Detector for detecting radiation, method for detecting radiation, assessment system

Abstract

A detector and method of detecting radiation are disclosed. In one arrangement, a plurality of pixel elements are provided. Each pixel element comprises a corresponding pixel substrate, a collector electrode and a readout circuit. The pixel substrate is configured such that illumination of the pixel substrate by the target radiation generates charge carriers in the pixel substrate. The readout circuit is configured to provide an output in response to collection of the charge carriers by the corresponding collector. The control system implements a plurality of selectable resolution modes by controlling the potentials applied to the control electrodes and the collectors to define a respective plurality of mappings between the pixel substrate generating charge carriers and the collectors collecting those charge carriers.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to European application No. 22188821.7 filed on August 4, 2022 and European application No. 22203271.6 filed on October 24, 2022, and the entire contents of these European applications are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to detectors and methods for detecting radiation and evaluation systems. Background Art

[0004] When manufacturing semiconductor integrated circuit (IC) chips, undesirable pattern defects caused by, for example, optical effects and accidental particles inevitably appear on substrates (i.e., wafers) or masks during the manufacturing process, thereby reducing yield. Therefore, monitoring the extent of undesirable pattern defects is an important process in the manufacture of IC chips. More generally, evaluation such as inspection and / or measurement of the surface of a substrate or other object / material is an important process during and / or after its manufacture.

[0005] Evaluation tools, referred to herein as evaluation systems, are known to use a charged particle beam to evaluate an object, which may be referred to as a sample or substrate, for example to detect pattern defects. Various systems for making such measurements are well known, including scanning electron microscopes (SEMs), which are often used to measure critical dimensions (CDs), and specialized tools for measuring overlay (the alignment accuracy of two layers in a device).

[0006] In the SEM, a primary electron beam of relatively high energy electrons is targeted and landed on the sample with a relatively low landing energy using a final deceleration step. The electron beam is focused as a detection spot on the sample. The interaction between the material structure at the detection spot and the landing electrons from the electron beam results in the emission of signal electrons from the surface, such as secondary electrons, backscattered electrons, or Auger electrons. Signal electrons can be emitted from the material structure of the sample. By scanning the primary electron beam as a detection spot on the sample surface, signal electrons can be emitted across the surface of the sample. By collecting these emitted signal electrons from the sample surface, the pattern inspection system can obtain an image representing the characteristics of the material structure of the sample surface.

[0007] Various forms of scatterometers have been developed for use in the field of lithography. These devices direct a radiation beam onto a target and measure one or more properties of the scattered radiation—for example, intensity at a single reflection angle as a function of wavelength; intensity at one or more wavelengths as a function of reflection angle; or polarization as a function of reflection angle—to obtain a diffraction "spectrum" that can be used to determine a property of interest of the target.

[0008] The evaluation system applies a series of different types of radiation to the sample and detects signal radiation from the sample. The signal radiation may include particles (e.g., charged particles such as electrons) or electromagnetic radiation. The signal radiation is detected by a detector that needs to be adapted to the nature of the signal radiation and / or the desired different detection modes. For example, it may be desirable to controllably vary one or more parameters of the detection, such as the sensitivity or spatial resolution of the detection.

[0009] A known method for varying the resolution of a detector to provide multi-resolution capabilities is to controllably group the pixels of the detector. For example, a detector may be configured to provide the highest resolution mode by allowing each pixel to independently detect radiation impinging on the pixel, and to group pixels together to form superpixels, wherein the pixels in each superpixel indistinguishably contribute to one or more lower resolution modes of a single output from the superpixel. Grouping pixels in this manner may be referred to as binning.

[0010] The detector can be configured so that the radiation irradiated to the detector generates charge carriers (e.g., electrons or holes) in the pixel. Pixel merging can be implemented in such an arrangement that the charges generated in multiple pixels are summed using a single common capacitor. The change in gain can be provided by changing the capacitance of the common capacitor. For example, a high gain mode can be provided using a lower capacitance (so that the voltage across the capacitor increases more significantly as a function of the charge imbalance across the capacitor), and a low gain mode can be provided using a higher capacitance. Known arrangements of this type consume relatively large amounts of power and / or provide relatively poor performance (e.g., low detection efficiency and / or high noise), especially in modes involving merging of more than about 2 or 4 pixels. High power consumption can be caused, for example, by requiring all pixels to actively promote the detection process, even when merged into superpixels. A lower total charge-to-voltage conversion gain can be generated due to increased parasitic capacitance. Some methods involve allowing the charge collection element of a selected pixel to float during pixel merging to redirect the charge to an adjacent pixel, but this may cause a longer charge collection time due to insufficient electric field strength, which may result in reduced collection efficiency.

[0011] Pixel binning can also be implemented by summing the voltages from groups of pixels, but this would involve adding amplifier noise, which would increase noise. In addition, all participating pixels would need to be active, which would increase power consumption. Furthermore, it is difficult to provide binning flexibility in such a system, as this would result in complex signal routing requirements.

[0012] It is known to produce drifting detectors that produce a single low capacitance pixel. Arrays of such detectors can be provided, but it is difficult to provide multi-resolution capabilities. Summary of the invention

[0013] It is an object of the present disclosure to provide an improved detector and method for detecting radiation which at least partially solves one or more of the above mentioned disadvantages and / or provides other advantages.

[0014] According to one aspect of the present invention, there is provided a detector for detecting radiation, comprising: a plurality of pixel elements, the plurality of pixel elements comprising corresponding pixel substrates, collectors and readout circuits, wherein the pixel substrates are configured such that irradiation of the pixel substrates with target radiation generates charge carriers in the pixel substrates, and the readout circuits are configured to provide outputs in response to collection of the charge carriers by the corresponding collectors; a plurality of control electrodes; and a control system, the control system being configured to achieve a plurality of selectable resolution modes by controlling the potentials applied to the control electrodes and the collectors to define a corresponding plurality of mappings between the pixel substrates that generate the charge carriers and the collectors that collect those charge carriers.

[0015] According to one aspect of the present invention, there is provided a method for detecting radiation, comprising: applying a potential to a control electrode and a collector in a plurality of pixel elements, the plurality of pixel elements comprising a corresponding pixel substrate, a collector and a readout circuit, wherein: irradiation of the pixel substrate with target radiation generates charge carriers in the pixel substrate, the readout circuit provides an output in response to collection of the charge carriers by the corresponding collector, and the method detects radiation in a plurality of resolution modes, each resolution mode being defined by controlling the potential applied to the control electrode and the collector to define a corresponding mapping between the pixel substrate generating the charge carriers and the collector collecting those charge carriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments taken in conjunction with the accompanying drawings.

[0017] Figure 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus.

[0018] Figure 2 The diagram is Figure 1 Schematic diagram of an exemplary multi-beam apparatus of portions of an exemplary charged particle beam inspection apparatus.

[0019] Figure 3 is a schematic diagram of an exemplary electron optical column including a condenser lens array, an objective lens array, and a detector array.

[0020] Figure 4 is a schematic cross-sectional view of a portion of an exemplary arrangement of an objective lens array and a detector array.

[0021] Figure 5 yes Figure 4 Bottom view of a portion of the detector array.

[0022] Figure 6 yes Figure 4 Bottom view of a modified version of a portion of the objective lens array.

[0023] Figure 7 is a schematic diagram of an exemplary electron optical device including an objective lens array and a beam splitter.

[0024] Figure 8 (a)-(b) show (a) a schematic diagram of a dark-field scatterometer for measuring a target using a first pair of illumination apertures, and (b) detail of the diffraction spectrum of the target grating for a given illumination direction.

[0025] Fig. 9 is relative to Fig.10 Schematic side cross-sectional view of plane AA' of a detector for detecting radiation.

[0026] Fig.10 is shown as being controlled in high resolution mode Fig.10 Schematic top view of a pixel element of a detector.

[0027] Fig.11 is shown being controlled to operate as a superpixel in low resolution mode Fig.10 Schematic top view of a pixel element.

[0028] Fig.12 Depicts a pixel element controlled to operate as a larger superpixel with control electrodes providing intermediate equipotentials.

[0029] Fig.13 is a schematic depiction of Fig.13 The dashed line BB' in the graph is a graph of the change in potential.

[0030] Fig.14 Depicted is a pixel element controlled to operate as a larger superpixel with a control electrode providing an intermediate equipotential and multiple active collectors for increasing full well capacity.

[0031] Fig.15 is a schematic diagram showing example routing of voltage lines to control electrodes defining three superpixels.

[0032] Fig.16 is a schematic diagram showing how diodes arranged in series can be used to control the voltage applied to the control electrode. DETAILED DESCRIPTION

[0033] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments set forth in the following description of the exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with aspects of the present invention as recited in the appended claims.

[0034] The enhanced computing power of electronic devices can be achieved by significantly increasing the packing density of circuit elements such as transistors, capacitors, diodes, etc. on IC chips, which reduces the physical size of the device. This has been achieved by increasing the resolution, so that smaller structures can be made. For example, the IC chip of a smartphone that is the size of a thumbnail and available in 2019 or earlier may include more than 2 billion transistors, each of which is less than 1 / 1000 of the size of a human hair. Therefore, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. Even an error in one step may significantly affect the function of the final product. In some cases, even a single defect may cause device failure. The goal of the manufacturing process is to improve the overall yield of the process. For example, for a 50-step process (wherein the step can indicate the number of layers formed on the wafer), in order to obtain a yield of 75%, each individual step must have a yield greater than 99.4%. If each individual step has a yield of 95%, the total process yield will be as low as 7%.

[0035] Although high process yields are desirable in IC chip manufacturing facilities, it is also essential to maintain high substrate (i.e., wafer) throughput (defined as the number of substrates processed per hour). High process yields and high substrate throughput may be affected by the presence of defects. This is particularly true in cases where operator intervention is required to detect defects. Therefore, high-throughput detection and identification of micron- and nanometer-scale defects by inspection systems (such as scanning electron microscopes ("SEMs")) is critical to maintaining high yields and low costs.

[0036] The SEM includes a scanning device and a detector device. The scanning device includes: an irradiation device, the irradiation device including an electron source for generating primary electrons; and a projection device, the projection device for scanning a sample, such as a substrate, using one or more focused beams of primary electrons. At least the irradiation device or irradiation system and the projection device or projection system can be collectively referred to as an electron optical device or column. The primary electrons interact with the sample and generate secondary electrons. The inspection device captures the secondary electrons from the sample while scanning the sample, so that the SEM can generate an image of the scanned area of ​​the sample. In order to perform high-throughput inspections, some of the inspection devices use multiple focused beams of primary electrons, i.e., multi-beams. The constituent beams of the multi-beams can be referred to as sub-beams or beamlets. Multiple beams can scan different parts of the sample at the same time. Therefore, a multi-beam inspection device can inspect the sample much faster than a single-beam inspection device.

[0037] An embodiment of a known multi-beam inspection apparatus is described below.

[0038] The drawings are schematic. Therefore, for the sake of clarity, the relative sizes of the components in the drawings are exaggerated. 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 a single embodiment are described. Although the present specification and drawings are directed to electron-optical devices, it should be understood that the embodiments are not intended to limit the present disclosure to specific charged particles. Therefore, more generally, references to electrons throughout this article can be considered as references to charged particles, where the charged particles are not necessarily electrons.

[0039] Reference now Figure 1 , Figure 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus 100 , which may also be referred to as a charged particle beam evaluation system or simply an evaluation system. Figure 1 The charged particle beam inspection apparatus 100 includes a main chamber 10, a load lock chamber 20, an electron beam apparatus 40, an equipment front end module (EFEM) 30, and a controller 50. The controller may be distributed between different components of the evaluation system, including, for example, in the electron beam apparatus 40. The electron beam apparatus 40 is located in the main chamber 10.

[0040] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include additional loading ports. For example, the first loading port 30a and the second loading port 30b may receive a front opening unified pod (FOUP) including a substrate (e.g., a semiconductor substrate or a substrate made of (multiple) other materials) or a sample to be inspected (hereinafter, the substrate, wafer, and sample are collectively referred to as a "sample"). One or more robot arms (not shown) of the EFEM 30 transport the sample to the load lock chamber 20.

[0041] The load lock chamber 20 is used to remove the gas around the sample. This creates a vacuum, which is a local gas pressure that is lower than the pressure in the surrounding environment. The load lock chamber 20 can be connected to a load lock vacuum pump system (not shown), which removes gas particles in the load lock chamber 20. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robot arms (not shown) transport the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles in the main chamber 10 so that the pressure around the sample reaches a second pressure lower than the first pressure. After reaching the second pressure, the sample is transported to an electron beam device, and the sample can be inspected by the electron beam device. The electron beam device 40 may include a multi-beam electron optical device.

[0042] The controller 50 is connected to the electron beam device 40, for example, as a distributed component of the controller 50, in a signal manner (e.g., electronically). The controller 50 can be a processor (such as a computer) configured to control the charged particle beam inspection device 100. The controller 50 can also include processing circuits configured to perform various signal and image processing functions. Although the controller 50 is Figure 1 Controller 50 is shown as being outside of a structure including main chamber 10, load lock chamber 20, and EFEM 30, but it should be understood that controller 50 may be part of the structure. Controller 50 may be located in one of the constituent elements of the charged particle beam inspection device, or controller 50 may be distributed on at least two of the constituent elements. Although the present disclosure provides an example of a main chamber 10 housing an electron beam inspection device, it should be noted that aspects of the present disclosure are not limited to chambers housing electron beam inspection devices in their broadest sense. On the contrary, it should be understood that the foregoing principles may also be applied to other systems and other equipment arrangements operating at a second pressure.

[0043] Reference Figure 2 , Figure 2is a schematic diagram illustrating an exemplary charged particle beam evaluation device 40. The electron beam device 40 may be configured as Figure 1 1. The electron beam device 40 includes an electron source 201 and a charged particle column (or device) 230. The charged particle device 230 may be referred to as or include a projection device for directing a primary charged particle beam 202 toward a sample 208. The electron source 201 and the associated and composed charged particle optical elements may be referred to as an irradiation device for generating the primary charged particle beam 202. The evaluation device includes a sample support supporting the sample 208. The sample support in this example includes a sample holder 207. The sample holder 207 holds the sample 208 (e.g., a substrate or a mask) for evaluation. The sample holder 207 is supported by a motorized or actuated stage 209. The electron beam device 40 also includes a detector 240. The detector 240 detects signal charged particles (e.g., electrons) from the sample 208. The detector 240 generates a detection signal based on the detection of the signal charged particles.

[0044] The electron source 201 may include a cathode (not shown) and an extractor or anode (not shown). During operation, the electron source 201 is configured to emit electrons from the cathode as primary electrons. The primary electrons are extracted or accelerated by the extractor and / or the anode to form a primary electron beam 202.

[0045] The charged particle device 230 is configured to convert the primary electron beam 202 into a plurality of charged particle beams 211, 212, 213 and direct each beam onto the sample 208. Although three beams are illustrated for simplicity, there may be tens, hundreds, thousands, tens of thousands, or even hundreds of thousands (or more) of beams. The beams may be referred to as beamlets or beamlets. The plurality of charged particle beams may be collectively referred to as multiple beams or beam grids. A beam grid having such a plurality of beams (e.g., more than a thousand beams) may have, for example, a field of view of more than 0.5 mm, such as a field of view in the range of 0.5 mm to 30 mm or 1 mm to 30 mm, such as a field of view in the range of 0.5 mm to 15 mm.

[0046] A controller 50 (eg, a control system including a distributed controller) may be connected to Figure 1 The controller 50 may be used to control various parts of the charged particle beam inspection device 100, such as the electron source 201, the electron detection device 240, the charged particle device 230, and the actuation platform 209. The controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals to control the operation of the charged particle beam inspection device 100, including the operation of the electron beam device 40.

[0047] For example, the charged particle device 230 can be configured to focus the beams 211, 212, and 213 to the sample 208 for inspection, and three detection spots 221, 222, and 223 can be formed on the surface of the sample 208. The charged particle device 230 can be configured to deflect the primary beams 211, 212, and 213 so that the detection spots 221, 222, and 223 are scanned across separate scanning areas in a section of the surface of the sample 208. In response to the primary beams 211, 212, and 213 being incident on the detection spots 221, 222, and 223 on the sample 208, electrons are generated from the sample 208, the electrons including secondary electrons and backscattered electrons, which can be referred to as signal charged particles. The secondary electrons typically have an electron energy of up to fifty electron volts (≤50 eV), and the backscattered electrons typically have an electron energy between fifty electron volts (50 eV) and the landing energy of the primary beams 211, 212, and 213.

[0048] The detector 240 may send detection signals generated in the detector 240 (e.g., as imaging or detection signals) to the controller 50 or a signal processing system (not shown, which may be part of the controller 50) to, for example, construct an image of the corresponding scanned area of ​​the sample 208. The detector 240 may be at least partially incorporated into the charged particle device 230 or may be separate from the charged particle device 230, for example, where a secondary optical column directs secondary electrons to the detector 240.

[0049] The controller 50 may include an image processing system, which includes an image acquisition device (not shown) and a storage device (not shown). For example, the controller may include a processor, a computer, a server, a mainframe computer, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquisition device may include at least a portion of the processing function of the controller. Therefore, the image acquisition device may include at least one or more processors. The image acquisition device may be connected to the detector 240 in a communication manner, thereby allowing signal communication, such as through an electrical conductor, an optical fiber cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, radio, and other means, or a combination thereof. The image acquisition device may receive a detection signal from the detector 240, may process the data included in the signal, and may construct an image based on the data. Therefore, the image acquisition device may acquire an image of the sample 208. The image acquisition device may also perform various post-processing functions, such as generating contours, superimposing indicators, etc. on the acquired image. The image acquisition device may be configured to perform, for example, adjusting the brightness and contrast of the acquired image. The storage may be a storage medium such as a hard disk, a flash drive, a cloud storage, a random access memory (RAM), other types of computer readable memory, etc. The storage may be coupled to the image acquirer and may be used to save the scanned raw image data as a raw image, and a post-processed image.

[0050] The image acquirer can acquire one or more images of the sample 208 based on the imaging signal received from the detector 240. The imaging signal can correspond to a scanning operation for performing charged particle imaging. The acquired image can be a single image including multiple imaging areas. The single image can be stored in a memory. The single image can be an original image that can be divided into multiple areas. Each area can include an imaging area containing features of the sample 208. The acquired image can include multiple images of a single imaging area of ​​the sample 208 sampled multiple times within a time period. The multiple images can be stored in the memory. The controller 50 can be configured to perform the image processing step using multiple images of the same position of the sample 208.

[0051] The controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons. The portion of the controller used for this function may be included in or close to the detector. 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 beams 211, 212, and 213 incident on the sample surface to reconstruct an image of the inspected sample structure. The reconstructed image may be used to reveal various features of the internal or external structure of the sample 208. Thus, the reconstructed image may be used to reveal any defects that may be present in and / or on the sample, thereby revealing any defects of the sample.

[0052] The controller 50 may control the actuation platform 209 to move the sample 208 during inspection of the sample 208, for example to provide a scanning motion of the platform relative to the path of the primary beam. The controller 50 may enable the actuation platform 209 to move the sample 208, preferably continuously, for example at a constant speed, at least during inspection of the sample, in a direction such as a portion of the scanning motion of the platform. The controller 50 may control the motion of the actuation platform 209 such that the controller varies the speed of motion of the sample 208 according to various parameters. For example, the controller may control the platform speed (including the platform direction) according to the characteristics of the inspection step and / or scan of the scanning process, for example as disclosed in EPA 21171877.0 filed on May 3, 2021, which is incorporated herein by reference with respect to at least the combined step and scan strategy of the platform. When controlling the actuation platform, actuation of the platform and therefore the sample may enable the sample to be positioned (e.g., dynamically) relative to the path of the primary beam.

[0053] Figure 3 4 is a schematic diagram of an exemplary charged particle device 41 for use in an evaluation device. For ease of illustration, the lens array is schematically depicted herein by an array of elliptical shapes. Each elliptical shape represents one of the lenses in the lens array. Conventionally, elliptical shapes are used to represent lenses, similar to the biconvex form often used in optical lenses. In the context of a charged particle device (such as the charged particle device discussed herein), it should be understood that the lens array will generally operate in an electrostatic manner, and therefore any physical element with a biconvex shape may not be required. As described below, the lens array may alternatively include a plurality of plates with holes. Each plate with a hole may be referred to as an electrode. The electrodes may be arranged in series along the path of a beam grid of a plurality of charged particle beams (which may also be referred to as sub-beams). Therefore, the electrodes are also connected in series along the path of the charged particle beam of the beam grid.

[0054] The electron source 201 guides electrons toward an array of condenser lenses 231 that form part of the charged particle device 230. The electron source 201 is desirably a high brightness thermal field emitter with a good compromise between brightness and total emission current. There may be tens, hundreds, or thousands or even tens of thousands of condenser lenses 231. The array 231 of condenser lenses may include a multi-electrode lens and have a configuration based on EP1602121A1, which is incorporated herein by reference, particularly the disclosure of a lens array that splits an electron beam into a plurality of sub-beams, wherein the array provides a lens for each sub-beam. The condenser lens array may be in the form of at least two (preferably three) plates, which are used as electrodes, wherein the holes in each plate are aligned with the holes in the other plates to define the path of the charged particle beam through the plate. At least two of the plates are maintained at different potentials during operation to achieve the desired lensing effect. Between the plates of the condenser lens array is an electrically insulating plate, for example, made of an insulating material such as ceramic or glass, which has one or more holes for the charged particle beam. Additionally or alternatively, one or more plates may be characterized by holes, i.e., each hole has their own electrode, such as an electrode array around the periphery of a group of holes or arranged in a group of holes having a common electrode. In a variant, one or more plates may include multiple sections or strips with multiple holes. In another alternative arrangement, a giant collimator is provided instead of a focusing lens array. The giant collimator can act on the beam from source 201 before it is split into multiple beams. The giant collimator can be implemented magnetically, electrostatically, or magnetically and electrostatically.

[0055] In some embodiments, the condenser lens array is formed by three plate arrays in which the charged particles have the same energy when they enter and leave each lens, an arrangement which can be referred to as an Einzel lens. Thus, dispersion occurs only within the Einzel lens itself (between the entry and exit electrodes of the lens), thereby limiting off-axis aberrations. When the thickness of the condenser lens is low (e.g., a few millimeters), such aberrations have a small or negligible effect.

[0056] Each condenser lens in the array directs electrons into a corresponding beam 211, 212, 213 focused at a corresponding intermediate focus 233. A collimator or array of collimators may be positioned to operate on a corresponding intermediate focus 233. The collimator may be in the form of a deflector 235 disposed at the intermediate focus 233. The deflector 235 is configured to bend the corresponding beam 211, 212, 213 by an amount effective to ensure that the chief ray (which may also be referred to as the beam axis) is incident on the sample 208 approximately orthogonal (i.e., approximately 90° to the nominal surface of the sample). It should be noted that in an arrangement with a giant condenser lens, the condenser lens may collimate the source beam (or, in an embodiment, multiple beams) or facilitate collimation of the source beam (or, in an embodiment, multiple beams).

[0057] An objective lens array 401 is provided down-beam of the deflector 235. The objective lens array 401 comprises an objective lens for each beam 211, 212, 213. The objective lens array 401 projects the beams 211, 212, 213 onto the sample 208. The objective lens array 401 may comprise two or more (preferably at least three) plate electrode arrays connected to corresponding potential sources.

[0058] Optionally, a control lens array 250 is arranged between the deflector 235 and the objective lens array 401. The control lens array 250 includes a control lens for each beam 211, 212, 213. The control lens array 250 provides an additional degree of freedom for controlling the properties of the beams 211, 212, 213. The control lens array 250 may include two or more (preferably at least three) plate electrode arrays connected to corresponding potential sources. The function of the control lens array 250 is to optimize the beam angle relative to the beam reduction rate and / or control the beam energy delivered to the objective lens, each of which directs the corresponding beam 211, 212, 213 onto the sample 208. In an embodiment, the control lens array can be regarded as part of the objective lens, for example an additional plate associated with the objective lens array.

[0059] Optionally, a scanning deflector array 260 is disposed between the control lens array 250 and the objective lens array 401. The scanning deflector array 260 includes a scanning deflector for each beam 211, 212, 213. Each scanning deflector is configured to deflect the corresponding beam 211, 212, 213 in one or two directions so that the beam is scanned across the sample 208 in one or two directions. Alternatively, a giant scanning deflector may be provided to scan the charged particle beam across the sample 208. The giant scanning deflector may be provided up-beam of the control lens array 250 beam. In an embodiment, such a giant scanning deflector may operate on the source beam and may exist together with a giant focusing lens.

[0060] The detector module 402 of the detector is arranged in the objective lens or between the objective lens and the sample 208 to detect signal electrons / particles from the sample 208. An exemplary construction of such a detector module 402 is described below. It should be noted that, in addition or alternatively, the detector can have a detector element upstream of the beam along the primary beam path of the objective lens array 401 or even the control lens array 250. The detector module can be an array of detector elements (e.g., a detector array). Each element can be associated with a separate beam, for example, each element can be positioned to detect signal particles generated by a separate beam.

[0061] Figure 3The charged particle device 41 can be configured to control the landing energy of the electrons on the sample 208 by changing the potential applied to the electrodes of the control lens and the objective lens. The control lens and the objective lens work together and can be referred to as an objective lens assembly. The landing energy can be selected to increase the emission and detection of secondary electrons depending on the properties of the sample being evaluated. The detector module can be included in the objective lens assembly.

[0062] The objective lens can be configured to reduce the electron beam by more than 10 times (i.e., to less than 1 / 10), desirably in the range of 50 times to 100 times or more. The objective lens can include three electrodes: an intermediate electrode, a lower electrode, and an upper electrode. The upper electrode can be omitted. An objective lens with only two electrodes can have lower aberrations than an objective lens with more electrodes. A three-electrode objective lens can have a larger potential difference between the electrodes and thus achieve a stronger lens. Additional electrodes (i.e., more than two electrodes) provide additional degrees of freedom for controlling the electron trajectory to, for example, focus secondary electrons as well as the incident beam.

[0063] In some embodiments, the objective lens array assembly includes a detector having a detector module 402 downstream of the beam of at least one electrode of the objective lens array 401. The detector module 402 may include or even be in the form of a detector array. In an embodiment, at least a portion of the detector is adjacent to the objective lens array 401 and / or integrated with the objective lens array 401. For example, the detector module 402 can be implemented by integrating a CMOS chip detector into the bottom electrode of the objective lens array 401. The integration of the detector module 402 into the objective lens array can replace the secondary column. Preferably, the CMOS chip is oriented to face the sample (due to the small distance between the sample and the bottom of the electron optical system, it can be, for example, in the range of 10 to 400 microns, desirably in the range of 50 to 200 microns, optionally about 100 microns). It should be noted that even in the case where the detector is located upstream of the beam of the electron optical element at the most downstream of the beam of the charged particle device, there may also be a close separation (e.g., with a similar distance) (e.g., about 100 microns) between the electron optical element at the most downstream of the beam and the sample. In an embodiment, the electrode for capturing signal charged particles is formed in the top metal layer of the CMOS device. The electrode can be formed in other layers of the substrate, such as the CMOS chip. The power and control signals of the CMOS can be connected to the CMOS through silicon vias. For robustness, preferably, the bottom electrode consists of two elements: the CMOS chip and a passive Si plate with holes. The plate shields the CMOS from high electron fields or high E fields.

[0064] In an embodiment, a single electrode surrounds at least some of the holes. In one arrangement, for example, a single electrode is allocated to surround each hole. In another embodiment, a plurality of electrode elements are arranged to surround each hole, for example as detector elements. The signal charged particles captured by the electrode elements surrounding a hole can be combined into a single detection signal or used to generate independent detection signals. The electrode elements can be divided radially (i.e., to form a plurality of concentric rings), angularly (i.e., to form a plurality of fan-shaped pieces), radially and angularly (providing an arrangement similar to a dark board), or in a grid (e.g., as a chessboard) or in any other convenient manner.

[0065] An exemplary embodiment of a detector integrated into the objective lens array 401 is shown in Figure 4 middle, Figure 4 A portion of an objective lens array 401 is illustrated in schematic cross section. In such an embodiment, the detector comprises a detector module 402 comprising a plurality of detector elements 405 (e.g. sensor elements such as capture electrodes) (e.g. an array of detector elements 405), preferably as an array of detector elements (i.e. a plurality of detector elements preferably in a pattern or arrangement on a two-dimensional surface). In such an embodiment, the detector module 402 is arranged on the output side of the objective lens array. The output side is the output side of the objective lens array 401. Figure 5 4 is a bottom view of a detector module 402, which includes a substrate 404 on which a plurality of detector elements (or capture electrodes 405) are disposed, each of which surrounds a beam aperture 406. The beam aperture 406 may be formed by etching through the substrate 404. Figure 5 In the arrangement shown in FIG. 1 , the beam holes 406 are shown in a rectangular array. The beam holes 406 may also be arranged differently, for example, as shown in FIG. Figure 6 The hexagonal closed packing array arrangement depicted in .

[0066] The integrated detector module 402 described above is particularly advantageous when used with an evaluation device (e.g., including a device) having a tunable landing energy, because secondary electron capture can be optimized for a certain range of landing energies. The detector module having an array or in the form of an array can also be integrated into other electrode arrays, not just into the lowest electrode array. Further details and alternative arrangements of the detector module integrated into the objective lens can be found in European application number 20184160.8, which is incorporated herein by reference.

[0067] A power source may be provided to apply corresponding potentials to the electrodes of the control lenses of the control lens array 250 and the objective lenses of the objective lens array 401 and the condenser lenses of the condenser lens array or any electron optical component (e.g., detector module) of the charged particle device 41 (such as when integrated into the objective lens array, or when the objective lens and the detector module are separate components). The controller 50 may control the potentials applied to the electron optical components (such as the electrodes of the condenser lens array, the objective lens array, and / or the control lens array).

[0068] The charged particle device 41 may include other electron optical components such as charged particle correctors, for example as a corrector array for aligning the source to the sample and between beams of a plurality of beams, and for adjusting the focus of different groups of beam grids or of individual beams of a beam grid. Such correctors may be controlled to operate dynamically and / or statically, for example during boost, maintenance, or during calibration of the charged particle device 41.

[0069] In an embodiment, a charged particle device array (or device array) is provided. The array may include a plurality of any charged particle devices described herein (e.g., electron optical columns). Each of the charged particle devices in the array focuses a corresponding plurality of charged particle beams onto different regions of the same sample 208. Each charged particle device in the array may derive a corresponding plurality of charged particle beams from different corresponding sources 201. Each corresponding source 201 may be one of the plurality of sources 201. At least a subset of the plurality of sources 201 may be provided as a source array. The source array may include a plurality of emitters on a common substrate. Focusing a plurality of charged particle beams from different charged particle devices simultaneously onto different regions of the same sample allows the area of ​​the sample 208 to be simultaneously exposed to the charged particle beam to be increased. Therefore, an increased sample area may be processed (e.g., evaluated) at one time. The charged particle devices in the device array may be arranged adjacent to each other so as to project the corresponding plurality of beams onto adjacent regions of the sample 208. Any number of charged particle devices may be used in the array. Preferably, the number of charged particle devices is in the range of 9 to 200. Each charged particle device in the array may be configured in any of the ways described herein when referring to a single charged particle device, electron optical device or system or column.Alternatively or additionally, one or more of the charged particle devices in the array may be configured to project a single beam.

[0070] Figure 7 Another example of a charged particle device 41 is schematically depicted. Features identical to those described above are given the same reference numerals. For the sake of simplicity, no reference is made to the Figure 7Such features are described in detail. For example, the source 201, the condenser lens 231, the objective lens array 401 and the sample 208 (e.g., on the sample support 207) can be as described above. In this example, a giant collimator 270 is provided instead of the one described above with reference to Figure 3 An array of deflectors of the type described. Such a giant collimator may be a giant lens, which may be magnetic, electrostatic, or both. In other embodiments, the array of deflectors may be used to at least facilitate collimation of the beam, thereby providing a finer deflection toward collimation than the effect of the giant collimator 270. Such an arrangement may also include an array of multiple deflectors (e.g., wherein each hole has multiple electrodes) for even finer collimation. In one arrangement, the focusing lens 231 may include a single plate defining an array of beam limiting holes, in which a plurality of holes are defined, the single plate having one or more giant electrodes associated with the individual holes. Such an array of beam limiting holes and associated giant electrodes may also form a focusing lens array to focus the resulting beam at an intermediate focus, which desirably corresponds to the position of the collimator 270.

[0071] As described above, in some embodiments, the detector may be disposed between the objective lens array 401 and the sample 208. The detector may face the sample 208. Alternatively, Figure 7 As shown in FIG. 2 , the detector 240 may be implemented such that the objective lens array 401 is located between the detector 240 and the sample 208 .

[0072] In an embodiment, the deflector array 95 is disposed between the detector 240 and the objective lens array 401. In an embodiment, the deflector array 95 comprises an array of Wien filters, so that the deflector array 95 can be referred to as a beam splitter. The deflector array 95 is configured to provide a magnetic field and an electrostatic field. The electrostatic field and the magnetic field operate together to separate the charged particles projected onto the sample 208 from the signal particles (e.g., electrons from the sample 208). The operation of the field directs the signal particles toward the detector 240.

[0073] In an embodiment, the detector 240 is configured to detect signal particles by reference to the energy of the charged particles (i.e., according to the band gap), i.e., a semiconductor-based type detector. Such a detector 240 may be referred to as an indirect current detector. The secondary electrons emitted from the sample 208 obtain energy from the field between the electrodes. The secondary electrons have sufficient energy once they reach the detector 240. In a different arrangement, the detector 240 may be an electron-to-photon converter (such as a scintillator array, for example, with fluorescent stripes between beams), which is positioned upstream of the beam relative to the Wiener filter along the primary beam path. The primary beam passing through the Wiener filter array has a substantially parallel path upstream and downstream of the beam of the Wiener filter array (magnetic and electrostatic strips are orthogonal to the primary beam path), while the signal electrons from the sample are guided toward the scintillator array by the Wiener filter array. The electron-to-photon converter may be photonically connected to the photon-to-electron converter to convert any photons generated in the electron-to-photon converter and emitted by the electron-to-photon converter. The photon-to-electron converter may be electrically connected to an electronic circuit to process the detection signal. In various embodiments, the photon to electron converter may be within the charged particle device or external to the charged particle device. In embodiments, photon coupling may be performed via a photon transport unit (eg, an optical fiber array) to a remote optical detector that generates a detection signal regarding the detection of a photon.

[0074] Figure 3 (a) shows a metrology device that can be used in connection with embodiments of the present disclosure, which can also be referred to as an optical measurement system. For example, an alternative metrology device can use EUV radiation such as disclosed in WO2017 / 186483A1. Figure 3(b) illustrates in more detail the target structure T and the diffracted rays of the measuring radiation used to illuminate the target structure. The illustrated metrology apparatus is of a type known as a dark field metrology apparatus. The metrology apparatus may be a separate device or incorporated into a lithography apparatus or into a lithography unit, for example at a measuring station. An optical axis having several branches running through the apparatus is represented by a dotted line O. In such an apparatus, light emitted by a source 11 (e.g. a xenon lamp) is directed onto a substrate W via a beam splitter 15 by an optical system comprising lenses 12, 14 and an objective lens 16. These lenses are arranged in a double sequence of a 4F arrangement. Different lens arrangements may be used, provided that the lens arrangement still provides an image of the substrate onto the detector and at the same time allows access to an intermediate pupil plane for spatial frequency filtering. Thus, the angular range of radiation incident on the substrate may be selected by defining the spatial intensity distribution in a plane presenting the spatial spectrum of the substrate plane, referred to herein as the (conjugate) pupil plane. In particular, this selection can be made by inserting an aperture plate 13 (or 13') of suitable form between lens 12 and lens 14 in the plane of the back-projected image of the objective pupil plane. In the example shown, lens 12 is implemented as a lens group including lenses 12a to 12c. In the illustrated example, aperture plate 13 has different forms (marked as 13N and 13S), thereby allowing different illumination modes to be selected. The illumination system in this example forms an off-axis illumination mode. In a first illumination mode, aperture plate 13N provides off-axis from a direction designated as "north" for the sake of description only. In a second illumination mode, aperture plate 13S is used to provide similar illumination, but from the opposite direction marked as "south". By using different apertures, other illumination modes are possible. The rest of the pupil plane is desirably dark, because any unnecessary light outside the desired illumination mode will interfere with the desired measurement signal.

[0075] like Figure 3 As shown in (b), the target structure T is placed with the substrate W perpendicular to the optical axis O of the objective lens 16. The substrate W may be supported by a support (not shown). A measurement radiation ray I impinging on the target structure T from an angle on the axis O produces a zero-order ray (solid line 0) and two first-order rays (dash-dotted line +1 and dash-dotted line -1). It should be remembered that in the case of an overfilled small target structure, these rays are only one of many parallel rays covering the substrate area including the measurement target structure T and other features. Since the hole in the plate 13 has a finite width (necessary to allow a useful amount of light), the incident ray I will actually occupy an angular range, and the diffracted rays 0 and +1 / -1 will be slightly spread out. Depending on the point spread function of the small target, each order +1 and -1 will be further spread across the angular range, rather than a single ideal ray as shown. It should be noted that the grating spacing and the illumination angle of the target structure can be designed or adjusted so that the first-order rays entering the objective lens are closely aligned with the central optical axis. Figure 3(a) and Figure 3 The rays illustrated in (b) are shown slightly off-axis simply to enable them to be more easily distinguished in the figure.

[0076] At least the 0th and 1st orders diffracted by the target structure T on the substrate W are collected by the objective lens 16 and directed back through the beam splitter 15. Figure 3 (a), illustrates both the first illumination mode and the second illumination mode by designating diametrically opposite apertures labeled North (N) and South (S). When the measurement radiation incident ray I comes from the north side of the optical axis, i.e. when the first illumination mode is applied using aperture plate 13N, the +1 diffracted ray labeled +1 (13N) enters the objective lens 16. In contrast, when the second illumination mode is applied using aperture plate 13S, the -1 diffracted ray (labeled -1 (13S)) is the diffracted ray that enters the lens 16.

[0077] A second beam splitter 17 divides the diffracted beam into two measurement branches. In the first measurement branch, an optical system 18 uses the zero-order diffracted beam and the first-order diffracted beam to form a diffraction spectrum (pupil plane image) of the target structure on a first sensor 19 (e.g., a CCD or CMOS sensor), which may also be referred to as a detector 19. Each diffraction order hits a different point on the sensor, so that image processing can compare and contrast several orders. The pupil plane image captured by the sensor 19 can be used to focus the metrology device and / or normalize the intensity measurement of the first-order beam. The pupil plane image can also be used for many measurement purposes such as reconstruction.

[0078] In the second measurement branch, the optical system 20, 22 forms an image of the target structure T on a sensor 23 (e.g. a CCD or CMOS sensor), which may also be referred to as a detector 23. In the second measurement branch, an aperture stop 21 (or 21') is provided in a plane conjugate to the pupil plane. The aperture stop 21 serves to block the zeroth order diffraction beam so that the image of the target formed on the sensor 23 is formed only by the -1st or +1st order beams. A top view and a side cross-sectional view, respectively marked 21a and 21b, of an example form for the aperture stop 21 are shown. The images captured by the sensors 19 and 23 are output to a processor PU which processes the images, the functionality of which will depend on the specific type of measurement being performed. It should be noted that the term "image" is used in this context in a broad sense. If only one of the -1st and +1st orders is present, then no image of the grating lines will therefore be formed.

[0079] When monitoring a lithographic process, it is desirable to monitor the focus of the lithographic beam on the substrate. A known method of determining the focus setting from a printed structure is by measuring the critical dimension (CD) of the printed structure. CD is a measurement of the smallest feature (e.g., the line width of an element). The printed structure may be a target specifically formed for focus monitoring (such as a line space grating). As is well known, CD typically shows a second-order response to focus, resulting in what is known as a "Bossung curve" on a graph of CD (y-axis) relative to focus (x-axis). A Poisson curve is a roughly symmetrical curve that is roughly symmetrical around a peak representing the best focus. A Poisson curve may be roughly parabolic in shape. There are several disadvantages to this approach. One disadvantage is that the method shows low sensitivity near the optimal focus (due to the parabolic shape of the curve). Another disadvantage is that the method is insensitive to the sign of any defocus (this is because the curve is primarily symmetrical around the optimal focus). In addition, this approach is particularly sensitive to dose and process variations (crosstalk).

[0080] To address these issues, diffraction based focusing (DBF) was devised. Diffraction based focusing can use a target on a reticle that prints a target that is designed to have an asymmetry that depends on the focus setting during printing. This asymmetry can then be measured using scatterometry based inspection methods, for example by measuring the intensity asymmetry between the intensity of +l and -1 order radiation diffracted from the target, to obtain a measurement of the focus setting. For example, a scatterometry based inspection method can be used, for example Figure 3 The method is performed using the measurement tool shown in (a).

[0081] As discussed in the introductory portion of the description, known detectors have various disadvantages. Embodiments of the present disclosure address one or more of these disadvantages and / or provide other advantages.

[0082] refer to Figures 9 to 15 An example detector 60 is described. The detector 60 is configured to detect radiation 61 incident on the detector 60. The radiation 61 may include electromagnetic radiation (e.g., visible and invisible, such as X-rays), charged particles (such as electrons), or both electromagnetic radiation and charged particles. The radiation 61 that the detector 60 is configured to detect may be referred to as target radiation. The detector 60 includes a plurality of pixel elements 62 and a plurality of control electrodes 66. Figures 9 to 15 In the example shown in FIG. 6 , the pixel elements 62 are arranged in a closed-pack hexagonal array. Fig.10 , Fig.11 , Fig.12 and Fig.14 Each of the smallest hexagons shown in corresponds to a different single pixel element 62.

[0083] Fig. 9 For about Fig.10 A side cross-sectional view of the plane AA' shown in FIG. Fig. 9 The cross-sectional view cuts through three individual pixel elements 62 (at Fig. 9 Each pixel element 62 includes a corresponding pixel substrate 63 (for Fig. 9 The three pixel elements shown in FIG. 6 are labeled 63A, 63B, 63C), the corresponding collector electrode 64 (for Fig. 9 The three pixel elements shown in FIG. 6 are labeled 64A, 64B, 64C), and corresponding readout circuitry 68 (for Fig. 9 The three pixel elements shown in the figure are labeled as 68A, 68B, 68C). The pixel substrate 63 is configured so that the irradiation of the pixel substrate 63 by the target radiation generates charge carriers in the pixel substrate 63. The pixel substrate 63 may, for example, include a semiconductor material, and the charge carriers may include electron-hole pairs. The semiconductor material may include silicon or other materials (low bandgap or wide bandgap materials). The readout circuit 68 is configured to provide an output in response to the collection of charge carriers by each collector. The charge carriers are driven to the collector 64 by the electric field in the pixel substrate 63. The electric field is generated and controlled by the collector 64 and the control electrode 66. The readout circuit 68 can be configured to convert the charge into a voltage, for example, by integrating the current associated with the flow of charge carriers generated using a capacitor and using the voltage across the capacitor to provide an output. The readout circuit 68 can be controlled by a suitable control signal to periodically sample the voltage across the capacitor and reset the circuit at, for example, a series of time intervals (which may be referred to as a measurement frame). In some embodiments, two samples of the voltage may be obtained per measurement frame, thereby performing correlated double sampling. The detailed configuration of the readout circuit 68 is not particularly limited. Any technique suitable for measuring the charge flowing to the collector may be used.

[0084] Fig. 9 The detector 60 shown in FIG. 1 is configured for front-side illumination. In such a mode, radiation 61 impinges on the detector 60 on the side opposite to the side where the collector electrode 64 and the control electrode 66 are located (from Fig. 9 In other embodiments, the detector 60 may be operated in a backside illumination mode, where radiation impinges on the side of the detector 60 where the collector electrode 64 and the control electrode 66 are located. The collector and / or control electrode 66 may be formed of a transparent material.

[0085] The detector 60 includes a control system 70. The control system 70 controls the detector 60 to perform various functions described below. The control system 70 may include the following references: Figure 1 and Figure 8The controller 50 or processor PU of any one of the described forms or by the controller 50 or processor PU. In addition, the control system 70 can control the elements of the evaluation device or evaluation system. The control system 70 may include a single unit configured to perform all control functionalities, or may include a distributed unit system that allows the desired functions to be realized together. Such a distributed system may have one or more elements that are located in different parts or modules and / or associated with different parts or modules. The control system 70 may be implemented by a computer at least in part. Any suitable combination of elements (e.g., CPU, RAM, data storage, data connection, sensor, etc.) may be provided and appropriately programmed to realize some or even all specified functions. Any reference to the equipment, device or system configured to perform a function herein is intended to cover the situation where the control system 70 is configured to cause the execution of a function (e.g., by being appropriately programmed to provide a control signal that causes the function to occur).

[0086] The control system 70 controls the potentials applied to the control electrode 66 and the collector electrode 64 via corresponding routing lines 71. The control system 70 implements a plurality of selectable resolution modes by controlling the potentials. The control system 70 allows a user to select between a plurality of resolution modes by providing suitable instructions to the control system 70. Alternatively or additionally, the control system 70 may be configured to automatically switch between different resolution modes, for example based on predetermined criteria or input data representing a state and / or operating mode of an evaluation system using the detector 60.

[0087] Multiple selectable resolution modes are implemented by controlling the potential to define a corresponding plurality of mappings (e.g., one mapping per resolution mode) between the pixel substrate 63 where charge carriers are generated and the collector 64 where those charge carriers are collected. This can be achieved because the potential defines the electric field in the pixel substrate 63, and the electric field will define how the charge carriers move in the pixel substrate 63.

[0088] At least two resolution modes can be provided, wherein mapping is such that different numbers of collectors 64 are used to collect charge carriers from all pixel elements 62. The resolution modes can include a high-resolution mode and one or more low-resolution modes. The low-resolution mode can provide different resolutions by grouping pixel elements into superpixels of different sizes and / or superpixels that are different in other ways (such as by providing different collection capacitors in the superpixels). Grouping pixels into superpixels reduces resolution, but can improve (increase) frame rate, reduce power consumption, and / or increase field of view (FOV).

[0089] In an embodiment, the control system 70 is configured to implement a high resolution mode defined by a one-to-one mapping between pixel substrates 63 and collector electrodes 64. The one-to-one mapping causes the charge carriers generated in each pixel substrate 63 to be collected exclusively by the collector electrode 64 of the same pixel substrate 63. Fig. 9 , for example, the charge generated by the charge carriers generated by the radiation impinging on the pixel substrate 63A will flow to and be collected by the collector 64A associated with (e.g., in direct contact with) the pixel substrate 63A. Similarly, the charge carriers generated in the pixel substrate 63B will cause the charge to be collected by the collector 64B, and the charge carriers generated in the pixel substrate 63C will cause the charge to be collected by the collector 64C. Thus, the output from each readout circuit 68 will provide independent information about the radiation impinging on a single corresponding pixel element in the pixel elements 62.

[0090] In an embodiment, the control system 70 implements the high resolution mode by applying an equal potential to the control electrode 66 along a path separating all pixel substrates 63 from each other when viewed perpendicular to the plane of the detector 60. The plane of the detector 60 may be perpendicular to the average direction of incidence of the target radiation to be detected on the detector 60. The plane of the detector 60 is perpendicular to Fig. 9 in the plane of the page and parallel to Fig.10 , Fig.11 , Fig.12 and Fig.14 The plane of the page is shown in bold. Fig.10 Schematically depicting the implementation of the high resolution mode. The path surrounds each of the seven pixel elements 62 shown individually. In an embodiment, the equipotential can be a ground voltage. Applying the equipotential to the path surrounding all pixel elements 62 effectively isolates each pixel element 62 from all other pixel elements. Charge carriers cannot propagate between different pixel elements 62. During the high resolution mode, a common potential can be applied to the collector 64 (i.e., the same potential is applied to each collector 64). This can ensure that the electric field distribution is the same in each pixel element 62 (where each pixel element 62 has the same shape), and thereby ensure spatially uniform performance of the detector 60 (e.g., each pixel element 62 performs in the same manner as each other pixel element 62).

[0091] In an embodiment, the control system 70 implements a low-resolution mode defined by a mapping in which at least a subset of pixel elements 62 are grouped to form corresponding superpixels 72. Charge carriers generated in all pixel substrates 63 of each superpixel 72 are collected by a subset (i.e., less than all) of the collectors 64 in the pixel elements 62 of the superpixel 72. The subset may consist of a single collector 64 (which may be referred to as a common collector 64), or a plurality of collectors 64 consisting of less than all of the collectors 64 of the pixel elements 62. An example of a superpixel 72 including seven pixel elements 62 is shown in FIG. Fig.11 In this example, the subset of collectors 64 consists of a single collector 64 in the center. The active nature of the collector 64 is schematically depicted by showing the collector 64 as a filled black circle. All other collectors 64 in the superpixel 72 are inactive (i.e., not used to collect charge) and are schematically depicted as open circles.

[0092] The control system 70 can define the mapping of the low-resolution mode by controlling the potential of the control electrode 66 and the collector electrode 64 to allow charge carriers to flow between the pixel substrate 63 of each superpixel 72 while remaining within the corresponding superpixel 72. Fig.10 Compared with the case where the charge carriers are restricted to move within the pixel substrate 63 where the charge carriers are generated, Fig.11 In the low-resolution mode of FIG. 6 , charge carriers may move between different pixel substrates 63 , such as from the outermost pixel elements 62 to the center pixel elements 62 .

[0093] In some embodiments, Fig.11 , Fig.12 and Fig.14 As illustrated in FIG. 1 , when viewed perpendicular to the plane of the detector 60, for each superpixel 72, the control system 72 defines the mapping of the low-resolution pattern by applying an external equipotential to the control electrodes along an external path 66A defining all pixel substrates 63 surrounding the superpixel 72. The external path 66A is shown in bold at Fig.11 and can be seen surrounding all seven pixel elements 62. Fig.12 and Fig.14 , outer path 66A surrounds all 37 pixel elements 62 .

[0094] In some embodiments, Fig.11 , Fig.12 and Fig.14As illustrated in , the control system 70 defines mapping of the low-resolution mode by defining equipotentials along a plurality of paths 66A, 66B, 66C, 66D, each shown in bold. The paths may form generally concentric loops. For example, for each superpixel 72, when viewed perpendicular to the plane of the detector 60, the control system 70 may apply an external equipotential along a control electrode of an outer path 66A that defines all of the pixel substrates 63 (and therefore the pixel element 62) that surround the superpixel 72. Additionally, a different internal equipotential is applied to a control electrode of an inner path 66B that defines at least one of the pixel substrates 63 that surround the superpixel 72. Fig.12 and Fig.14 In the example of , one or more additional intermediate equipotentials are applied along the respective intermediate paths, as discussed in more detail below. Thus, different potentials are applied to control electrodes surrounding different regions in the superpixel 72.

[0095] Internal path 66B may surround pixel substrate 63 of pixel element 62 that includes a collector electrode 64 of a subset of collector electrodes for collecting charge from pixel elements of superpixel 72 (in the case where there is only one active collector electrode 64) or at least one of collector electrodes 64 (in the case where there are more than one active collector electrode 64). Fig.11 and Fig.12 As illustrated in FIG. 1 , interior path 66B surrounds a single active collector 64 (filled black circle), where only one such collector 64 is present per superpixel 72. In the case where multiple active collectors 64 are present in a superpixel 72, interior path 66B may surround at least one of the active collectors 64, and optionally all of the active collectors 64 (e.g., Fig.14 ). Thus, at least one collector 64 for collecting charge in a superpixel 72 is surrounded by concentric equipotential paths that define potential gradients and corresponding electric fields that effectively drive charge carriers generated in a pixel substrate 63 of a pixel element 62 of the superpixel 72 toward an active collector 64 (or multiple active collectors 64).

[0096] In an embodiment, Fig.11 , Fig.12 and Fig.14As illustrated in , the outer path 66A defines a shape having a geometric center (the center of the innermost hexagon in the example shown). At least one of the collectors 64 in a subset of the collectors 64 of the superpixel 72 (i.e., one or more active collectors 64) is closer to the geometric center than all other collectors 64 of the superpixel 72. In the case where the subset consists of a single collector 64, the single collector 64 can be closer to the geometric center than all other collectors 64 of the superpixel 72. In an embodiment, at least one of the collectors 64 in the subset is approximately coincident and / or overlapped with the geometric center. Therefore, the control system provides an active collector 64 that is approximately centered within the superpixel 72. This can help provide spatially uniform collection efficiency within each superpixel 72.

[0097] In an embodiment, Fig.12 and Fig.14 As illustrated in , when implementing the low-resolution mode, the control system 70 is also configured to apply an intermediate equipotential along the intermediate paths 66C, 66D. The intermediate paths 66C, 66D surround a subset of the pixel substrates 63 of the superpixel 72. The subset includes a plurality of pixel substrates 63. The intermediate equipotential has a potential between the external equipotential (along path 66A) and the internal equipotential (along path 66B). Fig.12 In the example, two intermediate equal potentials are applied along corresponding intermediate paths 66C and 66D, but more or less than two intermediate paths may be provided. Potentials are applied to the paths (66A, 66B, 66C, 66D and any other paths defining equal potentials) to define a potential gradient toward one or more active collectors 64 to enhance collection efficiency and / or frame rate. An example potential gradient along line BB' is depicted at Fig.13 The constant gradient towards the center of the superpixel 72 defines a uniform electric field.

[0098] In an embodiment, the low-resolution mode includes a plurality of sub-modes. Each of the sub-modes is such that in each sub-mode, a subset of the collectors for collecting charge carriers in each superpixel 72 (i.e., Fig.11 , Fig.12 and Fig.14 The active collectors shown by the filled black circles in the figure include different numbers of collectors. Each superpixel 72 using a different number of active collectors can provide different collection capacitances in each sub-mode. Providing the ability to switch between sub-modes of different properties can make it possible to adapt to changes in the flux of target radiation. For example, a sub-mode with a larger number of active collectors per superpixel 72 can be selected for relatively large radiation flux. A sub-mode with a smaller number of active collectors 64 per superpixel 72 (e.g., a single active collector 64 per superpixel 72) can be selected for relatively small radiation flux. Fig.12An example sub-mode is depicted having a single active collector per superpixel 72, which may be suitable for relatively low radiation fluxes. Fig.14 An example sub-mode is depicted having seven active collectors 64 per superpixel 72, which may be suitable for larger radiation fluxes.

[0099] In some embodiments, the mapping of the low-resolution mode is configured to provide a plurality of substantially identical superpixels 72, each superpixel 72 optionally including the same number of pixel elements 62. In other embodiments, the mapping of the low-resolution mode may provide different resolution zones. Such a low-resolution mode may be referred to as a mixed resolution mode. The different resolution zones may include individual pixel elements and / or superpixels having different sizes. Alternatively or additionally, the different resolution zones may be provided by pixel elements 62 of different sizes. The different resolution zones may have different ratios of pixel elements to collectors 64 (active collectors 64) configured to collect charge carriers. For example, one or more zones may have a 1:1 ratio of pixel elements 62 to collectors 64 configured to collect charge carriers (i.e., providing high spatial resolution), and one or more other zones may have an N:1 ratio of pixel elements 62 to active collectors 64, where N is equal to or greater than 2. The zone having an N:1 ratio of pixel elements 62 to active collectors 64 may provide a lower spatial resolution. This arrangement may be useful in situations where it is expected that the information of greatest interest will be located in a particular region of the image captured by the detector 60 (such as in a central region), and other regions of the image (such as peripheral regions) may be less valuable. Thus, the different resolution regions may include a central region and one or more peripheral regions, wherein the central region is configured to have a higher resolution than one or all of the one or more peripheral regions. The control system 70 may use the ability to spatially vary the resolution to enhance the resolution of the portion of the detector 60 corresponding to the region of interest and reduce the resolution in other regions, thereby reducing data transmission requirements, thereby enhancing the frame rate and / or reducing power consumption. For example, the different resolution regions may include a higher flux region (e.g., a central region) having a higher resolution and one or more lower flux regions (e.g., one or more peripheral regions) having a lower resolution. In use, the flux of the target radiation is higher in the higher flux region than in the one or more lower flux regions. Thus, the region of interest where the resolution is to be enhanced may correspond to a region where a higher flux of the target radiation is expected and / or occurs.

[0100] The geometric arrangement of the pixel elements 62 is not particularly limited. In some embodiments, the pixel bases 63 of the pixel elements 62 are arranged in a mosaic pattern to provide efficient space filling. In some embodiments, the pixel bases 63 are hexagonal, such as Figures 10 to 14, as illustrated in . This provides good spatial filling and facilitates grouping the pixel elements 62 into roughly circular superpixels 72. This can facilitate the generation of a roughly uniform electric field for the superpixel 72, which can improve spatial uniformity performance, such as uniform collection efficiency and good readout speed, as well as facilitate the routing of electrical connections to provide control electrodes. In the example shown, all pixel substrates 63 are the same size. This can facilitate providing spatial uniformity performance. In other embodiments, the pixel substrates 63 can have a range of different sizes (e.g., two or more different sizes). In the case of a hexagonal array of pixel elements 62, roughly circular superpixels 72 can be obtained by grouping the pixels into hexagonal shapes (e.g., Fig.11 , Fig.12 and Fig.14 ). Progressively larger superpixels 72 can be obtained by progressively adding rings of pixel elements 62 around a single starting pixel element 62. The total number of pixel elements 62 in such a hexagonal superpixel 72 will be given by the formula for the number of centered hexagons: Therefore, in Fig.10 and Fig.11 In the example of FIG. 5 , the superpixel 72 includes 7 pixel elements 62 (corresponding to n=2 in the formula), and Fig.12 and Fig.14 In the example of , the superpixel 72 includes 37 pixel elements 62 (corresponding to n=4 in the formula).

[0101] In other embodiments, the pixel elements 62 may have other shapes and / or arrangements. For example, the pixel elements 62 may be regular or irregular polygons having fewer than or more than six sides, including rectangles and squares, or may be circular or elliptical.

[0102] Fig.15 Schematically depicts an example routing of electrical connections to the control electrodes of three superpixels 72 in an active pixel region 74. Superpixels 72 each have control electrodes that provide three different equipotentials along three paths 66A, 66B, and 66C, as described above with reference to Fig.14 As described. In such a particular example, different equipotentials are independently controlled via voltages V1, V2, and V3 applied in the peripheral region 76. As indicated by the solid line, dotted line, and dashed line, respectively, voltage V1 corresponds to path 66A, voltage V2 corresponds to path 66C, and voltage V3 corresponds to path 66B. Routing can be provided by a pure metal path or a combination of metal and semiconductor (such as polysilicon) to allow smooth control of voltage via resistive voltage drop. Highly doped paths of semiconductors can be used to provide conduction. Semiconductor materials (such as polysilicon) can be used to implement equipotentials in which there is negligible current.

[0103] In an embodiment, partially or fully enclosed shallow or deep trench isolations are provided between pixel elements 62 .

[0104] In some embodiments, the voltage applied to control electrode 66 can be controlled using a potential divider arrangement. Using a potential divider arrangement can facilitate routing requirements. For example, in one arrangement, a high resistance element (such as a polysilicon strip) can be connected between a reference voltage (e.g., ground) and one of control electrodes 66 (e.g., Fig.12 The voltage will vary smoothly between the voltages applied at either end as a function of position along the strip. Any desired intermediate voltage can be obtained by branching electrical connections from the strip at appropriate locations. Fig.12 As an illustration, if one end of the strip is connected to ground and the other end is connected to control electrode 66B, the voltages for control electrodes 66D, 66C and 66A can be obtained via various branch connections at locations along the strip that are progressively further away from control electrode 66B.

[0105] Alternatively or additionally, a diode arrangement may be used to provide the different voltages. For example, this may be implemented using a MOSFET configured to act as a diode. Such diodes may be arranged in series along an overall path similar to the high resistance strips discussed above. For example, the series diodes may be connected to Fig.12 The connection to the intermediate control electrodes 66C and 66D can be made from locations in the series diodes between different corresponding diode pairs. An example configuration is schematically depicted in Fig.16 The examples shown are based on Fig.12 66A (on the left). Voltage V1 is applied at control electrode 66B and, as explained below, can be used to control the voltage at all other control electrodes connected to the series arrangement of diodes. Thus, a single voltage connection can provide control of multiple different control electrodes 66, which facilitates routing requirements. In the example shown, the voltage at control electrode 66D is labeled V2, the voltage at control electrode 66C is labeled V3, and the voltage at control electrode 66A is labeled V4.

[0106] Each diode 78 operates to isolate one side of the diode from the other side of the diode (i.e., to operate in a blocking mode) unless the voltage applied across the diode is of the correct polarity and magnitude above the minimum threshold voltage Vt of the diode 78 (in which case the diode operates in a forward mode and conducts electricity). Fig.16In the example of FIG. 1 , if the voltage V1 applied to control electrode 66B is less than Vt, diode 78DB will be in blocking mode and there will be no connection to any of control electrodes 66D, 66C and 66A. All control electrodes 66 are isolated from each other. In such a case, pixel element 62 can be in a state corresponding to Fig.10 The pixel is operated in a high resolution mode similar to the case in FIG. 6 , where the charge carriers are confined to move within the pixel substrate 63 where they are generated. In this mode, all collector electrodes 64 are active.

[0107] Increasing V1 above Vt will allow pixel elements 62 to be merged into superpixels 72. The magnitude of V1 determines the number of control electrodes 66 that are energized, and therefore determines the size of superpixels 72. For example, if Vt=1V, increasing V1 to 1.5V will make diode 78DB between control electrodes 66D and 66B conductive, which will change V2 to 0.5V. The potential difference across the next diode 78CD (between control electrodes 66C and 66D) will be lower than Vf and will therefore be in blocking mode. Therefore, applying 1.5V to control electrode 66B will power control electrode 66B and the next control electrode 66D. Seven pixel elements 62 are merged to produce superpixels 72, and a suitable electric field is established to guide charge carriers toward a single collector 64 at the center of superpixel 72. Increasing the voltage applied to control electrode 66B to above 2V, for example to 2.5V, will cause the lower control electrode 66C to be energized (where V3 = 0.5V, V2 = 1.5V and V1 = 2.5V), which can be used to merge 19 pixel elements together into a single superpixel 72. Increasing the voltage applied to control electrode 66B to above 3V, for example to 3.5V, will cause the next control electrode 66A to be energized (where V4 = 0.5V, V3 = 1.5V, V2 = 2.5V and V1 = 3.5V), which can be used to merge 37 pixel elements together into a single superpixel 72.

[0108] Detectors according to the embodiments described above provide enhanced flexibility for changing resolution and other operating parameters. This means that the same detector can be effectively used in a wider range of scenarios than might be possible without the described functionality. The need to use multiple different detectors can be avoided, thereby saving cost and / or space. The enhanced flexibility can be particularly effectively utilized in the context of evaluation systems used in lithography, such as for checking samples for defects or for measuring structures to obtain information about performance (such as, overlay or CD). These processes can use a variety of different types of radiation, including charged particles (e.g., for SEM or similar processes) and electromagnetic radiation (e.g., for optical measurements), and / or require different resolutions, speeds (frame rates), fields of view (FOVs), and / or full well potentials. Detectors according to the embodiments disclosed herein can be controlled to change these operating parameters, thereby providing suitable operating properties for the application being addressed.

[0109] In an embodiment, an evaluation system is provided, the evaluation system comprising both: a charged particle device configured to expose a sample to charged particles; and an optical measurement system configured to expose the sample to electromagnetic radiation. The charged particle device (e.g., an electron optical column) may be present as described above with reference to Figures 1 to 7 Any of the forms described or other forms. The optical measurement system may be in the form of Figure 8 Any form or other forms in the described forms. In such an arrangement, the detector 60 according to any of the embodiments described herein can be configured to receive charged particles propagated from the sample 208 to the detector 60 due to the charged particle device exposing the sample 208 with charged particles. For example, the detector 60 can be used to perform any of the functions of the detector 240 and / or the detector module 402 mentioned above. The same detector 60 can be configured to receive electromagnetic radiation propagated from the sample 208 to the detector due to the optical measurement system exposing the sample with electromagnetic radiation. For example, the detector 60 can be used to perform any of the functions of the sensors 19 and 23 mentioned above. The control system 70 can be configured to select different resolution modes to detect charged particles and electromagnetic radiation respectively. For example, the control system 70 can select a first resolution mode to detect charged particles, and select a second resolution mode different from the first resolution mode to detect electromagnetic radiation. Compared to the second resolution mode, the first resolution mode can generally be a lower resolution mode involving the use of fewer collectors. The first resolution mode may be faster, and / or provide a larger field of view (FOV), and / or involve lower power consumption than the second resolution mode.

[0110] Reference to a component or system or element of a component that can be controlled to manipulate a charged particle beam in a certain manner includes configuring a controller or control system or control unit to control the component to manipulate the charged particle beam in the manner described, and optionally using other controllers or devices (e.g., voltage supplies and / or current supplies) to control the component to manipulate the charged particle beam in this manner. For example, a voltage supply can be electrically connected to one or more components to apply a potential to the component, such as a component in a non-limiting list including control lens array 250, objective lens array 241, and detector array 240.

[0111] References to upper and lower, upward and downward, above and below, etc. should be understood to refer to directions parallel to the (typically, but not necessarily always, vertical) beam upstream and beam downstream of the charged particle beam impinging on the sample 208. Thus, references to beam upstream and beam downstream are intended to refer to directions about the beam path that are independent of any gravitational field that is present.

[0112] The electron-optical device described herein may be in the form of a series of hole arrays or electron-optical elements arranged in an array along a beam or multi-beam path. Such electron-optical elements may be electrostatic. In an embodiment, for example, all electron-optical elements from the beam-limiting hole array to the last electron-optical element in the beam path before the sample may be electrostatic, and / or may be in the form of a hole array or a plate array. In some arrangements, one or more of the electron-optical elements are manufactured as a micro-electromechanical system (MEMS) (i.e., using MEMS manufacturing technology). The electron-optical element may have a magnetic element and an electrostatic element. For example, a composite array lens may be characterized by a giant magnetic lens covering a multi-beam path, having an upper pole plate and a lower pole plate arranged within the magnetic lens and along the multi-beam path. In the pole plate may be an array of holes for the beam path of the multi-beam. Electrodes may be present above, below, or between the pole plates to control and optimize the electromagnetic field of the composite lens array.

[0113] Evaluation devices, tools, or systems according to the present disclosure may include devices that perform qualitative evaluations of samples (e.g., pass / fail), devices that perform quantitative measurements of samples (e.g., size of features), or devices that produce mapped images of samples. Examples of evaluation devices, tools, or systems are inspection tools (e.g., for identifying defects), review tools (e.g., for classifying defects), and metrology tools, or tools that are capable of performing any combination of evaluation functions associated with inspection tools, review tools, or metrology tools (e.g., metrology inspection tools).

[0114] The function provided by the controller or control system or control unit can be implemented by a computer.Any suitable combination of elements can be used to provide the desired function, including for example CPU, RAM, SSD, mainboard, network connector, firmware, software and / or other elements known in the art that allow the required computing operations to be performed.The required computing operations can be limited by one or more computer programs.One or more computer programs can be provided in the form of a medium storing computer-readable instructions, optionally a non-temporary medium.When the computer-readable instructions are read by a computer, the computer performs the required method steps.The computer can be composed of a self-contained unit or a distributed computing system with a plurality of different computers connected to each other via a network.

[0115] Although the present invention has been described in conjunction with various embodiments, other embodiments of the present invention will be apparent to those skilled in the art from consideration of this specification and practice of the invention disclosed herein. It is intended that the present specification and examples be considered exemplary only, with the true scope and spirit of the present invention being indicated by the following claims and aspects.

[0116] Embodiments of the present disclosure are defined in the following numbered aspects.

[0117] 1. A detector for detecting radiation, comprising:

[0118] a plurality of pixel elements, the plurality of pixel elements comprising corresponding pixel substrates, collector electrodes, and readout circuitry, wherein the pixel substrates are configured such that impingement of the pixel substrates with target radiation generates charge carriers in the pixel substrates, and the readout circuitry is configured to provide an output responsive to collection of the charge carriers by the corresponding collector electrodes;

[0119] a plurality of control electrodes; and

[0120] A control system configured to implement a plurality of selectable resolution modes by controlling the potentials applied to the control electrode and the collector electrode to define a corresponding plurality of mappings between a pixel substrate generating charge carriers and a collector electrode collecting those charge carriers.

[0121] 2. A detector according to aspect 1, wherein each of said mappings causes a corresponding different number of said collectors to be used to collect charge carriers from all said pixel elements.

[0122] 3. A detector according to aspect 1 or 2, wherein the resolution mode includes a high-resolution mode defined by a one-to-one mapping between the pixel substrate and the collector, wherein the one-to-one mapping causes the charge carriers generated in each pixel substrate to be collected by the collector of the same pixel substrate.

[0123] 4. A detector according to aspect 3, wherein the control system is configured to achieve the high-resolution mode by applying an equal potential to the control electrode along a path that separates all of the pixel substrates from each other when viewed perpendicular to the plane of the detector.

[0124] 5. A detector according to aspect 4, wherein the control system is configured in the high resolution mode to apply a common potential to all of the collecting electrodes.

[0125] 6. A detector according to any of the preceding numbered aspects, wherein the resolution mode includes a low-resolution mode, the low-resolution mode being defined by a mapping in which at least a subset of the pixel elements are grouped to form corresponding superpixels, and the charge carriers generated in all the pixel substrates of each superpixel are collected only by a subset of collectors in the pixel elements of the superpixel, the subset consisting of a single collector, or a plurality of collectors less than all the collectors of the pixel elements corresponding to the superpixel.

[0126] 7. A detector according to aspect 6, wherein the control system is configured to limit the mapping of the low-resolution pattern by controlling the potential of the control electrode and the collector to allow charge carriers to flow between pixel bases of each superpixel while remaining within the corresponding superpixel.

[0127] 8. A detector according to clause 6 or 7, wherein the control system is configured to define, for each superpixel, a mapping of the low-resolution pattern when viewed perpendicular to the plane of the detector by:

[0128] An external equipotential is applied along a control electrode defining an external path surrounding the substrate of all pixels of the superpixel.

[0129] 9. The detector of aspect 8, wherein when defining the mapping of the low-resolution mode, the control system is further configured to:

[0130] An internal equipotential different from the external equipotential is applied to a control electrode defining an internal path of at least one of the pixel substrates surrounding the superpixel.

[0131] 10. The detector of clause 9, wherein the internal path surrounds a pixel substrate of a pixel element comprising a collector or at least one collector in a subset of the collectors.

[0132] 11. A detector according to aspect 9 or 10, wherein:

[0133] The outer path defines a shape having a geometric center; and

[0134] At least one collector in the subset of the collectors of the superpixel is closer to the geometric center than all other collectors of the superpixel.

[0135] 12. A detector according to clause 11, wherein the subset consists of the single collector and the single collector is closer to the geometric center than all other collectors of the superpixel.

[0136] 13. A detector according to any one of aspects 9 to 12, wherein when defining the mapping of the low resolution mode, the control system is further configured to:

[0137] An intermediate equipotential is applied along an intermediate path of a subset of pixel substrates surrounding the superpixel, the subset comprising a plurality of pixel substrates, wherein the intermediate equipotential has a potential between that of the outer equipotential and that of the inner equipotential.

[0138] 14. A detector according to any one of aspects 6 to 13, wherein the low-resolution mode includes multiple sub-modes, each sub-mode being configured so that a subset of collectors for collecting charge carriers in each superpixel includes a different number of collectors in each sub-mode, thereby providing different corresponding collection capacitors in each sub-mode.

[0139] 15. A detector according to any one of aspects 6 to 14, wherein the mapping of the low-resolution pattern is configured to provide different resolution areas, the different resolution areas comprising individual pixel elements and / or superpixels having different sizes.

[0140] 16. The detector of aspect 15, wherein the different resolution zones include a central zone and one or more peripheral zones, wherein the central zone is configured to have a higher resolution than one or all of the one or more peripheral zones.

[0141] 17. The detector according to any of the preceding numbered aspects, wherein the pixel substrates of the pixel elements are provided in a mosaic pattern.

[0142] 18. The detector of clause 17, wherein each of the pixel bases is hexagonal.

[0143] 19. A detector according to any preceding aspect, wherein the pixel bases are all of the same size.

[0144] 20. A detector according to any one of aspects 1 to 18, wherein the pixel substrates have a range of different sizes.

[0145] 21. An evaluation system comprising:

[0146] a charged particle device configured to expose the sample with charged particles;

[0147] an optical measurement system configured to expose the sample with electromagnetic radiation; and

[0148] According to any one of the aforementioned numbered aspects, the detector is configured to receive charged particles propagating from the sample to the detector due to exposure of the sample to charged particles, and to receive electromagnetic radiation propagating from the sample to the detector due to exposure of the sample to electromagnetic radiation, wherein the control system is configured to select different resolution modes for detecting the charged particles and the electromagnetic radiation, respectively.

[0149] 22. A method for detecting radiation, comprising:

[0150] applying a potential to a control electrode and a collector electrode in a plurality of pixel elements, the plurality of pixel elements comprising a corresponding pixel substrate, a collector electrode, and a readout circuit, wherein:

[0151] Irradiation of the pixel substrate with target radiation generates charge carriers in the pixel substrate,

[0152] The readout circuitry provides an output responsive to collection of the charge carriers by the corresponding collector, and

[0153] The method detects radiation in a plurality of resolution modes, each resolution mode being defined by controlling the potentials applied to the control electrode and the collector electrode to define a corresponding mapping between a pixel substrate generating charge carriers and a collector electrode collecting those charge carriers.

[0154] 23. A method according to aspect 22, wherein:

[0155] The resolution mode includes a first resolution mode and a second resolution mode different from the first resolution mode;

[0156] The first resolution mode is used to detect charged particles; and

[0157] The second resolution mode is used to detect electromagnetic radiation.

[0158] 24. The method of clause 23, wherein the first resolution mode is a lower resolution mode involving the use of fewer collector electrodes than the second resolution mode.

[0159] 25. A method according to any one of aspects 22 to 24, wherein the resolution mode comprises a mixed resolution mode in which the mapping provides different resolution regions, the different resolution regions comprising a higher flux region and a lower flux region, wherein:

[0160] The target radiation has a higher flux in the higher flux region than in the lower flux region; and

[0161] The resolution is higher in the higher flux region than in the lower flux region.

Claims

1. A detector for detecting radiation, comprising: a plurality of pixel elements, the plurality of pixel elements comprising corresponding pixel substrates, collector electrodes, and readout circuitry, wherein the pixel substrates are configured such that impingement of the pixel substrates with target radiation generates charge carriers in the pixel substrates, and the readout circuitry is configured to provide an output responsive to collection of the charge carriers by the corresponding collector electrodes; a plurality of control electrodes; as well as A control system configured to implement a plurality of selectable resolution modes by controlling the potentials applied to the control electrode and the collector electrode to define a corresponding plurality of mappings between a pixel substrate generating charge carriers and a collector electrode collecting those charge carriers.

2. The detector of claim 1, wherein each of said mappings causes a corresponding different number of said collectors to be used to collect charge carriers from all of said pixel elements.

3. A detector according to claim 1 or 2, wherein the resolution mode includes a high-resolution mode defined by a one-to-one mapping between the pixel substrate and the collector, wherein the one-to-one mapping causes the charge carriers generated in each pixel substrate to be collected by the collector of the same pixel substrate.

4. A detector according to claim 3, wherein the control system is configured to achieve the high-resolution mode by applying an equal potential to the control electrode along a path that separates all of the pixel substrates from each other when viewed perpendicular to the plane of the detector.

5. The detector of claim 4, wherein the control system is configured in the high resolution mode to apply a common potential to all of the collecting electrodes.

6. A detector according to any of the preceding claims, wherein the resolution mode includes a low-resolution mode, the low-resolution mode being defined by a mapping in which at least a subset of the pixel elements are grouped to form corresponding superpixels, and the charge carriers generated in all the pixel substrates of each superpixel are collected only by a subset of collectors in the pixel elements of the superpixel, the subset consisting of a single collector, or a plurality of collectors less than all the collectors of the pixel elements corresponding to the superpixel.

7. A detector according to claim 6, wherein the control system is configured to limit the mapping of the low-resolution pattern by controlling the potential of the control electrode and the collector to allow charge carriers to flow between pixel bases of each superpixel while remaining within the corresponding superpixel.

8. A detector according to claim 6 or 7, wherein the control system is configured to define, for each superpixel, a mapping of the low-resolution pattern when viewed perpendicular to the plane of the detector by: An external equipotential is applied along a control electrode defining an external path surrounding the substrate of all pixels of the superpixel.

9. The detector of claim 8, wherein the control system is further configured to, when defining the mapping of the low-resolution mode: applying an internal equipotential different from the external equipotential to a control electrode defining an internal path of at least one of the pixel substrates surrounding the superpixel, Optionally, the internal path surrounds a pixel substrate of a pixel element including a collector in a subset of the collectors or at least one collector.

10. The detector according to claim 9, wherein: The outer path defines a shape having a geometric center; and at least one collector in the subset of collectors of the superpixel is closer to the geometric center than all other collectors of the superpixel, Optionally, the subset consists of the single collector, and the single collector is closer to the geometric center than all other collectors of the superpixel.

11. The detector according to claim 9 or 10, wherein the control system is further configured to, when defining the mapping of the low-resolution mode: An intermediate equipotential is applied along an intermediate path of a subset of pixel substrates surrounding the superpixel, the subset comprising a plurality of pixel substrates, wherein the intermediate equipotential has a potential between that of the outer equipotential and that of the inner equipotential.

12. A detector according to any one of claims 6 to 11, wherein the low-resolution mode comprises a plurality of sub-modes, each sub-mode being configured such that a subset of collectors for collecting charge carriers in each superpixel comprises a different number of collectors in each sub-mode, thereby providing different corresponding collection capacitances in each sub-mode.

13. A detector according to any one of claims 6 to 12, wherein the mapping of the low-resolution mode is configured to provide different resolution zones, the different resolution zones comprising individual pixel elements and / or superpixels having different sizes, wherein optionally, the different resolution zones comprise a central zone and one or more peripheral zones, wherein the central zone is configured to have a higher resolution than one or all of the one or more peripheral zones.

14. An evaluation system comprising: a charged particle device configured to expose the sample with charged particles; an optical measurement system configured to expose the sample with electromagnetic radiation; and A detector according to any of the preceding claims, the detector being configured to receive charged particles propagating from the sample to the detector due to exposure of the sample with charged particles, and to receive electromagnetic radiation propagating from the sample to the detector due to exposure of the sample with electromagnetic radiation, wherein the control system is configured to select different resolution modes for detecting the charged particles and the electromagnetic radiation, respectively.

15. A method for detecting radiation, comprising: applying a potential to a control electrode and a collector electrode in a plurality of pixel elements, the plurality of pixel elements comprising a corresponding pixel substrate, a collector electrode, and a readout circuit, wherein: Irradiation of the pixel substrate with target radiation generates charge carriers in the pixel substrate, The readout circuitry provides an output responsive to collection of the charge carriers by the corresponding collector, and The method detects radiation in a plurality of resolution modes, each resolution mode being defined by controlling the potentials applied to the control electrode and the collector electrode to define a corresponding mapping between a pixel substrate generating charge carriers and a collector electrode collecting those charge carriers.

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