Registration determination method and computer program

Abstract

The invention relates to a method for determining an alignment of an electron-optical component in a charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to beamlets passing through a corresponding aperture in the aperture array, the method comprising: scanning each beamlet in a plane of the aperture array over a portion of the aperture array in which a corresponding aperture of the aperture array is defined, thereby allowing the charged particles of each beamlet to pass through the corresponding aperture, detecting any charged particles corresponding to each beamlet passing through the corresponding aperture during the scan, generating detection pixels for each beamlet based on the detection of the charged particles corresponding to each beamlet per time interval of the scan, and collecting information contained in the detection pixels, such as the intensity of the charged particles.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Patent Application No. 21217750.5, filed December 24, 2021, the entire contents of which are incorporated by reference into this specification.

[0002] FIELD OF THE DISCLOSURE

[0002] Embodiments provided herein generally relate to methods and computer programs for determining alignment of electron optical components capable of acting on multiple beamlets in a charged particle device. [Background technology]

[0003]

[0003] When manufacturing semiconductor integrated circuit (IC) chips, undesirable pattern defects often occur on substrates (i.e., wafers) or masks during the manufacturing process, thereby reducing yields. Such defects can arise, for example, as a result of optical effects and associated particles, as well as in subsequent processing steps such as etching, deposition, or chemical-mechanical polishing. Thus, monitoring the extent of undesirable pattern defects is an important process in the manufacture of IC chips. More generally, inspection and / or measurement (or together evaluation) of the surface of a substrate or other object / material is an important process during and / or after its manufacture.

[0004]

[0004] Charged particle beam pattern inspection tools are used to inspect objects, for example to detect pattern defects. These tools typically use electron microscopy techniques, such as scanning electron microscopes (SEMs). In an SEM, a primary electron beam (or primary beam) of relatively high energy electrons is targeted with a final deceleration step to land on a sample with a relatively low landing energy. The electron beam is focused as a probing spot on the sample. Interaction of the landing electrons from the electron beam with the material structure at the probing spot causes signal electrons, such as secondary electrons, backscattered electrons or Auger electrons, to be emitted from the surface. The generated signal electrons can be emitted from the material structure of the sample. Scanning the primary beam as a probing spot across the sample surface can cause signal electrons (or signal particles) to be emitted across the surface of the sample. By collecting these emitted signal electrons (or signal particles) from the sample surface, the pattern inspection tool can obtain an image that represents the characteristics of the material structure of the surface of the sample.

[0005]

[0005] There is a general need to improve the throughput and other characteristics of charged particle characterization devices. In particular, the alignment of various elements of the charged particle characterization device must be determined and, if necessary, corrected. This is a time-consuming process and needs to be improved. Summary of the Invention

[0006]

[0006] Embodiments provided herein disclose a method and computer program for determining the alignment of an electron optical component capable of acting on multiple beamlets in a charged particle device.

[0007] According to a first aspect of the present invention, there is provided a method for determining alignment of an electron-optical component operable on a plurality of beamlets in a charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to the beamlets passing through corresponding apertures in the aperture array, the detector being positioned on a down beam side relative to the aperture array along a path of the beamlets, the method comprising: scanning each beamlet in the plane of the aperture array over a portion of the aperture array, where a corresponding aperture of the aperture array is defined such that charged particles of each beamlet pass through the corresponding aperture; Detecting any charged particles corresponding to each beamlet passing through a corresponding aperture during the scan; generating a detection pixel for each beamlet based on detection of the charged particles corresponding to each beamlet for each time interval of the scan; Collecting information contained in the detection pixels, such as the intensity of the charged particles Includes.

[0008]

[0008] According to a second aspect of the present invention, there is provided a computer program comprising instructions for determining an alignment of an electron-optical component operable on a plurality of beamlets in a charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to the beamlets passing through corresponding apertures in the aperture array, the detector being positioned on a down beam side relative to the aperture array along a path of the beamlets, the computer program comprising instructions, the instructions comprising: controlling the charged particle device to scan each beamlet in the plane of the aperture array over a portion of the aperture array where a corresponding aperture of the aperture array is defined such that the charged particles of each beamlet pass through the corresponding aperture; controlling the charged particle device to detect any charged particle corresponding to each beamlet passing through a corresponding aperture during the scan; generating a detection pixel for each beamlet based on detection of the charged particles corresponding to each beamlet for each time interval of the scan; Collect information contained in the detection pixels, such as the intensity of the charged particles It is configured as follows.

[0009]

[0009] The above and other aspects of the present disclosure will become more apparent from the following description of exemplary embodiments taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus. [Diagram 2]

[0011] 2 is a schematic diagram illustrating an example multi-beam device that is part of the example charged particle beam evaluation device of FIG. 1. [Diagram 3]

[0012] 1 is a schematic diagram of an exemplary multi-beam device according to one embodiment. [Figure 4]

[0013] 2 is a schematic cross-sectional view of an objective lens of an evaluation apparatus according to one embodiment. FIG. [Diagram 5]

[0014] FIG. 5 is a bottom view of the objective lens of FIG. [Figure 6]

[0015] FIG. 5 is a bottom view of a modified embodiment of the objective lens of FIG. [Figure 7]

[0016] FIG. 5 is an enlarged schematic cross-sectional view of a detector incorporated in the objective lens of FIG. [Figure 8]

[0017] 1 is a schematic diagram of an exemplary multi-beam device according to one embodiment. [Figure 9]

[0018] FIG. 2 is a schematic diagram illustrating an exemplary multi-beam device according to an embodiment operating in an evaluation and calibration mode. [Figure 10]1 is a schematic diagram illustrating an exemplary multi-beam device according to an embodiment operating in an evaluation and calibration mode. [Figure 11A]

[0019] 2 is a schematic diagram of a detector array and associated cell array according to one embodiment. [Figure 11B] 1 is a schematic diagram of a cell of a cell array and a cell of the cell array according to one embodiment; [Figure 12]

[0020] 1 is a schematic cross-sectional view of a wiring route illustrating a circuit wire and shielding configuration according to one embodiment. [Figure 13]

[0021] FIG. 1 is a schematic diagram of a charged particle device with misaligned electron optical components. [Figure 14]

[0022] FIG. 1 is a schematic diagram of a charged particle device in which multiple beamlets are scanned over an aperture array. [Figure 15]

[0023] FIG. 1 is a schematic diagram of a beamlet being scanned on the XY plane of an aperture array. [Figure 16]

[0024] 1 is an exemplary image based on a number of detected pixels representing intensities of charged particles corresponding to beamlets. [Figure 17]

[0025] 1 is an exemplary composite image based on multiple images, showing the intensity of charged particles corresponding to multiple beamlets. [Figure 18]

[0026] 1 is an exemplary beamlet scanning pattern. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0027] 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, in which the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present invention. Instead, the implementations are merely examples of apparatus and methods consistent with related aspects of the present invention, as described in the appended claims.

[0012]

[0028] Increases in the computational power of electronic devices, which reduces the physical size of the device, can be achieved by greatly increasing the packing density of circuit components such as transistors, capacitors, and diodes on an IC chip. This has been made possible by improvements in resolution that allow for the creation of even smaller structures. For example, an IC chip in a smartphone the size of a thumbnail and available before 2019 can contain over 2 billion transistors, each transistor less than 1 / 1000 the size of a human hair. It is therefore not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. An error in even one step can dramatically affect the functionality of the final product. Only one defect can cause the device to fail. The goal of a manufacturing process is to improve the overall yield of the process. For example, to obtain a 75% yield for a process with 50 steps (where a step can refer to the number of layers formed on a wafer), the individual steps must have a yield of greater than 99.4%. If each individual step had a yield of 95%, the overall process yield would be as low as 7%.

[0013]

[0029] In IC chip manufacturing facilities, while high process yields are desirable, 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 can be affected by the presence of defects. This is especially true when operator intervention is required to investigate the defects. Thus, high throughput detection and identification of micro- and nano-scale defects by characterization tools, such as scanning electron microscopes ("SEMs"), is essential to maintain high yields and low costs.

[0014]

[0030] The SEM includes a scanning device and a detector device. The scanning device includes, for example, an illumination device including an electron source for generating primary electrons of a source beam (or primary beam) and a projection device for scanning a sample, such as a substrate, with one or more focused beams of primary electrons. Together, at least the illumination device or illumination system and the projection device or projection system may be jointly referred to as an electron optical system or device. The primary electrons interact with the sample and generate secondary electrons. The detector device captures the secondary electrons from the sample as it is scanned so that the SEM can generate an image of the scanned area of ​​the sample. The detector device may comprise semiconductor elements such as PIN detector elements, charge detector elements such as capture electrodes, and / or electron-to-photon converter elements such as scintillators. For high throughput inspection, some evaluation devices use multiple focused beams of primary electrons, i.e. multibeams. The component beams of the multibeam may be referred to as sub-beams or beamlets. The multibeams can scan different parts of the sample simultaneously. Thus, multibeam evaluation devices can inspect samples much faster than single-beam evaluation devices.

[0015]

[0031] Known implementations of multi-beam evaluation devices are described below.

[0016]

[0032] The drawings are schematic. Thus, the relative dimensions of the components in the drawings are exaggerated for clarity. In the following description of the drawings, the same or similar reference numbers refer to the same or similar components or entities, and only the differences to the individual embodiments are described. Although the description and drawings are directed to an electro-optical device, it is understood that the embodiments are not used to limit the present disclosure to a particular charged particle. Thus, throughout this specification, references to electrons can be considered to be references to charged particles more generally, and charged particles are not necessarily electrons.

[0017]

[0033] Reference is now made to Figure 1, which is a schematic diagram illustrating an exemplary charged particle beam characterization apparatus 100. The charged particle beam characterization apparatus 100 (or charged particle beam device 100) of Figure 1 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, a front-end equipment module (EFEM) 30, and a controller 50. The electron beam device 40 is located within the main chamber 10.

[0018]

[0034] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include one or more additional load ports. The first load port 30a and the second load port 30b may receive, for example, a substrate front-opening integrated pod (FOUP) that contains a substrate (e.g., a semiconductor substrate or a substrate made of other material) or a sample to be inspected (hereinafter, substrates, wafers and samples are collectively referred to as "samples"). One or more robotic arms (not shown) in the EFEM 30 transport the sample to the load lock chamber 20.

[0019]

[0035] The load lock chamber 20 is used to remove gas from around the sample. This creates a vacuum, which is a local gas pressure lower than the pressure of the surrounding environment. The load lock chamber 20 may be connected to a load lock vacuum pumping system (not shown), which removes gas particles in the load lock chamber 20. Operation of the load lock vacuum pumping system allows the load lock chamber to reach a first pressure below atmospheric pressure. After the first pressure is reached, one or more robotic 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 pumping system (not shown). The main chamber vacuum pumping system removes gas particles in the main chamber 10 such that the pressure around the sample reaches a second pressure below the first pressure. After the second pressure is reached, the sample is transported to an electron beam tool, where the sample can be inspected by the electron beam tool. The electron beam device 40 may include a multi-beam electron optical device.

[0020]

[0036] The controller 50 is electronically connected to the electron beam device 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle beam device 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although in FIG. 1 the controller 50 is shown as being external to the structure including the main chamber 10, the load lock chamber 20 and the EFEM 30, it is understood that the controller 50 may be part of the structure. The controller 50 may be located within one of the component elements of the charged particle beam evaluation device, or the controller 50 may be distributed among at least two of the component elements. It is noted that although the present disclosure provides an example of a main chamber 10 housing an electron beam evaluation tool, aspects of the present disclosure are not limited in the broad sense to a chamber housing an electron beam evaluation tool. Rather, it is understood that the principles described above may be applied to other tools and other arrangements of the device operating under a second pressure.

[0021]

[0037] Reference is now made to Figure 2, which is a schematic diagram illustrating an exemplary electron beam device 40 including a multi-beam evaluation tool that is part of the exemplary charged particle beam evaluation device 100 of Figure 1. The multi-beam electron beam device 40 (also referred to herein as tool 40) comprises an electron source 201, a projection device 230, a moving stage 209, and a sample holder 207 (which may also be referred to as a sample support). The electron source 201 and the projection device 230 may collectively be referred to as an illumination device. The sample holder 207 is supported by the moving stage 209 to hold a sample 208 (e.g., a substrate or a mask) for inspection. The multi-beam electron beam device 40 further includes a detector device (e.g., an electron detection device 240).

[0022]

[0038] The electron source 201 may include a cathode (not shown) and an extractor or anode (not shown). In 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 anode to form a primary beam 202.

[0023]

[0039] The projection device 230 is configured to convert the primary beam 202 into multiple sub-beams 211, 212, 213 and direct each sub-beam onto the sample 208. Although three sub-beams are shown for simplicity, there may be tens, hundreds, or thousands of sub-beams. The sub-beams may be referred to as beamlets.

[0024]

[0040] The controller 50 may be connected to various parts of the charged particle beam evaluation apparatus 100 of Fig. 1, such as the electron source 201, the electron detection device 240, the projection device 230, and the motorized stage 209. The controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals for controlling the operation of the charged particle beam evaluation apparatus, including the charged particle multi-beam device.

[0025]

[0041] The projection device 230 may be configured to focus the sub-beams 211, 212 and 213 onto the sample 208 for evaluation, forming three probe spots 221, 222 and 223 on the surface of the sample 208. The projection device 230 may be configured to deflect the primary sub-beams 211, 212 and 213 to scan the probe spots 221, 222 and 223 over respective scan areas within a section of the surface of the sample 208. In response to the incidence of the primary sub-beams 211, 212 and 213 on the probe spots 221, 222 and 223 on the sample 208, electrons including secondary electrons and backscattered electrons are generated from the sample 208. The secondary electrons typically have an electron energy of 50 eV or less, and the backscattered electrons typically have an electron energy between 50 eV and the landing energy of the primary sub-beams 211, 212 and 213.

[0026]

[0042] The electron detection device 240 is configured to detect the secondary electrons and / or backscattered electrons (also known as signal particles) and generate corresponding signals, which are transmitted to the controller 50 or a signal processing system (not shown) (e.g., to construct an image of a corresponding scanned area of ​​the sample 208). Preferably, the electron detection device is integrated into the projection apparatus. Alternatively, the electron detection device may be separate therefrom, with a secondary electron optical column being provided to direct the secondary electrons and / or backscattered electrons to the electron detection device.

[0027]

[0043] The controller 50 may include an image processing system including an image acquirer (not shown) and a storage device (not shown). For example, the controller may include a processor, a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer may include at least a portion of the processing functions of the controller. Thus, the image acquirer may include at least one or more processors. The image acquirer may be communicatively coupled to an electronic detection device 240 of the apparatus 40 that allows for signal communication, such as electrical conductors, fiber optic cables, portable storage media, IR, Bluetooth, Internet, wireless networks, wireless radios, or combinations thereof, among others. The image acquirer may receive signals from the electronic detection device 240, process data contained in the signals, and construct an image therefrom. Thus, the image acquirer may acquire an image of the sample 208. The image acquirer may also perform various post-processing functions. The image acquirer may be configured to perform adjustments, such as brightness and contrast, of the acquired image. The storage may be any suitable storage medium. A storage may be coupled with the image acquirer and may be used to store the raw scanned image data as the original image or to store the post-processed image.

[0028]

[0044] The image acquirer may acquire one or more images of the sample based on the imaging signal received from the electronic detection device 240. The imaging signal may correspond to a scanning operation to perform charged particle imaging. The acquired image may be a single image including multiple imaging areas. The single image may be stored in a storage device. The single image may be an original image that may be divided into multiple regions. Each of these regions may include one imaging area that includes a feature of the sample 208. The acquired image may include multiple images of a single imaging area of ​​the sample 208 sampled multiple times over a period of time. The multiple images may be stored in a storage device. The controller 50 may be configured to perform an image processing step using multiple images of the same location of the sample 208.

[0029]

[0045] The controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of detected secondary electrons. The electron distribution data collected during the detection time window, in combination with the corresponding scan path data of each of the primary sub-beams 211, 212 and 213 incident on the sample surface, may be used to reconstruct an image of the sample structure under inspection. 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 the sample.

[0030]

[0046] The controller 50 may control the actuation stage 209 to move the sample 208 during evaluation of the sample 208. The controller 50 may enable the actuation stage 209 to move the sample 208 continuously or discontinuously in one or more selected directions. In some configurations, the movement may be performed at a constant velocity. The movement of the sample 208 may be referred to as scanning. Thus, the scanning may be continuous or discontinuous. The controller 50 may control the movement of the actuation stage 209 such that the actuation stage 209 varies the speed of movement of the sample 208 in response to various parameters. For example, the controller may control the stage velocity (including its direction) in response to characteristics of the evaluation step of the scanning process.

[0031]

[0047] FIG. 3 is a schematic diagram of an evaluation tool including an electron source 201 and an electron optical column (or electron optical device). (In another configuration, the source is part of the electron optical column). The electron optical device comprises a number of electron optical elements. An electron optical element is any element that can affect (e.g., direct, shape, or focus) an electron beam, and can use electric and / or magnetic fields. The electron source 201 directs electrons towards an array of condenser lenses 231 that are part of the electron optical column. The electron source is preferably a high-brightness thermal field emitter with a good compromise between brightness and total emission current. There can be tens, hundreds, or thousands of condenser lenses 231. The condenser lenses 231 can include multi-electrode lenses and can have a structure based on EP 1 602 121 A1, the disclosure of which is incorporated herein by reference, in particular of a lens array for splitting the electron beam into multiple sub-beams (providing one lens per sub-beam). The condenser lens array thus functions as a beam divider, beam splitter, beam generator, or beam separator. The condenser lens array can take the form of at least two plates that function as electrodes, with apertures in each plate aligned with each other and corresponding to the location of the path of the sub-beam. At least two of the plates are maintained at different potentials during operation to achieve the desired lensing effect. The plates thus have an array of apertures, each corresponding to the path of a sub-beam. The plate located most up-beam is the beam separator and can be referred to as the beam limiting aperture. In a different configuration, the beam separator may be part of the condenser lens array or associated with the condenser lens array, with a separate functional form lensing the sub-beam.

[0032]

[0048] In one configuration, the focusing lens array is formed from a three-plate array in which the charged particles have the same energy when they enter and exit each lens, and this configuration can be called an Einzel lens. The beam energy is the same when it enters and leaves the Einzel lens. Thus, dispersion occurs only within the Einzel lens itself (between the entrance and exit electrodes of the lens), thereby limiting off-axis chromatic aberration. If the thickness of the focusing lens is small, e.g., a few mm, the effect of such aberrations is small or negligible.

[0033]

[0049] Each focusing lens in the array directs electrons into a respective sub-beam 211, 212, 213 that is focused at a respective intermediate focus 233. The sub-beams diverge with respect to each other. At the intermediate focus 233 is a deflector 235. The deflector 235 is located in the beamlet path at or at least around the position of the corresponding intermediate focus 233 or focus (i.e., the point of focus). The deflector is located in the beamlet path at the intermediate image plane of the associated beamlet, i.e., at its focus or focus position. The deflector 235 is configured to act on each beamlet 211, 212, 213. The deflector 235 is configured to bend each beamlet 211, 212, 213 by an amount effective to ensure that the main beam (which may also be referred to as the beam axis) is incident on the sample 208 substantially perpendicularly (i.e., at substantially 90° to the nominal surface of the sample). The deflector 235 may be referred to as a collimator or a collimator-deflector. The deflector 235 effectively collimates the paths of the beamlets such that before the deflector the beamlet paths diverge with respect to each other. On the down-beam side of the deflector the beamlet paths are substantially parallel with respect to each other, i.e. substantially collimated. A suitable collimator is the deflector disclosed in European Patent Application No. 20156253.5, filed on February 7, 2020, which is incorporated herein by reference with respect to the application of the deflector to a multi-beam array.

[0034]

[0050] Below the deflector 235 (i.e. on the down-beam side of the electron source 201 or further from the electron source 201) there is a control lens array 250 that includes a control lens 251 for each sub-beam 211, 212, 213. The control lens array 250 may include at least two, for example three, plate electrode arrays in contact with respective potential sources. The function of the control lens array 250 is to optimize the beam opening angle with respect to the beam demagnification ratio and / or to control the beam energy delivered to the objective lenses 234, each of which directs the respective sub-beam 211, 212, 213 onto the sample 208. The objective lenses 234 are in the objective lens array 241. The control lenses prefocus the sub-beams (e.g. apply a focusing action to the sub-beams before they reach the objective lens array 241). Prefocusing can reduce the divergence of the sub-beams or increase the convergence ratio of the sub-beams. The control lens array and the objective lens array work together to provide a composite focal length. The composite action without intermediate foci can reduce the risk of aberrations. It should be noted that references to demagnification ratios and opening angles are intended to refer to variations of the same parameters. In an ideal configuration, the product of the demagnification ratio and the corresponding opening angle is constant over a range of values.

[0035]

[0051] The control lens array 250 can be considered to provide electrodes in addition to, for example, the electrodes of the objective lens array. The objective lens array can have any number of additional electrodes associated with and adjacent to the objective lens array. Such additional electrodes, for example of the control lens array 250, allow for further degrees of freedom for controlling the electron-optical parameters of the sub-beams. Such additional associated electrodes can be considered as additional electrodes of the objective lens array, allowing for additional functionality of the respective objective lenses of the objective lens array. In one configuration, such electrodes can be considered as part of the objective lens array, providing additional functionality to the objective lenses of the objective lens array. Thus, the control lenses are considered to be part of the corresponding objective lenses, even to the extent that the control lenses are only referred to as being part of the objective lenses.

[0036]

[0052] The objective lens 234 is arranged in an objective lens array, such as the objective lens array 241. The objective lens 234 may be configured to demagnify the electron beam by a factor of more than 10, preferably by a factor in the range of 50-100 or more. The objective lens 234 may be an Einzel lens. At least chromatic aberrations produced in the beam by the condenser lens and the corresponding down beam objective lens may be mutually cancelled.

[0037]

[0053] Each plate electrode of the objective lens array is preferably mechanically connected to and electrically isolated from adjacent plate electrode arrays by an isolation element, such as a spacer, which may comprise ceramic or glass. Such a spacer may mechanically connect adjacent electrode plates and electrically insulate the adjacent electrode plates. Isolation elements, which may alternatively be referred to as insulating structures, may be provided to separate any adjacent electrodes provided. If more than one electrode is provided, multiple isolation elements (i.e., insulating structures) may be provided. For example, there may be a series of insulating structures. Insulating spacers may be present between any other electro-optical elements of the electro-optical device 240.

[0038]

[0054] An electron detection device 240 is provided between the objective lens 234 and the sample 208 to detect secondary and / or backscattered electrons emitted from the sample 208. An exemplary structure of the electron detection system is described below.

[0039]

[0055] Optionally, an array of scan deflectors 260 is provided between the control lens array 250 and the array of objective lenses 234. The array of scan deflectors 260 includes one scan deflector 261 for each sub-beam 211, 212, 213. Each scan deflector is configured to deflect a respective sub-beam 211, 212, 213 in one or two directions to scan the sub-beam in one or two directions across the sample 208.

[0040]

[0056] The system of FIG. 3 may be configured to control the landing energy of the electrons on the sample. The landing energy may be selected to increase the emission and detection of secondary electrons depending on the nature of the sample being evaluated. A controller provided for controlling the objective lens 234 may be configured to control the landing energy by varying the potentials applied to the electrodes of the control lens and the objective lens. The control lens and the objective lens work together and may be referred to as the objective lens assembly. The landing energy may be selected to increase the emission and detection of secondary electrons depending on the nature of the sample being evaluated. The controller may be configured to control the landing energy to any desired value within a predetermined range or to a desired one of a plurality of predetermined values. In one embodiment, the landing energy may be controlled to a desired value in the range of 1000 eV to 5000 eV.

[0041]

[0057] Preferably, the landing energy is varied primarily by controlling the energy of the electrons exiting the control lens. The potential difference in the objective lens is preferably kept constant during this variation so that the electric field in the objective lens remains as high as possible. The potential applied to the control lens can be used to optimize the beam opening angle and the beam reduction ratio. The control lens can also be called a refocusing lens, as it can function to correct the focal position to account for changes in landing energy. The use of a control lens array allows the objective lens array to operate at its optimal electric field strength. Details of electrode structures and potentials that can be used to control the landing energy are disclosed in European Patent Application No. 20158804.3, which is incorporated herein by reference.

[0042]

[0058] The landing energy of the electrons can be controlled in the system of Figure 4 because any off-axis aberrations that occur in the beamlet path occur at, or at least primarily at, the condenser lens 231. The objective lens 234 in the system shown in Figure 3 does not need to be an Einzel lens because, since the beam is collimated, no off-axis aberrations occur at the objective lens. Off-axis aberrations can be better controlled in the condenser lens than in the objective lens 234.

[0043]

[0059] In some embodiments, the charged particle evaluation tool further includes one or more aberration correctors that reduce one or more aberrations in the sub-beams. In one embodiment, each of at least a subset of the aberration correctors is positioned at or directly adjacent to a respective one of the intermediate foci (e.g., in or adjacent to an intermediate image plane). The sub-beams have a minimum cross-sectional area in or near a focal plane such as the intermediate plane. This provides more space for the aberration correctors available elsewhere (i.e., on the up-beam or down-beam side of the intermediate plane) (or more space than would be available in an alternative configuration that does not have an intermediate image plane).

[0044]

[0060] In one embodiment, an aberration corrector positioned in or directly adjacent to the intermediate focus (or intermediate image plane or focus) includes a deflector to correct the source 201 to appear at different positions in the different beams. The corrector may be used to correct macro-aberrations originating from the source that prevent good alignment between each sub-beam and the corresponding objective lens. In some circumstances, it is desirable to position the corrector as far up the beam as possible. In this way, a small angular correction can result in a large displacement at the sample, so that a weaker corrector can be used. Desirably, the corrector is positioned to minimize the introduction of additional aberrations. Additionally or alternatively, other non-uniformities in the primary beam may be corrected. That is, the uniformity of the aberrations in the primary beam may be corrected.

[0045]

[0061] The aberration correctors may correct other aberrations that prevent proper column alignment. Such aberrations may also lead to misalignment between the sub-beams and the correctors. For this reason, it may be desirable to additionally or alternatively position the aberration correctors at or near the condenser lenses 231 (e.g., each such aberration corrector is integrated with or directly adjacent to one or more of the condenser lenses 231). This is desirable because aberrations at or near the condenser lenses 231 will not yet lead to deviations of the corresponding sub-beams because the condenser lenses 231 are close to or coincident with the beam aperture in the perpendicular direction. That is, correction of any angular error by the corrector will require a smaller position shift than if the corrector were located further down the beam. Correcting such aberrations further down the beam, for example at the intermediate focus, may be affected by misalignment between the sub-beams 211, 212, 213 and the correctors. However, a challenge with locating the correctors at or near the condenser lens 231 is that each sub-beam has a relatively large cross-sectional area and a relatively small pitch at this location compared to locations further down the beam. In volume-constrained situations, the corrector array or additional corrector arrays may be located away from these preferred locations, for example between the condenser lens array and the intermediate focus position.

[0046]

[0062] The aberration corrector can be a CMOS-based individual programmable deflector as disclosed in EP 2702595A1, the description of which is incorporated herein by reference, or an array of multipole deflectors as disclosed in EP 2715768A2. There may be an aberration corrector of this design for each beamlet, i.e. there may be individual beamlet correctors. The individual beamlet correctors may be arrayed across the multibeam, which may be referred to as a corrector array.

[0047]

[0063] In one embodiment, the objective lens array mentioned in the previous embodiment is an array-like objective lens. Each element in the array is a microlens that acts on a different beam or group of beams in the multi-beam. The electrostatic array objective lens has at least two plates, each plate having a number of holes or apertures. The position of each hole in a plate corresponds to the position of a corresponding hole in the other plate. The corresponding holes act on the same beam or group of beams in the multi-beam when in use. A suitable example of a type of lens for each element in the array is a two-electrode deceleration lens. Each electrode can be considered as a lens in itself, and each electrode can be considered as an electro-optical element.

[0048]

[0064] The bottom electrode of the objective lens is a CMOS chip detector integrated into the multi-beam manipulator array. Integrating the detector array into the objective lens replaces the secondary column of other electron-optical designs. The CMOS chip is desirably oriented to face the sample (due to the short distance between the sample and the bottom of the electron-optical system (e.g., 100 μm)). In one embodiment, a charge-based detector element, e.g., a capture electrode, is provided for capturing the secondary electron signal. The capture electrode may be formed in a metal layer, e.g., of a CMOS device. The capture electrode may form the bottom layer of the objective lens. The capture electrode may form the bottom surface of the CMOS chip. The CMOS chip may be a CMOS chip detector. The CMOS chip may be integrated into the sample-facing surface of the objective lens assembly. The capture electrode is an example of a sensor unit for detecting secondary electrons. The capture electrode may be formed in another layer. Power and control signals of the CMOS may be connected to the CMOS by through-silicon vias. For robustness, the bottom electrode preferably consists of two elements: the CMOS chip and a passive Si plate with holes. The plate shields the CMOS from high electric fields.

[0049]

[0065] A sensor unit associated with the bottom or sample-facing surface of the objective lens is beneficial because secondary and / or backscattered electrons can be detected before encountering and being manipulated by the electron-optical elements of the electron-optical system. Advantageously, the time required to detect electrons emitted from such a sample can be reduced, preferably minimized.

[0050]

[0066] To maximize detection efficiency, it is desirable to make the electrode surface as large as possible so that nearly all the area of ​​the objective lens array (excluding the aperture) is occupied by electrodes and each electrode has a diameter approximately equal to the array pitch. In one embodiment, the electrode outline is circular, but can be made square to maximize the detection area. The diameter of the substrate through-holes can also be minimized. The typical size of the electron beam is about 5-15 micrometers.

[0051]

[0067] In one embodiment, a single charge detector element, such as a capture electrode, surrounds each aperture. In another embodiment, multiple electrode elements are provided around each aperture. The electrode elements are examples of sensor elements. Electrons captured by the electrode elements surrounding an aperture may be combined into a single signal or may be used to generate independent signals. The electrode elements may be divided radially (i.e., to form multiple concentric rings), angularly (i.e., to form multiple sectors), both radially and angularly, or in any other convenient manner.

[0052]

[0068] However, a larger electrode surface leads to a larger parasitic capacitance and therefore a narrower bandwidth. For this reason, it may be desirable to limit the outer diameter of the electrodes, especially if a larger electrode not only gives a slightly higher detection efficiency but also a slightly higher capacitance. Circular (annular) electrodes may offer a good compromise between collection efficiency and parasitic capacitance.

[0053]

[0069] A larger outer diameter of the electrode can also lead to greater crosstalk (sensitivity to signals of neighboring holes), which may also be a reason for making the electrode outer diameter smaller, especially when larger electrodes provide slightly greater detection efficiency but also significantly greater crosstalk.

[0054]

[0070] The signal particles, e.g. backscattered electrons and / or secondary electrons collected by the electrodes as a current, are amplified. The purpose of the amplifier is to allow a sufficiently sensitive measurement of the current received or collected by the sensor unit, and thus the number of backscattered electrons and / or secondary electrons, to be measured. This can be measured by a current measurement, or a potential difference across a resistor. Several types of amplifier designs can be used to amplify the backscattered electron current and / or secondary electron current collected by the electrodes, e.g. transimpedance amplifiers.

[0055]

[0071] An exemplary embodiment of a multi-beam objective 401 is shown in a schematic cross-section in FIG. 4. At the output side of the objective 401, which is the side facing the sample 208, a detector module 402 is provided. The detector module 402 is an example of an electronic detection device. FIG. 5 shows a bottom view of the detector module 402 with a substrate 404 on which a number of capture electrodes 405 are provided, each of which surrounds a beam aperture 406. The beam aperture 406 is large enough not to block any primary beam. The capture electrodes 405 can be considered as an example of a sensor unit, which contains backscattering or secondary electrodes and generates a detection signal, in this case a current. The capture electrodes can be considered as charge detector elements. The beam aperture 406 can be formed by etching the substrate 404. In the configuration shown in FIG. 5, the beam aperture 406 is shown as a rectangular array. The beam apertures 406 may also be arranged in different manners, such as in a close-packed hexagonal array as depicted in FIG.

[0056]

[0072] 7 depicts a portion of the detector module 402 in cross section and to a larger scale. Charge detector elements such as capture electrodes 405 form the bottom-most surface of the detector module 402, i.e. the surface closest to the sample. In operation, the array of capture electrodes 405 faces the sample 208. Between the capture electrodes 405 and the body of the silicon substrate 404 is a logic layer 407. The logic layer 407 may include amplifiers (e.g. transimpedance amplifiers), analog-to-digital converters, and readout logic. In one embodiment, there is one amplifier and one analog-to-digital converter per capture electrode 405. The logic layer 407 and capture electrodes 405 may be fabricated using a CMOS process, with the capture electrodes 405 forming the final metallization layer.

[0057]

[0073] The wiring layer 408 is provided on the back side of the substrate 404 and is connected to the logic layer 407 by through silicon vias 409. The number of through silicon vias 409 does not need to be the same as the number of beam apertures 406. In particular, if the electrode signals are digitized in the logic layer 407, only a few through silicon vias may be needed to provide a data bus. The wiring layer 408 may include control lines, data lines, and power lines. It is noted that there is enough space for all the necessary connections despite the beam apertures 406. The detection module 402 may also be manufactured by using bipolar manufacturing techniques or other manufacturing techniques. Printed circuit boards and / or other semiconductor chips may be provided on the back side of the detector module 402.

[0058]

[0074] Although FIG. 4 depicts a three-electrode objective lens, it will be appreciated that any other form of objective lens having the required number of electrodes, including associated electrodes, may also be used, for example a two-electrode lens.

[0059]

[0075] 8 is a schematic diagram of another design of an exemplary electron-optical system. The electron-optical system may include a source 201 and an electron-optical device comprising a plurality of electron-optical elements. Alternatively, the electron-optical device includes the source 201.) The electron-optical column may include an objective array assembly as shown and described in connection with FIG. 3. Such an objective array assembly may feature a control lens array 250, an objective lens array 241, and a detector array. Although not shown in FIG. 8, the system may further include an electronic detection device (e.g., the electronic detection device 240 shown in FIG. 3).

[0060]

[0076] 8, the objective lens array may also feature an upper beam limiter 252, a collimator element array 271, a scanning deflector array 260, and a beam shaping limiter 242. (Note that in a different configuration, these features are not located in a common lens assembly, but rather the electron optical column includes these features.) Source 201 provides a beam of charged particles (e.g., electrons). Multiple beams that are focused onto sample 208 are derived from the beam provided by source 201. Sub-beams may be derived from the beam, for example, using a beam limiter, e.g., upper beam limiter 252, that defines an array of beam-limiting apertures.

[0061]

[0077] The upper beam limiter 252 defines an array of beam limiting apertures and functions as a beam separator or sub-beam generator. The upper beam limiter 252 may comprise a plate (which may be a plate-like body) with a number of apertures. The upper beam limiter 252 forms sub-beams from the beam of charged particles emitted by the source 201. Portions of the beam other than the beam that contributes to forming the sub-beams may be blocked (e.g., absorbed) by the upper beam limiter 252 so as not to interfere with the sub-beams on the down beam side. The upper beam limiter 252 may be referred to as a sub-beam defining aperture array.

[0062]

[0078] The collimator element array 271 is provided on the down beam side of the upper beam limiter. Each collimator element collimates a respective sub-beam. The collimator element array 271 may be made spatially compact, which may be realized by MEMS processing. In some embodiments illustrated in FIG. 3, the collimator element array 271 is the first deflection or focusing electro-optic array element in the beam path on the down beam side of the source 201. In another configuration, the collimator may be partially or completely in the form of a macro collimator (not shown). Such a macro collimator may be on the up beam side of the upper beam limiter 252. The macro collimator thus acts on the beam from the source before the generation of the multi-beam. A magnetic lens may be used as the macro collimator.

[0063]

[0079] On the down-beam side of the collimator element array are one or more additional electrodes, such as a control lens array 250. The control lens array 250 comprises a plurality of control lenses. Each control lens comprises at least two electrodes (e.g., three electrodes) connected to a respective potential source. Any additional electrodes, such as the control lens array 250, may comprise two or more (e.g., three) plate electrode arrays connected to a respective potential source. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are placed near each other and / or mechanically connected to each other and / or controlled together as an array unit). The control lens array 250 is placed on the up-beam side of the objective lens array 241. The control lenses pre-focus the sub-beams (e.g., apply a focusing action to the sub-beams prior to the sub-beams reaching the objective lens array 241). Pre-focusing may reduce the divergence of the sub-beams or increase the convergence rate of the sub-beams.

[0064]

[0080] The scan deflector array 260 comprises a plurality of scan deflectors. The scan deflector array 260 may be formed using MEMS fabrication techniques. Each scan deflector scans a respective sub-beam on the sample 208. Thus, the scan deflector array 260 may comprise a scan deflector for each sub-beam. Each scan deflector may deflect the light rays in the sub-beam unidirectionally (e.g., parallel to a single axis, such as the X-axis) or bidirectionally (e.g., about two non-parallel axes, such as the X-axis and the Y-axis). The deflection is such that the sub-beam is scanned across the sample 208 in one or two directions.

[0065]

[0081] In one embodiment, the scan deflector array 260 may be implemented as described in EP 2425444, which is incorporated herein by reference in its entirety, particularly with respect to the scan deflector. The scan deflector array 260 is positioned between the objective lens array 241 and the control lens array 250. In the illustrated embodiment, the scan deflector array 260 is provided in place of a macro scan deflector. The scan deflector array 260 (e.g., formed using MEMS fabrication methods as described above) may be more spatially compact than a macro scan deflector.

[0066]

[0082] In other embodiments, both a macro scan deflector and a scan deflector array 260 are provided. In such configurations, scanning the sub-beams over the sample surface can be achieved by controlling the macro scan deflector and the scan deflector array 260 together, preferably in a synchronized manner.

[0067]

[0083] The smaller movement on the beam shaping limiter results in a smaller portion of each control lens being used. Therefore, the contribution of the control lens to the aberration is smaller. To minimize or at least reduce the contribution of the control lens to the aberration, the beam shaping limiter is used to shape the beam down from at least one electrode of the control lens. This is different from the different type of charged particle device 41 shown and described in relation to FIG. 3, that is, the charged particle device 41 is part of or associated with the first scanning array in the beam path, and generally generates multiple beams from a single beam from the source, in which the beam shaping limiter is provided only as an aperture array.

[0068]

[0084] In the embodiment of FIG. 8, a collimator element array 271 is provided instead of a macro collimator. Although not shown, in the embodiment of FIG. 8, it is possible to use a macro collimator to provide an embodiment with a macro collimator and a scanning deflector array 260. Another variation may have a macro collimator and a macro scanning deflector. It is also possible to have a variation of the embodiment of FIG. 8 with a macro scanning deflector and a collimator element array. Each collimator element collimates a respective sub-beam. The collimator element array 271 (formed, for example, using MEMS fabrication methods) may be more spatially compact than a macro collimator. Thus, space can be saved by providing the collimator element array 271 and the scanning deflector array 260 together. In such an embodiment, there may be no macro condenser lens or condenser lens array. Thus, in this scenario, the control lens provides the possibility to optimize the beam opening angle and the expansion ratio for a change in landing energy.

[0069]

[0085] As mentioned above, to generate multiple beams, multiple electron-optical components in an electron-optical column (e.g., in a multi-beam SEM or multi-beam lithography machine) are typically required. The electron-optical components form the electron-optical apertures, lenses, deflectors, and perform other manipulations of the beams. These electron-optical components may include MEMS elements and need to be precisely aligned to allow all beams to land on the target (e.g., sample or detector). MEMS elements that are adjacent to each other can be stacked on top of each other and are relatively easy to align.

[0070]

[0086] The MEMS elements that need to be spaced apart may be mechanically aligned in columns with a certain tolerance, for example the elements need to be mechanically aligned with tolerances on the order of 10 μm and / or 1 mrad. For operation, finer electro-optical tolerances are required, for example 10-20 nm, for alignment to the beam source. Achieving tighter tolerances in the final alignment is done electro-optically, for example using electro-optical correctors such as deflectors as described herein above.

[0071]

[0087] Corrections for alignment may be across a multi-electron beam configuration for a group of sub-beams, including multi-electron beam configurations such as strip correctors, or may be specific to each sub-beam and may vary, for example, from sub-beam to sub-beam, for alignment using, for example, individual beam correctors. In particular, the strip correctors may be configured as described in International Publication No. WO 2021204734A1, filed April 4, 2021, and International Publication No. WO 2021204733A1, filed April 4, 2021, which are incorporated herein by reference, particularly with respect to their disclosure of correctors. The individual beam correctors can be configured according to U.S. Patent Application Publication No. 20120305798A1, filed May 30, 2012, and U.S. Patent Application Publication No. 20120273690A1, filed April 27, 2012, which are incorporated herein by reference, particularly for their disclosure of an array of multipole electrodes, each of which is controllable to control the path of a respective sub-beam. The process of properly aligning elements, e.g., for final alignment, is called column alignment. Column alignment takes into account the positions of the sub-beams in the multi-electron beam in the plane of the sample, i.e., their relative displacement in the sample plane, expressed, e.g., in Cartesian coordinates of X and Y.

[0072]

[0088] Known processes for column alignment use as a target a detector, for example placed at the sample position on a sample stage. Desirably, the detector is capable of detecting all beams simultaneously to minimize the time required for the column alignment procedure. Known detectors require a detector plate held on a movable stage (for example on the sample stage) that can be positioned at the target location. The detector plate has a patterned surface with a pattern that can correspond to an array of sub-beams in the multi-electron beam. The patterned surface is a plane of the sample surface. The alignment is effectively in the plane of the sub-beams, expressed in Cartesian coordinates, an alignment in the X-axis and the Y-axis. On the down-beam side of the patterned surface is a scintillator, which emits a flash of light when struck by the electron beam. A photonic detector, such as a camera, for example a CCD device, may be located on the down-beam side of the scintillator to detect a parameter of the light generated by each beam, for example its intensity. To resolve different beams, for example generated by a scintillator, which may be only on the order of 50-100 micrometers apart, alignment between the detector plate and the camera is challenging. The detector unit 333 described below in FIG. 13 is an example of such a sensor. In particular, the detector may be constructed as described in U.S. Patent Application Publication No. 20070057204A1, filed September 14, 2006, which is incorporated herein by reference, particularly for its disclosure of electron detection using a scintillator. Such detector units 333 are often located in the focal plane of the beam or beamlet. Such detector units often comprise blocking elements, which may take the form of a two-dimensional pattern. Such blocking elements are in the focal plane of the beam or beamlet.

[0073]

[0089] The relative alignment of the elements of the electron optical column (particularly the array of apertures, such as the condenser lens array and the objective lens array, which may be MEMS elements) for column alignment can be achieved using a charged particle detector, such as a detector array, which can simultaneously detect multiple beams at fixed positions in the electron optical column. The detector can be located towards the bottom of the electron optical column, preferably at the bottom of the electron optical column. In particular, the detector may be configured according to the description in WO2021140035A1, filed on December 23, 2020, which document is incorporated by reference herein, in particular with respect to the disclosure of the detector array associated with the objective lens array. Other configurations are known in which the detector is located further up the beam side in the column, for example associated with one or more electrodes of the objective lens array, or associated with the objective lens array, or even above the objective lens array. The detector is preferably close to the plane of the sample surface, so that the detector can receive a sufficient number of secondary electrons for a detection signal from the sample, for example during evaluation. The detector may be located closer to the sample surface than the scintillator and photonic detector of the sensor, for example, on the stage.

[0074]

[0090] The detector may be the same as the detector used to detect the signal particles during the inspection. The charged particle detector is preferably a detector module used in a charged particle device to detect the signal particles generated when the primary electrons are incident on the sample. The charged particle detector may therefore have two functions. The charged particle detector has the function of detecting the properties of the sample when the evaluation tool operates in an evaluation mode (as shown by the charged particle device 41 in FIG. 9). Another function of the charged particle detector is to detect the charged particles to evaluate the alignment when the evaluation tool operates in a calibration mode. The calibration mode is beam-related and may include two parts: a monitor or measurement part, where measurements are performed to obtain information about the sub-beam from the sub-beam, and an adjustment part. In the adjustment part, one or more components, or at least the settings of one or more components, may be adjusted depending on the information obtained from the sub-beam. It should be noted that in the calibration mode, the charged particles detected by the detector are signal particles generated by a primary sub-beam directed towards a calibrated surface (as shown by the charged particle device 41 in FIG. 9), which has a known response to multiple sub-beams (which may be referred to as a multi-beam configuration). In a different configuration, another surface of the sample or substrate support, or at least the stage, may be set to a potential to redirect, e.g., mirror-reflect, the primary sub-beam of the multi-beam configuration back into the up-beam direction, as described later in this specification (as shown by the charged particle device 41 in FIG. 10). Details of these calibration modes are described in PCT / EP2021 / 081134, filed November 9, 2021, the disclosure of which is incorporated herein by reference, at least with respect to the calibration mode.

[0075]

[0091] Various techniques may be used to provide the charged particle detector with a charged particle flow that depends on the column alignment. Preferably, the current of electrons received in the calibration mode to each detector element (e.g. in the returning primary sub-beam as shown and described with reference to FIG. 10) is proportional (or at least has a monotonic relationship) to the current of the respective sub-beam at the sample position. In case of misalignment, the sub-beam current will decrease, for example because part of the sub-beam intersects an element of the electron optical column and is scattered or absorbed. Thus, optimal alignment of the beamlets is achieved when the current signal from the associated detector is maximum. Upon detection of a misalignment, the detector signal is used to control the associated charged particle component, such as a corrector as described above, to increase the detector signal of the respective sub-beam, preferably to maximize the detector signal.

[0076]

[0092] The present invention is applicable to tools featuring a multi-electron beam configuration, such as evaluation and lithography tools of various different architectures, including those shown herein and others. The exemplary evaluation device 40 shown in Figures 9 and 10 has a charged particle source 201 that emits charged particles towards an aperture plate 111 (or a beam-limiting aperture array), which generates a number of sub-beams from the charged particles (e.g., by splitting, separating or dividing), very similar to the one shown and described with reference to Figure 3. However, the same principles may apply when applying this configuration to the charged particle device 41 shown in and described with reference to Figure 8. The aperture plate thus functions as a sub-beam generator. A condenser lens 231 directs each sub-beam to an intermediate focus. A deflector 235 (which may be a macroscopic deflector or a deflector array) adjusts the direction of propagation of the sub-beams. An objective lens array 234 focuses each sub-beam towards the sample 208. An electron detection device 240 or detector module detects returning electrons, for example secondary electrons emitted by the sample.

[0077]

[0093] In an embodiment of the invention, a charged particle mirror, for example an electron mirror for an electron beam, is used to reflect the primary charged particle beam back towards the charged particle detector, as shown in FIG. 10. The charged particle mirror can be constructed by placing an object 600 on the down-beam side of the charged particle detector and the last electron optical element of the electron optical column. The object 600 can be a sample, a sample holder, or another object held by a sample holder. The object 600 is set to a predefined negative potential difference with respect to the cathode of the charged particle source 201 using a potential source 601. If the charged particle beam contains positively charged particles instead of electrons, a positive potential would be used. The predefined potential difference can be on the order of -1 to -100V, for example -50V. Desirably, the predefined potential difference is larger than the spread in the beam energy and the spread between the beam energies. The potential difference between the object and the cathode reverses the direction of each beam towards the charged particle detector. The greater the magnitude of the potential difference, the shorter the distance required to reverse the trajectory of the charged particle.To optimize the detection yield, the objective lens array can be set to a specific voltage.

[0078]

[0094] As shown in FIG. 11A, the surface of the detector array or detector module (preferably facing or even proximate to the sample in use) features an array of detector elements (or array of detectors). Each detector element is associated with an aperture. Each detector element is associated with an assigned surface area of ​​the detector module's substrate. The substrate is layered, for example by having a CMOS structure, so that each layer in the substrate is located relative to, and preferably proximate to, each detector element. Commercially available CMOS structures have a typical range of layers, for example 3-10 layers, typically about 5 layers. (For example, for ease of explanation, two functional layers may be provided, which may be referred to as circuit layers. These two layers of wiring and logic layers may represent as many layers as needed, and each layer is not limited to wiring or logic, respectively.) The number of layers is limited by commercial availability, and any number of layers is feasible.

[0079]

[0095] Ideally, the circuit layers of the substrate, which may be wiring and / or logic layers, have a portion assigned to each detector element (or detector). The assigned portions of the different layers may be referred to as cells 550. The arrangement of portions in the substrate for a complete multi-beam configuration may be referred to as a cell array 552. The cells 550 may be the same shape as the surface area assigned to each detector element, for example, hexagonal, or any reasonable shape that can be tiled and all shapes and / or areas may be similar, such as rectangular shapes. Having rectangular or linear shapes is more easily used with a placing and routing design. Such designs are generally implemented with software suitable for defining the chip in orthogonal directions with a rectangular type architecture, rather than an architecture that requires acute or obtuse angles, such as in a hexagonal architecture. In FIG. 11A, the cells 550 are shown as hexagons and the cell array 552 is shown as hexagons with individual cells. However, ideally, each is similarly positioned relative to the detector elements. Wiring routes 554 may connect to each cell 550. Wiring routes 554 may be routed between other cells of cell array 552 .

[0080]

[0096] The circuit layer of the cell 550 is connected to the detector elements of each cell. The circuit layer comprises circuitry with amplification and / or digitization functions, for example, it may comprise an amplifier circuit. The cell 550 may comprise a transimpedance amplifier (TIA) 556 and an analog-to-digital converter (ADC) 558, as shown in FIG. 11B. This figure shows the cell 550 in a schematic manner with an associated detector element, such as a capture electrode, and a feedback resistor 562 connected to the transimpedance amplifier 556, and the analog-to-digital converter 558. A digital signal line 559 from the analog-to-digital converter 558 leaves the cell 550. Note that the detector elements are shown as detector elements 560, and the feedback resistor is shown associated with the detector area as a disk 562, rather than associated with the transimpedance amplifier 556. This schematic is intended to show each of the detector elements and feedback resistor as an area to show their relative sizes.

[0081]

[0097] Circuit wires 570 connect the transimpedance amplifiers in cells 550 to associated analog-to-digital converters 558. Circuit wires 570 transmit analog signals. Unlike digital signals, data paths transmitting analog signals are susceptible to interference. Signal interference can come from crosstalk with other circuit wires, as well as external electric fields, such as those generated by sub-beams of the multi-beam, and electric fields from nearby charged particle optical components, such as objective lens array 241.

[0082]

[0098] The circuit wires 570 are routed through the wiring route 554 as shown in FIG. 11A. The wiring route 554 is routed such that the area of ​​the cell and its layer is used for the amplifier circuitry present on the cell. Thus, the wiring route 554 uses only the portion of the circuit layer on which the wiring route is present, i.e., between adjacent cells 550 (e.g., at least around the beam apertures 504, 406 of adjacent cells 550, through adjacent cells 550 facing the periphery of the cell, or between the circuitry in the layer assigned to adjacent cells 550, or any configuration between the configurations described). This routing avoids structural interference between the amplifier circuitry and the architecture of the wiring route 554. The circuit wires are routed along the wiring route in the cell array in an outward direction, e.g., radially outward. There may be more circuit wires 570 closer to the periphery of the cell array 552 than in the portion of the wiring route 554 away from the periphery. The wiring route may have multiple circuit wires 570, which are present between the cells of the array, as described above. Thus, some of the wiring routes 554 may have more than one circuit wire 570. However, placing the circuit wires in close proximity to one another creates a risk of crosstalk between the circuit wires and interference with the analog signals transmitted by the circuit wires 570.

[0083]

[0099] The risk of crosstalk and signal interference can be at least reduced or even prevented by shielding the circuit wires 570 from each other within the wiring route. FIG. 12 shows a cross section of an exemplary configuration of a wiring route 554. Within the wiring route 554, there are one or more circuit wires 470 shown to run in the same direction as the wiring route 554, and a shielding arrangement. The circuit wires are shown in the same layer. Above the circuit wires 570 there is an upper shielding layer 572, and below the circuit wires 570 there is a lower shielding layer 574 (or a more down beam shielding layer 574). The upper and lower shielding layers of the shielding arrangement shield the circuit wires 570 from electric fields above and below the wiring route 554 and outside the wiring route 554. The shielding arrangement has a shielding element in the same layer as the circuit wires 570. The shielding element may be an outer element 576 at the outer edge of the layer that includes the circuit wires 570. The outer element 576 shields the circuit wire 570 from electric fields external to the routing 554. The shielding elements may include an intermediate shielding element 578 that resides in a layer between adjacent circuit wires. Thus, the intermediate shielding element 578 may at least reduce, if not prevent, crosstalk between the circuit wires 570. In operation, a common potential is applied to the shielding layers 572, 574 and the shielding elements 576, 578. The potential may be a reference potential, such as ground potential.

[0084]

[0100] As discussed above, charged particle optical components (e.g., electron optical components, etc.) in a charged particle device are used to form and manipulate multiple beamlets. The electron optical components may include electron optical apertures, lenses, deflectors, and other manipulations of the beamlets. These electron optical elements must be precisely aligned to allow all of the beamlets to be directed to a target (e.g., a sample). These electron optical components are typically mechanically aligned in a charged particle device in combination with electron optical alignment by changing settings of the electron optical components, e.g., deflectors and / or lenses.

[0085]

[0101] Existing techniques require all of the beamlets to pass through apertures in an aperture array to impact the target such that any signal particles emitted by the sample in response to each beamlet are simultaneously detected by the detector array as corresponding detection signals. However, if the charged particle device does not achieve the desired alignment, the beamlets will not impact the target simultaneously. That is, the alignment within the charged particle device, for example, between different charged particle components and between one or more charged particle components, and the paths of the sub-beams of a multi-beam configuration, should meet certain specifications for proper operation of the charged particle device. Proper operation may require the relative alignment between and to one or more charged particle components specified, and the paths of the sub-beams to be within a predetermined range.

[0086]

[0102] FIG. 13 shows a charged particle device in which the charged particle optical components are not aligned (i.e., unaligned). The charged particle device shown in FIG. 13 comprises a source 201 and an aperture plate 111, configured to convert a primary beam into multiple beamlets 211, 212, which may be collectively referred to as a multi-beam configuration. As shown in FIG. 13, the source beam is collimated by a macro-collimator 229 before being split into multiple beamlets in the multi-beamlet configuration. The macro-collimator 229 is shown as an electrostatic collimator lens, but may also be magnetic and have features of a magnetic collimator, which may be used in the configuration shown and described with reference to FIG. 8 instead of the collimator array 271. As shown, the beamlet 212 passing through the aperture array 112 contacts the sample 208, while another beamlet 211 is directed towards the plate forming the aperture array 112, for example by a deflector and / or by a disturbance in the charged particle component 232. The other beamlets 212 do not pass through the plate by passing through an aperture in the plate. The beamlets 212 are prevented from reaching the target (e.g., sample 209) by the action of a deflector that causes the beamlets 212 to impinge on the plate of the aperture array 112. Deflection caused by disturbances in the charged particle component 232 results in undesired misalignment of the beams 211, 212 on the aperture array 112. (Note: the charged particle component 232 may comprise a series of plates in the form of a lens array, such as a condenser lens array, so that the beamlets have an intermediate focus between the two aperture arrays 111, 112. Additionally or alternatively, the charged particle component 232 may comprise a deflector array. The defector array may comprise individually controllable detectors, each of which may be assigned to a beamlet 211, 212. The presence of such a deflector array can be used to optimize the alignment of the beamlets 211, 212 on the aperture array 112.)

[0087]

[0103] The detected signal of the detector may be weak as a result of some beamlets failing to reach the target. Such a weak signal may represent a misalignment. However, the weak signal may have insufficient information to determine whether to implement one or more corrections (or changes) to the settings to achieve the desired alignment. It is often beneficial to apply different combinations of settings (or settings) of the various electron-optical components until the desired alignment is obtained. For example, in the apparatus of FIG. 13, the settings (or settings) of the deflectors 235, 232 may be changed to achieve the desired alignment. (Note that in the collimation function, the deflectors of the charged particle component 232 may apply fine corrections with respect to the collimation achieved by the macro collimator 229, which may be controllable to optimize the alignment). In many cases, the settings of the various electron-optical components for the desired alignment are determined by experimentation and trial and error. Determining the settings of the different electron-optical components using trial and error may be a time-consuming process. Each component may have its own settings, and the settings of one or more components may depend at least on the settings of another electron-optical component. For an electro-optical device 41 having multiple electro-optical components, there are many different combinations of settings that may exist. Running through different combinations of settings for multiple different electro-optical components can be time consuming and potentially reduces the availability of the electro-optical device.

[0088]

[0104] The present disclosure relates to a method that aims to reduce the time required to determine the alignment of electron-optical components of a charged particle device. The method may allow a parameter set (or a plurality of parameter sets) to be determined, including values ​​corresponding to at least one of the relative positions, shapes and sizes of the beamlets, for example. These parameter sets may be used to inform updates of one or more values ​​of settings of the charged particle device, such as settings of the electron-optical components in the charged particle device 41. In this way, a desired alignment may be achieved in a reduced time due to less trial and error required. In one configuration, one or more settings of the charged particle optical device 41 are automatically optimized.

[0089]

[0105] The method is applicable to charged particle devices as shown in Figures 8-10, 13 and 14. For example, the charged particle device 500 shown in Figure 14 comprises an aperture array 112 and a detector 240, 333. The aperture array 112, which may be a plate, defines a number of apertures through which the paths of the beamlets 215 pass. The aperture array may be included in the charged particle device 41. (The beamlets 215 include the same beamlets 211, 212 that are referred to as part of a multi-beam configuration, which is given the reference 215 for ease of reference). The detector 240, 333 is configured to detect charged particles corresponding to the multiple beamlets 215 passing through corresponding apertures in the aperture array 112. The detector is located on the down beam side relative to the aperture array 112 along the paths of the beamlets 215. (The expected form of the detector is described later in this specification). The detector 240 may be included in the charged particle device 41. Additionally or alternatively, the detector 333 is included in the stage and / or is coplanar with the sample 208. The charged particle apparatus 500, such as the charged particle device 41, further comprises electron-optical components capable of acting on the plurality of beamlets 215. The electron-optical components may comprise components arranged on the up-beam side of the aperture array 112, such as the deflector 235. The electron-optical components may include the aperture array 112.

[0090]

[0106] This method is not suitable for determining the alignment of electronic optical components located on the down-beam side of the aperture array 112 along which the beamlets are scanned, since the alignment is performed relative to the aperture array 112 based on information collected by scanning the beamlets over the aperture array 112, where charged particle optical components on the up-beam side of the aperture array 112 act on the beamlets of the multi-beam configuration. The characteristics of the beamlets relate to information on the up-beam side of the charged particle optical elements. However, the beamlets have not yet interacted with the charged particle optical components on the down-beam side of the aperture array 112. Therefore, the characteristics of the beamlets are not related to information on such down-beam side charged particle optical components.

[0091]

[0107] Each beamlet 215 is scanned over a respective portion of the aperture array 112 in the plane of the aperture array 112. An aperture is defined in each of the respective portions of the aperture array. As a result, charged particles of each beamlet 215 may pass through a corresponding aperture during scanning. Two or more apertures are optionally defined in each of the respective portions of the aperture array.

[0092]

[0108] 14 includes a deflector 235 disposed on the up-beam side of the aperture array. The deflector 235 can be used to steer the beamlets to scan over respective portions of the aperture array 112.

[0093]

[0109] 15 represents a view of a plane XY of the aperture array 112 in which a plurality of apertures 113 are defined. A beamlet 215 is scanned in a direction D along the plane XY of the aperture array. The beamlet 215 is scanned across a respective portion of the aperture array 112 such that the beamlet 215 is scanned across the aperture 113. Thus, at certain times during the scan, the beamlet 215 may pass through the aperture 113 as shown. At other times during the scan, some or all of the beamlets may be partially or completely blocked (or blocked) by the aperture array 112. Such blocked beamlets may partially or completely fail to pass through the aperture array 112 to the down beam side of the aperture array 112, for example to a region on the down beam side of the aperture array 112.

[0094]

[0110] As the beamlets 215 are scanned across a portion of the aperture array 112, any charged particles corresponding to each beamlet passing through the corresponding aperture are detected by the detector. Based on the detection of the charged particles corresponding to each beamlet during each time interval of the scan, a detection pixel value is generated for each beamlet. The detection pixel value may be binary (i.e., indicative of detection of fewer or more particles than a threshold) or multi-valued.

[0095]

[0111] The scanning and detection is preferably performed simultaneously for multiple beamlets. More preferably, scanning and detection is performed simultaneously for all of the beamlets projected through the aperture array, as shown in Figure 15. Alternatively, each beamlet or group of beamlets in the multi-beam configuration may be scanned and detected individually at a separate time. However, implementations of the present invention take more time than simultaneous scanning and detection of all beamlets.

[0096]

[0112] The detection optionally includes detecting any charged particles corresponding to each beamlet passing through the corresponding aperture for each time interval during the scan. In other words, the detection is performed at separate times during the scan, such that data for the charged particles corresponding to each beamlet is captured only for each time interval during the scan. Alternatively, the detection may be performed continuously during the scan, and detection pixels corresponding to each time interval may be generated by subsequently discretizing the data based on the detection of the charged particles corresponding to each beamlet.

[0097]

[0113] Each detection pixel includes information related to a corresponding beamlet and a time interval during the scan, e.g., a detection pixel value. Specifically, each detection pixel includes information of the intensity of the charged particles corresponding to each beamlet passing through the corresponding aperture for each time interval during the scan. This information is collected by storing or processing the information contained in the detection pixel. This information may be stored or processed remotely or locally to the charged particle device. An alignment of one or more of the electronic optical components relative to the aperture array may be determined based on the collected information.

[0098]

[0114] The information of the intensity of the charged particles is correlated with the information of the current of the charged particles. This information can therefore allow a comparison of the relative intensity or current between different beamlets. This also allows a comparison of the relative intensity or current of a single beamlet at different time intervals during a scan. In this way, it can be determined whether the optical components of the charged particle device are aligned so that all the beamlets pass through the apertures in the aperture array in a desired manner, for example simultaneously.

[0099]

[0115] The detection pixels are preferably processed by generating an image for each beamlet, such as image 710 of FIG. 16. The image represents the intensity of the detected signal particles corresponding to the scanning of the beamlet over the portion of the aperture array in which the corresponding aperture is defined. In image 710, the brightness level of the image represents the intensity of the detected charged particles, with brighter pixels indicating greater intensity. Alternatively, different levels of intensity in the composite image can be represented in different ways, for example by using different colors for high and low intensities.

[0100]

[0116] The image preferably includes collected information for each time interval for a beamlet, as shown in FIG. 16. In particular, each detection pixel forms a pixel of the image 710. Thus, each pixel (or element) of the image may correspond to a detection pixel generated at a different time during the scan. For example, pixels 711 and 712 provide information of the intensity of the charged particles corresponding to this beamlet for different time intervals during the scan of this beamlet on the respective portion of the aperture array. The relative intensity corresponding to each detection pixel is shown in FIG. 16 by the different brightness of each pixel. In FIG. 16, pixel 711 is brighter than another pixel 712, which means that the intensity of the charged particles detected for this beamlet for each time interval corresponding to pixel 711 is higher than that detected for each time interval of the scan corresponding to the other pixel 712.

[0101]

[0117] A composite image 700 as shown in FIG. 17 may be generated. The composite image 700 represents the scanning of multiple beamlets on the aperture array and is based on multiple images. In the composite image 700, the level of brightness of the image represents the intensity of the detected charged particles, with brighter pixels indicating higher intensity. Alternatively, different levels of intensity can be represented in the composite image in different ways, for example by using different colors for high and low intensities. The pixels with higher brightness represent information about the beamlets that may be extractable from the image. The pixels with higher brightness tend to cluster together. The pixels with higher brightness form spots in the image. The spots can be considered to represent the corresponding beamlets.

[0102]

[0118] The composite image 700 includes information for all beamlets of the plurality of beamlets. The composite image 700 includes information for each detection pixel associated with each of the plurality of beamlets. The composite image includes collected information for each time interval for the plurality of beamlets. If desired, for example to save storage space and / or processing time, the composite image may instead be generated based on images of only a subset of the plurality of beamlets. Additionally or alternatively, the composite image may not include information for all detection pixels associated with the beamlets included in the composite image, and thus the composite image does not include information for some time intervals. That is, the composite image may include a selection of images of beamlets of a multi-beam configuration.

[0103]

[0119] The composite image 700 is based on multiple images 710, e.g., images 720, 730. The composite image 700 may correspond to images generated by scanning beamlets 215 over respective apertures of the aperture array 112. The positions of the images 710, 720, 730 represented in the composite image 700 are determined based on the physical positions of the apertures in the aperture array. The apertures correspond to the beamlets associated with each of the images 710, 720, 730. For example, the distance between the images 710, 720, 730 represented in the composite image is determined, in part, based on the distance between corresponding apertures in the aperture array 112.

[0104]

[0120] The composite image can be used to compare various parameters of different beamlets, such as relative positions, size shapes, and intensities corresponding to different beamlets. The parameters of the different beamlets can be present as features and characteristics of the corresponding spots in the composite image. Combining images 710, 720, 730 assembles the image using the measured relative positions of the apertures. However, in each image, pixels with greater brightness, such as spots, may have different positions. Thus, the distance between similar features of spots in the composite image can provide information of the corresponding beamlets relative to each other, such as the alignment of the beamlets on that aperture array 112. As shown in FIG. 17 for example, image 710 is brighter than image 720. This can indicate that there is some misalignment associated with the beamlet corresponding to the spot in image 720, at least with respect to other beamlets of the multi-beam configuration in the aperture array 112. The spot in image 730 is completely dark, indicating a low intensity. This may indicate, for example, a blockage at an aperture of the aperture array corresponding to this beamlet, or another issue associated with the beamlet, for example, at the aperture array or at a charged particle optical element acting on the beamlet on the up-beam side of the aperture array. Such an issue may be unwanted charging on a surface interacting with the beamlet, or other unwanted deflection of the beamlet. The true cause may be determined by varying settings associated with the up-beam side charged particle optical component acting on the beamlet, as described further below in this specification.

[0105]

[0121] The information contained in the detection pixels may be used to determine a parameter set for at least one beamlet, the parameter set including at least one parameter value.

[0106]

[0122] The parameter set may relate to dimensions of the beamlet in the plane of the aperture array. In particular, the parameter set may include dimensions of one or more beamlets. For example, the parameter set may include a value representing the shape of the beamlet, e.g., a value indicating whether the beamlet is circular or elliptical in the plane of the aperture array. Alternatively or in addition, the parameter set may include a value representing the width and / or a value representing the length of the beamlet in the plane of the aperture array.

[0107]

[0123] The parameter set may additionally or alternatively include information characteristics of the detection pixels, preferably of the pixels defining the spots corresponding to the beamlets. For example, the parameter set may preferably include values ​​representing the variation of a characteristic of the detection pixels, e.g. the variation of the intensity of the detection pixels, over the image, at least over one or more respective spots in the image. For example, the parameter set may include values ​​representing the intensity of the detection pixels in the image as a function of the position in the image. Alternatively or additionally, the spots are fitted to detection pixels having a high brightness in the image, e.g. pixels above an intensity threshold, or pixels having a similar intensity within a range, but greater than other pixels of the image. The intensity threshold may be set relatively low and the intensity range may be set narrow. The pixels corresponding to the spots may have a uniform intensity and therefore may have a top-hat function profile. In such a top-hat function, the pixels representing the spots may have a substantially uniform intensity, while the pixels of the image outside the spots may have a very low intensity. The different beam positions and their relative positions may be determined by considering the center of each spot. These different methods can determine whether the beamlets pass through corresponding apertures as expected at different times in the scan, which corresponds to different positions of the beamlets on the portion of the aperture array, so that analysis with respect to the parameter sets can identify any misalignments.

[0108]

[0124] The parameter set may be associated with a plurality of beamlets. Desirably, the parameter set is associated with all of the beamlets in the charged particle device. Determining the parameter set may include determining a plurality of individual beam parameter sets, each associated with a single beamlet, and generating the parameter set from the individual beam parameter sets. Alternatively, the parameter set may be determined from a composite image including detection pixels associated with a plurality of beamlets.

[0109]

[0125] The parameter sets associated with the plurality of beamlets may include alignment parameter sets for the plurality of beamlets in the plane of the aperture array. The alignment parameter sets may include relative intensities, positions, and / or shapes of the beamlets represented in the parameter sets. For example, the alignment parameter sets may include a beam pitch between two or more of the beamlets in the plane of the aperture array. Desirably, the beam pitch included in the alignment parameter sets represents all beamlets in the plane of the aperture array.

[0110]

[0126] Then, based on the parameters of the individual beamlets and / or the parameters of the multiple beamlets, the parameter set may be analyzed to determine whether there is any misalignment. The parameters of the parameter set relating to the misalignment (e.g., in a Cartesian coordinate system) may include one of the following: position with respect to an orthogonal direction in the plane of the aperture array 12, displacement from the ideal position of the beamlet in either of two directions, offset, pitch error, etc.

[0111]

[0127] The charged particle device has a set of settings corresponding to a configuration of electron-optical components arranged on the up-beam side of an aperture array along which the beamlets are scanned, and in a configuration with an additional aperture array on the up-beam side of the aperture array, the settings correspond to a configuration of electron-optical components arranged on the up-beam side of the aperture array and on the down-beam side of the additional aperture array.

[0112]

[0128] A setting of the setting set may be altered to change the operation of one or more beamlets by a corresponding electron-optical component. At least one setting of the setting set may be altered based on the parameter set. At least one setting may be automatically altered based on the parameter set. Alternatively, a user may input an alteration to at least one setting based on user review of the parameter set.

[0113]

[0129] The setting set may include, for example, settings of an aberration corrector or settings of a collimator. The collimator may comprise a lens or a deflector, which is optionally arranged in an array. The setting set may include, for example, settings associated with the operation of an individual beamlet of the plurality of beamlets. In other words, the settings may be associated with an individual beam corrector, which may be included in an array of individual beam correctors. Additionally or alternatively, the setting set may include settings associated with the operation of the plurality of beamlets. For example, the settings may correspond to settings of a meso-lens or a meso-deflector. Additionally or alternatively, the settings may be associated with an array, and the setting set may include settings associated with the operation of all of the plurality of beamlets. For example, the settings may correspond to settings of a macro-lens or a macro-deflector, which may act magnetically or electrostatically. The deflector may be as described in U.S. Patent Application Publication No. 20150069259A1, filed September 4, 2014, the disclosure of which is incorporated by reference herein, at least insofar as it relates to disclosure of deflectors for sub-beams of a multi-beam configuration, or as described in International Publication No. 2021156121A1, filed January 27, 2021, the disclosure of which is incorporated by reference herein, at least insofar as it relates to disclosure of strip electrodes that function as a deflector array. Suitable correctors include, for example, correctors associated with an objective lens array, e.g., correctors integrated within and even within the objective lens array, as shown and described with reference to Figures 3, 8, 13 and 14, as well as correctors integrated into a condenser lens array or embodiment, as shown and described with reference to Figure 3; correctors associated with or integrated into a deflector array acting as a collimator array, e.g., on the immediate up beam side or immediate down beam side of the deflector array 232, 235, which may be located at the intermediate focus 233 of the beamlet, as shown and described in relation to Figures 3 and 13.Such a corrector is disclosed in WO 2021204734A1, filed on April 4, 2021, and WO 2021204733A1, filed on April 4, 2021, the disclosures of which are incorporated herein by reference, at least insofar as they relate to the disclosure of the corrector. Such a corrector may be a macro corrector located on the up-beam side of the beam-limiting aperture array 111, 231, 252, and may be combined with or incorporated into any macro charged particle optical component between the source 201 and the beam-limiting aperture array 111, 231, 252. Such a corrector is disclosed in European Patent Application No. 21215703.6, filed on December 17, 2021, the disclosure of which is incorporated herein by reference, at least insofar as it relates to the disclosure, the macro corrector.

[0114]

[0130] 13 having an additional aperture array, such as beam-limiting aperture array 111, the position of the additional aperture array relative to aperture array 112 may be changed by actuation, such as an automatic actuation, based on at least one parameter of the parameter set. For example, it may be determined from the parameter set that aperture array 112 is not aligned with respect to the additional aperture array 111.

[0115]

[0131] The scanning comprises scanning each beamlet along a scan path defining a scan pattern in the plane of the aperture array. Desirably, the scan path has a main-scan direction and a cross-scan direction. The main-scan direction is different from the cross-scan direction. The main-scan and cross-scan directions may be substantially mutually orthogonal.

[0116]

[0132] In the embodiment shown in FIG. 18, the scan pattern 800 is a raster scan pattern. The main scan direction is direction X. The sub-scan direction Y is perpendicular to the main scan direction X. The directions X and Y in FIG. 18 optionally correspond to the X and Y directions in FIG. 15, which indicate the XY plane of the aperture array. In this way, each portion of the aperture array is effectively scanned. The main scan direction can be considered as the direction along the rows. The sub-scan direction can be considered as the step between adjacent rows. As shown in FIG. 18, the main scan direction can alternate between adjacent rows. In a different configuration, the main scan direction can be the same for all rows.

[0117]

[0133] For each beamlet, a scan path is configured to cover a respective portion of the aperture array, including the aperture. Each detection pixel corresponds to a position 801 of the beamlet on the scan path. Thus, each detection pixel provides information of the detected intensity of a charged particle corresponding to a particular beamlet at a position.

[0118]

[0134] The multiple beamlets have a beam pitch, which is the distance between corresponding positions of adjacent beamlets in the plane of the aperture array. The distance over which each beamlet is scanned in the main-scan direction on the corresponding portion of the aperture array is less than a multiple of the beam pitch. In particular, the distance over which each beamlet is scanned in the main-scan direction on the corresponding portion of the aperture array is preferably equal to or less than the beam pitch. In this way, the aperture can be scanned efficiently, since each beamlet scans a respective portion of the aperture array that does not overlap with the portions scanned by the other beamlets. In a variant in which each beamlet is assigned to a respective portion of an aperture array that includes more than one aperture, the same scan path can be applied on that portion. It should be noted that the respective portions may be contiguous or overlapping, such that multiple beamlets scan the same aperture of the aperture array 112.

[0119]

[0135] In some configurations, the beam pitch may be constant for the plurality of beamlets. In other words, the distance between corresponding features of adjacent beamlets, such as corresponding positions, e.g., centers of adjacent beamlets, (which may be calculated based on an image of each beamlet) is the same for any two adjacent beamlets of the plurality of beamlets. In other configurations, the beam pitch may vary for the plurality of beamlets. In other words, the distance between corresponding positions, e.g., the distance between the centers of a first beamlet and a second beamlet adjacent to the first beamlet, is greater than the distance between the corresponding positions in the second beamlet and a third beamlet adjacent to the second beamlet.

[0120]

[0136] The detector may comprise a charged particle detector array arranged on the down-beam side of the aperture array. The detector may be an electronic detection device 240 or a detector module configured to detect signal particles generated in response to sub-beams of the multi-beam configuration or reflected (or mirror-reflected) sub-beams of the multi-beam configuration. The charged particle device may be configured in a calibration mode such that the detector detects signal particles emitted by the sample. The charged particle device may be configured to detect primary charged particles reflected by an electronic mirror back to the detector. Such a detector may comprise a charge detector element, a semiconductor-based detector element such as a PIN detector element, and / or an electron-photon converter element such as a scintillator. The electron-photon converter may be photonically coupled to a phonon-electrical signal converter connected to an electronic circuit.

[0121]

[0137] The detector may comprise a component arranged on the down-beam side of the aperture array. For example, the detector may comprise a detector plate arranged on the down-beam side of the aperture array. The detector plate may comprise a scintillator, and the detector may further comprise a photonic detector, which may be arranged on the down-beam side of the scintillator. The light generated by the scintillator is proportional to the current and thus to the intensity of the charged particles. Therefore, detection pixels can be easily obtained using this type of detector.

[0122]

[0138] In a different arrangement, the detector may be incorporated into or supported by the stage 209 of the apparatus of Figures 13 and 14 as a detector unit 333. In either of the arrangements of Figures 3 and 9, a detector of this type may be provided on the stage in addition to or instead of the electronic detection device 240. In one arrangement, the detector plate is desirably located within the detector unit 333.

[0123]

[0139] In one configuration, a detector such as a monitor detector (e.g., in the form of a detector array having a detector element for each sub-beam of the multi-beam configuration) on the down-beam side of the aperture array 112 may be used to generate detection signals in the calibration mode for generating a composite image. Such a monitor detector is, for example, a dedicated detector for monitoring the sub-beams of the multi-beam configuration in the charged particle device, associated with the charged particle optical component or even integrated in the respective charged particle component. Such a monitor detector may be separate from the detector 240 used to detect the signal particles in the evaluation mode. Details of suitable monitoring detectors are disclosed in European Patent Application Nos. 21215700.2, filed December 17, 2021, and 21216063.4, filed December 20, 2021, both of which are incorporated herein by reference, at least insofar as the disclosure of the monitoring detector is concerned.

[0124]

[0140] The electron optical component of the charged particle device may comprise an additional aperture array, arranged along the path of the beamlets, on the up-beam side of the path of the beamlets relative to the aperture array. The multiple beamlets are directed through the additional aperture array 111 towards the aperture array 112. The additional aperture array preferably comprises a beam-limiting aperture array for generating or shaping the multiple beamlets. As shown in Figures 8 to 10, 13 and 14, the additional aperture array may be an aperture plate 111 configured to convert the primary electron beam into multiple beamlets 211, 212. Alternatively, the additional aperture array may be arranged on the down-beam side of the electron optical component that converts the primary electron beam into multiple beamlets. Such an additional aperture array may be any electrode acting on the up-beam side of the aperture array 112. In such a situation, there must be a generating beam-limiting aperture array on the up-beam side of the additional aperture array in order to generate multiple beamlets on the up-beam side of the additional aperture array. Such an additional aperture array may be a lens electrode of the charged particle optical component 232 or a condenser lens array 231. The additional aperture array may comprise a corrector array, a lens array, or any other aperture array. Such a corrector array may act differently on different beamlets of the multi-beam configuration. For example, the corrector may be an array of individually controllable multipoles. Such a corrector may be referred to as an individual beam corrector. In one configuration, the additional aperture array is a macro-electronic optical element, for example with a single aperture for either the source beam or all beamlets of the multi-beam configuration. In such a configuration situation, the generating beam limiting aperture array for generating multiple beamlets should be on either the up beam side or the down beam side of the macro-electronic optical element.

[0125]

[0141] The deflector is preferably located on the up beam side of the aperture array 112 along which the beamlets are scanned. The deflector is preferably located on the down beam side of the additional aperture array. The deflector is preferably configured to steer each of the beamlets to cause them to be scanned over the aperture array to perform the scan.

[0126]

[0142] Alignment of the additional aperture array relative to the aperture array can be determined based on the collected information. Alignment can be achieved by controlling potentials applied to one or more of the charged particle optical elements in the charged particle device, such as the deflectors 229, 232, 235, 271, 260 and the correctors. Additionally or alternatively, alignment can be achieved by actuating one or more charged particle optical components to adjust their position within the charged particle optical device 41.

[0127]

[0143] The charged particle device 40 optionally comprises a further aperture array located on the down beam side from the aperture array in the path of the beamlets. The further aperture array should not be a beam limiting aperture array. Desirably, the path of the beamlets passes through apertures in the further aperture array. The further aperture array does not obstruct or block the path of the beamlets on the down beam side of the aperture array 112 along which the beamlets of the multi-beam configuration are scanned.

[0128]

[0144] Further deflectors may be provided on the up beam side of the further aperture array and on the down beam side of the aperture array. The further deflectors may be configured to steer the beamlets to scan over the further aperture array. Thus, the alignment of the electronic optical components arranged on the up beam side of the further aperture array and on the down beam side of the aperture array may be determined with respect to the further aperture array. This may be achieved by scanning each of the beamlets over the further aperture array, as described above, in the same way that the beamlets are scanned over the aperture array of, for example, FIG. 14.

[0129]

[0145] The method may be implemented using a computer program. In particular, the computer program includes instructions configured to control a charged particle device. The instructions are configured to control the charged particle device to scan each beamlet in a plane of the aperture array over a portion of the aperture array where a corresponding aperture of the aperture array is defined, thereby allowing the charged particles of each beamlet to pass through the corresponding aperture. The instructions are configured to control the charged particle device to detect any charged particles corresponding to each beamlet passing through the corresponding aperture during the scan. The instructions are configured to control the charged particle device to generate a detection pixel for each beamlet based on the detection of the charged particles corresponding to each beamlet per time interval of the scan, and to collect information contained in the detection pixel, such as the intensity of the charged particle.

[0130]

[0146] The instructions may be configured to generate an image, for example, as shown and described with reference to Figs. 16 and 17. The instructions may process the information and calculate one or more corrections, optionally depending on a user input in response to the image. The calculation may relate to another parameter of the parameter set. The calculation may provide an adjustment to one or more settings of the setting set. The instructions may be configured to control, for example, the controller 50, to adjust one or more settings of one or more charged particle components of the charged particle device 41. The controlled one or more charged particle components may comprise the source 201. The instructions may be configured to control the charged particle device 41 to optimize at least one of: an alignment of the sub-beams with respect to one another and the multi-beam configuration; an alignment between two or more charged particle components of the charged particle device 41; an alignment of at least one of the charged particle components and the sub-beams of the multi-beam configuration; an electron-optical performance of at least one of the components by applying a setting corresponding to the adjustment of one or more of the sub-beams of the charged particle multi-beam configuration.

[0131]

[0147] The image may be a graphical representation. The graphical image may be used to determine the alignment of an electronic optical component capable of acting on multiple beams of a beam grid in a charged particle device, for example as described with reference to any of Figures 2, 3, 8 and 13, for example as shown therein. Such a charged particle device may include an aperture array and a detector array. A plurality of apertures are defined in the aperture array. The detector may be configured to detect charged particles corresponding to the beams passing through the apertures. The detector may be located on a beam down side of the aperture array. The graphical representation includes a beam grid image of the beam grid based on a plurality of series of pixels derived from the respective beams.

[0132]

[0148] A series of pixels may correspond to a series of spaced apart positions of each beam along the scan path. The scan path of the beam on the aperture array has a main-scan direction and a cross-scan direction. The main-scan direction is different from the cross-scan direction. A series of pixels of each beam is rendered in a beam image of each beam in the beam grid image. A beam image in the beam grid image may represent each beam of the beam grid. The beam images of the beam grid may be located in the beam grid image based on the position of each aperture in the aperture array. The beam images may correspond to each aperture in the aperture. An image, such as a graphical representation, may include information about the beam grid and / or the beams of the beam grid as a whole.

[0133]

[0149] Such information obtainable from the image may include the following information as a non-limiting list: Such information may include parameters of a parameter set: the relative position of the sub-beams with respect to the respective apertures of the aperture array through which the sub-beams are scanned; the relative positions of the sub-beams with respect to each other, for example in the plane of the aperture array through which the sub-beams are scanned. Such information is useful for determining the alignment of the sub-beams with respect to each other in a multi-beam configuration. One or more of various types of alignment may be determined (e.g. between the multi-beam configuration and another charged particle optical component on the up-beam side of the array through which the multi-beam configuration is scanned, between two of the charged particle components); parameters of each sub-beam, such as their shape, e.g. their ellipticity, which may represent the astigmatism of the respective source beam. The features of the sub-beams may correspond to features and may correspond to one or more parameters of the primary beam (or source beam). That is, outlining the features allows the identification of one or more parameters of the primary charged particle beam and thus information regarding one or more parameters of the source beam. The one or more parameters of the sub-beams collected in the information may relate to one or more other characteristics of the charged particle beam, such as alignment, brightness, emission intensity, and / or source beam uniformity (e.g., effective coverage of the multi-beam configuration, tilt and shift of the source beam relative to the aperture array from which the multi-beam configuration is generated, cross-sectional shape of the multi-beam configuration). One or more parameters of the source beam and / or at least the sub-beams of the multi-beam configuration may relate to one or more aberrations, such as distortion of a macroscopic lens.

[0134]

[0150] Such a computer program may include instructions directing the controller 50 to perform the following steps: The controller 50 controls the charged particle beam device 40 to project the charged particle beam towards the sample 208. In one embodiment, the controller 50 controls at least one charged particle optical component (e.g., an array of multiple deflectors or scanning deflectors 260) to act on the charged particle beam in the charged particle beam path. Additionally or alternatively, in one embodiment, the controller 50 controls at least one charged particle optical element (e.g., the detector 240) to act on the charged particle beam emitted from the sample 208 in response to the charged particle beam. The controller may control the charged particle component by controlling, e.g., adjusting, the settings of a configuration set.

[0135]

[0151] The computer that uses the instructions may be located in the charged particle device or may be remote from the device, for example in a different room.

[0136]

[0152] The method of the present invention can alternatively be described as a method for generating a beam grid image for aligning an electronic optical component capable of acting on a plurality of individual beams of a beam grid in a charged particle device comprising an aperture array 112 and a detector. The aperture array has a plurality of apertures 113. The detector is configured to detect charged particles associated with the beam passing through the apertures. The detector is located on the down-beam side of the aperture array. Such a method for implementing the present invention includes scanning the individual beams of the beam grid over a corresponding portion of the aperture array D, detecting the charged particles associated with the individual beams as a respective series 710 of pixels 711, 712 for each time interval during the scan, where the charged particles of the associated beams have passed through the associated apertures of the aperture array, and generating a beam grid image 700 of the beam grid based on the corresponding series of pixels 710 derived from the individual beams of the beam grid. The scanning includes scanning the beams along respective scan paths on the aperture array having a main-scan direction and a cross-scan direction. The main scan direction is different from the cross scan direction. A set of pixels associated with each beam is associated with a set of positions of the individual beams spaced along the scan path. Each different set of pixels is rendered in a beam image of a different individual beam in the beam grid image.

[0137]

[0153] The method of the invention may alternatively be described as a method for generating a beam grid image for aligning electronic optical components capable of acting on a plurality of beams of a beam grid in a charged particle device, the charged particle device comprising an aperture array 112 and a detector array. The aperture array has a plurality of apertures 113. The detector is configured to detect charged particles of the beam passing through the apertures. The detector is located on a down-beam side of the aperture array. The method includes scanning, detecting, and generating. Scanning includes scanning the beams of the beam grid over respective portions of the aperture array, each portion having an aperture of the aperture array. Detecting includes detecting charged particles of the beam passing through the apertures of the respective portions. The detection of the beam is performed as a respective series 710 of pixels 711, 712 for each time interval during the scan. Generating includes generating a beam grid image of the beam grid based on the respective series 710 of pixels derived from the beams of the beam grid.

[0138]

[0154] The scanning includes scanning the beam along a respective scan path over respective positions of the aperture array. The scan path has a main-scan direction and a cross-scan direction. The main-scan direction is different from the cross-scan direction. Each series of pixels corresponds to a respective series of positions of the beam spaced along the scan path. Each series of pixels is rendered in a beam image of a different beam in the beam grid image. The different beam images in the beam grid image represent different beams in the beam grid and correspond to respective apertures in the aperture. The different beam images in the beam grid are located in the beam grid image based on the positions of the respective apertures in the aperture array.

[0139]

[0155] The method of the present invention may be applied to a charged particle device configured to project a single beam of charged particles towards a sample. Such a method for generating a beam image is for aligning electron optical components operable on a beam in a charged particle device, the charged particle device including an aperture plate and a detector. The aperture plate has an aperture 113 defined therein. The detector is configured to detect charged particles corresponding to the beam passing through the aperture. The detector is located on a beam-down side of the aperture plate. The method includes scanning, detecting, and generating. Scanning includes scanning the beam along a serpentine path over a portion D of the aperture plate such that the charged particles of the beam pass through the aperture. Detecting includes detecting the charged particles of the beam passing through the aperture array as a series 710 of pixels 711, 712 along the serpentine path for each time interval. Generating includes generating a beam image of the beam based on a series of pixels derived from the beam.

[0140]

[0156] The pixels represent at least the intensity of the detected signal particles. The shape of the image represents the beam corresponding to the apertures in the aperture. The shape of the set of pixels is the shape of the charged particle beam, and preferably the set of pixels are adjacent to form the shape. The shape of the set of pixels corresponds to the apertures in the aperture. The shape of the beam located in the beam image is based on the position of the apertures in the aperture plate.

[0141]

[0157] References to a component or system of components or elements being controllable to manipulate and act on a charged particle beam in a particular way include configuring a controller or control system or control unit to control the component to manipulate the charged particle beam in the described manner, as well as, 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 may be electrically connected to and apply a potential to one or more components under the control of a controller or control system or control unit, including, for example, the control lens array 250, the objective lens array 234, the condenser lens 231, the corrector, and the scan deflector array 260, as a non-limiting list. An actuatable component, such as a stage, may be controllable to be actuated and thus moved relative to another component, such as a beam path, using one or more controllers, control systems, or control units to control the actuation of the component.

[0142]

[0158] Any element or collection of elements in the electron-optical device 40 may be replaceable or replaceable on-site. One or more of the charged particle optical components in the electron-optical device 40, particularly those that act on or generate sub-beams, such as aperture arrays and manipulator arrays, may comprise one or more MEMS elements, such as a MEMS stack.

[0143]

[0159] An evaluation tool according to an embodiment of the invention may be a tool that performs a qualitative measurement (e.g., pass / fail) of a sample, a tool that performs a quantitative evaluation of a sample (e.g., size of a feature), or a tool that generates an image of a map of a sample. Thus, the evaluation tool may be any suitable device, apparatus, or system used for evaluation. For example, the evaluation tool may be either a part of a charged particle beam apparatus 40, or more specifically a charged particle optical device 41 (which may be a charged particle optical column), and / or a charged particle optical device as part of an optical lens array assembly, when used for evaluation. Examples of evaluation tools are inspection tools (e.g., to identify defects), review tools (e.g., to classify defects), and metrology tools, or tools capable of performing any combination of evaluation functions associated with an inspection tool, a review tool, or a metrology tool (e.g., a metrology inspection tool). The charged particle beam device 41 (which may be a charged particle optical column) may be a component of an evaluation tool, e.g., an inspection tool or a metrology inspection tool, or a part of an electron beam lithography tool. Any reference herein to a tool is intended to encompass a device, apparatus or system, where the tool comprises various components that may or may not coexist.

[0144]

[0160] In any of the above embodiments, the device or apparatus may further comprise a source configured to emit at least one source beam from which a plurality of sub-beams are generated. The plurality of sub-beams may be generated from a plurality of sources, for example using a plurality of columns.

[0145]

[0161] The invention is applicable to a variety of different tool architectures. For example, the charged particle beam device 40 may be a single beam tool, or may comprise multiple single beam columns, or may comprise multiple columns (i.e. sub-beams) of a multi-beam. The columns may comprise a charged particle optical device as described in any of the above embodiments or aspects. As a multiple column (or multi-column tool), the devices may be arranged in an array that may have a number of columns between 2 and 100. The charged particle device 41 may take the form of an embodiment as described in relation to and shown in FIG. 3 or as described in relation to and shown in FIG. 8, but preferably comprises an electrostatic scanning deflector array and / or an electrostatic collimator array, for example in an objective lens array assembly. The charged particle optical device may be a charged particle optical column. The charged particle column may optionally comprise a source.

[0146]

[0162] The term "image" is used herein to refer to a two-dimensional array of values. Although an image can be displayed by mapping the values ​​to an intensity or color scale, use of the term image should not be considered to require that the array of values ​​be so displayed, or that it represent anything that can be perceived by a human.

[0147]

[0163] The terms "sub-beam" and "beamlet" are used interchangeably herein and are both understood to encompass any radiation beam that is derived from a parent radiation beam by splitting or separating the parent radiation beam. The term "manipulator" is used to encompass any element that affects the path of a sub-beam or beamlet, such as a lens or deflector.

[0148]

[0164] References to top and bottom, upper and lower, bottommost, up and down, upward and downward should be understood to refer to directions parallel to (typically perpendicular, but not always perpendicular to) the up beam and down beam directions of the electron beam or multi-beam impinging on the sample 208. Thus, references to up beam and down beam are intended to refer to directions relative to the beam path, regardless of any gravitational fields that may be present.

[0149]

[0165] References to a number of elements being aligned along a beam path or sub-beam path are understood to mean that each element is located along the beam path or sub-beam path.

[0150]

[0166] Exemplary embodiments of the present invention are described below in the following clauses.

[0151]

[0167] Clause 1: A method for determining the alignment of an electronic optical component capable of acting on a plurality of beamlets in a charged particle device, the charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to the beamlets passing through corresponding apertures in the aperture array, the detector being located on the beam down side relative to the aperture array along the path of the beamlets, the method comprising: scanning each beamlet in the plane of the aperture array over a portion of the aperture array where a corresponding aperture of the aperture array is defined so that the charged particles of each beamlet can pass through the corresponding aperture; detecting any charged particles corresponding to each beamlet passing through the corresponding aperture during the scan; generating a detection pixel for each beamlet based on the detection of the charged particles corresponding to each beamlet per time interval of the scan; and collecting information contained in the detection pixel, such as the intensity of the charged particles. Preferably, the aperture array and optionally the detector are included in the charged particle device. The charged particle device is included in the charged particle device.

[0152]

[0168] Clause 2: The method of clause 1, wherein detecting includes detecting any charged particle corresponding to each beamlet passing through a corresponding aperture for each time interval during the scan.

[0153]

[0169] Clause 3: A method as described in clause 1 or 2, further comprising generating an image representing the intensity of detected signal particles corresponding to the scanning of the beamlet over a portion of the aperture array in which a corresponding aperture is defined for each beamlet, preferably the image comprising collected information at each time interval relating to the beamlet, preferably the portion comprising two or more apertures.

[0154]

[0170] Clause 4: The method of clause 3, comprising generating a composite image representing a scanning of the multiple beamlets over the aperture array, preferably over corresponding portions of the aperture array in which corresponding apertures are defined, based on the multiple images for the multiple beamlets, preferably the composite image comprising collected information at each time interval for the multiple beamlets, preferably for all of the multiple beamlets, preferably the portions comprising two or more corresponding apertures such that the corresponding portions overlap.

[0155]

[0171] Clause 5: The method of clause 4, wherein the positions of the images represented in the composite image are determined based on the physical positions of corresponding apertures in the aperture array.

[0156]

[0172] Clause 6: The method of clause 4 or 5, wherein the distance between the images represented in the composite image is determined based on the relative positions of corresponding apertures in the aperture array.

[0157]

[0173] Clause 7: A method described in any one of clauses 3 to 6, further comprising determining a set of parameters for at least one beamlet related to a dimension of the beamlet or each beamlet in the plane of the aperture array based on an image of the beamlet or each beamlet.

[0158]

[0174] Clause 8: The method of clause 7, wherein the parameter set includes a shape of the or each beamlet in the plane of the aperture array.

[0159]

[0175] Clause 9: The method of clause 7 or 8, wherein the set of parameters includes one or more dimensions of the or each beamlet in the plane of the aperture array.

[0160]

[0176] Clause 10: A method according to any one of clauses 7 to 9, wherein the parameter set includes information characteristics of the detection pixel, such as, for example, the variation of the intensity of the detection pixel, preferably over the image, such as the current / intensity of the detection pixel in the image as a function of its position in the image.

[0161]

[0177] Clause 11: The method of any one of clauses 7 to 10, wherein the parameter set is associated with a plurality of beamlets.

[0162]

[0178] Clause 12: The method of clause 11, wherein determining the parameter set includes determining a plurality of individual beam parameter sets, each associated with a single beamlet, generating the parameter set from the plurality of individual beam parameter sets, or determining the parameter set from a composite image including detection pixels associated with a plurality of beamlets.

[0163]

[0179] Clause 13: The method of clause 11 or 12, wherein the parameter set includes a set of alignment parameters for a plurality of beamlets in a plane of the aperture array.

[0164]

[0180] Clause 14: The method of clause 13, wherein the set of alignment parameters includes a beam pitch between two or more beamlets in the plane of the aperture array, preferably a beam pitch representative of all beamlets in the plane of the aperture array.

[0165]

[0181] Clause 15: The method of clause 13 or 14, wherein the alignment parameter set includes relative intensities, positions, and / or shapes of the beamlets represented in the parameter set.

[0166]

[0182] Clause 16: A method according to any one of clauses 7 to 15, wherein the charged particle device has a set of settings, the method further comprising varying at least one setting of the set of settings based on the parameter set.

[0167]

[0183] Clause 17: The method of clause 16, wherein the set of settings includes aberration corrector settings or collimator settings.

[0168]

[0184] Clause 18: A method according to any one of the preceding clauses, wherein the scanning comprises scanning each beamlet along a scan path having a main-scan direction and a cross-scan direction, preferably the main-scan direction being different from the cross-scan direction, and preferably the scan path defining a scan pattern in the plane of the aperture array.

[0169]

[0185] Clause 19: The method of clause 18, wherein the scanning pattern is a raster scanning pattern.

[0170]

[0186] Clause 20: A method as described in clause 18 or 19, wherein the multiple beamlets preferably have a beam pitch in the plane of the aperture array, and the distance over which each beamlet is scanned in the main scanning direction over a corresponding portion of the aperture array is less than or equal to a multiple of the beam pitch, for example less than or equal to the beam pitch.

[0171]

[0187] Clause 21: A method according to any one of clauses 18 to 20, wherein each detection pixel whilst scanning the part corresponds to a position of a beamlet on the scan path, preferably the detection pixel relates to an image.

[0172]

[0188] Clause 22: A method according to any one of the preceding clauses, wherein detection is performed simultaneously for multiple beamlets.

[0173]

[0189] Clause 23: The method of clause 22, wherein detection is performed simultaneously for all of the beamlets projected through the aperture array.

[0174]

[0190] Clause 24: A method according to any one of the preceding clauses, wherein the detector comprises a detector plate arranged on the down-beam side of the aperture array.

[0175]

[0191] Clause 25: The method of clause 24, wherein the detector plate is disposed on a stage configured to support the sample.

[0176]

[0192] Clause 26: The method of clause 25, wherein the detector plate comprises a scintillator.

[0177]

[0193] Clause 27: The method of clause 26, wherein the detector comprises a photonic detector positioned on the downbeam side of the scintillator.

[0178]

[0194] Clause 28: A method according to any one of clauses 1 to 23, wherein the detector comprises a charged particle detector array arranged on the down-beam side of the aperture array.

[0179]

[0195] Clause 29: The method of clause 28, wherein the detector is an electron optical component of a charged particle device.

[0180]

[0196] Clause 30: A method according to any one of the preceding clauses, wherein the electron optical component of the charged particle device further comprises an additional aperture array arranged along the path of the beamlets on the up-beam side of the path of the beamlets relative to the aperture array, and the method further comprises directing the plurality of beamlets towards the aperture array through the additional aperture array arranged on the up-beam side of the aperture array, and the scanning preferably comprises directing the beamlets through corresponding apertures in the aperture array.

[0181]

[0197] Clause 31: A method as described in clause 30, determining an alignment of one or more, preferably additional, aperture arrays of the electronic optical components relative to the aperture array based on the collected information.

[0182]

[0198] Clause 32: The method of clause 30 or 31, wherein the additional aperture array comprises at least one of a beam-limiting aperture array, a corrector array, a lens array, or any other aperture array for generating or shaping the aperture array.

[0183]

[0199] Clause 33: A method according to any one of the preceding clauses, wherein the charged particle device comprises a further aperture array located in the path of the beamlets on the down beam side from the aperture array.

[0184]

[0200] Clause 34: A method according to any one of the preceding clauses, wherein scanning is performed by deflecting each beamlet, preferably the deflection being by a deflector on the up beam side of the aperture array, preferably on the down beam side of an additional aperture array.

[0185]

[0201] Clause 35: A method of generating a beam grid image for aligning an electronic optical component operable on a plurality of individual beams of a beam grid in a charged particle device, the charged particle device comprising an aperture array having a plurality of apertures and a detector configured to detect charged particles associated with the beam passing through the apertures, the detector being located on a beam down side of the aperture array, the method comprising: scanning the individual beams of the beam grid over a corresponding portion of the aperture array; detecting, for each time interval during the scan, the charged particles associated with the individual beams as a respective series of pixels, the charged particles of the associated beam having passed through an associated aperture of the aperture array; and generating a beam grid image of the beam grid based on the corresponding series of pixels derived from the individual beams of the beam grid.

[0186]

[0202] Clause 36: A method as described in clause 35, wherein scanning includes scanning the beam along a corresponding scan path on the aperture array having a main scan direction and a cross-scan direction, preferably the main scan direction is different from the cross-scan direction, preferably a series of pixels are associated with each beam associated with a series of positions of the individual beam spaced along the scan path, preferably different corresponding series of pixels are rendered in beam images of different individual beams in the beam grid image.

[0187]

[0203] Clause 37: A method for generating a beam grid image for aligning an electronic optical component operable to act on multiple beams of a beam grid in a charged particle device, the charged particle device comprising an aperture array having a multiple apertures and a detector configured to detect charged particles of the beam passing through the apertures, the detector being located on a down beam side of the aperture array, the method comprising: scanning a beam of the beam grid over a corresponding portion of the aperture array, the corresponding portion having an aperture of the aperture array; detecting charged particles of the beam passing through the aperture of the corresponding portion, the detection of the beam being detected as a respective series of pixels for each time interval during the scan; and generating a beam grid image of the beam grid based on the corresponding series of pixels derived from the beam of the beam grid.

[0188]

[0204] Clause 38: The method of clause 37, wherein the scanning includes scanning the beam along a respective scan path over each position of the aperture array, the scan path having a main scan direction and a cross-scan direction, the main scan direction being different from the cross-scan direction, and each series of pixels corresponding to a respective series of positions of the beam spaced apart along the scan path, and corresponding series of pixels being rendered in beam images of different beams in the beam grid image.

[0189]

[0205] Clause 39: A method as described in clause 37 or 38, wherein different beam images of the beam grid image represent different beams in the beam grid and correspond to respective apertures in the aperture array, and the different beam images of the beam grid are located in the beam grid image based on the position of each aperture in the aperture array.

[0190]

[0206] Clause 40: A method of generating a beam image for aligning an electron optical component capable of acting on a beam in a charged particle device, the charged particle device comprising an aperture plate having an aperture defined therein, and a detector configured to detect charged particles corresponding to the beam passing through the aperture, the detector being located on a down-beam side of the aperture plate, the method comprising: scanning the beam along a serpentine path over a portion of the aperture plate such that the charged particles of the beam pass through the aperture; detecting the charged particles of the beam passing through the aperture array as a series of pixels along the serpentine path at time intervals; and generating a beam image of the beam based on the series of pixels derived from the beam.

[0191]

[0207] Clause 41: The method of clause 40, wherein a pixel represents at least the intensity of a detected signal particle.

[0192]

[0208] Clause 42: A method according to clause 40 or 41, wherein the shape of the series of pixels is a charged particle beam and corresponds to an aperture of an aperture plate, and the shape of the beam located in the beam image is based on the position of the aperture in the aperture plate.

[0193]

[0209] Clause 43: A computer program comprising instructions configured to control a charged particle tool to carry out a method according to any one of the preceding clauses.

[0194]

[0210] Clause 44: A computer program comprising instructions for determining an alignment of an electronic optical component operable on a plurality of beamlets in a charged particle device, the charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to the beamlets passing through corresponding apertures in the aperture array, the detector being located on a down beam side relative to the aperture array along the paths of the beamlets, the computer program comprising instructions configured to: control the charged particle device to scan each beamlet in the plane of the aperture array over a portion of the aperture array where a corresponding aperture of the aperture array is defined thereby allowing the charged particles of each beamlet to pass through the corresponding aperture; control the charged particle device to detect, during the scan, any charged particles corresponding to each beamlet passing through the corresponding aperture; generate detection pixels for each beamlet based on detection of charged particles corresponding to each beamlet per time interval of the scan; and collect information contained in the detection pixels, such as the intensity of the charged particles.

[0195]

[0211] Clause 45: A graphical representation for determining alignment of an electronic optical component operable on multiple beams of a beam grid in a charged particle device, the charged particle device comprising an aperture array having a plurality of apertures defined therein, and a detector configured to detect charged particles corresponding to the beams passing through the apertures, the detector being located on a beam down side of the aperture array, the graphical representation including a beam grid image of the beam grid based on a plurality of series of pixels derived from respective beams.

[0196]

[0212] Clause 46: The graphical representation of clause 45, wherein a series of pixels corresponds to a series of positions of each beam spaced along the scan path.

[0197]

[0213] Clause 47: A graphical representation of clause 46, wherein a scan path of the beam on the aperture array has a main-scan direction and a cross-scan direction, the main-scan direction being different from the cross-scan direction.

[0198]

[0214] Clause 48: A graphical representation according to any one of clauses 45 to 47, wherein a series of pixels for each beam is rendered in a beam image for each beam in the beam grid image.

[0199]

[0215] Clause 49: A graphical representation according to any one of clauses 45 to 48, wherein the beam images in the beam grid image represent corresponding beams in the beam grid and correspond to corresponding apertures in the aperture array, and the beam images in the beam grid are located in the beam grid image based on the position of each aperture in the aperture array.

[0200]

[0216] While the invention has been described in conjunction with various embodiments, other embodiments of the invention will become apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and the provisions of this specification.

Claims

1. 1. A method for determining an alignment of an electron-optical component operable on a plurality of beamlets in a charged particle device, the charged particle device comprising an aperture array and a detector configured to detect charged particles corresponding to the beamlets passing through corresponding apertures in the aperture array, the detector being positioned beam down relative to the aperture array along paths of the beamlets, the method comprising: scanning each beamlet in a plane of the aperture array over a portion of the aperture array, where a corresponding aperture of the aperture array is defined such that charged particles of each beamlet pass through the corresponding aperture; detecting any charged particles corresponding to each beamlet passing through the corresponding aperture during the scan; generating a detection pixel for each beamlet based on detection of the charged particles corresponding to each beamlet for each time interval of the scan; and collecting information contained in said detection pixels, such as intensities of charged particles.

2. The method of claim 1 , wherein the detecting comprises detecting any charged particles corresponding to each beamlet passing through the corresponding aperture during each of the time intervals during the scan.

3. The method of claim 1 or 2, further comprising generating, for each beamlet, an image representing the intensity of detected signal particles corresponding to the scanning of the beamlet over the portion of the aperture array in which the corresponding aperture is defined.

4. The method of claim 3 , comprising generating a composite image representing the scanning of the multiple beamlets across the aperture array based on a plurality of the images for the multiple beamlets.

5. The method of claim 4 , wherein the composite image includes the collected information at each time interval for the multiple beamlets.

6. The method of claim 4 or 5, wherein the positions of the images represented in the composite image are determined based on the physical positions of the corresponding apertures in the aperture array.

7. A method according to any one of claims 4 to 6, wherein the distance between the images represented in the composite image is determined based on the relative positions of the corresponding apertures in the aperture array.

8. The method of any one of claims 3 to 7, further comprising determining a set of parameters for at least one beamlet related to a dimension of the or each beamlet in the plane of the aperture array based on the image corresponding to the or each beamlet.

9. 9. The method of claim 8, wherein the set of parameters includes a shape of the or each beamlet in the plane of the aperture array and / or one or more dimensions of the or each beamlet in the plane of the aperture array.

10. The method according to claim 7 or 9, wherein the parameter set comprises an information characteristic of the detection pixels, for example a variation of the characteristic of the detection pixels, such as a variation of the intensity of the detection pixels.

11. The method according to any one of claims 8 to 10, wherein the parameter sets relate to a number of beamlets.

12. The method of claim 11 , wherein determining the parameter set comprises determining a plurality of individual beam parameter sets, each associated with a single beamlet, and generating the parameter set from the plurality of individual beam parameter sets, or determining the parameter set from a composite image including detection pixels associated with a plurality of beamlets.

13. The method of claim 11 or 12, wherein the set of parameters comprises a set of alignment parameters for the plurality of beamlets in the plane of the aperture array.

14. The method of claim 13 , wherein the set of alignment parameters includes relative intensities, positions, and / or shapes of the beamlets represented in the set of parameters.

15. The method according to any one of claims 8 to 14, wherein the charged particle device has a set of settings, the method further comprising varying at least one setting of the set of settings based on the set of parameters.

Images