Electro-optical assembly with electromagnetic shielding

Abstract

Disclosed herein is an electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path toward a target, the electron optical assembly including an electromagnetic shield configured to surround the charged particle beam path and shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield including multiple sections extending along different positions along the beam path, each section surrounding the charged particle beam, and the sections being separable.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 63 / 075,289, filed September 7, 2020, European Patent Application No. 20200740.7, filed October 8, 2020, and U.S. Patent Application No. 63 / 126932, filed December 17, 2020, each of which is incorporated by reference in its entirety into this specification.

[0002]

[0002] Embodiments provided herein generally describe the provision of electron-optical assemblies, modules, and electron-optical columns for use in, for example, charged particle beam inspection devices. Embodiments also provide methods for manufacturing electron-optical assemblies, replacing modules, and projecting a charged particle beam along a beam path toward a target. [Background technology]

[0003]

[0003] When manufacturing semiconductor integrated circuit (IC) chips, undesired pattern defects inevitably occur on substrates (i.e., wafers) or masks during the fabrication process, for example, as a result of optical effects and accidental particles, thereby reducing yield. Therefore, monitoring the extent of undesired pattern defects is an important process in the manufacture of IC chips. More generally, inspection and / or measurement of the surface of a substrate or other object / material is an important process during and / or after its manufacture.

[0004]

[0004] Pattern inspection tools using charged particle beams have been used to inspect objects, for example, to detect pattern defects. These tools typically use electron microscopy techniques, such as scanning electron microscopes (SEMs). In an SEM, a primary electron beam of relatively high-energy electrons is targeted with a final deceleration step to land on the target with a relatively low landing energy. The electron beam is focused on the target as a probing spot. Interaction of the landing electrons from the electron beam with the material structure at the probing spot causes electrons, such as secondary electrons, backscattered electrons, or Auger electrons, to be emitted from the surface. The generated secondary electrons can be emitted from the material structure of the target. By scanning the primary electron beam as the probing spot across the target surface, secondary electrons can be emitted across the surface of the target. By collecting these emitted secondary electrons from the target surface, the pattern inspection tool can obtain an image representative of the material structure characteristics of the surface of the target.

[0005]

[0005] Another application of electron optical columns is in lithography. A charged particle beam reacts with a resist layer on the surface of a substrate. A desired pattern in the resist can be created by controlling the location on the resist layer where the charged particle beam is directed.

[0006]

[0006] An electron optical column may be a device for generating, illuminating, projecting, and / or detecting one or more charged particle beams. The charged particle beam path is controlled by electromagnetic fields. Stray electromagnetic fields can undesirably deflect the beam.

[0007]

[0007] There is a general need for improved control of charged particle beam paths. Summary of the Invention

[0008]

[0008] According to a first aspect of the present invention, there is provided an electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path towards a target, the electron optical assembly including an electromagnetic shield configured to surround the charged particle beam path and to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield including a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, and the sections being separable.

[0009]

[0009] According to a second aspect of the present invention, there is provided a module comprising an electron optical device and an electromagnetic shield of a beam path passing through the module when in an electron optical column for projecting a charged particle beam along the beam path towards a target, wherein the electromagnetic shield comprises an up beam section of an up beam of the electron optical device and a down beam section of a down beam of the electron optical device, and at least one of the up beam section and the down beam section has an interface extending radially relative to the beam path.

[0010]

[0010] According to a third aspect of the present invention, there is provided an electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path towards a target, the electron optical assembly including an electromagnetic shield surrounding the charged particle beam path and configured to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield extending along the beam path and including a plurality of sections surrounding the beam path, each section surrounding the charged particle beam path, at least two of the sections being separable and including adjacent ends that electromagnetically engage with each other.

[0011]

[0011] According to a fourth aspect of the present invention, there is provided a method for manufacturing an electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path towards a target, the method comprising providing an electromagnetic shield to surround the charged particle beam and shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, and the sections being separable.

[0012]

[0012] According to a fifth aspect of the present invention, there is provided a method for replacing a module of an electron optical column for projecting a charged particle beam along a beam path towards a target, the method comprising removing the module from the electron optical column, the electron optical column comprising an electromagnetic shield configured to surround the charged particle beam path and to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, at least one of the sections being contained within the module and separable from other of the up beam and / or down beam sections of the module.

[0013]

[0013] According to a sixth aspect of the present invention, there is provided a method for projecting a charged particle beam along a beam path towards a target, the method comprising shielding the charged particle beam from an electromagnetic field external to an electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, and the sections being separable.

[0014]

[0014] According to a seventh aspect of the present invention, there is provided a method of operating an electron-optical assembly configured to project a charged particle beam along a beam path towards a target, the assembly comprising a plurality of electromagnetic shield sections configured to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, and a module comprising an electron-optical device and configured to be removable from the assembly, the method comprising removing the module from the assembly, the removal comprising radially moving a section of the electromagnetic shield within the module relative to the beam path.

[0015]

[0015] According to an eighth aspect of the present invention, there is provided a multi-column apparatus comprising electron optical columns configured to project respective charged particle beams along respective beam paths towards a target, a charged particle source configured to generate charged particle beams for one or more of the electron optical columns, and an electromagnetic shield surrounding the charged particle beam path of at least one of the electron optical columns, wherein the electromagnetic shield comprises a plurality of sections extending along different positions along the respective beam paths, each section surrounding a charged particle beam path, and the sections are separable.

[0016]

[0016] Advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which are set forth, by way of illustration and example, specific embodiments of the invention.

[0017]

[0017] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus. [Figure 2]

[0019] 2 is a schematic diagram illustrating an example multi-beam electron optical column that is part of the example inspection apparatus of FIG. 1. [Figure 3]

[0020] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 4]

[0021] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 5]

[0022] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 6]

[0023] 1 is a schematic diagram of a portion of an electron-optical assembly according to an embodiment. [Figure 7]

[0024] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 8]

[0025] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 9]

[0026] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 10]

[0027] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 11]

[0028] 1 is a schematic diagram of an electron-optical assembly according to an embodiment. [Figure 12]

[0029] 1 is a schematic diagram of an electron optical column according to an embodiment. [Figure 13]

[0030] 1 is a schematic diagram of an electron optical column according to an embodiment. [Figure 14]

[0031] 1 is a schematic diagram of an electron optical column according to an embodiment. [Figure 15]

[0032] 1 is a schematic diagram of an electron optical column according to an embodiment. [Figure 16]

[0033] FIG. 1 is a schematic diagram of a multi-column apparatus according to an embodiment. [Figure 17]

[0034] FIG. 1 is a schematic diagram of a multi-column apparatus according to an embodiment. [Figure 18]

[0035] FIG. 1 is a schematic diagram of a multi-column apparatus according to an embodiment. [Figure 19]

[0036] FIG. 1 is a schematic diagram of a multi-column apparatus according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019]

[0037] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. Instead, the implementations are merely examples of apparatus and methods consistent with aspects related to the present invention, as set forth in the appended claims.

[0020]

[0038] The reduction in device physical size and the increase in computing power of electronic devices can be achieved by significantly increasing the packing density of circuit components such as transistors, capacitors, and diodes on IC chips. This has been made possible by improvements in resolution, which allow for the creation of ever-smaller structures. Semiconductor IC manufacturing is a complex and time-consuming process involving hundreds of individual steps. An error in any step of the process for manufacturing IC chips can adversely affect the functionality of the final product. A single defect can cause device failure. It is desirable to improve the overall yield of a process. For example, to achieve a 75% yield for a 50-step process (where steps can refer to the number of layers formed on a wafer), each individual step must have a yield greater than 99.4%. If each individual step has a 95% yield, the overall process yield is as low as 7–8%.

[0021]

[0039] It is also desirable to maintain a high substrate (i.e., wafer) throughput, defined as the number of substrates processed per hour. High process yields and high substrate throughput can be affected by the presence of defects. This is especially true when operator intervention is required to investigate the defects. High-throughput detection and identification of microscale and nanoscale defects by inspection tools (such as scanning electron microscopes ("SEMs")) is desirable to maintain high yields and low costs for IC chips.

[0022]

[0040] An SEM includes a scanning device and a detector. The scanning device includes an illumination device, including an electron source, for generating primary electrons and a projection device for scanning a target, such as a substrate, with one or more focused beams of primary electrons. The primary electrons interact with the target and generate interaction products, such as secondary electrons and / or backscattered electrons. The detector captures the secondary electrons and / or backscattered electrons from the target as it is scanned so that the SEM can generate an image of the scanned area of ​​the target. Electron-optical tool designs embodying these SEM features may have a single beam. For higher throughput, such as for inspection, some designs use multiple focused beams of primary electrons, or multibeams. The component beams of a multibeam are sometimes called subbeams or beamlets. A multibeam can simultaneously scan different portions of the target. Therefore, a multibeam inspection system can inspect a target much faster than a single-beam inspection system, for example by moving the target at a higher speed.

[0023]

[0041] In a multi-beam inspection apparatus, some paths of the primary electron beam are displaced away 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). To ensure that all electron beams reach the sample surface at substantially the same angle of incidence, sub-beam paths with a greater radial distance from the central axis need to be steered to move through a larger angle than sub-beam paths closer to the central axis. This stronger steering can cause aberrations that blur the resulting image and defocus the image. One example is spherical aberration, which causes the focal point of each sub-beam path to a different focal plane. Specifically, for sub-beam paths that are not on the central axis, the change in the focal plane of the sub-beam increases with radial displacement from the central axis. Such aberrations and defocusing effects can remain associated with secondary electrons from the target when they are detected, for example, affecting the shape and size of the spot formed by the sub-beam on the target. Therefore, such aberrations degrade the quality of the resulting image produced during inspection.

[0024]

[0042] Known implementations of multi-beam inspection devices are described below.

[0025]

[0043] The figures are schematic. Accordingly, in the drawings, the relative dimensions of components 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 differences relative to individual embodiments are described. While the description and drawings are directed to electron-optical devices, it is understood that the embodiments are not used to limit the present disclosure to specific charged particles. Thus, throughout this document, references to electrons and items referred to in relation to electrons can be considered to be references to charged particles and items referred to in relation to charged particles more generally, and charged particles are not necessarily electrons.

[0026]

[0044] Referring now to Figure 1, Figure 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus 100. The inspection apparatus 100 of Figure 1 includes a vacuum chamber 10, a load lock chamber 20, an electron optical column 40 (also known as an electron beam tool), a front-end equipment module (EFEM) 30, and a controller 50. The electron optical column 40 may be located within the vacuum chamber 10.

[0027]

[0045] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include one or more additional load ports. The first load port 30a and the second load port 30b can receive, for example, substrates to be inspected (e.g., semiconductor substrates or substrates made of other materials) or substrate front opening unified pods (FOUPs) containing targets (hereinafter, substrates, wafers, and samples are collectively referred to as "targets"). One or more robotic arms (not shown) of the EFEM 30 transport the targets to the load lock chamber 20.

[0028]

[0046] The load lock chamber 20 is used to remove gas from around the target. The load lock chamber 20 may be connected to a load lock vacuum pumping system (not shown), which removes gas particles from the load lock chamber 20. Operation of the load lock vacuum pumping system allows the load lock chamber to reach a first pressure below atmospheric pressure. The main chamber 10 is connected to a main chamber vacuum pumping system (not shown). The main chamber vacuum pumping system removes gas molecules from the main chamber 10 so that the pressure around the target reaches a second pressure below the first pressure. After reaching the second pressure, the target is transported to the electron optical column 40, where it can be inspected. The electron optical column 40 may include a single-beam or multi-beam electron optical device.

[0029]

[0047] The controller 50 is electronically connected to the electron optical column 40. The controller 50 may be a processor (e.g., a computer) configured to control the charged particle beam inspection apparatus 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. While FIG. 1 illustrates the controller 50 as external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it is understood that the controller 50 may be part of the structure. The controller 50 may be located within one of the component elements of the charged particle beam inspection apparatus, or the controller 50 may be distributed among at least two of the component elements. While the present disclosure provides an example of a main chamber 10 housing an electron beam inspection tool, it should be noted that aspects of the present disclosure, in a broad sense, are not limited to chambers housing electron beam inspection tools. Rather, it is understood that the principles described above may also be applied to other tools and other arrangements of apparatus operating under a second pressure.

[0030]

[0048] Referring now to FIG. 2, FIG. 2 is a schematic diagram of an exemplary multi-beam electron optical column 40 of the inspection apparatus 100 of FIG. 1. In an alternative embodiment, the inspection apparatus 100 is a single-beam inspection apparatus. The electron optical column 40 may include an electron source 301, a beamformer array 372 (also known as a gunn aperture plate, a Coulomb aperture array, or a pre-sub-beam forming aperture array), a condenser lens 310, a source converter (or micro-optic array) 320, an objective lens 331, and a target 308. In one embodiment, the condenser lens 310 is magnetic. The target 308 may be supported by a support on a stage. The stage may be motorized. The stage moves so that the target 308 is scanned by the incident electrons. The electron source 301, the beamformer array 372, and the condenser lens 310 may be components of an illumination system included by the electron optical column 40. A source converter 320 (also known as a source conversion unit), which will be described in more detail below, and an objective lens 331 may be components of a projection system contained by the electron optical column 40 .

[0031]

[0049] The electron source 301, beamformer array 372, condenser lens 310, source converter 320, and objective lens 331 are aligned with a primary electron optical axis 304 of the electron optical column 40. The electron source 301 may generate a primary beam 302 generally along the electron optical axis 304 and with a (virtual or real) source crossover 301S. During operation, the electron source 301 is configured to emit electrons. The electrons are extracted or accelerated by an extractor and / or an anode to form the primary beam 302.

[0032]

[0050] The beamformer array 372 blocks peripheral electrons from the primary electron beam 302 to reduce the resulting Coulomb effect. The primary electron beam 302 may be reduced by the beamformer array 372 to a specified number of sub-beams (e.g., three sub-beams 311, 312, and 313). It should be understood that this description is intended to apply to an electron optical column 40 having any number of sub-beams, such as one, two, or four or more. In operation, the beamformer array 372 is configured to block peripheral electrons to reduce the Coulomb effect. The Coulomb effect may increase the size of each of the probe spots 391, 392, and 393 and thus reduce the inspection resolution. The beamformer array 372 reduces aberrations due to Coulomb interactions between electrons projected onto the beam. The beamformer array 372 may include multiple apertures to generate primary sub-beams even before the source transducer 320.

[0033]

[0051] The source converter 320 is configured to convert the beam (including sub-beams, if any) transmitted by the beamformer array 372 into sub-beams that are projected toward the target 308. In an embodiment, the 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 beamlets from the sub-beams.

[0034]

[0052] As shown in FIG. 2 , in one embodiment, the electron optical column 40 includes a beam-limiting aperture array 321 having an aperture pattern (i.e., apertures arranged in a certain pattern) configured to define the outer dimensions of the beamlets (or sub-beams) projected toward the target 308. In one embodiment, the beam-limiting aperture array 321 is part of the source converter 320. In an alternative embodiment, the beam-limiting aperture array 321 is part of the main column's up-beam system. In one embodiment, the beam-limiting aperture array 321 splits one or more of the sub-beams 311, 312, 313 into beamlets such that the number of beamlets projected toward the target 308 is greater than the number of sub-beams transmitted through the beamformer array 372. In an alternative embodiment, the beam-limiting aperture array 321 maintains the number of sub-beams incident on the beam-limiting aperture array 321, in which case the number of sub-beams may be equal to the number of beamlets projected toward the target 308.

[0035]

[0053] 2, in one embodiment, the electron optical column 40 includes a pre-bend deflector array 323 with pre-bend deflectors 323_1, 323_2, and 323_3 for bending the sub-beams 311, 312, and 313, respectively. The pre-bend deflectors 323_1, 323_2, and 323_3 may bend the paths of the sub-beams 311, 312, and 313 onto the beam-limiting aperture array 321.

[0036]

[0054] The electron optical column 40 may also include an image forming element array 322 with image forming deflectors 322_1, 322_2, and 322_3. There is a respective deflector 322_1, 322_2, and 322_3 associated with each beamlet path. The deflectors 322_1, 322_2, and 322_3 are configured to deflect the beamlet path toward the electron optical axis 304. The deflected beamlets form virtual images (not shown) of the source crossover 301S. In this embodiment, these virtual images are projected onto the target 308 by the objective lens 331, forming probe spots 391, 392, and 393 on the target. The electron optical column 40 may also include an aberration compensator array 324 configured to compensate for aberrations that may be present in each sub-beam. In some embodiments, the aberration compensator array 324 includes lenses configured to act on each beamlet. The lenses may take the form of a lens array. The array of lenses may act on different beamlets of the multi-beam. The aberration compensator array 324 may include, for example, a field curvature compensator array (not shown) with, for example, microlenses. The field curvature compensators and microlenses may be configured to compensate individual sub-beams for field curvature aberrations that are significant at, for example, the probe spots 391, 392, and 393. The aberration compensator array 324 may include an astigmatism compensator array (not shown) with microastigmatists. The microastigmatists may be controlled to act on the sub-beams to compensate for astigmatism that would otherwise be present at, for example, the probe spots 391, 392, and 393.

[0037]

[0055] The source converter 320 may further include a pre-bend deflector array 323 with pre-bend deflectors 323_1, 323_2, and 323_3 for bending the sub-beams 311, 312, and 313, respectively. The pre-bend 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-bend micro-deflector array 323 may be configured to bend the sub-beam paths of the sub-beams toward a plane perpendicular to the plane on the beam-limiting aperture array 321. In an alternative embodiment, the condenser lens 310 may adjust the path directions of the sub-beams onto the beam-limiting aperture array 321. The collecting 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, so 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-bending deflector array 323 may not be necessary.

[0038]

[0056] The image forming element array 322, the aberration compensator array 324, and the pre-bending deflector array 323 may include multiple layers of sub-beam steering devices, some of which may be in the form of a form or an array (e.g., micro-deflectors, micro-lenses, or micro-astigmatists). The beam paths may be rotationally steered. The rotational correction may be provided by magnetic lenses. Additionally or alternatively, the rotational correction may be realized by existing magnetic lenses, such as in a focusing lens arrangement.

[0039]

[0057] In this example of electron optical column 40, the beamlets are deflected by deflectors 322_1, 322_2, and 322_3, respectively, of imaging element array 322 toward electron optical axis 304. It is understood that the beamlet paths may already coincide with electron optical axis 304 before reaching deflectors 322_1, 322_2, and 322_3.

[0040]

[0058] The objective lens 331 focuses the beamlets onto the surface of the target 308, i.e., the objective lens 331 projects three virtual images onto the target surface. The three images formed on the target surface by the three sub-beams 311-313 form three probe spots 391, 392, and 393 on the target surface. In some embodiments, the deflection angles of the sub-beams 311-313 are adjusted to pass through or approach the front focus of the objective lens 331 to reduce or limit off-axis aberrations of the three probe spots 391-393. In some configurations, the objective lens 331 is magnetic. Although three beamlets are mentioned, this is merely an example. Any number of beamlets may be present.

[0041]

[0059] The manipulators are configured to manipulate one or more charged particle beams. The term manipulator encompasses deflectors, lenses, and apertures. The pre-bending deflector array 323, the aberration compensator array 324, and the image forming element array 322, individually or in combination with each other, may be referred to as the manipulator array 34 because they manipulate one or more charged particle sub-beams or beamlets. The lenses and deflectors 322_1, 322_2, and 322_3 may be referred to as manipulators because they manipulate one or more charged particle sub-beams or beamlets.

[0042]

[0060] In some embodiments, a beam separator (not shown) is provided. The beam separator may be located in the down-beam of the source converter 320. The beam separator may be, for example, a Wien filter including an electrostatic dipole field and a magnetic dipole field. The beam separator may be positioned between adjacent sections 32 of the shield 31 (described in more detail below) in the direction of the beam path. The inner surface 39 of the shield may be located radially inside the beam separator. Alternatively, the beam separator may be located within the shield 31. In operation, the beam separator may be configured to exert an electrostatic force on individual electrons of the sub-beam by the electrostatic dipole field. In some embodiments, the electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted on individual primary electrons of the sub-beam by the magnetic dipole field of the beam separator. Thus, the sub-beams may pass at least substantially straight through the beam separator with at least substantially zero deflection angle. The direction of the magnetic force depends on the direction of electron movement, and the direction of the electrostatic force does not depend on the direction of electron movement. Thus, because the secondary and backscattered electrons generally move in the opposite direction compared to the primary electrons, the magnetic force on the secondary and backscattered electrons no longer cancels the electrostatic force, and as a result, the secondary and backscattered electrons traveling through the beam separator are deflected away from the electron optical axis 304.

[0043]

[0061] In some embodiments, a secondary column (not shown) is provided that includes detector elements for detecting a corresponding secondary charged particle beam. Upon incidence of the secondary beam on a detector 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 detector element may include one or more pixels. The intensity signal output of a detector element may be the sum of signals generated by all pixels within the detector element.

[0044]

[0062] In some embodiments, a secondary projection device and associated electron detection device (not shown) are provided. The secondary projection device and associated electron detection device may be aligned with the secondary electron optical axis of the secondary column. In some embodiments, a beam separator is positioned 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 regions of the electron detection device. The secondary projection device and associated electron detection device may register and generate an image of the target 308 using the secondary electrons or backscattered electrons.

[0045]

[0063] In one embodiment, the inspection device 100 includes a single source.

[0046]

[0064] Any element or group of elements may be replaceable or field replaceable within the electron-optical column. One or more electron-optical components within the column, particularly those that act on or generate sub-beams, such as the aperture array and manipulator array, may include one or more microelectromechanical systems (MEMS). The pre-bending deflector array 323 may be a MEMS. MEMS are miniature mechanical and electromechanical elements fabricated using microfabrication techniques. In one embodiment, the electron-optical column 40 includes apertures, lenses, and deflectors formed as MEMS. In one embodiment, the manipulators, such as lenses and deflectors 322_1, 322_2, and 322_3, can be passively, actively, as an entire array, individually, or in groups within the array to control the charged particle beamlets projected toward the target 308.

[0047]

[0065] In certain embodiments, the electron optical column 40 may include alternative and / or additional components in the charged particle path, such as lenses and other components (some of which are described above with reference to FIGS. 1 and 2 ). Specifically, embodiments include an electron optical column 40 that splits a charged particle beam from a source into multiple sub-beams. Multiple respective objective lenses may project the sub-beams onto a sample. In some embodiments, multiple condenser lenses are provided from the objective lens to the up-beam. The condenser lenses focus each sub-beam to an intermediate focus at the up-beam of the objective lens. In some embodiments, a collimator is provided from the objective lens to the up-beam. Correctors may be provided to reduce focus errors and / or aberrations. In some embodiments, such correctors are integrated into the objective lens or positioned directly adjacent to the objective lens. If a collecting lens is provided, such a corrector may additionally or alternatively be integrated into the collecting lens or positioned directly adjacent to the collecting lens and / or positioned at or positioned directly adjacent to the intermediate focus. A detector is provided to detect charged particles emitted by the sample. The detector may be integrated into the objective lens. The detector may be located on the bottom surface of the objective lens facing the sample in use. The collecting lens, objective lens, and / or detector may be formed as MEMS or CMOS devices.

[0048]

[0066] 3 illustrates an electron optical assembly according to one embodiment of the present invention. The electron optical assembly is for an electron optical column 40. The electron optical column 40 is for projecting a charged particle beam along a beam path toward a target 308. In one embodiment, the beam path is in the axial direction of the electron optical column 40. The axial direction coincides with the electron optical axis 304. Alternatively, the beam path may be angled relative to the electron optical axis 304.

[0049]

[0067] 3, in one embodiment, the electron-optical assembly includes an electromagnetic shield 31. The electromagnetic shield is configured to surround the charged particle beam and shield the charged particle beam from electromagnetic fields external to the electromagnetic shield 31.

[0050]

[0068] In the electron optical column 40, the path of the charged particle beam is controlled by electromagnetic fields. For example, an internal electromagnetic field may be used (i.e., inside the shield 31) to control the charged particle beam path. Therefore, the internal electromagnetic field is predetermined in the design and operation of the electron optical assembly. External (i.e., stray) electromagnetic fields may undesirably deflect the charged particle beam from its intended path. Here, external means outside the shield. The electromagnetic shield 31 is configured to attenuate external electromagnetic fields. The electromagnetic shield 31 is configured to reduce the effect of external electromagnetic fields on the charged particle beam path.

[0051]

[0069] In some embodiments, the electromagnetic shield 31 is configured to shield the charged particle beam from electric fields. In some embodiments, the electromagnetic shield 31 includes a conductive material. For example, the electromagnetic shield 31 may include a conductive material such as a metal, such as copper, nickel, iron, or cobalt, or a doped semiconductor, or a metal coating. Such a metal coating may be provided on a metal or a non-metallic material, such as plastic. The shield 31 may have a low resistance connection to its ground connection. By surrounding the beam with a low-ohmic material, the effects of stray electric fields can be attenuated. In some embodiments, the electromagnetic shield 31 is connected to a DC potential. In some embodiments, the DC potential is ground potential. Alternatively, the DC potential may be a fixed potential different from ground to provide an electrostatic lens.

[0052]

[0070] In some embodiments, electromagnetic shield 31 is configured to shield the charged particle beam from magnetic fields. In some embodiments, electromagnetic shield 31 includes a magnetically permeable material. For example, electromagnetic shield 31 may include an alloy. The alloy may include nickel and / or iron and / or cobalt. In some embodiments, electromagnetic shield 31 includes one or more rare earth elements. In some embodiments, electromagnetic shield 31 includes a material having a relative magnetic permeability of at least 5,000, 10,000, optionally at least 20,000, optionally at least 50,000, and optionally at least 100,000. In some embodiments, electromagnetic shield 31 is heat treated. In some embodiments, electromagnetic shield 31 undergoes a magnetic annealing process. In some embodiments, electromagnetic shield 31 is heated in a hydrogen atmosphere.

[0053]

[0071] As shown in FIG. 3 , in one embodiment, the electromagnetic shield 31 includes multiple sections 32. The sections 32 of the electromagnetic shield 31 extend along different positions along the beam path. In the orientation shown in FIG. 3 , the beam path extends from top to bottom. Three sections 32 are shown in FIG. 3 . The middle section 32 extends along the portion of the beam path that is in the down beam of the top section 32 shown and in the up beam of the bottom section 32 shown. Each section 32 is configured to surround a charged particle beam. The beam may be a multi-beam.

[0054]

[0072] As shown in FIG. 3 , in some embodiments, sections 32 of electromagnetic shield 31 are separable. By providing sections 32 as separable, it is easier to disassemble portions of electron optical column 40 and / or replace one or more portions of electron optical column 40. Portions of electron optical column 40 can be removed one by one. Sections 32 can be removed one by one to remove and / or replace portions of electron optical column 40. Some embodiments of the present invention are expected to make it easier to maintain electron optical column 40.

[0055]

[0073] In FIG. 3 (and in some other figures), the electromagnetic shield 31 is shown as being symmetrically positioned around the beam path. In reality, the origin and direction of the external stray magnetic field may be unknown. The symmetric electromagnetic shield 31 may have a predetermined attenuation factor regardless of the direction of the stray magnetic field. However, it is not essential to the present invention that the electromagnetic shield 31 be positioned symmetrically around the beam path. The electromagnetic shield may also be positioned off-center from the beam path. In some cases, the direction of the external magnetic field may be known (e.g., because the source of the magnetic field is known). In some embodiments, the electromagnetic shield 31 is designed to attenuate the effect of the magnetic field in one particular direction more than in another direction.

[0056]

[0074] As shown in FIG. 3 , in some embodiments, the sections 32 are arranged such that gaps 33 in the electromagnetic shield 31 are formed between adjacent sections 32 in the direction of the beam path. For example, two gaps 33 are shown between three sections 32. The three exemplary sections may be referred to as an up-beam section 32′ for the up beam of the central section 32 and a down-beam section 32″ for the down beam of the central section 32. As shown in FIG. 3 , in some embodiments, the sections 32 are arranged such that at least one section 32, e.g., the central section 32, is movable radially relative to the beam path independently from another one of the sections 32, e.g., the up-beam and down-beam sections 32′, 32″. In the orientation shown in FIG. 3 , the radial direction is the left-right direction (i.e., across the vertical edges of the page). In some embodiments, one of the sections 32 is shiftable in an angular direction, preferably perpendicular to the beam path, independently from another one of the sections 32. In some embodiments, the sections 32 are shiftable independently of one another in a direction angled relative to a direction perpendicular to the beam path.

[0057]

[0075] Certain embodiments of the present invention are expected to make it easier to remove and / or replace portions along the electron optical column 40. Disassembly and assembly can be performed by moving sections 32 in an angled direction (optionally perpendicular) to the beam path. Disassembly and assembly may also be possible by moving sections 32 in the direction of the beam path, e.g., by removing sections one by one. The gap 33 makes it easier for a section 32 to be shifted into or out of the beam path independently of the other sections 32 (e.g., without contacting or interfering with the other sections 32). In certain embodiments, the shield 31 includes an aperture through which the beam path extends. In certain embodiments, the aperture has a dimension of at least 2 mm, optionally at least 5 mm, in a direction perpendicular to the beam path. In certain embodiments, the beam has a dimension within the range of 1 to 2 mm. The beam fits into the aperture before and after replacing sections 32 of the shield 31.

[0058]

[0076] As shown in FIG. 3 , in some embodiments, adjacent sections 32 have opposing surfaces 34. The opposing surfaces 34 of a section face the opposing surfaces 34 of the adjacent sections 32 of the electromagnetic shield 31. The opposing surfaces 34 are arranged to extend away from the beam path, preferably in a radial direction relative to the beam path. The opposing surfaces 34 of adjacent sections 32 may be parallel. In the arrangement shown in FIG. 3 , the opposing surfaces 34 of the top and middle sections 32 extend farther, preferably in a radial direction, than the opposing surfaces 34 of the middle and bottom sections 32. In some embodiments, the opposing surfaces 34 define the extent of the gap 33 in the direction of the beam path.

[0059]

[0077] In one embodiment, the facing surfaces 34 preferably extend radially away from the beam path by a distance at least as large as the gap 33 between adjacent sections 32. As shown in FIG. 3 , the gap 33 between the top section 32 and the middle section 32 has a distance D1. The distance D1 is measured in the direction of the beam path. The facing surfaces 34 on either side of the gap 33 preferably extend radially away from the beam path by a width W1. The width W1 is measured radially (which may be perpendicular to the direction of the beam path). The width W1 is measured from the inner surface of the section 32 to the radially outer edge of the facing surfaces 34. In one embodiment, W1≧D1. That is, the width W1 can be greater than or equal to the distance D1.

[0060]

[0078] 3, the gap 33 between the bottom and middle sections 32, 32' has a distance D2 in a direction parallel to the beam path. Facing surfaces 34 on either side of the gap 33 extend radially (width W2), e.g., relative to the beam path. In some embodiments, W2≧D2. That is, width W2 can be greater than or equal to distance D2.

[0061]

[0079] The radial extent of the facing surfaces 34 can help the sections 32 attenuate the effects of stray electromagnetic fields. Generally, increasing the radial extent of the facing surfaces 34 relative to the size of the gaps 33 reduces the effects of stray electromagnetic fields. In some embodiments, the facing surfaces 34 extend radially a distance at least twice as large as the gaps 33 between adjacent sections 32. In some embodiments, the facing surfaces 34 extend radially a distance at least three times as large as the gaps 33 between adjacent sections 32. In some embodiments, the facing surfaces 34 extend radially a distance at least four times as large as the gaps 33 between adjacent sections 32. In some embodiments, the facing surfaces 34 extend radially a distance at least five times as large as the gaps 33 between adjacent sections 32.

[0062]

[0080] In the arrangement shown in FIG. 3 , the opposing surfaces 34 on either side of the gap 33 extend an equal distance in the radial direction. However, this is not necessarily the case. In an alternative embodiment, the opposing surfaces 34 on either side of the gap 33 may extend different distances in the radial direction. In some embodiments, the shorter of the two opposing surfaces 34 extends radially a distance at least as large as (or two, three, four, or five times as large as) the size of the gap 33. Some embodiments of the present invention are expected to reduce the effects of stray electromagnetic fields on the beam path. In some arrangements, the opposing surfaces 34 may extend non-uniform distances around and relative to the beam path. For example, in opposite radial directions relative to the beam path, the opposing surfaces may extend farther from the beam than in the other direction.

[0063]

[0081] As shown in FIG. 3 , in some embodiments, at least one end of section 32 in the direction of the beam path includes a flange 35 extending radially relative to the beam path. In some embodiments, flange 35 includes a facing surface 34. In some embodiments, the electromagnetic shield is preferably flared radially away from the beam path. Flange 35 helps increase the radial extent of facing surface 34 without unduly increasing the thickness of electromagnetic shield 31. By keeping the thickness of electromagnetic shield 31 relatively small, material costs for the electromagnetic shield are limited. Some embodiments of the present invention are expected to reduce the effects of stray electromagnetic fields on the beam without unduly increasing manufacturing costs.

[0064]

[0082] FIG. 4 shows a schematic diagram of a portion of an electron optical column 40 according to an embodiment of the present invention. It is not necessary to provide a flange, as shown in FIG. 4. In the arrangement shown in FIG. 4, the top section 32′ of the electromagnetic shield 31 has an outer diameter that may be constant. The facing surface 34 extends in a radial direction. The radial extent of the facing surface 34 is provided by increasing the thickness of the section 32 (compared to the central section 32). The radial extent of the facing surface 34 is provided by the thickness of the top section 32. The facing surface is therefore provided by the wall of the shield 31. That is, the shield is a tube with a facing surface that coincides with the end surface of the tube. The thickness of the tube may therefore define widths W1 and W2 away from the beam path, at least at the ends that provide the walls.

[0065]

[0083] The middle section 32 shown in FIG. 4 is similar to the middle section 32 shown in FIG. 3. The bottom section 32″ shown in FIG. 4 includes a flange 35. The bottom section 32 has thicker walls than the walls of the middle section 32. In the bottom section 32″, the radial extent of the facing surface 34 is provided in part by the increased thickness of the bottom section 32″ (compared to the middle section 32) and in part by the provision of the flange 35.

[0066]

[0084] As shown in FIG. 4 , in some embodiments, the electron-optical assembly includes at least one electron-optical element between adjacent sections 32 of the electromagnetic shield 31. The electron-optical element is configured to act on the beam path. For example, in some embodiments, one or more deflectors 36 are provided between adjacent sections 32. (The deflectors are shown in cross section as well as in section.) In some embodiments, one or more lenses 37 are provided between adjacent sections 32. (An electrostatic lens includes two or more plates, but for simplicity, these lenses are shown schematically.) Other types of electron-optical elements may be positioned between adjacent sections 32. A magnetic lens may include a coil outside the shield 31 and a core positioned between adjacent sections 32. In some embodiments, the electron-optical element between sections 32 is a MEMS element. For example, the deflector 36 and / or the lens 37 may be a MEMS.

[0067]

[0085] In some embodiments, the electromagnetic shield 31 is configured to extend around the multi-beam path. In some embodiments, the electromagnetic shield 31 includes multiple sections 32: an up-beam section 32′ for the up-beam of the electron-optical element, a down-beam section 32″ for the down-beam of the electron-optical element, and an element section 32 associated with the electron-optical element. In some embodiments, the element section 32 is configured to be removable from a tool with the electron-optical element. In some embodiments, a small gap exists between adjacent sections 32 along the beam path.

[0068]

[0086] In the embodiment shown in FIG. 4, the deflector 36 acts on the beam passing through the gap 33. In the embodiment shown in FIG. 4, the deflector 36 is positioned radially outside the outer extent of the section 32. In an alternative embodiment, the deflector 36 may be positioned at least partially inside the outer radial extent of the section 32. The outer radial extent of the section 32 may correspond to a longitudinal surface that may be parallel to the direction of the beam path. In an embodiment, the deflector 36 is located within the gap 33, for example, between the opposing surfaces 34 that define the gap 33. Positioning the deflector 36 closer to the beam reduces undesirable attenuation of the deflector 36's effect on the beam by the shield 31. In an embodiment, the deflector 36 is aligned with the inner surface 39 of the section 32. In an embodiment, the deflector 36 is closer to the beam path than the inner surface 39 of the section 32.

[0069]

[0087] 4, in some embodiments, lens 37 extends radially outward beyond the radially inner edge of section 32 of electromagnetic shield 31. The outer periphery of lens 37 is located within gap 33. In some embodiments, lens 37 is a lens array. Additionally or alternatively, an array of deflectors or apertures may be positioned between adjacent sections 32.

[0070]

[0088] FIG. 5 illustrates a portion of an electron-optical column 40 according to an embodiment. As shown in FIG. 5 , in an embodiment, the electron-optical column 40 includes a module 405. In an embodiment, the module 405 includes an electron-optical assembly. The module 405 may include a section 32 of the electromagnetic shield 31. As shown in FIG. 5 , in an embodiment, the module 405 includes an electron-optical element 38. In an embodiment, the electron-optical element 38 includes one or more manipulators, such as an aperture, a deflector, and a lens. The electron-optical element 38 may be a manipulator array. In an embodiment, the electron-optical element is a MEMS element. As shown in FIG. 5 , in an embodiment, the section 32 in the module 405 is flared. The electron-optical element includes surface portions facing the opposing surfaces 34 of the section 32 on either side of the electron-optical element 38.

[0071]

[0089] In the module 405 shown in FIG. 5 , two sections 32 of the electromagnetic shield 31 are provided. An electron-optical element 38 is located between these sections 32. Gaps of distances D3 and D4 are formed between the sections 32 and the surface portions, i.e., the surfaces of the electron-optical element 38 in the direction of the beam path opposite the opposing surfaces of the sections 32. The opposing surfaces of the sections 32 together with the opposing surface portions define corresponding gaps. The opposing surfaces that define the gap together with the surface portion gap extend radially by distances W3 and W4, respectively. In some embodiments, W3 is at least as large as D3. In some embodiments, W3 is twice (or three times, or four times, or five times) as large as D3. In some embodiments, W4 is at least as large as D4. In some embodiments, W4 is twice (or three times, or four times, or five times) as large as D4.

[0072]

[0090] In some embodiments, the module 405 includes electron-optical components on a stage that allows actuation for component positioning. In some embodiments, the module 405 includes a stage. In some arrangements, the stage and module can be an integral part of the electron-optical column 40. In some arrangements, the module 405 is limited to the stage and the electron-optical device it supports. In some arrangements, the stage is removable. In an alternative design, the module 405, including the stage, is removable. The portion of the electron-optical column 40 related to the module 405 is isolable, i.e., this portion of the electron-optical column 40 is defined by a valve on the up beam of the module 405 and a valve on the down beam of the module 405. The valves can be operated to isolate the environment between the valves from the up beam and down beam vacuums, respectively, allowing the module 405 to be removed from the electron-optical column 40 while maintaining the up beam and down beam vacuums of the portion of the column associated with the module 405. In some embodiments, the module 405 includes a stage. The stage is configured to support the electron-optical device relative to the beam path. In an embodiment, the module 405 includes one or more actuators. The actuators are associated with the stage. The actuators are configured to move the electro-optical device relative to the beam path. In an embodiment, the actuators are external to the electromagnetic shield 31. In an embodiment, sections 32 of the electromagnetic shield 31 associated with the electro-optical device are provided on either side of the stage.

[0073]

[0091] If the electron-optical device is alignable with respect to the beam path by an actuator, at least one of the sections 32 associated with the electron-optical device may be actuable. In an embodiment, one or more actuators are configured to actuate the sections 32 of the electromagnetic shield 31 relative to a frame of the electron-optical column 40. The frame may be associated with a stage of the module 405. In an embodiment, the sections 32 are actuable relative to the stage of the module 405. In an embodiment, the sections 32 are fixed relative to the electron-optical device. At least one of the shield sections 32 may be actuable with the electron-optical device in the module 405, which may be a MEMS.

[0074]

[0092] In some embodiments, module 405 is a MEMS module. In some embodiments, module 405 is configured to be replaceable within electron-optical column 40. In some embodiments, module 405 is configured to be field-replaceable. Field-replaceable is intended to mean that the module can be removed and replaced with the same or a different module while maintaining the vacuum in which the electron-optical column is located. Only the section of the column corresponding to the module is vented in order for the module to be removed and replaced or replaced.

[0075]

[0093] In one embodiment, module 405 includes an internal electron-optical shield. Modules can be removed, inserted, or replaced without having to retract the electromagnetic shield 31 along the beam path. It is not necessary for section 32 to be axially movable. In conventional arrangements, the shield is a continuous tube that needs to be removed, or a series of adjacent sections that need to be mechanically disassembled starting from one end or the other of the electron-optical column.

[0076]

[0094] FIG. 6 illustrates a portion of an electron optical column 40. As shown in FIG. 6, in one embodiment, the final section 32''' of the electromagnetic shield 31 up-beam of the target 308 includes a facing surface 34. The facing surface 34 faces the target 308. The facing surface 34 is positioned a distance D5 from the target 308. The distance D5 is in the direction of the beam path. The facing surface 34 extends away from the beam path, preferably radially relative to the beam path, by a width W5. The width W5 is measured perpendicular to the direction of the beam path. As shown in FIG. 6, in one embodiment, the section 32 includes a flange 35. Alternatively, as described above, the radial extent of the facing surface 34 can be provided by having a thicker wall of the electromagnetic shield 31.

[0077]

[0095] In some embodiments, W5 is at least as large as D5. In some embodiments, W5 is twice (or three times, or four times, or five times) as large as D5. As shown in FIG. 6, in some embodiments, target 308 extends radially a distance at least as large as width W5. Target 308 may help attenuate the effects of stray electromagnetic fields on the beam.

[0078]

[0096] 7 schematically illustrates a portion of the electron optical column 40, according to one embodiment. FIG. 7 also illustrates the radial position of the electromagnetic shield 31 relative to other components of the electron optical column 40. The surface of the target 308, or, if beyond the outer periphery of the target 308, the surface of the target support, may extend away from the beam path. In one embodiment, the surface of the target and / or target support may extend away from the beam path at least as far as the facing surface 34 of the last section 32.

[0079]

[0097] As shown in FIG. 7 , in some embodiments, the electron optical column 40 includes a thermal conditioner 204. The thermal conditioner 204 is configured to thermally condition at least a portion of the electron optical column 40. In some embodiments, the thermal conditioner 204 includes a plurality of thermal conditioning channels. The channels may contain a conditioning fluid configured to exchange heat with one or more other portions of the electron optical column 40. In some embodiments, the thermal conditioner 204 is configured to remove heat generated within the electron optical column. Alternatively, the thermal conditioner 204 may have modes in which it can provide heat to the electron optical column 40. In some embodiments, the thermal conditioner 204 is configured to deliver heat to different portions of the inspection tool 100. In some embodiments, the thermal conditioner is configured to thermally condition a portion of the electron optical column 40 such that it is maintained at a stable temperature.

[0080]

[0098] 7, in one embodiment, electromagnetic shield 31 is radially inward of thermal conditioner 204. Electromagnetic shield 31 is configured to shield the beam from electromagnetic fields, including those generated by thermal conditioner 204.

[0081]

[0099] 7, in some embodiments, the electron optical column 40 includes at least one pump 220. The pump 220 is configured to control the pressure within the electron optical column 40. In some embodiments, the pump 220, e.g., a pump unit of the pump 220, can be connected to a negative pressure to reduce the pressure within the electron optical column 40, e.g., to create and maintain a vacuum within which the column 40 is positioned. In some embodiments, the pump 220, e.g., a vent valve of the pump 220, can be connected to a positive pressure to increase the pressure within which the electron optical column 40 is positioned.

[0082]

[0100] 7, in one embodiment, the electromagnetic shield 31 is radially inward of the pump 220 relative to the beam path. The electromagnetic shield 31 is configured to shield the beam from electromagnetic fields generated by the pump 220.

[0083]

[0101] 7, in an embodiment, the electron optical column 40 includes an electron optical element such as a collimator 5. The collimator 5 is configured to at least partially collimate the charged particle beam. Under the operation of the collimator 5, the beam path may be at least in the direction of the ideal beam path, i.e., at least less divergent, or even converging, beam path. In an embodiment, the electron optical column 40 includes an electron optical element such as a deflector. The deflector may be configured to deflect the charged particle beam.

[0084]

[0102] 7, in one embodiment, the inner surface 39 of the electromagnetic shield 31 is radially inward of an electron optical element such as a collimator 5. The collimator 5 acts on the beam. The collimator 5 is positioned so that the electromagnetic field it generates affects the beam on the beam path. The collimator 5 is positioned between two adjacent sections 32 of the electromagnetic shield 31.

[0085]

[0103] 7, the collimator 5 is radially outward of the radially inner surface 39 of the electromagnetic shield 31. In an alternative embodiment, a portion of the collimator 5 (e.g., the radially inner edge of the collimator 5) is at the same radial position as the radially inner surface 39 of at least one of the sections 32 immediately up or down the beam. Locating the collimator 5 at the same distance or close to the inner surface 39 of an adjacent section relative to the beam path helps reduce the likelihood that the electromagnetic shield 31 will undesirably attenuate the effect of the collimator 5 on the beam.

[0086]

[0104] 8 shows a schematic representation of a portion of an electron optical column 40, according to one embodiment, and also shows an alternative radial position of the electromagnetic shield 31 relative to other components of the electron optical column 40.

[0087]

[0105] As shown in FIG. 8 , in some embodiments, the electromagnetic shield 31 is radially inward of the thermal conditioner 204 and the pump 220. The electromagnetic shield 31 is radially outward of electron-optical elements such as the collimator 5. As shown in FIG. 8 , in some embodiments, the gap 33 between adjacent sections 32 allows fluid communication between the pump 220 and a volume within the electromagnetic shield 31 that is close to and even includes the electron-optical axis 304. As shown in FIGS. 7 and 8 , by defining the pump 220 outside the electromagnetic shield 31, there is greater design freedom for the pump 220 because electron-optical properties (e.g., voltage, current) are shielded from the beam. By defining the pump 220 outside the electromagnetic shield 31, the pump 220 may not be required to meet such high electron-optical requirements, thereby increasing design freedom. By defining the pump 220 away from the electromagnetic shield 31, the risk of vibrations being transmitted from the pump 220 to the column 40 may be reduced. Such vibrations can adversely affect the performance of the electron optical column 40 .

[0088]

[0106] Because the electromagnetic devices are within the shield 31 and the devices have power sources external to the shield 31, the routing to the devices is designed to minimize the generation of electromagnetic fields within the shield 31. For example, because two routing connections are required to connect to electrodes of the electromagnetic device (to complete an electrical circuit), these routings are positioned adjacent to each other so that the electromagnetic fields generated by the routings substantially cancel each other. Thus, if the electromagnetic device is an array, the routing to each electrode for each opening in the array is designed so that the routing is positioned with its opposite routing so that the generated electromagnetic fields substantially cancel each other.

[0089]

[0107] 9 shows a schematic representation of a portion of an electron optical column 40, according to one embodiment, and also shows an alternative radial position of the electromagnetic shield 31 relative to other components of the electron optical column 40.

[0090]

[0108] 9, in one embodiment, the electromagnetic shield 31 is radially inward of the thermal conditioner 204. The electromagnetic shield 31 is radially outward of the electron optical elements such as the pump 220 and the collimator 5. By providing that the pump 220 is radially inward of the electromagnetic shield 31, an improved vacuum can be achieved around the beam.

[0091]

[0109] As shown in FIG. 9 , in some embodiments, a lens or an array of lenses 37 is provided between adjacent sections 32. Other types of electronic optical elements may be positioned between adjacent sections 32. In some embodiments, the electronic optical elements between sections 32 are MEMS elements. For example, deflector 36 and / or lens 37 may be MEMS. Lens 37 may be positioned in gap 33 between adjacent sections 32. In some arrangements, multiple manipulators may be present between adjacent sections 32. The multiple manipulators may include a collection of manipulators of the same type, such as lenses, deflectors, or astigmatism correctors, and / or may include manipulators of different types, such as lenses, deflectors, and / or correctors. Different manipulators may include arrays of elements. A corrector array including multiple correctors may be provided. A collimator array including multiple collimators may be provided.

[0092]

[0110] 10 is a schematic diagram of a portion of an electron optical column 40, according to one embodiment, showing an alternative radial location of the electromagnetic shield 31 relative to other components of the electron optical column 40.

[0093]

[0111] 10, in one embodiment, the electromagnetic shield 31 is radially outward of the electron optical elements such as the thermal conditioner 204, the pump 220, and the collimator 5. Variations on this arrangement may have the pump 220 external to the shield 31. Different arrangements of the manipulators, such as those depicted in FIG. 9, may be applied to these arrangements.

[0094]

[0112] FIG. 11 illustrates an electron-optical assembly as part of an electron-optical column 40, according to one embodiment. As shown in FIG. 11, in one embodiment, at least two of the sections 32 include adjacent ends that electromagnetically engage with one another. In one arrangement, the electromagnetic engagement between adjacent sections 32 is non-contacting. A gap may exist between adjacent surfaces of adjacent sections 32. The sections 32 combine to shield the beam from stray electromagnetic fields. The sections 32 are electromagnetically engaged such that stray electromagnetic fields cannot affect the beam within the shield 31.

[0095]

[0113] 11, in some embodiments, adjacent ends are sized as needed to be coaxially positioned. Alternatively, sections 32 may not be coaxial if, for example, electromagnetic shield 31 is required to fit into a particular shaped space within electron optical column 40. It is not necessary that the shield be symmetrically positioned around the beam path.

[0096]

[0114] As shown in Figure 11, in some embodiments, adjacent ends are sized so that one end can be inserted into the other. In some embodiments, adjacent sections 32 overlap along the beam path. As shown in Figure 11, an overlap 11 can be formed between adjacent sections 32 in the direction of the beam path. The overlap ensures that external electromagnetic fields do not undesirably affect the beam, such as by diverting it from the beam path.

[0097]

[0115] In some embodiments, adjacent ends of adjacent sections 32 are physically separated from one another. In some embodiments, adjacent ends are electromagnetically engaged with one another. The sections 32 are movable in the direction of the beam path. The sections 32 can be removed or replaced one by one to perform maintenance on portions of the electron optical column 40.

[0098]

[0116] In some arrangements, the electromagnetic shield 31 includes different types of sections 32, such as sections with gaps between adjacent sections and sections that are coaxially engaged with adjacent sections. In such an arrangement, the shield 31 may include sections in modules that may be removable from the electron-optical column 40. In such an arrangement, the sections may be adapted to coaxially engage an adjacent section at one end and have a facing surface at the other end that faces the facing surface of the adjacent section.

[0099]

[0117] In one embodiment, the electromagnetic shield 31 described herein may be applied to a tool featuring one or more MEMS electro-optical elements, such as a MEMS objective lens.

[0100]

[0118] As noted above, in some embodiments, the electron optical column 40 may include alternative and / or additional components on the charged particle path, such as lenses and other components (some of which are described above with reference to FIGS. 1 and 2 ). Specifically, an embodiment includes an electron optical column 40 that generates multiple sub-beams from a charged particle beam from a source. In some embodiments, an electromagnetic shield 31 is configured to surround all of the sub-beams at a given location within the electron optical column 40. In some alternative embodiments, each sub-beam is provided with its own surrounding electromagnetic shield 31. In some embodiments, one group of sub-beams of a multi-beam is provided with an electromagnetic shield 31, preferably comprising a series of sections 32. In some embodiments, the sub-beams of a multi-beam are assigned groups such that the multi-beam is comprised of multiple groups of sub-beams. The multiple groups of sub-beams may have a shield 31 designed with a series of sections along and around the path of the sub-beams of each group.

[0101]

[0119] In one embodiment, the electromagnetic shield 31 has a circular cross section. Alternatively, the cross-sectional shape may be rectangular, or square, or rectangular with rounded corners, or square with rounded corners.

[0102]

[0120] 3-5, the inner diameter is the same for all sections 32. Alternatively, the inner diameter may vary from section to section. This may help reduce the volume of the electromagnetic shield 31.

[0103]

[0121] In one embodiment, the sections 32 are aligned concentrically along the beam path. In an alternative embodiment, one or more of the sections 32 may be off-center relative to one another. This may result in a magnetic lensing effect on the beam.

[0104]

[0122] In some embodiments, separate electrostatic and magnetic shields are provided. The electrostatic shield is configured to shield the beam from electrostatic fields. The magnetic shield is configured to shield the beam from magnetic fields. The electrostatic shield may have features as described above for electromagnetic shield 31. The magnetic shield may have features as described above for electromagnetic shield 31. In some embodiments, the magnetic shield is radially outward of the electrostatic shield. Alternatively, the magnetic shield may be radially inward of the electrostatic shield. In a further arrangement, the magnetic and electric shields may be combined into one shield set.

[0105]

[0123] As described above, in some embodiments, a secondary column (not shown) is provided that includes a detection element for detecting a corresponding secondary charged particle beam. In some embodiments, an electron-optical assembly including an electromagnetic shield may be provided as part of the secondary column. For example, the source and / or detector of the secondary column may include the electromagnetic shield described above, except as specified herein. The shield need not extend to the up-beam of the source. The shield need not extend to the down-beam of the detector. In some embodiments, the Wien filter is housed by a shield 31 having a Y-shaped section. The Y-shaped section may include multiple sections, which may simplify manufacturing and assembly. In some embodiments, the sections have flanges as described above. In some embodiments, the sections are field-replaceable. In some alternative embodiments, the flanges may be used to bolt the sections to a frame or to each other.

[0106]

[0124] 12 is a schematic diagram of an electron optical column 4 according to one embodiment. As shown in FIG. 12, in one embodiment, multiple sections 32a-32d of an electromagnetic shield 31 are provided. The sections 32a-32d are provided at different positions along a direction parallel to the beam path. The different sections 32a-32d correspond to different portions of an electron optical column 40.

[0107]

[0125] For example, in one embodiment, the first section 32a corresponds to a source portion of the electron optical column 40. The source portion of the electron optical column 40 extends from a source 301. The source 301 is configured to generate a primary beam 302 of charged particles. As shown in FIG. 12 , in one embodiment, the cross-sectional area of ​​the primary beam 302 increases until the primary beam 302 is collimated. In one embodiment, the first section 32a extends in a direction parallel to the beam path until the primary beam 302 is collimated. In one embodiment, the first section 32a radially surrounds the source 301. Alternatively, the up-beam end of the first section 32a is in the down-beam of the source 301. The down-beam end of the first section 32a is in the up-beam of a collimator configured to collimate the primary beam 302.

[0108]

[0126] In some embodiments, the second section 32b corresponds to the collimator portion of the electron optical column 40. The collimator portion of the electron optical column 40 extends from the collimator. In some embodiments, the collimator includes a condenser lens 310 (e.g., as shown in FIG. 2). In some embodiments, the condenser lens 310 is magnetic. As shown in FIG. 12, in some embodiments, the cross-sectional area of ​​the collimated beam may remain substantially constant at the down beam of the collimator until the primary beam 302 is split into sub-beams 311. In some embodiments, the second section 32b extends in a direction parallel to the beam path up to where the primary beam 302 is split. In some embodiments, the up beam end of the second section 32b is at the up beam of the collimator. The second section 32b may radially surround the collimator. Alternatively, the up beam end of the second section 32b may be at the down beam of the collimator. The down beam end of the second section 32 b is at the up beam of a beam limiting aperture array 321 configured to split the primary beam 302 .

[0109]

[0127] In one embodiment, the third section 32c corresponds to the beam splitter portion of the electron optical column 40. The beam splitter portion of the electron optical column 40 extends from a component configured to form the sub-beams 311, such as a beam-limiting aperture array 321. As shown in FIG. 12 , in one embodiment, six sub-beams 311 may be formed in the down beam of the beam-limiting aperture array 321. Those skilled in the art will appreciate that any number of sub-beams, such as hundreds or thousands of sub-beams, may be formed. The cross-sectional area of ​​the sub-beams 311 may remain substantially constant throughout the length of the third section 32c. In one embodiment, the third section 32c extends in a direction parallel to the beam path until the sub-beams 311 are focused onto the target 208. In one embodiment, the up beam end of the third section 32c is at the up beam of the beam-limiting aperture array 321 (or other beam splitter). The third section 32c may radially surround the beam-limiting aperture array 321. Alternatively, the up-beam end of the third section 32c may be in the down-beam of the beam-limiting aperture array 321. The down-beam end of the third section 32c is in the up-beam of an objective lens configured to focus the sub-beam 311 onto the target 208.

[0110]

[0128] In some embodiments, the fourth section 32d corresponds to the objective lens portion of the electron optical column 40. The objective lens portion of the electron optical column 40 extends from a component configured to manipulate the sub-beam 311 to control the characteristics of the sub-beam 311 incident on the target 208, such as the objective lens 331 (as shown in FIG. 2). As shown in FIG. 12, in some embodiments, the sub-beam 311 is focused into a down-beam at the objective lens 331. The cross-sectional area of ​​the sub-beam 311 may decrease through at least part (and optionally all) of the length of the fourth section 32d. In some embodiments, the fourth section 32d extends in a direction parallel to the beam path up to where the sub-beam 311 is incident on the target 208. In some embodiments, the up-beam end of the fourth section 32d is in the up-beam of the objective lens 331 (or other manipulator). The fourth section 32d may surround the objective lens 331, for example, radially. Alternatively, the up beam end of the fourth section 32d may be in the down beam of the objective lens 331. The down beam end of the fourth section 32d is in the up beam of the target 208.

[0111]

[0129] In each portion of the electron optical column 40, the charged particle beam is shielded from external fields by sections 32a-32d of the electromagnetic shield 31. Although four portions with four corresponding sections 32a-32d are shown in the arrangement of FIG. 12, there may be a different number of sections 32. For example, the length of the beam may be divided into two, three, or five or more portions with corresponding sections 32 of the electromagnetic shield 31. In one arrangement, the shield sections may extend from the beam-limiting aperture array down the beam to the objective lens array.

[0112]

[0130] As explained above, the sections 32 do not overlap in a direction parallel to the beam path. In certain embodiments, the electron optical column 40 is arranged so that at least one of the portions can be replaced without having to handle or move the other portions. As described above in connection with Figures 3 and 4, in certain embodiments, the sections 32 are flared at the ends facing the gaps 33 between adjacent sections 32. Providing flared ends can reduce the reduction in shielding effectiveness caused by the gaps 33.

[0113]

[0131] In some embodiments, at least one of sections 32a-32d radially surrounds at least one component selected from the group consisting of charged particle source 301, condenser lens 310, collimator, source converter 320, deflector array 323, aperture array 321, aberration compensator array 324, imaging element array 322, objective lens 331 or objective lens array, and detector array. In some embodiments, the component is a MEMS component.

[0114]

[0132] In some embodiments, at least one of sections 32a-32d is arranged to be movable radially relative to the beam path, together with the components it surrounds, independently of another one of sections 32a-32d. For example, as shown in FIG. 12 , in some embodiments, electron optical column 40 includes collimator module 405b. In some embodiments, collimator module 405b includes second section 32b and a collimator. In some embodiments, second section 32b and the collimator are in fixed positions relative to each other. Second section 32b, along with the collimator, is field-replaceable. As shown in FIG. 12 , in some embodiments, electron optical column 40 includes objective lens module 405d. In some embodiments, objective lens module 405d includes fourth section 32d and objective lens 331 (or an objective lens array). In some embodiments, fourth section 32d and the objective lens are in fixed positions relative to each other. Fourth section 32d, along with the objective lens, is field-replaceable.

[0115]

[0133] Although not shown in FIG. 12, in some embodiments, electron optical column 40 includes a source module and / or a beam splitter module corresponding to the source and beam splitter sections described above, respectively.

[0116]

[0134] In some embodiments, each module 405 is field replaceable. In some embodiments, each module 405 is slidable out of the electron-optical column 40, and the replacement module is slidable into the electron-optical column 40. The sliding may be in a direction perpendicular to the beam path, e.g., transverse in the orientation shown in FIG. 12.

[0117]

[0135] By providing that module 405 is replaceable, certain embodiments of the present invention are expected to make it easier and / or cheaper to maintain an electron-optical column. Certain embodiments of the present invention are expected to reduce the time and / or effort required to undo and redo in order to replace one or more components of electron-optical column 40.

[0118]

[0136] As shown in FIG. 12 , in some embodiments, the electron optical column 40 includes a chimney member 52. In some embodiments, the chimney member 52 includes the same material as the section 32 of the electromagnetic shield 31. The chimney member 52 is configured to protect the beam path. For example, the chimney member 52 may electromagnetically shield the beam path. As shown in FIG. 12 , in some embodiments, the chimney member 52 includes a hole defined in, for example, a plane or plate through which control wires may extend. The control wires may be for controlling the electron optical components of the electron optical column 40. The surface of the plate defining the hole may be flared.

[0119]

[0137] As shown in FIG. 12 , in some embodiments, intentional gaps 33b-33d are provided between adjacent sections 32a-32d. In some embodiments, gaps 33a and 33e are provided at both ends of shield 31. In some embodiments, first gap 33a is provided between chimney member 52 and first section 32a. In some embodiments, second gap 33b is provided between first section 32a and second section 33b. In some embodiments, third gap 33c is provided between second section 32b and third section 33c. In some embodiments, fourth gap 33d is provided between third section 32c and fourth section 33d. In some embodiments, fifth gap 33e is provided between fourth section 32d and target 208. Some embodiments of the present invention are expected to enable easier replacement of one or more components of electron optical column 40. Certain embodiments of the present invention are expected to reduce the amount of part movement required for one or more components to be replaced. Gap 33 may facilitate movement of module 405 relative to other components of electron optical column 40.

[0120]

[0138] As shown in FIG. 12, an intentional gap 33e is provided adjacent to the target 208. Some embodiments of the present invention are expected to reduce the likelihood of the electromagnetic shield 31 undesirably contacting the target 208. The presence of the fourth gap 33d between the third section 32c and the fourth section 32d allows the shield sections 32c, 32d to be made nominally shorter. Some embodiments of the present invention are expected to reduce crowding of the sections 32c, 32d during assembly.

[0121]

[0139] FIG. 13 is a schematic diagram of an electron optical column 40 according to one embodiment of the present invention. Descriptions of features identical to those described above in connection with FIG. 12 are omitted for brevity. As shown in FIG. 13 , in one embodiment, four sections 32a-32d of the electromagnetic shield 31 are provided. The four sections 32a-32d relate to different portions of the electron optical column 40. A first section 32a is provided for a source portion where the source 301 is provided. A second section 32b is provided for a collimator portion where the beam is collimated by a collimator, e.g., a condenser lens 310. A third section 32c is provided for a beam splitter portion where the beam is split. For example, in the embodiment shown in FIG. 13 , the electron optical column 40 includes an upper beam limiter 252. The upper beam limiter 252 defines an array of beam-limiting apertures. The upper beam limiter 252 is sometimes referred to as an upper beam-limiting aperture array or an upper beam-limiting aperture array. The upper beam restrictor 252 may include a plate (which may be a slab-shaped body) having a plurality of apertures. The upper beam restrictor 252 forms sub-beams from the charged particle beam emitted by the source 301. Portions of the beam other than those contributing to the formation of the sub-beams may be blocked (e.g., absorbed) by the upper beam restrictor 252 so as not to interfere with the sub-beams of the down beam. The upper beam restrictor 252 is sometimes referred to as a sub-beam-defining aperture array.

[0122]

[0140] As shown in FIG. 13 , in one embodiment, there is a control lens array 250. Such an arrangement is described in European Patent Application Publication No. 20196714.8, filed September 17, 2020, which is incorporated herein by reference with respect to at least the electro-optical architecture shown with respect to three different embodiments shown in FIGS. 3, 5, and 6 of this application. 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 respective potential source. The control lens array 250 may include two or more (e.g., three) plate electrode arrays connected to respective potential sources. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are positioned near each other and / or mechanically connected to each other and / or controlled together as a unit). The control lens array 250 is positioned in the up beam of the objective lens array 241. The control lenses prefocus the sub-beams (e.g., apply a focusing action to the sub-beams before they reach the objective lens array 241). Prefocusing can reduce the divergence of the sub-beams or increase the convergence of the sub-beams.

[0123]

[0141] A fourth section 32d is provided for the objective lens portion where the sub-beams are manipulated in preparation for incidence on the target 208. An objective lens array 241 including multiple objective lenses is provided to guide the sub-beams onto the sample 208. Each objective lens includes at least two electrodes (e.g., two or three electrodes) connected to a respective potential source. The objective lens array 241 may include two or more (e.g., three) plate electrode arrays connected to respective potential sources. As shown in FIG. 13 , in some embodiments, the objective lens array 241 may include a beam-shaping limiter 242. The beam-shaping limiter 242 defines an array of beam-limiting apertures. The beam-shaping limiter 242 may be referred to as a lower beam limiter, a lower beam-limiting aperture array, or a final beam-limiting aperture array. The beam-shaping limiter 242 may include a plate (which may be a slab) having multiple apertures. The beam shaping limiter 242 is in the down beam from at least one electrode (optionally from all electrodes) of the control lens array 250. In some embodiments, the beam shaping limiter 242 is in the down beam from at least one electrode (optionally from all electrodes) of the objective lens array 241.

[0124]

[0142] FIG. 14 is a schematic diagram of an electron-optical column 40 according to one embodiment of the present invention. Descriptions of features identical to those described above in connection with FIG. 12 are omitted for brevity. As shown in FIG. 14 , in one embodiment, seven sections 32a-32g of the electromagnetic shield 31 are provided. The seven sections 32a-32g relate to different portions of the electron-optical column 40. A first section 32a is provided for the source portion, where the source 301 is provided. A second section 32b is provided for the collector portion. As shown in FIG. 14 , in one embodiment, a collector lens array 231 is provided between the source 301 and the control lens array 250. Such an arrangement is described in European Patent Application Publication No. 20206984.5, filed November 11, which is incorporated herein by reference, at least with respect to the electron-optical architecture as shown in FIG. 4 of this application. The collector lens array 231 includes a plurality of collector lenses. There may be tens, hundreds, or even thousands of condenser lenses. The condenser lenses may include multi-electrode lenses and may have a structure based on EP 1 602 121 A1, which is incorporated herein by reference, particularly for its disclosure of a lens array for splitting the electron beam into multiple sub-beams, the array providing one lens per sub-beam. The second section 32b may surround the condenser lens array 231. The condenser lens array 231 is configured to split the main beam into sub-beams 311-313.

[0125]

[0143] A third section 32c is provided for the control lens array 250. A fourth section is provided for the objective lens portion. For example, the fourth section 32d may surround the objective lens array 241, similar to the embodiment shown in FIG.

[0126]

[0144] 14, in one embodiment, a fifth section 32e is provided between the second section 32b and the third section 32c. The fifth section 32e may surround a deflector 235. The deflector 235 is provided at the intermediate focus. The deflector 235 is configured to bend each sub-beam 311-313 by an amount effective to ensure that the chief ray is incident on the sample 208 substantially normal (i.e., substantially 90° relative to the nominal plane of the sample). The deflector 235 may also be referred to as a collimator.

[0127]

[0145] As shown in FIG. 14 , in one embodiment, a sixth section 32f is provided between the third section 32c and the fourth section 32d. The sixth section 32f may surround a scan deflector array 260. The scan deflector array 260 includes multiple scan deflectors. The scan deflector array 260 may be formed using MEMS fabrication techniques. Each scan deflector scans a respective sub-beam across the sample 208. Thus, the scan deflector array 260 may include a scan deflector for each sub-beam. Each scan deflector may deflect the sub-beam in one direction (e.g., parallel to a single axis, such as the X axis) or in two directions (e.g., relative to two non-parallel axes, such as the X axis and the Y axis). The deflection is such that the sub-beam is scanned across the sample 208 in one or two directions (i.e., one-dimensionally or two-dimensionally).

[0128]

[0146] 14, in one embodiment, the seventh section 32g is provided between the fourth section 32d and the target 208. The seventh section 32g may surround the detector module 402. The detector module 402 detects charged particles emitted from the sample 208. The detector module 402 includes multiple detector elements (e.g., sensor elements such as capture electrodes). In this embodiment, the detector module 402 is provided on the output side of the objective lens array 241. The output side is the side facing the sample 208. In some variations, adjacent sections and modules may be combined. For example, one section may surround the detector module 402, the objective lens array, optionally the control lens array 250, and the objective lens array assembly, which may optionally include a scanning deflector.

[0129]

[0147] 12 and 13, in the embodiment shown in FIG. 14, each section 32a-32g, along with its associated components, can be moved in and out of the electron-optical column 40. The electron-optical column 40 is modular. Intentional gaps 33 are provided between the sections 32a-32g. This facilitates movement of the sections 32a-32g relative to one another as the sections 32a-32g are moved in and out of the electron-optical column 40.

[0130]

[0148] FIG. 15 is a schematic diagram of an electron optical column according to an embodiment of the present invention. As shown in FIG. 13, in an embodiment, at least one of the sections 32 includes mechanical reference members 51c and 51d configured to allow the position of the section 32 to be determined. In an embodiment, the mechanical reference members 51c and 51d are configured to allow the position of the section 32 to be determined in a direction perpendicular to the beam path. In an embodiment, the mechanical reference members 51c and 51d are configured to allow the position of the section 32 to be determined in a direction parallel to the beam path. The third section 32c includes an associated mechanical reference member 51c. The fourth section 32d includes associated mechanical reference members 51d and 51e. Although not shown in FIG. 15, in an embodiment, the third section 32c may include additional mechanical reference members for determining the position of the third section 32c relative to the second section 32b. Each section 32 may include one or more mechanical reference members 51.

[0131]

[0149] In some embodiments, the mechanical reference member 51 is in a fixed position relative to the associated section 32 of the shield 31. The mechanical reference member 51 may also be indirectly fixed to the associated section 32 of the shield 31. For example, the mechanical reference member 51 may be fixed to the electronic optical component that the section 32 surrounds, or to a frame to which the component and section 32 are fixed. In some embodiments, the position of the component or frame is determined by the mechanical reference member 51, and the position of the section 32 of the shield 31 is derived from its position relative to the component or frame.

[0132]

[0150] In some embodiments, the mechanical reference member 51c is configured to mechanically engage with another one of the sections 32d or a corresponding mechanical reference member 51d of the column 40. For example, the mechanical reference members 51c, 51d may include complementary surfaces configured to engage with each other. In some embodiments, these surfaces are flat. In some alternative embodiments, the surfaces are configured to limit movement perpendicular to the beam path, for example, by interengagement between adjacent sections. In some embodiments, one of the surfaces includes a groove that fits a complementary shaped recess or protrusion of the complementary surface. This limits lateral movement of the sections 32c, 32d relative to each other. In some embodiments, the surfaces are configured to limit movement in two degrees of freedom perpendicular to the beam path. For example, one of the surfaces may include a recess that fits a hemispherical shape of the complementary surface. One of the mechanical reference members 32d may dock within the other mechanical reference member 51c.

[0133]

[0151] It is not necessary for the mechanical reference members 51 to be mechanically engaged with one another. In an embodiment, the mechanical reference members 51 include a reflective surface for reflecting radiation used in distance measurements. The distance measurements can be, for example, measurements of the vertical position of section 32d relative to target 208 or another section 32c. In an embodiment, the mechanical reference members 51 are used to perform interferometric measurements.

[0134]

[0152] In one embodiment, the mechanical reference member 51 comprises a conductive and / or dielectric material suitable for capacitance measurements. Capacitive measurements can be made that indicate the position of the mechanical reference member 51, and thereby the position of the section 32.

[0135]

[0153] In some embodiments, one or more of the sections 32 are fixed in place within the column 40. In some embodiments, one or more mechanical fastening points are configured to secure the sections 32 within the column 40. For example, rails, bolts, and / or preload springs are provided to control the position of the sections 32.

[0136]

[0154] Figure 16 is a schematic diagram of a beam inspection apparatus 100 that includes multiple electron optical columns 40. The apparatus 100 is sometimes referred to as a multi-column apparatus. Figure 16 shows an embodiment in which the apparatus 100 includes three electron optical columns 40a-40c. In alternative embodiments, the apparatus 100 includes two, four, or more electron optical columns 40.

[0137]

[0155] In one embodiment, each column 40a-40c includes a source 301a-301c. Alternatively, two or more columns 40 may share a common source 301. In one embodiment, each column 40a-40c has a main beam generated by a source 301a-301c. The main beam is collimated and then split into sub-beams 311a-311c, 312a-312c, and 313a-313c, which are incident on the target 208.

[0138]

[0156] As shown in FIG. 16, columns 40a-40c can be considered to be divided into different portions. Each portion has a corresponding section 32a-32c of shield 31. In some embodiments, at least one of sections 32a-32c radially surrounds the beam paths of two or more of electron-optical columns 40a-40c. For example, first section 32a surrounds the source portions of all three columns 40a-40c. Sources 310a-310c are configured to generate main beams 302a-302c for the respective columns 40a-40c. Second section 32b surrounds the collimator portions of all three columns 40a-40c. Third section 32c surrounds the beam splitter portions of all three columns 40a-40c. The number of different portions and corresponding sections 32 may be 2, 4, 5, 6, 7, 8 or more, ie as few or as many as required.

[0139]

[0157] 16, all sections 32 surround the beam paths of all columns 40. However, this is not necessarily the case. For example, one or more sections 32 may surround the beam paths of only one of the columns 40. This is shown, for example, in FIG. 19.

[0140]

[0158] As shown in FIG. 16 , in one embodiment, the apparatus 100 includes a source module 405a. The source module 405a includes the first section 32a. In one embodiment, the source module 405a includes the sources 301a-301c. The source module 405a is replaceable independently of the other modules 405b, 405c. In one embodiment, the apparatus 100 includes a collimator module 405b. The collimator module 405b includes the second section 32b. In one embodiment, the collimator module 405b includes one or more collimators configured to collimate the main beams 302a-302c. The collimator module 405b is replaceable independently of the other modules 405a, 405c. In one embodiment, the apparatus 100 includes a beam splitter module 405c. The beam splitter module 405c includes the third section 32c. In one embodiment, the beam splitter module 405c includes one or more beam splitters configured to split the main beams 302a-302c into sub-beams 311-313. The beam splitter module 405c is replaceable independently from the other modules 405a, 405b.

[0141]

[0159] Figure 17 is a schematic diagram of an inspection beam apparatus 100, according to one embodiment of the present invention. The apparatus 100 is a multi-column apparatus. Figure 17 shows three columns 40a-40c. In alternative embodiments, the number of columns 40 may be two, four, five or more.

[0142]

[0160] 17, in one embodiment, the apparatus includes six sections 32 of the shield 31 associated with different portions of the column 40. A first section 32a is provided for the source portion. The first section 32a and the sources 301a-301c may be integrated in a source module that is replaceable independently of the other portions of the apparatus 100. A third section 32c is provided for the beam splitter portion. The third section 32c and the upper beam restrictor 252 may be integrated in a beam splitter module that is replaceable independently of the other portions of the apparatus 100.

[0143]

[0161] A fifth section 32e of the collimator portion is provided in which a collimator element array 271 is provided. Each collimator element collimates a respective sub-beam. Therefore, providing the collimator element array 271 and the scanning deflector array 260 (described below) together can result in space savings.

[0144]

[0162] An eighth section 32h is provided for the control lens portion of column 40 in which control lens array 250 is provided. Eighth section 32h and control lens array 250 may be integrated in a control lens module that is interchangeable independently of the rest of apparatus 100. Similar to the embodiment shown in FIG. 14, in some embodiments, a sixth section 32f is provided for the scan deflector portion of column 40. In some embodiments, sixth section 32f may be combined with scan deflector array 260 in a scan deflector module that is interchangeable independently of the rest of apparatus 100. Similar to the embodiment shown in FIG. 13, in some embodiments, fourth section 32d corresponds to the objective lens portion of electron-optical column 40. Fourth section 32d may be combined with objective lens array 241 in an objective lens module that is interchangeable independently of the rest of apparatus 100.

[0145]

[0163] Figure 17 shows an arrangement with columns that are electrostatically equivalent to the arrangement shown in and described with respect to Figure 13, but the columns may be any suitable electro-optical columns such as those shown in and described with respect to Figure 14. The number of shield sections may be adjusted to the number of different modules requiring field replaceable functionality.

[0146]

[0164] Figure 18 is a schematic diagram of an inspection beam apparatus 100, according to one embodiment of the present invention. The apparatus 100 is a multi-column apparatus. Figure 18 shows three columns 40a-40c. In alternative embodiments, the number of columns 40 may be two, four, five or more, for example 20 or 100 or more. Descriptions of features that are the same as those described above in relation to Figure 16 are omitted for the sake of brevity.

[0147]

[0165] In the embodiment shown in FIG. 16 , the beam paths of all columns 40 are radially surrounded by sections 32. However, this is not necessarily the case. As shown in FIG. 18 , in some embodiments, the beam path of at least one of the electron-optical columns 40 is radially outside at least one of the sections 32. For example, the beam paths of the second column 40 b and the third column 40 c are radially outside the first section 32 a provided for the first column 40 a. In some embodiments, at least one of the sections 32 radially surrounds the beam path of only one of the electron-optical columns 40. For example, the first section 32 a of the first column 40 a radially surrounds the beam path of only the first column 40 a.

[0148]

[0166] As shown in FIG. 18 , in one embodiment, different sections 32 of the electromagnetic shield 31 radially surround the beam paths of different electron-optical columns 40, and these different sections 32 are positioned to overlap in a direction parallel to the beam paths. For example, as shown in FIG. 18 , in one embodiment, the second section 32b of the first column 40a radially surrounds the beam path of only the first column 40a. The third section 32c of the first column 40a radially surrounds the beam path of only the first column 40a. The first section 32a′ of the second column 40b radially surrounds the beam path of only the second column 40b. The second section 32b′ of the second column 40b radially surrounds the beam path of only the second column 40b. The third section 32c′ of the second column 40b radially surrounds the beam path of only the second column 40b. The first section 32a'' of the third column 40c radially surrounds the beam path of only the third column 40c. The second section 32b'' of the third column 40c radially surrounds the beam path of only the third column 40c. The third section 32c'' of the third column 40c radially surrounds the beam path of only the third column 40c.

[0149]

[0167] 18, in some embodiments, multiple sections 32 that are positioned to overlap in a direction parallel to the beam path are arranged to be movable together in a radial direction relative to the beam path independently of another one of the sections 32. For example, in some embodiments, all of the first sections 32a, 32a', 32a'' are movable together. The first sections 32a, 32a', 32a'' may be fixed relative to one another. The first sections 32a, 32a', 32a'' may be integrated in an integrated source module that is replaceable independently of other modules of the apparatus 100.

[0150]

[0168] Similar to the embodiments described above and shown in FIGS. 12-17, sections 32 are provided for different portions of columns 40a-40c. Sections 32 can be replaced independently of the other sections 32. Sections 32 may be combined with corresponding components in modules that are independently replaceable from other modules. For example, as shown in FIG. 18, in one embodiment, second section 32b'' of third column 40c may be combined with a collimator in collimator module 405b'' that is independently replaceable from other modules. Although not shown in FIG. 18, in one embodiment, each section 32 corresponds to a separate module of apparatus 100. In variations of the embodiment shown in and described with respect to FIG. 18, multiple groups of columns may correspond to each depicted column location, e.g., in a row across a multi-column arrangement, in a grid such that each cell of the grid may have multiple columns, or both. The sections surrounding each group of columns may have features and functions as described with respect to and illustrated in FIG. 17.

[0151]

[0169] Figure 19 is a schematic diagram of an inspection beam apparatus 100, according to one embodiment of the present invention. The apparatus 100 is a multi-column apparatus. Figure 19 shows three columns 40a-40c. In alternative embodiments, the number of columns 40 may be two, four, five or more, for example 25 or 100 or more. Descriptions of features that are the same as those described above in relation to Figures 16-18 are omitted for the sake of brevity.

[0152]

[0170] In the embodiment shown in Figures 16-17, each section 32 of the shield 31 surrounds the beam path of multiple columns 40. In the embodiment shown in Figure 18, each section 32 surrounds the beam path of only one column 40. These features are combined in the embodiment shown in Figure 19. As shown in Figure 19, in one embodiment, a single first section 32a is provided for the source portions of multiple columns 40a-40c. Separate second sections 32b, 32b', 32b'' are provided for the collimator portions of each column 40a-40c. Separate third sections 32c, 32c', 32c'' are provided for the beam splitter portions of each column 40a-40c.

[0153]

[0171] In some embodiments, each section corresponds to a separate module that can be replaced independently. For example, as shown in FIG. 19, in some embodiments, the second section 32b" of the third column 40c may be combined with a collimator in a collimator module 405b" that is replaceable independently from the other modules.

[0154]

[0172] 19, in some embodiments, one section 32 may be provided for a particular portion of one column 40, while another section 32 is provided to surround the beam path of the same portion of multiple other columns 40. For example, a first section 32a may surround the beam path in the source portion of only the first column 40a, while an additional section 32 may surround the beam path in the source portions of both the second column 40b and the third column 40c.

[0155]

[0173] As mentioned above, in some embodiments, there may be more than three columns 40, for example, nine, or even one hundred or more. In some embodiments, a first section 32a surrounds the beam path of the source portions of a first plurality of columns 40, while a further section 32a may surround the beam path of the source portions of a second plurality of columns 40. Of course, this feature may also be applied to other portions of the columns 40, such as the collimator portions.

[0156]

[0174] In variations of the arrangement shown in and described with respect to FIG. 19, references to a single column may refer to a group of columns in a multi-column arrangement, for example as described with respect to FIG.

[0157]

[0175] Certain embodiments of the present invention are expected to provide advantages with respect to a multi-column, multi-beam inspection beam apparatus 100. As shown in Figures 16-19, in certain embodiments, multiple multi-beam columns 40 are configured to inspect different locations on the same target 208 or different locations on different targets 208. In certain embodiments, the electron-optical components of the columns 40 (e.g., condenser lenses, objective lenses) are MEMS. Certain embodiments of the present invention are expected to reduce and / or limit the radial extent of each of the individual columns 40.

[0158]

[0176] In some embodiments, the MEMS components are field replaceable. Certain embodiments of the present invention are expected to facilitate maintenance of device 100, which includes fragile components that may be susceptible to contamination from particulates present in the ambient atmosphere, for example.

[0159]

[0177] Figures 16-19 show a few specific part combinations, any other combination of field replaceable arrays and individually replaceable parts is of course possible.

[0160]

[0178] It is also possible that multiple electronic optical elements, such as a beam splitter and a micro-astigmatism corrector, or an objective lens and a detector, or an objective lens, a detector and a height sensor, for the part of column 40, can be integrated into the interchangeable part of the array.

[0161]

[0179] For any of the field-replaceable portions or arrays shown above, the sections 32 may be flared as described above. In some embodiments, two or more sections 32 may be combined in a replaceable module. For example, one section 32 may be provided for the up beam of the electro-optical components and one section may be provided for the down beam of the electro-optical components. The sections 32 may be combined with the components in a field-replaceable module.

[0162]

[0180] The electron optical column 40 or multi-column device may be a component of an inspection (or metro inspection) tool, or part of an electron beam lithography tool. Multi-beam charged particle devices can be used in many different applications, including not only SEM but also electron microscopy in general, and lithography.

[0163]

[0181] Throughout the embodiments, an electron optical axis 304 is described. This electron optical axis 304 represents the path of charged particles through the source 301 and out of the source 301. All of the sub-beams and beamlets of the multi-beam may be substantially parallel to the electron optical axis 304, at least through the manipulator. The electron optical axis 304 may be the same as or different from the mechanical axis of the electron optical column 40.

[0164]

[0182] While the invention has been described in connection with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

[0165]

[0183] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims and clauses set out below.

[0166]

[0184] A number of provisions are provided.

[0167]

[0185] Clause 1: An electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path toward a target, the electron optical assembly including an electromagnetic shield configured to surround the charged particle beam path and shield the charged particle beam from electromagnetic fields outside the electromagnetic shield, the electromagnetic shield including multiple sections extending along different positions along the beam path, each section surrounding the charged particle beam path, and the sections being separable.

[0168]

[0186] Clause 2: An electron-optical assembly as described in clause 1, wherein the sections are arranged such that a gap in the electromagnetic shield is formed between adjacent sections in the direction of the beam path.

[0169]

[0187] Clause 3: An electron-optical assembly as described in clause 2, wherein adjacent sections have opposing surfaces extending radially relative to the beam path, preferably by a distance at least as large as the gap between the adjacent sections.

[0170]

[0188] Clause 4: An electron-optical assembly according to any one of the preceding clauses, wherein at least one end of the section in the direction of the beam path comprises a flange extending radially relative to the beam path.

[0171]

[0189] Clause 5: An electron-optical assembly described in any one of the preceding clauses, comprising at least one electron-optical element between adjacent sections, preferably the electron-optical element comprising a plurality of manipulators, preferably a manipulator array.

[0172]

[0190] Clause 6: An electron-optical assembly according to any one of the preceding clauses, wherein the electromagnetic shield is configured to shield the charged particle beam from an electric field.

[0173]

[0191] Clause 7: An electron optical assembly according to any one of the preceding clauses, wherein the electromagnetic shield is configured to shield the charged particle beam from magnetic fields.

[0174]

[0192] Clause 8: An electro-optical assembly according to any one of the preceding clauses, wherein the electromagnetic shield comprises a magnetically permeable material.

[0175]

[0193] Clause 9: An electron-optical assembly according to any one of the preceding clauses, wherein the sections are arranged such that at least one section is movable radially relative to the beam path independently of another one of the sections.

[0176]

[0194] Clause 10: An electro-optical assembly according to any one of the preceding clauses, wherein at least two of the sections include adjacent ends that electromagnetically engage with one another.

[0177]

[0195] Clause 11: An electro-optical assembly as described in clause 10, wherein adjacent ends are dimensioned so as to be coaxially arranged.

[0178]

[0196] Clause 12: An electron optical column according to clause 10 or 11, wherein the adjacent ends are sized so that one end can be inserted into the other end.

[0179]

[0197] Clause 13: An electron optical column according to any one of clauses 10 to 12, wherein adjacent ends are physically separated and electrically engaged.

[0180]

[0198] Clause 14: An electro-optical assembly according to any one of the preceding claims, wherein at least one of the sections comprises a mechanical reference member configured to enable the position of the section to be determined.

[0181]

[0199] Clause 15: An electro-optical assembly as claimed in claim 14, wherein the mechanical reference member is configured to mechanically engage with a corresponding mechanical reference member of another one of the sections or columns.

[0182]

[0200] Clause 16: A module including an electro-optical assembly according to any one of the preceding clauses.

[0183]

[0201] Clause 17: A module comprising an electron optical device and an electromagnetic shield of a beam path through the module when in an electron optical column for projecting a charged particle beam along the beam path towards a target, wherein the electromagnetic shield includes an up beam section of an up beam of the electron optical device and a down beam section of a down beam of the electron optical device, and at least one of the up beam section and the down beam section has an interface extending radially relative to the beam path.

[0184]

[0202] Clause 18: The module of clause 17, wherein a boundary surface of the upbeam section forms a boundary surface with an upbeam element of the column.

[0185]

[0203] Clause 19: A module as described in Clause 18, wherein the up beam element of the column includes an upper beam section of an electromagnetic shield, and wherein the boundary surface of the up beam section is spaced apart from the upper beam section by a gap when the module is present in the electron optical column, preferably the gap being at most as large as the radial extent of the boundary surface of the up beam section, and preferably at least one of the up beam section and down beam section includes a flange extending radially relative to the beam path.

[0186]

[0204] Clause 20: A module according to any one of clauses 17 to 19, wherein the interface of the down beam section forms an interface with the up beam element of the column, the interface of the up beam interface being a facing surface, preferably the interface providing a flange.

[0187]

[0205] Clause 21: A module as described in clause 20, wherein the down beam element of the column includes a lower beam section of an electromagnetic shield, and the boundary surface of the down beam section is spaced apart from the lower beam section by a gap when the module is present in the electron optical column, preferably the gap being at most as large as the radial extent of the boundary surface of the down beam section.

[0188]

[0206] Clause 22: A module according to any one of clauses 17 to 21, wherein the electro-optical device is a MEMS device.

[0189]

[0207] Clause 23: The module according to any one of clauses 16 to 22, wherein the module is a MEMS module.

[0190]

[0208] Clause 24: A module according to any one of clauses 16 to 23, wherein the module is configured to be replaceable within an electron optical column.

[0191]

[0209] Clause 25: The module of clause 24, wherein the module is configured to be field replaceable.

[0192]

[0210] Clause 26: A module as claimed in any one of claims 16 to 25, further comprising a mechanical reference member configured to enable the position of the module relative to the column, when within the electron optical column, to be determined.

[0193]

[0211] Clause 27: An electron optical column comprising a module according to any one of clauses 16 to 25.

[0194]

[0212] Clause 28: An electron-optical column comprising an electron-optical assembly according to any one of clauses 1 to 15.

[0195]

[0213] Clause 29: An electron optical column as described in clause 27 or 28, wherein the electromagnetic shield is radially inward of one or more of the electron optical elements, such as a thermal conditioner configured to thermally condition at least a portion of the electron optical column, a pump configured to reduce pressure within the electron optical column, and a collimator configured to collimate the charged particle beam or a deflector configured to deflect the charged particle beam.

[0196]

[0214] Clause 30: An electron-optical assembly as described in clause 29, wherein the thermal conditioner is configured to remove heat generated within the electron-optical column.

[0197]

[0215] Clause 31: An electron optical column as described in any one of claims 27 to 30, wherein at least one of the sections radially surrounds at least one component selected from the group consisting of a charged particle source, a focusing lens, a collimator, a source converter, a deflector array, an aperture array, an aberration compensator array, an image forming element array, an objective lens array, and a detector array.

[0198]

[0216] Clause 32: An electron-optical column according to claim 31, wherein the component is a MEMS component.

[0199]

[0217] Clause 33: An electron optical column according to claim 31 or 32, wherein a section is arranged so as to be movable together with the component it surrounds in a radial direction relative to the beam path independently of another one of the sections.

[0200]

[0218] Clause 34: An electron optical column according to any one of claims 31 to 33, wherein the section together with the components it surrounds is field replaceable.

[0201]

[0219] Clause 35: An apparatus comprising two or more of the electron optical columns according to any one of claims 31 to 34.

[0202]

[0220] Clause 36: The apparatus of claim 35, wherein at least one of the sections radially surrounds the beam paths of two or more of the electron optical columns.

[0203]

[0221] Clause 37: An apparatus as claimed in claim 35 or 36, wherein the beam path of at least one of the electron optical columns is radially outside at least one of the sections.

[0204]

[0222] Clause 38: An apparatus according to any one of claims 35 to 37, wherein at least one of the sections radially surrounds the beam path of only one of the electron optical columns.

[0205]

[0223] Clause 39: An apparatus as claimed in any one of claims 35 to 38, wherein different sections of the electromagnetic shield radially surround the beam paths of each different electron optical column, the different sections being in overlapping positions in a direction parallel to the beam paths.

[0206]

[0224] Clause 40: An apparatus according to any one of claims 35 to 39, wherein a plurality of sections positioned to overlap in a direction parallel to the beam path are arranged so as to be movable together in a radial direction relative to the beam path independently of one another of the sections.

[0207]

[0225] Clause 41: A multi-column apparatus comprising: electron optical columns configured to project respective charged particle beams along respective beam paths toward a target; a charged particle source configured to generate charged particle beams for one or more of the electron optical columns; and an electromagnetic shield surrounding the charged particle beam path of at least one of the electron optical columns, wherein the electromagnetic shield includes a plurality of sections extending along different positions along the respective beam paths, each section surrounding a charged particle beam path, and the sections being separable.

[0208]

[0226] Clause 42: A multi-column apparatus according to claim 41, wherein the column is a multi-beam column configured to project respective multiple beams of charged particles along respective beam paths towards the target.

[0209]

[0227] Clause 43: A multi-column apparatus according to claim 41 or 42, wherein the sections are arranged such that gaps in the electromagnetic shield are formed between adjacent sections in the direction of the beam path.

[0210]

[0228] Clause 44: A multi-column apparatus according to claim 43, wherein adjacent sections have opposing surfaces extending radially relative to the beam path, preferably by a distance at least as large as the gap between the adjacent sections.

[0211]

[0229] Clause 45: A multi-column apparatus according to any one of claims 41 to 44, wherein the sections are arranged such that at least one section is movable radially relative to the beam path independently of another one of the sections.

[0212]

[0230] Clause 46: A multi-column apparatus according to any one of claims 41 to 45, wherein at least one of the sections is provided with a mechanical reference member configured to enable the position of the section in a direction parallel to the beam path to be determined.

[0213]

[0231] Clause 47: A multi-column apparatus as claimed in any one of claims 41 to 46, wherein at least one of the sections radially surrounds at least one component selected from the group consisting of a charged particle source, a focusing lens array, a collimator array, a source converter, a deflector array, an aperture array, a corrector array, an aberration compensator array, an image forming element array, an objective lens array, and a detector array.

[0214]

[0232] Clause 48: A multi-column apparatus according to any one of claims 41 to 47, wherein a section is arranged so as to be movable together with the component it surrounds in a radial direction relative to the beam path independently of another one of the sections.

[0215]

[0233] Clause 49: A multi-column apparatus according to any one of claims 41 to 48, wherein at least one of the sections radially surrounds the beam paths of two or more of the electron optical columns.

[0216]

[0234] Clause 50: An electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path towards a target, the electron optical assembly including an electromagnetic shield surrounding the charged particle beam path and configured to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield including a plurality of sections extending along the beam path and surrounding the beam path, at least two of the sections being separable and including adjacent ends that electromagnetically engage with each other.

[0217]

[0235] Clause 51: An electron-optical assembly as described in clause 50, wherein each section defines an aperture configured for passage of a beam path.

[0218]

[0236] Clause 52: An electron-optical assembly as described in clause 50 or 51, wherein the multiple sections extend continuously along the beam path.

[0219]

[0237] Clause 53: A method of manufacturing an electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path toward a target, the method comprising providing an electromagnetic shield to surround the charged particle beam and shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, the sections being separable.

[0220]

[0238] Clause 54: The method of clause 53, wherein the electro-optical assembly is contained within a module.

[0221]

[0239] Clause 55: A method for replacing a module of an electron optical column for projecting a charged particle beam along a beam path toward a target, the method comprising removing the module from the electron optical column, the electron optical column comprising an electromagnetic shield configured to surround the charged particle beam path and to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, at least one of the sections being contained within the module and separable from other of the up beam and / or down beam sections of the module.

[0222]

[0240] Clause 56: A method of projecting a charged particle beam along a beam path towards a target, the method comprising shielding the charged particle beam from an electromagnetic field external to an electromagnetic shield, the electromagnetic shield comprising a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path, the sections being separable.

[0223]

[0241] Clause 57: The method of claim 56, comprising projecting a charged particle beam along a beam path of each electron optical column toward a target.

[0224]

[0242] Clause 58: A method according to claim 57, wherein at least one of the sections surrounds the beam paths of two or more of the electron optical columns and is arranged to be movable together with the one or more components it surrounds in a radial direction relative to the beam paths independently of another one of the sections.

[0225]

[0243] Clause 59: A method according to claim 57 or 58, wherein different sections of the electromagnetic shield radially surround the beam paths of respective different electron optical columns, the different sections being in overlapping positions in a direction parallel to the beam paths, and the different sections being arranged so that they are movable together radially relative to the beam paths independently of one another of the sections.

[0226]

[0244] Clause 60: A method of operating an electron-optical assembly configured to project a charged particle beam along a beam path toward a target, the assembly including a plurality of electromagnetic shield sections configured to shield the charged particle beam from electromagnetic fields external to the electromagnetic shield, and a module including an electron-optical device and configured to be removable from the assembly, the method including removing the module from the assembly, the removing including radially moving a section of the electromagnetic shield within the module relative to the beam path.

[0227]

[0245] Clause 61: The method of clause 60, further comprising exchanging a module in an assembly, comprising moving a section of the electromagnetic shield in the module radially relative to the beam path so that the section faces an adjacent section of the electromagnetic shield along the beam path in the assembly.

Claims

1. 1. An electron optical assembly for an electron optical column for projecting a charged particle beam along a beam path toward a target, said electron optical assembly comprising: an electromagnetic shield surrounding the charged particle beam path and shielding the charged particle beam from electromagnetic fields external to the electromagnetic shield; Including, the electromagnetic shield includes a plurality of sections extending along different positions along the beam path, each section surrounding the charged particle beam path; the sections are separable and arranged such that a gap in the electromagnetic shield is formed in the direction of the beam path between at least two adjacent sections, the adjacent sections having opposing surfaces extending radially relative to the beam path, and at least one of the opposing surfaces including a flange extending radially relative to the beam path; The electro-optic assembly, wherein the opposing surfaces comprise a magnetically permeable material.

2. 2. The electron-optical assembly of claim 1, wherein the opposing surfaces extend radially relative to the beam path a distance at least as large as the gap between the adjacent sections.

3. 3. An electro-optical assembly according to claim 1 or 2, comprising at least one electro-optical element between adjacent sections.

4. 4. An electron-optical assembly according to claim 3, wherein the electron-optical element comprises a plurality of manipulators, preferably a manipulator array.

5. 5. An electron-optical assembly according to any one of claims 1 to 4, wherein the electromagnetic shield shields the charged particle beam from electric and / or magnetic fields.

6. 6. An electro-optical assembly according to any one of claims 1 to 5, wherein the electromagnetic shield comprises a magnetically permeable material.

7. An electron-optical assembly according to any one of claims 1 to 6, wherein the sections are arranged such that at least one section is radially movable relative to the beam path independently of another one of the sections.

8. An electro-optic assembly according to any preceding claim, wherein at least two of the sections include adjacent ends that electromagnetically engage with one another.

9. 9. An electro-optic assembly as claimed in claim 8, wherein the adjacent ends are sized to be coaxially arranged.

10. 10. An electro-optic assembly according to claim 8 or 9, wherein the adjacent ends are physically separated and electromagnetically engaged.

11. 11. An electro-optical assembly according to any one of the preceding claims, wherein at least one of the sections is provided with a mechanical reference member that enables the position of the section to be determined.

12. 12. The electro-optic assembly of claim 11, wherein the mechanical reference member mechanically engages a corresponding mechanical reference member of another one of the sections or the column.

13. 1. The module comprising: an electron optical device; and an electromagnetic shield for a beam path passing through the module when the module is in an electron optical column for projecting a charged particle beam along a beam path toward a target, wherein the electromagnetic shield includes an up beam section for an up beam of the electron optical device and a down beam section for a down beam of the electron optical device, at least one of the up beam section and the down beam section having a boundary surface extending radially with respect to the beam path, and at least one of the up beam section and the down beam section including a flange extending radially with respect to the beam path; The module, wherein the boundary surface comprises a magnetically permeable material.

14. The module of claim 13 , wherein the interface of the up beam section forms an interface with an up beam element of the column, the interface of the up beam interface being a facing surface.

15. 15. The module of claim 14, wherein the up beam element of the column includes an upper beam section of the electromagnetic shield, the boundary surface of the up beam section being spaced apart from the upper beam section by a gap when the module is present in an electron optical column, preferably the gap being at most as large as the radial extent of the boundary surface of the up beam section.

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