Charged particle beam apparatus with fast focus correction and method thereof

Abstract

Systems and methods for imaging a sample using a charged particle beam device are disclosed. The apparatus may include a charged particle source configured to emit charged particles, the emitted charged particles forming a primary charged particle beam along a primary optical axis; an objective lens including a magnetic lens; a charged particle detector located downstream of the objective lens with respect to a path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and the voltage control board is positioned between the charged particle detector and the pole piece of the magnetic lens. The voltage control plate may include: a horizontal portion including an opening; and an elongated portion extending downwardly from the opening into the aperture of the charged particle detector relative to the path of the primary charged particle beam.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 351,273, filed on June 10, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments provided herein disclose a charged particle beam apparatus, particularly an electron beam inspection apparatus with fast focus adjustment for imaging three-dimensional (3D) structures on a substrate. Background Art

[0004] During the manufacture of integrated circuits (ICs), unfinished or completed circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as scanning electron microscopes (SEMs), may be employed. As device architectures increase in complexity, accurate detection of 3D structures becomes increasingly important. Although high landing energy beams can be used to image high aspect ratio structures, and the focus of such high energy beams can be adjusted between the top and bottom surfaces of a 3D structure, focus adjustment techniques can interfere with signal detection or signal collection by charged particle detectors (e.g., backscattered electron detectors). Summary of the invention

[0005] One aspect of the present disclosure relates to a charged particle beam device for imaging a sample. The charged particle beam device may include a charged particle source configured to emit charged particles, and the emitted charged particles form a primary charged particle beam along a primary optical axis. The device may also include: an objective lens, which includes a magnetic lens; a charged particle detector, which is located downstream of the objective lens relative to the path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and a voltage control board, which is located between the charged particle detector and the pole piece of the magnetic lens. The voltage control board may include a horizontal portion, which includes an opening; and an elongated portion, which extends downward from the opening to the hole of the charged particle detector relative to the path of the primary charged particle beam.

[0006] Another aspect of the present disclosure relates to a method for imaging a sample using a charged particle beam apparatus. The method may include forming a primary charged particle beam from charged particles emitted by a charged particle source, detecting signal electrons generated from the sample when the primary charged particle beam interacts with the sample using a charged particle detector, and adjusting an electrical signal applied to a voltage control board. The voltage control board may include a horizontal portion and an elongated portion, the horizontal portion including an opening, the elongated portion extending downward from the opening to a hole of the charged particle detector relative to the path of the primary charged particle beam.

[0007] Another aspect of the present disclosure relates to a non-transitory computer-readable medium storing an instruction set 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 may include forming a primary charged particle beam from charged particles emitted by a charged particle source, detecting signal electrons generated from a sample when the primary charged particle beam interacts with the sample using a charged particle detector, and adjusting an electrical signal applied to a voltage control board. The voltage control board may include a horizontal portion and an elongated portion, the horizontal portion including an opening, the elongated portion extending downward from the opening to a hole of the charged particle detector relative to the path of the primary charged particle beam.

[0008] Another aspect of the present disclosure relates to an electron-optical assembly. The electron-optical assembly may include: an objective lens, the objective lens including a magnetic lens; a charged particle detector, the charged particle detector located downstream of the objective lens relative to the path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and a voltage control board, the voltage control board located between the charged particle detector and a pole piece of the magnetic lens. The voltage control board may include a horizontal portion and an elongated portion, the horizontal portion including an opening, the elongated portion extending downward from the opening to a hole of the charged particle detector relative to the path of the primary charged particle beam, wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass through.

[0009] Another aspect of the present disclosure relates to a plate insertable between a charged particle detector and a pole piece of an objective lens of a charged particle beam device. The plate may include a horizontal portion and an elongated portion, the horizontal portion including an opening, the elongated portion extending downwardly from the opening into a hole of the charged particle detector relative to the path of the primary charged particle beam, wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

[0010] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, which set forth certain embodiments of the present invention by way of illustration and example. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure.

[0012] Figure 2 is a schematic diagram illustrating an exemplary electron beam tool that may be consistent with embodiments of the present disclosure. Figure 1 Components of an exemplary electron beam inspection system.

[0013] Figure 3is a schematic diagram of an exemplary charged particle beam apparatus including a charged particle detector consistent with embodiments of the present disclosure.

[0014] Figure 4 is a schematic diagram illustrating a portion of an exemplary charged particle beam apparatus including a voltage control board consistent with embodiments of the present disclosure.

[0015] Figure 5 is a schematic diagram illustrating a portion of an exemplary charged particle beam apparatus including a voltage control board consistent with embodiments of the present disclosure.

[0016] Fig. 6A is a schematic illustration of a top view of an exemplary voltage control board consistent with embodiments of the present disclosure.

[0017] Figure 6B and Figure 6C is an exemplary voltage control board according to an embodiment of the present disclosure along A-A'( Fig. 6A Schematic illustration of a cross-sectional view of a shaft (shown).

[0018] Figure 7 It means that the embodiment consistent with the present disclosure Figure 4 or Figure 5 A process flow chart of an exemplary method for imaging a sample using a high landing energy charged particle beam in a charged particle beam apparatus. DETAILED DESCRIPTION

[0019] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein the same numbers in different drawings refer to the same or similar elements, unless otherwise specified. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations. Instead, they are merely examples of devices and methods consistent with aspects related to the disclosed embodiments described in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the present disclosure is not limited thereto. Other types of charged particle beams may be similarly applied. In addition, other imaging systems such as optical imaging, light detection, x-ray detection, etc. may be used.

[0020] Electronic devices are made up of circuits formed on a silicon wafer called a substrate. Many circuits can be formed together on the same silicon wafer, called an integrated circuit or IC. The size of these circuits has been reduced significantly so that more circuits can be mounted on a substrate. For example, the IC chip in a smartphone can be as small as a thumbnail, but can include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair.

[0021] Manufacturing these extremely small integrated circuits is a complex, time-consuming, and expensive process that typically involves hundreds of individual steps. An error in even one step can result in a defect in the finished IC, rendering it useless. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs that are manufactured in the process, that is, to increase the overall yield of the process.

[0022] An integral part of improving yields is monitoring the chip manufacturing process to ensure that sufficient numbers of functional integrated circuits are produced. One way to monitor the process is to inspect the chip circuit structures at different stages of chip formation. This inspection can be done using a scanning electron microscope (SEM). The SEM can be used to image these extremely small structures, in effect taking a "photograph" of them. The image can be used to determine if the structure was formed correctly and if it was formed in the correct location. If the structure is defective, the process can be adjusted so that the defect is less likely to occur again.

[0023] In existing inspection systems, such as SEM, three-dimensional structures such as high aspect ratio (HAR) contact holes can be imaged using an electron beam with high landing energy. For a given set of conditions, higher landing energy of the incident electrons can increase the interaction volume with the sample and generate more backscattered electrons, which can provide information associated with underlying features in the sample. However, focusing a high landing energy electron beam to form high-resolution images of the top and bottom surfaces of such structures while maintaining measurement accuracy and throughput can be challenging.

[0024] In complex device architectures, such as 3D-NAND devices, high landing energy beams can be used to inspect or measure 3D structures with a depth of several microns (μm). By using a high landing energy electron beam, the interaction volume can be enhanced, and therefore the backscattered signal electron intensity can be enhanced. However, compared to the inspection of two-dimensional planar structures, adjusting the focal length of the high landing energy electron beam to image the top and bottom surfaces of the 3D structure can make the inspection process significantly longer. In some cases, although the focus of the high landing energy electron beam can be adjusted or corrected by applying a voltage signal to the electrostatic lens, the adjustment of the focal length per unit voltage applied can be undesirably small. In other words, a very large voltage signal can be applied to make a small adjustment to the focal length of the high landing energy beam. The large voltage signal applied to the electrostatic lens can negatively affect the detection efficiency of the backscattered electron detector, thereby affecting the inspection throughput.

[0025] One of several methods for achieving focus adjustment for 3D structure imaging includes using an electron detector as an electrode to adjust the electrostatic field near the sample, thereby adjusting the focal length of the primary electron beam. However, this type of configuration can have several disadvantages. For example, the voltage signal applied to the electron detector to adjust the electrostatic field can change the landing energy of the backscattered electrons that it is mainly configured to detect. The change in the voltage applied to the electron detector can also affect, for example, the photon emission intensity of the scintillator, thereby producing low-quality images and causing inaccurate inspection and measurement of the imaging structure. In addition, in this type of configuration, the accumulation of charge or contaminants on the inner surface of the central hole of the backscattered electron detector can affect the rotational symmetry and smoothness, which can induce higher-order electric fields, such as quadrupole fields. High-order fields can interfere with the electrostatic field experienced by the primary electron beam and can have a negative impact on the probe spot size or probe spot shape. Although the inner surface of the backscattered electron detector can be cleaned, polishing the inner surface to maintain smoothness can be challenging. In contrast, the voltage control board can be configured to provide an excellent inner surface by, for example, reworking, polishing or cleaning its inner surface. The accumulation of charge or contaminants on the inner surface of the central aperture of a backscattered electron detector can affect rotational symmetry and smoothness, which can induce higher order electric fields, such as quadrupole fields. Higher order fields can interfere with the electrostatic field experienced by the primary electron beam and can negatively affect the probe spot size or probe spot shape. The ability to clean or polish the inner surface of the voltage control plate, in addition to a smooth surface, allows the ellipticity of the inner surface to be maintained, thereby allowing high quality images to be reliably obtained while maintaining throughput. The voltage control plate can be an insertable plate made of a conductive material such as a metal or a non-magnetic material. Therefore, while the dual functionality of the electron detector can increase inspection throughput, the quality of the images produced may be affected, making the inspection system inadequate. Therefore, it may be desirable to achieve focus correction of a high landing energy electron beam to inspect the top and bottom surfaces of 3D structures while maintaining the resolution and throughput of the SEM and the electron detection capabilities of the detector.

[0026] Some embodiments of the present disclosure relate to an apparatus and method for imaging a sample with a high landing energy charged particle beam. The apparatus may include a voltage control board located between a backscattered electron detector and a pole piece of a magnetic lens of a composite objective. The voltage control board may include a horizontal portion having an aperture and an elongated portion extending downward from the aperture into a central hole of the backscattered electron detector. The voltage control board may include a cavity formed by an inner surface of the aperture and the elongated portion. The voltage control board may be configured to receive a voltage signal, which, when applied or adjusted, may affect the electrostatic field experienced by a primary electron beam passing through the cavity, thereby adjusting the focal length of the primary electron beam to be incident on the sample. The voltage control board may be used to adjust the focal length of the primary electron beam without interfering with the backscatter collection efficiency, thereby enabling high imaging quality while maintaining inspection and measurement accuracy and yield.

[0027] For the sake of clarity, the relative sizes of the components in the figures may be exaggerated. In the following description of the accompanying drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the various embodiments are described. As used herein, unless otherwise expressly stated, the term "or" includes all possible combinations unless not feasible. For example, if it is specified that a component may include A or B, then, unless otherwise specifically stated or not feasible, the component may include A, B, or A and B. As a second example, if it is specified that a component may include A, B, or C, then, unless otherwise specifically stated or not feasible, the component may include A, B, C, A and B, A and C, B and C, A and C, B and C.

[0028] Reference now Figure 1 , Figure 1 An exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure is illustrated. Figure 1 As 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 in the main chamber 10. Although the description and drawings are directed to electron beams, it should be understood that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0029] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional (one or more) load ports. The first load port 30a and the second load port 30b receive a wafer front opening unified box (FOUP) containing wafers (e.g., semiconductor wafers or wafers made of (one or more) other materials) or samples to be inspected (wafers and samples are collectively referred to as "wafers" hereinafter). One or more robotic arms (not shown) in the EFEM 30 transport the wafers to the load lock chamber 20.

[0030] The load lock chamber 20 is connected to a load lock vacuum pump system (not shown) that removes gas molecules in the load lock chamber 20 to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the wafer 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 in the main chamber 10 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam inspection tool.

[0031] 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. Figure 1 3 as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, but it should be understood that the controller 50 may be a component of the structure.

[0032] Although the present disclosure provides an example of a main chamber 10 housing an electron beam inspection system, it should be noted that the broad aspects of the present disclosure are not limited to chambers housing electron beam inspection systems. Rather, it should be understood that the aforementioned principles may also be applied to other chambers.

[0033] Reference now Figure 2 , Figure 2 A schematic diagram illustrating an exemplary configuration of an electron beam tool 40 is shown, which may be Figure 1 Components of an exemplary charged particle beam inspection system 100 are consistent with embodiments of the present disclosure. The electron beam tool 40 (also referred to herein as the device 40) may include an electron emitter, which may include a cathode 203, an extraction electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 may also include a Coulomb aperture array 224, a converging lens 226, a beam limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. The electron beam tool 40 may also include a sample holder 236 supported by a motorized stage 234 to hold a sample 250 to be inspected. It should be understood that other related components may be added or omitted as needed.

[0034] In some embodiments, the electron emitter may include a cathode 203, an anode 222, where primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 204, which forms a primary beam intersection 202. The primary electron beam 204 may be considered to be emitted from the primary beam intersection 202.

[0035] In some embodiments, the electron emitter, focusing lens 226, objective lens assembly 232, beam limiting aperture array 235, and electron detector 244 may be aligned with the primary optical axis 201 of device 40. In some embodiments, the electron detector 244 may be positioned outside the primary optical axis 201 along a secondary optical axis (not shown).

[0036] In some embodiments, the objective lens assembly 232 may include a modified swinging objective delayed immersion lens (SORIL) including a pole piece 232a, a control electrode 232b, a beam manipulator assembly including deflectors 240a, 240b, 240d, and 240e, and an excitation coil 232d. In a general imaging process, a primary electron beam 204 emitted from the tip of the cathode 203 is accelerated by an accelerating 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 converging lens 226 so as to pass through the apertures of the beam limiting aperture array 235 in whole or in part. The electrons passing through the apertures of the beam limiting aperture array 235 can be focused by the modified SORIL lens to form a probe spot on the surface of the sample 250, and deflected by one or more deflectors of the beam manipulator assembly to scan the surface of the sample 250. Secondary electrons emitted from the sample surface may be collected by electron detector 244 to form an image of the scanned area of ​​interest.

[0037] In the objective lens assembly 232, the excitation coil 232d and the pole piece 232a can generate a magnetic field. The components 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 creates an electric field. The electric field can reduce the energy of the primary electron beam 204 that impacts the surface of the sample 250 near and on the surface. The control electrode 232b electrically insulated from the pole piece 232a can control the electric field above and above the sample 250, for example, to reduce the aberration of the objective lens assembly 232, and control the focusing of the signal electron beam to obtain high 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 the scanning process, 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, thereby providing data for image reconstruction of different components of the sample 250. It should be noted that in different embodiments, the order of 240a-240e may be different.

[0038] Upon receiving the primary electron beam 204, backscattered electrons (BSE) and secondary electrons (SE) may be emitted from the component of the sample 250. The beam splitter may direct (one or more) secondary or scattered electron beams including backscattered electrons and secondary electrons toward the sensor surface of the electron detector 244. The detected secondary electron beam may form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 may generate a signal (e.g., voltage, current) representing the intensity of the received secondary electron beam spot and provide the signal to a processing system, such as the controller 50. The intensity of the secondary or backscattered electron beam and the resulting secondary electron beam spot may vary depending on the external or internal structure of the sample 250. In addition, as described above, the primary electron beam 204 may be deflected to different locations on the top surface of the sample 250 to generate secondary or scattered electron beams (and the resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot with the location of the sample 250, the processing system may reconstruct an image reflecting the internal or external structure of the wafer sample 250.

[0039] In some embodiments, the controller 50 may include an image processing system including an image acquisition device (not shown) and a memory (not shown). The image acquisition device may include one or more processors. For example, the image acquisition device may include a computer, a server, a mainframe, a terminal, a personal computer, any kind of mobile computing device, or the like, or a combination thereof. The image acquisition device may be communicatively coupled to the electronic detector 244 of the device 40 via a medium such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, radio, or the like, or a combination thereof. In some embodiments, the image acquisition device may receive a signal from the electronic detector 244 and may construct an image. The image acquisition device may thus acquire an image of an area of ​​the sample 250. The image acquisition device may also perform various post-processing functions, such as generating contours, superimposing indicators on the acquired image, and the like. The image acquisition device may be configured to adjust the brightness and contrast of the acquired image, and the like. In some embodiments, the memory may be a storage medium, such as a hard disk, a flash drive, a cloud storage device, a random access memory (RAM), other types of computer-readable memory, and the like. The memory may be coupled to the image acquisition device and may be used to save the scanned raw image data as raw images and post-processed images.

[0040] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of the detected 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 sample (e.g., wafer) surface, can be used to reconstruct an image of the inspected wafer structure. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 250, and thus can be used to reveal any defects that may be present in the wafer.

[0041] In some embodiments, the controller 50 can control the motorized stage 234 to move the sample 250 during the inspection. In some embodiments, the controller 50 can enable the motorized stage 234 to continuously move the sample 250 in one direction at a constant speed. In other embodiments, the controller 50 can enable the motorized stage 234 to change the movement speed of the sample 250 over time according to the steps of the scanning process.

[0042] Reference now Figure 3 , Figure 3A schematic diagram of an exemplary charged particle beam device 300 (also referred to as device 300) consistent with an embodiment of the present disclosure is illustrated. Device 300 may include a charged particle source, such as an electron source configured to emit primary electrons from a cathode 301 and extract using an extractor electrode 302 to form a primary electron beam 300B1 along a primary optical axis 300-1. Device 300 may also include an anode 303, a converging lens 304, a beam limiting aperture array 305, signal electron detectors 306 and 313, a composite objective 307, a scanning deflection unit including primary electron beam deflectors 308, 309, 310 and 311, and a control electrode 314. In some embodiments, signal electron detector 313 may be a backscattered electron detector, and signal electron detector 306 may be a secondary electron detector. It should be understood that relevant components may be appropriately added, omitted, or reordered.

[0043] The electron source (not shown) may include a thermionic source configured to emit electrons when thermal energy is supplied to overcome the work function of the source; a field emission source configured to emit electrons when exposed to a large electrostatic field, etc. In the case of a field emission source, the electron source may be electrically connected to a controller such as Figure 2 A controller 50 is provided that is configured to apply and adjust voltage signals based on desired landing energy, sample analysis, source characteristics, etc. The extractor electrode 302 can be configured to extract or accelerate electrons emitted from the field emission gun, for example, to form a primary electron beam 300B1 that forms a virtual or real primary beam crossover (not shown) along the primary optical axis 300-1. The primary electron beam 300B1 can be considered to be emitted from the primary electron beam crossover. In some embodiments, the controller 50 can be configured to apply and adjust voltage signals to the extractor electrode 302 to extract or accelerate electrons generated from the electron source. The amplitude of the voltage signal applied to the extraction electrode 302 can be different from the amplitude of the voltage signal applied to the cathode 301. In some embodiments, the difference between the amplitudes of the voltage signals applied to the extractor electrode 302 and the cathode 301 can be configured to accelerate electrons downstream along the primary 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 the primary electron beam 300B1 starting from the electron source toward the sample 315. Figure 3 With respect to the positioning of elements of the device 300 of FIG. 1 , “downstream” may refer to the position of an element below or after another element along the path of the primary electron beam from the electron source, and “immediately downstream” refers to the position of a second element below or after the first element along the path of the primary electron beam 300B1, such that there are no other active elements between the first element and the second element. For example, Figure 3 As shown, the signal electron detector 306 can be positioned immediately downstream of the beam limiting aperture array 305, such that no other optical or electron-optical elements are placed between the beam limiting aperture array 305 and the electron detector 306. As used in the context of the present disclosure, "upstream" can refer to the position of an element located above or before another element along the path of the primary electron beam starting from the electron source, and "immediately upstream" refers to the position of a second element located above or before a first element along the path of the primary electron beam 300B1, such that there are no other active elements between the first element and the second element. As used herein, an "active element" can refer to any element or component whose presence can change the electrostatic field or electromagnetic field between the first element and the second element by generating an electric field, a magnetic field, or an electromagnetic field.

[0044] The apparatus 300 may include a converging lens 304 configured to receive a portion or a majority of the primary electron beam 300B1 and focus the primary electron beam 300B1 onto a beam limiting aperture array 305. The converging lens 304 may be substantially similar to Figure 2 The converging lens 226 can perform substantially similar functions. Figure 3 The converging lens 304 is shown as a magnetic lens in the figure, but the converging lens 304 can be an electrostatic lens, a magnetic lens, an electromagnetic lens, or a compound electromagnetic lens, etc. The converging lens 304 can be electrically coupled to the controller 50, such as Figure 2 Controller 50 may apply electrical excitation signals to converging lens 304 to adjust the focusing capability of converging lens 304 based on factors including, but not limited to, the mode of operation, the application, the desired analysis, the sample material being examined, and the like.

[0045] The apparatus 300 may further include a beam limiting aperture array 305 configured to limit a beam current of the primary electron beam 300B1 passing through one of a plurality of beam limiting apertures of the beam limiting aperture array 305. Figure 3 Only one beam limiting aperture is shown in FIG. 3 , but the beam limiting aperture array 305 may include any number of apertures having uniform or non-uniform aperture sizes, cross-sections, or pitches. In some embodiments, the beam limiting aperture array 305 may be disposed downstream of the converging lens 304 or immediately downstream of the converging lens 304 (e.g., Figure 3300-1). 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 may be configured to instruct the supply of voltage to the beam limiting aperture array 305. The supplied voltage may be a reference voltage, such as a 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.

[0046] The apparatus 300 may include one or more signal electron detectors 306 and 313. The interaction of primary charged particles such as electrons of the primary electron beam 300B1 with the surface of the sample 315 may generate signal electrons. The signal electrons may include secondary electrons, backscattered electrons, or Auger electrons, etc. The signal electron detectors 306 and 313 may be configured to detect substantially all of the secondary electrons and a portion of the backscattered electrons based on emission energy or emission angle, etc. In some embodiments, the signal electron detectors 306 and 313 may be configured to detect secondary electrons, backscattered electrons, or Auger electrons. The signal electron detector 313 may be disposed downstream of the signal electron detector 306. In some embodiments, the signal electron detector 313 may be disposed downstream of the objective lens 307. Signal electrons having low emission energy (typically ≤50 eV) may include (one or more) secondary electron beams 300B4, while signal electrons having high emission energy (typically >50 eV) may include (one or more) backscattered electron beams 300B2. In some embodiments, 300B4 may include secondary electrons, low energy backscattered electrons, or high energy backscattered electrons. It should be understood that, although not shown, a portion of the backscattered electrons may be detected by the signal electron detector 306, and a portion of the secondary electrons may be detected by the signal electron detector 313. In the inspection of 3D structures such as deep holes, grooves, or contact holes, a primary electron beam with high landing energy may be used, which generates signal electrons with high emission energy. The signal electron detector 313 may be used to detect a portion of the high emission energy signal electrons, such as backscattered electrons.

[0047] The device 300 may also include a compound objective 307 configured to focus the primary electron beam 300B1 on the surface of the sample 315. The controller 50 may apply an electrical excitation signal to the coil 307C of the compound objective 307 to adjust the focusing ability of the compound objective 307 based on factors including but not limited to the primary beam energy, the application, the desired analysis, the sample material being inspected, etc. The compound objective 307 may also be configured to focus signal electrons, such as secondary electrons or backscattered electrons, on a detection surface of a signal electron detector (e.g., signal electron detector 306 or 313). The compound objective 307 may be coupled to a detector 306 or 313. Figure 2 The objective lens assembly 232 is substantially similar or performs substantially similar functions. In some embodiments, the composite objective lens 307 may include an electromagnetic lens including a magnetic lens 307M and an electrostatic lens 307ES formed by a control electrode 314, a pole piece 307P and a sample 315.

[0048] As used herein, a composite objective lens is an objective lens that generates overlapping magnetic and electrostatic fields near the sample for focusing the primary electron beam. In this disclosure, references to magnetic lenses such as 307M refer to objective magnetic lenses, while references to electrostatic lenses such as 307ES refer to objective electrostatic lenses, although focusing lens 304 may also be a magnetic lens. Figure 3 As shown, the magnetic lens 307M and the electrostatic lens 307ES work together, such as focusing the primary electron beam 300B1 on the sample 315, to form a composite objective lens 307. The lens body and coil 307C of the magnetic lens 307M can generate a magnetic field, while the electrostatic field can be generated by, for example, creating a potential difference between the sample 315 and the pole piece 307P. In some embodiments, the control electrode 314 or other electrodes located between the pole piece 307P and the sample 315 can also be a component of the electrostatic lens 307ES.

[0049] As disclosed herein, the pole piece of a magnetic lens (e.g., magnetic lens 307M) is a piece of magnetic material near the magnetic pole of the magnetic lens, and the magnetic pole is the end of the magnetic material where the external magnetic field is the strongest. Figure 3 As shown, the device 300 includes pole pieces 307P and 307O. As an example, pole piece 307P can be a piece of magnetic material near the north pole of magnetic lens 307M, and pole piece 307O can be a piece of magnetic material near the south pole of magnetic lens 307M. When the current in magnetic lens coil 307C changes direction, the polarity of the magnetic poles can also change. In the context of the present disclosure, an electronic detector (e.g., Figure 3 The signal of the electronic detector 313, or Figure 4 signal electronic detector 413), beam deflector (e.g., Figure 3 beam deflectors 308-311), electrodes (e.g., Figure 3The positioning of the control electrode 314) can be described with reference to the position of the pole piece 307P closest to the point where the primary optical axis 300-1 intersects the sample 315. The pole piece 307P of the magnetic lens 307M may include a magnetic pole made of a soft magnetic material such as an electromagnet that substantially concentrates the magnetic field within the cavity of the magnetic lens 307M. For example, the pole pieces 307P and 307O may be high-resolution pole pieces, multi-purpose pole pieces, or high-contrast pole pieces.

[0050] like Figure 3 As shown, the pole piece 307P may include an opening 307R configured to allow the primary electron beam 300B1 to pass through and allow the signal electrons to reach the signal electron detector 306. The cross-section of the opening 307R of the pole piece 307P may be circular, substantially circular, or non-circular. In some embodiments, the geometric center of the opening 307R of the pole piece 307P may be aligned with the primary optical axis 300-1. In some embodiments, as Figure 3 As shown, pole piece 307P can be the most downstream horizontal section of magnetic lens 307M and can be substantially perpendicular to primary optical axis 300-1. Pole pieces (such as 307P and 307O) are one of several distinguishing features of magnetic lenses over electrostatic lenses. Because pole pieces are magnetic components adjacent to the magnetic poles of a magnetic lens, and because electrostatic lenses do not generate magnetic fields, electrostatic lenses do not have pole pieces.

[0051] The apparatus 300 may further include a scanning deflection unit including 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 may enable a desired area or desired area of ​​interest of the sample 315 to be scanned, such as in a raster scanning mode, to generate SE and BSE for sample inspection. One or more primary electron beam deflectors 308, 309, 310, and 311 may be configured to deflect the primary electron beam 300B1 on an X-axis or a Y-axis or a combination of an X-axis and a Y-axis. As used herein, the X-axis and the Y-axis form Cartesian coordinates, and the primary electron beam 300B1 propagates along a Z-axis or a primary optical axis 300-1.

[0052] As the demand for data processing and computing power of electronic devices increases, integrated circuit (IC) chips need to perform more complex tasks at higher speeds and higher efficiency. These requirements require an increase in device density (the number of devices per unit area of ​​the chip), which can be achieved by manufacturing 3D structures and other strategies. Although 3D structures can be inspected using high landing energy charged particle beams, the speed at which the focus can be adjusted to image the top and bottom surfaces of the 3D structure can limit the yield, making the device unsuitable for inspection or metrology applications. Although a backscattered electron detector located near the sample and configured to detect high emission energy signal electrons can also be used as an electrode to control the electrostatic field experienced by the primary electron beam, doing so can change the landing energy of the backscattered electrons on the detection surface of the backscattered electron detector, thereby negatively affecting the detector gain or detector collection efficiency. Therefore, it is desirable to control the electrostatic field to adjust the focal length of the high landing energy electron beam without affecting the collection efficiency of the backscattered electron detector to obtain high resolution images while maintaining yield.

[0053] Reference now Figure 4 , Figure 4 A schematic diagram of a portion of an exemplary charged particle beam apparatus 400 (also referred to as apparatus 400) consistent with embodiments of the present disclosure is illustrated. Compared to apparatus 300, apparatus 400 may additionally include a voltage control board 420. Apparatus 400 may also include a backscattered electron detector 413 (similar to Figure 3 signal electronic detector 313) and control electrode 414 (similar to Figure 3 control electrode 314).

[0054] Backscattered electrons (BSEs) (e.g., signal electrons of beam 400B2) can be generated by elastic scattering events of incident electrons from deeper layers below (such as the bottom surface of a deep trench or a high aspect ratio hole) and have high emission energy - between 50 eV and the incident energy of the primary electron beam. Therefore, it can be desirable to maintain high backscattered electron detection efficiency to obtain high-quality imaging of 3D structures. In some embodiments, the device 400 may include a signal electron detector, such as a backscattered electron detector 413 located between the sample 415 and the objective lens 407. The backscattered electron detector 413 can be positioned along a plane 413P that is substantially perpendicular to the primary optical axis 400-1. It should be understood that the horizontal plane 413P along which the backscattered electron detector 413 extends, represented by a dashed line (dotted line), is an imaginary plane used only for visual aids and illustration purposes. Plane 413P represents the center plane of the backscattered electron detector 413 relative to the thickness of the backscattered electron detector 413 in a direction parallel to the primary optical axis 400-1. In the context of the present disclosure, the term "substantially perpendicular" refers to the positioning of an element such that the element is sufficiently perpendicular with negligible offset, if any, which does not negatively affect the intended function and intended performance of the element. For example, a substantially perpendicular backscattered electron detector 413 may form 90°±0.05° with the primary optical axis 400-1 such that the orientation of the backscattered electron detector 413 does not affect its detection efficiency. The backscattered electron detector may form an angle between 89.95° and 90.05° with the primary optical axis 400-1 such that the electrostatic field is not affected. A larger angular offset between the backscattered electron detector (e.g., the backscattered electron detector 413) and the primary optical axis (e.g., the primary optical axis 400-1), such as 0.1° or greater than 90°, may generate additional deflection fields, which may deflect the primary electron beam and increase the landing angle, thereby negatively affecting the resolution of the image generated thereby.

[0055] In some embodiments, the backscattered electron detector 413 may include a central aperture aligned with the primary optical axis 400-1. Figure 4 As shown, the central hole of the backscattered electron detector 413 may have an inner diameter d1. In some embodiments, the inner diameter d1 of the backscattered electron detector 413 may be smaller than the objective lens 407 (similar to Figure 3 The objective lens 307) has an opening (eg, Figure 3 However, in some embodiments, the inner diameter d1 may be determined based on factors including, but not limited to, the field of view (FOV), the working distance of the device, resolution requirements, mechanical limitations, or physical space constraints.

[0056] The device 400 may also include a voltage control board 420. In some embodiments, the voltage control board 420 may be a conductive element configured to receive an electrical signal. In some embodiments, the voltage control board 420 may be made of a non-magnetic material. The voltage control board 420 may be electrically connected to the voltage control unit 425 or the controller 50 or both. The voltage control unit 425 or the controller 50 may include a circuit device configured to apply an electrical signal (such as a voltage signal) to the voltage control board 420. The voltage control unit 425 or the controller 50 may also include a circuit device configured to adjust the applied electrical signal. Adjusting the applied electrical signal may include adjusting the voltage so that the electrostatic field experienced by the primary electrons passing through can be adjusted, thereby adjusting the focal length of the primary electron beam to be incident on the surface of the sample 415.

[0057] In some embodiments, the voltage control board 420 can be made of a conductive material such as metal. Relative to the path of the primary electron beam 400B1 along the primary optical axis 400-1, the voltage control board 420 can be located downstream of the pole piece 407P of the objective lens 407 and upstream of the backscattered electron detector 413. The voltage control board 420 can be positioned along a plane substantially perpendicular to the primary optical axis 400-1 and substantially parallel to the horizontal plane 413P. It should be understood that the objective lens 407 can be a composite objective lens including a magnetic lens and an electrostatic lens, and the pole piece (e.g., pole piece 407P) refers to the pole piece of the magnetic lens of the objective lens 407.

[0058] Fig. 6A A top view of an exemplary voltage control board 620 similar to the voltage control board 420 is shown. The voltage control board 620 may include an opening 622 aligned with the primary optical axis 600-1. As used herein, the term "aligned" refers to the positioning of the voltage control board 620 such that the geometric center of the opening 622 coincides with the primary optical axis 600-1. In some embodiments, as Figure 4 and Figure 5 As shown in (discussed later), the diameter of the opening 622 of the voltage control plate 620 can be smaller than the diameter of the hole of the backscattered electron detector 413, but large enough to allow the primary electron beam 400B1 and the secondary electron beam 400B4 to pass through without blocking or obstructing the path of the primary or secondary electrons. The voltage control plate 620 can be made of a single piece of material, such as but not limited to metal or other conductive materials. For example, the voltage control plate 620 can be made of a single continuous metal sheet, and the opening 622 can be formed by removing metal from corresponding positions. The opening 622 can be formed in the horizontal portion 621 by a material removal process, and the material removal process includes but is not limited to etching, cutting, drilling, punching and other material removal techniques. In some embodiments, although not shown, two or more pieces of conductive material can be attached together to form a voltage control plate 620 including an opening 622 with a desired diameter.

[0059] Figure 6B The voltage control board 620 is shown along the A-A' axis (eg Fig. 6A As shown in the cross-sectional view. Figure 6B As shown, the voltage control plate 620 may further include a vertical elongated portion 624 extending downward from the opening 622 along the primary optical axis 600-1 and substantially perpendicular to the horizontal portion 621 of the voltage control plate 620. The elongated portion 624 may be substantially parallel to the primary optical axis 600-1, along which the primary electron beam 600B1 is directed toward the sample (e.g., Figure 4 The direction of travel of the primary electron beam 600B1 is determined by Figure 6B Indicated by the solid arrow in . The elongated portion 624 can have an inner diameter substantially similar to the diameter of the opening 622. The elongated portion 624 can be cylindrical so that its inner diameter is uniform over its length L and is similar to the diameter of the opening 622. In such a configuration, the opening 622 and the elongated portion 624 can form a cavity 628 having a diameter substantially similar to the diameter of the opening 622 for the primary and secondary electrons to pass through. The cavity 628 can be defined by the space between imaginary planes 625 and 626 representing the upstream and downstream ends of the voltage control plate 620, respectively. It should be understood that the imaginary planes 625 and 626 marked as dashed lines are visual aids for illustration purposes only. Closer to the objective lens (e.g., Figure 4 The imaginary plane 625 of the objective lens 407 can define the upper boundary of the cavity 628, which is closer to the sample (e.g., Figure 4 The imaginary plane 626 of the sample 415) can define the lower boundary of the cavity 628 of the voltage control plate 620. As used herein, the "cavity" of the voltage control plate refers to the space defined by the aperture 622 and the elongated portion 624 of the voltage control plate 620, which is configured to allow the primary electron beam 600B1 to pass through, wherein the space is rotationally symmetric about the primary optical axis 600-1. The term "within the cavity of voltage control plate" or "inside the cavity of voltage control plate" refers to the space defined by the imaginary planes 625 and 626 and the inner surface of the opening 622 and the elongated portion 624 directly exposed to the primary electron beam 600B1. The imaginary planes 625 and 626 can be substantially perpendicular to the primary optical axis 600-1. Although Figure 4 , Figure 5 , Fig. 6A , Figure 6B and Figure 6CA cylindrical cavity is illustrated, but the cross-section of cavity 628 may be cylindrical, conical, staggered cylindrical, staggered conical, or any suitable cross-section.

[0060] like Figure 6B As shown, the voltage control board 620 can be formed or made of a single piece of conductive material so that the horizontal portion 621 and the elongated portion 624 form a continuous structure. The voltage control board 620 can be manufactured so that the inner surface of the opening 622 of the horizontal portion 621 and the inner surface of the elongated portion 624 are substantially aligned with each other.

[0061] Alternatively, Figure 6C As shown, the horizontal portion 631 and the elongated portion 634 can be coupled together to form the voltage control board 630. In some embodiments, the horizontal portion 631 and the elongated portion 634 can be coupled using a coupling mechanism, such as but not limited to welding, gluing, bonding or brazing or hardware assembly or other suitable mechanisms. The voltage control board 630 can be manufactured, formed or assembled so that the inner surface of the opening 632 of the horizontal portion 631 and the inner surface of the elongated portion 634 are substantially aligned with each other. It should be understood that the horizontal portion 631 and the elongated portion 634 can be formed of the same material to avoid problems associated with contact resistance, mismatched thermal coefficients, different electrical conductivities, etc.

[0062] Back to Figure 4 , the voltage control board 420 of the device 400 may include a monolithic voltage control board (e.g., Figure 6B voltage control board 620) or a coupled voltage control board (eg, Figure 6C The primary electron beam 400B1 may include a high landing energy electron beam. The voltage control board 420 may be located between the objective lens 407 and the backscattered electron detector 413. In some embodiments, the voltage control board 420 may be located between the pole piece 407P of the objective lens 407 and the backscattered electron detector 413. The voltage control board 420 may be located upstream of the backscattered electron detector 413 so that the elongated portion (e.g., Figure 6B The elongated portion 624 or Figure 6C The elongated portion 634 of the backscattered electron detector 413 extends downward into the space defined by the central hole of the backscattered electron detector 413. The diameter D1 of the central hole of the backscattered electron detector 413 may be slightly larger than the outer diameter of the elongated portion of the voltage control plate 420. The central hole of the backscattered electron detector 413 and the opening of the voltage control plate 420 (e.g., Figure 6B The center of the opening 622) can be aligned with the primary optical axis 400-1.

[0063] In practice, the voltage control board 420 and the backscattered electron detector 413 may be electrically insulated from each other. In some embodiments, the diameter d1 of the central hole of the backscattered electron detector 413 may be sufficiently larger than the outer diameter of the elongated portion of the voltage control board 420 to provide electrical insulation. Additionally or alternatively, a portion of the outer surface of the backscattered electron detector 413 may be coated with an electrically insulating material to provide electrical insulation between the voltage control board 420 and the backscattered electron detector 413. In some embodiments, a portion of the non-detection surface of the backscattered electron detector 413 may be coated with an insulating material. In some embodiments, the entire non-detection surface of the backscattered electron detector 413 may be coated with an insulating material. The voltage control board 420 may be disposed on an insulator-coated portion of the surface of the backscattered electron detector 413. The insulating material used to coat the surface of the backscattered electron detector 413 may include, but is not limited to, dielectrics, ceramics, glass, or other suitable insulating materials. However, in some embodiments, the voltage control board 420 may not be disposed on the surface of the backscattered electron detector 413 coated with an insulator, but may be mounted on or coupled to the objective lens 407. In some embodiments, the voltage control board 420 may be a separate structure that is neither disposed on the backscattered electron detector 413 nor coupled to the objective lens 407. In such a configuration, the voltage control board 420 may be held in place by attaching the voltage control board 420 to a frame of the apparatus 400 or any suitable holding mechanism such that the voltage control board 420 is coaxial with the primary optical axis 400-1.

[0064] The device 400 may include a voltage control board 420, which is configured to adjust the focal length of the primary electron beam 400B1 incident on the sample. The voltage control board 420 may include a conductive plate electrically insulated from the backscattered electron detector 413. Electrical insulation can allow a voltage signal to be applied to the voltage control board 420 without affecting the landing energy of the backscattered electrons on the backscattered electron detector 413, etc. The addition of the voltage control board 420 between the objective lens 407 and the backscattered electron detector 413 has many advantages over existing focus correction techniques in charged particle beam devices. The voltage control board, also referred to as a conductive plate or an aperture plate herein, may have some or all of the advantages discussed herein.

[0065] i. Independent control of focal length --like Figure 4 and Figure 5 As shown, a voltage control board (eg, voltage control board 420) can allow the focus of the primary electron beam to be controlled without affecting the signal electron detector (eg, Figure 4 The voltage to the voltage control board can be independently applied or adjusted to increase the gain of the backscattered electron detector 413) or to affect the landing energy of the backscattered electrons on the backscattered electron detector.

[0066] ii. Small focus adjustment voltage - Opening (e.g. Figure 6B opening 622) and a cavity (e.g., Figure 6B The inner diameter of the cavity 628 is smaller than the inner diameter of the backscattered electron detector, but is large enough to allow the primary and secondary electron beams to pass through. Due to its small inner diameter, a small voltage signal applied to the voltage control board can cause a significant adjustment of the focus of the primary electron beam passing therethrough. For example, by applying a voltage signal of less than 100V, the focus of the primary electron beam can be adjusted by up to 10μm.

[0067] iii. Wide range of focal lengths Because the inner diameter of the voltage-controlled plate's aperture is smaller, the focusing power per unit voltage applied can be larger. This can allow a wider range of focal lengths to be obtained by applying a small voltage signal.

[0068] iv. Improved security When positioned between the objective lens and the backscattered electron detector, the voltage control board can block stray electrons (primary or secondary) and substantially prevent rear surfaces or hardware (including wiring associated with the backscattered electron detector) from being exposed to stray electrons. Blocking stray electrons from being incident on the back of the backscattered electron detector can minimize the risk of potential electrical or mechanical failure or unwanted charge accumulation.

[0069] v. Improved reliability - Long-term use of the inspection device can cause contaminants, debris, or charge to accumulate on surfaces exposed to primary or secondary electrons. The accumulation of charge or contaminants on the inner surface of the central aperture of the backscattered electron detector can affect the rotational symmetry and smoothness, which can induce higher-order electric fields, such as quadrupole fields. Higher-order fields can interfere with the electrostatic field experienced by the primary electron beam and can negatively affect the probe spot size or probe spot shape. Although the inner surface of the backscattered electron detector can be cleaned, polishing the inner surface to maintain smoothness can be challenging. In contrast, polishing or cleaning the inner surface of a voltage control plate made of metal can be easier, allowing high-quality images to be obtained reliably while maintaining yield.

[0070] vi. Improved stability - In metrology applications, the stability of the overall magnification of the electron-optical system can determine the stability and minimize the effort to calibrate the charged particle system. Adjusting the small voltage applied to the voltage control plate to adjust the focus of the primary electron beam does not affect the overall magnification of the electron-optical system. This is because the voltage control plate can be located close to the sample, so the voltage required to adjust the focusing ability of the voltage control plate can be small, which does not negatively affect the overall magnification of the lenses of the electron-optical system.

[0071] vii. Design Flexibility - voltage control board, backscattered electron detector, control electrode (e.g. Figure 4 The concentricity of the control electrode 414) or the objective lens can be controlled during the assembly process or adjusted by a suitable mechanism to avoid tolerance-induced deflection fields that can negatively affect the probe spot characteristics.

[0072] In charged particle beam inspection systems such as SEMs, one of several methods of adjusting image resolution may include adjusting the working distance of an objective lens, among other things. In this case, the working distance refers to the distance between the pole piece (e.g., Figure 4 The pole piece 407P) and the sample surface (eg, Figure 4 The distance between the sample 415) and the objective lens can be reduced. Higher image resolution can be obtained by reducing the working distance of the objective lens. However, in a high landing energy beam system using a backscattered electron detector to inspect 3D structures, reducing the working distance to obtain higher resolution can make the tool unsuitable due to throughput limitations, focusing power limitations, detector collection efficiency limitations, or physical space limitations. For inspection or metrology applications, it can be beneficial to obtain high resolution images while maintaining throughput and accuracy of feature measurement or defect detection during wafer inspection.

[0073] Figure 4 A schematic diagram of an apparatus 400 consistent with an embodiment of the present disclosure is illustrated, the apparatus 400 being configured to image a sample using a high landing energy charged particle beam 400B1. The apparatus 400 can be configured to image a sample 415 using a voltage control board 420 with fast focus correction, with higher throughput and higher signal electronic detection efficiency.

[0074] like Figure 4 As shown, the elongated portion of the voltage control board 420 (eg, Figure 6BThe elongated portion 624 of the voltage control plate 420 may extend downwardly into the central hole of the backscattered electron detector 413, so that the downstream end of the elongated portion of the voltage control plate 420 is aligned with the horizontal plane 413P along which the backscattered electron detector 413 extends. In such a configuration, the diameter d1 of the central hole of the backscattered electron detector 413 can be very small, enabling a higher backscattered electron collection efficiency to be achieved by collecting backscattered electrons over a wide range of emission angles and emission energies. In the device 400, the working distance (WD1) between the pole piece 407P and the sample 415 can be increased to accommodate the voltage control plate 420. This configuration can be useful in applications that require higher throughput and higher BSE detector collection efficiency while maintaining high quality images and measurement accuracy. It should be understood that although the diameter of the central hole of the backscattered electron detector 413 can be smaller, it can be large enough to allow the primary electron beam 400B1 and the secondary electron beam 400B4 to pass through unimpeded.

[0075] Reference now Figure 5 , Figure 5 A schematic diagram of a portion of an exemplary charged particle beam apparatus 500 consistent with embodiments of the present disclosure is illustrated. Apparatus 500 can be configured to image a sample 515 using a voltage control board 520 with fast focus correction.

[0076] In some embodiments, the apparatus 500 may include an objective lens 507 configured to focus the primary electron beam 500B1 on the surface of the sample 515, a voltage control board 520 configured to receive an electrical signal from a voltage control unit 525, a backscattered electron detector 513 configured to detect the signal electron beam 500B2, a control electrode 514, a secondary electron detector 506 configured to detect the signal electron beam 500B4, and a controller 50 (similar to Figure 2 and Figure 3 It should be understood that, although not shown in the figure, the device 500 may include other components as appropriate.

[0077] The voltage control board 520 of the device 500 may include a monolithic voltage control board (e.g., Figure 6B voltage control board 620) or a coupled voltage control board (eg, Figure 6C In some embodiments, the voltage control board 520 may be configured to adjust the focus of the primary electron beam 500B1 to be incident on the sample 515. The primary electron beam 500B1 may include a high landing energy electron beam.

[0078] like Figure 5 As shown, the elongated portion of the voltage control board 520 (eg, Figure 6BThe elongated portion 624 of the voltage control plate 520 may extend downward into the central hole of the backscattered electron detector 513, so that the downstream end of the elongated portion of the voltage control plate 520 extends beyond the horizontal plane 513P. Similar to the plane 413P, the plane 513P represents the central plane of the backscattered electron detector 513 relative to the thickness of the backscattered electron detector 513 in the direction parallel to the primary optical axis 500-1. In this type of configuration, the diameter d2 of the central hole of the backscattered electron detector 513 can be larger than the diameter d1 of the backscattered electron detector 413 to accommodate the voltage control plate 520 while maintaining electrical insulation. In the device 500, the working distance (WD2) between the pole piece 507P and the sample 515 can be shorter than WD1, which can enable high-resolution images to be obtained. This configuration can be useful in applications that require higher image resolution while maintaining high throughput and measurement accuracy. The electron collection efficiency of the backscattered electron detector 513 can be lower than the electron collection efficiency of the backscattered electron detector 413.

[0079] Reference Figure 7 , Figure 7 700 is a process flow diagram of an exemplary method of imaging a sample consistent with an embodiment of the present disclosure. Figure 2 As shown, one or more steps of method 700 may be performed by controller 50 of EBI system 100. For example, controller 50 may instruct modules of a charged particle beam device to activate a charged particle source to generate a primary charged particle beam (e.g., an electron beam), apply an electrical signal to a voltage control board, and perform other functions.

[0080] In step 710, a charged particle source is activated to emit charged particles. The charged particles may pass through an aperture to form a charged particle beam (e.g., Figure 4 Primary charged particle beam 400B1 or Figure 5 The electron source may be controlled by a controller (e.g., Figure 3 For example, the electron source can be controlled to emit primary electrons along the primary optical axis (e.g., Figure 4 The primary optical axis is 400-1 or Figure 5 The electron source may be remotely activated, for example, by using software, an application, or an instruction set of a processor of the controller to power the electron source through a control circuit device. The primary electron beam may pass through a Coulomb aperture array (e.g., Figure 2 Coulomb aperture array 224) and beam limiting aperture array (e.g., Figure 3 The beam limiting aperture array 305 is used to adjust the beam size or beam current of the primary electron beam and form a beam incident on the sample (e.g., Figure 4 Sample 415 or Figure 5of the sample 515).

[0081] In step 720, a signal electronic detector (e.g., Figure 4 Backscattered electron detector 413 or Figure 5 The backscattered electron detector 513) can detect signal electrons (e.g., Figure 4 Backscattered electron beam 400B2 or Figure 5 Backscattered electrons (BSE) can be generated by elastic scattering events of incident electrons from deeper layers below (such as the bottom surface of a deep trench or a high aspect ratio hole) and have high emission energy - between 50 eV and the incident energy of the primary electron beam. The backscattered electron detector can be located between the sample and the objective lens. The diameter of the central aperture of the backscattered electron detector can be varied based on the desired collection efficiency. For example, a smaller diameter of the central aperture of the backscattered electron detector can enable the collection of BSEs with a wider emission angle and emission energy range.

[0082] Charged particle beam devices (e.g. Figure 4 The device 400 or Figure 5 The device 500 may include a voltage control board configured to receive an electrical signal (e.g., Figure 4 Voltage control board 420 or Figure 5 The electrical signal may be generated by a voltage control unit (eg, Figure 4 The voltage control unit 425 or Figure 5 The voltage control board may include a conductive board made of a conductive material such as metal. In some embodiments, the voltage control board may be made of a non-magnetic material.

[0083] In step 730, the voltage control unit may adjust the voltage signal applied to the voltage control plate to adjust the voltage across the cavity (eg, Figure 6B The electrostatic field experienced by the primary electron beam passing through the cavity 628) of the sample. Changes in the electrostatic field can affect the focal length of the primary electron beam incident on the sample by passing through. The voltage control board is a separate component that can independently apply and control voltage without affecting the landing energy of the backscattered electrons on the backscattered electron detector. The voltage control board and the backscattered electron detector can be electrically insulated from each other.

[0084] A non-transitory computer-readable medium storing a controller (eg, Figure 1Instructions of a processor of a controller 50 in the controller 50) to perform image inspection, image acquisition, activation of a charged particle source, adjustment of electrical excitation of an stigmator, adjustment of landing energy of electrons, adjustment of objective lens excitation, application of electrical signals to a voltage control board to change the electrostatic field experienced by the primary electron beam, adjustment of electrical signals to adjust the focus of the primary electron beam, stage motion control, activation of a beam deflector to deflect the primary electron beam, application of electrical excitation signals including AC voltages, etc. Common forms of non-transitory media include, for example, floppy disks, diskettes, hard disks, solid-state drives, magnetic tapes or any other magnetic data storage media, compact disk read-only memories (CD-ROMs), any other optical data storage media, any physical media having a pattern of holes, random access memories (RAMs), programmable read-only memories (PROMs) and erasable programmable read-only memories (EPROMs), flash-EPROMs or any other flash memory, non-volatile random access memories (NVRAMs), cache memory, registers, any other memory chips or cartridges, and network versions thereof.

[0085] The embodiments of the present disclosure may also be described using the following terms:

[0086] 1. A charged particle beam device, comprising:

[0087] a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam along a primary optical axis;

[0088] Objective lens, including magnetic lens;

[0089] a charged particle detector located downstream of the objective lens relative to the path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and

[0090] A voltage control board is located between the charged particle detector and the pole piece of the magnetic lens, and the voltage control board includes:

[0091] a horizontal portion, including the opening; and

[0092] An elongated portion extends downwardly from the opening relative to the path of the primary charged-particle beam into a bore of the charged-particle detector.

[0093] 2. A device according to clause 1, wherein the slender portion includes an inner diameter that is substantially similar to the opening diameter of the horizontal portion.

[0094] 3. A device according to clause 2, wherein the diameter of the opening is smaller than the diameter of the hole of the charged particle detector.

[0095] 4. The device according to any of clauses 1-3, wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

[0096] 5. The apparatus of clause 4, wherein the cavity comprises a cylindrical cavity that is rotationally symmetric about the primary optical axis.

[0097] 6. A device according to any of clauses 4 and 5, wherein an inner surface of the elongated portion and an inner surface of the opening forming the cavity are aligned with each other.

[0098] 7. An apparatus according to any of clauses 4-6, further comprising a controller, the controller comprising a circuit arrangement, the circuit arrangement being configured to:

[0099] applying an electrical signal to the voltage control board; and

[0100] The electrical signal is adjusted to affect an electrostatic field experienced by a primary charged particle beam passing through the cavity, wherein the electrical signal comprises a voltage signal.

[0101] 8. Apparatus according to clause 7, wherein adjustment of the electrical signal is configured to cause a voltage control board to adjust the focus of the primary charged particle beam to be incident on a sample.

[0102] 9. The apparatus according to any of clauses 7 and 8, wherein an applied voltage signal of 100 V or less enables adjustment of the focus of the primary charged particle beam by up to 10 μm.

[0103] 10. The device according to any of clauses 1-9, wherein the charged particle detector and the voltage control board are electrically insulated from each other.

[0104] 11. An apparatus according to any of clauses 1-10, wherein the downstream end of the elongated portion extends into the hole of the charged particle detector and beyond a horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0105] 12. An apparatus according to any of clauses 1-10, wherein the downstream end of the elongated portion extends into the hole of the charged particle detector and is substantially aligned with a horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0106] 13. The apparatus according to any of clauses 1-12, further comprising a control electrode located downstream of the charged particle detector.

[0107] 14. The device according to clause 13, wherein the voltage control plate, the charged particle detector, the control electrode and the objective lens are coaxial.

[0108] 15. The device of any of clauses 1-14, wherein the voltage control plate comprises a conductive plate.

[0109] 16. The device of any of clauses 1-15, wherein the horizontal portion of the voltage control plate is formed from a monolithic substrate.

[0110] 17. The device of any of clauses 1-16, wherein the horizontal portion of the voltage-controlled plate is formed by coupling two or more plates.

[0111] 18. The device of any of clauses 1-17, wherein the elongated portion is fluidly connected to a horizontal portion of the voltage control plate.

[0112] 19. The device of any of clauses 1-18, wherein the elongated portion is coupled to the horizontal portion using hardware assembly, welding, gluing, bonding or brazing.

[0113] 20. An apparatus according to any of clauses 1-19, wherein the charged particle detector comprises a backscattered electron detector configured to detect backscattered electrons.

[0114] 21. The device of any of clauses 3-20, wherein the elongated portion comprises an outer diameter, and wherein the outer diameter is smaller than the diameter of the aperture of the charged particle detector.

[0115] 22. An apparatus according to any of clauses 6 to 21, wherein the inner surface of the elongated portion and the inner surface of the opening can be configured to provide a surface that is superior to the inner surface of an aperture of a charged particle detector.

[0116] 23. The device of any of clauses 6-22, wherein the inner surface of the elongated portion and the inner surface of the opening are configurable to maintain the elliptical nature of the cavity.

[0117] 24. An apparatus according to clause 23, wherein the ellipticity of the cavity allows the primary charged particle beam to pass through the cavity substantially without deflection.

[0118] 25. The device of any of clauses 1-24, wherein the voltage control plate comprises a non-magnetic material.

[0119] 26. A method of imaging a sample using a charged particle beam apparatus, the method comprising:

[0120] The charged particles emitted by the charged particle source form a primary charged particle beam;

[0121] detecting, using a charged particle detector, signal electrons generated from the sample when the primary charged particle beam interacts with the sample; and

[0122] adjusting an electrical signal applied to a voltage control board, wherein the voltage control board comprises:

[0123] a horizontal portion, the horizontal portion comprising an opening; and

[0124] An elongated portion extends downwardly from an opening into a bore of the charged particle detector relative to the path of the primary charged particle beam.

[0125] 27. The method of clause 26, wherein the voltage control plate is located between the charged particle detector and a pole piece of an objective lens.

[0126] 28. A method according to any of clauses 26 and 27, wherein the elongated portion comprises an inner surface substantially similar to a diameter of the opening of the horizontal portion.

[0127] 29. The method of clause 28, wherein the diameter of the opening is smaller than the diameter of the aperture of the charged particle detector.

[0128] 30. A method according to any of clauses 26-29, wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

[0129] 31. A method according to clause 30, wherein the cavity comprises a cylindrical cavity that is rotationally symmetric about the primary optical axis.

[0130] 32. A method according to any of clauses 30 and 31, wherein an inner surface of the elongated portion and an inner surface of the opening are aligned with each other.

[0131] 33. The method according to any one of clauses 30-32, further comprising:

[0132] applying a voltage signal to the voltage control board; and

[0133] The voltage signal is adjusted to affect the electrostatic field experienced by the primary charged particle beam passing through the cavity.

[0134] 34. A method according to clause 33, wherein adjusting the voltage signal causes adjustment of the focus of the primary charged particle beam incident on the sample.

[0135] 35. The method of clause 34, wherein adjusting the voltage signal by 100 V or less adjusts the focus of the primary charged particle beam by up to 10 μm.

[0136] 36. The method of any of clauses 26-35, wherein the voltage control board and the charged particle detector are electrically insulated from each other.

[0137] 37. The method of clause 36, wherein electrically insulating the voltage control board and the charged particle detector comprises forming an electrically insulating layer on a non-detecting surface of the charged particle detector.

[0138] 38. A method according to any one of clauses 26-37, wherein the downstream end of the slender portion extends into the hole of the charged particle detector and beyond a horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0139] 39. A method according to any one of clauses 26-37, wherein the downstream end of the slender portion extends into the hole of the charged particle detector and is substantially aligned with a horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0140] 40. The method of any of clauses 26-39, wherein the voltage control board and the charged particle detector are aligned with the primary optical axis.

[0141] 41. The method of any of clauses 26-40, wherein the voltage control plate comprises a conductive plate.

[0142] 42. A method according to any of clauses 26-41, wherein the horizontal portion of the voltage control plate is formed from a monolithic substrate.

[0143] 43. A method according to any of clauses 26-42, wherein the horizontal portion is formed by coupling two or more plates.

[0144] 44. The method of any of clauses 26-43, wherein the elongated portion is fluidly connected to a horizontal portion of the voltage control plate.

[0145] 45. A method according to any of clauses 26-44, wherein the elongated portion is coupled to the horizontal portion using hardware assembly, welding, gluing, bonding or brazing.

[0146] 46. ​​A method according to any of clauses 26-45, wherein the charged particle detector comprises a backscattered electron detector configured to detect backscattered electrons.

[0147] 47. A method according to any of clauses 26-46, wherein the elongated portion comprises an outer diameter that is smaller than a diameter of the aperture of the charged particle detector.

[0148] 48. The method of any of clauses 32-47, further comprising modifying the inner surface of the elongated portion and the inner surface of the opening to provide a surface that is superior to an inner surface of the aperture of the charged particle detector.

[0149] 49. The method of clause 48, wherein modifying comprises cleaning, polishing or remachining the inner surface of the elongated portion and the inner surface of the opening to maintain the ellipticity of the cavity.

[0150] 50. The method of clause 49, wherein maintaining the ellipticity of the cavity allows the primary charged particle beam to pass through the cavity substantially undeflected.

[0151] 51. The method of any of clauses 26-50, wherein the voltage control plate comprises a non-magnetic material.

[0152] 52. 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 comprising:

[0153] acquiring a signal from a charged particle detector, wherein the signal is produced by the charged particle detector detecting signal electrons generated from the sample when the primary charged particle beam interacts with the sample; and

[0154] adjusting an electrical signal applied to a voltage control board to enable adjustment of a focus of the primary charged particle beam to be incident on the sample, wherein the voltage control board comprises:

[0155] a horizontal portion, including the opening; and

[0156] An elongated portion extends downwardly from the opening relative to the path of the primary charged-particle beam into the aperture of the charged-particle detector.

[0157] 53. The non-transitory computer-readable medium of clause 52, wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged-particle beam to pass therethrough.

[0158] 54. The non-transitory computer-readable medium of clause 53, wherein the set of instructions executable by the one or more processors of the charged particle beam device causes the charged particle beam device to further perform:

[0159] applying a voltage signal to the voltage control board; and

[0160] The voltage signal is adjusted to affect the electrostatic field experienced by the primary charged particle beam passing through the cavity.

[0161] 55. The non-transitory computer-readable medium of clause 54, wherein adjusting the voltage signal causes adjustment of a focus of the primary charged particle beam incident on the sample.

[0162] 56. The non-transitory computer-readable medium of clause 55, wherein adjusting the voltage signal by 100 V or less adjusts the focal length of the primary charged-particle beam by up to 10 μm.

[0163] 57. The non-transitory computer-readable medium of any of clauses 52-56, wherein the voltage control board and the charged particle detector are electrically insulated from each other.

[0164] 58. The non-transitory computer-readable medium of clause 57, wherein electrically insulating the voltage control board and the charged-particle detector comprises: forming an electrically insulating layer on a non-detecting surface of the charged-particle detector.

[0165] 59. A non-transitory computer-readable medium according to any of clauses 52-58, wherein the downstream end of the elongated portion extends into the aperture of the charged particle detector and beyond a horizontal plane along which the charged particle detector extends, the horizontal plane comprising a center plane relative to the thickness of the charged particle detector.

[0166] 60. A non-transitory computer-readable medium according to any of clauses 52-58, wherein the downstream end of the elongated portion extends into the aperture of the charged particle detector and is substantially aligned with a horizontal plane along which the charged particle detector extends, the horizontal plane comprising a center plane relative to the thickness of the charged particle detector.

[0167] 61. An electro-optical assembly comprising:

[0168] Objective lens, including magnetic lens;

[0169] a charged particle detector located downstream of the objective lens relative to the path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; and

[0170] A voltage control board is located between the charged particle detector and the pole piece of the magnetic lens, and the voltage control board includes:

[0171] a horizontal portion, including the opening; and

[0172] an elongated portion extending downwardly from the opening into the aperture of the charged particle detector relative to the path of the primary charged particle beam,

[0173] Wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

[0174] 62. An assembly according to clause 61, wherein the slender portion includes an inner diameter that is substantially similar to the diameter of the opening of the horizontal portion.

[0175] 63. A component according to clause 62, wherein the diameter of the opening is smaller than the diameter of the aperture of the charged particle detector.

[0176] 64. An assembly according to any of clauses 61-63, wherein the cavity comprises a cylindrical cavity that is rotationally symmetric about the primary optical axis.

[0177] 65. An assembly according to any of clauses 61-64, wherein an inner surface of the elongated portion and an inner surface of the opening forming the cavity are aligned with each other.

[0178] 66. An assembly according to any of clauses 61-65, further comprising a controller, the controller comprising circuitry configured to:

[0179] applying an electrical signal to the voltage control board; and

[0180] The electrical signal is adjusted to affect an electrostatic field experienced by the primary charged particle beam passing through the cavity, wherein the electrical signal comprises a voltage signal.

[0181] 67. An assembly according to clause 66, wherein adjustment of the electrical signal is configured to cause the voltage control board to adjust the focus of the primary charged particle beam to be incident on a sample.

[0182] 68. An assembly according to any of clauses 66 and 67, wherein the applied voltage signal of 100 V or less causes the adjustment of the focus of the primary charged particle beam by up to 10 μm.

[0183] 69. An assembly according to any of clauses 61-68, wherein the charged particle detector and the voltage control board are electrically insulated from each other.

[0184] 70. A component according to any of clauses 61-69, wherein the downstream end of the slender portion extends into the hole of the charged particle detector and beyond the horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0185] 71. A component according to any of clauses 61-69, wherein the downstream end of the slender portion extends into the aperture of the charged particle detector and is substantially aligned with the horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

[0186] 72. An assembly according to any of clauses 61-71, further comprising a control electrode located downstream of the charged particle detector.

[0187] 73. An assembly according to clause 72, wherein the voltage control board, the charged particle detector, the control electrode and the objective lens are coaxial.

[0188] 74. An assembly according to any of clauses 61-73, wherein the voltage control plate comprises a conductive plate.

[0189] 75. The assembly of any of clauses 61-74, wherein the horizontal portion of the voltage control plate is formed from a monolithic substrate.

[0190] 76. The assembly of any of clauses 61-74, wherein the horizontal portion of the voltage control plate is formed by coupling two or more plates.

[0191] 77. An assembly according to any of clauses 61-76, wherein the elongated portion is fluidly connected to a horizontal portion of the voltage control plate.

[0192] 78. An assembly according to any of clauses 61-76, wherein the elongated portion is coupled to the horizontal portion using hardware assembly, welding, gluing, bonding or brazing.

[0193] 79. An assembly according to any of clauses 61-78, wherein the charged particle detector comprises a backscattered electron detector configured to detect backscattered electrons.

[0194] 80. An assembly according to any of clauses 63-79, wherein the elongated portion comprises an outer diameter that is smaller than a diameter of the aperture of the charged particle detector.

[0195] 81. A component according to any of clauses 65-80, wherein the inner surface of the slender portion and the inner surface of the opening can be configured to provide a surface that is superior to the inner surface of the aperture of the charged particle detector.

[0196] 82. An assembly according to any of clauses 65-81, wherein the inner surface of the elongated portion and the inner surface of the opening are configurable to maintain the elliptical nature of the cavity.

[0197] 83. An assembly according to clause 82, wherein the ellipticity of the cavity allows the primary charged particle beam to pass through the cavity substantially without deflection.

[0198] 84. An assembly according to any of clauses 61-83, wherein the voltage control plate comprises a non-magnetic material.

[0199] 85. A plate insertable between a charged particle detector and a pole piece of an objective lens of a charged particle beam device, the plate comprising:

[0200] a horizontal portion, including the opening; and

[0201] an elongated portion extending downwardly from the opening into the aperture of the charged particle detector relative to the path of the primary charged particle beam,

[0202] Wherein the opening portion and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

[0203] It should be understood that the embodiments of the present disclosure are not limited to the exact structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in conjunction with various embodiments, and other embodiments of the present invention will be apparent to those skilled in the art in view of the description and practice of the invention disclosed herein. The description and embodiments are to be considered as exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

[0204] The above description is intended to be illustrative rather than limiting. Therefore, it will be apparent to those skilled in the art that modifications as described can be made without departing from the scope of the claims set forth below.

Claims

1. A charged particle beam device, comprising: a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam along a primary optical axis; Objective lens, including magnetic lens; a charged particle detector located downstream of the objective lens relative to the path of the primary charged particle beam and along a horizontal plane substantially perpendicular to the primary optical axis; as well as A voltage control board is located between the charged particle detector and the pole piece of the magnetic lens, and the voltage control board includes: a horizontal portion, including the opening; and An elongated portion extends downwardly from the opening relative to the path of the primary charged-particle beam into a bore of the charged-particle detector.

2. The device of claim 1, wherein the elongated portion has an inner diameter substantially similar to a diameter of the opening of the horizontal portion.

3. The device of claim 2, wherein the diameter of the opening is smaller than the diameter of the aperture of the charged particle detector.

4. The apparatus of claim 1, wherein the opening and the elongated portion form a cavity configured to allow the primary charged particle beam to pass therethrough.

5. The apparatus of claim 4, wherein the cavity comprises a cylindrical cavity that is rotationally symmetric about the primary optical axis.

6. The device of claim 5, wherein an inner surface of the elongated portion and an inner surface of the opening forming the cavity are aligned with each other.

7. The apparatus of claim 5, further comprising a controller, the controller comprising a circuit arrangement, the circuit arrangement being configured to: applying an electrical signal to the voltage control board; and The electrical signal is adjusted to affect an electrostatic field experienced by the primary charged particle beam passing through the cavity, wherein the electrical signal comprises a voltage signal.

8. The apparatus of claim 7, wherein the adjustment of the electrical signal is configured to cause the voltage control board to adjust the focus of the primary charged particle beam to be incident on a sample.

9. The apparatus of claim 7, wherein the applied voltage signal of 100 V or less enables the adjustment of the focus of the primary charged particle beam by up to 10 μm.

10. The apparatus of claim 1, wherein the charged particle detector and the voltage control board are electrically insulated from each other.

11. An apparatus according to claim 1, wherein the downstream end of the slender portion extends into the hole of the charged particle detector and beyond the horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

12. An apparatus according to claim 1, wherein the downstream end of the elongated portion extends into the hole of the charged particle detector and is substantially aligned with the horizontal plane along which the charged particle detector extends, the horizontal plane including a center plane relative to the thickness of the charged particle detector.

13. The apparatus of claim 3, wherein the elongated portion comprises an outer diameter, and wherein the outer diameter is smaller than the diameter of the aperture of the charged particle detector.

14. The apparatus of claim 6, wherein the inner surface of the elongated portion and the inner surface of the opening are configurable to provide a surface that is superior to an inner surface of the aperture of the charged particle detector.

15. A method for imaging a sample using a charged particle beam apparatus, the method comprising: The charged particles emitted by the charged particle source form a primary charged particle beam; detecting, using a charged particle detector, signal electrons generated from the sample when the primary charged particle beam interacts with the sample; as well as adjusting an electrical signal applied to a voltage control board, wherein the voltage control board comprises: a horizontal portion, including the opening; as well as An elongated portion extends downwardly from the opening relative to the path of the primary charged-particle beam into the aperture of the charged-particle detector.

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