Forked lens barrel accelerating tube scanning electron microscope

Abstract

Embodiments of the present disclosure include systems, methods, algorithms, and non-transitory media storing computer readable instructions for charged particle imaging and microanalysis. The charged particle beam system may include an objective lens assembly defining an aperture that mates with the first shaft. The system may include a bifurcated acceleration tube. The acceleration tube may include a main section, an auxiliary section intersecting the main section, and a common section disposed at least partially in the bore, the auxiliary section having an included angle alpha with respect to the first axis. The system may include a separator. The separator may include one or more charged particle optical elements disposed in the common segment and configured to apply a deflecting force to electrons at a negative velocity in the first direction. The deflecting force may redirect the electrons to a second direction substantially aligned with the second axis.

Description

[0001] Cross-citation of related applications

[0002] This application claims priority to U.S. nonprovisional application 18 / 660,569, filed May 10, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments of this disclosure relate to charged particle microscopy systems and algorithms and methods for operating them. In particular, some embodiments relate to secondary electron microscopy and microanalysis techniques in multi-beam systems. background

[0004] Charged particle microscopy is a well-known and increasingly important technique for imaging microscopic objects, particularly in the form of electron microscopy. Basic types of electron microscopes are practically used in various instrument types such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM), as well as various subtypes.

[0005] In SEM, irradiation of the sample by a scanning electron beam promotes the emission of "auxiliary" radiation from the sample, such as secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible, and / or ultraviolet photons). One or more components of this emitted radiation are then detected and used for image accumulation purposes.

[0006] As an alternative to using electrons as the illumination beam, charged particle microscopy can also be performed using other types of charged particles. In this regard, the phrase "charged particle" can be understood to encompass, for example, electrons, positive ions (e.g., Ga or He ions), negative ions, protons, and positrons. In addition to imaging and performing (local) surface modifications (e.g., milling, etching, deposition, etc.), charged particle microscopy can also have other functionalities, such as performing spectroscopy, examining diffraction patterns, etc.

[0007] In all cases, charged particle microscopy (CPM) will typically include at least a radiation source (e.g., an electron source or ion gun), a beam guiding system, a sample holder, and a detector.

[0008] Depending on the radiation being detected, detectors can take many different forms. Examples include photodiodes, CMOS detectors, CCD detectors, photovoltaic cells, X-ray detectors (such as silicon drift detectors and Si(Li) detectors), etc. Generally, a CPM can include several different types of detectors, the selection of which can be invoked in different situations.

[0009] Summarize

[0010] The terms and expressions used are descriptive rather than restrictive, and their use is not intended to exclude any equivalents of the features shown and described or portions thereof. Rather, it should be recognized that various modifications are possible within the scope of the claimed subject matter. Therefore, it should be understood that although the subject matter claimed in this disclosure has been specifically disclosed by way of embodiments and optional features, modifications and alterations to the concepts disclosed herein can be made by those skilled in the art, and such modifications and alterations are considered to be within the scope of this disclosure as defined by the appended claims. For example, the foregoing aspects and various embodiments may be combined with one or more other aspects and / or embodiments of the same or other aspects.

[0011] In the first aspect, Figure 1-7B A charged particle beam system is described. The system may include an objective lens assembly defining an aperture mates with a first axis; the system may include an accelerating tube defining a bifurcation. The accelerating tube may include a main section substantially concentric with the first axis; an auxiliary section intersecting the main section at the bifurcation, the auxiliary section being oriented substantially concentric with a second beam axis at an angle α relative to the first axis; and a common section, at least partially disposed within the aperture. The system may include a separator. The separator may include one or more charged particle optical elements disposed in the common section and configured to apply a deflecting force to electrons with a negative velocity in a first direction. This deflecting force may redirect the electrons to a second direction substantially aligned with a second axis.

[0012] In some embodiments, the accelerating tube is configured to increase the negative velocity of electrons by an order of magnitude in the first direction. One or more charged particle optical elements may include a Wien filter. The Wien filter may be coupled to control circuitry. The control circuitry may configure the Wien filter to apply a negligible or essentially non-existent deflection force to primary electrons with a positive velocity in the first direction. The separator may be coupled to a bias circuitry configured to apply a bias voltage potential to the separator.

[0013] In some embodiments, the system includes a projection system. The projection system may be arranged along a second axis. The projection system may include one or more electromagnetic elements disposed within the accelerating tube and coupled to a bias circuit configured to apply a potential to the electromagnetic elements. The projection system may also include one or more electromagnetic elements disposed outside the accelerating tube. The projection system may include an astigmatism correction assembly.

[0014] In some embodiments, the electrons are secondary electrons. The system may include an array of aperture elements disposed on a first beam axis and configured to generate multiple sub-beams of primary electrons with non-zero velocities along the first beam axis in a first direction. Angle α may be a first angle. One or more charged particle optical elements may include magnetic prisms configured to redirect electrons from the first direction to a second direction and redirect primary electrons from a third direction to the first direction, the third direction being at an angle β relative to the first direction.

[0015] In some embodiments, the objective assembly includes a multi-gap objective. The objective assembly may include a magnetic lens and an immersion lens, or a magnetic lens and an electrostatic lens. The angle α may be from about 5 degrees to about 40 degrees.

[0016] In the second aspect, such as Figure 1 as well as Figure 3-7B As shown, the accelerator tube includes a main section substantially concentric with a first axis; an auxiliary section connected to the main section at a bifurcation of the accelerator tube, the auxiliary section being oriented substantially concentric with a second axis at an angle α relative to the first axis; and a common section. The accelerator tube may include a separator. The separator may include one or more charged particle optical elements disposed in the common section and configured to apply a deflecting force to charged particles with a negative velocity in a first direction. This deflecting force can redirect electrons to a second direction substantially aligned with the second axis.

[0017] In some embodiments, the accelerator tube may be configured to increase the negative velocity of charged particles in the first direction by an order of magnitude. One or more charged particle optical elements may include a Wien filter. The Wien filter may be coupled to control circuitry configuring the Wien filter to apply a negligible or essentially non-existent deflection force to primary charged particles having a positive velocity in the first direction.

[0018] An accelerator tube may include a dielectric material serving as a physical tube, with internal optical components biased to a tube potential and externally coupled to ground or biased to a potential different from the tube potential. The accelerator tube may include an accelerator assembly. The accelerator assembly may be disposed in a common section. The accelerator assembly may include multiple ring electrodes. The accelerator assembly may be coupled to a bias circuit configured to apply bias to the ring electrodes. The accelerator tube may include a substrate disposed in the common section and coupled to the accelerator assembly, the substrate defining multiple apertures configured to selectively transmit a portion of charged particles incident onto the substrate.

[0019] While this disclosure relates in its entirety to the specific context of charged particle microscopy, and more specifically to electron microscopy, such description is not intended to be limiting, and the apparatuses and methods disclosed herein can be applied to any suitable context within the scope of this disclosure. Attached Figure Description

[0020] The foregoing aspects and many accompanying advantages of this disclosure will become more readily understood when taken in conjunction with the accompanying drawings and the following detailed description.

[0021] Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam system according to some embodiments of the present disclosure.

[0022] Figure 2This is a schematic diagram illustrating an exemplary charged particle multi-beam system according to some embodiments of the present disclosure.

[0023] Figure 3 This is a schematic diagram illustrating an exemplary charged particle multi-beam system according to some embodiments of the present disclosure.

[0024] Figures 4A-4C This is a schematic diagram illustrating an exemplary separator according to some embodiments of the present disclosure.

[0025] Figure 5 This is a schematic diagram illustrating an exemplary optical system according to some embodiments of the present disclosure.

[0026] Figures 6A-6B This demonstrates some implementation schemes according to this disclosure. Figure 5 A schematic diagram showing details of the exemplary optical system.

[0027] Figures 7A-7B This is a schematic diagram illustrating an exemplary optical system (including a third axis) according to some embodiments of the present disclosure.

[0028] In the accompanying drawings, unless otherwise specified, the same reference numerals denote the same parts in each view. Where appropriate, it is not necessary to label all instances of elements to reduce confusion in the drawings. The drawings are not necessarily drawn to scale, but rather focus on illustrating the principles described. Detailed description

[0029] While illustrative embodiments have been described and illustrated, it should be understood that various changes may be made therein without departing from the spirit and scope of this disclosure. In the following paragraphs, embodiments of charged particle beam systems, components, and techniques for separating secondary charged particles emitted from a sample location are described. For simplicity, embodiments of this disclosure focus on electron microscopy and microanalysis, and related systems. Therefore, embodiments are not limited to such systems, but are considered for charged particle beam systems (in which conventional techniques for detecting secondary charged particles become complex due to the diversity of primary charged particle beams) and / or samples for which a bias voltage needs to be applied to the sample surface to detect them. Similarly, while embodiments of this disclosure are particularly concerned with scanning electron microscopy and multi-beam electron microscopy systems, additional and / or alternative beam systems, including but not limited to focused ion beam systems, dual-beam systems, or similar products, may be considered.

[0030] Embodiments of this disclosure include systems, methods, algorithms, and non-transitory media for charged particle imaging and microanalysis, as well as computer-readable instructions. In an illustrative example, a charged particle beam system may include: an objective assembly defining an aperture mates with a first beam axis; an accelerating tube defining a bifurcation; the accelerating tube including a main section, an auxiliary section, oriented substantially concentric with a second beam axis at an angle α relative to the first beam axis; and a common section at least partially disposed within the aperture. The charged particle beam system may also include a splitter comprising one or more charged particle optical elements disposed in the common section and configured to apply a deflection force to electrons traveling at a negative velocity in a first direction substantially aligned with the common section of the accelerating tube. This deflection force may redirect electrons to a second direction substantially aligned with the second beam axis. Advantageously, embodiments of this disclosure improve the sensitivity, robustness, and operational flexibility of multi-beam charged particle systems, while also allowing the analysis of non-conductive and / or dielectric samples unsuitable for current systems and / or technologies.

[0031] Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam system according to some embodiments of the present disclosure. Example system 100 includes multiple parts, including an electron source 101, a primary lens barrel 105, and a vacuum chamber 110. The electron source 101 includes a high-voltage power supply component, a vacuum system component, and an electron emitter configured to generate an electron beam accelerated into the beam lens barrel 105. The beam lens barrel 105 includes an electromagnetic lens element configured to shape the electron beam from the electron source into a generally circular beam, such that the cross-section of the beam is generally uniform with respect to the beam axis A, and to adjust the beam to be focused onto a sample 125 through an objective lens assembly 115. The objective lens assembly 115 defines an aperture 117. Example system 100 also includes a bifurcated accelerator tube 130 defining a branch, a portion of which is aligned with the primary lens barrel 105 and another portion with the secondary lens barrel 107.

[0032] Electron beams are typically characterized by beam current and accelerating voltage applied to generate the beam, among other criteria. The ranges of beam current and accelerating voltage can vary between instruments and are usually chosen based on the material properties of the sample or the type of analysis being performed. However, in scanning electron microscopy, electron beams are typically characterized by energies from about 0.1 keV (e.g., for an accelerating voltage of 0.1 kV) to about 50 keV and beam currents from picoamperes to microamperes.

[0033] Vacuum chamber 110 and / or beam tubes 105-107 may include multiple detectors for various signals, including but not limited to secondary electrons generated by the interaction between the electron beam and the sample, X-ray photons (e.g., EDAX), other photons (e.g., visible light and / or infrared cameras), and / or molecular components (e.g., TOF-SIMS). Figure 1 The following is described in more detail. The vacuum chamber 110 may also include a sample stage 120 operably coupled to a multi-axis translation / rotation control system, allowing the sample 125 to be repositioned relative to the beam axis A as a means of measuring and / or imaging the sample 125. For this purpose, one or more charged particle and / or radiation sensors may be disposed in the vacuum chamber 110 and / or the beam tube 105 and configured to detect characteristic signals emitted from the sample (e.g., reflected and / or transmitted).

[0034] Example charged system 100 is shown as a single-beam SEM instrument to focus the description on the components of example system 100.

[0035] In some implementations, example system 100 may incorporate additional and / or alternative components to include an ion beam source (e.g., a focused ion beam, or a FIB as part of a dual-beam system), thus suited for applications such as sample modification or microanalysis. Similarly, charged system 100 may include a photon source, such as a laser or other electromagnetic radiation source. Figure 2 As described in more detail below, embodiments of this disclosure include components of an example system 100 that enables an electron source 101 to generate multiple sub-beams of charged particles. Advantageously, the multiple sub-beams can be performed in parallel for charged particle microscopy and microanalysis, thereby increasing the throughput and efficiency of analyzing large samples.

[0036] Detection of secondary electrons in multi-beam microscope samples involves several application-specific limitations. In particular, resolving secondary electron information from a single sub-beam is a significant challenge due to the ease with which secondary electron sub-beams overlap in space, posing a major challenge to the detection of distinct secondary electron signals. To address this, embodiments of this disclosure include a bifurcated accelerating tube 130 that extends at least partially into an aperture 117 of an objective assembly 115. The bifurcated accelerating tube 130 can energize (e.g., accelerate) secondary electrons emitted from a sample 125 into the bifurcated accelerating tube 130 and passing through a separator 135. The separator 135 can be configured to redirect the secondary electrons into a secondary tube 107 containing charged particle optics. The secondary tube 107 can then shape, redirect, form, focus, defocus, and / or project (and otherwise transform) the secondary electrons to impact one or more detectors 140 coupled to the secondary tube 107.

[0037] In the following paragraphs and Figure 2Section -7 details and describes in detail various aspects, details, features, and / or implementations of Example System 100 and other charged particle beam systems. In some implementations, the bifurcation acceleration tube 130 is a physical entity (e.g., a dielectric tube) defining the bifurcation and common section. In some implementations, the common section is at least partially disposed in the aperture 117 of the objective assembly 115. Thus, secondary electrons generated on or near the surface of the sample 125 can be accelerated into the common section and separated from the primary electrons of the beam (or sub-beam), and directed to the secondary tube 107 and detector 140. Advantageously, accelerating the secondary electrons to a relatively high voltage can reduce chromatic aberration and geometric aberrations in the separator and projection system. Accelerating the secondary electrons reduces relative energy diffusion, collimates the sub-beams, and reduces the degree of crosstalk between sub-beams. Compared to conventional techniques in multibeam electron microscopy that apply a bias voltage to the sample 125 itself, embodiments of this disclosure can be used for samples 125 that are non-conductive or otherwise sensitive to applied kilovolt-level voltages (e.g., insulating samples, nanoparticle samples that may be separated from the sample surface and propelled into the microscope tube, etc.) as a method to accelerate electrons away from the sample 125 and into the microscope tube optics.

[0038] Figure 2 This is a schematic diagram illustrating an exemplary charged particle multi-beam system 200 according to some embodiments of the present disclosure. The example system 200 includes a charged particle source 205 configured to generate a highly divergent electron beam 210; and an aperture array (ALA) 215, through which the beam 210 is converted into a plurality of sub-beams 225 via a plurality of apertures 220 defined therethrough. The sub-beams 225 pass through a first condenser lens 230, which is substantially positioned on the beam axis A corresponding to a first sub-beam intersection. The first condenser lens 230 redirects the sub-beams 225 to a first common intersection, at which a second condenser lens 235 is positioned. The divergent sub-beams exiting from the second condenser lens 235 converge and focus to the second sub-beam intersection, at which a third condenser lens 240 is positioned. Below the third condenser lens 240 on axis A, an objective lens 250 is positioned at a second common intersection of the sub-beams 225, between the third condenser lens 240 and a sample position 255. In some embodiments, additional and / or alternative optical devices are included, and sub-beams 225 may exhibit more or less crossover. Beam axis A may include straight and / or curved sections.

[0039] The average energy of sub-beam 225 is consistent with the typical energy of primary electrons (e.g., from about 1 kV to about 100 kV) and is directed to the sample (e.g., Figure 1The sample 225 is a discrete region. Multibeam microscopy and microanalysis involve scanning the sub-beams 225 on the sample surface using a scanning mode suitable for each sub-beam 225, thus covering a relatively large sample area compared to a typical single-beam system. This allows for secondary electron imaging of relatively large areas of the sample by processing detector data in a relatively short time (e.g., stitching sub-images or "tiles" together to form a larger composite image), without the need for frequent movement of the sample relative to the beam axis A as in other single-beam systems.

[0040] However, multi-beam technology introduces several significant technical challenges, including separating secondary electrons generated by the interaction of each corresponding sub-beam 225 with the sample, and generating different secondary electron detector data for each corresponding sub-beam 225.

[0041] For this purpose, example system 200 may include a pixelated or otherwise segmented detector and optics configured to project secondary electrons onto the detector. This technique is not shown. Figure 2 This is in the middle, but you can refer to the following. Figure 3 The description in -7.

[0042] like Figure 1 As shown, crosstalk between sub-beams in a multi-beam system can be addressed by accelerating electrons (e.g., thereby reducing the relative energy diffusion of the sub-beams). To this end, the exemplary multi-beam system 200 can accelerate secondary electrons emitted from sample location 255 in several ways. A first method of accelerating secondary electrons involves applying a DC bias voltage (e.g., on the order of 1 kV–10 kV) to the sample and using this electric field to push the secondary electrons away from the sample and towards the detector (e.g., into…). Figure 1 The second method involves using an accelerator tube to attract secondary electrons emitted from sample position 255, such as... Figure 1 As shown, and with reference Figure 3 A more detailed description is provided in section -7. Advantageously, accelerating secondary electrons to higher average energies reduces detector planar spatial overlap or "crosstalk" (e.g., data from the respective sub-beams 225) between channels. Furthermore, applying the second accelerating tube method according to embodiments of this disclosure eliminates the significant effects of applying a strong bias to dielectric and / or insulating and / or semiconductor material samples that are unsuitable for the first method.

[0043] Figure 3 This is a schematic diagram illustrating an exemplary charged particle optical system 300 according to some embodiments of the present disclosure. Example system 300 is... Figure 1An embodiment of at least a portion of the example system 100 is described. Example system 300 includes an objective lens assembly 305 defining an aperture 310 that mates with a first axis A; and an acceleration tube 315 defining a bifurcation 320. The acceleration tube 315 includes a main section 325, an auxiliary section 330, and a common section 335. The exemplary layout also includes a separator 340 and a secondary lens barrel 360 (e.g., Figure 1 (Secondary microscope tube 107).

[0044] In some embodiments, the main segment 325 is substantially concentric with the first axis A. Similarly, the aperture 310 may be substantially concentric with the first axis A. Herein, "substantially concentric" means an orientation about the first axis A such that the electromagnetic field used to form, shape, redirect, deflect, or otherwise transform a beam of charged particles is substantially aligned with the first axis A, achieving substantial axisymmetry about the first axis A. For example, one or more electromagnetic lenses of the objective assembly 305 may produce a substantially axisymmetric field, with the beam axis A serving as the axis of symmetry. However, it should be understood that the axis of symmetry may deviate from the beam axis A within permissible tolerances (i.e., not perfectly coincident).

[0045] In some implementations, the auxiliary segment 330 is oriented via and substantially concentric with a second axis B. The second axis B may be oriented at an angle α relative to the first axis A. Angle α may be greater than approximately 5 degrees, including its subranges, fractions, and interpolations. As described in more detail in Figure 6, angles less than approximately 5 degrees may involve spatial constraints and induce electromagnetic interference between primary beam particles (e.g., primary electrons) and measurement particles (e.g., secondary electrons), which can distort detector data and hinder the operation of the separator 340. For example, angle α may be approximately 20 degrees, approximately 22 degrees, approximately 24 degrees, etc.

[0046] The common segment 335 may include a portion on the first axis A and the second axis B located between the bifurcation 320 and the separator 340. Between the separator 340 and the sample position 355, the common segment 335 may be substantially concentric with the first axis A. The common segment 335 may be at least partially disposed within the aperture 310. In the example system 300, the separator 340 is also at least partially disposed within the aperture 310 of the objective lens assembly 305.

[0047] Accelerator tube 315 can be a physical component or an invisible "virtual" tube. For this purpose, accelerator tube 315 can define a space within which charged particle optical components (e.g., beam-limiting apertures, lenses, astigmatism reducers, etc.) are biased to a given voltage. Components outside the space of accelerator tube 315 can be coupled to ground or other voltages. In an illustrative example, magneto-optical devices (e.g., used as lenses) can be disposed outside accelerator tube 315 and coupled to the ground potential. Figure 3In the example shown, example system 300 includes a secondary lens barrel 360 disposed along the secondary beam axis B. The secondary lens barrel 360 may include one or more electro-optical elements disposed within the interior space of the accelerating tube 315 and coupled to an electrical bias circuit configured to apply a potential to the electro-optical elements, as described in more detail in Figure 7.

[0048] The separator 340 may be an assembly of one or more charged particle optical elements, configured to apply a deflection force in a specific direction. For this purpose, the separator 340 may be located in a common segment and configured to apply a deflection force to electrons with a negative velocity in the first direction; see reference [link to relevant documentation]. Figures 4A-4C A more detailed description follows. In the context of example system 300, the first direction is substantially aligned with the common segment of the accelerating tube and the first axis A, and points towards the sample position 355. Accordingly, a deflection force can redirect electrons with negative velocities in the first direction to a second direction substantially aligned with the second axis B, as illustrated in Figure 6.

[0049] Accelerator tube 315 is configured to increase the negative velocity order of electrons in a first direction. In this context, "negative velocity order" means accelerating electrons in a given direction (e.g., by electrostatic attraction and / or repulsion) without a change in the sign of the velocity component in a given coordinate system. In some embodiments, accelerator tube 315 includes a plurality of annular electrode elements (as shown in Figure 6) spaced apart by an insulating or dielectric medium (e.g., a ceramic gasket, vacuum, etc.) electrically coupled to a DC voltage source (e.g., a high-voltage power supply) configured to bias the electrode elements. The annular electrode elements can be configured to generate a substantially linear electric field that is positioned along the first direction and whose magnitude is such that secondary electrons are attracted to accelerator tube 315 and accelerated against the first direction.

[0050] In the illustrative example, secondary electrons can be generated by irradiating the sample with a primary beam of charged particles substantially aligned with the electron beam axis A and propagating along a first direction. (The second example is in the first direction.) Figure 3 In the orthogonal coordinate space defined by the symbols “X” and “Y”, secondary electrons can leave the sample surface with a negative velocity component in the first direction and a non-zero velocity in the normal direction (“Y” or “Z”), also known as the transverse direction. Secondary electrons can be attracted to the electric field of the accelerating tube 315, accelerated against the first direction or along the “-X” direction, and attracted into the separator 340.

[0051] Advantageously, by using an accelerating tube 315, which is at least partially disposed in the aperture 310 of the objective assembly 305, to accelerate electrons, the performance of the separator 340 is improved at least partially by reducing interference between secondary electrons that could impair the spatial resolution of the signal in multi-beam operation, and by significantly increasing the magnitude of the velocity component in the first direction "X" and reducing the proportion of the "Y" component in the total electron energy. This improves the sensitivity of the separator 340 to the velocity component in the normal "Y" direction. Compared to alternative methods for accelerating electrons (e.g., a biased sample stage or the sample itself), the accelerating tube 315, which is at least partially located in the aperture 310 and separated from the sample stage, can be shared with non-conductive, semi-conductive, and / or composite samples (e.g., integrated circuit samples) or potentially bias-incompatible (e.g., ground-limited) active / operating semiconductor devices.

[0052] Objective lens assembly 305 may include a multi-gap objective lens. For example... Figure 3 As shown, the multi-gap objective includes a magnetic lens configured to guide a charged particle beam to a sample position in the focal plane. The magnetic lens may include a plurality of pole shoes 343 defining at least two axial gaps 347 and at least two independent coils 345 respectively communicating with the at least two axial gaps 347, and the coils are configured to generate a magnetic field such that the magnetic lens operates as a single objective with a variable master objective plane. The variable master objective plane allows selective adjustment of the magnification of the charged particle beam at the focal plane without immersing the sample position in the magnetic field generated by the coils of the magnetic lens.

[0053] The magnetic lens may include a lens body 349, a first coil 345-1 supported by the lens body, and a second coil 345-2 supported by the lens body. The first coil 345-1 is configured to generate a first magnetic field, and the second coil 345-2 is configured to generate a second magnetic field. The lens body 349 defines an aperture 310, a first pole piece 343-1, a second pole piece 343-2, and a third pole piece 343-3 configured to receive a beam of charged particles passing through the magnetic lens. The first pole piece 343-1 may extend circumferentially about the central aperture. The second pole piece 343-2 may extend circumferentially about the aperture 310 and may be at least partially concentric with the first pole piece 343-1, with an inner radius larger than that of the first pole piece 343-1. Similarly, the third pole piece 343-3 may extend circumferentially around the hole 310 and may be at least partially concentric with the first pole piece 343-1 and the second pole piece 343-2, with its inner radius being larger than the inner radii of the first pole piece 343-1 and the second pole piece 343-2.

[0054] However, in some embodiments, objective assembly 305 includes a single-gap magnetic lens and an immersion lens, or a single-gap magnetic lens and an electrostatic lens. Advantageously, compared to alternative objective assembly 305, Figure 3The multi-gap objectives described herein can improve the overall performance of Example System 300 by widening the operating window of the accelerating voltage (e.g., primary beam energy), beam current, and working distance, as well as other operating parameters of the charged particle beam system. In this way, Example System 300 can be more readily adapted for microscopic examination and microanalysis of a wider range of samples involving different operating parameters.

[0055] Objective assembly 305 may be configured to generate one or more magnetic fields that deflect charged particles of a charged particle beam to guide and / or focus the charged particle beam onto a local region of sample location 355. In examples where the charged particle beam comprises multiple sub-beams, objective assembly 305 may be configured to guide the sub-beams to correspondingly spaced-apart focus positions on the plane of sample location 355. In some examples, sample location 355 corresponds to the focal point of the charged particle beam. Alternatively or as an alternative, sample location may correspond to the location (e.g., a plane) corresponding to the minimum characteristic beam size (e.g., minimum beam width or diameter) and / or optimal focusing conditions of the charged particle beam. Thus, as used herein, sample location 355 may represent a location (e.g., a point and / or plane) where a sample and / or a portion thereof (e.g., an exposed surface of the sample) can be positioned during operational use of example system 300, regardless of whether a sample is present at sample location 355.

[0056] A first coil 345-1 may be configured to generate a first magnetic field, and a second coil 345-2 may be configured to generate a second magnetic field. Each of these can act (e.g., apply a Lorentz force to) on particles of a charged particle beam passing through the objective lens assembly 305 to focus the charged particle beam onto the sample location 355. In various examples, the objective lens assembly 305 is configured such that when the objective lens assembly 305 generates each of the first and second magnetic fields, the first and second magnetic fields overlap (e.g., spatially) to form a total magnetic field as the sum of the first and second magnetic fields.

[0057] The first magnetic field can be characterized by a first field amplitude at each point in the space surrounding the first coil 345-1, and the second magnetic field can be characterized by a second field amplitude at each point in the space surrounding the second coil 345-2. Therefore, the total magnetic field can be characterized by the total field amplitude at each point in the space surrounding the first coil 345-1 and the second coil 345-2, which is the sum of the first and second field amplitudes at that point. The first and second magnetic fields can at least partially overlap within the aperture 310 of the objective lens assembly 305, such that the charged particle beam passing through the aperture 310 converges to the focal point in response to the force of the total magnetic field.

[0058] In various examples, the characteristics and / or operation of the objective assembly 305 can be described based on a first magnetic field only, a second magnetic field only, a first magnetic field and a second magnetic field, and / or a total magnetic field. Unless otherwise stated, descriptions of the first magnetic field, the second magnetic field, and / or the total magnetic field generally refer to examples where the reference magnetic field has a non-zero amplitude.

[0059] Similar to state-of-the-art magnetic lenses, the objective assembly 305 can be configured to selectively adjust the focal length and / or focus position of the charged particle beam by adjusting the ratio of the first field amplitude of the first magnetic field to the second field amplitude of the second magnetic field.

[0060] As described in more detail below, the lens body 349 may be configured to position the total magnetic field away from the sample location 355. In particular, the lens body 349 may be configured such that when the objective assembly 305 operates to generate the total magnetic field, a beam of charged particles passing through the lens body 349 is subjected to each of a first magnetic field and a second magnetic field, and each of the first magnetic field and the second magnetic field is confined and / or positioned to a region away from the sample location 355.

[0061] Objective lens assembly 305 can be configured to adjust the position of the primary objective plane by adjusting the ratio of the first field amplitude to the second field amplitude. Advantageously, adjusting the position of the primary objective plane can also adjust the magnification of the optical system, including objective lens assembly 305, while allowing the working distance of objective lens assembly 305 to remain constant (or change slightly), and simultaneously shielding and / or isolating the sample at or near sample position 355 from the total magnetic field.

[0062] In this way, objective assembly 305 can be configured to substantially isolate the sample from the first and second magnetic fields, respectively, during operation, while maintaining the ability to selectively adjust the aperture angle and optical barrel magnification without using immersion lenses. Therefore, objective assembly 305 can be used with magnetically sensitive samples and / or samples that are not originally suitable for use with immersion magnetic lenses. As another advantage, Figure 3 The multi-gap magnetic lens shown also improves the performance of the bifurcated accelerator tube 315 under a wide range of operating conditions and in multi-beam systems, at least in part because the effect of the relatively small or negligible magnetic field on secondary electrons near the sample position 355 has been attenuated.

[0063] To this end, objective assembly 305 can be configured to localize the total magnetic field to any suitable degree to produce a relatively small and / or negligible magnetic field at sample location 355. In some examples, the localization of the total magnetic field can be characterized and / or quantified by comparing the corresponding amplitudes of the magnetic field within aperture 310 and at sample location 355. For example, the total magnetic field can be characterized by the maximum focused field amplitude, representing the maximum amplitude of the total magnetic field at any point within aperture 310, and the amplitude of the total magnetic field measured at sample location 355 can be up to 5%, up to 2%, up to 1%, up to 0.5%, and / or up to 0.1% of the maximum focused field amplitude.

[0064] The lens body 349 may have any suitable structure and / or configuration for locating the total magnetic field as described herein. For example, as Figure 3 As shown, the lens body 349 may include a first pole piece 343-1, a second pole piece 343-2, and a third pole piece 343-3, each of which extends at least partially circumferentially around the aperture 310. The second pole piece 343-2 may be at least partially concentric with the first pole piece 343-1, and the third pole piece 343-3 may be at least partially concentric with the second pole piece 343-3. The objective lens assembly 305 represents an example where each of the first coil 345-1, the second coil 345-2, the first pole piece 343-1, the second pole piece 343-2, and the third pole piece 343-3 is rotationally symmetrical and completely concentric with the first axis A. However, in some embodiments, the first pole piece 343-1, the second pole piece 343-2, and / or the third pole piece 343-3 may be described as a rotating entity extending partially around the first axis A.

[0065] Figures 4A-4C This is a schematic diagram illustrating an exemplary separator 400 according to some embodiments of the present disclosure. Figures 4A-4C Example separator 400 indicates Figure 1 The separator 135 and / or Figure 3 An embodiment of at least a portion of the separator 340. An exemplary separator 400 includes one or more charged particle optical elements forming a Wien filter, such as... Figure 4A The schematic diagram shows that it includes a magnetic element 405 and an electrostatic element 410, which are arranged and configured to generate orthogonal magnetic and electric fields, respectively.

[0066] One of a plurality of optical elements may be operatively coupled to a control circuit 415 that configures the Wien filter along a first direction ( Figures 4A-4C The “X” in the diagram applies a negligible or essentially non-existent deflection force to a primary particle 420 at approximately a given velocity. In the electron beam system of this disclosure (e.g., Figure 1In example system 100), primary particles 420 can be generated in one or more electron beams, provided that a general trajectory 425 (e.g., a first axis A) is aligned with the system's electron beam axis and has a positive velocity in a first direction. In contrast, the Wien filter can be configured to deviate from the given velocity "v" in the first direction. x The charged particle exerts a deflection force. As an illustrative example, a secondary particle 430 (e.g., a secondary electron) that has a negative velocity component in the first direction and is generally much smaller in magnitude in the first direction can be deflected from the initial trajectory 435 to the second trajectory 440.

[0067] The deflection force can be generated by the Lorentz force, which is induced by the motion of charged particles through a magnetic field of 445°. This force partially balances the opposing electrostatic force exerted by the electric field. Each force is perpendicular to the first direction X (in...). Figures 4A-4C (where "Y" represents the value in the middle). For the Wien filter, the following expression describes the corresponding force acting on charged particles (e.g., primary electrons, secondary electrons, etc.):

[0068]

[0069]

[0070]

[0071] Equation (3) describes the velocity in the first direction, where the Lorentz force and the electrostatic force are equal in magnitude and opposite in direction (i.e., Equation (1) + Equation (2) = 0), where a simple derivation is omitted. Thus, embodiments of this disclosure include a Wien filter whose electric field strength and magnetic field strength 445 are configured to satisfy the condition of Equation (3) for primary particles 420 of the incident beam. The force imbalance generated on secondary particles 430 guided by the accelerating tube 315 to the exemplary separator 400 will redirect the trajectory 440 of the secondary particles 430 toward the second axis B. Figures 4A-4B The image shows an example of a single particle trajectory in each direction. In contrast, in... Figure 4C In the illustrated embodiment, multiple sub-beams 450 are guided in a first direction and each sub-beam is substantially aligned with the first direction "X", and multiple secondary particle trajectories 455 have negative velocities in the first direction.

[0072] Assuming a uniform magnetic field 445 and a uniform electric field exist in the given YZ plane, the deflection forces exerted by the magnetic field on the two charged particles in parallel trajectories should be equal. Thus, when these fields satisfy equation (3), the primary particle beam 450 will not deflect, and the secondary particle 430 will follow a parallel deflection trajectory 455, assuming that the velocities of the secondary particles are substantially equal in the first direction. The secondary particle trajectory 455 represents a simplification, assuming that the energy is substantially distributed in a Dirac manner (e.g., with a narrower relative energy distribution achieved partly by acceleration). The following... Figure 5 Detailed analysis is provided in section -6.

[0073] Embodiments of this disclosure include control circuitry 415 operatively coupled to an example separator 400 and configured to maintain necessary electric and magnetic fields to satisfy the energies of primary particles 420 obtainable via equation (3). Control circuitry 415 may include elements of a control system coded in software, embodied in hardware, and / or provided as firmware, through which control circuitry 415 can automatically (e.g., unattended), pseudo-automatically (e.g., manually initiated), and / or manually (e.g., manually controlled) modify, set, or otherwise specify a set of operating conditions for separator 400. In some embodiments, control circuitry 415 may be integrated with other systems and / or subsystems of charged particle beam systems (e.g., Figure 1 System 100 Figure 3 The system 300, etc., is operably coupled so that the control circuit 415 can determine and implement the operating parameters that satisfy equation (3) by referring to the operating parameters of other systems (e.g., by reading the accelerating voltage of the source).

[0074] like Figure 3 and Figure 7A As shown, the bias circuit 460 can be configured to apply a bias voltage to one or more elements of the separator, approximately at the voltage of the accelerating tube 315. This allows the optical system and other components of the system described in this disclosure to function without interfering with the trajectory of charged particles. In an illustrative example, the negative electrode of the sample separator 400 can be negative relative to the positive electrode, such that both electrodes are positively biased. Similarly, the positive electrode of the exemplary separator 400 can be positive relative to the negative electrode, such that both electrodes are negatively biased. The magnetic field 445 can be generated by a magnet and / or electromagnet placed outside the accelerating tube 315. Alternatively, the magnet and / or electromagnet can be disposed within the accelerating tube 315 and also coupled to the bias circuit 460.

[0075] Figure 5 This is a schematic diagram illustrating an exemplary optical system 500 according to some embodiments of the present disclosure. The example system 500 includes... Figure 1-4B The implementation scheme of the system in (e.g., Figure 1 Example system 100 and / or Figure 3 Example system 300). Exemplary optical system 500 includes a bifurcated accelerator tube 505, a splitter 510, an objective lens assembly 515, and a projection system 520. Projection system 520 is... Figure 1 Secondary tube 107 and / or Figure 3 An exemplary embodiment of the secondary lens tube 360. The bifurcated acceleration tube includes a defined common section (e.g., Figure 3 Fork in the common segment 335) (e.g., Figure 3 The bifurcation 320), which is at least partially disposed in the aperture of the objective lens assembly (e.g., Figure 1 In the orifice 310), the separator is at least partially disposed within and / or around the common section. The bifurcation acceleration tube 505 also includes a main section (e.g., Figure 3 The main paragraph (325) and auxiliary paragraphs (e.g., Figure 3 The auxiliary segment 330 is oriented to be basically aligned with the first axis A and the second axis B, respectively, and the angle between the second axis and the first axis A is α.

[0076] Projection system 520 may include various charged particle optical elements, such as electromagnetic lenses. Projection system 520 may be configured to form, shape, deflect, and / or collimate the beam propagating from separator 510 to an auxiliary section of the bifurcation accelerator tube and toward a detector (e.g., Figure 1 One or more charged particle beams (detector 140). Figure 1-4B A more detailed description is provided, starting from the sample location (e.g., Figure 1 Sample 125 Figure 3 The charged particles emitted from the sample at position 355 can be described by an energy distribution, which depends at least in part on the energy of the charged particles incident on the beam, the composition and surface morphology of the sample, and other factors. Therefore, Figure 5 The dashed line filled with shade represents the charged particle "beam" 525, indicating the region where charged particles are most likely to be detected. As described in more detail in Figure 6, charged particles (e.g., secondary electrons) can be incident on the separator 510 with a range of entry angles and energies. Advantageously, the accelerating tube 505 can reduce the energy variance / standard deviation of the charged particles entering the separator, thereby narrowing the energy distribution in the beam 525 entering the auxiliary section of the accelerating tube 505. Considering the Wien filter, a narrower energy distribution related to velocity in the first direction allows the projection system 520 to achieve a narrower deflection force distribution and better performance.

[0077] The projection system 520 may include one or more electro-optical elements disposed outside the accelerating tube 505. For example... Figure 1As described in more detail in sections 4 and 7, the accelerator tube 505 can be a physical tube or a “virtual” tube, where individual components are biased to a relatively high accelerator tube voltage, while other components may be grounded or held at a relatively low voltage. In some embodiments, components that function by generating a magnetic field to guide charged particles through (e.g., a magnetic projector lens) are located outside the accelerator tube 505. Throughout this document, the term “external” is used to refer to a physical location outside the physical accelerator tube, or a location at a relatively low voltage or substantially no voltage applied relative to the accelerator tube voltage, at a distance from the electron beam so that these components do not interfere with the shape and / or orientation of the electron beam.

[0078] Figures 6A-6B This demonstrates some implementation schemes according to this disclosure. Figure 5 A schematic diagram showing details of the exemplary optical system 500. Figure 6A -B omits the optical lens assembly 515 and projection system 520, focusing instead on the components of the acceleration tube 505 and the splitter 510. Figure 6A -B describes the optical transformation applied to the stream of charged particles 600 emitted from sample position 605, whose velocity in the first "X" direction is negative. The accelerator tube components include an inlet aperture 610 and an accelerator assembly 615.

[0079] Charged particles 600 may include secondary electrons 620, backscattered electrons 630, Auger electrons, secondary ions, backscattered ions, etc., including combinations thereof. Embodiments of this disclosure include optical components 510, 610, and 615 configured to select secondary electrons 620 with energies and / or velocities within a given range, such that the secondary electrons 620 are directed by separator 510 toward a second axis B (e.g., ...). Figure 1 The second axis B (and / or 3-5) redirects and defines one or more secondary electron beams 625. Backscattered electrons 630, shown as an example trajectory with dashed lines, are typically characterized as having energies similar to or substantially equal to the primary electrons of the incident beam. Therefore, the energy of the backscattered electrons 630 passing through the aperture 610 at the separator 510 can be significantly higher than that of the secondary electrons 620 (e.g., about an order of magnitude higher). Thus, the backscattered electrons 630 are unlikely to be redirected towards the second axis B, and consequently, the amount of deflection of these backscattered electrons 630 into the projector system 520 is actually less than that of the secondary electrons 620. In this way, the separator 510 can selectively direct the secondary electrons 620 towards the secondary lens tube (e.g., Figure 1 (Secondary microscope tube 107).

[0080] Figure 6A The example shown is for a single incident beam, but embodiments of this disclosure include components of an accelerating tube (e.g., Figure 3 Accelerator tube 315, Figure 5Accelerator tube 505, etc.), which is configured for use with Figure 6B The multi-beam system shown. Figure 6B The diagram illustrates four sub-bundles, but embodiments of this disclosure can be configured to accommodate more or fewer sub-bundles. In examples of multi-bundle systems, such as... Figure 2 As described in the text, a single sub-bundle (e.g., Figure 2 The sub-beams 225 can be directed to corresponding sample locations 605 on the sample surface, which may be spaced apart from each other by about one micrometer or more. Without being restricted by any specific physical operating mechanism, secondary electrons 620 emitted from designated sample locations 605 can propagate into the accelerator assembly 615 with very little or virtually no crosstalk to adjacent sample locations 605, at least in part because of the large distance between sample locations 605 compared to the angular distribution of the secondary electrons 620 emission.

[0081] Embodiments of this disclosure include a substrate 635 defining a plurality of apertures 610, each aperture oriented substantially coincident with a sub-beam (e.g., having a region defined by the scanning range of the sub-beam, substantially centered within the aperture 610), and for limiting incident charged particles 600 to a subset of initial trajectories outside the full range of the initial trajectory starting from sample position 605. This limits crosstalk between adjacent sub-beams.

[0082] exist Figures 6A-6B In the middle, the first axis A (for example, Figure 1 The first axis A (and / or 3-5) represents the hypothetical trajectory of a primary beam of charged particles (e.g., electrons, ions, etc.) that stimulates the charged particles 600 to be re-emitted toward the accelerator assembly 615 of the aperture 610 and the accelerating tube. The accelerator assembly 615 may include one or more loop wires (e.g., conductive metal ring elements) spaced apart from each other by a dielectric or non-conductive pad, support, housing, etc. The accelerator assembly 615 may include and / or be operatively coupled to a bias circuit. The bias circuit may be configured to apply a bias to the loop wires or a subset of loop wires such that the combined electric field is substantially parallel within the internal volume defined by the loop wires and substantially aligned with the first axis A. The electric field in the accelerator assembly 615 may be oriented relative to a first direction “X” so that the charged particles 600 emitted from the sample location are accelerated toward the separator 510. In the example of secondary electrons 620, the electric field of the accelerator assembly 615 may be oriented toward the first direction.

[0083] Accelerator assembly 615 can be configured to accelerate electrons from energies of about 10 eV to about 100 eV to energies of about 1 keV to about 10 keV, including its subrange, fraction, and interpolation. For this purpose, the electric field strength generated by accelerator assembly 615 can be from about 100 keV / m to about 10000 keV / m, including its subrange, fraction, and interpolation. Figure 5As described in more detail, a smaller acceleration can increase crosstalk by causing charged particles to deflect excessively and can narrow the separator's operating window, at least in part because the energy difference between the main beam particles and the charged particles 600 entering the separator 510 from the accelerator assembly 615 is relatively large. Conversely, a larger acceleration can bring the charged particles 600 closer to the energy that the separator has calibrated (e.g., the primary beam energy in the first direction), thereby reducing the effectiveness of the separator 510 in redirecting the charged particles 600 toward the second axis B.

[0084] Figures 7A-7B This is a schematic diagram illustrating an exemplary charged particle optical system 700 (including a third axis C) according to some embodiments of this disclosure. The example system 700 represents... Figure 1 Example system 100 Figure 3 Example system 300 Figure 5 Examples of implementations, such as Example System 500, include optical elements to define a third axis C. For this purpose, Example System 700 includes a bifurcated acceleration tube 705 (e.g., Figure 1 The bifurcated accelerator tube 130, Figure 3-4C 315 and Figure 5 The objective lens assembly 710 defining the aperture 715, the separator, the projection system 725 disposed on the second axis B, and one or more electro-optical systems 730 disposed on the second axis B between the projection system 725 and the image plane 735. Figures 7A-7B In this system, one or more beams of charged particles (e.g., multiple sub-beams) are substantially aligned with a third axis C and guided to a separator 720. For this purpose, an example system 700 may include a charged particle source and one or more concentrator optics.

[0085] Figure 7A and Figure 7B The example system described herein illustrates an embodiment of this disclosure, in which an incident beam of primary charged particles (e.g., primary electrons, primary ions, etc.) moves along a curved trajectory, initially substantially aligned with a third axis C, and then redirected to substantially aligned with a first axis A. Thus, a primary microscope tube (e.g., Figure 1 One tube of the microscope was 105. Figure 2One or more charged particle optical elements in Example System 700 may include a plurality of electromagnetic optical devices configured to redirect secondary electrons from a substantially aligned first direction (e.g., X) to a second direction substantially aligned with a second axis B (e.g., by operation of Separator 720), and to redirect primary electrons from a third direction (e.g., substantially aligned with a first axis C) to the first direction, the third direction being at an angle β relative to the first direction. Advantageously, Example System 700 can improve the range of operating conditions under which the charged particle beam system described herein can operate. For example, additional and / or alternative charged particle optical elements may be included to decouple the energy of the primary charged particle beam from the operating parameters of Separator 720, thereby allowing the Separator to have a wider operating window to improve the overall sensitivity and robustness of Example System 700.

[0086] Example system 700 is shown with a “virtual” accelerator tube, some components of which are coupled to a bias circuit configured to apply a bias voltage to the components, while other components are coupled to ground and positioned at a distance from the beam to reduce the risk of interference with charged particles. Advantageously, the virtual accelerator tube can simplify the internal structure used in the primary and secondary lens tubes. For example, projection system 725 may include a magnetic lens that can be positioned “outside” the accelerator tube. However, in some cases, projection system 725 may include one or more electro-optical elements disposed within the accelerator tube and coupled to an electrical bias circuit configured to apply a potential to electro-optical elements. For example, example system 700 may include an astigmatism correction assembly 747. Astigmatism correction assembly 747 may be disposed on a third axis C and may be configured to realign the primary charged particle beam with a proper incident trajectory into separator 720, thereby substantially aligning separator 720 with the first axis A. Similarly, optical system 730 may include an astigmatism correction assembly disposed on a second axis B and configured to realign the charged particle beam with a detector positioned at image plane 735.

[0087] In some implementations, at least a portion of the accelerating tube uses a physical material. For example, Figure 7A This includes a common segment (e.g., at least partially disposed in the aperture 715 of the objective lens assembly 710) Figure 3 The physical portion of the common segment 335). In this example, as Figure 3 In a more detailed description, the magnetic field applied by the objective lens element can be transmitted through the material of the accelerating tube (e.g., a dielectric or other non-conductive material).

[0088] Figure 7B An example system 700, including opposing bending trajectories, is shown. Figure 7BIn the example, separator 720 may be configured to apply a first Lorentz bending force to a primary charged particle introduced along the third axis C and entering separator 720 at the first side 755, and a second Lorentz bending force to a secondary charged particle introduced along the first axis A and entering separator 720 at the second side 760. For example system 750, where the second axis B and the third axis C are symmetrically distributed on opposite sides of the first axis A, separator 720 may be configured to apply a reverse bending force (e.g., opposite sign) to the primary charged particle relative to the secondary charged particle. The bending forces may be substantially equal or different, depending at least in part on the operating parameters of other components of example system 750. Thus, separator 720 may be configured to simultaneously apply a first force to a primary charged particle of a first energy and a second force to a secondary charged particle of a second energy in one or more beams, see reference [reference needed]. Figures 4A-4C A more detailed description is available in the text.

[0089] Various embodiments have been described in the foregoing description. Specific configurations and details have been set forth for illustrative purposes to provide a thorough understanding of the embodiments. However, it will also be apparent to those skilled in the art that these embodiments can be practiced without these specific details. Furthermore, well-known features may have been omitted or simplified to avoid obscuring the described embodiments. While the exemplary embodiments described herein focus on charged particle beam systems, particularly multi-beam SEM systems, these are intended to be non-limiting exemplary embodiments. The embodiments disclosed herein are not limited to such embodiments, but are intended to address analytical instrument systems in which a wide array of material samples can be analyzed to determine chemical, biological, physical, structural, or other properties, as well as other aspects, including but not limited to chemical structure, crystal structure, physical structure, electronic properties, electrical properties, trace elemental composition, etc.

[0090] Some embodiments of this disclosure include systems having one or more data processors and / or logic circuits. In some embodiments, the system includes a non-transitory computer-readable storage medium containing instructions that, when executed on one or more data processors and / or logic circuits, cause the one or more data processors and / or logic circuits to perform part or all of the one or more methods disclosed herein and / or part or all of one or more processes and workflows. Some embodiments of this disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium, the computer program product including instructions configured to cause one or more data processors and / or logic circuits to perform part or all of the one or more methods disclosed herein and / or part or all of one or more processes.

[0091] The terms and expressions used herein are descriptive rather than restrictive, and their use is not intended to exclude any equivalents of the features shown and described or portions thereof; rather, it should be understood that various modifications are possible within the scope of the claims. Therefore, it should be understood that while this disclosure includes specific embodiments and optional features, modifications and alterations to the concepts disclosed herein can be made by those skilled in the art, and such modifications and alterations are considered to be within the scope of the appended claims.

[0092] When a term is used without a clear definition, it should be understood that unless the term has a special and / or specific meaning in the field of charged particle microscopy systems or other related fields, it refers to the general meaning of the word. The terms “about” or “substantially” are used to indicate a deviation from the stated property, where the deviation has little or no effect on the corresponding function, property, or attribute of the described structure. In the example shown where a dimensional parameter is described as “substantially equal” to another dimensional parameter, the term “substantially” is intended to reflect that the two parameters being compared may be unequal within permissible limits (such as confidence intervals inherent in manufacturing tolerances or system operation). Similarly, where geometric parameters (such as alignment or angular orientation) are described as “approximately” perpendicular, “substantially” perpendicular, or “substantially” parallel, the terms “approximately” or “substantially” are intended to reflect that the alignment or angular orientation may differ from the precisely stated condition (e.g., not precisely perpendicular) within permissible limits. For numerical values ​​(such as diameter, length, width, etc.), the term “about” can be understood to describe a deviation of up to ±10% from the stated value. For example, the size "about 10mm" can describe sizes ranging from 9mm to 11mm.

[0093] This description provides exemplary embodiments and is not intended to limit the scope, applicability, or configuration of this disclosure. Rather, the subsequent description of exemplary embodiments will provide those skilled in the art with an enabling description for implementing various embodiments. It should be understood that various changes may be made to the function and arrangement of elements without departing from the spirit and scope set forth in the appended claims. Specific details are given in the description to provide a thorough understanding of the embodiments. However, it should be understood that embodiments may be practiced without these specific details. For example, specific system components, systems, processes, and other elements of this disclosure may be shown schematically or omitted from the illustrations to avoid obscuring the embodiments with unnecessary details. In other instances, well-known circuits, processes, components, structures, and / or techniques may be shown without unnecessary details.

Claims

1. A charged particle beam system, comprising: Objective lens assembly, defining a hole that mates with the first axis; Accelerator tube, limited bifurcation, including: The main segment is basically concentric with the first axis; The auxiliary segment intersects the main segment at the bifurcation point. The auxiliary segment is oriented to be basically concentric with the second axis, with an angle of α relative to the first axis. The common section is at least partially located in the hole; The separator includes one or more charged particle optical elements disposed in a common segment and configured to apply a deflecting force to electrons with a negative velocity in a first direction, which redirects these electrons to a second direction substantially aligned with a second axis.

2. The charged particle beam system of claim 1, wherein the accelerating tube is configured to increase the negative velocity of electrons by an order of magnitude in a first direction.

3. The charged particle beam system of claim 1, wherein one or more charged particle optical elements include a Wien filter coupled to a control circuitry configuring the Wien filter to apply a negligible or substantially non-existent deflection force to primary electrons having a positive velocity in a first direction.

4. The charged particle beam system of claim 1, wherein the separator is coupled to a bias circuit configured to apply a bias potential to the separator.

5. The charged particle beam system according to claim 1 further includes a projection system disposed along the second axis.

6. The charged particle beam system of claim 5, wherein the projection system comprises one or more electromagnetic elements disposed in an accelerating tube and coupled to a bias circuit configured to apply a potential to the electromagnetic elements.

7. The charged particle beam system of claim 5, wherein the projection system comprises one or more electromagnetic elements disposed outside the accelerating tube.

8. The charged particle beam system of claim 5, wherein the projection system includes an astigmatism correction assembly.

9. The charged particle beam system according to claim 1, wherein the electrons are secondary electrons.

10. The charged particle beam system of claim 1 further comprises a aperture array element disposed on the first beam axis and configured to generate a plurality of sub-beams of primary electrons with non-zero velocity along the first beam axis in the first direction.

11. The charged particle beam system of claim 1, wherein the angle α is a first angle, and one or more charged particle optical elements include a magnetic prism configured to redirect electrons from a first direction to a second direction and redirect primary electrons from a third direction to the first direction, wherein the angle between the third direction and the first direction is a second angle β.

12. The charged particle beam system of claim 1, wherein the objective assembly comprises a multi-gap objective.

13. The charged particle beam system of claim 1, wherein the objective lens assembly comprises a magnetic lens and an immersion lens or a magnetic lens and an electrostatic lens.

14. The charged particle beam system according to claim 1, wherein the angle α is about 5 degrees to about 40 degrees.

15. Accelerator tube, comprising: The main segment is basically concentric with the first axis; The auxiliary section is connected to the main section at the bifurcation of the accelerator tube. The auxiliary section is oriented to be basically concentric with the second axis at an angle α relative to the first axis. Common section; The separator includes one or more charged particle optical elements disposed in a common section and configured to apply a deflecting force to charged particles with a negative velocity in a first direction, which redirects these electrons to a second direction substantially aligned with a second axis.

16. The accelerator tube of claim 15, wherein the accelerator tube is configured to increase the negative velocity of charged particles by an order of magnitude in a first direction.

17. The accelerator tube of claim 15, wherein one or more charged particle optical elements include a Wien filter coupled to a control circuitry configuring the Wien filter to apply a negligible or substantially non-existent deflection force to a primary charged particle having a positive velocity in a first direction.

18. The accelerator tube of claim 15, further comprising a dielectric material serving as a physical tube, wherein internal optical components are biased to the tube potential, while externally, the optical components are coupled to ground or biased to a potential different from the tube potential.

19. The accelerator tube of claim 15, wherein the accelerator tube further comprises an accelerator assembly disposed in a common section and including a plurality of annular electrodes, the accelerator assembly being coupled to a bias circuit configured to apply a bias voltage to the annular electrodes.

20. The accelerator tube of claim 19, wherein the accelerator tube may include a substrate disposed in a common section and coupled to an accelerator assembly, the substrate defining a plurality of holes configured to selectively transmit a portion of charged particles incident onto the substrate.

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