System and method for energy discrimination of backscattered charged particles

Abstract

Disclosed are systems and methods for imaging a sample using a charged particle beam device. The charged particle beam device may include a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis, and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample, each segment of the plurality of concentric segments configured to collect emitted charged particles having an energy level range and a predominant energy level.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser. No. 63 / 429,684, filed December 2, 2022, which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE INVENTION

[0002] The description herein relates to charged particle detectors and detection methods, and more particularly to detectors and detection methods that may be applicable to backscattered charged particles. [Background technology]

[0003] Detectors may be used to detect physically observable phenomena. For example, a charged particle beam tool such as an electron microscope may be equipped with a detector that receives charged particles emitted from a sample and outputs a detection signal. The detection signal may be used to reconstruct an image of the sample structure under inspection, for example, to reveal defects in the sample. Detecting defects in samples is becoming increasingly important in the manufacture of semiconductor devices, which may contain many densely packed miniature integrated circuit (IC) components. An inspection system may be provided as a dedicated tool for this purpose.

[0004] As semiconductor device miniaturization continues, performance demands on inspection systems, including detectors, may continue to increase. For example, as a result of increasing aspect ratios of vertical structures sometimes used in memory devices and continually shrinking design rules that may require tighter overlay performance in DRAM and logic devices, electron beam (E-beam) systems with high landing energy (LE) capabilities, such as 30 keV or higher, have attracted significant interest. High LE systems have shown great potential in applications such as trench / hole bottom inspection, buried defect / void detection, and overlay / see-through metrology due to the strong penetration capabilities of primary electrons (PEs) and the large momentum of backscattered electrons (BSEs), which may allow BSEs to escape the sample material and reach the detector. However, the large energy of PEs in such systems may result in a much larger interaction volume in the sample, potentially causing degradation of imaging quality. Summary of the Invention

[0005]

[0005] Embodiments of the present disclosure provide systems and methods for charged particle beam-based defect detection and metrology. One aspect of the present disclosure is directed to a charged particle detector for use in a charged particle beam device. The charged particle detector may include a plurality of concentric segments of a charged particle sensitive material configured to detect charged particles emitted from a sample, each segment of the plurality of concentric segments configured to detect the emitted charged particles having an energy level range and a corresponding predominant energy level.

[0006] Another aspect of the present disclosure is directed to a charged particle beam device that may include a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis, and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material configured to detect charged particles emitted from a sample after interaction of the primary charged particle beam with the sample, each segment of the plurality of concentric segments configured to collect the emitted charged particles having an energy level range and a predominant energy level.

[0007] Another aspect of the present disclosure is directed to a charged particle beam device that may include a compound objective lens including a magnetic lens and an electrostatic lens configured to focus a primary charged particle beam onto a surface of a sample, and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material configured to detect charged particles emitted from the sample upon interaction of the primary charged particle beam with the sample, each segment of the plurality of concentric segments configured to collect emitted charged particles having an energy level range and a predominant energy level.

[0008] Another aspect of the present disclosure is directed to a charged particle beam device that may include a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis that is incident on a sample, a control electrode positioned immediately upstream of the sample and configured to affect an electrostatic field adjacent to the sample based on an applied voltage signal, and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material configured to detect charged particles emitted from the sample upon interaction of the primary charged particle beam with the sample, each segment of the plurality of concentric segments configured to collect emitted charged particles having an energy level range and a predominant energy level.

[0009] Another aspect of the present disclosure is directed to a charged particle beam device that may include a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis, a charged particle detector including a plurality of segments concentric with the primary charged particle beam and configured to detect charged particles emitted from a sample, and a controller including circuitry configured to: illuminate a region of the sample including a feature with the primary charged particle beam; generate a plurality of images of the illuminated region, each image of the plurality of images being generated from charged particles detected by a corresponding segment of the charged particle detector; determine a characteristic of the feature based on the plurality of images; and wherein segmenting the charged particle detector enables differentiation of the emitted charged particles by a corresponding predominant energy level and corresponding energy level range of each segment.

[0010] Another aspect of the present disclosure is directed to a method for imaging a sample using a charged particle beam device. The method may include irradiating a region of the sample with a primary charged particle beam, the region including a feature, detecting charged particles emitted from the region of the sample using each segment of a plurality of concentric segments of a charged particle detector, generating a plurality of images of the feature, each image of the plurality of images generated from charged particles detected by a corresponding segment of the plurality of concentric segments of the charged particle detector, and determining a characteristic of the feature based on the plurality of images, each segment of the plurality of concentric segments configured to detect emitted charged particles having an energy level range and a predominant energy level.

[0011] Another aspect of the present disclosure is directed to a method for imaging a sample using a charged particle beam device, which may include irradiating a region of the sample with a primary charged particle beam, the region including a feature, detecting charged particles emitted from the region of the sample using each segment of a plurality of concentric segments of a charged particle detector, each segment of the plurality of concentric segments configured to detect emitted charged particles having an energy level range and a predominant energy level, and generating an image of a portion of the feature from the charged particles collected by the segments of the plurality of concentric segments.

[0012] Another aspect of the present disclosure is directed to a non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method. The method may include activating a charged particle source to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis, illuminating a region of a sample including a feature with the primary charged particle beam, detecting the charged particles emitted from the sample using a charged particle detector including multiple segments concentric with the primary charged particle beam, generating multiple images of the irradiated region, each image of the multiple images generated from charged particles detected by a corresponding segment of the charged particle detector, and determining a characteristic of the feature based on the multiple images, wherein segmenting the charged particle detector allows for differentiation of the emitted charged particles by a corresponding predominant energy level and by a corresponding range of energy levels of each segment.

[0013] Another aspect of the present disclosure is directed to a non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method that may include activating a charged particle source to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis, illuminating a region of a sample including a feature with the primary charged particle beam, detecting charged particles emitted from the region of the sample using each segment of a plurality of concentric segments of a charged particle detector, each segment of the plurality of concentric segments configured to detect emitted charged particles having an energy level range and a predominant energy level, and generating an image of a portion of the feature from the charged particles collected by a segment of the plurality of concentric segments.

[0014]

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to limit the disclosed embodiments as may be claimed.

[0015]

[0015] The above and other aspects of the present disclosure will become more apparent from the description of the exemplary embodiments read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagrammatic representation of an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure. [Figure 2]

[0017] FIG. 2 is a schematic diagram illustrating an example electron beam tool that may be part of the example electron beam inspection system of FIG. 1 consistent with embodiments of the present disclosure. [Figure 3]

[0018] 1 is a schematic diagram of an exemplary charged particle beam device including a charged particle detector consistent with embodiments of the present disclosure. [Figure 4A]

[0019] 1 is a schematic diagram of an exemplary charged particle beam device including a segmented backscattered electron (BSE) detector consistent with embodiments of the present disclosure. [Figure 4B]

[0020] FIG. 4B is a top view of the example segmented BSE detector of FIG. 4A consistent with embodiments of the present disclosure. [Figure 5A]

[0021] 10 shows simulation results of the spatial and energy distribution of backscattered electrons detected on an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 5B]

[0022] 1 shows a graphical representation of peak energies of charged particles detected in each segment of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 6]

[0023] 10 shows a simulation of the trajectories of backscattered electrons emitted from a substrate at different emission polar angles, consistent with embodiments of the present disclosure. [Figure 7A]

[0024] 10 shows a comparison of energy distribution profiles of backscattered electrons detected by an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 7B] 10 shows a comparison of energy distribution profiles of backscattered electrons detected by an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 7C] 10 shows a comparison of energy distribution profiles of backscattered electrons detected by an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 7D] 10 shows a comparison of energy distribution profiles of backscattered electrons detected by an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 8]

[0025] 10 shows a graphical representation of backscattered electron collection efficiency for multiple segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 9]

[0026] 1 illustrates the spatial distribution of backscattered electrons detected by radially concentric segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. [Figure 10A]

[0027] FIG. 1 is a schematic diagram of an exemplary charged particle beam device with a segmented BSE detector and an adjustable working distance consistent with embodiments of the present disclosure. [Figure 10B]

[0028] 10 is a data plot of BSE collection efficiency across multiple segments of an exemplary segmented BSE detector for a range of working distances consistent with embodiments of the present disclosure. [Figure 11A]

[0029] 10 illustrates a simulation of the paths of backscattered electrons emitted from a substrate adjusted to different heights, with a constant emission energy, and emitted at different emission polar angles, consistent with embodiments of the present disclosure. [Figure 11B]

[0030] 10 shows simulations of backscattered electron trajectories emitted from substrates adjusted to different heights with a range of emission energies and at a constant emission polar angle, consistent with embodiments of the present disclosure. [Figure 12]

[0031] 10 shows a graphical representation of the collection efficiency, peak energy, and energy spread of backscattered electrons collected by segments of an exemplary segmented BSE detector for various electric field strengths on a sample consistent with embodiments of the present disclosure. [Figure 13A]

[0032] 10 shows a data plot of a simulation of peak BSE energy for each segment of a segmented BSE detector for various electric field strengths on a sample consistent with embodiments of the present disclosure. [Figure 13B]

[0032] Figure 10 shows a data plot of a simulation of the BSE collection efficiency of each segment of a segmented BSE detector for various electric field strengths on a sample consistent with embodiments of the present disclosure. [Figure 14A]

[0033] 10 is a graphical representation of BSE collection efficiency of a segment of an exemplary segmented BSE detector as a function of objective lens magnetic field, consistent with embodiments of the present disclosure. [Figure 14B] 10 is a graphical representation of the BSE collection efficiency of a segment of an exemplary segmented BSE detector as a function of objective lens magnetic field, consistent with embodiments of the present disclosure. [Figure 15]

[0034] 10 shows a series of data plots from a simulation illustrating the effect of adjusting the magnetic field strength of the objective lens on the BSE collection efficiency of a segment of a segmented BSE detector consistent with embodiments of the present disclosure. [Figure 16A]

[0035] FIG. 1 shows a schematic diagram of an exemplary charged particle beam device configured to compensate for focus changes by adjusting objective lens magnetic field strength, consistent with embodiments of the present disclosure. [Figure 16B]

[0035] A schematic diagram of an exemplary charged particle beam device configured to compensate for focus changes by adjusting the objective lens magnetic field strength consistent with embodiments of the present disclosure is shown. [Figure 16C]

[0035] A schematic diagram of an exemplary charged particle beam device configured to compensate for focus changes by adjusting the objective lens magnetic field strength consistent with embodiments of the present disclosure is shown. [Figure 17]

[0036] FIG. 1 is a schematic diagram of an exemplary charged particle beam device including a BSE detector with adjustable z-height, consistent with embodiments of the present disclosure. [Figure 18]

[0037] 1 shows a graphical representation of the relationship between different BSE energy components and their corresponding collection efficiencies (CEs) for a range of z-height positions of a BSE detector consistent with embodiments of the present disclosure. [Figure 19]

[0038] 1 is a flowchart illustrating an exemplary method for imaging a sample using a charged particle beam device consistent with embodiments of the present disclosure. [Figure 20]

[0039] 1 is a flowchart illustrating an exemplary method for imaging a sample using a charged particle beam device consistent with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017]

[0040] 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, unless otherwise specified, represent the same or similar elements. 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, systems, and methods consistent with aspects related to the subject matter as recited in the appended claims. Without limiting the scope of the present disclosure, some embodiments may be described in connection with providing detection systems and methods in systems utilizing electron beams ("e-beams"). However, the present disclosure is not so limited. Other types of charged particle beams (e.g., including protons, ions, muons, or any other particles carrying an electric charge) may be applied as well. Furthermore, the systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, or any imaging system.

[0018]

[0041] Electronic devices are constructed from circuits formed on a piece of silicon called a substrate. Semiconductor materials may include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium. Many circuits may be formed together on the same piece of silicon, which is called an integrated circuit, or IC. Advances in technology have dramatically reduced the size of these circuits, allowing more circuits to fit on a substrate. For example, an IC chip in a smartphone can be about the size of a fingernail yet contain over 2 billion transistors, each less than 1 / 1000 the thickness of a human hair.

[0019]

[0042] Fabricating these tiny ICs is a complex, time-consuming, and expensive process, often involving hundreds of individual steps. An error in any one step can result in defects in the finished IC, rendering it unusable. Therefore, one of the goals of a manufacturing process is to avoid such defects and maximize the number of functional ICs produced by the process, thereby improving the overall yield of the process.

[0020]

[0043] One element of improving yield is monitoring the chip manufacturing process to ensure that a sufficient number of functional integrated circuits are being produced. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be performed using a scanning electron microscope (SEM). The SEM can be used to image these tiny structures, essentially taking a "picture" of them. This image can be used to determine whether the structures were formed properly and whether they were formed in the correct location. If the structures are defective, the process can be adjusted to reduce the chance of the defect recurring. To increase throughput (e.g., number of samples processed per hour), it is desirable to perform inspection as quickly as possible.

[0021]

[0044] An SEM image may be composed of pixels corresponding to locations illuminated by the primary electron beam as the beam scans across the surface of the sample, e.g., in a raster pattern. Higher pixel resolution (e.g., the number of individual pixels that make up the image) typically results in higher image quality. More pixels result in finer image detail. As structures of interest within ICs become smaller and smaller, producing higher resolution SEM images can become increasingly important for accurately observing the structures. However, using a primary electron beam with a high landing energy (LE) can negatively impact resolution.

[0022]

[0045] The landing energy of the primary electrons may be based, for example, on the difference between the source voltage and the sample voltage. For example, if the source is operated at -10 kV and -5 kV is applied to the sample, the landing energy of the primary electrons may be 5 keV. Typically, in an SEM, the landing energy may range from 0.2 keV to 50 keV, depending on the application, the material being investigated, and the condition of the tool, among other factors. Some methods for changing the landing energy of the primary electrons of the primary electron beam may include, among other techniques, adjusting the potential difference between the cathode and the extractor, adjusting the sample potential, or adjusting both simultaneously.

[0023]

[0046] However, for some applications, it may be desirable to use a high landing energy in an SEM system. The electron source of an SEM may generate a high-LE primary electron beam that is projected onto a sample. High-energy electrons can penetrate deeper into the sample's material, revealing additional information about the sample and thus may be useful for imaging. High-LE SEM systems may enable or enhance the ability to inspect the bottom of trenches or holes, detect buried features such as defects or voids, and perform overlay metrology (e.g., analyzing the alignment of stacked structures). However, the high energy of the electrons in the primary electron beam means that when they strike the sample, they may interact with a relatively large volume of the sample's material (i.e., the "interaction volume"). While high-energy electrons may penetrate deeper, they may also scatter in other random directions before exiting the sample's material. Because pixels are sometimes used to form two-dimensional maps and electrons can scatter laterally, such scattering can cause problems with imaging resolution.

[0024]

[0047] As explained above, an SEM image may be formed from pixels. As the SEM's primary beam scans across a sample, secondary particles, such as secondary electrons (SEs) and backscattered electrons (BSEs), may be detected by a detector, and the information gathered therefrom may be used to form each pixel in the image. However, a higher LE may increase the interaction volume in the sample. The increased interaction volume may encompass multiple lateral regions (e.g., regions to the sides within a two-dimensional plane defining the image consisting of pixels). A pixel may be formed based on information from detected electrons, but information from adjacent pixels may overlap. For example, detected electrons corresponding to one pixel may contain information about structures more appropriately located in adjacent pixels. Such effects may reduce the resolution of the SEM image and result in a blurred image.

[0025]

[0048] The accuracy, reliability, and throughput of high-density IC chip inspection using SEM can depend, among other things, on the system's image quality. One of several ways to achieve and maintain high image quality is to maximize the collection efficiency of signal electrons, such as secondary electrons (SEs) and backscattered electrons (BSEs). When primary electrons strike the sample surface, they interact with a volume of the sample and generate multiple signal electrons, depending on, among other factors, the landing energy, sample material, and spot size. BSEs have higher energy and originate from deeper regions within the interaction volume, thus providing information related to the composition and distribution of materials. Therefore, maximizing detection of backscattered electrons can be desirable to achieve high-quality images of underlying defects or metrology of high-aspect-ratio vertical features.

[0026]

[0049] Existing metrology or defect detection techniques using SEMs may form a three-dimensional image of a feature of interest by performing multiple scans. In such cases, each scan generates an image based on BSE signals from BSEs of a particular energy, and each scan may correspond to a particular depth in the sample from which the BSEs are emitted. As an example, when a high-aspect-ratio feature such as a via is imaged, multiple scans may be required to image the entire height or depth of the via, with each scan collecting BSEs of different energies corresponding to different depths in the via and providing information about the portion of the via at or near that depth. This approach has several drawbacks, including longer exposure times of the feature to the probing beam, which increases the likelihood of beam damage, and lower inspection throughput, among other issues.

[0027]

[0050] One method for overcoming the problems associated with multiple scans of a feature of interest may include performing a single scan that collects a significant portion of the generated BSEs. A single BSE scan may contain a range of BSE energies corresponding to the entire depth of the interaction volume between the primary beam and the sample, making it difficult to extract information about a feature of interest at a particular depth. In some cases, however, an energy filter may be used to allow only a desired range of energy levels of BSEs emitted from a desired sample depth to pass to the BSE detector. However, in applications requiring high landing energies to increase image contrast for defect inspection and metrology of three-dimensional structures, a bottom BSE detector positioned between the objective lens and the sample may be desirable to increase BSE collection efficiency. In such cases, using an energy filter may be difficult due to physical space constraints between the sample and the objective lens. Therefore, it may be desirable to provide a system and method for discriminating BSE signals detected by a bottom BSE detector based on the energy levels of the incoming BSEs.

[0028]

[0051] Furthermore, in some applications, an energy-discriminating device, such as a reflective energy filter, may be introduced before the in-lens detector to filter out secondary electrons (by reflecting them back) and allow BSEs to pass through a high-voltage grid electrode or filtering grid electrode. The potential of the high-voltage grid electrode may be set very high (e.g., greater than 10 keV) to act as a potential barrier to BSE electrons. While energy filters can be useful in low-landing-energy applications where the secondary electrons have energies comparable to BSEs and the BSEs have small polar emission angles, in high-landing-energy applications, energy filters with very high grid electrode voltages can adversely affect BSE collection efficiency, thereby affecting image quality. Furthermore, it may be necessary to adjust the voltage applied to the grid to collect images of different BSE energies, making it impossible to collect multiple images simultaneously. This approach can adversely affect inspection throughput, among other challenges.

[0029]

[0052] Some aspects of the present disclosure may address some challenges by providing a segmented charged particle detector (e.g., a segmented BSE detector) configured to discriminate incoming charged particles emitted from a sample based on their energy levels. The charged particle detector may include multiple concentric segments of a charged particle-sensitive material. The multiple concentric segments of the charged particle detector may be separated by a charged particle-insensitive material. Each concentric segment may be configured to collect BSEs having a corresponding energy level range and a predominant energy level within the energy level range of the BSEs detected by that segment. The predominant energy level of the detected BSEs may correspond to BSEs emitted from a particular depth in the sample, thereby providing information related to a feature of interest at the particular depth. The BSE signals detected by each concentric segment may be used to simultaneously generate multiple images, which may be further used to form a three-dimensional image of the feature, or a high-contrast image of a particular depth of the feature of interest may be obtained.

[0030]

[0053] The objects and advantages of the present disclosure can be achieved by the elements and combinations described in the embodiments discussed herein. However, no embodiment of the present disclosure is necessarily required to achieve such exemplary objects or advantages, and some embodiments may not achieve any of the described objects or advantages.

[0031]

[0054] Without limiting the scope of the present disclosure, some embodiments may be described in connection with providing systems and methods in systems that utilize electron beams ("e-beams"). However, the disclosure is not so limited. Other types of charged particle beams may be applied as well. Furthermore, the systems and methods for wafer inspection or overlay metrology may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0032]

[0055] As used herein, unless otherwise stated, the term "or" includes all possible combinations unless it is not feasible. For example, if a component is stated to include A or B, the component may include A, or B, or A and B, unless otherwise stated or not feasible. As a second example, if a component is stated to include A, B, or C, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless otherwise stated or not feasible. Phrases such as "at least one" do not necessarily modify the entire subsequent list, and do not necessarily modify each element of the list; "at least one of A, B, and C" should be understood to include only one of A, only one of B, only one of C, or any combination of A, B, and C. The phrases "one of A and B" or "either one of A and B" shall be construed in the broadest sense to include one of A or one of B.

[0033]

[0056] Reference is now made to FIG. 1, which illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. As shown in FIG. 1, the charged particle beam inspection system 100 includes a main chamber 10, a load-lock chamber 20, an electron beam tool 40, and a front-end equipment module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. While the description and drawings are directed to electron beams, it should be understood that the embodiments are not intended to limit the present disclosure to any particular charged particle.

[0034]

[0057] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b receive wafer front-opening integrated pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (wafers and samples are hereinafter collectively referred to as "wafers"). One or more robotic arms (not shown) within the EFEM 30 transport the wafers to the load-lock chamber 20.

[0035]

[0058] The load-lock chamber 20 is connected to a load-lock vacuum pumping system (not shown) that removes gas molecules within the load-lock chamber 20 to reach a first pressure below atmospheric pressure. After the first pressure is reached, one or more robotic arms (not shown) transfer the wafer from the load-lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pumping system (not shown) that removes gas molecules within the main chamber 10 to reach a second pressure below the first pressure. After the second pressure is reached, the wafer is subjected to inspection by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single-beam inspection tool.

[0036]

[0059] The controller 50 may be electronically connected to the electron beam tool 40 and may be electronically connected to other components as well. The controller 50 may be a computer configured to perform various controls of the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. While the controller 50 is shown in FIG. 1 as being external to the structure including the main chamber 10, the load-lock chamber 20, and the EFEM 30, it should be understood that the controller 50 may be part of this structure.

[0037]

[0060] It should be noted that while this disclosure provides an example of a main chamber 10 that houses an electron beam inspection system, aspects of this disclosure are not limited to chambers that house electron beam inspection systems in the broadest sense. Rather, it should be understood that the principles described above may also be applied to other chambers.

[0038]

[0061] Reference is now made to FIG. 2, which illustrates a schematic diagram illustrating an exemplary configuration of an electron beam tool 40 that may be part of the exemplary charged particle beam inspection system 100 of FIG. 1 consistent with embodiments of the present disclosure. The electron beam tool 40 (also referred to herein as apparatus 40) may include an electron emitter, which may include a cathode 203, an extraction electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 may further include a Coulomb aperture array 224, a condenser lens 226, a beam-limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. The electron beam tool 40 may further include a sample holder 236 supported by a motorized stage 234 for holding a sample 250 to be inspected. It should be understood that other associated components may be added or omitted as desired.

[0039]

[0062] In some embodiments, the electron emitter may include a cathode 203, an anode 222, and primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 204 that forms the primary beam crossover 202. The primary electron beam 204 may be visualized as being emitted from the primary beam crossover 202.

[0040]

[0063] In some embodiments, the electron emitter, condenser lens 226, objective lens assembly 232, beam-limiting aperture array 235, and electron detector 244 may be aligned with the primary optical axis 201 of apparatus 40. In some embodiments, the electron detector 244 may be positioned off-axis from the primary optical axis 201 along a second optical axis (not shown).

[0041]

[0064] In some embodiments, the objective lens assembly 232 may comprise a modified swing objective retarding immersion lens (SORIL) including a pole piece 232 a, a control electrode 232 b, a beam manipulator assembly including deflectors 240 a, 240 b, 240 d, and 240 e, and an excitation coil 232 d. In a typical imaging process, a primary electron beam 204 emitted from the tip of the cathode 203 is accelerated by an acceleration voltage applied to the anode 222. A portion of the primary electron beam 204 passes through the gun aperture 220 and the apertures of the Coulomb aperture array 224, and is focused by the condenser lens 226 so that it passes fully or partially through the apertures of the beam-limiting aperture array 235. Electrons passing through the apertures of the beam-limiting aperture array 235 may be focused by a modified SORIL lens to form a probe spot on the surface of the sample 250 and deflected by one or more deflectors of the beam manipulator assembly to scan the surface of the sample 250. Secondary electrons emitted from the sample surface may be collected by the electron detector 244 to form an image of the scanned region of interest.

[0042]

[0065] In the objective lens assembly 232, the excitation coil 232d and the pole piece 232a may generate a magnetic field. A portion of the sample 250 scanned by the primary electron beam 204 may be immersed in the magnetic field and charged, thereby generating an electric field. The electric field may reduce the energy of the impinging primary electron beam 204 at and near the surface of the sample 250. A control electrode 232b electrically isolated from the pole piece 232a may control the electric field on and above the sample 250, for example, to reduce aberrations of the objective lens assembly 232, control the focusing of the signal electron beam to increase detection efficiency, or avoid arcing to protect the sample. One or more deflectors in the beam manipulator assembly may deflect the primary electron beam 204 to facilitate beam scanning over the sample 250. For example, in the scanning process, deflectors 240a, 240b, 240d, and 240e can be controlled to deflect primary electron beam 204 to different locations on the top surface of sample 250 at different times to provide data for image reconstruction of different portions of sample 250. Note that the order of 240a-e may be different in different embodiments.

[0043]

[0066] Backscattered electrons (BSE) and secondary electrons (SE) may be emitted from portions of the sample 250 upon receiving the primary electron beam 204. The beam separator 240c may direct the secondary or scattered electron beam, including the backscattered electrons and secondary electrons, to a sensor surface of the electron detector 244. The detected secondary electron beam may form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 may generate a signal (e.g., voltage, current) representing the intensity of the received secondary electron beam spot and provide the signal to a processing system such as the controller 50. The intensity of the secondary or backscattered electron beam, and the resulting secondary electron beam spot, may vary depending on the external or internal structure of the sample 250. Furthermore, as described above, the primary electron beam 204 may be deflected to different locations on the top surface of the sample 250 to generate secondary or scattered electron beams (and resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot to the location of the sample 250 , the processing system can reconstruct an image reflecting the internal or external structure of the wafer sample 250 .

[0044]

[0067] In some embodiments, the controller 50 may include an image processing system including an image capture unit (not shown) and storage (not shown). The image capture unit may include one or more processors. For example, the image capture unit may include a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, and the like, or a combination thereof. The image capture unit may be communicatively coupled to the electronic detector 244 of the device 40 via a medium such as a conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, wireless radio, or a combination thereof, among others. In some embodiments, the image capture unit may receive signals from the electronic detector 244 and construct an image. Thus, the image capture unit may capture an image of an area of ​​the sample 250. The image capture unit may also perform various post-processing functions, such as contouring, overlaying indicators on the captured image, etc. The image capture unit may be configured to adjust the brightness and contrast of the captured image, etc. In some embodiments, the storage may be a storage medium such as a hard disk, a flash drive, cloud storage, random access memory (RAM), or other type of computer-readable memory. The storage may be coupled to the image acquisition unit and may be used to store raw scanned image data as original images and to store post-processed images.

[0045]

[0068] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of detected secondary and backscattered electrons. Electron distribution data collected during the detection time window can be used in combination with corresponding scan path data of the primary beam 204 incident on the sample (e.g., wafer) surface to reconstruct an image of the wafer structure under inspection. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 250, thereby revealing any defects that may be present in the wafer.

[0046]

[0069] In some embodiments, the controller 50 may control the motorized stage 234 to move the sample 250 during inspection. In some embodiments, the controller 50 may enable the motorized stage 234 to continuously move the sample 250 at a constant speed in a constant direction. In other embodiments, the controller 50 may enable the motorized stage 234 to vary the speed of movement of the sample 250 over time depending on the step in the scanning process.

[0047]

[0070] As is commonly known in the art, interaction of charged particles, such as electrons in a primary electron beam, with a sample (e.g., sample 315 in FIG. 3 , described below) can produce signal electrons that contain compositional and topographical information about the probed region of the sample. Secondary electrons (SEs) can be identified as signal electrons with low emission energies, and backscattered electrons (BSEs) can be identified as signal electrons with higher emission energies. Because of their low emission energies, the objective lens assembly can guide the SEs along the electron path and focus them onto the detection plane of an in-lens electron detector located within the SEM column. BSEs traveling along the electron path can also be detected by the in-lens electron detector. However, in some cases, BSEs with large emission angles may be detected using additional electron detectors, such as a backscattered electron detector, or may remain undetected, resulting in a reduction in sample information needed to inspect the sample or measure critical dimensions.

[0048]

[0071] Inspection of surface features and compositional analysis of defective particles may be beneficial when attempting to detect and inspect certain defects in semiconductor manufacturing processes, such as particles embedded during photolithography, metal deposition, dry etching, or wet etching, among others. In such scenarios, information obtained from secondary electron detectors and backscattered electron detectors may be desirable for users to, among other things, identify the defects, analyze the composition of the defects, and adjust process parameters based on the obtained information.

[0049]

[0072] In other situations, it may be desirable to measure the precise critical dimensions of three-dimensional features several microns deep. For example, it may be desirable to accurately measure the critical dimensions of features such as high-aspect-ratio vias with sloped walls at multiple depths. In such scenarios, the information obtained from secondary electrons is limited to the near-surface region and can be insufficient and misleading. BSEs, which have higher emission energies and leak from deeper below the surface, may provide the desired information about the feature being inspected.

[0050]

[0073] SE and BSE emissions follow Lambert's law and have a large energy spread. SEs and BSEs are generated from different depths of a sample when the primary electron beam interacts with it and have different emission energies. For example, secondary electrons originate from the surface and can have emission energies of 50 eV or less, depending on the sample material and the volume of interaction, among other things. SEs are useful for providing information about surface features or surface geometry. On the other hand, BSEs are primarily generated by elastic scattering events of incident electrons from the primary electron beam and typically have higher emission energies compared to SEs, ranging from 50 eV to roughly the landing energy of the incident electrons, providing compositional and contrast information about the material being inspected. The number of BSEs generated can depend on factors including, but not limited to, the number of atoms of the material in the sample and the accelerating voltage of the primary electron beam, among other factors.

[0051]

[0074] Based on differences in emission energy or emission angle, among other things, SEs and BSEs may be separately detected using separate electron detectors, segmented electron detectors, energy bandpass filters, etc. An example implementation of an energy bandpass filter based on the relationship between BSE energy and orbital depth is provided in U.S. Provisional Patent Application No. 63 / 254,838, which is incorporated herein by reference in its entirety.

[0052]

[0075] Reference is now made to FIG. 3 , which shows a schematic diagram of an exemplary charged particle beam device 300 (also referred to as device 300) consistent with embodiments of the present disclosure. Device 300 may include a charged particle source, such as an electron source configured to emit primary electrons from a cathode 301 and extract them using an extraction electrode 302 to form a primary electron beam 300B1 along a primary optical axis 300-1. Device 300 may further include an anode 303, a condenser lens 304, a beam-limiting aperture array 305, a signal electron detector 306, a compound objective lens 307, a scan deflection unit including primary electron beam deflectors 308, 309, 310, and 311, and a control electrode 314. In the context of the present disclosure, signal electron detector 306 may be an in-lens electron detector located within the electron optical column of the SEM and may be arranged rotationally symmetrically about primary optical axis 300-1. In some embodiments, the signal electron detector 306 may be referred to as a through-lens detector, an immersion lens detector, a top detector, or a secondary electron detector. It should be understood that associated components may be added, omitted, or rearranged as desired.

[0053]

[0076] The electron source (not shown) may include a thermionic electron source configured to emit electrons when thermal energy is supplied to overcome the work function of the radiation source, a field emission source configured to emit electrons when exposed to a large electrostatic field, etc. In the case of a field emission source, the electron source may be electrically connected to a controller, such as the controller 50 of FIG. 2 , configured to apply and adjust a voltage signal based on, among other things, the desired landing energy, sample analysis, radiation source characteristics, etc. The extraction electrode 302 may be configured, for example, to extract or accelerate electrons emitted from the field emission gun to form a primary electron beam 300B1 that forms a virtual or real primary beam crossover (not shown) along the primary optical axis 300-1. The primary electron beam 300B1 may be visualized as being emitted from the primary beam crossover. In some embodiments, the controller 50 may be configured to apply and adjust a voltage signal to the extraction electrode 302 to extract or accelerate electrons generated from the electron source. The amplitude of the voltage signal applied to the extraction electrode 302 may be different from the amplitude of the voltage signal applied to the cathode 301. In some embodiments, the difference between the amplitudes of the voltage signals applied to the extraction electrode 302 and the cathode 301 may be configured to accelerate electrons downstream along the primary optical axis 300-1 while maintaining stability of the electron source. As used in the context of this disclosure, "downstream" refers to a direction along the path of the primary electron beam 300B1 originating from the electron source and directed toward the sample 315. With reference to the arrangement of elements of a charged particle beam device (e.g., device 300 of FIG. 3), "downstream" may refer to the position of an element below or after another element along the path of the primary electron beam 300B1 originating from the electron source, and "immediately downstream" refers to the position of a second element below or after a first element along the path of the primary electron beam 300B1 such that there are no other active elements between the first and second elements. For example, as shown in FIG. 3, the signal electron detector 306 may be positioned immediately downstream of the beam-limiting aperture array 305 such that there are no other optical or electronic optical elements between the beam-limiting aperture array 305 and the electron detector 306.As used in the context of this disclosure, "upstream" may refer to the position of an element above or in front of another element along the path of the primary electron beam originating from the electron source, and "immediately upstream" refers to the position of a second element above or in front of a first element along the path of the primary electron beam 300B1 such that there are no other active elements between the first and second elements. As used herein, "active element" may refer to any element or component whose presence may modify the electromagnetic field between the first and second elements, either by generating an electric field, a magnetic field, or an electromagnetic field.

[0054]

[0077] The apparatus 300 may include a condenser lens 304 configured to receive a portion or a majority of the primary electron beam 300B1 and focus the primary electron beam 300B1 onto a beam-limiting aperture array 305. The condenser lens 304 may be substantially similar to the condenser lens 226 of FIG. 2 and may perform substantially similar functions. While the condenser lens 304 is shown in FIG. 3 as a magnetic lens, it may be an electrostatic lens, a magnetic lens, an electromagnetic lens, or a hybrid electromagnetic lens, among others. As shown in FIG. 2, the condenser lens 304 may be electrically coupled to a controller 50. The controller 50 may apply an electrical excitation signal to the condenser lens 304 to adjust the focusing power of the condenser lens 304 based on factors including, but not limited to, the mode of operation, the application, the desired analysis, and the sample material being examined, among others.

[0055]

[0078] The apparatus 300 may further include a beam-limiting aperture array 305 configured to limit the beam current of the primary electron beam 300B1 passing through one of a plurality of beam-limiting apertures of the beam-limiting aperture array 305. Although only one beam-limiting aperture is shown in FIG. 3 , the beam-limiting aperture array 305 may include any number of apertures having uniform or non-uniform aperture sizes, cross-sections, or pitches. In some embodiments, the beam-limiting aperture array 305 may be positioned downstream of the condenser lens 304 or immediately downstream of the condenser lens 304 (as shown in FIG. 3 ) and substantially perpendicular to the primary optical axis 300-1. In some embodiments, the beam-limiting aperture array 305 may be configured as a conductive structure including a plurality of beam-limiting apertures. The beam-limiting aperture array 305 may be electrically connected to the controller 50 via a connector (not shown), and the controller 50 may be configured to command a voltage to be supplied to the beam-limiting aperture array 305. The supply voltage may be a reference voltage, such as ground potential. The controller 50 may also be configured to maintain or adjust the supply voltage. The controller 50 may also be configured to adjust the position of the beam-limiting aperture array 305.

[0056]

[0079] The apparatus 300 may include a signal electron detector 306, which may be configured to detect substantially all secondary electrons and a portion of the backscattered electrons based on, among other things, the emission energy, emission polar angle, and emission azimuth angle of the backscattered electrons. In some embodiments, the signal electron detector 306 may be configured to detect secondary electrons, backscattered electrons, or Auger electrons. Signal electrons emitted from the sample 315 with low emission energies (typically 50 eV or less) or small emission polar angles may comprise the secondary electron beam 300B4, while signal electrons with high emission energies (typically greater than 50 eV) and medium emission polar angles may comprise the backscattered electron beam 300B2. In some embodiments, 300B4 may include secondary electrons, low-energy backscattered electrons, or high-energy backscattered electrons with small emission polar angles. While not shown, it should be understood that some of the backscattered electrons may be detected by the signal electron detector 306. In overlay metrology and inspection applications, the signal electron detector 306 may be useful for detecting secondary electrons generated from surface layers and backscattered electrons generated from deeper underlying layers, such as deep trenches or high aspect ratio holes.

[0057]

[0080] The apparatus 300 may further include a compound objective lens 307 configured to focus the primary electron beam 300B1 onto the surface of the sample 315. The controller 50 may apply electrical excitation signals to the coils of the compound objective lens 307 to adjust the focusing power of the compound objective lens 307 based on factors including, but not limited to, the primary beam energy, the application needs, the desired analysis, and the sample material being examined, among others. The compound objective lens 307 may further be configured to focus signal electrons, such as secondary electrons with low emission energy or backscattered electrons with high emission energy, onto a detection surface of a signal electron detector (e.g., the in-lens signal electron detector 306). The compound objective lens 307 may be substantially similar to or perform substantially similar functions as the objective lens assembly 232 of FIG. 2. In some embodiments, the compound objective lens 307 may include an electromagnetic lens, including a magnetic lens, and an electrostatic lens formed by the control electrode 314, the pole pieces of the objective lens, and the sample 315.

[0058]

[0081] As used herein, a compound objective lens is an objective lens that generates overlapping magnetic and electrostatic fields near the sample to focus the primary electron beam. In this disclosure, the focusing lens 304 may also be a magnetic lens, but unless otherwise noted, references to a magnetic lens refer to the objective magnetic lens and references to an electrostatic lens refer to the objective electrostatic lens. As shown in FIG. 3 , the objective magnetic lens and the objective electrostatic lens may act in conjunction to focus, for example, the primary electron beam 300B1 onto the sample 315 to form the compound objective lens 307. A lens body composed of a magnetic lens and a coil can generate the magnetic field, while the electrostatic field may be generated, for example, by creating a potential difference between the sample 315 and the pole pieces of the objective lens. In some embodiments, the control electrode 314 or other electrode disposed between the pole pieces and the sample 315 may also be part of the objective electrostatic lens.

[0059]

[0082] The apparatus 300 may further include a scan deflection unit including primary electron beam deflectors 308, 309, 310, and 311 configured to dynamically deflect the primary electron beam 300B1 over the surface of the sample 315. In some embodiments, the scan deflection unit including the primary electron beam deflectors 308, 309, 310, and 311 may be referred to as a beam manipulator or beam manipulator assembly. By dynamically deflecting the primary electron beam 300B1, a desired area or region of interest of the sample 315 may be scanned, for example, in a raster scan pattern, to generate SEs and BSEs for sample inspection. The one or more primary electron beam deflectors 308, 309, 310, and 311 may be configured to deflect the primary electron beam 300B1 in the X-axis or Y-axis, or a combination of the X-axis and Y-axis. As used herein, the X and Y axes form a Cartesian coordinate system, and the primary electron beam 300B1 propagates along the Z axis or primary optical axis 300-1.

[0060]

[0083] Electrons are negatively charged particles that may pass through an electron optical column at high speed and energy. One way to deflect electrons is to pass them through an electric or magnetic field, for example, generated by a pair of plates held at two different potentials, or by passing a current through a deflection coil, among other techniques. Varying the electric or magnetic field across a deflector (e.g., primary electron beam deflectors 308, 309, 310, and 311 in FIG. 3) can change the deflection angle of electrons in primary electron beam 300B1 based on factors including, but not limited to, electron energy, the magnitude of the applied electric field, the dimensions of the deflector, etc.

[0061]

[0084] In some embodiments, the sample 315 may be positioned in a plane substantially perpendicular to the primary optical axis 300-1. The position of the plane of the sample 315 may be adjusted along the primary optical axis 300-1 so that the distance between the sample 315 and the BSE detector 313 can be adjusted. In some embodiments, the sample 315 may be electrically connected to a controller 50 via a connector (not shown), and the controller 50 may be configured to supply a voltage to the sample 315 to adjust its position as needed. The controller 50 may also be configured to maintain or adjust the supplied voltage.

[0062]

[0085] In existing SEMs, signals generated by the detection of secondary electrons and backscattered electrons are used in combination to, among other things, image surfaces, detect and analyze defects, obtain topographical information, and accurately measure critical dimensions of high-aspect-ratio features. By detecting secondary and backscattered electrons, several upper and lower layers can be imaged simultaneously, potentially capturing underlying defects such as buried particles, measuring critical dimensions, and detecting overlay errors. However, the overall image quality can be affected by the detection efficiency of the secondary and backscattered electrons. While high-efficiency detection of secondary electrons can provide high-quality images of surfaces, low detection efficiency of backscattered electrons can result in insufficient overall image quality. Therefore, it can be beneficial to improve the detection efficiency of backscattered electrons to obtain high-quality imaging while maintaining high throughput.

[0063]

[0086] One of several ways to improve image quality and signal-to-noise ratio may include detecting more backscattered electrons emitted from the sample. The angular distribution of backscattered electron emission can be described by a cosine dependence of the emission polar angle (cos(θ), where θ is the emission polar angle between the backscattered electron beam and the primary optical axis). While a signal electron detector can efficiently detect backscattered electrons with moderate emission polar angles, backscattered electrons with large emission polar angles may remain undetected or may be insufficiently detected to contribute to the overall imaging quality. Therefore, it may be desirable to add another signal electron detector, such as a backscattered electron (BSE) detector 313, to capture backscattered electrons with large angles.

[0064]

[0087] In some embodiments, the signal electron detector 313 may include a signal electron detector disposed between the signal electron detector 306 and the control electrode 314. In some embodiments, the signal electron detector 313 may be disposed immediately downstream and outside the pole pieces of the objective lens, as shown in Figure 3. In configurations where the signal electron detector 313 is outside the pole pieces, it may be desirable to position the signal electron detector 313 closer to the compound objective lens 307 or farther from the control electrode 314, but aligned with the primary optical axis 300-1, to minimize electrical damage to the signal electron detector 313 caused, for example, by arcing.

[0065]

[0088] It should be appreciated that some existing imaging techniques for defect detection or metrology simultaneously capture multiple images from collected BSE signals using a segmented detector, such as FEI's directional BSE detector (DBS), as disclosed in the publication "Information from Every Angle - Directional BSE Detector for Next-Level Imaging," FEI Technologies, Inc. The DBS includes a concentric ring design that separates BSEs based on emission angle (e.g., polar emission angle), with four separate rings enabling simultaneous detection of multiple BSE signals, and by utilizing all four rings of the DBS, four images can be formed simultaneously. This publication further discloses that BSEs with larger emission angles may be collected by rings positioned farther from the optical axis, while BSEs with smaller emission angles may be collected by rings positioned closest to the primary optical axis. While this FEI publication discloses discriminating incoming BSEs based on emission angle, it does not contemplate configuring the rings to discriminate incoming BSEs based on their energy level. Furthermore, modifying the FEI DBS to perform energy discrimination using the DBS design of a charged particle detector would not be obvious to one skilled in the art, as this publication does not discuss or suggest configuring each segment to resolve the energy levels of the incoming BSE signal. In contrast, embodiments disclosed in this disclosure provide a segmented BSE detector for high landing energy applications. Each segment of a segmented BSE detector may be configured to detect a signal based on the predominant energy level or range of energy levels of the incoming BSE. Configuring may include, for example, adjusting the width of the segment. Other techniques for configuring each segment include, among others, adjusting the z-axis position of the sample, adjusting the z-position of the detector, adjusting the magnetic field strength of the objective lens, adjusting the extraction potential, and adjusting the electrostatic field adjacent to the sample, each of which is discussed in detail in this disclosure.

[0066]

[0089] For high landing energy applications, a bottom BSE detector positioned between the sample and the pole piece of the objective lens may be used to collect BSEs with medium to large emission angles in the range of 15° to 65°. Details of systems and methods using a bottom BSE detector to improve collection efficiency are discussed in U.S. Patent Application Publication No. 2021 / 0319977A1, which is incorporated herein by reference in its entirety. As previously mentioned, research has revealed a strong correlation between the trajectory depth of BSEs and their emission energy. In other words, BSE signals with higher or lower energies have been found to originate from relatively shallow or deep locations within the sample material, respectively. In some cases, an energy filtering device may be used to selectively allow electrons of desired energy levels to pass to the detector, but physical space constraints in an apparatus using a bottom BSE detector may make this impossible. Therefore, it may be desirable to provide a bottom BSE detector that detects BSEs with energy discrimination capabilities while maintaining high BSE collection efficiency and high inspection throughput.

[0067]

[0090] Reference is now made to FIG. 4A, which shows a schematic diagram of a portion of an exemplary charged particle beam device 400 including a segmented backscattered electron (BSE) detector 413. The device 400 may include an objective lens 407 that is substantially similar to and performs substantially similar functions as the compound objective lens 307 of the device 300. The primary electron beam B1 may travel through an electron optical column that includes the objective lens 407, a central aperture of the segmented BSE detector 413, and a central aperture of a control electrode 414, and interact with a region of a sample 415. As a result of the interaction of the primary electron beam B1 with the sample 415, secondary charged particles may be emitted from the sample 415, including secondary electrons, backscattered electrons, Auger electrons, and x-rays, among other particles.

[0068]

[0091] As shown in FIG. 4A , BSE beam B2 and BSE beam B3 may each contain electrons with different energies or energy levels E1 and E2, where E1 is less than E2. In some embodiments, the polar emission angle θ1 of BSE beam B2 may be less than the polar emission angle θ2 of BSE beam B3. In some embodiments, not shown, the polar emission angles of BSE beams B2 and B3 may be substantially similar, while the energy levels E1 and E2 may be different. As used herein, substantially similar polar emission angles refer to a similarity in emission angles such that variations in the emission angles of electrons, or beams containing electrons, emitted from a sample are negligible and within acceptable limits.

[0069]

[0092] In some embodiments, the BSE detector 413 may be a bottom BSE detector positioned between the sample 415 and the pole piece of the objective lens 407. In some embodiments, the BSE detector 413 may be positioned between the control electrode 414 and the pole piece of the objective lens 407. The BSE detector 413 may be positioned to be substantially perpendicular to the primary optical axis along which the primary electron beam B1 passes through the electron optical column of the apparatus 400. As used herein, the term "substantially perpendicular" refers to the perpendicularity of an element relative to an axis or another element such that there is a negligible offset or deviation between them, typically less than 0.1° or within a tolerance, from a 90° angle. In some embodiments, the BSE detector 413 may be positioned such that the BSE detector 413 is substantially perpendicular to the primary optical axis and the central aperture of the BSE detector 413 is aligned with the primary optical axis, as shown in FIG. 4A . It should be understood that the dimensions, spacing, and sizes of the elements of device 400 are not drawn to scale and their relative positions and locations are symbolic.

[0070]

[0093] In some embodiments, the BSE detector 413 may be a segmented BSE detector including multiple radial concentric segments 413-1, 413-2, 413-3, and 413-4 of charged particle-sensitive material separated by a non-sensitive material or substrate. A top view of an exemplary segmented BSE detector including four concentric segments consistent with some embodiments of the present disclosure is shown in FIG. 4B . The charged particle-sensitive material may be sensitive to charged particles, such as ionizing radiation, electrons, x-rays, or photons, among other charged particles, such that the detector may be configured to detect incident charged particles and generate a corresponding signal in response to the detection. The non-sensitive material separating the concentric segments may include the substrate material of the BSE detector 413 or any material with low sensitivity for detecting charged particles. The BSE detector 413 may be positioned within the device 400 such that its central opening is aligned with the primary optical axis of the device 400. In some embodiments, each segment of BSE detector 413 may be configured to detect BSEs of different energy levels or ranges of energy levels. For example, segment 413-1 may be configured to detect BSEs having emission energies in the range of 2-5 keV, segment 413-2 may be configured to detect BSEs having emission energies in the range of 5-10 keV, segment 413-3 may be configured to detect BSEs having emission energies in the range of 10-20 keV, and segment 413-4 may be configured to detect BSEs having emission energies in the range of 20-50 keV. It should be understood that the number of segments and the energy ranges detected by each segment described above are non-limiting examples, and that a BSE detector may include fewer or more segments, and that the energy thresholds of each segment may be adjustable, as discussed in later sections of this disclosure. It should further be understood that the width of each segment may be uniform or non-uniform.

[0071]

[0094] In some embodiments, the BSE detection signals may be used to reconstruct an image of the sample structure being inspected or observed. The image may be a two-dimensional image or a three-dimensional image generated from multiple two-dimensional images. In some embodiments, a three-dimensional image may be formed from multiple images generated by signals detected by each segment of the BSE detector 413. Additionally or alternatively, a three-dimensional image may be formed from multiple images generated from signals detected by a single segment. The signal detected by a single segment may have a certain energy range, thereby representing BSEs emitting from a particular depth or a particular depth range. It may be desirable to generate a three-dimensional image from multiple images based on signals detected by a single segment to gather information about features at a particular depth, such as a critical dimension at a certain height. In other cases, it may be desirable to generate a three-dimensional image from multiple images based on signals detected by multiple segments simultaneously.

[0072]

[0095] Reference is now made to FIG. 5A , which illustrates simulation results for the spatial and energy distribution of backscattered electrons detected on an exemplary segmented BSE detector, such as BSE detector 413, consistent with embodiments of the present disclosure. In some embodiments, BSE detector 413 may be referred to as a bottom BSE detector (BBD). In the example illustrated in FIG. 5A , BSE detector 413 is a BBD having four segments. It should be understood that a “segment” of a segmented BSE detector may alternatively be referred to as a “section” herein. Thus, a segmented BSE detector, such as BSE detector 413, may include multiple sections, as referenced in FIG. 5A . The simulation results include the spatial distribution of BSE, as shown in the top image of FIG. 5A . The top image illustrates the spatial distribution of BSE on a BBD (e.g., BSE detector 413 of FIG. 4B ) and the spatial distribution of BSE on individual segments or sections of the BBD.

[0073]

[0096] In some embodiments, section 1 may correspond to segment 413-1 of BSE detector 413 of Figure 4B. Section 1 may be the segment closest to the central aperture of the BSE detector and may be configured to detect low-energy BSE signals representative of BSEs emanating from deeper regions of the sample, thereby providing information related to and about features present in that region. Sections 2, 3, and 4 may correspond to segments 413-2, 413-3, and 413-4 of BSE detector 413 of Figure 4B.

[0074]

[0097] The bottom image of FIG. 5A shows the simulated energy distribution of BSEs collected on the BBD and on individual segments of the BBD. For each segment, the energy distribution plot shown in the bottom shows the broad distribution of emitted energy collected by the corresponding segment. The energy distribution plot also shows the predominant energy level, or peak energy, of detected BSEs associated with each segment. FIG. 5B shows the relationship between the peak energies of detected BSEs associated with each segment of a segmented BSE detector (e.g., BSE detector 413 of FIG. 4B). As shown in this figure, the peak energy of detected BSEs collected by each segment increases as the radial distance from the center of the BSE detector aperture increases. In other words, a BSE detector (e.g., BSE detector 413 of FIG. 4B) may be segmented based on the peak energy of the detected BSEs. The relationship between BSE collection efficiency, BSE emission energy, and BSE detector segments is discussed in more detail with reference to FIG. 8.

[0075]

[0098] FIG. 6 illustrates simulated trajectories of BSEs emitted from a substrate at different emission polar angles, consistent with embodiments of the present disclosure. Data capture plot 620 illustrates simulated trajectories of BSEs for a range of radiation energies emitted at a polar emission angle of 20°. In some embodiments, the emission energy of the BSEs can be in the range of 1 keV to 50 keV, 2 keV to 50 keV, 3 keV to 50 keV, 4 keV to 50 keV, 5 keV to 50 keV, 10 keV to 50 keV, 15 keV to 50 keV, or any suitable range of BSE emission energies. In some embodiments, the BSE emission energy can range from 1 keV to the landing energy of the primary electron beam. BSE detector 613 is configured to detect BSEs emitted from the substrate. Although all of the BSEs shown in data capture plot 620 are emitted at a polar emission angle of 20°, some of the BSEs with lower emission energies may be collected in regions of the BSE detector 613 that are radially closer to the primary optical axis, and some of the BSEs with higher emission energies may be collected in regions of the BSE detector 613 that are radially farther from the primary optical axis. In other words, some of the BSEs with lower emission energies may be incident on the detection surface of the BSE detector 613 at smaller off-axis distances, and some of the BSEs with higher emission energies may be incident on the detection surface of the BSE detector 613 at larger off-axis distances. In the context of this disclosure, off-axis distance refers to the horizontal distance from the primary optical axis.

[0076]

[0099] In some embodiments, a magnetic field generated by an objective lens (e.g., objective lens 407 in FIG. 4A ) can affect the path of BSEs emitted from a surface based on the energy of the BSEs. Low-energy BSEs can be more strongly affected than higher-energy BSEs. In this context, affecting the path of a BSE by the objective lens's magnetic field refers to changing the trajectory of the BSE so that the BSE is deflected toward the primary optical axis. In some cases, deflecting the trajectory of low-energy BSEs can cause the BSEs to escape through the central aperture of the BSE detector 613 without being detected, resulting in a loss of collection efficiency. One of several methods for capturing low-energy, low-emission-angle BSEs can include reducing the cross-section of the central aperture of the BSE detector 613. However, in some situations, this can obstruct the path of the primary electron beam directed toward the sample, among other challenges. As shown in data capture plot 620 of FIG. 6, the radial spacing between BSEs of different radiant energies on the detection face of BSE detector 613, emitted at a polar emission angle of 20°, is small.

[0077]

[0100] Data capture plots 630 and 640 show simulated trajectories of BSEs with a range of emission energies emitted at polar emission angles of 30° and 40°, respectively. Compared to data capture plot 620, the radial spacing or radial resolution of BSEs of different emission energies on the detection surface of BSE detector 613 emitted at larger emission angles is increased, as shown in data capture plots 630 and 640.

[0078]

[0101] Data capture plot 645 shows a simulation of the trajectories of BSEs with a range of emission energies emitted at a polar emission angle of 45°. As shown, the radial spacing between BSEs of different emission energies can be greater than the radial spacing or radial resolution of BSEs with a polar emission angle of 40°. Furthermore, the emission yield of BSEs is higher at a polar emission angle of 45°. Therefore, it may be desirable to use a radially segmented BSE detector, such as BSE detector 413 of FIG. 4B, to maximize detection of BSEs emitted at a polar emission angle of, for example, 45°, based on the emission energy of the BSEs incident on the BSE detector.

[0079]

[0102] In data capture plots 655 and 660, which show simulations of trajectories of BSEs with a range of emission energies emitted at polar emission angles of 55° and 60°, respectively, although the polar emission angles are larger, the detectability based on radial spacing, and therefore emission energy, may not be high. This may be due to the fact that BSEs with larger emission angles are deflected more, causing the BSEs to be absorbed or reflected back towards the substrate, thereby reducing the number of BSEs collected by BSE detector 613.

[0080]

[0103] As previously mentioned, a radially segmented BSE detector, such as BSE detector 413 of FIG. 4B, may be used to discriminate incoming BSEs based on their emission energy. Furthermore, each segment (e.g., segments 413-1 through 413-4 of FIG. 4B) may be configured to detect BSEs having BSE emission energies within a particular energy level range, and each segment may have an associated dominant energy level or peak energy. Because each segment has an associated peak energy within the distribution of detected BSE emission energies, a greater number of spatially arranged segments may result in higher energy filtering resolution. In other words, the resolution of a segmented BSE detector may be improved by increasing the number of segments based on the dominant energy level of the BSEs it is designed to detect.

[0081]

[0104] Reference is now made to FIGS. 7A-7D, which illustrate energy distribution profiles of backscattered electrons detected by an exemplary segmented BSE detector consistent with embodiments of the present disclosure. FIG. 7A illustrates a schematic top view of a BSE detector 713 having four segments (e.g., segments 1, 2, 3, and 4) with segment-1 activated. Data plot 710 illustrates the spatial energy distribution profile of segment-1 configured to detect incoming BSEs upon activation. In this regard, activating a segment of a BSE detector may include enabling collection or detection of BSEs incident on a detector surface associated with the segment. The segments of a segmented BSE detector may include materials sensitive to charged particles, including, but not limited to, ionizing radiation, electrons, and x-rays, among other particles.

[0082]

[0105] In some embodiments, a controller (e.g., controller 50 of FIG. 2 ) may be configured to apply an electrical signal, such as a voltage signal or a current signal, to activate one or more segments sequentially or in parallel. For example, controller 50 may activate segment-1 to collect BSEs arriving from deeper regions of the sample and thereby having lower emission energies. In some embodiments, controller 50 may be further configured to generate an image (e.g., a backscattered electron image) based on BSE signals generated by the BSEs collected or detected by segment-1. It should be understood that controller 50 may be configured, among other functions, to generate multiple images or process multiple images to form a composite image. An image processor controlled by controller 50 may be configured to form a composite image. In this regard, a composite image may be formed by stitching together multiple images captured by the image acquisition unit. For example, a composite image may include a three-dimensional image formed by stitching together multiple two-dimensional images captured at different depths.

[0083]

[0106] In some embodiments, the BSE detector may be segmented into m segments, where m is a positive integer and is greater than or equal to 2. An exemplary BSE detector 713-1 having eight segments is shown in FIG. 7A . It should be understood that the number of segments, the width of each segment, or the material of each segment may be appropriately adjusted as needed. Furthermore, it should be understood that one or more segments of the BSE detector 713-1 may be activated individually, simultaneously, or based on a predetermined timing. For example, the controller may be configured to activate one of the multiple segments for a predetermined time while not activating the other segments. After the predetermined time has elapsed, another segment may be activated for a second predetermined time. In some embodiments, one or more segments may be activated based on a predetermined duty cycle.

[0084]

[0107] Data plot 720 shows the BSE energy distribution profile and peak energy levels identified for segments 1 and 2 of BSE detector 713-1. Compared to BSE detector 713 having a single peak or predominant energy for a given BSE emission energy range, BSE detector 713-1 may be configured to have two segments (e.g., segments 1 and 2) and therefore two predominant energy levels, which may be used to further resolve incoming BSEs based on their energies. Higher energy resolution may enable a user to obtain information or form images from specific depths while filtering out other BSE signals, which may result in more accurate inspections and measurements.

[0085]

[0108] As an example, the controller 50 may activate only segment 1 or segment 2 at a time to generate an image based on a BSE signal having an emission energy distribution within a particular range or having a particular peak energy level, which may correlate with a particular depth into the sample at which the BSE signal may occur.

[0086]

[0109] As shown in FIG. 7B, data plot 730 shows the BSE energy distribution profile for segment 2 of segmented BSE detector 713. Segment 2 of BSE detector 713 is shown as activated. In comparison, a narrower energy distribution and more clearly distinguishable peak energy levels can be obtained from segments 3 and 4 of BSE detector 713-1. Data plot 740 represents the energy distribution profiles for segments 3 and 4 of BSE detector 713-1. As shown in FIG. 7C, data plots 750 and 760 show the BSE energy distribution profiles for segment 3 of BSE detector 713 and segments 5 and 6 of BSE detector 713-1, respectively. As shown in FIG. 7D, data plots 770 and 780 show the BSE energy distribution profiles for segment 4 of BSE detector 713 and segments 7 and 8 of BSE detector 713-1, respectively.

[0087]

[0110] FIG. 8 shows a graphical representation of a simulation of the collection efficiency of backscattered electrons for multiple segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. In FIG. 8, data plot 800 represents the collection efficiency of individual segments of the exemplary segmented BSE detector for BSEs having emission energies ranging from 5 keV to 30 keV and a polar emission angle of 45°. It should be understood that the emission energy range used for simulation purposes is exemplary and non-limiting, and other energy ranges may be used as well. A BSE detector may include eight segments (e.g., BSE detector 713-1 in FIGS. 7A-7D ), identified as segments 1 through 8. Segment 0 in data plot 800 does not represent an actual detection segment, but instead represents the central aperture of the segmented BSE detector. In this regard, the collection efficiency of segment 0 is not an actual collection efficiency because no BSEs are collected or detected therein, but instead can be considered the number of BSEs lost or leaking through the central aperture of the BSE detector.

[0088]

[0111] As shown in data plot 800, the number of BSEs lost through the central aperture of the BSE detector may decrease as the BSE emission energy increases. As an example, about 45% of low-energy BSEs (e.g., below 5 keV) and about 5% of high-energy BSEs (e.g., above 25 keV) may pass through the central aperture without being detected by the BSE detector. This may be because low-energy BSEs are more strongly affected by the objective lens's magnetic field than high-energy BSEs, which deflects the BSEs closer to the primary optical axis.

[0089]

[0112] As further shown in data plot 800, in terms of collection efficiency, there may be distinct dominant or peak energy components for each segment of a segmented BSE detector. In other words, a segment may detect BSEs having a particular energy that is greater than other energy components of the BSE signal. For example, segment 1 may have the highest collection efficiency for 10 keV BSEs, segment 3 may have the highest collection efficiency for 15 keV BSEs, segment 4 may have the highest collection efficiency for 20 keV BSEs, segment 5 may have the highest collection efficiency for 25 keV BSEs, and segment 6 may have the highest collection efficiency for 30 keV BSEs.

[0090]

[0113] As further shown in data plot 800, the greater the BSE energy, the greater the likely location of the peak of maximum collection efficiency within a segment located at a greater off-axis distance. In other words, segments located farther from the primary optical axis may be configured to selectively detect BSEs with greater energy, thereby enabling the use of a segmented BSE detector to discriminate between different energy components of the incoming BSEs. This may be because BSEs with high kinetic energy are less susceptible to the magnetic field of the objective lens and can travel longer distances without deflecting or deviating from the desired trajectory.

[0091]

[0114] In some embodiments, a BSE detector may be configured such that segments of the detector detect different ranges of predominant energy BSE signals. Configuring a BSE detector (e.g., BSE detector 713-1 in FIGS. 7A-7D) may include adjusting the radial width of the segments, adjusting the electromagnetic field of the objective lens, adjusting the distance between the substrate and the BSE detector (described below with reference to FIGS. 10A and 10B), adjusting the height of the BSE detector relative to the substrate position, adjusting the electric field on the sample, adjusting an extraction voltage between the charged particle source (e.g., the electron source) and the substrate, adjusting the magnetic field strength of the objective lens, or compensating for focus due to changes in the magnetic field strength of the objective lens. One or more of the factors, such as the magnetic field strength of the objective lens, the distance between the substrate and the BSE detector, the extraction voltage, the control electrode voltage, the height of the BSE detector, or a combination thereof, may be adjusted to optimize the spatial distribution and image contrast of the BSE signal on the segmented BSE detector, such that each segment is configured to detect a distinct range of BSE signals of predominant energy, as shown, for example, in data plot 800.

[0092]

[0115] Reference is now made to FIG. 9, which illustrates the spatial distribution of BSEs detected by radially concentric segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. In FIG. 9, multiple simulated images 905, 910, 915, 920, 925, and 930 represent the detection footprint or spatial distribution of BSEs with energies of 5 keV, 10 keV, 15 keV, 20 keV, 25 keV, and 30 keV, respectively, on a segmented BSE detector (e.g., BSE detector 713-1 of FIGS. 7A-7D). For example, substantially all BSEs with energies of 10 keV or less may be collected by the segments closest to the primary optical axis, such as segments 1, 2, 3, and 4. As shown in simulated image 910, the distribution of BSEs spans four segments, but the distribution density of BSE signals is highest in segment 1, consistent with data plot 800. As another example, substantially all BSEs having energies of 20 keV or less may be collected by segments 1 through 7. As shown in simulated image 920, the distribution of BSEs spans seven segments, but the distribution density of BSE signals is highest in segment 4, consistent with data plot 800. Thus, each segment may have a predominant energy level of BSEs that can be configured to detect, allowing for discrimination and filtering of BSE signals based on their emission energy.

[0093]

[0116] 10A shows a schematic diagram of an exemplary charged particle beam device 1000 with a segmented BSE detector consistent with embodiments of the present disclosure. Objective lens 1007, BSE detector 1013, and control electrode 1014 may be substantially similar to, and perform substantially similar functions as, objective lens 407, BSE detector 413, and control electrode 414 of device 400, respectively.

[0094]

[0117] Compared to apparatus 400, the position of sample 1015 in the z-axis may be adjustable in apparatus 1000. In some embodiments, the z-axis position of sample 1015 may be adjusted to change the distance between BSE detector 1013 and sample 1015, i.e., the working distance. As shown, the working distance may be increased by adjusting the z-axis position of sample 1015 from an initial position P1 to P2 (represented by the dashed rectangle). BSE beam B3 may be emitted from the surface of sample 1015 at position P1, and BSE beam B2 may be emitted from sample 1015 at position P2. Changes in the trajectories of BSE beams B2 and B3 caused by changes in the z-axis position of the surface of sample 1015 from which BSE beams B2 and B3 originate may result in changes in the peak energies of the collected BSEs incident on the segments of BSE detector 1013. For example, BSE beam B2 and BSE beam B3 may have different peak energy levels but may land on the same segment of BSE detector 1013 based on the z-axis position of sample 1015.

[0095]

[0118] In some embodiments, adjusting the z-axis position of the sample 1015 may change the BSE energy detection range of the BSE detector 1013. For example, increasing the working distance, as shown in FIG. 10A, may increase the BSE energy range detectable by the BSE detector 1013. In some embodiments, adjusting the z-axis position of the sample 1015 may change the BSE collection efficiency. For example, increasing the working distance may cause more BSEs to be deflected by the magnetic field of the objective lens 1007 closer to the primary optical axis along which the primary electron beam B1 travels, thereby allowing more BSEs to escape through the central opening of the BSE detector 1013. In some embodiments, adjusting the z-axis position of the sample 1015 may change the uniformity of the BSE collection efficiency across multiple segments of the BSE detector 1013, as shown in FIG. 10B. For example, increasing the working distance may improve the uniformity of the BSE collection efficiency across multiple segments of a segmented BSE detector (e.g., the BSE detector 1013).

[0096]

[0119] In some embodiments, not shown, the peak energy of BSEs collected by a segment of multiple segments may vary based on working distance. This may allow for further filtering of incoming BSEs based on energy. In other words, the working distance may be adjusted to filter BSEs within a particular segment of the BSE detector 1013. The ability to adjust the peak energy of detected BSEs, the energy detection range of BSEs, or the uniformity of BSE collection efficiency across multiple segments by adjusting the z-axis position of the sample can provide improved sensitivity and accuracy for metrology or defect inspection.

[0097]

[0120] In some embodiments, the z-axis position of the sample may be adjusted based on the landing energy of the charged particles forming the primary charged particle beam B1. It may be desirable to adjust the z-axis position of the sample based on the landing energy of the primary charged particle beam B1 to allow for better discrimination of BSE energies between multiple segments of the BSE detector 1013.

[0098]

[0121] Reference is now made to Figures 11A and 11B, which show simulations of BSE trajectories with varying emission angles and a constant polar emission angle, respectively, consistent with embodiments of the present disclosure. Figure 11A shows simulations of BSE trajectories with a constant emission energy (e.g., 30 keV) at various polar emission angles and various working distances.

[0099]

[0122] In some embodiments, BSEs with smaller polar emission angles may be detected by segments closer to the primary optical axis or may escape through the central aperture of the BSE detector without being detected. BSEs with larger polar emission angles may land on segments at larger off-axis distances, be intercepted by other components such as control electrodes (e.g., control electrodes 1014 in FIG. 10A ), or be reflected back to the substrate. As the working distance increases, the magnetic field generated by the objective lens (e.g., objective lens 1007 in FIG. 10A ) becomes weaker, causing the BSEs to be less affected and allowing them to move without substantial deflection or deviation. This may allow BSEs with the same energy content to land on different segments at different working distances. In other words, at different working distances, a particular radial segment may collect or detect BSEs with different emission energies.

[0100]

[0123] As previously mentioned, the BSE emission yield may be greatest at a polar emission angle of 45°. Figure 11B shows simulations of BSE trajectories for different energy components emitted at a fixed polar emission angle of 45° as the working distance is varied. As the working distance increases, the BSEs may move farther from the primary optical axis before being collected by the BSE detector, thereby experiencing greater focusing forces from the objective lens (e.g., objective lens 1007 in Figure 10A ), which deflects the BSEs back toward the primary optical axis. In some embodiments, not shown, adjusting the working distance may change the peak BSE energy detected by a segment of the BSE detector (e.g., BSE detector 1013 in Figure 10A ).

[0101]

[0124] In some embodiments, the BSE spatial distribution, BSE collection efficiency, or detected peak BSE energy on one or more segments of a segmented BSE detector (e.g., BSE detector 713-1 in FIGS. 7A-7D) may be adjusted by adjusting the electric field strength at the surface of the sample (e.g., sample 415 in FIG. 4). Adjusting the electric field strength at the sample surface may include, but is not limited to, adjusting the voltage of a control electrode (e.g., control electrode 414 in FIG. 4) near the sample or adjusting the potential difference between the sample and a pole piece of an objective lens (e.g., objective lens 407 in FIG. 4A). In some embodiments, controller 50 may be configured to apply or adjust the voltage applied to the control electrode, such that adjusting the applied voltage adjusts one or more of the BSE collection efficiency, peak BSE energy, or BSE energy spread.

[0102]

[0125] FIG. 12 shows a graphical representation of simulated data illustrating the effect of adjusting electric field strength on the variation of collection efficiency, peak energy, and energy spread of BSEs collected by different segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. In some embodiments, the electric field strength on the sample may be adjusted by adjusting the voltage to the control electrode. Data plot 1210 shows a comparison of BSE collection efficiencies of eight segments for BSEs having a particular energy and emission angle. For example, applying a voltage of 3 kV to the control electrode may increase the BSE collection efficiency of the outer segments of the segmented BSE detector (e.g., segments 5 and 6) while substantially maintaining the peak detection BSE energy level shown in data plot 1220 and the energy spread distribution of BSEs detected by those segments of the segmented BSE detector shown in data plot 1230.

[0103]

[0126] In some embodiments, applying a higher voltage to the control electrodes may increase the BSE collection efficiency of the outer segments (e.g., segments 5 and 6) and decrease the BSE collection efficiency of the inner segments (e.g., segments 1-4). Applying a higher voltage to the control electrodes may affect the path of low-energy BSEs closer to the primary optical axis, causing them to deflect toward the primary optical axis and escape through the central opening of the BSE detector, thereby causing a decrease in BSE collection efficiency. For high-energy BSEs, applying a higher voltage to the control electrodes may deflect the BSEs so that they are detected by the BSE detector, thereby causing an increase in the BSE collection efficiency of the outer segments of the BSE detector. In the context of this disclosure, outer segments refer to segments of a segmented BSE detector located farther from the primary optical axis at a greater off-axis distance, and inner segments refer to segments located closer to the primary optical axis at a shorter off-axis distance. In some embodiments, by way of example, segments 1, 2, 3, and 4 may comprise inner segments, and segments 5, 6, 7, and 8 may comprise outer segments.

[0104]

[0127] The peak energy of each segment may be adjusted based on the voltage signal applied to the control electrode, as shown in data plot 1220. The ability to adjust the peak energy by adjusting the control electrode voltage may improve image contrast for a particular depth in the sample, thereby increasing the accuracy of defect inspection or feature metrology.

[0105]

[0128] In some embodiments, the electric field strength on the sample may be adjusted by adjusting the extraction voltage. In this context, extraction voltage refers to the potential difference between the sample and the pole pieces of the objective lens. As an example, if the same voltage is applied to the pole pieces of the objective lens and the sample, the potential difference between them, and therefore the extraction voltage, will be zero. In other words, the objective lens and the sample are at equipotential. If the voltage applied to the sample is higher than the voltage applied to the pole pieces of the objective lens, the sample will be biased positively with respect to the objective lens, which may increase the electric field strength between them, thereby extracting or "pushing" more electrons from the sample.

[0106]

[0129] In some embodiments, the extraction voltage may be adjusted to adjust the detection of peak BSE energy by the segments of a segmented BSE detector. Data plot 1310 in FIG. 13A shows a comparison of the peak BSE energy detected by each segment of a segmented BSE detector for two different extraction voltages, 0 kV and 5 kV. As shown, the peak energy of BSEs detected by segments 1 and 7 is different at an extraction voltage of 5 kV (e.g., lower peak energy for a higher extraction field) compared to the peak energy of BSEs detected when the extraction voltage is 0 kV. A higher peak BSE energy detected for one or more segments of a BSE detector may be beneficial for improving image contrast at a specific depth for defect inspection or metrology applications. Although not shown, the width of the energy distribution of BSEs detected by each segment may also be adjusted, as needed, by adjusting the extraction voltage.

[0107]

[0130] Reference is now made to FIG. 13B, which shows a data plot of simulated values ​​of the BSE collection efficiency of each segment of the BSE detector for two different extraction voltages, 0 kV and 5 kV. A stronger extraction voltage, e.g., 5 kV or higher, may improve the BSE collection efficiency of each segment of the BSE detector. Increased BSE collection efficiency may be beneficial for improving the signal-to-noise (SNR) ratio and improving detector gain. Detector gain is proportional to the energy of the electrons received by the detector; therefore, when the voltage difference between the objective lens and the sample is large, the electrons emitted from the surface of the sample have higher kinetic energy, resulting in a higher detector gain.

[0108]

[0131] In some embodiments, the magnetic field strength of the objective lens may be adjusted to adjust the BSE collection efficiency of a segment of a segmented BSE detector (e.g., BSE detector 713-1 in Figures 7A-7D). Adjusting the magnetic field strength of the objective lens may include adjusting the excitation of the objective lens. In some embodiments, the magnetic field strength of the objective lens may be expressed as ampere-turns (AT), which is a unit of magnetomotive force (MMF) and is represented by 1 ampere of direct current flowing through a single-turn loop in a vacuum. As an example, 2 amperes of current flowing through a 10-turn coil can generate 20 AT of MMF.

[0109]

[0132] 14A and 14B illustrate the relationship between the BSE collection efficiency of each segment of a segmented BSE detector based on the objective lens magnetic field strength, consistent with embodiments of the present disclosure. Data plot 1410 in FIG. 14A represents the BSE collection efficiency of eight segments of a segmented BSE detector when the objective lens magnetic field strength is 3193 AT, the detector is at a nominal height, the landing energy is 30 keV, and there is no electric field at the surface of the sample. In contrast, data plot 1420 in FIG. 14B represents the BSE collection efficiency of eight segments of a segmented BSE detector when the objective lens magnetic field strength is higher, approximately 3222 AT. For example, as shown in data plot 1420 in FIG. 14B, the BSE collection efficiency of segment 4 for 20 keV BSE can be higher compared to the collection efficiency of segment 3 when the objective lens magnetic field strength is higher.

[0110]

[0133] Reference is now made to FIG. 15, which further illustrates the effect of adjusting the magnetic field strength of the objective lens on the BSE collection efficiency of a segment of a segmented BSE detector, consistent with embodiments of the present disclosure. As referenced in FIG. 15, a segmented BSE detector may refer to an eight-segment BSE detector, such as BSE detector 713-1 of FIGS. 7A-7D. In FIG. 15, each subfigure corresponds to an individual segment of the eight-segment BSE detector. Thus, subfigure 1510 corresponds to segment 1 of the BSE detector, subfigure 1520 corresponds to segment 2 of the BSE detector, subfigure 1530 corresponds to segment 3 of the BSE detector, subfigure 1540 corresponds to segment 4 of the BSE detector, subfigure 1550 corresponds to segment 5 of the BSE detector, subfigure 1560 corresponds to segment 6 of the BSE detector, subfigure 1570 corresponds to segment 7 of the BSE detector, and subfigure 1580 corresponds to segment 8 of the BSE detector.

[0111]

[0134] Referring to FIG. 15, each sub-figure (1510-1580) shows the relationship between different BSE energy components and their corresponding collection efficiencies (CEs) with respect to the maximum CE within a particular energy range. In this regard, a CE ratio of 100% indicates that the energy component has the highest collection efficiency in that segment. Furthermore, in each sub-figure (1510-1580), individual curves represent the change in collection efficiency for each segment at a particular objective lens excitation to generate a particular magnetic field. The behavior of different curves differs because the strength of the magnetic field can affect the BSE energy or spatial distribution on the BSE detector.

[0112]

[0135] As shown, each subfigure in Figure 15 represents the BSE collection efficiency of an individual segment for magnetic field strength values ​​ranging from 0 AT to 3293 AT. At 0 AT, which indicates the absence of a magnetic field from the objective lens, BSEs of all energy components emitted from the sample may travel along the same electron trajectory, and therefore, the collection efficiency (CE) may be substantially similar or the same for each energy component. This is represented by the data point at 100% CE ratio on the y-axis of each subfigure. The nominal excitation of the objective lens may refer to excitation of the objective lens such that the generated magnetic field focuses the primary electron beam on the surface of the sample. Objective lens excitation outside the nominal excitation range may indicate that the primary electron beam is either underfocused or overfocused.

[0113]

[0136] Furthermore, if the collection efficiency of one energy component is much higher than that of other energy components, the achievable image contrast may be higher. In other words, if the difference in collection efficiency between one energy component and another is greater, the image contrast may be higher. In some embodiments, adjusting the magnetic field of the objective lens may allow for adjustment of the collection efficiency of one or more individual energy components, which can be used to further enhance image contrast.

[0114]

[0137] As shown in each subfigure, each curve represents the change in BSE collection efficiency of an individual segment for a particular objective lens excitation. In some embodiments, the objective lens excitation, and therefore the magnetic field strength, may be adjusted in intervals of 10 AT or more, 20 AT or more, 50 AT or more, 100 AT or more, or any suitable range to determine the maximum difference between the BSE collection efficiencies of the segments, which can optimize image contrast and improve energy filtering resolution.

[0115]

[0138] As an example, in sub-diagram 1530, decreasing the objective excitation (represented by the downward arrow) such that the magnetic field strength is lower than the nominal excitation can increase the difference in collection efficiency between segment 3 and the other segments. This may indicate that decreasing the magnetic field strength can enable acquisition of images associated with a particular depth region of the sample with higher contrast. In contrast, in sub-diagram 1550, increasing the objective excitation (represented by the upward arrow) such that the magnetic field strength is higher than the nominal excitation can increase the difference in collection efficiency between segment 5 and the other segments. This may indicate that increasing the magnetic field strength can enable acquisition of images associated with a particular depth region of the sample with higher contrast. In some embodiments, controller 50 may be configured to adjust the objective lens excitation to enable adjustment of the magnetic field strength, thereby enabling acquisition of images with better contrast and higher accuracy measurements.

[0116]

[0139] In some embodiments, adjusting the magnetic field of the objective lens can increase image contrast, but it can also change the focus of a primary charged particle beam, such as a primary electron beam, that traverses its path toward the sample. Adjusting the magnetic field of the objective lens may include decreasing or increasing the magnetic field based on the desired BSE collection efficiency for each segment of the segmented BSE detector, thereby allowing a user to select a desired range of BSE energies from a particular depth in the sample and further optimize the contrast of the image generated from the detected BSEs. However, the benefit of obtaining better image contrast by adjusting the magnetic field of the objective lens can be significantly diminished if adjusting the magnetic field defocuses the primary charged particle beam. Therefore, to maintain high image contrast and high resolution, it may be desirable to compensate for the focus change introduced by adjusting the magnetic field.

[0117]

[0140] Reference is now made to Figure 16A, which shows a schematic diagram of an exemplary charged particle beam device 1600A consistent with embodiments of the present disclosure. Compared to device 400, device 1600A may additionally include a focus compensation lens 1605 configured to compensate for changes in the focus of a primary charged particle beam 1602 along a primary optical axis 1601. The changes in the focus of the primary charged particle beam 1602 may be caused, among other things, due to changes in the magnetic field of an objective lens 1607 to increase the BSE collection efficiency of individual segments of a segmented BSE detector 1613.

[0118]

[0141] In some embodiments, the focus compensation lens 1605 may be implemented by one or more deflectors of a scanning deflection unit or beam manipulator assembly (e.g., primary electron beam deflectors 308, 309, 310, or 311 in FIG. 3). In some embodiments, the focus compensation lens 1605 may be formed by the deflector closest to the BSE detector 1613 (e.g., deflector 311 in FIG. 3). In such a scenario, the focus compensation lens 1605 may compensate for focus changes caused by adjustments to the magnetic field of the objective lens 1607 while minimizing the impact on the overall magnification of the imaging system. In some embodiments, the focus compensation lens 1605 may be positioned immediately upstream of the pole piece 1607P of the objective lens 1607. If the focus compensation lens 1605 is formed by the deflector closest to the pole piece 1607P of the objective lens 1607, which has a smaller inner diameter, a stronger focusing force may be obtained by applying a lower voltage to it compared to other deflectors of the scan deflection unit upstream from the deflector closest to the pole piece 1607P of the objective lens 1607. In some embodiments, the focus compensation lens 1605 may be realized by applying the same potential to all electrodes of the scan deflector to form a lens field to focus the passing charged particle beam.

[0119]

[0142] In some embodiments, the beam scanning deflector 1605 may include a quadrupole, hexapole, or octopole configuration. In some embodiments, the focus compensation lens 1605 may be implemented by applying the same potential to all electrodes of the scanning deflector to form a lens field to focus the passing charged particle beam.

[0120]

[0143] 16A, the objective lens may be nominally energized such that the primary charged particle beam 1602 is focused at the surface of the sample 1615. In such a scenario, the focus compensation lens 1605 may be deactivated and may not function as a focus compensation lens.

[0121]

[0144] In some embodiments, the magnetic field of the objective lens 1607 may be reduced by decreasing the objective lens excitation to increase the difference in collection efficiency between segments of the BSE detector 1613, as shown in sub-figure 1530 of Figure 15. If the magnetic field of the objective lens 1607 is weaker, the primary charged particle beam 1602 may become underfocused on the surface of the sample 1615, as shown in Figure 16B. In such a scenario, the focus compensation lens 1605 may be activated to compensate for the change in focus due to the adjustment of the objective lens excitation and adjust the focus of the primary charged particle beam 1602 to form a focused primary charged particle beam 1606.

[0122]

[0145] In some embodiments, the magnetic field of the objective lens 1607 may be increased by increasing the objective lens excitation to enhance the difference in collection efficiency between segments of the BSE detector 1613, as shown in subfigure 1550 of FIG. 15 . If the magnetic field of the objective lens 1607 is stronger than the nominal excitation, the primary charged particle beam 1602 may become overfocused on the surface of the sample 1615, as shown in FIG. 16C . In such a scenario, to compensate for the change in focus, the focusing power of the collector lens 1605 may be reduced to form a focus-compensated divergent primary charged particle beam 1609, which may then be focused at the surface of the sample 1615 by a stronger objective lens magnetic field. In some embodiments, reducing the focusing power of the collector lens 1605 may reduce the probe current of the divergent primary charged particle beam 1609. To compensate for the reduced probe current, a larger Coulomb aperture from the Coulomb aperture array 1608 may be used to allow a larger beam to pass through to the collector lens 1605.

[0123]

[0146] Reference is now made to FIG. 17 , which shows a schematic diagram of an exemplary charged particle beam device 1700 including a segmented BSE detector consistent with embodiments of the present disclosure. The device 1700 may include an objective lens 1707, a segmented BSE detector 1713 positioned at least substantially perpendicular to a primary optical axis 1701, a control electrode 1714 positioned downstream of the BSE detector 1713, and a sample 1715. During operation, a primary charged particle beam B1 may be generated from a charged particle source (not shown) and traverse downward toward the sample 1715. As charged particles of the primary charged particle beam B1 interact with regions of the sample 1715, based on the interaction volume, signal charged particles forming a BSE beam B2 may be emitted from different depths of the sample 1715 and collected at a detection surface of the BSE detector 1713.

[0124]

[0147] In some embodiments, the z-height of the BSE detector 1713 may be referred to as the vertical distance between the detection plane 1713P, along which the detection surface of the BSE detector 1713 extends, and the top surface of the sample 1713. As shown in FIG. 17 , the z-height of the BSE detector 1713 may be adjustable within a range of positions relative to the position of the sample 1715. The z-axis position of the BSE detector 1713, along which the detection surface extends along the detection plane 1713P, may be referred to as the nominal position of the BSE detector 1713. For the nominal position, ΔZ=0, where ΔZ is the difference in z-axis position relative to the nominal position. If the z-axis position of the BSE detector 1713 is adjusted so that the detection surface moves upstream of the sample 1715 and closer to the objective lens 1707, then ΔZ=[-distance]. If the z-axis position of the BSE detector 1713 is adjusted so that the detection plane moves downstream closer to the sample 1715, then ΔZ=[+distance].

[0125]

[0148] FIG. 18 shows a graphical representation of a simulation of the relationship between the BSE collection efficiency of individual segments of a segmented BSE detector and the BSE emission energy for a range of z-height positions of the BSE detector consistent with embodiments of the present disclosure. Simulation data plot 1810 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = -1 mm, simulation data plot 1820 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = -0.5 mm, simulation data plot 1830 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = 0 mm (the nominal position of the BSE detector 1713), simulation data plot 1840 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = +0.5 mm, simulation data plot 1850 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = +1.0 mm, and simulation data plot 1860 shows the BSE collection efficiency of individual segments for a z-height position of the BSE detector ΔZ = +1.5 mm. In some embodiments, the nominal position of the BSE detector 1713 may be determined based at least on, but not limited to, the BSE collection efficiency at different segments of the BSE detector, the primary charged particle beam resolution, the objective lens magnetic field strength, and the high voltage stability between the BSE detector and the control electrode, among others.

[0126]

[0149] As shown in simulated data plots 1810-1860, the energy components of the incoming BSE signal may be resolved based on the BSE collection efficiency of each individual segment for a range of z-axis positions. In some embodiments, determining whether the energy components of the incoming BSE signal are "resolved" may include determining whether there is a clearly distinguishable energy component for which the BSE collection efficiency of each individual segment is highest. In this context, the term "clearly distinguishable" energy component refers to an energy component whose BSE collection efficiency is substantially higher than the BSE collection efficiency of other energy components, such that the difference in BSE collection efficiency between any two energy components is higher than a threshold. In some embodiments, the threshold may be predetermined or may be based on the image contrast resulting from the difference in BSE collection efficiency. For example, as shown in simulated data plot 1850, when the BSE detector is located at ΔZ=+1 mm, the BSE collection efficiency of segment 2 for the 10 keV energy component is substantially higher than the other energy components; therefore, moving the BSE detector closer to the sample 1715 may resolve the energy component.

[0127]

[0150] In some embodiments, determining whether the energy components of the incoming BSE signal are resolved may include determining whether the BSE collection efficiency for each individual segment is greater than a threshold BSE collection efficiency. In some embodiments, the threshold BSE collection efficiency may be a predetermined threshold efficiency such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 15%, etc., or any suitable BSE collection efficiency or range of BSE collection efficiencies. For example, as shown in simulated data plot 1820, when BSE detector 1713 is located at ΔZ=−0.5 mm, the BSE collection efficiency of each segment for an energy component is at least greater than a threshold BSE collection efficiency of 10%.

[0128]

[0151] In some embodiments, determining whether the energy components of the incoming BSE signal are resolved may include determining whether there are as many clearly identifiable energy components as possible. For example, as shown in simulated data plot 1820, when BSE detector 1713 is located at ΔZ=−0.5 mm, substantially all energy components may be clearly identifiable based on the BSE collection efficiency of each segment for a particular energy component.

[0129]

[0152] In some embodiments, the z-height of the BSE detector may be optimized based on whether the energy components of the incoming BSE signal are resolved. One or more of the factors described above with respect to determining whether the energy components are resolved may be used to optimize the z-height of the BSE detector.

[0130]

[0153] Reference is now made to Figure 19, which shows a process flow diagram illustrating an exemplary method 1900 of imaging a sample using a charged particle beam device, such as device 300 of Figure 3, consistent with embodiments of the present disclosure.

[0131]

[0154] In step 1910, a region of the sample containing the feature is irradiated with a primary charged particle beam. The primary charged particle beam may include a primary electron beam. A controller (e.g., controller 50 of FIG. 1 ) is configured to apply a voltage signal to a cathode of an electron source configured to generate a plurality of primary electrons that form the primary electron beam. The electron source may be operated remotely, for example, by using software, an application, or a set of instructions for a processor of the controller to power the electron source via control circuitry.

[0132]

[0155] In step 1920, charged particles emitted from the sample upon interaction with the primary electron beam (e.g., beam 300B1 in FIG. 3) are detected using a charged particle detector, such as a BSE detector (e.g., BSE detector 713 in FIGS. 7A-7D). The BSE detector may include multiple concentric segments of charged particle-sensitive material configured to detect backscattered electrons emitted from the sample. Each segment may be configured to collect emitted charged particles having a range of energy levels and a predominant energy level within the range of energy levels. The energy of a BSE may be correlated to the depth into the sample from which the BSE is emitted. For example, a higher energy BSE may be emitted from a shallower region of the interaction volume of the sample, and a lower energy BSE may be emitted from a deeper region of the interaction volume. Based on this correlation, the peak BSE energy detected by a segment of the BSE detector may correspond to the depth into the sample from which the BSE is emitted.

[0133]

[0156] In step 1930, multiple images of features within the region of the sample are generated. Each segment of the multiple concentric segments is configured to generate an image based on the total number of BSEs detected by that segment. The image generated by each segment may carry information associated with features at a particular depth. For example, a segment closer to the primary optical axis (e.g., primary optical axis 300-1 in FIG. 3 ) may detect BSEs with lower peak energies compared to a segment further from the primary optical axis that may detect BSEs with higher peak energies. A BSE with a lower peak energy may indicate that the BSE is emitted from a deeper region of the sample and therefore carries information related to the bottom of the feature. A BSE with a higher peak energy may indicate that the BSE is emitted from a shallower region of the sample and therefore carries information related to the top of the feature.

[0134]

[0157] In step 1940, a three-dimensional (3D) image may be formed from the multiple images generated in step 1930. The formed 3D image may provide a high quality image of the features of interest in a single scan of the sample.

[0135]

[0158] Reference is now made to Figure 20, which shows a process flow diagram illustrating an exemplary method 2000 of imaging a sample using a charged particle beam device, such as device 300 of Figure 3, consistent with embodiments of the present disclosure.

[0136]

[0159] In step 2010, a region of the sample containing the feature is irradiated with a primary charged particle beam. The primary charged particle beam may include a primary electron beam. A controller (e.g., controller 50 of FIG. 1 ) is configured to apply a voltage signal to a cathode of an electron source configured to generate a plurality of primary electrons that form the primary electron beam. The electron source may be operated remotely, for example, by using software, an application, or a set of instructions for a processor of the controller to power the electron source via control circuitry.

[0137]

[0160] In step 2020, charged particles emitted from the sample upon interaction with the primary electron beam (e.g., beam 300B1 in FIG. 3) are detected using a charged particle detector, such as a BSE detector (e.g., BSE detector 713 in FIGS. 7A-7D). The BSE detector may include multiple concentric segments of charged particle-sensitive material configured to detect backscattered electrons emitted from the sample. Each segment may be configured to collect emitted charged particles having a range of energy levels and a predominant energy level within the range of energy levels. The energy of a BSE may be correlated to the depth into the sample from which the BSE is emitted. For example, a higher energy BSE may be emitted from a shallower region of the interaction volume of the sample, and a lower energy BSE may be emitted from a deeper region of the interaction volume. Based on this correlation, the peak BSE energy detected by a segment of the BSE detector may correspond to the depth into the sample from which the BSE is emitted.

[0138]

[0161] In step 2030, an image (e.g., a two-dimensional image) of a desired portion of the feature may be generated from BSEs detected by one of the multiple concentric segments of the BSE detector. For example, if the desired portion of the feature is the top, a high-contrast image may be generated from BSEs detected by one or more segments further from the primary optical axis (e.g., primary optical axis 300-1 in FIG. 3) that are configured to detect high-energy BSEs. In some embodiments, a three-dimensional (3D) image may be formed using multiple high-contrast 2D images generated based on BSEs detected by segments having a desired peak energy and a desired range of energy levels.

[0139]

[0162] Although the listed examples and apparatus discuss a single-beam inspection system, it should be understood that the disclosed systems and methods for energy discrimination of BSEs at the bottom BSE detector can also be implemented in a multi-beam inspection system.

[0140]

[0163] A non-transitory computer-readable medium may be provided that stores instructions for a processor of a controller (e.g., a central processing unit or electronic controller configured to control a charged particle beam device) to perform a method according to the exemplary flowcharts or other methods consistent with embodiments of the present disclosure. For example, the instructions stored on the non-transitory computer-readable medium may be executed by circuitry of the controller to implement a method, in part or in whole. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, a hard disk, a solid-state drive, a magnetic tape or any other magnetic data storage medium, a compact disk read-only memory (CD-ROM), any other optical data storage medium, any physical medium with a pattern of holes, random access memory (RAM), programmable read-only memory (PROM) and erasable programmable read-only memory (EPROM), flash EPROM or any other flash memory, non-volatile random access memory (NVRAM), cache, registers, any other memory chip or cartridge, and network-connected versions thereof.

[0141]

[0164] The block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block in the schematic diagrams may represent a specific arithmetic or logical operation that may be implemented using hardware, such as electronic circuits. The blocks may also represent modules, segments, or portions of code that include one or more executable instructions for performing the specified logical function(s). It should be understood that in some alternative implementations, the functions shown in the blocks may occur in a different order than that depicted in the figures. For example, depending on the functionality involved, two blocks shown in succession may be executed or performed substantially simultaneously, or the two blocks may sometimes be executed in the reverse order. Some blocks may also be omitted. It should also be understood that each block of the block diagrams, and combinations of blocks, may be implemented by a dedicated hardware-based system that performs the specified functions or operations, or by a combination of dedicated hardware and computer instructions.

[0142]

[0165] The embodiments may be further described using the following clauses: 1. A charged particle beam device comprising: a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; a charged particle detector including a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample; A charged particle beam device, wherein each segment of the plurality of concentric segments is configured to collect emitted charged particles having an energy level range and a predominant energy level. 2. The apparatus of clause 1, wherein the segments of the plurality of concentric segments are separated by a charged particle insensitive material. 3. A device described in any one of clauses 1 and 2, wherein the plurality of concentric segments are arranged concentrically around the primary optical axis. 4. A device described in any one of clauses 1 to 3, wherein the predominant energy level of segments located at off-axis distances smaller than the threshold off-axis distance is lower than the predominant energy level of segments located at off-axis distances greater than the threshold off-axis distance. 5. An apparatus described in any one of clauses 1 to 4, wherein the charged particle detector includes a detection surface configured to directly receive charged particles emitted from the sample, the detection surface including a plurality of concentric segments of charged particle sensitive material. 6. An apparatus described in any one of clauses 1 to 5, wherein the z-axis position of the sample is adjustable along the primary optical axis, and the adjustment of the z-axis position of the sample is based on the landing energy of the primary charged particles. 7. The apparatus of clause 6, wherein adjusting the z-axis position of the sample relative to the charged particle detector allows for influencing the predominant energy level of one of the multiple concentric segments. 8. The apparatus of clause 7, further enabling adjustment of the z-axis position of the sample relative to the charged particle detector to affect the range of energy levels detected by segments of the charged particle detector. 9. An apparatus described in any one of clauses 7 and 8, wherein adjusting the z-axis position of the sample relative to the charged particle detector further enables the uniformity of the collection efficiency of emitted charged particles across multiple concentric segments to be affected. 10. The apparatus described in clause 9, wherein adjusting the z-axis position of the sample relative to the charged particle detector increases the working distance between the sample and the charged particle detector, and the increase in working distance allows for an increase in the uniformity of the collection efficiency of the emitted charged particles for the multiple concentric segments. 11. The apparatus of clause 1, wherein the z-axis position of the charged particle detector is adjustable along the primary optical axis. 12. The apparatus of clause 11, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level for each segment of the plurality of concentric segments. 13. The apparatus of clause 12, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the collection efficiency of emitted charged particles corresponding to a predominant energy level for each segment of the charged particle detector. 14. The apparatus of clause 13, wherein the collection efficiency of emitted charged particles corresponding to the predominant energy level for each segment of the charged particle detector is at least 10%. 15. The apparatus of clause 13, wherein the collection efficiency of emitted charged particles corresponding to the predominant energy level for each segment of the charged particle detector is at least 15%. 16. A charged particle beam device comprising: a compound objective lens including a magnetic lens and an electrostatic lens configured to focus the primary charged particle beam onto the surface of the sample; a charged particle detector including a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from the sample upon interaction of the primary charged particle beam with the sample; A charged particle beam device, wherein each segment of the plurality of concentric segments is configured to collect emitted charged particles having an energy level range and a predominant energy level. 17. The apparatus described in clause 16, wherein the compound objective lens is configured to provide an adjusted excitation signal that enables to influence the collection efficiency of emitted charged particles of certain segments of a plurality of concentric segments of the charged particle detector. 18. The apparatus of clause 17, configured such that an increase in the excitation signal of the compound objective lens causes an increase in the collection efficiency of a dominant energy level of the emitted charged particles relative to the collection efficiency of a non-dominant energy level of a segment of a plurality of concentric segments of the charged particle detector. 19. The apparatus of clause 17, configured such that a decrease in the excitation signal of the compound objective lens causes an increase in the collection efficiency of a dominant energy level of the emitted charged particles relative to the collection efficiency of a non-dominant energy level of a segment of a plurality of concentric segments of the charged particle detector. 20. An apparatus described in any one of clauses 17 to 19, wherein the adjustment of the excitation signal of the compound objective lens is configured to adjust the magnetic field strength, which influences the spatial distribution of emitted charged particles on multiple concentric segments of the charged particle detector. 21. An apparatus described in any one of clauses 17 to 20, configured to enable adjustment of the excitation signal of the compound objective lens to affect the contrast of an image generated from charged particles detected by a segment of the plurality of concentric segments. 22. An apparatus described in any one of clauses 17 to 21, wherein the excitation signal includes a nominal excitation signal that, when applied to the compound objective lens, enables the compound objective lens to focus the primary charged particle beam onto the sample. 23. An apparatus according to any one of clauses 16 to 22, wherein the charged particle detector is positioned between the compound objective lens and the sample. 24. An apparatus according to any one of clauses 16 to 23, further comprising a beam scanning deflector configured to compensate for changes in the focus of the primary charged particle beam incident on the surface of the sample. 25. An apparatus according to clause 24, wherein the beam scanning deflector is located immediately upstream of the pole pieces of the magnetic lens. 26. An apparatus according to any one of clauses 24 and 25, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 27. The apparatus of clause 26, wherein the beam scanning deflector is configured to receive an excitation signal to form a lens field, and adjusting the excitation signal adjusts compensation of the focus of the primary charged particle beam. 28. The apparatus according to clause 27, wherein the excitation signal of the beam scanning deflector is deactivated when a nominal excitation signal is applied to the compound objective lens. 29. An apparatus according to any one of clauses 24 to 28, wherein a voltage signal is applied to the beam scanning deflector when the excitation signal of the compound objective lens is lower than the nominal excitation signal. 30. The apparatus of clause 29, wherein the voltage signal applied to the beam scanning deflector is configured to enable the beam scanning deflector to focus the primary charged particle beam onto the surface of the sample. 31. The apparatus of any one of clauses 24 to 30, further comprising a focusing lens positioned upstream of the compound objective lens. 32. An apparatus according to clause 31, wherein when the excitation signal of the compound objective lens is higher than the nominal excitation, the focusing power of the condenser lens is adjusted to compensate for changes in the focus of the primary charged particle beam. 33. The apparatus of clause 32, wherein the focusing power of the condenser lens is reduced to form a diverging primary charged particle beam. 34. The apparatus of clause 33, further comprising an aperture array disposed upstream of the focusing lens, the aperture array comprising a plurality of apertures configured to adjust the beam current of the primary charged particle beam based on the portion of the primary charged particle beam allowed to pass. 35. Apparatus according to clause 34, wherein that portion of the primary charged particle beam allowed to pass compensates for a reduction in beam current caused by a reduction in the focusing power of the collector lens. 36. A charged particle beam device comprising: a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam that is incident on the sample along a primary optical axis; a control electrode positioned immediately upstream of the sample and configured to influence an electrostatic field adjacent to the sample based on an applied voltage signal; a charged particle detector including a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from the sample upon interaction of the primary charged particle beam with the sample; A charged particle beam device, wherein each segment of the plurality of concentric segments is configured to collect emitted charged particles having an energy level range and a predominant energy level. 37. The apparatus of clause 36, wherein the control electrode is positioned between the sample and the charged particle detector. 38. A device according to any one of clauses 36 and 37, wherein the applied voltage signal to the control electrode makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 39. The apparatus of clause 38, wherein the applied voltage signal is configured to increase collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 40. The apparatus of clause 39, wherein the applied voltage signal is configured to reduce collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 41. An apparatus described in any one of clauses 36 to 40, wherein adjustment of the applied voltage signal to the control electrode makes it possible to influence the predominant energy level of emitted charged particles detected by a segment of the plurality of concentric segments of the charged particle detector. 42. An apparatus as described in clause 41, wherein adjustment of the applied voltage signal to the control electrode enables the range of energy levels of emitted charged particles detected by a segment of the plurality of concentric segments of the charged particle detector to be affected. 43. An apparatus according to any one of clauses 36 to 42, further comprising a compound objective lens disposed immediately upstream of the charged particle detector, the compound objective lens comprising a magnetic lens and an electrostatic lens. 44. The apparatus of clause 43, wherein the compound objective lens is configured to receive a voltage signal to generate an electric field between the sample and the compound objective lens. 45. An apparatus according to clause 44, wherein the generated electric field makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 46. ​​The device according to clause 45, wherein the generated electric field makes it possible to increase the collection efficiency of emitted charged particles for each segment of the plurality of concentric segments of the charged particle detector. 47. An apparatus as described in any one of clauses 44 to 46, wherein the generated electric field is further capable of influencing the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 48. The apparatus of clause 47, wherein the generated electric field further enables increasing the energy level range of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 49. An apparatus as described in any one of clauses 44 to 46, wherein the generated electric field is further capable of influencing the predominant energy level of the charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 50. The apparatus of clause 49, wherein the generated electric field further enables an increase in the predominant energy level of the charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 51. The apparatus of clause 49, wherein the generated electric field further enables a reduction in the predominant energy level of the charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 52. A charged particle detector for use in a charged particle beam device, comprising: a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from the sample; A charged particle detector, wherein each segment of the plurality of concentric segments is configured to detect emitted charged particles having a range of energy levels and a corresponding predominant energy level. 53. A charged particle detector as described in clause 52, wherein the segments of the plurality of concentric segments are separated by a charged particle insensitive material. 54. A charged particle detector according to any one of clauses 52 and 53, wherein the plurality of concentric segments are arranged concentrically around the primary optical axis of the charged particle beam device. 55. A charged particle detector according to any one of clauses 54, further comprising a detection surface configured to directly receive the emitted charged particles, the detection surface comprising a charged particle sensitive material. 56. A charged particle detector according to clause 55, wherein the detection surface is arranged perpendicular to the primary optical axis. 57. A charged particle detector according to any one of clauses 52 to 56, wherein the corresponding predominant energy levels of segments located at off-axis distances greater than the threshold off-axis distance are higher than the corresponding predominant energy levels of segments located at off-axis distances less than the threshold off-axis distance. 58. A charged particle detector according to any one of clauses 52 to 57, wherein each segment of the plurality of concentric segments is circular. 59. A charged particle detector according to any one of clauses 52 to 57, wherein each segment of the plurality of concentric segments is a polygon. 60. A charged particle detector according to any one of clauses 52 to 59, further comprising a central aperture aligned with the primary optical axis and configured to pass the primary charged particle beam. 61. A charged particle detector according to any one of clauses 52 to 60, wherein the width of each segment of the plurality of concentric segments is substantially similar. 62. A charged particle detector according to any one of clauses 52 to 61, wherein the emitted charged particles include backscattered electrons. 63. A method for imaging a sample, comprising: irradiating a region of a sample with a primary charged particle beam, the region including a feature; using each of the plurality of concentric segments of the charged particle detector to detect charged particles emitted from the region of the sample; generating a plurality of images of the feature, each image of the plurality of images being generated from the charged particles detected by a corresponding segment of the plurality of concentric segments of the charged particle detector; determining a characteristic of the feature based on the plurality of images; A method, wherein each segment of the plurality of concentric segments is configured to detect emitted charged particles having a range of energy levels and a predominant energy level. 64. The method of clause 63, wherein the range of energy levels of the detected charged particles corresponds to the range of depths in the sample from which the charged particles are emitted. 65. A method according to any one of clauses 63 and 64, wherein the predominant energy level of the detected charged particles corresponds to the depth in the sample from which the charged particles are emitted. 66. A method according to any one of clauses 63 to 65, wherein multiple images of the feature are generated simultaneously during a single scan of an area of ​​the sample with the primary charged particle beam. 67. A method according to any one of clauses 63 to 66, wherein configuring each segment comprises adjusting the z-axis position of the sample along the primary optical axis of the primary charged particle beam. 68. The method of clause 67, wherein adjusting the z-axis position of the sample allows for influencing the predominant energy levels detected by the segments of the charged particle detector. 69. The method of any one of clauses 67 and 68, wherein adjusting the z-axis position of the sample further enables the range of energy levels detected by the segments of the charged particle detector to be influenced. 70. The method of any one of clauses 67 to 69, wherein adjusting the z-axis position of the sample further enables the uniformity of collection efficiency of multiple segments across the charged particle detector to be affected. 71. The method of clause 70, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and increasing the working distance makes it possible to increase the uniformity of the collection efficiency of multiple segments of the charged particle detector. 72. The method of any one of clauses 63 to 71, wherein configuring each segment includes adjusting the z-axis position of the charged particle detector relative to the sample. 73. The method of clause 72, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level detected by each segment of the charged particle detector. 74. The method of clauses 72 and 73, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the collection efficiency of emitted charged particles of a predominant energy level for each of a plurality of segments of the charged particle detector. 75. The method of any one of clauses 63 to 74, wherein configuring each segment further comprises adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of a compound objective lens, the compound objective lens comprising a magnetic lens and an electrostatic lens. 76. The method according to clause 75, wherein adjusting the magnetic field strength makes it possible to influence the spatial distribution of emitted charged particles incident on the detection surface of each segment of the charged particle detector. 77. A method according to any one of clauses 75 and 76, wherein adjusting the magnetic field strength makes it possible to influence, for each segment of the charged particle detector, the collection efficiency of the predominant energy level of the emitted charged particles. 78. A method according to any one of clauses 75 to 77, wherein increasing the magnetic field strength enables increasing the collection efficiency of non-dominant energy levels of emitted charged particles for a first segment of a plurality of segments of the charged particle detector. 79. The method of clause 78, wherein reducing the magnetic field strength enables increasing the collection efficiency of a non-dominant energy level of emitted charged particles for a second segment of the plurality of segments of the charged particle detector. 80. The method of any one of clauses 75 to 79, wherein adjusting the magnetic field strength allows for affecting the image contrast of the generated multiple images. 81. The method of any one of clauses 75 to 80, wherein adjusting the excitation signal includes adjusting a voltage signal applied to a magnetic lens of the compound objective lens. 82. The method of any one of clauses 75 to 81, wherein configuring each segment further comprises adjusting the electric field between the sample and the composite objective lens by adjusting a voltage signal applied to an electrostatic lens of the composite objective lens. 83. The method according to clause 82, wherein adjusting the electric field makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 84. The method of clause 83, wherein adjusting the electric field enables increasing the collection efficiency of emitted charged particles for each segment of the plurality of concentric segments of the charged particle detector. 85. The method of any one of clauses 82 to 84, wherein adjusting the electric field further enables influencing the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 86. The method of clause 85, wherein adjusting the electric field further enables increasing the energy level range of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 87. The method of any one of clauses 82 to 86, wherein adjusting the electric field further enables influencing the predominant energy level of the emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 88. The method of clause 87, wherein adjusting the electric field further enables increasing the predominant energy level of the emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 89. The method of clause 87, wherein adjusting the electric field further enables reducing a predominant energy level of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 90. The method of any one of clauses 75 to 81, further comprising using a beam scanning deflector to compensate for focus changes in the primary charged particle beam caused by adjusting the magnetic field strength of the compound objective lens. 91. The method of clause 90, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 92. The method according to any one of clauses 90 and 91, wherein adjusting the excitation signal of the beam scanning deflector makes it possible to adjust compensation for changes in focus of the primary charged particle beam. 93. The method of clause 92, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector. 94. The method of any one of clauses 92-93, further comprising deactivating the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample. 95. The method of any one of clauses 90 to 94, further comprising adjusting the focusing power of a focusing lens positioned upstream of the compound objective lens when the excitation signal applied to the compound objective lens is higher than the nominal excitation signal. 96. The method of clause 95, wherein adjusting the focusing power includes decreasing the focusing power of the focusing lens to enable formation of a diverging primary charged particle beam. 97. The method of clause 96, further comprising passing the primary charged particle beam through an aperture of an aperture array arranged upstream of the focusing lens, the aperture being configured to pass a portion of the primary charged particle beam, the passed portion compensating for a reduced beam current of the diverging primary charged particle beam. 98. The method of any one of clauses 90 to 97, wherein configuring each segment includes adjusting the electrostatic field adjacent to the sample by applying a voltage signal to a control electrode located immediately upstream of the sample. 99. The method according to clause 98, wherein adjusting the electrostatic field makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 100. The method of clause 99, wherein adjusting the electrostatic field enables increasing the collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 101. The method of clause 100, wherein adjusting the electrostatic field enables reducing the collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 102. A method according to any one of clauses 98 to 101, wherein adjusting the electrostatic field makes it possible to influence the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 103. The method of clause 102, wherein adjusting the electrostatic field allows for influencing the range of energy levels of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 104. Determining the characteristics of a feature forming a three-dimensional image of the feature from the plurality of images; and determining features from the three-dimensional image. 105. The method of any one of clauses 63-104, wherein the characteristics include feature overlay, sidewall angle, critical dimension, or depth profile. 106. A charged particle beam device comprising: a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; a charged particle detector including a plurality of segments concentric with the primary charged particle beam and configured to detect charged particles emitted from the sample; A controller including circuitry, irradiating an area of ​​the sample containing the feature with a primary charged particle beam; generating a plurality of images of the illuminated area, each image of the plurality of images being generated from the charged particles detected by a corresponding segment of the charged particle detector; determining feature characteristics based on the plurality of images; and a controller including circuitry configured such that segmenting the charged particle detector enables discrimination of emitted charged particles according to the corresponding predominant energy level and corresponding energy level range of each segment. 107. The apparatus of clause 106, wherein the segments of the plurality of concentric segments are separated by a charged particle insensitive material. 108. A device according to any one of clauses 106 and 107, wherein the plurality of concentric segments are arranged concentrically around the primary optical axis. 109. An apparatus described in any one of clauses 106 to 108, wherein the predominant energy level of a segment located at an off-axis distance less than the threshold off-axis distance is lower than the predominant energy level of a segment located at an off-axis distance greater than the threshold off-axis distance. 110. An apparatus according to any one of clauses 106 to 109, wherein the charged particle detector includes a detection surface configured to directly receive charged particles emitted from the sample, the detection surface including a plurality of concentric segments of charged particle sensitive material. 111. An apparatus described in any one of clauses 106 to 110, wherein the z-axis position of the sample is adjustable along the primary optical axis, and the adjustment of the z-axis position of the sample is based on the landing energy of the primary charged particles. 112. The apparatus of clause 111, wherein adjusting the z-axis position of the sample relative to the charged particle detector allows for influencing the predominant energy level of one of the multiple concentric segments. 113. The apparatus of clause 112, further enabling adjustment of the z-axis position of the sample relative to the charged particle detector to affect the range of energy levels detected by segments of the charged particle detector. 114. An apparatus described in any one of clauses 112 and 113, wherein adjusting the z-axis position of the sample relative to the charged particle detector further enables the uniformity of the collection efficiency of emitted charged particles across multiple concentric segments to be influenced. 115. The apparatus of clause 114, wherein adjusting the z-axis position of the sample relative to the charged particle detector increases the working distance between the sample and the charged particle detector, and the increased working distance enables increased uniformity in the collection efficiency of the emitted charged particles for the multiple concentric segments. 116. The apparatus of clause 115, wherein the z-axis position of the charged particle detector is adjustable along the primary optical axis. 117. The apparatus of clause 116, wherein adjustment of the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level of each segment of the plurality of concentric segments. 118. An apparatus according to clause 117, wherein adjustment of the z-axis position of the charged particle detector relative to the sample makes it possible to influence the collection efficiency of emitted charged particles corresponding to the predominant energy level of each segment of the charged particle detector. 119. The apparatus according to clause 118, wherein the collection efficiency of emitted charged particles corresponding to the predominant energy level of each segment of the charged particle detector is at least 10%. 120. The apparatus according to clause 118, wherein the collection efficiency of emitted charged particles corresponding to the predominant energy level of each segment of the charged particle detector is at least 15%. 121. An apparatus according to any one of clauses 106 to 120, further comprising a compound objective lens comprising a magnetic lens and an electrostatic lens, configured to focus the primary charged particle beam onto the surface of the sample. 122. The apparatus described in clause 121, wherein the compound objective lens is configured to provide an excitation signal adjusted to enable the collection efficiency of emitted charged particles of a segment of a plurality of concentric segments of the charged particle detector to be influenced. 123. The apparatus described in clause 122, configured such that an increase in the excitation signal of the compound objective lens causes an increase in the collection efficiency of a dominant energy level of the emitted charged particles relative to the collection efficiency of a non-dominant energy level of a segment of a plurality of concentric segments of the charged particle detector. 124. The apparatus described in clause 122, configured such that a decrease in the excitation signal of the compound objective lens causes an increase in the collection efficiency of a dominant energy level of the emitted charged particles relative to the collection efficiency of a non-dominant energy level of a segment of a plurality of concentric segments of the charged particle detector. 125. An apparatus described in any one of clauses 122 to 124, wherein the adjustment of the excitation signal of the compound objective lens is configured to adjust the magnetic field strength, which influences the spatial distribution of emitted charged particles on multiple concentric segments of the charged particle detector. 126. An apparatus described in any one of clauses 122 to 125, configured such that adjustment of the excitation signal of the compound objective lens can affect the contrast of an image generated from charged particles detected by a segment of the plurality of concentric segments. 127. An apparatus described in any one of clauses 122 to 126, wherein the excitation signal includes a nominal excitation signal, which is configured to enable the compound objective lens to focus the primary charged particle beam onto the sample when applied to the compound objective lens. 128. An apparatus according to any one of clauses 121 to 127, wherein the charged particle detector is positioned between the compound objective lens and the sample. 129. An apparatus according to any one of clauses 121 to 128, further comprising a beam scanning deflector configured to compensate for changes in the focus of the primary charged particle beam incident on the surface of the sample. 130. An apparatus according to clause 129, wherein the beam scanning deflector is located immediately upstream of the pole pieces of the magnetic lens. 131. An apparatus according to any one of clauses 129 and 130, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 132. The apparatus according to clause 131, wherein the beam scanning deflector is configured to receive an excitation signal to form a lens field, and adjusting the excitation signal adjusts compensation of the focus of the primary charged particle beam. 133. The apparatus according to clause 132, wherein the excitation signal of the beam scanning deflector is deactivated when a nominal excitation signal is applied to the compound objective lens. 134. An apparatus according to any one of clauses 129 to 133, wherein a voltage signal is applied to the beam scanning deflector when the excitation signal of the compound objective lens is lower than the nominal excitation signal. 135. The apparatus of clause 134, wherein the voltage signal applied to the beam scanning deflector is configured to enable the beam scanning deflector to focus the primary charged particle beam onto the surface of the sample. 136. The apparatus of any one of clauses 129 to 135, further comprising a focusing lens positioned upstream of the compound objective lens. 137. An apparatus according to clause 136, wherein when the excitation signal of the compound objective lens is higher than the nominal excitation, the focusing power of the condenser lens is adjusted to compensate for changes in the focus of the primary charged particle beam. 138. An apparatus according to clause 137, wherein the focusing power of the condenser lens is reduced to form a diverging primary charged particle beam. 139. The apparatus of clause 138, further comprising an aperture array disposed upstream of the focusing lens, the aperture array comprising a plurality of apertures configured to adjust the beam current of the primary charged particle beam based on the portion of the primary charged particle beam allowed to pass. 140. Apparatus according to clause 139, wherein that portion of the primary charged particle beam allowed to pass compensates for a reduction in beam current caused by a reduction in the focusing power of the collector lens. 141. The apparatus of any one of clauses 106-140, further comprising a control electrode located immediately upstream of the sample and configured to influence an electrostatic field adjacent to the sample based on an applied voltage signal. 142. The apparatus according to clause 141, wherein the control electrode is disposed between the sample and the charged particle detector. 143. A device according to any one of clauses 141 and 142, wherein the applied voltage signal to the control electrode makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 144. The apparatus of clause 143, wherein the applied voltage signal is configured to increase collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 145. The apparatus of clause 144, wherein the applied voltage signal is configured to reduce collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 146. An apparatus described in any one of clauses 141 to 145, wherein adjustment of the applied voltage signal to the control electrode enables influencing the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 147. The apparatus of clause 146, wherein adjustment of the applied voltage signal to the control electrode allows for affecting the range of energy levels of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 148. A method for imaging a sample, comprising: irradiating a region of a sample with a primary charged particle beam, the region including a feature; using each of the plurality of concentric segments of the charged particle detector to detect charged particles emitted from that region of the sample; each segment of the plurality of concentric segments configured to detect emitted charged particles having a range of energy levels and a predominant energy level; generating an image of a portion of the feature from the charged particles collected by a segment of the plurality of concentric segments. 149. The method of clause 148, wherein the range of energy levels of the detected charged particles corresponds to the range of depths in the sample from which the charged particles are emitted. 150. A method according to any one of clauses 148 and 149, wherein the predominant energy level of the detected charged particles corresponds to the depth into the sample from which the charged particles are emitted. 151. The method of any one of clauses 148-150, wherein configuring each segment includes adjusting the z-axis position of the sample along the primary optical axis of the primary charged particle beam. 152. The method of clause 151, wherein adjusting the z-axis position of the sample allows for influencing the predominant energy levels detected by the segments of the charged particle detector. 153. The method of any one of clauses 151 and 152, wherein adjusting the z-axis position of the sample further enables influencing the range of energy levels detected by the segments of the charged particle detector. 154. The method of any one of clauses 151 to 153, wherein adjusting the z-axis position of the sample further enables the uniformity of collection efficiency of multiple segments across the charged particle detector to be affected. 155. The method of clause 154, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and increasing the working distance makes it possible to increase the uniformity of the collection efficiency of multiple segments of the charged particle detector. 156. The method of any one of clauses 151-155, wherein configuring each segment includes adjusting the z-axis position of the charged particle detector relative to the sample. 157. The method of clause 156, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level detected by each segment of the charged particle detector. 158. The method of clauses 156 and 157, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the collection efficiency of emitted charged particles of a predominant energy level for each of a plurality of segments of the charged particle detector. 159. The method of clauses 148-158, wherein configuring each segment further comprises adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of a compound objective lens, the compound objective lens comprising a magnetic lens and an electrostatic lens. 160. The method according to clause 159, wherein adjusting the magnetic field strength makes it possible to influence the spatial distribution of emitted charged particles incident on the detection surface of each segment of the charged particle detector. 161. A method according to any one of clauses 159 and 160, wherein adjusting the magnetic field strength makes it possible to influence, for each segment of the charged particle detector, the collection efficiency of the predominant energy level of the emitted charged particles. 162. A method according to any one of clauses 159 to 161, wherein increasing the magnetic field strength enables increasing the collection efficiency of non-dominant energy levels of emitted charged particles for a first segment of a plurality of segments of the charged particle detector. 163. The method of clause 162, wherein reducing the magnetic field strength enables increasing the collection efficiency of a non-dominant energy level of emitted charged particles for a second segment of the plurality of segments of the charged particle detector. 164. The method of any one of clauses 159 to 163, wherein adjusting the magnetic field strength allows for influencing the image contrast of the generated plurality of images. 165. The method of any one of clauses 159-164, wherein adjusting the excitation signal includes adjusting a voltage signal applied to a magnetic lens of the compound objective lens. 166. The method of any one of clauses 159 to 165, wherein configuring each segment further comprises adjusting the electric field between the sample and the composite objective lens by adjusting a voltage signal applied to an electrostatic lens of the composite objective lens. 167. The method according to clause 166, wherein adjusting the electric field makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 168. The method of clause 167, wherein adjusting the electric field enables increasing the collection efficiency of emitted charged particles for each segment of the plurality of concentric segments of the charged particle detector. 169. The method of any one of clauses 166 to 168, wherein adjusting the electric field further enables influencing the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 170. The method of clause 169, wherein adjusting the electric field further enables increasing the energy level range of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 171. The method of clauses 166-170, wherein adjusting the electric field further enables influencing the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 172. The method of clause 171, wherein adjusting the electric field further enables increasing a predominant energy level of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 173. The method of clause 171, wherein adjusting the electric field further enables reducing a predominant energy level of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 174. A method according to any one of clauses 159 to 164, further comprising using a beam scanning deflector to compensate for focus changes in the primary charged particle beam caused by adjusting the magnetic field strength of the compound objective lens. 175. The method of clause 174, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 176. The method according to any one of clauses 174 and 175, wherein adjusting the excitation signal of the beam scanning deflector makes it possible to adjust compensation for focus changes of the primary charged particle beam. 177. The method of clause 176, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector. 178. The method of any one of clauses 176-177, further comprising deactivating the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample. 179. The method of any one of clauses 174 to 178, further comprising adjusting the focusing power of a focusing lens positioned upstream of the compound objective lens when the excitation signal applied to the compound objective lens is higher than the nominal excitation signal. 180. The method of clause 179, wherein adjusting the focusing power includes decreasing the focusing power of the focusing lens to enable the formation of a diverging primary charged particle beam. 181. The method of clause 180, further comprising passing the primary charged particle beam through an aperture of an aperture array arranged upstream of the focusing lens, the aperture being configured to pass a portion of the primary charged particle beam, the passed portion compensating for a reduced beam current of the diverging primary charged particle beam. 182. The method of any one of clauses 174-181, wherein configuring each segment includes adjusting the electrostatic field adjacent to the sample by applying a voltage signal to a control electrode located immediately upstream of the sample. 183. The method according to clause 182, wherein adjusting the electrostatic field makes it possible to influence the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 184. The method of clause 183, wherein adjusting the electrostatic field enables increasing the collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 185. The method of clause 184, wherein adjusting the electrostatic field enables reducing the collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 186. A method according to any one of clauses 182 to 185, wherein adjusting the electrostatic field makes it possible to influence the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 187. The method of clause 186, wherein adjusting the electrostatic field allows for influencing the range of energy levels of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 188. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method, the method comprising: activating a charged particle source to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; irradiating an area of ​​the sample containing the feature with a primary charged particle beam; detecting the charged particles emitted from the sample using a charged particle detector including a plurality of segments concentric with the primary charged particle beam; generating a plurality of images of the illuminated area, each image of the plurality of images being generated from charged particles detected by a corresponding segment of the charged particle detector; determining a characteristic of a feature based on the plurality of images, wherein segmenting the charged particle detector enables differentiation of emitted charged particles by a corresponding predominant energy level and a corresponding energy level range of each segment. 189. The non-transitory computer-readable medium of clause 188, wherein the range of energy levels of the detected charged particles corresponds to a range of depths into the sample from which the charged particles are emitted. 190. The non-transitory computer-readable medium of any one of clauses 188 and 189, wherein a predominant energy level of the detected charged particles corresponds to a depth into the sample from which the charged particles are emitted. 191. A non-transitory computer-readable medium according to any one of clauses 188 to 190, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further generate multiple images simultaneously during a single scan of an area of ​​the sample with the primary charged particle beam. 192. A non-transitory computer-readable medium according to any one of clauses 188 to 191, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment includes adjusting a z-axis position of the sample along a primary optical axis of the primary charged particle beam. 193. The non-transitory computer-readable medium of clause 192, wherein adjusting the z-axis position of the sample allows for influencing the predominant energy level detected by the segments of the charged particle detector. 194. The non-transitory computer-readable medium of any one of clauses 192 and 193, wherein adjusting the z-axis position of the sample further enables affecting the energy level range detected by the segments of the charged particle detector. 195. The non-transitory computer-readable medium of any one of clauses 192 to 194, wherein adjusting the z-axis position of the sample further enables affecting the uniformity of collection efficiency of multiple segments across the charged particle detector. 196. The non-transitory computer-readable medium of clause 195, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and increasing the working distance enables increasing the uniformity of collection efficiency of multiple segments of the charged particle detector. 197. A non-transitory computer-readable medium according to any one of clauses 188 to 196, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment further comprises adjusting a z-axis position of the charged particle detector relative to the sample. 198. The non-transitory computer-readable medium of clause 197, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level detected by each segment of the charged particle detector. 199. The non-transitory computer-readable medium of clauses 197 and 198, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for affecting the collection efficiency of emitted charged particles of a predominant energy level for each of a plurality of segments of the charged particle detector. 200. The non-transitory computer-readable medium of clauses 188-199, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to configure each segment, and configuring each segment further includes adjusting a magnetic field strength experienced by the emitted charged particles by adjusting an excitation signal of a compound objective lens, and the compound objective lens includes a magnetic lens and an electrostatic lens. 201. The non-transitory computer-readable medium of clause 200, wherein adjusting the magnetic field strength enables influencing the spatial distribution of emitted charged particles incident on a detection surface of each segment of the charged particle detector. 202. The non-transitory computer-readable medium of any one of clauses 200 and 201, wherein adjusting the magnetic field strength enables affecting the collection efficiency of a predominant energy level of emitted charged particles for each segment of the charged particle detector. 203. The non-transitory computer-readable medium of any one of clauses 200-202, wherein increasing the magnetic field strength enables increasing the collection efficiency of non-dominant energy levels of emitted charged particles for a first segment of a plurality of segments of a charged particle detector. 204. The transient computer-readable medium of clause 203, wherein reducing the magnetic field strength enables increasing collection efficiency of a non-dominant energy level of emitted charged particles for a second segment of the plurality of segments of the charged particle detector. 205. The non-transitory computer-readable medium of any one of clauses 200-204, wherein adjusting the magnetic field strength allows for affecting image contrast of the generated plurality of images. 206. A non-transitory computer-readable medium according to any one of clauses 200 to 205, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to adjust a voltage signal applied to a magnetic lens of the compound objective lens. 207. A non-transitory computer-readable medium according to any one of clauses 200 to 206, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment further comprises adjusting an electric field between the sample and the composite objective lens by adjusting a voltage signal applied to an electrostatic lens of the composite objective lens. 208. The non-transitory computer-readable medium of clause 207, wherein adjusting the electric field enables affecting the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 209. The non-transitory computer-readable medium of clause 208, wherein adjusting the electric field enables increasing the collection efficiency of emitted charged particles for each segment of the plurality of concentric segments of the charged particle detector. 210. A non-transitory computer-readable medium described in any one of clauses 207 to 209, wherein adjusting the electric field further enables affecting the energy level range of emitted charged particles detected by a segment of multiple concentric segments of the charged particle detector. 211. The non-transitory computer-readable medium of clause 210, wherein adjusting the electric field further enables increasing the energy level range of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 212. A non-transitory computer-readable medium described in any one of clauses 207 to 211, wherein adjusting the electric field further enables influencing the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 213. The non-transitory computer-readable medium of clause 212, wherein adjusting the electric field further enables increasing a predominant energy level of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 214. The non-transitory computer-readable medium of clause 212, wherein adjusting the electric field further enables reducing a predominant energy level of emitted charged particles detected by the segment of a plurality of concentric segments of the charged particle detector. 215. A non-transitory computer-readable medium according to any one of clauses 200-206, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to use a beam scanning deflector to further compensate for changes in focus of the primary charged particle beam caused by adjustment of the magnetic field strength of the compound objective lens. 216. The non-transitory computer-readable medium of clause 215, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 217. The non-transitory computer-readable medium of any one of clauses 215 and 216, wherein adjusting the excitation signal of the beam scanning deflector enables adjusting compensation for focus changes of the primary charged particle beam. 218. The non-transitory computer-readable medium of clause 217, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to adjust an excitation signal of a beam scanning deflector, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector. 219. A non-transitory computer-readable medium according to any one of clauses 217-218, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to deactivate an excitation signal of a beam scanning deflector when the primary charged particle beam is focused on the sample. 220. A non-transitory computer-readable medium according to any one of clauses 215 to 219, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further adjust the focusing power of a focusing lens positioned upstream of the compound objective lens when the excitation signal applied to the compound objective lens is higher than the nominal excitation signal. 221. The non-transitory computer-readable medium of clause 220, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to reduce the focusing power of the focusing lens to enable the formation of a diverging primary charged particle beam. 222. The non-transitory computer readable medium of clause 221, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to allow the primary charged particle beam to pass through an aperture of an aperture array located upstream of the focusing lens, the aperture being configured to allow a portion of the primary charged particle beam to pass through, the portion allowed to pass compensating for a reduction in beam current of the diverging primary charged particle beam. 223. The non-transitory computer-readable medium of any one of clauses 215-222, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to configure each segment, and configuring each segment includes adjusting an electrostatic field adjacent to the sample by applying a voltage signal to a control electrode located immediately upstream of the sample. 224. The non-transitory computer-readable medium of clause 223, wherein adjusting the electrostatic field enables affecting the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 225. The non-transitory computer-readable medium of clause 224, wherein adjusting the electrostatic field enables increasing collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 226. The non-transitory computer-readable medium of clause 225, wherein adjusting the electrostatic field enables reducing collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 227. A non-transitory computer-readable medium described in any one of clauses 223 to 226, wherein adjusting the electrostatic field enables influencing the predominant energy level of emitted charged particles detected by a segment of multiple concentric segments of the charged particle detector. 228. The non-transitory computer-readable medium of clause 227, wherein adjusting the electrostatic field enables affecting the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 229. Determining the characteristics of a feature is forming a three-dimensional image of the feature from the plurality of images; and determining features from the three-dimensional image. 230. The non-transitory computer-readable medium of any one of clauses 188-229, wherein the characteristics include feature overlay, sidewall angle, critical dimension, or depth profile. 231. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method, the method comprising: activating a charged particle source to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; irradiating an area of ​​the sample containing the feature with a primary charged particle beam; using each of the plurality of concentric segments of the charged particle detector to detect charged particles emitted from that region of the sample; each segment of the plurality of concentric segments configured to detect emitted charged particles having a range of energy levels and a predominant energy level; and generating an image of a portion of the feature from charged particles collected by a segment of the plurality of concentric segments. 232. The non-transitory computer-readable medium of clause 231, wherein a range of energy levels of the detected charged particles corresponds to a range of depths into the sample from which the charged particles are emitted. 233. The non-transitory computer-readable medium of any one of clauses 231 and 232, wherein a predominant energy level of the detected charged particles corresponds to a depth into the sample from which the charged particles are emitted. 234. A non-transitory computer-readable medium according to any one of clauses 231 to 233, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment includes adjusting a z-axis position of the sample along a primary optical axis of the primary charged particle beam. 235. The non-transitory computer-readable medium of clause 234, wherein adjusting the z-axis position of the sample allows for influencing the predominant energy level detected by the segments of the charged particle detector. 236. The non-transitory computer-readable medium of any one of clauses 234 and 235, wherein adjusting the z-axis position of the sample further enables affecting the energy level range detected by the segments of the charged particle detector. 237. The non-transitory computer-readable medium of any one of clauses 234 to 236, wherein adjusting the z-axis position of the sample further enables affecting the uniformity of collection efficiency of multiple segments across the charged particle detector. 238. The non-transitory computer-readable medium of clause 237, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and increasing the working distance enables increasing the uniformity of collection efficiency of multiple segments of the charged particle detector. 239. The non-transitory computer-readable medium of any one of clauses 234 to 238, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment further includes adjusting a z-axis position of the charged particle detector relative to the sample. 240. The non-transitory computer-readable medium of clause 239, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level detected by each segment of the charged particle detector. 241. The non-transitory computer-readable medium of clauses 239 and 240, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables affecting the collection efficiency of emitted charged particles of a predominant energy level for each of a plurality of segments of the charged particle detector. 242. A non-transitory computer-readable medium according to any one of clauses 231 to 241, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to configure each segment, and configuring each segment further comprises adjusting the magnetic field strength experienced by the emitted charged particles by adjusting an excitation signal of a compound objective lens, the compound objective lens including a magnetic lens and an electrostatic lens. 243. The non-transitory computer-readable medium of clause 242, wherein adjusting the magnetic field strength enables influencing the spatial distribution of emitted charged particles incident on the detection surface of each segment of the charged particle detector. 244. The non-transitory computer-readable medium of any one of clauses 242 and 243, wherein adjusting the magnetic field strength allows for influencing the collection efficiency of the predominant energy level of emitted charged particles for each segment of the charged particle detector. 245. The non-transitory computer-readable medium of any one of clauses 242-244, wherein increasing the magnetic field strength enables increasing the collection efficiency of non-dominant energy levels of emitted charged particles for a first segment of a plurality of segments of a charged particle detector. 246. The transient computer-readable medium of clause 245, wherein reducing the magnetic field strength enables increasing the collection efficiency of a non-dominant energy level of the emitted charged particles for a second segment of the plurality of segments of the charged particle detector. 247. The non-transitory computer-readable medium of any one of clauses 242 to 246, wherein adjusting the magnetic field strength allows for affecting the image contrast of the generated plurality of images. 248. A non-transitory computer-readable medium according to any one of clauses 242 to 247, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to adjust an excitation signal, wherein adjusting the excitation signal includes adjusting a voltage signal applied to a magnetic lens of the compound objective lens. 249. A non-transitory computer-readable medium according to any one of clauses 242 to 248, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to further configure each segment, and configuring each segment further comprises adjusting an electric field between the sample and the compound objective lens by adjusting a voltage signal applied to an electrostatic lens of the compound objective lens. 250. The non-transitory computer-readable medium of clause 249, wherein adjusting the electric field enables affecting the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 251. The non-transitory computer-readable medium of clause 250, wherein adjusting the electric field enables increasing the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 252. A non-transitory computer-readable medium described in any one of clauses 249 to 251, wherein adjusting the electric field further enables influencing the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 253. The non-transitory computer-readable medium of clause 252, wherein adjusting the electric field further enables increasing the energy level range of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 254. A non-transitory computer-readable medium described in any one of clauses 249 to 253, wherein adjusting the electric field further enables influencing the predominant energy level of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector. 255. The non-transitory computer-readable medium of clause 254, wherein adjusting the electric field further enables increasing a predominant energy level of emitted charged particles detected by the segment of the plurality of concentric segments of the charged particle detector. 256. The non-transitory computer-readable medium of clause 254, wherein adjusting the electric field further enables reducing a predominant energy level of emitted charged particles detected by the segment of a plurality of concentric segments of the charged particle detector. 257. A non-transitory computer-readable medium according to any one of clauses 231 to 256, wherein the set of instructions is executable by one or more processors to cause the charged particle beam device to use a beam scanning deflector to further compensate for changes in focus of the primary charged particle beam caused by adjustment of the magnetic field strength of the compound objective lens. 258. The non-transitory computer-readable medium of clause 257, wherein the beam scanning deflector comprises a plurality of electrodes, the plurality of electrodes being equipotential and forming a lens field. 259. The non-transitory computer-readable medium of any one of clauses 257 and 258, wherein adjusting the excitation signal of the beam scanning deflector enables adjusting compensation for focus changes of the primary charged particle beam. 260. The non-transitory computer-readable medium of clause 259, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector. 261. The non-transitory computer-readable medium of any one of clauses 259 and 260, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to deactivate an excitation signal of a beam scanning deflector when the primary charged particle beam is focused on the sample. 262. A non-transitory computer-readable medium according to any one of clauses 257 to 261, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to adjust the focusing power of a focusing lens positioned upstream of the compound objective lens when the excitation signal applied to the compound objective lens is higher than the nominal excitation signal. 263. The non-transitory computer-readable medium of clause 262, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to adjust the focusing power, wherein adjusting the focusing power includes decreasing the focusing power of the focusing lens to enable formation of a diverging primary charged particle beam. 264. The non-transitory computer readable medium of clause 263, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to allow the primary charged particle beam to pass through an aperture of an aperture array located upstream of the focusing lens, the aperture being configured to allow a portion of the primary charged particle beam to pass through, the portion allowed to pass compensating for a reduction in beam current of the diverging primary charged particle beam. 265. A non-transitory computer-readable medium according to any one of clauses 257 to 264, wherein the set of instructions is executable by one or more processors to further cause the charged particle beam device to configure each segment, and configuring each segment further comprises adjusting an electrostatic field adjacent to the sample by applying a voltage signal to a control electrode located immediately upstream of the sample. 266. The non-transitory computer-readable medium of clause 265, wherein adjusting the electrostatic field enables affecting the collection efficiency of emitted charged particles for each segment of a plurality of concentric segments of the charged particle detector. 267. The non-transitory computer-readable medium of clause 266, wherein adjusting the electrostatic field enables increasing collection efficiency of emitted charged particles for segments located at off-axis distances greater than a threshold off-axis distance. 268. The non-transitory computer-readable medium of clause 267, wherein adjusting the electrostatic field enables reducing collection efficiency of emitted charged particles for segments located at off-axis distances less than a threshold off-axis distance. 269. A non-transitory computer-readable medium described in any one of clauses 265 to 268, wherein adjusting the electrostatic field enables influencing the predominant energy level of emitted charged particles detected by a segment of multiple concentric segments of a charged particle detector. 270. The non-transitory computer-readable medium of clause 269, wherein adjusting the electrostatic field enables affecting the energy level range of emitted charged particles detected by a segment of a plurality of concentric segments of the charged particle detector.

[0143]

[0166] It will be understood that the embodiments of the present disclosure are not limited to the exact construction described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof.

Claims

1. 1. A charged particle beam device, comprising: a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; a charged particle detector including a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample; A charged particle beam device, wherein each segment of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a predominant energy level.

2. The apparatus of claim 1 , wherein segments of the plurality of concentric segments are separated by a charged particle insensitive material.

3. The apparatus of claim 1 , wherein the plurality of concentric segments are arranged concentrically about the primary optical axis.

4. 2. The apparatus of claim 1, wherein the dominant energy level of segments located at off-axis distances less than a threshold off-axis distance is lower than the dominant energy level of segments located at off-axis distances greater than the threshold off-axis distance.

5. 2. The apparatus of claim 1, wherein the charged particle detector includes a detection surface configured to directly receive the emitted charged particles from the sample, the detection surface including the charged particle sensitive material of the plurality of concentric segments.

6. 10. The apparatus of claim 1, wherein a z-axis position of the sample is adjustable along the primary optical axis, and the adjustment of the z-axis position of the sample is based on a landing energy of the primary charged particles.

7. 7. The apparatus of claim 6, wherein adjusting the z-axis position of the sample relative to the charged particle detector allows for influencing the dominant energy level for a segment of the plurality of concentric segments.

8. 8. The apparatus of claim 7, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector further enables the range of energy levels detected by segments of the charged particle detector to be affected.

9. 8. The apparatus of claim 7, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector further enables affecting uniformity of collection efficiency of emitted charged particles across the plurality of concentric segments.

10. 10. The apparatus of claim 9, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector increases a working distance between the sample and the charged particle detector, the increase in the working distance enabling an increase in the uniformity of collection efficiency of the emitted charged particles for the plurality of concentric segments.

11. The apparatus of claim 1 , wherein a z-axis position of the charged particle detector is adjustable along the primary optical axis.

12. 12. The apparatus of claim 11, wherein adjusting the z-axis position of the charged particle detector relative to the sample allows for influencing the predominant energy level for each segment of the plurality of concentric segments.

13. 13. The apparatus of claim 12, wherein the adjustment of the z-axis position of the charged particle detector relative to the sample enables affecting collection efficiency of emitted charged particles corresponding to the predominant energy level for each segment of the charged particle detector.

14. 14. The apparatus of claim 13, wherein the collection efficiency of emitted charged particles corresponding to the predominant energy level for each segment of the charged particle detector is at least 10%.

15. 1. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the device to perform a method, the method comprising: activating a charged particle source to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a primary optical axis; irradiating an area of ​​a sample containing a feature with the primary charged particle beam; detecting charged particles emitted from the sample using a charged particle detector including a plurality of segments concentric with the primary charged particle beam; generating a plurality of images of the illuminated area, each image of the plurality of images being generated from the charged particles detected by a corresponding segment of the charged particle detector; determining characteristics of the feature based on the plurality of images, wherein segmenting the charged particle detector enables differentiation of the emitted charged particles by a corresponding predominant energy level and a corresponding energy level range for each segment.

Images