System and method for energy differentiation of backscatter charged particles

Abstract

Systems and methods for imaging a sample using a charged particle beam device are disclosed. The charged particle beam apparatus 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 comprising a plurality of concentric segments of charged particle sensitive material, the plurality of concentric segments configured to detect charged particles emitted from the sample after the primary charged particle beam interacts with the sample, wherein each segment of the plurality of concentric segments is configured to collect the emitted charged particles having a range of energy levels and a primary energy level.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority to U.S. Application No. 63 / 429,684, filed on December 2, 2022, and the U.S. Application is hereby incorporated by reference in its entirety. Technical Field

[0003] The description herein relates to charged particle detectors and detection methods, and more particularly, to detectors and detection methods that can be applied to backscattered charged particles. Background Art

[0004] Detectors can be used to sense physically observable phenomena. For example, charged particle beam tools such as electron microscopes can include detectors that receive charged particles projected from a sample and output a detection signal. The detection signal can be used to reconstruct an image of the structure of the sample being inspected and can be used, for example, to reveal defects in the sample. Detecting defects in samples has become increasingly important in the manufacture of semiconductor devices, which may include a large number of densely packaged micro integrated circuit (IC) components. Inspection systems can be provided as dedicated tools for this purpose.

[0005] As semiconductor devices continue to miniaturize, the performance requirements for detection systems including detectors may also continue to increase. For example, as the aspect ratio of the vertical structure that can be used in memory devices continues to increase and design rules that may require more stringent overlay performance in DRAM and logic devices continue to shrink, electron beam (E-beam) systems with high landing energy (LE) capabilities (e.g., 30 keV and above) have attracted great interest. High LE systems show great potential in applications such as trench / hole bottom inspection, buried defect / cavity detection, and overlay / perspective metrology due to the strong penetration ability of primary electrons (PE) and the larger momentum of backscattered electrons (BSE) that can allow BSE to escape from the sample material and reach the detector. However, a large amount of energy of the PE in such systems may cause a much larger interaction volume in the sample and may cause a degradation in imaging quality. Summary of the Invention

[0006] Embodiments of the present disclosure provide systems and methods for defect detection and metrology based on charged particle beams. One aspect of the present disclosure is directed to a charged particle detector for a charged particle beam device. The charged particle detector can include a plurality of concentric segments of charged particle sensitive material configured to detect charged particles emitted from a sample, wherein each segment of the plurality of concentric segments is configured to detect the emitted charged particles having an energy level range and a corresponding main energy level.

[0007] Another aspect of the present disclosure is directed to a charged particle beam device. The charged particle beam device may include: a charged particle source configured to generate primary charged particles that form a primary charged particle beam along a main optical axis; and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material, the plurality of concentric segments being configured to detect charged particles emitted from a sample after interaction of the primary charged particle beam with the sample, wherein each of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a main energy level.

[0008] Another aspect of the present disclosure is directed to a charged particle beam device. The charged particle beam device may include: a compound lens including a magnetic lens and an electrostatic lens, the compound lens being configured to focus the primary charged particle beam on a surface of a sample; and a charged particle detector including a plurality of concentric segments of a charged particle sensitive material, the plurality of concentric segments being configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample, wherein each of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a main energy level.

[0009] Another aspect of the present disclosure is directed to a charged particle beam device. The charged particle beam device may include: a charged particle source configured to generate primary charged particles that form a primary charged particle beam along a main optical axis to be incident on a sample; a control electrode located 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, the plurality of concentric segments being configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample, wherein each of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a main energy level.

[0010] Another aspect of the present disclosure is directed to a charged particle beam apparatus. The charged particle beam apparatus may include: a charged particle source configured to generate primary charged particles that form a primary charged particle beam along a main optical axis; a charged particle detector including a plurality of segments that are concentric with the primary charged particle beam and configured to detect charged particles emitted from a sample; and a controller including circuitry configured to irradiate a region of the sample including a feature with the primary charged particle beam; generate a plurality of images of the irradiated region, wherein each of the plurality of images is 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, wherein segmenting the charged particle detector allows the emitted charged particles to be distinguished for each segment according to a corresponding main energy level and according to a corresponding energy level range.

[0011] Another aspect of the present disclosure is directed to a method of imaging a sample using a charged particle beam apparatus. The method may include: irradiating a region of the sample including a feature with a primary charged particle beam; detecting, using each of a plurality of concentric segments of a charged particle detector, charged particles emitted from the region of the sample; generating a plurality of images of the feature, wherein each of the plurality of images is generated from charged particles detected by a corresponding one of the plurality of concentric segments of the charged particle detector; and determining a characteristic of the feature based on the plurality of images, wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having an energy level range and a main energy level.

[0012] Another aspect of the present disclosure is directed to a method of imaging a sample using a charged particle beam apparatus. The method may include: irradiating a region of the sample including a feature with a primary charged particle beam; using each of a plurality of concentric segments of a charged particle detector to detect charged particles emitted from the region of the sample, wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having an energy level range and a main energy level; generating an image of a portion of the feature from the charged particles collected by the segments of the plurality of concentric segments.

[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 apparatus to cause the charged - particle beam apparatus to perform a method. The method may include: activating a charged - particle source to generate primary charged particles that form a primary charged - particle beam along a main optical axis; irradiating a region of a sample including 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 irradiated region, wherein each image of the plurality of images is generated from the charged particles detected by a corresponding segment of the charged - particle detector; and determining a characteristic of the feature based on the plurality of images, wherein segmenting the charged - particle detector allows the emitted charged particles to be distinguished for each segment according to a corresponding main energy level and within a corresponding energy - level range.

[0014] 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 apparatus to cause the charged - particle beam apparatus to perform a method. The method may include: activating a charged - particle source to generate primary charged particles that form a primary charged - particle beam along a main optical axis; irradiating a region of a sample including a feature with the primary charged - particle beam; detecting, using each of a plurality of concentric segments of a charged - particle detector, charged particles emitted from the region of the sample, wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having an energy - level range and a main 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.

[0015] It should be understood that both the foregoing general description and the following detailed description are merely exemplary and explanatory and do not limit the disclosed embodiments, as may be claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments taken in conjunction with the accompanying drawings.

[0017] Figure 1 Schematic representation of an exemplary electron - beam inspection (EBI) system consistent with embodiments of the present disclosure.

[0018] Figure 2 Illustrating an exemplary electron - beam tool capable of being part of Figure 1 an exemplary electron - beam inspection system consistent with embodiments of the present disclosure.

[0019] Figure 3Schematic diagram of an exemplary charged particle beam apparatus including a charged particle detector consistent with an embodiment of the present disclosure.

[0020] Figure 4A Schematic diagram of an exemplary charged particle beam apparatus including a segmented backscattered electron (BSE) detector consistent with an embodiment of the present disclosure.

[0021] Figure 4B Consistent with an embodiment of the present disclosure Figure 4A Top view of an exemplary segmented BSE detector.

[0022] Figure 5A Shows simulation results of the spatial and energy distributions of backscattered electrons detected on an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0023] Figure 5B Shows a graphical representation of the peak energy of charged particles detected in each segment of an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0024] Figure 6 Shows simulation trajectories of backscattered electrons emitted from a substrate at different emitter angles consistent with an embodiment of the present disclosure.

[0025] Figures 7A to 7D Shows a comparison of the energy distribution curves of backscattered electrons detected by an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0026] Figure 8 Shows a graphical representation of the collection efficiency of backscattered electrons for multiple segments of an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0027] Figure 9 Shows the spatial distribution of backscattered electrons detected by the radially concentric segments of an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0028] Figure 10A Schematic diagram of an exemplary charged particle beam apparatus including a segmented BSE detector and an adjustable working distance consistent with an embodiment of the present disclosure.

[0029] Figure 10B Data chart of BSE collection efficiency for a range of working distances across the segments of an exemplary segmented BSE detector consistent with an embodiment of the present disclosure.

[0030] Figure 11A Shows simulation paths of backscattered electrons with a fixed emission energy, emitted at different emitter angles, and emitted from a substrate adjusted to different heights consistent with an embodiment of the present disclosure.

[0031] Figure 11B Shows simulated trajectories of backscattered electrons with an emission energy range, at a fixed emitter angle, and emitted from substrates adjusted to different heights, in accordance with embodiments of the present disclosure.

[0032] Figure 12 Shows graphical representations of the collection efficiency, peak energy, and energy width of backscattered electrons collected by segments of an exemplary segmented BSE detector, for varying electric field strengths on a sample, in accordance with embodiments of the present disclosure.

[0033] Figure 13A and Figure 13B Show data graphs of the simulated peak BSE energy and BSE collection efficiency for each segment of a segmented BSE detector, for varying electric field strengths on a sample, in accordance with embodiments of the present disclosure.

[0034] Figure 14A and Figure 14B Shows a graphical representation of the BSE collection efficiency of segments of an exemplary segmented BSE detector, according to the objective lens magnetic field, in accordance with embodiments of the present disclosure.

[0035] Figure 15 Shows a series of simulated data graphs showing the effect of adjusting the magnetic field strength of the objective lens on the BSE collection efficiency of segments of a segmented BSE detector, in accordance with embodiments of the present disclosure.

[0036] Figures 16A to 16C Shows a schematic diagram of an exemplary charged particle beam apparatus configured to compensate for focus changes caused by adjusting the objective lens magnetic field strength, in accordance with embodiments of the present disclosure.

[0037] Figure 17 Is a schematic diagram of an exemplary charged particle beam apparatus including a BSE detector with an adjustable z-height, in accordance with embodiments of the present disclosure.

[0038] Figure 18 Is a graphical representation of the relationship between different BSE energy components and their corresponding collection efficiency (CE) for a range of BSE detector z-height positions, in accordance with embodiments of the present disclosure.

[0039] Figure 19 Is a flowchart of an example method of imaging a sample using a charged particle beam apparatus, in accordance with embodiments of the present disclosure.

[0040] Figure 20 Is a flowchart of an example method of imaging a sample using a charged particle beam apparatus, in accordance with embodiments of the present disclosure. Detailed Description

[0041] Reference will now be made in detail to exemplary embodiments, which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same reference numerals in different drawings denote the same or similar elements unless otherwise specified. The implementations set forth in the description of the following exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses, systems, and methods consistent with aspects related to the subject matter that may be recited in the appended claims. Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing a detection system and a detection method in a system that utilizes electron beams (“e-beams”). However, the present disclosure is not limited thereto. Other types of charged particle beams (e.g., including protons, ions, muons, or any other particle carrying a charge) may be similarly applied. Further, 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.

[0042] An electronic device is composed of circuits formed on a silicon wafer (referred to as a substrate). The semiconductor material may include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium, etc. Many circuits can be formed together on the same silicon wafer and are referred to as an integrated circuit or IC. With the advancement of technology, the size of these circuits has been significantly reduced, enabling more circuits to be installed on the substrate. For example, the IC chip in a smartphone can be as small as a fingernail, but may include more than 2 billion transistors, each transistor being less than 1 / 1000 the width of a human hair.

[0043] Fabricating these extremely small ICs is a complex, time-consuming, and expensive process, typically involving hundreds of individual steps. Even an error in one step can cause a defect in the finished IC, rendering it unusable. Thus, one goal of the manufacturing process is to avoid such defects to maximize the number of functional ICs fabricated in the process, that is, to increase the overall yield of the process.

[0044] One element in increasing the yield is to monitor the chip manufacturing process to ensure that it is producing a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip circuit structure at various stages of its formation. The inspection can be performed using a scanning electron microscope (SEM). The SEM can be used to image these extremely small structures, effectively taking “photos” of these structures. The images can be used to determine whether the structures are formed correctly and whether they are formed in the correct positions. If the structures are defective, the process can be adjusted so that the defect is less likely to occur again. To increase throughput (e.g., the number of samples processed per hour), it is desirable to perform the inspection as soon as possible.

[0045] SEM images can be composed of pixels that correspond to positions irradiated by a primary electron beam as the beam scans across the surface of the sample in a raster pattern, for example. A higher pixel resolution (e.g., the number of individual pixels that make up the image) generally corresponds to higher image quality. The more pixels, the finer the image details. As the structures of interest in an IC become smaller and smaller, it may be more important to generate SEM images with higher resolution to accurately observe the structures. However, when a primary electron beam with a high landing energy (LE) is used, the resolution may be negatively affected.

[0046] The landing energy of the primary electrons can be determined based on, for example, the difference between the source voltage and the sample voltage. For example, if the source is operated at -10 kV and the sample is applied with -5 kV, the landing energy of the primary electrons may be 5 keV. Generally, in an SEM, depending on the application, the material being studied, the tool condition, etc., the landing energy may range from 0.2 keV to 50 keV. Some of the ways to change the landing energy of the primary electrons in the primary electron beam can include adjusting the potential difference between the cathode and the extractor, adjusting the sample potential, or adjusting both simultaneously, as well as other techniques.

[0047] However, in some applications, it may be desirable to use a high landing energy in an SEM system. The electron source of the SEM can generate a primary electron beam with a high LE that is projected onto the sample. High-energy electrons can contribute to imaging because they can penetrate deeper into the material of the sample and can reveal additional information about the sample. A high-LE SEM system can achieve or enhance the inspection of the bottom of trenches or holes, the detection of buried features (such as defects or voids), and the performance of performing overlay metrology (e.g., analyzing the alignment of stacked structures). However, the higher energy of the electrons in the primary electron beam means that the electrons may interact with a relatively large volume of the sample's material (i.e., the "interaction volume") after hitting the sample. Although high-energy electrons can penetrate deeper, they may also scatter in other random directions before leaving the sample's material. Since pixels can be used to form a 2D image and the electrons may disperse in the left and right directions, such scattering may cause problems in imaging resolution.

[0048] As described above, an SEM image can be formed by pixels. When the primary electron beam of the SEM scans across the sample, secondary particles (such as secondary electrons (SE) and backscattered electrons (BSE)) can be detected by a detector, and the information collected therefrom can be used to form each pixel in the image. However, with a higher LE, the interaction volume in the sample may be increased. The increase in the interaction volume may cover a lateral region (e.g., a region defining the sides in the two-dimensional plane of the image composed of pixels). Pixels can be formed based on the information from the detected electrons, but the information from adjacent pixels may overlap. For example, the detected electrons corresponding to one pixel may include information related to structures that would be more appropriately located in an adjacent pixel. Such an effect may result in a poor resolution of the SEM image, and the resulting image may be blurred.

[0049] The accuracy, reliability, and throughput of using an SEM to inspect high-density IC chips may depend on, among other things, the image quality of the system. One way among several ways to obtain and maintain high image quality is to maximize the collection efficiency of signal electrons (such as secondary electrons (SE) and backscattered electrons (BSE)). When the primary electron strikes the surface of the sample, it interacts with a certain volume of the sample based on the landing energy, sample material, spot size, etc., and generates multiple signal electrons. BSEs have a higher energy and originate from a deeper region within the interaction volume, thus providing information related to the composition and distribution of the material. Therefore, in order to obtain a high-quality image of underlying defects or metrology of vertical high aspect ratio features, it may be desirable to maximize the detection of backscattered electrons.

[0050] In existing metrology or defect detection techniques using an SEM, a three-dimensional image of a feature of interest can be formed by performing multiple scans. In such a case, each scan generates an image based on the BSE signal from BSEs of a certain energy, and each scan may correspond to a certain depth of the sample from which the BSEs are emitted. As an example, if a high aspect ratio feature (such as a via) is to be imaged, multiple scans may be required to image the entire height or depth of the via, and each scan can collect BSEs of different energies corresponding to different depths of the via and provide information about the portion of the via located at or near that depth. This method has several drawbacks, including an increased exposure time of the feature under the probing beam, thus causing a higher likelihood of beam damage, low inspection throughput, and other problems.

[0051] One method among several methods for overcoming problems associated with multiple scans of a feature of interest may include performing a single scan that collects a substantial portion of the generated BSEs. A single BSE scan may include a range of BSE energies that correspond to the entire depth of the interaction volume of the primary beam with the sample, and extracting information about a feature of interest at a certain depth can be challenging. Although in some cases, an energy filter can be employed to allow only BSEs within a desired energy level range emitted from a desired sample depth to pass through the BSE detector. However, in high landing energy applications, for high image contrast for defect inspection and metrology of three-dimensional structures, a bottom BSE detector located between the objective lens and the sample may be desired to enhance BSE collection efficiency. In such cases, due to physical space limitations between the sample and the objective lens, employing an energy filter can be challenging. Thus, it may be desirable to provide systems and methods for differentiating BSE signals detected by the bottom BSE detector based on the energy level of the incoming BSEs.

[0052] In addition, in some applications, an energy discrimination device (such as a reflection-type energy filter) can be introduced in front of the in-lens detector to filter out (by reflecting back) secondary electrons and allow BSEs to pass through a high-voltage grid or a filter grid. The potential of the high-voltage grid can be set very high (e.g., >10 keV) to act as a barrier for BSE electrons. Although an energy filter may be useful in low landing energy applications where the energy of secondary electrons is comparable to that of BSEs and the BSEs have a small emission angle, for high landing energy applications, an energy filter with a very high grid voltage may have a negative impact on the BSE collection efficiency, thus affecting the quality of the image. In addition, the voltage applied to the grid may need to be adjusted to collect images with different BSE energies, making it impossible to collect multiple images simultaneously. Among other challenges, this method may have a negative impact on the inspection throughput.

[0053] Some aspects of the present disclosure can address some challenges by providing a segmented charged particle detector (e.g., a segmented BSE detector) configured to distinguish incoming charged particles emitted from a sample based on their energy levels. The charged particle detector can include a plurality of concentric segments of charged particle sensitive material. The concentric segments of the charged particle detector can be separated by charged particle insensitive material. Each concentric segment can be configured to collect BSEs having a corresponding energy level range and a primary energy level within the energy level range of the BSEs detected by the segment. The primary energy level of the detected BSEs can correspond to BSEs emitted from a certain depth of the sample, thereby providing information associated with features of interest at a certain depth. The BSE signals detected by each concentric segment can be used to simultaneously generate images, which can be further used to form a three-dimensional image of the features, or a high-contrast image of a certain depth of the features of interest can be obtained.

[0054] The objects and advantages of the present disclosure can be achieved by the elements and combinations thereof set forth in the embodiments discussed herein. However, the embodiments of the present disclosure are not necessarily required to achieve such exemplary objects or advantages, and some embodiments may not achieve any of the objects or advantages set forth.

[0055] Without limiting the scope of the present disclosure, some embodiments may be described in the context of systems and methods in a system utilizing electron beams (“e-beams”). However, the present disclosure is not limited thereto. Other types of charged particle beams can be similarly applied. In addition, systems and methods for wafer inspection or overlay measurement can be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0056] As used herein, unless otherwise expressly stated, the term “or” encompasses all possible combinations, unless infeasible. For example, if it is stated that a component includes A or B, then, unless otherwise expressly stated or infeasible, the component can include A, or B, or A and B. As a second example, if it is stated that a component includes A, B, or C, then, unless otherwise expressly stated or infeasible, the component can include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as “at least one of...” do not necessarily have to modify the entire following list and also do not necessarily have to modify each member of the list, such that “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 phrase “one of A and B” or “any one of A and B” should be understood most broadly to include one of A or one of B.

[0057] Now refer to Figure 1 , Figure 1 which shows an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. As Figure 1 shown, the charged particle beam inspection system 100 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, and an equipment front end module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. Although the specification and drawings are directed to electron beams, it should be understood that these embodiments are not intended to limit the present disclosure to a particular charged particle.

[0058] 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 a wafer front opening unified pod (FOUP) that contains wafers (e.g., semiconductor wafers or wafers made of other materials) or samples (wafers and samples are collectively referred to as "wafers" hereinafter) to be inspected. One or more robotic arms (not shown) in the EFEM 30 transfer the wafers to the load lock chamber 20.

[0059] The load lock chamber 20 is connected to a load / lock vacuum pump system (not shown) that removes gas molecules from the load lock chamber 20 to achieve a first pressure below atmospheric pressure. After achieving the first pressure, one or more robotic arms (not shown) transfer the wafers from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown) that removes gas molecules from the main chamber 10 to achieve a second pressure below the first pressure. After achieving the second pressure, the wafers are subjected to inspection by the electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam inspection tool.

[0060] The controller 50 may be electrically connected to the electron beam tool 40 and may also be electrically connected to other components. 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. Although the controller 50 is Figure 1 shown as being located outside the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it should be understood that the controller 50 can be part of the structure.

[0061] While the present disclosure provides examples of a main chamber 10 that houses an electron beam inspection system, it should be noted that aspects of the present disclosure are not limited, in their broadest sense, to a chamber that houses an electron beam inspection system. Rather, it should be understood that the foregoing principles can also be applied to other chambers.

[0062] Now referring Figure 2 , Figure 2 shows a schematic diagram of an exemplary configuration of an electron beam tool 40 that is part of an exemplary charged particle beam inspection system 100 that can be Figure 1 in accordance with an embodiment of the present disclosure. The electron beam tool 40 (also referred to herein as the apparatus 40) can include an electron emitter that can include a cathode 203, an extractor electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 can also 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 can also include a sample stage 236 supported by a motorized stage 234 for holding a sample 250 to be inspected. It should be understood that other relevant components can be added or omitted as needed.

[0063] In some embodiments, the electron emitter can include a cathode 203 and an anode 222, where primary electrons can be emitted from the cathode and extracted or accelerated to form a primary electron beam 204 that forms a primary beam crossover 202. The primary electron beam 204 can be visualized as being emitted from the primary beam crossover 202.

[0064] In some embodiments, the electron emitter, the condenser lens 226, the objective lens assembly 232, the beam limiting aperture array 235, and the electron detector 244 can be aligned with a main optical axis 201 of the apparatus 40. In some embodiments, the electron detector 244 can be placed off the main optical axis 201, along a secondary optical axis (not shown).

[0065] In some embodiments, the objective lens assembly 232 may include a modified swing-deceleration immersion objective lens (SORIL) that includes a pole piece 232a, a control electrode 232b, a beam manipulator assembly including deflectors 240a, 240b, 240d, and 240e, and an excitation coil 232d. During a general imaging process, the primary electron beam 204 emitted from the tip of the cathode 203 is accelerated by the acceleration voltage applied to the anode 222. A portion of the primary electron beam 204 passes through the apertures of the gun aperture 220 and the Coulomb aperture array 224 and is focused by the condenser lens 226 so as to completely or partially pass through the apertures of the beam limiting aperture array 235. The electrons passing through the apertures of the beam limiting aperture array 235 may be focused by the modified SORIL lens to form a detection point 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. The 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.

[0066] 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 can be immersed in the magnetic field and can be charged, which in turn generates an electric field. This electric field can reduce the energy of the primary electron beam 204 near and on the surface of the sample 250. The control electrode 232b, which is electrically isolated from the pole piece 232a, can control, for example, the electric field above and on the sample 250 to reduce the aberration of the objective lens assembly 232 and control the focusing of the signal electron beam to improve the detection efficiency, or avoid arc discharge to protect the sample. One or more deflectors of the beam manipulator assembly can deflect the primary electron beam 204 to facilitate beam scanning on the sample 250. For example, during scanning, the deflectors 240a, 240b, 240d, and 240e can be controlled to deflect the primary electron beam 204 to different positions on the top surface of the sample 250 at different time points to provide data for image reconstruction for different portions of the sample 250. It should be noted that the order of 240a - e may vary in different embodiments.

[0067] After receiving the primary electron beam 204, backscattered electrons (BSE) and secondary electrons (SE) can be emitted from portions of the sample 250. The beam splitter 240c can direct the (multiple) secondary or scattered electron beam including the backscattered electrons and secondary electrons to the sensor surface of the electron detector 244. The detected secondary electron beam can form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 can 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 generated secondary electron beam spot can vary according to the external or internal structure of the sample 250. Additionally, as described above, the primary electron beam 204 can be deflected to different positions on the top surface of the sample 250 to generate secondary electron beams or scattered electron beams (and the generated beam spots) of different intensities. Thus, by mapping the intensity of the secondary electron beam spots to the positions of the sample 250, the processing system can reconstruct an image reflecting the internal or external structure of the wafer sample 250.

[0068] In some embodiments, the controller 50 can include an image processing system that includes an image acquirer (not shown) and a storage device (not shown). The image acquirer can include one or more processors. For example, the image acquirer can include a computer, server, mainframe, terminal, personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer can be communicatively coupled to the electron detector 244 of the device 40 via a medium (such as an electrical conductor, fiber optic cable, portable storage medium, IR, Bluetooth, Internet, wireless network, radio, etc., and a combination thereof). In some embodiments, the image acquirer can receive signals from the electron detector 244 and construct an image. Thus, the image acquirer can acquire an image of an area of the sample 250. The image acquirer can also perform various post-processing functions, such as generating contours, superimposing indicators on the acquired image, etc. The image acquirer can be configured to adjust the brightness, contrast, etc. of the acquired image. In some embodiments, the storage can be a storage medium, such as a hard disk, flash drive, cloud storage device, random access memory (RAM), other types of computer-readable memory, etc. The storage device can be coupled to the image acquirer and can be used to save the scanned raw image data as the raw image and the post-processed image.

[0069] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the detected distributions of secondary electrons and backscattered electrons. The electron distribution data collected during the detection time window, combined with the corresponding scan path data of the primary beam 204 incident on the surface of the sample (e.g., a wafer), can be used to reconstruct an image of the wafer structure being inspected. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 250 and, thereby, can be used to reveal any defects that may be present in the wafer.

[0070] In some embodiments, the controller 50 may control the stage 234 to move the sample 250 during inspection. In some embodiments, the controller 50 may cause the stage 234 to continuously move the sample 250 in a certain direction at a constant speed. In other embodiments, the controller 50 may cause the stage 234 to vary the speed of movement of the sample 250 over time depending on the steps of the scanning process.

[0071] As is well known in the art, the interaction of charged particles (such as electrons of a primary electron beam) with a sample (e.g., Figure 3 the sample 315 to be discussed later) can generate signal electrons containing compositional and topographical information about the probed region of the sample. Secondary electrons (SE) can be identified as signal electrons having low emission energy, and backscattered electrons (BSE) can be identified as signal electrons having higher emission energy. Due to their low emission energy, the objective lens assembly can direct the SE along the electron path and focus the SE on the detection surface of an in-lens electron detector located within the SEM column. BSE traveling along the electron path can also be detected by the in-lens electron detector. However, in some cases, BSE having a large emission angle may be detected using an additional electron detector (such as a backscattered electron detector) or may still go undetected, resulting in loss of sample information required for inspecting the sample or measuring critical dimensions.

[0072] The detection and inspection of some defects (such as buried particles during lithography, metal deposition, dry etching, or wet etching, etc.) in semiconductor manufacturing processes can benefit from the inspection of surface features and the compositional analysis of defect particles. In such scenarios, the user may expect to obtain information from the secondary electron detector and the backscattered electron detector to identify the defect(s), analyze the composition of the defect(s), and adjust process parameters, etc. based on the information obtained.

[0073] In other scenarios, precise critical dimension measurements of three-dimensional features spanning several microns in depth may also be desirable. For example, it may be desirable to precisely measure the critical dimensions of features at multiple depths, such as vias with high aspect ratios having sloped walls. In such scenarios, information obtained from secondary electrons confined to the near-surface region may be insufficient and misleading. Backscattered electrons (BSEs) with higher emission energies and escaping from deeper within the surface can provide the desired information about the features being inspected.

[0074] The emission of SE and BSE follows Lambert's law and has a large energy divergence. SE and BSE are generated from different depths within the sample after the interaction of the primary electron beam with the sample and have different emission energies. For example, secondary electrons originate from the surface and may have emission energies ≤ 50 eV, depending on the sample material, the volume of interaction, etc. SE can be used to provide information about surface features or surface geometry. On the other hand, BSEs are mainly generated by elastic scattering events of the incident electrons of the primary electron beam and typically have higher emission energies compared to SEs, ranging from 50 eV to approximately the landing energy of the incident electrons, and provide information on the composition and contrast of the material being inspected. The number of BSEs generated may depend on factors including but not limited to the atomic number of the materials in the sample, the acceleration voltage of the primary electron beam, etc.

[0075] Based on differences such as emission energy or emission angle, SE and BSE can be detected separately using separate electron detectors, segmented electron detectors, energy bandpass filters, etc. An example of the implementation of an energy bandpass filter based on the relationship between BSE energy and trajectory depth is provided in U.S. Provisional Application No. 63 / 254,838, which is hereby incorporated by reference in its entirety.

[0076] Now refer to Figure 3 , Figure 3FIG. 0 shows a schematic diagram of an exemplary charged particle beam apparatus 300 (also referred to as apparatus 300) consistent with embodiments of the present disclosure. Apparatus 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 extractor electrode 302 to form a primary electron beam 300B1 along a main optical axis 300-1. Apparatus 300 may also include an anode 303, a condenser lens 304, a beam limiting aperture array 305, a signal electron detector 306, a composite lens 307, a scanning 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 inside the electron optical column of an SEM and may be rotationally symmetrically arranged around main optical axis 300-1. In some embodiments, signal electron detector 306 may be referred to as a through-lens detector, an immersion lens detector, an upper detector, or a secondary electron detector. It should be understood that relevant components may be added, omitted, or reordered as needed.

[0077] The electron source (not shown) may include: a thermionic electron source configured to emit electrons after being supplied with thermal energy to overcome the work function of the source; a field emission source configured to emit electrons after being exposed to a large electrostatic field, and so on. In the case of a field emission source, the electron source may be electrically connected to a controller (such as Figure 2 controller 50) configured to apply and adjust a voltage signal based on a desired landing energy, sample analysis, source characteristics, etc. The extractor electrode 302 may be configured to extract or accelerate electrons emitted from a field emission gun, for example, to form a primary electron beam 300B1 that forms a virtual or real main beam crossover (not shown) along main optical axis 300-1. The primary electron beam 300B1 may be visualized as being emitted from the primary beam crossover. In some embodiments, controller 50 may be configured to apply and adjust a voltage signal to extractor electrode 302 to extract or accelerate electrons generated from the electron source. The amplitude of the voltage signal applied to extractor electrode 302 may be different from the amplitude of the voltage signal applied to cathode 301. In some embodiments, the difference between the amplitudes of the voltage signals applied to extractor electrode 302 and cathode 301 may be configured to accelerate electrons downstream along main optical axis 300-1 while maintaining the stability of the electron source. As used in the context of the present disclosure, "downstream" refers to the direction along the path of primary electron beam 300B1 from the electron source towards sample 315. Referring to a charged particle beam apparatus (e.g., Figure 3For the positioning of the components of the device 300), "downstream" may refer to the position of a component that is below or after another component along the path of the primary electron beam starting from the electron source, and "directly downstream" refers to the position of a second component that is below or after the first component along the path of the primary electron beam 300B1 such that there are no other active components between the first component and the second component. For example, as Figure 3 shown, the signal electron detector 306 may be positioned directly downstream of the beam-limiting aperture array 305 such that there are no other optical or electro-optical components between the beam-limiting aperture array 305 and the electron detector 306. As used in the context of the present disclosure, "upstream" may refer to the position of a component that is above or before another component along the path of the primary electron beam starting from the electron source, and "directly upstream" refers to the position of a second component that is above or before the first component along the path of the primary electron beam 300B1 such that there are no other active components between the first component and the second component. As used herein, an "active component" may refer to any component or assembly whose presence can change the electromagnetic field between a first component and a second component by generating an electric field, a magnetic field, or an electromagnetic field.

[0078] The device 300 may include a focusing lens 304 configured to receive a portion or a substantial portion of the primary electron beam 300B1 and focus the primary electron beam 300B1 on the beam-limiting aperture array 305. The focusing lens 304 may be substantially similar to Figure 2 the focusing lens 226 and may perform substantially similar functions. Although shown as a magnetic lens in Figure 3 , the focusing lens 304 may be an electrostatic lens, a magnetic lens, an electromagnetic lens, a composite electromagnetic lens, or the like. As Figure 2 shown, the focusing lens 304 may be electrically coupled to the controller 50. The controller 50 may apply an electrical excitation signal to the focusing lens 304 to adjust the focusing ability of the focusing lens 304 based on, including but not limited to, the operating mode, the application, the desired analysis, the sample material being inspected, etc.

[0079] The device 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 the plurality of beam-limiting apertures of the beam-limiting aperture array 305. Although only one beam-limiting aperture is shown in Figure 3 , the beam-limiting aperture array 305 may include any number of apertures having uniform or non-uniform aperture sizes, cross-sectional areas, or pitches. In some embodiments, the beam-limiting aperture array 305 may be disposed downstream or directly downstream of the focusing lens 304 (as Figure 3as shown in FIG. 0), and is substantially perpendicular to the main 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 instruct that a voltage be supplied to the beam-limiting aperture array 305. The supplied voltage may be a reference voltage, such as, for example, ground potential. The controller 50 may also be configured to maintain or adjust the supplied voltage. The controller 50 may be configured to adjust the position of the beam-limiting aperture array 305.

[0080] The apparatus 300 may include a signal electron detector 306, which may be configured to detect substantially all secondary electrons and a portion of backscattered electrons based on, for example, the emission energy, emission angle, emission azimuth angle, etc. 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 energy (usually ≤50 eV) or small emission angle may include (a plurality of) secondary electron beams 300B4, and signal electrons with high emission energy (usually >50 eV) and medium emission angle may include (a plurality of) backscattered electron beams 300B3. In some embodiments, 300B4 may include secondary electrons, low-energy backscattered electrons, or high-energy backscattered electrons with a small emission angle. It should be understood that although not shown in the figure, a portion of the backscattered electrons may be detected by the signal electron detector 306. In overlay metrology and inspection applications, the signal electron detector 306 can be used to detect secondary electrons generated from the surface layer and backscattered electrons generated from deeper layers below (such as deep trenches or high-aspect-ratio holes).

[0081] The apparatus 300 may further include a compound lens 307, which is configured to focus the primary electron beam 300B1 onto the surface of the sample 315. The controller 50 may apply an electrical excitation signal to the coil of the compound lens 307 to adjust the focusing ability of the compound lens 307 based on, including but not limited to, the primary electron beam energy, application requirements, desired analysis, sample material to be inspected, etc. The compound lens 307 may also be configured to focus signal electrons (such as secondary electrons with low emission energy or backscattered electrons with high emission energy) onto the detection surface of a signal electron detector (e.g., the in-lens signal electron detector 306). The compound lens 307 may be substantially similar to Figure 2 the objective lens assembly 232 of Figure 2 or perform functions substantially similar to those of the objective lens assembly 232 of

[0082] As used herein, a compound lens is an objective lens that generates both overlapping magnetic and electrostatic fields near the sample for focusing the primary electron beam. In the present disclosure, although the condenser lens 304 may also be a magnetic lens, unless otherwise specified, references to magnetic lenses refer to objective magnetic lenses, and references to electrostatic lenses refer to objective electrostatic lenses. As Figure 3 shown, the objective magnetic lens and the objective electrostatic lens that work together to focus the primary electron beam 300B1 on the sample 315, for example, can form a compound lens 307. The lens body of the magnetic lens and the coil can generate a magnetic field, while the electrostatic field can be generated by creating a potential difference between the sample 315 and the objective pole piece. In some embodiments, the control electrode 314 or other electrodes located between the pole piece and the sample 315 can also be part of the objective electrostatic lens.

[0083] The apparatus 300 may also include a scanning deflection unit that includes primary electron beam deflectors 308, 309, 310, and 311, configured to dynamically deflect the primary electron beam 300B1 on the surface of the sample 315. In some embodiments, the scanning deflection unit including the primary electron beam deflectors 308, 309, 310, and 311 may be referred to as a beam manipulator or a beam manipulator assembly. The dynamic deflection of the primary electron beam 300B1 can cause a desired region or region of interest of the sample 315 to be scanned (e.g., in a raster scan mode) to generate SE and BSE for sample inspection. One or more of the primary electron beam deflectors 308, 309, 310, and 311 may be configured to deflect the primary electron beam 300B1 in the X-axis or the Y-axis or a combination of the X-axis and the Y-axis. As used herein, the X-axis and the Y-axis form a Cartesian coordinate, and the primary electron beam 300B1 propagates along the Z-axis or the primary optical axis 300-1.

[0084] Electrons are negatively charged particles and travel through an electron column and can travel at high energy and high speed. One way to deflect electrons is to make them pass through an electric or magnetic field generated, for example, by a pair of plates held at two different potentials, or to pass a current through a deflection coil, among other techniques. Changing the electric or magnetic field across the deflector (e.g., Figure 3 the primary electron beam deflectors 308, 309, 310, and 311 in ) can change the deflection angle of the electrons in the primary electron beam 300B1 based on factors including but not limited to electron energy, the magnitude of the applied electric field, the size of the deflector, etc.

[0085] In some embodiments, the sample 315 can be disposed in a plane substantially perpendicular to the principal optical axis 300-1. The position of the plane of the sample 315 can be adjusted along the principal optical axis 300-1 such that the distance between the sample 315 and the BSE detector 313 can be adjusted. In some embodiments, the sample 315 can be electrically connected to the controller 50 via a connector (not shown), and the controller 50 can be configured to supply a voltage to the sample 315 to adjust the position as needed. The controller 50 can also be configured to maintain or adjust the supplied voltage.

[0086] In current existing SEMs, signals generated by detecting secondary electrons and backscattered electrons are combined for imaging the surface, detecting and analyzing defects, obtaining topography information, precisely measuring the critical dimensions of high aspect ratio features, etc. By detecting secondary electrons and backscattered electrons, the top several layers and the bottom layer can be imaged simultaneously, thus possibly capturing underlying defects (such as buried particles), measuring critical dimensions, detecting overlay errors, etc. However, the overall image quality may be affected by the detection efficiency of secondary electrons as well as backscattered electrons. Although efficient secondary electron detection can provide a high-quality image of the surface, the overall image quality may be insufficient due to poor backscattered electron detection efficiency. Therefore, it may be beneficial to improve the backscattered electron detection efficiency while maintaining high throughput to obtain high-quality imaging.

[0087] One method among several methods for improving image quality and signal-to-noise ratio can include detecting more backscattered electrons emitted from the sample. The angular distribution of the emission of backscattered electrons can be represented by the cosine dependence of the emission angle (cos(θ), where θ is the emission angle between the backscattered electron beam and the principal optical axis). Although the signal electron detector can efficiently detect backscattered electrons with medium emission angles, backscattered electrons with large emission angles may still not be detected or be insufficiently detected to affect the overall imaging quality. Therefore, it may be desirable to add another signal electron detector, such as the backscattered electron (BSE) detector 313, to capture large-angle backscattered electrons.

[0088] In some embodiments, the signal electron detector 313 can include a signal electron detector located between the signal electron detector 306 and the control electrode 314. In some embodiments, the signal electron detector 413 can be located immediately downstream and outside of the pole piece of the objective lens, as Figure 3 shown. In the configuration where the signal electron detector 313 is outside the pole piece, it may be desirable to place the signal electron detector 313 closer to the composite objective lens 307 or farther from the control electrode 314, but aligned with the principal optical axis 300-1 to minimize electrical damage to the signal electron detector 313 caused by, for example, an arc.

[0089] It should be understood that some existing imaging techniques for defect detection or metrology capture multiple images simultaneously from BSE signals collected using segmented detectors such as the Directional BSE Detector (DBS) of FEI, as disclosed in the publication “Information from Every Angle – Directional BSE Detector for Next-Level Imaging” of FEI Technologies, Inc. The DBS includes a concentric ring design to separate BSEs based on the emission angle (e.g., the polar emission angle), and four separate rings allow for the simultaneous detection of multiple BSE signals and the formation of four images simultaneously by utilizing all four rings of the DBS. Additionally, the publication discloses that BSEs with larger emission angles can be collected by rings farther from the optical axis, and BSEs with smaller emission angles can be collected by the ring closest to the principal optical axis. Although the FEI publication discloses differentiating incoming BSEs based on the emission angle, it does not contemplate that the rings are configured to differentiate incoming BSEs based on their energy levels. Moreover, it would not be obvious to one of ordinary skill in the art to modify the FEI DBS to perform energy discrimination using the DBS design of a charged particle detector, as the publication does not discuss or suggest configuring each segment to resolve the energy levels of incoming BSE signals. In contrast, the embodiments disclosed in the present disclosure provide a segmented BSE detector for high landing energy applications. Each segment of the segmented BSE detector can be configured to detect signals based on the principal energy level or energy level range of the incoming BSE. The configuration can include adjusting, for example, the width of the segment. Other techniques for configuring each segment can include 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, adjusting the electrostatic field near the sample, etc., and each of these techniques will be discussed in detail in the present disclosure.

[0090] For high landing energy applications, a bottom BSE detector located between the sample and the objective pole piece can be employed to collect BSEs with medium to large emission angles in the range of 15° to 65°. Details of systems and methods for using a bottom BSE detector to improve collection efficiency have been discussed in U.S. Patent Publication No. 2021 / 0319977A1, which is incorporated herein by reference in its entirety. As previously mentioned, studies have revealed a strong correlation between the track depth of BSEs and the emission energy. In other words, BSE signals with higher or lower energies can be found to originate from relatively shallower or deeper positions within the material of the sample, respectively. While in some cases an energy filtering device can be used to selectively allow electrons of a desired energy level to pass through the detector, physical space limitations in devices using a bottom BSE detector may not permit this. Thus, it may be desirable to provide a bottom BSE detector that can detect BSEs with energy discrimination capabilities while maintaining high BSE collection efficiency and high inspection throughput.

[0091] Now referring to Figure 4A , Figure 4A FIG. shows a schematic view of a portion of an exemplary charged particle beam apparatus 400 that includes a segmented backscattered electron (BSE) detector 413. The apparatus 400 can include an objective lens 407, which is substantially similar to the composite objective lens 307 of the apparatus 300 and performs substantially similar functions as the composite objective lens 307 of the apparatus 300. A primary electron beam B1 can travel through an electron optical column that includes the objective lens 407, a central opening of the segmented BSE detector 413, and a central opening of a control electrode 414, and interact with an area of the sample 415. As a result of the interaction of the primary electron beam B1 with the sample 415, secondary charged particles can be emitted from the sample 415, including secondary electrons, backscattered electrons, Auger electrons, X-rays, and other particles.

[0092] As Figure 4A shown therein, the BSE beam B2 and the BSE beam B3 can respectively include electrons having different energies or energy levels E1 and E2, such that E1 < E2. In some embodiments, the polar emission angle θ1 of the BSE beam B2 can be less than the polar emission angle θ2 of the BSE beam B3. In some embodiments, although not shown in the figure, the polar emission angles of the BSE beams B2 and B3 can be substantially similar, while the energy levels E1 and E2 can be different. As used herein, substantially similar polar emission angles refer to a similarity of emission angles such that the variation in the emission angles of electrons or beams including electrons emitted from the sample can be negligible and within acceptable limits.

[0093] In some embodiments, the BSE detector 413 can be a bottom BSE detector located between the sample 415 and the pole piece of the objective lens 407. In some embodiments, the BSE detector 413 can be located between the control electrode 414 and the pole piece of the objective lens 407. The BSE detector 413 can be positioned such that it is substantially perpendicular to the principal optical axis along which the primary electron beam B1 travels through the electron optical column of the device 400. As used herein, the term "substantially perpendicular" refers to the perpendicularity of an element with respect to an axis or another element such that there is a negligible offset or deviation from a 90° angle between the two, typically less than 0.1° or within an acceptable range. In some embodiments, the BSE detector 413 can be positioned such that it is substantially perpendicular to the principal optical axis and such that its central aperture is aligned with the principal optical axis, as Figure 4A shown. It should be understood that although the dimensions, spacings, and sizes of the elements of the device 400 are not shown to scale, their relative positioning and locations are representative.

[0094] In some embodiments, the BSE detector 413 can be a segmented BSE detector that includes a plurality of radially concentric segments 413-1, 413-2, 413-3, 413-4 of charged particle sensitive material separated by non-sensitive material or a substrate. Consistent with some embodiments of the present disclosure, a top view of an exemplary segmented BSE detector including four concentric segments is shown in Figure 4Bis shown. The charged particle sensitive material can be sensitive to charged particles (such as ionizing radiation, electrons, X-rays or photons, and other charged particles), such that it can 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 can include the substrate material of the BSE detector 413 or any material that has low detection sensitivity to charged particles. The BSE detector 413 can be placed in the device 400 such that its central opening is aligned with the main optical axis of the device 400. In some embodiments, each segment of the BSE detector 413 can be configured to detect BSEs at different energy levels or different ranges of energy levels. For example, segment 413-1 can be configured to detect BSEs having an emission energy in the range of 2-5 keV, segment 413-2 can be configured to detect BSEs having an emission energy in the range of 5-10 keV, segment 413-3 can be configured to detect BSEs having an emission energy in the range of 10-20 keV, and segment 413-4 can be configured to detect BSEs having an emission energy in the range of 20-50 keV. It should be understood that the number of segments and the energy ranges detected by each segment are non-limiting examples, and the BSE detector can include fewer or more segments, and the energy thresholds for each segment can be adjusted, as discussed in subsequent portions of the present disclosure. It should also be understood that the width of each segment can be uniform or non-uniform.

[0095] In some embodiments, the BSE detection signal can be used to reconstruct an image of the structure of the sample being examined or observed. These images can be two-dimensional images or three-dimensional images generated from a plurality of two-dimensional images. In some embodiments, the three-dimensional image can be formed from images generated from the signals detected in each segment of the BSE detector 413. Additionally or alternatively, the three-dimensional image can be formed from a plurality of images generated from the signals detected by a single segment. The signal detected by a single segment can represent BSEs having an energy range, and thus emitted from a certain depth or a certain depth range. It may be desirable to generate a three-dimensional image from a plurality of images based on the signal detected by a single segment to gather information about features at a specific depth, such as critical dimensions at a certain height. In other cases, it may be desirable to generate a three-dimensional image from a plurality of images based on the signals detected by a plurality of segments simultaneously.

[0096] Now referring to Figure 5A , Figure 5A shows simulation results of the spatial distribution and energy distribution of backscattered electrons detected on an exemplary segmented BSE detector (such as the BSE detector 413) consistent with embodiments of the present disclosure. In some embodiments, the BSE detector 413 can be referred to as a bottom BSE detector (BBD). In Figure 5AIn the example shown, the BSE detector 413 is a BBD having four segments. It should be understood that the "segments" of a segmented BSE detector may also be interchangeably referred to herein as "sections". Thus, a segmented BSE detector (such as BSE detector 413) may include multiple sections, as mentioned in Figure 5A The simulation results include the spatial distribution of BSE, as shown in the image on the top row in Figure 5A The image on the top row shows the spatial distribution of BSE on the BBD (e.g., the BSE detector 413 in Figure 4B ) and the spatial distribution of BSE on the individual segments or sections of the BBD.

[0097] In some embodiments, section 1 may correspond to segment 413-1 of the BSE detector 413 in Figure 4B . Section 1 may be the segment closest to the central opening of the BSE detector and may be configured to detect low-energy BSE signals, which represent BSE emitted from deeper regions of the sample, thereby providing information associated with the features present in that region and information about the features present in that region. Sections 2, 3, and 4 may correspond to segments 413-2, 413-3, and 413-4 of the BSE detector 413 in Figure 4B .

[0098] Figure 5A The image shown in the bottom row of Figure 5B shows the simulation results of the energy distribution of BSE collected on the BBD and the energy distribution of BSE on the individual segments of the BBD. The energy distribution graphs shown for each segment in the bottom row show a broad distribution of the emitted energy collected by the corresponding segment. The energy distribution graphs also show the main energy level associated with each segment or the peak energy of the detected BSE. As shown in Figure 5B Figure 5B shows the relationship between the peak energies of the detected BSE associated with each segment of a segmented BSE detector (e.g., the BSE detector 413 in Figure 4B ). The peak energy of the detected BSE collected by each segment increases as the radial distance from the center of the opening of the BSE detector increases. In other words, a BSE detector (e.g., the BSE detector 413 in Figure 4B ) can be segmented based on the peak energy of the detected BSE. The relationship between BSE collection efficiency, BSE emission energy, and the segments of the BSE detector is discussed in detail with reference to Figure 8 .

[0099] Figure 6Shows simulated trajectories of BSEs emitted from a substrate at different emission angles, consistent with embodiments of the present disclosure. Data capture graph 620 shows simulated trajectories of BSEs with an emission energy range 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 BSE emission energy range. In some embodiments, the BSE emission energy can be in the range of 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 BSEs shown in data capture graph 620 are emitted at a polar emission angle of 20°, the portion of the BSEs with low emission energy can be collected in a region radially closer to the principal optical axis of BSE detector 613, and the BSEs with higher emission energy can be collected in a region radially farther from the principal optical axis of BSE detector 613. In other words, the portion of the BSEs with low emission energy can be incident on the detection surface of BSE detector 613 at a smaller off-axis distance, and the portion of the BSEs with higher emission energy can be incident on the detection surface of BSE detector 613 at a larger off-axis distance. In the context of the present disclosure, the off-axis distance refers to the horizontal distance from the principal optical axis.

[0100] In some embodiments, the magnetic field generated by the objective lens (e.g., Figure 4A objective lens 407) may affect the path of BSEs emitted from the surface based on the energy of the BSEs. The low-energy BSEs may be affected more greatly than the higher-energy BSEs. In this context, the magnetic field of the objective lens affecting the path of the BSEs refers to changing the trajectory of the BSEs such that the BSEs are deflected towards the principal optical axis. In some cases, the deflection of the trajectory of the low-energy BSEs may cause the BSEs to escape through the central opening of BSE detector 613 without being detected, resulting in a loss of collection efficiency. One method among several methods of capturing low-energy, low-emission-angle BSEs can include reducing the cross-section of the central opening of BSE detector 613. However, in some scenarios, this may obstruct the path of the primary electron beam directed towards the sample, among other challenges. As Figure 6 illustrated by data capture graph 620 of

[0101] Data capture graphs 630 and 640 respectively show the simulated trajectories of BSEs with an emission energy range emitted at polar emission angles of 30° and 40°. Compared with data capture graph 620, the radial separation or radial resolution of BSEs with different emission energies emitted at a higher emission angle on the detection surface of BSE detector 613 increases, as shown in data capture graphs 630 and 640.

[0102] Data capture graph 645 shows the simulated trajectories of BSEs with an emission energy range emitted at a polar emission angle of 45°. As shown, the radial separation between BSEs with different emission energies can be greater than the radial separation or radial resolution for BSEs with a polar emission angle of 40°. Additionally, the emission yield of BSEs at a polar emission angle of 45° is higher. Therefore, it may be desirable to use a radially segmented BSE detector (such as Figure 4B BSE detector 413) to maximize the detection of BSEs, for example, emitted at a polar emission angle of 45° based on the emission energy of the BSEs incident on the BSE detector.

[0103] Data capture graphs 655 and 660 respectively show the simulated trajectories of BSEs with an emission energy range emitted at polar emission angles of 55° and 60°. Although the polar emission angles are higher, the radial separation and thus the detectability based on emission energy may not be high. This may be attributed to the larger deflection of high-emission-angle BSEs, causing the BSEs to be absorbed or reflected back to the substrate, thereby reducing the number of BSEs collected by BSE detector 613.

[0104] As previously mentioned, a radially segmented BSE detector (such as Figure 4B BSE detector 413 in Figure 4B can be used to distinguish incoming BSEs based on their emission energy. Additionally, each segment (e.g., Figure 4B segments 413-1 to 413-4 of Figure 4B ) can be configured to detect BSEs with BSE emission energies within a specific energy level range, and each segment can have an associated primary energy level or peak energy. Since each segment has an associated peak energy within the distribution of the detected BSE emission energies, a larger number of spatially arranged segments can result in a higher energy filtering resolution. In other words, the resolution of the segmented BSE detector can be improved by increasing the number of segments based on the primary energy level of the BSEs it is configured to detect.

[0105] Now referring to Figures 7A to 7D , Figures 7A to 7D shows the energy distribution curve of backscattered electrons detected by an exemplary BSE detector consistent with an embodiment of the present disclosure. Figure 7AA top - view schematic diagram of a BSE detector 713 having four segments (e.g., segment 1, segment 2, segment 3, and segment 4) is shown, where segment 1 is activated. The data graph 710 shows the spatial energy distribution curve of segment 1, which is configured to detect incident BSEs after activation. In this context, activating a segment of the BSE detector can include enabling the collection or detection of BSEs incident on the detector surface associated with that segment. The segments of the segmented BSE detector can include materials sensitive to charged particles, which include but are not limited to ionizing radiation, electrons, X - rays, and other particles.

[0106] In some embodiments, a controller (e.g., Figure 2 controller 50) can be configured to apply an electrical signal (such as a voltage or current signal) to activate one or more segments sequentially or in parallel. For example, controller 50 can activate segment 1 to collect BSEs from a deeper region of the sample, thereby having a lower emission energy. In some embodiments, controller 50 can also be configured to generate an image (e.g., a backscattered electron image) based on the BSE signal generated from the BSEs collected or detected by segment 1. It should be understood that controller 50 can be configured to generate multiple images, or process multiple images to form a composite image, among other functions. The image processor controlled by controller 50 can be configured to form a composite image. In this context, a composite image can be formed by stitching together multiple images captured by an image acquirer. For example, a composite image can include a three - dimensional image formed by stitching together multiple two - dimensional images captured at different depths.

[0107] In some embodiments, the BSE detector can be segmented into m number of segments, where m is a positive integer and m≥2. An exemplary BSE detector 713 - 1 having eight segments is shown in Figure 7A FIG. It should be understood that the number of segments, the width of each segment, or the material of each segment can be appropriately adjusted as needed. It should also be understood that one or more segments of BSE detector 713 - 1 can be activated individually, or simultaneously, or activated based on a predetermined timing. For example, the controller can be configured to activate one segment of the multiple segments within a predetermined time while other segments are deactivated. After the predetermined time has passed, another segment can be activated within a second predetermined time. In some embodiments, one or more segments can be activated based on a predetermined duty cycle.

[0108] Data graph 720 shows the BSE energy distribution curves and peak energy levels identified for segments 1 and 2 of BSE detector 713-1. Compared to a BSE detector 713 that has a single peak energy or dominant energy within a given BSE emission energy range, BSE detector 713-1 can be configured to have two segments (e.g., segment 1 and segment 2), and thus two dominant energy levels, which can be used to further resolve these incident BSEs based on the energy of the incoming BSEs. Higher energy resolution can allow a user to obtain information or form an image from a specific depth while filtering out other BSE signals, resulting in a more precise inspection and metrology.

[0109] As an example, controller 50 can activate only segment 1 or segment 2 at a time, and thus generate an image based on BSE signals having an emission energy distribution within a certain range or having a specific peak energy level, which image can be related to a specific depth of the sample from which the BSE signals may originate.

[0110] As Figure 7B shown, data graph 730 shows the BSE energy distribution curve for segment 2 of segmented BSE detector 713. Segment 2 of BSE detector 713 is indicated as being activated. In contrast, a narrower energy distribution and a more clearly identifiable peak energy level can be obtained from segments 3 and 4 of BSE detector 713-1. Data graph 740 represents the energy distribution curves for segments 3 and 4 of BSE detector 713-1. Data graphs 750 and 760 respectively show the BSE energy distribution curve for segment 3 of BSE detector 713 and the BSE energy distribution curves for segments 5 and 6 of BSE detector 713-1, as Figure 7C shown. Data graphs 770 and 780 respectively show the BSE energy distribution curve for segment 4 of BSE detector 713 and the BSE energy distribution curves for segments 7 and 8 of BSE detector 713-1, as Figure 7D shown.

[0111] Figure 8 shows a graphical representation of the simulated collection efficiency of backscattered electrons for multiple segments of an exemplary segmented BSE detector consistent with embodiments of the present disclosure. In Figure 8 it, data graph 800 represents the collection efficiency of individual segments of an exemplary segmented BSE detector for BSEs having an emission energy ranging from 5 keV to 30 keV and a polar emission angle of 45°. It should be understood that the range of emission energies used for simulation purposes is exemplary and not limiting, and other energy ranges can also be used. The BSE detector can include eight segments (e.g., Figures 7A to 7DThe BSE detector 713-1) in [description], is identified as segments 1 to 8. Segment 0 in the data graph 800 does not represent an actual detection segment, but rather represents the central opening of the segmented BSE detector. In this regard, the collection efficiency of segment 0 is not an actual collection efficiency because BSEs are not collected or detected. Instead, it can be regarded as the number of BSEs that are lost or escape through the central opening of the BSE detector.

[0112] As shown in the data graph 800, as the BSE emission energy increases, the number of BSEs that are lost through the central opening of the BSE detector decreases. As an example, approximately 45% of low-energy BSEs (e.g., 5 keV or less) and approximately 5% of high-energy BSEs (e.g., 25 keV or more) may pass through the central opening without being detected by the BSE detector. This may be because low-energy BSEs may be more affected by the objective lens magnetic field than high-energy BSEs, and the magnetic field of the objective lens deflects the BSEs closer to the principal optical axis.

[0113] As further illustrated in the data graph 800, with regard to the collection efficiency, there may be distinct primary energy components or peak energy components for the segments of the segmented BSE detector. In other words, a segment can detect BSEs with a specific energy that is more than other energy components of the BSE signal. For example, segment 1 may have the maximum collection efficiency for BSEs at 10 keV, segment 3 may have the maximum collection efficiency for BSEs at 15 keV, segment 4 may have the maximum collection efficiency for BSEs at 20 keV, segment 5 may have the maximum collection efficiency for BSEs at 25 keV, and segment 6 may have the maximum collection efficiency for BSEs at 30 keV.

[0114] As further illustrated in the data graph 800, the higher the BSE energy, the peak position of the maximum collection efficiency can be in segments at a greater off-axis distance. In other words, segments located farther from the principal optical axis can be configured to selectively detect BSEs with higher energies, thereby enabling the differentiation of different energy components of incoming BSEs by using the segmented BSE detector. This may be because high-kinetic-energy BSEs may be less affected by the magnetic field of the objective lens and can travel a greater distance without being deflected or deviating from their intended trajectory.

[0115] In some embodiments, the BSE detector can be configured such that the segments of the detector detect different ranges of the primary energy BSE signal. Configuring the BSE detector (e.g., Figures 7A to 7D the BSE detector 713-1) can 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 (to be referred to later with reference to Figure 10A and Figure 10Bdiscussion), adjusting the height of the BSE detector relative to the substrate position, adjusting the electric field on the sample, adjusting the extraction voltage between the charged particle source (e.g., electron source) and the substrate, adjusting the magnetic field strength of the objective lens, or compensating for the focus shift due to the change in the magnetic field strength of the objective lens. One or more of these 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 BSE detector height, or a combination thereof, can be adjusted to adjust the spatial distribution of the BSE signal on the segmented BSE detector and optimize the image contrast such that each segment is configured to detect a different range of primary energy BSE signals, as illustrated, for example, in data graph 800.

[0116] Now referring to Figure 9 , Figure 9 shows the spatial distribution of BSEs detected by the radially concentric segments of an exemplary segmented BSE detector in accordance with an embodiment of the present disclosure. In Figure 9 , a plurality of simulated images 905, 910, 915, 920, 925, and 930 respectively represent the detection coverage areas or spatial distributions of BSEs having energies of 5 keV, 10 keV, 15 keV, 20 keV, 25 keV, and 30 keV on a segmented BSE detector (e.g., Figures 7A to 7D 's BSE detector 713-1). For example, substantially all BSEs having an energy of 10 keV or less can be collected by the segments closest to the principal optical axis, such as segments 1, 2, 3, and 4. As illustrated in simulated image 910, although the distribution of BSEs spans four segments, the distribution density of the BSE signal is highest in segment 1, which is consistent with data graph 800. As another example, substantially all BSEs having an energy of 20 keV or less can be collected by segments 1 through 7. As illustrated in simulated image 920, although the distribution of BSEs spans seven segments, the density of the distribution of the BSE signal is highest in segment 4, which is consistent with data graph 800. Thus, each segment can have a primary energy level of BSEs that it can be configured to detect, allowing the BSE signals to be distinguished and filtered based on their emission energy.

[0117] Figure 10A shows a schematic diagram of an exemplary charged particle beam apparatus 1000 including a segmented BSE detector in accordance with an embodiment of the present disclosure. The objective lens 1007, the BSE detector 1013, and the control electrode 1014 can be substantially similar and can respectively perform functions substantially similar to those of the objective lens 407, the BSE detector 413, and the control electrode 414 of apparatus 400.

[0118] In apparatus 1000, compared to apparatus 400, the position of sample 1015 along the z-axis can be adjustable. In some embodiments, the z-axis position of sample 1015 can be adjusted to vary the distance between BSE detector 1013 and sample 1015, i.e., the working distance. As shown, adjusting the z-axis position of sample 1015 from an initial position P1 to P2 (represented by the dashed rectangle) can increase the working distance. BSE beam B3 can be emitted from the surface of sample 1015 at position P1, and BSE beam B2 can be emitted from the surface of sample 1015 at position P2. Changes in the trajectories of BSE beams B2 and B3 caused by the change in the z-axis position of the surface of sample 1015 from which BSE beams B2 and B3 originate can result in changes in the peak energy of the collected BSEs incident on a segment of BSE detector 1013. For example, although BSE beams B2 and B3 can have different peak energies, they may land on the same segment of BSE detector 1013 based on the z-axis position of sample 1015.

[0119] In some embodiments, adjusting the z-axis position of sample 1015 can change the BSE energy detection range of BSE detector 1013. For example, increasing the working distance as shown in Figure 10A can increase the range of BSE energies detectable by BSE detector 1013. In some embodiments, adjusting the z-axis position of sample 1015 can change the BSE collection efficiency. For example, increasing the working distance can cause more BSEs to be deflected by the magnetic field of objective 1007 closer to the principal optical axis along which primary electron beam B1 travels, thus allowing more BSEs to escape through the central aperture of BSE detector 1013. In some embodiments, adjusting the z-axis position of sample 1015 can change the uniformity of BSE collection efficiency across multiple segments of BSE detector 1013, as Figure 10B illustrated. For example, increasing the working distance can improve the uniformity of BSE collection efficiency across multiple segments of a segmented BSE detector (e.g., BSE detector 1013).

[0120] In some embodiments, although not shown, the peak energy of the BSEs collected by a segment among multiple segments can vary based on the working distance. This can allow for further filtering of incoming BSEs based on the energy of the incoming BSEs. In other words, the working distance can be adjusted to filter BSEs within a specific segment of BSE detector 1013. The ability to adjust the peak energy of the detected BSEs, the BSE energy detection range, or the uniformity of BSE collection efficiency across multiple segments by adjusting the z-axis position of the sample can provide enhanced sensitivity and accuracy for metrology or defect inspection.

[0121] In some embodiments, the z-axis position of the sample can be adjusted based on the landing energy of the charged particles forming the primary charged particle beam B1. It is 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 the BSE energy between the multiple segments of the BSE detector 1013.

[0122] Now refer to Figure 11A and Figure 11B , Figure 11A and Figure 11B respectively show the simulated trajectories of BSEs at different emission angles and a fixed pole emission angle in accordance with embodiments of the present disclosure. Figure 11A Shows the simulated trajectories of BSEs with a fixed emission energy (e.g., 30 keV) at various pole emission angles and various working distances.

[0123] In some embodiments, BSEs with a smaller pole emission angle can be detected by segments closer to the principal optical axis, or can escape through the central opening of the BSE detector without being detected. BSEs with a larger pole emission angle can land on segments at a larger off-axis distance, or be blocked by other components such as a control electrode (e.g., Figure 10A the control electrode 1014 in Figure 10A ), or can be reflected back to the substrate. As the working distance increases, the magnetic field generated by the objective lens (e.g.,

[0124] the objective lens 1007 in Figure 11B weakens, and the BSE is less affected, making it easier for the BSE to travel substantially undeflected or without deviation. This can allow BSEs with the same energy component to land on different segments at different working distances. In other words, a certain radial segment can collect or detect BSEs with different emission energies at different working distances. Figure 10A the objective lens 1007 in Figure 10A ), causing the BSE to be deflected back towards the principal optical axis. In some embodiments, although not shown, adjusting the working distance can change the peak BSE energy detected by the segments of the BSE detector (e.g.,

[0125] In some embodiments, a segmented BSE detector (e.g., Figures 7A to 7DThe BSE spatial distribution, BSE collection efficiency, or detected peak BSE energy on one or more segments of the BSE detector 713-1) can 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 surface of the sample can include, but is not limited to, adjusting the voltage of a control electrode near the sample (e.g., control electrode 414 in FIG. 4), or adjusting the potential difference between the sample and the pole piece of the objective lens (e.g., Figure 4A the objective lens 407 in FIG. 4). In some embodiments, the controller 50 can be configured to apply or adjust the voltage applied to the control electrode such that an adjustment of the applied voltage adjusts one or more of the BSE collection efficiency, peak BSE energy, or BSE energy width.

[0126] Figure 12 FIG. 6 shows a graphical representation of simulation data consistent with an embodiment of the present disclosure showing the effect of adjusting the electric field strength on the collection efficiency, peak energy, and energy width variation of BSEs collected by different segments of an exemplary segmented BSE detector. In some embodiments, the electric field strength on the sample can be adjusted by adjusting the voltage applied to the control electrode. Data graph 1210 shows a comparison of the BSE collection efficiency for eight segments of BSEs having a specific energy and a specific emission angle. For example, applying a voltage of 3 kV to the control electrode can increase the BSE collection efficiency of the outer segments (e.g., segments 5 and 6) of the segmented BSE detector and substantially maintain the detected peak BSE energy level (illustrated in data graph 1220) and the energy width distribution of the BSEs detected by the segments of the segmented BSE detector (illustrated in data graph 1230).

[0127] In some embodiments, a higher voltage applied to the control electrode can increase the BSE collection efficiency for the outer segments (e.g., segments 5 and 6) and decrease the BSE collection efficiency for the inner segments (e.g., segments 1 to 4). A higher voltage applied to the control electrode may affect the path of low-energy BSEs to be closer to the principal optical axis, such that the BSEs are deflected towards the principal optical axis and may escape through the central opening of the BSE detector, thereby causing a decrease in the BSE collection efficiency. For high-energy BSEs, a higher voltage applied to the control electrode may deflect the BSEs that will be 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 the present disclosure, the outer segments refer to the segments of the segmented BSE detector that are located at a greater distance from the principal optical axis and at a larger off-axis distance, and the inner segments refer to the segments that are located closer to the principal optical axis and at a shorter off-axis distance. In some embodiments, by way of example, segments 1, 2, 3, and 4 can include inner segments, and segments 5, 6, 7, and 8 can include outer segments.

[0128] As shown in data graph 1220, the peak energy for each segment can be adjusted based on the voltage signal applied to the control electrode. The adjustability of the peak energy by adjusting the control electrode voltage can improve the image contrast for a specific depth of the sample, thereby enhancing the accuracy of defect inspection or feature metrology.

[0129] In some embodiments, the electric field strength on the sample can be adjusted by adjusting the extraction voltage. In this context, the extraction voltage refers to the potential difference between the sample and the pole piece of the objective lens. As an example, if the same voltage is applied to the pole piece of the objective lens and the sample, the potential difference between them is zero, so the extraction voltage between them is zero. In other words, the objective lens and the sample are equipotential. If the voltage applied to the sample is higher than the voltage applied to the pole piece of the objective lens, the sample is positively biased relative to the objective lens, and the electric field strength between them can be increased, thereby extracting or "pushing out" more electrons from the sample.

[0130] In some embodiments, the extraction voltage can be adjusted to adjust the peak BSE energy detected by the segments of the segmented BSE detector. Figure 13A Data graph 1310 shows a comparison of the peak BSE energy detected by each segment of the segmented BSE detector for two different extraction voltages of 0 kV and 5 kV. As shown, the peak energy of the BSE detected by segments 1 and 7 at an extraction voltage of 5 kV is different compared to the peak energy of the BSE detected at an extraction voltage of 0 kV (e.g., for a higher extraction electric field, the peak energy is lower). A higher peak BSE energy detected for one or more segments of the BSE detector can be beneficial for improving the image contrast at a certain depth for defect inspection or metrology applications. Although not shown, the width of the energy distribution of the BSE detected by each segment can also be adjusted as the case may be by adjusting the extraction voltage.

[0131] Now refer to Figure 13B , Figure 13B which shows a data graph of the simulated values of the BSE collection efficiency for each segment of the BSE detector for two different extraction voltages of 0 kV and 5 kV. A stronger extraction voltage (e.g., 5 kV or more) can increase the BSE collection efficiency for each segment of the BSE detector. The increased BSE collection efficiency can be beneficial for increasing the signal-to-noise (SNR) ratio and improving the detector gain. The detector gain is proportional to the electron energy it receives. Therefore, when the voltage difference between the objective lens and the sample is higher, the electrons emitted from the surface of the sample have higher kinetic energy, resulting in better detector gain.

[0132] In some embodiments, the magnetic field strength of the objective lens can be adjusted to adjust the segmented BSE detector (e.g., Figures 7A to 7DThe BSE collection efficiency of segments of the BSE detector 713-1) in []. Adjusting the magnetic field strength of the objective lens can include adjusting the excitation of the objective lens. In some embodiments, the magnetic field strength of the objective lens can be expressed in ampere-turns (AT), which is a unit of magnetomotive force (MMF) represented by a direct current of 1 ampere flowing through a single-turn coil in a vacuum. As an example, a current of 2 amperes flowing through a 10-turn coil can generate an MMF of 20 AT.

[0133] Figure 14A and Figure 14B shows the relationship between the BSE collection efficiency based on the objective lens magnetic field strength for each segment of a segmented BSE detector consistent with embodiments of the present disclosure. Figure 14A The data chart 1410 in [] represents the BSE collection efficiency of the eight segments of the segmented BSE detector when the magnetic field strength of the objective lens is 3193 AT, the nominal height of the detector, a landing energy of 30 keV, and no electric field on the surface of the sample. In contrast, Figure 14B the data chart 1420 in [] represents the BSE collection efficiency of the eight segments of the segmented BSE detector when the magnetic field strength of the objective lens is higher (about 3222 AT). For example, when the magnetic field strength of the objective lens is higher, the BSE collection efficiency of segment 4 for 20 keV BSE can be higher compared to the collection efficiency of segment 3, as shown in Figure 14B the data chart 1420 in [].

[0134] Now refer to Figure 15 , Figure 15 which further shows the effect of adjusting the magnetic field strength of the objective lens on the BSE collection efficiency of the segments of a segmented BSE detector consistent with embodiments of the present disclosure. As mentioned in Figure 15 [], the segmented BSE detector can refer to an eight-segment BSE detector, such as the Figures 7A to 7D BSE detector 713-1. In Figure 15 [], each subplot corresponds to a separate segment of the eight-segment BSE detector. Thus, subplot 1510 corresponds to segment 1 of the BSE detector, subplot 1520 corresponds to segment 2 of the BSE detector, subplot 1530 corresponds to segment 3 of the BSE detector, subplot 1540 corresponds to segment 4 of the BSE detector, subplot 1550 corresponds to segment 5 of the BSE detector, subplot 1560 corresponds to segment 6 of the BSE detector, subplot 1570 corresponds to segment 7 of the BSE detector, and subplot 1580 corresponds to segment 8 of the BSE detector.

[0135] Refer to Figure 15, each sub - graph (1510 to 1580) shows the relationship between the collection efficiency (CE) of different BSE energy components and their corresponding maximum CE relative to a specific energy range. In this regard, a CE ratio of 100% indicates that the energy component has the highest collection efficiency in that segment. Additionally, in each sub - graph (1510 to 1580), the individual curves represent the variation of the collection efficiency for each segment when a specific magnetic field is generated under a specific objective lens excitation. Since the strength of the magnetic field can affect the BSE energy or spatial distribution on the BSE detector, the different curves behave differently.

[0136] As shown in the figure, Figure 15 each sub - graph in shows the BSE collection efficiency for an individual segment for a range of magnetic field strength values from 0 AT to 3293 AT. At 0 AT, it indicates that there is no magnetic field from the objective lens, and all energy components of the BSE emitted from the sample can travel along the same electron trajectory. Therefore, for each energy component, the collection efficiency (CE) can be substantially similar or the same. This is represented by the data points where the CE ratio on the y - axis of each sub - graph is 100%. The nominal excitation of the objective lens can refer to the excitation of the objective lens such that the generated magnetic field focuses the primary electron beam on the surface of the sample. An objective lens excitation outside the nominal range of the excitation can indicate under - focusing or over - focusing of the primary electron beam.

[0137] Furthermore, if the collection efficiency for an energy component is much higher than that of other energy components, the achievable image contrast may be higher. In other words, if the difference between the collection efficiency of an energy component and that of other energy components is high, the image contrast may be high. In some embodiments, adjusting the magnetic field of the objective lens can allow for adjusting the collection efficiency for one or more individual energy components, which can be used to further enhance the image contrast.

[0138] As shown in each sub - graph, each curve represents the variation of the BSE collection efficiency for an individual segment for a specific objective lens excitation. In some embodiments, the objective lens excitation and thus the magnetic field strength can be adjusted at intervals of 10 AT or greater, 20 AT or greater, 50 AT or greater, 100 AT or greater, or any suitable range to determine the maximum difference between the BSE collection efficiencies for the segments such that the image contrast can be optimized and the energy filtering resolution can be enhanced.

[0139] As an example, in sub - figure 1530, reducing the objective lens excitation (represented by the downward - pointing arrow) such that the magnetic field strength is lower than the nominal excitation can enhance the difference in collection efficiency between segment 3 and other segments. This can indicate that reducing the magnetic field strength can enable the capture of an image with higher contrast associated with a specific depth region of the sample. In contrast, in sub - figure 1550, increasing the objective lens excitation (represented by the upward - pointing arrow) such that the magnetic field strength is higher than the nominal excitation can enhance the difference in collection efficiency between segment 5 and other segments. This can indicate that increasing the magnetic field strength can enable the capture of an image with higher contrast associated with a specific depth region of the sample. In some embodiments, the controller 50 can be configured to adjust the objective lens excitation so as to adjust the magnetic field strength, thereby enabling the capture of an image with better contrast and high metrology accuracy.

[0140] In some embodiments, adjustment of the magnetic field of the objective lens can enhance image contrast, but this may change the focus of the primary charged particle beam (such as a primary electron beam) passing through the path towards the sample. Adjusting the magnetic field of the objective lens can include reducing or increasing the magnetic field based on the desired BSE collection efficiency for individual segments of the segmented BSE detector, thereby allowing the user to select the desired BSE energy range originating from a certain depth of the sample and further optimizing the contrast of the image generated from the detected BSEs. However, if the adjustment of the magnetic field causes the primary charged particle beam to lose its focus, the advantage of better image contrast obtained by adjusting the magnetic field of the objective lens may be severely compromised. Therefore, it may be desirable to compensate for the focus change introduced by the adjustment of the magnetic field to maintain high image contrast and high resolution.

[0141] Now referring to Figure 16A , Figure 16A , a schematic diagram of an exemplary charged particle beam device 1600A consistent with embodiments of the present disclosure is shown. Compared with device 400, device 1600A can additionally include a focus compensation lens 1605, which is configured to compensate for changes in the focus of the primary charged particle beam 1602 along the main optical axis 1601. The change in the focus of the primary charged particle beam 1602 can be caused by, among other things, a change in the magnetic field of the objective lens 1607 to improve the BSE collection efficiency of individual segments of the segmented BSE detector 1613.

[0142] In some embodiments, the focus compensation lens 1605 can be implemented by one or more deflectors of a scanning deflector unit or a beam manipulator assembly (e.g., Figure 3 primary electron beam deflector 308, primary electron beam deflector 309, primary electron beam deflector 310, or primary electron beam deflector 311). In some embodiments, the focus compensation lens 1605 can be the deflector closest to the BSE detector 1613 (e.g., Figure 3is formed by the deflector 311). In such a scenario, the focusing compensation lens 1605 can have a minimal impact on the overall magnification of the imaging system while compensating for the focus change caused by the adjustment of the magnetic field of the objective lens 1607. In some embodiments, the focusing compensation lens 1605 can be located immediately upstream of the pole piece 1607P of the objective lens 1607. If the focusing compensation lens 1605 is formed by a deflector with a smaller inner diameter that is closest to the pole piece 1607P of the objective lens 1607, a stronger focusing ability can be obtained by applying a lower voltage compared to other deflectors upstream of the deflector closest to the pole piece 1607P of the objective lens 1607 in the scanning deflector unit. In some embodiments, the focusing compensation lens 1605 can 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.

[0143] In some embodiments, the beam scanning deflector 1605 can include a quadrupole, hexapole, or octapole arrangement. In some embodiments, the focusing compensation lens 1605 can 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.

[0144] As Figure 16A shown, the objective lens can be nominally excited such that the primary charged particle beam 1602 is focused on the surface of the sample 1615. In such a scenario, the focusing compensation lens 1605 can be deactivated and can not be used as a focusing compensation lens.

[0145] In some embodiments, the magnetic field of the objective lens 1607 can be reduced by decreasing the objective lens excitation to enhance the difference in collection efficiency between segments of the BSE detector 1613, as Figure 15 shown in sub - figure 1530 of Figure 16B If the magnetic field of the objective lens 1607 is weak, the primary charged particle beam 1602 may be under - focused on the surface of the sample 1615, as

[0146] shown. In such a scenario, the focusing compensation lens 1605 can be activated to compensate for the change in focus caused by 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.

[0146] In some embodiments, the magnetic field of the objective lens 1607 can be increased by increasing the objective lens excitation to enhance the difference in collection efficiency between segments of the BSE detector 1613, as Figure 15 shown in sub - figure 1550 of Figure 16CAs shown. In such a scenario, to compensate for the change in focus, the focusing ability of the condenser lens 1605 can be reduced to form a focus-compensated divergent primary charged particle beam 1609, which can then be focused onto the surface of the sample 1615 by a stronger objective lens magnetic field. In some embodiments, reducing the focusing ability of the condenser lens 1605 may cause a decrease in the detection current of the divergent primary charged particle beam 1609. To compensate for the decrease in the detection current, a larger Coulomb aperture from the Coulomb aperture array 1608 can be used to allow a larger beam to pass through the condenser lens 1605.

[0147] Now referring to Figure 17 , Figure 17 , a schematic diagram of an exemplary charged particle beam apparatus 1700 including a segmented BSE detector in accordance with an embodiment of the present disclosure is shown. The apparatus 1700 may include an objective lens 1707, a segmented BSE detector 1713 that is at least substantially perpendicular to the main optical axis 1701, a control electrode 1714 located downstream of the BSE detector 1713, and a sample 1715. In operation, a primary charged particle beam B1 can be generated from a charged particle source (not shown) and travel downward toward the sample 1715. After the charged particles of the primary charged particle beam B1 interact with regions of the sample 1715, signal charged particles that form the BSE beam B2 can be emitted from different depths of the sample 1715 based on the interaction volume and collected at the detection surface of the BSE detector 1713.

[0148] In some embodiments, the z-axis height of the BSE detector 1713 can be referred to as the vertical distance between the top surface of the sample 1713 and the detection plane 1713P along which the detection surface of the BSE detector 1713 extends. As Figure 17 shown, the z-axis height of the BSE detector 1713 can be adjusted within a range of positions relative to the position of the sample 1715. The z-axis position of the BSE detector 1713 having a detection surface that extends along the detection plane 1713P can be referred to as the nominal position of the BSE detector 1713. For the nominal position, ΔZ = 0, where ΔZ is the difference in the z-axis position relative to the nominal position. If the z-axis position of the BSE detector 1713 is adjusted such that its detection surface moves upstream from 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 such that its detection surface moves downstream and closer to the sample 1715, then ΔZ = [+distance].

[0149] Figure 18A simulated graphical representation showing the relationship between the BSE collection efficiency of individual segments of a segmented BSE detector consistent with embodiments of the present disclosure and the BSE emission energy for a range of z-height positions of the BSE detector. The simulated data graph 1810 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = -1 mm of the BSE detector, the simulated data graph 1820 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = -0.5 mm of the BSE detector, the simulated data graph 1830 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = 0 mm (nominal position of the BSE detector 1713) of the BSE detector, the simulated data graph 1840 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = +0.5 mm of the BSE detector, the simulated data graph 1850 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = +1.0 mm of the BSE detector, and the simulated data graph 1860 shows the BSE collection efficiency for individual segments for a z-height position ΔZ = +1.5 mm of the BSE detector. In some embodiments, the nominal position of the BSE detector 1713 may be determined based on at least but not limited to: the BSE collection efficiency at different segments of the BSE detector, the primary charged particle beam resolution, the objective magnetic field strength, the high voltage stability between the BSE detector and the control electrode, etc.

[0150] As shown in simulated data graphs 1810 to 1860, the energy components of the incoming BSE signal can be resolved based on the BSE collection efficiency of individual segments 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 identifiable energy component for which the BSE collection efficiency of the individual segment is the highest. In this context, the term "clearly identifiable" energy component refers to an energy component such that the BSE collection efficiency for that energy component is significantly higher than the BSE collection efficiency of other energy components, such that the difference between the BSE collection efficiencies of any two energy components is higher than a threshold. In some embodiments, the threshold may be predetermined or based on the image contrast obtained as a result of the difference in BSE collection efficiency. For example, as shown in simulated data graph 1850, where the BSE detector is located at ΔZ = +1 mm, the BSE collection efficiency of segment 2 for the energy component of 10 keV is significantly higher than other energy components, and thus, if the BSE detector is moved closer to the sample 1715, the energy components can be resolved.

[0151] In some embodiments, determining whether the energy components of an incoming BSE signal are resolved may include determining whether the BSE collection efficiency for each individual segment is higher 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%, or any suitable BSE collection efficiency or range of BSE collection efficiencies. For example, as shown in simulation data graph 1820, where the BSE detector 1713 is located at ΔZ = -0.5 mm, the BSE collection efficiency for the energy components of each segment is at least 10% higher than the threshold BSE collection efficiency.

[0152] In some embodiments, determining whether the energy components of an incoming BSE signal are resolved may include determining whether there are as many clearly identifiable energy components as possible. For example, as shown in simulation data graph 1820, where the BSE detector 1713 is located at ΔZ = -0.5 mm, based on the BSE collection efficiency for a particular energy component of each segment, substantially all energy components may be clearly identifiable.

[0153] 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 discussed above regarding determining whether the energy components are resolved may be used to optimize the z-height of the BSE detector.

[0154] Now referring Figure 19 , Figure 19 FIG. shows a process flow diagram of an exemplary method 1900 of imaging a sample using a charged particle beam apparatus (such as Figure 3 apparatus 300 in

[0155] In step 1910, a region of the sample including a feature is irradiated with a primary charged particle beam. The primary charged particle beam may include a primary electron beam. A controller (e.g., Figure 1 controller 50 of

[0156] is configured to apply a voltage signal to the cathode of an electron source configured to generate a plurality of primary electrons to form a primary electron beam. The electron source may be remotely activated, e.g., by using software, an application, or a set of instructions for a processor of the controller to supply power to the electron source through control circuitry. Figure 3 In step 1920, charged particles emitted from the sample after interacting with the primary electron beam (e.g., Figures 7A to 7DThe BSE detector may include multiple concentric segments of charged particle sensitive material, and the multiple concentric segments are configured to detect backscattered electrons emitted from the sample. Each segment can be configured to collect the emitted charged particles, and the charged particles have a range of energy levels and a main energy level from the range of energy levels. The energy of the BSE can be related to the depth of the sample from which the BSE is emitted. For example, higher energy BSE can be emitted from a shallower area of ​​the interaction volume of the sample, and lower energy BSE can be emitted from a deeper area of ​​the interaction volume. Based on this correlation, the peak BSE energy detected by the segment of the BSE detector can correspond to the depth of the sample from which the BSE is emitted.

[0157] In step 1930, a plurality of images of features in a region of the sample are generated. Each segment of the plurality of concentric segments is configured to generate an image based on the total number of BSEs detected by the segment. The image generated by each segment may carry information associated with the feature at a certain depth. For example, a segment closer to the principal optical axis (e.g., a segment farther from the principal optical axis) may detect BSEs with higher peak energies than a segment further away from the principal optical axis. Figure 3 A segment of the main optical axis 300-1 in the sample can detect a BSE with a lower peak energy. A BSE with a lower peak energy can indicate that the BSE is emitted from a deeper region of the sample and therefore carries information associated with the bottom of the feature. A BSE with a higher peak energy can indicate that the BSE is emitted from a shallower region of the sample and therefore carries information associated with the top of the feature.

[0158] 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 features of interest in a single scan of the sample.

[0159] Reference now Figure 20 , Figure 20 A method consistent with the present disclosure of using a charged particle beam device such as Figure 3 300) in an exemplary method 2000 for imaging a sample.

[0160] In step 2010, a region of a sample including a feature is irradiated using a primary charged particle beam. The primary charged particle beam may include a primary electron beam. A controller (e.g., Figure 1 The controller 50 in the embodiment of the present invention is configured to apply a voltage signal to a cathode of an electron source, the electron source being configured to generate a plurality of primary electrons to form a primary electron beam. The electron source can be remotely activated, for example, by using software, an application or a set of instructions for a processor of the controller to power the electron source through the control circuit system.

[0161] In step 2020, charged particles emitted from the sample after interacting with a primary electron beam (e.g., beam 300B1 in Figure 3 ) are detected using a charged particle detector such as a BSE detector (e.g., BSE detector 713 in Figures 7A to 7D ). The BSE detector may include a plurality of concentric segments of charged particle sensitive material configured to detect backscattered electrons emitted from the sample. Each segment may be configured to collect the emitted charged particles that have an energy level range and a primary energy level from that energy level range. The energy of the BSE may be related to the depth in the sample from which the BSE is emitted. For example, higher energy BSEs may be emitted from shallower regions of the interaction volume of the sample, and lower energy BSEs may be emitted from deeper regions 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 in the sample from which the BSE is emitted.

[0162] In step 2030, an image (e.g., a two-dimensional image) of a desired portion of the feature may be generated from the BSEs detected by a segment among the plurality of concentric segments of the BSE detector. For example, if the desired portion of the feature is the top portion, a high-contrast image may be generated from the BSEs detected by one or more segments that are farther from the principal optical axis (e.g., principal optical axis 300-1 in Figure 3 ) and are configured to detect high energy BSEs. In some embodiments, a three-dimensional (3D) image may be formed using a plurality of high-contrast 2D images generated based on the BSEs detected by the segments that have a desired peak energy and a desired energy level range.

[0163] It should be understood that although the listed examples and apparatuses discuss a single beam inspection system, the disclosed system and method for energy discrimination of BSEs in a bottom BSE detector may also be implemented in a multi-beam inspection system.

[0164] 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 an electronic control unit configured to control a charged particle beam device) for performing a method of an exemplary flowchart or other methods consistent with embodiments of the present disclosure. For example, the instructions stored in the non-transitory computer-readable medium may be executed by circuitry of the controller to perform these methods, in whole or in part. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid state drives, magnetic tape, or any other magnetic data storage medium, compact disc read-only memory (CD-ROM), any other optical data storage medium, any physical medium with a hole pattern, 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 memory, and networked versions thereof.

[0165] The block diagrams in the figures may illustrate the possible architectures, functions, and operations 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 diagram may represent certain arithmetic or logical operation processing that can be implemented using hardware such as electronic circuits. A block may also represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function. It should be understood that in some alternative implementations, the functions indicated in the blocks may not occur in the order shown in the figures. For example, two blocks shown in succession may be executed or implemented substantially concurrently, or the two blocks may sometimes be executed in reverse order, depending on the functions involved. Some blocks may also be omitted. It should also be understood that each block in the block diagram, and combinations of blocks, may be implemented by a system based on dedicated hardware that performs the specified functions or actions, or by a combination of dedicated hardware and computer instructions.

[0166] Embodiments may also be described using the following clauses:

[0167] 1. A charged particle beam device, comprising:

[0168] a charged particle source configured to generate primary charged particles that form a primary charged particle beam along a main optical axis; and

[0169] a charged particle detector comprising 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,

[0170] Each of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a primary energy level.

[0171] 2. The apparatus according to clause 1, wherein the segments in the plurality of concentric segments are separated by a charged particle insensitive material.

[0172] 3. The apparatus according to any one of clauses 1 and 2, wherein the plurality of concentric segments are arranged concentrically about the main optical axis.

[0173] 4. The apparatus according to any one of clauses 1 to 3, wherein the primary energy level of the segments located at an off-axis distance smaller than a threshold off-axis distance is lower than the primary energy level of the segments located at an off-axis distance larger than the threshold off-axis distance.

[0174] 5. The apparatus according to any one of clauses 1 to 4, wherein the charged particle detector includes a detection surface configured to directly receive the emitted charged particles from the sample, and the detection surface includes the charged particle sensitive material of the plurality of concentric segments.

[0175] 6. The apparatus according to any one of clauses 1 to 5, wherein the z-axis position of the sample can be adjusted along the main optical axis, and the adjustment of the z-axis position of the sample is based on the landing energy of the primary charged particles.

[0176] 7. The apparatus according to clause 6, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector enables the primary energy level for the segments in the plurality of concentric segments to be affected.

[0177] 8. The apparatus according to clause 7, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector also enables the energy level range detected by the segments of the charged particle detector to be affected.

[0178] 9. The apparatus according to any one of clauses 7 and 8, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector also enables the uniformity of the collection efficiency of the emitted charged particles across the plurality of concentric segments to be affected.

[0179] 10. The apparatus according to clause 9, wherein the adjustment of 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 the working distance enables the uniformity of the collection efficiency of the emitted charged particles for the plurality of concentric segments to be increased.

[0180] 11. The device according to clause 1, wherein the z-axis position of the charged particle detector is adjustable along the main optical axis.

[0181] 12. The device according to clause 11, wherein the adjustment of the z-axis position of the charged particle detector relative to the sample enables the influencing of the main energy level for each of the plurality of concentric segments.

[0182] 13. The device according to clause 12, wherein the adjustment of the z-axis position of the charged particle detector relative to the sample enables the influencing of the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector.

[0183] 14. The device according to clause 13, wherein the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector is at least 10%.

[0184] 15. The device according to clause 13, wherein the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector is at least 15%.

[0185] 16. A charged particle beam device, comprising:

[0186] A compound lens including a magnetic lens and an electrostatic lens, the compound lens being configured to focus a primary charged particle beam onto the surface of a sample; and

[0187] A charged particle detector including a plurality of concentric segments of a charged particle sensitive material, the plurality of concentric segments being configured to detect charged particles emitted from the sample after interaction of the primary charged particle beam with the sample, wherein each of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a main energy level.

[0188] 17. The device according to clause 16, wherein the compound lens is configured to provide an adjusted excitation signal to enable influencing the collection efficiency of the emitted charged particles for segments of the plurality of concentric segments of the charged particle detector.

[0189] 18. The device according to clause 17, wherein an increase in the excitation signal of the compound lens is configured to cause an increase in the collection efficiency of the main energy level of the emitted charged particles relative to the collection efficiency of the non-main energy levels for segments of the plurality of concentric segments of the charged particle detector.

[0190] 19. The device according to clause 17, wherein a decrease in the excitation signal of the compound lens is configured to cause an increase in the collection efficiency of the main energy level of the emitted charged particles relative to the collection efficiency of the non-main energy levels of the segments in the plurality of concentric segments of the charged particle detector.

[0191] 20. The device according to any one of clauses 17 to 19, wherein the adjustment of the excitation signal of the compound lens is configured to adjust a magnetic field strength that affects a spatial distribution of the emitted charged particles on the plurality of concentric segments of the charged particle detector.

[0192] 21. The device according to any one of clauses 17 to 20, wherein the adjustment of the excitation signal of the compound lens is configured to enable an influence on a contrast of an image generated from the charged particles detected by the segments in the plurality of concentric segments.

[0193] 22. The device according to any one of clauses 17 to 21, wherein the excitation signal includes a nominal excitation signal, and wherein the nominal excitation signal, when applied to the compound lens, is configured to enable the compound lens to focus the primary charged particle beam onto the sample.

[0194] 23. The device according to any one of clauses 16 to 22, wherein the charged particle detector is located between the compound lens and the sample.

[0195] 24. The device according to any one of clauses 16 to 23, further comprising a beam scanning deflector configured to compensate for a change in a focus of the primary charged particle beam to be incident on the surface of the sample.

[0196] 25. The device according to clause 24, wherein the beam scanning deflector is located immediately upstream of a pole piece of the magnetic lens.

[0197] 26. The device according to any one of clauses 24 and 25, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at an equal potential to form a lens field.

[0198] 27. The device according to clause 26, wherein the beam scanning deflector is configured to receive an excitation signal to form the lens field, and wherein an adjustment of the excitation signal adjusts the compensation for the focus of the primary charged particle beam.

[0199] 28. The device according to clause 27, wherein the excitation signal of the beam scanning deflector is deactivated when the nominal excitation signal is applied to the compound lens.

[0200] 29. The device 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.

[0201] 30. The device according to clause 29, wherein the voltage signal applied to the beam scanning deflector is configured such that the beam scanning deflector can focus the primary charged particle beam onto the surface of the sample.

[0202] 31. The device according to any one of clauses 24 to 30, further comprising a condenser lens located upstream of the compound objective lens.

[0203] 32. The device according to clause 31, wherein the focusing ability of the condenser lens is adjusted to compensate for a change in the focus of the primary charged particle beam when the excitation signal of the compound objective lens is higher than the nominal excitation signal.

[0204] 33. The device according to clause 32, wherein the focusing ability of the condenser lens is reduced to form a divergent primary charged particle beam.

[0205] 34. The device according to clause 33, further comprising an aperture array located upstream of the condenser lens, the aperture array including 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 through.

[0206] 35. The device according to clause 34, wherein the portion of the primary charged particle beam allowed to pass through compensates for a decrease in the beam current caused by the reduced focusing ability of the condenser lens.

[0207] 36. A charged particle beam device, comprising:

[0208] A charged particle source configured to generate primary charged particles that form a primary charged particle beam incident on a sample along a principal optical axis;

[0209] A control electrode located immediately upstream of the sample and configured to affect the electrostatic field near the sample based on an applied voltage signal; and

[0210] A charged particle detector, the charged particle detector including a plurality of concentric segments of charged particle sensitive material, the plurality of concentric segments being configured to detect charged particles emitted from a sample after interaction of a primary charged particle beam with the sample, wherein each segment of the plurality of concentric segments is configured to collect the emitted charged particles having an energy level range and a primary energy level.

[0211] 37. The apparatus according to clause 36, wherein the control electrode is located between the sample and the charged particle detector.

[0212] 38. The apparatus according to any one of clauses 36 and 37, wherein the voltage signal applied to the control electrode enables the collection efficiency of the emitted charged particles to be affected for each segment of the plurality of concentric segments of the charged particle detector.

[0213] 39. The apparatus according to clause 38, wherein the applied voltage signal is configured to increase the collection efficiency of the emitted charged particles for segments located at an off-axis distance greater than a threshold off-axis distance.

[0214] 40. The apparatus according to clause 39, wherein the applied voltage signal is configured to decrease the collection efficiency of the emitted charged particles for segments located at an off-axis distance less than the threshold off-axis distance.

[0215] 41. The apparatus according to any one of clauses 36 to 40, wherein adjustment of the voltage signal applied to the control electrode enables the primary energy level of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector to be affected.

[0216] 42. The apparatus according to clause 41, wherein the adjustment of the voltage signal applied to the control electrode enables the energy level range of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector to be affected.

[0217] 43. The apparatus according to any one of clauses 36 to 42, further comprising a compound lens located immediately upstream of the charged particle detector, the compound lens including a magnetic lens and an electrostatic lens.

[0218] 44. The apparatus according to clause 43, wherein the compound lens is configured to receive a voltage signal to generate an electric field between the sample and the compound lens.

[0219] 45. The device according to clause 44, wherein the generated electric field enables the collection efficiency of each of the multiple concentric segments of the charged particle detector for the emitted charged particles to be affected.

[0220] 46. The device according to clause 45, wherein the generated electric field enables the collection efficiency of each of the multiple concentric segments of the charged particle detector for the emitted charged particles to be increased.

[0221] 47. The device according to any one of clauses 44 to 46, wherein the generated electric field also enables the energy level range of the emitted charged particles detected by the segments of the multiple concentric segments of the charged particle detector to be affected.

[0222] 48. The device according to clause 47, wherein the generated electric field also enables the energy level range of the emitted charged particles detected by the segments of the multiple concentric segments of the charged particle detector to be increased.

[0223] 49. The device according to any one of clauses 44 to 46, wherein the generated electric field also enables the main energy level of the charged particles detected by the segments of the multiple concentric segments of the charged particle detector to be affected.

[0224] 50. The device according to clause 49, wherein the generated electric field also enables the main energy level of the charged particles detected by the segments of the multiple concentric segments of the charged particle detector to be increased.

[0225] 51. The device according to clause 49, wherein the generated electric field also enables the main energy level of the charged particles detected by the segments of the multiple concentric segments of the charged particle detector to be decreased.

[0226] 52. A charged particle detector for use in a charged particle beam device, the charged particle detector comprising:

[0227] multiple concentric segments of charged particle sensitive material, the multiple concentric segments being configured to detect charged particles emitted from a sample,

[0228] wherein each of the multiple concentric segments is configured to detect the emitted charged particles having an energy level range and a corresponding main energy level.

[0229] 53. The charged particle detector according to clause 52, wherein the segments of the multiple concentric segments are separated by charged particle insensitive material.

[0230] 54. A charged particle detector according to any one of clauses 52 and 53, wherein the plurality of concentric segments are concentrically arranged about the main optical axis of the charged particle beam device.

[0231] 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 the charged particle sensitive material.

[0232] 56. A charged particle detector according to clause 55, wherein the detection surface is arranged perpendicular to the main optical axis.

[0233] 57. A charged particle detector according to any one of clauses 52 to 56, wherein the corresponding main energy level of the segments located at an off-axis distance greater than the threshold off-axis distance is higher than the corresponding main energy level of the segments located at an off-axis distance less than the threshold off-axis distance.

[0234] 58. A charged particle detector according to any one of clauses 52 to 57, wherein each of the plurality of concentric segments is circular.

[0235] 59. A charged particle detector according to any one of clauses 52 to 57, wherein each of the plurality of concentric segments is polygonal.

[0236] 60. A charged particle detector according to any one of clauses 52 to 59, further comprising a central opening aligned with the main optical axis and configured to allow the primary charged particle beam to pass through.

[0237] 61. A charged particle detector according to any one of clauses 52 to 60, wherein the width of each of the plurality of concentric segments is substantially similar.

[0238] 62. A charged particle detector according to any one of clauses 52 to 61, wherein the emitted charged particles include backscattered electrons.

[0239] 63. A method of imaging a sample, the method comprising:

[0240] irradiating a region of the sample, the region including features, with a primary charged particle beam; detecting, using each of a plurality of concentric segments of a charged particle detector, charged particles emitted from the region of the sample;

[0241] generating a plurality of images of the features, wherein each of the plurality of images is generated from the charged particles detected by the corresponding segment of the plurality of concentric segments of the charged particle detector; and

[0242] Determine the characteristics of the feature based on the plurality of images.

[0243] Wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having an energy level range and a primary energy level.

[0244] 64. The method according to clause 63, wherein the energy level range of the detected charged particles corresponds to a range of depths of the sample from which the charged particles are emitted.

[0245] 65. The method according to any one of clauses 63 and 64, wherein the primary energy level of the detected charged particles corresponds to the depth of the sample from which the charged particles are emitted.

[0246] 66. The method according to any one of clauses 63 to 65, wherein the plurality of images of the feature are generated simultaneously during a single scan of the sample region using the primary charged particle beam.

[0247] 67. The method according to any one of clauses 63 to 66, wherein configuring each segment includes: adjusting the z-axis position of the sample along the primary optical axis of the primary charged particle beam.

[0248] 68. The method according to clause 67, wherein adjusting the z-axis position of the sample enables influencing the primary energy level detected by the segments of the charged particle detector.

[0249] 69. The method according to any one of clauses 67 and 68, wherein adjusting the z-axis position of the sample further enables influencing the energy level range detected by the segments of the charged particle detector.

[0250] 70. The method according to any one of clauses 67 to 69, wherein adjusting the z-axis position of the sample further enables influencing the uniformity of the collection efficiency across the plurality of segments of the charged particle detector.

[0251] 71. The method according to clause 70, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and wherein increasing the working distance enables improving the uniformity of the collection efficiency of the plurality of segments of the charged particle detector.

[0252] 72. The method according to 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.

[0253] 73. The method according to clause 72, wherein the z-axis position of the charged particle detector relative to the sample is adjusted such that the main energy level detected by each segment of the charged particle detector can be affected.

[0254] 74. The method according to clauses 72 and 73, wherein the z-axis position of the charged particle detector relative to the sample is adjusted such that the collection efficiency of the emitted charged particles of the main energy level for each segment of the charged particle detector can be affected.

[0255] 75. The method according to clauses 63 to 74, wherein configuring each segment further includes: adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of the compound lens, the compound lens including a magnetic lens and an electrostatic lens.

[0256] 76. The method according to clause 75, wherein the magnetic field strength is adjusted such that the spatial distribution of the emitted charged particles incident on the detection surface of each segment of the charged particle detector can be affected.

[0257] 77. The method according to any one of clauses 75 and 76, wherein the magnetic field strength is adjusted such that the collection efficiency of the main energy level of the emitted charged particles for each segment of the charged particle detector can be affected.

[0258] 78. The method according to any one of clauses 75 to 77, wherein increasing the magnetic field strength enables the collection efficiency of the non-main energy level of the emitted charged particles for the first segment of the plurality of segments of the charged particle detector to be improved.

[0259] 79. The method according to clause 78, wherein decreasing the magnetic field strength enables the collection efficiency of the non-main energy level of the emitted charged particles for the second segment of the plurality of segments of the charged particle detector to be improved.

[0260] 80. The method according to any one of clauses 75 to 79, wherein the magnetic field strength is adjusted such that the image contrast of the plurality of generated images can be affected.

[0261] 81. The method according to any one of clauses 75 to 80, wherein adjusting the excitation signal includes: adjusting the voltage signal applied to the magnetic lens of the compound lens.

[0262] 82. The method according to any one of clauses 75 to 81, wherein configuring each segment further includes: adjusting the electric field between the sample and the compound lens by adjusting the voltage signal applied to the electrostatic lens of the compound lens.

[0263] 83. The method according to clause 82, wherein the electric field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be affected.

[0264] 84. The method according to clause 83, wherein the electric field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be increased.

[0265] 85. The method according to any one of clauses 82 to 84, wherein adjusting the electric field further enables affecting the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0266] 86. The method according to clause 85, wherein adjusting the electric field further enables increasing the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0267] 87. The method according to any one of clauses 82 to 86, wherein adjusting the electric field further enables affecting the main energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0268] 88. The method according to clause 87, wherein adjusting the electric field further enables increasing the main energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0269] 89. The method according to clause 87, wherein adjusting the electric field further enables decreasing the main energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0270] 90. The method according to any one of clauses 75 to 81, further comprising: using a beam scanning deflector to compensate for a change in the focus of the primary charged particles, the change in the focus being caused by the adjustment of the magnetic field strength of the complex lens.

[0271] 91. The method according to clause 90, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at the same potential to form a lens field.

[0272] 92. The method according to any one of clauses 90 and 91, wherein the excitation signal of the beam scanning deflector is adjusted such that the compensation for the change in the focus of the primary charged particle beam can be adjusted.

[0273] 93. The method according to clause 92, wherein adjusting the excitation signal of the beam scanning deflector comprises: adjusting a voltage signal applied to the beam scanning deflector.

[0274] 94. The method according to any one of clauses 92 and 93, further comprising: deactivating the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample.

[0275] 95. The method according to any one of clauses 90 to 94, further comprising: adjusting the focusing ability of a condenser lens located upstream of the compound lens when the excitation signal applied to the compound lens is higher than a nominal excitation signal.

[0276] 96. The method according to clause 95, wherein adjusting the focusing ability comprises: reducing the focusing ability of the condenser lens so as to enable the formation of a divergent primary charged particle beam.

[0277] 97. The method according to clause 96, further comprising: allowing the primary charged particle beam to pass through an aperture of an aperture array located upstream of the condenser lens, the aperture being configured to allow a portion of the primary charged particle beam, wherein the allowed portion compensates for a reduced beam current of the divergent primary charged particle beam.

[0278] 98. The method according to any one of clauses 90 to 97, wherein configuring each segment comprises: adjusting an electrostatic field near the sample by applying a voltage signal to a control electrode located immediately upstream of the sample.

[0279] 99. The method according to clause 98, wherein adjusting the electrostatic field enables affecting the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector.

[0280] 100. The method according to clause 99, wherein adjusting the electrostatic field enables increasing the collection efficiency of the emitted charged particles for segments located at an off-axis distance greater than a threshold off-axis distance.

[0281] 101. The method according to clause 100, wherein adjusting the electrostatic field enables reducing the collection efficiency of the emitted charged particles for segments located at an off-axis distance less than the threshold off-axis distance.

[0282] 102. The method according to any one of clauses 98 to 101, wherein adjusting the electrostatic field enables affecting the main energy level of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector.

[0283] 103. The method according to clause 102, wherein the electrostatic field is adjusted such that it is capable of affecting the range of energy levels of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0284] 104. The method according to any one of clauses 63 to 103, wherein determining the property of the feature includes:

[0285] forming a three-dimensional image of the feature from the plurality of images; and

[0286] determining the property from the three-dimensional image.

[0287] 105. The method according to any one of clauses 63 to 104, wherein the property includes the overlay, sidewall angle, critical dimension, or depth profile of the feature.

[0288] 106. A charged particle beam apparatus, comprising:

[0289] a charged particle source configured to generate primary charged particles, the primary charged particles forming a primary charged particle beam along a main optical axis;

[0290] a charged particle detector including a plurality of segments that are concentric with the primary charged particle beam and are configured to detect charged particles emitted from the sample; and

[0291] a controller including circuitry configured to:

[0292] irradiate a region of the sample including a feature with the primary charged particle beam;

[0293] generate a plurality of images of the irradiated region, wherein each of the plurality of images is generated from the charged particles detected by a corresponding segment of the charged particle detector;

[0294] determine a property of the feature based on the plurality of images,

[0295] wherein segmenting the charged particle detector allows the emitted charged particles to be differentiated for each segment according to a corresponding main energy level and according to a corresponding energy level range.

[0296] 107. The apparatus according to clause 106, wherein the segments of the plurality of concentric segments are separated by a charged particle-insensitive material.

[0297] 108. The apparatus according to any one of clauses 106 and 107, wherein the plurality of concentric segments are concentrically arranged around the main optical axis.

[0298] 109. The device according to any one of clauses 106 to 108, wherein the main energy level of the segment located at an off-axis distance smaller than the threshold off-axis distance is lower than the main energy level of the segment located at an off-axis distance larger than the threshold off-axis distance.

[0299] 110. The device according to any one of clauses 106 to 109, wherein the charged particle detector includes a detection surface configured to directly receive the emitted charged particles from the sample, and the detection surface includes the charged particle sensitive material of the plurality of concentric segments.

[0300] 111. The device according to any one of clauses 106 to 110, wherein the z-axis position of the sample can be adjusted along the main optical axis, and the adjustment of the z-axis position of the sample is based on the landing energy of the primary charged particles.

[0301] 112. The device according to clause 111, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector enables the influence on the main energy level for the segments in the plurality of concentric segments.

[0302] 113. The device according to clause 112, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector further enables the influence on the energy level range detected by the segments of the charged particle detector.

[0303] 114. The device according to any one of clauses 112 and 113, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector further enables the influence on the uniformity of the collection efficiency of the emitted charged particles across the plurality of concentric segments.

[0304] 115. The device according to clause 114, wherein the adjustment of 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 the working distance enables the increase in the uniformity of the collection efficiency of the emitted charged particles for the plurality of concentric segments.

[0305] 116. The device according to clause 115, wherein the z-axis position of the charged particle detector can be adjusted along the main optical axis.

[0306] 117. The device according to clause 116, wherein the adjustment of the z-axis position of the charged particle detector relative to the sample enables the influence on the main energy level for each segment in the plurality of concentric segments.

[0307] 118. The apparatus according to clause 117, wherein the z-axis position of the charged particle detector relative to the sample is adjusted such that it can affect the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector.

[0308] 119. The apparatus according to clause 118, wherein the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector is at least 10%.

[0309] 120. The apparatus according to clause 118, wherein the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector is at least 15%.

[0310] 121. The apparatus according to any one of clauses 106 to 120, further comprising a compound lens, the compound lens including a magnetic lens and an electrostatic lens, the compound lens being configured to focus a primary charged particle beam onto the surface of the sample.

[0311] 122. The apparatus according to clause 121, wherein the compound lens is configured to provide an adjusted excitation signal so as to be able to affect the collection efficiency of the emitted charged particles for segments in the plurality of concentric segments of the charged particle detector.

[0312] 123. The apparatus according to clause 122, wherein an increase in the excitation signal of the compound lens is configured to cause an increase in the collection efficiency of the main energy level of the emitted charged particles relative to the collection efficiency of the non-main energy level for segments in the plurality of concentric segments of the charged particle detector.

[0313] 124. The apparatus according to clause 122, wherein a decrease in the excitation signal of the compound lens is configured to cause an increase in the collection efficiency of the main energy level of the emitted charged particles relative to the collection efficiency of the non-main energy level for segments in the plurality of concentric segments of the charged particle detector.

[0314] 125. The apparatus according to any one of clauses 122 to 124, wherein the adjustment of the excitation signal of the compound lens is configured to adjust the magnetic field strength, and the magnetic field strength affects the spatial distribution of the emitted charged particles on the plurality of concentric segments of the charged particle detector.

[0315] 126. The device according to any one of clauses 122 to 125, wherein the adjustment of the excitation signal of the compound lens is configured to enable the contrast of an image generated from charged particles detected by segments of the plurality of concentric segments to be affected.

[0316] 127. The device according to any one of clauses 122 to 126, wherein the excitation signal includes a nominal excitation signal, and wherein the nominal excitation signal, when applied to the compound lens, is configured to enable the compound lens to focus the primary charged particle beam onto the sample.

[0317] 128. The device according to any one of clauses 121 to 127, wherein the charged particle detector is located between the compound lens and the sample.

[0318] 129. The device according to any one of clauses 121 to 128, further comprising a beam scanning deflector configured to compensate for variations in the focus of the primary charged particle beam to be incident on the surface of the sample.

[0319] 130. The device according to clause 129, wherein the beam scanning deflector is located immediately upstream of the pole pieces of the magnetic lens.

[0320] 131. The device according to any one of clauses 129 and 130, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at the same potential to form a lens field.

[0321] 132. The device according to clause 131, wherein the beam scanning deflector is configured to receive an excitation signal to form the lens field, and wherein the adjustment of the excitation signal adjusts the compensation for the focus of the primary charged particle beam.

[0322] 133. The device according to clause 132, wherein the excitation signal of the beam scanning deflector is deactivated when the nominal excitation signal is applied to the compound lens.

[0323] 134. The device 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 lens is lower than the nominal excitation signal.

[0324] 135. The device according to 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.

[0325] 136. The device according to any one of clauses 129 to 135 further includes a condenser lens, and the condenser lens is located upstream of the compound objective lens.

[0326] 137. The device according to clause 136, wherein the focusing ability of the condenser lens is adjusted to compensate for the change in the focus of the primary charged particle beam when the excitation signal of the compound objective lens is higher than the nominal excitation signal.

[0327] 138. The device according to clause 137, wherein the focusing ability of the condenser lens is reduced to form a divergent primary charged particle beam.

[0328] 139. The device according to clause 138 further includes an aperture array, and the aperture array is located upstream of the condenser lens. The aperture array includes a plurality of apertures, and the plurality of apertures are configured to adjust the beam current of the primary charged particle beam based on the allowed passing portion of the primary charged particle beam.

[0329] 140. The device according to clause 139, wherein the allowed passing portion of the primary charged particle beam compensates for the decrease in the beam current caused by the reduced focusing ability of the condenser lens.

[0330] 141. The device according to any one of clauses 106 to 140 further includes a control electrode, and the control electrode is located immediately upstream of the sample and is configured to affect the electrostatic field near the sample based on an applied voltage signal.

[0331] 142. The device according to clause 141, wherein the control electrode is located between the sample and the charged particle detector.

[0332] 143. The device according to any one of clauses 141 and 142, wherein the voltage signal applied to the control electrode enables the collection efficiency of each of the plurality of concentric segments of the emitted charged particles for the charged particle detector to be affected.

[0333] 144. The device according to clause 143, wherein the applied voltage signal is configured to increase the collection efficiency of the emitted charged particles for the segments located at an off-axis distance greater than the threshold off-axis distance.

[0334] 145. The device according to clause 144, wherein the applied voltage signal is configured to decrease the collection efficiency of the emitted charged particles for the segments located at an off-axis distance less than the threshold off-axis distance.

[0335] 146. The apparatus according to any one of clauses 141 to 145, wherein the adjustment of the voltage signal applied to the control electrode enables influencing the main energy level of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector.

[0336] 147. The apparatus according to clause 146, wherein the adjustment of the voltage signal applied to the control electrode enables influencing the range of energy levels of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector.

[0337] 148. A method of imaging a sample, the method comprising:

[0338] irradiating a region of the sample, the region including a feature, with a primary charged particle beam; detecting charged particles emitted from the region of the sample using each of a plurality of concentric segments of a charged particle detector,

[0339] wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having a range of energy levels and a main energy level; and

[0340] generating an image of a portion of the feature from the charged particles collected by segments of the plurality of concentric segments.

[0341] 149. The method according to clause 148, wherein the range of energy levels of the detected charged particles corresponds to a range of depths of the sample from which the charged particles are emitted.

[0342] 150. The method according to any one of clauses 148 and 149, wherein the main energy level of the detected charged particles corresponds to the depth of the sample from which the charged particles are emitted.

[0343] 151. The method according to any one of clauses 148 to 150, wherein configuring each segment includes: adjusting the z-axis position of the sample along the main optical axis of the primary charged particle beam.

[0344] 152. The method according to clause 151, wherein adjusting the z-axis position of the sample enables influencing the main energy level detected by segments of the charged particle detector.

[0345] 153. The method according to 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 segments of the charged particle detector.

[0346] 154. The method according to any one of clauses 151 to 153, wherein adjusting the z-axis position of the sample further enables affecting the uniformity of the collection efficiency across the plurality of segments of the charged particle detector.

[0347] 155. The method according to clause 154, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and wherein increasing the working distance enables improving the uniformity of the collection efficiency of the plurality of segments of the charged particle detector.

[0348] 156. The method according to any one of clauses 151 to 155, wherein configuring each segment includes: adjusting the z-axis position of the charged particle detector relative to the sample.

[0349] 157. The method according to clause 156, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables affecting the main energy level detected by each segment of the charged particle detector.

[0350] 158. The method according to clauses 156 and 157, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables affecting the collection efficiency of the emitted charged particles at the main energy level for each segment of the plurality of segments of the charged particle detector.

[0351] 159. The method according to clauses 148 to 158, wherein configuring each segment further includes: adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of a compound lens, the compound lens including a magnetic lens and an electrostatic lens.

[0352] 160. The method according to clause 159, wherein adjusting the magnetic field strength enables affecting the spatial distribution of the emitted charged particles incident on the detection surface of each segment of the charged particle detector.

[0353] 161. The method according to any one of clauses 159 and 160, wherein adjusting the magnetic field strength enables affecting the collection efficiency of the main energy level of the emitted charged particles for each segment of the charged particle detector.

[0354] 162. The method according to any one of clauses 159 to 161, wherein increasing the magnetic field strength enables improving the collection efficiency of the non-main energy level of the emitted charged particles for the first segment of the plurality of segments of the charged particle detector.

[0355] 163. The method according to clause 162, wherein reducing the magnetic field strength enables the collection efficiency of the second of the plurality of segments of the charged particle detector for the non-primary energy level of the emitted charged particles to be increased.

[0356] 164. The method according to any one of clauses 159 to 163, wherein adjusting the magnetic field strength enables the image contrast of the plurality of generated images to be affected.

[0357] 165. The method according to any one of clauses 159 to 164, wherein adjusting the excitation signal includes: adjusting the voltage signal applied to the magnetic lens of the compound lens.

[0358] 166. The method according to any one of clauses 159 to 165, wherein configuring each segment further includes: adjusting the electric field between the sample and the compound lens by adjusting the voltage signal applied to the electrostatic lens of the compound lens.

[0359] 167. The method according to clause 166, wherein adjusting the electric field enables the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector to be affected.

[0360] 168. The method according to clause 167, wherein adjusting the electric field enables the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector to be increased.

[0361] 169. The method according to any one of clauses 166 to 168, wherein adjusting the electric field further enables the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector to be affected.

[0362] 170. The method according to clause 169, wherein adjusting the electric field further enables the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector to be increased.

[0363] 171. The method according to any one of clauses 166 to 170, wherein adjusting the electric field further enables the primary energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector to be affected.

[0364] 172. The method according to clause 171, wherein adjusting the electric field further enables the primary energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector to be increased.

[0365] 173. The method according to clause 171, wherein adjusting the electric field further enables reducing the main energy level of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0366] 174. The method according to any one of clauses 159 to 164, further comprising: using a beam scanning deflector to compensate for a change in the focus of the primary charged particle beam, the change in the focus being caused by the adjustment of the magnetic field strength of the combined lens.

[0367] 175. The method according to clause 174, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at the same potential to form a lens field.

[0368] 176. The method according to any one of clauses 174 and 175, wherein adjusting the excitation signal of the beam scanning deflector enables adjusting the compensation for the change in the focus of the primary charged particle beam.

[0369] 177. The method according to clause 176, wherein adjusting the excitation signal of the beam scanning deflector includes: adjusting the voltage signal applied to the beam scanning deflector.

[0370] 178. The method according to any one of clauses 176 and 177, further comprising: deactivating the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample.

[0371] 179. The method according to any one of clauses 174 to 178, further comprising: adjusting the focusing ability of a condenser lens located upstream of the combined lens when the excitation signal applied to the combined lens is higher than the nominal excitation signal.

[0372] 180. The method according to clause 179, wherein adjusting the focusing ability includes: reducing the focusing ability of the condenser lens to enable forming a divergent primary charged particle beam.

[0373] 181. The method according to clause 180, further comprising: allowing the primary charged particle beam to pass through an aperture of an aperture array located upstream of the condenser lens, the aperture being configured to allow a portion of the primary charged particle beam, wherein the allowed portion compensates for the reduced beam current of the divergent primary charged particle beam.

[0374] 182. The method according to any one of clauses 174 to 181, wherein configuring each segment includes: adjusting the electrostatic field near the sample by applying a voltage signal to a control electrode located immediately upstream of the sample.

[0375] 183. The method according to clause 182, wherein the electrostatic field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be affected.

[0376] 184. The method according to clause 183, wherein the electrostatic field is adjusted such that the collection efficiency of the emitted charged particles for segments located at an off-axis distance greater than a threshold off-axis distance can be increased.

[0377] 185. The method according to clause 184, wherein the electrostatic field is adjusted such that the collection efficiency of the emitted charged particles for segments located at an off-axis distance less than the threshold off-axis distance can be decreased.

[0378] 186. The method according to any one of clauses 182 to 185, wherein the electrostatic field is adjusted such that the main energy level of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector can be affected.

[0379] 187. The method according to clause 186, wherein the electrostatic field is adjusted such that the energy level range of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector can be affected.

[0380] 188. A non-transitory computer-readable medium storing a set of instructions that can be executed 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:

[0381] Activating a charged particle source to generate primary charged particles that form a primary charged particle beam along a main optical axis;

[0382] Radiating a region of the sample including features with the primary charged particle beam; detecting charged particles emitted from the sample using a charged particle detector, the charged particle detector including a plurality of segments that are concentric with the primary charged particle beam; generating a plurality of images of the irradiated region, wherein each of the plurality of images is generated from the charged particles detected by a corresponding segment of the charged particle detector; and

[0383] Determining a characteristic of the feature based on the plurality of images, wherein segmenting the charged particle detector allows the emitted charged particles to be distinguished for each segment according to a corresponding main energy level and according to a corresponding energy level range.

[0384] 189. The non-transitory computer-readable medium according to clause 188, wherein the detected energy level range of the charged particles corresponds to a range of depths of the sample from which the charged particles are emitted.

[0385] 190. The non-transitory computer-readable medium according to any one of clauses 188 and 189, wherein the detected main energy level of the charged particles corresponds to the depth of the sample from which the charged particles are emitted.

[0386] 191. The non-transitory computer-readable medium according to any one of clauses 188 to 190, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform generating the plurality of images simultaneously during a single scan of the sample region using the primary charged particle beam.

[0387] 192. The non-transitory computer-readable medium according to any one of clauses 188 to 191, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform configuring each segment, where configuring each segment includes adjusting the z-axis position of the sample along the main optical axis of the primary charged particle beam.

[0388] 193. The non-transitory computer-readable medium according to clause 192, wherein adjusting the z-axis position of the sample enables influencing the detected main energy level by the segments of the charged particle detector.

[0389] 194. The non-transitory computer-readable medium according to any one of clauses 192 and 193, wherein adjusting the z-axis position of the sample also enables influencing the detected energy level range by the segments of the charged particle detector.

[0390] 195. The non-transitory computer-readable medium according to any one of clauses 192 to 194, wherein adjusting the z-axis position of the sample also enables influencing the uniformity of the collection efficiency across the plurality of segments of the charged particle detector.

[0391] 196. The non-transitory computer-readable medium according to clause 195, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and wherein increasing the working distance enables improving the uniformity of the collection efficiency of the plurality of segments of the charged particle detector.

[0392] 197. The non-transitory computer-readable medium according to any one of clauses 188 to 196, wherein the set of instructions is executable by the one or more processors to cause the charged particle beam device to further perform configuring each segment, and wherein configuring each segment further includes adjusting the z-axis position of the charged particle detector relative to the sample.

[0393] 198. The non-transitory computer-readable medium according to clause 197, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables influencing the main energy level detected by each segment of the charged particle detector.

[0394] 199. The non-transitory computer-readable medium according to clauses 197 and 198, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables influencing the collection efficiency of the emitted charged particles of the main energy level for each segment of the charged particle detector.

[0395] 200. The non-transitory computer-readable medium according to clauses 188 to 199, wherein the set of instructions is executable by the one or more processors to cause the charged particle beam device to further perform configuring each segment, and wherein configuring each segment further includes adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of the combined lens, the combined lens including a magnetic lens and an electrostatic lens.

[0396] 201. The non-transitory computer-readable medium according to clause 200, wherein adjusting the magnetic field strength enables influencing the spatial distribution of the emitted charged particles incident on the detection surface of each segment of the charged particle detector.

[0397] 202. The non-transitory computer-readable medium according to any one of clauses 200 and 201, wherein adjusting the magnetic field strength enables influencing the collection efficiency of the main energy level of the emitted charged particles for each segment of the charged particle detector.

[0398] 203. The non-transitory computer-readable medium according to any one of clauses 200 to 202, wherein increasing the magnetic field strength enables increasing the collection efficiency of the non-main energy level of the emitted charged particles for the first segment of the plurality of segments of the charged particle detector.

[0399] 204. The non-transitory computer-readable medium according to any one of clause 203, wherein decreasing the magnetic field strength enables increasing the collection efficiency of the non-main energy level of the emitted charged particles for the second segment of the plurality of segments of the charged particle detector.

[0400] 205. The non-transitory computer-readable medium according to any one of clauses 200 to 204, wherein the magnetic field strength is adjusted such that the image contrast of the plurality of generated images can be affected.

[0401] 206. The non-transitory computer-readable medium according to any one of clauses 200 to 205, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform adjusting a voltage signal applied to the magnetic lens of the composite lens.

[0402] 207. The non-transitory computer-readable medium according to any one of clauses 200 to 206, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform configuring each segment, and configuring each segment further includes adjusting an electric field between the sample and the composite lens by adjusting a voltage signal applied to the electrostatic lens of the composite lens.

[0403] 208. The non-transitory computer-readable medium according to clause 207, wherein the electric field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be affected.

[0404] 209. The non-transitory computer-readable medium according to clause 208, wherein the electric field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be increased.

[0405] 210. The non-transitory computer-readable medium according to any one of clauses 207 to 209, wherein adjusting the electric field further enables affecting the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0406] 211. The non-transitory computer-readable medium according to clause 210, wherein adjusting the electric field further enables increasing the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0407] 212. The non-transitory computer-readable medium according to any one of clauses 207 to 211, wherein adjusting the electric field further enables affecting the main energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector.

[0408] 213. The non-transitory computer-readable medium according to clause 212, wherein adjusting the electric field further enables increasing the main energy level of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0409] 214. The non-transitory computer-readable medium according to clause 212, wherein adjusting the electric field further enables decreasing the main energy level of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0410] 215. The non-transitory computer-readable medium according to any one of clauses 200 to 206, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform compensating for a change in the focus of the primary charged particle beam using a beam scanning deflector, the change in the focus being caused by the adjustment of the magnetic field strength of the compound lens.

[0411] 216. The non-transitory computer-readable medium according to clause 215, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at the same potential to form a lens field.

[0412] 217. The non-transitory computer-readable medium according to any one of clauses 215 and 216, wherein adjusting the excitation signal of the beam scanning deflector enables adjusting the compensation for the change in the focus of the primary charged particle beam.

[0413] 218. The non-transitory computer-readable medium according to clause 217, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform adjusting the excitation signal of the beam scanning deflector, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector.

[0414] 219. The non-transitory computer-readable medium according to any one of clauses 217 and 218, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform deactivating the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample.

[0415] 220. The non-transitory computer-readable medium according to any one of clauses 215 to 219, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform adjusting the focusing ability of a converging lens located upstream of the compound lens when the excitation signal applied to the compound lens is higher than a nominal excitation signal.

[0416] 221. The non-transitory computer-readable medium according to clause 220, wherein the set of instructions is executable by the one or more processors to further cause the charged particle beam device to perform reducing the focusing ability of the condenser lens such that a divergent primary charged particle beam can be formed.

[0417] 222. The non-transitory computer-readable medium according to clause 221, wherein the set of instructions is executable by the one or more processors to further cause the charged particle beam device to perform allowing the primary charged particle beam to pass through an aperture of an aperture array located upstream of the condenser lens, the aperture being configured to allow a portion of the primary charged particle beam, wherein the allowed portion compensates for a reduced beam current of the divergent primary charged particle beam.

[0418] 223. The non-transitory computer-readable medium according to any one of clauses 215 to 222, wherein the set of instructions is executable by the one or more processors to further cause the charged particle beam device to perform configuring each segment, and wherein configuring each segment includes adjusting an electrostatic field near the sample by applying a voltage signal to a control electrode located directly upstream of the sample.

[0419] 224. The non-transitory computer-readable medium according to clause 223, wherein adjusting the electrostatic field enables affecting a collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector.

[0420] 225. The non-transitory computer-readable medium according to clause 224, wherein adjusting the electrostatic field enables increasing the collection efficiency of the emitted charged particles for segments located at an off-axis distance greater than a threshold off-axis distance.

[0421] 226. The non-transitory computer-readable medium according to clause 225, wherein adjusting the electrostatic field enables reducing the collection efficiency of the emitted charged particles for segments located at an off-axis distance less than the threshold off-axis distance.

[0422] 227. The non-transitory computer-readable medium according to any one of clauses 223 to 226, wherein adjusting the electrostatic field enables affecting a main energy level of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector.

[0423] 228. The non-transitory computer-readable medium according to clause 227, wherein adjusting the electrostatic field enables affecting an energy level range of the emitted charged particles detected by segments of the plurality of concentric segments of the charged particle detector.

[0424] 229. The non - transient computer - readable medium according to any one of clauses 188 to 228, wherein determining the property of the feature includes:

[0425] forming a three - dimensional image of the feature from the plurality of images; and

[0426] determining the property from the three - dimensional image.

[0427] 230. The non - transient computer - readable medium according to any one of clauses 188 to 229, wherein the property includes overlay, sidewall angle, critical dimension, or depth profile of the feature.

[0428] 231. A non - transient computer - readable medium storing a set of instructions that can be executed by one or more processors of a charged - particle beam device to cause the charged - particle beam device to perform a method, the method including:

[0429] activating a charged - particle source to generate primary charged particles, the primary charged particles forming a primary charged - particle beam along a main optical axis;

[0430] radiating a region of the sample including the feature with the primary charged - particle beam; using each of a plurality of concentric segments of a charged - particle detector to detect charged particles emitted from the region of the sample,

[0431] wherein each of the plurality of concentric segments is configured to detect the emitted charged particles having an energy - level range and a main energy level; and

[0432] generating an image of a portion of the feature from the charged particles collected by the segments of the plurality of concentric segments.

[0433] 232. The non - transient computer - readable medium according to clause 231, wherein the energy - level range of the detected charged particles corresponds to a range of depths of the sample from which the charged particles are emitted.

[0434] 233. The non - transient computer - readable medium according to any one of clauses 231 and 232, wherein the main energy level of the detected charged particles corresponds to the depth of the sample from which the charged particles are emitted.

[0435] 234. The non - transient computer - readable medium according to any one of clauses 231 to 233, wherein the set of instructions can be executed by the one or more processors to cause the charged - particle beam device to further perform configuring each segment, wherein configuring each segment includes adjusting a z - axis position of the sample along the main optical axis of the primary charged - particle beam.

[0436] 235. The non-transitory computer-readable medium according to clause 234, wherein the z-axis position of the sample is adjusted such that it can affect the main energy level detected by the segments of the charged particle detector.

[0437] 236. The non-transitory computer-readable medium according to any one of clauses 234 and 235, wherein adjusting the z-axis position of the sample further enables affecting the range of energy levels detected by the segments of the charged particle detector.

[0438] 237. The non-transitory computer-readable medium according to any one of clauses 234 to 236, wherein adjusting the z-axis position of the sample further enables affecting the uniformity of the collection efficiency across the plurality of segments of the charged particle detector.

[0439] 238. The non-transitory computer-readable medium according to clause 237, wherein adjusting the z-axis position of the sample adjusts the working distance between the sample and the charged particle detector, and wherein increasing the working distance enables improving the uniformity of the collection efficiency of the plurality of segments of the charged particle detector.

[0440] 239. The non-transitory computer-readable medium according to any one of clauses 234 to 238, wherein the set of instructions can be executed by the one or more processors to further cause the charged particle beam device to configure each segment, and wherein configuring each segment further includes adjusting the z-axis position of the charged particle detector relative to the sample.

[0441] 240. The non-transitory computer-readable medium according to clause 239, wherein adjusting the z-axis position of the charged particle detector relative to the sample enables affecting the main energy level detected by each segment of the charged particle detector.

[0442] 241. The non-transitory computer-readable medium according to 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 the emitted charged particles of the main energy level for each of the plurality of segments of the charged particle detector.

[0443] 242. The non-transitory computer-readable medium according to any one of clauses 231 to 241, wherein the set of instructions can be executed by the one or more processors to further cause the charged particle beam device to configure each segment, and wherein configuring each segment further includes adjusting the magnetic field strength experienced by the emitted charged particles by adjusting the excitation signal of the combined lens, the combined lens including a magnetic lens and an electrostatic lens.

[0444] 243. The non-transitory computer-readable medium according to clause 242, wherein the magnetic field strength is adjusted such that the spatial distribution of the emitted charged particles incident on the detection surface of each segment of the charged particle detector can be affected.

[0445] 244. The non-transitory computer-readable medium according to any one of clauses 242 and 243, wherein the magnetic field strength is adjusted such that the collection efficiency of the main energy level of the emitted charged particles for each segment of the charged particle detector can be affected.

[0446] 245. The non-transitory computer-readable medium according to any one of clauses 242 to 244, wherein the magnetic field strength is increased such that the collection efficiency of the non-main energy level of the emitted charged particles for the first segment of the plurality of segments of the charged particle detector can be improved.

[0447] 246. The non-transitory computer-readable medium according to clause 245, wherein the magnetic field strength is decreased such that the collection efficiency of the non-main energy level of the emitted charged particles for the second segment of the plurality of segments of the charged particle detector can be improved.

[0448] 247. The non-transitory computer-readable medium according to any one of clauses 242 to 246, wherein the magnetic field strength is adjusted such that the image contrast of the plurality of generated images can be affected.

[0449] 248. The non-transitory computer-readable medium according to any one of clauses 242 to 247, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further execute adjusting the excitation signal, and wherein adjusting the excitation signal includes adjusting the voltage signal applied to the magnetic lens of the compound lens.

[0450] 249. The non-transitory computer-readable medium according to any one of clauses 242 to 248, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further execute configuring each segment, and wherein configuring each segment further includes adjusting the electric field between the sample and the compound lens by adjusting the voltage signal applied to the electrostatic lens of the compound lens.

[0451] 250. The non-transitory computer-readable medium according to clause 249, wherein adjusting the electric field enables affecting the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector.

[0452] 251. The non-transitory computer-readable medium according to clause 250, wherein the electric field is adjusted such that the collection efficiency of the emitted charged particles for each of the plurality of concentric segments of the charged particle detector can be increased.

[0453] 252. The non-transitory computer-readable medium according to any one of clauses 249 to 251, wherein adjusting the electric field further enables influencing the energy level range of the emitted charged particles detected by a segment among the plurality of concentric segments of the charged particle detector.

[0454] 253. The non-transitory computer-readable medium according to clause 252, wherein adjusting the electric field further enables increasing the energy level range of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0455] 254. The non-transitory computer-readable medium according to any one of clauses 249 to 253, wherein adjusting the electric field further enables influencing the main energy level of the emitted charged particles detected by a segment among the plurality of concentric segments of the charged particle detector.

[0456] 255. The non-transitory computer-readable medium according to clause 254, wherein adjusting the electric field further enables increasing the main energy level of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0457] 256. The non-transitory computer-readable medium according to clause 254, wherein adjusting the electric field further enables decreasing the main energy level of the emitted charged particles detected by the segment among the plurality of concentric segments of the charged particle detector.

[0458] 257. The non-transitory computer-readable medium according to any one of clauses 231 to 256, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further perform compensating for a change in the focus of the primary charged particle beam using a beam scanning deflector, the change in the focus being caused by the adjustment of the magnetic field strength of the complex lens.

[0459] 258. The non-transitory computer-readable medium according to clause 257, wherein the beam scanning deflector includes a plurality of electrodes, and wherein the plurality of electrodes are at the same potential to form a lens field.

[0460] 259. The non-transitory computer-readable medium according to any one of clauses 257 and 258, wherein the excitation signal of the beam scanning deflector is adjusted such that compensation for the change in the focus of the primary charged particle beam can be adjusted.

[0461] 260. The non-transitory computer-readable medium according to clause 259, wherein adjusting the excitation signal of the beam scanning deflector includes adjusting a voltage signal applied to the beam scanning deflector.

[0462] 261. The non-transitory computer-readable medium according to any one of clauses 259 and 260, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further deactivate the excitation signal of the beam scanning deflector when the primary charged particle beam is focused on the sample.

[0463] 262. The non-transitory computer-readable medium according to any one of clauses 257 to 261, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further adjust the focusing ability of a condenser lens located upstream of the compound lens when the excitation signal applied to the compound lens is higher than a nominal excitation signal.

[0464] 263. The non-transitory computer-readable medium according to clause 262, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further adjust the focusing ability, and wherein adjusting the focusing ability includes reducing the focusing ability of the condenser lens such that a divergent primary charged particle beam can be formed.

[0465] 264. The non-transitory computer-readable medium according to clause 263, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further allow the primary charged particle beam to pass through an aperture of an aperture array located upstream of the condenser lens, the aperture being configured to allow a portion of the primary charged particle beam, wherein the allowed portion compensates for a reduced beam current of the divergent primary charged particle beam.

[0466] 265. The non-transitory computer-readable medium according to any one of clauses 257 to 264, wherein the set of instructions can be executed by the one or more processors to cause the charged particle beam device to further configure each segment, and wherein configuring each segment further includes adjusting an electrostatic field near the sample by applying a voltage signal to a control electrode located immediately upstream of the sample.

[0467] 266. The non-transitory computer-readable medium according to clause 265, wherein the electrostatic field is adjusted such that the collection efficiency for each of the plurality of concentric segments of the charged particle detector for the emitted charged particles can be affected.

[0468] 267. The non-transitory computer-readable medium according to clause 266, wherein the electrostatic field is adjusted such that the collection efficiency for the segments located at an off-axis distance greater than a threshold off-axis distance for the emitted charged particles can be increased.

[0469] 268. The non-transitory computer-readable medium according to clause 267, wherein the electrostatic field is adjusted such that the collection efficiency for the segments located at an off-axis distance less than the threshold off-axis distance for the emitted charged particles can be decreased.

[0470] 269. The non-transitory computer-readable medium according to any one of clauses 265 to 268, wherein the electrostatic field is adjusted such that the main energy level of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector can be affected.

[0471] 270. The non-transitory computer-readable medium according to clause 269, wherein the electrostatic field is adjusted such that the energy level range of the emitted charged particles detected by the segments of the plurality of concentric segments of the charged particle detector can be affected.

[0472] It should be understood that the embodiments of the present disclosure are not limited to the exact configurations already described and shown in the drawings, and various modifications and changes can be made without departing from its scope.

Claims

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

2. The device according to claim 1, wherein the segments among the plurality of concentric segments are separated by charged particle insensitive material.

3. The device according to claim 1, wherein the plurality of concentric segments are concentrically arranged around the main optical axis.

4. The device according to claim 1, wherein the main energy level of a segment located at an off-axis distance smaller than a threshold off-axis distance is lower than the main energy level of a segment located at an off-axis distance larger than the threshold off-axis distance.

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

6. The device according to claim 1, wherein the z-axis position of the sample can be adjusted along the main 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 device according to claim 6, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector enables influencing the main energy level for the segments among the plurality of concentric segments.

8. The device according to claim 7, wherein the adjustment of the z-axis position of the sample relative to the charged particle detector further enables influencing the energy level range detected by the segments of the charged particle detector.

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

10. The device according to claim 9, wherein the adjustment of 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 the working distance enables increasing the uniformity of the collection efficiency of the emitted charged particles for the plurality of concentric segments.

11. The device according to claim 1, wherein the z-axis position of the charged particle detector can be adjusted along the main optical axis.

12. The device according to claim 11, wherein the adjustment of the z-axis position of the charged particle detector relative to the sample enables influencing the main energy level for each of the segments among the plurality of concentric segments.

13. The apparatus according to claim 12, wherein the z-axis position of the charged particle detector relative to the sample is adjusted such that it is possible to affect the collection efficiency of the emitted charged particles for the main energy level for each segment of the charged particle detector.

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

15. A non-transitory computer-readable medium storing a set of instructions that can be executed by one or more processors of a charged particle beam apparatus to cause the charged particle beam apparatus to perform a method, the method comprising: Activating a charged particle source to generate primary charged particles that form a primary charged particle beam along a main optical axis; Irradiating a region of the sample that includes a feature with the primary charged particle beam; Detecting charged particles emitted from the sample using a charged particle detector that includes a plurality of segments concentric with the primary charged particle beam; Generating a plurality of images of the irradiated region, wherein each image of the plurality of images is generated from the charged particles detected by a corresponding segment of the charged particle detector; and Determining a characteristic of the feature based on the plurality of images, wherein segmenting the charged particle detector allows the emitted charged particles to be distinguished by corresponding main energy levels and by corresponding energy level ranges for each segment.

Images