Insulating spacer for an electro-optical assembly

Abstract

The charged particle optical assembly manipulates one or more charged particle beams. The assembly includes an up-beam element, a down-beam element, and an insulating spacer. The up-beam element and the down-beam element each include a plate having one or more apertures around a beam path of one or more charged particle beams. The spacer is for electrically insulating the up-beam element and the element from each other. The spacer defines a spacer aperture around a beam path of one or more charged particle beams. The spacer includes an up-beam portion adjacent to the up-beam element, a down-beam portion adjacent to the down-beam element, and an intermediate portion between the up-beam portion and the down-beam portion. Since the up-beam portion and the down-beam portion protrude with respect to the intermediate portion, the spacer aperture has an increased dimension in the intermediate portion compared to the up-beam portion and the down-beam portion.

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims the priority of European Application No. 22184444.2 filed on July 12, 2022, which is hereby incorporated by reference in its entirety.

[0002]

[0002] Embodiments provided herein generally relate to an insulating spacer, a charged particle optical assembly, a charged particle optical device, a charged particle optical apparatus, a method of electrically insulating an up - beam charged particle optical element and a down - beam charged particle optical element from each other, a method of controlling a charged particle optical assembly, a method of fabricating an insulating spacer, and a method of fabricating a charged particle optical assembly.

Background Art

[0003]

[0003] When manufacturing a semiconductor integrated circuit (IC) chip, unwanted pattern defects can 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 in chemical mechanical polishing, etc. 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 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 device) 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 device. 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 device has a single beam and may be called a single beam SEM. Attempts have been made to introduce multi-electron beam inspection into a device (or "multi-beam tool") that may be called a multi-beam SEM (MBSEM).

[0006]

[0006] Another use of an electron optical device (or column) is in 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 electron 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). The floating electromagnetic field can undesirably deflect the direction of the beam.

[0008]

[0008] In some electron optical devices, the electrostatic field is typically generated between two electrodes. It is necessary to apply a high voltage to those electrodes. Electron creep and / or discharge may undesirably occur between the electrodes.

Summary of the Invention

[0009]

[0009] The present invention provides an architecture suitable for applying a desired high voltage while reducing the risk of electron creep and / or discharge.

[0010]

[0010] According to a first aspect of the present invention, there is provided an insulating spacer for a charged particle optical assembly for manipulating one or more charged particle beams between an up-beam charged particle optical element and a down-beam charged particle optical element that can be controlled to have opposite polarities with respect to each other. This insulating spacer is configured to electrically insulate the up-beam charged particle optical element and the down-beam charged particle optical element from each other. Inside the insulating spacer, a spacer aperture is defined around the beam path of one or more charged particle beams. The insulating spacer includes an up-beam portion configured to be adjacent to the up-beam charged particle optical element, a down-beam portion configured to be adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion. The up-beam portion and the down-beam portion protrude with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in the direction crossing the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion.

[0011]

[0011] According to a second aspect of the present invention, there is provided a charged particle optical assembly configured to manipulate one or more charged particle beams, the charged particle optical assembly comprising an up-beam charged particle optical element and a down-beam charged particle optical element each comprising a plate having one or more apertures around a beam path of the one or more charged particle beams, and an insulating spacer configured to electrically insulate the up-beam charged particle optical element from the down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams, the insulating spacer including an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0012] According to a third aspect of the present invention, there is provided a method for electrically insulating an up-beam charged particle optical element and a down-beam charged particle optical element from each other in a charged particle optical assembly configured to manipulate one or more charged particle beams. The method includes providing an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around a beam path of the one or more charged particle beams, and electrically insulating the up-beam charged particle optical element and the down-beam charged particle optical element from each other using an insulating spacer. The insulating spacer defines a spacer aperture around the beam path of the one or more charged particle beams. The insulating spacer includes an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion. The up-beam portion and the down-beam portion protrude with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion.

[0013] According to a fourth aspect of the present invention, there is provided a method for controlling a charged particle optical assembly to manipulate one or more charged particle beams, the method comprising applying a potential difference between an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around a beam path of the one or more charged particle beams; changing the potential difference such that the direction of the electric field between the up-beam charged particle optical element and the down-beam charged particle optical element is reversed; and optionally using a controller to control the potential differences applied to the up-beam charged particle optical element and the down-beam charged particle optical element, an insulating spacer electrically insulating the up-beam charged particle optical element and the down-beam charged particle optical element from each other, the insulating spacer defining spacer apertures around the beam path of the one or more charged particle beams, the insulating spacer including an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer apertures have an increased dimension in a direction crossing the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion.

[0014] According to a fifth aspect of the present invention, there is provided a method for fabricating an insulating spacer for a charged particle optical assembly configured to manipulate one or more charged particle beams, the insulating spacer being configured to electrically insulate an up-beam charged particle optical element and a down-beam charged particle optical element from each other, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams, the method comprising shaping two or more planar parts of a dielectric to have an aperture for the path of the one or more charged particle beams, different apertures having an inner rim, and fixing the two or more planar parts together to form the insulating spacer, whereby the insulating spacer has an inner surface including the inner rims of the two or more planar parts, whereby the insulating spacer comprises an up-beam portion for fixing to the up-beam charged particle optical element, a down-beam portion for fixing to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0015]

[0015] According to a sixth aspect of the present invention, there is provided a method for fabricating a charged particle optical assembly configured to manipulate one or more charged particle beams, the method comprising providing an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around a beam path of the one or more charged particle beams, and fixing the up-beam charged particle optical element and the down-beam charged particle optical element on both sides of an insulating spacer configured to electrically insulate the up-beam charged particle optical element from the down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams, wherein the insulating spacer includes an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, and the up-beam portion and the down-beam portion protrude with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0016]

[0016] The advantages of the present invention will become apparent by reading the following description in conjunction with the accompanying drawings in which specific embodiments of the invention are illustrated and shown by way of example.

[0017]

[0017] 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

[0018]

Figure 1

[0018] It is a schematic diagram showing an exemplary electron beam inspection apparatus.

Figure 2

[0019] It is a schematic diagram showing an exemplary multi-beam electron optical device which is a part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 3

[0020] Schematic diagram of an exemplary electron optical device including a collimator element array and a scanning deflector array, which is part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 4

[0021] Schematic diagram of an exemplary electron optical device array including the electron optical device of FIG. 3.

Figure 5

[0022] Schematic diagram of an alternative exemplary electron optical device that is part of the exemplary electron beam inspection apparatus of FIG. 1.

Figure 6

[0023] Schematic diagram of an exemplary electron optical assembly that can be part of the electron optical devices of FIGS. 3, 4, and 5.

Figure 7

[0024] Schematic diagram of an exemplary electron optical assembly that may be part of the electron optical devices of FIGS. 3, 4, and 5.

Figure 8

[0025] Enlarged view of a part of the exemplary electron optical assembly.

Figure 9

[0026] Enlarged view of a part of the exemplary electron optical assembly.

Figure 10

[0027] Schematic diagram of an exemplary electron optical assembly that may be part of the electron optical devices of FIGS. 3, 4, and 5.

Figure 11

[0028] Schematic diagram of an insulating spacer of the exemplary electron optical assembly.

Figure 12

[0029] Schematic diagram of an insulating spacer of the exemplary electron optical assembly.

Figure 13

[0030] Schematic diagram of an insulating spacer of the exemplary electron optical assembly.

Mode for Carrying Out the Invention

[0019]

[0031] Here, exemplary embodiments will be referred to in detail, and examples thereof 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 apparatuses and methods that are consistent with aspects related to the present invention, as described in the appended claims.

[0020]

[0032] 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, which enables 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%.

[0021]

[0033] 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.

[0022]

[0034] 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 more focused beams of primary electrons. The primary electrons interact with the target to generate interaction products, such as signal particles including 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. To achieve a higher throughput, such as for 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.

[0023]

[0035] In a multi-beam inspection apparatus, the paths of some of the primary electron beams are offset 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 having 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 foci of each sub-beam path to different focal planes. In particular, for sub-beam paths not on the central axis, the change in the focal plane of the sub-beam becomes larger with 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. Thus, such aberrations degrade the quality of the resulting image generated during the inspection.

[0024]

[0036] An implementation of a known multi-beam inspection apparatus will be described below.

[0025]

[0037] 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 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. Thus, 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 limited to electrons.

[0026]

[0038] Refer to FIG. 1 here. FIG. 1 is a schematic diagram showing an exemplary electron beam evaluation apparatus or inspection apparatus 100. The inspection apparatus 100 in 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 inside the vacuum chamber 10. The electron optical apparatus may include an electron optical device 40 (also known as an electron optical device or an electron beam device) and an electric or actuated stage.

[0027]

[0039] 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 (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") in a front-opening unified pod (FOUP). One or more robot arms (not shown) within the EFEM 30 carry the target to the load lock chamber 20.

[0028]

[0040] 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 the operation of 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 may include either a single-beam or multi-beam electron optical apparatus.

[0029]

[0041] 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 may 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 can also be applied to other devices and other arrangements of devices operating under a second pressure.

[0030]

[0042] Now, refer to FIG. 2. FIG. 2 is a schematic diagram of a multi-beam electron optical device 40 of an exemplary evaluation apparatus such as the inspection apparatus 100 of FIG. 1. In an alternative embodiment, the inspection apparatus 100 is a single-beam evaluation apparatus. 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 presub-beam forming aperture array), a condenser lens 310, a source converter (or 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 apparatus may have the same features as a multi-beam evaluation apparatus, except that the electron optical components having the array apertures 372 and 320 may have a single aperture. The 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 attendant 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 source converter 320 (also known as a 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.

[0031]

[0043] The electron source 201, the beam former array 372, the condenser lens 310, the 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) 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.

[0032]

[0044] 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 electrons at the edge 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 the 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.

[0033]

[0045] 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.

[0034]

[0046] As shown in FIG. 2, in one embodiment, the electro - 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, in which case the number of sub - beams may be equal to the number of beamlets projected toward the target 308.

[0035]

[0047] As shown in FIG. 2, in one embodiment, the electro - optical device 40 includes a pre - bending deflector array 323 having pre - bending deflectors 323_1, 323_2, and 323_3 that bend the 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 311, 312, and 313 onto the beam - limiting aperture array 321.

[0036]

[0048] The electron optical device 40 may also include an image forming element array 322 having image forming 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, and 393 on the target 308. The electron 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 a 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 aberration, which is clearly distinguishable at the probe spots 391, 392, and 393. The aberration compensator array 324 may include an astigmatism compensator array (not shown) with microastigmatism correctors. The microastigmatism correctors may be controlled to act on the sub-beams so as to compensate for astigmatism that would otherwise be present at the probe spots 391, 392, and 393.

[0037]

[0049] The radiation source converter 320 may further include a pre-bending deflector array 323 having pre-bending deflectors 323_1, 323_2, and 323_3 that bend the 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 may, for example, focus (collimate) the three sub-beams 311, 312, and 313 into a beam that is substantially parallel along the primary electron optical axis 304, such that the three sub-beams 311, 312, and 313 are incident on the radiation source converter 320 substantially perpendicularly, 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.

[0038]

[0050] The imaging 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 achieved by an existing magnetic lens such as a condenser lens configuration.

[0039]

[0051] In the current example of the electron optical device 40, the beamlets are each deflected towards 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.

[0040]

[0052] The objective lens 331 focuses the beamlets onto the surface of the target 308, i.e., projects three virtual images onto the target surface. The three images formed by the three sub-beams 311 - 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 - 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 - 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.

[0041]

[0053] 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 either 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.

[0042]

[0054] 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 disposed between a plurality of shield sections (described in more detail below) 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 due to the 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 due to 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 linearly with at least substantially zero deflection angle. The direction of the magnetic force depends on the direction of electron movement, while the direction of the electrostatic force does not depend on the direction of electron movement. 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 secondary electrons and backscattered electrons (or signal particles) no longer cancels out the electrostatic force, and as a result, secondary electrons and backscattered electrons moving through the beam separator are deflected away from the electron optical axis 304.

[0043]

[0055] 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 (e.g., 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.

[0044]

[0056] 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 use secondary electrons or backscattered electrons (or signal particles) to register and generate an image of the target 308.

[0045]

[0057] 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 having 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 of 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.

[0046]

[0058] In one embodiment, the inspection apparatus 100 includes a single radiation source.

[0047]

[0059] Any element or set of elements within an electro-optical device can be replaceable or field-replaceable. One or more electro-optical components within the electro-optical device, particularly 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 electro-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.

[0048]

[0060] 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, in 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 onto 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, for example detection elements, corresponding to an array of beamlets in a multi-beam configuration. The detectors (or detection elements) within 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.

[0049]

[0061] Figure 3 is a schematic diagram of another design of an exemplary electro-optical device 40. The electro-optical device 40 may include an emission source 201 and one or more electro-optical assemblies. Alternatively, an electro-optical apparatus 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). A multi-beam that converges on the sample 208 is extracted from the beam provided by the emission source 201. The sub-beams may be extracted 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.

[0050]

[0062] 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 the formation of the sub-beams may be blocked (e.g., absorbed) by the upper beam limiter 252 so as not to interfere with the sub-beams of the down-beam. The upper beam limiter 252 may be referred to as a sub-beam defining aperture array.

[0051]

[0063] 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 the 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 wholly 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.

[0052]

[0064] 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 respective potential sources. The control lens array 250 can include an array of two or more (e.g., three) plate electrodes connected to respective potential sources. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are placed near each other and / or mechanically connected to each other and / or controlled together as a unit). The control lens array 250 is placed in the up beam of the objective lens array 241. The control lenses pre - focus the sub - beams (e.g., apply a focusing action to the sub - beams before the sub - beams reach the objective lens array 241). By pre - focusing, the divergence of the sub - beams can be reduced or the convergence rate of the sub - beams can be increased.

[0053]

[0065] 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, 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-beam. 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 an additional degree of freedom for the objective lens, for example. The control lens array 241 may not be distinguishable from the objective lens array 250 and may be part of it, but in this specification, the control lens array 250 is distinguished from the objective lens array 241 and considered a separate entity.

[0054]

[0066] 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, in the context of charged particle mechanisms such as those considered in this specification, it should be understood that 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.

[0055]

[0067] 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 in one or two directions (i.e., one-dimensionally or two-dimensionally) across the entire sample 208. 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 to or equal to that of the scanning deflector array.

[0056]

[0068] 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 the plate electrode arrays 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 within a plate coincides with the position of a corresponding aperture (or apertures) within 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.

[0057]

[0069] 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 regarded as forming 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 outgoing beam. Advantageously, the potential difference of such a two-electrode lens array enables it to function as either an accelerating or decelerating lens array.

[0058]

[0070] The objective lens array can 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.

[0059]

[0071] 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 241, 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 portions of the sub-beams passing through the central portions of the respective apertures within the objective lens array reach the sample. The central portion may have a circular cross-section and / or may be centered on the beam axis of the sub-beam.

[0060]

[0072] 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, and at this 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.

[0061]

[0073] A power supply may 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.

[0062]

[0074] 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 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 provides 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). Therefore, 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.

[0063]

[0075] In one embodiment, the landing energy can be controlled to a desired value within a predetermined range, for example, 1000 eV to 5000 eV. The landing energy is preferably varied 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. Further, 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 change 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, the magnification can be controlled using one of those electrodes, and the landing energy can be individually controlled using another electrode. 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.

[0064]

[0076] 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 (e.g., emitted) and / or backscattered electrons from the sample 208. The detector can be an array providing 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 signal generated by the detection of electrons by the elements of the array is sent to a processor to generate an image. The signal can correspond to the pixels of the image.

[0065]

[0077] In other embodiments, both a macro scanning deflector and a scanning deflector array 260 may 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.

[0066]

[0078] 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 focuses each respective multi-beam simultaneously onto different regions of the same sample. Each electron optical device may form a plurality of sub-beams from one charged particle beam from a different respective radiation source 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.

[0067]

[0079] 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 from 9, up 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 in 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 with respect to a single electron optical device, for example, with respect to the embodiments illustrated and described with particular reference to FIGS. 5 or 6 as above. 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.

[0068]

[0080] In the example of FIG. 4, the array 500 includes a plurality of electron optical devices of the type described above with reference to FIG. 3. Thus, each electron 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 electron optical device array 500 due to their spatial compactness, which facilitates placing the electron optical devices close to each other. This configuration of the electron optical devices may be preferred over other configurations that use magnetic lenses as collimators. Incorporating magnetic lenses into electron 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.

[0069]

[0081] In an alternative design of a multi-beam electron optical device, there may be the same features as described with respect to FIG. 3, but the points described below and illustrated in FIG. 5 are different. An alternative design of a multi-beam electron 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 February 21, 2020, which application is incorporated herein by reference with respect to the description of a multi-beam device having a collimator and its 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.

[0070]

[0082] 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 may be at the intermediate focus instead of being associated with the objective lens array assembly 241.

[0071]

[0083] 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 may be associated with, for example, the condenser lens array, the intermediate focus, and the objective lens array assembly and be present in the multi-beam path. The detector 240 may be incorporated within the objective lens 241. The detector 240 may be on the bottom surface of the objective lens 241 so as to face the sample during use.

[0072]

[0084] In an embodiment of the configuration described with reference to FIG. 5 shown in this figure, the detector may be disposed at substantially the same location within the electron optical device 40 described with reference to the electron optical device shown in FIG. 3. The detector 240 may be incorporated into the objective lens array 241 and the control lens array 250 (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 250 may be included within an integrated assembly, which may be 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 including the objective lens 241. The detector 240 may be provided with an electrical connector 60 as described elsewhere in this specification. In a variant form, the detector has a detector array disposed in the up-beam of the objective lens array (and optionally, the control lens array 250), 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.

[0073]

[0085] 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. Further alternative designs of the multi-beam device include a plurality of single-beam devices. The single beam generated for the purposes of the 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 apparatus may be arranged in an array of 3, 4, 9, 19, 50, 100, or even 200 devices, where each device generates 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.

[0074]

[0086] The electron optical device 40 may be a component of an inspection (or metrology inspection) apparatus or part of an electron beam lithography apparatus. 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.

[0075]

[0087] 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 mentioned, 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., along the electron optical axis 304) between the collimation (e.g., the location of the collimator array 271 corresponding to the plane of the intermediate focus as shown in FIG. 5 or the location of the upper beam limiter 252) and the surface of the sample 208.

[0076]

[0088] The electron optical device 40 may include an electron optical assembly 700 as shown in FIG. 6 or FIG. 7 to manipulate electron beamlets. For example, the electron optical assembly 700 may include one or more of (as a non-limiting list) an objective lens array 241, and / or a condenser lens array 231, 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 include the electron optical assembly 700.

[0077]

[0089] 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.

[0078]

[0090] As shown in FIG. 7, in one embodiment, at least one of the plurality of plates has a stepped thickness such that the array plate is thinner in a region corresponding to the array of apertures than in another region 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. When the plate bends, it may 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 array of apertures, 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 array of apertures. That is, the array of apertures 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 deformation of the beamlets. In one embodiment, the plate has a uniform thickness including the region corresponding to the array of apertures.

[0079]

[0091] The exemplary electron optical assembly shown in FIG. 6 includes an up-beam plate 710 of an up-beam electron optical element, a down-beam plate 720 of a down-beam electron optical element, and an insulating spacer 60. In the up-beam plate 710, at least one aperture 711 (optionally, an array of apertures 711 as shown in FIG. 7) is defined with respect to the path of an electron beamlet. The up-beam plate 710 may be referred to as an array plate (note, however, that in one embodiment, the up-beam plate 710 has a single aperture 711). The down-beam plate 720 may be referred to as an adjacent plate. The number of apertures in the up-beam plate 710 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 aperture may extend across the multi-beam path. The aperture may be a strip or a slit. In another 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 spacer 60 is disposed between the plates to separate them. The electron optical assembly 700 is configured to provide a potential difference between the up-beam plate 710 and the down-beam plate 720. In one embodiment, the up-beam plate 710 includes a radially inner portion 712. The radially inner portion 712 is adjacent to a spacer aperture 70 defined by the insulating spacer 60, as will be described in more detail below.

[0080]

[0092] In the down-beam plate 720, another aperture 721 (or an array of apertures 721 as shown in FIG. 7) is defined with respect to the path of the electron beamlets. As shown in FIG. 7, in one embodiment, the down-beam plate 720 may also have a stepped thickness such that adjacent plates are thinner in a region corresponding to the array of apertures than another region of the down-beam plate. (Alternatively, the down-beam plate 720 is substantially planar and / or has a uniform thickness). The array of apertures 721 defined within the down-beam plate 720 preferably has the same pattern as the array of apertures 711 defined within the up-beam plate 710. In one configuration, the patterns of apertures in these two plates may be different. For example, the number of apertures in the down-beam plate 720 may be less than or greater than the number of apertures in the up-beam plate 710. As shown in FIG. 6, in one configuration, there is a single aperture within the down-beam plate for all paths of the sub-beams of the multi-beam. The apertures in the up-beam plate 710 and the down-beam plate 720 are preferably substantially well-aligned with each other. This alignment between the apertures is to limit lens aberration.

[0081]

[0093] The up-beam plate and the down-beam 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 down-beam plate (i.e., the plate closer to the sample) may have a thickness between 100 μm and 300 μm at the thickest part. The down-beam plate preferably has a thickness between 200 μm and 150 μm at the thickest part. The up-beam plate (i.e., the plate farther from the sample) may have a thickness of up to 500 μm at the thickest part.

[0082]

[0094] For example, the surface of the up-beam plate between the thinner region of the plate 710 that provides a step and another region of the plate, such as a thicker region of the plate, is preferably orthogonal to the surface of the plate facing the down-beam plate 720 and / or the path of the multi-beam. Similarly, the surface of the down-beam plate 720 at the location of the step between the thicker region (radially outer) and the inner region (radially inner) can preferably be orthogonal to the surface of the down-beam plate facing the up-beam plate 710.

[0083]

[0095] A coating may be applied on the surface of the up-beam plate and / or the down-beam plate. The coating is preferably applied on both the up-beam plate and the down-beam plate. Surface charging that may cause undesirable beam distortion in the absence of the coating is reduced by the coating.

[0084]

[0096] The coating is configured to withstand the dielectric breakdown phenomenon that may occur between the array plate and the adjacent plate. It is preferable to apply a low-resistance coating, and it is more preferable to apply a coating with a resistance of 1 ohm / square or less. The coating is preferably applied on the surface of the down-beam plate. The coating is more preferably applied between at least one of these plates and an insulator. The low-resistance coating reduces the undesirable surface charging of the plate.

[0085]

[0097] The up-beam plate and / or the down-beam 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. The up-beam plate and / or the down-beam plate more preferably includes doped silicon. The plate having a low bulk resistance has the advantage of having a low probability of failure because the discharge current is supplied / discharged through the bulk rather than, for example, through a thin coating layer.

[0086]

[0098] The up-beam plate includes a first wafer. The first wafer may be etched to produce regions of different thicknesses. The first wafer may be etched in a 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 produce 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 produced by laser drilling or machining.

[0087]

[0099] 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 spacer. The second wafer may be disposed on the surface of the first wafer in a region that does not correspond 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.

[0088]

[0100] One of the up-beam plate and the down-beam plate is negatively charged with respect to the other plate. In one embodiment, in one operating mode, the up-beam plate has a higher potential than the down-beam plate, for example, with reference to the ground potential, the radiation source, or the sample. In one embodiment, in another operating mode, the up-beam plate has a lower 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 up-beam plate and the down-beam plate. The potential difference is preferably 10 kV or more. The potential difference is more preferably 20 kV or more.

[0089]

[0101] The insulating spacer 60 is preferably disposed between the up-beam plate and the down-beam plate such that the opposing surfaces of these plates are in the same plane. The insulating spacer 60 has an inner surface 61 facing the path of the beamlet. The insulating spacer 60 defines a spacer aperture 70 for the path of the electron beamlet.

[0090]

[0102] A conductive coating may be applied to the insulating spacer 60. It is preferable to apply a low-resistance coating, and more preferably to apply a coating of 0.5 ohm / square or less.

[0091]

[0103] Preferably, the coating is on the surface of the space facing the negatively charged plate, which is negatively charged with respect to the other plates. The coating may be placed at the same potential as one of the plates. Preferably, the coating is on the surface of the insulating spacer 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 spacer and the negatively charged plate.

[0092]

[0104] If there is no such coating on the insulating spacer, electric field enhancement may occur in such gaps. This electric field enhancement may lead to electrical breakdown in those gaps, thereby causing the potential of the negatively charged plate, such as the lower electrode, to become unstable. However, in one embodiment, the upper electrode may be negatively charged, and thus the same type of coating may be applied to the surface between the upper electrode and the insulating spacer. Due to this potential instability, the intensity of the lens changes over time, thereby causing a focus shift of the electron beam.

[0093]

[0105] In one embodiment, the inner surface 61 is shaped such that the creep path between the plates across the inner surface is longer than the minimum distance between the plates, for example, the minimum distance above the inner surface of the spacer between two different plates. Preferably, the inner surface 61 of the insulating spacer 60 is shaped to provide a creep length of 10 kV / mm or less, preferably 3 kV / mm or less.

[0094]

[0106] The exemplary electro - optical assembly 700 of FIG. 6 includes an insulating spacer 60 that defines a spacer aperture 70. In one embodiment, the insulating spacer 60 has a stepped shape. The insulating spacer 60 is configured to electrically insulate an up - beam electro - optical element from a down - beam electro - optical element. In one embodiment, the insulating spacer 60 is configured to support two electro - optical elements. The insulating spacer 60 defines a spacer aperture 70 around the beam path of one or more electron beams. The spacer aperture 70 is a through - hole for the path of an electron beam (optionally a multi - beam) from the up - beam side of the insulating spacer 60 to the down - beam side of the insulating spacer 60.

[0095]

[0107] As shown in FIG. 6 or FIG. 7, for example, in one embodiment, the insulating spacer 60 includes an up - beam portion 62, a down - beam portion 64, and an intermediate portion 63. The up - beam portion 62 is adjacent to the up - beam electro - optical element. The down - beam portion 64 is adjacent to the down - beam electro - optical element. The intermediate portion 63 is between the up - beam portion 62 and the down - beam portion 64. In one embodiment, the up - beam portion 62 and the down - beam portion 64 protrude with respect to the intermediate portion 63. The inward protrusion of the up - beam portion 62 and the down - beam portion 64 with respect to the intermediate portion 63 causes the spacer aperture 70 to have an increased dimension in the direction crossing the beam path in the intermediate portion 63 compared to the up - beam portion 62 and the down - beam portion 64. In one embodiment, the spacer aperture 70 has a larger diameter between the up - beam side and the down - beam side than on either the up - beam side or the down - beam side of the insulating spacer 60.

[0096]

[0108] As shown in FIG. 6, in one embodiment, the spacer aperture 70 has different dimensions at different positions along the direction of the electron beam. In one embodiment, the spacer aperture 70 has an up-beam dimension 72, a down-beam dimension 74, and an intermediate dimension 73. The intermediate dimension is at an intermediate position between the up-beam dimension 72 and the down-beam dimension 74. As shown in FIG. 6 or FIG. 7, for example, in one embodiment, the intermediate dimension 73 is larger than the up-beam dimension 72. In one embodiment, the intermediate dimension 73 is larger than the down-beam dimension 74. In one embodiment, the dimension may be a diameter. The dimension may also be referred to as a width. The dimension is generally in a direction transverse to the beam path and, optionally, orthogonal to the beam path.

[0097]

[0109] The insulating spacer 60 may be defined with a spacer aperture 70 or an opening that defines a through-passage having a surface. The through-passage may have at least three different diameters along the beam path passing through the spacer aperture 70. In one embodiment, for example, the stepped surface between portions of the through-passage having different diameters is angled and preferably parallel to at least one of the up-beam plate 710 and the down-beam plate 720 and / or orthogonal to the beam path.

[0098]

[0110] As shown in FIG. 6 or FIG. 7, for example, in one embodiment, the spacer aperture 70 defined within the insulating spacer 60 has a smaller dimension (or width) on the down-beam side of the insulating spacer 70 than in the intermediate portion 63 of the insulating spacer 60. In one embodiment, the spacer aperture 70 defined within the insulating spacer 60 has a smaller dimension on the up-beam side of the insulating spacer 60 than in the intermediate portion 63 of the insulating spacer 60.

[0099]

[0111] In one embodiment, one of the up beam plate 710 and the down beam plate 720 is positively charged with respect to the other plate. In one embodiment, the spacer aperture 70 (or spacer hole) facing the negatively charged plate has a smaller dimension than the opening (or hole) facing the positively charged plate. By defining that the spacer aperture 70 has a varying width in the direction between the up beam plate 710 and the down beam plate 720, the electron creep length across the inner surface 61 of the insulating spacer 60 may be increased. One embodiment of the present invention is expected to increase the electron creep length between the up beam plate 710 and the down beam plate 720.

[0100]

[0112] FIG. 8 is an enlarged view of a part of the electro - optical assembly 700 shown in, for example, FIG. 6 or FIG. 7. As shown in FIG. 8, the down beam triple point 78 is formed at the junction between the insulating spacer 60, the down beam plate 720, and the spacer aperture 70 (which may represent the junction with the vacuum). The up beam triple point 75 may be formed between the insulating spacer 60, the up beam plate 710, and the spacer aperture 70. Generally, the dielectric constant of the material of the insulating spacer 60 is expected to be different from that of the spacer aperture 70 (in one embodiment, vacuum). By shaping the insulating spacer 60 such that the spacer aperture 70 facing the negatively charged plate has a smaller dimension than the intermediate portion 63, the electric field near the triple point adjacent to the negatively charged plate may be reduced.

[0101]

[0113] For example, when the down beam plate 720 is a negatively charged plate, the electric field at or near the down beam triple point 78 may be reduced. When the up beam plate 710 is a negatively charged plate, the electric field at or near the up beam triple point 75 may be reduced. By reducing the electric field near the triple point, the possibility of discharge between the up beam plate 710 and the down beam plate 720 is reduced. One embodiment of the present invention is expected to reduce the possibility of dielectric breakdown that causes undesirable discharge.

[0102]

[0114] FIG. 9 is an enlarged view of a part of the electron optical assembly 700 shown in FIG. 6 or FIG. 7, for example. FIG. 9 shows the simulation results indicating the decrease in the electric field strength near the down beam triple point 78 illustrated in FIG. 8 and described with reference to this figure. In the example shown in FIG. 9, the down beam plate 720 is a negatively charged plate. The wavy line across this figure (between the down beam plate 720 and the upper part of this figure) is a line of constant potential. As shown in FIG. 9, the local electric field near the down beam triple point 78 is reduced compared to other parts of the surface of the insulating spacer 60. The possibility of dielectric breakdown is reduced. In particular, generally, it is sometimes expected that discharge or electron creep starts at or near such a triple point. By reducing the electric field near such a triple point, the possibility of discharge and / or electron creep may be reduced. This result is different from the similar design of the spacer whose diameter changes in at least three parts along the beam path. In such a design, the middle part of the spacer has a beam path aperture with a smaller diameter than the up beam part and the down beam part. The creep length between the up beam plate and the down beam plate of the spacer, that is, the creep length across the inner surface of the spacer aperture, can be made longer than the minimum distance, but such a configuration undesirably increases or concentrates the local electric field near the down beam triple point 78 between the spacer and one of the adjacent plates, for example, the down beam plate, and the beam aperture (i.e., vacuum), causing a risk of dielectric breakdown.

[0103]

[0115] As described elsewhere, in one embodiment, the insulating spacer 60 is shaped such that the spacer aperture 70 facing both the up-beam plate 710 and the down-beam plate 720 is smaller in dimension than the intermediate portion 63 of the insulating spacer 60. Thereby, regardless of whether the up-beam plate 710 or the down-beam plate 720 is the negatively charged plate, the possibility of electron creep and / or dielectric breakdown can be reduced. The insulating spacer 60 can reduce the possibility of electron creep and / or dielectric breakdown in both possible directions (polarities) of the electric field. In the case of an electric field with reversed polarity, the insulating spacer 60 can maintain its performance, i.e., maintain the dielectric breakdown potential. It is possible to reduce or prevent the enhancement of the electric field near the negatively charged plate. The negatively charged plate generally serves as a source of electrons when electron creep and / or dielectric breakdown occur. Therefore, the present invention is an improvement over known designs to meet the desired performance use.

[0104]

[0116] One embodiment of the present invention is expected to be able to reverse the electric field between two adjacent electrodes such as the up-beam plate 710 and the down-beam plate 720 without unduly increasing the possibility of electron creep and / or dielectric breakdown. For example, it may be desirable to reverse the direction / plural states of the electric field in order to widen the range of possible potentials that can be applied to different electrodes within the electron optical assembly 700. The electron optical assembly 700 may be, for example, an objective lens and / or a control lens, or may include them. By widening the range of potentials that can be applied to different electrodes, the electron optical assembly 700 can support a wider range of landing energies. The landing energy is the energy of an electron when it reaches the sample position. One embodiment of the present invention is expected to support the retention of the electric field in both directions. Embodiments of the present invention are desirably and beneficially, such as when using the present invention in an evaluation apparatus having one embodiment of the charged particle device disclosed herein, for charged particle evaluation applications, an improved operating parameter range, and a desirably improved opportunity can be provided.

[0105]

[0117] As shown in FIG. 6 or FIG. 7, for example, in one embodiment, the insulating spacer 60 is shaped such that the spacer aperture 70 has substantially the same dimensions in the direction crossing the beam path in the up-beam portion 62 and the down-beam portion 64. In one embodiment, the spacer aperture 70 has the same dimensions in the up-beam portion 62 and the down-beam portion 64. However, it is not essential that the dimensions of the spacer aperture 70 be the same at the up-beam and down-beam portions 62, 64 (or the up-beam end and the down-beam end). In one embodiment, the insulating spacer 60 is shaped such that the spacer aperture 70 has a larger dimension in the direction crossing the beam path in the up-beam portion 62 than in the down-beam portion 64. Alternatively, the spacer aperture 70 may have smaller dimensions in the up-beam portion 62 and the down-beam portion 64.

[0106]

[0118] In one embodiment, the insulating spacer 60 is shaped to be symmetric about a plane transverse to the beam path. This plane may pass through the intermediate portion 63. The insulating spacer 60 may have a specularly reflective shape. The up-beam half of the insulating spacer 60 may be a reflective counterpart of the down-beam half of the insulating spacer 60. The insulating spacer 60 may be opposed with respect to the direction of the electric field between the up-beam plate 710 and the down-beam plate 720. The electric field may be applied in any direction between the up-beam plate 710 and the down-beam plate 720 having the insulating spacer 60 therebetween. One embodiment of the present invention is expected to be able to equally reduce the possibility of electron creep and / or dielectric breakdown regardless of the direction of the electric field.

[0107]

[0119] In one embodiment, the electron optical assembly 700 includes a voltage source electrically connected to at least one of the electron optical elements. In one embodiment, the controller 50 is configured to control the potential difference applied by the voltage source between the electron optical elements. The controller 50 may control the voltage source to apply different voltages to the up-beam plate 710 and the down-beam plate 720. The controller 50 may control the voltage source to control how the electron beam is manipulated by the electron optical assembly 700.

[0108]

[0120] In one embodiment, when a potential difference is applied between electron optical elements, the insulating spacer 60 is shaped such that the potential becomes a position extremum at the protruding corners 76, 77 of the up-beam portion 62 and / or the down-beam portion 64, which are locations where the dimensions of the spacer aperture 70 change. As shown in FIG. 8, in one embodiment, the insulating spacer 60 includes the protruding corner 76 of the up-beam portion 62 and the protruding corner 77 of the down-beam portion 64. As shown in FIG. 8, in one embodiment, the dimensions of the spacer aperture 70 change at the protruding corners 76, 77. The dimensions may change stepwise (e.g., the diameter of the spacer aperture 70 at the protruding corners 76, 77). The protruding corner 76 of the up-beam portion 62 is at the transition between the up-beam portion 62 and the intermediate portion 63. The protruding corner 77 of the down-beam portion 64 is at the transition between the intermediate portion 63 and the down-beam portion 64.

[0109]

[0121] In the configuration shown in FIG. 9, the down-beam plate 720 is a negatively charged plate. The insulating spacer 60 may be shaped such that the potential difference at the protruding corner 77 (i.e., with respect to the selected relative potential of the charged particle device 40 such as ground) becomes a local maximum (i.e., with respect to the rest of the spacer). This means that the potential decreases from the protruding corner 77 towards the down-beam triple point 78. The potential decreases along the step on the surface of the down-beam portion in the direction across the beam path from the protruding corner 77. (Note that if this scenario is applied by making the up-beam plate 710 a negatively charged plate, the relative potential will be the same with respect to the up-beam portion 62 and the protruding corner 76. Further, if this scenario has one of the positively charged plates 720, 710, the described relative potential characteristics will be opposite to those of the described scenario.) By defining that the protruding corners 76, 77 are at extreme values, the possibility of electron creep through the protruding corners 76, 77 may be reduced. The protruding corners 76, 77 may form electron traps. Electrons may be effectively trapped at the protruding corners 76, 77 and do not have enough energy to creep in either direction along the interface (shown horizontally in the figure) between the intermediate portion 63 of the insulating spacer 60 and the up-beam portion 62 or the down-beam portion 64.

[0110]

[0122] As shown in FIGS. 6 to 9, in one embodiment, the insulating spacer 60 is shaped such that there is a stepwise change in the dimensions of the spacer aperture 70 in a direction transverse to the beam path between the intermediate portion 63 and the up-beam portion 62 and / or the down-beam portion 64. A stepwise change means that there is a sudden (i.e., discontinuous) change in the value of the dimension of the spacer aperture 70. By providing a stepwise change, the possibility of electron creep between the intermediate portion 63 and the up-beam portion 62 and / or the down-beam portion 64 may be reduced. In one embodiment, the protruding corners 76, 77 are sharp corners. However, it is not essential that the protruding corners 76, 77 be sharp. In an alternative embodiment, the protruding corners 76, 77 may be rounded. The radius of curvature of the corner, and thus the radius of the rounding of the corner, is desirably limited so as to achieve the advantages described herein for the protruding corners 76, 77.

[0111]

[0123] In one embodiment, the insulating spacer 60 is shaped such that the difference in the dimensions of the spacer aperture 70 in the direction transverse to the beam path in the intermediate portion 63 compared to the up-beam portion 62 and / or the down-beam portion 64 is at least 10%, optionally at least 20%, optionally at least 50%, optionally at least 100%, optionally at least 200%, optionally at least 500%, optionally at least 1000% of the thickness 80 of the insulating spacer 60.

[0112]

[0124] The thickness 80 of the insulating spacer 60 may be as shown in FIG. 8. The difference in the dimensions of the spacer aperture 70 in the direction transverse to the beam path in the intermediate portion 63 compared to the up-beam portion 62 and the down-beam portion 64 may be as shown in FIG. 8. In particular, this difference in dimensions corresponds to twice the width 84, 85 of the steps of the up-beam portion 62 and the down-beam portion 64, respectively. In one embodiment, the width of these steps is of the same order as the thickness of the insulating spacer 60. By providing a sufficiently wide step, the creep length is significantly increased due to the shape of the inner surface 61 of the insulating spacer 60.

[0113]

[0125] In one embodiment, the thickness 82 of the intermediate portion 63 is substantially the same as the thickness 81 of the up-beam portion 62 and / or the thickness 83 of the down-beam portion 64. The thickness of the intermediate portion 63 may be greater than or less than the thickness 81 of the up-beam portion 62 and / or the thickness 83 of the down-beam portion 64.

[0114]

[0126] In one embodiment, the thickness 80 of the insulating spacer 60 is at least 0.2 mm, optionally at least 0.5 mm, optionally at least 1 mm, optionally at least 2 mm, and optionally at least 3 mm. In one embodiment, the thickness 80 of the insulating spacer 60 is at most 20 mm, optionally at most 10 mm, optionally at most 5 mm, and optionally at most 3 mm.

[0115]

[0127] In one embodiment, the width 84 of the step of the up-beam portion 62 and / or the width 85 of the step of the down-beam portion 64 is at least 0.5 mm, optionally at least 1 mm, optionally at least 2 mm, optionally at least 5 mm, optionally at least 10 mm, and optionally at least 20 mm. In one embodiment, the width 84 of the step of the up-beam portion 62 and / or the width 85 of the step of the down-beam portion 64 is at most 20 mm, optionally at most 10 mm, optionally at most 5 mm, and optionally at most 2 mm.

[0116]

[0128] In one embodiment, the thickness 81 of the up-beam portion 62 and / or the thickness 83 of the down-beam portion 64 is at least 0.2 mm, optionally at least 0.5 mm, and optionally at least 1 mm. In one embodiment, the thickness 81 of the up-beam portion 62 and / or the thickness 83 of the down-beam portion 64 is at most 5 mm, optionally at most 2 mm, and optionally at most 1 mm.

[0117]

[0129] In one embodiment, the thickness 82 of the intermediate portion 63 is at least 0.2 mm, optionally at least 0.5 mm, and optionally at least 1 mm. In one embodiment, the thickness 82 of the intermediate portion 63 is at most 5 mm, optionally at most 2 mm, and optionally at most 1 mm.

[0118]

[0130] In one embodiment, the thickness 82 of the intermediate portion 63 is at least 10%, optionally at least 20%, optionally at least 50%, and optionally at least 80% of the total thickness of the up-beam portion 62, the intermediate portion 63, and the down-beam portion 64. In one embodiment, the thickness 82 of the intermediate portion 63 is at most 90%, optionally at most 80%, optionally at most 50%, and optionally at most 20% of the total thickness of the up-beam portion 62, the intermediate portion 63, and the down-beam portion 64.

[0119]

[0131] In one embodiment, the intermediate portion 63 is centered in the vertical direction (i.e., the thickness of the up-beam portion 62 may be the same as the thickness of the down-beam portion 64). Alternatively, the thickness of the up-beam portion 62 may be different from the thickness of the down-beam portion 64.

[0120]

[0132] As described above, in one embodiment, the electro - optical assembly 700 is an electro - optical lens assembly. For example, the electro - optical lens assembly may include an objective lens assembly or may be an objective lens assembly. Alternatively, the electro - optical lens assembly may include a condenser lens assembly. However, it is not essential that the electro - optical assembly 700 is or includes an electro - optical lens assembly. In addition to or instead of this, the electro - optical assembly 700 may include, for example, as individual arrays, one or more elements of a collimator, correctors such as individual beam correctors, a detector array, a deflector, and / or a Wien filter array. Generally, any two adjacent electrodes (for example, plates set at different potentials) within the electro - optical system may be electrically insulated from each other by an insulating spacer 60 according to one embodiment of the present invention. The electro - optical assembly 700 may be a macro - component that operates on a single beam (which may be split into multiple beams as a down - beam) passing through a large aperture within the electro - optical assembly 700, as shown in FIG. 6 for example. Alternatively, the electro - optical assembly 700 may include an array of apertures and may be configured to operate on multiple electron beams passing through the apertures, as shown in FIG. 7 for example.

[0121]

[0133] As shown in FIG. 10, in one embodiment, the electro - optical assembly 700 includes at least four electro - optical elements each including plates 710, 720, 730, 740. (The illustrated configuration can be considered as a configuration where, among five electro - optical elements, the fifth element may be a detector 240 as disclosed herein.) Each plate 710, 720, 730, 740 has one or more apertures around the beam path of one or more electron beams. The configuration shown in FIG. 10 shows four length plates 710, 720, 730, 740, and the detector plate of the detector 240. These plates may be electrically insulated from each other. As shown in FIG. 10, the above - mentioned insulating spacer 60 electrically insulates the up - beam plate 710 from the down - beam plate 720. This up - beam plate and down - beam plate are arranged between the most up - beam electro - optical element (including the most up - beam plate 730) and the most down - beam electro - optical element (including the most down - beam plate 740) among at least four electro - optical elements. As shown in FIG. 10, in one embodiment, one or more plates may be arranged in the down - beam of the most down - beam electro - optical element among at least four electro - optical elements. For example, the detector plate forming the detector 240 may be arranged in the down - beam of the most down - beam plate 740 of the lens elements. In one embodiment, the detector 240 is set to a potential different from that of the adjacent electro - optical element 740 along the path of the charged - particle beam, as disclosed herein.

[0122]

[0134] In one embodiment, the potential applied to the plate 740 of the lens element that is the most down-beam is controlled to have a fixed potential with respect to the sample 208. In a certain operation mode of the electron optical device 40 including the electron optical assembly 700, the potential (or voltage) applied to the plate 740 that is the most down-beam may be maintained substantially constant. In one embodiment, the voltage (or potential) applied to the plate 750 that is the most up-beam may be controlled to be fixed with respect to the radiation source 201 of the electron optical device 40. When controlling the voltage (potential) to control the landing energy, the electric field within the electron optical assembly 700 may change. When the electric field changes, the focus of the electron beam at the sample position may undesirably change. In one embodiment, the controller 50 is configured to control the voltage (potential) applied to the up-beam plate 710 and / or the down-beam plate 720 to compensate for the change in focus caused by the change in the electric field. The present invention enables changing a plurality of electric fields between the up-beam plate 710 and the down-beam plate 720 without unduly increasing the risk of dielectric breakdown and / or electron creep. In one embodiment, the detector 240 may be regarded as a further electron optical element, because the detector 240 may be set to a potential different from that of the adjacent electron optical element 740 along the path of the charged particle beam. Alternatively, the detector is set to the same potential as the adjacent electron optical element.

[0123]

[0135] As shown in FIG. 10, the other plates of the electro - optical assembly 700 may be separated by different types of insulating spacers 750, 760, 770. Some of these spacers 750, 760, 770 may be structurally stepped. Others may have a uniform cross - section. As shown in FIG. 10, in one embodiment, the detector 240 may be attached to one of the spacers 770 by a connecting element 79. The connecting element 79 may be an electrical insulator with an aperture that may have the surface topography of any other insulator disclosed herein, such as in one embodiment of the present invention. As shown, this insulator has a uniform diameter along the path of the charged particle beam. The detector may have an electrical connection separate from the adjacent electro - optical element 740 along the path of the charged particle beam (e.g., multi - beam).

[0124]

[0136] In one embodiment, the outer dimension of the spacer in the direction transverse to the beam path may be larger than the outer dimension of the plate of the electro - optical element. Alternatively, the outer dimension of the spacer in the direction transverse to the beam path may be substantially the same as the outer dimension of the plate of the electro - optical element.

[0125]

[0137] In one embodiment, the electro - optical assembly 700 includes one or more electro - optical elements including micro - electro - mechanical components. The electro - optical assembly 700 may be a module, such as an electro - optical module that may be called a MEMS module (e.g., from the perspective of the nature of one or more of the electro - optical components included within the module). In one embodiment, the electro - optical assembly 700 is exchangeable within the electro - optical device 40.

[0126]

[0138] In the configuration described herein, the objective lens (e.g., electron optical assembly 700) is a reduction lens. Such an objective lens is suitable for evaluation using signal particles that are secondary signal particles (e.g., secondary electrons from sample 208). For evaluation using signal particles that are backscattered signal particles (e.g., backscattered electrons from the sample), the charged particle beam is composed of high-energy charged particles. In such an evaluation, the objective lens is an acceleration objective lens. The detector facing the sample surface may have an applied potential that repels secondary signal particles. For example, the applied potential is set to the maximum energy of the secondary signal particles (e.g., 50 eV). Such an applied repulsive filter for signal particles towards the detector detects only backscattered signal particles. To optimize, desirably maximize, the acceleration of the charged particle beam, it is desirable to set the potential applied to the control lens to decelerate the charged particle beam, thereby causing a crossover or intermediate focus of the charged particle beam to exist inside the control lens. The potentials applied to the most up-beam electrode and the most down-beam objective lens may be optimized, desirably maximized, to desirably accelerate the charged particle beam towards the sample. Such a configuration, characterized by a control lens that decelerates with an intermediate focus, an objective lens that accelerates, and a repulsive bottom element of an electron optical device such as a detector array, is disclosed in U.S. Patent Application Serial No. 17 / 559,950, filed December 21, 2022, which is hereby incorporated by reference in its entirety for all purposes related to these enumerated features and others.

[0127]

[0139] Using one embodiment of the present invention, a configured charged particle device can be used such that it has an accelerating objective lens for evaluation using backscattered signal particles and is set to operate as a decelerating objective lens by switching the potential applied to the objective lens while reducing, if not preventing, the risk of dielectric breakdown without replacing the electron optical components in the charged particle device. The U.S. patent application with serial number 17 / 559,950 discloses a spacer that can operate in a bidirectional file and has a smaller diameter middle portion. Therefore, it was unexpected to the inventor that the spacer of the present invention with a larger diameter middle portion improved the performance of the bidirectional field.

[0128]

[0140] In one embodiment, the up-beam electron optical element and / or the down-beam electron optical element includes a semiconductor, such as silicon. In one embodiment, each electron optical element is provided with an electrical element configured to connect the electron optical element to a power source, such as a voltage supply source. A separate voltage supply source may be provided for each electron optical element. Alternatively, a plurality of electron optical elements may be connected to the same power source. In one embodiment, a plurality of power sources are provided for different portions of the same electron optical element.

[0129]

[0141] A voltage supply source configured to be electrically connected to an electron optical element. In one embodiment, the voltage supply source is configured to apply a potential to different electron optical elements including the up-beam electron optical element and the down-beam electron optical element.

[0130]

[0142] In one embodiment, the controller 50 is configured to control a voltage supply source. In one embodiment, the controller 50 is configured to control the supply of potential to the up-beam electron optical element and the down-beam electron optical element such that a plurality of electric fields between the electron optical elements are reversed (or inverted). Thereby, the controller 50 may be able to compensate for a change in the focus of the electron beam that may be caused by controlling the landing energy of the electron beam at the position of the sample.

[0131]

[0143] In one embodiment, the voltage supply source is a high-voltage power supply. In one embodiment, the voltage supply 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, and optionally at least 20kV, such as 25kV or even 30kV or more, to a part of the electron optical assembly 700 with reference to the reference potential of the electron optical device 40. In one embodiment, the voltage supply source is configured to apply a positive voltage with reference to the reference potential. In an alternative embodiment, the voltage supply source is configured to apply a negative voltage with reference to the reference potential. The reference potential may be ground. In one embodiment, one or more of the plates 710, 720 of the electron optical assembly 700 are configured to be connected to a high voltage during use of the electron optical device 40.

[0132]

[0144] In one embodiment, the electro - optical assembly 700 may be controlled to manipulate one or more electron beams. Such a method may include applying a potential difference between an up - beam electro - optical element and a down - beam electro - optical element. The potential difference may be varied such that the direction of the electric field between the up - beam electro - optical element and the down - beam electro - optical element is reversed. In one embodiment, the controller 50 is used to control the potential difference applied to the up - beam electro - optical element and the down - beam electro - optical element. The insulating spacer 60 electrically insulates the electro - optical element from the down - beam electro - optical element. The insulating spacer 60 defines a spacer aperture 70 around the beam path of one or more electron beams.

[0133]

[0145] As shown in FIG. 6 or FIG. 7, for example, in one embodiment, the insulating spacer 60 is a single dielectric component. The dielectric may include at least one of ceramic, glass, and quartz. The insulating spacer 60 may be formed as an integral component.

[0134]

[0146] Alternatively, as shown in FIG. 11, in one embodiment, the insulating spacer 60 includes two or more components 65, 66 of dielectric fixed together. The dielectric components 65, 66 may be fixed together. For example, one component 65 may be attached to the other component 66. In one embodiment, the components 65, 66 are joined together at a surface 67. In one embodiment, the components 65, 66 are glued together and / or adhered to each other.

[0135]

[0147] As shown in FIG. 11, in one embodiment, the dielectric parts 65, 66 have substantially the same thickness as each other. Thereby, it becomes possible to use plates of the same shape as the starting components for both dielectric parts 65, 66. Thereby, the number of different types of components required to manufacture the electro - optical assembly 700 can be reduced. One embodiment of the present invention is expected to provide an improved insulating spacer 60 without unduly increasing the manufacturing cost. In one embodiment, the dielectric parts 65, 66 are substantially the same in shape as each other. Thereby, it becomes possible to form the parts 65, 66 using the same process before fixing the parts 65, 66 together to form the insulating spacer 60. This may help reduce the manufacturing cost of the insulating spacer 60 by reducing the number of different processes required.

[0136]

[0148] It is not essential that the dielectric parts 65, 66 have the same thickness as each other or the same shape. As shown in FIG. 12, in one embodiment, the parts 65, 66 may have different thicknesses and / or different shapes compared to each other. As shown in FIG. 12, in one embodiment, at least one of the dielectric parts 66 has a uniform cross - section in a direction parallel to the beam path. The lower part 66 shown in FIG. 12 does not have a stepped structure. Instead, a uniform cross - section results in a flat plate. The lower dielectric part 66 may have a particularly simple shape, which may help reduce the manufacturing cost. On the other hand, the other part 65, for example, the upper part, may be formed to have a stepped structure before the parts 65, 66 are fixed together from the insulating spacer 60.

[0137]

[0149] As shown in FIG. 13, in one embodiment, at least three parts 65, 66, 68 of the dielectric are fixed together to form the insulating spacer 60. As shown in FIG. 13, in one embodiment, each of the dielectric parts 65, 66, 68 has a uniform cross-section in a direction parallel to the beam path. This makes it possible to form all of the dielectric parts 65, 66, 68 to have particularly simple shapes. There is no need to form a stepped shape on any single component that forms the insulating spacer 60. This may help to reduce the manufacturing cost of the insulating spacer 60. When the dielectric parts 65, 66, 68 are fixed together, the insulating spacer 60 is formed to have a stepped structure.

[0138]

[0150] As described above, one or more components that form the insulating spacer 60 may be processed to have a stepped structure. For example, in one embodiment, to form the stepped structure, a plate is crushed, machined, punched, and / or cut. In one embodiment, the component that forms the insulating spacer 60 may be shaped by laser ablation. In laser ablation, for example, there may be fewer particles generated during manufacturing, which may be desirable.

[0139]

[0151] In one embodiment, a method for fabricating the insulating spacer 60 as described above is provided. The insulating spacer 60 is for an electro - optical assembly 700 configured to manipulate one or more electron beams. In one embodiment, the method includes forming two or more planar parts 65, 66 of a dielectric so as to have an aperture 70 for the path of one or more electron beams. In one embodiment, the method may include fixing the two or more planar parts 65, 66 together to form the insulating spacer 60, whereby the insulating spacer 60 comes to have an inner surface 61 including the inner rims of the two or more planar parts 65, 66. As a result, the insulating spacer 60 includes an up - beam portion 62 for fixing to an up - beam electro - optical element, a down - beam portion 64 for fixing to a down - beam electro - optical element, and an intermediate portion 63 between the up - beam portion 62 and the down - beam portion 64. The up - beam portion 62 and the down - beam portion 64 protrude with respect to the intermediate portion 63 such that the spacer aperture 70 has an increased dimension in a direction crossing the beam path in the intermediate portion 63 as compared to the up - beam portion 62 and the down - beam portion 64.

[0140]

[0152] In one embodiment, a method for fabricating an electro - optical assembly 700 as described above is provided. In one embodiment, the method includes providing an up - beam electro - optical element and a down - beam electro - optical element each including a plate having one or more apertures around the beam path of one or more electron beams. In one embodiment, the method includes fixing (e.g., firmly attaching) the up - beam electro - optical element and the down - beam electro - optical element on both sides of a spacer 60 configured to electrically insulate the up - beam electro - optical element and the down - beam electro - optical element from each other. The insulating spacer 60 may be as described elsewhere in this specification.

[0141]

[0153] The electro - optical assembly 700 may include or be such a lens assembly for manipulating an electron beamlet. 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 include an additional lens array having at least two plates, such as the control lens array 250.

[0142]

[0154] In one embodiment, the electro - optical assembly 700 includes one or more electro - optical elements, which are elements that may be called 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 electro - optical functionality. The electro - optical assembly 700, or at least the 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 precise 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, a sample, and / or the path of the beam grid. One embodiment of the present invention is expected to enable more precise positioning (e.g., alignment) of such elements within a stack of such electro - optical assemblies 700 during operation, for example, without distortion of the electro - optical assembly 700, due to, for example, externally applied forces or moments. In addition to or instead of this, one embodiment of the present invention may enable more precise positioning (e.g., alignment) of such elements, and thus of a stack of electro - optical assemblies 700 including such elements within the device 40, with respect to other elements within the device 40.

[0143]

[0155] 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.

[0144]

[0156] In one embodiment, the electro - optical assembly 700 includes a collimator. For example, in one embodiment, the electro - optical assembly 700 includes a magnetic collimator in combination with an electrostatic condenser lens array. The electro - optical assembly 700 may include a single aperture lens array with one or two macro - electrodes disposed away from the virtual source conjugate plane.

[0145]

[0157] In an alternative embodiment, the electro - 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 electro - optical assembly 700 includes a combination of a magnetic macro - lens, an electrostatic macro - lens, and a down - beam slit deflector.

[0146]

[0158] Generally, the electro - optical assembly 700 may include any plate such as a plate of a detector array, a plate of lens electrodes (where 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.

[0147]

[0159] The embodiments described herein have mainly focused on the multi - beam electro - optical device 40. The present invention is equally applicable to a single - beam electro - optical device 40.

[0148]

[0160] A plurality of electro - optical devices may be included within an electro - optical device array. The electro - optical devices of the electro - optical device array are preferably configured to simultaneously focus their respective multi - beams on different regions of the same sample.

[0149]

[0161] Although the present invention has been described in connection with various embodiments, other embodiments of the present 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 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 desired. The electrical connector 60 may be placed 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 a zero - electric - field region. This specification and examples are intended to be regarded merely as examples, and the true scope and spirit of the present invention are indicated by the following claims.

[0150]

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

[0151]

[0163] The following clauses are provided.

[0152]

[0164] An insulating spacer for a charged particle optical assembly for manipulating one or more charged particle beams between an up-beam charged particle optical element and a down-beam charged particle optical element that are controllable to have polarities that are inverted with respect to each other, the insulating spacer being configured to electrically insulate the up-beam charged particle optical element and the down-beam charged particle optical element from each other, a spacer aperture being defined around the beam path of the one or more charged particle beams in the insulating spacer, the insulating spacer including an up-beam portion configured to be adjacent to the up-beam charged particle optical element, a down-beam portion configured to be adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion. The insulating spacer, wherein the spacer aperture has an increased dimension in a direction transverse to the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion, and the up-beam portion and the down-beam portion protrude with respect to the intermediate portion.

[0153]

[0165] A charged particle optical assembly configured to manipulate one or more charged particle beams, including an up-beam charged particle optical element and a down-beam charged particle optical element each including a plate having one or more apertures around the beam path of the one or more charged particle beams, and the insulating spacer according to clause 1, the up-beam charged particle optical element being configured to be adjacent to the up-beam portion and the down-beam charged particle optical element being configured to be adjacent to the down-beam portion.

[0154]

[0166] Clause 3. A charged particle optical assembly configured to manipulate one or more charged particle beams (or a plurality of charged particle beams), comprising an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around the beam path of one or more charged particle beams (the up-beam charged particle optical element and the down-beam charged particle optical element each comprising a plate with a plurality of apertures around one or more of the plurality of charged particle beams), and an insulating spacer configured to electrically insulate the up-beam charged particle optical element from the down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of one or more charged particle beams, wherein the insulating spacer includes an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0155]

[0167] Clause 4. The charged particle optical assembly according to clause 2 or 3, wherein the insulating spacer is shaped such that the spacer aperture has substantially the same dimension in a direction crossing the beam path in the up-beam portion and the down-beam portion.

[0156]

[0168] Clause 5. The charged particle optical assembly according to any one of clauses 2 to 4, wherein the insulating spacer is shaped to be symmetric about a plane crossing the beam path.

[0157]

[0169] Clause 6. The charged particle optical assembly according to clause 5, wherein the plane passes through the intermediate portion.

[0158]

[0170] Clause 7. The insulating spacer is shaped such that when a potential difference is applied between those charged particle optical elements, the potential at the protruding corners of the up-beam portion and / or the down-beam portion where the dimensions of the spacer aperture change becomes an extreme value. Optionally, the charged particle optical assembly includes a voltage source electrically connected to at least one of the charged particle optical elements, and a controller configured to control the potential difference applied by the voltage source between the charged particle optical elements. The charged particle optical assembly according to any one of Clauses 2 to 6.

[0159]

[0171] Clause 8. The insulating spacer is shaped such that there is a stepwise change in the dimensions of the spacer aperture in a direction crossing the beam path between the intermediate portion and the up-beam portion and / or the down-beam portion. The charged particle optical assembly according to any one of Clauses 2 to 7.

[0160]

[0172] Clause 9. The stepwise change in dimensions corresponds respectively to the protruding corners of the up-beam portion and / or the down-beam portion. The charged particle optical assembly according to Clause 8.

[0161]

[0173] Clause 10. The insulating spacer is shaped such that the difference in the dimensions of the spacer aperture in the direction crossing the beam path in the intermediate portion compared to the up-beam portion and / or the down-beam portion is at least 20%, optionally at least 50%, optionally at least 100%, optionally at least 200%, optionally at least 500% of the thickness of the insulating spacer. The charged particle optical assembly according to any one of Clauses 2 to 9.

[0162]

[0174] Clause 11. The insulating spacer is a single part of a dielectric. The charged particle optical assembly according to any one of Clauses 2 to 10.

[0163]

[0175] Clause 12. The insulating spacer includes two or more parts of a dielectric fixed together. The charged particle optical assembly according to any one of Clauses 2 to 10.

[0164]

[0176] Clause 13. The dielectric component is the charged particle optical assembly according to Clause 12, having substantially the same thickness as each other.

[0165]

[0177] Clause 14. The dielectric component is the charged particle optical assembly according to Clause 13, having substantially the same shape as each other.

[0166]

[0178] Clause 15. At least one of the dielectric components has a uniform cross-section in a direction parallel to the beam path, and is the charged particle optical assembly according to any one of Clauses 12 to 14.

[0167]

[0179] Clause 16. Each of the dielectric components has a uniform cross-section in a direction parallel to the beam path, and is the charged particle optical assembly according to Clause 15.

[0168]

[0180] Clause 17. The dielectric includes at least one of ceramic, glass, and quartz, and is the charged particle optical assembly according to any one of Clauses 11 to 16.

[0169]

[0181] Clause 18. The charged particle optical assembly is the charged particle optical assembly according to any one of Clauses 1 to 17, and is a charged particle optical lens assembly.

[0170]

[0182] Clause 19. The charged particle optical lens assembly includes an objective lens assembly, and is the charged particle optical assembly according to Clause 18.

[0171]

[0183] Clause 20. The charged particle optical lens assembly is an objective lens assembly, and is the charged particle optical assembly according to Clause 18.

[0172]

[0184] Clause 21. The objective lens assembly includes at least one of the objective lens and the control lens. Desirably, the charged particle lens assembly is the control lens. Desirably, the objective lens includes at least two charged particle optical elements each having a plate with one or more apertures around the beam path of one or more charged particle beams. Desirably, the control lens array includes at least three charged particle optical elements each having a plate with one or more apertures around the beam path of one or more charged particle beams. Desirably, the most up-beam charged particle optical element of the objective lens includes the most down-beam charged particle optical element of the control lens. The charged particle optical assembly according to Clause 19 or 20.

[0173]

[0185] Clause 22. The charged particle optical lens assembly includes a condenser lens assembly. The charged particle optical assembly according to Clause 18.

[0174]

[0186] Clause 23. The charged particle optical assembly includes a collimator. The charged particle optical assembly according to any one of Clauses 2 to 22.

[0175]

[0187] Clause 24. The charged particle optical assembly includes an individual beam corrector. The charged particle optical assembly according to any one of Clauses 2 to 23.

[0176]

[0188] Clause 25. The charged particle optical assembly includes a deflector. The charged particle optical assembly according to any one of Clauses 2 to 24.

[0177]

[0189] Clause 26. The charged particle optical assembly includes at least four charged particle optical elements each having a plate with one or more apertures around the beam path of one or more charged particle beams. The charged particle optical assembly according to any one of Clauses 2 to 25.

[0178]

[0190] Clause 27. The up-beam charged particle optical element and the down-beam charged particle optical element that are electrically insulated from each other by the insulating spacer are arranged between the most up-beam charged particle optical element and the most down-beam charged particle optical element among at least four of those charged particle optical elements, in the charged particle optical assembly according to Clause 26.

[0179]

[0191] Clause 28. The charged particle optical assembly according to any one of Clauses 2 to 27, comprising one or more charged particle optical elements including microelectromechanical components.

[0180]

[0192] Clause 29. The up-beam charged particle optical element and / or the down-beam charged particle optical element includes a semiconductor, such as silicon, in the charged particle optical assembly according to any one of Clauses 2 to 28.

[0181]

[0193] Clause 30. For each charged particle optical element, the charged particle optical assembly according to any one of Clauses 2 to 29 further includes an electrical connection configured to connect the charged particle optical element to a power source, such as a voltage supply source.

[0182]

[0194] Clause 31. A charged particle optical device for projecting a plurality of charged particle beams along respective beam paths toward a sample position, including the insulating spacer according to Clause 1 or the charged particle optical assembly according to any one of Clauses 2 to 30.

[0183]

[0195] Clause 32. The charged particle optical device according to Clause 31 further includes a voltage supply source configured to be electrically connected to the charged particle optical element and apply a potential, preferably, to different charged particle optical elements including the up-beam charged particle optical element and the down-beam charged particle optical element.

[0184]

[0196] Clause 33. A charged particle optical device according to clause 32, further comprising a controller configured to control a voltage supply, preferably a potential, applied to an up-beam charged particle optical element and a down-beam charged particle optical element such that the polarity of the electric field between those charged particle optical elements is reversed / inverted.

[0185]

[0197] Clause 34. A charged particle optical apparatus comprising the insulating spacer according to clause 1, a charged particle optical assembly according to any one of clauses 2 to 30, or a charged particle optical device according to any one of clauses 31 to 33, and an operable stage configured to support a sample.

[0186]

[0198] In a charged particle optical assembly configured to manipulate one or more charged particle beams, a method for electrically insulating an up-beam charged particle optical element and a down-beam charged particle optical element from each other, the method comprising providing an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around a beam path of the one or more charged particle beams, and electrically insulating the up-beam charged particle optical element and the down-beam charged particle optical element from each other using an insulating spacer, the insulating spacer defining a spacer aperture around a beam path of the one or more charged particle beams, the insulating spacer including an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion.

[0187]

[0199] A method for controlling a charged particle optical assembly to manipulate one or more charged particle beams, the method comprising: applying a potential difference between an up-beam charged particle optical element and a down-beam charged particle optical element, each having a plate with one or more apertures around a beam path of the one or more charged particle beams; changing the potential difference such that the direction of the electric field between the up-beam charged particle optical element and the down-beam charged particle optical element is reversed; and optionally using a controller to control the potential difference applied to the up-beam charged particle optical element and the down-beam charged particle optical element, wherein an insulating spacer electrically insulates the up-beam charged particle optical element and the down-beam charged particle optical element from each other, the insulating spacer defining a spacer aperture around a beam path of the one or more charged particle beams, the insulating spacer including an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0188]

[0200] A method for fabricating an insulating spacer for a charged particle optical assembly configured to manipulate one or more charged particle beams, the insulating spacer being configured to electrically insulate an up-beam charged particle optical element from a down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams, the method comprising shaping two or more planar parts of a dielectric to have an aperture for the path of the one or more charged particle beams, different apertures having an inner rim, and fixing together the two or more planar parts to form the insulating spacer, whereby the insulating spacer has an inner surface including the inner rims of the two or more planar parts, whereby the insulating spacer comprises an up-beam portion for fixing to the up-beam charged particle optical element, a down-beam portion for fixing to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, the up-beam portion and the down-beam portion protruding with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction transverse to the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion.

[0189]

[0201] Clause 38. The two or more parts of the dielectric have substantially the same thickness as each other, and preferably, shaping the two or more planar parts comprises shaping the two or more planar parts to have substantially the same thickness as each other, the method according to clause 37.

[0190]

[0202] Clause 39. At least one of the parts of the dielectric has a uniform cross-section in the direction of the beam path, preferably parallel to the beam path, and preferably, forming at least one of the planar parts comprises forming at least one planar part to have a uniform cross-section in the direction of the beam path, the method according to any one of clauses 37 or 38.

[0191]

[0203] Clause 40. Each component of the dielectric has a uniform cross-section in a direction parallel to the beam path. Desirably, forming a planar component includes forming the planar component to have a uniform cross-section in the direction of the beam path, the method according to clause 39.

[0192]

[0204] Clause 41. Forming a step on the inner rim of at least one of two or more planar components, the step having a thickness thinner than that of the planar component in the direction of the path of one or more charged particle beams, and fixing includes fixing two or more planar components such that the inner surface includes at least one inner rim with a step, and one step or each step is included in the inner surface between one of the up-beam portion and the down-beam portion and the intermediate portion, the method according to any one of clauses 37 to 40.

[0193]

[0205] Clause 42. The components of the dielectric have substantially the same shape as each other. Desirably, forming two or more planar components includes forming the two or more planar components to have substantially the same shape, the method according to clause 37, 38, or 41.

[0194]

[0206] Clause 43. A method for manufacturing a charged particle optical assembly configured to manipulate one or more charged particle beams, including providing an insulating spacer including a method for manufacturing the insulating spacer according to any one of clauses 37 to 42, providing an up-beam charged particle optical element and a down-beam charged particle optical element each including a plate having one or more apertures around the beam path of one or more charged particle beams, and fixing the up-beam charged particle optical element and the down-beam charged particle optical element on both sides of the insulating spacer.

[0195]

[0207] A method for fabricating a charged particle optical assembly configured to manipulate one or more charged particle beams, the method comprising: providing an up-beam charged particle optical element and a down-beam charged particle optical element each having a plate with one or more apertures around a beam path of the one or more charged particle beams; fixing the up-beam charged particle optical element and the down-beam charged particle optical element on both sides of an insulating spacer configured to electrically insulate the up-beam charged particle optical element from the down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams, wherein the insulating spacer includes an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion, and the up-beam portion and the down-beam portion protrude with respect to the intermediate portion, whereby the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion as compared to the up-beam portion and the down-beam portion.

[0196]

[0208] The method according to clause 44, including forming the insulating spacer from a single piece of dielectric, preferably, the dielectric includes at least one of ceramic, glass, and quartz.

[0197]

[0209] The method according to clause 44, including forming the insulating spacer by fixing two or more parts of the dielectric together.

[0198]

[0210] The method according to clause 46, wherein the parts of the dielectric have substantially the same thickness as each other.

[0199]

[0211] The method according to clause 47, wherein the parts of the dielectric have substantially the same shape as each other.

[0200]

[0212] Method according to any one of clauses 46 to 48, wherein at least one of the dielectric parts has a uniform cross-section in a direction parallel to the beam path.

[0201]

[0213] Method according to clause 49, wherein each of the dielectric parts has a uniform cross-section in a direction parallel to the beam path.

Claims

1. A charged particle optical assembly configured to manipulate a plurality of charged particle beams, an up-beam charged particle optical element and a down-beam charged particle optical element each comprising a plate having a plurality of apertures around one or some of the plurality of charged particle beams, the beam path including the plurality of charged particle beams, the up-beam charged particle optical element and the down-beam charged particle optical element; an insulating spacer configured to electrically insulate the up-beam charged particle optical element from the down-beam charged particle optical element, the insulating spacer defining a spacer aperture around the beam path of the one or more charged particle beams; the insulating spacer having an up-beam portion adjacent to the up-beam charged particle optical element, a down-beam portion adjacent to the down-beam charged particle optical element, and an intermediate portion between the up-beam portion and the down-beam portion; wherein the up-beam portion and the down-beam portion project with respect to the intermediate portion, such that the spacer aperture has an increased dimension in a direction crossing the beam path in the intermediate portion compared to the up-beam portion and the down-beam portion, the charged particle optical assembly.

2. The charged particle optical assembly according to claim 1, wherein the insulating spacer is shaped such that the spacer aperture has substantially the same dimension in the direction crossing the beam path in the up-beam portion and the down-beam portion.

3. The charged particle optical assembly according to any one of claims 1 or 2, wherein the insulating spacer is shaped symmetrically about a plane crossing the beam path.

4. The charged particle optical assembly according to claim 3, wherein the plane passes through the intermediate portion.

5. The charged particle optical assembly according to any one of claims 1 to 4, wherein the insulating spacer is shaped such that, when a potential difference is applied between the charged particle optical elements, the potential reaches an extreme value at a protruding corner of the up-beam portion and / or the down-beam portion, which is a location where the dimension of the spacer aperture changes.

6. The charged particle optical assembly comprises a voltage supply source electrically connected to at least one of the charged particle optical elements; A controller configured to control a potential difference applied by the voltage supply source between the charged particle optical elements; The charged particle optical assembly according to claim 5, having the above.

7. The charged particle optical assembly according to any one of claims 1 to 6, wherein the insulating spacer is shaped such that there is a stepwise change in the dimension of the spacer aperture in the direction crossing the beam path between the intermediate portion and the up-beam portion and / or the down-beam portion.

8. The charged particle optical assembly according to claim 7, wherein the stepwise change in dimension corresponds to the protruding corners of the up-beam portion and / or the down-beam portion, respectively.

9. The charged particle optical assembly according to any one of claims 1 to 8, wherein the insulating spacer is a single part of a dielectric.

10. The charged particle optical assembly according to any one of claims 1 to 9, wherein the insulating spacer includes two or more parts of the dielectric fixed together.

11. The charged particle optical assembly according to claim 10, wherein the dielectric parts have substantially the same thickness as each other, and preferably, the dielectric parts have substantially the same shape as each other.

12. The charged particle optical assembly according to claim 10 or 11, wherein at least one of the dielectric parts has a uniform cross-section in a direction parallel to the beam path.

13. The charged particle optical assembly according to claim 12, wherein each of the dielectric parts has a uniform cross-section in a direction parallel to the beam path.

14. The charged particle optical assembly according to any one of claims 1 to 13, wherein the charged particle optical assembly is a charged particle optical lens assembly.

15. The charged particle optical assembly according to claim 14, wherein the charged particle optical lens assembly includes an objective lens assembly.

Images