Isolation spacer for electro-optical components

Abstract

The charged particle optical assembly manipulates one or more charged particle beams. The assembly includes an upstream element, a downstream element, and an isolation spacer. The upstream and downstream elements each include a plate having one or more apertures surrounding a beam path of the one or more charged particle beams. The spacer is used to electrically isolate the upstream element and the element from each other. The spacer defines a spacer aperture surrounding a beam path of the one or more charged particle beams. The spacer includes an upstream portion adjacent to the upstream element, a downstream portion adjacent to the downstream element, and an intermediate portion between the upstream portion and the downstream portion. The upstream and downstream portions protrude relative to the intermediate portion such that the spacer aperture has an increased dimension at the intermediate portion compared to the upstream and downstream portions.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 22184444.2 filed on July 12, 2022, and the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments provided herein generally relate to isolation spacers, charged particle optical components, charged particle optical devices, charged particle optical apparatuses, methods for electrically isolating upstream charged particle optical elements from downstream charged particle optical elements from each other, methods for controlling charged particle optical components, methods for manufacturing isolation spacers, and methods for manufacturing charged particle optical components. Background Art

[0004] When manufacturing semiconductor integrated circuit (IC) chips, undesirable pattern defects may appear on the substrate (e.g., wafer) or mask during the manufacturing process, thereby reducing the yield. Defects may be caused by optical effects and accidental particles or other processing steps (e.g., etching, chemical mechanical polishing deposition). Therefore, monitoring the degree of undesirable pattern defects is an important process in IC chip manufacturing. More generally, inspecting and / or measuring the surface of a substrate or other object / material is an important process during and / or after its manufacturing process.

[0005] Pattern inspection tools with charged particle beams have been used to inspect objects, such as detecting pattern defects. These tools typically use electron microscopy techniques, such as scanning electron microscopes (SEMs). In an SEM, a relatively high energy electron beam is targeted at a final deceleration step so that it lands on the target with a relatively low landing energy. The electron beam is focused to a probe point on the target. The interaction between the material structure at the probe point and the landing electrons of the electron beam causes electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons, which are collectively referred to as signal electrons or more generally as signal particles. The secondary electrons generated can be emitted from the material structure of the target.

[0006] The primary electron beam is scanned onto the target surface as a detection point, and secondary electrons may be emitted over the entire target surface. By collecting these secondary electrons emitted from the target surface, the pattern inspection tool (or device) may obtain an image-like signal representing the structural features of the target surface material. In this inspection, the collected secondary electrons are detected by a detector within the device. The detector generates a signal in response to an accidental particle. When an area of ​​the sample is inspected, the signal includes data that is processed to generate an inspection image corresponding to the inspected area of ​​the sample. The image may contain pixels. Each pixel may correspond to a portion of the inspected area. Typically, an electron beam inspection device has a single beam, which may be referred to as a single beam SEM. Attempts have been made to introduce multi-electron beam inspections into a device (or "multi-beam tool"), which may be referred to as a multi-beam SEM (MBSEM).

[0007] Another application of electron optical devices (or arrays of devices) is photolithography. A beam of charged particles reacts with a layer of resist on the surface of a substrate. By controlling the location of the resist layer where the charged particle beam is directed, a desired pattern can be created in the resist.

[0008] Electron-optical equipment can be a device used to generate, irradiate, project and / or detect 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). Stray electromagnetic fields may deflect the particle beam unnecessarily.

[0009] In some electron-optical devices, an electrostatic field is often generated between two electrodes. High voltages need to be applied to the electrodes. Unwanted electron creepage and / or discharges may occur between the electrodes. Summary of the invention

[0010] The present invention provides a suitable architecture to achieve the required high voltage applications while reducing the risk of electrical creepage and / or electrical discharge.

[0011] According to a first aspect of the present invention, there is provided an isolation spacer for a charged particle optical component for manipulating one or more charged particle beams between an upstream charged particle optical element and a downstream charged particle optical element, the upstream charged particle optical element and the downstream charged particle optical element being controllable to have reverse polarity relative to each other, the isolation spacer being configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, in which a spacer aperture is defined around a beam path of the one or more charged particle beams, the isolation spacer comprising: an upstream portion configured to be adjacent to the upstream charged particle optical element, a downstream portion configured to be adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture has an increased size to the upstream portion and the downstream portion in a direction across the beam path compared to the intermediate portion.

[0012] According to a second aspect of the present invention, a charged particle optical component is provided, which is configured to manipulate one or more charged particle beams, the charged particle optical component comprising: an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of one or more charged particle beams; and an isolation spacer, which is configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding the beam path of one or more charged particle beams; wherein the isolation spacer comprises an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion located between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture has a size at the intermediate portion along a direction across the beam path that is increased compared to that at the upstream portion and the downstream portion.

[0013] According to a third aspect of the present invention, there is provided a method for electrically isolating an upstream charged particle optical element and a downstream charged particle optical element from each other in a charged particle optical component configured to manipulate one or more charged particle beams, the method comprising: providing an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of one or more charged particle beams; electrically isolating the upstream charged particle optical element and the downstream charged particle optical element from each other using an isolation spacer, the isolation spacer defining a spacer aperture surrounding the beam path of one or more charged particle beams; wherein the isolation spacer comprises an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion located between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture has an increased size at the intermediate portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0014] According to a fourth aspect of the present invention, there is provided a method for controlling a charged particle optical component to manipulate one or more charged particle beams, the method comprising: applying a potential difference between an upstream charged particle optical element and a downstream charged particle optical element, each of the upstream charged particle optical element and the downstream charged particle optical element comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams; and changing the potential difference so that the direction of the electric field between the upstream charged particle optical element and the downstream charged particle optical element is reversed, optionally using a controller to control the potential difference applied to the upstream charged particle optical element and the downstream charged particle optical element. elements; wherein an isolation spacer electrically isolates an upstream charged particle optical element and a downstream charged particle optical element from each other, and the isolation spacer defines a spacer aperture surrounding a beam path of one or more charged particle beams; wherein the isolation spacer includes an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and a middle portion located between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the middle portion so that the spacer aperture has an increased size at the middle portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0015] According to a fifth aspect of the present invention, there is provided a method for manufacturing an isolation spacer for a charged particle optical component, the charged particle optical component being configured to manipulate one or more charged particle beams, the isolation spacer being configured to electrically isolate an upstream charged particle optical element and a downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding a beam path of one or more charged particle beams, the method comprising: shaping two or more planar dielectric pieces into apertures having paths for one or more charged particle beams, different apertures having inner edges; and fixing the two or more planar pieces together to form an isolation spacer, so that the isolation spacer has an inner surface including the inner edges of the two or more planar pieces, so that the isolation spacer comprises an upstream portion for fixing to an upstream charged particle optical element, a downstream portion for fixing to a downstream charged particle optical element, and an intermediate portion located between the upstream portion and the downstream portion, the upstream portion and the downstream portion protruding relative to the intermediate portion, so that the spacer aperture has an increased size at the intermediate portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0016] According to a sixth aspect of the present invention, there is provided a method for manufacturing a charged particle optical component configured to manipulate one or more charged particle beams, the method comprising: providing an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of one or more charged particle beams; and fixing the upstream charged particle optical element and the downstream charged particle optical element to either side of an isolation spacer, the isolation spacer being configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding the beam path of one or more charged particle beams; wherein the isolation spacer comprises an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture at the intermediate portion has an increased size along a direction passing through the beam path compared to that at the upstream portion and the downstream portion.

[0017] Advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which certain embodiments of the invention are set forth by way of illustration and example. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other aspects of the present disclosure will become more apparent through the description of exemplary embodiments with reference to the attached drawings.

[0019] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection apparatus.

[0020] Figure 2 is shown as Figure 1 A schematic diagram of an exemplary multi-beam electron optical device of a portion of an exemplary electron beam inspection apparatus.

[0021] Figure 3 is a schematic diagram of an exemplary electron-optical device including an array of collimator elements and an array of scanning deflectors, the electron-optical device being Figure 1 A portion of an exemplary electron beam inspection apparatus.

[0022] Figure 4 Yes Figure 3 Schematic diagram of an exemplary electron-optical device array of electron-optical devices.

[0023] Figure 5 As Figure 1 A schematic diagram of an alternative exemplary electron optical device of a portion of an exemplary electron beam inspection apparatus.

[0024] Figure 6 It can be used as Figure 3 , Figure 4 and Figure 5 Schematic diagram of an exemplary electron-optical assembly of a portion of an electron-optical device.

[0025] Figure 7 It can be used as Figure 3 , Figure 4 and Figure 5 Schematic diagram of an exemplary electron-optical assembly of a portion of an electron-optical device.

[0026] Figure 8 is a partial close-up view of an exemplary electron-optical assembly.

[0027] Fig. 9 is a partial close-up view of an exemplary electron-optical assembly.

[0028] Fig.10 It can be used as Figure 3 , Figure 4 and Figure 5 Schematic diagram of an exemplary electron-optical assembly of a portion of an electron-optical device.

[0029] Fig.11 is a schematic diagram of an isolation spacer of an exemplary electron-optical assembly.

[0030] Fig.12 is a schematic diagram of an isolation spacer of an exemplary electron-optical assembly.

[0031] Fig.13 is a schematic diagram of an isolation spacer of an exemplary electron-optical assembly.

[0032] Reference will now be made in detail to exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, wherein the same numbers in different figures represent the same or similar elements unless otherwise specified. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. Instead, they are merely examples of devices and methods consistent with aspects related to the present invention as described in the appended claims. DETAILED DESCRIPTION

[0033] The reduction in physical size of devices and the increase in computing power of electronic devices can be achieved by significantly increasing the packing density of circuit elements such as transistors, capacitors, diodes, etc. on IC chips. This is achieved by the increased resolution that enables the manufacture of smaller structures. Semiconductor IC manufacturing is a complex and time-consuming process involving hundreds of individual steps. An error in any step in the process of manufacturing IC chips has the potential to adversely affect the functionality of the final product. Just one defect can cause device failure. It is desirable to increase the yield of the entire process. For example, to achieve a 75% yield for a 50-step process (where a step may represent the number of layers formed on a wafer), the yield of each individual step must be greater than 99.4%. If the yield of a single step is 95%, the yield of the entire process will be as low as 7-8%.

[0034] Maintaining high substrate (i.e., wafer) throughput (defined as the number of substrates processed per hour) is also desirable. High process yield and high substrate throughput may be affected by the presence of defects. This is especially true if operator intervention is required to detect the defect. High throughput detection and identification of micro- and nano-scale defects by an inspection system (e.g., a scanning electron microscope ("SEM")) is ideal for maintaining high yield and low cost of IC chips.

[0035] The scanning electron microscope comprises a scanning device and a detector device. The scanning device comprises an irradiation device, the irradiation device comprises an electron source for producing primary electrons, and a projection device for scanning a target (e.g., a substrate) with one or more focused primary electron beams. The primary electrons interact with the target and produce interaction products, such as signal particles (e.g., secondary electrons and / or backscattered electrons). The secondary electrons can be considered to have an energy of up to 50 eV. Although the backscattered electrons have an energy spectrum from substantially zero to the maximum energy of the charged particle device, they are generally set to electrons (or signal electrons) with an energy of more than 50 eV. The detection device captures signal particles (e.g., secondary electrons and / or backscattered electrons) from the target while scanning the target so that the scanning electron microscope can create an image of the scanned area of ​​the target. The design of the electron optical device that embodies these scanning electron microscope features can have a single beam. In order to achieve higher throughput (e.g., for inspection), some device designs use multiple focused beams, i.e., multiple beams of primary electrons. The component beams of the multiple beams can be referred to as sub-beams or sub-beams. Multiple beams can scan different parts of the target simultaneously. Thus, a multi-beam inspection device can inspect an object more quickly than a single-beam inspection device, for example, by moving the object at a higher speed.

[0036] In a multi-beam inspection device, the paths of some primary electron beams deviate from the central axis of the scanning device, i.e., the midpoint of the primary electron optical axis (also referred to herein as the charged particle axis). In order to ensure that all electron beams arrive at the sample surface at substantially the same angle of incidence, it is necessary to manipulate the beamlet paths that are at a greater radial distance from the central axis so that they move at a greater angle than the beamlet paths whose paths are closer to the central axis. This stronger manipulation may cause aberrations, resulting in blurring and defocusing of the generated image. An example is spherical aberration, which brings the focus of each beamlet path into a different focal plane. In particular, for beamlet paths that are not on the central axis, the change in the focal plane in the beamlet is greater with radial displacement from the central axis. Such aberrations and defocusing effects may remain relevant to the signal particles (e.g., secondary electrons) from the target when they are detected, for example, the shape and size of the spot formed by the beamlet on the target will be affected. Therefore, such aberrations can reduce the quality of the image produced during the inspection process.

[0037] The following describes the implementation of a known multi-beam inspection device.

[0038] The drawings are schematic. Therefore, the relative sizes of the components in the figures are exaggerated for clarity. In the following description of the drawings, the same or similar reference numbers refer to the same or similar components or entities, and only the differences related to the various embodiments are described. Although the description and drawings are directed to electron-optical devices, it should be understood that the embodiments are not intended to limit the present disclosure to specific charged particles. Therefore, references to electrons and items mentioned with reference to electrons throughout this document may be more generally considered as references to charged particles, and items mentioned with reference to charged particles, where the charged particles are not necessarily electrons.

[0039] Reference now Figure 1 , which is a schematic diagram illustrating an exemplary electron beam evaluation apparatus or inspection apparatus 100 . Figure 1 The inspection apparatus 100 includes a vacuum chamber 10, a load lock chamber 20, an electron optical device, an equipment front end module (EFEM) 30, and a controller 50. The electron optical device 40 may be located in the vacuum chamber 10. The electron optical device may include the electron optical device 40 (also referred to as an electron optical device, an electron beam device, or an electron beam device) and a motorized or actuated stage.

[0040] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include additional loading ports. The first loading port 30a and the second loading port 30b may, for example, receive a substrate front opening pod (FOUP) containing a substrate (e.g., a semiconductor substrate or a substrate made of other materials) or an object to be inspected (substrates, wafers, and samples are collectively referred to as "objects" hereinafter). One or more robotic arms (not shown) in the EFEM 30 transport the object to the load lock chamber 20.

[0041] The load lock chamber 20 is used to remove gas around the target. The load lock chamber 20 can be connected to a load lock vacuum pump system (not shown), which removes gas particles in the load lock chamber 20. The operation of the load lock vacuum pump system causes the load lock chamber to reach a first pressure lower than 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 in the main chamber 10 so that the pressure around the target reaches a second pressure lower than the first pressure. After reaching the second pressure, the target is transferred to the electron optical device 40, through which it can be inspected. The electron optical device 40 may include a single beam electron optical device or a multi-beam electron optical device.

[0042] The controller 50 is electronically connected to the electron optical device 40. The controller 50 may be a processor (eg, a computer) configured to control the charged particle beam inspection apparatus 100. The controller 50 may also include processing circuits configured to perform various signal and image processing functions. Figure 1 The controller 50 is shown as being located outside 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 in one of the constituent elements of the charged particle beam inspection device, or can be distributed on at least two constituent elements. Although the present disclosure provides an example of a main chamber 10 that accommodates an electron beam inspection device, it should be noted that the aspects of the present disclosure in its broadest sense are not limited to a chamber that accommodates an electron optical device. On the contrary, it is understood that the aforementioned principles can also be applied to other devices and other device arrangements that operate at a second pressure.

[0043] Reference now Figure 2 , which is an evaluation device (e.g. Figure 1Schematic diagram of an exemplary multi-beam electron optical device 40 of an inspection device 100 of FIG. 1 . In an alternative embodiment, the inspection device 100 is a single beam evaluation device. The electron optical device 40 may include an electron source 201, a beam former array 372 (also known as a gun aperture plate, a Coulomb aperture array, or a pre-sub-beam forming aperture array), a converging lens 310, a source converter (or micro-optical array) 320, an objective lens 331, and a target 308. In one embodiment, the converging lens 310 is magnetic. (The single beam evaluation device may have the same features as the multi-beam evaluation device, except that the electron optical component 320 has a single aperture in addition to the array aperture 372. 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 driven by a motorized device. The stage moves so that the target 308 is scanned by the incident electrons. The electron source 201, the beam former array 372, and the focusing lens 310 may be components of an irradiation device included in the electron optical device 40. The source converter 320 (also referred to as a source conversion unit) (described in more detail below) and the objective lens 331 may be components of a projection device included in the electron optical device 40.

[0044] The electron source 201, the beam former array 372, the converging 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 generate a primary beam 302, which is substantially along the electron optical axis 304 and has a source intersection point (virtual or real) 301S. During operation, the electron source 201 is configured to emit electrons. The electrons are extracted or accelerated by the extractor and / or the anode to form the primary beam 302.

[0045] The beam former array 372 cuts off peripheral electrons of the primary electron beam 302 to reduce the ensuing Coulomb effect. The beam former array 372 can trim the primary electron beam 302 into a specified number of sub-beams, such as three sub-beams 311, 312, and 313. It should be understood that the description is intended to apply to an electron optical device 40 having any number of sub-beams (e.g., one, two, or more than three). The beam former array 372 is configured to block peripheral electrons in operation to reduce the Coulomb effect. The Coulomb effect may enlarge the size of each detection point 391, 392, 393, thereby reducing the inspection resolution. The beam former array 372 reduces aberrations caused by the Coulomb interaction between the electrons projected into the beam. The beam former array 372 may even include multiple openings for generating primary sub-beams before the source converter 320.

[0046] Source converter 320 is configured to convert the beam (including beamlets, if any) transmitted by beamformer array 372 into beamlets that are projected onto target 308. In one embodiment, source converter is a unit. Alternatively, the term source converter may simply be used as a collective term for a group of components that form a beamlet from a beamlet.

[0047] like Figure 2 As shown, in one embodiment, the electron optical device 40 includes a beam limiting aperture array 321, whose aperture pattern (i.e., apertures arranged in a certain shape) is configured to limit the outer size of a beamlet (or sub-beams) projected to the target 308. In one embodiment, the beam limiting aperture array 321 is part of the source converter 320. In an alternative embodiment, the beam limiting aperture array 321 is part of the system upstream of the main device. In one embodiment, the beam limiting aperture array 321 divides one or more sub-beams 311, 312, 313 into sub-beams, so that the number of sub-beams projected to the target 308 is greater than the number of sub-beams transmitted through the beam former 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 can be equal to the number of sub-beams projected to the target 308.

[0048] like Figure 2 As shown, in one embodiment, the electron optical device 40 includes a pre-bending deflector array 323 having pre-bending deflectors 323_1, 323_2 and 323_3 to respectively bend sub-beams 311, 312 and 313. 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.

[0049] 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. The path of each sub-beam has corresponding deflectors 322_1, 322_2 and 322_3. Deflectors 322_1, 322_2 and 322_3 are configured to deflect the path of the sub-beam to the electron optical axis 304. The deflected sub-beams form a virtual image (not shown) of the source intersection 301S. In the current embodiment, these virtual images are projected onto the target 308 by the objective lens 331 and form detection points 391, 392, 393 located thereon. The electron optical device 40 may also include an aberration compensator array 324, which is configured to compensate for the aberrations that may exist in each sub-beam. In one embodiment, the aberration compensator array 324 includes a lens configured to operate on the corresponding sub-beam. The lens may be in the form of a lens array. The lenses in the array may operate on different sub-beams of multiple beams. The aberration compensator array 324 may, for example, include a field curvature compensator array (not shown) having microlenses. The field curvature compensator and the microlenses may, for example, be configured to compensate for field curvature aberrations occurring in the detection points 391, 392, and 393 for each sub-beam. The aberration compensator array 324 may include an astigmatism compensator array (not shown) having micro-astigmatists. For example, the micro-astigmatists may be controlled to operate the sub-beams to compensate for the astigmatism aberrations existing in the detection points 391, 392, and 393.

[0050] The converter 320 may further include a pre-bending deflector array 323 having pre-bending deflectors 323_1, 323_2, and 323_3 to bend the sub-beams 311, 312, and 313, respectively. The pre-bending deflectors 323_1, 323_2, and 323_3 may bend the paths of the sub-beams onto the beam-limiting aperture array 321. In an embodiment, the pre-bending micro-deflector array 323 may be configured to bend the sub-beam paths of the sub-beams to an orthogonal direction of the plane of the beam-limiting aperture array 321. In an alternative embodiment, the converging lens 310 may adjust the paths of the sub-beams onto the beam-limiting aperture array 321. The converging lens 310 may, for example, focus (collimate) the three sub-beams 311, 312, and 313 into substantially parallel beams along the primary electron optical axis 304, such that the three sub-beams 311, 312, and 313 are substantially perpendicularly incident on the source converter 320, which may correspond to the beam-limiting aperture array 321. In such an alternative embodiment, the pre-bend deflector array 323 may not be necessary.

[0051] The imaging element array 322, the aberration compensator array 324 and the pre-bent deflector array 323 may include multiple layers of beamlet steering devices, some of which may be in array form, such as micro-deflectors, micro-lenses or micro-stigmators. The beam path may be rotationally steered. Rotational correction may be applied by magnetic lenses. Rotational correction may be additionally or alternatively achieved by existing magnetic lenses (e.g., converging lens devices).

[0052] In the present example of the electron optical device 40, the beamlets are respectively deflected by deflectors 322_1, 322_2 and 322_3 of the image forming element array 322 to the electron optical axis 304. It should be understood that the beamlet paths may already correspond to the electron optical axis 304 before reaching the deflectors 322_1, 322_2 and 322_3.

[0053] 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 on the target surface by the three beamlets 311 to 313 form three detection points 391, 392 and 393 thereon. In one embodiment, the deflection angles of the beamlets 311 to 313 are adjusted to pass through or approach the front focus of the objective lens 331 to reduce or limit the off-axis aberrations of the three detection points 391 to 393. In the arrangement, the objective lens 331 is magnetic. Although three beamlets are mentioned, this is only an example. There can be any number of beamlets.

[0054] The manipulator is configured to manipulate one or more charged particle beams. The term manipulator includes a deflector, a lens, and an aperture. The pre-bent deflector array 323, the aberration compensator array 324, and the imaging element array 322 can be referred to as a manipulator array individually or in combination with each other because they manipulate one or more charged particle sub-beams or beamlets. Lenses and deflectors 322_1, 322_2, and 322_3 can be referred to as manipulators because they manipulate one or more charged particle sub-beams or beamlets.

[0055] In one embodiment, a beam splitter (not shown) is provided. The beam splitter may be downstream of the source converter 320. The beam splitter may be, for example, a Wien filter including an electrostatic dipole field and a magnetic dipole field. The beam splitter may be upstream of the objective lens 331. The beam splitter may be located between adjacent shielding portions (described in more detail below) in the direction of the beam path. The inner surface of the shield may be located radially inwardly within the beam splitter. Alternatively, the beam splitter may be located within the shield. In operation, the beam splitter may be configured to apply an electrostatic force to each electron of a sub-beam through an electrostatic dipole field. In one embodiment, the magnitude of the electrostatic force is equal to the magnetic force applied by the magnetic dipole field of the beam splitter to each primary electron of the sub-beam, but in the opposite direction. Therefore, the sub-beam may pass through the beam splitter at least substantially straight, with a deflection angle of at least substantially zero. The direction of the magnetic force depends on the direction of motion of the electrons, while the direction of the electrostatic force does not depend on the direction of motion of the electrons. Therefore, since secondary electrons and backscattered electrons (or signal electrons) generally move in the opposite direction to primary electrons, the magnetic force applied to the secondary electrons and backscattered electrons (or signal particles) will no longer offset the electrostatic force, and therefore, the secondary electrons and backscattered electrons passing through the beam splitter will deviate from the electron optical axis 304.

[0056] In one embodiment, a secondary device (not shown) is provided, which includes a detection element for detecting a corresponding secondary charged particle beam. When the secondary beam is incident on the detection element, the element may generate a corresponding intensity signal output. The output may be directed to an image processing system (e.g., controller 50). Each detection element may include an array, which may be in the form of a grid. The array may have one or more pixels; each pixel may correspond to an element of the array. The intensity signal output of the detection element may be the sum of the signals generated by all pixels in the detection element.

[0057] In one embodiment, a secondary projection device and its associated electronic detection device (not shown) are provided. The secondary projection device and its associated electronic detection device can be aligned with the secondary electron optical axis of the secondary device. In one embodiment, the beam splitter is arranged 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 multiple detection areas of the electronic detection device. The secondary projection device and its associated electronic detection device can record and generate an image of the target 308 using secondary electrons or backscattered electrons (or signal particles).

[0058] Such Wien filter, secondary device and / or secondary projection device may be arranged in a single beam evaluation device. Additionally and / or alternatively, the detection device may be located below the beam of the objective lens, for example facing the sample during operation. In an alternative arrangement, the detection device is positioned along the path of the charged particle beam towards the sample. In such an arrangement, there is no Wien filter, secondary device and secondary projection device. The detection device may be located at one or more positions along the path of the charged particle beam towards the sample, for example facing the sample during operation, for example around the path of the charged particle beam. Such detection devices may have an aperture and may be annular. Different detection devices may be positioned along the path of the charged particles to detect signal particles with different characteristics. The electron optical element along the charged particle beam path may include one or more electrostatic plates with an aperture for the charged particle beam path, which may be arranged and controlled to focus signal particles with different respective characteristics to respective detection devices at different positions along the charged particle beam path. Such electrostatic plates may be arranged in series along the path of the charged particle beam. Two or more adjacent plates.

[0059] In one embodiment, inspection apparatus 100 includes a single source.

[0060] Any element or collection of elements within the electron-optical device may be replaced or field-replaced. One or more electron-optical components in the electron-optical device, particularly those that operate on or generate beamlets, such as aperture arrays and manipulator arrays, may include one or more micro-electromechanical systems (MEMS). The pre-bent deflector array 323 may be a MEMS. MEMS are micro-mechanical and electromechanical components manufactured using micromachining techniques. In one embodiment, the electron-optical device 40 includes an aperture, a lens, and a deflector formed as a MEMS. In one embodiment, the manipulators (e.g., lenses and deflectors 322_1, 322_2, and 322_3) may be controlled passively, actively, as an entire array, individually, or in groups within an array to control the charged particle beam projected toward the target 308.

[0061] In one embodiment, the electron optical device 40 may include alternative and / or additional components in the charged particle path, such as lenses and other components, some of which have been previously described with reference to Figure 1 and Figure 2 An example of such an arrangement is Figure 3 and Figure 4As shown, it will be described in more detail later. Specifically, an embodiment includes an electron optical device 40, which divides the charged particle beam from the source into a plurality of sub-beams. A plurality of corresponding objective lenses can project the sub-beams onto the sample. In some embodiments, a plurality of converging lenses are arranged upstream of the objective lens. The converging lens focuses each sub-beam onto the upstream of the intermediate focus of the objective lens. In some embodiments, a collimator is arranged upstream of the objective lens. A corrector can be provided to reduce focusing errors and / or aberrations. In some embodiments, such a corrector is integrated into the objective lens or is directly located near the objective lens. When a converging lens is provided, such a corrector can be additionally or alternatively integrated into the converging lens or directly positioned near the converging lens and / or positioned in the intermediate focus or directly positioned near the intermediate focus. A detector is provided to detect the charged particles emitted by the sample. The detector can be integrated into the objective lens. The detector can be located on the bottom surface of the objective lens so as to face the sample in use. The detector can include, for example, an array of detector elements, which can correspond to a beam array of a multi-beam arrangement. The detectors (or detector elements) in the detector array may generate detection signals associated with pixels of the generated image.The converging lens, the objective lens and / or the detectors may be formed as MEMS or CMOS devices.

[0062] Figure 3 is a schematic diagram of another design of an exemplary electron-optical device 40. The electron-optical device 40 may include a source 201 and one or more electron-optical components. Alternatively, an electron-optical device including the electron-optical device 40 may include the source 201. The electron-optical device 40 may include an upstream 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 source 201 provides a charged particle beam (e.g., electrons). The multiple beams focused on the sample 208 come from the beam provided by the source 201. Sub-beams can be obtained from the beam, for example, using a beam limiter that defines an array of beam-limiting apertures. The source 201 is preferably a high-brightness thermal field emitter that has a good compromise between brightness and total emission current.

[0063] The upstream limiter 252 defines a beam-limiting aperture array. The upstream limiter 252 may be referred to as an upstream limiting aperture array or an upstream beam-limiting aperture array. The upstream limiter 252 may include a plate (which may be a plate-like body) having a plurality of apertures. The upstream limiter 252 forms a sub-beam from the charged particle beam emitted by the source 201. Portions of the beam other than those that contribute to forming the sub-beam may be blocked (e.g., absorbed) by the upstream limiter 252 so as not to interfere with the downstream sub-beams. The upstream limiter 252 may be referred to as a sub-beam limiting aperture array.

[0064] The collimator element array 271 is located downstream of the upstream limiter. Each collimator element collimates a corresponding sub-beam. The collimator element array 271 can be formed using MEMS manufacturing technology, thereby being compact in space. In some embodiments, as shown in FIG. Figure 3 As shown, collimator element array 271 is the first deflection or focusing electron optical array element in the downstream path of source 201. In another arrangement, the collimator can be in the form of a macro-collimator in whole or in part. Such a macro-collimator can be upstream of the upstream limiter 252 so that it operates on the beam from the source before generating multiple beams. A magnetic lens can be used as a macro-collimator.

[0065] Downstream of the collimator element array 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 a corresponding potential source. The control lens array 250 may include two or more (e.g., three) plate electrode arrays connected to a corresponding potential source. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are close to each other and / or mechanically connected and / or controlled together as a unit). The control lens array 250 is located upstream 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). Pre-focusing can reduce the divergence of the sub-beams or increase the convergence rate of the sub-beams.

[0066] As mentioned above, the control lens array 250 is associated with the objective lens array 241. As mentioned above, the control lens array 250 can be regarded as providing additional electrodes in addition to 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 allow additional degrees of freedom to control the electron optical parameters of the sub-beams. In one embodiment, the control lens array 250 can be regarded as an additional electrode of the objective lens array 241, thereby realizing additional functions of the individual objective lenses of the objective lens array 241. In one arrangement, such electrodes can be regarded as part of the objective lens array, thereby providing additional functions for the objective lenses of the objective lens array 241. In this arrangement, the control lens is regarded as part of the corresponding objective lens, and even to some extent, the control lens is only referred to as part of the objective lens, for example in providing more additional degrees of freedom for the objective lens. Although the control lens array 241 may be difficult to distinguish from the objective lens array 250 and is part of the objective lens array 250, in this description, the control lens array 250 is regarded as different and separate from the objective lens array 241.

[0067] For ease of illustration, the lens array is schematically shown here as an array of ellipses. Each ellipse represents a lens in the lens array. Ellipses are often used to represent lenses, similar to the biconvex shapes often used in optical lenses. However, in the context of charged particle arrangements (such as the arrangements discussed herein), it should be understood that lens arrays are typically operated electrostatically, and therefore any physical elements that use biconvex shapes may not be required. As described above, the lens array can instead include multiple plates with apertures.

[0068] 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 techniques. Each scanning deflector scans a corresponding sub-beam on 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 into one direction (e.g., parallel to a single axis, such as the X-axis) or two directions (e.g., relative to two non-parallel axes, such as the X-axis and the Y-axis). The deflection causes the sub-beam to scan the sample 208 in one or two directions (i.e., one dimension or two dimensions). In one embodiment, the scanning deflector described in EP2425444 may be used to implement the scanning deflector array 260, which document is hereby incorporated by reference in its entirety, particularly its portion regarding the scanning deflector. The scanning deflector array 260 (e.g., formed using MEMS manufacturing techniques as described above) may be more compact in space than a macro scanning deflector. In another arrangement, a macro scanning deflector may be used for the beam of the upstream limiter 252. Its function may be similar or identical to that of a scanning deflector array, although it operates on the beams from the source prior to beam generation of the multiple beams.

[0069] The objective lens array 241 includes a plurality of objective lenses for directing sub-beams onto the sample 208. Each objective lens includes at least two electrodes (e.g., two or three electrodes) connected to corresponding potential sources. The objective lens array 241 may include two or more (e.g., three) plate electrode arrays connected to corresponding potential sources. Each objective lens formed by the plate electrode array may be a microlens that operates on different sub-beams. Each plate defines a plurality of apertures (also referred to as holes). The position of each aperture in the plate corresponds to the position of a corresponding aperture (or multiple apertures) in another plate (or multiple plates). The corresponding apertures define the objective lens, so that each group of corresponding apertures operates on the same sub-beam in multiple beams during use. Each objective lens projects a corresponding sub-beam of multiple beams onto the sample 208.

[0070] The aberration of an objective lens array 241 having only two electrodes can be smaller than an objective lens array 241 having more electrodes. The potential difference between the electrodes of a three-electrode objective lens can be larger, thereby enabling a stronger lens. Additional electrodes (i.e., more than two electrodes) provide additional degrees of freedom to control the trajectory of electrons, for example, focusing secondary electrons as well as the incident beam. It is contemplated that such additional electrodes may be used to form a control lens array 250. The advantage of a two-electrode lens over an Einzel lens is that the energy of the incident beam is not necessarily the same as the outgoing beam. Advantageously, the potential difference across such a two-electrode lens array enables it to be used as an acceleration or deceleration lens array.

[0071] The objective lens array may form part of an 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 also include a beam shaping limiter 242. The beam shaping limiter 242 defines a beam limiting aperture array. The beam shaping limiter 242 may be referred to as a downstream limiter, a downstream 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 body) having a plurality of apertures. The beam shaping limiter 242 is downstream of at least one electrode (optionally from all electrodes) of the control lens array 250. In some embodiments, the beam shaping limiter 242 is downstream of at least one electrode (optionally from all electrodes) of the objective lens array 241.

[0072] In one arrangement, the beam shaping limiter 242 is structurally integrated with the electrode 302 of the objective lens array 241. Ideally, the beam shaping limiter 242 is located in an area of ​​low electrostatic field strength. Each beam limiting aperture is aligned with a corresponding objective lens in the objective lens array 241. This alignment enables a portion of the sub-beam from the corresponding objective lens to pass through the beam limiting aperture and impinge on the sample 208. The aperture of the beam shaping limiter 242 can have a smaller diameter than the aperture of at least one of the objective lens array 241, the control lens array 250, the detector array 240, and the upstream limiter array 252. Each beam limiting aperture has a beam limiting effect, allowing only a selected portion of the sub-beam incident on the beam shaping limiter 242 to pass through the beam limiting aperture. The selected portion can be such that only a portion of the corresponding sub-beam that passes through the central portion of each aperture in the objective lens array reaches the sample. The central portion can have a circular cross-section and / or be centered on the beam axis of the sub-beam.

[0073] In one embodiment, the electronic 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) so that the focal length of the control lens is greater than the spacing between the control lens array 250 and the objective lens array 241. Therefore, the control lens array 250 and the objective lens array 241 can be positioned relatively close, and the focusing effect of the control lens array 250 is too weak to 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 to the same surface. Combined operation without an intermediate focus can reduce the risk of aberrations. 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.

[0074] A power source may be provided to apply corresponding potentials to electrodes of control lenses of the control lens array 250 and electrodes of objective lenses of the objective lens array 241 .

[0075] In addition to the objective lens array 241, a control lens array 250 is provided, which provides additional degrees of freedom for controlling the characteristics of the sub-beams. Even if the control lens array 250 and the objective lens array 241 are relatively close, for example, no intermediate focus is formed between the control lens array 250 and the objective lens array 241, additional degrees of freedom can be provided. The control lens array 250 can be used to optimize the opening angle of the beam relative to the reduction rate of the beam and / or control the beam energy transmitted to the objective lens array 241. The control lens may include two or three or more electrodes. If there are two electrodes, the reduction rate and the landing energy are controlled together. If there are three or more electrodes, the reduction rate and the landing energy can be controlled independently. Note that the most downstream electrode of the control lens array 250 can be the most upstream electrode of the objective lens array 241. That is, the control lens array 250 and the objective lens array 241 can share one electrode. The shared electrode provides different lens effects for each lens, and each lens effect is related to its two opposite surfaces (i.e., the upstream surface and the downstream surface). Therefore, the control lens can be configured to adjust the reduction ratio and / or beam opening angle of the corresponding sub-beam and / or the energy landing on the substrate (for example, using a power supply to apply appropriate corresponding potentials to the electrodes of the control lens and the objective lens). This optimization can be achieved without having too much negative impact on the number of objective lenses, and without excessively deteriorating the aberrations of the objective lens (for example, without reducing the strength of the objective lens). The use of a control lens array enables the objective lens array to operate at its optimal electric field strength. Note that references to reduction ratio and opening angle are intended to refer to changes in the same parameter. In an ideal arrangement, the product of the reduction ratio and the corresponding opening angle is constant. However, the opening angle may be affected by the use of the aperture.

[0076] In one embodiment, the landing energy can be controlled to a desired value within a predetermined range, for example from 1000 eV to 5000 eV. Ideally, the landing energy is changed primarily by controlling the energy of the electrons leaving the control lens. The potential difference within the objective lens is preferably kept constant during this change so that the electric field within the objective lens remains as high as possible. In addition, the potential applied to the control lens can be used to optimize the beam opening angle and the reduction ratio. The control lens can change the reduction ratio according to the change in the landing energy. Ideally, each control lens includes three electrodes to provide two independent control variables. For example, one of the electrodes can be used to control the magnification, while the other electrode can be used to independently control the landing energy. Alternatively, each control lens can have only two electrodes. When there are only two electrodes, one of the electrodes may need to control the magnification and the landing energy.

[0077] A detector array (not shown) is used to detect charged particles emitted from sample 208. The detected charged particles may include any charged particles (e.g., signal particles) detected by a scanning electron microscope, including secondary (e.g., emitted) and / or backscattered electrons from sample 208. The detector may be an array that provides a surface of an electron-optical device facing sample 208 (e.g., the bottom surface of an electron-optical device). Alternatively, the detector array may be upstream of the bottom surface, or upstream of, for example, an objective lens array or a control lens array. The elements of the detector array may correspond to beams of a multi-beam arrangement. The signals generated by the array elements detecting the electrons are transmitted to a processor to generate an image. The signals may correspond to pixels of an image.

[0078] In other embodiments, both a macro-scanning deflector and a scanning deflector array 260 are provided. In such an arrangement, scanning of the beamlets on the sample surface can be achieved by controlling the macro-scanning deflector and the scanning deflector array 260 simultaneously (preferably synchronously).

[0079] like Figure 4 As shown, an electron optical device array 500 is provided. The array 500 may include any number of electron optical devices described herein. Each electron optical device focuses respective multiple beams simultaneously onto different regions of the same sample. Each electron optical device may form sub-beams from charged particle beams from different respective sources 201. Each respective source 201 may be one of the multiple sources 201. At least one subset of the multiple sources 201 may be provided as a source array. The source array may include multiple sources 201 disposed on a common substrate. Focusing multiple multiple beams simultaneously onto different regions of the same sample allows a larger area of ​​the sample 208 to be processed (e.g., evaluated) simultaneously. The electro-optical devices in the array 500 may be arranged adjacent to each other to project corresponding multiple beams onto adjacent regions of the sample 208.

[0080] Any number of electron-optical devices may be used in array 500. Preferably, the number of electron-optical devices ranges from two (2), preferably nine (9), to one hundred (100), or even two hundred (200). In one embodiment, the electron-optical devices are arranged in a rectangular array or a hexagonal array. In other embodiments, the electron-optical devices are provided in an irregular array or a regular array having a geometric shape other than rectangular or hexagonal. Each electron-optical device in array 500 may be configured in any manner described herein with reference to a single electron-optical device, such as described above, particularly with reference to Figure 5 or Figure 6 Embodiment shown and described. Details of this arrangement are described in EPA 20184161.6 filed on July 6, 2020, which is incorporated herein by reference with respect to how the objective lens can be incorporated and adapted for use in a multi-device arrangement.

[0081] Figure 4 In the example of FIG. 5 , the array 500 includes a plurality of Figure 3 Electro-optical devices of the type described. Thus, each electron-optical device in this example includes 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 because of their spatial compactness, which facilitates positioning the electron-optical devices close to each other. This electron-optical device arrangement may be advantageous over other arrangements that use magnetic lenses as collimators. For example, incorporating magnetic lenses into electron-optical devices for multi-device arrangements (e.g., multi-device column arrangements) may be challenging due to magnetic interference between columns.

[0082] Alternative designs for multibeam electron optics can have Figure 3 The same features as described in Figure 5 As shown. An alternative design of the multi-beam electron optical device may include an upstream converging lens array 231 of the objective lens array device 241, as disclosed in EP application 20158804.3 filed on February 21, 2020, which is hereby incorporated by reference until the description of the multi-beam device with a collimator and its components. This design does not require a beam shaping limiter array 242 or an upstream limiter array 252, because the beam limiting aperture array associated with the converging lens array 231 can shape the sub-beams 211, 212, 213 of the multiple beams of the beam from the source 201. The beam limiting aperture array of the converging lens can also be used as an electrode in the lens array.

[0083] The paths of the beamlets 211, 212, 213 diverge from the converging lens array 231. The converging lens array 231 focuses the generated beams to an intermediate focus (i.e., toward the control lens array and the objective lens array) between the converging lens array 231 and the objective lens array assembly 241. The collimator array 271 may be located at the intermediate focus, rather than being associated with the objective lens array assembly 241.

[0084] The collimator can reduce the divergence of the divergent beam path. The collimator can collimate the divergent beam paths so that they are substantially parallel to the objective lens array assembly. A corrector array can be present in the multi-beam path, for example associated with a converging lens array, an intermediate focus, and an objective lens array assembly. The detector 240 can be integrated into the objective lens 241. The detector 240 can be located on the bottom surface of the objective lens 241 so as to face the sample in use.

[0085] exist Figure 5 In the embodiment of the arrangement shown and described, the detector may be located in a similar position in the electron optical device 40 as described with reference to Figure 3 The detector 240 may be integrated into the objective lens array 241 and the control lens array 250 (when present, because Figure 5 ). The detector may have a plurality of detectors at different positions along the sub-beam paths of the multiple beams, for example, each array being associated with a different electron optical element, such as an electrode of an objective lens array and / or a control lens array. The objective lens array 241 and associated electron optical elements (e.g., a control lens array 250) may be included in an assembly, which may be a monolithic assembly, which may be referred to as an electron optical assembly 700. In one embodiment, the detector 240 is associated with the plates 710, 720 of the electron optical assembly 700, or even integrated therein. For example, the detector 240 may be located on the bottom surface of the electron optical assembly 700 including the objective lens 241. The detector 240 may be equipped with an electrical connection 60, as described elsewhere herein. In one variant, the detector has a detector array located upstream (e.g., upstream of the electron optical assembly 700) of the objective lens array (optionally and the control lens array 250). Between the electron optical assembly 700 and the detector array may be a Wien filter array, which directs the charged particle beam to the sample in a downstream direction and directs the signal particles from the sample to the detector array.

[0086] An array of electron optical devices may have multiple multi-beam devices of this design, as shown in reference Figure 3 The multi-beam device described in Figure 4As shown. Multiple multi-beam devices can be arranged in a multi-beam device array. This arrangement is shown and described in EP application 20158732.6 filed on February 21, 2020, which is hereby incorporated by reference into a multi-device arrangement of a multi-beam device, which is characterized in that the disclosed multi-beam device design has a collimator at the intermediate focus. Another alternative design of the multi-beam device includes multiple single-beam devices. The single beam produced for the purpose of the invention described herein may be similar to or equivalent to the multiple beams produced by a single device. Each device may have an associated detector. This multi-device device can be arranged into a device array consisting of three, four, nine, nineteen, fifty, one hundred or even two hundred devices, each device producing a single beam or sub-beam (if it is a single beam device) or multiple beams (if it is a multi-beam device). In this further alternative design, the device array can have a common vacuum system, each device has a separate vacuum system or the device group is assigned a different vacuum system.

[0087] The electron optical device 40 may be a component of an inspection (or evaluation metrology inspection) device or part of an electron beam lithography device.Multi-beam charged particle devices can be used for a variety of different applications, including electron microscopy in general, not just scanning electron microscopy and lithography.

[0088] The electron optical axis 304 describes the path of the charged particles through the source 201 and out of the source 201. Unless explicitly mentioned, the beamlets and sub-beams of the multi-beam may all pass through at least a manipulator or an electron optical array (e.g., reference Figure 2 The arrangement shown and described) is substantially parallel to the electron optical axis 304. The electron optical axis 304 can be the same as or different from the mechanical axis of the electron optical device 40. Figures 2 to 5 In the arrangement shown and described, the electron optical axis can correspond to the path of the central beam of the multi-beam (e.g., beam 212). The beams of the multi-beam are collimated (e.g., the position of the collimator array 271 corresponds to the intermediate focal plane (e.g., Figure 5 As shown in FIG. 3 , the surfaces of the sample 208 (eg, along the electron optical axis 304 ) and the upstream limiter 252 ) are substantially parallel to each other.

[0089] The electronic optical device 40 may include Figure 6 or Figure 7 The electron optical assembly 700 shown is used to manipulate the electron beam. For example, the electron optical assembly 700 may include one or more of the following (non-limiting list): an objective lens array 241, and / or a converging lens array 231, and / or a collimator element array 271, and / or a separate beam corrector, and / or a deflector, and / or a Wien filter array. Specifically, the objective lens 331, and / or the converging lens 310, and / or the control lens 250 may include the electron optical assembly 700.

[0090] Electro-optical components are configured to provide a potential difference between two or more plates (or substrates). An electrostatic field is generated between the plates acting as electrodes. The electrostatic field causes an attractive force between the two plates. The attractive force may increase as the potential difference increases.

[0091] like Figure 7 As shown, in one embodiment, the thickness of at least one plate is stepped so that the thickness of the array plate in the area corresponding to the aperture array is thinner than the thickness of another area of ​​the array plate. It is advantageous to have a stepped thickness, for example, two parts of the plate have different thicknesses, because at a high potential difference, the plate is subjected to a higher electrostatic force, which can cause bending if the thickness of the plate is consistent and, for example, too thin. The bending of the plate can have an adverse effect on the uniformity between beams. Therefore, thick plates are beneficial for reducing bending. However, if the plate is too thick in the area of ​​the aperture array, it can cause undesirable electron beam deformation. Therefore, a thin plate around the aperture array is beneficial for reducing electron beam deformation. That is, the aperture array can be defined in an area of ​​the plate that is thinner than the rest of the plate. Therefore, the stepped thickness of the plate reduces the possibility of bending without increasing the possibility of beam deformation. In one embodiment, the plate has a uniform thickness, including in the area corresponding to the aperture array.

[0092] Figure 6 The exemplary electron optical assembly shown includes an upstream plate 710 of the upstream electron optical element, a downstream plate 720 of the downstream electron optical element, and an isolation spacer 60. In the upstream plate 710, at least one aperture 711 (optionally, as Figure 7 711). The upstream plate 710 may be referred to as an array plate (but note that in one embodiment, the upstream plate 710 has a single aperture 711). The downstream plate 720 may be referred to as an adjacent plate. The number of apertures in the upstream plate 710 may correspond to the number of sub-beams in the multi-beam arrangement. In one arrangement, there are fewer apertures than sub-beams in the multi-beam, so that the sub-beam path groups pass through the apertures. For example, the apertures may extend to the multi-beam paths; the apertures may be strips or slits. In another arrangement, the apertures may be arranged in a grid (or a two-dimensional array) so that the beam groups are arranged in a two-dimensional array of beam groups. The isolation spacer 60 is arranged between the plates to separate the plates. The electron-optical assembly 700 is configured to provide a potential difference between the upstream plate 710 and the downstream plate 720. In an embodiment, the upstream plate 710 includes a radially inward portion 712. The radially inward portion 712 is adjacent to the spacer aperture 70 defined by the isolation spacer 60, which will be described in more detail below.

[0093] In the downstream plate 720, another aperture 721 (or Figure 7 721 array as shown). Figure 7As shown, in one embodiment, the downstream plate 720 may also have a stepped thickness such that an adjacent plate is thinner in an area corresponding to the aperture array than another area of ​​the downstream plate. (Alternatively, the downstream plate 720 is substantially planar and / or has a uniform thickness.) Preferably, the aperture array 721 defined in the downstream plate 720 has the same pattern as the aperture array 711 defined in the upstream plate 710. In an arrangement, the pattern of the apertures in the two plates may be different. For example, the number of apertures in the downstream plate 720 may be less than or greater than the number of apertures in the upstream plate 710. As shown in FIG. Figure 6 As shown, in the arrangement, there is a single aperture in the downstream plate for all paths of the beamlets of the multibeam. Preferably, the holes in the upstream plate 710 and the downstream plate 720 are substantially well aligned with each other. This alignment between the apertures is to limit lens aberrations.

[0094] The upstream and downstream plates may each have a thickness of up to 1.5 mm, preferably 1 mm, more preferably 500 μm at the thickest point of the plate. In one arrangement, the downstream plate (i.e. the plate close to the sample) may have a thickness of between 100 μm and 300 μm at its thickest point. The downstream plate preferably has a thickness of between 200 μm and 150 μm at its thickest point. The upstream plate (i.e. the plate away from the sample) may have a thickness of up to 500 μm at its thickest point. The thickest point is μm.

[0095] The surface of the upstream plate located between the thinner region of the plate 710 and other regions of the plate (e.g., thicker regions) (e.g., providing a step) is preferably orthogonal to the surface of the plate facing the downstream plate 720 and / or the multiple beam paths. Similarly, the surface of the downstream plate 720 located at the step between the thicker region (radially outward) and the inner region (radially inward) is preferably orthogonal to the surface of the downstream plate facing the upstream plate 710.

[0096] The coating may be provided on the surface of the upstream plate and / or the downstream plate. Preferably, the coating is provided on both the upstream plate and the downstream plate. The coating may reduce surface charging which would otherwise cause unwanted beam distortion.

[0097] The coating is configured to withstand electrical breakdown events that may occur between an array plate and an adjacent plate. Preferably, a low ohmic coating is provided, more preferably a coating of 1 ohm / square or less is provided. The coating is preferably disposed on the surface of the downstream plate. The coating is more preferably disposed between at least one plate and the separator. The low ohmic coating reduces undesirable surface charging of the plate.

[0098] The upstream plate and / or the downstream plate may comprise a low volume resistivity material, preferably a material of 1 Ohm.m or less, optionally a material of 0.1 Ohm.m or less, optionally a material of 0.01 Ohm.m or less, optionally a material of 0.001 Ohm.m or less, and optionally a material of 0.0001 Ohm.m or less. More preferably, the upstream plate and / or the downstream plate comprises doped silicon. Plates with low volume resistivity have the advantage that they are less likely to fail because the discharge current is supplied / drained through the volume rather than, for example, through a thin coating.

[0099] The upstream plate includes a first wafer. The first wafer can be etched to produce regions with different thicknesses. The first wafer can be etched in regions corresponding to the aperture array so that the array plate is thinner in regions corresponding to the aperture array. For example, a first side of the wafer can be etched or both sides of the wafer can be etched to produce a step thickness of the plate. Etching can be performed by deep reactive ion etching. Alternatively or additionally, the step thickness of the plate can be produced by laser drilling or machining.

[0100] Alternatively, the upstream plate may include a first wafer and a second wafer. The aperture array may be defined in the first wafer. The first wafer may be arranged to contact the isolation spacer. The second wafer is arranged on the surface of the first wafer in an area not corresponding to the aperture array. The first wafer and the second wafer may be connected by wafer bonding. The thickness of the upstream plate in the area corresponding to the aperture array may be the thickness of the first wafer. The thickness of the array plate in another area other than the aperture array area, for example radially outward of the aperture array, may be the combined thickness of the first wafer and the second wafer. Therefore, the upstream plate has a stepped thickness between the first wafer and the second wafer.

[0101] One of the upstream plate and the downstream plate is negatively charged relative to the other plate. In one embodiment, in one operating mode, the upstream plate has a higher potential relative to, for example, ground potential, a source, or a sample than the downstream plate. In another operating mode, the upstream plate has a lower potential relative to, for example, ground potential, a source, or a sample than the downstream plate. The electron optical assembly can be configured to provide a potential difference of 5 kV or greater between the upstream plate and the downstream plate. Preferably, the potential difference is 10 kV or greater. More preferably, the potential difference is 20 kV or greater.

[0102] The isolation spacer 60 is preferably disposed between the upstream and downstream plates such that the opposing surfaces of the plates are coplanar with each other. The isolation spacer 60 has an inner surface 61 facing the beamlet path. The isolation spacer 60 defines a spacer aperture 70 for the electron beamlet path.

[0103] A conductive coating may be applied to the isolation spacers 60. Preferably, a low ohmic coating is provided, and more preferably, a coating of 0.5 ohms / square or less is provided.

[0104] The coating is preferably located on the surface of the negatively charged plate facing the space, which surface is negatively charged relative to the other plate. The coating may be at the same potential as one of the plates. The coating is preferably located on the surface of the isolating spacer facing the negatively charged plate. The coating is more preferably electrically connected to the negatively charged plate. The coating can ensure that an electrostatic field exists above the space between the isolating spacer and the negatively charged plate.

[0105] Without such a coating on the isolating spacer, an electric field enhancement may occur in these gaps. This electric field enhancement may cause electrical breakdown in these gaps, resulting in potential instability of the negatively charged plate (e.g., the lower electrode). However, in one embodiment, the upper electrode may be negatively charged, so the same type of coating may be applied to the surface between the upper electrode and the isolating spacer. This potential instability causes the lens intensity to vary over time, thereby defocusing the electron beam.

[0106] In one embodiment, the inner surface 61 is shaped so that the creepage path between the boards on the inner surface is longer than the minimum distance between the boards, for example on the inner surface of a spacer between two different boards. Preferably, the inner surface 61 of the isolating spacer 60 is shaped so that the creepage length is 10 kV / mm or less, preferably 3 kV / mm or less.

[0107] Figure 6 An exemplary electron optical assembly 700 includes an isolation spacer 60 that defines a spacer aperture 70. In one embodiment, the isolation spacer 60 has a stepped shape. The isolation spacer 60 is configured to electrically isolate an upstream electron optical element and a downstream electron optical element from each other. In one embodiment, the isolation spacer 60 is configured to support two electron optical elements. The isolation spacer 60 defines a spacer aperture 70 surrounding a beam path of one or more electron beams. The spacer aperture 70 is a through hole for the path of an electron beam (optionally multiple beams) from the upstream side of the isolation spacer 60 to the downstream side of the isolation spacer 60.

[0108] like Figure 6 or Figure 7As shown, in one embodiment, the isolation spacer 60 includes an upstream portion 62, a downstream portion 64, and a middle portion 63, wherein the upstream portion 62 is adjacent to the upstream electron optical element, and the downstream portion 64 is adjacent to the downstream electron optical element. The middle portion 63 is located between the upstream portion 62 and the downstream portion 64. In one embodiment, the upstream portion 62 and the downstream portion 64 protrude relative to the middle portion 63. The upstream portion 62 and the downstream portion 64 protrude inwardly relative to the middle portion 63, so that the size of the spacer aperture 70 in the direction across the beam path at the middle portion 63 is larger than the size at the upstream portion 62 and the downstream portion 64. In one embodiment, the diameter of the spacer aperture 70 between the upstream side and the downstream side is larger than the diameter at the upstream side or the downstream side of the isolation spacer 60.

[0109] like Figure 6 As shown, in one embodiment, the spacer aperture 70 has different sizes at different positions along the electron beam direction. In one embodiment, the spacer aperture 70 has an upstream size 72, a downstream size 74, and an intermediate size 73. The intermediate size is located at an intermediate position between the upstream size 72 and the downstream size 74. For example, Figure 6 or Figure 7 As shown, in one embodiment, the intermediate dimension 73 is larger than the upstream dimension 72. In one embodiment, the intermediate dimension 73 is larger than the downstream dimension 74. In one embodiment, the dimension may be a diameter. The dimension may be referred to as a width. The dimension is generally located in a direction across the beam path, optionally orthogonal to the beam path.

[0110] A spacer aperture 70 or opening is defined in the isolation spacer 60, which may define a through channel having a surface. The through channel may have at least three different diameters along the beam path through the spacer aperture 70. In one embodiment, the stepped surface (e.g., between portions of the through channel having different diameters) is angled and preferably parallel to at least one of the upstream plate 710 and the downstream plate 720 and / or orthogonal to the beam path.

[0111] like Figure 6 or Figure 7 As shown, for example, in one embodiment, the size (or width) of the spacer aperture 70 defined in the isolation spacer 60 is smaller on the downstream side of the isolation spacer 70 than in the middle portion 63 of the isolation spacer 60. In one embodiment, the size of the spacer aperture 70 defined in the isolation spacer 60 is smaller on the upstream side of the isolation spacer 60 than in the middle portion 63 of the isolation spacer 60.

[0112] In one embodiment, one of the upstream plate 710 and the downstream plate 720 is positively charged relative to the other plate. In one embodiment, the size of the spacer aperture 70 (or spacer hole) facing the negatively charged plate is smaller than the opening (or hole) facing the positively charged plate. By making the spacer aperture 70 have a width that varies in the direction between the upstream plate 710 and the downstream plate 720, the electron creepage length on the inner surface 61 of the isolation spacer 60 can be increased. One embodiment of the present invention is expected to increase the electron creepage length between the upstream plate 710 and the downstream plate 720.

[0113] Figure 8 yes Figure 6 or Figure 7 A close-up view of a portion of the electron-optical assembly 700 is shown in FIG. Figure 8 As shown, a downstream triple point 78 (which may represent a connection to a vacuum) is formed at the connection between the isolation spacer 60, the downstream plate 720, and the spacer aperture 70. An upstream triple point 75 may be formed between the isolation spacer 60, the upstream plate 710, and the spacer aperture 70. In general, the dielectric constant of the material of the isolation spacer 60 is expected to be different from the dielectric constant of the spacer aperture 70 (which is a vacuum in the embodiment). By shaping the isolation spacer 60 so that the size of the spacer aperture 70 facing the negatively charged plate is smaller than the size of the middle portion 63, the electric field near the triple point near the negatively charged plate can be reduced.

[0114] For example, when the downstream plate 720 is a negatively charged plate, the electric field at or near the downstream triple point 78 can be reduced. When the upstream plate 710 is a negatively charged plate, the electric field at or near the upstream triple point 75 can be reduced. By reducing the electric field near the triple point, the likelihood of discharge between the upstream plate 710 and the downstream plate 720 is reduced. Embodiments of the present invention are expected to reduce the likelihood of electrical breakdown leading to undesirable discharges.

[0115] Fig. 9 yes Figure 6 or Figure 7 A close-up view of a portion of electron-optical assembly 700 is shown in FIG. Fig. 9 The simulation results show that Figure 8 Shown and referenced Figure 8 The electric field strength near the downstream triple point 78 is reduced. Fig. 9 In the example shown, the downstream plate 720 is the negatively charged plate. The wavy line in the figure (between the downstream plate 720 and the top of the figure) is a constant potential line. Fig. 9As shown, the local electric field near the downstream triple point 78 is reduced relative to other portions of the surface of the isolation spacer 60. The likelihood of electrical breakdown is reduced. Specifically, it can be generally expected that discharge or electron creepage will begin at or near such a triple point. By reducing the electric field near such a triple point, the likelihood of discharge and / or electron creepage can be reduced. This result is different from a similar design of a spacer with different diameters in at least three sections along the beam path. In this design, the middle portion of the spacer has a hole for the beam path, which has a smaller diameter than the upstream and downstream portions. Although the creepage length between the upstream and downstream plates of the spacer can be made longer than the minimum distance on the inner surface of the spacer aperture, this arrangement has been found to disadvantageously increase or concentrate the local electric field near the downstream triple point 78 between the spacer, one of the adjacent plates (e.g., the downstream plate) and the beam hole (i.e., the vacuum), thereby posing a risk of electrical breakdown.

[0116] As described elsewhere, in one embodiment, the isolation spacer 60 is shaped so that the size of the spacer aperture 70 facing the upstream plate 710 and the downstream plate 720 is smaller than the size of the middle portion 63 of the isolation spacer 60. This allows the possibility of electron creepage and / or electrical breakdown to be reduced, regardless of which of the upstream plate 710 and the downstream plate 720 is the negatively charged plate. The isolation spacer 60 can reduce the possibility of electron creepage and / or electrical breakdown in both possible directions (polarities) of the electric field. For electric fields with opposite polarities, the isolation spacer 60 can maintain its performance, i.e., maintain the electrical breakdown potential. The electric field enhancement near the negatively charged plate can be reduced or prevented. When electron creepage and / or electrical breakdown occurs, the negatively charged plate is typically the source of electrons. Therefore, the present invention is an improvement on known designs to meet the required performance specifications.

[0117] Embodiments of the present invention are expected to allow the electric field between two adjacent electrodes (e.g., upstream plate 710 and downstream plate 720) to be reversed without unduly increasing the likelihood of electron creepage and / or electrical breakdown. For example, it may be desirable to reverse the direction / complexity of the electric field to increase the possible range of potentials that may be applied to different electrodes in electron optical assembly 700. Electron optical assembly 700 may be or may include, for example, an objective lens and / or a control lens. By increasing the range of potentials that may be applied to different electrodes, electron optical assembly 700 may support a wider range of landing energies. Landing energy is the energy when the electron arrives at the sample location. Embodiments of the present invention are expected to support maintaining the electric field in both directions. Embodiments of the present invention may advantageously provide an improved operating parameter range and improved charged particle evaluation application opportunities, such as using the present invention in an evaluation device having an embodiment of a charged particle device disclosed herein.

[0118] For example, Figure 6 or Figure 7As shown, in one embodiment, the isolation spacer 60 is shaped so that the spacer aperture 70 has similar sizes at the upstream portion 62 and the downstream portion 64 in the direction across the beam path. In one embodiment, the spacer aperture 70 has the same size at the upstream portion 62 and the downstream portion 64. However, the size of the spacer aperture 70 does not have to be the same at the upstream and downstream portions 62, 64 (or the upstream and downstream ends). In one embodiment, the isolation spacer 60 is shaped so that the size of the spacer aperture 70 at the upstream portion 62 in the direction across the beam path is larger than the size at the downstream portion 64. Alternatively, the size of the spacer aperture 70 at the upstream portion 62 and the downstream portion 64 can be smaller.

[0119] In one embodiment, the shape of the isolation spacer 60 is designed to be symmetrical about a plane across the beam path. The plane may pass through the middle portion 63. The isolation spacer 60 may have a mirror image shape. The upstream half of the isolation spacer 60 may reflect the downstream half of the isolation spacer 60. The isolation spacer 60 may be contradictory with respect to the direction of the electric field between the upstream plate 710 and the downstream plate 720. The electric field may be applied in either direction between the upstream plate 710 and the downstream plate 720, with the isolation spacer 60 located between the two. One embodiment of the present invention is expected to allow the likelihood of electronic creepage and / or electrical breakdown to be equally reduced regardless of the direction of the electric field.

[0120] In one embodiment, the electron optical assembly 700 includes a voltage source electrically connected to at least one electron optical element. In one embodiment, the controller 50 is configured to control the potential difference applied by the voltage source on the electron optical element. The controller 50 can control the voltage source to apply different voltages to the upstream plate 710 and the downstream plate 720. The controller 50 can control the voltage source to control how the electron optical assembly 700 manipulates the electron beam.

[0121] In one embodiment, the isolation spacer 60 is shaped so that when a potential difference is applied across the electron optical element, the potential at the protruding corners 76, 77 of the upstream portion 62 and / or the downstream portion 64 is at a localized extreme where the size of the spacer aperture 70 changes. Figure 8 As shown, in one embodiment, the isolation spacer 60 includes a protruding corner 76 of the upstream portion 62 and a protruding corner 77 of the downstream portion 64. Figure 8 As shown, in one embodiment, the size of the spacer aperture 70 changes at the protruding corners 76, 77. There may be a step change in the size (e.g., the diameter of the spacer aperture 70 at the protruding corners 76, 77). The protruding corner 76 of the upstream portion 62 is located at the transition between the upstream portion 62 and the middle portion 63. The protruding corner 77 of the downstream portion 64 is located at the transition between the middle portion 63 and the downstream portion 64.

[0122] exist Fig. 9 In the arrangement shown, the downstream plate 720 is a negatively charged plate. The shape of the isolation spacer 60 can be such that the potential difference at the protruding corner 77 (i.e., relative to a selected relative potential of the charged particle device 40, such as ground) is at a local maximum, i.e., relative to the rest of the spacer. This means that the potential decreases from the protruding corner 77 to the downstream triple point 78. The potential decreases in the direction across the beam path from the protruding corner 77 along the surface step of the downstream portion. (Note that if this situation applies to the upstream plate 710, i.e., a negatively charged plate, the relative potentials of the upstream portion 62 and its protruding corner 76 will be the same. In addition, if this situation causes one of the plates 720, 710 to be positively charged, the characteristics of the relative potential are opposite to the situation described.) By making the protruding corners 76, 77 at local extremes, the possibility of electrons creeping through the protruding corners 76, 77 can be reduced. The protruding corners 76, 77 can form electron traps. Electrons may be effectively trapped at the protruding corners 76 , 77 and not have sufficient energy to creep in either direction along the interface (shown as horizontal) between the intermediate portion 63 and the upstream portion 62 or the downstream portion 64 of the isolation spacer 60 .

[0123] like Figures 6 to 9 As shown, in one embodiment, the isolation spacer 60 is shaped so that the size of the spacer aperture 70 has a step change in the direction of the beam path between the middle portion 63 and the upstream portion 62 and / or the downstream portion 64. The step change means that the size value of the spacer aperture 70 has an abrupt (i.e., discontinuous) change. By providing a step change, the possibility of electrons crawling between the middle portion 63 and the upstream portion 62 and / or the downstream portion 64 can be reduced. In one embodiment, the protruding corners 76, 77 are sharp corners. However, the protruding corners 76, 77 are not necessarily sharp corners. In an alternative embodiment, the protruding corners 76, 77 can be rounded. Ideally, the radius of curvature of the corners and therefore the rounding of the corners are limited to achieve the advantages of the protruding corners 76, 77 described herein.

[0124] In one embodiment, the isolation spacer 60 is shaped such that in the direction across the beam path, the size difference between the spacer aperture 70 at the middle portion 63 and the upstream portion 62 and / or the downstream 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 isolation spacer 60.

[0125] The thickness 80 of the isolation spacer 60 may be as follows: Figure 8 The difference in size of the spacer aperture 70 in the middle portion 63 in the direction across the beam path compared to the upstream portion 62 and the downstream portion 64 may be as follows: Figure 8Specifically, the size difference corresponds to twice the step width 84, 85 of the upstream portion 62 and the downstream portion 64, respectively. In one embodiment, the width of the step is of the same order of magnitude as the thickness of the isolation spacer 60. By providing a sufficiently wide step, the shape of the inner surface 61 of the isolation spacer 60 significantly increases the creepage length.

[0126] In one embodiment, the thickness 82 of the middle portion 63 is similar to the thickness 81 of the upstream portion 62 and / or the thickness 83 of the downstream portion 64. The thickness of the middle portion 63 may be greater or less than the thickness 81 of the upstream portion 62 and / or the thickness 83 of the downstream portion 64.

[0127] In one embodiment, the thickness 80 of the isolation 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 isolation spacer 60 is at most 20 mm, optionally at most 10 mm, optionally at most 5 mm, and optionally at most 3 mm.

[0128] In one embodiment, the width 84 of the step of the upstream portion 62 and / or the width 85 of the step of the downstream 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 upstream portion 62 and / or the width 85 of the step of the downstream portion 64 is at most 20 mm, optionally at most 10 mm, optionally at most 5 mm and optionally at most 2 mm.

[0129] In one embodiment, the thickness 81 of the upstream portion 62 and / or the thickness 83 of the downstream 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 upstream portion 62 and / or the thickness 83 of the downstream portion 64 is at most 5 mm, optionally at most 2 mm, and optionally at most 1 mm.

[0130] In one embodiment, the thickness 82 of the middle 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 middle portion 63 is at most 5 mm, optionally at most 2 mm, and optionally at most 1 mm.

[0131] In one embodiment, the thickness 82 of the middle portion 63 is at least 10%, optionally at least 20%, optionally at least 50%, and optionally at least 80% of the combined thickness of the upstream portion 62, the middle portion 63, and the downstream portion 64. In one embodiment, the thickness 82 of the middle portion 63 is at most 90%, optionally at most 80%, optionally at most 50%, and optionally at most 20% of the combined thickness of the upstream portion 62, the middle portion 63, and the downstream portion 64.

[0132] In one embodiment, the middle portion 63 is vertically centered (ie, the thickness of the upstream portion 62 may be the same as the thickness of the downstream portion 64 ). Alternatively, the thickness of the upstream portion 62 may be different than the thickness of the downstream portion 64 .

[0133] As described above, in one embodiment, the electron-optical component 700 is an electron-optical lens component. For example, the electron-optical lens component may include an objective lens component, or may be an objective lens component. Alternatively, the electron-optical lens component may include a converging lens component. However, the electron-optical component 700 is not necessarily an electron-optical lens component or includes an electron-optical lens component. Additionally or alternatively, the electron-optical component 700 may include one or more elements such as a collimator, a corrector (e.g., a separate beam corrector), a detector array, a deflector, and / or a Wien filter array as corresponding arrays. Generally, according to embodiments of the present invention, any two adjacent electrodes (e.g., plates set to different potentials) within the electron-optical system may be electrically isolated from each other by an isolation spacer 60. The electron-optical component 700 may be a macro component that manipulates a single beam (which may be separated into multiple beams downstream) passing through a large aperture in the electron-optical component 700, such as Figure 6 Alternatively, the electron optical assembly 700 may include an aperture array and may be configured to steer multiple electron beams through the apertures, such as Figure 7 shown.

[0134] like Fig.10 As shown, in one embodiment, electron-optical assembly 700 includes at least four electron-optical elements, each of which includes plates 710, 720, 730, 740. (The depicted arrangement may be considered an arrangement of five electron-optical elements, where the fifth element may be detector 240, as will be disclosed herein.) Each plate 710, 720, 730, 740 has one or more apertures surrounding a beam path of one or more electron beams. Fig.10 The arrangement shown shows four length plates 710, 720, 730, 740 and a detector plate of the detector 240. These plates may be electrically isolated from each other. Fig.10As shown, the isolation spacer 60 electrically isolates the upstream plate 710 from the downstream plate 720. The upstream plate and the downstream plate are located between the most upstream electron optical element (including the most upstream plate 730) and the most downstream electron optical element (including the most downstream plate 740) among the at least four electron optical elements. Fig.10 As shown, in one embodiment, one or more plates can be located downstream of the most downstream electron optical element of the at least four electron optical elements. For example, the detector plate forming the detector 240 can be located downstream of the most downstream plate 740 in the lens element. In one embodiment, the detector 240 is set to a different potential than the adjacent electron optical element 740 along the charged particle beam path, as disclosed herein.)

[0135] In one embodiment, the potential applied to the most downstream plate 740 of the lens element is controlled to have a fixed potential relative to the sample 208. In the operating mode of the electron optical device 40 including the electron optical assembly 700, the potential (or voltage) applied to the most downstream plate 740 can be kept substantially constant. In one embodiment, the voltage (or potential) applied to the most upstream plate 750 is controlled to be fixed relative to the source 201 of the electron optical device 40. When the voltage (or potential) is controlled to control the landing energy, the electric field in the electron optical assembly 700 may change. When the electric field changes, the focus of the electron beam at the sample position may change undesirably. In one embodiment, the controller 50 is configured to control the voltage (potential) applied to the upstream plate 710 and / or the downstream plate 720 to compensate for the focus change caused by the changing electric field. The present invention allows the multiple electric fields between the upstream plate 710 and the downstream plate 720 to be changed without excessively increasing the risk of electrical breakdown and / or electron creepage. In one embodiment, detector 240 may be considered another electron-optical element in that it may be set to a different potential than an adjacent electron-optical element 740 along the charged particle beam path; alternatively, the detector is set to the same potential as the adjacent electron-optical element.

[0136] like Fig.10 As shown, the other plates of the electronic optical assembly 700 can be separated by different types of isolation spacers 750, 760, 770. Some of these spacers 750, 760, 770 can be stepped structures. Others can have a uniform cross-section. Fig.10 As shown, in one embodiment, the detector 240 can be attached to one of the spacers 770 by a connecting element 79. The connecting element 79 can be an electrical isolator with an aperture, which can have the surface topography of any other isolator disclosed herein, such as an embodiment of the present invention. As shown, the isolator has a uniform diameter along the path of the charged particle beam. The detector can have a separate electrical connection with an adjacent electron optical element 740 along the path of the charged particle beam (e.g., multiple beams).

[0137] In one embodiment, the outer dimensions of the spacer in the cross-beam path direction may be larger than the outer dimensions of the electron-optical element plate. Alternatively, the outer dimensions of the spacer in the cross-beam path direction may be substantially the same as the outer dimensions of the electron-optical element plate.

[0138] In one embodiment, the electron-optical assembly 700 includes one or more electron-optical components, which include micro-electromechanical components. The electron-optical assembly 700 can be a module, such as an electron-optical module that can be called a MEMS module (e.g., taking into account the properties of the one or more electron-optical components included in the module). In one embodiment, the electron-optical assembly 700 can be replaced within the electron-optical device 40.

[0139] In the arrangement described herein, the objective lens (e.g., the objective lens of the electron optical assembly 700) is a deceleration lens. Such an objective lens is suitable for evaluating the signal particles as secondary signal particles (e.g., secondary electrons from the sample 208). For evaluating the signal particles as backscattered signal particles (e.g., backscattered electrons from the sample), the charged particle beam is composed of high-energy charged particles. For this evaluation, the objective lens is an accelerating objective lens. The detector facing the sample surface can have an applied potential to repel the secondary signal particles, for example, the applied potential is set to the maximum energy of the secondary signal particles, such as 50eV. The signal particles filtered to the detector by this applied repulsion only detect the backscattered signal particles. In order to optimize (preferably maximize) the acceleration of the charged particle beam, the potential applied to the control lens is set to decelerate the charged particle beam, preferably so that the charged particle beam has a cross or intermediate focus in the control lens. The potential applied to the uppermost beam electrode and the lowermost beam of the objective lens can be optimized, preferably maximized, so that the charged particle beam is accelerated toward the sample. Such an arrangement having a deceleration control lens with an intermediate focus, an accelerating objective lens, and a repelling bottom element of an electron-optical device (e.g., a detector array) is disclosed in U.S. application serial number 17 / 559,950 filed on December 21, 2022, which is hereby incorporated by reference with respect to the listed features and the remainder thereof in its entirety.

[0140] Using one embodiment of the present invention, a device of a charged particle device can be used, which has an accelerating objective lens for evaluation with backscattered signal particles, and the potential applied to the objective lens is switched to set the decelerating objective lens without swapping out the electron optical components from the charged particle device and reducing or even preventing the risk of electrical failure. U.S. application serial number 17 / 559,950 discloses a spacer capable of operating in a bidirectional field, which has a middle portion with a smaller diameter. Therefore, it was not expected by the inventor that the present invention of a spacer with a middle portion with a larger diameter has improved bidirectional field performance.

[0141] In one embodiment, the upstream electron-optical element and / or the downstream electron-optical element comprises 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 source. A separate voltage source may be provided for each electron-optical element. Alternatively, multiple electron-optical elements may be connected to the same power source. In one embodiment, multiple power sources are provided for different parts of the same electron-optical element.

[0142] The voltage source is configured to be electrically connected to the electron-optical elements. In one embodiment, the voltage source is configured to apply a potential to different electron-optical elements, including an upstream electron-optical element and a downstream electron-optical element.

[0143] In one embodiment, the controller 50 is configured to control a voltage source. In one embodiment, the controller 50 is configured to control the potential supply of the upstream electron optical element and the downstream electron optical element so that multiple electric fields between the electron optical elements are reversed (or inverted). This can allow the controller 50 to compensate for changes in the electron beam focus that may be caused by controlling the landing energy of the electron beam at the sample position.

[0144] In one embodiment, the voltage source is a high voltage power supply. In one embodiment, the voltage 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 to a part of the electron optical assembly 700 relative to the reference potential of the electron optical device 40, such as 25kV or even 30kV or higher. In one embodiment, the voltage source is configured to apply a positive voltage relative to the reference potential. In an alternative embodiment, the voltage source is configured to apply a negative voltage relative to the reference potential. The reference potential can be grounded. In one embodiment, one or more plates 710, 720 of the electron optical assembly 700 are configured to be connected to high voltage during use of the electron optical device 40.

[0145] In one embodiment, the electron optical assembly 700 can be controlled to manipulate one or more electron beams. This method can include applying a potential difference between an upstream electron optical element and a downstream electron optical element. The potential difference can be changed so that the direction of the electric field between the upstream electron optical element and the downstream electron optical element is reversed. In one embodiment, a controller 50 is used to control the potential difference applied to the upstream electron optical element and the downstream electron optical element. The isolation spacer 60 electrically isolates the electron optical element and the downstream electron optical element from each other. The isolation spacer 60 defines a spacer aperture 70 around the beam path of the one or more electron beams.

[0146] like Figure 6 or Figure 7 As shown, in one embodiment, the isolation spacer 60 is a single dielectric member. The dielectric member may include at least one of ceramic, glass, and quartz. The isolation spacer 60 may be formed as an integral component.

[0147] Alternatively, Fig.11 As shown, in one embodiment, the isolation spacer 60 includes two or more dielectric pieces 65, 66 fixed together. The dielectric pieces 65, 66 can be fixed together. For example, one piece 65 can be connected to another piece 66. In one embodiment, the pieces 65, 66 are connected together at a surface 67. In one embodiment, the pieces 65, 66 are bonded together and / or adhered to each other.

[0148] like Fig.11 As shown, in one embodiment, the dielectric members 65, 66 have substantially the same thickness as each other. This allows the use of plates of the same shape as the starting components of the dielectric members 65, 66. This can reduce the number of different types of components required to manufacture the electronic optical assembly 700. Embodiments of the present invention are expected to provide an improved isolation spacer 60 without excessively increasing manufacturing costs. In one embodiment, the dielectric members 65, 66 have substantially the same shape as each other. This allows the same process to be used to form them before the members 65, 66 are fixed together to form the isolation space 60. This can help reduce the cost of manufacturing the isolation spacer 60 by reducing the number of different processes required.

[0149] The dielectric members 65, 66 do not necessarily have to have the same thickness or the same shape as each other. Fig.12 As shown, in one embodiment, the dielectric members 65, 66 may have different thicknesses and / or different shapes from each other. Fig.12 As shown, in one embodiment, at least one of the dielectric members 66 has a uniform cross-section in a direction parallel to the beam path. Fig.12The lower member 66 shown does not have a stepped structure. Instead, the uniform cross section results in a flat plate. The lower member of the dielectric member 66 can have a particularly simple shape, which can help reduce manufacturing costs. Meanwhile, another member 65, such as the upper member, can be formed to have a stepped structure before securing the members 65, 66 together from the isolation spacer 60.

[0150] like Fig.13 As shown, in one embodiment, at least three dielectrics 65, 66, 68 are secured together to form the isolation spacer 60. Fig.13 As shown, in one embodiment, each dielectric 65, 66, 68 has a uniform cross-section in a direction parallel to the beam path. This allows all dielectrics 65, 66, 68 to have a particularly simple shape. There is no need to form a stepped shape in any single component forming the isolation spacer 60. This can help reduce the manufacturing cost of the isolation spacer 60. When the dielectrics 65, 66, 68 are fixed together, the isolation spacer 60 is formed to have a stepped structure.

[0151] As described above, one or more components forming the isolation spacer 60 may be processed to have a stepped structure, for example, in one embodiment, a plate is milled, machined, stamped and / or cut to form the stepped structure. In one embodiment, the components forming the isolation spacer 60 may be formed by laser ablation. Laser ablation may produce fewer particles during the manufacturing process, which may be desirable.

[0152] In one embodiment, a method of manufacturing an isolation spacer 60 as described above is provided. The isolation spacer 60 is used in an electron optical assembly 700 configured to manipulate one or more electron beams. In one embodiment, the method includes shaping two or more planar dielectric members 65, 66 to have an aperture 70 for one or more electron beam paths. In one embodiment, the method includes fixing two or more planar members 65, 66 together to form the isolation spacer 60, so that the isolation spacer 60 has an inner surface 61, which includes the inner edge of the two or more planar members 65, 66. Therefore, the isolation spacer 60 includes an upstream portion 62 for fixing to an upstream electron optical element, a downstream portion 64 for fixing to a downstream electron optical element, and an intermediate portion 63 located between the upstream portion 62 and the downstream portion 64. The upstream portion 62 and the downstream portion 64 protrude relative to the intermediate portion 63, so that the spacer aperture 70 has an increased size in the direction of the beam path across the intermediate portion 63 compared to the upstream portion 62 and the downstream portion 64.

[0153] In one embodiment, a method of manufacturing an electron optical assembly 700 as described above is provided. In one embodiment, the method includes providing an upstream electron optical element and a downstream electron optical element, each element including a plate having one or more apertures surrounding a beam path of one or more electron beams. In one embodiment, the method includes fixing (e.g., fixing) the upstream electron optical element and the downstream electron optical element to either side of a spacer 60, the spacer being configured to electrically isolate the upstream electron optical element and the downstream electron optical element from each other. The isolation spacer 60 can be as described elsewhere herein.

[0154] Electron optical assembly 700 may include or be a lens assembly for manipulating an electron beam. The lens assembly may be, for example, an objective lens assembly or a converging lens assembly, or may be a part of an objective lens assembly or a converging lens assembly. The lens assembly (e.g., an objective lens assembly) may also include an additional lens array including at least two plates, such as control lens array 250.

[0155] In one embodiment, the electron-optical assembly 700 includes one or more electron-optical elements, which include elements that can be referred to as micro-electromechanical components (although such components may not contain moving or movable features), or can be manufactured using technologies suitable for manufacturing micro-electromechanical components (such as "MEMS technology"), some of which are designed to have electron-optical functions. The electron-optical assembly 700, or at least the components of the electron-optical assembly 700, can be manufactured using such technologies. The electron-optical assembly 700 may include one or more elements that can be considered as MEMS elements. During use, one or more such elements can be controlled to be set to a high potential difference relative to a reference potential (such as ground). Such elements may need to be precisely positioned (e.g., aligned) within the electron-optical assembly 700, such as relative to the path of the beam grid and relative to other electron-optical elements within the device (such as relative to the source, relative to the path of the sample and / or the beam grid). Embodiments of the present invention are expected to allow more precise positioning (e.g., alignment) within the stack of electron-optical assemblies 700, such as during operation, without deforming the electron-optical assembly 700 due to externally applied forces or moments. Embodiments of the invention may additionally or alternatively enable such elements to be more precisely positioned (eg, aligned) relative to other elements in device 40, thereby enabling stacks of electron-optical assemblies 700 within device 40 that include such elements to be more precisely positioned (eg, aligned).

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

[0157] In one embodiment, the electron optical assembly 700 includes a collimator. For example, in one embodiment, the electron optical assembly 700 includes a magnetic collimator combined with an electrostatic capacitor lens array. The electron optical assembly 700 can include a single aperture lens array with one or two macro electrodes, placed away from the virtual source conjugate plane.

[0158] In an alternative embodiment, the electron optical assembly 700 includes a combination of a magnetic microlens and an electrostatic slit deflector. The magnetic microlens can be used for collimation. As a further alternative, in one embodiment, the electron optical assembly 700 includes a combined magnetic and electrostatic microlens and a downstream slit deflector.

[0159] In general, the electron-optical assembly 700 may include any plates, such as detector array plates, lens electrode plates (in which multiple deflectors may be integrated), multiple deflector arrays, beam aperture arrays (such as upstream aperture arrays and / or final beam limiting arrays), deflector arrays (such as strip deflector arrays), and other types of corrective elements.

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

[0161] The electron-optical device array may comprise a plurality of electron-optical devices. The electron-optical devices of the electron-optical device array are preferably configured to focus the respective multi-beams onto different areas of the same sample simultaneously.

[0162] Although the present invention has been described in conjunction with various embodiments, other embodiments of the present invention will be apparent to those skilled in the art from the description and practice of the invention disclosed herein. For example, as described above, in one embodiment, the electronic optical assembly 700 includes an electrical connector 60. However, the electrical connector 60 of the present invention can be used anywhere in the electronic optical device 40 where electrical breakdown problems may exist. In one embodiment, the electronic optical device 40 includes an electrical connector 60 that is separate from the electronic optical assembly 700. For example, the electrical connector 60 can be located at a position where a low-force electrical connection is required to other parts of the electronic optical device 40 (e.g., the body or frame of the electronic optical device 40). The electrical connector 60 can be located at a position where a particularly low-force electrical connection is not required. The electrical connector 60 can make the electronic optical device 40 more compact while providing a field-free area. The description and examples should be regarded as exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

[0163] The above description is intended to be illustrative rather than limiting. Therefore, it will be appreciated by those skilled in the art that modifications may be made as described without departing from the scope of the claims and the following clauses.

[0164] The following terms are stipulated.

[0165] Item 1. An isolation spacer of a charged particle optical component, for manipulating one or more charged particle beams between an upstream charged particle optical element and a downstream charged particle optical element, wherein the upstream charged particle optical element and the downstream charged particle optical element are controllable to have reverse polarity relative to each other, wherein the isolation spacer is configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, wherein a spacer aperture is defined around a beam path of the one or more charged particle beams in the isolation spacer, wherein the isolation spacer comprises: an upstream portion configured to be adjacent to the upstream charged particle optical element, a downstream portion configured to be adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion,

[0166] wherein the upstream portion and the downstream portion protrude relative to the middle portion such that the spacer aperture has a larger dimension at the middle portion in a direction across the beam path than at the upstream portion and the downstream portion.

[0167] Item 2. A charged particle optical component configured to manipulate one or more charged particle beams, the charged particle optical component comprising: an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams; and an isolation spacer as described in Item 1, the upstream charged particle optical element being configured to be adjacent to the upstream portion, and the downstream charged particle optical element being configured to be adjacent to the downstream portion.

[0168] Item 3. A charged particle optical component configured to manipulate one or more charged particle beams (or multiple charged particle beams), the charged particle optical component comprising: an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams (the upstream charged particle optical element and the downstream charged particle optical element each comprising a plate having a plurality of apertures surrounding one or more charged particle beams in the multiple charged particle beams, the beam path comprising the multiple charged particle beams); and an isolation spacer configured to direct the upstream charged particle beams The optical element and the downstream charged particle optical element are electrically isolated from each other, and the isolation spacer defines a spacer aperture surrounding the beam path of one or more charged particle beams; wherein the isolation spacer includes an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and a middle portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the middle portion so that the spacer aperture has an increased size at the middle portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0169] Clause 4. A charged particle optical component according to clause 2 or 3, wherein the isolation spacer is shaped so that the spacer aperture has a similar size in the direction of the beam path across the upstream portion and the downstream portion.

[0170] Clause 5. A charged particle optical component according to any one of clauses 2 to 4, wherein the shape of the isolation spacer is symmetrical about a plane across the beam path.

[0171] Clause 6. A charged particle optical component according to clause 5, wherein the plane passes through the middle portion.

[0172] Item 7. A charged particle optical component according to any one of items 2 to 6, wherein the isolation spacer is shaped so that when a potential difference is applied across the charged particle optical element, the potential at the protruding corners of the upstream portion and / or the downstream portion is a local extreme value, and the size of the spacer aperture changes at the protruding corners, wherein optionally, the charged particle optical component 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 across the charged particle optical element.

[0173] Item 8. A charged particle optical component according to any one of items 2 to 7, wherein the isolation spacer is shaped so that there is a step change in the size of the spacer aperture in the direction across the beam path between the middle portion and the upstream portion and / or the downstream portion.

[0174] Clause 9. A charged particle optical component according to clause 8, wherein the step change in size corresponds to the protrusion angle of the upstream portion and / or the downstream portion, respectively.

[0175] Clause 10. A charged particle optical component according to any one of clauses 2 to 9, wherein the isolation spacer is shaped so that in the direction across the beam path, the difference in size of the spacer aperture at the intermediate portion compared to the upstream portion and / or the downstream portion is at least 20%, optionally at least 50%, optionally at least 100%, optionally at least 200% and optionally at least 500% of the thickness of the isolation spacer.

[0176] Clause 11. The charged particle optical component of any one of clauses 2 to 10, wherein the isolation spacer is a single dielectric member.

[0177] Clause 12. A charged particle optical component according to any one of clauses 2 to 10, wherein the isolation spacer comprises two or more of the dielectric members fixed together.

[0178] Clause 13. The charged particle optical component of Clause 12, wherein the dielectric members have substantially the same thickness as one another.

[0179] Clause 14. The charged particle optical component of Clause 13, wherein the dielectric members have substantially the same shape as one another.

[0180] Clause 15. A charged particle optical component according to any of clauses 12 to 14, wherein at least one of the dielectric elements has a uniform cross-section in a direction parallel to the beam path.

[0181] Clause 16. The charged particle optical component of Clause 15, wherein each of the dielectric elements has a uniform cross-section in a direction parallel to the beam path.

[0182] Clause 17. The charged-particle optical component of any one of clauses 11 to 16, wherein the dielectric comprises at least one of: ceramic, glass, and quartz.

[0183] Clause 18. A charged particle optical component according to any preceding clause, wherein the charged particle optical component is a charged particle optical lens assembly.

[0184] Clause 19. The charged particle optical component of Clause 18, wherein the charged particle optical lens component comprises an objective lens component.

[0185] Clause 20. The charged particle optical component of Clause 18, wherein the charged particle optical lens component is an objective lens component.

[0186] Clause 21. A charged particle optical component according to clause 19 or 20, wherein the objective lens component comprises at least one of an objective lens and a control lens, desirably, the charged particle lens component is the control lens, desirably, the objective lens comprises at least two charged particle optical elements, each charged particle optical element comprising a plate having one or more apertures surrounding the beam path of the one or more charged particle beams, desirably, the control lens array comprises at least three charged particle optical elements, each charged particle optical element comprising a plate having one or more apertures surrounding the beam path of the one or more charged particle beams, desirably, the most upstream charged particle optical element of the objective lens comprises the most downstream charged particle optical element of the control lens.

[0187] Clause 22. The charged particle optical assembly of Clause 18, wherein the charged particle optical lens assembly comprises a converging lens assembly.

[0188] Clause 23. The charged particle optical component according to any one of clauses 2 to 22, wherein the charged particle optical component comprises a collimator.

[0189] Clause 24. The charged particle optical component according to any one of clauses 2 to 23, wherein the charged particle optical component comprises a separate beam corrector.

[0190] Clause 25. The charged particle optical component according to any one of clauses 2 to 24, wherein the charged particle optical component comprises a deflector.

[0191] Clause 26. A charged particle optical component according to any one of clauses 2 to 25, wherein the charged particle optical component comprises at least four charged particle optical elements, each charged particle optical element comprising a plate having one or more apertures surrounding the beam path of the one or more charged particle beams.

[0192] Item 27. A charged particle optical component according to Item 26, wherein the upstream charged particle optical element and the downstream charged particle optical element electrically isolated from each other by the isolation spacer are located between the most upstream charged particle optical element and the most downstream charged particle optical element of the at least four charged particle optical elements.

[0193] Clause 28. A charged particle optical component according to any one of Clauses 2 to 27, wherein the charged particle optical component comprises one or more charged particle optical elements, the one or more charged particle optical elements comprising micro-electromechanical components.

[0194] Clause 29. A charged particle optical component according to any one of clauses 2 to 28, wherein the upstream charged particle optical element and / or the downstream charged particle optical element comprises a semiconductor, such as silicon.

[0195] Clause 30. The charged particle optical component according to any one of clauses 2 to 29, further comprising, for each charged particle optical element, an electrical connection configured to connect the charged particle optical element to a power source, such as a voltage source.

[0196] Clause 31. A charged particle optical device for projecting a plurality of charged particle beams along respective beam paths toward a sample location, the charged particle optical device comprising the isolation spacer of clause 1 or the charged particle optical component of any one of clauses 2 to 30.

[0197] Item 32. A charged particle optical device according to Item 31, further comprising a voltage source configured to be electrically connected to the charged particle optical element, desirably used to apply a potential to different charged particle optical elements, including the upstream charged particle optical element and the downstream charged particle optical element.

[0198] Item 33. A charged particle optical device according to Item 32, further comprising a controller configured to control the voltage source, desirably controlling the potential applied to the upstream charged particle optical element and the downstream charged particle optical element so that the polarity of the electric field between the charged particle optical elements is reversed / reversed.

[0199] Clause 34. A charged particle optical apparatus comprising: the isolation spacer of clause 1, the charged particle optical component of any one of clauses 2-30, or the charged particle optical device of any one of clauses 31-33; and an actuatable stage configured to support a sample.

[0200] Item 35. A method for electrically isolating an upstream charged particle optical element and a downstream charged particle optical element from each other in a charged particle optical component configured to manipulate one or more charged particle beams, the method comprising: providing an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of one or more charged particle beams; electrically isolating the upstream charged particle optical element and the downstream charged particle optical element from each other using an isolation spacer, the isolation spacer defining the spacer aperture surrounding the beam path of the one or more charged particle beams; wherein the isolation spacer comprises an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture at the intermediate portion has an increased size along a direction across the beam path compared to the upstream portion and the downstream portion.

[0201] Clause 36. A method for controlling a charged particle optical component to manipulate one or more charged particle beams, the method comprising: applying a potential difference across an upstream charged particle optical element and a downstream charged particle optical element, the upstream charged particle optical element and the downstream charged particle optical element each comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams; and changing the potential difference so that the direction of the electric field between the upstream charged particle optical element and the downstream charged particle optical element is reversed, optionally using a controller to control the potential difference applied to the upstream charged particle optical element and the downstream charged particle optical element; wherein , an isolation spacer electrically isolates the upstream charged particle optical element and the downstream charged particle optical element from each other, and the isolation spacer defines a spacer aperture surrounding the beam path of the one or more charged particle beams; wherein the isolation spacer includes an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion, so that the spacer aperture has an increased size at the intermediate portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0202] Item 37. A method for manufacturing an isolation spacer for a charged particle optical component, the charged particle optical component being configured to manipulate one or more charged particle beams, the isolation spacer being configured to electrically isolate an upstream charged particle optical element and a downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding a beam path of the one or more charged particle beams, the method comprising: shaping two or more planar sheets of a dielectric into apertures having paths for one or more charged particle beams, different apertures having inner edges; and fixing the two or more planar sheets together to form an isolation spacer, so that the isolation spacer has an inner surface including the inner edges of the two or more planar sheets, so that the isolation spacer includes an upstream portion for fixing to the upstream charged particle optical element, a downstream portion for fixing to the downstream charged particle optical element, and an intermediate portion located between the upstream portion and the downstream portion, the upstream portion and the downstream portion protruding relative to the intermediate portion, so that the spacer aperture has an increased size at the intermediate portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0203] Clause 38. The method of clause 37, wherein the two or more dielectric members have substantially the same thickness as one another, desirably the shaping of the two or more planar members comprises shaping the two or more planar members to have substantially the same thickness as one another.

[0204] Item 39., desirably parallel to the beam path, desirably, forming at least one of the planar members comprises forming the at least one planar member to have a uniform cross-section in the direction of the beam path.

[0205] Clause 40. The method of clause 39, wherein each of the dielectric members has a uniform cross-section in a direction parallel to the beam path, desirably, forming the planar member comprises forming the planar member to have a uniform cross-section in the direction of the beam path.

[0206] Clause 41. A method according to any one of clauses 37 to 40, comprising: forming a step in the inner edge of at least one of the two or more planar members, the step having a smaller thickness than the planar member in the direction of the path of one or more charged particle beams; and the fixing comprises fixing the two or more planar members so that the inner surface including at least one inner edge includes the step, and the step or each step is included in the inner surface between the middle portion and one of the upstream portion and the downstream portion.

[0207] Clause 42. The method of clause 37, 38 or 41, wherein the dielectric members have substantially the same shape as one another, desirably, the shaping of the two or more planar members comprises shaping the two or more planar members to have substantially the same shape.

[0208] Clause 43. A method for manufacturing a charged particle optical component configured to manipulate one or more charged particle beams, comprising providing an isolation spacer, the method comprising: the method of manufacturing the isolation spacer described in any of clauses 37 to 42; and providing an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams; and securing the upstream charged particle optical element and the downstream charged particle optical element to either side of the isolation spacer;

[0209] Item 44. A method for manufacturing a charged particle optical component configured to manipulate one or more charged particle beams, the method comprising: providing an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having one or more apertures surrounding a beam path of the one or more charged particle beams; and fixing the upstream charged particle optical element and the downstream charged particle optical element to either side of an isolation spacer, the isolation spacer being configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding the beam path of the one or more charged particle beams; wherein the isolation spacer comprises an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and an intermediate portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the intermediate portion so that the spacer aperture has an increased size at the intermediate portion along a direction across the beam path compared to the upstream portion and the downstream portion.

[0210] Clause 45. The method of Clause 44, comprising forming the isolation spacer from a single dielectric piece, desirably, the dielectric comprising at least one of: ceramic, glass, and quartz.

[0211] Clause 46. The method of Clause 44, comprising forming the isolation spacer by securing two or more dielectric pieces together.

[0212] Clause 47. The method of Clause 46, wherein the dielectric members have substantially the same thickness as one another.

[0213] Clause 48. The method of Clause 47, wherein the dielectric members have substantially the same shape as one another.

[0214] Clause 49. The method of any of Clauses 46 to 48, wherein at least one of the dielectric elements has a uniform cross-section in a direction parallel to the beam path.

[0215] Clause 50. The method of Clause 49, wherein each of the dielectric elements has a uniform cross-section in a direction parallel to the beam path.

Claims

1. A charged particle optical component configured to manipulate a plurality of charged particle beams, the charged particle optical component comprising: an upstream charged particle optical element and a downstream charged particle optical element, each element comprising a plate having a plurality of apertures surrounding one or some of the plurality of charged particle beams, a beam path comprising beam paths of the plurality of charged particle beams, and an isolation spacer configured to electrically isolate the upstream charged particle optical element and the downstream charged particle optical element from each other, the isolation spacer defining a spacer aperture surrounding the beam path of the one or more charged particle beams; The isolation spacer includes an upstream portion adjacent to the upstream charged particle optical element, a downstream portion adjacent to the downstream charged particle optical element, and a middle portion between the upstream portion and the downstream portion, wherein the upstream portion and the downstream portion protrude relative to the middle portion so that the spacer aperture has an increased size at the middle portion along the direction across the beam path compared to the upstream portion and the downstream portion.

2. A charged particle optical component according to claim 1, wherein the isolation spacer is shaped so that the spacer aperture has similar dimensions at the upstream portion and the downstream portion in a direction across the beam path.

3. A charged particle optical component according to any one of claims 1 or 2, wherein the isolation spacer is shaped to be symmetrical about a plane across the beam path. The charged particle optical component of claim 3 , wherein the plane passes through the middle portion.

5. A charged particle optical component according to any one of claims 1 to 4, wherein the isolation spacer is shaped so that when a potential difference is applied across the charged particle optical element, the potential at the protruding corners of the upstream portion and / or the downstream portion where the size of the spacer aperture changes is a local extreme value, 6. The charged particle optical component according to claim 5, wherein the charged particle optical component comprises: a voltage source electrically connected to at least one of the charged-particle optical elements; as well as A controller is configured to control the potential difference applied by the voltage source across the charged-particle optical element.

7. A charged particle optical component according to any one of claims 1 to 6, wherein the isolation spacer is shaped so that there is a step change in the size of the spacer aperture in the direction along the beam path between the middle part and the upstream part and / or the downstream part.

8. The charged particle optical component according to claim 7, wherein: The step change in size corresponds to the protrusion angle of the upstream portion and / or the downstream portion, respectively.

9. A charged particle optical component according to any one of claims 1 to 8, wherein the isolation spacer is a single dielectric member.

10. A charged particle optical component according to any one of claims 1 to 9, wherein the isolation spacer comprises two or more dielectric pieces fixed together.

11. The charged particle optical component of claim 10, wherein the dielectric members have substantially the same thickness as one another, and desirably the dielectric members have substantially the same shape as one another.

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

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

14. A charged particle optical component according to any preceding claim, wherein the charged particle optical component is a charged particle optical lens assembly.

15. The charged particle optical assembly of claim 14, wherein the charged particle optical lens assembly comprises an objective lens assembly.

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