Semiconductor charged particle detector and method thereof

Abstract

Systems and methods for charged particle detection using a charged particle detector in a charged particle beam apparatus are disclosed. The apparatus may include a charged particle detector including a substrate. The substrate may include a plurality of sensing elements configured to receive a plurality of charged particles generated from a sample. Each sensing element of the plurality of sensing elements includes a first device configured to detect a charged particle of the plurality of charged particles having an energy equal to or lower than a first threshold value, and to allow a charged particle of the plurality of charged particles having an energy greater than the first threshold value to pass therethrough. The sensing element also includes a second device configured to detect charged particles allowed to pass through the first device.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 63 / 395,278, filed on August 4, 2022, and the entire contents of which are incorporated herein by reference. Technical Field

[0003] The description herein relates to particle detection, and more particularly to systems and methods that can be applied to particle detection with a large dynamic range energy resolution. Background Art

[0004] During the manufacture of integrated circuits (ICs), unfinished or finished 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 the complexity of device architectures increases, accurately inspecting 3D structures and the defects therein becomes increasingly important.

[0005] Detectors can be used to sense physically observable phenomena. For example, a charged particle beam tool such as an electron microscope may include a detector that receives charged particles projected from a sample and outputs a detection signal. The detection signal can be used to reconstruct an image of the sample structure under inspection, and can be used, for example, to reveal defects in the sample. When manufacturing semiconductor devices that may include a large number of densely packed miniaturized integrated circuit (IC) components, it is increasingly important to detect defects in the sample. For this purpose, a dedicated inspection tool can be provided. Although charged particles such as secondary electrons or backscattered electrons can be individually detected using independent detectors with high efficiency, it is better to use a single detector that can detect electrons in a wide energy range. Summary of the invention

[0006] Embodiments of the present disclosure provide systems and methods for charged particle detection. One aspect of the present invention relates to a charged particle detector, comprising a substrate. The substrate may include a plurality of sensing elements configured to receive a plurality of charged particles generated from a sample. Each of the plurality of sensing elements includes a first device configured to detect charged particles whose energy is equal to or lower than a first threshold among the plurality of charged particles, and to allow charged particles whose energy is greater than the first threshold among the plurality of charged particles to pass. The sensing element also includes a second device configured to detect charged particles that are allowed to pass through the first device.

[0007] Another aspect of the present disclosure relates to a charged particle beam apparatus, including a charged particle source configured to emit charged particles forming a primary charged particle beam; and a charged particle detector configured to detect a plurality of signal charged particles generated when the charged particles of the primary charged particle beam interact with a sample. The charged particle detector may include a substrate. The substrate may include a plurality of sensing elements configured to receive a plurality of charged particles generated from the sample. Each of the plurality of sensing elements includes a first device configured to detect charged particles having an energy equal to or lower than a first threshold value among the plurality of charged particles, and to allow charged particles having an energy greater than the first threshold value among the plurality of charged particles to pass through. The sensing element also includes a second device configured to detect charged particles allowed to pass through the first device.

[0008] Another aspect of the present disclosure relates to a method for charged particle detection using a substrate including a plurality of sensing elements, the plurality of sensing elements being configured to receive a plurality of charged particles generated from a sample. Each of the plurality of sensing elements includes a first device and a second device. The method may include: using the first device to detect a first charged particle among the plurality of charged particles whose energy is equal to or lower than a first threshold; and after a second charged particle among the plurality of charged particles whose energy is greater than the first threshold passes through the first device, using the second device to detect a second charged particle.

[0009] Another aspect of the present disclosure relates to a non-transitory computer-readable medium storing a set of instructions that can be implemented by one or more processors of a charged particle beam device, the charged particle beam device including a charged particle beam detector using a substrate, the substrate including a plurality of sensing elements, the plurality of sensing elements configured to receive a plurality of charged particles generated from a sample. Each of the plurality of sensing elements may include a first device and a second device, the instructions causing the set to cause the charged particle beam device to perform a method. The method may include: activating a first device to enable detection of a first charged particle having an energy equal to or lower than a first threshold value among the plurality of charged particles; and after a second charged particle having an energy greater than the first threshold value among the plurality of charged particles passes through the first device, activating a second device to enable detection of a second charged particle.

[0010] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which certain embodiments of the present invention are set forth 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 according to an embodiment of the present invention.

[0012] Figure 2It is a diagram illustrating that the embodiment according to the present disclosure may be Figure 1 A schematic diagram of an exemplary electron beam tool that is a portion of an exemplary electron beam inspection system.

[0013] Figure 3 A schematic diagram of an exemplary arrangement of a charged particle detector configured to receive secondary charged particles from a sample according to an embodiment of the present disclosure is illustrated.

[0014] Figure 4 A schematic diagram of an exemplary charged particle detector including a sensing element according to an embodiment of the present disclosure is illustrated.

[0015] Figure 5A The embodiment according to the present disclosure is illustrated Figure 4 Schematic diagram of a cross-sectional view of an exemplary sensing element of a charged particle detector.

[0016] Figure 5B The embodiment according to the present disclosure is illustrated Figure 4 Schematic diagram of a cross-sectional view of an exemplary sensing element of a charged particle detector.

[0017] Fig. 6A , Figure 6B , Figure 6C and Fig.6D Various scenarios for discerning the energy of incoming charged particles at a charged particle detector according to embodiments of the present disclosure are illustrated.

[0018] Figure 7 Illustrated are data graphs of simulated responses of an exemplary detection device to receiving and detecting charged particles, such as electrons, over a wide range of energies, in accordance with embodiments of the present disclosure.

[0019] Figure 8 is a process flow diagram of an exemplary method for detecting charged particles according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] Reference is now made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations set forth in the following description of the example embodiments do not represent all implementations. Instead, they are merely examples of apparatus and methods according to 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 invention is not limited thereto. Similarly, other types of charged particle beams may be applied. Further, other imaging systems such as optical imaging, photon detection, x-ray detection, etc. may be used.

[0021] Electronic devices consist of circuits formed on a silicon wafer called a substrate. Many circuits can be formed together on the same silicon wafer and are called integrated circuits or ICs. The size of these circuits has been significantly reduced so that many of them can be mounted on a substrate. For example, an IC chip in a smartphone can be as small as a thumbnail and can also include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair.

[0022] Manufacturing these extremely small ICs is a complex, time-consuming and expensive process, typically involving hundreds of individual steps. An error in even one step can result in a defect in the finished IC, thereby rendering it useless. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs manufactured in the process, that is, to increase the overall yield of the process.

[0023] One component of improving yield is to monitor the chip manufacturing process to ensure that it produces a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip circuit structure at various stages of its formation. Inspection can be performed using a scanning electron microscope (SEM). For example, an SEM can be used to image these extremely small structures, in effect, taking a "photo" of the structure. The image can be used to determine whether the structure was formed correctly and whether 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.

[0024] In SEM, the interaction of the electrons of the primary detection electron beam with the sample can generate particles such as secondary electrons, backscattered electrons, Auger electrons, photons, x-rays, etc., which carry useful information about the sample. One of the several ways to extract sample information from the generated charged particles is to detect the charged particles and convert the information they carry into a readable format such as an image. The energy of the emitted energy or the energy of the charged particles leaving the sample can be an indication of the emission depth and the type of interaction, and therefore, can be used to obtain information associated with the sample. As an example, low-energy secondary electrons can interact with the first few nanometers of the sample surface, thereby providing information about topological features, surface morphology, etc., and the higher energy backscattered electrons emitted from the deeper areas of the interaction volume can provide information associated with the chemical composition and overall properties of the material. The large interaction volume of the primary electrons with the sample material can generate charged particles with a wide energy range from 1eV to 100eV or more, and in some cases equal to the landing energy of the primary electrons. In order to maximize the extraction of useful information, it may be desirable to detect as many charged particles as possible and charged particles with as wide an energy range as possible.

[0025] Parsing or distinguishing the energy level of the detected charged particles can achieve advantages such as accurate high-resolution imaging, accurate reconstruction of images from the detected signals, etc. One of several prior arts for parsing energy levels and identifying incoming electrons on an electron detector (such as a PIN diode) includes setting thresholds. One or more thresholds can be set to classify incoming charged particles based on their energy. For example, a first threshold at the lowest electron energy can be used to identify whether the sensing element has received an electron, or whether its output is caused by interference or dark current, etc. A second threshold at an intermediate electron energy can be used to identify whether the electron received by the sensing element is a secondary electron from a sample or a backscattered electron from a sample. A third threshold at the highest electron energy can be used to identify whether the sensing element has received more than one electron. Although setting a threshold is a useful technique for distinguishing detected charged particles, it may face limitations due to a narrow energy discrimination range. For example, setting a threshold can be used to parse energy levels between 10eV and 20eV or between 5eV and 10eV, etc. However, for larger dynamic energy ranges (such as from 1 eV to 100 eV or greater), setting a threshold may not be sufficient due to the small number of charge carriers generated by low energy electrons within the semiconductor substrate. One of several ways to detect low energy electrons can include using a single photon avalanche diode (SPAD) device, which can generally provide high signal gain and high sensitivity. However, SPAD devices may face limitations in resolving both higher and lower electron energies. Therefore, it is desirable to provide improved detection systems and methods that can resolve a wide dynamic range of electron energy levels while maintaining detection throughput, cost-effectiveness, and ease of operation.

[0026] Some aspects of the present disclosure may address some limitations by providing a charged particle detector comprising a SPAD and a PIN diode device. The charged particle detector may include an array of sensing elements, and each sensing element may include a SPAD device and a PIN diode device fabricated on the same substrate. The PIN diode device may be formed below the SPAD device relative to the incident direction of the incoming charged particles emitted from the sample. The SPAD device may be configured to detect charged particles having energies below a predetermined threshold while allowing charged particles having energies above the threshold to pass through to be detected by the PIN device. Combining a SPAD device and a PIN device for resolving energy may enable greater dynamic range discrimination. The SPAD device may also count arrival events of charged particles and time-stamp or determine arrival times of the charged particles.

[0027] For the sake of clarity, the relative size of the parts in the accompanying drawings may be enlarged. In the following description of the drawings, the same or similar reference numerals refer to the same or similar parts or entities, and only describe the difference about individual embodiments. As used herein, unless otherwise specifically stated, the term "or" encompasses all possible combinations, except infeasible situations. For example, if the description component can include A or B, then unless otherwise specifically stated or infeasible, the component can include A, or B, or A and B. As a second example, if the description component can include A, B or C, then unless otherwise specifically stated or infeasible, the component can include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0028] Now, refer to Figure 1 , Figure 1 An exemplary electron beam inspection (EBI) system 100 is illustrated in accordance with an embodiment of the present disclosure. Figure 1 As shown, the charged particle beam detection system 100 includes a main chamber 10, a load-lock chamber 20, an electron beam tool 40, and an equipment front end module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. Although the description and drawings are directed to electron beams, it should be appreciated that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0029] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include one or more additional loading ports. The first loading port 30a and the second loading port 30b receive a wafer front opening unification unit (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 transfer 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) transfer the wafer from the load-lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum 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 implement various controls for the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to implement various signal and image processing functions. Figure 1 Controller 50 is shown as being outside of the structure including main chamber 10, load-lock chamber 20, and EFEM 30, but it should be appreciated that controller 50 may be part 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 aspects of the present disclosure in its broadest sense are not limited to chambers housing electron beam inspection systems. Rather, it should be appreciated that the aforementioned principles may also be applied to other chambers.

[0033] Now, refer to Figure 2 , Figure 2 is a schematic diagram illustrating an exemplary configuration of an electron beam tool 40 according to an embodiment of the present disclosure, which may be Figure 1 2. 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 extractor 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 appreciated that other related components may be added or omitted as desired.

[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 cross 202 (virtual or real). The primary electron beam 204 may be visualized as being emitted from the primary beam cross 202.

[0035] In some embodiments, the electron emitter, focusing lens 226, objective lens assembly 232, beam-limiting aperture array 235, and electron detector 244 can be aligned with the primary optical axis 201 of apparatus 40. In some embodiments, the electron detector 244 can be positioned offset from 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 deceleration 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 in the gun aperture 220 and the Coulomb aperture array 224, and is focused by the focusing lens 226 so as to pass through the apertures in the beam limiting aperture array 235 in whole or in part. Electrons passing through the apertures in the beam limiting aperture array 235 may be focused by the modified SORIL lens to form a detection 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 region of interest.

[0037] In the objective lens assembly 232, the excitation coil 232d and the pole piece 232a can generate a magnetic field. A portion of the sample 250 scanned by the primary electron beam 204 can be immersed in the magnetic field and can be charged, which in turn generates an electric field. The electric field can reduce the energy of the primary electron beam 204 that strikes the surface of the sample 250 near and on the surface of the sample 250. The control electrode 232b electrically isolated from the pole piece 232a can control the electric field above and on 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 to provide data for image reconstruction of different parts of the sample 250. It should be noted that the order of 240a to 240e may be different in different embodiments.

[0038] Upon receiving the primary electron beam 204, backscattered electrons (BSE) and secondary electrons (SE) may be emitted from a portion of the sample 250. The beam splitter may direct one or more secondary electron beams or scattered electron beams including backscattered electrons and secondary electrons to 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 a controller 50). The intensity of the secondary electron beam or backscattered electron beam and the resulting secondary electron beam spot may vary depending on the external structure or internal structure of the sample 250. Moreover, as discussed above, the primary electron beam 204 may be deflected to different locations on the top surface of the sample 250 to generate secondary electron beams or scattered electron beams (and resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot with the position of the sample 250 , the processing system can reconstruct an image of the wafer sample 250 that reflects the internal structure 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 storage device (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, etc., or a combination thereof. The image acquisition device may be communicatively coupled to the electronic detector 244 of the device 40 through a medium such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, radio, etc., 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. Thus, the image acquisition device may acquire images of various regions 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, etc. The image acquisition device may be configured to perform adjustments such as brightness and contrast on the acquired image. In some embodiments, the storage device 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, etc. The storage device may be coupled to the image acquirer and may be used to save the scanned raw image data as an initial image and to save a post-processed image.

[0040] In some embodiments, the controller 50 may include a measurement circuit system (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 exist in the wafer.

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

[0042] As is well known, secondary electrons (SE) can be identified as signal electrons with lower emission energy, while backscattered electrons (BSE) can be identified as signal electrons with higher emission energy. The emission of SE and BSE follows Lambert's law and has a large energy spread. SES and BSE are generated from different depths of the sample when the primary electron beam interacts with the sample, and have different emission energies. For example, secondary electrons originate from the surface or near the surface, and can have an emission energy of ≤50eV, depending on the sample material or the interaction volume, etc. SE is used to provide information about surface features or surface geometry. On the other hand, BSE is mainly generated by the elastic scattering event of the incident electron of the primary electron beam, and generally has a higher emission energy (in the range from 50eV to the landing energy of the approximate incident electron) compared to SE, and provides composition information and contrast information of the material being inspected. The number of generated BSEs can depend on various factors, including but not limited to the atomic number of the material in the sample, the accelerating voltage of the primary electron beam, etc.

[0043] Now, refer to Figure 3 , Figure 3 A schematic diagram of an exemplary charged particle detector configured to receive charged particles originating from a sample according to some embodiments of the present disclosure is illustrated. A primary charged particle beam 304 along a primary optical axis 301 may illuminate a sample 350 (similar to Figure 2When interacting with the charged particles of the primary charged particle beam 304, the sample 350 can generate one or more secondary charged particle beams 305, which include secondary charged particles such as but not limited to secondary electrons, backscattered electrons, photons, x-rays, Auger electrons, etc. Figure 2 The charged particle detector 344 of the charged particle detector 244 can be placed upstream of the sample 350. As used in the context of the present disclosure, "upstream" refers to a charged particle beam that is located along the path of the primary charged particle beam (e.g., Figure 2 The path of the primary electron beam 204) is located above or in front of another element. It should be appreciated that the charged particle detector (although not shown) can be configured to detect electrons, x-rays, photons or any charged particles.

[0044] Charged particle detector 344 can be configured as a detector plate having a front surface 352 and a rear surface 354 separated by the thickness of the detector plate. Rear surface 354 can be opposite to front surface 352. As used herein, the "front" surface refers to the downstream horizontal surface facing the sample. As used in the context of the present disclosure, "downstream" refers to the downstream direction of the primary charged particle beam (e.g., Figure 2 The position of an element that is located below or behind another element in the path of the primary electron beam 204. For example, the front surface 352 of the charged particle detector 344 can be a downstream surface, while the rear surface 354 can be an upstream surface relative to the path of the primary charged particle beam 304 along the primary optical axis 301 toward the sample 350.

[0045] like Figure 3 As illustrated, charged particle detector 344 may include an array of sensing elements including sensing elements 360. The sensing elements may be arranged in a planar two-dimensional array, the plane of the array being substantially perpendicular to the incident direction of the incoming charged particles. In some embodiments, charged particle detector 344 may be arranged to be tilted at an angle relative to the incident direction.

[0046] Charged particle detector 344 may include a substrate having an array of sensing elements. In some embodiments, the substrate may include a semiconductor substrate. Sensing element 360 may include a semiconductor charged particle detection device such as a photodiode, a PIN diode, a single photon avalanche photodiode (SPAD), a photomultiplier tube, an electron multiplier tube (EMT), etc. In some embodiments, a semiconductor electron detector may be used Figure 1The device 40 in the EBI system 100 of the invention. The EBI system 100 may be a high-speed wafer imaging SEM including an image processor. The electron beam generated by the EBI system 100 may irradiate the surface of the sample or may penetrate the sample. The EBI system 100 may be used to image the surface of the sample or the structure below the surface, such as for analyzing layer alignment. In some embodiments, the EBI system 100 may detect and report process defects related to the manufacture of semiconductor wafers by, for example, comparing the SEM image with the SEM image of the same pattern at the device layout pattern or other locations on the inspected wafer. The semiconductor electron detector may include a semiconductor PIN diode that may operate under a negative bias. The PIN diode may be configured so that the incoming electrons generate relatively large and different detection signals. In some embodiments, the PIN diode may be configured so that the incoming electrons may generate several electron-hole pairs. As mentioned herein, the PIN diode may include a stacked configuration of a p-type semiconductor (P), an intrinsic semiconductor (I), and an n-type semiconductor (N). In some embodiments, the sensing element 360 may include a PIN diode, a single photon avalanche photodiode (SPAD), an electron multiplier tube (EMT), or a combination thereof. In some embodiments, the sensing element 360 may include a combination of a PIN diode and a SPAD fabricated on the same substrate, as shown in FIG. Figure 5A discussed.

[0047] In some embodiments, one or more sensing elements 360 may be fabricated on the substrate such that the sensing elements 360 partially or substantially completely protrude from the front surface 352. Alternatively, although not shown, one or more sensing elements may be fabricated such that they are substantially completely recessed into the substrate of the charged particle detector 344.

[0048] Now, refer to Figure 4 , Figure 4 A schematic diagram of an exemplary charged particle detector 444 according to some embodiments of the present disclosure is illustrated. The charged particle detector 444 may be used with Figure 3 The charged particle detector 344 is substantially similar to and may perform the same Figure 3The charged particle detector 444 may have substantially similar functionality to the charged particle detector 344. In some embodiments, the charged particle detector 444 may include an array of sensing elements including sensing elements 460 formed on the surface 452. The sensing elements may be arranged in a planar two-dimensional array, such as, but not limited to, a rectangular array, a circular array, or other suitable arrangement. The charged particle detector 444 may also include an area 456 that does not contain active components (such as sensing elements). The area 456 may include an aperture or through-hole 458 to allow a primary charged particle beam (e.g., a primary electron beam) to pass through. The charged particle detector 444 may be positioned so that the geometric center of the charged particle detector 444 and the aperture 458 is aligned with the primary charged particle beam (e.g., Figure 2 The primary electron beam 204) basically coincides with the primary optical axis 401 along which the primary electron beam 204 travels.

[0049] The sensing element may generate an electrical signal equivalent to the charged particles received in the active region of the sensing element. For example, the sensing element may generate a current signal equivalent to the energy of the received electrons. The preprocessing circuit system may convert the generated current signal into a voltage signal that may represent the intensity of the electron beam spot or a portion thereof. The preprocessing circuit system may include, for example, a pre-amplification circuit system. The pre-amplification circuit system may include, for example, a charge transfer amplifier (CTA), a transimpedance amplifier (TIA), or an impedance conversion circuit coupled to a CTA or TIA. In some embodiments, a signal processing circuit system that provides an output signal in arbitrary units in time may be included. One or more substrates, such as a die, may be provided, which may form a circuit layer for processing the output of the sensing element. The die may be stacked together in the thickness direction of the charged particle detector. Other circuit systems may also be provided for other functions. For example, a switch actuation circuit system may be provided, which may control a switch element for connecting the sensing elements to each other.

[0050] Now, refer to Figure 5A , Figure 5A FIG. 5 shows a cross-sectional view of an exemplary sensing element 500 according to an embodiment of the present disclosure. The sensing element 500 may be Figure 4 The sensing element 460 or Figure 3 360. The sensing element 500 may include a substrate 528, which may be a semiconductor substrate such as, but not limited to, a silicon substrate. The substrate 528 may include a doping density of 1×10 12 Atom / cm 3The high resistivity semiconductor substrate of or less. The high resistivity substrate may be desirable as a fully depleted substrate layer and may contribute to the signal generated by a charge detection device such as a PIN diode. In some embodiments, the substrate 528 may have a plurality of layers stacked in a direction substantially parallel to the incident direction of a charged particle beam such as the secondary electron beam 504. For example, the substrate 528 may include one or more doped semiconductor material layers, trenches, vias, or other structures.

[0051] In some embodiments, the sensing element 500 of the charged particle detector may include two or more charged particle detection devices formed on a substrate. Figure 5A As shown, sensing element 500 may include a SPAD device 520 and a PIN diode device 540. SPAD device 520 and PIN diode device 540 may be fabricated on the same substrate 528 such that PIN diode device 540 is adjacent to SPAD device 520 and is configured to receive charged particles that pass through SPAD device 520. It should be appreciated that the dashed lines marking the approximate boundaries of SPAD device 520 and PIN diode device 540 are visual aids for illustration purposes only and do not represent the actual boundaries of the devices.

[0052] In some embodiments, the SPAD device 520 may include a highly doped p ++ Region 512 and highly doped n ++ The pn junction device provided by region 514. The highly doped region may include a concentration ranging from, for example, 10 13 Atom / cm 3 Up to 10 18 Atom / cm 3 SPAD device 520 may also include contact pads 516 and 518 configured to be electrically connected to highly doped p-region 512 and highly doped n-region 514, respectively. Contact pads 516 and 518 may be configured to apply a control circuit system (e.g., Figure 2 The contact pads 516 and 518 can be connected to external circuitry such as, but not limited to, signal processing circuitry, voltage control circuitry, timing circuitry, etc. In some embodiments, although not shown, the highly doped p-type SPAD device 520 may be connected to a plurality of external circuits. ++Region 512 may be electrically connected to another doped p-region 532 through a via (not shown) etched into substrate 528 and filled with a conductive material such as, but not limited to, copper, titanium, tungsten, etc. In some embodiments, doped p-region 532 may form a contact bus line configured to form a connection with an array of sensing elements (e.g., Figure 4 The sensing element array 460) has a plurality of sensing elements of a highly doped p ++ Electrical connection of region 512. Doped region 512 or 532 of sensing element 500 may include a pure or nearly pure amorphous boron layer, as further described in U.S. Publication No. 2020 / 0212246, which is incorporated herein by reference in its entirety.

[0053] Sensing element 500 may also include a PIN diode device 540 as a charged particle detector. PIN diode device 540 may include a p-region and an n-region 522 provided by a high resistivity, lightly doped p-type substrate 528. Additionally or alternatively, PIN diode device 540 may include a highly doped n-region atop n-region 522. ++ Region 524 is formed to facilitate electrical connection and minimize resistance between contact 526 and n-region 522. A PIN diode under reverse bias may form a depletion region (not shown) or an intrinsic region that is free of charge carriers. In some embodiments, a depletion region may be formed and may span a portion of the length of p-type substrate 528 and a portion of the length of n-region 522. In the depletion region, charge carriers may be removed and new charge carriers generated by incoming charged particles may be swept according to their charge. For example, when an incoming charged particle arrives, electron-hole pairs may be generated, and holes may be attracted toward p-type substrate 528, while electrons may be attracted toward n-region 522, thereby forming a region depleted of charge.

[0054] In operation, the depletion region of the detection device can be used as a trapping region. Incoming charged particles can interact with the semiconductor material in the depletion region and generate new charges. For example, the detection device can be configured so that charged particles with a certain energy or greater can cause electron displacement of the crystal lattice of the semiconductor material, thereby generating electron-hole pairs. For example, due to the electric field in the depletion region, the resulting electrons and holes can be caused to travel in opposite directions. The generation of carriers traveling toward the terminals of the sensing element can correspond to the flow of current in the detection device, thereby generating a measurable signal comparable to the energy of the incoming charged particles.

[0055] Background noise in the detector may be caused in particular by dark current in the diode. For example, defects in the crystal structure of a semiconductor device that is a diode may cause current fluctuations. Dark current in the detector may be caused by defects in the material forming the detector, and may occur even when there is no incident illumination. "Dark" current may refer to the fact that the current fluctuation is independent of any incoming charged particles. The diode may be configured to generate electron-hole pairs when particles (e.g., photons or electrons) with an energy level not less than a certain level enter the diode. For example, when photons with an energy level not less than a certain level enter the photodiode, the photodiode may only generate electron-hole pairs. This may be due to, for example, the band gap of the material forming the photodiode. Photons with energy equal to a certain level can generate only one electron-hole pair, and even if the photon has more energy than a certain level, it can still generate only one electron-hole pair. No additional electron-hole pairs will be generated. At the same time, the electron detector may be configured so that whenever an electron enters a depletion region of a detector device that may include a diode, as long as the electron has an energy not less than a certain amount (e.g., about 3.6 eV), electron-hole pairs can be generated. If the electron has more energy than the bit quantity, more electron-hole pairs can be generated during the arrival event of the incoming electron.

[0056] In a diode configured for charged particle detection, defects in the diode may cause random generation of electron-hole pairs in the diode due to, for example, defects in the lattice of the semiconductor structure. The dark current may be amplified by an amplification effect such as avalanche amplification. The signal generated by the dark current may continue to be input to a counting circuit where it may be recorded as an arrival event. Such an event may be referred to as a "dark count", which is an artifact and may cause false counts. Furthermore, the amplifier itself may cause noise. Therefore, various noise sources such as dark current, thermal energy, extraneous radiation, etc. may cause unexpected current fluctuations and inaccuracies in the detector output.

[0057] One of the several challenges associated with charge detection by an array of sensing elements in a charged particle detector, such as an electron detector in a SEM, can include factors such as crosstalk caused by the proximity between multiple sensing elements, defocused beams, etc. In order to reduce the occurrence of crosstalk and its negative impact on signal fidelity, a trench 530 can be formed around the sensing element to isolate it from adjacent sensing elements. The trench 530 can be filled with an electrically insulating material, such as a dielectric including oxides, nitrides, oxynitrides, and the like. In some embodiments, the trench 530 can be appropriately biased to act as a barrier to charge from adjacent sensing elements to avoid affecting the output signal.

[0058] In a SEM, the interaction of charged particles (such as electrons of a primary detection electron beam) with a sample can generate charged particles such as secondary electrons, backscattered electrons, Auger electrons, photons, x-rays, etc. The emission energy of such charged particles generated can range from 1 eV to the landing energy of the primary charged particle beam. The emission energy can be an indication of the emission depth and the type of interaction, and can therefore be used to obtain information associated with the sample. For example, low-energy secondary electrons can interact with the first few nanometers of the sample surface, thereby providing information about topological features, surface morphology, etc., and higher-energy backscattered electrons emitted from deeper regions of the interaction volume can provide information associated with the chemical composition and overall properties of the material. Therefore, it may be desirable to detect signals with a wide range of emission energies to accurately reconstruct an image of the structure of the sample under inspection, thereby identifying and revealing defects in the sample.

[0059] One of several prior art techniques for resolving energy levels and identifying incoming electrons on an electron detector includes setting thresholds. One or more thresholds may be set to classify incoming charged particles based on the energy of the charged particles. For example, a first threshold at the lowest electron energy may be used to identify whether a sensing element has received an electron, or whether its output is caused by interference or dark current, etc. A second threshold at an intermediate electron energy may be used to identify whether the electron received by the sensing element is a secondary electron from a sample or a backscattered electron from a sample. A third threshold at the highest electron energy may be used to identify whether the sensing element has received more than one electron. Although high electron energy levels may be resolved by setting thresholds, resolving electron energies that span a wide range from 1eV to the landing energy of a primary charged particle may be challenging. This may be due to the small number of charge carriers generated by low-energy electrons within a semiconductor substrate. One of several ways to detect low-energy electrons may include using a SPAD device that provides high gain or signal amplification. The SPAD device may be reverse biased at a voltage exceeding the breakdown voltage of the diode, so that impact ionization that generates an avalanche current may occur. However, SPAD devices may face limitations in resolving higher electron energies. Therefore, it may be desirable to be able to resolve a larger dynamic range of electron energy levels for improved detection systems and methods while maintaining detection throughput, cost efficiency, and compact systems.

[0060] The SPAD device 520 of the sensing element 500 may be configured to detect low energy charged particles (eg, low energy secondary electrons) while allowing high energy charged particles to pass through to be detected by the PIN diode device 540 adjacent to the SPAD device 520. Figure 5AAs illustrated, the PIN diode device 540 can be formed directly below the SPAD device 520 relative to the direction of the incoming charged particles in the charged particle beam 504 generated from the sample. In some embodiments, the SPAD device 520 and the PIN diode device 540 can be fabricated on the same substrate, such as substrate 528. Semiconductor fabrication techniques such as, but not limited to, ion implantation, etching, photolithography, etc. can be used to fabricate the regions of the SPAD device 520 and the PIN diode device 540.

[0061] In operation, one or more secondary charged particle beams (e.g. Figure 3 The secondary charged particle beam 305) can be incident on a sensing element array that is configured to detect the charged particles and generate corresponding signals that can be processed to extract information associated with the detected charged particles. Low energy electrons can be detected by Figure 3 The front surface of the sensing element 360 of the sensing element 500 (eg, Figure 3 The SPAD device 520 fabricated on the front surface 352 of the embodiment of the present invention can be detected by the SPAD device 520 fabricated on the front surface 352 of the embodiment of the present invention. The SPAD device 520 can be reverse biased so that the highly doped n ++ Region 514 may be connected to the positive terminal of a power supply (not shown) and may be highly doped with p ++ Region 512 may be connected to the negative terminal of a power supply. A reverse bias applied to the SPAD device may form a depletion region around the pn junction that is depleted of charge carriers. The SPAD device 520 may be reverse biased at a voltage above the breakdown voltage. A SPAD device operating under this high voltage condition is referred to as operating in Geiger mode or counting mode. Under this bias, the electric field is very high, typically above 10 5 V / cm, so that a single charge carrier injected into the depletion region may trigger avalanche breakdown. Therefore, SPAD devices such as SPAD device 520 can be used to detect low energy electrons. However, in contrast, avalanche photodiodes (APDs) can be operated at reverse biases below the breakdown voltage, and the signal amplification may not be as high as with SPAD devices.

[0062] In some embodiments, the SPAD device 520 may be configured to detect energy below a threshold energy Th s charged particles, and allow energies above the threshold energy (Th s ) charged particles pass through. In some embodiments, the highly doped n ++ Region 514 or highly doped p ++ The thickness of region 512 or both may be suitable for detecting low energy charged particles. The thickness of individual layers or SPAD device 520 may determine the threshold energy Th s , at the threshold energy Th sAbove, the charged particles can escape from the SPAD region and can enter the PIN diode region. As an example, a highly doped n ++ The thickness of region 514 may be in the range of 0.1 to 1 μm, or 0.2 to 1 μm, or 0.3 to 1 μm, or 0.4 to 1 μm, or 0.5 to 1 μm, or 0.6 to 1 μm, or 0.7 to 1 μm, or 0.8 to 1 μm, or 0.9 to 1 μm. ++ The thickness of region 512 may be in the range of 0.1 to 1 μm, or 0.2 to 1 μm, or 0.3 to 1 μm, or 0.4 to 1 μm, or 0.5 to 1 μm, or 0.6 to 1 μm, or 0.7 to 1 μm, or 0.8 to 1 μm, or 0.9 to 1 μm. It should be appreciated that the thickness ranges listed herein are exemplary and may vary, as appropriate.

[0063] In some embodiments, the highly doped n ++ Region 514 or highly doped p ++ The threshold energy Th is determined by the doping concentration of region 512 or both. s Intrinsic semiconductors such as silicon (Si) can be doped with impurities to change electrical, optical, or structural properties. Exemplary dopants for n-type semiconductors can include donor-type dopants such as phosphorus, antimony, or bismuth. Exemplary dopants for p-type semiconductors can include acceptor-type dopants such as aluminum, gallium, or boron. Highly doped n ++ Region 514 or highly doped p ++ The dopant concentration or doping density of region 512 may be 1×10 13 Atom / cm 3 or larger, 1×10 14 Atom / cm 3 or larger, 1×10 15 Atom / cm 3 or larger, 1×10 16 Atom / cm 3 or larger, 1×10 17 Atom / cm 3 or larger, 1×10 18 Atom / cm 3 or larger, or between 1×10 13 Atom / cm 3 and any suitable dopant concentration between the degenerate doping concentration.

[0064] In some embodiments, the threshold energy Th may be determined based on a voltage applied to the SPAD device 520 or an electric field across a pn junction of the SPAD device 520. s Voltage can be applied independently to the highly doped n-type transistors via contact pads 518 or 516, respectively. ++ Region 514 or highly doped p++ Area 512. Controller (e.g., Figure 2 The controller 50 may include circuitry configured to independently apply voltages to one or both regions of the SPAD device 520. In some embodiments, the SPAD device 520 and the PIN diode device 540 may be independently enabled, disabled, or adjusted as desired.

[0065] In some embodiments, the SPAD device 520 may be configured to perform charged particle counting, which may include determining individual charged particle arrival events occurring at the detector. For example, when electrons arrive at the detector, the electrons may be detected one by one. In some embodiments, the electrons incident on the detector may generate an electrical signal that is routed to a signal processing circuit system and then read out to an interface such as a digital controller. The detector may be configured to parse the signal generated by the incident electrons and distinguish individual electrons with discrete counts. In some embodiments, information associated with the particle count may also be used to determine the arrival time of the charged particles at the detector. In some embodiments, the SPAD device 520 may be operated in a Geiger mode or a counting mode to determine the number of charged particles detected by the detector. For example, in Geiger mode, each incoming charged particle with sufficiently high energy may generate an electron-hole pair. Then, due to internal impact ionization, this electron-hole pair may be multiplied by avalanche gain, thereby ultimately generating several electron-hole pairs. Therefore, each incoming charged particle may generate several electron-hole pairs. Due to the strong internal electric field from the high reverse bias voltage, the multiplication process may continue. The multiplication may be self-sustaining. When the external radiation disappears, the current flow in the diode may not necessarily stop. The current in the diode can be stopped by disconnecting the diode from the power supply. After disconnection, the current flow in the diode can then subside. The current output of a diode operating in Geiger mode can be exhibited to include a long tail behavior. For example, the output can gradually decrease after an initial peak. In Geiger mode, the diode can be provided with a quenching circuit. The quenching circuit can include a passive or active quenching circuit. Actuating the quenching circuit can allow the diode to be turned off after each charged particle arrival event. Quenching can be used to reset the diode.

[0066] In some embodiments, the energy of the charged particle can be determined based on the characteristics of the current output signal of the detector. The characteristics may include a timeout threshold of the signal. For a given threshold energy level, the length of time that the current output of the diode is above the threshold energy can be used to determine the energy of the incoming charged particle. A larger timeout threshold can indicate that the incoming charged particle has a higher energy. Conversely, a shorter timeout threshold can indicate that the incoming charged particle has a lower energy.

[0067] The diode may be configured to operate at a gain level. For example, the diode may be configured to operate at a gain of less than 100. This may refer to the gain imparted by operating the diode by applying a voltage. The gain may amplify the signal up to, for example, 100 times relative to the original strength of the signal. It should be appreciated that other specific gain levels may also be used.

[0068] The gain effect using a diode such as one biased to avalanche mode or Geiger counting mode may involve time-dependent phenomena. For example, a diode biased to avalanche mode may impart gain through avalanche multiplication. There may be a finite time associated with the gain effect. The diode may have a speed related to the time it takes for the gain effect to occur. In some cases, there may be a recovery time after the arrival event of a charged particle at the diode. A diode operating in Geiger counting mode may have an associated recovery time. The recovery time may limit the ability of the diode to detect discrete signals that are closely continuous. A diode operating in Geiger counting mode may need to be quenched after a charged particle arrival event in order to accurately detect the next event.

[0069] Reference again Figure 5A , the PIN diode device 540 may be configured to detect energy above a threshold energy Th s The PIN diode device 540 may include a p-type substrate 528, an n-type region 522, and an n-type region 524. ++ Doped region 524. ++ The doped layer may serve as a common backside contact to provide electrical connection to one or more regions of the sensing element 500 .

[0070] PIN diodes can be used for charged particle (e.g., electron) counting. PIN diodes can have high inherent internal gain, so even in the case of a single electron arrival event, a stronger measurable signal that can be easily distinguished from a relatively low floor level of background noise can be generated. The need to provide an amplifier or complex system (such as an avalanche diode) on the chip to enhance the signal can be reduced or eliminated. On the contrary, the signal generated by the PIN diode itself or together with an amplifier with a relatively low gain can be well suited for electron counting because it is generated quickly in response to an electron arrival event and stands out relative to background noise. However, a single detector element including a PIN diode with one output may not be able to handle counts for all beam current ranges. For example, for a 1nA electron beam, it is well known that about 64 electrons can be incident on the detector within a typical sampling period of 10ns. In some SEM systems, the detector can run at a sampling rate of 100MHz, thus corresponding to a sampling period of 10ns. In a sampling period of 10ns, 64 electron arrival events may occur, so it is not easy to distinguish the signal generated from the individual electron arrival event. Even in a high speed detector, such as one running at a sampling rate of 800 MHz, there may be approximately 8 incident electrons per sampling period, which may overload the detector.

[0071] A PIN diode or a semiconductor diode with a PIN structure can be operated in various modes. For example, in a first mode, the diode can be operated with a normal reverse bias. In this mode, each incoming charged particle with a high enough energy can generate only one electron-hole pair. When the external radiation (e.g., the incoming charged particle) disappears, the current flow in the diode can stop immediately. In a second mode, the diode can be operated with a reverse bias higher than the reverse bias in the first mode. The second mode may introduce impact ionization. This may also be referred to as an avalanche photodiode mode. In this mode, each incoming charged particle with a high enough energy can generate an electron-hole pair. Then, due to internal impact ionization, this electron-hole pair can be multiplied by avalanche gain, so that several electron-hole pairs can be generated in the end. Therefore, each incoming charged particle may cause the generation of several electron-hole pairs. When the external radiation disappears, the current flow in the diode can stop immediately. The second mode may include a linear region and a nonlinear region.

[0072] In some embodiments, the PIN diode device 540 can be configured to have two or more discrimination levels to resolve incoming high-energy charged particles. Two or more levels can be formed by using thresholds. Instead of or in addition to generating statistical results of the received electron energy plotted relative to the number of electrons at each energy level, information about the threshold can also be generated. Two or more thresholds can be set in a manner that can further resolve high-energy electrons. For example, a first threshold can distinguish charged particles with energies between the range of 10eV to 20eV, a second threshold can distinguish charged particles with energies between the range of 20eV to 40eV, and a third threshold can identify charged particles with energies higher than 40eV. In some embodiments, the number of threshold levels can be determined based on the readout channel noise.

[0073] In some embodiments, the sensing element 500 may include an isolation region or trench 530 to provide isolation and prevent crosstalk between adjacent sensing elements of the sensing element array. The trench 530 may be formed using semiconductor fabrication techniques commonly used for deep trench isolation structures to provide electrical isolation. In some embodiments, the sensing element 500 may also include a sensing element separator 534, which may also be used to adjust the electric field across the trench 530. A voltage may be applied to the sensing element separator 534 via a contact pad 536 to achieve the formation of an energy barrier for current that leaks through or interferes with adjacent sensing elements.

[0074] In some embodiments, the order of the SPAD device 520 and the PIN diode device 540 can be reversed, such as Figure 5B 540 . In this configuration, low energy charged particles with sufficient energy can be detected by the PIN diode device 540, while high energy charged particles can be detected by the SPAD device 520. The threshold energy for detecting high energy charged particles using the SPAD device 520 can be determined based on the thickness of the p-type substrate 528. Charged particles to be detected by the SPAD device 520 may have to have very high energy to possibly travel through the thickness of the substrate 528 before being incident on the SPAD device 520. In some embodiments, the charged particle detector (e.g., Figure 3 The sensing element array of the charged particle detector 344) may include sensing element 500, or sensing element 580, or both.

[0075] Fig. 6A , Figure 6B , Figure 6C and Fig.6DVarious scenarios for discerning the energy of incoming charged particles at a charged particle detector according to embodiments of the present disclosure are illustrated. In some embodiments, one or more external circuit systems may be configured to process and generate outputs based on information received from a sensing element. For example, Fig. 6A As shown, if neither the SPAD device 520 nor the PIN diode device 540 is triggered, there may be two possible reasons—the sensing element 500 is not receiving a detectable signal, or the SPAD device 520 may be recovering from a dead time. In the context of the present disclosure, the "dead" time of a detector device refers to the time when an arriving charged particle cannot be counted by the detector device. The dead time may be affected by the design or characteristics of the event detector or other characteristics such as the threshold level set to determine that an arrival event has occurred.

[0076] Figure 6B The diagram shows a situation where the SPAD device 520 may be triggered but the PIN diode device 540 may not be triggered. In this case, there may be two possible reasons - the arrival of low energy charged particles to record or the sensing element 500 to count dark current (false positive signal). In the case where the SPAD device 520 is not triggered but the PIN diode device 540 presents an output, such as Figure 6C As shown, the SPAD device 520 may recover from the dead time or there may be stray light effects, causing the PIN diode device to present an output signal. If both the SPAD device 520 and the PIN diode device 540 are triggered, such as Fig.6D As shown, the high-energy charged particles are received by the PIN diode device 540 .

[0077] Now, refer to Figure 7 , Figure 7 A data graph 700 illustrates simulation results obtained from an exemplary combined SPAD and PIN charged particle detector according to an embodiment of the present disclosure. A semiconductor simulator tool can be used to simulate the response of a combined SPAD and PIN diode detector when subjected to charged particles having a wide range of energies. Exemplary conditions for simulation include: high doping n ++ Depth of region = 0.1μm to 0.5μm; highly doped p ++Depth of n-region = 0.1 μm to 0.5 μm; Depth of n-region = 0.5 μm to 2.5 μm; Spacing between SPAD region and n-region = 1 μm to 5 μm; Lightly doped p-type substrate; Charge number for low energy charged particle simulation in the range of 1000 electrons to 2000 electrons; and Charge number for high energy charged particle simulation in the range of 2500 electrons to 4000 electrons. The simulation is performed for signal detection of a short duration of several picoseconds. A sufficiently high voltage bias is applied to the SPAD device to ensure that the electric field is higher than the breakdown voltage of the SPAD device to generate avalanche breakdown, and an appropriate voltage of several volts (V) is applied to the PIN diode device.

[0078] As illustrated in data graph 700, the SPAD device instantaneously detects incoming low energy electrons, while the PIN diode device detects higher energy electrons. During the 0.1 ns signal integration time, high energy electrons are not detected by the SPAD device, instead they pass through the underlying PIN diode device and are detected by it, as indicated by the drop in the potential of the PIN diode. On the other hand, low energy electrons are substantially detected in the SPAD region. It should be appreciated that longer signal collection and integration times on the order of several nanoseconds may allow more charges to be detected, thereby increasing signal strength.

[0079] Now, refer to Figure 8 , Figure 8 A process flow diagram representing an exemplary method 800 for detecting charged particles using a charged particle detector according to an embodiment of the present disclosure is illustrated. The method 800 can be used to detect charged particles of a wide dynamic energy range using a charged particle detection device including a single photon avalanche diode (SPAD) and a PIN diode formed on the same substrate.

[0080] In step 810, a system including a plurality of sensing elements (eg, Figure 3 The sensing element 360 or Figure 5A The sensing elements may be configured to receive charged particles generated from the sample when the primary charged particle beam interacts. Each of the sensing elements may include a first charged particle detection device (e.g., Figure 5A SPAD device 520 and a second charged particle detection device (eg, Figure 5A PIN diode device 540).

[0081] The charged particle source is activated to emit charged particles. The charged particles may form a charged particle beam (e.g., Figure 2 The electron source may be controlled by a controller (e.g., Figure 2For example, the electron source may be controlled to emit primary electrons so as to emit electrons along the primary optical axis (e.g., Figure 2 The electron source may be remotely activated, for example, by using software, an application, or a set of instructions to cause a processor of a controller to power the electron source through a control circuit system. 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 2 of the sample 250).

[0082] In step 820, a first device (SPAD) is used to detect charged particles (eg, secondary electrons or backscattered electrons). The energy of the charged particles may be equal to or below a first threshold, which may be a predetermined threshold energy level.

[0083] In step 830, after a second charged particle having energy greater than a first threshold value among the plurality of charged particles passes through the first device, the second device can be used to detect the second charged particle. The charged particles passing through can have energy greater than the first threshold value and can include high-energy electrons. The first device (SPAD) can pass charged particles having energy greater than the first threshold value toward the second device (PIN diode device). A PIN diode device is fabricated below the SPAD device relative to the incident direction of the incoming charged particles from the sample.

[0084] A non-transitory computer readable medium storing instructions for causing a controller (eg, Figure 1 A processor of a controller 50) performs inspection images, acquisition of images, activation of a charged particle source, irradiation of an area of ​​a sample with primary charged particles, independent activation or deactivation of charged particle detection equipment, application of voltages to charged particle detectors, receiving and processing signals generated by charged particle detectors in response to the arrival of charged particles, etc. Common forms of non-transitory media include, for example, floppy disks, flexible disks, 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 with 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), caches, registers, any other memory chips or boxes, and networked versions thereof.

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

[0086] 1. A charged particle detector, comprising:

[0087] A substrate comprising a plurality of sensing elements configured to receive a plurality of charged particles generated from a sample, each of the plurality of sensing elements comprising:

[0088] The first device is configured as:

[0089] detecting charged particles having energy equal to or lower than a first threshold value among the plurality of charged particles;

[0090] allowing charged particles having energy greater than the first threshold among the plurality of charged particles to pass; and

[0091] A second device is configured to detect the charged particles allowed to pass through the first device.

[0092] 2. A charged particle detector according to clause 1, wherein the first device is further configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0093] 3. A charged particle detector according to any one of clauses 1 and 2, wherein the first device comprises a single photon avalanche diode (SPAD).

[0094] 4. A charged particle detector according to clause 3, wherein the first device is further configured to operate in a Geiger mode or a counting mode.

[0095] 5. A charged particle detector according to any one of clauses 1 to 4, wherein the first threshold value depends on a depth of the first device, the depth being equal to the sum of the thicknesses of the individual layers of the first device.

[0096] 6. A charged particle detector according to any of clauses 1 to 5, wherein the first threshold value is dependent on a doping concentration of one or more layers of the first device.

[0097] 7. A charged particle detector according to any one of clauses 1 to 6, wherein the first threshold value depends on a voltage applied to the first device.

[0098] 8. A charged particle detector according to any one of clauses 1 to 7, wherein in response to detecting the charged particle among the plurality of charged particles, the first device is configured to generate a first signal corresponding to an arrival time of the charged particle.

[0099] 9. A charged particle detector according to any one of clauses 1 to 8, wherein the second device is formed below the first device relative to a path of incoming charged particles.

[0100] 10. A charged particle detector according to any of clauses 1 to 9, wherein the second device comprises a PIN diode.

[0101] 11. A charged particle detector according to any one of clauses 1 to 10, wherein in response to detecting the charged particle among the plurality of charged particles, the second device is configured to generate a second signal based on the energy of the detected charged particle.

[0102] 12. A charged particle detector according to clause 11, wherein the energy of the detected charged particle is determined based on the amplitude of the generated signal.

[0103] 13. A charged particle detector according to clause 12, wherein the energy of the detected charged particle is determined based on the duration that the amplitude of the generated signal is above a predetermined threshold energy.

[0104] 14. A charged particle detector according to any of clauses 11 to 13, wherein the energy of the charged particles detected by the second device is above the first threshold and below a second threshold.

[0105] 15. A charged particle detector according to clause 13, wherein the energy of the charged particles detected by the second device is above a second threshold.

[0106] 16. A charged particle detector according to clause 1, wherein the first device comprises a PIN diode.

[0107] 17. A charged particle detector according to clause 16, wherein the first threshold is determined based on a depth of the first device.

[0108] 18. A charged particle detector according to any one of clauses 16 to 17, wherein in response to detecting the charged particle among the plurality of charged particles, the first device is configured to generate a first signal based on the energy of the detected charged particle.

[0109] 19. A charged particle detector according to any of clauses 16 to 18, wherein the second device comprises a single photon avalanche diode (SPAD).

[0110] 20. A charged particle detector according to clause 19, wherein the SPAD is configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0111] 21. A charged particle detector according to any of clauses 19 to 20, wherein the SPAD is configured to operate in a Geiger mode or a counting mode.

[0112] 22. A charged particle detector according to any of clauses 19 to 21, wherein the SPAD is formed below the first device relative to a path of incoming charged particles.

[0113] 23. A charged particle detector according to any one of clauses 1 to 22, wherein the first device and the second device are independently controlled by a controller having circuitry.

[0114] 24. A charged particle detector according to any one of clauses 1 to 23, wherein a sensing element of the plurality of sensing elements is isolated from adjacent sensing elements.

[0115] 25. A charged particle beam device comprising:

[0116] a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam; and

[0117] A charged particle detector configured to detect a plurality of signal charged particles generated when the charged particles of the primary charged particle beam interact with a sample, the charged particle detector comprising:

[0118] A substrate comprising a plurality of sensing elements, each of the plurality of sensing elements comprising:

[0119] a first device configured to detect charged particles having energies equal to or lower than a first threshold energy among the plurality of charged particles, and to allow charged particles having energies greater than the first threshold energy among the plurality of charged particles to pass; and

[0120] A second device is configured to detect the charged particles allowed to pass through the first device.

[0121] 26. A charged particle beam apparatus according to clause 25, wherein the first device is further configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0122] 27. Charged particle beam apparatus according to any of clauses 25 and 26, wherein the first device comprises a single photon avalanche diode (SPAD).

[0123] 28. A charged particle beam apparatus according to clause 27, wherein the first device is further configured to operate in a Geiger mode or a counting mode.

[0124] 29. Charged particle beam apparatus according to any of clauses 25 to 28, wherein the first threshold value depends on a depth of the first device, the depth being equal to the sum of the thicknesses of the individual layers of the first device.

[0125] 30. Charged particle beam apparatus according to any of clauses 25 to 29, wherein the first threshold value is dependent on a doping concentration of one or more layers of the first device.

[0126] 31. Charged particle beam apparatus according to any of clauses 25 to 30, wherein the first threshold value is dependent on a voltage applied to the first device.

[0127] 32. A charged particle beam apparatus according to any of clauses 25 to 31, wherein in response to detecting the charged particle of the plurality of charged particles, the first device is configured to generate a first signal corresponding to an arrival time of the charged particle.

[0128] 33. A charged particle beam apparatus according to any of clauses 25 to 32, wherein the second device is formed below the first device relative to a path of incoming charged particles.

[0129] 34. Charged particle beam apparatus according to any of clauses 25 to 33, wherein the second device comprises a PIN diode.

[0130] 35. A charged particle beam apparatus according to any of clauses 25 to 34, wherein in response to detecting the charged particle of the plurality of charged particles, the second device is configured to generate a second signal based on an energy of the detected charged particle.

[0131] 36. A charged particle beam apparatus according to clause 35, wherein the energy of the detected charged particle is determined based on the amplitude of the generated signal.

[0132] 37. A charged particle beam apparatus according to clause 36, wherein the energy of the detected charged particle is determined based on the duration that the amplitude of the generated signal is above a predetermined threshold energy.

[0133] 38. A charged particle beam apparatus according to any of clauses 35 to 37, wherein the energy of the charged particles detected by the second device is above the first threshold and below a second threshold.

[0134] 39. A charged particle beam apparatus according to clause 37, wherein the energy of the charged particles detected by the second device is above a second threshold.

[0135] 40. The charged particle beam apparatus of clause 25, wherein the first device comprises a PIN diode.

[0136] 41. A charged particle beam apparatus according to clause 40, wherein the first threshold value is dependent on a depth of the first device.

[0137] 42. A charged particle beam apparatus according to any of clauses 40 to 41, wherein in response to detecting the charged particle of the plurality of charged particles, the first device is configured to generate a first signal based on an energy of the detected charged particle.

[0138] 43. A charged particle beam apparatus according to any of clauses 40 to 42, wherein the second device comprises a single photon avalanche diode (SPAD).

[0139] 44. A charged particle beam apparatus according to clause 43, wherein the SPAD is configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0140] 45. A charged particle beam apparatus according to any of clauses 43 to 44, wherein the SPAD is configured to operate in a Geiger mode or a counting mode.

[0141] 46. ​​A charged particle beam apparatus according to any of clauses 43 to 45, wherein the SPAD is formed below the first device relative to a path of incoming charged particles.

[0142] 47. A charged particle beam apparatus according to any of clauses 25 to 46, wherein the first device and the second device are independently controlled by a controller having circuitry.

[0143] 48. Charged particle beam device according to any of clauses 25 to 47, wherein a sensing element of the plurality of sensing elements is isolated from adjacent sensing elements.

[0144] 49. A method for charged particle detection using a substrate comprising a plurality of sensing elements, the plurality of sensing elements being configured to receive a plurality of charged particles generated from the sample, each of the plurality of sensing elements comprising a first device and a second device, the method comprising:

[0145] detecting, using the first device, a first charged particle among the plurality of charged particles whose energy is equal to or lower than a first threshold; and

[0146] After a second charged particle having energy greater than the first threshold among the plurality of charged particles passes through the first device, the second charged particle is detected using the second device.

[0147] 50. The method of clause 49, further comprising operating the first device at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0148] 51. A method according to any of clauses 49 and 50, wherein the first device comprises a single photon avalanche diode (SPAD).

[0149] 52. The method of clause 51, wherein the first device is further configured to operate in a Geiger mode or a counting mode.

[0150] 53. A method according to any of clauses 49 to 52, wherein the first threshold value depends on a depth of the first device, the depth being equal to the sum of the thicknesses of the individual layers of the first device.

[0151] 54. A method according to any of clauses 49 to 53, wherein the first threshold value is dependent on a doping concentration of one or more layers of the first device.

[0152] 55. A method according to any of clauses 49 to 54, wherein the first threshold value is dependent on a voltage applied to the first device.

[0153] 56. A method according to any one of clauses 49 to 55, wherein in response to detecting the charged particle of the plurality of charged particles, the first device is further configured to generate a first signal corresponding to an arrival time of the charged particle.

[0154] 57. A method according to any of clauses 49 to 56, wherein the second device is formed below the first device relative to a path of incoming charged particles.

[0155] 58. A method according to any of clauses 49 to 57, wherein the second device comprises a PIN diode.

[0156] 59. A method according to any one of clauses 49 to 58, wherein in response to detecting the charged particle of the plurality of charged particles, the second device is configured to generate a second signal based on the energy of the detected charged particle.

[0157] 60. The method of clause 59, wherein the energy of the detected charged particle is determined based on the amplitude of the generated signal.

[0158] 61. A method according to clause 60, wherein the energy of the detected charged particle is determined based on the duration that the amplitude of the generated signal is above a predetermined threshold energy.

[0159] 62. A method according to any of clauses 59 to 61, wherein the energy of the charged particles detected by the second device is above the first threshold and below a second threshold.

[0160] 63. The method of clause 61, wherein the energy of the charged particles detected by the second device is above a second threshold.

[0161] 64. The method of clause 49, wherein the first device comprises a PIN diode.

[0162] 65. The method of clause 64, wherein the first threshold value is dependent on a depth of the first device.

[0163] 66. A method according to any one of clauses 64 to 65, wherein in response to detecting the charged particle of the plurality of charged particles, the first device is configured to generate a first signal based on an energy of the detected charged particle.

[0164] 67. A method according to any of clauses 64 to 66, wherein the second device comprises a single photon avalanche diode (SPAD).

[0165] 68. The method of clause 65, wherein the SPAD is configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

[0166] 69. A method according to any of clauses 67 to 68, wherein the SPAD is configured to operate in a Geiger mode or a counting mode.

[0167] 70. A method according to any of clauses 67 to 69, wherein the SPAD is formed below the first device relative to a path of incoming charged particles.

[0168] 71. A method according to any one of clauses 49 to 70, wherein the first device and the second device are independently controlled by a controller having a circuit system.

[0169] 72. A method according to any of clauses 49 to 71, wherein a sensing element of the plurality of sensing elements is isolated from adjacent sensing elements.

[0170] 73. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a charged particle beam apparatus, the charged particle beam apparatus comprising a charged particle detector using a substrate comprising a plurality of sensing elements, the plurality of sensing elements being configured to receive a plurality of charged particles generated from a sample, each of the plurality of sensing elements comprising a first device and a second device, the set of instructions causing the charged particle beam apparatus to perform a method comprising:

[0171] activating the first device to enable detection of a first charged particle having energy equal to or lower than a first threshold value among the plurality of charged particles; and

[0172] After a second charged particle of the plurality of charged particles having energy greater than the first threshold passes through the first device, the second device is activated to enable detection of the second charged particle.

[0173] It should be appreciated that the embodiments of the present invention are not limited to the exact configurations described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope of the present invention. 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, given the specification and practice of the invention disclosed herein. The specification and embodiments are to be considered exemplary only, with the true scope and spirit of the present invention being indicated by the appended claims.

[0174] The above description is intended to be illustrative rather than limiting. Therefore, it will be apparent to those skilled in the art that modifications may be made from the description without departing from the scope of the claims set forth below.

Claims

1. A charged particle detector, comprising: A substrate comprising a plurality of sensing elements configured to receive a plurality of charged particles generated from a sample, each of the plurality of sensing elements comprising: The first device is configured as: detecting charged particles having energy equal to or lower than a first threshold value among the plurality of charged particles; allowing charged particles among the plurality of charged particles having energy greater than the first threshold to pass; and A second device is configured to detect the charged particles allowed to pass through the first device. 2 . The charged particle detector of claim 1 , wherein the first device is further configured to operate at a reverse bias voltage that is higher than a breakdown voltage of the first device.

3. The charged particle detector of claim 1, wherein the first device comprises a single photon avalanche diode (SPAD). 4 . The charged particle detector of claim 3 , wherein the first device is further configured to operate in a Geiger mode or a counting mode.

5. The charged particle detector of claim 1, wherein the first threshold depends on a depth of the first device, the depth being equal to the sum of thicknesses of individual layers of the first device.

6. The charged particle detector of claim 1, wherein the first threshold value is dependent on a doping concentration of one or more layers of the first device.

7. The charged particle detector of claim 1, wherein the first threshold value depends on a voltage applied to the first device.

8. The charged particle detector of claim 1, wherein in response to detecting the charged particle of the plurality of charged particles, the first device is configured to generate a first signal corresponding to an arrival time of the charged particle.

9. The charged particle detector of claim 1, wherein the second device is formed below the first device relative to a path of incoming charged particles.

10. The charged particle detector of claim 1, wherein the second device comprises a PIN diode.

11. The charged particle detector of claim 1, wherein in response to detecting the charged particle of the plurality of charged particles, the second device is configured to generate a second signal based on energy of the detected charged particle.

12. A charged particle detector according to claim 11, wherein the energy of the detected charged particle is determined based on the amplitude of the generated signal.

13. A charged particle detector according to claim 12, wherein the energy of the detected charged particle is determined based on the duration that the amplitude of the generated signal is above a predetermined threshold energy.

14. The charged particle detector of claim 11, wherein the energy of the charged particle detected by the second device is above the first threshold and below a second threshold.

15. A non-transitory computer readable medium storing a set of instructions, the set of instructions being executable by one or more processors of a charged particle beam apparatus, the charged particle beam apparatus comprising a charged particle detector using a substrate, the substrate comprising a plurality of sensing elements, the plurality of sensing elements being configured to receive a plurality of charged particles generated from a sample, each of the plurality of sensing elements comprising a first device and a second device, the set of instructions causing the charged particle beam apparatus to perform a method comprising: activating the first device to enable detection of a first charged particle having energy equal to or lower than a first threshold value among the plurality of charged particles; as well as After a second charged particle of the plurality of charged particles having energy greater than the first threshold passes through the first device, the second device is activated to enable detection of the second charged particle.

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