Readout design for charged particle counting detector

Abstract

The charged particle beam detector may include a plurality of sensing elements, each sensing element connected to a dedicated array of signal detection units. Each signal detection unit may include a solid state current control device configured to rapidly extract charge from the sensing element during a detection event. Each signal detection unit may also include a simplified structure that automatically enables the next signal detection unit upon the occurrence of a valid detection. The detection unit may store the detection signal until the controller is ready to read out the signal. Accordingly, each detection unit can be quickly and continuously enabled to receive and store the received and stored signals with a simple and reliable structure.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application 63 / 408,755, filed on September 21, 2022, which is hereby incorporated by reference. Technical Field

[0003] The description herein relates to detectors useful in the field of charged particle beam systems, and more particularly, to systems and methods applicable to charged particle detection using charged particle counting. Background Art

[0004] 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 structure of the sample under inspection, and can be used, for example, to reveal defects in the sample. In the manufacture of semiconductor devices that may include a large number of densely packed, miniaturized integrated circuit (IC) components, it is increasingly important to detect defects in samples. An inspection system can be provided for this purpose.

[0005] As semiconductor devices continue to miniaturize, inspection systems can use lower and lower beam currents in charged particle beam tools. Existing detection systems can be limited by signal-to-noise ratio (SNR) and system throughput, especially when beam current is reduced to, for example, the picoampere range. Electron counting has been proposed to enhance the SNR and increase throughput in electron beam inspection systems, where the intensity of the incident electron beam is obtained by counting the number of electrons arriving at the detector and then analyzing the frequency of electron arrival events. Summary of the invention

[0006] Embodiments of the present disclosure provide systems and methods for detection based on charged particle beams. The method according to an embodiment of the present disclosure may include: enabling a first solid-state current control device (SSCCD) of a first signal detection unit to be placed in an on state, in which the first SSCCD is capable of conducting a current from a charged particle sensing element of a charged particle counting detector; outputting a first current pulse from the charged particle sensing element in response to a first charged particle reaching the charged particle sensing element, wherein the first current pulse triggers the first SSCCD to the on state. The method may also include: in response to the first SSCCD being triggered to the on state, conducting the first current pulse from the input of the first SSCCD to the output of the first SSCCD; and receiving a second enable signal at a second signal detection unit including a second SSCCD, the second enable signal being based on the first current pulse. The second enable signal may enable the second SSCCD of the second signal detection unit to be placed in an on state, in which the second SSCCD may conduct a current from the charged particle sensing element.

[0007] Some embodiments of the present disclosure may include a non-transitory computer-readable medium. The non-transitory computer-readable medium may store an instruction set, and the instruction set may be executed by at least one processor of a device to enable the device to perform the above method.

[0008] Some embodiments of the present disclosure provide a charged particle counting detector. The charged particle counting detector may include: a charged particle sensing element, which is configured to output a first current pulse in response to a first charged particle reaching the charged particle sensing element; a first signal detection unit, including a first solid-state current control device (SSCCD). The SSCCD may be configured to: a) be enabled by a first enable signal to be placed in an on state, in which the first SSCCD can conduct current from the charged particle sensing element, b) be triggered to the on state by a first current pulse, and c) conduct the first current pulse to the output of the first SSCCD in response to the first SSCCD being triggered to the on state.

[0009] The charged particle counting detector may further include a second signal detection unit configured to receive a second enable signal. The second signal detection unit may include a second SSCCD configured to be enabled by the second enable signal to be placed in an on state, in which the second SSCCD may conduct current from the charged particle sensing element.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as may be claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other aspects of the present disclosure will become more apparent through the description of exemplary embodiments with reference to the attached drawings.

[0012] Figure 1 is a diagrammatic representation of an exemplary electron beam inspection (EBI) system according to an embodiment of the present disclosure.

[0013] Figure 2A - Figure 2B is a diagram illustrating a charged particle beam apparatus according to an embodiment of the present disclosure, which may be an example of an electron beam tool.

[0014] Figure 3A - Figure 3C is a diagram of an exemplary structure of a detector consistent with an embodiment of the present disclosure.

[0015] Figure 4 is a diagram of a circuit used for charged particle counting.

[0016] Figure 5 is a diagram of a circuit for charged particle counting according to an embodiment of the present disclosure.

[0017] Figure 6 is an example graphical representation of a single signal detection unit consistent with embodiments of the present disclosure.

[0018] Figure 7 is a diagram of a circuit for charged particle counting according to an embodiment of the present disclosure.

[0019] Figure 8 is an example graphical representation of a single signal detection unit consistent with embodiments of the present disclosure.

[0020] Fig.9A - Fig. 9B is a flow chart illustrating a method that may be used for electron counting according to an embodiment of the present disclosure.

[0021] Fig. 10A - Fig. 10B is a flow chart illustrating a method that may be used for electron counting according to an embodiment of the present disclosure.

[0022] Fig.11A - Fig. 11B is a flow chart illustrating a method that may be used for electron counting according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, in which the same numbers in different figures represent the same or similar elements, unless otherwise stated. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. On the contrary, they are merely examples of devices, systems and methods that conform to aspects related to the subject matter that can be recited in the appended claims. For example, although some embodiments are described in the context of utilizing charged particle beams (e.g., electron beams), the present disclosure is not limited thereto. Other types of charged particle beams (e.g., photon beams) may be similarly applied. In addition, other imaging systems may be used, such as optical imaging, photoelectric detection, x-ray detection, etc.

[0024] Electronic devices consist of circuits formed on a silicon wafer called a substrate. Many circuits can be formed together on the same piece of silicon and are called an integrated circuit or IC. As technology has advanced, 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 fingernail and can also include more than 2 billion transistors, each of which is less than 1 / 1000 the width of a human hair.

[0025] Manufacturing these ICs with extremely small structures or components is a complex, time-consuming and expensive process, often involving hundreds of individual steps. Even an error in one step can result in a defect in the finished IC, rendering it useless. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs manufactured in the process, i.e., to increase the overall yield of the process.

[0026] One component of improving yield is to monitor the chip manufacturing process to ensure that it produces a sufficient number of integrated circuits that are capable of functioning. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspections can be performed using a scanning charged particle microscope ("SCPM"). For example, the SCPM can be a scanning electron microscope (SEM). The SEM can be used to image these extremely small structures, in effect, being able to take "photos" of these structures. 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. In order to increase throughput (e.g., the number of samples processed per hour), it is desirable to perform inspections as quickly as possible.

[0027] The working principle of SEM is similar to that of a camera. A camera takes pictures by receiving and recording the intensity of light reflected or emitted from a person or object. SEM takes "pictures" by receiving and recording the energy or amount of electrons reflected or emitted from a wafer structure. Before taking such a "photo", an electron beam can be projected onto the structure, and when electrons are reflected or emitted ("leave") from the structure (e.g., from the wafer surface, from the structure below the wafer surface, or both), the detector of the SEM can receive and record the energy or amount of those electrons to generate an inspection image. In order to take such a "photo", the electron beam can be scanned through the wafer (e.g., in a line-by-line or zigzag manner), and the detector can receive the outgoing electrons (called "beam spot") from the area under the projection of the electron beam. The detector can receive and record the electrons leaving each beam spot one at a time, and combine the information recorded for all beam spots to generate an inspection image. Some SEMs use a single electron beam (called a "single beam SEM") to take a single "image" to generate an inspection image, while some SEMs use multiple electron beams (called a "multi-beam SEM") to take multiple "sub-images" of the wafer in parallel and stitch them together to generate an inspection image. By using multiple electron beams, the SEM can provide more electron beams to the structure to obtain these multiple "sub-images", resulting in more electrons being ejected from the structure. Therefore, the detector can receive more outgoing electrons at the same time and generate inspection images of the wafer structure with higher efficiency and faster speed.

[0028] Typically, the detection process involves measuring the magnitude of an electrical signal generated when an electron falls on a detector. In another approach, electron counting can be used, where the detector can count individual electron arrival events as they occur. In either approach, the intensity of the secondary beam can be determined based on an electrical signal generated in the detector that changes in proportion to changes in the intensity of the secondary beam. However, using electron counting, the discrete number of electrons that arrive at the detector from the secondary electron beam can be determined, and the detection results can be output in digital form. The intensity of the beam can be determined by analyzing the frequency with which electron arrival events occur.

[0029] Electron counting helps improve the signal-to-noise ratio (SNR) and throughput of charged particle beam systems. In particular, at low levels of primary beam current, SNR can be a problem. Therefore, electron counting can be an attractive approach in applications such as metrology and overlay inspection where beam current is typically low. Electron counting can also be used to separate signals generated by different types of electrons (e.g., secondary electrons and backscattered electrons). In some applications, it may be desirable to generate SEM images based entirely or primarily on secondary electrons, entirely or primarily on backscattered electrons, or on a combination.

[0030] Electron counting requires that each electron reception on the detector surface be detected individually, which can place extreme demands on the accuracy and speed of the detector circuitry. For example, the surface of an electron counting detector can be subdivided into a large grid of tiny sensing elements, each with its own dedicated signal processing circuitry. This arrangement can allow electrons to land at different locations on the detector surface while still being detected individually.

[0031] Even within these subsections, each detection signal is processed very quickly in order to reset the circuit before another primary electron hits it. There may not be enough time between two electron receptions for the circuit to process the signal. Therefore, each sensing element can be connected to multiple identical detection circuits, which can be referred to as detection cells. When one detection cell receives a signal from an electron reception, it can start signal processing while the next cell is connected to the sensing element to wait for the next electron reception. In this way, in theory, there should always be a detection cell ready and waiting to process an electronic detection signal at each sensing element.

[0032] However, providing a circuit structure that can quickly select and control all of these different detection units in real time can be complex and expensive. The increased complexity leads to increased cost, power consumption, and a higher risk of system failure. In addition, when using control circuits that actively select each detection unit in rapid succession at the sensing element level, there is an upper limit to the speed that can be achieved.

[0033] Embodiments of the present disclosure can provide a sensing element level circuit that is simple, cost-effective, fast and stable for faults and system failures. The circuit can be arranged so that each detection unit automatically performs many tasks that otherwise may require active control. For example, once the detection unit is enabled, it can be configured to turn on its signal detection component when a signal is received, and turn itself off after the signal ends. The detection unit can be configured to automatically generate a signal to notify the controller that detection has been achieved, and store the detection signal until the controller is ready to read it. The signal detection unit can include components such as solid-state current control devices (SSCCDs) that are designed to quickly extract electrical signals from sensing elements. The detection unit can also be configured to automatically pass an enable signal to the next detection unit in the row so that it can be enabled without any direct command from the controller. In this way, a simplified control structure can reduce costs and improve signal processing speed.

[0034] The objects and advantages of the present disclosure can be achieved by the elements and combinations set forth in the embodiments discussed herein. However, the embodiments of the present disclosure do not necessarily need to achieve such exemplary objects or advantages, and some embodiments may not achieve any of the objects or advantages.

[0035] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing detection systems and detection methods in systems that utilize an electron beam ("e-beam"). However, the present invention is not limited to this. Other types of charged particle beams (e.g., proton beams) may be similarly applied. In addition, systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, proton detection, x-ray detection, ion detection, etc. Photon detection may include light in the infrared, visible, UV, DUV, EUV, x-ray, or any other wavelength range. Therefore, although the detectors in the present disclosure may be disclosed for electron detection, some embodiments of the present disclosure may be directed to detecting other charged particles or photons.

[0036] As used herein, unless specifically stated otherwise, the term "or" encompasses all possible combinations unless not feasible. For example, if a component is stated to include A or B, then unless otherwise explicitly stated or not feasible, the component may include A or B, or A and B. As a second example, if a component is stated to include A, B, or C, then unless otherwise explicitly stated or not feasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0037] View now Figure 1 , which illustrates an exemplary electron beam inspection (EBI) system 10 that can be used for wafer inspection according to an embodiment of the present disclosure. Figure 1 As shown, the EBI system 10 includes a main chamber 11, a load / lock chamber 20, an electron beam tool 100 (e.g., a scanning electron microscope (SEM)), and an equipment front end module (EFEM) 30. The electron beam tool 100 is located in the main chamber 11 and can be used for imaging. The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b receive a wafer front opening transport box (FOUP), which contains wafers (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (wafers and samples may be collectively referred to as "wafers" herein).

[0038] One or more robotic arms (not shown) in the EFEM 30 can transfer the wafer to the load / lock chamber 20. The load / lock chamber 20 is connected to a load / lock vacuum pump system (not shown), which removes gas molecules in the load / lock chamber 20 to reach a first pressure lower than atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) can transfer the wafer from the load / lock chamber 20 to the main chamber 11. The main chamber 11 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules in the main chamber 11 to reach a second pressure lower than the first pressure. After reaching the second pressure, the wafer is inspected by the electron beam tool 100. The electron beam tool 100 can be a single beam system or a multi-beam system. The controller 109 is electrically connected to the electron beam tool 100 and can also be electrically connected to other components. The controller 109 can be a computer configured to perform various controls of the EBI system 10. Although the controller 109 is Figure 1 1 is shown as being external to the structure including the main chamber 11, the load / lock chamber 20 and the EFEM 30, but it should be understood that the controller 109 may be part of the structure.

[0039] In some embodiments, the controller 109 may include one or more processors (not shown). The processor may be a general or special electronic device capable of manipulating or processing information. For example, the processor may include any number of central processing units (or "CPUs"), graphics processing units (or "GPUs"), optical processors, programmable logic controllers, microcontrollers, microprocessors, digital signal processors, intellectual property (IP) cores, programmable logic arrays (PLAs), programmable array logic (PALs), general array logic (GALs), complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), systems on chips (SoCs), application specific integrated circuits (ASICs), and any combination of any type of circuit capable of data processing. The processor may also be a virtual processor, which includes one or more processors distributed on multiple machines or devices connected via a network.

[0040] In some embodiments, the controller 109 may further include one or more memories (not shown). The memory may be a general or special electronic device capable of storing code and data accessible by a processor (e.g., via a bus). For example, the memory may include any number of random access memories (RAM), read-only memories (ROM), optical disks, magnetic disks, hard drives, solid-state drives, flash drives, secure digital (SD) cards, memory sticks, compact flash (CF) cards, or any combination of any type of storage device. The code and data may include an operating system (OS) and one or more applications (or "applications") for a specific task. The memory may also be a virtual memory, which includes one or more memories distributed on multiple machines or devices connected via a network.

[0041] Charged particle beam microscope, for example, formed by EBI system 10 or can be included in EBI system 10, can be able to reach the resolution of for example nanometer level, and can be used as the practical tool of IC components on inspection wafer.Utilize electron beam system, the electron of primary electron beam can be focused on the detection point on the wafer being inspected.The interaction of primary electron and wafer can cause to form secondary particle beam.Secondary particle beam can comprise backscattered electron, secondary electron or Auger electron etc. generated by the interaction of primary electron and wafer.The characteristic (for example, intensity) of secondary particle beam can change based on the property of internal or external structure or material of wafer, and therefore can indicate whether wafer comprises defect.

[0042] The intensity of the secondary particle beam can be determined using a detector. The secondary particle beam can form a beam spot on the surface of the detector. The detector can generate an electrical signal (e.g., electric current, charge, voltage, etc.) representing the intensity of the detected secondary particle beam. The electrical signal can be measured using a measuring circuit, which can include other components (e.g., analog-to-digital converter) to obtain the distribution of the detected electronics. The electronic distribution data collected during the detection time window, in conjunction with the corresponding scan path data of the primary electron beam incident on the wafer surface, can be used to reconstruct the image of the wafer structure or material being inspected. The reconstructed image can be used to display the various features of the internal or external structure or material of the wafer, and can be used to display the defects that may be present in the wafer.

[0043] Figure 2A A charged particle beam apparatus according to an embodiment of the present disclosure is shown, which may be an example of an electron beam tool 100 . Figure 2A An apparatus is shown for simultaneously scanning multiple locations on a wafer using multiple beamlets formed from a primary electron beam.

[0044] like Figure 2AAs shown, the electron beam tool 100A may include an electron source 202, an electron gun aperture 204, a focusing lens 206, a primary electron beam 210 emitted from the electron source 202, a source conversion unit 212, a plurality of sub-beams 214, 216 and 218 of the primary electron beam 210, a primary projection optical system 220, a wafer stage ( Figure 2A The primary projection optical system 220 may include a beam splitter 222, a deflection scanning unit 226, and an objective lens 228. The electronic detection device 244 may include detection sub-areas 246, 248, and 250.

[0045] Electron source 202, electron gun aperture 204, focusing lens 206, source conversion unit 212, beam splitter 222, deflection scanning unit 226 and objective lens 228 can be aligned with the primary optical axis 260 of apparatus 100A. Secondary optical system 242 and electron detection device 244 can be aligned with secondary optical axis 252 of apparatus 100A.

[0046] The electron source 202 may include a cathode, an extractor, or an anode, where primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 210 having a crossover (virtual or real) 208. The primary electron beam 210 may be visualized as being emitted from the crossover 208. The electron gun aperture 204 may block peripheral electrons of the primary electron beam 210 to reduce the size of the detection spots 270, 272, and 274.

[0047] The source conversion unit 212 may include an imaging element array ( Figure 2A not shown) and the beam limiting aperture array ( Figure 2A 201 ). Examples of source conversion unit 212 can be found in U.S. Patent No. 9,691,586; U.S. Publication No. 2017 / 0025243; and International Application No. PCT / EP2017 / 084429, the entire contents of which are incorporated herein by reference. The imaging element array may include a microdeflector or a microlens array. The imaging element array may form a plurality of parallel images (virtual images or real images) of intersection 208 with the plurality of sub-beams 214, 216, and 218 of the primary electron beam 210. The beam limiting aperture array may limit the plurality of sub-beams 214, 216, and 218.

[0048] The converging lens 206 can focus the primary electron beam 210. The current of the sub-beams 214, 216 and 218 downstream of the source conversion unit 212 can be changed by adjusting the focusing power of the converging lens 206 or by changing the radial size of the corresponding beam limiting holes in the beam limiting hole array. The converging lens 206 can be an adjustable converging lens, which can be configured so that the position of its first principal plane is movable. The adjustable converging lens can be configured to be magnetic, which can cause the off-axis sub-beams 216 and 218 to fall on the sub-beam limiting aperture at a rotation angle. The rotation angle varies with the focusing power of the adjustable converging lens and the position of the first principal plane. In some embodiments, the adjustable converging lens can be an adjustable anti-rotation converging lens, which includes an anti-rotation lens having a movable first principal plane. Examples of adjustable converging lenses are further described in U.S. Publication No. 2017 / 0025241, the entire contents of which are incorporated herein by reference.

[0049] Objective lens 228 can focus beamlets 214, 216, and 218 onto wafer 230 for inspection, and can form a plurality of detection spots 270, 272, and 274 on the surface of wafer 230. Secondary electron beamlets 236, 238, and 240 can be formed, emitted from wafer 230 and traveling back toward beam splitter 222.

[0050] The beam splitter 222 can be a Wien filter type beam splitter that generates an electrostatic dipole field and a magnetic dipole field. In some embodiments, if an electrostatic dipole field is applied, the force applied by the electrostatic dipole field to the electrons of the sub-beams 214, 216, and 218 can be equal in magnitude and opposite in direction to the force applied by the magnetic dipole field to the electrons. Therefore, the sub-beams 214, 216, and 218 can pass directly through the beam splitter 222 at a zero deflection angle. However, the total dispersion of the sub-beams 214, 216, and 218 generated by the beam splitter 222 can also be non-zero. The beam splitter 222 can separate the secondary electron beams 236, 238, and 240 from the sub-beams 214, 216, and 218, and direct the secondary electron beams 236, 238, and 240 to the secondary optical system 242.

[0051] The deflection scanning unit 226 can deflect the beamlets 214, 216 and 218 to scan the detection points 270, 272 and 274 on the area on the surface of the wafer 230. In response to the incidence of the beamlets 214, 216 and 218 at the detection points 270, 272 and 274, secondary electron beams 236, 238 and 240 can be emitted from the wafer 230. The secondary electron beams 236, 238 and 240 may include electrons having an energy distribution including secondary electrons and backscattered electrons. The secondary optical system 242 can focus the secondary electron beams 236, 238 and 240 onto the detection sub-areas 246, 248 and 250 of the electron detection device 244. The detection sub-areas 246, 248 and 250 can be configured to detect the corresponding secondary electron beams 236, 238 and 240 and generate corresponding signals for reconstructing the surface image of the wafer 230.

[0052] The generated signals may represent the intensities of the secondary electron beams 236, 238, and 240 and may be provided to an image processing system (e.g., as described below) that communicates with the detection device 244, the primary projection optical system 220, and the motorized wafer stage. Figure 2B The image processing system 199 provided in FIG. 2 ). The movement speed of the motorized wafer stage can be synchronized and coordinated with the beam deflection controlled by the deflection scanning unit 226 so that the movement of the scanning detection points (e.g., scanning detection points 270, 272, and 274) can orderly cover the area of ​​interest on the wafer 230. The parameters of this synchronization and coordination can be adjusted to accommodate different materials of the wafer 230. For example, different materials of the wafer 230 can have different resistance-capacitance characteristics, which can generate different signal sensitivities to the movement of the scanning detection points.

[0053] The intensities of the secondary electron beams 236, 238, and 240 may vary depending on the external or internal structure of the wafer 230, and thus may indicate whether the wafer 230 includes a defect. In addition, as described above, the sub-beams 214, 216, and 218 may be projected onto different locations on the top surface of the wafer 230, or different sides of a local structure of the wafer 230, to generate the secondary electron beams 236, 238, and 240 that may have different intensities. Therefore, by mapping the intensities of the secondary electron beams 236, 238, and 240 to the areas of the wafer 230, the image processing system may reconstruct an image reflecting the features of the internal or external structure of the wafer 230.

[0054] Detection sub-regions 246, 248, and 250 may include separate detector packages, separate sensing elements, or separate regions of an array detector. In some embodiments, each detection sub-region may include a single sensing element.

[0055] Now refer to Figure 2BAnother example of a charged particle beam apparatus is discussed. An electron beam tool 100B (also referred to herein as apparatus 100B) may be an example of an electron beam tool 100 and may be similar to Figure 2A The electron beam tool 100A is shown. However, unlike the tool 100A, the tool 100B may be a single beam tool that uses only one primary electron beam to scan one location on the wafer at a time.

[0056] like Figure 2B As shown, the apparatus 100B includes a wafer holder 136 supported by a motorized stage 134 to hold a wafer 150 to be inspected. The electron beam tool 100B includes an electron emitter, which may include a cathode 103, an anode 121, and an electron gun aperture 122. The electron beam tool 100B also includes a beam limiting aperture 125, a converging lens 126, a column aperture 135, an objective lens assembly 132, and a detector 144. In some embodiments, the objective lens assembly 132 may be a modified SORIL lens, which includes a pole piece 132a, a control electrode 132b, a deflector 132c, and an excitation coil 132d. In the detection or imaging process, the electron beam 161 emitted from the tip of the cathode 103 may be accelerated by the voltage of the anode 121, pass through the electron gun aperture 122, the electron beam limiting aperture 125, the converging lens 126, and be focused by the modified SORIL lens into a detection point 170, and irradiate onto the surface of the wafer 150. The detection point 170 can be scanned across the surface of the wafer 150 by a deflector, such as the deflector 132c in the SORIL lens or other deflectors. The detector 144 can collect secondary or scattered particles, such as secondary electrons or scattered primary electrons, emitted from the wafer surface to determine the intensity of the beam so that an image of the region of interest on the wafer 150 can be reconstructed.

[0057] An image processing system 199 may also be provided, which includes an image acquirer 120, a memory 130 and a controller 109. The image acquirer 120 may include one or more processors. For example, the image acquirer 120 may include a computer, a server, a mainframe, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer 120 may be communicatively coupled to the detector 144 of the electron beam tool 100B through a medium such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, radio, or a combination thereof. The image acquirer 120 may receive a signal from the detector 144 and may construct an image. Thus, the image acquirer 120 may acquire an image of the wafer 150. The image acquirer 120 may also perform various post-processing functions, such as image averaging, generating contours, superimposing indicators on the acquired image, etc. The image acquirer 120 may be configured to perform adjustments to the brightness and contrast of the acquired image, etc. The memory 130 may be a storage medium such as a hard disk, a random access memory (RAM), a cloud storage, other types of computer-readable memory, etc. The memory 130 may be coupled to the image acquirer 120 and may be used to save the scanned raw image data as raw images and post-processed images. The image acquirer 120 and the memory 130 may be connected to the controller 109. In some embodiments, the image acquirer 120, the memory 130 and the controller 109 may be integrated together as an electronic control unit.

[0058] In some embodiments, the image acquirer 120 may acquire one or more images of the sample based on the imaging signal received from the detector 144. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image including a plurality of imaging regions, which may contain various features of the wafer 150. The single image may be stored in the memory 130. Imaging may be performed based on imaging frames.

[0059] The convergence and illumination optics of an electron beam tool may include or be supplemented by an electromagnetic quadrupole electron lens. Figure 2B As shown, the electron beam tool 100B may include a first quadrupole lens 148 and a second quadrupole lens 158. In some embodiments, the quadrupole lenses may be used to control the electron beam. For example, the first quadrupole lens 148 may be controlled to adjust the beam current, and the second quadrupole lens 158 may be controlled to adjust the beam spot size and beam shape.

[0060] Figure 2B A charged particle beam apparatus is shown that can use a single primary beam configured to generate secondary electrons by interacting with a wafer 150. A detector 144 can be placed along the optical axis 105, such as Figure 2BThe primary electron beam may be configured to travel along the optical axis 105. Thus, the detector 144 may include a hole at its center so that the primary electron beam may pass through to reach the wafer 150. Figure 2B An example of a detector 144 having an opening at its center is shown. However, some embodiments may use a detector that is placed off-axis relative to the optical axis along which the primary electron beam travels. For example, as discussed above Figure 2A In the illustrated embodiment, a beam splitter 222 may be provided to direct the secondary electron beam to an off-axis detector. The beam splitter 222 may be configured to direct the secondary electron beam to the electron detection device 244 at an angle a, such as Figure 2A shown.

[0061] The detector in the charged particle beam system may include one or more sensing elements. The detector may include a single element detector or an array having multiple sensing elements. The sensing element may be configured for charged particle counting. Sensing elements of detectors that can be used for charged particle counting are discussed in U.S. Publication No. 2019 / 0379682, the entire contents of which are incorporated herein by reference.

[0062] The sensing element may include a diode or a diode-like element that can convert incident energy into a measurable signal. For example, the sensing element in the detector may include a PIN diode. Throughout this disclosure, such as in the accompanying drawings, the sensing element may be represented as a diode, although the sensing element or other components may deviate from the ideal circuit behavior of electrical elements such as diodes, resistors, capacitors, etc.

[0063] Figure 3A - Figure 3C : shows an exemplary structure of a detector according to an embodiment of the present disclosure. The detector may be a segmented detector. Figure 3A - Figure 3C The detectors shown as detector 300A, detector 300B or detector 300C may be provided as Figure 2A The charged particle detection device 244 shown or Figure 2B The detector 144 is shown. Figure 3A , detector 300A includes a sensor layer 301 and a signal processing layer 302. Sensor layer 301 may include a sensor die consisting of a plurality of sensing elements including sensing elements 311, 312, 313, and 314. In some embodiments, a plurality of sensing elements may be provided in a sensing element array, and each sensing element may have a uniform size, shape, and arrangement.

[0064] Signal processing layer 302 may include a plurality of signal processing circuit devices, including circuits 321, 322, 323, and 324. The circuits may include interconnects (e.g., wiring paths) configured to communicatively couple sensing elements. Each sensing element of sensor layer 301 may have a corresponding signal processing circuit device in signal processing layer 302. The sensing elements and their corresponding circuits may be configured to operate independently. Figure 3A As shown, circuits 321 , 322 , 323 , and 324 may be configured to be communicatively coupled to outputs of sensing elements 311 , 312 , 313 , and 314 , respectively, as indicated by the four dashed lines between sensor layer 301 and signal processing layer 302 .

[0065] In some embodiments, the signal processing layer 302 may be configured as a single die on which multiple circuits are provided. The sensor layer 301 and the signal processing layer 302 may be in direct contact. Figure 3B As shown, a detector 300B is shown, with the signal processing layer 302 directly adjacent to the sensor layer 301 .

[0066] In some embodiments, components and functions of different layers may be combined or omitted. For example, the signal processing layer 302 may be combined with the sensor layer 301. In addition, circuits for charged particle counting may be integrated at various points in the detector, such as in a separate readout layer of the detector or on a separate chip.

[0067] like Figure 3C As shown, a detector 300C may be provided. The detector 300C may include a sensor layer 301. The detector 300C may be configured for backside illumination, and the sensor layer 301 may be the only layer provided. A first side of the sensor layer 301 may be configured to receive charged particles, and a circuit may be provided on a second side opposite the first side. The circuit may include an electronic counting circuit provided separately for each sensing element.

[0068] Reference now Figure 4 , which shows a circuit 400 for charged particle counting. The circuit 400 may be one of a plurality of circuits, each provided for a corresponding sensing element in an array detector. The detector may include only one sensing element, and only one circuit 400 may be provided. Alternatively, the circuit 400 may be provided in a layer forming a sensing element in the detector (e.g., integrated with the sensing element), or in another layer. For example, the circuit 400 may be provided in a sensor layer, or may be provided in another layer of the detector.

[0069] Circuit 400 can be configured to process signals generated from sensing element 411. Sensing element 411 can be configured to generate a response to a charged particle event. A charged particle event can include an electron arrival event. For example, in response to an incoming electron arriving at sensing element 411, sensing element 411 can be configured to generate a charge or current due to the energy of the incoming electron. The charge or current can be generated within the sensing element and can be fed to a circuit connected to the sensing element. In some cases, the circuit can be integrated with the sensing element.

[0070] like Figure 4 As shown, the circuit 400 includes an input stage 410, a threshold detector 420, a storage cell multiplexer 430, a storage cell array 440, a converter 450, and a control unit 490. The array 440 may include a plurality of storage cells, including a first storage cell 441, a second storage cell 442, and so on, until, for example, an Nth storage cell 449. The storage cells 441 to 449 may include charge storage cells.

[0071] The input stage 410 can be configured to have a low input impedance so that all or substantially all of the charge is quickly extracted from the sensing element 411 after the charge is generated in the sensing element 411. The sensing element 411 can be configured to operate with an applied bias so that a depletion region is formed in the sensing element 411, which can act as a trapping region for incoming charged particles. The incoming charged particles can interact with the material of the sensing element 411 and can generate charge by impact ionization. The input stage 410 can be configured so that all of the charge is pulled out of the sensing element 411 once all of the charge is generated in the sensing element 411 and fed to other components of the circuit 400.

[0072] The input stage 410 may include a component configured to impart gain. For example, the input stage 410 may include an amplifier. The amplifier may be configured to apply a current gain so that the current signal from the sensing element 411 may be amplified. In addition, the input stage 410 may be configured to have a conversion function. The input stage 410 may include a component configured to convert an electrical signal from one form to another form. For example, the input stage 410 may include a component configured to convert a current signal from the sensing element 411 into an electrical signal of another form (e.g., voltage).

[0073] The circuit 400 may include a threshold detector 420. The threshold detector 420 may be connected to the input stage 410. The threshold detector 420 may be configured to detect a signal level of an input current from the sensing element 411 or a signal level of a converted signal. The converted signal may include a signal having a level proportional to the input current from the sensing element 411.

[0074] Threshold detector 420 can be configured to determine that a charged particle event has occurred. The determination from threshold detector 420 can be used to control other operations of circuit 400. Threshold detector 420 can be configured to detect the start or stop of a charged particle event. The start or stop of a charged particle event can trigger the recording of information from sensing element 411. For example, an integration function can be performed in response to determining that a charged particle event has occurred. Integration can refer to the process of obtaining an accumulated value of charge or current over time (e.g., an area under a curve).

[0075] The threshold detector 420 can be configured to operate using one or more thresholds. For example, the threshold detector 420 can be configured to use two values ​​that can be defined and set in the threshold detector 420. The two values ​​can include a1 and a2 that can be the same or different from each other. The values ​​of a1 and a2 can be set to be higher than the total noise level of the detector. The noise level can be the noise floor from the sensing element 411, its amplified value or its converted value. The relationship between a1 and a2 can be, for example, a1≥a2. The threshold can be set to avoid erroneous detection of the start or stop point of the electron arrival event due to noise.

[0076] Circuit 400 may include a storage cell multiplexer 430 after input stage 410. Input stage 410 may be optional, for example, when providing a circuit for an integration function with very low input impedance. Hereinafter, the phrase "output of input stage 410" may refer to the output of input stage 410 or the output of sensing element 411. The output of input stage 410 may represent an output signal from sensing element 411, for example, whether it is amplified or converted.

[0077] Multiplexer 430 (or "mux") may be configured to connect the output of input stage 410 to the memory cells of array 440. Multiplexer 430 may include a switch element. Multiplexer 430 may include a data selector configured to select between several output lines and forward the input signal to the selected output line. Multiplexer 430 may be configured to connect only one output line to the input at a time. For example, multiplexer 430 may be configured to route a signal from the output of input stage 410 to only one of memory cells 441, 442, 449 at a time. In addition, multiplexer 430 may be configured so that the output of input stage 410 is not connected to the memory cells of array 440 at a particular time during the operation of circuit 400. Similarly, multiplexer 430 may be configured so that the output of input stage 410 is connected to other components besides the memory cells of array 440. Multiplexer 430 may be controlled by control unit 490.

[0078] Array 440 may include one or more memory cells. The output of each memory cell may be connected to converter 450. The signal input to the memory cell of array 440 may be converted to another form (e.g., by integration). As an example, the current or charge input to the memory cell of array 440 may be accumulated to form a voltage signal. Converter 450 may be configured to sample the memory cells of array 440. Converter 450 may be configured to process analog signals from the memory cells of array 440 or analog signals passed to it from other sensing element circuits. Converter 450 may generate a digital signal for data representing the analog signal.

[0079] Converter 450 may include, for example, a voltage detector or an analog-to-digital converter (ADC). Converter 450 may include a comparator having multiple inputs connected directly to the memory cells of array 440. Converter 450 may include a single comparator connected to the multiple inputs through a multiplexer.

[0080] The circuit 400 may be configured to perform interrogation (e.g., an interrogation function) on the memory cells of the array 440 after integration in the memory cells is complete. Integration may refer to accumulation of signals from, for example, the sensing element 411 or the input stage 410. Interrogation may refer to obtaining information from a component, such as by using a data converter or comparator to determine a voltage value used to determine, for example, the energy level of an electron arrival event. The circuit 400 may be configured to detect (e.g., interrogate) only the memory cells that are not selected by the memory cell multiplexer 430. For example, interrogation may be performed on memory cells separate from integration so as not to interfere with integration.

[0081] Converter 450 may include one or more voltage comparators. The voltage comparator may be used to compare the voltage from the memory cell of array 440 with a reference voltage. The number of voltage comparators and the number of reference voltages may be the same or different. A voltage buffer may be provided. For example, a voltage buffer may be provided in front of a plurality of voltage comparators to reduce the load effect of the input impedance of the voltage comparator on the voltage of the memory cell of array 440. Converter 450 may also include one or a group of ADCs, each ADC having a predetermined bit resolution.

[0082] Control unit 490 may be configured to perform various functions associated with circuit 400. For example, control unit 490 may be configured to: (i) control the operation of the sensing element level circuit, (ii) generate data based on the detection results of the electron arrival event, (iii) communicate with a higher level control unit (not shown), and (iv) communicate with an adjacent control unit in an adjacent sensing element level circuit similar to or identical to, for example, circuit 400. Control unit 490 may be configured for bidirectional data flow between itself and an adjacent control unit of an adjacent sensing element level circuit. A higher level control unit may be configured for bidirectional data flow between itself and control unit 490, and between itself and an adjacent control unit in an adjacent sensing element level circuit.

[0083] The circuit 400 can be configured to count charged particles incident on the detector. If the level of the incoming current signal from the sensing element 411 crosses a threshold, the circuit 400 can be configured to start a counting operation. For example, if the threshold detector 420 determines that a1 is exceeded, integration can be performed. The control unit 490 can control the storage unit multiplexer 430 to connect the output of the input stage 410 to the first storage unit 441. When the current or charge from the sensing element 411 accumulates, the capacitor in the first storage unit 441 can be charged. At the same time, the converter 450 can detect the voltage in one or more other storage units (e.g., the second storage unit 442 to the Nth storage unit 449) that are not selected by the storage unit multiplexer 430.

[0084] Converter 450 may be configured with different reference values ​​that may be used for different purposes, such as the following. Reference values ​​may be used to confirm the arrival of an incoming electron. Reference values ​​may be used to identify the type of incoming electron (e.g., to determine whether the incoming electron is a secondary electron or a backscattered electron). Reference values ​​may be used to determine whether more than one electron arrives during an electron arrival event. Reference values ​​may be used to determine whether a sensing element or storage cell is in an overflow state due to an electron arrival event. Reference values ​​may also be used to determine the energy range of the incoming electron or the exact energy level of the incoming electron.

[0085] As an example of using a reference value, if only one predetermined reference voltage or predetermined value is set (e.g., in the case of using an ADC with a one-bit resolution), then this one reference value can be used to identify whether the electron entering at the time of an electron arrival event is a secondary electron or a backscattered electron, the result of which is stored in the storage unit under interrogation. Alternatively, the reference value can be used to confirm that an electron arrival event has occurred (e.g., even after the threshold a1 has been exceeded, thus indicating the start of an electron arrival event, the reference value of the converter 450 can be used to confirm that the signal from the sensing element 411 corresponds to the detection of a secondary electron or a backscattered electron from the sample, and therefore the electron should be counted).

[0086] In the second case, one of the reference voltages or values ​​can be used to identify the type of electron entering during an electron arrival event; the other reference voltage or value can be used to determine whether one or more electrons arrived at the sensing element during the electron arrival event.

[0087] In a third case, one of the reference voltages or values ​​can be used to determine whether one or more electrons arrive at the sensing element during an electron arrival event; and the other reference voltage or value can be used to determine whether the memory cell is in an overflow state. The overflow state can correspond to a situation where more than two electrons arrive at the sensing element during an electron arrival event.

[0088] It should be understood that more situations can be established by combining different tasks (such as the tasks discussed above). Other predetermined voltages or values ​​can be used based on the requirements of a particular application. In addition, after the information query, the storage unit can be reset and the information stored in the storage unit can be removed from the storage unit (for example, the voltage across the capacitor in the storage unit can be reset to a predetermined value, such as zero).

[0089] There may be a time period associated with an electron arrival event. For example, as described above, the expression "during an electron arrival event" may refer to a time period based on the threshold detector 420 determining when a signal from the sensing element 411 crosses (e.g., exceeds) a1 and when a signal crosses (e.g., falls below) a2. A predetermined time period may be set so that an electron arrival event lasts for a maximum duration from when a1 is exceeded until the end of a predetermined time period. If a stop point is not detected after a predetermined time period (e.g., the signal crosses the same or another threshold), the counting of a given electron arrival event may be forced to stop. If no confirmed electrons are detected during an electron arrival event, a detection error signal may be generated and recorded by the control unit 490.

[0090] The control unit 490 may be configured for further tasks. For example, when the threshold detector 420 determines that a threshold has been crossed, various functions may be performed. When the threshold detector 420 detects the start of an electronic arrival event, the control unit 490 may record a timestamp of the start point. The control unit 490 may be configured to monitor whether a subsequent stop point is detected only when a start point is detected. For example, the threshold detector 420 may not use the second threshold a2 unless or until the first threshold a1 has been crossed. In addition, a timestamp may be recorded for the stop point. The threshold associated with the start point may be higher than the threshold associated with the stop point. The event period may be determined based on the start and stop points.

[0091] When the threshold detector 420 determines that the signal from the sensing element 411 exceeds a1, a first charged particle event can be detected. The integration of the first charged particle event can be performed using the first storage unit 441. After the first charged particle event, the integration of the second charged particle event can be performed using a different storage unit (e.g., the second storage unit 442). The term "after the first charged particle event" can refer to a situation where the signal from the sensing element 411 drops below a2. "After" the first charged particle event can refer to a situation where a predetermined period of time has passed since the threshold detector 420 has determined that the signal from the sensing element 411 exceeds a1.

[0092] Integration and information interrogation can occur simultaneously. For example, when performing information interrogation on a cell-by-cell basis, or when performing information interrogation in parallel with multiple cells not selected by the storage cell multiplexer 430, the circuit 400 may perform integration at the cell selected by the storage cell multiplexer 430. Integration may cause the signal from the output of the input stage 410 to be transmitted to the selected storage cell of the array 440. Integration may continue until the threshold detector 420 determines that the signal from the sensing element 411 drops below the threshold a2 (or otherwise determines a stopping point). In response to the signal level dropping below a2, the storage cell multiplexer 430 may disconnect the connection between the input stage 410 (or the output of the integrated circuit) and the currently selected storage cell. Thereafter, the circuit 400 may immediately connect the output of the input stage 410 to another storage cell. The storage cell that is then connected may be a storage cell that has been reset. Integration may then be performed again using the newly selected storage cell. Integration may not start immediately when connected to a new storage cell unless, for example, the threshold detector 420 determines that a1 is exceeded again.

[0093] When the detector is operating, integration and interrogation can be performed. The integration results stored in the storage unit can be interrogated, and the count results can be sent to the control unit 490. This operation can occur at the sensing element level. Therefore, for all sensing elements of the detector, a separate integration and interrogation process can be performed. The data can be processed and sent to the upper control unit of the detector. The higher level control unit can be configured to determine the electronic count based on data from a lower level control unit (e.g., a control unit 490 at the sensing element level of the detector).

[0094] The control unit 490 can be configured to determine the overflow state of the sensing element or storage unit (e.g., set an overflow flag). Regarding overflow, there can be several different types. Overflow is discussed in U.S. Publication No. 2019 / 0379682.

[0095] For example, the overflow may include a first type of overflow. The first type of overflow may involve a signal level associated with a charged particle event that exceeds a predetermined value. The predetermined value may be a value determined based on the limitations of a circuit associated with the sensing element. For example, the predetermined value may be a percentage of the processing limit of the circuit. The first type of overflow may correspond to a situation where multiple charged particles arrive during a charged particle event. For example, multiple charged particles may arrive at the sensing element in such close succession, or even substantially simultaneously, that the signals from multiple charged particle arrival events may overlap strongly in the time domain. The integrated results from these multiple charged particle arrival events may be greater than the results that the circuit 400 is equipped to process. Therefore, the circuit may be configured to record the overflow event in this case by, for example, setting an overflow flag indicating a first type of overflow.

[0096] A first type of overflow may be encountered when a component of a circuit connected to a sensing element is in an overflow state. For example, a first type of overflow may be encountered when a component of a circuit connected to a sensing element for counting charged particles within a specific energy range is in an overflow state. For example, when the query result indicates that the electron arrival event recorded by the storage unit involves more than a certain number of incoming electrons, a first type of overflow flag may be set. For example, the specific number may be one or two. Whether the specific number is 1 or 2 may depend on the requirements of a specific application and the corresponding reference voltage (or value) setting. In addition, if the dynamic range of the circuit is increased (for example, the input stage, storage multiplexer, storage unit and converter can operate at a higher signal swing), the frequency of occurrence of the first type of overflow may be reduced. In addition, the first type of overflow may be reduced by increasing the capacitance of the storage unit or reducing the signal swing of the input stage. However, this may be at the expense of energy resolution loss.

[0097] Overflow may also include a second type of overflow. The second type of overflow may involve a situation where another charged particle event occurs during the signal detection and processing of one charged particle event. The second type of overflow may be encountered when one charged particle arrives at the sensing element and a subsequent charged particle arrives in a state where the sensing element and its associated circuitry are unable to give an appropriate response to the subsequent charged particle arrival event.

[0098] The second type of overflow can be indicated by a flag. When there are no available storage cells for the storage cell multiplexer 430 to select, the second type of overflow flag can be set. If a sufficiently large number of storage cells are provided, the second type of overflow can be avoided. This can be based on the change of the reference voltage or value used in the converter 450 and the operating speed of the components in the converter 450. The rate of the second type of overflow can be reduced by further enhancing the speed of the sensing element 411, the input stage 410, the threshold detector 420, the storage cell multiplexer 430 and the converter 450.

[0099] The use of overflow indications helps identify miscounts or false detections of charged particle arrival events. Circuit 400 can be configured to use overflow tags to monitor the error count rate at storage units 441 to 449. By indicating that detection information has been lost due to, for example, type 1 or type 2 overflow, circuit 400 can provide more accurate results. For example, overflow information can be used to estimate corrections to measurements to account for lost information, assign confidence weights to measurements, or provide corrections in the circuit to prevent losses in subsequent measurements.

[0100] Circuit 400 can use analog pipelines in the detection circuit, and can provide a sufficient number of converters in the signal processing part of the circuit to ensure that the total processing rate of the detection circuit is higher than the average rate at which the sensing element generates signals in response to the charged particle arrival event. This can reduce or avoid the second type of overflow. In addition, the detector or charged particle beam device can be configured to reduce the occurrence of the first type of overflow. The occurrence of the first type of overflow can be based on the speed of the sensing element that generates the signal in response to the charged particle arrival event and the bandwidth of the analog front end of the detection circuit. If the detection current increases beyond a certain level, the detection circuit may encounter a first type of overflow indicating the occurrence of an event with information loss. This may be due to the inability of the front end of the detection circuit to distinguish between multiple charged particle arrival events, or may be due to speed limitations in the threshold detector 420, the storage unit multiplexer 430, the storage unit array 440, the converter 450 or the control unit 490. For example, multiple charged particles may arrive at the sensing element in close succession or substantially simultaneously. In order to reduce the first type of overflow, the speed of the sensing element and the bandwidth of the front end can be increased. Alternatively or additionally, the charged particle optics may be tuned such that the intensity distribution of the charged particles reaching the detection surface becomes more uniform and spread evenly over a larger area, thereby covering more sensing elements.

[0101] Further discussion of electronic counting circuits can be found in International Application No. PCT / EP2021 / 068676, which is incorporated herein by reference in its entirety.

[0102] Figure 4The analog pipeline and memory cell array structure can be complex and costly to manufacture, especially for systems that do not need to exploit its energy level discrimination capabilities. The increased complexity introduces increased risk of failure. In addition to cost and risk of failure, the structure can have undesirably high power consumption in each sensing element level readout circuit.

[0103] Embodiments of the present disclosure provide a new sensing element level readout circuit design that improves the above analog signal pipeline and memory cell array architecture. The new design can be configured to use a streamlined and simplified circuit structure to achieve Figure 4 All functions of the circuit 400 of the comparative embodiment are provided, and the circuit structure is stable and cost-effective. In addition, when the incoming electron energy level discrimination function is not required, some embodiments can provide further simplification. Therefore, some embodiments can greatly simplify the signal readout process to a pure electron counting operation. By using the sensing element readout circuit design disclosed in the present invention, the manufacturing cost and power consumption of the readout circuit in the electron counting detector can be advantageously reduced.

[0104] Figure 5 A simplified block diagram illustrating a sense element level readout circuit design 500 with its corresponding sense element 511 according to an embodiment of the present disclosure. The sense element 511 may correspond to, for example Figure 3A - Figure 3C Any one of the sensing elements 311-314 of the present invention. Sensing element 511 may be a charged particle sensing element configured to generate an electrical signal in response to a charged particle arrival event. The electrical signal may be, for example, a charge, a current, or a voltage. In some embodiments, sensing element 511 may be a photon sensing element.

[0105] Circuit 500 may include an array 540 of signal detection units, such as signal detection units 541, 542, etc., up to 549. Signal detection unit 549 may be the Nth detection unit in the array. In other words, array 540 may generally include any number of signal detection units, where signal detection unit 549 represents the final signal detection unit in array 540. Each signal detection unit may include multiple inputs and outputs. For example, each signal detection unit may include: an analog signal input A I ;Analog signal output A O ; Enable signal input EN I ; Enable signal output EN O ; bypass input BP; operation status output OP; sampling control signal input SP; and reset signal input R.

[0106] Analog signal input A of the detection unit IThe sensing element 511 may be configured to receive an electrical signal from the sensing element 511 via the input bus 512 and pass the electrical signal to an internal circuit ( Figure 5 (not shown). For example, the internal circuit may include a storage capacitor. Analog signal output A O The analog signal output A can be configured to output the detection result signal from the signal detection unit to the converter 550 via the analog signal bus 551 within the sensing element level circuit 500. O May include information about the energy stored in the storage capacitor. Analog Signal Output A O Information used for energy level discrimination and, for example, generating an overflow flag (such as a type 1 overflow flag) may be output.

[0107] Enable signal input EN I Can be configured to receive an enable signal. The enable signal input EN I The enable signal may be delivered to the internal circuit of the enable signal detection unit ( Figure 5 For example, in the enabled state, the internal circuit of the signal detection unit can be configured to receive and store the signal from the sensing element 511. Enable signal output EN O Another enable signal input EN can be configured to pass another enable signal to the next signal detection unit in the array I For example, the enable signal output EN of the signal detection unit 541 O The enable signal may be passed to the enable signal input EN of the next signal detection unit 542 I As discussed further below, when the signal detection unit is to be enabled, it may be enabled via an enable signal input EN I The signal detection unit receives the enable signal, and when the signal detection unit is to activate the next signal detection unit, it can output EN via the enable signal O For example, after the signal detection unit 541 has performed signal detection, the signal detection unit 541 may output an EN enable signal via the enable signal. O Sending an enabling signal to the signal detection unit 542, for example, by receiving or storing an electrical signal from the sensing element 511, or by outputting an enable signal to the analog signal output A O The output is generated at the enable signal EN O After sending the enable signal to activate the additional signal detection unit 542, the signal detection unit 541 may be in an inactive state. In the inactive state, the signal detection unit 541 may not be configured to receive additional charge from the sensing element 511. However, the signal detection unit 541 may perform other functions in the inactive state, such as storing charge or generating an output signal.

[0108] The signal detection unit bypass input BP may be configured to receive a bypass signal and activate a bypass circuit of its signal detection unit ( Figure 5 ). For example, when the bypass circuit is activated, the signal detection unit may be placed in a bypass state. In the bypass state, the signal detection unit may not be configured for signal detection. For example, the signal detection unit may not be configured to receive or store charge from the sensing element 511 in the bypass state. The signal detection unit may be configured to pass any enable signal to the next signal detection unit instead of using the enable signal to activate its own circuit.

[0109] For example, if a signal detection unit is not functioning properly or if fewer signal detection units are needed, the signal detection unit may be bypassed. For example, when the frequency of electron arrival events is so low that not all signal detection units are needed, it may be desirable to bypass unnecessary signal detection units to isolate their circuits, minimize parasitic parameters, and reduce power consumption. Additionally, the bypass function may be used when a signal detection unit has detected and stored a signal from an electron arrival event, but the signal has not yet been processed by the signal processing circuit device. In this case, the signal detection unit may remain inactive until its signal has been processed.

[0110] The operating state output OP may be configured to output an operating state signal to the control unit 590. The operating state output may, for example, include information about the operating state of the signal detection unit. For example, the operating state signal may include information about whether its signal detection unit is in an enabled state, an inactive state, a bypass state, or another operating state. In some embodiments, the operating state output OP may output information about whether its signal detection unit is currently storing charge, or may output information used in electron counting, as discussed further below.

[0111] The sampling control signal input SP may be configured to receive a sampling control signal from the control unit 590. The sampling control signal may enable an internal circuit (not shown) to control whether the analog signal captured by the signal detection unit is output by the analog signal output A. O The analog signal is output to the converter 550 via the analog signal bus 551 .

[0112] The reset signal input R may be configured to receive a reset signal from the control unit 590. The reset signal may cause an internal circuit (not shown) to reset the signal detection unit to an initial state. For example, the initial state may be an inactive state, in which the signal detection unit is ready to be activated by the enable signal input EN. I Resetting the signal detection unit to the initial state may include, for example, discharging any charge stored within the signal detection unit, for example stored in a storage capacitor.

[0113] Transistor M00 and switch K 00 A charge release path may be formed from the sensing element 511 to the ground G. For example, the switch K 00 The circuit element M may be, for example, an analog switch configured to selectively pass or block the flow of charge to the ground G based on a control signal from the control unit 590. 00 M may optionally be included, for example as a current or voltage buffer. 00 It can be configured to have a reference voltage V ref2 When the sensing element 511 is not used, the switch K 00 can be closed so that the charge generated at the sensing element 511 can be transferred to the ground G and not accumulated in the sensing element.

[0114] The logic gate XOR may be configured as, for example, an XOR or other logic gate device. The logic gate XOR may be configured to output EN based on the left input from the control unit 590 and the enable signal from the final signal detection unit 549 in the array 540. O The right input of 540 is used to activate the first signal detection unit 541 in the array 540. For example, the logic gate XOR can be configured to Figure 5 Each of the left and right inputs shown receives a binary signal represented by 0 or 1. The logic gate XOR can be configured to output a signal value of 1 only when its inputs are different. For example, when the left input and the right input are both 1 or both 0, the logic gate XOR may not output a signal value of 1. However, when the first input is 1 and the other input is 0, the logic gate XOR can be configured to output a signal value of 1. The logic gate XOR can be used to enable and repeat a signal detection cycle in the array 540, as discussed further below. The logic gate XOR can be part of the control unit 590.

[0115] The converter 550 may receive analog signals from the signal detection units 541-549 via the analog signal bus 551 and convert them into digital signals. Alternatively, the converter 550 may receive signals from adjacent signal detection units of adjacent sensing elements via the analog signal bus 551. The converter 550 may be similar to Figure 4 The converter 550 may include a voltage detector or an analog-to-digital converter (ADC). The converter 550 may include a comparator having multiple inputs directly connected to the converter 550. The converter 550 may include a single comparator connected to the multiple inputs through a multiplexer. The converter 550 may be part of the control unit 590.

[0116] The control unit 590 may be configured for bidirectional data flow. The control unit 590 may be configured for various functions and may be similar to, for example, Figure 4 The control unit 590 may be configured to control the sensing element 511 and the signal detection units 541-549. The control unit 590 may be configured to receive and process inputs from the outputs of the signal detection units. For example, the control unit 590 may be configured to receive an operating state signal from the operating state output OP, and digital signals from the converter 550, including signals from the analog signal output A O The converted analog signal. The control unit 590 can be configured to generate an output signal and send it to the input of the signal detection unit. For example, the control unit 590 can be configured to send a signal detection unit bypass signal to bypass BP, a sampling control signal to sampling control signal input SP, and a reset signal to reset signal input R. The control unit 590 may also include inputs and outputs not shown here. For example, additional inputs and outputs may functionally couple the control unit 590 to the sensing element 511, the detector level data and control circuitry, and other sensing element level readout circuitry of adjacent sensing elements.

[0117] The above-mentioned input, output and other components consistent with the embodiments of the present disclosure are now described. Figure 5 The detection operation of the circuit 500 can be performed in the detector, for example Figure 2A The electron detection device 244 of the electron beam tool 100A, or Figure 2B The electron detection device 144 of the electron beam tool 100B. The detector can be, for example Figure 1 Part of the EBI system 10.

[0118] Alternatively, the operations may be performed in another electronic detector or another type of detector, such as a proton, photon, or other detector.Thus, while embodiments may discuss operations and elements in terms of electronics, it should be understood that other embodiments are possible.

[0119] When the sensing element 511 is to be enabled to detect a signal, the control unit 590 may place the sensing element 511 in a sensing state. For example, the control unit 590 may disconnect the switch K 00 The control unit may also output a signal value of 1 to the left input terminal of the logic gate XOR. Since the signal detection unit 549 is in the initial state, it does not currently output the enable signal EN. O The signal value 1 is output to the right input of the logic gate XOR. Therefore, the enable signal output EN of the signal detection unit 549 OThe output of the signal value 0 is caused (wherein the signal value 0 may refer to no signal or to a binary signal value other than 1). Because the left and right inputs of the logic XOR are different, the logic gate XOR may output a signal value 1 as an enable signal to enable the signal input EN of the signal detection unit 541. I Later, when the signal detection unit 541 changes the enable signal from the enable signal output EN O The enable signal input EN sent to the next signal detection unit (eg, detection unit 542) I , the control unit 590 may stop outputting the signal value 1 to the left input of the logic gate XOR so that the left input receives the signal value 0. For example, the control unit 590 may determine that the signal detection unit 541 has output the enable signal based on the operation state output signal from the operation state output OP of the signal detection unit 541.

[0120] When the enable signal input EN of the signal detection unit 541 I Upon receiving the enable signal from the logic gate XOR, the signal detection unit is enabled for receiving and storing charge from the sensing element 511. All other signal detection units in the array 540 may remain in an inactive state, such as an initial state or a bypass state. The signal detection unit 541 may remain enabled, for example, until it records an electron detection. Alternatively, the signal detection unit may remain enabled until it is disabled by the control unit 590, for example, by sending a reset signal to the reset signal input terminal R or sending a bypass signal to the bypass input terminal BP.

[0121] When electron landing occurs at the sensing element 511, an analog signal may be generated and transmitted to the analog signal input terminal A of the signal detection unit 541. I The signal detection unit 541 may receive and store charge from the generated analog signal using, for example, a solid-state current control device and a storage capacitor (not shown), as described below with respect to Figure 6 In addition to storing charge, the reception of an analog signal can trigger the enable signal output EN O The enable signal at the operation status output OP and the transmission of the operation status signal at the operation status output OP.

[0122] The operating status signal can indicate to the control unit 590 that, for example, an electron arrival event has been registered in the signal detection unit 541. The control unit 590 can interrogate the detection unit by, for example, outputting a sampling control signal to the sampling control signal input SP. Based on the sampling control signal, the detection unit 541 can output the sampling control signal to the analog signal output A. OThe detection result signal can be sent to the converter 550 via the analog signal bus 551. Alternatively, the detection result signal can be sent to another converter at, for example, an adjacent sensing element. The detection result signal can include information about the electronic detection. For example, the information can simply indicate that the electronic arrival has occurred at the sensing element 511, or it can include information about the energy level associated with the electronic arrival.

[0123] After the signal query signal, the control unit 590 may output a reset signal to reset the signal input R, thereby returning the signal detection unit 541 to its initial inactive state. For example, the reset signal may cause the switch K 14 closed, so that the storage capacitor C 11 The solid state current control device SSCCD can be reset.

[0124] Before, after or at the same time as the operation status signal is generated, the enable signal output EN of the signal detection unit 541 O The enable signal may be sent to the enable signal input EN of the signal detection unit 542. I to activate the next signal detection unit 542. Alternatively, if the signal detection unit 542 is in the bypass state, the enable signal can directly pass through the signal detection unit 542 and reach the next signal detection unit until the enable signal reaches the signal detection unit that is not in the bypass state. After activating the next available signal detection unit, the above process can be repeated.

[0125] This process may cycle through the signal detection cells in array 540 until it reaches final detection cell 549. When final signal detection cell 549 outputs its enable signal EN O When the enable signal is output, it can be sent to the right input terminal of the logic gate XOR as a signal value 1. Because the control unit has stopped the transmission of the value 1 signal as described above, the left input terminal receives the signal value 0, and the logic outputs a new enable signal to enable the signal input terminal EN of the first signal detection unit 541. I In this way, the array 540 of signal detection units 541 - 549 can repeatedly cycle through the detection process.

[0126] The sensing element level readout circuit design 500 may provide a simple and cost-effective architecture configured to passively trigger the sequential activation of a series of signal detection units without requiring complex control circuitry to manage the process.

[0127] Figure 6 A simplified diagram showing an example of the internal circuitry of the signal detection unit 641 according to some embodiments of the present disclosure. The signal detection unit 641 may be, for example Figure 5 A possible implementation of the signal detection units 541-549. The various circuit elements and other components of the signal detection unit 641 will be discussed in turn below.

[0128] The signal detection unit 641 may include three transistors M 11 、M 12 and M 13 The transistor may be, for example, a MOSFET or other transistor, and may be configured, for example, as a common-gate amplifier. The common-gate amplifier arrangement may be used to stabilize the signal detection unit 641 and its associated sensing element (eg, Figure 5 In some embodiments, transistor M can be omitted. 11 、M 12 or M 13 .

[0129] Transistor M 11 Can be set at analog input A I . Transistor M 11 It can be configured to have a reference voltage V ref2 The common gate amplifier MOSFET. Transistor M 11 The voltage at the anode of the sensing element to which it is connected can be stabilized. As a result, the bias voltage across the sensing element can be stabilized. The speed and parasitic capacitance changes caused by bias voltage fluctuations during normal operation can be offset by introducing transistor M 11 The transistor M 11 It is also possible to minimize the presence of residual charge in the sensing element during operation. 11 The resulting common gate amplifier can further perform the function of a charge extractor. Undesirable electrical effects, such as parasitic capacitance, can cause fluctuations in the charge extraction current during the electron detection process. Transistor M 11 It can have a low input impedance. This can help to better extract charge from the sensing element 511 and reduce the influence of parasitic capacitance in the sensing element on the detection result.

[0130] Similar to transistor M 11 , transistor M 12 It can be configured to have a reference voltage V ref3 The common gate amplifier MOSFET. Transistor M 12 Can be stably located in transistor M 11 and M 12 The solid-state current control device SSCCD may be, for example, a silicon controlled rectifier, a thyristor, or another solid-state current control device, as discussed further below.13 A reference voltage V ref4 The third common-gate amplifier, the reference voltage V ref4 is configured as a stabilizing capacitor C 11 The voltage value at .

[0131] The signal detection unit 641 may further include an enable circuit and a bypass circuit, which are configured to switch the signal detection unit 641 from an initial state to, for example, an enable state or a bypass state based on an enable or bypass signal. 11 Can be set to Figure 6 In the upper position shown, switch K 12 Can be set to the lower position, switch K 14 Can be set to the disconnected state. In addition, the control unit (e.g. Figure 5 590) can output a signal in advance to reset the input R so that the switch K 14 is set to the closed state to switch K 14 Before being placed in the disconnected state, the storage capacitor C 11 The control unit can output another signal to sample the control signal input SP so that the switch K 15 Can be set to disconnected state.

[0132] In the enabled state, the signal detection unit 641 may be activated for detection. In the enabled state, the signal detection unit 641 will be ready to transfer charge from its associated sensing element (e.g., Figure 5 The sensing element 511 in the embodiment is transferred to the storage capacitor C 11 The enabling circuit may include: an enabling signal input EN I ; Enable signal output EN O ; and switch K 11 and K 12 The bypass circuit may include a bypass signal input BP and a switch K 11 and K 12 In some embodiments, the bypass circuit may be omitted.

[0133] The enabling circuit can be configured to put the signal detection unit 641 into an enabled state from an initial state. 11 In the initial configuration, the enable signal can be input from the enable signal EN I Transmitted to AND gate G 11 The enable signal may be, for example, a high level voltage, or a value of "1" in digital terms. For example, if the signal detection unit 641 is an array (such as Figure 5The enable signal may be a first signal detection unit in the array 540 of FIG. 1 , and the enable signal may be a first signal detection unit in the array 540 of FIG. 1 . Figure 5 Alternatively, the enable signal may come from a signal detection unit array (e.g. Figure 5 The enable signal output EN of the previous signal detection unit in the array 540) O In the initial state, the trigger circuit F 11 The reverse output (discussed below) can be configured to provide an AND gate G 11 The lower input terminal of the AND gate G outputs another signal value 1, making the AND gate G 11 The AND gate G receives a signal value of 1 from its upper and lower input terminals. 11 Then the output signal can be used to close another switch K 13 , thereby activating the current detection circuit to put the signal detection unit 641 into an enabled state. For example, the switch K 13 The closing of can short the control gate CG to the anode of the solid-state current control device SSCCD, changing the way it responds to the signal it receives at its anode. This allows the solid-state current control device SSCCD to be triggered when the signal (e.g., voltage value) from its associated sensing element exceeds a predetermined threshold. When the solid-state current control device SSCCD is triggered, it can act as a switch to quickly conduct charge from the anode to the cathode.

[0134] Alternatively, the bypass circuit of the signal detection unit 641 may receive a bypass signal at the bypass signal input terminal BP. For example, the bypass signal may be received from a control unit (eg, Figure 5 The bypass signal can make the switch K 11 and K 12 from Figure 6 The position shown is reversed so that switch K 11 In the lower position, switch K 12 In this case, the enable signal will not be fed from the enable signal input EN I Passed to AND gate G 11 Instead, the enable signal will pass through switch K 12 To enable the signal output EN O And leave the signal detection unit 641. In addition, the AND gate G 11 The upper input terminal can be switched by switch K 11 The new position of the switch K is grounded so that the upper input terminal receives a signal value of, for example, 0. Thus, the switch K is prevented from 13 closed, and the current sense circuit may not be enabled.

[0135] The signal detection unit 641 may further include a current detection circuit configured to receive a current, determine that a charged particle event such as an electron arrival event has occurred based on the received current, and store a charge corresponding to the current. The current detection circuit may include: a solid-state current control device SSCCD; an analog switch K 13 ; Transistor M 12 ; Storage capacitor C 11 ; Voltage comparator A11; Resistor R11; Buffer amplifier A13; Voltage comparator A12; Trigger F 11 ; and AND gate G 11 .

[0136] A solid-state current control device SSCCD may be used as an electronic input event detector in each signal detection unit. The solid-state current control device SSCCD may be, for example, a silicon controlled rectifier, a thyristor, or another solid-state element configured to conduct current in one direction. For example, the solid-state current control device SSCCD may include four layers of alternating p-type and n-type materials. The solid-state current control device SSCCD may include, for example, a combination of a pnp bipolar transistor and an npn bipolar transistor.

[0137] The solid-state current control device SSCCD may include a control gate CG configured to turn the solid-state control device on and off in response to an electron arrival event. For example, when charge is generated at an electrode of the sensing element due to, for example, an electron arrival event, the charge may generate a signal that generates a voltage value at the control gate CG. If the voltage value at the control gate CG meets or exceeds a trigger threshold, the control gate CG may trigger the solid-state current control device to be in an "on" state through which current may pass. The solid-state current control device SSCCD may remain in this on state until a majority of the charge from the sensing element has been extracted and transferred to the storage capacitor C 11 , storage capacitor C 11 It can be configured to store the charge delivered by the solid-state current control device SSCCD. When the current drops below the holding current value, the solid-state current control device SSCCD can be configured to switch from the on state to the off state and prevent further switching. Therefore, the solid-state current control device SSCCD can be configured to self-deactivate after the current pulse drops below the holding current. The trigger threshold voltage and the holding current threshold can be programmable.

[0138] The solid state current control device SSCCD can be configured to detect when electrons reach the sensing element via the analog input A IExtract charge quickly and efficiently from the associated sensing element. For example, the solid-state current control device SSCCD can be configured as a thyristor. When triggered to the on state, the thyristor can advantageously present a negative resistance so that the current can be increased at a low voltage. This can result in rapid extraction of charge from the sensing element, which can increase the speed of the detection process.

[0139] As mentioned above, the solid state current control device SSCCD may be a thyristor. The on / off function of the thyristor may represent an alternative to existing configurations (e.g. Figure 4 The control gate of the thyristor can advantageously require a short response time (e.g., on the order of nanoseconds) to trigger the thyristor to the on state and begin receiving current. In this way, the charge extraction process can be enabled quickly after an electron arrival event occurs. Similarly, the thyristor can be automatically turned off when the holding current threshold is met. Therefore, the thyristor can be configured to operate in a fast manner with low power consumption and a simplified control architecture. In addition to thyristors or silicon-controlled rectifiers, other solid-state current control devices can be configured to achieve these advantages.

[0140] When the signal detection unit 641 closes the switch K 13 When the solid-state current control device SSCCD is enabled and the electron arrival event triggers the control gate CG to turn on, the charge can be transferred to the storage capacitor C 11 And is stored. Storage capacitor C 11 The signal at can be output to the voltage comparator A via amplifier or buffer A13. 12 In some embodiments, the storage capacitor C 11 Can form an amplifier or buffer A 13 In some embodiments, the storage capacitor C 11 Can be a separate component. If the storage capacitor C 11 If the signal at is high enough to indicate that an electron arrival event has been detected, the voltage comparator A 12 A high level voltage (or 1 as digital data) can be output to the flip-flop F 11 The data input terminal D of the trigger F 11 The flip-flop F may be, for example, a data or D-type flip-flop circuit and may be configured to pass data at the data input D based on a signal from the clock input CLK. In some embodiments, the flip-flop F 11 It could be another type of flip-flop, a latch, or other logic circuit.

[0141] Voltage Comparator A 11 and resistor R 11 The capacitor C 11The opposite side of the solid state current control device SSCCD. Voltage comparator A 11 and resistor R 11 During each electron arrival event, a trigger F 11 The clock input CLK outputs a negative pulse. The rising positive edge of the negative pulse can be used as an edge trigger to input data from the voltage comparator A at the data input D. 12 Passed to trigger F 11 The output Q and inverting output For example, the first signal from output Q can be a high level voltage or signal value 1, from the inverting output The second signal may be a low level voltage or a signal value of 0.

[0142] From the inverting output The signal value 0 can be output to the AND gate G 11 The lower input terminal of switch K 13 Actuated from closed to open. This may disable the signal detection unit 641 so that the solid state current control device SSCCD is no longer triggered to pass current.

[0143] At the same time, the signal value 1 from output Q can be transferred to the operating state output OP. The signal value 1 from output Q can also be transferred to the operating state output OP via switch K 12 Passed to the enable signal output EN O The operating status output OP can output a signal value 1 as an operating status signal to the control unit, for example Figure 5 The control unit 590 can be enabled. This can indicate to the control unit that an electron arrival event is detected at the signal detection unit 641. The control unit can assign a time stamp to the indicated electron arrival event based on the signal from the operating status output OP. Enable signal output EN O The signal value 1 can be output as an enable signal to another enable signal input EN at the next signal detection unit in the array I The next signal detection unit may then be enabled in the same manner as discussed above with respect to signal detection unit 641 .

[0144] Alternatively, the next signal detection unit in the array may be bypassed, in which case the enable signal may be passed by the bypass circuit through the next signal detection unit. This process may be repeated until the enable signal reaches the signal detection unit that is in an initial state and ready to be enabled. In this way, the signal detection unit may be automatically selected and enabled quickly and continuously in the detection process. The sensing element level architecture according to an embodiment of the present disclosure may perform signal detection unit selection and switching with a fast, simplified, and stable design. In addition, unnecessary signal detection units may be disabled to reduce power consumption in the system. For example, in a bypass detection unit, the transistor M may be connected to the enable circuit, the bypass circuit, or (if present) the transistor M.11 Nonessential components can be powered down.

[0145] The signal detection unit 641 may further include a signal processing output circuit configured to output a signal corresponding to an electron arrival event. The signal processing output circuit may include: an operation state output OP; a sampling control signal input SP; an analog switch K 15 ; and analog signal output A O .

[0146] When the operation status output OP sends a signal to the control unit, for example, as described above, the control unit can determine that the signal detection unit 641 is, for example, storing the capacitor C 11 The control unit can then immediately or later interrogate the signal detection unit to read out the stored signal. The control unit can also generate a time stamp based on the operating state output OP signal to count the electron arrival events.

[0147] To read out the stored signal, a control signal may be sent to the sampling control signal input SP to switch the switch K 15 Actuates from an initial open state to a closed state. Internal amplifier or buffer A 13 can be used to minimize the 15 The state of the voltage comparator A changes 12 In addition, the amplifier or buffer A 13 It can help improve the signal-to-noise ratio (SNR) of the signal detection unit. 15 When closed, the current stored in the storage capacitor C 11 The signal in can be passed through an amplifier or buffer A 13 Transmitted to analog signal output A O and signal processing circuitry. For example, the stored signal may be sent to a voltage comparator, a group of voltage comparators or a data converter, such as Figure 5 The signal processing circuitry may determine, for example, Figure 4 The energy level and overflow information of the electron arrival event discussed. The overflow information may include, for example, a first type or a second type, or other categories of overflow information, such as those disclosed in U.S. Publication No. 2019 / 0379682.

[0148] For example, the analog output A OType 1 overflow may be determined based on information from the signal detection units in the array. Type 2 overflow information may be determined, for example, based on the operational state of the signal detection units in the array. For example, there may be a situation where all signal detection units that are not bypassed are in a state other than an enabled state within a predetermined period of time. Another state may be, for example, a storage state where an electron arrival event has been detected and the signal detection unit has not yet been read out or reset. This may indicate a loss of electron detection due to type 2 overflow during the predetermined period of time. The predetermined period of time may be based on, for example, an average frequency of electron arrival events, as determined by the timing of recent arrival events or by the electron beam current.

[0149] In some embodiments, signal processing in the sensing element level circuit can start when at least two signal detection units of the sensing element level circuit have captured and stored at least two electron arrival events. For example, in some embodiments, the automatic continuous activation of each next signal detection unit can be achieved by maintaining the enable signal from the previous signal detection unit until the next signal detection unit has detected the electron arrival event. This can be achieved by refraining from sending a reset signal to the previous signal detection unit before the next signal detection unit detects the electron arrival event. During the normal operating mode, for example, when only one signal detection unit currently storing information of the electron arrival event remains, the signal processing at the sensing element level circuit can be stopped. Alternatively, if the sensing element is switched from the normal operating mode to the shutdown mode, signal processing can be performed by all signal detection units storing information of the electron arrival event.

[0150] The signal detection unit 641 may further include a reset circuit configured to reset the signal detection unit to an initial state. The reset circuit may include: a reset input R; an analog switch K 14 ; and trigger F 11 . For example, the signal detection circuit may be reset to an initial state after the detection signal has been read out or counted, or when a disabled or bypassed signal detection unit is brought back to a working state. Alternatively, a reset signal may simply be sent to ensure that the signal detection unit is ready to be enabled. In some embodiments, the control unit may send a reset signal when the signal detection unit is a predetermined number of signal detection units downstream of a currently enabled signal detection unit. For example, when the downstream signal detection unit is, for example, five non-bypassed signal detection units away from the currently enabled signal detection unit, the control unit may send a reset signal to ensure that signal detection is ready to be enabled.

[0151] The reset input R can receive a reset signal to enable the switch K 14 This can be provided from the storage capacitor C 11 Clear the charge path. At the same time, a reset signal can be passed to the flip-flop F 11 The clear input CLR is used to clear the trigger F11 reset to their initial state. For example, clearing the reset signal at input CLR ensures that outputs Q and The values ​​are 0 and 1 respectively. The 0 output at Q can be enabled at the enable signal output EN O This can stop the enable signal input EN to the next signal detection unit. I Sends an enable signal. At the same time, The I output at the signal detection unit 641 can enable the signal detection unit 641 at its own enable signal input EN I In some embodiments, other signals may be sent to the signal detection unit 641, and other operations may be performed to reset the signal detection unit to an initial state. For example, if the switch K 15 If the switch K is set to the off state, a signal can be sent to the sampling control output SP. 11 and K 12 must be reversed from their current state, the bypass signal can be sent to the bypass input BP. After the reset is completed, the signal detection unit is in the initial state again and is ready to be activated at the enable signal input EN. I Receive an enable signal at.

[0152] The above circuits and components are provided as examples to illustrate the signal detection circuit (eg Figure 5 A possible implementation of a signal detection unit in the circuit 500 of FIG. 500. In some embodiments, the same or similar functions can be implemented by other combinations of switches, logic components, amplifiers, and other circuit elements. For example, in some embodiments, the AND gate G 11 Another logic gate may be included, such as OR, XOR, NOT, NAND, NOR, XNOR, etc. In such an embodiment, other circuits may be configured to provide logic gate G 11 Provide appropriate input so that it switches K in the desired manner 13 Or corresponding to switch K 13 Generally speaking, in some embodiments of the present invention, a variety of different configurations may be used to perform functions such as enable, bypass, current detection, readout, and reset circuits.

[0153] according to Figure 5 and Figure 6 Embodiments of the invention can advantageously provide energy level and overflow information of electron detection events. However, in some embodiments, such information may not be required. In this case, a more simplified and streamlined pure electron counting structure can be provided.

[0154] Figure 7A simplified block diagram illustrating a sense element level readout circuit design 700 with its corresponding sense element 711 according to an embodiment of the present invention is shown. The sense element 711 may correspond to Figure 3A - Figure 3C Any sensing element 311-314 or Figure 5 Sensing element 511. Sensing element 711 may be a charged particle sensing element configured to generate an electrical signal in response to a charged particle arrival event. The electrical signal may be, for example, a charge, a current, or a voltage. In some embodiments, sensing element 711 may be a photon sensing element.

[0155] The circuit 700 may include a signal detection unit array 740, such as signal detection units 741, 742, etc., until 749. In some embodiments, the circuit 700 may have Figure 5 The circuit 500 is similarly configured except for the differences discussed below. Similar components may be labeled with a leading 7 instead of a leading 5. In some embodiments, Figure 7 The differences in may represent structural differences, and in some embodiments, they may represent operational differences. For example, Figure 5 The components that exist in Figure 7 In some embodiments, this omission may represent a structural difference and may indicate that the component may not be present in the circuit 700. In some embodiments, this omission may represent an operational difference and may indicate that the component may be present but not used in the sensing element level readout circuit design 700. For example, the component may be powered off or electrically decoupled from the illustrated components of the circuit 700 because it is not necessary for the operation of the present disclosure. Figure 6 The same relationship associated with the signal detection unit 641 can be applied to Figure 8 The signal detection unit 841.

[0156] In the absence of a need for detailed information about each electron arrival event (e.g., energy level information), the sensing element circuits 741-749 can operate in a simpler manner, which requires a less active role from the control unit 790. The start process can be similar to that described above with respect to Figure 5 The signal detection unit (e.g., 741) may be enabled by an enable signal from, for example, a logic gate XOR. Alternatively, the signal detection unit 741 may be bypassed, in which case the enable signal may be passed to another signal detection unit. The triggering and detection of electron arrival events may also be similar to Figure 5 However, the signal detection unit in the array 740 may not be configured with an analog signal output A OOr sampling control signal input SP. Instead, signal detection can be registered at control unit 790 simply based on the signal from the operating state output OP of each unit in array 740. This mode of operation can be similar to a ring oscillator formed by one or more delay lines, for example. The signal can be time-stamped, for example, at the sensing element stage circuit 700 and used for simple and robust electron counting.

[0157] In some embodiments, the process of obtaining the count result can be further simplified. For example, the sensing element level circuit 700 can count the cycle of the array 740 instead of counting the signal detection at each signal detection unit. For example, by counting the number of first operating state output signals of, for example, the first signal detection unit 741 (assuming it is not bypassed or otherwise disabled), or the number of last operating state output signals of the last signal detection unit 749 (assuming it is not bypassed or otherwise disabled), or both, the sensing element level circuit 700 can determine how many times the entire array of signal detection units has been cycled through. Alternatively, the sensing element level circuit can be configured to output a final enable signal EN from a logic gate XOR or a final enable signal of, for example, the final signal detection unit 749. O To this end, the logic gate XOR or final enable signal output EN of the final signal detection unit 749 OAnother output (not shown) coupled to the control unit 790 may be included. In this way, the control unit can count the number of cycles of the array 740 without receiving any operating state signal from the operating state output OP until a residue count (hereinafter) is required. When the number of cycles of the array 740 is known, electron counting can be achieved. For example, the control unit can multiply the number of entire detection cycles by the number of signal detection units in the array 740 that are not bypassed, and add the residue (e.g., the number of residual detections remaining in the last partial cycle of the array 740). In order to obtain the residue, the operating state of all non-bypassed units can be obtained by the control unit 790. Using this counting system, only the last remaining cycle needs to count each signal detection unit. In addition, by bypassing a specific number of signal detection units, the cycle length can be modified as needed. Doing so can adapt the cycle length to operating conditions such as beam current. For example. When the beam current is high, the frequency of events where electrons arrive at the sensing element may be high, which may result in a high frequency of the entire detection cycle. Because the reset operation of the signal detection unit requires a certain amount of time, it may be necessary to reduce the cycle frequency to avoid, for example, type 2 overflow. To reduce the cycle frequency, more signal detection units can be started to increase the cycle length. However, when the frequency of electron arrival events is low (e.g. due to low beam current), so many signal detection units may not be needed. In this case, the cycle length can be shortened by bypassing some signal detection units to reduce power consumption or increase the life of the signal detection units.

[0158] Figure 8 A simplified diagram showing an example of the internal circuitry of the signal detection unit 841 according to some embodiments of the present disclosure. The signal detection unit 841 may be, for example Figure 7 A possible implementation of the signal detection units 741-749.

[0159] The signal detection unit 841 can be similar to Figure 6 However, since the signal detection unit 841 can be designed for electron counting without detecting energy levels, etc., the signal detection unit 841 can be made simpler. For example, the signal detection unit 841 can be omitted. Figure 6 The sampling control signal input SP, analog signal output A O and amplifier or buffer A 13 As mentioned above Figure 7 As described above, electronic counting can be simply realized by, for example, outputting a signal from the operating state output OP. The signal from the operating state output OP can be, for example, based on the signal from the comparator A 12 The input from the flip-flop F 11 However, once the comparator A 12This output is sent to the flip-flop F 11 , capacitor C is no longer needed 11 To store the charge it receives from the solid-state current control device SSCCD.

[0160] Because the capacitor C 11 There is no need to hold the charge for later readout, so the reset operation at the reset input R can be performed after the next signal detection unit has registered an electron arrival event. The signal detection unit 841 may provide lower power consumption and manufacturing cost than other designs.

[0161] Fig.9A 1 is a flow chart showing a method 900A for charged particle detection according to an embodiment of the present disclosure. The method 900A may be implemented by, for example, a sensing element level circuit (such as Figure 5 The sensing element level circuit 500 may include circuits (e.g., memory and processor) programmed to implement the method 900. The signal detection unit, such as Figure 6 The signal detection unit 641 may operate according to the method 900. Processing consistent with the method 900 may be performed on a sensing element by sensing element basis.

[0162] In step 901, a first signal detection unit may receive an enable signal to activate the signal detection unit from an initial state. The first signal detection unit may be a first non-bypass signal detection unit in an array of signal detection units. The first signal detection unit may receive an enable signal from, for example, a logic gate based on an enable signal from a control unit. When enabled by the enable signal, a solid-state current control device within the first signal detection unit may be configured to receive a signal from a sensing element. For example, the enable signal may close a switch, thereby allowing a control gate of the solid-state current control device to receive current. The solid-state current control device may be, for example, a silicon-controlled rectifier or other thyristor. Alternatively, the first signal detection unit of method 900A may receive an enable signal from an enable signal output of a previous signal detection unit.

[0163] In step 902, the signal detection unit receives a signal from the sensing element. The sensing element can be coupled to the analog signal input of the detection unit via, for example, an input bus. The signal detection unit can be coupled to the analog signal input of each signal detection unit of the array via an input bus. The signal can be generated at the sensing element by an arrival event (e.g., an electron arrival event) and passed to the solid-state current control device. If the signal exceeds the trigger threshold at the control gate of the solid-state current control device, the solid-state current control device can be turned on and begin to extract current from the sensing element. The solid-state current control device can remain turned on and continue to extract current while the current remains at or above the holding current. The extracted current can be passed to a storage capacitor and stored. When the current drops below the holding current, the solid-state current control device can be turned off and the extraction can be stopped.

[0164] In step 903, the signal detection unit may generate an operating state output signal. The operating state output signal may indicate to the control unit that an electron arrival event has occurred. For example, the control unit may generate a timestamp for counting electron arrival events based on the operating state output signal. When, for example, a trigger circuit transmits a data input signal from another voltage comparator at another terminal of the storage capacitor based on a clock input signal from a voltage comparator at one terminal of the storage capacitor, an operating state output signal may be generated. The data may be transferred to the output of the trigger. The output of the trigger may generate an operating state output signal. The output of the trigger may also generate a new enable signal to the enable signal output discussed in step 906.

[0165] At step 904, the signal detection unit may generate an analog output signal. For example, after the control unit determines that an electron arrival event has occurred based on the operating state output signal, the control unit may send a sampling control signal to the switch via a sampling control signal input. The switch may close a path between the charge stored in the signal storage circuit and the analog output of the signal detection unit to generate the analog output signal. The analog output signal may be transmitted to, for example, a signal processing circuit device via an analog signal bus.

[0166] At step 905, the analog output signal may be processed by a signal processing circuit device. For example, the signal processing circuit device may include a voltage comparator, a group of voltage comparators, or a data converter such as an analog-to-digital converter (ADC). The signal processing circuit device may process the analog output signal to determine information about the relevant detection event, such as energy level or overflow information.

[0167] At step 906, the first signal detection unit may generate a next enable signal to activate the next signal detection unit in the array. For example, as discussed above in step 903, the enable signal may be generated simultaneously with the generation of the operating state output signal. The enable signal may proceed from the enable signal output of the first signal detection unit to the enable signal input of the next signal detection unit. At this point, the process may return to step 901 and repeat for the next signal detection unit.

[0168] On the other hand, if the next signal detection unit is in the bypass state, the enable signal can pass directly through the next signal detection unit along the bypass circuit to its own enable signal output terminal. Then, the enable signal can be passed to another enable signal input terminal of another signal detection unit. This can continue until the enable signal reaches the non-bypass signal detection unit, at which time the non-bypass signal detection unit can be enabled.

[0169] The second loop of method 900A is illustrated by the language in brackets at steps 901 and 906. In the second iteration of step 901, the next signal detection unit may receive the enable signal sent by the first signal detection unit in the first iteration of step 906. After the next signal detection unit receives and processes the electron arrival event in the second iteration of steps 902-905, the next signal detection unit may generate another enable signal in the second iteration of step 906 to activate another signal detection unit in the array.

[0170] Fig. 9B is a flow chart showing a method 900B for charged particle detection according to an embodiment of the present disclosure. The method 900B includes a reset method and may be combined with, for example, Fig.9A For example, method 900B may be initiated after the detection operation is enabled at step 901 of method 900A, and may continue for the duration of the detection operation. Method 900B may be performed by, for example, a sensing element level circuit (such as a detector) in a detector of a charged particle beam system. Figure 5 The sensing element level circuit 500 may include circuits (e.g., memory and processor) programmed to implement the method 900. The signal detection unit, such as Figure 6 The signal detection unit 641 may operate according to method 900. Processing consistent with method 900B may be performed on a sensing element by sensing element basis.

[0171] In step 910, a control unit (e.g., a control unit of a sensing element level circuit, a higher level control unit of a charged particle detector, or another control unit of a charged particle beam device) may determine whether more than one signal detection unit has received and processed an electron arrival event. For example, the control unit may make this determination based on the operating state of the signal detection unit output generated in step 903 of method 900A. In some embodiments, method 900B may not continue until the dual unit condition is met, as indicated by a "no" output "N" leading back to the input of step 910. When the condition is met, the method may proceed to step 911.

[0172] In step 911, the control unit may determine whether information from more than one signal detection unit (e.g., information from an analog signal output) has been processed. For any signal detection unit that has information that has been processed, the method may proceed to step 912. Otherwise, the method may return to step 910, and the processing cycle may begin again.

[0173] In step 912, the control unit may determine whether any signal detection unit through step 911 is storing the most recently captured electron arrival event. For the signal detection unit storing the most recently captured electron arrival event, the process also returns to step 910. In this way, the signal detection unit storing the most recently captured electron arrival event may continue to enable the currently enabled signal detection unit.

[0174] However, at step 913, the remaining signal detection units may be reset to an initial state, for example, by transmitting a reset signal to a reset input of the signal detection unit. The reset signal may clear any charge at the storage capacitor, for example by closing a switch to discharge any stored charge. The reset signal may also restore the internal logic circuit to an initial state. For example, the reset signal may be transmitted to a clear input of a flip-flop circuit to prepare another enable signal for the flip-flop. Once placed in the initial state, the signal detection unit may prepare another enable signal to repeat the process of method 900B and, for example, method 900A.

[0175] Methods 900A and 900B may provide a fast, simplified, robust signal detection method that reduces the need for active control circuitry to keep the process moving while maintaining, for example, Figure 4 All functionality of the disclosed comparison system. However, if complex detection information such as energy levels and spillover is not required, an approach using a simpler architecture can be adopted.

[0176] Fig. 10A1 is a flow chart showing a method 1000A for charged particle detection according to an embodiment of the present disclosure. The method 1000A may be implemented by, for example, a sensing element level circuit (such as Figure 5 The sensing element level circuit 500 or Figure 7 The sensing element level circuit may include circuits (e.g., memory and processor) programmed to implement method 1000A. A signal detection unit, such as Figure 6 The signal detection unit 641 or Figure 8 The signal detection unit 841 may operate according to the method 1000A. Processing consistent with the method 1000A may be performed on a sensing element by sensing element basis. Fig. 10A Steps 1001, 1002 and 1004 may be performed similarly to Fig.9A The method is performed in the manner of steps 901, 902 and 906. Therefore, a detailed description is omitted here.

[0177] Step 1003 may also be performed in a similar manner to the counting and time stamping referenced in step 903. For example, when the operating status output signal is sent to the control unit, the control unit may generate a time stamp representing the electron arrival event. The control unit may use the time stamp or other digital information based on the operating status output signal to keep a count of events (e.g., electron arrival events) during the detection process.

[0178] In this way, when the energy level discrimination function is not required, Fig. 10A The method 1000A can also be performed on a simplified circuit. For example, steps 1001-1004 of the method 1000A can be performed on a simplified circuit. Figure 7 The sensing element level circuit 700 uses, for example Figure 8 The signal detection unit shown is designed for implementation without using components for example for reading out energy level information.

[0179] Fig. 10B is a flow chart showing a method 1000B for charged particle detection according to an embodiment of the present disclosure. The method 1000B includes a reset method and may be combined with, for example, Fig. 10A Method 1000A may be performed. Method 1000B may be, for example, a simplified version of method 900B. For example, Fig. 10B Steps 1010-1012 can be respectively performed similar to Fig. 9B Therefore, detailed description is omitted here. However, method 1000B may omit the step of determining whether the information from the signal detection unit has been processed (e.g., in Fig. 9B In step 911 of Fig. 10A - Fig. 10B Therefore, step 1011 may proceed directly to the reset step 1012 without making such a determination and without waiting for information from the analog signal output to be processed before resetting the signal detection unit.

[0180] Furthermore, in some embodiments of the present disclosure, the amount of counting may be reduced by counting the entire cycle of the signal detection unit instead of counting each detection event of each signal detection unit. Fig.11A and 11B 1 is a flow chart illustrating methods 1100A and 1100B for charged particle detection according to an embodiment of the present disclosure. For example, when a separate timestamp is not required for each electron arrival event, methods 1100A and 1100B may be preferred. Methods 1100A-1100B may be implemented, for example, by a sensing element level circuit (such as Figure 5 The sensing element level circuit 500 or Figure 7 The sensing element level circuit may include circuits (eg, memory and processor) programmed to implement the methods 1100A-1100B. Figure 6 The signal detection unit 641 or Figure 8 The signal detection unit of the signal detection unit 841 may operate according to the methods 1100A-1100B. Processing consistent with the methods 1100A-1100B may be performed on a sensing element by sensing element basis. Fig.11A Steps 1101, 1102 and 1104 may be performed similar to Fig.9A Steps 901, 902 and 906 or Fig. 10A Therefore, the detailed description is omitted here. In addition, the reset operation can be performed according to, for example, steps 1001, 1002 and 1004. Fig. 10B The method 1000B is performed.

[0181] In step 1103, the signal detection unit may be similar to Fig.9A Step 903 or Fig. 10A The operating status output is generated in the manner of step 1003. The generation of a new enable signal at step 1104 can be performed as described above. However, step 1103 can be different because not every timestamp of each signal detection unit can be counted. Instead, the control unit can count electron arrival events in multiples of the entire detection cycle.

[0182] Fig. 11BMethod 1100B of FIG. 1100B illustrates a cycle counting method that can be used, for example, in conjunction with method 1100A. Method 1100B can count detection cycles during a sampling period set by, for example, a control unit. In step 1105, the control unit can determine an operating status output (e.g., Fig.11A The control unit may determine whether the signal detection unit generating the operating status output is a counting unit. The counting unit may be, for example, a signal detection unit used to determine whether a full cycle of signal detection has occurred in the array of signal detection units. For example, the first non-bypass signal detection unit in the array, the last non-bypass signal detection unit in the array, or both may be used as counting units. In general, any signal detection unit may be used as a counting unit. Alternatively, method 1100 may include a final enable signal output EN from, for example, a logic gate XOR or a final signal detection unit in the array. O Receive individual cycle output signals. In addition, a full or partial cycle may be determined by other detection units in the array. For example, if there are any signal detection units other than the first or last signal detection unit used as a counting unit that have a high value (or 1) at its operating state output OP, the cycle may be determined to be not a full cycle. In this way, the control unit may count the number of cycles of the array without summing each operating state signal from the operating state output OP unless a residual count is required.

[0183] If the detection does represent a full cycle, the method 1100B may proceed to step 1106 where a full detection cycle time stamp is generated at the control unit. If the detection does not represent a full cycle, the method may proceed to step 1107.

[0184] At step 1107, the control unit may determine whether the sampling period has ended. The sampling period may occur based on a predetermined timing setting set by, for example, the control unit. In some embodiments, the sampling period may correspond to a normal operating period of the charged particle beam device. In some embodiments, the sampling period may correspond to another timing interval. If the sampling period has not ended, processing continues as shown in step 1108. If the sampling period has ended, the method may proceed to step 1109.

[0185] At step 1109, the remainder may be counted and added to the entire detection cycle. The remainder may include a timestamp from an operating state signal retained by the control unit from the last partial cycle of the signal detection unit. For example, if the signal detection unit array includes ten active units, each full cycle represents ten signal detection events. However, as described above, the sampling cycle may partially end in the entire detection cycle, for example, when only five signal detection units record an event. In this case, the control unit may count the individual operating state output signals from the signal detection unit to generate an accurate count of the detection event. The full cycle may be added to the remainder to determine the full count of the detection event. For example, in the example of 10 units above, the control unit may multiply the number of full cycle counts by the number of valid units in the array (10). Then add the remainder (5 in the above embodiment). The sum of the full cycle and the remainder may represent the total count of the charged particle detection event during the sampling cycle. Method 1100B may be used to generate an accurate count of the detection event while minimizing the actual count performed by the signal processing circuit device.

[0186] The data from all sensing element level circuits within the charged particle detector can be summed on a sampling period by sampling period basis. In this way, detection results similar to or the same as the counting method described above can be generated.

[0187] Additionally, the method 1100B can customize the detection operation by selecting an optimal number of signal detection units in the array. Signal bypass circuits can be used to power down and bypass unneeded signal detection units.

[0188] As an alternative to counting method 1100B, a higher level control unit, such as a detector level control unit, can obtain full cycle timestamps for each sensing element level circuit, for example, when they are generated. Thus, the detector can sum all full cycle counts from each sensing element in the detector. A non-transitory computer readable medium can be provided that stores information for use by a controller (e.g., Figure 5 Controller 590 or Figure 7Instructions for a processor of a controller 790 in the embodiment of the present invention to detect charged particles according to the exemplary flow charts of (for example) Figures 9-11 are consistent with embodiments of the present invention. For example, instructions stored in a non-transitory computer readable medium can be executed by circuitry of a controller to perform method 900, method 1000, or method 1100 in part or in whole. 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 cartridges, and networked versions thereof.

[0189] Embodiments of the present disclosure may be further described by the following clauses:

[0190] 1. A method for detecting charged particle events in a charged particle counting detector, comprising:

[0191] enabling, by the charged particle counting detector, a first solid-state current control device, i.e., a first SSCCD, of a first signal detection unit to place the first SSCCD in an on-state in which the first SSCCD is capable of conducting current from a charged particle sensing element of the charged particle counting detector;

[0192] outputting, by the charged particle sensing element, a first current pulse from the charged particle sensing element in response to a first charged particle arriving at the charged particle sensing element, wherein the first current pulse triggers the first SSCCD to the on state;

[0193] in response to the first SSCCD being triggered to the on-state, conducting the first current pulse from an input to an output of the first SSCCD; and

[0194] receiving a second enable signal at a second signal detection unit including a second SSCCD, the second enable signal being based on the first current pulse,

[0195] The second enabling signal enables the second SSCCD of the second signal detecting unit to put the second SSCCD into an on state in which the second SSCCD can conduct current from the charged particle sensing element.

[0196] 2. The method of clause 1, wherein the first SSCCD or the second SSCCD comprises a thyristor.

[0197] 3. The method of clause 1, wherein enabling the first SSCCD of the first signal detection unit comprises closing an enable switch to couple a first control gate of the first SSCCD to an anode of the first SSCCD.

[0198] 4. The method of clause 1, wherein enabling the first SSCCD of the first signal detection unit comprises receiving an initial enable signal from a control unit of a sensing element level circuit of the charged particle counting detector.

[0199] 5. The method according to clause 1, further comprising:

[0200] In response to the first current pulse exceeding a threshold, current is initiated through the first SSCCD.

[0201] 6. The method according to clause 1, further comprising:

[0202] In response to the first current pulse falling below a threshold, conducting current by the first SSCCD is ceased.

[0203] 7. The method of clause 6, wherein ceasing conduction of current by the first SSCCD comprises ceasing conduction of current by self-stopping of the first SSCCD.

[0204] 8. The method according to clause 1, further comprising:

[0205] transmitting the first current pulse output from the first SSCCD to a storage capacitor by a current detection circuit of the first signal detection unit; and

[0206] A signal corresponding to the first current pulse is stored at the storage capacitor.

[0207] 9. The method according to clause 1, further comprising:

[0208] An operation state output signal is generated by a signal processing output circuit of the first signal detection unit based on the first current pulse.

[0209] 10. The method according to clause 9, further comprising:

[0210] transmitting the operating status output signal to a signal processing circuit device by the signal processing output circuit; and

[0211] Charged particle arrival events are detected at the signal processing circuitry based on the operating state output signal.

[0212] 11. The method according to clause 9, further comprising:

[0213] transmitting the operating status output signal to a signal processing circuit arrangement via the signal processing output circuit; and

[0214] counting full cycles of charged particle arrival events at the signal processing circuitry based on the operating state output signal,

[0215] Wherein the number of charged particle arrival events counted in the full cycle corresponds to the number of non-bypassed signal detection units coupled to the output of the charged particle sensing element.

[0216] 12. The method according to clause 1, further comprising:

[0217] The second enable signal is generated by an enable circuit of the first signal detection unit based on the first current pulse.

[0218] 13. The method according to clause 1, further comprising:

[0219] generating a detection result signal at an analog signal output of the first signal detection unit by a signal processing output circuit of the first signal detection unit; and

[0220] The detection result signal is transmitted to the signal processing circuit device.

[0221] 14. The method according to clause 13, further comprising:

[0222] The energy level information of the detection result signal is processed at the signal processing circuit device.

[0223] 15. The method according to clause 13, further comprising:

[0224] Overflow information of the detection result signal is processed at the signal processing circuit device.

[0225] 16. The method according to clause 13, further comprising:

[0226] A sampling control signal is inputted to the sampling control signal input terminal of the first signal detection unit by the control unit of the sensing element level circuit to generate the detection result signal at the analog signal output.

[0227] 17. The method according to clause 1, further comprising:

[0228] The first signal detection unit is reset to an initial state by a reset circuit of the first signal detection unit,

[0229] Wherein in the initial state, the first signal detection unit is configured to be enabled by another enabling signal.

[0230] 18. The method according to clause 1, further comprising:

[0231] bypassing the third signal detection unit including the third SSCCD by the bypass circuit of the third signal detection unit,

[0232] The bypass circuit is configured to enable a signal to pass from the enable signal input of the third signal detection unit to the enable signal output of the third signal detection unit without enabling the third SSCCD of the third detection unit to place the third SSCCD in the on-state in which the third SSCCD is able to conduct current from the charged particle sensing element.

[0233] 19. The method of clause 1, wherein the charged-particle sensing element comprises a PIN diode.

[0234] 20. The method of clause 1, wherein the first charged particles reaching the charged-particle sensing element include electrons.

[0235] 21. A charged particle counting detector, comprising:

[0236] a charged particle sensing element configured to output a first current pulse in response to a first charged particle arriving at the charged particle sensing element;

[0237] a first signal detection unit, comprising a first solid-state current control device, i.e., a first SSCCD, the first solid-state current control device being configured to: a) be enabled by a first enable signal to be placed in an on-state in which the first SSCCD is capable of conducting current from the charged-particle sensing element, b) be triggered to the on-state by the first current pulse, and c) conduct the first current pulse to an output of the first SSCCD in response to the first SSCCD being triggered to the on-state; and

[0238] A second signal detection unit is configured to receive a second enable signal and includes a second SSCCD configured to be enabled by the second enable signal to be placed in an on-state in which the second SSCCD can conduct current from the charged-particle sensing element.

[0239] 22. A charged particle counting detector according to clause 21, wherein the first SSCCD or the second SSCCD comprises a thyristor.

[0240] 23. The charged particle counting detector of clause 21, the first SSCCD of the first signal detection unit being configured to be enabled by closing an enable switch to couple a first control gate of the first SSCCD to an anode of the first SSCCD.

[0241] 24. The charged particle counting detector according to clause 21, the first signal detection unit being configured to receive the first start signal from a control unit.

[0242] 25. The charged particle counting detector of clause 21, wherein the first SSCCD is configured to begin conducting current in response to the first current pulse exceeding a threshold value.

[0243] 26. The charged particle counting detector of clause 21, wherein the first SSCCD is configured to cease conducting current in response to the first current pulse falling below a threshold value.

[0244] 27. The charged particle counting detector of clause 26, wherein ceasing to conduct current through the first SSCCD comprises ceasing to conduct current through self-deactivation of the first SSCCD.

[0245] 28. A charged particle counting detector according to clause 21, wherein:

[0246] The first SSCCD is configured to transmit the first current pulse to a storage capacitor; and

[0247] The storage capacitor is configured to store a signal corresponding to the first current pulse.

[0248] 29. The charged particle counting detector of clause 21, wherein the first signal detection unit is configured to generate an operating status output signal based on the first current pulse.

[0249] 30. The charged particle counting detector according to clause 29, further comprising a signal processing circuit device;

[0250] in:

[0251] The first signal detection unit is configured to transmit the operating status output signal to the signal processing circuit device; and

[0252] The signal processing circuitry is configured to detect a charged particle arrival event based on the operating state output signal.

[0253] 31. The charged particle counter according to clause 29 further comprising a signal processing circuit device,

[0254] in:

[0255] The first signal detection unit is configured to transmit the operating state output signal to the signal processing circuit device;

[0256] The signal processing circuitry is configured to count full cycles of charged particle detection events based on the operating state output signal; and

[0257] The number of charged particle arrival events counted in the full cycle corresponds to the number of non-bypassed signal detection units coupled to the output of the charged particle sensing element.

[0258] 32. The charged particle counting detector of clause 21, wherein the first signal detection unit is configured to generate the second start signal based on the first current pulse.

[0259] 33. A charged particle counting detector according to clause 21, further comprising a signal processing circuit device,

[0260] Wherein the first signal detection unit is configured as:

[0261] generating a detection result signal at an analog signal output of the first signal detection unit; and

[0262] The detection result signal is transmitted to the signal processing circuit device.

[0263] 34. A charged particle counting detector according to clause 33, wherein the signal processing circuit device is configured to process energy level information of the detection result signal.

[0264] 35. A charged particle counting detector according to clause 33, wherein the signal processing circuit device is configured to process overflow information of the detection result signal.

[0265] 36. A charged particle counting detector according to clause 33, wherein the first signal detection unit is configured to generate the detection result signal at the analog signal output in response to receiving a sampling control signal at a sampling control signal input of the first signal detection unit.

[0266] 37. A charged particle counting detector according to clause 21, wherein:

[0267] The first signal detection unit is configured to be reset to an initial state by a reset signal; and

[0268] In the initial state, the first signal detection unit is configured to be enabled by another enabling signal.

[0269] 38. A charged particle counting detector according to clause 21, wherein:

[0270] The first signal detection unit includes a bypass circuit; and

[0271] The bypass circuit is configured to cause a signal to pass from an enable signal input of the first signal detection unit to an enable signal output of the first signal detection unit without enabling the first detection unit to place the first detection unit in an on-state in which the first SSCCD is capable of conducting current from the charged particle sensing element.

[0272] 39. The charged particle counting detector of clause 21, wherein the charged particle sensing element comprises a PIN diode.

[0273] 40. The charged particle counting detector of clause 21, wherein the first charged particles reaching the charged particle sensing element comprise electrons.

[0274] 41. The charged particle counting detector according to clause 21, wherein the second signal detection unit is configured to receive the second start signal from the first signal detection unit.

[0275] 42. A charged particle counting detector, comprising:

[0276] Charged particle sensing element;

[0277] A first signal detection unit is coupled to the output of the charged particle sensing element and is configured to:

[0278] receiving a first charged particle arrival signal from the charged particle sensing element based on a first charged particle arrival event at the charged particle sensing element, and

[0279] generating a detection output based on the first charged-particle arrival signal, the detection output comprising information about the first charged-particle arrival event; and

[0280] A second signal detection unit is coupled to the output of the charged particle sensing element and is configured to receive an enable signal based on the first charged particle arrival signal, and the enable signal is configured to enable the second signal detection unit to receive a second charged particle arrival signal from the charged particle sensing element based on a second charged particle arrival event at the charged particle sensing element.

[0281] 43. A signal detection unit for a charged particle counting detector, comprising:

[0282] an enable signal input configured to receive a first enable signal to enable the signal detection unit to detect a charged particle arrival signal from a charged particle sensing element;

[0283] an analog signal input configured to receive the charged particle arrival signal from the charged particle sensing element;

[0284] an operation status output unit configured to output an operation status signal based on the charged particle arrival signal; and

[0285] An enable signal output is configured to output a second enable signal to be provided to another signal detection unit based on the charged particle arrival signal.

[0286] 44. The signal detection unit according to clause 43, further comprising:

[0287] The analog signal output is configured to output a detection signal based on the charged particle arrival signal.

[0288] 45. The signal detection unit of clause 44, wherein the analog signal output comprises energy level information of the charged particle arrival signal.

[0289] 46. ​​The signal detection unit of clause 44, wherein the analog signal output comprises overflow information of the charged particle arrival signal.

[0290] 47. The signal detection unit according to clause 44, further comprising:

[0291] a sampling control signal input configured to receive a sampling control signal;

[0292] The analog signal output is configured to output the detection signal in response to receiving the sampling control signal.

[0293] 48. The signal detection unit according to clause 43, further comprising:

[0294] A bypass signal input is configured to input a bypass signal;

[0295] Wherein the bypass signal is configured to close a path between the enable signal input and the enable signal output.

[0296] 49. The signal detection unit according to clause 43, further comprising:

[0297] A reset signal input configured to receive a reset signal;

[0298] The reset signal is configured to reset the signal detection unit to an initial state, wherein in the initial state the signal detection unit is configured to be enabled by a third enabling signal.

[0299] 50. A non-transitory computer readable medium storing a set of instructions executable by at least one processor of a device to cause the device to perform a method comprising:

[0300] enabling a first solid-state current control device, i.e., a first SSCCD, of a first signal detection unit to place the first SSCCD in an on-state in which the first SSCCD is capable of conducting current from a charged particle sensing element of a charged particle counting detector;

[0301] outputting a first current pulse from the charged particle sensing element in response to a first charged particle arriving at the charged particle sensing element, wherein the first current pulse triggers the first SSCCD to the on-state;

[0302] in response to the first SSCCD being triggered to the on-state, conducting the first current pulse from an input to an output of the first SSCCD; and

[0303] receiving a second enable signal at a second signal detection unit including the second SSCCD, the second enable signal being based on the first current pulse,

[0304] The second start signal enables the second SSCCD of the second signal detection unit to put the second SSCCD into an on state in which the second SSCCD can conduct current from the charged particle sensing element.

[0305] 51. The non-transitory computer-readable medium of clause 50, wherein the first SSCCD or the second SSCCD comprises a thyristor.

[0306] 52. The non-transitory computer-readable medium of clause 50, wherein enabling the first SSCCD of the first signal detection unit comprises closing an enable switch to couple a first control gate of the first SSCCD to an anode of the first SSCCD.

[0307] 53. The non-transitory computer-readable medium of clause 50, wherein enabling the first control gate of the first SSCCD of the first signal detection unit comprises receiving an initial enable signal from a control unit of the sensing element level circuit of the charged particle detector.

[0308] 54. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0309] In response to the first current pulse exceeding a threshold, current is initiated through the first SSCCD.

[0310] 55. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0311] In response to the first current pulse falling below a threshold, conducting current by the first SSCCD is ceased.

[0312] 56. The non-transitory computer-readable medium of clause 55, wherein ceasing to conduct current through the first SSCCD comprises ceasing to conduct current through self-deactivation of the first SSCCD.

[0313] 57. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0314] transmitting the first current pulse from the output of the first SSCCD to a storage capacitor: and

[0315] A signal corresponding to the first current pulse is stored at the storage capacitor.

[0316] 58. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0317] An operating status output signal is generated based on the first current pulse.

[0318] 59. The non-transitory computer-readable medium of clause 58, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0319] transmitting the operating status output signal to a signal processing circuit device; and

[0320] Charged particle arrival events are detected at the signal processing circuitry based on the operating state output signal.

[0321] 60. The non-transitory computer-readable medium of clause 58, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0322] transmitting the operating status output signal to a signal processing circuit device; and

[0323] counting full cycles of charged particle arrival events at the signal processing circuitry based on the operating state output signal,

[0324] Wherein the number of charged particle arrival events counted in the full cycle corresponds to the number of non-bypassed signal detection units coupled to the output of the charged particle sensing element.

[0325] 61. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0326] The second enable signal is generated based on the first current pulse.

[0327] 62. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0328] generating a detection result signal at an analog signal output of the first signal detection unit; and

[0329] The detection result signal is transmitted to the signal processing circuit device.

[0330] 63. The non-transitory computer-readable medium of clause 62, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0331] The energy level information of the detection result signal is processed at the signal processing circuit device.

[0332] 64. The non-transitory computer-readable medium of clause 62, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0333] Overflow information of the detection result signal is processed at the signal processing circuit device.

[0334] 65. The non-transitory computer-readable medium of clause 62, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0335] A sampling control signal is input to a sampling control signal input of the first signal detection unit to generate the detection result signal at the analog signal output.

[0336] 66. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0337] resetting the first signal detection unit to an initial state,

[0338] Wherein in the initial state, the first control gate of the first signal detection unit is configured to be enabled by another enabling signal.

[0339] 67. The non-transitory computer-readable medium of clause 50, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform:

[0340] bypassing the third signal detection unit including the third SSCCD by the bypass circuit of the third signal detection unit,

[0341] The bypass circuit is configured to enable a signal to pass from the enable signal input of the third signal detection unit to the enable signal output of the third signal detection unit without enabling the third SSCCD of the third detection unit, placing the third SSCCD in an on state in which the third SSCCD is able to conduct current from the charged particle sensing element.

[0342] 68. The non-transitory computer-readable medium of clause 50, wherein the charged-particle sensing element comprises a PIN diode.

[0343] 69. The non-transitory computer-readable medium of clause 50, wherein the first charged particles reaching the charged-particle sensing element include electrons.

[0344] 70. The non-transitory computer-readable medium of clause 50, wherein the device comprises a sensing element level circuit of a charged particle detector.

[0345] 71. A non-transitory computer readable medium storing a set of instructions executable by at least one processor of a device to cause the device to perform a method comprising:

[0346] enabling a first solid-state current control device SSCCD, i.e., a first SSCCD, of a first signal detection unit of a charged particle detector to place the first SSCCD in an on-state in which the first SSCCD is capable of conducting current from a charged particle sensing element of the charged particle counting detector, wherein

[0347] the charged particle sensing element being configured to output a first current pulse in response to the first charged particle arriving at the charged particle sensing element, wherein the first current pulse triggers the first SSCCD to the on-state;

[0348] in response to the first SSCCD being triggered to the on-state, causing the first signal detection unit to conduct the first current pulse to the output of the first SSCCD, and

[0349] receiving an enable signal at a second signal detection unit including a second SSCCD, the enable signal being based on the first current pulse, wherein

[0350] The second SSCCD of the second signal detection unit is enabled by the enable signal to put the second SSCCD into an on-state in which the second SSCCD can conduct current from the charged-particle sensing element.

[0351] The block diagrams in the figures may illustrate the possible implementation architecture, functions and operations of the systems, methods and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block in the schematic diagram may represent certain arithmetic or logic operations that can be implemented using hardware such as electronic circuits. A block may also represent a module, segment or portion of a code including one or more executable instructions for implementing a specified logical function. It should be understood that in some alternative implementations, the functions indicated in the blocks may not occur in the order shown in the figure. For example, depending on the functions involved, two boxes shown in succession may be executed or implemented substantially simultaneously, or sometimes two boxes may be executed in reverse order. Some blocks may also be omitted. It should also be understood that each box of the block diagram and the combination of boxes may be implemented by a dedicated hardware-based system that performs a specified function or action, or by a combination of dedicated hardware and computer instructions.

[0352] It should be understood that the embodiments of the present invention are not limited to the exact configurations described above and illustrated in the accompanying drawings, and various modifications and changes may be made without departing from the scope of the present invention. For example, the charged particle inspection system may be only one example of a charged particle beam system consistent with embodiments of the present disclosure.

Claims

1. A non-transitory computer-readable medium storing a set of instructions, the set of instructions being executable by at least one processor of a device to cause the device to perform a method, the method comprising: enabling a first solid state current control device (SSCCD) of a first signal detection unit to be placed in an on-state in which the first SSCCD is capable of conducting current from a charged particle sensing element of a charged particle counting detector; outputting a first current pulse from the charged particle sensing element in response to a first charged particle arriving at the charged particle sensing element, wherein the first current pulse triggers the first SSCCD to the on-state; in response to the first SSCCD being triggered to the on-state, conducting the first current pulse from an input to an output of the first SSCCD; as well as receiving a second enable signal at a second signal detection unit including a second SSCCD, the second enable signal being based on the first current pulse, The second enabling signal enables the second SSCCD of the second signal detecting unit to be placed in an on state where the second SSCCD can conduct current from the charged-particle sensing element. 2 . The non-transitory computer readable medium of claim 1 , wherein the first SSCCD or the second SSCCD comprises a thyristor. 3 . The non-transitory computer readable medium of claim 1 , wherein enabling the first SSCCD of the first signal detection unit comprises closing an enable switch to couple a first control gate of the first SSCCD to an anode of the first SSCCD.

4. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: In response to the first current pulse exceeding a threshold, current is initiated through the first SSCCD.

5. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: In response to the first current pulse falling below a threshold, conducting current by the first SSCCD is ceased.

6. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: An operating status output signal is generated based on the first current pulse.

7. The non-transitory computer readable medium of claim 6, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: transmitting the operating status output signal to a signal processing circuit device; and Charged particle arrival events are detected at the signal processing circuitry based on the operating state output signal.

8. The non-transitory computer readable medium of claim 6, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: transmitting the operating status output signal to a signal processing circuit device; and counting full cycles of charged particle arrival events at the signal processing circuit arrangement based on the operating state output signal, Wherein the number of charged particle arrival events counted in the full cycle corresponds to the number of non-bypassed signal detection units coupled to the output of the charged particle sensing element.

9. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: The second enable signal is generated based on the first current pulse.

10. The non-transitory computer readable medium of claim 1, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: generating a detection result signal at an analog signal output of the first signal detection unit; and The detection result signal is transmitted to the signal processing circuit device.

11. The non-transitory computer readable medium of claim 10, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: The energy level information of the detection result signal is processed at the signal processing circuit device.

12. The non-transitory computer readable medium of claim 10, wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: Overflow information of the detection result signal is processed at the signal processing circuit device.

13. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: resetting the first signal detection unit to an initial state, Wherein in the initial state, the first control gate of the first signal detection unit is configured to be enabled by another enabling signal.

14. The non-transitory computer readable medium of claim 1 , wherein the set of instructions executable by the at least one processor of the device causes the device to further perform: By bypassing the third signal detection unit including the third SSCCD through the bypass circuit of the third signal detection unit, The bypass circuit is configured to enable a signal to pass from the enable signal input of the third signal detection unit to the enable signal output of the third signal detection unit without enabling the third SSCCD of the third detection unit to place the third SSCCD in an on state capable of conducting current from the charged particle sensing element.

15. A charged particle counting detector, comprising: a charged particle sensing element configured to output a first current pulse in response to a first charged particle arriving at the charged particle sensing element; a first signal detection unit, comprising a first solid-state current control device (SSCCD), the first solid-state current control device being configured to: a) be enabled by a first enable signal to place the first SSCCD in an on-state capable of conducting current from the charged-particle sensing element, b) be triggered to the on-state by the first current pulse, and c) conduct the first current pulse to an output of the first SSCCD in response to the first SSCCD being triggered to the on-state; as well as A second signal detection unit is configured to receive a second enable signal and includes a second SSCCD configured to be enabled by the second enable signal to be placed in an on-state in which the second SSCCD can conduct current from the charged-particle sensing element.

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