Sensing-element-level circuit design for electron-counting detection devices

Abstract

To provide a basic circuit for performing electron counting for improving SNR and increasing throughput in an electron beam inspection system.SOLUTION: The charged particle beam detector may include circuitry comprising storage cells configured to receive the signals representative of the outputs of the sensing elements, a storage cell multiplexer configured to selectively transmit the signals representative of the outputs of the sensing elements to the storage cells, a threshold detector configured to compare the signals representative of the outputs of the sensing elements to a threshold, and a converter configured to perform signal processing on the signals transmitted from the storage cells.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 63 / 050628, filed July 10, 2020, U.S. Patent Application No. 63 / 113171, filed November 12, 2020, and U.S. Patent Application No. 63 / 151585, filed February 19, 2021, which patent applications are incorporated by reference in their entireties into this specification.

[0002] TECHNICAL FIELD

[0002] The description herein relates to detectors that may be useful in the field of charged particle beam systems, and more particularly to systems and methods that may be applicable to charged particle detection using charged particle counting. [Background technology]

[0003]

[0003] Detectors can be used to sense physically observable phenomena. For example, a charged particle beam tool such as an electron microscope may include a detector that receives charged particles projected from a sample and outputs a detection signal. The detection signal can be used to reconstruct an image of the sample structure under inspection, and can be used, for example, to reveal defects in the sample. Detection of sample defects is becoming increasingly important in the manufacture of semiconductor devices, which may include a large number of densely packed and miniaturized integrated circuit (IC) components. Inspection systems can be provided for this purpose.

[0004]

[0004] As semiconductor devices continue to shrink, inspection systems are increasingly using lower beam currents in charged particle beam tools. Existing detection systems can be limited by signal-to-noise ratios (SNRs) and system throughput, especially when beam currents are reduced, e.g., to the picoampere range. To improve SNR and increase throughput in electron beam inspection systems, electron counting has been proposed, in which the intensity of an incident electron beam is obtained by counting the number of electrons reaching a detector and then analyzing the frequency of the electron arrival events. However, basic circuits for implementing electron counting face challenges due to the stochastic (e.g., random) nature of the electron arrival events and can suffer from high miscount rates. Therefore, improved detection systems and methods are desirable. Summary of the Invention

[0005]

[0005] Embodiments of the present disclosure provide charged particle beam-based detection systems and methods. In some embodiments, a charged particle beam system including a detector can be provided. The detector can include circuitry that can be useful for counting charged particles. The circuitry can include storage cells configured to receive signals representative of the outputs of the sensing elements, a storage cell multiplexer configured to selectively transmit the signals representative of the outputs of the sensing elements to the storage cells, a threshold detector configured to compare the signals representative of the outputs of the sensing elements with a threshold, and a converter configured to perform signal processing on the signals transmitted from the storage cells.

[0006]

[0006] It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to limit the disclosed embodiments as may be claimed.

[0007]

[0007] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagrammatic representation of an exemplary electron beam inspection (EBI) system consistent with an embodiment of the present disclosure. [Figure 2A]

[0009] FIG. 1 illustrates a charged particle beam device, which may be an example of an electron beam tool, consistent with embodiments of the present disclosure. [Figure 2B]

[0009] FIG. 1 illustrates a charged particle beam device that may be an example of an electron beam tool consistent with an embodiment of the present disclosure. [Figure 3A]

[0010] 1 is a diagrammatic representation of an exemplary structure of a detector, consistent with embodiments of the present disclosure. [Figure 3B] 1 is a diagrammatic representation of an exemplary structure of a detector consistent with an embodiment of the present disclosure. [Figure 3C] 1 is a diagrammatic representation of an exemplary structure of a detector consistent with an embodiment of the present disclosure. [Figure 4]

[0011] 1 is a diagrammatic representation of a circuit for charged particle counting, consistent with an embodiment of the present disclosure. [Figure 5A]

[0012] 1 illustrates an exemplary implementation of a circuit for charged particle counting consistent with embodiments of the present disclosure. [Figure 5B] 1 illustrates an exemplary implementation of a circuit for charged particle counting consistent with an embodiment of the present disclosure. [Figure 5C] 1 illustrates an exemplary implementation of a circuit for charged particle counting consistent with an embodiment of the present disclosure. [Figure 6]

[0013] 1 is a flowchart of a method for charged particle detection consistent with an embodiment of the present disclosure. [Figure 7A]

[0014] 1 is a flowchart of a method for charged particle detection consistent with an embodiment of the present disclosure. [Figure 7B] 1 is a flowchart of a method for charged particle detection consistent with an embodiment of the present disclosure. [Figure 7C]1 is a flowchart of a method for charged particle detection consistent with an embodiment of the present disclosure. [Figure 7D] 1 is a flowchart of a method for charged particle detection consistent with an embodiment of the present disclosure. [Figure 8]

[0015] 1 illustrates the effect of a charged particle arrival event at a detection plane, consistent with embodiments of the present disclosure. [Figure 9]

[0016] 1 is a diagrammatic representation of a detector with interconnected detection cells, consistent with an embodiment of the present disclosure. [Figure 10]

[0017] 1 illustrates an interconnect arrangement consistent with an embodiment of the present disclosure. [Figure 11]

[0018] 1 illustrates an interconnect arrangement consistent with an embodiment of the present disclosure. [Figure 12A]

[0019] 1 illustrates a circuit with interconnects consistent with an embodiment of the present disclosure. [Figure 12B]

[0020] 1 is a diagrammatic representation of an analog signal routing multiplexer consistent with an embodiment of the present disclosure. [Figure 13]

[0021] 1 is a flowchart illustrating a method that may be useful for electron counting, consistent with embodiments of the present disclosure. [Figure 14]

[0022] 1 is a flowchart illustrating a method that may be useful for electron counting, consistent with embodiments of the present disclosure. [Figure 15]

[0023] 1 is a flowchart illustrating a method that may be useful for electron counting, consistent with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0024] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements unless otherwise stated. The implementations described in the following description of exemplary embodiments do not represent all implementations consistent with the present invention. Instead, the implementations are merely examples of apparatus, systems, and methods consistent with aspects related to the subject matter recited in the appended claims.

[0010]

[0025] Electronic devices are built with circuits formed on a piece of silicon called a substrate. Many circuits can be formed together on the same piece of silicon, called an integrated circuit, or IC. As technology advances, the size of these circuits has dramatically decreased, allowing more circuits to fit on a substrate. For example, an IC chip in a smartphone may be only about the size of a fingernail, yet it can contain over 2 billion transistors, each less than 1 / 1000 the width of a human hair.

[0011]

[0026] Creating these tiny ICs is a time-consuming, complex, and expensive process, often involving hundreds of individual steps. An error in even one step can result in a defect in the finished IC, rendering it useless. Therefore, one of the goals of a manufacturing process is to avoid such defects in order to maximize the number of functioning ICs produced by the process, i.e., to increase the overall yield of the process.

[0012]

[0027] One factor in improving yield is monitoring the chip creation process to ensure that it produces a sufficient number of functioning integrated circuits. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be done using a scanning electron microscope (SEM). An SEM can be used to image these extremely small structures, in effect taking a "picture" of the structure. The image can be used to determine whether the structure was formed correctly and can also be used to determine whether the structure was formed in the correct location. If the structure is defective, the process can be adjusted to make the defect less likely to recur. To increase throughput (e.g., number of samples processed per hour), it is desirable to perform the inspection as quickly as possible.

[0013]

[0028] An image of a wafer can be formed by scanning the primary beam (e.g., a "probe" beam) of the SEM system across the wafer and collecting particles (e.g., secondary electrons) generated from the wafer surface with a detector. The secondary electrons can form a beam (a "secondary beam") that is directed toward the detector. Secondary electrons that land on the detector can generate electrical signals (e.g., current, charge, voltage, etc.) at the detector. These signals can be output from the detector and processed by an image processor to form an image of the sample.

[0014]

[0029] Typically, the detection process involves measuring the magnitude of the electrical signal generated when an electron lands on the detector. Another approach can use electron counting, in which 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 the electrical signal generated at the detector, which changes proportionally to changes in the intensity of the secondary beam. However, using electron counting, the discrete number of electrons that reach the detector from the secondary electron beam can be determined and the detection result can be output in digital form (e.g., 1s and 0s rather than an analog signal). The intensity of the beam can be determined by analyzing the frequency of the electron arrival events.

[0015]

[0030] Electron counting can help improve the signal-to-noise ratio (SNR) and throughput of charged particle beam systems. SNR can be particularly concerning at low levels of primary beam current. Therefore, electron counting can be an attractive method for applications such as metrology and overlay inspection, where beam currents are typically low. Electron counting can also help separate signals generated by different types of electrons (e.g., secondary electrons and backscattered electrons). In some applications, it is desirable to generate SEM images based purely on secondary electrons, purely on backscattered electrons, or a combination thereof.

[0016]

[0031] However, due to bandwidth limitations and the random nature of electron arrival events, it can be difficult to implement electron counting using conventional circuits; therefore, basic circuits can encounter problems with high miscount rates. Electrons can be emitted from a sample at different energy levels and in random directions. Electron arrivals at a detector's sensing element can occur in close succession, resulting in two electron arrivals being miscounted as a single electron arrival event. For example, a simple combination of a voltage comparator and logic circuitry may not achieve the desired goal of an electron counting detection system: high accuracy and low miscount rates. Additionally, the detector must be capable of distinguishing between particles of different energies, for example, to distinguish between secondary and backscattered electrons. Some circuit designs may not be able to collect information about electron arrival events with sufficient accuracy and may have low accuracy in energy discrimination.

[0017]

[0032] Embodiments of the present disclosure may provide a detection system and method that enables charged particle counting in a detector. The detector may be provided with a layer of circuitry configured to perform charged particle counting. The circuitry may be provided, for example, in a separate readout layer of a semiconductor chip that constitutes the detector, in a separate semiconductor chip, or integrated together with the sensing elements. In a detector configured with layers including a sensing element layer and a signal processing layer, the circuitry may be provided in the signal processing layer, which processes signals generated by the sensing elements and converts them into digital signals. The circuitry may be configured to temporarily store signals related to the energy of incident charged particles. The circuitry may be configured to generate output signals representing the number of charged particles that arrive at the sensing element during a certain time period (e.g., to identify electron arrival events), the energy associated with the charged particles (e.g., to distinguish between secondary electrons or backscattered electrons), and whether more than a certain number of charged particles have arrived during a certain time period (e.g., to determine the overflow status of the sensing element).

[0018]

[0033] A circuit may act as a memory or a pipeline to store or process information related to charged particle arrival events. A "pipeline" approach to a circuit may refer to a circuit architecture configured to break down a sequential process into several subprocesses. The subprocesses may run in parallel, similar to an assembly line, where workers at each stage perform specific tasks and pass a partially completed product along the line to the next worker. A circuit acting as a memory or a pipeline may enhance a detector's ability to process signals. For example, signal processing of electron arrival events may require a certain amount of time. For example, using a 1 nA current beam, the electron arrival rate may correspond to approximately 6.25 billion secondary electrons arriving at the detector per second (meaning that electrons arrive approximately once every few nanoseconds). The detector's signal processing speed may be slower than the time rate at which the detector can generate a measurable signal in response to an electron arrival event, thus resulting in miscounting or other difficulties. By providing memory functionality, the detector may have the additional ability to record signals to temporarily represent individual electron arrival events, which can then be processed and output simultaneously or at different times (e.g., "asynchronously").

[0019]

[0034] Furthermore, fast circuit processing speed alone may not be sufficient to ensure accurate electron counting. Due to the random nature of electron arrival events, even if the circuit processing speed is faster than the average rate at which the sensing element generates a signal in response to an electron arrival event (the “average rate”), the detector may still encounter problems in electron counting. For example, if an analog pipeline is not provided, even if the time rate at which the sensing element generates a signal in response to an electron arrival event is faster than the average rate, there may still be instances where two electrons arrive in close succession and the detector is unable to accurately process the events. On the other hand, if the circuit processing speed is slower than the average rate, the circuit may constantly overflow. Embodiments of the present disclosure can address this situation by (1) adding an analog pipeline to the detection circuit to reduce or minimize miscounting due to processing speed, and (2) providing a converter in the processing circuit to ensure that the circuit's overall processing speed is faster than the average rate at which the sensing element generates a signal in response to an electron arrival event. Analog pipelining can reduce or minimize miscounts caused by a single converter's processing speed being slower than the time rate at which the sensing element generates a signal in response to an electronic arrival event. Multiple converters can ensure some improvement in processing speed within a particular probe current range over the average rate at which the sensing element generates a signal in response to an electronic arrival event.

[0020]

[0035] The objects and advantages of the present disclosure can be achieved by the elements and combinations as described in the embodiments discussed herein, but no embodiment of the present disclosure is necessary to achieve such exemplary object or advantage, and some embodiments may not achieve any of the described objects or advantages.

[0021]

[0036] 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 utilizing electron beams ("e-beams"). However, the disclosure is not so limited. Other types of charged particle beams may be applied as well. Moreover, the detection systems and methods may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc. Additionally, the term "beamlet" may refer to a beam component or a separate beam component extracted from an original beam. The term "beam" may refer to a beam or a beamlet.

[0022]

[0037] As used herein, unless specifically stated otherwise, the term "or" includes all possible combinations except where impracticable. For example, if it is stated that a component includes A or B, then the component may include A or B, or A and B, unless specifically stated otherwise or where impracticable. As a second example, if it is stated that a component may include A, B, or C, then the component may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless specifically stated otherwise or where impracticable.

[0023]

[0038] Referring now to FIG. 1 , FIG. 1 illustrates an exemplary electron beam inspection (EBI) system 10 that can be used for wafer inspection consistent with embodiments of the present disclosure. As shown in FIG. 1 , 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 within the main chamber 11 and can be used for imaging. The EFEM 30 includes a first load port 30 a and a second load port 30 b. The EFEM 30 may include additional load ports. The first load port 30 a and the second load port 30 b receive wafer front-opening integrated pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (wafers and samples may be collectively referred to herein as “wafers”).

[0024]

[0039] One or more robot arms (not shown) of the EFEM 30 can transfer wafers to the load / lock chamber 20. The load / lock chamber 20 is connected to a load / lock vacuum pumping system (not shown), which removes gas molecules from the load / lock chamber 20 to reach a first pressure below atmospheric pressure. After the first pressure is reached, one or more robot arms (not shown) can transfer the wafers from the load / lock chamber 20 to the main chamber 11. The main chamber 11 is connected to a main chamber vacuum pumping system (not shown), which removes gas molecules from the main chamber 11 to reach a second pressure below the first pressure. After the second pressure is reached, the wafers are inspected by the electron beam tool 100. The electron beam tool 100 can be a single-beam system or a multi-beam system. A controller 109 is electronically connected to the electron beam tool 100 and can be electronically connected to other components as well. The controller 109 may be a computer configured to perform various controls of the EBI system 10. In Figure 1, the controller 109 is shown as being external to the structure including the main chamber 11, the load / lock chamber 20, and the EFEM 30, but it is understood that the controller 109 may also be part of the structure.

[0025]

[0040] Charged particle beam microscopes, such as those formed by or included in EBI system 10, may be capable of resolution down to the nanometer scale, for example, and may serve as practical tools for inspecting IC components on wafers. Using an e-beam system, electrons from a primary electron beam can be focused at a probe spot on the wafer under inspection. The interaction of the primary electrons with the wafer can form a secondary particle beam. The secondary particle beam can include backscattered electrons, secondary electrons, Auger electrons, or the like, resulting from the interaction of the primary electrons with the wafer. The characteristics (e.g., intensity) of the secondary particle beam can vary based on the internal or external structure or material properties of the wafer, thereby indicating whether the wafer contains defects.

[0026]

[0041] 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., current, charge, voltage, etc.) representing the intensity of the detected secondary particle beam. The electrical signal can be measured by a measurement circuit, which can include additional components (e.g., an analog-to-digital converter) to obtain a distribution of detected electrons. The electron distribution data collected during the detection time window can be combined with corresponding scan path data of the primary electron beam incident on the wafer surface to reconstruct an image of the wafer structure or material under inspection. The reconstructed image can be used to reveal various features of the internal or external structure or material of the wafer, and can be used to reveal defects that may be present in the wafer.

[0027]

[0042] 2A illustrates a charged particle beam device that may be an example of an electron beam tool 100 consistent with embodiments of the present disclosure. FIG. 2A illustrates a device that uses multiple beamlets formed from a primary electron beam to simultaneously scan multiple locations on a wafer.

[0028]

[0043] As shown in FIG. 2A , the electron beam tool 100A may include an electron source 202, a gun aperture 204, a condenser lens 206, a primary electron beam 210 emitted from the electron source 202, a source conversion unit 212, multiple beamlets 214, 216, and 218 of the primary electron beam 210, a primary projection optics 220, a wafer stage (not shown in FIG. 2A ), multiple secondary electron beams 236, 238, and 240, a secondary optics 242, and an electron detection device 244. The electron source 202 may generate primary particles, such as electrons, in the primary electron beam 210. A controller, an image processing system, and the like may be coupled to the electron detection device 244. The primary projection optics 220 may include a beam separator 222, a deflection scanning unit 226, and an objective lens 228. The electron detection device 244 may include detection subregions 246, 248, and 250.

[0029]

[0044] Electron source 202, gun aperture 204, condenser lens 206, source conversion unit 212, beam separator 222, deflection scanning unit 226, and objective lens 228 can be aligned with a primary optical axis 260 of apparatus 100A. Secondary optics 242 and electron detection device 244 can be aligned with a secondary optical axis 252 of apparatus 100A.

[0030]

[0045] The electron source 202 may include a cathode, extractor, or anode, and primary electrons may be emitted from the cathode and then extracted or accelerated to form a primary electron beam 210 with a crossover (virtual or real) 208. The primary electron beam 210 may be visualized as being emitted from the crossover 208. The gun aperture 204 may block electrons at the periphery of the primary electron beam 210 to reduce the size of the probe spots 270, 272, 274.

[0031]

[0046] The source conversion unit 212 may include an image-forming element array (not shown in FIG. 2A ) and a beam-limiting aperture array (not shown in FIG. 2A ). Examples of the source conversion unit 212 can be found in U.S. Pat. No. 9,691,586, U.S. Patent Application Publication No. 2017 / 0025243, and International Patent Application No. PCT / EP2017 / 084429, all of which are incorporated herein by reference in their entirety. The image-forming element array may include a micro-deflector or a micro-lens array. The image-forming element array may form multiple parallel images (virtual or real) of the crossover 208 using multiple beamlets 214, 216, and 218 of the primary electron beam 210. The beam-limiting aperture array may limit the multiple beamlets 214, 216, and 218.

[0032]

[0047] The condenser lens 206 can focus the primary electron beam 210. The current of the beamlets 214, 216, and 218 downstream of the source conversion unit 212 can be varied by adjusting the focusing power of the condenser lens 206 or by changing the radial size of the corresponding beam-limiting aperture in the beam-limiting aperture array. The condenser lens 206 can be an adjustable condenser lens that can be configured to move the position of its first principal plane. The adjustable condenser lens can be configured to be magnetic, so that the off-axis beamlets 216 and 218 land on the beamlet-limiting aperture at a rotation angle. The rotation angle varies with the focusing power and the position of the first principal plane of the adjustable condenser lens. In some embodiments, the adjustable condenser lens can be an adjustable anti-rotation condenser lens including an anti-rotation lens with a movable first principal plane. Examples of adjustable focusing lenses are further described in U.S. Patent Application Publication No. 2017 / 0025241, which is incorporated by reference herein in its entirety.

[0033]

[0048] The objective lens 228 can focus the beamlets 214, 216, 218 onto the wafer 230 for inspection and can form multiple probe spots 270, 272, 274 on the surface of the wafer 230. Secondary electron beamlets 236, 238, 240 can be formed to emit from the wafer 230 and return towards the beam separator 222.

[0034]

[0049] The beam separator 222 may be a Wien filter-type beam separator that generates an electrostatic dipole field and a magnetic dipole field. In some embodiments, when these fields are applied, the force exerted on the electrons of the beamlets 214, 216, and 218 by the electrostatic dipole field may be equal in magnitude and opposite in direction to the force exerted on the electrons by the magnetic dipole field. Thus, the beamlets 214, 216, and 218 may pass straight through the beam separator 222 with zero deflection angle. However, the total dispersion of the beamlets 214, 216, and 218 generated by the beam separator 222 may be non-zero. The beam separator 222 may separate the secondary electron beams 236, 238, and 240 from the beamlets 214, 216, and 218 and direct the secondary electron beams 236, 238, and 240 toward the secondary optics 242.

[0035]

[0050] The deflection scanning unit 226 can deflect the beamlets 214, 216, 218 to scan the probe spots 270, 272, 274 across the surface area of ​​the wafer 230. In response to the beamlets 214, 216, 218 impinging on the probe spots 270, 272, 274, secondary electron beams 236, 238, 240 can be emitted from the wafer 230. The secondary electron beams 236, 238, 240 can include electrons with a distribution of energies, including secondary electrons and backscattered electrons. The secondary optics 242 can focus the secondary electron beams 236, 238, 240 onto detection subregions 246, 248, 250 of the electron detection device 244. The detection subregions 246, 248, 250 can be configured to detect the corresponding secondary electron beams 236, 238, 240 and generate corresponding signals used to reconstruct an image of the surface of the wafer 230. The detection sub-regions 246, 248, 250 may comprise separate detector packages, separate sensing elements, or separate regions of an array detector. In some embodiments, each detection sub-region may comprise a single sensing element.

[0036]

[0051] Another example of a charged particle beam device will now be discussed with reference to Figure 2B. Electron beam tool 100B (also referred to herein as device 100B) may be an example of electron beam tool 100 and may be similar to electron beam tool 100A shown in Figure 2A. However, unlike device 100A, device 100B may be a single-beam tool that uses only one primary electron beam to scan locations on a wafer one at a time.

[0037]

[0052] 2B, apparatus 100B includes a wafer holder 136 supported by a motorized stage 134 for holding a wafer 150 to be inspected. Electron beam tool 100B includes an electron emitter, which may include a cathode 103, an anode 121, and a gun aperture 122. Electron beam tool 100B further includes a beam-limiting aperture 125, a condenser lens 126, a column aperture 135, an objective lens assembly 132, and a detector 144. Objective lens assembly 132 may be a modified SORIL lens in some embodiments and includes a pole piece 132a, a control electrode 132b, a deflector 132c, and an excitation coil 132d. In the detection or imaging process, an electron beam 161 emanating from the tip of the cathode 103 is accelerated by the voltage on the anode 121, passes through the gun aperture 122, the beam limiting aperture 125, the condenser lens 126, and is focused by a modified SORIL lens to a probe spot 170, which can impinge on the surface of the wafer 150. The probe spot 170 can be scanned across the surface of the wafer 150 by a deflector, such as deflector 132c or other deflectors of a SORIL lens. Secondary or scattered particles (such as secondary electrons or scattered primary electrons emanating from the wafer surface) are collected by a detector 144 to determine the intensity of the beam, so that an image of the area of ​​interest on the wafer 150 can be reconstructed.

[0038]

[0053] An image processing system 199 may also be provided, including the image acquirer 120, the storage 130, and the 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 host, a terminal, a personal computer, any type of mobile computing device, and the like, or a combination thereof. The image acquirer 120 may be connected 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, a wireless radio, or a combination thereof. The image acquirer 120 may receive signals from the detector 144 and 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, contouring, overlaying indicators on the acquired image, and the like. The image acquirer 120 may be configured to perform adjustments, such as brightness and contrast, of the acquired image. The storage 130 may be a storage medium such as a hard disk, random access memory (RAM), cloud storage, other types of computer-readable memory, and the like. The storage 130 may be coupled to the image acquirer 120 and used to store raw scanned image data as original images or to store post-processed images. The image acquirer 120 and the storage 130 may be connected to the controller 109. In some embodiments, the image acquirer 120, the storage 130, and the controller 109 may be integrated together as a single electronic control unit.

[0039]

[0054] In some embodiments, the image acquirer 120 can acquire one or more images of the sample based on an imaging signal received from the detector 144. The imaging signal can correspond to a scanning motion to perform charged particle imaging. The acquired image can be a single image including multiple imaging areas that can include various features of the wafer 150. The single image can be stored in the storage 130. The imaging can be performed based on imaging frames.

[0040]

[0055] The collection and illumination optics of an electron beam tool can include or be supplemented by electromagnetic quadrupole electron lenses. For example, as shown in FIG. 2B , electron beam tool 100B can include a first quadrupole lens 148 and a second quadrupole lens 158. In some embodiments, the quadrupole lenses can be used to control the electron beam. For example, first quadrupole lens 148 can be controlled to adjust the beam current, and second quadrupole lens 158 can be controlled to adjust the beam spot size and beam shape.

[0041]

[0056] FIG. 2B illustrates a charged particle beam device that can use a single primary beam configured to generate secondary electrons by interacting with a wafer 150. As in the embodiment illustrated in FIG. 2B, the detector 144 can be positioned along the optical axis 105. The primary electron beam can be configured to travel along the optical axis 105. Accordingly, the detector 144 can include a hole in its center to allow the primary electron beam to pass through and reach the wafer 150. FIG. 2B illustrates an example of a detector 144 with an opening in its center. However, some embodiments can use a detector positioned off-axis with respect to the optical axis along which the primary electron beam travels. For example, as in the embodiment illustrated in FIG. 2A discussed above, a beam separator 222 can be provided to direct the secondary electron beam toward the off-axis detector. The beam separator 222 can be configured to redirect the secondary electron beam by an angle α toward the electron detection device 244, as shown in FIG. 2A.

[0042]

[0057] The detector of the charged particle beam system may include one or more detecting elements. The detector may include a single element detector or an array having multiple detecting elements. The detecting elements may be configured to count charged particles. Detector detecting elements that may be useful for charged particle counting are discussed in U.S. Patent Application Publication No. 2019 / 0378682, the entire contents of which are incorporated herein by reference.

[0043]

[0058] The sensing element may include a diode or a diode-like element capable of converting incident energy into a measurable signal. For example, the sensing element of a detector may include a PIN diode. Throughout this disclosure, sensing elements may be represented in figures as, for example, diodes, although sensing elements or other components may deviate from the ideal circuit behavior of electrical elements such as diodes, resistors, capacitors, etc.

[0044]

[0059] 3A-3C illustrate exemplary structures of a detector consistent with embodiments of the present disclosure. The detector may be a segmented detector. A detector, such as detector 300A, detector 300B, or detector 300C shown in FIGS. 3A-3C, may be provided as charged particle detection device 244 shown in FIG. 2A or detector 144 shown in FIG. 2B. In FIG. 3A, detector 300A includes a sensor layer 301 and a signal processing layer 302. Sensor layer 301 may include a sensor die comprised of multiple sensing elements (including sensing elements 311, 312, 313, and 314). In some embodiments, the multiple sensing elements may be provided in an array of sensing elements, each of which may have a uniform size, shape, and arrangement.

[0045]

[0060] The signal processing layer 302 may include multiple signal processing circuits (including circuits 321, 322, 323, and 324). The circuits may include interconnects (e.g., wiring paths) configured to communicatively couple the sensing elements. Each sensing element in the sensor layer 301 may have a corresponding signal processing circuit in the signal processing layer 302. The sensing elements and their corresponding circuits may be configured to operate independently. As shown in FIG. 3A , circuits 321, 322, 323, and 324 may be configured to communicatively couple to the outputs of sensing elements 311, 312, 313, and 314, respectively, as indicated by the four dashed lines between the sensor layer 301 and the signal processing layer 302.

[0046]

[0061] In some embodiments, the signal processing layer 302 can be configured as a single die with multiple circuits provided thereon. The sensor layer 301 and the signal processing layer 302 can be in direct contact. For example, as shown in FIG. 3B illustrating detector 300B, the signal processing layer 302 directly abuts the sensor layer 301.

[0047]

[0062] In some embodiments, components and functionality of different layers can be combined or omitted, for example, the signal processing layer 302 can be combined with the sensor layer 301. Furthermore, circuitry for charged particle counting can be integrated at various points in the detector (e.g., in a separate readout layer of the detector or on a separate chip).

[0048]

[0063] As shown in FIG. 3C, a detector 300C can be provided. The detector 300C can include a sensor layer 301. The detector 300C can be configured for backside illumination, and the sensor layer 301 can be the only layer provided. A first surface of the sensor layer 301 can be configured to receive charged particles, and circuitry can be provided on a second surface opposite the first surface. The circuitry can include electron counting circuitry provided separately for each sensing element.

[0049]

[0064] Referring now to FIG. 4, FIG. 4 illustrates a circuit 400 that may be useful for charged particle counting, consistent with embodiments of the present disclosure. The circuit 400 may be provided at the sensing element level of a detector, such as the electronic detection device 244 of FIG. 2A or the detector 144 of FIG. 2B. The circuit 400 may be one of multiple circuits, each of which is provided for a corresponding sensing element of an array detector. In some embodiments, the detector includes only one sensing element, and only one circuit 400 is provided. In some embodiments, the circuit 400 may be provided in the layer in which the sensing element of the detector is formed (e.g., integrated with the sensing element), or may be provided in a separate layer. For example, the circuit 400 may be provided in the sensor layer 301 of FIG. 3, or may be provided in a separate layer.

[0050]

[0065] The circuit 400 can be configured to process signals generated from the sensing element 311. The sensing element 311 can be configured to generate a response to a charged particle event. The charged particle event can include an electron arrival event. For example, in response to the arrival of an incident electron at the sensing element 311, the sensing element 311 can be configured to generate a charge or current that is due to the energy of the incident electron. The charge or current can be generated within the sensing element and supplied to a circuit connected to the sensing element. In some embodiments, the circuit can be integrated with the sensing element.

[0051]

[0066] 4, 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. Array 440 may include a plurality of storage cells, such as a first storage cell 441, a second storage cell 442, and so on, up to, for example, an Nth storage cell 449. Storage cells 441-449 may include charge storage cells.

[0052]

[0067] 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 311 after it has been generated therein. The sensing element 311 can be configured to operate with a bias such that a depletion region of the sensing element 311 is formed, which can act as a trapping region for incident charged particles. The incident charged particles can interact with the material of the sensing element 311 and generate charge through impact ionization. The input stage 410 can be configured so that all charge is extracted from the sensing element 311 as soon as it is generated therein and provided to other components of the circuit 400.

[0053]

[0068] The input stage 410 may include components configured to provide gain. For example, the input stage 410 may include an amplifier. The amplifier may be configured to provide a current gain so that the current signal from the sensing element 311 can be amplified. Additionally, the input stage 410 may be configured to have a conversion function. The input stage 410 may include components configured to convert an electrical signal from one form to another. For example, the input stage 410 may include components configured to convert the current signal from the sensing element 311 into another form of electronic signal (e.g., voltage).

[0054]

[0069] The circuit 400 may include a threshold detector 420. The threshold detector 420 may be attached to the input stage 410. The threshold detector 420 may be configured to detect a signal level of the incident current from the sensing element 311 or a signal level of the converted signal. The converted signal may include a signal having a level proportional to the incident current from the sensing element 311.

[0055]

[0070] The threshold detector 420 can be configured to determine that a charged particle event has occurred. The determination from the threshold detector 420 can be used to control other operations of the circuit 400. The threshold detector 420 can be configured to detect the start or end of a charged particle event. The start or end of the charged particle event can trigger the recording of information from the sensing element 311. 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., area under a curve).

[0056]

[0071] 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, where a1 and a2 can be the same or different. The values ​​of a1 and a2 can be set to be higher than the overall noise level of the detector. The noise level can be the noise floor from the sensing element 311, its amplification value, or its conversion value. The relationship between a1 and a2 can be, for example, a1≧a2. The thresholds can be set to avoid false detection of the start or end of an electronic arrival event due to noise.

[0057]

[0072] Circuit 400 may include a storage cell multiplexer 430 following input stage 410. In some embodiments, input stage 410 may be optional, for example, when a circuit for an integration function with very low input impedance is provided. Hereinafter, the reference to the "output of input stage 410" may refer to the output of input stage 410 or the output of the integration circuit immediately following sensing element 311. The output of input stage 410 may represent, for example, the output signal from sensing element 311, whether amplified or not, or whether or not it has been converted.

[0058]

[0073] The multiplexer 430 (or "mux") can be configured to connect the output of the input stage 410 to the storage cell array 440. The multiplexer 430 can include a switching element. The multiplexer 430 can include a data selector configured to select from several output lines and route an input signal to the selected output line. The multiplexer 430 can be configured to connect only one output line to the input at a time. For example, the multiplexer 430 can be configured to route signals from the output of the input stage 410 to only one storage cell 441, 442, 449 at a time. Moreover, the multiplexer 430 can be configured to prevent the output of the input stage 410 from being connected to any storage cell in the array 440 at certain times during operation of the circuit 400. Similarly, the multiplexer 430 can be configured to connect the output of the input stage 410 to other components other than the storage cell array 440. The multiplexer 430 can be controlled by the control unit 490.

[0059]

[0074] The array 440 may include one or more storage cells. The output of each storage cell may be connected to a converter 450. The signal input to the storage cell array 440 may be converted to another form (e.g., through integration). As an example, a current or charge input to the storage cell array 440 may accumulate to form a voltage signal. The converter 450 may be configured to sample the storage cell array 440. The converter 450 may be configured to process analog signals from the storage cell array 440. The converter 450 may generate a digital signal for data representing the analog signal.

[0060]

[0075] Converter 450 may include, for example, a voltage detector or an analog-to-digital converter (ADC). Converter 450 may include a comparator with multiple inputs connected directly to converter 450. In some embodiments, converter 450 may include a single comparator connected to multiple inputs through a multiplexer.

[0061]

[0076] Circuit 400 can be configured to perform a query (e.g., a query function) on storage cell array 440. Querying can refer to obtaining information (e.g., sending a signal) from a component. In some embodiments, circuit 400 can be configured to detect (e.g., query) only storage cells that were not selected by storage cell multiplexer 430. For example, in some embodiments, the query can be performed on the storage cells separately from the integration so as not to interfere with the integration. However, in some embodiments, the query can occur simultaneously with the integration using the same storage cells.

[0062]

[0077] Converter 450 may include one or more voltage comparators. The voltage comparators may be used to compare the voltage from storage cell array 440 to a reference voltage. The number of voltage comparators and the number of reference voltages may be the same or different. In some embodiments, a voltage buffer may be provided. For example, a voltage buffer may be provided before multiple voltage comparators to reduce the loading effect of the input impedance of the voltage comparators on the voltage of storage cell array 440. Converter 450 may also include one or a group of ADCs, each having a predefined bit resolution.

[0063]

[0078] The control unit 490 can be configured for bidirectional data flow. The control unit 490 can be configured for various functions. For example, the control unit 490 can be configured to (i) control data (e.g., including timing information) to the sensing elements, (ii) determine counting results from the sensing elements, and (iii) determine sensing element overflow flags with overflow type data.

[0064]

[0079] The circuit 400 can be configured to count charged particles incident on the detector. When the level of the incident current signal from the sensing element 311 crosses a threshold, the circuit 400 can be configured to initiate a counting operation. For example, when the threshold detector 420 determines that a1 has been exceeded, integration can be performed. The control unit 490 can control the storage cell multiplexer 430 to connect the output of the input stage 410 to the first storage cell 441. The capacitor of the first storage cell 441 can charge as current or charge accumulates from the sensing element 311. Simultaneously, the voltage of one or more other storage cells not selected by the storage cell multiplexer 430 (e.g., the second storage cell 442 through the Nth storage cell 449) can be detected by the converter 450.

[0065]

[0080] Converter 450 can be configured with different reference values ​​that can be used for different purposes, such as: The reference value can be used to confirm the arrival of an incident electron; The reference value can be used to identify the type of incident electron (e.g., to determine whether the incident electron is a secondary electron or a backscattered electron); The reference value can be used to determine whether multiple electrons arrive during an electron arrival event; The reference value can be used to determine whether a sensing element or storage cell is in an overflow state due to an electron arrival event; and The reference value can also be used to determine the energy range or exact energy level of the incident electron.

[0066]

[0081] As an example of the use of a reference value, if only one predefined reference voltage or value (e.g., in cases where an ADC is used) is set, the single reference value can be used to identify whether the incident electrons are secondary electrons or backscattered electrons when an electron arrival event occurs whose result is stored in the storage cell being interrogated, or the reference value can be used to confirm that an electron arrival event has occurred (e.g., even after threshold a1 is exceeded (thus indicating the start of an electron arrival event), the reference value of converter 450 can be used to confirm that the signal from sensing element 311 corresponds to the detection of secondary or backscattered electrons from the sample, and therefore that electrons should be counted).

[0067]

[0082] When multiple reference values ​​are used, a variety of scenarios may be possible. The reference values ​​may be set according to a particular application or purpose. For example, if two predefined reference voltages or predefined values ​​(e.g., in cases where an ADC is used) are set, the following scenarios may be set up: In the first scenario, one of the reference voltages or values ​​may be used to confirm the arrival of electrons during an electron arrival event. The other reference voltage or value may be used to determine whether one electron reaches the sensing element during an electron arrival event or whether multiple electrons reach the sensing element during an electron arrival event.

[0068]

[0083] In the second scenario, one of the reference voltages or values ​​can be used to identify the type of incident electron during an electron arrival event, and the other reference voltage or value can be used to determine whether one electron or multiple electrons reached the sensing element during the electron arrival event.

[0069]

[0084] In a third scenario, one of the reference voltages or values ​​can be used to determine whether one electron or multiple electrons reach the sensing element during an electron arrival event. The other reference voltage or value can be used to determine whether the storage cell is in an overflow state. An overflow state can correspond to a situation in which more than two electrons reach the sensing element during an electron arrival event.

[0070]

[0085] It will be appreciated that more scenarios can be set up by combining different tasks such as those discussed above. Further predefined voltages or values ​​can be used based on the requirements for a particular application. Furthermore, after the information query, the storage cell can be reset and the information stored in the storage cell can be removed from the storage cell (e.g., the voltage across the capacitor of the storage cell can be reset to a predefined value, such as zero).

[0071]

[0086] There may be a time associated with an electronic arrival event. For example, as discussed above, the phrase "during an electronic arrival event" may refer to a time based on when the threshold detector 420 determines that the signal from the sensing element 311 crossed (e.g., exceeded) a1 or when the signal crossed (e.g., fell below) a2. In some embodiments, a predetermined time may be set such that the electronic arrival event lasts for a maximum duration from crossing a1 until the end of the predetermined time. If an end point is not detected (e.g., the signal crosses the same or a different threshold) after the predetermined time has elapsed, the counting of a given electronic arrival event may be forced to end. If no electron detection is confirmed during an electronic arrival event, a detection error signal may be generated and recorded by the control unit 490.

[0072]

[0087] The control unit 490 can be configured for additional tasks. For example, various functions can be performed when the threshold detector 420 determines that a threshold has been crossed. When the threshold detector 420 detects the start of an electronic arrival event, the control unit 490 can record a timestamp of the start point. In some embodiments, only if the start point is detected, the control unit 490 can monitor whether a subsequent end point is detected. For example, the threshold detector 420 may not use the second threshold a2 unless or until the first threshold a1 is crossed. Furthermore, a timestamp can also be recorded at the end point. The threshold associated with the start point may be higher than the threshold associated with the end point. An event time can be determined based on the start and end points.

[0073]

[0088] A first charged particle event can be detected when the threshold detector 420 determines that the signal from the sensing element 311 exceeds a1. Integration of the first charged particle event can be performed using the first storage cell 441. After the first charged particle event, integration of the second charged particle event can be performed using a different storage cell (e.g., the second storage cell 442). The term "after" the first charged particle event can refer to the instance when the signal from the sensing element 311 drops below a2. In some embodiments, "after" the first charged particle event can refer to the instance when a predetermined time has passed since the threshold detector 420 determined that the signal from the sensing element 311 exceeded a1.

[0074]

[0089] Integration and information interrogation can occur simultaneously. For example, while performing information interrogation, either cell by cell or in parallel with multiple cells not selected by storage cell multiplexer 430, circuit 400 can proceed with integration on the cell selected by storage cell multiplexer 430. Integration can send a signal from the output of input stage 410 to a selected storage cell in array 440. Integration can proceed until threshold detector 420 determines that the signal from sensing element 311 falls below threshold a2 (or an endpoint is otherwise determined). In response to the signal level falling below a2, storage cell multiplexer 430 can disconnect the connection between input stage 410 (or the output of the integration circuit) and the currently selected storage cell. Immediately thereafter, circuit 400 can connect the output of input stage 410 to another storage cell. The next connected storage cell can be the already reset storage cell. Integration can then proceed again using the newly selected storage cell. In some embodiments, integration does not begin immediately after disconnecting the previous storage cell unless, for example, threshold detector 420 determines that a1 has been exceeded again.

[0075]

[0090] When the detector is operating, integration and interrogation may be ongoing. Integration results stored in storage cells may be interrogated, and count results may be sent to control unit 490. Such operations may occur at the sensing element level. Thus, a separate integration and interrogation process may be performed for every sensing element of the detector. Data may be processed and sent to an upper level control unit of the detector. For example, controller 109 of FIG. 1 or FIG. 2B may be an upper level control unit configured to determine electron counts based on data from a lower level control unit (e.g., control unit 490 at the sensing element level of the detector).

[0076]

[0091] The control unit 490 can be configured to determine an overflow condition of the sensing element or storage cell (e.g., set an overflow flag). There can be several different types of overflow. Overflow is discussed in U.S. Patent Application Publication No. 2019 / 0378682.

[0077]

[0092] For example, the overflow may include a first type of overflow. The first type of overflow may involve a level of a signal associated with a charged particle event exceeding a predetermined value. The predetermined value may be determined based on the limits 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 the arrival of multiple charged particles during a single charged particle event. For example, multiple charged particles may arrive at the sensing element in close succession. The circuit may not be able to discretely process outputs associated with multiple charged particles during a single charged particle arrival event. Accordingly, the circuit may record the overflow event, for example, by setting an overflow flag indicating the first type of overflow.

[0078]

[0093] A first type of overflow may be encountered when a component of a circuit connected to the sensing element is in an overflow state. In some embodiments, a first type of overflow may be encountered when a component of a circuit connected to the sensing element for counting charged particles in a specific energy range is in an overflow state. For example, a first type of overflow flag may be set when a query result indicates that an electron arrival event recorded by the storage cell involves more than a certain number of incident electrons. The certain number may be, for example, one or two. Whether the certain number is one or two may depend on the requirements of a particular application and the corresponding reference voltage (or value) setting scenario. Furthermore, the frequency of occurrence of a first type of overflow may be reduced if the dynamic range of the circuit is increased (e.g., the input stage, storage multiplexer, storage cell, and converter may operate under a higher signal swing). Additionally, a first type of overflow may be reduced by increasing the capacitance of the storage cell or reducing the signal swing of the input stage. In some embodiments, this comes at the expense of a loss of energy resolution.

[0079]

[0094] Overflow may also include a second type of overflow. The second type of overflow may involve a situation in which another charged particle event occurs during signal detection and processing of one charged particle event. The second type of overflow may be encountered when one charged particle arrives at a sensing element and a subsequent charged particle arrives without the sensing element and its associated circuitry being able to provide a correct response to the subsequent charged particle arrival event. This may be due to the circuit (e.g., circuit 400) being in the process of processing the first charged particle arrival event when the subsequent charged particle arrives.

[0080]

[0095] The second type of overflow can be indicated by a flag. The second type of overflow flag can be set when there are no storage cells available for storage cell multiplexer 430 to select. In some embodiments, the second type of overflow can be avoided if a sufficiently large number of storage cells are provided. This can be based on the various reference voltages or values ​​used in converter 450 and the operating speed of the components of converter 450. The rate of the second type of overflow can be reduced by further improving the speed of sensing element 311, input stage 410, threshold detector 420, storage cell multiplexer 430, and converter 450.

[0081]

[0096] The use of an overflow indication can help reduce or avoid miscounting or false detection of charged particle events. Some embodiments can be configured to reduce the miscount rate at the expense of missing some details (e.g., information loss) of the event marked as overflow. For example, marking an event as a second type of overflow may result in missing some details, such as the specific energy of each charged particle arriving after the first charged particle during a charged particle event, but may still provide useful information indicating that multiple charged particles arrived during the charged particle event rather than just one. Without the use of an overflow flag, any information from subsequent charged particle events may be missed.

[0082]

[0097] Some embodiments of the present disclosure may use analog pipelines in the detection circuit and may provide converters in the signal processing portion of the circuit to ensure that the overall processing speed of the detection circuit is faster than the average rate at which the sensing element generates a signal in response to a charged particle arrival event. Some embodiments may reduce or avoid the second type of overflow. To provide further improvement, the detector or charged particle beam device may be configured to reduce the occurrence of the first type of overflow. The occurrence of the first type of overflow may be based on the speed at which the sensing element generates a signal in response to a charged particle arrival event and the bandwidth of the analog front end of the detection circuit. If the probe current increases beyond a certain level, the detection circuit may experience a first type of overflow, indicating the occurrence of an event with information loss. This may be because the front end of the detection circuit cannot distinguish between multiple charged particle arrival events. For example, multiple charged particles may arrive at the sensing element in close succession or substantially simultaneously. To reduce the first type of overflow, the speed of the sensing element and the bandwidth of the front end may be increased. Alternatively or additionally, the detector can be configured so that the intensity distribution of charged particles arriving at the detection surface is more uniform and spread evenly over a larger area, thus covering more sensing elements.

[0083]

[0098] In a comparative embodiment, the electron counting circuit may have a signal path beginning with an analog front end, which may include a transimpedance amplifier (TIA), after the sensing element or detector. The analog front end is then followed by a threshold detector, a window detector, or a data converter (e.g., an ADC). In such a configuration, the energy of the signal representing an incident electron event may not be successfully collected if the detector and TIA combination does not have sufficient analog bandwidth to transmit all of the frequency components of the signal from the detector. This may reduce the accuracy of energy detection or discrimination of incident electrons and may also result in a degradation of the SNR.

[0084]

[0099] In some embodiments of the present disclosure, the segmented detector can be combined with sensing element level signal processing circuitry. Some embodiments can achieve the following: 1. Each sensing element of a segmented detector may have a small area and relatively small parasitic capacitance, for example, compared to a single large-area sensing element, allowing the analog signal path connected to each sensing element to achieve a wide bandwidth. The analog bandwidth of the analog signal path may be wide enough to transmit all or substantially all frequency components of an electronic arrival event signal through the analog signal path. 2. Downstream of the analog signal path, the signal can be fed to an integrator (e.g., an integration circuit). The result from the integrator can be a voltage with an amplitude proportional to the energy of the incident electrons. Such a configuration can improve the accuracy of electron energy discrimination. Some comparison designs can use peak detection-based circuits to determine the energy level of the incident electrons. The comparison method can have low energy discrimination accuracy. This may be because the peak level of the signal is not always proportional to the energy level of the incident electrons. The shape of the signal waveform can also affect the signal peak level. Using an integrator to integrate the signal can reduce or eliminate the effects of signal waveform fluctuations. 3. The frequency component loss of the detection signal can be reduced or eliminated, improving the overall SNR during the electron counting process. Such SNR improvement can help improve the electron counting accuracy and energy discrimination accuracy.

[0085]

[0100] Additionally, in some embodiments, an analog pipeline configuration can be provided for the integrator circuit and the converter (e.g., a circuit including a level detector or an ADC), achieving a wide dynamic range for electron beam detection. The detection signals can be continuously routed from the sensing elements to their associated signal processing circuits. Each stage of the signal processing circuit (e.g., the converter 450, which may include a voltage detector or an ADC) may have an upper limit on its processing speed. If the time between two electron arrival events is shorter than the time it takes the converter to perform signal processing, miscounting can occur. Using analog pipelines in the integrator circuit can reduce the miscount rate because the time between two electron arrival events can vary due to the stochastic behavior of electrons. Each sensing element level circuit can be provided with additional level detector circuits or ADCs, allowing more level detector circuits or ADCs to operate in parallel.

[0086]

[0101] Comparative electron counting systems can typically be designed for applications involving extremely low probe currents. In such cases, the time between any two electron arrival events can be long. If the probe current is increased, the time between two electron arrival events becomes shorter. Comparative designs may not be able to recognize separate electron arrival events that occur in close succession, and under such conditions, a high miscount rate may occur. However, some embodiments of the present disclosure can enable accurate charged particle counting even when the time between two electron arrival events at a single sensing element is shortened (e.g., near zero). Approaches that attempt to increase the speed of the converter (e.g., voltage detector or ADC) and the analog bandwidth of the signal path may not achieve accurate charged particle counting with a miscount rate below an acceptable level. In some embodiments of the present disclosure, a high-speed level detection circuit can be combined with a signal path having a wide analog bandwidth and a fast analog signal processing pipeline. In some embodiments, the miscount rate can be significantly reduced compared to comparative embodiments.

[0087]

[0102] 5A, which shows a diagrammatic representation of an implementation of a circuit 400A that may be useful for electron counting, consistent with embodiments of the present disclosure. Similar to circuit 400 of FIG. 4, circuit 400A may include sensing element 311, input stage 410, threshold detector 420, storage cell multiplexer 430, first storage cell 441, second storage cell 442, converter 450, and control unit 490. Examples of such elements include a current-controlled current source (CCCS) 411 that may have a current gain β, a current detector 421, a switch K, and a threshold detector 420. 11 , capacitor C 11 , C 12 , voltage buffer 451 and voltage comparators 453, 455, 457. The sensing element 311 is connected to a bias voltage v bias The sensing element 311 can be configured to output a current signal to the CCCS 411. The CCCS 411 amplifies the charge or current received from the sensing element 311 and outputs an amplified signal βi s The CCCS 411 may be configured to output a signal, e.g., one going to the threshold detector 420 and one used as the output of the input stage 410. Each of the outputs of the CCCS 411 outputs the same signal (e.g., the amplified signal βi s ) can be output.

[0088]

[0103] The circuit 400A outputs the amplified signal βi s For example, the determination of when to start and stop counting electrons can be made by a current detector 421. The current detector 421 determines whether βi s can be compared with thresholds a1 and a2 to determine when the thresholds are passed. For example, the current detector 421 can detect βi s When a1 exceeds a1, the electron arrival event begins, and βi s The current detector 421 can determine that the electron arrival event ends when βi s When exceeds a1, the integration start signal is determined, and βi s The integration end signal can be determined when a falls below a2.

[0089]

[0104] The storage cell multiplexer 430 is connected to the switch K 11 The circuit 400A may include two storage cells of the array. The multiplexer 430 outputs the amplified signal βi s to any of the storage cells. A storage cell may be formed by a storage capacitor and a corresponding reset switch connected in parallel with the storage capacitor. For example, the first storage cell 441 may be formed by a capacitor C 11 and switch K 21 The second storage cell 442 can be formed by a capacitor C 12 and switch K 22 Further storage cells can be added, and switch K 11 It will be appreciated that the input stage 410 may be switched between more than two states. Additionally, a single storage cell may be provided. In some embodiments, the single storage cell includes a switch K that can be switched between a first state connecting the output of the input stage 410 to the storage cell and a second state connecting the output of the input stage 410 to ground. 11 While the integration result is being processed, switch K 11 may be in a second state. If signal processing of the first electronic arrival event is in progress when the second electronic arrival event occurs, the circuitry may be configured so that the second electronic arrival event does not interfere with the signal processing of the first electronic arrival event. In such a case, an overflow (e.g., a second type of overflow) may be recorded when the second electronic arrival event occurs.

[0090]

[0105] Converter 450 may have only one input channel and may include a voltage buffer 451. The voltage buffer 451 may be used to reduce the load on the storage cells and improve performance in cases where multiple voltage comparators are used simultaneously in one converter. 31may be provided to allow converter 450 to access all storage cells of the storage cell array. 31 A multiplexer, which may include a multiplexer, may be provided between the storage cell array and the converter 450. The converter 450 may be formed as a voltage detector using a voltage buffer 451 and multiple voltage comparators 453, 455, and 457. Multiple reference voltages having different values ​​may be used. Based on the difference between the value of the input voltage and the value of the reference voltage, the voltage comparators 453, 455, and 457 may react to the input voltage and generate an output signal. The output signal from the voltage comparators 453, 455, and 457 may be used as information about the corresponding charged particle arrival event.

[0091]

[0106] Switch K 11 , K. 31 The switch K can be configured so that only one storage cell is selected while the integration is being performed. As shown in FIG. 5A, 11 can be connected to position 1 and perform the integration using the first storage cell 441. In some embodiments, switch K 11 , K. 31 can be configured to never select the same storage cell while performing an integration. For example, switch K 11 is connected to position 1, while switch K 31 can be connected to position 1. An integration can be performed using one storage cell while a query is performed on another storage cell. Moreover, switch K 11 , K. 31 can also be switched to a disconnect position in which no storage cells of array 440 are selected.

[0092]

[0107] In some embodiments, switch K 11 , K. 31 can be configured so that the same storage cell is selected at a given time. For example, the circuit can be configured so that switches K11 , K. 31 can be configured to operate. During the processing time of a particular integration result, the reference voltage setting can be adjusted depending on the overlap time, for example, to compensate for effects introduced by selecting the same storage cell. Moreover, in some embodiments, the voltage buffer 451 can be configured to operate in conjunction with the storage cell and the switch K 31 A plurality of voltage buffers may be provided.

[0093]

[0108] Integration can be performed by changing the state of the reset switch of a storage cell from closed to open. For example, integration using the first storage cell 441 can be performed by changing the state of the reset switch of the storage cell from closed to open. 21 The reset switch for each storage cell can remain closed after the storage cell is reset and until the storage cell is used for integration. The control unit 490 uses the switch K to select the storage cell. 11 and a switch (e.g., switch K 21 or switch K 22 ) to begin integration. The decision to start or end integration may be based on a determination by threshold detector 420 (e.g., by determining an integration start or end signal). For example, threshold detector 420 may send an integration start signal to control unit 490, which may then activate switch K 21 or switch K 22 It can activate switches such as

[0094]

[0109] An interrogation can be initiated by connecting a storage cell to the converter 450. Once the converter 450 is connected to the storage cell, the signal input to the converter 450 can be processed. The signal processing that occurs in the converter 450 can take a certain amount of time. For example, the voltage buffer 451 can output a signal to multiple voltage comparators. Multiple decisions can be made based on a comparison between the input voltage and a reference voltage. Based on such decisions, a decision can be made to count electrons or other information can be determined. For example, it can be determined that two electrons arrived at the sensing element 311 during an electron arrival event, so the count should be incremented by two. Furthermore, it can be determined, for example, that one of the electrons was a secondary electron and the other was a backscattered electron.

[0095]

[0110] However, while such processing is ongoing, additional electrons may arrive at sensing element 311. To avoid missing such additional electron arrival events, circuit 400A can perform integration using a different storage cell when a new electron arrival event is detected. This integration can be performed while interrogation or signal processing of the previous electron arrival event is still in progress. For example, threshold detector 420 can detect that a first electron arrival event has begun when threshold a1 is exceeded, and control unit 490 can begin integration using the first storage cell. Threshold detector 420 can also detect that the first electron arrival event has ended when the signal input to threshold detector 420 falls below threshold a2. Threshold detector 420 can then detect a second electron arrival event when threshold a1 is again exceeded. However, at this point, interrogation or signal processing of the first electron arrival event, which may be based on determining the charge collected in the first storage cell, may not yet be complete. Nevertheless, circuit 400A can accept a second electronic arrival event and record it using a second storage cell. Multiplexer 430 can connect the output of input stage 410 to the second storage cell, thus properly recording information for the second electronic arrival event. In this manner, information for a subsequent electronic arrival event can be recorded even while signal processing related to the previous electronic arrival event is still in progress. Circuit 400A can substantially continuously capture information from sensing element 311 while operations such as signal processing and electron count determination occur asynchronously. In some embodiments, as soon as integration using one storage cell is completed, multiplexer 430 can connect the output of input stage 410 to the next available storage cell, which has already been reset. The detection signal can be continuously routed from the sensing element to the signal processing circuitry.

[0096]

[0111] In some embodiments, the determination of whether a new electronic arrival event has occurred may be based on a different threshold than that used to detect the first electronic arrival event. The threshold may be set to a level based on the pileup effect caused by the new electronic arrival event. For example, the threshold detector 420 may detect the beginning of a first electronic arrival event when a threshold a1 is exceeded. The detected signal level (e.g., voltage, current, etc.) may begin to drop. However, the signal level may not drop below a threshold a2, which in another embodiment may indicate the end of the electronic arrival event. However, the signal level fluctuation may reach a level that passes a threshold a3, stop dropping, and begin to rise again. Passing the threshold a3 may indicate the end of the first electronic arrival event. An increase in the signal level after passing the threshold a3 may indicate the start of a second electronic arrival event. The second electronic arrival event may partially overlap in time with the first electronic arrival event. The level of the threshold a3 may be based on the behavior of closely spaced consecutive electronic arrival events. The threshold relationship may be, for example, a1 ≥ a3 ≥ a2. The determination of whether a new electron arrival event has occurred may be based on signal level and time-dependent behavior.

[0097]

[0112] Referring now to FIG. 5B, FIG. 5B shows a diagrammatic representation of an implementation of a circuit 400B that may be useful for electron counting, consistent with embodiments of the present disclosure. Circuit 400B may be a variation of circuit 400 of FIG. 4 and, similar to circuit 400A of FIG. 5A, circuit 400B may include various examples of general-purpose components. Circuit 400B of FIG. 5B may include a wideband operational amplifier (OPA) 402 connected to sensing element 311. Unlike the previous example, no input stage is used. OPA 402 includes a storage capacitor C 11 , C 12 to achieve an integration function. The output of the OPA 402 may be similar to the output of the input stage 410 discussed in the previous example. The signal from the sensing element 311 may be sent to a storage cell without passing through an input stage.

[0098]

[0113] As shown in FIG. 5B, circuit 400B includes a switch K 12 and switch K 13 The multiplexer 430 may include a switch K 11 , K. 12 , K. 13 Switch K 12 and switch K 13 By adding switch K, the isolation between the OPA 402 and the storage cells not used for integration can be improved. Moreover, compensation of the OPA 402 used in the integration circuit can be easily implemented. In addition, switch K 12 and switch K 13 By adding the integrator circuit, the interference between the integrator circuit and the converter 450 can be reduced, and the energy measurement accuracy can be improved.

[0099]

[0114] The circuit 400B outputs the amplified signal βi s The amplified signal βi can be configured to perform an action using a decision based on the amplified signal βi s can be sampled or mirrored from the OPA 402. The determination of the start and end of electron counting can be made by the current detector 422. The current detector 422 detects βi s is compared with thresholds a1 and a2, for example, βi s When a1 exceeds a1, the electron arrival event begins, and βi s It can be determined that the electron arrival event ends when falls below a2.

[0100]

[0115] Circuit 400B can be configured to perform operations similar to those of circuit 400A. For example, circuit 400B can be configured to count charged particles by performing integration using a storage cell and to interrogate the storage cell using transducer 450. The integration can be performed by changing the state of a reset switch of the storage cell from closed to open. After processing the information from the storage cell, the storage cell can be reset, for example, by activating the reset switch using transducer 450.

[0101]

[0116] Referring now to FIG. 5C, FIG. 5C shows a diagrammatic representation of an implementation of a circuit 400C that may be useful for electron counting, consistent with an embodiment of the present disclosure. The circuit 400C may be a variation of the circuit 400 of FIG. 4 and may be similar to the circuit 400A of FIG. 5A and the circuit 400B of FIG. 5B, and the circuit 400C may include various examples of general-purpose components. The circuit 400C of FIG. 5C may include a wideband transimpedance amplifier (TIA) 403 connected to the sensing element 311. An input stage 410 may be formed by an amplifier, such as the TIA 403. The TIA 403 may include an OPA. The output of the input stage 410 may be a voltage signal.

[0102]

[0117] The circuit 400C may include multiple amplifiers. A first amplifier may be formed by a TIA 403. A second amplifier may be formed by an OPA 404. The OPA 404 has a storage capacitor C 11 , C 12 can be used in conjunction with to achieve an integral function.

[0103]

[0118] The circuit 400C includes a resistor R 11 The output of the input stage 410 may be a voltage signal, and may include a resistor R 11 The OPA 404 may be configured to convert the output of the input stage 410 into a current signal having a signal level proportional to the output of the input stage 410. The OPA 404 may be an amplifying device configured for use with external feedback components (e.g., resistors and capacitors) between its output and input terminals. The OPA 404 is connected to a resistor R 11 The sensing element 311 can receive a current signal from the sensing element 311 and use it to perform integration using storage cells (e.g., first storage cell 441 and second storage cell 442). The signal from the sensing element 311 can be converted into various formats before being sent to the storage cells.

[0104]

[0119] The circuit 400C can be configured to perform actions using decisions based on the converted signal from the sensing element 311. For example, the input stage 410 can convert the current or charge signal from the sensing element 311 to a voltage signal and provide the voltage signal to the threshold detector 420. The threshold detector 420 can include a voltage comparator 423. The voltage comparator 423 can compare the voltage signal input to the threshold detector 420 to a threshold. Multiple thresholds can be used, such as a1 and a2. The threshold can include a reference voltage. Determination of the start and end of electron counting can be made by the voltage comparator 423. For example, the voltage comparator 423 can determine that an electron arrival event begins when a1 is exceeded. In some embodiments, multiple voltage comparisons can be used to account for hysteresis effects, improving performance and reducing false count rates.

[0105]

[0120] Circuit 400C can be configured to perform operations similar to those of circuit 400A or circuit 400B. For example, circuit 400C can be configured to count charged particles by performing integration using a storage cell and to interrogate the storage cell using transducer 450. The integration can be performed by changing the state of a reset switch of the storage cell from closed to open. After processing the information from the storage cell, the storage cell can be reset, for example, by activating the reset switch using transducer 450.

[0106]

[0121] Referring now to FIG. 6, FIG. 6 is a flowchart illustrating a method 600 that may be useful for electron counting consistent with an embodiment of the present disclosure. Method 600 may be performed by a controller of a charged particle inspection system (e.g., controller 109 of FIG. 1 or FIG. 2B, control unit 490 of FIGS. 4 and 5A-5C, or a combination thereof). The controller may include circuitry (e.g., memory and a processor) programmed to implement method 600. For example, the controller may be an internal controller or an external controller coupled to the charged particle inspection system. Circuitry that may be used for charged particle counting (e.g., circuit 400 of FIG. 4) may operate according to method 600. Processing consistent with method 600 may be performed on a sensing element by sensing element basis.

[0107]

[0122] As shown in FIG. 6, method 600 can begin with a "start" step. In the start step, a charged particle beam can be generated. The beam can be generated by the electron beam tool 100. The generation of primary charged particles can form a secondary beam that is directed to a detector of the charged particle beam device. Detection can begin when the charged particles begin to impact the detector. The detector can include a sensing element (e.g., sensing element 311).

[0108]

[0123] Method 600 may include performing multiple processes in parallel. Each process may be a background operation that may be ongoing while the detector is operating. For example, as shown in FIG. 6, method 600 may include steps 601, 602, 603, and 604. Step 601 may include performing sensing element signal level detection. Step 602 may include performing integration. Step 603 may include performing signal processing. Step 604 may include performing overflow monitoring. Other steps may also be performed in parallel.

[0109]

[0124] As shown in FIG. 7A, certain processing may occur following step 601. Following "A," method 600 may include step 7101 of monitoring a sensing element signal level. Step 7101 may include receiving a signal representative of the signal coming from or its output (e.g., an amplified signal). The magnitude of the signal may be measured. In step 7102, it may be determined whether a first threshold has been crossed. Step 7102 may include using threshold detector 420 to determine whether the output of input stage 410 has crossed (e.g., exceeded) threshold a1.

[0110]

[0125] If the first threshold is not exceeded as determined in step 7102, then the signal coming from the sensing element 311 may be determined to be noise. The method may return to step 7101 to continue monitoring the sensing element signal level.

[0111]

[0126] If the first threshold is determined to be exceeded in step 7102, it may be determined that an electronic arrival event has begun. In response to exceeding the first threshold in step 7102, the method may proceed to step 7103 and generate an integration start signal. The integration start signal may be generated and transmitted from threshold detector 420. In some embodiments, control unit 490 may generate the integration start signal. For example, control unit 490 may generate the integration start signal based on an output from threshold detector 420. Additionally, step 7104 may be performed to generate a timestamp. The timestamp may be associated with the integration start signal.

[0112]

[0127] 7A, step 7105 may be performed to perform sensing element signal level detection. The signal level of the signal from sensing element 311 may continue to be monitored. In step 7106, it may be determined whether a second threshold has been crossed. Step 7106 may include using threshold detector 420 to determine whether the output of input stage 410 has crossed (e.g., fallen below) threshold a2.

[0113]

[0128] If in step 7106 it is determined that the signal level is not below the second threshold, it may be determined that the electronic arrival event is still in progress, and the method may return to step 7105 to continue monitoring the sensing element signal level.

[0114]

[0129] If it is determined in step 7106 that the signal level has fallen below the second threshold, it may be determined that the electronic arrival event has ended. In response to passing the second threshold in step 7106, the method may proceed to step 7107, where an end-of-integration signal may be generated. Additionally, step 7108 may be performed, where a timestamp may be generated. The timestamp may be associated with the end-of-integration signal. After step 7108, the method may return to step 7101 and repeat.

[0115]

[0130] As shown in FIG. 7B, certain processing may occur following step 602. Following "B," method 600 may include step 7201 of monitoring an integration start signal. Step 7201 may include receiving a signal from control unit 490. Step 7202 may include determining, using control unit 490 or another controller, whether an integration start signal is being generated or received. The integration start signal may have been generated in step 7103 of FIG. 7A.

[0116]

[0131] As shown in FIG. 7B, if in step 7202 it is determined, for example, that the integration start signal has not been received, the method may return to step 7201 to continue monitoring for the integration start signal.

[0117]

[0132] If it is determined in step 7202 that an integration start signal has been received, the method may proceed to step 7203, where integration may be performed. Step 7203 may include performing signal integration using a currently selected storage cell. For example, storage cell multiplexer 430 may select a storage cell of array 440 (see FIG. 4). At the start of method 600, the storage cell may be in a reset state. The corresponding reset switch of the selected storage cell may be closed.

[0118]

[0133] In step 7203, integration can be performed, which may involve accumulating charge or current over time (e.g., area under a curve) using the signal from the sensing element 311. Step 7203 may include actuating a reset switch. For example, when integration begins using the first storage cell 441 (see FIG. 5A), switch K 21 can be set to an open state. During integration, the sensing element 311 outputs an amplifiable charge or current that can be transmitted to the first storage cell 441, and the charge or current is stored in the capacitor C 11 Accumulates in.

[0119]

[0134] In step 7204, it may be determined whether an end of integration signal has been received. If in step 7204 it is determined that an end of integration signal has not been received, the method may return to step 7203 and continue integration.

[0120]

[0135] If it is determined in step 7204 that an integration termination signal has been received, signal integration corresponding to the electronic arrival event may be aborted. The method may proceed to step 7205. In step 7205, signal integration in the currently selected storage cell may be terminated. The current storage cell may be the one selected by multiplexer 430. Additionally, step 7206 may be performed. In step 7206, an integrator busy indicator may be set. The integrator busy indicator may be associated with an overflow condition.

[0121]

[0136] In step 7207, a result analysis request indicator can be set and the address of the currently selected storage cell can be added to an address list. Setting the result analysis indicator can be based on criteria. For example, once integration is performed using a storage cell, it can be determined that analysis should be performed on that storage cell when integration is complete. The criteria can include whether integration start and end signals are received in succession. A decision to set the result analysis request indicator can be automatically made in response to receiving an integration start signal followed by an integration end signal. In some embodiments, the criteria can include whether an operator has requested imaging results. In some embodiments, the criteria can include whether an operator has requested detailed results (such as results showing electron energy). The storage cell address can refer to information that can be used to identify the storage cell. Result analysis can correspond to, for example, counting or signal processing related to determining the resulting energy associated with an electron arrival event. The address list can be a list used to store addresses of storage cells containing data to be analyzed. Storage cells can be queried based on whether they are listed in the address list.

[0122]

[0137] In step 7208, the next available storage cell may be located. For example, if array 440 includes multiple storage cells and the currently selected storage cell has just been used for integration, it may be determined whether another storage cell in array 440 is available. Step 7208 may include incrementing the storage cell selector. The storage cell may be incremented by one.

[0123]

[0138] In step 7209, it may be determined whether at least one storage cell is available. If no additional storage cells are available, the method may return to step 7208 to wait for the next available storage cell. If it is determined that a storage cell is available, the method may proceed to step 7210. In step 7210, the storage cell multiplexer may select the next available storage cell. Step 7210 may include activating a switch to connect the output of input stage 410 to a storage cell (e.g., the next of storage cells 441, 442, ... 449). For example, assuming storage cell 441 (see FIG. 4) has just been used for integration, multiplexer 430 may connect the output of input stage 410 to storage cell 442. Additionally, in step 7211, an integrator busy indicator may be cleared. The integrator busy indicator may be cleared once a connection between the next available storage cell and the output of input stage 410 is established. Thus, the integrator busy indicator may be set in step 7206 and maintained in that set state until step 7211. After step 7211, the method may return to step 7201 and repeat.

[0124]

[0139] 7C, certain processing may occur following step 603. Following "C," method 600 may include step 7301 of monitoring an analysis request indicator. Step 7301 may include receiving a signal from control unit 490.

[0125]

[0140] If it is determined in step 7302 that an analysis request indicator has not been received, the method may return to step 7301 to continue monitoring for an analysis request indicator.

[0126]

[0141] If in step 7302 it is determined that an analysis request indicator has been received, the method may proceed to step 7303. Step 7303 may include obtaining an address of a storage cell in an address list.

[0127]

[0142] In step 7304, a query may be performed, which may involve obtaining information (e.g., transmitting a signal) from a component such as a storage cell. Step 7304 may include selecting a storage cell. For example, step 7304 may involve activating a switch (e.g., switch K in FIG. 5A) to connect the storage cell to be queried to converter 450. 31 The storage cells to be queried may include storage cells that were integrated in step 7203 (see FIG. 7B). The priority of the query may be based on the time since the integration was performed using the sensing element. For example, the storage cell to be next queried may be prioritized as the storage cell that has waited the longest since being integrated.

[0128]

[0143] Step 7304 may also include performing signal processing. Step 7304 may include using converter 450 to make a determination about the queried signal from the selected storage cell. For example, a signal may be sent from first storage cell 441 to converter 450, and a reference value (e.g., v in FIG. 5A) may be transmitted to converter 450. ref11, v ref12 , v ref13 ) are made. Converter 450 can output data to control unit 490 that can be used to derive information about the electron arrival event (e.g., confirmation of the electron arrival event, whether one electron or multiple electrons were received, or the specific energy level of the received electrons).

[0129]

[0144] In step 7305, the selected storage cell may be reset to release charge therefrom. Step 7305 may include activating a reset switch of the selected storage cell.

[0130]

[0145] Also, in step 7305, the address of the selected storage cell may be removed from the address list. In step 7306, it may be determined whether there are any more addresses in the address list. If it is determined in step 7306 that there are addresses remaining in the address list, the method may return to step 7303 and obtain the top address of the list. If it is determined in step 7306 that there are no addresses remaining in the address list, the method may proceed to step 7307 and clear the analysis request indicator. After step 7307, the method may return to step 7301 and repeat.

[0131]

[0146] As shown in Figure 7D, certain processing may be performed following step 604. Following "D", method 600 may include step 7401 of monitoring an integration start signal. Step 7401 may be similar to step 7201 of Figure 7B.

[0132]

[0147] If it is determined in step 7402 that the integration start signal has not been received, the method may return to step 7401 to continue monitoring for the integration start signal.

[0133]

[0148] If it is determined in step 7402 that an integration start signal has been received, the method may proceed to step 7403 and check an integration circuit busy indicator. Step 7403 may include monitoring a signal such as that generated in step 7206 (see FIG. 7B). For example, storage cell multiplexer 430 may select a storage cell of array 440 (see FIG. 4).

[0134]

[0149] If it is determined in step 7404 that the busy indicator is not set, the method may return to step 7401 to continue monitoring for an upcoming integration start signal.

[0135]

[0150] If it is determined in step 7404 that the busy indicator is set, the method may proceed to step 7405 and generate an overflow signal. The overflow signal may be associated with a second type of overflow, such as that discussed herein. Step 7405 may include generating a timestamp associated with the overflow signal. After step 7405, the method may return to step 7401 and repeat.

[0136]

[0151] Signal processing such as that of step 7304 (see FIG. 7C) may require a certain amount of time. If signal processing for a first storage cell (e.g., the storage cell interrogated in step 7304) is not complete by the time integration of a new electron arrival event should begin, a second storage cell can be selected for integration. For example, if signal processing is being performed on a first storage cell while the sensing element signal level is measured and again crosses the first threshold, a different storage cell than the first storage cell can be selected for the next integration. As long as additional storage cells are available, the next integration can proceed.

[0137]

[0152] The method 600 can continue cycles of integrating and performing analysis (e.g., interrogation and signal processing) on ​​storage cells. However, the speed at which the integration and signal processing are completed varies, and therefore it may be beneficial to have more storage cells available to receive signals from the sensing element 311. Integration can then continue uninterrupted while interrogation and signal processing occur asynchronously. The more storage cells provided, the greater the number of integrations that can be handled while signal processing of information from the previous storage cell is in progress. By using circuitry in such a manner, the detector can handle more signals.

[0138]

[0153] Method 600 and circuit 400 can be used, for example, to enable electron counting with dramatically improved SEM image SNR and overall throughput. The probe current range over which electron counting is possible can be expanded with improved energy measurement accuracy and reduced miscount rates.

[0139]

[0154] Moreover, in some embodiments, interconnections between the circuits associated with individual sensing elements can be provided. A detector can include sensing cells, each of which can include a sensing element and circuitry associated with the sensing element. For example, sensing element 311 and circuit 400 (see FIG. 4) can form a sensing cell. The circuitry associated with each sensing element can include an analog signal processor, a data converter, and a local control unit. Interconnections can be provided between the circuits of different sensing cells. For example, interconnections can be provided between the analog signal processors of neighboring sensing cells or between the local control units of neighboring sensing cells.

[0140]

[0155] In some embodiments, the detector may include a pixelated array of sensing elements. The array of sensing elements may be formed in a two-dimensional plane. Thus, a sensing element may have one or more neighboring (e.g., adjacent) sensing elements. Interconnections between sensing elements may improve detection accuracy and enhance processing. Moreover, in some embodiments, interconnections between sensing elements may improve processing and further improve miscount rate reduction. For example, interconnections may help reduce miscounts in situations where a transient ionization region induced by a single incident electron arrival event extends to the volume of multiple sensing elements.

[0141]

[0156] Referring now to FIG. 8, FIG. 8 illustrates the effect of a charged particle arrival event on a detection surface. In FIG. 8, the detector may include multiple detection elements, including detection element 36a, detection element 36b, detection element 36c, and detection element 36d. A charged particle may strike (e.g., impact) near the boundary between detection elements 36a and 36c at the detector surface. When an electron impacts the detector, a charge may be generated within a volume of the detector. The volume may span two or more detection elements. For example, an ionization region 37 may grow that penetrates multiple detection elements. The growth of charge across multiple detection elements can lead to a situation where an electron is counted multiple times or not counted at all.

[0142]

[0157] In some embodiments, the interconnects can help reduce miscounts of electrons reaching the detector's detection surface. Some miscounts may be due to electron arrival events occurring near the boundaries between sensing elements. When electrons from the SEM's electron optical column reach the detector's detection surface, the locations at which the electrons enter the detector may be randomly distributed. Due to the ionization process after each electron enters the detector, a temporary ionization region within the detector may be generated. The temporary ionization region may extend beyond the depletion region of a sensing element. For example, the temporary ionization region may extend into the depletion region of a neighboring sensing element, into another region different from the depletion region of the sensing element, or into a region within the volume of a neighboring sensing element different from the depletion region of that sensing element. The extension of the temporary ionization region into the depletion region of a neighboring sensing element may result in the generation of a signal in the neighboring sensing element. The ionization region formed by each electron entering the detector may have a volume related to the energy of each incident electron and the material forming the detector. Due to the randomness of the location at which each electron enters the detector, the temporary ionization region induced by each incident electron may cross the boundary between adjacent sensing elements. Thus, multiple sensing elements of a detector may generate output signals corresponding to a particular incident electron. The individual output signals may be lower than the signal generated if a transient ionization region were contained within one sensing element, and the output signals may not reach a high enough level to trigger detection of an electron arrival event. Thus, the electron arrival event may go uncounted. Alternatively, in some embodiments, the output signals of each of the multiple sensing elements may be high enough to trigger detection, and multiple detections may be registered for the same electron arrival event. Thus, miscounting may occur.

[0143]

[0158] To address the above issues, some embodiments may employ the following: The sensing elements may be configured to have a predetermined size and shape; The array of sensing elements may include sensing elements arranged in a pattern, such as a grid; The size of each sensing element in the detector may be chosen such that the size of the sensing element in any direction is equal to or greater than the maximum penetration depth of the incident electrons; The sensing elements may be configured such that no dimension (e.g., length, width, height) of the sensing element is less than the maximum penetration depth; The maximum penetration depth may be based on the material used to form the detector; for example, electrons penetrate some materials more easily than others; In this way, each incident electron may impact up to four sensing elements at a time; as discussed below, this may help further improve signal processing.

[0144]

[0159] Referring now to FIG. 9 , FIG. 9 is a diagrammatic representation of a detector with interconnected detection cells consistent with an embodiment of the present disclosure. FIG. 9 may represent a cross-sectional view of the detector through the thickness of the detector. As shown in FIG. 9 , the detector may be provided with multiple detection elements, including detection element 331. Each detection element may be connected to a circuit. The circuit may include a detection-element-level signal processing and control unit. For example, detection element 331 is connected to a detection-element-level signal processing and control unit 950. The detection element 331 and the detection-element-level signal processing and control unit 950 may comprise one detection cell. The detection-element-level signal processing and control unit 950 may include an analog signal processor 910, a data converter 930, and a local control unit 940.

[0145]

[0160] As shown in FIG. 9 , multiple detection cells can be connected to various higher-level components (e.g., data routing layer 960). Data routing layer 960 can include a high-speed data routing layer. Data routing layer 960 can be connected to memory unit 970. Memory unit 970 can include high-speed memory with a memory controller. Memory unit 970 can be connected to processor 980. Processor 980 can include a high-speed processor. Processor 980 can include controller 109 (see FIG. 1 or FIG. 3 ). Processor 980 can be connected to interface 990. Interface 990 can include a high-speed interface. The term “higher-level” can mean that a processing function is delegated to a certain type of processor. A higher-level component can be configured to perform processing based on information received from multiple lower-level components. A higher-level component can be configured to have a processing speed such that it can handle the output from multiple lower-level components to which it is connected.

[0146]

[0161] 9, between each of two adjacent sensing element level signal processing and control units (including, for example, unit 950), analog signals and digitally formatted data can be transferred through analog signal paths and data paths, respectively. Interconnect 920 can be provided. Interconnect 920 can include analog signal path 921 and data path 922.

[0147]

[0162] Although shown as a one-dimensional array in FIG. 9 , it will be understood that the sensing elements and associated circuitry can be provided in a two-dimensional arrangement. Sensing elements can be provided with their associated circuitry adjacent to the sensing element in the thickness direction of the detector or in some other direction. Sensing element-level circuitry for each sensing element can be embedded in each sensing element. Each sensing element-level signal processing and control unit can have multiple analog signal paths and data paths. Each of the multiple analog signal paths or data paths can be connected to one of the sensing element-level signal processing and control units adjacent to the sensing element. The electronic sensing element array and the array of sensing element-level signal processing and control units can be formed on the same chip or on multiple chips.

[0148]

[0163] The analog signal processor 910 may include the input stage 410, storage cell multiplexer 430, and storage cell array 440 discussed above with respect to FIG. 4 . Additionally, other analog signal routing multiplexers may be provided. For example, an analog signal routing multiplexer 460 may be provided (see FIG. 12A ). In some embodiments, the analog signal routing multiplexer 460 may be included in the sensing element-level signal processing and control unit 950. The analog signal routing multiplexer 460 may be part of the analog signal processor 910. The analog signal routing multiplexer 460 may be arranged between the storage cell array 440 and the converter 450. The analog signal routing multiplexer 460 may be configured to enable bidirectional analog signal flow between the analog signal routing multiplexer and other (e.g., neighboring) sensing element-level circuit components (such as voltage detectors / ADCs of neighboring sensing element-level circuits). The neighboring sensing element-level circuits may be circuits of neighboring sensing cells. The analog signal routing multiplexer 460 can be configured to transmit an analog signal in the form of a voltage, current, or charge that can represent the energy level of a particular electron incident event.

[0149]

[0164] The analog signal processing path can be formed by components of the circuit 400, including the input stage 410, the storage cell multiplexer 430, the array 440, the analog signal routing multiplexer 460, and the converter 450. The analog signal path 921 can be connected to the analog signal processor 910 (e.g., can be connected to the analog signal routing multiplexer 460 of FIG. 12A), and the analog signal path 921 can be configured to communicate with an analog signal routing multiplexer of another circuit (e.g., a sensing element-level circuit of a neighboring detection cell). The analog signal routing multiplexer 460 can be connected to the converter 450. In some embodiments, the converter 450 can include an ADC. The data converter 930 of FIG. 9 can include such an ADC. The data path 922 can be connected downstream of such an ADC. For example, as shown in FIG. 4, the converter 450 can be connected to the control unit 490. The local control unit 940 of FIG. 9 can include the control unit 490. The data path 922 may be connected to a local control unit 940, as shown in FIG. 9, and may be configured to communicate with control units of other circuits.

[0150]

[0165] In some embodiments, an interconnect can be provided that includes an analog signal routing multiplexer configured to enable bidirectional analog signal flow between the interconnect and a sensing element-level signal processing and control unit associated with another sensing element. The interconnect can include a data path configured to transmit digital data to a control unit associated with another sensing element.

[0151]

[0166] 9, each of the sensing element-level signal processing and control units 950 may have a data communication link with a data routing layer 960 following the sensing element-level signal processing and control unit array. A memory unit 970 may be configured to organize and store data coming from the sensing element-level signal processing and control unit array. The data routing layer 960 may be configured to manage data transfer from the sensing element-level signal processing and control unit array to the memory unit 970.

[0152]

[0167] The processor 980 may be configured to follow the memory unit 970 and perform data processing and operational control of the detector. For data processing, the processor 980 may accomplish data processing tasks including:

[0153]

[0168] For example, the processor 980 can be configured to perform SEM image pixel data generation based on predefined conditions (e.g., pixel ratio, pixel size, and sharpness). For each SEM image pixel, parameters such as pixel size, pixel ratio, and local sharpness can be the same in all frames of an SEM image under certain conditions. In some embodiments, the parameters can vary between frames of an SEM image but remain the same within each SEM image. In some embodiments, the parameters can vary from pixel to pixel within an SEM image.

[0154]

[0169] The processor 980 can be configured to perform adjustment and enhancement of SEM image parameters based on predefined conditions, such as image brightness and contrast adjustment, image sharpness enhancement, color SEM image generation, etc., based on the energy level of the incident electrons.

[0155]

[0170] The processor 980 can be configured to perform a pre-inspection based on the acquired SEM image, which can include pattern recognition, edge extraction, etc.

[0156]

[0171] The processor 980 may be configured to pass the raw data of the electronic counting results without any manipulation.

[0157]

[0172] The processor 980 can be configured to perform SEM projection tracking. SEM projection tracking can include generating information about a projected grid of beam spots formed on a detector (e.g., shape, size, location, distortion, movement, and distortion prediction). SEM projection tracking can also include generating information about each of the beam spots (e.g., location, size, shape, and movement history) and future movement prediction. Moreover, information such as that discussed above can be used to perform on-the-fly SEM image compensation. The processor 980 can be configured to determine a trade-off between collection speed and crosstalk, or between known SEM designs based on crosstalk reduction and known SEM designs based on increased collection speed.

[0158]

[0173] The interface 990 may be configured to receive data from the processor 980 and may perform further tasks such as: For example, the interface 990 may perform lossless data compression; The interface 990 may be configured to reduce the load on the data link between the detector and a higher-level system (e.g., a controller for the charged particle beam device or a general-purpose controller).

[0159]

[0174] The interface 990 may perform data encoding for error correction and may be configured to reduce errors that occur during data transport from the electronic detection device to a higher-level system.

[0160]

[0175] In some embodiments, the interface 990 can pass data directly to a higher-level system without any processing. The interface 990 can include high-speed transceivers and drivers to facilitate communication between the detector and the higher-level system.

[0161]

[0176] Referring now to FIG. 10 , FIG. 10 illustrates an interconnect arrangement consistent with embodiments of the present disclosure. Interconnects may be provided between each of adjacent sensing elements. The detector may include a two-dimensional array of sensing elements. Sensing elements of the array may have neighboring sensing elements in the horizontal and vertical directions. For example, sensing element 311 may be adjacent to sensing elements 318 and 312 in the horizontal direction and adjacent to sensing elements 313 and 316 in the vertical direction. Interconnect 1001 may be provided between sensing element 311 and sensing element 312. Similarly, interconnect 1002 may be provided between sensing element 311 and sensing element 313, interconnect 1003 may be provided between sensing element 311 and sensing element 316, and interconnect 1004 may be provided between sensing element 311 and sensing element 318. It will be understood that the interconnects in FIG. 10 may be between circuitry associated with the sensing elements rather than directly connecting the sensing elements themselves.

[0162]

[0177] Referring now to FIG. 11 , FIG. 11 illustrates an interconnect arrangement consistent with embodiments of the present disclosure. Interconnects may be provided between diagonally adjacent sensing elements. Moreover, in some embodiments, interconnects may be provided between diagonally adjacent sensing elements and horizontally and vertically adjacent sensing elements. As shown in FIG. 11 , interconnects may be provided such that circuitry associated with sensing element 311 is connected to all circuitry associated with sensing elements 312-319. The interconnects shown in FIGS. 10 and 11 may correspond to interconnect 920 discussed above with respect to FIG. 9 . For example, interconnect 1001 shown in FIG. 10 may include an analog signal path or a data path.

[0163]

[0178] In some embodiments, the interconnects may include switches that can control the flow of signals through the interconnects. Control of the interconnects may be managed by a control unit, such as control unit 490 or processor 980.

[0164]

[0179] Referring now to FIG. 12A, FIG. 12A illustrates a circuit 800A with interconnections consistent with an embodiment of the present disclosure. Similar to FIG. 4, the circuit 800A may include an input stage 410, a threshold detector 420, a storage cell multiplexer 430, a first storage cell 441 through an Nth storage cell 449, a converter 450, and a control unit 490. Additionally, the circuit 800A may include an analog signal routing multiplexer 460. The input stage 410 may be configured to receive a signal S from the sensing element 311. An analog signal processor 910 may be formed by components including the input stage 410, the threshold detector 420, the multiplexer 430, the storage cells 441, 442, ..., 449, and the analog signal routing multiplexer 460. The converter 450 may be configured to process analog signals from the storage cells of the array 440 or analog signals passed from other sensing element circuitry. The converter 450 may generate a digital signal for data representing the analog signal.

[0165]

[0180] In some embodiments, analog signal path 921 can be connected to analog signal routing multiplexer 460. In some embodiments, analog signal routing multiplexer 460 can be included in analog signal processor 910. Analog signal routing multiplexer 460 can be configured to perform analog signal routing. In some embodiments, converter 450 can include a voltage detector or an ADC. Converter 450 can be configured to output data in digital format. The digital data can also be output by control unit 490. Data path 922 can be connected to control unit 490. In some embodiments, data path 922 can be connected to converter 450. Circuit 800A can correspond to sensing element-level signal processing and control unit 950 discussed above with respect to FIG. 9 .

[0166]

[0181] As shown in FIG. 12A , circuit 800A may include a bidirectional analog signal path and a bidirectional data path. For example, analog signal path 921 and data path 922 may be provided. The addition of such paths may enable signal and data exchange in both analog and digital formats between any two adjacent sensing element level signal processing and control units (see FIG. 9 ). The analog signal exchange may be configured to transfer signals from adjacent electronic sensing elements corresponding to a single electron incident event associated with one of the sensing element level signal processing and control units so that the signals can be summed in an analog manner. Summing or processing of analog signals using such analog signals may improve processing resolution and accuracy. Signal summation may be performed digitally by exchanging data digitally between adjacent sensing element level signal processing and control units.

[0167]

[0182] Analog signal path 921 can be configured to enable bidirectional analog signal flow between analog signal routing multiplexers of neighboring sensing element-level circuits. For example, analog signal path 921 can be configured to carry an analog signal in the form of a voltage, current, or charge representing the energy level of a particular charged particle arrival event. Data path 922 can be configured to enable bidirectional data flow between control units of neighboring sensing element-level circuits. For example, data path 922 can be configured to carry charged particle arrival event data (including energy level, detection confirmation, timestamp, etc.). Control unit 490 can also be configured to enable bidirectional data flow with higher-level components. Control unit 490 can be configured to transmit data D. Control unit 490 can be configured to control (i) the flow of data (including timing information) to the sensing elements, (ii) the flow of counting results from the sensing elements, and (iii) the flow of sensing element overflow flags with overflow-type data.

[0168]

[0183] In some embodiments, digital signal processing methods can provide additional information about the electron landing position on the detector surface (e.g., beyond information about the energy level of the incident electron). This can help improve beam projection tracking accuracy and can also provide additional information about the performance of the SEM system. In some embodiments, analog signal processing methods can include summing or processing signals from adjacent detector elements. Analog methods can be configured to prioritize accuracy. Analog and digital methods can be used separately or in combination. In some embodiments, when summing signals of incident electron events is desired, analog or digital methods can be selected to reduce miscount rates and correctly identify the energy level of each incident electron. In some embodiments, when a combined method is used, the first step can be to obtain signals in digital form from the signal processing and control units at all detector element levels involved in the process. Then, summing (or processing) of the analog signals can be performed. Using a combined method can benefit from both analog and digital methods. The detector can be configured to provide a deeper analog signal pipeline in the signal processing and control units at all detector element levels.

[0169]

[0184] FIG. 12B is a diagrammatic representation of an analog signal routing multiplexer consistent with embodiments of the present disclosure. FIG. 12B may represent another view of the analog signal routing multiplexer 460 discussed above with respect to FIG. 12A. As shown in FIG. 12B, the analog signal routing multiplexer 460 may include circuitry that can be used for signal routing and control. The analog signal routing multiplexer 460 may include various switches, wiring paths, other electrical components, and the like. The analog signal routing multiplexer 460 may include switches K61, K62...K6m, switches K71, K72...K7m, K8, and a switch control signal bus 461 that can control the switches. The analog signal path 921 may be configured for bidirectional flow to allow signals to be sent to and from neighboring cell circuits.

[0170]

[0185] Additionally, the analog signal routing multiplexer 460 may include an amplifier 465 and a buffer 466. The amplifier 465 may include a summing amplifier. The buffer 466 may include a voltage buffer. The switch control signal bus 461 may be connected to a control unit 490 (see FIG. 12A), which may be configured to control the switch using a switch control signal C. The switch K8 may be configured to connect the buffer 466 to one of the storage cells of the array 440 such that the signal S1 flows from the selected storage cell to the buffer 466. It will be appreciated that some components of the analog signal routing multiplexer 460 and the converter 450 may be combined or overlapped. For example, the buffer 466 may include a voltage buffer 451 (see FIGS. 5A-5C). The amplifier 465 may be connected to the control unit 490 and send the signal S2 to the control unit 490.

[0171]

[0186] The analog signal routing multiplexer 460 can be configured to operate in multiple scenarios. For example, in a first scenario, the sensing element level circuits can be configured to receive analog signals from neighboring circuits. For those analog signal paths through which analog signals are transmitted from neighboring circuits, switches K61, K62, ..., K6m are set to position 2, and their corresponding switches K71, K72, ..., K7m are set to open. If the corresponding analog signal path is not used to receive a signal, some of the switches K61, K62, ..., K6m can be set to position 2, and their corresponding switches K71, K72, ..., K7m can be set to closed. K8 is set to a position that connects a storage cell that stores the signal of the event being processed.

[0172]

[0187] In the second scenario, the sensing element level circuitry can be configured to transmit analog signals to neighboring circuits. For those analog signal paths through which analog signals are transmitted to neighboring circuits, switches K61, K62, ..., K6m are set to position 1 and their corresponding switches K71, K72, ..., K7m are set to closed. If the corresponding analog signal path is not used to receive a signal, some of switches K61, K62, ..., K6m can be set to position 2 and their corresponding switches K71, K72, ..., K7m can be set to closed. K8 is set to a position connecting a storage cell that stores the signal of the event being processed.

[0173]

[0188] 13, which is a flowchart illustrating a method 8000 that may be useful for electron counting consistent with an embodiment of the present disclosure. Method 8000 may be performed by a component including circuitry of a charged particle inspection system (e.g., 800A of FIG. 12A), a controller such as controller 109 of FIG. 1 or 2B, or a processor such as control unit 490 of FIG. 4, FIGS. 5A-5C, FIG. 12A, processor 980, or a combination thereof. The component may include circuitry (e.g., memory and a processor) programmed to implement method 8000. Method 8000 may include an analog signal processing method.

[0174]

[0189] As shown in Figure 13, method 8000 can begin with a "start" step, where the detection process may already be underway. Method 8000 can begin, for example, after the processing of step A and Figure 7A has occurred.

[0175]

[0190] Method 8000 may include step 8101 of determining to connect circuits associated with different sensing elements. The determination may be made to connect different detection cells. Step 8101 may include a first method of determining to connect, a second method of determining to connect, or other methods. The first method of determining to connect may include determining whether electron arrival events of neighboring detection cells were caused by the same incident electron solely by comparing the event start times. For example, if the start times are the same, the events can be determined to be caused by the same incident electron. The second method of determining to connect may include determining whether events of neighboring detection cells were caused by the same incident electron by comparing both the start time and the end time or by using the duration of the events. If the start time and end time of both events are the same, the events can be determined to be caused by the same incident electron. If the start times are the same and the events have the same duration, the events can be determined to be caused by the same incident electron.

[0176]

[0191] The first method for determining to connect may include determining that the start time of the electronic arrival event of the first sensing element is substantially the same as the start time of the electronic arrival event of the second sensing element. In some embodiments, the start times may be considered to be substantially the same if the times are within a predetermined amount of each other. The predetermined amount may be based on the clock speed of the detector, the mean separation time of the electronic arrival events, or a parameter of the sensing element (dead time of the sensing element). The predetermined amount may be, for example, a fraction of the mean separation time of the electronic arrival events.

[0177]

[0192] In some embodiments, accuracy can be prioritized and a second method for determining which connections to make can be used. For example, the second method can enable higher accuracy and require more computation than the first method. In some embodiments, response speed can be prioritized and a first method for determining which connections to make can be used. For example, the first method can enable lower power consumption and shorter latency than the second method. There can be trade-offs between parameters such as detection accuracy, process latency, and power consumption of the detection system. Such parameters can be changed on the fly by configuring the system to operate in one of different modes. Moreover, in some embodiments, longer latency increases the likelihood of causing a Type 2 overflow. To reduce Type 2 overflows due to longer latency, a deeper analog pipeline can be used in each detection cell.

[0178]

[0193] In some embodiments, step 8101 may be based on the process from FIG. 7A . For example, step 8101 may be based on an integration start signal or timestamps from two or more different sensing elements. It may be determined that an integration start signal has been generated, that the start timestamps of the different sensing elements are substantially the same, and that the signals from the two sensing elements should be merged. Step 8101 may include comparing signals from only neighboring sensing elements. Neighboring sensing elements may be adjacent to each other in the horizontal or vertical direction of the array of sensing elements on the detector. In some embodiments, neighboring sensing elements may include diagonally adjacent sensing elements. Step 8101 may be performed pairwise (e.g., one determination is performed for two neighboring sensing elements, and another determination is performed for the other two neighboring sensing elements). Step 8101 may be performed pairwise when analog signal processing methods are used. In some embodiments, step 8101 may be performed on a different basis, for example, when digital signal processing methods are used.

[0179]

[0194] Method 8000 may include step 8103 of forming a connection via an interconnect. Step 8103 may include connecting neighboring detection cells using interconnect 920. Step 8103 may include actuating a switch of the interconnect. Step 8103 may include connecting neighboring detection cells using analog signal path 921.

[0180]

[0195] Method 8000 may include step 8105 of outputting a signal from the analog signal processing path. Step 8105 may include outputting a signal from converter 450. Step 8105 may include outputting a signal from analog signal processor 910. Step 8105 may include outputting a signal from analog signal routing multiplexer 460. Step 8105 may include outputting a signal from one or more detection cells. Step 8105 may include interrogating. Step 8105 may include interrogating a switch (such as switch K discussed above with respect to FIG. 5A).31 Step 8105 may include selecting a storage cell via a DMA transfer command (e.g., a DMA transfer command), etc. Step 8105 may include step 7304 and subsequent steps discussed above with respect to FIG. 7C.

[0181]

[0196] In some embodiments, interconnects can be provided downstream of the storage cell array and upstream of the control unit 490. For example, the interconnects can be provided in the form of analog signal routing multiplexers 460 (see FIGS. 12A and 12B). In step 8105, signals from the storage cells can be tapped and sent through the interconnects to other detection cells where processing can occur using components of other detection cells. The signals from the storage cells can be in analog form. The analog signal routing can include performing signal summation, and switches in the analog signal routing multiplexers of all participating detection cells can be controlled to select storage cells that simultaneously store signals of the same electronic arrival event. The detector can be configured to provide synchronization between all participating detection cells.

[0182]

[0197] In some embodiments, signal routing may include performing digital signal processing. In some embodiments, digital interconnects may be used, eliminating the need for synchronization of cell selection and switch control.

[0183]

[0198] Method 8000 may include step 8107 of performing signal summation or processing. Step 8107 may include summing signals of different detection cells. The signals from the different detection cells may then be processed together. In some embodiments, in step 8107, signals of the same electronic arrival event from different detection cells may be summed.

[0184]

[0199] Method 8000 may include a step 8109 of performing an analysis. The analysis of step 8109 may be performed on the signals summed or processed in step 8107. The analysis may be performed on the summed signals. Signals from two or more detection cells may be summed and then processed together.

[0185]

[0200] Charged particle arrival events occurring near the boundaries of a sensing element can create ionization regions that extend into the volume of neighboring sensing elements. The signals generated at the neighboring sensing elements can be summed with the signal generated at the sensing element where the charged particle first landed. The summed signal can be processed, and the summed signal can more accurately represent the single charged particle arrival event that occurred.

[0186]

[0201] Analyzing signals from two or more detection cells may involve using the same or different thresholds as those used for analyzing a single detection cell. For example, a reference value (e.g., v discussed above with respect to Figures 5A-5C) may be used. ref11 ) can be compared. The reference value used in analyzing signals from two or more detection cells can be the same, and the analysis results can be more accurate. In some embodiments, the reference value can be adjusted, for example, to account for losses that may be involved when signals are transmitted through interconnects. The amount of adjustment can be determined through calibration. Calibration can include, for example, numerical simulation or experimentation. Converter 450 can include multiple reference values, and a desired reference value can be selected based on the circumstances of the signal analysis.

[0187]

[0202] 14, which is a flow chart illustrating a method 8200 that may be useful for electron counting consistent with an embodiment of the present disclosure. Method 8200, like method 8000, may be performed by components including circuits, control units, processors, or combinations thereof of a charged particle inspection system. Method 8200 may include digital signal processing methods.

[0188]

[0203] As shown in Figure 14, method 8200 can begin with a "start" step, where the detection process may already be underway. Method 8200 can begin, for example, after the processing of step A and Figure 7A has occurred.

[0189]

[0204] Method 8200 may include step 8201 of determining to connect circuits associated with different sensing elements. The decision to connect different sensing cells may be made. Step 8201 may be based on the process from FIG. 7A . Step 8201 may include a first method of determining to connect, a second method of determining to connect, or another method, similar to step 8101 discussed above with respect to FIG. 13 . For example, step 8201 may be based on integration start signals or timestamps from two or more different sensing elements. It may be determined that an integration start signal has been generated, that the start timestamps of the different sensing elements are substantially the same, and that the signals from the two sensing elements should be merged. Step 8201 may include comparing only signals from neighboring sensing elements. Neighboring sensing elements may be adjacent to each other in the horizontal or vertical direction of the array of sensing elements on the detector. In some embodiments, neighboring sensing elements may include diagonally adjacent sensing elements. Step 8201 may be performed pairwise (e.g., one decision is performed for two neighboring sensing elements and another decision is performed for two other neighboring sensing elements), or on some other basis.

[0190]

[0205] Method 8200 may include a step 8203 of forming a connection via an interconnect. Step 8203 may include connecting neighboring detection cells using interconnect 920. Step 8203 may include actuating a switch of the interconnect. Step 8203 may include connecting neighboring detection cells using data path 922.

[0191]

[0206] Method 8200 may include a step 8205 of outputting a digital signal. Step 8205 may include outputting a signal from converter 450. Step 8205 may include outputting a signal from data converter 930. Step 8205 may include outputting a signal from one or more detection cells. Step 8205 may include interrogating. Step 8205 may include interrogating a switch (such as switch K discussed above with respect to FIG. 5A). 31 The selected storage cell may be interrogated by a comparator (such as a voltage comparator). The output from step 8205 may be a digital signal transmitted on data path 922.

[0192]

[0207] Method 8200 may include step 8207 of performing processing. Step 8207 may include performing processing of digital signals from two or more detector cells. Step 8207 may include summing or filtering some of the digital signals from two or more detector cells. For example, a signal from one of the detector cells may be determined to be associated with the same charged particle arrival event as one occurring at another detector cell, and that signal may be ignored. For example, if both detector cells receive a signal sufficient to trigger detection of a charged particle event, the charged particle event may be double-counted. To avoid such miscounting, step 8207 may include filtering out one of the counting results. In some embodiments, signals representing partial energies received by multiple detector cells may be processed to determine the energy of the incident electrons with improved accuracy. For example, signals from different detector cells may be summed so that the energy level of the incident electrons can be accurately determined. Furthermore, a combined signal may be generated from several signals associated with the same electron arrival event, reducing the miscounting rate.

[0193]

[0208] Step 8207 may include performing processing using the control unit 940, which may be a local or lower-level control unit. The processing of step 8207 may include distributed processing. Information such as the address of a sensing element or the impact location of a charged particle event may be determined locally. Further processing may then be performed using a higher-level control unit. For example, it may be determined locally between two sensing cells that one sensing cell received a certain portion (e.g., one-third) of the total energy of the charged particle arrival event. Based on this, impact location information may be determined. For example, it may be estimated that the charged particle arrived one-third of the way from the edge of the sensing element. Such determination may be performed two-dimensionally. For example, such determination may be performed horizontally for two neighboring sensing elements and vertically for two neighboring sensing elements. Based thereon, two-dimensional coordinates (e.g., x, y position) for the impact location of the sensing element may be determined.

[0194]

[0209] 15, which is a flow chart illustrating a method 8300 that may be useful for electron counting, consistent with an embodiment of the present disclosure. Method 8300, similar to method 8000 or method 8200, may be performed by components including circuitry, a control unit, a processor, or combinations thereof, of a charged particle inspection system. Method 8300 may include combined signal processing methods (e.g., combining analog and digital signal processing).

[0195]

[0210] 15, method 8300 can begin with a "start" step, where the detection process may already be underway. Method 8200 can begin, for example, after the processing of step A and FIG. 7A has occurred.

[0196]

[0211] Method 8300 may include step 8301 of obtaining digitally formatted signals from a group of detector cells. In some embodiments, the group may include all sensing element level signal processing and control units involved in processing a particular sub-area on the detector. The digitally formatted signals from the group of detector cells may be used to perform pre-processing. In some embodiments, step 8301 may include determining to connect circuitry associated with different sensing elements, similar to steps 8101 and 8201 discussed above with respect to FIGS. 13 and 14 .

[0197]

[0212] The method 8300 may include a step 8303 of performing analog signal processing. Step 8303 may include performing the method of FIG.

[0198]

[0213] The method 8300 may include a step 8305 of performing digital signal processing. Step 8305 may include performing the method of FIG.

[0199]

[0214] After performing method 8000, 8200, or 8300, further processing may be performed, such as data processing including SEM image pixel data generation, SEM image parameter adjustment, pre-inspection, projection tracking, etc. The further processing may be performed, for example, by processor 980. Moreover, analog signal processing (e.g., step 8303 of FIG. 15) and digital signal processing (e.g., step 8305 of FIG. 15) may be performed jointly.

[0200]

[0215] The method may include determining which of a different processing mode to use: analog, digital, or a combination thereof. Determining the operating mode may be controlled based on a different processor than may be available to implement the analog, digital, or combination thereof processing mode. For example, a higher-level processor may determine which operating mode to use.

[0201]

[0216] Moreover, in some embodiments, the method may include determining which detection cell to use for processing. The determination of which detection cell to use for processing may be based on a charged particle arrival event occurring near a neighboring detection element. For example, the detection cell to use for processing may be determined based on the detection element that receives the majority of the energy of the charged particle arrival event. In some embodiments, the determination may be based on other factors, such as an overflow or busy signal indicator. If a detection cell is busy, another detection cell of the neighboring detection cells may be used. If two detection elements receive the energy of the charged particle arrival event approximately equally and one is busy, it may be determined to use the other. The determination of which detection cell to use may take into account the processing load.

[0202]

[0217] Aspects of the present disclosure are set forth in the following numbered clauses. 1. A circuit for a charged particle detector, comprising: a storage cell configured to receive a signal representative of the output of the sensing element; a storage cell multiplexer configured to selectively transmit signals representative of the outputs of the sensing elements to the storage cells; a threshold detector including circuitry configured to determine a start of integration signal based on a comparison of a signal representative of the output of the sensing element to a threshold; a converter including circuitry configured to perform signal processing on the signal transmitted from the storage cell; The circuit includes: 2. The circuit of clause 1, wherein the storage cell is one of a plurality of storage cells included in the circuit, the plurality of storage cells being configured to receive a signal representative of the output of the sensing element. 3. A control unit including circuitry configured to monitor the results analysis request indicator. 3. The circuit of clause 1 or 2, further comprising: The control unit performing signal processing on the first storage cell in response to determining that the results analysis request indicator is set; and receiving an output from the transducer based on signal processing; A circuit configured to: 4. A circuit configured to convert the output of the sensing element into an electrical signal of a different form. 4. The circuit of any one of clauses 1 to 3, further comprising: 5. The circuit of any one of clauses 1 to 4, wherein the multiplexer includes a switch. 6. A switch configured to connect storage cells to a converter, the switch configured to connect one storage cell to the converter at a time. 6. The circuit of any one of clauses 1 to 5, further comprising: 7. An input stage including circuitry configured to generate an output proportional to the current or charge received from the sensing element by the input stage. 7. The circuit of any one of clauses 1 to 6, further comprising: 8. The circuit of clause 7, wherein the input stage includes a current-controlled current source configured to output an amplified signal based on a current or charge received by the input stage from the sensing element, and the threshold detector includes a current detector configured to compare the amplified signal to a current threshold. 9. The circuit of clause 7, wherein the input stage includes a transimpedance amplifier configured to output a voltage signal based on a current or charge received by the input stage from the sensing element, and the threshold detector includes a voltage comparator configured to compare the voltage signal to a reference. 10. The control unit receiving an integration start signal; receiving an end-of-integration signal based on a comparison of the signal representative of the output of the sensing element with a second threshold; controlling the storage cell multiplexer to change a connection state between the storage cell and the sensing element in response to receiving the integration end signal; 4. The circuit of claim 3, configured to: 11. The control unit In response to receiving the integration end signal, setting an integration circuit busy indicator, and maintaining the integration circuit busy indicator until changing the connection state between the storage cell and the sensing element. 11. The circuit of claim 10, configured to: 12. The control unit and responsive to determining that the results analysis request indicator is set, obtaining from the address list the address of the storage cell to be interrogated. 4. The circuit of claim 3, configured to: 13. responsive to the signal representing the output of the sensing element crossing a first threshold, performing an integration of the signal representing the output of the sensing element using a first storage cell corresponding to the first charged particle event; performing integration of the signal representative of the output of the sensing element using a second storage cell corresponding to a second charged particle event in response to the signal representative of the output of the sensing element crossing a first threshold after the first charged particle event; A method comprising: 14. generating an integration start signal when the output of the sensing element crosses a first threshold; generating an end-of-integration signal when the output of the sensing element crosses a second threshold; 14. The method of clause 13, further comprising: 15. Generating a first timestamp for the integration start signal and a second timestamp for the integration end signal. 15. The method of clause 14, further comprising: 16. Changing the connection state of the storage cell multiplexer so that a signal from the sensing element is provided to one of the first storage cell and the second storage cell. 16. The method of any one of clauses 13 to 15, further comprising: 17. The method of clause 16, wherein the signal provided from the sensing element to one of the first storage cell and the second storage cell is an amplified signal. 18. Changing the connection state of the switch such that one of the first storage cell and the second storage cell is connected to a converter configured to perform signal processing on a signal transmitted from one of the first storage cell and the second storage cell. 17. The method of any one of clauses 13 to 16, further comprising: 19. Comparing the signal transmitted from the first storage cell or the second storage cell with a reference. 19. The method of any one of clauses 13 to 18, further comprising: 20. The method of clause 19, wherein the reference is one of a plurality of references, and wherein comparing the signal transmitted from the first storage cell or the second storage cell comprises comparing the signal transmitted from the first storage cell or the second storage cell with each of the plurality of references and outputting the result to the control unit. 21. Counting the number of charged particles received at the sensing element 21. The method of any one of clauses 13 to 20, further comprising: 22. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a controller of a charged particle beam device to cause the charged particle beam device to perform a method, the method comprising: generating a charged particle beam; integrating the signal representative of the output of the sensing element of the detector using a first storage cell corresponding to the first charged particle event when the signal representative of the output of the sensing element of the detector exceeds a first threshold; integrating the signal representative of the output of the sensing element using a second storage cell corresponding to a second charged particle event when the signal representative of the output of the sensing element exceeds a first threshold after the first charged particle event; Including, media. 23. The instruction set is generating a start integration signal when the output of the sensing element crosses a first threshold; generating an end-of-integration signal when the output of the sensing element crosses a second threshold; 23. A medium according to clause 22, executable to cause a charged particle beam device to perform 24. A storage cell; a multiplexer configured to transmit signals from the electronic sensing elements to the storage cells; a voltage detector configured to detect a voltage of the storage cell to enable determination of the energy level of the incident electrons; an electron counting detector, 25. The electron counting detector of clause 24, wherein the voltage detector is configured to determine the number of electrons detected during an electron arrival event. 26. An input stage configured to amplify a signal received from the electronic sensing element and output an amplified signal. 26. An electronic counting detector according to clause 24 or 25, further comprising: 27. The storage cell is one of multiple storage cells included in an electron counting detector; a multiplexer configured to transmit the signal from the electronic sensing element or an amplified version thereof to any of the plurality of storage cells; 27. An electron counting detector according to any one of clauses 24 to 26, wherein the multiplexer and the plurality of storage cells enable substantially continuous capture of signals from the electron sensing elements and associated electron counting. 28. A threshold detector configured to detect when a signal from an electronic sensing element crosses a first threshold indicating the start of an electronic detection event and when it crosses a second threshold indicating the end of the electronic detection event. 28. The electronic counting detector of any one of clauses 24 to 27, further comprising: 29. A detector for a charged particle beam device, comprising: a plurality of sensing elements; a circuit for each of the sensing elements, a storage cell configured to receive a signal representative of the output of the sensing element; a multiplexer configured to selectively provide a signal representative of the output of the sensing element to a storage cell; a threshold detector including circuitry configured to determine a start of integration corresponding to a charged particle arrival event; a transducer including circuitry configured to determine information about a charged particle arrival event; a circuit including a detector. 30. A detector as described in clause 29, comprising a segmented detector array. 31. A detector according to clause 29 or 30, wherein the information comprises the energy level of the charged particle arrival event. 32. A detector according to any one of clauses 29 to 31, wherein the information includes an overflow indicator. 33. The detector of clause 32, wherein the overflow indicator indicates whether more than a predetermined number of charged particles arrive during a charged particle arrival event. 34. The circuit of clause 8, wherein the current threshold comprises a first threshold and a second threshold. 35. The detector of clause 29, wherein the threshold detector includes circuitry configured to determine an end of integration corresponding to a charged particle arrival event. 36. The circuit of clause 3, wherein the results analysis request indicator is set in response to receiving an integration end signal after an integration start signal. 37. A circuit as described in clause 4, wherein the output of a sensing element being converted into an electrical signal of a different form includes the output of a sensing element being converted into a voltage. 38. A circuit as described in clause 4, including an output of a sensing element being converted into an electrical signal of a different form, the output of the sensing element being converted into an amplified current. 39. An input stage configured to amplify the charge signal received from the electronic sensing element and output an amplified charge signal; a charge storage cell; a mux configured to send the amplified charge signal to the charge storage cell; a voltage detector configured to detect a voltage of the charge storage cell to enable a determination of the number of detected electrons; an electron counting detector, 40. The charge storage cell is one of a plurality of charge storage cells; a mux configured to transmit the amplified charge signal to any one of the plurality of charge storage cells; 40. The detector of clause 39, wherein the mux and the plurality of charge storage cells enable substantially continuous capture of the amplified charge signal and associated electron counting. 41. When the charge signal received from the electron sensing element crosses a first threshold indicating the start of an electron detection event; and When the charge signal received from the electron sensing element crosses a second threshold indicating the end of the electron sensing event. a threshold detector configured to detect them 41. The detector of clause 39 or 40, further comprising: 42. The detector of clause 41, wherein the mux is configured to change a connection state between the input stage and the plurality of charge storage cells in response to the threshold detector detecting that the charge signal received from the electronic sensing element has crossed a second threshold. 43. A control unit configured to monitor a result analysis request indicator. 43. The detector of clause 41 or 42, further comprising: in response to determining that the results analysis request indicator is set, the voltage detector detects a voltage of the charge storage cell. 44. The detector of clause 40, wherein the configuration of the voltage detector further enables determination of whether each detected electron is a backscattered electron or a secondary electron. 45. A detector as described in clause 40, wherein the configuration of the voltage detector further allows for determination of the energy level of the detected electrons. 46. ​​An interconnect configured to transmit an analog signal from a storage cell to the circuitry of another detection cell. The circuit of any one of clauses 1-12, 34, 36-38, further comprising: 47. The circuit of clause 46, wherein the circuit of the other detection cell includes an analog signal routing multiplexer. 48. The circuit of clause 46, wherein the interconnect includes a data path configured to transmit digital data to a control unit of another detection cell. 49. An interconnection configured to transmit an analog signal from a storage cell or a digital signal including the voltage of the storage cell to the circuitry of another detection cell. 29. The electronic counting detector of any one of clauses 24 to 28, further comprising: 50. An interconnection configured to transmit an analog signal from the storage cell or a data signal determined by the converter to the circuitry of another detection cell. 36. The detector of any one of clauses 29 to 33, 35, further comprising: 51. An interconnect configured to transmit an analog signal from the charge storage cell or a data signal including the voltage of the charge storage cell to another detection cell circuit. 46. ​​The detector of any one of clauses 39 to 45, further comprising: 52. An electronic counting detector as described in clause 49, wherein the other electronic sensing elements include neighboring sensing elements in a horizontal, vertical or diagonal direction of the electronic counting detector. 53. A detector according to clause 50, wherein the other detector cells include neighboring detector cells in a horizontal, vertical or diagonal direction of the detector. 54. A detector according to clause 51, wherein the other detector cells include neighboring detector cells in a horizontal, vertical or diagonal direction of the detector. 55. A circuit for a charged particle detector, comprising: a storage cell configured to receive a signal representative of the output of the sensing element; a storage cell multiplexer configured to selectively transmit signals representative of the outputs of the sensing elements to the storage cells; an interconnect configured to transmit the output of the storage cell to a sensing element level signal processing and control unit of another detection cell; The circuit includes: 56. A converter including circuitry configured to perform signal processing on a signal transmitted from a storage cell. 56. The circuit of claim 55, further comprising: 57. The circuit of clause 56, wherein the interconnect is located downstream of a voltage comparator or ADC included in the converter. 58. The circuit of any one of clauses 55-57, wherein the interconnect is configured to transmit an analog signal from the storage cell to the circuitry of another detection cell. 59. The circuit of any one of clauses 55 to 57, wherein the interconnect comprises a data path configured to transmit digital data to a control unit of another detection cell. 60. The circuit of any one of clauses 46 to 48, wherein another detection cell comprises a neighboring detection cell in a horizontal, vertical or diagonal direction. 61. A circuit for a charged particle detector, comprising: a sensing element level signal processing and control unit including circuitry configured to perform signal processing on signals transmitted from a storage cell configured to receive signals representative of the output of the sensing element in response to a charged particle arrival event; an interconnect configured to connect an analog signal path or a data path from another sensing element; The circuit includes: 62. The interconnection is an analog signal path configured to transmit an analog signal from the storage cell to the circuitry of another detection cell; or a data path configured to transmit digital data to a control unit associated with another sensing element; 61. The circuit described in clause 61, including: 63. A local control unit configured to perform processing using a signal from the storage cell of the first detection cell and a signal from the storage cell of the second detection cell. 63. The circuit of clause 61 or 62, further comprising: 64. The circuit of any one of clauses 61 to 63, wherein the analog signal routing multiplexer is connected to a converter configured to receive a summed signal including the signal transmitted from the storage cell and the signal transmitted from the storage cell of the other sensing element. 65. The circuit of clause 64, wherein the other sensing elements include neighboring sensing elements. 66. A method for determining the number of charged particles, comprising: connecting a first circuit associated with the first sensing element and a second circuit associated with the second sensing element via an interconnect; using the first circuit to perform processing based on a first signal from the first circuit and a second signal from the second circuit; determining a number of charged particles based on the processing; A method comprising: 67. Processing Determining the energy level of the incident charged particles included in the number of charged particles 67. The method of claim 66, including: 68. Processing adding the first signal and the second signal to form a sum signal; Determining whether the summed signal crosses a threshold value 68. The method of clause 66 or 67, comprising: 69. The method of clause 66, wherein the first signal and the second signal are digital signals, and the processing comprises adding or filtering the first signal or the second signal. 70. Deciding to connect a first circuit to a second circuit 70. The method of any one of clauses 66 to 69, further comprising: 71. The method of clause 70, wherein determining to connect the first circuit and the second circuit is based on timestamps or energy levels of charged particle arrival events occurring at each of the first sensing element and the second sensing element. 72. The determination to connect a first circuit and a second circuit is determining that a start time of the electronic arrival event of the first sensing element is substantially the same as a start time of the electronic arrival event of the second sensing element; 72. The method of claim 71, including: 73. The decision to connect a first circuit and a second circuit is determining that an end time of the electronic arrival event of the first sensing element is substantially the same as an end time of the electronic arrival event of the second sensing element; 73. The method of claim 72, including: 74. The decision to connect a first circuit and a second circuit is determining that a time of the electronic arrival event at the first sensing element is substantially the same as a time of the electronic arrival event at the second sensing element; 73. The method of claim 72, including: 75. Activating a switch to connect an interconnection 75. The method of any one of clauses 66 to 74, further comprising: 76. Determining the address of a sensing element that receives a charged particle. 76. The method of any one of clauses 66 to 75, further comprising: 77. Determining the location of collisions of charged particles 77. The method of any one of clauses 66 to 76, further comprising: 78. A computer-readable medium storing a set of instructions executable by one or more processors of a system to cause the system to perform a method, the method comprising: connecting a first circuit associated with the first sensing element and a second circuit associated with the second sensing element via an interconnect; using the first circuit to perform processing based on a first signal from the first circuit and a second signal from the second circuit; determining a number of charged particles based on the processing; Including, media. 79. Processing Determining the energy level of the incident charged particles included in the number of charged particles 78. The media described in clause 78, including: 80. Processing adding the first signal and the second signal to form a sum signal; Determining whether the summed signal crosses a threshold value 79. The medium according to clause 78 or 79, 81. The medium of clause 80, wherein the first signal and the second signal are digital signals, and the processing includes adding or filtering the first signal or the second signal. 82. The instruction set is determining to connect the first circuit and the second circuit; The medium of any one of clauses 78 to 81, executable by one or more processors of a system to cause the system to further execute the 83. The medium of clause 82, wherein the determination to connect the first circuit and the second circuit is based on a timestamp or energy level of a charged particle arrival event occurring at each of the first sensing element and the second sensing element. 84. The instruction set is Activating a switch to connect an interconnection The medium of any one of clauses 78 to 83, executable by one or more processors of a system to cause the system to further execute the 85. The instruction set is Determining the address of the sensing element that receives the charged particle The medium of any one of clauses 78 to 84, executable by one or more processors of a system to cause the system to further execute the 86. The instruction set is Determining the location of collisions of charged particles The medium of any one of clauses 78 to 85, executable by one or more processors of a system to cause the system to further execute the

[0203]

[0218] A non-transitory computer-readable medium can be provided that stores instructions for a processor of a controller (e.g., controller 109 of FIG. 1) for detecting charged particles according to the exemplary flowcharts of FIGS. 6 and 13-15 consistent with embodiments of the present disclosure. For example, the instructions stored on the non-transitory computer-readable medium can be executed by circuitry of the controller to perform part or all of method 600. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, a hard disk, a solid-state drive, magnetic tape or any other magnetic data storage medium, a compact disk read-only memory (CD-ROM), any other optical data storage medium, any physical medium having a pattern of holes, random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), flash EPROM or any other flash memory, non-volatile random access memory (NVRAM), cache, registers, any other memory chip or cartridge, and network-connected versions thereof.

[0204]

[0219] The block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block in the schematic diagrams may represent an arithmetic or logical operation that can be implemented using hardware, such as electronic circuits. A block may also represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function(s). It should be understood that in some alternative implementations, the functions shown in the blocks may occur out of the order depicted in the figures. For example, two blocks shown in succession may be executed or performed substantially simultaneously, or the two blocks may be executed in the reverse order, depending on the functionality involved. Some blocks may also be omitted. It should also be understood that each block and combination of blocks in the block diagrams can be implemented by a special-purpose hardware-based system that performs the specified functions or acts, or by a combination of special-purpose hardware and computer instructions.

[0205]

[0220] It will be understood that embodiments of the present disclosure are not limited to the exact configurations described above and illustrated in the accompanying drawings, and that various modifications and variations can be made without departing from the scope thereof. For example, a charged particle inspection system is just one example of a charged particle beam system consistent with embodiments of the present disclosure.

Claims

1. 1. A circuit for a charged particle detector, comprising: a storage cell configured to receive a signal representative of the output of the sensing element; a storage cell multiplexer configured to selectively transmit the signal representing the output of the sensing element to the storage cell; a threshold detector including circuitry configured to determine a start of integration signal based on a comparison of the signal representative of the output of the sensing element with a threshold; a converter including circuitry configured to perform signal processing on the signal transmitted from the storage cell; The circuit includes:

2. 2. The circuit of claim 1, wherein the storage cell is one of a plurality of storage cells included in the circuit, the plurality of storage cells configured to receive a signal representative of the output of the sensing element.

3. a control unit including circuitry configured to monitor a results analysis request indicator; further comprising The control unit performing the signal processing on a first storage cell in response to determining that the results analysis request indicator is set; and receiving an output from the transducer based on the signal processing; The circuit of claim 1 configured to:

4. a circuit configured to convert the output of the sensing element into an electrical signal of a different form; The circuit of claim 1 further comprising:

5. The circuit of claim 1 , wherein the multiplexer comprises a switch.

6. a switch configured to connect the storage cells to the converter, the switch configured to connect one storage cell to the converter at a time; The circuit of claim 1 further comprising:

7. an input stage including circuitry configured to generate an output proportional to the current or charge received from the sensing element by the input stage; The circuit of claim 1 further comprising:

8. 8. The circuit of claim 7, wherein the input stage includes a current-controlled current source configured to output an amplified signal based on the current or charge received by the input stage from the sensing element, and the threshold detector includes a current detector configured to compare the amplified signal to a current threshold.

9. 8. The circuit of claim 7, wherein the input stage includes a transimpedance amplifier configured to output a voltage signal based on the current or charge received by the input stage from the sensing element, and the threshold detector includes a voltage comparator configured to compare the voltage signal to a reference.

10. The control unit receiving the integration start signal; receiving an end-of-integration signal based on a comparison of the signal representative of the output of the sensing element with a second threshold; controlling the storage cell multiplexer to change a connection state between the storage cell and the sensing element in response to receiving the integration end signal; The circuit of claim 3 configured to:

11. The control unit In response to receiving the integration end signal, setting an integration circuit busy indicator, and maintaining the integration circuit busy indicator until changing the connection state between the storage cell and the sensing element. The circuit of claim 10 configured to:

12. The control unit retrieving an address of a storage cell to be interrogated from an address list in response to determining that the results analysis request indicator is set; The circuit of claim 3 configured as follows:

13. 1. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a controller of a charged particle beam device to cause the charged particle beam device to perform a method, the method comprising: generating a charged particle beam; integrating a signal representative of an output of a sensing element of a detector using a first storage cell corresponding to a first charged particle event when the signal representative of the output of the sensing element exceeds a first threshold; integrating the signal representing the output of the sensing element using a second storage cell corresponding to a second charged particle event when the signal representing the output of the sensing element exceeds the first threshold after the first charged particle event; Including, media.

14. The instruction set comprises: generating a start integration signal when the output of the sensing element crosses the first threshold; generating an end-of-integration signal when the output of the sensing element crosses a second threshold; The medium of claim 13 , executable to cause the charged particle beam device to perform

15. The instruction set comprises: generating a first timestamp for the integration start signal and a second timestamp for the integration end signal; The medium of claim 14 , executable to cause the charged particle beam device to perform

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