System and method for counting particles on a detector during inspection - Patents.com

Abstract

The systems, devices, and methods include a detector including a plurality of detection elements configured to generate an electrical signal in response to a particle being incident on a detection element of the plurality of detection elements; a plurality of current sources configured to drive an electrical current in response to the electrical signal, the outputs of the plurality of current sources connected to enable the currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources connected to respective detection elements of the plurality of detection elements; and an analog-to-digital converter (ADC) configured to convert the combined current into a digital value indicative of the electrical signal output by the plurality of detection elements.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63 / 391,200, filed July 21, 2022, and U.S. Application No. 63 / 455,251, filed March 28, 2023, which applications are incorporated by reference in their entireties into this specification.

[0002] TECHNICAL FIELD

[0002] The description herein relates to the field of inspection systems, and more particularly to systems that count particles on a detector during inspection. [Background technology]

[0003]

[0003] During the integrated circuit (IC) manufacturing process, unfinished and finished circuit components are inspected to ensure they are manufactured according to design and are free of defects. Inspection systems based on optical microscopes typically have a resolution down to a few hundred nanometers, with resolution limited by the wavelength of light. As the physical size of IC components continues to decrease down to sub-100 nanometers, or even sub-10 nanometers, inspection systems capable of higher resolution than those based on optical microscopes are needed.

[0004]

[0004] Charged particle (e.g., electron) beam microscopes, such as scanning electron microscopes (SEMs) or transmission electron microscopes (TEMs), capable of resolution down to less than 1 nanometer, serve as practical tools for inspecting IC components with feature sizes that are sub-100 nanometers. With an SEM, electrons from a single primary electron beam, or from multiple primary electron beams, can be focused onto a location of interest on a wafer under inspection. The primary electrons interact with the wafer and can be backscattered or can cause the wafer to emit secondary electrons. The intensity of the electron beam, including the backscattered and secondary electrons, can vary based on the characteristics of the wafer's internal and external structure, thereby indicating whether the wafer has defects. Summary of the Invention

[0005]

[0005] Embodiments of the present disclosure provide apparatus, systems, and methods for counting particles on a detector. In some embodiments, the systems, methods, and non-transitory computer-readable media may include a detector including a plurality of detection elements configured to generate an electrical signal in response to a particle being incident on a detection element of the plurality of detection elements, a plurality of current sources configured to drive an electrical current in response to the electrical signal, the outputs of the plurality of current sources connected to enable the currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources connected to respective detection elements of the plurality of detection elements, and an analog-to-digital converter (ADC) configured to convert the combined current into a digital value indicative of the electrical signal output by the plurality of detection elements.

[0006]

[0006] In some embodiments, the system, method, and non-transitory computer-readable medium may include a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources associated with a detection element of the plurality of detection elements; a discriminator configured to output a first value when a particle incident on a detection element is detected and to output a second value when a particle incident on the detection element is not detected; a corresponding current source configured to drive a current when the first value is output; and an ADC configured to determine the number of particles incident on the plurality of detection elements based on the combined drive current of the plurality of current sources.

[0007]

[0007] In some embodiments, the system, method, and non-transitory computer-readable medium may include a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources associated with a detection element of the plurality of detection elements, and each current source of the plurality of current sources configured to drive a current in response to a particle being incident on a corresponding detection element; and a controller including circuitry configured to cause the system to determine a sum of the drive currents of the plurality of current sources and to determine the number of particles incident on the plurality of detection elements based on the determined sum of the drive currents. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure. [Figure 2A]

[0009] 2 is a schematic diagram illustrating an example multi-beam system that is part of the example charged particle beam inspection system of FIG. 1, consistent with an embodiment of the present disclosure. [Figure 2B]

[0010] 2 is a schematic diagram illustrating an example single beam system that is part of the example charged particle beam inspection system of FIG. 1, consistent with an embodiment of the present disclosure. [Figure 3A]

[0011] 1 is a schematic representation of an exemplary structure of a detector consistent with embodiments of the present disclosure. [Figure 3B]

[0012] 1 is a schematic diagram of a cross-sectional structure of a substrate of a detector consistent with an embodiment of the present disclosure. [Figure 3C]

[0013] 1 is a schematic diagram of a cross-sectional structure of a substrate of a detector consistent with an embodiment of the present disclosure. [Figure 3D]

[0014] FIG. 1 is a schematic diagram of an individual sensing element consistent with an embodiment of the present disclosure. [Figure 3E]

[0015] FIG. 1 is a schematic diagram of an individual sensing element consistent with an embodiment of the present disclosure. [Figure 4A]

[0016] FIG. 1 is an example circuit diagram of an example sensing element consistent with embodiments of the present disclosure. [Figure 4B]

[0017] FIG. 1 is an example circuit diagram of an example plurality of sensing elements consistent with embodiments of the present disclosure. [Figure 4C]

[0018] FIG. 1 is an example circuit diagram of an example plurality of sensing elements consistent with embodiments of the present disclosure. [Figure 5A]

[0019] 1 is a schematic representation of an exemplary structure of a detector consistent with embodiments of the present disclosure. [Figure 5B]

[0020] FIG. 5B is an exemplary circuit diagram of FIG. 5A, consistent with an embodiment of the present disclosure. [Figure 5C]

[0021] FIG. 1 is an example circuit diagram of an example plurality of sensing elements consistent with embodiments of the present disclosure. [Figure 6]

[0022] FIG. 1 is an example circuit diagram of an example plurality of sensing elements consistent with embodiments of the present disclosure. [Figure 7]

[0023] 1 is a flowchart illustrating an exemplary process for counting particles on a detector consistent with embodiments of the present disclosure. [Figure 8]

[0024] FIG. 1 is a schematic diagram illustrating an exemplary level sensor consistent with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0025] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements unless otherwise noted. The implementations described in the following description of exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with aspects related to the subject matter recited in the appended claims. For example, while some embodiments are described in the context of utilizing electron beams, the disclosure is not so limited. Other types of charged particle beams may be similarly applicable. Furthermore, other imaging systems, such as optical imaging, light detection, x-ray detection, extreme ultraviolet inspection, deep ultraviolet inspection, etc., may be used, which produce corresponding types of images.

[0010]

[0026] Electronic devices consist of circuits formed on a piece of silicon called a substrate. Many circuits can be formed together on the same piece of silicon and are called integrated circuits, or ICs. The dimensions of these circuits have been dramatically reduced so that many more circuits can fit on a substrate. For example, the IC chip in a smartphone can be as small as a thumbnail, but can contain over 2 billion transistors, each smaller than 1 / 1000 the size of a human hair.

[0011]

[0027] Fabricating these extremely small ICs is a complex, time-consuming, and expensive process, often involving hundreds of individual steps. An error in just one step can result in a defect in the finished IC, rendering it unusable. Therefore, one of the goals of a manufacturing process is to avoid such defects and maximize the number of functional ICs produced in the process, i.e., to improve the overall yield of the process.

[0012]

[0028] One component of improving yield is monitoring the chip fabrication process to ensure that a sufficient number of functional integrated circuits are being produced. One way to monitor the process is to inspect the chip circuit structures at various stages in their formation. Inspection may be performed using a scanning electron microscope (SEM). An SEM can be used to image these very small structures, essentially taking a "picture" of them on the wafer. This image can be used to determine whether the structures were formed properly and whether they were formed in the proper location. If the structures are defective, the process can be adjusted to reduce the likelihood of the defect recurring. Defects can occur during various stages of semiconductor processing. For the reasons stated above, it is important to find defects as quickly, accurately, and efficiently as possible.

[0013]

[0029] The operating principle of an SEM is similar to that of a camera. A camera takes a picture by receiving and recording the brightness and color of light reflected or emitted from a person or object. An SEM takes a "photo" by receiving and recording the energy or quantity of electrons reflected or emitted from a structure. Before taking such a "photo," an electron beam may be directed onto the structure. As electrons reflect or emit (emit) from the structure, the SEM's detector receives and records the energy or quantity of those electrons, generating an image. To take such a "photo," some SEMs use a single electron beam (called a "single-beam SEM"), while others use multiple electron beams (called a "multi-beam SEM") to take multiple "photos" of the wafer. By using multiple electron beams, the SEM can provide more electron beams onto the structure to obtain these multiple "photos," resulting in more electrons exiting the structure. Thus, the detector simultaneously receives more exiting electrons, allowing for more efficient and faster generation of images of the wafer's structures.

[0014]

[0030] For example, a typical detector (e.g., including multiple detector elements) may be pixelated such that each detector element may receive particles (e.g., charged particles such as photons, electrons, protons, etc.) projected from the sample and output a detection signal. The detection signal may be used to reconstruct an image of the sample structure under inspection, for example, to reveal defects within the sample.

[0015]

[0031] The detection system may include a controller that may be configured to determine that particles are incident on one or more detection elements of the detector. The controller may be configured to determine the number of particles incident on the detection elements of the detector within a frame. For example, the controller may perform particle counting, such as electron counting, as described in U.S. Pat. No. 11,508,547, which is incorporated herein by reference in its entirety. The particle counting may be performed on a frame-by-frame basis. The detector may be configured such that each detection element outputs a detection signal on a time basis. The detection signal may be transmitted to the controller.

[0016]

[0032] The controller may determine that a discrete number of particles arrive at the detector element based on the detection signal. The detector circuitry may be configured to process outputs from the multiple detector elements and increment a counter in response to a particle arrival event on the detector element of the detector. For example, the detector element circuitry may output a "1" when a particle strikes the detector element and output a "0" when no particle strikes the detector element within a certain period of time. A typical detector circuitry may determine the total number of particles striking the detector by counting the number of "1" outputs from the detector elements. By counting the number of particles received on the detector, the intensity of the incoming beam may be determined, which may be used to obtain spatial sample data and generate an image (e.g., a grayscale image).

[0017]

[0033] However, typical detection systems face challenges due to limitations. A typical inspection system may include a large detector pixel array (e.g., 1000 or more detector elements on the detector) and may require acquiring frames at a high frame rate (e.g., greater than 100 MHz). Digitally counting the total number of particles received on the detector requires a long period of time, increases power consumption, and may not be feasible at high frame rates (e.g., the maximum time to count a detector pixel array with 7000 pixels at 300 MHz may be only 3 ns).

[0018]

[0034] Typical detection systems may not be able to accommodate a high dynamic range of particles. That is, they may not be able to accurately measure a range that covers low to high particle flux. These typical detection systems may also not be able to accurately count the number of particles received on the detector, particularly particles that produce lower electrical signals (e.g., photons). In addition, typical detection systems have difficulty counting particles at lower velocities, resulting in less accurate particle measurements.

[0019]

[0035] These limitations of typical detection systems can also adversely affect systems that include the detection systems. For example, the limitations of typical detection systems can adversely affect alignment techniques or systems used in lithographic equipment and processes, as described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, which applications are incorporated by reference in their entireties. The limitations of typical detection systems can also adversely affect level or height sensors that use the detection systems, as described below with respect to FIG. 8.

[0020]

[0036] Some of the disclosed embodiments provide systems and methods that address some or all of these drawbacks by using drive currents for the detector elements to count particles on a pixelated detector in an analog manner. The disclosed embodiments may include driving a current in a current source associated with the detector element when a particle is incident on the detector element, determining a sum of drive currents for multiple current sources associated with the pixelated detector, and determining a total number of particles incident on the pixelated detector based on the determined sum of drive currents, thereby analogically counting particles on the pixelated detector at high frame rates with reduced power consumption, improved accuracy, reduced phase lag of the electrical signal (e.g., improved phase stability), and in a scalable manner.

[0021]

[0037] The disclosed embodiments include using detector elements with discriminators that can output stepped integer values or real analog values, thereby allowing the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, by using detectors with the above-mentioned discriminators at each detector element, they can be adapted to count particles over a high dynamic range with greater accuracy.

[0022]

[0038] Disclosed embodiments include using a detector element with an ADC connected to multiple bit lines to increase the speed and accuracy of particle counting on the detector compared to using a detector element with a single output.

[0023]

[0039] The disclosed embodiments further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems.

[0024]

[0040] The relative dimensions of components in the drawings may be exaggerated for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the individual embodiments are described.

[0025]

[0041] As used herein, unless otherwise stated, the term "or" includes all possible combinations unless impracticable. For example, if a component is described as being able to include A or B, the component can include A, or B, or A and B, unless otherwise stated or impracticable. As a second example, if a component is described as being able to include A, B, or C, the component can include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless otherwise stated or impracticable.

[0026]

[0042] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing detectors and detection methods in systems utilizing electron beams. However, the disclosure is not so limited. Other types of charged particle beams may be similarly applied. Furthermore, the systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0027]

[0043] FIG. 1 illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. The EBI system 100 can be used for imaging. As shown in FIG. 1, the EBI system 100 includes a main chamber 101, a load / lock chamber 102, an electron beam tool 104, and an equipment front-end module (EFEM) 106. The electron beam tool 104 is disposed inside the main chamber 101. The EFEM 106 includes a first load port 106a and a second load port 106b. The EFEM 106 may include additional load ports. The first load port 106a and the second load port 106b receive wafer front-opening unified pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples (wafers and samples may be used interchangeably) to be inspected. A "lot" is a plurality of wafers that can be loaded for processing as a batch.

[0028]

[0044] One or more robot arms (not shown) in the EFEM 106 can transfer wafers to the load / lock chamber 102. The load / lock chamber 102 is connected to a load / lock vacuum pumping system (not shown), which removes gas molecules from the load / lock chamber 102 to reach a first pressure lower than atmospheric pressure. After the first pressure is reached, one or more robot arms (not shown) can transfer the wafers from the load / lock chamber 102 to the main chamber 101. The main chamber 101 is connected to a main chamber vacuum pumping system (not shown), which removes gas molecules from the main chamber 101 to reach a second pressure lower than the first pressure. After the second pressure is reached, the wafers are subjected to inspection by the electron beam tool 104. The electron beam tool 104 can be a single beam system or a multi-beam system.

[0029]

[0045] The controller 109 is electronically connected to the electron beam tool 104. The controller 109 may be a computer configured to control various aspects of the EBI system 100. While the controller 109 is shown in FIG. 1 as being external to the structure that includes the main chamber 101, the load / lock chamber 102, and the EFEM 106, it will be understood that the controller 109 may also be part of this structure.

[0030]

[0046] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a general-purpose or specialized electronic device capable of manipulating or processing information. For example, a processor may include any number and combination of central processing units (i.e., "CPUs"), graphics processing units (i.e., "GPUs"), optical processors, programmable logic controllers, microcontrollers, microprocessors, digital signal processors, intellectual property (IP) cores, programmable logic arrays (PLAs), programmable array logic (PALs), general-purpose array logic (GALs), complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), systems-on-chips (SoCs), application-specific integrated circuits (ASICs), and any type of circuitry capable of processing data. A processor may also be a virtual processor, including one or more processors distributed across multiple machines or devices coupled via a network.

[0031]

[0047] In some embodiments, controller 109 may further include one or more memories (not shown). Memory may be a general-purpose or specialized electronic device capable of storing code and data accessible to a processor (e.g., via a bus). For example, memory may include any combination of any number of random access memories (RAMs), read-only memories (ROMs), optical disks, magnetic disks, hard drives, solid-state drives, flash drives, security digital (SD) cards, memory sticks, compact flash (CF) cards, or any type of storage device. Code may include an operating system (OS) and one or more application programs (i.e., "apps") for specific tasks. Memory may also be virtual memory, including one or more memories distributed across multiple machines or devices coupled via a network.

[0032]

[0048] Embodiments of the present disclosure may provide a single charged particle beam imaging system ("single beam system"). In comparison to a single beam system, a multiple charged particle beam imaging system ("multi-beam system") may be designed to optimize throughput for different scanning modes. Embodiments of the present disclosure provide a multi-beam system that has the ability to optimize throughput for different scanning modes by using beam arrays with different geometries and accommodating different throughput and resolution requirements.

[0033]

[0049] 2A, which is a schematic diagram illustrating an exemplary electron beam tool 104 including a multi-beam inspection tool that is part of the EBI system 100 of FIG. 1, consistent with embodiments of the present disclosure. In some embodiments, the electron beam tool 104 can be operated as a single-beam inspection tool that is part of the EBI system 100 of FIG. 1. The multi-beam electron beam tool 104 (also referred to herein as apparatus 104) includes an electron source 201, a Coulomb aperture plate (or "gun aperture plate") 271, a condenser lens 210, a source conversion unit 220, a primary projection system 230, a motorized stage 209, and a sample holder 207 supported by the motorized stage 209 for holding a sample 208 (e.g., a wafer or photomask) to be inspected. The multi-beam electron beam tool 104 can further include a secondary projection system 250 and an electron detection device 240. The primary projection system 230 can include an objective lens 231. The electronic detection device 240 may include a number of detection elements 241, 242, and 243. A beam separator 233 and a deflection scanning unit 232 may be arranged inside the primary projection system 230.

[0034]

[0050] The electron source 201, the Coulomb aperture plate 271, the condenser lens 210, the radiation source conversion unit 220, the beam separator 233, the deflection scanning unit 232, and the primary projection system 230 may be aligned with a primary optical axis 204 of the apparatus 104. The secondary projection system 250 and the electron detection device 240 may be aligned with a secondary optical axis 251 of the apparatus 104.

[0035]

[0051] The electron source 201 may include a cathode (not shown) and an extractor or anode (not shown), and in operation the electron source 201 is configured to emit primary electrons from the cathode, which are extracted or accelerated by the extractor and / or anode to form a primary electron beam 202 that forms a (virtual or real) primary beam crossover 203. The primary electron beam 202 may be visible as it is emitted from the primary beam crossover 203.

[0036]

[0052] The source conversion unit 220 may include an image-forming element array (not shown), an aberration compensator array (not shown), a beam-limiting aperture array (not shown), and a pre-bend micro-deflector array (not shown). In some embodiments, the pre-bend micro-deflector array deflects multiple primary beamlets 211, 212, 213 of the primary electron beam 202 so that they properly enter the beam-limiting aperture array, the image-forming element array, and the aberration compensator array. In some embodiments, the apparatus 104 can be operated as a single-beam system so that a single primary beamlet is generated. In some embodiments, the condenser lens 210 is designed to focus the primary electron beam 202 into a parallel beam and at normal incidence on the source conversion unit 220. The imaging element array may include a plurality of micro-deflectors or micro-lenses for influencing the plurality of primary beamlets 211, 212, and 213 of the primary electron beam 202 and for forming a plurality of (virtual or real) parallel images of the primary beam crossover 203, one for each of the primary beamlets 211, 212, and 213. In some embodiments, the aberration compensator array may include a field curvature compensator array (not shown) and an astigmatism compensator array (not shown). The field curvature compensator array may include a plurality of micro-lenses for compensating for field curvature aberration of the primary beamlets 211, 212, and 213. The astigmatism compensator array may include a plurality of micro-stigmators for compensating for astigmatism of the primary beamlets 211, 212, and 213. The beam-limiting aperture array may be configured to limit the diameter of each of the primary beamlets 211, 212, and 213. 2A shows three primary beamlets 211, 212, and 213 by way of example, it will be understood that the source conversion unit 220 may be configured to form any number of primary beamlets. The controller 109 may be connected to various parts of the EBI system 100 of FIG. 1, such as the source conversion unit 220, the electron detection device 240, the primary projection system 230, or the motorized stage 209. In some embodiments, the controller 109 may perform various image and signal processing functions, as described in more detail below.The controller 109 may also generate various control signals to govern the operation of the charged particle beam inspection system.

[0037]

[0053] The condenser lens 210 is configured to focus the primary electron beam 202. The condenser lens 210 may be further configured to adjust the current of the primary beamlets 211, 212, and 213 downstream of the radiation source conversion unit 220 by changing the focusing power of the condenser lens 210. Alternatively, the current can be changed by changing the radial size of a beam-limiting aperture in a beam-limiting aperture array corresponding to each primary beamlet. The current can be changed by changing both the radial size of the beam-limiting aperture and the focusing power of the condenser lens 210. The condenser lens 210 may be an adjustable condenser lens that may be configured such that the position of its first-principles plane is movable. The adjustable condenser lens may be configured to be magnetic, which may result in the off-axis beamlets 212 and 213 irradiating the radiation source conversion unit 220 with a rotation angle. The rotation angle varies depending on the focusing power or the position of the first-principles plane of the adjustable condenser lens. Collector lens 210 may be an anti-rotation collector lens that may be configured to not change its rotation angle when the focusing power of collector lens 210 is changed. In some embodiments, collector lens 210 may be an adjustable anti-rotation collector lens that does not change its rotation angle when its focusing power and the position of its first-principles plane are changed.

[0038]

[0054] The objective lens 231 may be configured to focus the beamlets 211, 212, and 213 onto the sample 208 for inspection, which in the current embodiment may form three probe spots 221, 222, and 223 on the surface of the sample 208. The Coulomb aperture plate 271 is operatively configured to block peripheral electrons of the primary electron beam 202 to reduce the Coulomb effect, which can increase the size of the probe spots 221, 222, and 223 of the primary beamlets 211, 212, and 213, respectively, thereby degrading inspection resolution.

[0039]

[0055] The beam separator 233 may be, for example, a Wien filter including electrostatic deflectors that generate electrostatic and magnetic dipole fields (not shown in FIG. 2A ). In operation, the beam separator 233 may be configured to exert an electrostatic force due to the electrostatic dipole field on individual electrons of the primary beamlets 211, 212, and 213. This electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted on the individual electrons by the magnetic dipole field of the beam separator 233. Thus, the primary beamlets 211, 212, and 213 may pass at least approximately straight through the beam separator 233 with at least approximately zero deflection angle.

[0040]

[0056] The deflection scanning unit 232 is operatively configured to deflect the primary beamlets 211, 212, and 213 to scan the probe spots 221, 222, and 223 over respective scan areas within a section of the surface of the sample 208. In response to the incidence of the primary beamlets 211, 212, and 213 or the probe spots 221, 222, and 223 on the sample 208, electrons emerge from the sample 208 and generate three secondary electron beams 261, 262, and 263. Each of the secondary electron beams 261, 262, and 263 typically includes secondary electrons (having an electron energy of 50 eV or less) and backscattered electrons (having an electron energy between 50 eV and the landing energy of the primary beamlets 211, 212, and 213). The beam separator 233 is configured to deflect the secondary electron beams 261, 262, and 263 towards the secondary projection system 250. The secondary projection system 250 then focuses the secondary electron beams 261, 262, and 263 onto detector elements 241, 242, and 243 of the electron detection device 240. The detector elements 241, 242, and 243 are arranged to detect corresponding secondary electron beams 261, 262, and 263 and generate corresponding signals that are sent to the controller 109 or a signal processing system (not shown), for example, to construct an image of a corresponding scanned area of the sample 208.

[0041]

[0057] In some embodiments, detector elements 241, 242, and 243 detect corresponding secondary electron beams 261, 262, and 263, respectively, and generate corresponding intensity signal outputs (not shown) to an image processing system (e.g., controller 109). In some embodiments, each detector element 241, 242, and 243 may include one or more pixels. The intensity signal output of a detector element may be the sum of signals generated by all of the pixels in the detector element.

[0042]

[0058] In some embodiments, the controller 109 may include an image processing system including an image acquirer (not shown) and storage (not shown). The image acquirer may include one or more processors. For example, the image acquirer may include a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer may be communicatively coupled to the electronic detection device 240 of the apparatus 104 by a medium such as electrical conductors, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, a wireless radio, or a combination thereof, among others. In some embodiments, the image acquirer may receive signals from the electronic detection device 240 and construct an image. The image acquirer may thus acquire an image of the sample 208. The image acquirer may also perform various post-processing functions, such as generating contours and superimposing indicators on the acquired image. The image acquirer may be configured to adjust the brightness and contrast of the acquired image, etc. In some embodiments, the storage may be a storage medium, such as a hard disk, a flash drive, cloud storage, random access memory (RAM), or other types of computer-readable memory. A storage may be coupled to the image acquirer and can be used to store raw scanned image data as original images and to store post-processed images.

[0043]

[0059] In some embodiments, the image acquirer may acquire one or more images of the sample based on an imaging signal received from the electronic detection device 240. The imaging signal may correspond to a scanning motion for performing charged particle imaging. The acquired image may be a single image including multiple imaging areas. The single image may be stored in storage. The single image may be an original image that may be divided into multiple regions. Each of these regions may include an imaging area that includes a feature of the sample 208. The acquired image may include multiple images of a single imaging area of the sample 208 sampled multiple times over a time series. The multiple images may be stored in storage. In some embodiments, the controller 109 may be configured to perform image processing steps using multiple images of the same location on the sample 208.

[0044]

[0060] In some embodiments, the controller 109 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of detected secondary electrons. The electron distribution data collected during the detection time window may be used in combination with the corresponding scan path data for each of the primary beamlets 211, 212, and 213 incident on the wafer surface to reconstruct an image of the wafer structure under inspection. The reconstructed image may be used to reveal various features of the internal or external structure of the sample 208, and thereby reveal any defects that may be present in the wafer.

[0045]

[0061] In some embodiments, the controller 109 may control the motorized stage 209 to move the sample 208 during inspection of the sample 208. In some embodiments, the controller 109 may enable the motorized stage 209 to continuously move the sample 208 in one direction at a constant velocity. In other embodiments, the controller 109 may enable the motorized stage 209 to vary the speed of movement of the sample 208 over time depending on the steps in the scanning process.

[0046]

[0062] 2A shows that the apparatus 104 uses three primary electron beams, it will be understood that the apparatus 104 can use one, two, or more primary electron beams. This disclosure does not limit the number of primary electron beams used in the apparatus 104. In some embodiments, the apparatus 104 can be an SEM used for lithography. In some embodiments, the electron beam tool 104 can be a single beam system or a multi-beam system.

[0047]

[0063] For example, as shown in FIG. 2B , electron beam tool 100B (also referred to herein as apparatus 100B) may be a single-beam inspection tool for use in EBI system 10 consistent with embodiments of the present disclosure. 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. In some embodiments, objective lens assembly 132 may be a modified SORIL lens, which includes a pole piece 132a, a control electrode 132b, a deflector 132c, and an excitation coil 132d. In the 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 may be focused by a modified SORIL lens to a probe spot 170, impinging on the surface of the wafer 150. The probe spot 170 may be scanned across the surface of the wafer 150 by a deflector, such as the deflector 132c of the SORIL lens or other deflectors. Secondary particles or scattered primary particles, such as secondary electrons or scattered primary electrons emanating from the wafer surface, may be collected by a detector 144 to determine the intensity of the beam and so that an image of the area of interest on the wafer 150 may be reconstructed.

[0048]

[0064] 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, etc., 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 electrical conductors, 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. The image acquirer 120 may thus acquire an image of the wafer 150. The image acquirer 120 may also perform various post-processing functions, such as generating contours and superimposing indicators on the acquired image. The image acquirer 120 may be configured to adjust the brightness and contrast of the acquired image, etc. The storage 130 may be a storage medium such as a hard disk, random access memory (RAM), cloud storage, or other types of computer-readable memory. The storage 130 may be coupled to the image acquirer 120 and may be used to store raw scanned image data as original images and 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 one electronic control unit.

[0049]

[0065] In some embodiments, the image acquirer 120 may acquire one or more images of the sample based on an imaging signal received from the detector 144. The imaging signal may correspond to a scanning motion for performing charged particle imaging. The acquired image may be a single image including multiple imaging areas that may include various features of the wafer 150. The single image may be stored in the storage 130. The imaging may be performed on an imaging frame-by-frame basis.

[0050]

[0066] The condenser and illumination optics of the electron beam tool may include or be assisted by electromagnetic quadrupole electron lenses. For example, as shown in FIG. 2B , electron beam tool 100B may include a first quadrupole lens 148 and a second quadrupole lens 158. In some embodiments, the quadrupole lenses are used to control the electron beam. For example, first quadrupole lens 148 may be controlled to adjust the beam current, and second quadrupole lens 158 may be controlled to adjust the beam spot size and beam shape.

[0051]

[0067] 2B illustrates a charged particle beam device in which the inspection system may use a single primary beam that may be configured to generate secondary electrons by interacting with the wafer 150. The detector 144 may be positioned along the optical axis 105, as in the embodiment shown in FIG. 2B. The primary electron beam may be configured to travel along the optical axis 105. Thus, the detector 144 may include a hole in its center to allow the primary electron beam to pass through and reach the wafer 150.

[0052]

[0068] Reference is now made to Figure 3A, which shows a schematic representation of an exemplary structure of a detector 300, consistent with embodiments of the present disclosure. Detector 300 may be provided as detector 144 or electron detection device 240 in connection with Figures 2A and 2B. While one array is shown in Figure 3A, it should be understood that detector 300 may include multiple arrays, such as one array for each secondary electron beam.

[0053]

[0069] Detector 300 may include an array of detector elements, including detector elements 311, 312, and 313. The detector elements may be arranged in a planar, two-dimensional array, with the plane of the array approximately perpendicular to the direction of incidence of the incoming charged particles. In some embodiments, detector 300 may be arranged so that it is tilted relative to the direction of incidence.

[0054]

[0070] The detector 300 may include a substrate 310. The substrate 310 may be a semiconductor substrate that may include a detector element. The detector element may be a diode. The detector element may also be a diode-like element that can convert incident energy into a measurable signal. The detector element may include, for example, a PIN diode, an avalanche diode, an electron multiplier tube (EMT), or the like, or a combination thereof. Additionally, the term "detector element" may include or cover a "sensing element," "sensor element," "detector cell," or "detector segment," etc. In some embodiments, a pixel on a detector may be a detector element.

[0055]

[0071] Area 325 may be provided between adjacent detector elements. Area 325 may be an isolation area for isolating sides or corners of adjacent detector elements from each other. Area 325 may include an insulating material that is a different material from other areas of the detector surface of detector 300. Area 325 may be provided as a cross-shaped area as seen in the plan view of FIG. 3A. Area 325 may be provided as a rectangle. In some embodiments, area 325 may not be provided between adjacent sides of detector elements. For example, in some embodiments, there may be no isolation area provided on the detector surface.

[0056]

[0072] The detector element may generate an electrical signal proportional to the charged particles received at the active area of the detector element. For example, the detector element may generate a current signal proportional to the energy of the received electrons. A pre-processing circuit may convert the generated current signal into a voltage that may represent the intensity of the electron beam spot or a portion thereof. The pre-processing circuit may include, for example, a pre-amplifier circuit. The pre-amplifier circuit may include, for example, a charge transfer amplifier (CTA), a transimpedance amplifier (TIA), or an impedance conversion circuit coupled to the CTA or TIA. In some embodiments, a signal processing circuit may be provided that provides an output signal at any time interval. One or more substrates, such as dies, may be provided that may form circuit layers for processing the output of the detector element. The dies may be stacked across the thickness of the detector. Other circuits for other functions may also be provided. For example, a switch actuation circuit may be provided that may control switch elements for connecting the detector elements to each other.

[0057]

[0073] Reference is now made to FIG. 3B , which illustrates a schematic diagram of a cross-sectional structure of a substrate 310 consistent with embodiments of the present disclosure. The substrate 310 may be an example of a structure included in a PIN detector. The substrate 310 may include one or more layers. For example, the substrate 310 may be configured to have multiple layers stacked in a thickness direction, with the thickness direction being approximately parallel to the direction of incidence of the electron beam. In some embodiments, the substrate 310 may have multiple layers stacked in a direction perpendicular to the direction of incidence of the electron beam. The substrate 310 may be provided with a sensor surface 301 for receiving incident charged particles. Detecting elements (e.g., detecting elements 311, 312, and 313) may be provided in a sensing layer of the substrate 310. An area 325 may be provided between adjacent detecting elements. For example, the substrate 310 may include a trench or other structure made of or filled with an insulating material. In some embodiments, the area 325 may extend completely or partially through the substrate 310.

[0058]

[0074] As shown in FIG. 3C , in some embodiments, area 325 may not be provided between sensing elements, consistent with embodiments of the present disclosure. For example, there may be no insulating material provided between sides of adjacent sensing elements in a cross-sectional view. Multiple sensing elements may be contiguous in a cross-sectional view. Isolation between adjacent sensing elements may still be achieved by other means, such as by controlling an electric field. For example, an electric field may be controlled between each sensing element.

[0059]

[0075] Although the diagram may show the detector elements 311, 312, and 313 as separate units, in reality, such division may not exist. For example, the detector elements may be formed by semiconductor devices that constitute a PIN diode device. The PIN diode device may be fabricated as a substrate having multiple layers, including a p-type region, an intrinsic region, and an n-type region. One or more of such layers may be continuous in cross-section. However, in some embodiments, the detector elements may have physical separations between them. Also, in addition to the sensor layer, additional layers, such as a circuit layer and a readout layer, may be provided.

[0060]

[0076] As an example of additional layers, the detector 300 may include one or more circuit layers adjacent to the sensor layer. The one or more circuit layers may include electrical wires, interconnects, and various electronic circuit components. The one or more circuit layers may include a processing system. The one or more circuit layers may include signal processing circuitry. The one or more circuit layers may be configured to receive detected output currents from the sensing elements of the sensor layer. The one or more circuit layers and the sensor layer may be provided on the same or separate dies, for example.

[0061]

[0077] 3D and 3E show schematic diagrams of an individual detector element consistent with embodiments of the present disclosure, which may be an example of one of detector elements 311, 312, and 313. For example, FIG. 3D shows detector element 311A. Detector element 311A may include a semiconductor structure of p-type layer 321, intrinsic layer 322, and n-type layer 323. Detector element 311A may include two terminals, such as an anode and a cathode. Detector element 311A may be reverse-biased, and a depletion region 330 may form spanning a portion of the length of p-type layer 321, substantially the entire length of intrinsic layer 322, and a portion of the length of n-type layer 323. Charge carriers may be removed in depletion region 330, and new charge carriers generated in depletion region 330 may be swept away according to their charge. For example, when an incoming charged particle reaches the sensor surface 301, an electron-hole pair may be created, and the hole 351 may be attracted towards the p-type layer 321 while the electron 352 may be attracted towards the n-type layer 323. In some embodiments, a protective layer may be provided on the sensor surface 301.

[0062]

[0078] 3E, sensing element 311B may operate in a manner similar to that of sensing element 311A, except that the orientation is changed. For example, p-type layer 321 may include sensor surface 301. P-type layer 321 may be exposed to incident charged particles. In this manner, the incident charged particles may interact with p-type layer 321 and depletion region 330, generating electron-hole pairs. In some embodiments, a metal layer may be provided on top of p-type layer 321.

[0063]

[0079] During operation, the depletion region of the detector element can function as a capture region. Incoming charged particles can interact with the semiconductor material of the depletion region and generate new charges. For example, the detector element can be configured so that charged particles having an energy above a certain amount can remove electrons from the lattice of the semiconductor material, thereby creating electron-hole pairs. The resulting electrons and holes can be forced to travel in opposite directions, for example, due to the electric field in the depletion region. The generation of carriers traveling toward the terminals of the detector element can correspond to the flow of current through the detector element.

[0064]

[0080] In a comparative example, a photodiode can be configured to generate charge in response to receiving a photon. The photon can have an energy corresponding to its wavelength or frequency. Typically, a photon in the visible light spectrum can have an energy of about 1 eV. However, in a semiconductor photodiode, it can typically require about 3.6 eV to generate one electron-hole pair. Therefore, photodiodes can face the following current generation detection challenges:

[0065]

[0081] Generally, the energy level of a photon may be similar to the level required to generate an electron-hole pair in a semiconductor photodiode. Therefore, to reliably generate a current, high-energy photons may be required to be incident on the semiconductor photodiode. When the photon's frequency is above a certain level, it may have enough energy to generate one electron-hole pair.

[0066]

[0082] Furthermore, the current generated by the electron-hole pair in response to a photon arrival event may be relatively low. The current generated in response to a photon arrival event may not be sufficient to overcome background noise. Some diodes, such as photodiodes biased in avalanche or Geiger counting mode, may use amplification to generate higher levels of current so that a useful detection signal can be generated. In some embodiments, the photodiode may be biased in an avalanche mode of operation. In some embodiments, the amplification may be provided by a gain block attached to the photodiode. The avalanche effect may be generated from a strong internal electric field resulting from the bias voltage. The avalanche effect may be used to achieve amplification by impact ionization.

[0067]

[0083] Reference is now made to FIG. 4A , which illustrates a circuit diagram 400A of an exemplary detector element (e.g., detector elements 241, 242, and 243 of FIG. 2A , detector elements 311, 312, and 313 of FIGS. 3A-3E , etc.) consistent with embodiments of the present disclosure. Circuit diagram 400A may include a PIN diode 410, a preamplifier 411 a, a pulse shaper 411 b, a discriminator 412, and a current source 413 (e.g., a MOSFET). In some embodiments, when a particle (e.g., a charged particle such as a photon or an electron) is incident on the detector element, PIN diode 410 (corresponding to the detector element) may generate an electrical signal, and preamplifier 411 a and pulse shaper 411 b may amplify or shape the generated electrical signal. Discriminator 412 may output a first value “1” based on the amplified / shaped signal from preamplifier 411 a and pulse shaper 411 b. Based on the "1" output from the discriminator 412, the current source 413 may drive or enable a current. For example, the current source 413 may be configured to drive a current in response to an electrical signal. When a particle is not incident on the detection element within a certain period of time, the discriminator 412 may output a second value "0" so that the current source 413 does not drive or enable a current. In some embodiments, the discriminator 412 may have a discriminator threshold that distinguishes whether an event has occurred. It should be understood that the discriminator threshold may be set to help achieve optimal results. For example, the discriminator threshold may be set above the noise level, thereby counting real events without counting noise pulses.

[0068]

[0084] In some embodiments, the discriminator 412 may output a first value from a range of values (e.g., values not limited to "1" and "0"). For example, the values may be "stepped" integer values (e.g., 0, 1, 2, 3, 4, etc.) such that the discriminator 412 outputs a digital value corresponding to a current value. In some embodiments, the discriminator 412 may output stepped integer values for application of a low particle flux (e.g., a low number of photons received on a detection element in a period or "frame").

[0069]

[0085] In some embodiments, the values may be "real" analog values (e.g., 0, 0.14, 1, 2.5, etc.) corresponding to successive voltage applications, in which case the current source 413 may be controlled by the applied voltage. In some embodiments, the discriminator 412 may output real analog values for applications of high particle flux (e.g., a high number of photons received on the detector element in a period or "frame").

[0070]

[0086] Advantageously, the use of a discriminator that can output stepped integer values or true analog values allows the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, the detectors described in the disclosed embodiments can be adapted to count particles over a high dynamic range with greater accuracy.

[0071]

[0087] The detectors described in the disclosed embodiments may further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0072]

[0088] Reference is now made to Figure 4B, which illustrates a circuit diagram 400B of an exemplary plurality of sensing elements (e.g., sensing elements 241, 242, and 243 of Figure 2A, sensing elements 311, 312, and 313 of Figures 3A-3E, etc.) consistent with embodiments of the present disclosure. Circuit diagram 400B may include components corresponding to the plurality of sensing elements, each of which may include the components and configurations shown in circuit diagram 400A of Figure 4A.

[0073]

[0089] For example, a first sensing element may include group 440a of components including PIN diode 441a, preamplifier 442a, pulse shaper 443a, discriminator 444a, and node 445a. Similarly, a second sensing element may include group 440b of components including PIN diode, preamplifier, pulse shaper, discriminator, and node 445b, a third sensing element may include group 440c of components including PIN diode, preamplifier, pulse shaper, discriminator, and node 445c, a fourth sensing element may include group 440d of components including PIN diode, preamplifier, pulse shaper, discriminator, and node 445d, and a fifth sensing element may include group 440b of components including PIN diode, preamplifier, pulse shaper, discriminator, and node 445e. It should be understood that the number of detector elements in the system is not limited to the five detector elements shown in FIG. 4B (e.g., there may be 1,000, fewer than 1,000, or more than 1,000 detector elements in the system). In some embodiments, to increase throughput (e.g., during inspection), more detector elements may be used for a correspondingly greater number of beams. For example, in a particular application of the present technology, it may be desirable to achieve a particular throughput. To achieve this throughput, it has been determined that more than 1,000 detector elements (and corresponding current sources) may be used for more than 1,000 particle beams to achieve this target throughput. In some embodiments, all of the detector elements may be on one die. In other embodiments, the detector elements may be on multiple dies. For example, some detector elements may be on a first die and some may be on a second die.

[0074]

[0090] In some embodiments, the values from nodes 445a, 445b, 445c, 445d, and 445e may be summed at node 450. While circuit diagram 400B shows an exemplary plurality of sensing elements, reference is now made to Figure 4C, which shows a possible implementation of Figure 4B.

[0075]

[0091] 4C, which illustrates a circuit diagram 400C of an exemplary plurality of sensing elements (e.g., sensing elements 241, 242, and 243 of FIG. 2A , sensing elements 311, 312, and 313 of FIGS. 3A-3E , etc.) consistent with embodiments of the present disclosure. Circuit diagram 400C may include components corresponding to the plurality of sensing elements, each of which may include the components and configurations shown in circuit diagram 400A of FIG. 4A and circuit diagram 400B of FIG. 4B . For example, the first detection element may include a group 420a (e.g., group 440a in FIG. 4B) of components including a PIN diode 421a (e.g., PIN diode 441a in FIG. 4B), a preamplifier 422a (e.g., preamplifier 442a in FIG. 4B), a pulse shaper 423a (e.g., pulse shaper 443a in FIG. 4B), a discriminator 424a (e.g., discriminator 444a in FIG. 4B), and a current source 425a (e.g., node 445a in FIG. 4B). Similarly, the second sensing element may include a group 420b (e.g., group 440b in FIG. 4B) of components including a PIN diode, a preamplifier, a pulse shaper, a discriminator, and a current source 425b (e.g., node 445b in FIG. 4B), and the third sensing element may include a group 420c (e.g., group 440c in FIG. 4B) of components including a PIN diode, a preamplifier, a pulse shaper, a discriminator, and a current source 425c (e.g., node 445c in FIG. 4B). For example, the fourth sensing element may include a group 420d of components (e.g., group 440d in FIG. 4B) including a PIN diode, a preamplifier, a pulse shaper, a discriminator, and a current source 425d (e.g., node 445d in FIG. 4B), and the fifth sensing element may include a group 420e of components (e.g., group 440e in FIG. 4B) including a PIN diode, a preamplifier, a pulse shaper, a discriminator, and a current source 425e (e.g., node 445e in FIG. 4B). It should be understood that the number of sensing elements in the system is not limited to the five sensing elements shown in FIG. 4C (e.g., there may be 1000 sensing elements, fewer than 1000 sensing elements, or more than 1000 sensing elements in the system).In some embodiments, to increase throughput (e.g., during inspection), more detector elements may be used for a correspondingly larger number of beams. For example, in a particular application of the present technology, it may be desirable to achieve a particular throughput. To achieve this throughput, it has been determined that more than 1000 detector elements (and corresponding current sources) may be used for more than 1000 particle beams to achieve this throughput. In some embodiments, all of the detector elements may be on one die. In other embodiments, the detector elements may be on multiple dies. For example, some detector elements may be on a first die and some detector elements may be on a second die.

[0076]

[0092] In some embodiments, when a particle (e.g., a charged particle such as a photon or an electron) is incident on a detection element, a corresponding PIN diode (e.g., PIN diode 421a) may generate an electrical signal, and a corresponding amplifier / shaper (e.g., preamplifier 422a and pulse shaper 423a) may amplify or shape the generated electrical signal. A discriminator of the detection element may output a first value “1” based on the amplified / shaped signal. A corresponding current source may drive or enable a current based on the “1” output from the discriminator. For example, the current source may be configured to drive a current in response to the electrical signal. When a particle is not incident on the detection element within a certain period of time, the corresponding discriminator may output a second value “0” so that the current source does not drive or enable a current. In some embodiments, the discriminator may have a discriminator threshold that distinguishes whether an event has occurred. It should be understood that the discriminator threshold may be set to help achieve optimal results. For example, the discriminator threshold may be set above the noise level, thereby counting real events without counting noise pulses.

[0077]

[0093] For example, discriminator 424a may output a first value "1" based on the amplified / shaped signal from its corresponding pulse shaper 423a when a particle is incident on its corresponding detection element. Based on the "1" output from discriminator 424a, current source 425a may drive or enable a current. A discriminator from another detection element (e.g., from group 420b, 420c, 420d, or 420e) may output a second value "0" so that the corresponding current source does not drive or enable a current if a particle does not incident on that detection element within a time period.

[0078]

[0094] In some embodiments, the discriminator 424a may output a first value from a range of values (e.g., values not limited to "1" and "0"). For example, the values may be "stepped" integer values (e.g., 0, 1, 2, 3, 4, etc.) such that the discriminator 424a outputs a digital value corresponding to a current value. In some embodiments, the discriminator 424a may output stepped integer values for application of a low particle flux (e.g., a low number of photons received on a detection element in a period or "frame").

[0079]

[0095] In some embodiments, the values may be "real" analog values (e.g., 0, 0.14, 1, 2.5, etc.) corresponding to successive voltage applications, in which case current source 425a may be controlled by the applied voltage. In some embodiments, discriminator 424a may output real analog values for applications of high particle flux (e.g., a high number of photons received on a detector element in a period or "frame").

[0080]

[0096] Advantageously, the use of a discriminator that can output stepped integer values or true analog values allows the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, the detectors described in the disclosed embodiments can be adapted to count particles over a high dynamic range with greater accuracy.

[0081]

[0097] The detectors described in the disclosed embodiments may further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0082]

[0098] In some embodiments, current sources 425a-425e may be configured to be in parallel and coupled to a common resistor 434 (e.g., node 450 in FIG. 4B). An analog-to-digital converter (ADC) 435 (e.g., node 450 in FIG. 4B) may be configured to measure the voltage across resistor 434. Resistor 434 may be configured to combine or determine the sum of the currents from the current sources (e.g., the sum of the driven or enabled currents from current sources 425a-425e). For example, the configuration may allow the currents output by the current sources to be combined to create a combined current. A circuit such as ADC 435 in the detection system may determine the total number of particles incident on the detector (e.g., multiple detection elements) based on the current values corresponding to particles landing on the detection elements, the determined sum of the currents from the current sources, the resistance of resistor 434, and the voltage measured across resistor 434 (e.g., the total number of particles incident on the detector may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of resistor 434). For example, ADC 435 may be configured to convert the resultant current into a digital value indicative of the electrical signal output by the detection elements.

[0083]

[0099] As noted above, analog particle counting on a pixelated detector advantageously reduces power consumption and determines the total number of particles incident on the detector at high frame rates in a scalable manner. This is in contrast to digital particle counting, which may be undesirable because it requires counting each detector element using digital logic, which may result in slower particle counting, increased power consumption, or false particle counts.

[0084]

[0100] Furthermore, the CMOS technology used for the current sources has extremely low leakage current, which reduces inaccuracies and power dissipation in inactive current sources (e.g., current sources that are not driven or enabled, corresponding to a discriminator that outputs a "0"). Low leakage current is advantageous in that the signal of a single active detection element current source (e.g., a single current source with a driven or enabled current) may be distinguishable even if the remaining current sources are inactive.

[0085]

[0101] Reference is now made to Figure 5A, which shows a schematic representation of an exemplary structure of a detector 500A consistent with embodiments of the present disclosure. Detector 500A may be provided as detector 144, electronic detection device 240, or detector 300 in connection with Figures 2A, 2B, and 3A.

[0086]

[0102] Detector 500A may include groups 510, 520, 530, and 540 of sensing elements. For example, group 510 may include sensing element 511, group 520 may include sensing element 521, group 530 may include sensing element 531, and group 540 may include sensing element 541. Circuit diagram 400A of FIG. 4A, circuit diagram 400B of FIG. 4B, and circuit diagram 400C of FIG. 4C may be applied to each group of sensing elements, advantageously allowing for scalability of the detection system. While FIG. 5A shows a somewhat uniformly shaped grouping of sensing elements, it should be understood that groupings of sensing elements are configurable, as described in U.S. Patent Application Publication No. 2020 / 0219696, which is incorporated by reference in its entirety.

[0087]

[0103] For example, reference is now made to FIG. 5B, which illustrates a circuit diagram 500B, consistent with an embodiment of the present disclosure. Each detection element (e.g., detection elements 511, 521, 531, and 541) in each group (e.g., groups 510, 520, 530, and 540) may include a PIN diode (e.g., PIN diode 410 of FIG. 4A, PIN diode 421a of FIG. 4C), an amplifier / shaper (e.g., amplifier / shaper 411 of FIG. 4A, preamplifier 422a of FIG. 4C, pulse shaper 423a of FIG. 4C), a discriminator (e.g., discriminator 412, discriminators 412a-412h of FIG. 4B, discriminator 424a of FIG. 4C), and a current source (e.g., current source 413 of FIG. 4A, current sources 413a-413h of FIG. 4B, current sources 425a-425c of FIG. 4C) (e.g., a MOSFET).

[0088]

[0104] Similar to the embodiments described above with respect to FIGS. 4A, 4B, and 4C, when a particle (e.g., a charged particle such as a photon, an electron, etc.) is incident on a detector element, a corresponding PIN diode (e.g., PIN diode 410 in FIG. 4A) generates an electrical signal, and a corresponding amplifier / shaper (e.g., amplifier / shaper 411 in FIG. 4A) may amplify or shape the generated electrical signal. A discriminator (e.g., discriminator 412a in FIG. 4A) of the detector element may output a first value “1” based on the amplified / shaped signal. Based on the “1” output from the discriminator, a corresponding current source (e.g., current source 413a in FIG. 4A) may drive or enable a current. For example, the current source may be configured to drive a current in response to the electrical signal. When a particle does not strike a detection element within a certain period of time, the corresponding discriminator (e.g., discriminator 412b in FIG. 4A) may output a second value of "0" so that the current source (e.g., current source 413b in FIG. 4A) does not drive or enable current. In some embodiments, the discriminator may have a discriminator threshold that distinguishes whether an event has occurred. It should be understood that the discriminator threshold may be set to help achieve optimal results. For example, the discriminator threshold may be set above the noise level, thereby counting real events without counting noise pulses.

[0089]

[0105] In some embodiments, the discriminator may output a first value from a range of values (e.g., values not limited to "1" and "0"). For example, the values may be "stepped" integer values (e.g., 0, 1, 2, 3, 4, etc.) such that the discriminator outputs a digital value corresponding to a current value. In some embodiments, the discriminator may output stepped integer values for application of a low particle flux (e.g., a low number of photons received on the detection element in a period or "frame").

[0090]

[0106] In some embodiments, the values may be "real" analog values (e.g., 0, 0.14, 1, 2.5, etc.) corresponding to successive voltage applications, where the corresponding current source may be controlled by the applied voltage. In some embodiments, the discriminator may output real analog values for applications of high particle flux (e.g., a high number of photons received on the detector element in a period or "frame").

[0091]

[0107] Advantageously, the use of a discriminator that can output stepped integer values or true analog values allows the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, the detectors described in the disclosed embodiments can be adapted to count particles over a high dynamic range with greater accuracy.

[0092]

[0108] The detectors described in the disclosed embodiments may further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0093]

[0109] In some embodiments, circuit diagram 500B may include group 510b of sense elements corresponding to group 510 of Figure 5A, group 520b corresponding to group 520 of Figure 5A, group 530b corresponding to group 530 of Figure 5A, and group 540b corresponding to group 540 of Figure 5A. Each of groups 510b-540b of sense elements (which may include sense element 511 of Figure 5A) may include a PIN diode, a preamplifier, a pulse shaper, a discriminator, and a current source for each sense element in the group.

[0094]

[0110] 4A, 4B, and 4C above, the current sources of a group of sensing elements (e.g., groups 510b-540b) may be configured to be in parallel and coupled to a common resistor 514, and the current sources of another group of sensing elements (e.g., another one of groups 510b-540b) may be configured to be in parallel and coupled to a separate common resistor 524. An analog-to-digital converter (ADC) 515 may be configured to measure the voltage across resistor 514, and ADC 525 may be configured to measure the voltage across resistor 524. Resistor 514 may be configured to determine the sum of the currents from the current sources of group 510b, and resistor 524 may be configured to determine the sum of the currents from the current sources of group 520b. For example, the configuration may allow the currents output by the current sources of group 510b to be combined to create a first combined current and the currents output by the current sources of group 520b to be combined to create a second combined current. Circuitry within the detection system, such as ADC 515, may determine the total number of particles incident on group 510b of detection elements (which may include, for example, detection element 511 of FIG. 5A ) based on the current values corresponding to particles landing on detection elements 511, the determined sum of the currents from the current sources of group 510b, the resistance of resistor 514, and the voltage measured across resistor 514 (e.g., the total number of particles incident on group 510b of detection elements may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of resistor 514). For example, ADC 515 may be configured to convert the combined currents into digital values indicative of the electrical signals output by the detection elements.

[0095]

[0111] Similarly, circuitry within the detection system, such as ADC 525, may determine the total number of particles incident on group 520b of detection elements (e.g., including detection element 521) based on the current values corresponding to particles landing on detection element 521, the determined sum of the currents from the current sources of group 520b, the resistance of resistor 524, and the voltage measured across resistor 524 (e.g., the total number of particles incident on group 520b of detection elements may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of resistor 524). For example, ADC 525 may be configured to convert the resultant current into a digital value indicative of the electrical signal output by the detection element.

[0096]

[0112] Circuitry within the detection system can determine the total number of particles incident on the detector by determining the sum of particles incident on group of detector elements 510b and particles incident on group of detector elements 520b. This embodiment determines the number of particles incident on a detector having a large number of detector elements (e.g., greater than 1000 detector elements) by determining in an analog manner the number of particles incident on a group of detector elements on the detector. The detector elements may be pixels of the detector. This advantageously provides a highly scalable determination of the number of particles incident on the detector, can be performed at high frame rates, and can be performed with reduced power consumption.

[0097]

[0113] It should also be understood that the number of groups of sensing elements in a system is not limited to those shown in Figures 5A and 5B (e.g., there may be more than two groups of sensing elements in a system).

[0098]

[0114] Reference is now made to FIG. 5C, which shows a circuit diagram 500C of an exemplary plurality of detection elements (e.g., detection elements 241, 242, 243 of FIG. 2A, detection elements 311, 312, 313 of FIG. 3A-FIG. 3E, detection elements 511, 521, 531, and 541 of FIG. 5A, etc.) consistent with an embodiment of the present disclosure. Each detection element includes a PIN diode (e.g., PIN diode 410 in FIG. 4A, PIN diode 421a in FIG. 4C), an amplifier / shaper (e.g., amplifier / shaper 411 in FIG. 4A, preamplifier 422a in FIG. 4C, pulse shaper 423a in FIG. 4C), a first discriminator 5100 (e.g., discriminator 412, discriminators 412a-412h in FIG. 4B, discriminator 424a in FIG. 4C), a first current source 5112 associated with the first discriminator 5100 (e.g., current source 4112 in FIG. 4A), a second current source 5112 associated with the first discriminator 5100 (e.g., current source 4112 in FIG. 4B), a third current source 5112 associated with the first discriminator 5100 (e.g., current source 4112 in FIG. 4C), a fourth current source 5112 associated with the first discriminator 5100 (e.g., current source 4112 in FIG. 4B), a fifth current source 5112 associated with the first discriminator 5100 (e.g., current source 4112 in FIG. 4C ... sixth current source 5112 associated with the 4B, current sources 413a-413h, and current sources 425a-425c of FIG. 4C) (e.g., a MOSFET), a second discriminator 5200 (e.g., discriminator 412, discriminators 412a-412h, and discriminator 424a of FIG. 4C), and a second current source 5212 (e.g., current source 413 of FIG. 4A, current sources 413a-413h, and current sources 425a-425c of FIG. 4C) (e.g., a MOSFET) associated with second discriminator 5200.

[0099]

[0115] Similar to the embodiments described above with respect to FIGS. 4A, 4B, and 4C, when a particle (e.g., a charged particle such as a photon, an electron, etc.) is incident on a detector element, a corresponding PIN diode (e.g., PIN diode 410 in FIG. 4A) generates an electrical signal, and a corresponding amplifier / shaper (e.g., amplifier / shaper 411 in FIG. 4A) may amplify or shape the generated electrical signal. A discriminator (e.g., discriminator 412a in FIG. 4A) of the detector element may output a first value “1” based on the amplified / shaped signal. Based on the “1” output from the discriminator, a corresponding current source (e.g., current source 413a in FIG. 4A) may drive or enable a current. For example, the current source may be configured to drive a current in response to the electrical signal. When a particle does not strike a detection element within a certain period of time, the corresponding discriminator (e.g., discriminator 412b in FIG. 4A) may output a second value of "0" so that the current source (e.g., current source 413b in FIG. 4A) does not drive or enable current. In some embodiments, the discriminator may have a discriminator threshold that distinguishes whether an event has occurred. It should be understood that the discriminator threshold may be set to help achieve optimal results. For example, the discriminator threshold may be set above the noise level, thereby counting real events without counting noise pulses.

[0100]

[0116] In some embodiments, the discriminator may output a first value from a range of values (e.g., values not limited to "1" and "0"). For example, the values may be "stepped" integer values (e.g., 0, 1, 2, 3, 4, etc.) such that the discriminator outputs a digital value corresponding to a current value. In some embodiments, the discriminator may output stepped integer values for application of a low particle flux (e.g., a low number of photons received on the detection element in a period or "frame").

[0101]

[0117] In some embodiments, the values may be "real" analog values (e.g., 0, 0.14, 1, 2.5, etc.) corresponding to successive voltage applications, where the corresponding current source may be controlled by the applied voltage. In some embodiments, the discriminator may output real analog values for applications of high particle flux (e.g., a high number of photons received on the detector element in a period or "frame").

[0102]

[0118] Advantageously, the use of a discriminator that can output stepped integer values or true analog values allows the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, the detectors described in the disclosed embodiments can be adapted to count particles over a high dynamic range with greater accuracy.

[0103]

[0119] The detectors described in the disclosed embodiments may further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0104]

[0120] In some embodiments, the first discriminator 5100 may have a first discriminator threshold for high energy particles (e.g., high energy electrons), and the second discriminator 5200 may have a second discriminator threshold for low energy particles (e.g., low energy electrons).

[0105]

[0121] 4A, 4B, 4C, 5A, and 5B above, a first group 5110 of current sources of the detection elements may be configured in parallel and coupled to a common resistor 5114, and a second group 5210 of current sources of the detection elements may be configured in parallel and coupled to a separate common resistor 5214. In some embodiments, the first group 5110 may correspond to a first discriminator 5100 for high-energy particles of the multiple detection elements, and the second group 5210 may correspond to a second discriminator 5200 for low-energy particles of the multiple detection elements.

[0106]

[0122] Analog-to-digital converter (ADC) 5116 may be configured to measure the voltage on resistor 5114, and ADC 5216 may be configured to measure the voltage on resistor 5214. Resistor 5114 may be configured to determine the sum of the currents from the current sources in group 5110, and resistor 5214 may be configured to determine the sum of the currents from the current sources in group 5210. For example, the configuration may allow the currents output by the current sources in group 5110 to be combined to create a first combined current, and the currents output by the current sources in group 5210 to be combined to create a second combined current.

[0107]

[0123] Circuitry within the detection system, such as ADC5116, may determine the total number of energetic particles incident on the detection elements of group 5110 based on the current values corresponding to particles landing on the detection elements, the determined sum of the currents from the current sources of group 5110, the resistance of resistor 5114, and the voltage measured across resistor 5114 (e.g., the total number of particles incident on the detection elements of group 5110 may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of resistor 5114). For example, ADC5116 may be configured to convert the resultant current into a digital value indicative of the electrical signal output by the detection elements.

[0108]

[0124] Similarly, circuitry within the detection system, such as ADC 5216, may determine the total number of low-energy particles incident on the detection elements of group 5210 based on the current values corresponding to particles landing on the detection elements, the determined sum of the currents from the current sources of group 5210, the resistance of resistor 5214, and the voltage measured across resistor 5214 (e.g., the total number of particles incident on the detection elements of group 5210 may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of resistor 5214). For example, ADC 5216 may be configured to convert the resultant current into a digital value indicative of the electrical signal output by the detection elements.

[0109]

[0125] Circuitry within the detection system may determine the total number of particles incident on the detector by determining the sum of the particles incident on the detector elements of group 5110 and the particles incident on the detector elements of group 5210. This embodiment determines the number of particles incident on a detector having a large number of detector elements (e.g., greater than 1000 detector elements) by discriminating between high-energy particles and low-energy particles and determining in an analog manner the number of particles incident on the detector elements. This advantageously provides a highly scalable determination of the number of particles incident on the detector, runs at high frame rates, and runs with reduced power consumption.

[0110]

[0126] It should also be understood that the number of groups of detector elements in the system is not limited to those shown in FIG. 5C (eg, there may be more than two levels of energy discrimination in the system).

[0111]

[0127] 6, which illustrates a circuit diagram 600 of an exemplary plurality of sensing elements (e.g., sensing elements 241, 242, and 243 of FIG. 2A , sensing elements 311, 312, and 313 of FIGS. 3A-3E , etc.) consistent with embodiments of the present disclosure. Circuit diagram 600 may include components corresponding to the plurality of sensing elements.

[0112]

[0128] For example, a first sensing element may include a group of components 640a, including a PIN diode 641a, a preamplifier 642a, a pulse shaper 643a, an ADC 644a, and a node 645a. Similarly, a second sensing element may include a group of components 640b, including a PIN diode, a preamplifier, a pulse shaper, an ADC, and a node 645b, a third sensing element may include a group of components 640c, including a PIN diode, a preamplifier, a pulse shaper, an ADC, and a node 645c, a fourth sensing element may include a group of components 640d, including a PIN diode, a preamplifier, a pulse shaper, an ADC, and a node 645d, and a fifth sensing element may include a group of components 640b, including a PIN diode, a preamplifier, a pulse shaper, an ADC, and a node 645e. It should be understood that the number of detector elements in the system is not limited to the five detector elements shown in FIG. 6 (e.g., there may be 1,000, fewer than 1,000, or more than 1,000 detector elements in the system). In some embodiments, to increase throughput (e.g., during inspection), more detector elements may be used for a correspondingly greater number of beams. For example, in a particular application of the present technology, it may be desirable to achieve a particular throughput. To achieve this throughput, it has been determined that more than 1,000 detector elements (and corresponding current sources) may be used for more than 1,000 particle beams to achieve this target throughput. In some embodiments, all of the detector elements may be on one die. In other embodiments, the detector elements may be on multiple dies. For example, some detector elements may be on a first die and some may be on a second die.

[0113]

[0129] In some embodiments, when a particle (e.g., a charged particle such as a photon, electron, etc.) is incident on a detection element, a corresponding PIN diode (e.g., PIN diode 641a) may generate an electrical signal, and a corresponding amplifier / shaper (e.g., preamplifier 642a and pulse shaper 643a) may amplify or shape the generated electrical signal.

[0114]

[0130] In some embodiments, the ADC of a detection element (e.g., ADC 644a of detection element 640a) can be connected to one or more bit lines. For example, each detection element can be connected to a first bit line BIT <1> and any number of additional bit lines BIT <n>Different combinations of bit lines of the ADC may be activated (e.g., "on" or "off") based on the electrical signals generated from the corresponding photodiodes (e.g., the generated electrical signals may include multiple binary digits (bits), with each bit being a digital value corresponding to a bit line).

[0115]

[0131] In some embodiments, nodes 645a, 645b, 645c, 645d, and 645e may each correspond to a different sensing element connected to the same bit line. In some embodiments, the values from nodes 645a, 645b, 645c, 645d, and 645e may be summed at node 650. In some embodiments, each bit line of a plurality of bit lines (e.g., bit line BIT <n>) can be summed at the corresponding node.

[0116]

[0132] In some embodiments, nodes 645a, 645b, 645c, 645d, and 645e may be current sources for the corresponding bit lines, and the current sources may be configured to be in parallel and coupled to a common resistor (e.g., at node 650). An ADC (e.g., at node 650) may be configured to measure the voltage across the resistor. The resistor may be configured to combine or determine a sum of the currents from the current sources (e.g., the sum of the driven or enabled currents from nodes 645a, 645b, 645c, 645d, and 645e). For example, the configuration may allow the currents output by the current sources to be combined to create a combined current. A circuit within the detection system, such as an ADC at a bit line node 650, determines the voltage across the bit line (e.g., BIT <1> ) may be determined. For example, the ADC at node 650 may be configured to convert the resultant current to a digital value corresponding to the electrical signal output by the sensing element. The ADC at each node corresponding to a bit line may determine its corresponding value in the same manner as the ADC at node 650.

[0117]

[0133] Multiple bit lines (e.g., BIT <n>) can determine the total number of particles incident on the detector element based on the determined sum of each bit line node 650.

[0118]

[0134] Advantageously, using a detector element with an ADC connected to multiple bit lines increases the speed and accuracy of particle counting on the detector compared to using a detector element with a single output.

[0119]

[0135] The detectors described in the disclosed embodiments further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Pat. Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0120]

[0136] Reference is now made to Figure 7, a flowchart illustrating an exemplary process 600 for counting particles on a detector consistent with embodiments of the present disclosure. The steps of method 600 may illustratively be performed on a computing device (e.g., controller 109 of Figures 1, 2A, and 2B) or by a system using features of a computing device. It should be understood that the described method 600 may be modified to modify the order of steps and to include additional steps.

[0121]

[0137] In step 701, a current source (e.g., current source 413 in FIG. 4A, current sources 413a-413h in FIG. 4B, current sources 532, 542 in FIG. 5B, nodes 645a-645e in FIG. 6, etc.) may drive or enable a current when a particle (e.g., a charged particle such as a photon or an electron) is incident on a corresponding detection element (e.g., detection elements 241, 242, 243 in FIG. 2A, detection elements 311, 312, 313 in FIGS. 3A-3E, detection elements 511, 521 in FIG. 5B, detection elements 640a-640e in FIG. 6, etc.). For example, when a particle is incident on a detection element, a corresponding PIN diode (e.g., PIN diode 410 in FIG. 4A or PIN diode 641a in FIG. 6) may generate an electrical signal, and a corresponding amplifier / shaper (e.g., amplifier / shaper 411 in FIG. 4A or preamplifier 642a and pulse shaper 643a in FIG. 6) may amplify or shape the generated electrical signal. A discriminator of the detection element may output a first value “1” based on the amplified / shaped signal. A corresponding current source may drive or enable a current based on the “1” output from the discriminator. For example, the current source may be configured to drive a current in response to the electrical signal. When a particle is not incident on the detection element within a certain period of time, the corresponding discriminator may output a second value “0” so that the current source does not drive or enable a current. In some embodiments, the discriminator may have a discriminator threshold that distinguishes whether an event has occurred. It should be understood that the discriminator threshold may be set to help achieve optimal results. For example, the discriminator threshold may be set above the noise level, thereby counting real events without counting noise pulses.

[0122]

[0138] In some embodiments, the discriminator may output a first value from a range of values (e.g., values not limited to "1" and "0"). For example, the values may be "stepped" integer values (e.g., 0, 1, 2, 3, 4, etc.) such that the discriminator outputs a digital value corresponding to a current value. In some embodiments, the discriminator may output stepped integer values for application of a low particle flux (e.g., a low number of photons received on the detection element in a period or "frame").

[0123]

[0139] In some embodiments, the values may be "real" analog values (e.g., 0, 0.14, 1, 2.5, etc.) corresponding to successive voltage applications, where the corresponding current source may be controlled by the applied voltage. In some embodiments, the discriminator may output real analog values for applications of high particle flux (e.g., a high number of photons received on the detector element in a period or "frame").

[0124]

[0140] Advantageously, the use of a discriminator that can output stepped integer values or true analog values allows the detector architecture to be moved to silicon, which reduces the capacitors per detector element, reduces overall noise, and increases the speed at which the detector can count particles. Furthermore, the detectors described in the disclosed embodiments can be adapted to count particles over a high dynamic range with greater accuracy.

[0125]

[0141] The detectors described in the disclosed embodiments may further increase particle counting accuracy and improve the phase stability of electrical signals in detection systems, thereby improving alignment systems and level sensors that use these detection systems. For example, the detectors described in the disclosed embodiments may be used in alignment systems such as those described in U.S. Patent Nos. 9,927,726, 7,440,079, and 6,628,406, and may be used in level or height sensors, as described below with respect to FIG. 8, which applications are incorporated by reference in their entireties. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the alignment of features on a sample. In some embodiments, values (e.g., electrical signals, digital values, etc.) determined by the detector may be used in measuring the level (e.g., height) of features on a sample.

[0126]

[0142] In some embodiments, each detection element may include an ADC (e.g., ADC 644a in FIG. 6). In some embodiments, the ADC of a detection element may be connected to one or more bit lines. For example, each detection element may be connected to a first bit line (e.g., bit line BIT <1> ) and any number of additional bit lines (e.g., bit line BIT <n>), different combinations of bit lines of the ADC may be activated (e.g., "on" or "off") based on the electrical signals generated from the corresponding photodiodes (e.g., the generated electrical signals may include multiple bits, each bit being a digital value corresponding to a bit line).

[0127]

[0143] In step 703, a resistor (e.g., resistor 414 in FIG. 4B, resistors 533, 543 in FIG. 5B, etc.) may be configured to determine the sum of the currents from the multiple current sources (e.g., the sum of the driven or enabled currents from the current sources). For example, the multiple current sources may be configured to be in parallel and coupled to a common resistor. An analog-to-digital converter (ADC) (e.g., ADC 415 in FIG. 4B, ADCs 534, 544 in FIG. 5B, etc.) may be configured to measure the voltage across the resistor.

[0128]

[0144] In some embodiments (e.g., FIG. 6 ) in which each sense element includes an ADC, the current sources for the bit lines may be configured to be in parallel and coupled to a common resistor (e.g., at node 650 in FIG. 6 ). The ADC (e.g., at node 650 in FIG. 6 ) may be configured to measure a voltage across the resistor. The resistor may be configured to combine or determine a sum of the currents from the current sources (e.g., the sum of the driven or enabled currents from nodes 645a, 645b, 645c, 645d, and 645e in FIG. 6 ). For example, the configuration may allow the currents output by the current sources to be combined to create a combined current. Circuitry within the sense system, such as a bit line ADC, may determine a value corresponding to a bit line connected to multiple sense elements (e.g., sense elements 640a, 640b, 640c, 640d, 640e in FIG. 6 ) based on the determined sum of the currents from the current sources, the resistances of the bit line nodes, and the voltages measured across the resistors of the bit line nodes. For example, an ADC at a node of the bit line can be configured to convert the resultant current into a digital value corresponding to the electrical signal output by the sensing element.

[0129]

[0145] In step 705, a circuit within the detection system, such as an ADC, may determine the total number of particles incident on the detector (e.g., on multiple detection elements) based on the determined sum of the drive currents from the current sources. For example, the configuration may allow currents output by the current sources to be combined to create a composite current. For example, the ADC may determine the total number of particles incident on the detector based on current values corresponding to particles landing on the detection elements, the determined sum of the currents from the current sources, the resistance of the resistors, and the voltage measured across the resistors. The total number of particles incident on the detector may be determined based on a direct relationship between the voltage and the product of the total number of particles, the sum of the currents, and the resistance of the resistors. For example, the ADC may be configured to convert the composite current into a digital value indicative of the electrical signal output by the detection elements.

[0130]

[0146] In some embodiments (e.g., FIG. 6) where each detection element includes an ADC, each bit line (e.g., BIT <n>) can determine the total number of particles incident on the detector's detector elements based on the determined sums of the nodes of each bit line.

[0131]

[0147] Reference is now made to FIG. 8, a schematic diagram illustrating an exemplary level sensor system 800 consistent with embodiments of the present disclosure.

[0132]

[0148] A topography measurement system, such as a level sensor or height sensor, may be integrated into a lithography apparatus and positioned to measure the topography of a substrate or wafer's upper surface. A map of the substrate's topography, also called a height map, may be generated from these measurements, showing the substrate's height as a function of position on the substrate. This height map may be used to correct the substrate's position during transfer of a pattern onto the substrate to provide an aerial image of the patterning device at a properly focused position on the substrate. "Height" in this context should be understood to refer to the dimension extending from the plane to the substrate (also called the Z-axis). Typically, a level sensor or height sensor performs measurements at a fixed position (relative to its own optics), and relative movement between the substrate and the optics of the level sensor or height sensor results in height measurements at positions across the substrate.

[0133]

[0149] An example of a level or height sensor LS801 is shown schematically in FIG. 8 . In some embodiments, the level sensor LS801 includes an optical system, which includes a projection unit LSP803 and a detection unit LSD805. The projection unit LSP803 includes a radiation source LSO807 that provides a radiation beam LSB809 provided by a projection grating PGR811 of the projection unit LSP803. The radiation source LSO807 may be polarized or unpolarized, pulsed or continuous, for example, a narrowband radiation source or a broadband radiation source such as a supercontinuum light source, a polarized or unpolarized laser beam, or the like. The radiation source LSO807 may include multiple radiation sources having different colors or wavelength ranges, such as multiple LEDs. The radiation source LSO807 of the level sensor LS801 is not limited to visible light, but may additionally or alternatively encompass ultraviolet (UV) or infrared (IR) light and any range of wavelengths suitable for reflecting from the surface of a substrate.

[0134]

[0150] The projection grating PGR811 is a periodic grating that includes a periodic structure that results in a radiation beam BE1 813 having a periodically varying intensity. The radiation beam BE1 813 having a periodically varying intensity is directed towards a measurement location MLO815 on the substrate W817 with an angle of incidence ANG819 with respect to an axis normal to the incident substrate plane (Z-axis) that is between 0 and 90 degrees, typically between 70 and 80 degrees. At the measurement location MLO815, the patterned radiation beam BE1 813 is reflected by the substrate W817 (indicated by arrow BE2 821) and directed towards the detection unit LSD805.

[0135]

[0151] To determine the height level at the measurement location MLO815, the level sensor 801 further includes a detection system including a detection grating DGR823, a detector DET825 (e.g., any of the detectors described in the disclosed embodiments, such as the detection device 240 of FIG. 2A, the detector 144 of FIG. 2B, the detector 300 of FIGS. 3A-3E, or the detector 500A of FIG. 5A), and a processing unit (not shown) for processing an output signal of the detector DET825. The detection grating DGR823 may be identical to the projection grating PGR811. The detector DET825 produces a detector output signal indicative of the received light, e.g., indicative of the intensity of the received light, such as a photodetector, or representing the spatial distribution of the received intensity, such as a camera. The detector DET825 may include any combination of one or more detector types.

[0136]

[0152] Using triangulation techniques, the height level of the measurement location MLO 815 can be determined. The detected height level is typically related to the signal strength measured by the detector DET 825, in particular the signal strength having a periodicity that depends on the design of the projection grating PGR 811 and the angle of incidence (oblique angle) ANG 819.

[0137]

[0153] The projection unit LSP803 or the detection unit LSD805 may include further optics, such as lenses or mirrors, along the path of the patterned radiation beam between the projection grating PGR811 and the detection grating DGR823 (not shown).

[0138]

[0154] In some embodiments, the detection grid DGR 823 may be omitted and the detector DET 825 may be placed at the location where the detection grid DGR 823 is located. Such a configuration may result in more direct detection of the image of the projection grid PGR 811.

[0139]

[0155] To effectively cover the surface of the substrate W817, the level sensor LS801 may be configured to project an array of measurement beams BE1 813 onto the surface of the substrate W817, thereby generating an array of measurement areas MLO815 or spots that cover a larger measurement range.

[0140]

[0156] Various height sensors of the general type are disclosed, for example, in U.S. Patent Nos. 7,265,364 and 7,646,471, both of which are incorporated herein by reference in their entireties. A height sensor that uses ultraviolet light instead of visible or infrared light is disclosed in U.S. Patent Application Publication No. 2010233600A1, which is incorporated by reference in its entirety. WO 2016102127A1, which is incorporated by reference in its entirety, describes a compact height sensor that uses a multi-element detector to detect and recognize the position of a grating image without the need for a detection grating.

[0141]

[0157] A non-transitory computer-readable medium may be provided that stores instructions for a processor of a controller (e.g., controller 109 of FIGS. 1, 2A, 2B, etc.) to control an electron beam tool or to control a detection system of other systems and servers (e.g., detection device 240 of FIG. 2A , detector 144 of FIG. 2B , detector 300 of FIGS. 3A-3E , detector 500A of FIG. 5A , detector DET of FIG. 8 , etc.) consistent with embodiments of the present disclosure. These instructions may enable one or more processors to perform image processing, data processing, beamlet scanning, database management, graphical display, operation of a charged particle beam instrument or another imaging device, etc. In some embodiments, a non-transitory computer-readable medium may be provided that stores instructions for a processor to perform the steps of process 700. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid state drives, magnetic tape, or any other magnetic data storage medium, compact disk read-only memory (CD-ROM), any other optical data storage medium, any physical medium with a perforated pattern, random access memory (RAM), programmable read-only memory (PROM), and erasable programmable read-only memory (EPROM), FLASH-EPROM, or any other flash memory, non-volatile random access memory (NVRAM), cache, registers, any other memory chip or cartridge, and network versions of any of the foregoing.

[0142]

[0158] The following clauses may be used to further describe the embodiments. 1. A detector comprising: a plurality of detector elements configured to generate an electrical signal in response to a particle being incident on a detector element of the plurality of detector elements; a plurality of current sources configured to drive current in response to an electrical signal, the outputs of the plurality of current sources being connected to allow the currents output by the plurality of current sources to be combined to create a combined current, a plurality of current sources connected to a respective sensing element of the plurality of sensing elements; an analog-to-digital converter (ADC) configured to convert the combined current into a digital value indicative of the electrical signals output by the plurality of sensing elements; A detector comprising: 2. A detector according to clause 1, wherein the particles are charged particles. 3. A detector according to clause 1, wherein the particles are photons. 4. A detector as described in any one of clauses 1 to 3, wherein a plurality of current sources are configured to be connected in parallel to create a composite current. 5. A detector as described in any one of clauses 1 to 4, wherein converting the resultant current into a digital value includes determining the number of particles incident on the multiple detection elements based on the resistance and voltage of the multiple detection elements. 6. The detector of clause 5, further comprising resistors coupled to the plurality of current sources, the resistances corresponding to the resistors. 7. A detector as described in clause 6, wherein the voltage is measured across a resistor. 8. A detector according to any one of clauses 1 to 7, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 9. A detector according to any one of clauses 1 to 8, wherein the plurality of detection elements are a first group of detection elements. 10. Further comprising a second group of detection elements configured to generate an electrical signal in response to a particle being incident on a detection element of the second group of detection elements; 10. The detector of clause 9, wherein the second group of sensing elements has a corresponding current source configured to drive a current in response to an electrical signal generated by a sensing element of the second group of sensing elements. 11. A detector as described in clause 9, wherein the current sources corresponding to the second group of detector elements are configured to be connected in parallel to create a resultant current. 12. A detector as described in any one of clauses 9 to 11, wherein converting the resultant current into a digital value includes determining the number of particles incident on the plurality of sensing elements based on a first resistance and a first voltage of the sensing elements of the first group, and a second resistance and a second voltage of the sensing elements of the second group. 13. The detector of clause 12, further comprising a first resistor coupled to a current source corresponding to the first group of detection elements and a second resistor coupled to a current source corresponding to the second group of detection elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 14. A detector according to clause 12 or 13, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 15. A method comprising: directing particles to a plurality of detector elements configured to generate an electrical signal in response to the particle being incident on a detector element of the plurality of detector elements; driving currents in response to the electrical signal by a plurality of current sources, the outputs of the plurality of current sources being connected to enable the currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources being connected to respective sensing elements of the plurality of sensing elements; converting, by an analog-to-digital converter (ADC), the composite current into a digital value indicative of the electrical signals output by the plurality of sensing elements; A method comprising: 16. The method of clause 15, wherein the particles are charged particles. 17. The method of clause 15, wherein the particles are photons. 18. The method of any one of clauses 15 to 17, further comprising connecting a plurality of current sources in a parallel fashion to create a composite current. 19. The method of any one of clauses 15 to 18, wherein converting the resultant current into a digital value includes determining the number of particles incident on the plurality of detection elements based on the resistance and voltage of the plurality of detection elements. 20. The method of clause 19, further comprising coupling resistors to the plurality of current sources, the resistances corresponding to the resistors. 21. The method of clause 20, further comprising measuring a voltage across the resistor. 22. The method of any one of clauses 15-21, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 23. The method of any one of clauses 15 to 22, wherein the plurality of detection elements is a first group of detection elements. 24. Further comprising a second group of detection elements configured to generate an electrical signal in response to a particle being incident on a detection element of the second group of detection elements; 24. The method of clause 23, wherein the second group of sensing elements has a corresponding current source configured to drive a current in response to an electrical signal generated by a sensing element of the second group of sensing elements. 25. The method of clause 23, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a resultant current. 26. The method of any one of clauses 23-25, wherein converting the resultant current into a digital value includes determining the number of particles incident on the plurality of sensing elements based on a first resistance and a first voltage of the sensing elements of the first group, and a second resistance and a second voltage of the sensing elements of the second group. 27. The method of clause 26, further comprising coupling a first resistor to a current source corresponding to the first group of sensing elements and coupling a second resistor to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 28. The method of clause 26 or 27, further comprising measuring a first voltage across the first resistor and measuring a second voltage across the second resistor. 29. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of a device to cause the device to perform a method, the method comprising: directing particles to a plurality of detector elements configured to generate an electrical signal in response to the particle being incident on a detector element of the plurality of detector elements; driving currents in response to the electrical signal by a plurality of current sources, the outputs of the plurality of current sources being connected to enable the currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources being connected to respective sensing elements of the plurality of sensing elements; converting, by an analog-to-digital converter (ADC), the composite current into a digital value indicative of the electrical signals output by the plurality of sensing elements; 1. A non-transitory computer-readable medium comprising: 30. The non-transitory computer-readable medium of clause 29, wherein the particles are charged particles. 31. The non-transitory computer-readable medium of clause 29, wherein the particles are photons. 32. A non-transitory computer-readable medium according to any one of clauses 29 to 31, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to connect a plurality of current sources so as to be connected in parallel to create a composite current. 33. A non-transitory computer-readable medium described in any one of clauses 29 to 32, wherein the set of instructions executable by at least one processor of the computing device to further cause the computing device to convert the resultant current into a digital value includes determining the number of particles incident on the multiple sensing elements based on the resistances and voltages of the multiple sensing elements. 34. The non-transitory computer-readable medium of clause 33, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to: couple resistors to a plurality of current sources, the resistances corresponding to the resistors. 35. The non-transitory computer-readable medium of clause 34, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a voltage across the resistor. 36. The non-transitory computer-readable medium of any one of clauses 29 to 35, wherein the plurality of sensing elements includes more than 1000 sensing elements and the plurality of current sources includes more than 1000 current sources. 37. The non-transitory computer-readable medium of any one of clauses 29 to 36, wherein the plurality of detection elements are a first group of detection elements. 38. Further including a second group of detection elements configured to generate an electrical signal in response to a particle being incident on a detection element of the second group of detection elements; 38. The non-transitory computer-readable medium of clause 37, wherein the second group of sensing elements has a corresponding current source configured to drive a current in response to an electrical signal generated by a sensing element of the second group of sensing elements. 39. The non-transitory computer-readable medium of clause 37, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a resultant current. 40. The non-transitory computer-readable medium of any one of clauses 37-39, wherein converting the resultant current into a digital value includes determining the number of particles incident on the plurality of sensing elements based on a first resistance and a first voltage of the sensing elements of the first group, and a second resistance and a second voltage of the sensing elements of the second group. 41. The non-transitory computer-readable medium of clause 40, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to: couple a first resistor to a current source corresponding to a first group of sensing elements, and couple a second resistor to a current source corresponding to a second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 42. The non-transitory computer-readable medium of clause 40 or 41, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a first voltage on the first resistor and measure a second voltage on the second resistor. 43. A system for counting particles, comprising: a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; a discriminator configured to output a first value when a particle incident on the detector element is detected and to output a second value when a particle incident on the detector element is not detected; a corresponding current source configured to drive a current when the first value is output; an analog-to-digital converter (ADC) configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A system comprising: 44. The system of clause 43, wherein the particles are charged particles. 45. The system according to clause 43, wherein the particle is a photon. 46. A system according to any one of clauses 43 to 45, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 47. A system according to any one of clauses 43 to 46, wherein determining the number of particles incident on the plurality of detection elements is based on the resistance and voltage of a plurality of current sources. 48. The system of clause 47, further comprising a resistor configured to receive a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 49. The system of clause 48, wherein the ADC is configured to measure a voltage across the resistor. 50. The system of any one of clauses 43-49, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 51. A system according to any one of clauses 43 to 50, wherein the plurality of detection elements are a first group of detection elements. 52. The system of clause 51, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 53. The system of clause 52, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 54. A system described in any one of clauses 51 to 53, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 55. The system of clause 54, further comprising a first resistor coupled to a current source corresponding to the first group of sensing elements and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 56. The system of clause 54 or 55, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 57. A method for counting particles, comprising: directing particles to a plurality of detection elements, each detection element of the plurality of detection elements being associated with a current source of a plurality of current sources; outputting a first value when a particle incident on the detection element is detected by the discriminator, and outputting a second value when a particle incident on the detection element is not detected by the discriminator; driving a current by a corresponding current source when the first value is output; determining, by an analog-to-digital converter (ADC), a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A method comprising: 58. The method of clause 57, wherein the particles are charged particles. 59. The method according to clause 57, wherein the particles are photons. 60. The method of any one of clauses 57-59, further comprising connecting a plurality of current sources in a parallel fashion to create a composite drive current. 61. The method of any one of clauses 57 to 60, wherein determining the number of particles incident on the plurality of detection elements is based on the resistance and voltage of a plurality of current sources. 62. The method of clause 61, further comprising receiving, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 63. The method of clause 62, further comprising measuring the voltage across the resistor by the ADC. 64. The method of any one of clauses 57-63, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 65. The method of any one of clauses 57 to 64, wherein the plurality of detection elements is a first group of detection elements. 66. The method of clause 65, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 67. The method of clause 66, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 68. A method according to any one of clauses 65 to 67, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 69. The method of clause 68, further comprising coupling a first resistor to a current source corresponding to the first group of sensing elements and coupling a second resistor to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 70. The method of clause 68 or 69, further comprising measuring a first voltage across the first resistor and measuring a second voltage across the second resistor. 71. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of a device to cause the device to perform a method, the method comprising: directing particles to a plurality of detection elements, each detection element of the plurality of detection elements being associated with a current source of a plurality of current sources; outputting a first value when a particle incident on the detection element is detected by the discriminator, and outputting a second value when a particle incident on the detection element is not detected by the discriminator; driving a current by a corresponding current source when the first value is output; determining, by an analog-to-digital converter (ADC), a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; 1. A non-transitory computer-readable medium comprising: 72. The non-transitory computer-readable medium of clause 71, wherein the particles are charged particles. 73. The non-transitory computer-readable medium of clause 71, wherein the particles are photons. 74. A non-transitory computer-readable medium according to any one of clauses 71 to 73, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to connect a plurality of current sources so as to be connected in parallel to create a composite drive current. 75. The non-transitory computer-readable medium of any one of clauses 71-74, wherein determining the number of particles incident on the plurality of detection elements is based on resistances and voltages of a plurality of current sources. 76. The non-transitory computer-readable medium of clause 75, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to receive, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 77. The non-transitory computer-readable medium of clause 76, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure, by the ADC, a voltage across the resistor. 78. The non-transitory computer-readable medium of any one of clauses 71-77, wherein the plurality of sensing elements includes more than 1000 sensing elements and the plurality of current sources includes more than 1000 current sources. 79. The non-transitory computer-readable medium of any one of clauses 71 to 78, wherein the plurality of detection elements are a first group of detection elements. 80. The non-transitory computer-readable medium of clause 79, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 81. The non-transitory computer-readable medium of clause 80, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a resultant drive current. 82. A non-transitory computer-readable medium described in any one of clauses 79 to 81, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 83. The non-transitory computer-readable medium of clause 82, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to: couple a first resistor to a current source corresponding to a first group of sensing elements, and couple a second resistor to a current source corresponding to a second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 84. The non-transitory computer-readable medium of clause 82 or 83, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a first voltage on the first resistor and measure a second voltage on the second resistor. 85. A system for counting particles, comprising: a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources associated with a sensing element of the plurality of sensing elements; a plurality of current sources, each current source of the plurality of current sources configured to drive a current in response to a particle being incident on a corresponding detector element; determining a sum of the drive currents of the plurality of current sources; and a controller including circuitry configured to cause the system to determine a number of particles incident on the plurality of detector elements based on the determined sum of the drive currents; A system comprising: 86. The system according to clause 85, wherein the particles are charged particles. 87. The system according to clause 85, wherein the particle is a photon. 88. A system according to any one of clauses 85 to 87, wherein a plurality of current sources are configured to be connected in parallel to create a sum of composite currents. 89. The system of any one of clauses 85-88, wherein determining the number of particles incident on the plurality of detection elements is based on the resistance and voltage of the plurality of detection elements. 90. The system of clause 89, further comprising resistors coupled to the plurality of current sources, the resistances corresponding to the resistors. 91. The system of clause 90, wherein the voltage is measured across a resistor. 92. The system of any one of clauses 85-91, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 93. A system according to any one of clauses 85 to 92, wherein the plurality of detection elements is a first group of detection elements. 94. The system of clause 93, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 95. The system of clause 93, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a sum of the drive currents. 96. A system described in any one of clauses 93 to 95, wherein determining the number of particles incident on the first group of sensing elements is based on a first resistance and a first voltage of the sensing elements of the first group, and determining the number of particles incident on the second group of sensing elements is based on a second resistance and a second voltage of the sensing elements of the second group. 97. The system of clause 96, further comprising a first resistor coupled to a current source corresponding to the first group of sensing elements and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 98. The system of clause 96 or 97, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 99. A method for counting particles, comprising: directing particles to a plurality of detection elements, each detection element of the plurality of detection elements being associated with a current source of a plurality of current sources; Driving a current by a corresponding current source in response to a particle being incident on the corresponding detector element; determining a sum of the drive currents of the plurality of current sources; determining a number of particles incident on the plurality of detector elements based on the determined sum of the drive currents; A method comprising: 100. The method of clause 99, wherein the particles are charged particles. 101. The method of clause 99, wherein the particle is a photon. 102. The method of any one of clauses 99-101, further comprising connecting multiple current sources in parallel to create a sum of the drive currents. 103. The method of any one of clauses 99-102, wherein determining the number of particles incident on the plurality of detector elements is based on the resistance and voltage of the plurality of detector elements. 104. The method of clause 103, further comprising coupling resistors to the plurality of current sources, the resistances corresponding to the resistors. 105. The method of clause 104, wherein the voltage is measured across a resistor. 106. The method of any one of clauses 99-105, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 107. The method of any one of clauses 99 to 106, wherein the plurality of detection elements is a first group of detection elements. 108. The method of clause 107, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 109. The method of clause 107, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a sum of the drive currents. 110. The method of any one of clauses 107 to 109, wherein determining the number of particles incident on the first group of sensing elements is based on a first resistance and a first voltage of the sensing elements of the first group, and determining the number of particles incident on the second group of sensing elements is based on a second resistance and a second voltage of the sensing elements of the second group. 111. The method of clause 110, further comprising coupling a first resistor to a current source corresponding to the first group of sensing elements and coupling a second resistor to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 112. The method of clause 110 or 111, further comprising measuring a first voltage across the first resistor, and a second voltage is measured across the second resistor. 113. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of a device to cause the device to perform a method, the method comprising: directing particles to a plurality of detection elements, each detection element of the plurality of detection elements being associated with a current source of a plurality of current sources; Driving a current by a corresponding current source in response to a particle being incident on the corresponding detector element; determining a sum of the drive currents of the plurality of current sources; determining a number of particles incident on the plurality of detector elements based on the determined sum of the drive currents; 1. A non-transitory computer-readable medium comprising: 114. The non-transitory computer-readable medium of clause 113, wherein the particles are charged particles. 115. The non-transitory computer-readable medium of clause 113, wherein the particles are photons. 116. A non-transitory computer-readable medium according to any one of clauses 113 to 115, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to connect multiple current sources in parallel to create a sum of the drive currents. 117. The non-transitory computer-readable medium of any one of clauses 113-116, wherein determining the number of particles incident on the plurality of detection elements is based on the resistance and voltage of the plurality of detection elements. 118. The non-transitory computer-readable medium of any one of clauses 117, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to perform the coupling of resistors to a plurality of current sources, the resistances corresponding to the resistors. 119. The non-transitory computer-readable medium of clause 118, wherein the voltage is measured across a resistor. 120. The non-transitory computer-readable medium of any one of clauses 113-119, wherein the plurality of sensing elements includes more than 1000 sensing elements and the plurality of current sources includes more than 1000 current sources. 121. The non-transitory computer-readable medium of any one of clauses 113-120, wherein the plurality of detection elements is a first group of detection elements. 122. The non-transitory computer-readable medium of clause 121, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 123. The non-transitory computer-readable medium of clause 121, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a sum of the drive currents. 124. A non-transitory computer-readable medium described in any one of clauses 121 to 123, wherein determining the number of particles incident on the first group of sensing elements is based on a first resistance and a first voltage of the first group of sensing elements, and determining the number of particles incident on the second group of sensing elements is based on a second resistance and a second voltage of the second group of sensing elements. 125. The non-transitory computer-readable medium of clause 124, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to: couple a first resistor to a current source corresponding to a first group of sensing elements, and couple a second resistor to a current source corresponding to a second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 126. The non-transitory computer-readable medium of clause 124 or 125, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a first voltage across the first resistor, and a second voltage is measured across the second resistor. 127. The detector of any one of clauses 1-14, wherein the plurality of sensing elements are further configured to determine a value associated with a corresponding current based on the generated electrical signal. 128. A detector according to clause 127, wherein the value is an integer, the integer representing the number of electrons or photons detected. 129. The detector of clause 127, wherein the value is a real value. 130. The detector of any one of clauses 1-14, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 131. The detector of clause 130, wherein the electrical signal comprises a plurality of binary digits output by each second ADC. 132. The detector of clause 130 or 131, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 133. The detector of clause 132, wherein the first group of current sources corresponds to a first group of binary digits of the plurality of binary digits, and the second group of current sources corresponds to a second group of binary digits of the plurality of binary digits. 134. A system according to any one of clauses 85-98, wherein each detection element of the plurality of detection elements generates a value associated with a corresponding current in response to a particle being incident on the corresponding detection element. 135. The system of clause 134, wherein the value is an integer. 136. The system of clause 134, wherein the value is a real value. 137. A system according to any one of clauses 85 to 98, wherein each detection element of the plurality of detection elements is configured to generate a plurality of values in response to a particle being incident on the corresponding detection element. 138. The system of clause 137, wherein each current source of the plurality of current sources is configured to drive a current based on an associated value of the plurality of values. 139. The system of clause 137 or 138, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 140. The system of clause 139, wherein the first group of current sources corresponds to a first group of values of the plurality of values and the second group of current sources corresponds to a second group of values of the plurality of values. 141. A system for counting particles, comprising: a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; a first analog-to-digital converter (ADC) configured to output a value when a particle incident on the detector element is detected; a corresponding current source configured to drive a current when the value is output; a second ADC configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A system comprising: 142. The system according to clause 141, wherein the particle is a photon. 143. The system of clause 141 or 142, wherein a plurality of current sources are configured to be connected in parallel to create a composite current. 144. The system of any one of clauses 141-143, wherein determining the number of particles incident on the plurality of detection elements is based on resistances and voltages of a plurality of current sources. 145. The system of clause 144, further comprising a resistor configured to receive a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 146. The system of clause 145, wherein the second ADC is configured to measure a voltage across the resistor. 147. The system of any one of clauses 141-146, wherein the first ADC includes a plurality of first ADCs, each first ADC corresponding to a detection element of the plurality of detection elements. 148. The system of any one of clauses 141-147, wherein the value includes multiple values. 149. The system of clause 148, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 150. The system of clause 149, wherein a first group of current sources corresponds to a first group of values of a plurality of values, and a second group of current sources corresponds to a second group of values. 151. The system of clause 150, wherein each first ADC of the plurality of first ADCs is configured to output a value from the first group of values and to output a value from the second group of values. 152. The system of any one of clauses 141-151, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 153. A system according to any one of clauses 141 to 152, wherein the plurality of detection elements are a first group of detection elements. 154. The system of clause 153, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 155. The system of clause 154, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 156. The system described in clause 154 or 155, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 157. The system of clause 156, further comprising a first resistor coupled to a current source corresponding to the first group of sensing elements and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 158. The system of clause 157, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 159. A system for counting particles, comprising: a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; a discriminator configured to output a value when a particle incident on the detector element is detected; a corresponding current source configured to drive a current when the value is output; an analog-to-digital converter (ADC) configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A system comprising: 160. The system according to clause 159, wherein the particle is a photon. 161. The system of clause 159 or 160, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 162. The system of any one of clauses 159-161, wherein determining the number of particles incident on the plurality of detection elements is based on resistances and voltages of a plurality of current sources. 163. The system of clause 162, further comprising a resistor configured to receive a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 164. The system of clause 163, wherein the second ADC is configured to measure a voltage across the resistor. 165. The system of any one of clauses 159 to 164, wherein the value is an integer. 166. The system of any one of clauses 159-164, wherein the value is a real value. 167. The system of any one of clauses 159-166, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 168. A system according to any one of clauses 159 to 167, wherein the plurality of detection elements are a first group of detection elements. 169. The system of clause 168, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 170. The system of clause 169, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 171. The system described in clause 169 or 17, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 172. The system of clause 171, further comprising a first resistor coupled to a current source corresponding to the first group of sensing elements and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 173. The system of clause 172, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 174. The method of any one of clauses 15-28, further comprising determining, by the plurality of sensing elements, a value associated with a corresponding current based on the electrical signals generated. 175. The method of clause 174, wherein the value is an integer. 176. The method of clause 174, wherein the value is a real value. 177. The method of any one of clauses 15-28, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 178. The method of clause 177, wherein the electrical signal comprises a plurality of binary digits output by each second ADC. 179. The method of clause 177 or 178, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 180. The method of clause 179, wherein the first group of current sources corresponds to a first group of binary digits of the plurality of binary digits, and the second group of current sources corresponds to a second group of binary digits of the plurality of binary digits. 181. The non-transitory computer-readable medium of any one of clauses 29-42, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to determine, based on the electrical signals generated by the plurality of sensing elements, a value associated with a corresponding current. 182. The non-transitory computer-readable medium of clause 181, wherein the value is an integer. 183. The non-transitory computer-readable medium of clause 181, wherein the value is a real value. 184. The non-transitory computer-readable medium of any one of clauses 29-42, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 185. The non-transitory computer-readable medium of clause 184, wherein the electrical signal includes a plurality of binary digits output by each second ADC. 186. The non-transitory computer-readable medium of clause 184 or 185, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 187. The non-transitory computer-readable medium of clause 186, wherein the first group of current sources corresponds to a first group of binary numbers of the plurality of binary numbers, and the second group of current sources corresponds to a second group of binary numbers of the plurality of binary numbers. 188. A system according to any one of clauses 43 to 56, wherein the plurality of detection elements are configured to determine a value associated with a corresponding current based on an electrical signal generated in response to a particle being incident on the detection element. 189. The system of clause 188, wherein the value is an integer. 190. The system of clause 188, wherein the value is a real value. 191. The system of any one of clauses 43-56, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 192. The system of clause 191, wherein the electrical signal generated in response to a particle being incident on the detection element comprises a plurality of binary digits output by each second ADC. 193. The system of clause 191 or 192, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 194. The system of clause 193, wherein the first group of current sources corresponds to a first group of binary digits of the plurality of binary digits, and the second group of current sources corresponds to a second group of binary digits of the plurality of binary digits. 195. The method of any one of clauses 57-70, further comprising determining, by the plurality of detection elements, a value associated with a corresponding current based on electrical signals generated in response to particles being incident on the detection elements. 196. The method of clause 195, wherein the value is an integer. 197. The method of clause 195, wherein the value is a real value. 198. The method of any one of clauses 57-70, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 199. The method of clause 198, wherein the electrical signal generated in response to the particle being incident on the detection element comprises a plurality of binary numbers output by each second ADC. 200. The method of clause 198 or 199, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 201. The method of clause 200, wherein a first group of current sources corresponds to a first group of binary numbers of the plurality of binary numbers and a second group of current sources corresponds to a second group of binary numbers of the plurality of binary numbers. 202. The non-transitory computer-readable medium of any one of clauses 71-84, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to determine, based on electrical signals generated by the plurality of detection elements in response to particles being incident on the detection elements, values associated with corresponding currents. 203. The non-transitory computer-readable medium of clause 202, wherein the value is an integer. 204. The non-transitory computer-readable medium of clause 202, wherein the value is a real value. 205. The non-transitory computer-readable medium of any one of clauses 71-84, further comprising a plurality of second ADCs, each second ADC corresponding to a detection element of the plurality of detection elements. 206. The non-transitory computer-readable medium of clause 205, wherein the electrical signal generated in response to the particle being incident on the detection element comprises a plurality of binary digits output by each second ADC. 207. The non-transitory computer-readable medium of any one of clauses 205-206, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 208. The non-transitory computer-readable medium of clause 207, wherein the first group of current sources corresponds to a first group of binary numbers of the plurality of binary numbers, and the second group of current sources corresponds to a second group of binary numbers of the plurality of binary numbers. 209. The method of any one of clauses 99-112, further comprising determining, based on electrical signals generated by the plurality of detection elements in response to particles being incident on the detection elements, values associated with corresponding currents. 210. The method of clause 209, wherein the value is an integer. 211. The method of clause 209, wherein the value is a real value. 212. The method of any one of clauses 99-112, further comprising a plurality of ADCs, each ADC corresponding to a detection element of the plurality of detection elements. 213. The method of clause 212, wherein the electrical signal generated in response to a particle being incident on the detection element comprises a plurality of binary numbers output by respective ADCs. 214. The method of clause 212 or 213, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 215. The method of clause 214, wherein the first group of current sources corresponds to a first group of binary numbers of the plurality of binary numbers and the second group of current sources corresponds to a second group of binary numbers of the plurality of binary numbers. 216. The non-transitory computer-readable medium of any one of clauses 113-126, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to determine, based on electrical signals generated by the plurality of detection elements in response to particles being incident on the detection elements, values associated with corresponding currents. 217. The non-transitory computer-readable medium of clause 216, wherein the value is an integer. 218. The non-transitory computer-readable medium of clause 216, wherein the value is a real value. 219. The non-transitory computer-readable medium of any one of clauses 113-126, further comprising a plurality of ADCs, each ADC corresponding to a detection element of the plurality of detection elements. 220. The non-transitory computer-readable medium of clause 219, wherein the electrical signal generated in response to a particle being incident on the detection element comprises a plurality of binary numbers output by each ADC. 221. The non-transitory computer-readable medium of clause 219 or 220, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 222. The non-transitory computer-readable medium of clause 221, wherein a first group of current sources corresponds to a first group of binary numbers of the plurality of binary numbers, and a second group of current sources corresponds to a second group of binary numbers of the plurality of binary numbers. 223. A method for counting particles, comprising: directing particles to a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; outputting a value by a first analog-to-digital converter (ADC) when a particle incident on the detector element is detected; driving a current when the value is output by a corresponding current source; determining, by a second ADC, a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A method comprising: 224. The method of clause 223, wherein the particle is a photon. 225. The method of clause 223 or 224, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 226. The method of any one of clauses 223-225, wherein determining the number of particles incident on the plurality of detector elements is based on resistances and voltages of a plurality of current sources. 227. The method of clause 226, further comprising receiving, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 228. The method of clause 227, further comprising measuring, by a second ADC, a voltage across the resistor. 229. The method of any one of clauses 223-228, wherein the first ADC includes a plurality of first ADCs, each first ADC corresponding to a detection element of the plurality of detection elements. 230. The method of any one of clauses 223 to 229, wherein the value includes a plurality of values. 231. The method of clause 230, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 232. The method of clause 231, wherein the first group of current sources corresponds to a first group of values of the plurality of values and the second group of current sources corresponds to a second group of values. 233. The method of clause 232, wherein each first ADC of the plurality of first ADCs is configured to output a value from the first group of values and to output a value from the second group of values. 234. The method of any one of clauses 223-233, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 235. The method of any one of clauses 223-234, wherein the plurality of detection elements is a first group of detection elements. 236. The method of clause 235, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 237. The method of clause 236, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 238. The method of clause 236 or 237, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 239. The method of clause 238, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 240. The method of clause 239, further comprising measuring a first voltage across the first resistor and measuring a second voltage across the second resistor. 241. A method for counting particles, comprising: directing particles to a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; outputting a value when a particle incident on the detector element is detected by the discriminator; driving a current when the value is output by a corresponding current source; determining, by an analog-to-digital converter (ADC), a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A method comprising: 242. The method according to clause 241, wherein the particle is a photon. 243. The method of clause 241 or 242, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 244. The method of any one of clauses 241-243, wherein determining the number of particles incident on the plurality of detector elements is based on resistances and voltages of a plurality of current sources. 245. The method of clause 244, further comprising receiving, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 246. The method of clause 245, further comprising measuring, by a second ADC, a voltage across the resistor. 247. The method of any one of clauses 241 to 246, wherein the value is an integer. 248. The method of any one of clauses 241 to 246, wherein the value is a real value. 249. The method of any one of clauses 241-248, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 250. The method of any one of clauses 241-249, wherein the plurality of detection elements is a first group of detection elements. 251. The method of clause 250, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 252. The method of clause 251, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a composite drive current. 253. The method of clause 251 or 252, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 254. The method of clause 253, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 255. The method of clause 254, further comprising measuring a first voltage across the first resistor and measuring a second voltage across the second resistor. 256. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of the device to cause the device to perform a method, the method comprising: directing particles to a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; outputting a value by a first analog-to-digital converter (ADC) when a particle incident on the detector element is detected; driving a current when the value is output by a corresponding current source; determining, by a second ADC, a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A method comprising: 257. The non-transitory computer-readable medium of clause 256, wherein the particles are photons. 258. The non-transitory computer-readable medium of clause 256 or 257, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 259. The non-transitory computer-readable medium of any one of clauses 256-258, wherein determining the number of particles incident on the plurality of detection elements is based on resistances and voltages of a plurality of current sources. 260. The non-transitory computer-readable medium of clause 259, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to receive, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 261. The non-transitory computer-readable medium of clause 260, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure, by a second ADC, a voltage across the resistor. 262. The non-transitory computer-readable medium of any one of clauses 256-261, wherein the first ADC includes a plurality of first ADCs, each of which corresponds to a detection element of the plurality of detection elements. 263. The non-transitory computer-readable medium of any one of clauses 256 to 262, wherein the value includes multiple values. 264. The non-transitory computer-readable medium of clause 263, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 265. The non-transitory computer-readable medium of clause 264, wherein a first group of current sources corresponds to a first group of values of the plurality of values, and a second group of current sources corresponds to a second group of values. 266. The non-transitory computer-readable medium of clause 265, wherein each first ADC of the plurality of first ADCs is configured to output a value from the first group of values and to output a value from the second group of values. 267. The non-transitory computer-readable medium of any one of clauses 256-266, wherein the plurality of sensing elements includes more than 1000 sensing elements and the plurality of current sources includes more than 1000 current sources. 268. The non-transitory computer-readable medium of any one of clauses 256-267, wherein the plurality of detection elements is a first group of detection elements. 269. The non-transitory computer-readable medium of clause 268, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 270. The non-transitory computer-readable medium of clause 269, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a resultant drive current. 271. The non-transitory computer-readable medium of clause 269 or 270, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to: determine a number of particles incident on a first group of sensing elements based on a first resistance and a first voltage; and determine a number of particles incident on a second group of sensing elements based on a second resistance and a second voltage. 272. The non-transitory computer-readable medium of clause 271, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 273. The non-transitory computer-readable medium of clause 272, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a first voltage on the first resistor and measure a second voltage on the second resistor. 274. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of the device to cause the device to perform a method, the method comprising: directing particles to a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; outputting a value when a particle incident on the detector element is detected by the discriminator; driving a current when the value is output by a corresponding current source; determining, by an analog-to-digital converter (ADC), a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; 1. A non-transitory computer-readable medium comprising: 275. The non-transitory computer-readable medium of clause 274, wherein the particles are photons. 276. The non-transitory computer-readable medium of clause 274 or 275, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 277. The non-transitory computer-readable medium of any one of clauses 274-276, wherein determining the number of particles incident on the plurality of detection elements is based on resistances and voltages of a plurality of current sources. 278. The non-transitory computer-readable medium of clause 277, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to receive, by a resistor, a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 279. The non-transitory computer-readable medium of clause 278, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure, by a second ADC, a voltage across the resistor. 280. The non-transitory computer-readable medium of any one of clauses 274 to 279, wherein the value is an integer. 281. The non-transitory computer-readable medium of any one of clauses 274 to 279, wherein the value is a real value. 282. The non-transitory computer-readable medium of any one of clauses 274-281, wherein the plurality of sensing elements includes more than 1000 sensing elements and the plurality of current sources includes more than 1000 current sources. 283. The non-transitory computer-readable medium of any one of clauses 274-282, wherein the plurality of detection elements is a first group of detection elements. 284. The non-transitory computer-readable medium of clause 283, further comprising a second group of detection elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detection elements of the second group. 285. The non-transitory computer-readable medium of clause 284, wherein the current sources corresponding to the second group of sensing elements are configured to be connected in parallel to create a resultant drive current. 286. The non-transitory computer-readable medium of clause 284 or 285, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 287. The non-transitory computer-readable medium of clause 286, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 288. The non-transitory computer-readable medium of clause 287, wherein the set of instructions is executable by at least one processor of the computing device to further cause the computing device to measure a first voltage on the first resistor and measure a second voltage on the second resistor. 289. A detector, a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; a first analog-to-digital converter (ADC) configured to output a value when a particle incident on the detector element is detected; a corresponding current source configured to drive a current when the value is output; a second ADC configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A detector comprising: 290. A detector according to clause 289, wherein the particles are photons. 291. The detector of clause 289 or 290, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 292. The detector of any one of clauses 289-291, wherein determining the number of particles incident on the plurality of detector elements is based on resistances and voltages of a plurality of current sources. 293. The detector of clause 292, further comprising a resistor configured to receive a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 294. The detector of clause 293, wherein the second ADC is configured to measure a voltage across the resistor. 295. The detector of any one of clauses 289-294, wherein the first ADC includes a plurality of first ADCs, each first ADC corresponding to a detection element of the plurality of detection elements. 296. The detector of any one of clauses 289 to 295, wherein the value comprises a plurality of values. 297. The detector of clause 296, wherein the plurality of current sources includes a first group of current sources and a second group of current sources. 298. The detector of clause 297, wherein the first group of current sources corresponds to a first group of values of the plurality of values, and the second group of current sources corresponds to a second group of values. 299. The detector of clause 298, wherein each first ADC of the plurality of first ADCs is configured to output a value from the first group of values and to output a value from the second group of values. 300. A detector according to any one of clauses 289 to 299, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 301. A detector according to any one of clauses 289 to 300, wherein the plurality of detection elements are a first group of detection elements. 302. The detector of clause 301, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 303. The detector of clause 302, wherein the current sources corresponding to the second group of detector elements are configured to be connected in parallel to create a composite drive current. 304. A detector as described in clause 302 or 303, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 305. The detector of clause 304, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 306. The detector of clause 305, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 307. A detector, a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources being associated with a sensing element of the plurality of sensing elements; a discriminator configured to output a value when a particle incident on the detector element is detected; a corresponding current source configured to drive a current when the value is output; an analog-to-digital converter (ADC) configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A detector comprising: 308. A detector according to clause 307, wherein the particles are photons. 309. The detector of clause 307 or 308, wherein a plurality of current sources are configured to be connected in parallel to create a composite drive current. 310. The detector of any one of clauses 307-309, wherein determining the number of particles incident on the plurality of detector elements is based on resistances and voltages of a plurality of current sources. 311. The detector of clause 310, further comprising a resistor configured to receive a combined drive current of the plurality of current sources, the resistance corresponding to the resistor. 312. The detector of clause 311, wherein the second ADC is configured to measure a voltage across the resistor. 313. The detector of any one of clauses 307 to 312, wherein the value is an integer. 314. The detector of any one of clauses 307-312, wherein the value is a real value. 315. The detector of any one of clauses 307-314, wherein the plurality of sensing elements comprises more than 1000 sensing elements and the plurality of current sources comprises more than 1000 current sources. 316. A detector according to any one of clauses 307 to 315, wherein the plurality of detector elements is a first group of detector elements. 317. The detector of clause 316, further comprising a second group of detector elements having corresponding current sources configured to drive current in response to a particle being incident on the corresponding detector elements of the second group. 318. The detector of clause 316, wherein the current sources corresponding to the second group of detector elements are configured to be connected in parallel to create a composite drive current. 319. A detector as described in any one of clauses 316 to 318, wherein determining the number of particles incident on the first group of detection elements is based on a first resistance and a first voltage, and determining the number of particles incident on the second group of detection elements is based on a second resistance and a second voltage. 320. The detector of clause 319, further comprising: a first resistor coupled to a current source corresponding to the first group of sensing elements; and a second resistor coupled to a current source corresponding to the second group of sensing elements, wherein the first resistance corresponds to the first resistor and the second resistance corresponds to the second resistor. 321. The detector of clause 320, wherein a first voltage is measured across a first resistor and a second voltage is measured across a second resistor. 322. A detector according to any one of clauses 1 to 14 or clauses 127 to 133, wherein the digital values are used to measure the alignment of features on the sample. 323. A detector according to any one of clauses 1 to 14 or clauses 127 to 133, wherein the digital value is used to measure the level of a feature on the sample. 324. The method of any one of clauses 15-28 or 174-180, wherein the digital values are used to measure the alignment of features on the sample. 325. A detector according to any one of clauses 15 to 28 or clauses 174 to 180, wherein the digital value is used to measure the level of a feature on the sample. 326. The non-transitory computer-readable medium of any one of clauses 29-40 or 181-187, wherein the digital values are used to measure alignment of features on a sample. 327. The non-transitory computer-readable medium of any one of clauses 29-40 or 181-187, wherein the digital value is used to measure the level of a feature on a sample. 328. A system according to any one of clauses 43-56 or 188-194, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 329. A system according to any one of clauses 43-56 or 188-194, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 330. The method of any one of clauses 57-70 or 195-201, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 331. The method of any one of clauses 57-70 or 195-201, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 332. The non-transitory computer-readable medium of any one of clauses 71-84 or clauses 202-208, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 333. The non-transitory computer-readable medium of any one of clauses 71-84 or clauses 202-208, wherein the determined number of particles incident on the plurality of detector elements is used to measure a level of a feature on the sample. 334. A system according to any one of clauses 85-98 or 134-140, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 335. A system according to any one of clauses 85-98 or 134-140, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 336. The method of any one of clauses 99-112 or 209-215, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 337. The method of any one of clauses 99-112 or 209-215, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 338. The non-transitory computer-readable medium of any one of clauses 113-126 or 216-222, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 339. The non-transitory computer-readable medium of any one of clauses 113-126 or 216-222, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 340. A system according to any one of clauses 141 to 158, wherein the determined number of particles incident on the plurality of detector elements is used to measure the alignment of features on the sample. 341. A system according to any one of clauses 141 to 158, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 342. A system according to any one of clauses 159 to 173, wherein the determined number of particles incident on the plurality of detector elements is used to measure the alignment of features on the sample. 343. A system according to any one of clauses 159 to 173, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 344. The method of any one of clauses 223-240, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 345. The method of any one of clauses 223-240, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 346. The method of any one of clauses 241-255, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 347. The method of any one of clauses 241-255, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 348. The non-transitory computer-readable medium of any one of clauses 256-273, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 349. The non-transitory computer-readable medium of any one of clauses 256-273, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 350. The non-transitory computer-readable medium of any one of clauses 274-288, wherein the determined number of particles incident on the plurality of detector elements is used to measure alignment of features on the sample. 351. The non-transitory computer-readable medium of any one of clauses 274-288, wherein the determined number of particles incident on the plurality of detector elements is used to measure a level of a feature on the sample. 352. A detector according to any one of clauses 289 to 306, wherein the determined number of particles incident on the plurality of detector elements is used to measure the alignment of features on the sample. 353. A detector according to any one of clauses 289 to 306, wherein the determined number of particles incident on a plurality of detector elements is used to measure the level of a feature on the sample. 354. A detector according to any one of clauses 307 to 321, wherein the determined number of particles incident on the plurality of detector elements is used to measure the alignment of features on the sample. 355. A detector according to any one of clauses 307 to 321, wherein the determined number of particles incident on the plurality of detector elements is used to measure the level of a feature on the sample. 356. A system for detecting alignment of features on a sample using any one of the detectors described in clauses 1-14 or clauses 127-133. 357. A system for detecting the level of a feature on a sample using any one of the detectors described in clauses 1-14 or clauses 127-133. 358. A system for detecting alignment of features on a sample using any one of the detectors set forth in clauses 289-306. 359. A system for detecting the level of a feature on a sample using any one of the detectors set forth in clauses 289-306. 360. A system for detecting alignment of features on a sample using any one of the detectors set forth in clauses 307-321. 361. A system for detecting the level of a feature on a sample using any one of the detectors set forth in clauses 307-321.

[0143]

[0159] It should be understood that the 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 changes can be made without departing from the scope thereof.< / n> < / n> < / n> < / n> < / n>

Claims

1. A detector comprising: a plurality of detector elements configured to generate an electrical signal in response to a particle being incident on a detector element of the plurality of detector elements; a plurality of current sources configured to drive currents in response to the electrical signal, the outputs of the plurality of current sources being connected to allow the currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources being connected to respective sensing elements of the plurality of sensing elements; an analog-to-digital converter (ADC) configured to convert the combined current into a digital value indicative of the electrical signal output by the plurality of sensing elements; A detector comprising:

2. The detector of claim 1 , wherein the particles are charged particles.

3. The detector of claim 1 , wherein the particles are photons.

4. The detector of claim 1 , wherein the plurality of sensing elements are further configured to determine a value associated with the corresponding current based on the generated electrical signal.

5. 5. The detector of claim 4, wherein the value is an integer representing the number of charged particles or photons detected.

6. The detector of claim 1 , wherein converting the resultant current to a digital value comprises determining a number of particles incident on the plurality of detector elements based on resistances and voltages of the plurality of detector elements.

7. The detector of claim 6 , further comprising resistors coupled to the plurality of current sources, the resistances corresponding to the resistors.

8. 8. The detector of claim 7, wherein the voltage is measured across the resistor.

9. The detector of claim 1 , wherein the plurality of sensing elements comprises greater than 1000 sensing elements and the plurality of current sources comprises greater than 1000 current sources.

10. The detector of claim 1 , wherein the plurality of detector elements is a first group of detector elements.

11. a second group of detector elements configured to generate an electrical signal in response to a particle being incident on a detector element of the second group of detector elements; 11. The detector of claim 10, wherein the second group of sensing elements has a corresponding current source configured to drive a current in response to the electrical signal generated by a sensing element of the second group of sensing elements.

12. 12. The detector of claim 11, wherein the current sources corresponding to the second group of detector elements are configured to be connected in parallel to create the resultant current.

13. 12. The detector of claim 11, wherein converting the resultant current to a digital value comprises determining a number of particles incident on the plurality of sensing elements based on a first resistance and a first voltage of the first group of sensing elements and a second resistance and a second voltage of the second group of sensing elements.

14. 1. A non-transitory computer-readable medium comprising a set of instructions executable by one or more processors of a device to cause the device to perform a method, the method comprising: directing the particle to a plurality of detector elements configured to generate an electrical signal in response to the particle being incident on a detector element of the plurality of detector elements; driving currents in response to the electrical signal by a plurality of current sources, the outputs of the plurality of current sources being connected to enable currents output by the plurality of current sources to be combined to create a combined current, the plurality of current sources being connected to respective sensing elements of the plurality of sensing elements; converting, by an analog-to-digital converter (ADC), the combined current into a digital value indicative of the electrical signals output by the plurality of sensing elements; 1. A non-transitory computer-readable medium comprising:

15. 1. A system for counting particles, comprising: a detector including a plurality of detection elements; a plurality of current sources, each current source of the plurality of current sources associated with a sensing element of the plurality of sensing elements; a discriminator configured to output a first value when a particle incident on the detector element is detected and to output a second value when a particle incident on the detector element is not detected; a corresponding current source configured to drive a current when the first value is output; an analog-to-digital converter (ADC) configured to determine a number of particles incident on the plurality of detector elements based on a combined drive current of the plurality of current sources; A system comprising:

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