any) propagated by the beam former array 372 into sub-beams projected towards the target 308. In one embodiment, the radiation source converter is a unit. Alternatively, the term radiation source converter can be used simply as a general term for a group of components that form beamlets from sub-beams.

[0032]

[0042] As shown in FIG. 2, in one embodiment, the electron optical device 40 includes a beam limiting aperture array 321 having an aperture pattern (i.e., apertures arranged in a certain pattern) configured to define the outer dimensions of the beamlets (or sub - beams) projected toward the target 308. In one embodiment, the beam limiting aperture array 321 is part of the radiation source converter 320. In an alternative embodiment, the beam limiting aperture array 321 is part of the up - beam system of the main device. In one embodiment, the beam limiting aperture array 321 divides one or more of the sub - beams 311, 312, 313 into beamlets such that the number of beamlets projected toward the target 308 is greater than the number of sub - beams propagating through the beamformer array 372. In an alternative embodiment, the beam limiting aperture array 321 maintains the number of sub - beams incident on the beam limiting aperture array 321, and in this case, the number of sub - beams may be equal to the number of beamlets projected toward the target 308.

[0033]

[0043] As shown in FIG. 2, in one embodiment, the electron optical device 40 includes a preliminary bending deflector array 323 having preliminary bending deflectors 323_1, 323_2, and 323_3 that bend the sub - beams 311, 312, and 313, respectively. The preliminary bending deflectors 323_1, 323_2, and 323_3 can bend the paths of the sub - beams 311, 312, and 313 onto the beam limiting aperture array 321.

[0034]

[0044] The electro-optical device 40 may also include an imaging element array 322 having imaging deflectors 322_1, 322_2, and 322_3. There are respective deflectors 322_1, 322_2, and 322_3 associated with the path of each beamlet. The deflectors 322_1, 322_2, and 322_3 are configured to deflect the path of the beamlet toward the electron optical axis 304. The deflected beamlets form a virtual image (not shown) of the radiation source crossover 301S. In the present embodiment, these virtual images are projected onto the target 308 by the objective lens 331, forming probe spots 391, 392, 393 on the target 308. The electro-optical device 40 may also include an aberration compensator array 324 configured to compensate for aberrations that may be present in each sub-beam. In one embodiment, the aberration compensator array 324 includes lenses configured to act on respective beamlets. The lenses may take the form or an array of lenses. The array of lenses may act on different beamlets of the multi-beam. The aberration compensator array 324 may include, for example, an image plane curvature compensator array (not shown) with microlenses. The image plane curvature compensator and the microlenses may be configured to compensate individual sub-beams for image plane curvature aberrations, which are clearly visible at the probe spots 391, 392, and 393. The aberration compensator array 324 may include an astigmatism compensator array (not shown) with micro-astigmatism correctors. The micro-astigmatism correctors may be controlled to act on the sub-beams, for example, to compensate for astigmatism that would otherwise be present at the probe spots 391, 392, and 393.

[0035]

[0045] The source converter 320 may be the electron optical assembly 700 described herein. The source converter 320 may comprise a pre-bending deflector array 323, a beam limiting aperture array 321, an aberration compensator array 324, and an image forming element array 322. The pre-bending deflector array 323 may comprise pre-bending deflectors 323_1, 323_2, and 323_3 for bending sub-beams 311, 312, and 313 respectively. The pre-bending deflectors 323_1, 323_2 and 323_3 can bend the paths of the sub-beams onto the beam limiting aperture array 321. In one embodiment, the pre-bending micro-deflector array 323 may be configured to bend the sub-beam paths of the sub-beams in a direction perpendicular to the plane of the beam limiting aperture array 321. In an alternative embodiment, the condenser lens 310 may adjust the path direction of the sub-beams onto the beam limiting aperture array 321. The condenser lens 310 can, for example, focus (collimate) the three sub-beams 311, 312 and 313 into a beam substantially parallel along the primary electron optical axis 304, such that the three sub-beams 311, 312 and 313 are incident substantially perpendicular to the source converter 320, which may correspond to the beam limiting aperture array 321. In such an alternative embodiment, the pre-bending deflector array 323 may not be necessary.

[0036]

[0046] The image forming element array 322, the aberration compensator array 324 and the pre-bending deflector array 323 may include multiple layers of sub-beam manipulation devices, some of which may be in the form or array, such as micro-deflectors, micro-lenses or micro-astigmatism correctors. The beam path may be rotationally operated. The rotational correction may be applied by a magnetic lens. Additionally or alternatively, the rotational correction may also be realized by an existing magnetic lens such as a condenser lens configuration.

[0037]

[0047] In the current example of the electro-optical device 40, the beamlets are respectively deflected toward the electron optical axis 304 by the deflectors 322_1, 322_2, and 322_3 of the imaging element array 322. It should be understood that the beamlet paths may already coincide with the electron optical axis 304 before reaching the deflectors 322_1, 322_2, and 322_3.

[0038]

[0048] The objective lens 331 focuses the beamlets onto the surface of the target 308, that is, projects three virtual images onto the target surface. The three images formed by the three sub-beams 311 to 313 on the target surface form three probe spots 391, 392, and 393 on the target. In one embodiment, the deflection angles of the sub-beams 311 to 313 are adjusted to pass through or approach the front focal point of the objective lens 331 in order to reduce or limit the off-axis aberration of the three probe spots 391 to 393. In one configuration, the objective lens 331 is magnetic. Although three beamlets have been mentioned, this is merely an example. The number of beamlets can be arbitrary.

[0039]

[0049] The manipulator is configured to manipulate one or more charged particle beams. The term manipulator includes deflectors, lenses, and apertures. The pre-bending deflector array 323, the aberration compensator array 324, and the imaging element array 322 can be called a manipulator array individually or in combination with each other because they are for manipulating one or more sub-beams or beamlets of charged particles. The lens and the deflectors 322_1, 322_2, and 322_3 can be called a manipulator because they are for manipulating one or more sub-beams or beamlets of charged particles.

[0040]

[0050] In one embodiment, a beam separator (not shown) is provided. The beam separator can be in the down beam of the radiation source converter 320. The beam separator can be, for example, a Wien filter including an electrostatic dipole field and a magnetic dipole field. The beam separator can be in the up beam of the objective lens 331. The beam separator can be arranged between a plurality of shield sections adjacent in the direction of the beam path. The inner surface of the shield can be radially inside the beam separator. Alternatively, the beam separator can be inside the shield. During operation, the beam separator can be configured to apply an electrostatic force by an electrostatic dipole field to individual electrons of the sub-beam. In one embodiment, the electrostatic force has the same magnitude as the magnetic force acting on individual primary electrons of the sub-beam by the magnetic dipole field of the beam separator, but the directions are opposite. Therefore, the sub-beam can pass through the beam separator at least substantially in a straight line with at least substantially zero deflection angle. The direction of the magnetic force depends on the moving direction of the electrons, while the direction of the electrostatic force does not depend on the moving direction of the electrons. Therefore, since secondary electrons and backscattered electrons (or signal particles) generally move in the opposite direction compared to primary electrons, the magnetic force acting on the secondary electrons and backscattered electrons (or signal particles) no longer cancels out the electrostatic force. As a result, the secondary electrons and backscattered electrons moving through the beam separator are deflected so as to deviate from the electron optical axis 304.

[0041]

[0051] In one embodiment, a secondary device (not shown) including a detection element for detecting a corresponding secondary charged particle beam is provided. When the secondary beam is incident on the detection element, the element can generate a corresponding intensity signal output. This output can be directed to an image processing system (for example, the controller 50). Each detection element can include an array that can be in the form of a grid. The array can have one or more pixels, and each pixel can correspond to an element of the array. The intensity signal output of the detection element can be the sum of the signals generated by all the pixels in the detection element.

[0042]

[0052] In one embodiment, a secondary projection device and an associated electron detection device (not shown) are provided. The secondary projection device and the associated electron detection device can be aligned with the secondary electron optical axis of the secondary device. In one embodiment, the beam separator is configured to deflect the path of the secondary electron beam toward the secondary projection device. The secondary projection device then focuses the path of the secondary electron beam onto a plurality of detection regions of the electron detection device. The secondary projection device and the associated electron detection device can register and generate an image of the target 308 using secondary electrons or backscattered electrons (or signal particles).

[0043]

[0053] Such Wien filters, secondary devices, and / or secondary projection devices may be provided within a single beam evaluation device. In addition to and / or instead of this, for example, during operation facing the sample, a detection device may be present in the down beam of the objective lens. In an alternative configuration, the detection device is positioned along the path of the charged particle beam towards the sample. In such a configuration, there is no Wien filter, secondary device, and secondary projection device. The detection device may be positioned at one or more positions along the path of the charged particle beam towards the sample, for example, around the path of the charged particle beam, such that it faces the sample during operation. Such a detection device may have an aperture and may be annular. Different detection devices may be arranged along the path of the charged particle beam to detect signal particles with different characteristics. The electron optical elements along the path of the charged particle beam may include one or more electrostatic plates with apertures for the path of the charged particle beam, and those electron optical elements may be arranged and controlled to focus signal particles with different respective characteristics onto respective detector devices at different positions along the path of the charged particle beam. Such electrostatic plates may be arranged along the path of the charged particle beam as a series of two or more adjacent plates.

[0044]

[0054] In one embodiment, the inspection apparatus 100 includes a single radiation source.

[0045]

[0055] Any element or set of elements within an electron-optical device can be replaceable or field-replaceable. One or more electron-optical components within the electron-optical device, in particular those that act on or generate sub-beams, such as an aperture array and a manipulator array, can include one or more microelectromechanical systems (MEMS). The pre-bending deflector array 323 can be a MEMS. MEMS are small mechanical and electromechanical elements fabricated using microfabrication techniques. In one embodiment, the electron-optical device 40 includes an aperture, a lens, and a deflector formed as MEMS. In one embodiment, manipulators such as lenses and deflectors 322_1, 322_2, and 322_3 can be controlled passively or actively as a whole array, individually, or in groups within the array so as to control a beamlet of charged particles projected towards the target 308.

[0046]

[0056] In one embodiment, the electron optical device 40 may include alternative and / or additional components, such as lenses and other components as described above with reference to FIGS. 1 and 2, on the charged particle path. Examples of such configurations are shown in FIGS. 3 and 4, which will be described in more detail later. In particular, the embodiment includes an electron optical device 40 that splits one charged particle beam from a radiation source into a plurality of sub-beams. Each of the plurality of objective lenses can project the sub-beams onto the sample. In some embodiments, a plurality of condenser lenses are provided in the up-beam of the objective lens. The condenser lens focuses each sub-beam to an intermediate focus in the up-beam of the objective lens. In some embodiments, a collimator is provided in the up-beam of the objective lens. A corrector may be provided to reduce focus error and / or aberration. In some embodiments, such a corrector is integrated with the objective lens or disposed directly adjacent to the objective lens. Additionally or alternatively, when a condenser lens is provided, such a corrector may be integrated with the condenser lens or disposed directly adjacent to the condenser lens, and / or disposed at or directly adjacent to the intermediate focus. A detector is provided to detect charged particles emitted by the sample. The detector may be incorporated within the objective lens. The detector may be on the bottom surface of the objective lens so as to face the sample in use. The detector may include an array that may correspond to an array of beamlets in a multi-beam configuration. The detectors in the detector array can generate detection signals that can be associated with the pixels of the generated image. The condenser lens, objective lens, and / or detector may be formed as MEMS or CMOS devices.

[0047]

[0057] FIG. 3 is a schematic diagram of another design of an exemplary electro - optical device 40. The electro - optical device 40 may comprise an emission source 201 and one or more electro - optical assemblies. Alternatively, an electro - optical device including the electro - optical device 40 may include the emission source 201. The electro - optical device 40 may include an upper beam limiter 252, a collimator element array 271, a control lens array 250, a scanning deflector array 260, an objective lens array 241, a beam - shaping limiter 242, and a detector array. The emission source 201 provides a beam of charged particles (e.g., electrons). The multi - beam focused on the sample 208 is drawn from the beam provided by the emission source 201. Sub - beams may be drawn from the beam using, for example, a beam limiter that defines an array of beam - limiting apertures. The emission source 201 is desirably a high - brightness thermionic field emitter having a good compromise between brightness and total emission current.

[0048]

[0058] The upper beam limiter 252 defines an array of beam - limiting apertures. The upper beam limiter 252 may be referred to as an upper beam - limiting aperture array or an up - beam beam - limiting aperture array. The upper beam limiter 252 may include a plate (which may be a plate - like object) having a plurality of apertures. The upper beam limiter 252 forms sub - beams from the beam of charged particles emitted by the emission source 201. Beam portions other than those contributing to forming the sub - beams may be blocked (e.g., absorbed) by the upper beam limiter 252 so as not to interfere with the down - beam sub - beams. The upper beam limiter 252 may be referred to as a sub - beam - defining aperture array.

[0049]

[0059] The collimator element array 271 is provided in the down beam of the upper beam limiter. Each collimator element collimates its respective sub - beam. The collimator element array 271 can be formed using MEMS manufacturing technology so as to be spatially compact. In some embodiments, as illustrated in FIG. 3, the collimator element array 271 is a first deflection or focusing electron - optical array element in the beam path in the down beam of the radiation source 201. In another configuration, the collimator can take the form of a macro - collimator, either in whole or in part. Such a macro - collimator can be in the up beam of the upper beam limiter 252 and thus act on the beam from the radiation source before the multi - beam is generated. A magnetic lens can be used as the macro - collimator.

[0050]

[0060] In the down beam of the collimator element array, there is a control lens array 250. The control lens array 250 includes a plurality of control lenses. Each control lens includes at least two electrodes (e.g., two or three electrodes) connected to their respective potential sources. The control lens array 250 can include an array of two or more (e.g., three) plate electrodes connected to their respective potential sources. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are arranged near each other, and / or mechanically connected to each other, and / or controlled together as a unit). The control lens array 250 is arranged in the up beam of the objective lens array 241. The control lens pre - focuses the sub - beam (e.g., applies a focusing action to the sub - beam before the sub - beam reaches the objective lens array 241). By pre - focusing, the divergence of the sub - beam can be reduced or the convergence rate of the sub - beam can be increased. The control lens array 241 may not be distinguishable from the objective lens array 250 and may be a part thereof, but in this specification, the control lens array 250 is distinguished from the objective lens array 241 and considered as a separate entity.

[0051]

[0061] As described above, the control lens array 250 is associated with the objective lens array 241. As described above, the control lens array 250 can be regarded as providing additional electrodes for the electrodes 242 and 243 of the objective lens array 241, for example, as part of the objective lens array assembly. The additional electrodes of the control lens array 250 provide additional degrees of freedom when controlling the electron optical parameters of the sub-beams. In one embodiment, the control lens array 250 can be regarded as additional electrodes of the objective lens array 241 that enable additional functions for each objective lens of the objective lens array 241. In one configuration, such electrodes can be regarded as part of the objective lens array that provides additional functions for the objective lenses of the objective lens array 241. In such a configuration, the control lens is regarded as part of the corresponding objective lens, and in some cases, the control lens is only mentioned as being part of the objective lens in that it provides another additional degree of freedom for the objective lens, for example.

[0052]

[0062] For ease of illustration, in this specification, the lens array is schematically shown by an elliptical array. Each ellipse represents one of a plurality of lenses within the lens array. Ellipses are conventionally used to represent lenses by analogy with the biconvex shape often employed in optical lenses. However, it should be understood that in the context of charged particle mechanisms such as those considered in this specification, since the lens array typically operates electrostatically, it may not require physical elements with a biconvex shape. As described above, instead, the lens array can include a plurality of plates with apertures.

[0053]

[0063] A scanning deflector array 260 including a plurality of scanning deflectors may be provided. The scanning deflector array 260 may be formed using MEMS manufacturing technology. Each scanning deflector scans its respective sub-beam across the sample 208. Thus, the scanning deflector array 260 may include a scanning deflector for each sub-beam. Each scanning deflector may deflect the sub-beam in one direction (e.g., parallel to a single axis such as the X-axis) or in two directions (e.g., with reference to two non-parallel axes such as the X-axis and the Y-axis). The deflection is such that the sub-beam is scanned across the entire sample 208 in one or two directions (i.e., one-dimensionally or two-dimensionally). In one embodiment, the scanning deflector array 260 may be implemented using the scanning deflector described in European Patent Application Publication No. 2425444, which application is hereby incorporated by reference in its entirety, particularly with respect to the scanning deflector. The scanning deflector array 260 (e.g., formed using MEMS manufacturing technology as described above) may be more spatially compact than a macro scanning deflector. In another configuration, a macro scanning deflector may be used in the up-beam of the upper beam limiter 252. The macro scanning deflector acts on the beam from the radiation source before the multi-beam beamlets are generated, and its function may be similar or equal to that of the scanning deflector array.

[0054]

[0064] An objective lens array 241 including a plurality of objective lenses is provided for directing sub-beams toward a sample 208. Each objective lens includes at least two electrodes (e.g., two or three electrodes) connected to respective potential sources. The objective lens array 241 may include two or more (e.g., three) plate electrode arrays connected to respective potential sources. Each objective lens formed by a plate electrode array may be a microlens acting on different sub-beams. Each plate defines a plurality of apertures (which may also be called holes). The position of each aperture in a plate coincides with the position of a corresponding aperture (or apertures) in another plate (or plates). The corresponding apertures define an objective lens, and thus each set of corresponding apertures acts on the same sub-beam within a multi-beam during use. Each objective lens projects each sub-beam of the multi-beam onto the sample 208.

[0055]

[0065] In an objective lens array 241 having only two electrodes, the aberration may be smaller than that of an objective lens array 241 having more electrodes. In a three-electrode objective lens, a larger potential difference between the electrodes can be achieved, enabling a more powerful lens. The additional electrodes (i.e., three or more electrodes) provide additional degrees of freedom for controlling the electron trajectories, for example, to focus secondary electrons in addition to the incident beam. Such additional electrodes may be considered to form a control lens array 250. The advantage of a two-electrode lens over an Einzel lens is that the energy of the incident beam is not necessarily the same as that of the output beam. Advantageously, the potential difference of such a two-electrode lens array enables it to function as either an accelerating or decelerating lens array.

[0056]

[0066] The objective lens array may form part of the objective lens array assembly together with any or all of the scanning deflector array 260, the control lens array 250, and the collimator element array 271. The objective lens array assembly may further include a beam shaping limiter 242. The beam shaping limiter 242 defines an array of beam limiting apertures. The beam shaping limiter 242 may be referred to as a lower beam limiter, a lower beam limiting aperture array, or a final beam limiting aperture array. The beam shaping limiter 242 may include a plate (which may be a plate-like object) having a plurality of apertures. The beam shaping limiter 242 is in the down beam from at least one electrode (optionally all electrodes) of the control lens array 250. In some embodiments, the beam shaping limiter 242 is in the down beam from at least one electrode (optionally all electrodes) of the objective lens array 241.

[0057]

[0067] In one configuration, the beam shaping limiter 242 is structurally integral with the electrode 302 of the objective lens array 241. The beam shaping limiter 242 is desirably disposed in a region of low electrostatic field strength. Each beam limiting aperture is aligned with a corresponding objective lens within the objective lens array 241. This alignment is such that a portion of the sub-beam from the corresponding objective lens can pass through the beam limiting aperture and strike the sample 208. The apertures of the beam shaping limiter 242 may be smaller in diameter than the apertures of at least one of the objective lens array 242, the control lens array 250, the detector array 240, and the upper beam limiter array 252. Each beam limiting aperture has a beam limiting effect such that only a selected portion of the sub-beam incident on the beam shaping limiter 242 can pass through the beam limiting aperture. The selected portion may be such that only the portion of each sub-beam passing through the central portion of each aperture within the objective lens array reaches the sample. The central portion may have a circular cross-section and / or may be centered on the beam axis of the sub-beam.

[0058]

[0068] In one embodiment, the electro-optical device 40 is configured to control the objective lens array assembly (e.g., by controlling the potential applied to the electrodes of the control lens array 250) such that the focal length of the control lens is greater than the separation distance between the control lens array 250 and the objective lens array 241. Accordingly, the control lens array 250 and the objective lens array 241 can be disposed relatively close to each other, at which time the focusing action from the control lens array 250 is weak and does not form an intermediate focus between the control lens array 250 and the objective lens array 241. The control lens array and the objective lens array operate together to form a combined focal length on the same surface. The combined operation without an intermediate focus can reduce the risk of aberration. In other embodiments, the objective lens array assembly can be configured to form an intermediate focus between the control lens array 250 and the objective lens array 241.

[0059]

[0069] A power source can be provided to apply respective potentials to the electrodes of the control lenses of the control lens array 250 and the objective lenses of the objective lens array 241.

[0060]

[0070] By providing the control lens array 250 in addition to the objective lens array 241, the degree of freedom in controlling the characteristics of the sub-beams increases. For example, even when the control lens array 250 and the objective lens array 241 are provided relatively close to each other so that an intermediate focal point is not formed between the control lens array 250 and the objective lens array 241, an increase in the degree of freedom is brought about. The control lens array 250 can be used to optimize the beam opening angle with respect to the reduction ratio of the beam and / or to control the beam energy delivered to the objective lens array 241. The control lens array may include two or three or more electrodes. When there are two electrodes, the reduction ratio and the landing energy are controlled together. When there are three or more electrodes, the reduction ratio and the landing energy can be controlled individually. Note that the lowermost beam electrode of the control lens array 250 may be the uppermost beam electrode of the objective lens array 241. That is, the control lens array 250 and the objective lens array 241 may share an electrode. The shared electrode brings about different lens effects for each lens, and each lens effect is associated with one of its two opposing surfaces (i.e., the uppermost beam surface and the lowermost beam surface). Accordingly, the control lens can be configured to adjust the reduction ratio of each sub-beam and / or the beam opening angle and / or the landing energy on the substrate (e.g., by applying appropriate respective potentials to the electrodes of the control lens and the objective lens using a power supply). This optimization can be achieved without unduly affecting the number of objective lenses and without unduly deteriorating the aberration of the objective lenses (e.g., without reducing the intensity of the objective lenses). Using the control lens array makes it possible to operate the objective lens array at an optimal electric field strength. Note that the references to the reduction ratio and the opening angle are intended to refer to variants of the same parameter. In an ideal configuration, the product of the range of the reduction ratio and the corresponding opening angle is constant. However, the opening angle can be affected by the use of an aperture.

[0061]

[0071] In one embodiment, the landing energy can be controlled to a desired value within a predetermined range, for example, from 1000 eV to 5000 eV. It is desirable to vary the landing energy mainly by controlling the energy of the electrons exiting the control lens. The potential difference inside the objective lens is preferably kept constant during this variation so that the electric field inside the objective lens remains as high as possible. Furthermore, the beam opening angle and the reduction ratio can be optimized using the potential applied to the control lens. The control lens can function to vary the reduction ratio in consideration of the change in the landing energy. It is desirable for each control lens to include three electrodes so as to provide two independent control variables. For example, one of those electrodes can be used to control the magnification, and another electrode can be used to individually control the landing energy. Alternatively, each control lens may have only two electrodes. If there are only two electrodes, one of those electrodes may need to control both the magnification and the landing energy.

[0062]

[0072] To detect the charged particles emitted from the sample 208, a detector array (not shown) is provided. The detected charged particles can include any of the charged particles (e.g., signal particles) detected by the SEM, including secondary electrons and / or backscattered electrons from the sample 208. The detector can be an array that provides the surface of the electron optical device facing the sample 208, for example, the bottom surface of the electron optical device. Alternatively, the detector array is in the up-beam of the bottom surface or, for example, within or in the up-beam of the objective lens array or the control lens array. The elements of the detector array can correspond to the beamlets of the multi-beam configuration. The signals generated by the detection of electrons by the elements of the array are sent to a processor to generate an image. The signals can correspond to the pixels of the image.

[0063]

[0073] In other embodiments, both a macro scanning deflector and a scanning deflector array 260 can be provided. In such a configuration, the scanning of the sub-beam on the sample surface can be achieved by preferably synchronously controlling the macro scanning deflector and the scanning deflector array 260 together.

[0064]

[0074] In one embodiment, as illustrated in FIG. 4, an electron optical device array 500 is provided. The array 500 may include a plurality of any of the electron optical devices described herein. Each electron optical device simultaneously focuses each respective multi-beam onto different regions of the same sample. Each electron optical device may form a plurality of sub-beams from one charged particle beam from different respective radiation sources 201. Each respective radiation source 201 may be one of the plurality of radiation sources 201. At least a subset of the plurality of radiation sources 201 may be provided as a radiation source array. The radiation source array may include a plurality of radiation sources 201 provided on a common substrate. Simultaneously focusing a plurality of multi-beams onto different regions of the same sample can increase the area of the sample 208 that is simultaneously processed (e.g., evaluated). The electron optical devices within the array 500 may be arranged adjacent to each other so as to project each respective multi-beam onto adjacent regions of the sample 208.

[0065]

[0075] Any number of electron optical devices may be used within the array 500. The number of electron optical devices is preferably in the range from 2, desirably 9, to 100, and even up to 200. In one embodiment, the electron optical devices are arranged in a rectangular array or a hexagonal array. In other embodiments, the electron optical devices are provided in an irregular array or a regular array having a shape other than rectangular or hexagonal. Each electron optical device within the array 500 may be configured in any of the manners described herein when referring to a single electron optical device, for example, with respect to the embodiments illustrated and described above, particularly with reference to FIG. 6. Details of such a configuration are described in European Patent Application Publication No. A20184161.6 filed on Jul. 6, 2020, which application is incorporated herein by reference with respect to a method of incorporating and adapting an objective lens for use in a multi-device configuration.

[0066]

[0076] In the example of FIG. 4, the array 500 includes a plurality of electro-optical devices of the type described above with reference to FIG. 3. Thus, each electro-optical device in this example includes both a scanning deflector array 260 and a collimator element array 271. As described above, the scanning deflector array 260 and the collimator element array 271 are particularly suitable for incorporation into the electro-optical device array 500 due to their spatial compactness, which facilitates placing the electro-optical devices close to each other. This configuration of the electro-optical device may be preferred over other configurations that use magnetic lenses as collimators. Incorporating magnetic lenses into electro-optical devices intended for use in a multi-device configuration (e.g., a multi-column configuration) can be difficult, for example, due to magnetic interference between columns.

[0067]

[0077] In an alternative design of the multi-beam electro-optical device, there may be the same features as described with respect to FIG. 3, but differ in the points described below and illustrated in FIG. 5. An alternative design of the multi-beam electro-optical device may include a condenser lens array 231 in the up-beam of the objective lens array configuration 241, as disclosed in European Patent Application Publication No. 20158804.3, filed on Feb. 21, 2020, which application is incorporated herein by reference with respect to the description of multi-beam devices having collimators and their components. Such a design does not require a beam shaping limiter array 242 or an upper beam limiter array 252, because the beam limiting aperture array associated with the condenser lens array 231 can shape the beamlets 211, 212, 213 of the multi-beam from the beam of the radiation source 201. The beam limiting aperture array of the condenser lens may also function as an electrode within the lens array.

[0068]

[0078] The paths of the beamlets 211, 212, 213 diverge away from the condenser lens array 231. The condenser lens array 231 focuses the generated beamlets to an intermediate focus between the condenser lens array 231 and the objective lens array assembly 241 (i.e., towards the control lens array and the objective lens array). The collimator array 271 can be at the intermediate focus instead of being associated with the objective lens array assembly 241.

[0069]

[0079] The collimator can reduce the divergence of the diverging beamlet paths. The collimator can collimate the diverging beamlet paths such that the beamlet paths are substantially parallel towards the objective lens array assembly. The corrector array can be associated with, for example, the condenser lens array, the intermediate focus, and the objective lens array assembly and can be present in the multi-beam path. The detector 240 can be incorporated within the objective lens 241. The detector 240 can be on the bottom surface of the objective lens 241 so as to face the sample during use.

[0070]

[0080] In an embodiment of the configuration described with reference to FIG. 5, the detector may be disposed at substantially the same location within the electron optical device 241 shown in and described with reference to the electron optical device of FIG. 3. The detector 250 may be incorporated into the objective lens array 241 and the control lens array 240 (not shown in FIG. 5 but present if any). The detector may have a plurality of detectors at different positions along the paths of the plurality of sub-beams of the multi-beam, for example, at each array associated with different electron optical elements such as the electrodes of the objective lens array and / or the control lens array. Associated electron optical elements such as the objective lens array 241 and the control lens array 240 may be included within an integrated assembly, sometimes referred to as an electron optical assembly 700. In one embodiment, the detector 240 is associated with or even incorporated into the plates 710, 720 of the electron optical assembly 700. For example, the detector 240 may be on the bottom surface of the electron optical assembly 700 that includes the objective lens 241. The detector 240 may be provided with an electrical connector 60 as described elsewhere in this specification. In a variant, the detector has a detector array disposed in the up-beam of the objective lens array (and optionally, the control lens array 240), for example, the up-beam of the electron optical assembly 700. There may be a Wien filter array between the electron optical assembly 700 and the detector array, and this Wien filter array guides the charged particle beam in the down-beam direction towards the sample and guides the signal particles from the sample to the detector array.

[0071]

[0081] As shown in FIG. 4, the electron optical device array may have a plurality of multi-beam devices of this design as described with reference to the multi-beam device of FIG. 3. The plurality of multi-beam devices may be arranged in an array of multi-beam devices. Such a configuration is shown and described in European Application No. 20158732.6 filed on February 21, 2020, which is incorporated herein by reference with respect to the multi-device configuration of a multi-beam device featuring the design of a multi-beam device disclosed with a collimator at an intermediate focus.

[0072]

[0082] A further alternative design of the multi-beam device includes a plurality of single-beam devices. The single beam generated for the purposes of the present invention described herein may be similar or equivalent to the multi-beam generated by a single device. Each device may have an associated detector. Such a multi-device arrangement may be arranged in an array of 3, 4, 9, 19, 50, 100, or even 200 devices, each device generating a single beam or beamlet (in the case of a single-beam device) or a plurality of beams (in the case of a multi-beam device). In this further alternative design, the array of devices may have a common vacuum system, each device may have a separate vacuum system, or different vacuum systems may be assigned to each group of devices. Each device may have an associated detector.

[0073]

[0083] The electron optical device 40 may be a component of an evaluation (e.g., inspection or metrology inspection) device or part of an electron beam lithography device. The multi-beam charged particle device may be used for a number of different applications, including not only scanning electron microscopes but also electron microscopes in general and lithography.

[0074]

[0084] The electron optical axis 304 represents the path of charged particles output from the radiation source 201 passing through the radiation source 201. Unless otherwise explicitly stated, all sub-beams and beamlets of the multi-beam may be substantially parallel to the electron optical axis 304 passing through at least a manipulator or an electron optical array, for example, of the configuration illustrated in FIG. 2 and described with reference to this figure. The electron optical axis 304 may be the same as or different from the mechanical axis of the electron optical device 40. In the context of the configurations illustrated in FIGS. 2 to 5 and described with respect to these figures, the electron optical axis may correspond to the path of the central beam of the multi-beam, for example, beam 212. The beams of the multi-beam are substantially parallel to each other (e.g., the electron optical axis 304) between collimation (e.g., the location of the collimator array 271 corresponding to the plane of the intermediate focus (as shown in FIG. 5, for example) or the location of the upper beam limiter 252) and the surface of the sample 208.

[0075]

[0085] The electron optical device 40 may include an electron optical assembly 700 as shown in FIG. 6 to manipulate electron beamlets. For example, the electron optical assembly 700 may include one or more of (as a non-exhaustive list) an objective lens array 241, and / or a condenser lens array 231 that may constitute the electron optical assembly 700, and / or a collimator element array 271, and / or individual beam correctors, and / or deflectors, and / or a Wien filter array. In particular, the objective lens 331, and / or the condenser lens 310, and / or the control lens 250 may constitute the electron optical assembly 700.

[0076]

[0086] The electron optical assembly is configured to provide a potential difference between two or more plates (or substrates). An electrostatic field is generated between the plates functioning as electrodes. The electrostatic field provides an attractive force between the two plates. The attractive force may increase as the potential difference increases.

[0077]

[0087] In an electro-optical assembly, at least one of the plates has a stepped thickness such that the array plate is thinner in a region corresponding to the aperture array than in other regions of the array plate. Having a stepped thickness, for example, a state where two portions of the plate have different thicknesses, is advantageous because when the potential difference is high, the plate is exposed to a greater electrostatic force, and thus, if the plate has a constant thickness, for example, if it is too thin, the plate may bend. If the plate bends, it may adversely affect the uniformity between the beams. Therefore, a thick plate is advantageous for reducing bending. However, if the plate is too thick in the region of the aperture array, it may lead to undesirable deformation of the electron beamlets. Therefore, in order to reduce the deformation of the electron beamlets, a thin plate is advantageous around the aperture array. That is, the aperture array may be defined in a region of the plate that is thinner than the remaining portion of the plate. Therefore, by making the plate have a stepped thickness, the possibility of bending is reduced without increasing the possibility of beamlet deformation. In one embodiment, the plate has a uniform thickness including the region corresponding to the aperture array.

[0078]

[0088] The exemplary electro - optical assembly shown in FIG. 6 comprises an array plate 710, an adjacent plate 720, and an insulating member (or spacer) 730 (note that the term "array plate" is a term used to distinguish that plate from the other plates referred to in this specification). In the array plate, an array of apertures 711 is defined with respect to the path of the electron beamlets. The number of apertures in the aperture array may correspond to the number of sub - beams in a multi - beam configuration. In one configuration, the number of apertures is less than the number of sub - beams in the multi - beam such that a group of sub - beam paths passes through one aperture. For example, the apertures may extend across the multi - beam path, and the apertures may be strips or slits. In one configuration, the apertures may be arranged in a grid (or two - dimensional array) such that a plurality of groups of a plurality of beams are arranged in a two - dimensional array of a plurality of groups of a plurality of beams. The insulating member 730 is disposed between the plates to separate them. The electro - optical assembly is configured to provide a potential difference between the array plate 710 and the adjacent plate 720.

[0079]

[0089] In the adjacent plate 720, an array of another aperture 721 is defined with respect to the path of the electron beamlet. In one embodiment, the adjacent plate 720 may also have a stepped thickness such that it is thinner in the region corresponding to the array of apertures than in another region of the adjacent plate (alternatively, the adjacent plate 720 may be substantially planar and / or have a uniform thickness). The array of apertures 721 defined within the adjacent plate 720 desirably has the same pattern as the array of apertures 711 defined in the array plate 710. In one configuration, the patterns of the apertures in these two plates may be different. For example, the number of apertures in the adjacent plate 720 may be less than or more than the number of apertures in the array plate 710. In one configuration, there is a single aperture within the downbeam plate for all paths of the sub-beams of the multi-beam. The apertures of the array plate 710 and the adjacent plate 720 are preferably substantially well-aligned with each other. This alignment between the apertures is to limit lens aberration.

[0080]

[0090] The array plate and the adjacent plate may each have a thickness of up to 1.5 mm, preferably 1 mm, more preferably 500 μm at the thickest part of the plate. In one configuration, the downbeam plate (i.e., the plate closer to the sample) may have a thickness between 200 μm and 300 μm at its thickest part. The downbeam plate preferably has a thickness between 200 μm and 150 μm at its thickest point. The upbeam plate (i.e., the plate farther from the sample) may have a thickness of up to 500 μm at its thickest part.

[0081]

[0091] A coating may be applied on the surface of the array plate and / or the adjacent plate. The coating is preferably applied to both the array plate and the adjacent plate. The surface charging that may cause undesirable beam distortion in the absence of the coating is reduced by the coating.

[0082]

[0092] The coating is configured to withstand the dielectric breakdown phenomenon that may occur between the array plate and the adjacent plate. It is preferable that a low-resistance coating is applied, and it is more preferable that a coating with a resistance of 1 ohm / square or less is applied. The coating is preferably applied on the surface of the down beam plate. More preferably, the coating is applied between at least one of these plates and the insulating member. The low-resistance coating reduces undesirable surface charging of the plate.

[0083]

[0093] The array plate and / or the adjacent plate may include a low bulk resistance material, preferably 1 ohm-meter or less, optionally 0.1 ohm-meter or less, optionally 0.01 ohm-meter or less, optionally 0.001 ohm-meter or less, and optionally 0.0001 ohm-meter or less. More preferably, the array plate and / or the adjacent plate includes doped silicon. Plates having a low bulk resistance have the advantage of a low probability of failure because the discharge current is supplied / discharged through the bulk rather than, for example, through a thin coating layer.

[0084]

[0094] The array plate includes a first wafer. The first wafer may be etched to create regions of different thicknesses. The first wafer may be etched in the region corresponding to the array of apertures such that the array plate is thinner in the region corresponding to the array of apertures. For example, the first side of the wafer may be etched, or both sides of the wafer may be etched to create a stepped thickness of the plate. The etching may be by deep reactive ion etching. Alternatively or in addition, the stepped thickness of the plate may be created by laser drilling or machining.

[0085]

[0095] Alternatively, the up-beam plate may include a first wafer and a second wafer. The array of apertures may be defined within the first wafer. The first wafer may be disposed in contact with the insulating member. The second wafer may be disposed on the surface of the first wafer in a region not corresponding to the aperture array. The first wafer and the second wafer may be bonded by wafer bonding. The thickness of the up-beam plate in the region corresponding to the aperture array may be the thickness of the first wafer. The thickness of the array plate in another region other than the region of the aperture array, for example, radially outside the aperture array, may be the combined thickness of the first wafer and the second wafer. Accordingly, the up-beam plate has a stepped thickness between the first wafer and the second wafer.

[0086]

[0096] One of the array plate and the adjacent plate is the other's up-beam. One of the array plate and the adjacent plate is negatively charged with respect to the other plate. The up-beam plate preferably has a higher potential than the down-beam plate, for example, with reference to the ground potential, the radiation source, or the sample. The electron optical assembly may be configured to provide a potential difference of 5 kV or more between the array plate and the adjacent plate. The potential difference is preferably 10 kV or more. The potential difference is 20 kV or more, or less than 30 kV, and more preferably exceeds 30 kV.

[0087]

[0097] The insulating member 760 is preferably disposed between the array plate and the adjacent plate such that the opposing surfaces of these plates are on the same plane. The insulating member 760 has an inner surface 731 facing the path of the beamlet. The insulating member may be planar, and the main surface is on the same plane as the plates 710, 720. The insulating member 760 defines an opening 732 for the path of the electron beamlet.

[0088]

[0098] A conductive coating, such as coating 740, may be applied to the insulating member. It is preferable to apply a low-resistance coating, and more preferably a coating of 0.5 ohm / square or less.

[0089]

[0099] The coating is preferably on the surface of the space facing the negatively charged plate, which is negatively charged with respect to other plates. It is preferable that the down-beam plate is negatively charged with respect to the up-beam plate. The coating may be placed at the same potential as the negatively charged plate. The coating is preferably on the surface of the insulating member facing the negatively charged plate. More preferably, the coating is electrically connected to the negatively charged plate. The coating may ensure the presence of an electrostatic field in the gap between the insulating member and the negatively charged plate.

[0090]

[0100] If there is no such coating on the insulating member, electric field enhancement may occur in such gaps. This electric field enhancement may lead to dielectric breakdown in those gaps, thereby causing the potential of the lower electrode to become unstable. Due to this potential instability, the intensity of the lens changes over time, thereby causing a deviation in the focus of the electron beam.

[0091]

[0101] The inner surface 731 (or rim) of the spacer 760 is shaped such that the creep path between the plates across the inner surface is longer than the minimum distance between the plates. The inner surface may have a step 761. The step may be a step in the thickness of the insulating member. The step may have a surface on the same plane as the main surface of the insulating member. Accordingly, the creep length extends across the inner surface 731 of the spacer between two different plates, for example across the step 761. It is desirable that the inner surface of the insulating member is shaped to provide a creep length of 10 kV / mm or less, preferably 3 kV / mm or less.

[0092]

[0102] The electro - optical assembly 700 may comprise a lens assembly for manipulating an electron beamlet, or may be a lens assembly. The lens assembly may be, for example, an objective lens assembly or a condenser lens assembly, or a part thereof. A lens assembly such as an objective lens assembly may further comprise an additional lens array comprising at least two plates such as the control lens array 250.

[0093]

[0103] FIG. 7 is a schematic diagram of the electrical connector 60 of an exemplary electro - optical assembly 700. The electro - optical assembly 700 is configured to manipulate an electron beam. As shown in FIG. 7, in one embodiment, the electro - optical assembly 700 comprises a first electro - optical element comprising a plate 710 (note that if the electro - optical assembly 700 comprises only one first electro - optical element, that first electro - optical element may sometimes be referred to as the electro - optical element).

[0094]

[0104] In one embodiment, the electro - optical assembly 700 comprises a plurality of electro - optical elements each comprising a plate. For example, the electro - optical assembly 700 shown in FIG. 6 comprises a first electro - optical element comprising a plate 710 and a second electro - optical element comprising another plate 720. In one embodiment, the electro - optical assembly 700 comprises three or more electro - optical elements each comprising a plate. The electrical connector 60 described herein may be applied to connect either or each of the plates 710, 720 of the electro - optical assembly 700 to a power source (or power supply).

[0095]

[0105] In one embodiment, the plate 710 has one or more apertures 711 around the beam path of the electron beam. For example, as shown in FIG. 6, in one embodiment, the plate 710 comprises an array of apertures 711. In an alternative embodiment, the plate 710 comprises only one aperture. Each aperture 711 may be for the beam path of a single electron beam. Alternatively, one or more apertures 711 may be around the beam paths of multiple electron beams.

[0096]

[0106] FIG. 7 schematically shows an electrical connector 60. The electrical connector 60 is configured to electrically connect the plate 710 of the first electro - optical element to a power source. In one embodiment, the electro - optical device 40 comprises the electrical connector 60. In one embodiment, the electro - optical assembly 700 comprises the electrical connector 60.

[0097]

[0107] In one embodiment, the power source is a high - voltage power source. In one embodiment, the power source is configured to apply a voltage of at least 100V, optionally at least 200V, optionally at least 500V, optionally at least 1kV, optionally at least 2kV, optionally at least 5kV, optionally at least 10kV, optionally at least 20kV, optionally at least 30kV, and optionally 35kV or higher with respect to the reference potential of the electro - optical device 40 to a part of the electro - optical assembly 700. In one embodiment, the power source is configured to apply a positive voltage with respect to the reference potential. In an alternative embodiment, the power source is configured to apply a negative voltage with respect to the reference potential. The reference potential may be grounded. In one embodiment, one or more of the plates 710, 720 of the electro - optical assembly 700 are configured to be connected to a high voltage during use of the electro - optical device 40.

[0098]

[0108] FIG. 7 shows an electrical connector 60 for electrically connecting a plate 710 (i.e., a planar electron optical element) to a power source (e.g., a voltage supply). The planar electron optical element is configured to act on an electron beam along a beam path towards a sample position. The electron optical element may be configured to act on a single electron beam or a plurality of electron beams (e.g., a multi-beam) that may be formed as a beam grid. In one embodiment, the electron optical element comprises an aperture 711 (or an array of apertures) for the beam path.

[0099]

[0109] In one embodiment, the electrical connector 60 is for electrically connecting the plate 710 to a power source. The plate 710 may be part of an electron optical assembly 700 that may comprise, for example, an objective lens assembly or a condenser assembly. More generally, the electrical connector 60 may be configured to electrically connect any electron optical element of the electron optical device 40 to a power source.

[0100]

[0110] As shown in FIG. 7, in one embodiment, the electron optical assembly comprises a conductive body 61. The conductive body 61 is electrically connected to the electron optical element (i.e., the plate 710). In one embodiment, the conductive body 61 is included within the electrical connector 60. The conductive body 61 is for electrically connecting the plate 710 to a power source. The conductive body 61 includes a conductive material. The conductive body 61 may include a metal.

[0101]

[0111] As shown in FIG. 7, in one embodiment, a recess 611 (for example, having a concave surface) is defined within the conductive body 61. In one embodiment, the recess 611 is configured to provide an electric field-free volume 62. The opening defined in the end face 613 of the conductive body 61 is an opening to the recess 611 and thus to the electric field-free volume 62. In one embodiment, the electric field-free volume 62 is for inserting the high-voltage cable 64. In one embodiment, the high-voltage cable 64 is for electrically connecting an electron optical element to a power source. In one embodiment, the high-voltage cable 64 is configured to electrically connect the electron optical element to the power source via an electrical coupling 63. There is substantially no electric field in the electric field-free volume 62. In one embodiment, the conductive body 61 is configured to shield electrical components within the electric field-free volume 62 from an external electric field. In one embodiment, the conductive body 61 is configured to reduce the possibility of dielectric breakdown between electrical components within the electric field-free volume 62 and another member of the electron optical device 40.

[0102]

[0112] The high-voltage cable 64 may include an insulator 65 and a conductor 66. The conductor 66 is a transmission line. The insulator 65 is configured to insulate the conductor 66 from the environment.

[0103]

[0113] In one embodiment, the electrical coupling 63 is flexible. The flexible coupling may be in the electrical path between the plate 710 and the power source. In one embodiment, the flexible coupling is configured to electrically connect the plate 710 to the power source, for example, such that the electrical connector 60 can connect the plate 710 to the power source thereby. The plate 710 is electrically connectable to the power source via the flexible coupling 63. Thus, the plate 710 is electrically connectable to the power source via a cable. The electrical path may include the high-voltage cable 64, an electrical connector 60 including, for example, a flexible connector 63, and the plate 710.

[0104]

[0114] As shown in FIG. 7, in one embodiment, the flexible coupling 63 is located, for example, within an electric field-free volume 62 (or electric field-free region) defined in the conductive body 61. The flexible coupling 63 is intended to provide an electrical connection to the plate 710, for example, via an electrical connection to the conductive body 61. The conductive body 61 is configured to shield the flexible coupling 63 from an external electric field of the conductive body 61. Embodiments of the present invention are expected to reduce the possibility of dielectric breakdown associated with the (electrical) connection of the electro-optical device to a power source, for example, between the electrical connector 60 and another component of the electro-optical device 40, such as another component of the electro-optical assembly 700.

[0105]

[0115] The flexibility of the flexible coupling 63 reduces the possibility that the electrical connector 60 may undesirably affect the position and / or formation (e.g., shape) of the plate 710. Such a flexible coupling connected to the electro-optical device can reduce the risk that a force and / or moment is applied to the electro-optical device. The application of such a force or moment may undesirably affect the electro-optical performance of the electro-optical device during operation of the device. Such an impact on the performance of the electro-optical device is observable, for example, by the position of the device, and thus the alignment of the device with respect to one or more charged particle beams, and thus the alignment of the sample, and the alignment between the charged particle beams, as well as other aberrations. Such aberrations may be caused, for example, by a change in stress within the device and / or a change in the formation of the device, such as a deformation of the shape of the elements of the device, and cause distortion in the electric field generated within the device.

[0106]

[0116] As shown in FIG. 7, in one embodiment, the conductive body 61 includes an electrical insulator 70. In one embodiment, the electrical insulator 70 is spaced apart from the planar electron optical element. There may be a gap between components (such as the plate 710) of the planar electron optical element and the electrical insulator 70. In one embodiment, the electrical insulator 70 provides at least a portion of the surface of the conductive body 61. Alternatively, the electrical insulator 70 may be considered a component different from the conductive body 61 (thus, the conductive body 61 does not include the electrical insulator 70). In this case, the electrical insulator 70 is configured to cover at least a portion of the surface 612 of the conductive body 61. In one embodiment, the surface (or a portion of the surface) 612 of the conductive body 61 covered by the electrical insulator 70 faces away from the electron optical element.

[0107]

[0117] One embodiment of the present invention is expected to reduce the possibility of electron creep. Electron creep may occur between different components of the electron optical device 40. For example, as will be described in more detail below, in one embodiment, the electron optical assembly includes a plurality of conductive bodies 61 (of each of the plurality of electrical connectors 60). Electron creep may occur between the conductive bodies 61. In addition to or instead of this, electron creep may occur between the conductive body 61 and an electron optical component of the electron optical assembly other than the plate 710 to which the conductive body 61 is electrically connected. Such electron creep is undesirable.

[0108]

[0118] By providing an electrical insulator, the possibility of electrons being emitted from the conductive body 61 and causing electron creep is reduced. In the case of a high electric field, the possibility of undesirable electron creep is particularly high. By providing the electrical insulator 70, the electrical connector 60 may be able to withstand a higher electric field without overly increasing the risk of electron creep.

[0109]

[0119] Generally, when the outer surface of the conductive body 61 has relatively sharp edges and / or a smaller radius of curvature, the electric field around the conductive body 61 may become higher. By providing the electrical insulator 70, the size of the conductive body 61 can be volumetrically reduced without unduly increasing the risk of electron creep (this increases the electric field around the conductive body 61). An embodiment of the present invention is expected to increase the design freedom regarding the conductive body 61.

[0110]

[0120] As shown in FIG. 7, in one embodiment, the electron optical assembly includes a plurality of insulating members 750, 760. In one embodiment, the plate 710 is between the insulating members 750, 760 and is, for example, sandwiched by the insulating members 750, 760. To facilitate reference to the distinction between the two insulating members used herein, the two insulating members may be referred to as the up-beam insulating member 750 and the down-beam insulating member 760. However, descriptions regarding the up-beam insulating member may also apply to the down-beam insulating member and vice versa. Further, although these terms relate to the two insulating members, the electron optical module 700 may include, for example, additional insulating members positioned relatively up-beam or down-beam to the two insulating members 750. In one embodiment, the insulating members 750, 760 are substantially planar. The insulating members 750, 760 and the plate 710 may be laminated with respect to each other. The electron optical assembly may include a plurality of plates and a plurality of insulating members. A combination of plates and insulating members laminated with respect to each other may be referred to as a stack.

[0111]

[0121] In one embodiment, the down beam insulating member 760 is configured to support the electron optical element. In that embodiment, the down beam insulating member 760 is configured to electrically isolate the electron optical element. In one embodiment, the down beam insulating member 760 is positioned away from the beam path, for example, around the beam path. The down beam insulating member 760 may be a plate in which an aperture for the beam path is defined. The surface of the plate within the aperture may sometimes be referred to as a rim or an inner surface 731. The rim may be spaced apart from (or positioned away from) the beam path. The rim may be spaced apart from the beam path and from the position of one or more apertures 711, 721 of the plates 710, 720 with which the insulating member 760 contacts.

[0112]

[0122] As shown in FIG. 7, in one embodiment, the electron optical assembly includes a conductor 67. The conductor 67 is configured to electrically connect the plate 710 to the conductive body 61. In one embodiment, the conductor 67 includes a conductive layer recess such as a coating. The conductive layer may sometimes be formed on the down beam insulating member 760 as a coating, for example. The conductor 67 is electrically connected to the conductive body 61. For example, in one embodiment, in order to electrically connect the conductor 67 to the conductive body 61, a conductive adhesive (for example, an adhesive) in the form of a raised portion, for example, is provided. In addition to or instead of this, the conductor 67 may sometimes be electrically connected to the conductive body 61 by soldering and / or clamping, for example.

[0113]

[0123] As shown in FIG. 7, in one embodiment, the conductive body 61 is on the down-beam insulating member 760. In one embodiment, the down-beam insulating member 760 is configured to mechanically support the conductive body 61. As shown in FIG. 7, in one embodiment, both the plate 710 and the conductive body 61 electrically connected to the plate 710 are supported by the same down-beam insulating member 760. However, this is not necessarily the case. In one embodiment, the conductive body 61 and the plate to which it is electrically connected may be directly supported by different insulating members of the electron optical assembly. For example, in a modified version of the arrangement shown in FIG. 7, the conductive body 61 is electrically connected to another plate mechanically supported by the up-beam insulating member 750. The conductive body 61 may remain supported by the down-beam insulating member 760. However, the conductor 67 is on the up-beam insulating member 750 (rather than the down-beam insulating member 760) and extends towards the conductive body 61 and is electrically connected to the conductive body 61. In one embodiment, the conductor 67 is electrically connected to an intermediate position along the conductive body 61 in the direction of the beam path (rather than at the bottom of the conductive body 61 shown in FIG. 7).

[0114]

[0124] For example, as shown in FIG. 7, in one embodiment, the electrical insulator 70 is thicker than the conductive body 61, and the electrical insulator 70 covers the surface 612 of the conductive body 61. By providing the electrical insulator 70, the electrical insulator 70 enables a larger electric field around the conductive body 61, so that the size of the conductive body 61 can be reduced without unduly increasing the risk of dielectric breakdown. By reducing the size of the conductive body 61, the volume available for the electrical insulator 70 becomes larger. In the figures shown in FIG. 7 or FIG. 8, for example, the insulating cover 71 has a greater thickness than the conductive body 61 or the conductive element of the conductive body. In one embodiment, the thickness is measured in a direction away from the axial direction of the field-free volume 62. The conductive element may be within the electrical insulator 70. The conductive element may comprise, for example, a conductive layer on the electrical insulator 70. The conductive body may have an end face.

[0115]

[0125] FIG. 8 is a schematic view of parts of an electro - optical assembly. The electro - optical assembly shown in FIG. 8 may be a modified version of the electro - optical assembly shown in FIG. 7. The features of the electro - optical assembly shown in FIG. 8 that are the same as those described above with reference to FIG. 7 will not be described in detail below. Instead, the following description focuses on the features of the electro - optical assembly of FIG. 8 that are not shown in FIG. 7.

[0116]

[0126] As shown in FIG. 8, in one embodiment, the end face 613 of the conductive body 61 includes a portion of the surface of the conductive body 61 provided by the electrical insulator 70. In one embodiment, the electrical insulator 70 covers the end face 613 of the conductive body 61. An opening to the electric - field - free volume 62 is defined in the end face 613. The conductive body may have, for example, a sharp edge 68 or an end of the conductive layer 78. The sharp edge 68 may be provided by the opening in the end face 613 of the conductive body 61 and / or the interface between the insulator 71 or the insulating member 760 and the conductive material of the conductive body 61, such as the conductive layer 78. The sharp edges defined by the opening and the interface may be substantially the same in practice for a conductive body formed from a thin conductive layer such as a coating. A reference to one sharp edge in the following text may also apply to situations where the two sharp edges are different.

[0117]

[0127] As shown in FIG. 7, there may be a triple point at the end face 613 of the conductive body 61, for example, at the sharp edge 68. The triple point is a junction point between the conductive surface, the insulating surface, and the surrounding environment or atmosphere (which may be a low pressure, such as a vacuum). The triple point at the sharp edge 68 is a junction point between the conductive element of the conductive body 61, the electrical insulator 70, and the atmosphere. Generally, undesirable electron creep may start at or near such a triple point. As shown by the comparison between FIG. 8 and FIG. 7, in one embodiment, the sharp edge is covered by the electrical insulator 70. By covering the sharp edge 68, it is possible to prevent the sharp edge from functioning as a triple point. The sharp edge 68 shown in FIG. 7 can be considered to be captured or contained by the electrical insulator 70. By containment, the triple point is positioned within the field-free volume 62. As shown in FIG. 8, on the concave surface of the conductive body 61, there is an interface 69 with the insulating surface and the atmosphere. Substantially, the position of the triple point is moved from the sharp edge 68 at the end face 613 of the conductive body 61 into the field-free volume 62. By arranging the conductive body 61 such that the triple point is within the field-free volume 62, for example, at the interface 69, the possibility of electron creep is reduced. In particular, by shifting the triple point from the surface of the sharp edge 68 at the end face 613 of the conductive body to the interface 69 within the field-free volume 62, the surface required for electron creep to occur is increased. Moving the position of the triple point into the field-free region increases the size of the surface where electron creep occurs during discharge. Therefore, the discharge caused by electron creep can be prevented, or at least the risk can be reduced, by moving the triple point (i.e., as the starting point of such electron creep) into the field-free volume.

[0118]

[0128] In one embodiment, the sharp edge (or sharp end) 68 of the conductive body 61 is enclosed to reduce, if not prevent, the emission of electrons and to move the triple point into the field-free volume 62. As shown in FIG. 8, in one embodiment, the electrical insulator includes an insulating member 72 as the end face 613 of the conductive body 61. The insulating member covers the sharp edge 68. In one embodiment, the electrical insulator 70 at the end face includes an insulating member 72 that covers the end face 613 (or surface) of the conductive body 61. In one embodiment, the insulating member 72 is integrally formed. In one embodiment, the insulating member 72 is initially formed as a separate component from the rest of the electrical insulator 70. For example, in one embodiment, the electrical insulator 70 includes an insulating member 72 and an insulating cover 71. The insulating cover 71 is configured to cover at least a part of the outer surface 612 of the conductive body 61. In one embodiment, the electrical insulator 70 has at least two pieces.

[0119]

[0129] In one embodiment, the insulating member 72 includes an insulating plug that comprises (or at least covers) the end face of the conductive body 61. In one embodiment, the insulating plug extends through the opening to the field-free volume 62 and provides at least a part of the surface (or concave surface) of the recess 611. In one embodiment, the insulating plug extends into the field-free volume 62. The part of the plug that extends into the recess 611 may be referred to as the inward portion. In one embodiment, the insulating member 72 is an insulating plug that engages the end face 613 of the conductive body 61. The part of the plug that covers the end face of the conductive body 61 may be referred to as the cover portion. In one embodiment, the insulating member 72 is configured to engage the inner surface of the conductive body 61, for example, within the recess 611.

[0120]

[0130] The electrical insulator 70 includes an electrically insulating material. For example, in one embodiment, the electrical insulator includes a dielectric such as ceramic, glass (e.g., borosilicate glass), and epoxy or insulating adhesive. In one embodiment, the insulating cover 71 and the insulating member 72 are formed from the same dielectric material. Alternatively, the insulating cover 71 may include a material different from that of the insulating member 72.

[0121]

[0131] In one embodiment, the conductive body 61 is formed by milling, machining, cutting, or laser ablation of a mass of conductive material, or other such forming means. In one embodiment, the conductive body 61 has a rounded edge. In one embodiment, the conductor 67 has one or more rounded edges. The rounded edges can help reduce the electric field around the conductive body 61 and / or the conductor. This is because rounding the surface of the conductive body 61 can help limit local electric field enhancement within the insulator covering the conductive body 61. Limiting local electric field enhancement ensures that the electric field does not exceed the dielectric strength of the insulator. For example, if the electric field locally exceeds at the edge of the conductive body 61, dielectric breakdown of the insulator may occur. In one embodiment, the conductive body 61 is formed as a layer such as a coating. For example, a conductive material can be applied, such as coated, as a layer on the surface of the down-beam insulating member 760 and / or the electrical insulator 70 to form the conductive body 61 or at least the conductive elements of the conductive body 61. For example, the conductive layer 78 may be formed as one continuous layer. In another embodiment, the conductive layer 78 may be formed from at least a portion of the layer on the insulating member 760 and, for example, a layer on the surface of the electrical insulator of the insulating cover 71, and for example, the layer on the insulating member may be joined to the layer on the electrical insulator.

[0122]

[0132] It is not essential for the electrical insulator 70 to include the insulating member 72. Similarly, it is not essential for the electrical insulator 70 to include the insulating cover 71. In one embodiment, the electrical insulator 70 consists of the insulating member 72. A portion of the outer surface 612 of the conductive body 61 may be covered by the down-beam insulating member 760 and the insulating member 72, and other portions of the outer surface 612 of the conductive body 61 are open to the environment.

[0123]

[0133] As shown in FIG. 8, in one embodiment, the electrical insulator 70 extends from the end face 613 into the field-free volume 62. In one embodiment, the electrical insulator 70 provides a part of the inner surface of the conductive body 61 (or the concave surface of the recess 611). In one embodiment, the electrical insulator 70 provides a part of the inner surface of the conductive body that is away from the electron optical element. In one embodiment, the inner surface of the conductive body 61 defines the field-free volume 62. In one embodiment, the electrical insulator 70 extends into the field-free volume 62, covers a part of the inner surface of the conductive body 61, and this inner surface defines the field-free volume 62. In other words, the concave surface may comprise the surface of the inner direction part of the plug and a part of the conductive body 61. This part of the conductive body 61 may also be called the exposed part of the conductive body. The exposed part is the part of the surface of the conductive body in the recess 611 that remains exposed without being covered by, for example, a plug (or the insulating member 72).

[0124]

[0134] In one embodiment, at least a part of the electrical insulator 70 surrounds the cross-section of the conductive body 61. In the configuration shown in FIGS. 7 and 8, the cross-section of the conductive body 61 perpendicular to the axial direction of the field-free volume 62 is surrounded by the combination of the insulating cover 71 and the down-beam insulating member 760. In an alternative embodiment, the insulating cover 71 surrounds the cross-section of the conductive body 61. Embodiments of the present invention are expected to reduce, for example, the possibility of electron creep extending in any direction over the surface of the conductive body 61 from a triple point formed at the edge of the exposed (or uncovered) conductive surface of the conductive body.

[0125]

[0135] As shown in FIG. 7, in one embodiment, the longitudinal axis of the field-free volume 62 is shifted from the plate 710 of the electron optical element. In one embodiment, the field-free volume 62 defines an axial direction spaced from the plane of the planar electron optical element. The distance between the end of the conductive body 61 and the electron optical element of the stack may be increased to reduce the risk of discharge between the conductive body 61 and the stack. There may be a gap between the end of the conductive body 61 and the electron optical element of the stack.

[0126]

[0136] In one embodiment, the field-free volume 62 defines an axial direction that is angled with respect to the plane of the planar electron optical element. For example, in one embodiment, the axial direction of the field-free volume 62 is angled so as to exit the plane of the planar electron optical element. For example, in the orientation shown in FIG. 7, the field-free volume 62 may be oriented upward or downward with respect to the plate 710. By changing the angle of the conductive body 61, the end of the conductive body 61 can be further spaced apart from the stack, reducing the risk of discharge. This configuration can also facilitate electrically connecting the conductive body, and thus the electron optical element, for example when the available design volume is limited. However, it is not essential for the field-free volume 62 to be angled with respect to the plate 710. In an alternative embodiment, the axial direction defined by the field-free volume 62 is parallel to the plane of the plate 710, as shown, for example, in FIG. 7.

[0127]

[0137] FIG. 9 is a schematic plan view of an electron optical assembly comprising two electrical connectors 60. In one embodiment, the electrical connectors 60 are for electrically connecting the respective electron optical elements of the electron optical assembly to respective power supplies. As shown in FIG. 9, in one embodiment, the electron optical assembly comprises a plurality of conductive bodies 61. The conductive bodies 61 are electrically connected to one or more electron optical elements of the electron optical assembly. For example, the electrical connector 60 shown in the upper half of FIG. 9 is for electrically connecting the plate 710 to a power supply. The conductive body 61 is electrically connected to the plate 710 of the electron optical element. The plate may have one or more apertures defined for the path of one or more charged particle beams. The electrical connector 60 shown in the lower half of FIG. 9 may be for electrically connecting another plate in the stack of the electron optical assembly to the same or a different power supply.

[0128]

[0138] In one embodiment, an electro - optical device comprising an electro - optical assembly comprises a plurality of power supplies. In one embodiment, a controller 50 is provided to control the voltage applied to the electro - optical element by the power supply. In one embodiment, the controller 50 is configured to control different high voltages to be applied to different electro - optical elements of the electro - optical assembly. In addition to or instead of this, a plurality of power supplies may be connected to different parts of the same electro - optical element. The controller 50 can control the power supplies such that different high voltages are applied to different parts of the electro - optical element. The controller 50 is configured to control the voltage applied to the electro - optical element to control the operation of one or more electron beams by the electro - optical assembly.

[0129]

[0139] Many of the features shown in FIG. 9 have been described above in connection with other figures. These features are assigned the same reference numbers as those used previously in this specification. To avoid redundant description, these features will not be described in further detail. The following description focuses on features not shown in other figures.

[0130]

[0140] As shown in FIG. 9, in one embodiment, an electrical insulator 70 covers at least a part of the surface of a plurality of conductive bodies 61. For example, as shown in FIG. 9, in one embodiment, the electrical insulator 70 comprises potting 73. The potting contains an insulating material. The potting 73 is configured to cover the outer surface of one or more conductive bodies 61. The potting 73 is configured to reduce the possibility of electron emission from the conductive body 61. The potting 73 is provided to reduce or eliminate gas or vacuum gaps / pockets. These gaps / pockets can usually undesirably enhance the electric field. In one embodiment, the potting 73 is formed from a fluid that solidifies to form a dielectric layer. In one embodiment, the potting 73 includes, for example, epoxy or an insulating adhesive. In one embodiment, the electrical insulator 70 includes at least a part of the surface common to the plurality of conductive bodies 61. In one embodiment, the electrical insulator 70 is common to the plurality of conductive bodies 61.

[0131]

[0141] As shown in FIG. 9, in one embodiment, in a plan view, a plurality of conductive bodies 61 are positioned on the same side of the beam path. The beam path extends through the central region of the plate 710. For ease of illustration, the stack is shown as having a square outer shape in cross-section, but can have any desired shape as disclosed herein. As shown in FIG. 9, in one embodiment, the plurality of conductive bodies 61 define an electric-field-free volume 62 having an axial direction parallel to each other. The electrical connector 60 may extend from the same side of the stack of the electron optical assembly. This can reduce the space occupied by electrical connections on the other side of the stack and, for example, meet the volume constraints of the electron optical device.

[0132]

[0142] FIG. 10 is a schematic plan view of an electron optical assembly. Unless otherwise stated, this electron optical assembly has the same features with the same description as FIG. 9. The electron optical assembly shown in FIG. 10 has two conductive bodies 61 on both sides of the stack of the electron optical assembly. As shown in FIG. 10, in one embodiment, the two conductive bodies 61 are arranged so as to have a beam path therebetween. As shown, the cross-sectional shape of the stack across the beam path may be square. By positioning the conductive bodies 61 on different sides of the stack of the electron optical assembly, the conductive bodies 61 can be arranged further apart from each other. By arranging the conductive bodies 61 apart from each other, the length of the creep path between the conductive bodies 61 can be extended. However, it is not essential that the two conductive bodies 61 be arranged so as to have a beam path therebetween. For example, as shown in FIG. 9, in one embodiment, all the electrical connectors 60 are arranged on the same side of the electron optical assembly. In another embodiment, as shown in FIG. 9 and described with reference to FIG. 9, for example, to address volume constraints and increase the creep length between two conductive bodies (or between the triple points of two conductive bodies), the electrical connectors are arranged on adjacent sides.

[0133]

[0143] As shown in FIGS. 9 and 10, in one embodiment, the electrical insulator 70 includes a casing 74. In one embodiment, the casing 74 includes a dielectric such as ceramic and / or glass (e.g., borosilicate glass). In one embodiment, potting 73 is provided to fill the gap between the casing 74 and the conductive body 61. The potting 73 may be provided after the conductive body 61 is positioned relative to the casing 74 of the electrical insulator 70. As shown in FIG. 9 or FIG. 10, in one embodiment, when viewed in plan view, the casing 74 substantially surrounds the stack of the electron optical assembly. In one embodiment, the potting fills the space between the casing and the stack. The potting may fill the gap between the stack and the individual conductive bodies 61.

[0134]

[0144] FIG. 9 shows two conductive bodies 61 on the same side of the electron optical assembly. The conductive bodies 61 are adjacent to each other. As shown in FIG. 9, in one embodiment, the casing 74 defines an intermediate recess between the conductive bodies 61. In an alternative embodiment, the recess is filled with the material forming the casing 74. The casing 74 may be thicker in this region. In another embodiment, the casing 74 bridges the intermediate recess, for example, in a straight line between two conductive bodies 61. The intermediate recess is filled with potting 73. In this case, for example, compared with the aforementioned example where the casing 74 is thicker, the potting material is thicker.

[0135]

[0145] For example, in the configuration shown in FIG. 10, the conductive body 61 on the right side of FIG. 10 is electrically connected to the plate 710 by the conductor 67. The conductive body 61 on the left side of FIG. 10 is electrically insulated from the plate 710 by the potting 73 of the electrical insulator 70. The conductive body 61 on the left side of FIG. 10 is electrically connected to another electro-optical element of the electro-optical assembly including the plate 710. As shown in FIG. 10 (and similarly FIG. 9), in one embodiment, the electrical insulator 70 extends between the conductive body 61 and one or more additional electro-optical elements configured to act on the electron beam. The electrical insulator 70 is configured to reduce the possibility of dielectric breakdown between the conductive body 61 and other electro-optical elements of the electro-optical assembly. In one embodiment, the electrical insulator 70 extends towards one or more additional electro-optical elements configured to act on the electron beam. In one embodiment, the electrical insulator 70 extends to one or more additional electro-optical elements. In addition or alternatively, there is an insulating element between the conductive body 61 and one or more additional electro-optical elements. The insulating element 70 may be between the conductive body 61 and one or more electro-optical elements of the stack.

[0136]

[0146] As shown in FIG. 10, in one embodiment, the conductive body 61 may define an electric field-free volume 62 having an axial direction (although in opposite directions) parallel to each other. However, this is not necessarily the case. In an alternative embodiment, a plurality of conductive bodies 61 are arranged such that their electric field-free volumes define different axial directions, such as an angled axial direction or a perpendicular axial direction. FIG. 11 is a schematic plan view of an electro-optical assembly. The electrical insulator 70 is not shown in FIG. 11. The shape of the electrical insulator 70 may be the same as that shown, for example, in FIG. 9 or FIG. 10. As shown in FIG. 11, a plurality of conductive bodies 632-634 are arranged such that their electric field-free volumes 62 define different axial directions. The axial direction with respect to the electrical connector 60 (electrically connected to the plate 710) on the right side of FIG. 11 may be perpendicular to the axial directions with respect to the other electrical connectors shown at the top and bottom of FIG. 11. The electrical connectors 60 may be spaced apart from each other. In addition to or instead of this, a plurality of conductive bodies 632-634 may be positioned adjacent to each other. For example, a plurality of conductive bodies 632-634 may be positioned adjacent to each other in a substantially common axial direction or in adjacent axial directions.

[0137]

[0147] As shown in FIG. 11, each conductive body 61 may be associated with virtual lines 622 to 624 between the center 617 to 619 of the conductive body and the center 715 of the aperture (or plurality of apertures 711) of the plate 710 of the electron optical element. In FIG. 11, there is a first virtual line 622 between the center 617 of the conductive body 632 shown at the top of FIG. 11 and the center 715 of the aperture (or plurality of apertures 711). There is a second virtual line 623 between the center 618 of the conductive body 633 on the right side of FIG. 11 and the center 715 of the aperture. There is a third virtual line 624 between the center 619 of the conductive body 634 shown at the bottom of FIG. 11 and the center 715 of the aperture. The center 715 of the aperture may be the center of the plate 710. The center of the plate 710 may correspond to the path of the beam grid, for example, the midpoint of the beam grid. Different conductive bodies 61 may each have centers 617 to 619 corresponding to the center of the field-free volume defined by the conductive body 61.

[0138]

[0148] In one embodiment, the conductive bodies 632 to 634 are arranged such that the minimum angle formed by any pair of the virtual lines 622 to 624 is at least 360° / 2N. N is the number of the conductive bodies 632 to 634. For example, in the configuration shown in FIG. 11, there are three conductive bodies 632 to 634. The conductive bodies 632 to 634 are arranged such that the minimum angle formed by any pair of the virtual lines 622 to 624 is at least 360° / (2×3)=360° / 6 = 60°. As shown in FIG. 11, the angle 625 between the first virtual line 622 and the second virtual line 623 is 90°, which is greater than 60°. The angle 626 between the second virtual line 623 and the third virtual line 624 is 90°, which is greater than 60°. The angle 627 between the third virtual line 624 and the first virtual line 622 is 180°, which is greater than 60°. In one embodiment, the conductive bodies are arranged such that the angles formed by adjacent pairs of the virtual lines are equal. The conductive body 61 may be circumferentially and evenly distributed around the center 715 of the aperture of the plate 710 of the electron optical element. For example, in the case of three conductive bodies, the angle between the virtual lines may be 120°. The conductive bodies 632 to 634 may be equidistant from each other, or as shown in the figure, two of the three conductive bodies 632, 634 may be equidistant from the third conductive body 633.

[0139]

[0149] As shown in FIG. 11, in one embodiment, the axial directions of the conductive bodies 632 to 634 are based on the outer surface of the electron optical assembly. In one embodiment, the outer surface is a side surface of the electron optical assembly in a direction transverse to the beam path. In one embodiment, the outer surface is perpendicular to the beam path. In one embodiment, the side surface of the electron optical assembly is linear. In one embodiment, the side surface of the electron optical assembly is rectangular, for example square. For example, in the configuration shown in FIG. 11, the stack has a substantially square shape with rounded corners. In one embodiment, the electrical connector 60 is positioned on different side surfaces of the stack.

[0140]

[0150] It is not essential for the stack to have a rectangular shape. For example, in one embodiment, the stack may be, for example, circular, elliptical, triangular, pentagonal, hexagonal, heptagonal, octagonal, or any other straight shape (e.g., rhombus). It should be noted that a circular stack is beneficial for uniform heat dissipation across the cross-section of the stack for thermal management reasons. For example, when five electrical connectors 60 are provided, the stack may have a pentagonal shape, and each electrical connector 60 is provided on a different side of the electro-optical assembly. In addition to or instead of this, when viewed in plan view, one or more sides of the electro-optical assembly may have a plurality of electrical connectors associated therewith. Electrical connectors may also be provided at the rounded corners of the stack. The shape of the stack may be regular or irregular, for example having sides of the same length or different lengths, or a shape in which two or more sides have the same length. The cross-sectional shape of the electro-optical assembly may be the same as the cross-sectional shape of the stack and thus may take any of the shapes of the stacks disclosed herein. However, it is not necessary for the cross-sectional shapes of the stack and the electro-optical assembly to be the same. This is because the cross-sectional shape of the electro-optical assembly includes the insulating material 70 and / or the casing, and for example, a conductive body that does not exist in the stack is incorporated into the shape of the cross-section of the electro-optical assembly, so it may have a cross-sectional shape different from that of the stack. Even when the cross-sectional shapes of the stack and the electro-optical assembly are different, the same range of various cross-sectional shapes available for the stack may also be available for the electro-optical assembly.

[0141]

[0151] As described above, in one embodiment, the surface covered by the electrical insulator 70 may face away from the electro-optical element. For example, as shown in FIG. 7, in one embodiment, the surface 612 covered by the electrical insulator 70 faces away from the electro-optical element in a direction parallel to the beam path. In the orientation of FIG. 7, the beam path extends in the vertical direction (or the direction from the up beam to the down beam). The upper part of the electrical insulator 70 is directly above the conductive body 61 and is, for example, in contact with the conductive body 61, and the electrical insulator 70 covers the uppermost surface of the conductive body 61.

[0142]

[0152] In addition to or instead of this, in one embodiment, the surface covered by the electrical insulator 70 faces away from the electron optical element in a direction transverse to the beam path, desirably in a direction perpendicular to the beam path. For example, as shown in FIG. 7 or FIG. 8, in one embodiment, the end face 613 of the conductive body 61 that faces away from the electron optical element is covered by the insulating member 72 of the electrical insulator 70. In addition to or instead of this, in one embodiment, the electrical insulator 70 covers the inward-facing surface 614 of the conductive body 621, i.e., the surface facing the electron optical element.

[0143]

[0153] Further, two or more electrical connectors of the electro-optical assembly may be positioned at different positions relative to the stack in a direction parallel to the beam path, and / or two or more electrical connectors may be positioned at substantially the same position in a direction parallel to the beam path.

[0144]

[0154] This specification discloses various embodiments and various arrangements with respect to the various relative positionings of the individual electrical connectors 60 (and conductive bodies 61) relative to the stack, and the positionings of the stack and the various electrical connectors 60 (and associated conductive bodies 61) relative to each other, but the various variations can be combined in any reasonable manner.

[0145]

[0155] In one embodiment, the electro - optical assembly 700 includes one or more electro - optical elements, which are elements that may be referred to as micro - electro - mechanical components (such components may or may not include moving features or movable features), or elements that may be fabricated using techniques (e.g., "MEMS" technology) suitable for fabricating micro - electro - mechanical components designed to have an electro - optical function. The electro - optical assembly 700, or at least components of the electro - optical assembly 700, may be manufactured by such techniques. The electro - optical assembly 700 may include one or more elements that can be regarded as MEMS elements. One or more of such elements may be controlled to be set to a high potential difference with respect to a reference potential (e.g., ground) during use. Such elements may require accurate positioning (e.g., alignment) within the electro - optical assembly 700, for example, with respect to the path of a beam grid and with respect to other electro - optical elements within the device, for example, with respect to a radiation source, with respect to the sample and / or with respect to the path of the beam grid. One embodiment of the present invention is expected to enable more accurate positioning (e.g., alignment) of such elements within a stack of such electro - optical assemblies 700 during operation, such as without distortion of the electro - optical assembly 700, for example, due to externally applied forces or moments. In addition to or instead of this, one embodiment of the present invention may enable more accurate positioning (e.g., alignment) of such elements with respect to other elements within the device 40, and thus of a stack of electro - optical assemblies 700 including such elements within the device 40.

[0146]

[0156] As described above, in one embodiment, the electro - optical assembly 700 is an electro - optical lens assembly. The electro - optical lens assembly may include an objective lens assembly. The electro - optical lens assembly may be an objective lens assembly. In an alternative embodiment, the electro - optical lens assembly is an electro - optical condenser lens assembly.

[0147]

[0157] In one embodiment, the electron optical assembly 700 includes a collimator. For example, in one embodiment, the electron optical assembly 700 includes a magnetic collimator in combination with an electrostatic condenser lens array. The electron optical assembly 700 may include a single aperture lens array having one or two macroelectrodes disposed away from the virtual source conjugate plane.

[0148]

[0158] In an alternative embodiment, the electron optical assembly 700 includes a magnetic macro lens in combination with an electrostatic slit deflector. The magnetic macro lens may be for collimation. As a further alternative, in one embodiment, the electron optical assembly 700 includes a combination of a magnetic macro lens, an electrostatic macro lens, and a down beam slit deflector.

[0149]

[0159] Generally, the electron optical assembly 700 may include any plate such as a detector array plate, a lens electrode plate (wherein multiple deflectors may be integrated), a plurality of deflector arrays, a beam aperture array (e.g., an upper beam aperture array and / or a final beam limiting array), a deflector array (e.g., a strip deflector array), and other types of corrector elements.

[0150]

[0160] The embodiments described herein have mainly focused on the multi-beam electron optical device 40. The present invention is similarly applicable to a single-beam electron optical device 40.

[0151]

[0161] Although the present invention has been described in connection with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. For example, as described above, in one embodiment, the electro - optical assembly 700 includes the electrical connector 60. However, the electrical connector 60 of the present invention can be used anywhere within the electro - optical device 40 where there may be a problem that electrical breakdown can occur. In one embodiment, the electro - optical device 40 includes the electrical connector 60 separately from the electro - optical assembly 700. For example, the electrical connector 60 may be placed in a location where a weak - force electrical connection with other parts of the electro - optical device 40, such as the body or frame of the electro - optical device 40, is desirable. The electrical connector 60 may be placed in a location where the electrical connection does not particularly need to be a weak force. The electrical connector 60 can make the electro - optical device 40 more compact while providing an electric - field - free volume. This specification and the examples are intended to be regarded as merely illustrative, and the true scope and spirit of the present invention are indicated by the following claims.

[0152]

[0162] The above description is intended to be illustrative and not restrictive. Thus, it will be apparent to those skilled in the art that modifications can be made as described without departing from the scope and provisions of the claims set forth below.

[0153]

[0163] Clause 1. A charged particle optical assembly configured to direct a charged particle beam along a beam path towards a sample position, the charged particle optical assembly comprising a planar charged particle optical element configured to act on a charged particle beam traveling along the beam path towards the sample position, the planar charged particle optical element comprising an aperture for the beam path, and a conductive body electrically connected to the charged particle optical element, wherein a recess is defined within the conductive body and the conductive body is configured to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling. The conductive body is spaced apart from the planar charged particle optical element and comprises an electrical insulator providing at least a part of the surface of the conductive body.

[0154]

[0164] Clause 2. The charged particle optical assembly according to clause 1, wherein an end face of the conductive body includes at least a part of the surface of the conductive body, and an opening to the electric field-free volume is defined in the end face.

[0155]

[0165] Clause 3. The charged particle optical assembly according to clause 2, wherein the electrical insulator comprises an insulating member as an end face.

[0156]

[0166] Clause 4. The insulating member comprises an insulating plug, the insulating plug includes the end face of the conductive body, optionally extends through the opening, provides at least a part of the surface of the recess, and preferably extends into the electric field-free volume. The charged particle optical assembly according to clause 3.

[0157]

[0167] Clause 5. The electrical insulator extends from the end face into the electric field-free volume, preferably provides a part of the inner surface of the conductive body, preferably a part of the inner surface remote from the charged particle optical element, and preferably the inner surface defines the electric field-free volume. The charged particle optical assembly according to any one of clauses 2 to 4.

[0158]

[0168] Clause 6. At least a part of the electrical insulator surrounds a cross-section of the conductive body. The charged particle optical assembly according to any one of the preceding clauses.

[0159]

[0169] Clause 7. The charged particle optical assembly according to any one of the preceding clauses, comprising a plurality of conductive bodies electrically connected to one or more charged particle optical elements of the charged particle optical assembly.

[0160]

[0170] Clause 8. The charged particle optical assembly according to clause 7, wherein the electrical insulator includes at least a part of a surface common to the plurality of conductive bodies, and / or the electrical insulator is common to the plurality of conductive bodies.

[0161]

[0171] Clause 9. The charged particle optical assembly according to clause 8, wherein the electrical insulator further includes a continuous volume between the plurality of conductive bodies, and preferably provides a surface common to the plurality of conductive bodies.

[0162]

[0172] Clause 10. The charged particle optical assembly according to any one of clauses 7 to 9, wherein two of the conductive bodies are arranged so as to have a beam path therebetween.

[0163]

[0173] Clause 11. The charged particle optical assembly according to any one of clauses 7 to 10, wherein the plurality of conductive bodies are arranged so as to define axial directions with different field-free volumes.

[0164]

[0174] Clause 12. The charged particle optical assembly according to any one of clauses 7 to 11, wherein the plurality of conductive bodies are preferably positioned adjacent to each other having substantially common or adjacent axial directions.

[0165]

[0175] Clause 13. Each of the conductive bodies is associated with a virtual line between the center of the conductive body and the centers of the plurality of apertures, and the conductive bodies are arranged such that the minimum angle between any pair of virtual lines is at least 360° / 2N, where N is the number of conductive bodies. Desirably, the axial direction is based on the outer surface of the charged particle optical assembly. Desirably, the outer surface is the side surface of the charged particle optical assembly in a direction that crosses the beam path, desirably perpendicular to the beam path. Desirably, the side surface has a linear shape, such as a rectangle, such as a square. The charged particle optical assembly according to any one of Clauses 7 to 12.

[0166]

[0176] Clause 14. The conductive body includes a conductive element, the surface of the recess includes the surface of the conductive element, the electrical insulator of the conductive body is thicker than the conductive element, and desirably, the conductive element is inside the electrical insulator. The conductive element may include a conductive layer on the electrical insulator, for example. The charged particle optical assembly according to any one of the preceding clauses.

[0167]

[0177] Clause 15. The electrical insulator of the conductive body extends towards one or more further charged particle optical elements configured to act on the charged particle beam, desirably extends to one or more further charged particle optical elements, and / or there is an insulating element between the conductive body and one or more further charged particle optical elements. The charged particle optical assembly according to any one of the preceding clauses.

[0168]

[0178] Clause 16. The surface of the electrical insulator faces away from the charged particle optical element in a direction parallel to the path of the charged particle beam. The charged particle optical assembly according to any one of the preceding clauses.

[0169]

[0179] Clause 17. The surface of the electrical insulator faces away from the charged particle optical element in a direction crossing the path of the charged particle beam. The charged particle optical assembly according to any one of the preceding clauses.

[0170]

[0180] Clause 18. The charged particle beam comprises a plurality of beams along the beam path. Desirably, the charged particle optical element comprises a plurality of apertures, each aperture being individual with respect to each beam of the plurality of beams, the charged particle optical assembly according to any one of the preceding clauses.

[0171]

[0181] Clause 19. A charged particle optical assembly configured to direct a plurality of charged particle beams along a beam path towards a sample position, the planar charged particle optical element being configured to act on the charged particle beam travelling along the beam path towards the sample position, the planar charged particle optical element comprising an aperture for the beam path, and a conductive body electrically connected to the charged particle optical element, the conductive body having a recess defined therein and configured to provide an electric field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling, the charged particle optical assembly comprising an electrical insulator covering at least a part of the surface of the conductive body, the surface facing away from the charged particle optical element.

[0172]

[0182] Clause 20. The charged particle optical assembly according to clause 19, wherein the electrical insulator covers an end face of the conductive body, and an opening to the electric field-free volume is defined in the end face.

[0173]

[0183] Clause 21. The charged particle optical assembly according to clause 20, wherein the electrical insulator comprises an insulating member covering the end face of the conductive body at the end face.

[0174]

[0184] Clause 22. The charged particle optical assembly according to clause 21, wherein the insulating member is an insulating plug engaged with the end face of the conductive body.

[0175]

[0185] Clause 23. Desirably, in addition to covering the end face, the electrical insulator extends into the electric field-free volume and covers a part of the inner surface of the conductive body, the inner surface defining the electric field-free volume, the charged particle optical assembly according to any one of clauses 20 to 22.

[0176]

[0186] Clause 24. At least a part of the electrical insulator surrounds a cross-section of the conductive body, and is the charged particle optical assembly according to any one of Clauses 19 to 23.

[0177]

[0187] Clause 25. The charged particle optical assembly according to any one of Clauses 19 to 24, comprising a plurality of conductive bodies electrically connected to one or more charged particle optical elements of the charged particle optical assembly.

[0178]

[0188] Clause 26. The charged particle optical assembly according to Clause 25, wherein the electrical insulator covers at least a part of the surface of the plurality of conductive bodies.

[0179]

[0189] Clause 27. The charged particle optical assembly according to Clause 26, wherein the electrical insulator includes a continuous volume between the surfaces of the conductive bodies covered by the electrical insulator.

[0180]

[0190] Clause 28. The charged particle optical assembly according to any one of Clauses 25 to 27, wherein two of the conductive bodies are arranged so as to have a beam path therebetween.

[0181]

[0191] Clause 29. The charged particle optical assembly according to any one of Clauses 25 to 28, wherein the plurality of conductive bodies are arranged so as to define axial directions with different field-free volumes.

[0182]

[0192] Clause 30. The charged particle optical assembly according to any one of Clauses 25 to 29, wherein the plurality of conductive bodies are preferably positioned adjacent to each other having substantially the same axial direction or adjacent axial directions.

[0183]

[0193] Clause 31. Each of the conductive bodies is associated with a virtual line between the center of the conductive body and the center of the aperture, and the conductive bodies are arranged such that the minimum angle between any pair of virtual lines is at least 360° / 2N (where N is the number of conductive bodies).

[0184]

[0194] Clause 32. The electrical insulator is, for example, thicker than the conductive body in a direction away from the axial direction of the field-free volume, and the electrical insulator covers the surface of the conductive body and is the charged particle optical assembly according to any one of Clauses 19 to 31.

[0185]

[0195] Clause 33. The electrical insulator is the charged particle optical assembly according to any one of Clauses 19 to 32, which extends between the conductive body and one or more further charged particle optical elements configured to act on the charged particle beam.

[0186]

[0196] Clause 34. The surface covered by the electrical insulator faces away from the charged particle optical element in a direction parallel to the beam path, and is the charged particle optical assembly according to any one of Clauses 19 to 33.

[0187]

[0197] Clause 35. The surface covered by the electrical insulator faces away from the charged particle optical element in a direction crossing the beam path, preferably the path of the charged particle beam, and is the charged particle optical assembly according to any one of Clauses 19 to 34.

[0188]

[0198] Clause 36. The field-free volume defines an axial direction spaced from the plane of the planar charged particle optical element, and is the charged particle optical assembly according to any one of the preceding clauses.

[0189]

[0199] Clause 37. The field-free volume defines an axial direction angled with respect to the plane of the planar charged particle optical element, for example angled so as to extend from the plane of the planar charged particle optical element, and is the charged particle optical assembly according to any one of the preceding clauses.

[0190]

[0200] Clause 38. The charged particle optical assembly according to any one of the preceding clauses comprises an insulating member configured to support and electrically insulate the charged particle optical element and to be positioned away from the beam path.

[0191]

[0201] Clause 39. A charged particle optical device for projecting a plurality of charged particle beams along respective beam paths towards a sample position, the charged particle optical device comprising one or more charged particle optical assemblies as described in any one of the preceding clauses.

[0192]

[0202] Clause 40. A charged particle optical apparatus comprising a charged particle optical assembly as described in any one of Clauses 1 to 38, or a charged particle optical device as described in Clause 39, and an operable stage configured to support a sample.

[0193]

[0203] Clause 41. A method of electrically insulating a conductive body of a charged particle optical assembly configured to direct a charged particle beam towards a sample position, the method comprising covering at least a portion of the surface of the conductive body with one or more electrical insulators, the surface facing away from a planar charged particle optical element to which the conductive body is electrically connected, the charged particle optical element being configured to act on the charged particle beam along a beam path and comprising an aperture for the beam path, a recess being defined within the conductive body and configured to provide an electric field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling.

[0194]

[0204] Clause 42. A method of electrically insulating a conductive body of a charged particle optical assembly configured to direct a charged particle beam along a beam path towards a sample position, the charged particle optical assembly comprising a planar charged particle optical element for acting on the charged particle beam, the method comprising having a conductive body having a conductive concave surface of a recess of the conductive body, the conductive body comprising an electrical insulator spaced apart from the planar charged particle optical element, the planar charged particle optical element being electrically connected to the conductive body, a recess being configured within the conductive body to provide an electric field-free volume for inserting a high-voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling between the conductive body and a high-voltage cable.

[0195]

[0205] Clause 43. A charged particle optical assembly configured to direct a plurality of charged particle beams along a beam path towards a sample position, the charged particle optical assembly comprising: a planar charged particle optical element configured to act on a charged particle beam traveling along the beam path towards the sample position with a voltage, the planar charged particle optical element comprising an aperture for the beam path; and a conductive body electrically connected to the charged particle optical element, the conductive body having a recess defined therein and configured to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power source via an electrical coupling, wherein the conductive body comprises an electrical insulator, and the electrical insulator comprises at least an end face of the conductive body and an extending surface extending from the end face into the recess.

Claims

1. A charged particle optical assembly configured to direct a charged particle beam along a beam path towards a sample position, A planar charged particle optical element configured to act on a charged particle beam traveling along the beam path towards the sample position, the planar charged particle optical element comprising an aperture for the beam path, A conductive body electrically connected to the charged particle optical element, a recess being defined within the conductive body and configured to provide an electric field-free volume for inserting a high voltage cable for electrically connecting the charged particle optical element to a power supply via an electrical coupling, and a conductive body, The conductive body comprises an electrical insulator spaced apart from the planar charged particle optical element and providing at least a part of the surface of the conductive body. Charged particle optical assembly.

2. The end face of the conductive body includes at least a part of the surface of the conductive body, and an opening to the electric field-free volume is defined in the end face. The charged particle optical assembly according to claim 1.

3. The electrical insulator comprises an insulating member as the end face. The charged particle optical assembly according to claim 2.

4. The insulating member comprises an insulating plug, the insulating plug includes the end face of the conductive body, optionally extends through the opening, provides at least a part of the surface of the recess, and desirably extends into the electric field-free volume. The charged particle optical assembly according to claim 3.

5. The electrical insulator extends from the end face into the electric field-free volume, desirably provides a part of the inner surface of the conductive body, desirably a part of the inner surface away from the charged particle optical element, and desirably the inner surface defines the electric field-free volume. The charged particle optical assembly according to any one of claims 2 to 4.

6. At least a part of the electrical insulator surrounds a cross section of the conductive body. The charged particle optical assembly according to any one of claims 1 to 5.

7. The charged particle optical assembly according to any one of claims 1 to 6, comprising a plurality of conductive bodies electrically connected to one or more charged particle optical elements of the charged particle optical assembly.

8. The electrical insulator includes at least a part of a surface common to the plurality of conductive bodies, and / or the electrical insulator is common to the plurality of conductive bodies, the charged particle optical assembly according to claim 7.

9. The electrical insulator further includes a continuous volume between the plurality of conductive bodies, and preferably provides the surface common to the plurality of conductive bodies, the charged particle optical assembly according to claim 8.

10. a. Two of the conductive bodies are arranged so as to have the beam path therebetween. b. The plurality of conductive bodies are arranged so as to define axial directions with different field-free volumes thereof, and c. The plurality of conductive bodies are preferably positioned adjacent to each other having substantially common axial directions or proximate axial directions, The charged particle optical assembly according to any one of claims 7 to 9 including at least one of the above.

11. The conductive body includes a conductive element, the surface of the recess includes the surface of the conductive element, the electrical insulator of the conductive body is thicker than the conductive element, and preferably the conductive element is inside the electrical insulator, and the conductive element may include a conductive layer on the electrical insulator, for example, the charged particle optical assembly according to any one of claims 1 to 10.

12. The electrical insulator of the conductive body extends towards one or more further charged particle optical elements configured to act on the charged particle beam, preferably extends to the one or more further charged particle optical elements, and / or there is an insulating element between the conductive body and the one or more further charged particle optical elements, the charged particle optical assembly according to any one of claims 1 to 11.

13. The surface of the electrical insulator faces away from the charged particle optical element in a direction parallel to the path of the charged particle beam, the charged particle optical assembly according to any one of claims 1 to 12.

14. The surface of the electrical insulator faces away from the charged particle optical element in a direction transverse to the path of the charged particle beam, the charged particle optical assembly according to any one of claims 1 to 13.

15. The charged particle beam includes a plurality of beams along the beam path, and preferably, the charged particle optical element includes a plurality of apertures, and each beam of the plurality of beams is provided with an individual aperture, the charged particle optical assembly according to any one of claims 1 to 14.

Images