Automatic Anti-scan deflector alignment method on a multi-beam electron-optics system

Abstract

A method of quantifying an anti-scanning alignment of a secondary charged particle beam. Embodiments of the present disclosure provide a method of calculating a behavior of a secondary charged particle beam in response to anti-scanning and determining a mathematical model to calculate a relationship between a setting for an anti-scanning deflection unit and the corresponding behavior the secondary charged particle beam. The present disclosure also provides a method for quantifying an anti-scanning alignment of a secondary charged particle beam during a scanning operation in a charged particle beam apparatus. A desired behavior of a secondary charged particle beam in response to anti-scanning may be calculated to counteract an influence of scanning a primary charged particle beam. Anti-scanning alignment may be conducted more rapidly and with improved accuracy.

Description

2025P00060WQ 1AUTOMATIC ANTI-SCAN DEFLECTOR ALIGNMENT METHOD ON A MULTI-BEAM ELECTRON-OPTICS SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 777,416 which was filed on March 25,2025 and which is incorporated herein in its entirety by reference.FIELD

[0002] The embodiments provided herein relate to a charged-particle beam anti-scanning technology. A method may be used to automatically calculate an anti-scanning behavior of a secondary charged particle beam during scanning operation of a charged particle beam system, and to align the secondary charged particle beam based on the calculation to improve charged particle collection and image throughput.BACKGROUND

[0003] In manufacturing processes of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as a scanning electron microscope (SEM) can be employed. As the physical sizes of IC components continue to shrink, accuracy and yield in defect detection become increasingly important. Inspection images such as SEM images can be used to identify or classify defects of the manufactured ICs. Improvements to detection performance, image quality, or throughput of the inspection systems are desired.SUMMARY

[0004] The embodiments provided herein disclose a charged-particle beam inspection apparatus, and more particularly, a method of automatically calculating an anti-scanning behavior of a secondary charged particle beam and aligning a secondary charged particle beam during operation of a charged-particle beam system.

[0005] Some embodiments of the present disclosure provide a non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for calculating a behavior of a secondary charged particle beam resulting from anti-scanning deflection in a charged particle beam apparatus. The operations comprise changing a parameter of the secondary charged particle beam, using an antiscanning deflection unit, by a first adjustment according to a first target signal provided to the antiscanning deflection unit and by a second adjustment according to a second target signal provided to the anti-scanning deflection unit, determining a mathematical model that comprises a first formulation2025P00060WQ 2and a second formulation, wherein the first formulation comprises the first target signal and the first adjustment and the second formulation comprises the second target signal and the second adjustment, and calculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit for adjusting the parameter of the secondary charged particle beam.

[0006] In some embodiments, the present disclosure provides a non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for adjusting a secondary charged particle beam during operation of a charged particle beam apparatus. The operations comprise scanning of a primary charged particle beam in a first scanning direction and a second scanning direction on a sample, wherein a secondary charged particle beam is generated from incidence of the primary charged particle beam on the sample, determining a first displacement of a parameter of the secondary charged particle beam based on the first scanning direction and a second displacement of a parameter of the secondary charged particle beam based on the second scanning direction, calculating a first signal and a second signal to apply to an anti-scanning deflection unit for deflecting the secondary charged particle beam, wherein the first signal is calculated to counteract the first displacement, and the second signal is calculated to counteract the second displacement, determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first signal, the first displacement, and the first scanning direction of the primary charged particle beam, and the second formulation comprises the second signal, the second displacement, and the second scanning direction of the primary charged particle beam, and calculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit to align a secondary charged particle beam generated from scanning the primary charged particle beam in a third scanning direction.

[0007] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present disclosure.BRIEF DESCRIPTION OF FIGURES

[0008] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.

[0009] FIG. 1 is a schematic diagram illustrating an example charged-particle beam inspection system, consistent with embodiments of the present disclosure.

[0010] FIG.2 is a schematic diagram illustrating an example multi-beam tool that can be a part of the example charged-particle beam inspection system of FIG. 1, consistent with embodiments of the present disclosure.

[0011] FIG.3A is an example schematic of a primary charged particle beam scanning over a sample, consistent with embodiments of the present disclosure.2025P00060WQ 3

[0012] FIG.3B is an example schematic of a secondary charged particle imaging unit, consistent with embodiments of the present disclosure.

[0013] FIG.4A is an example schematic of a detector for collecting secondary charged particle beams.

[0014] FIG. 4B is an example schematic of scanning areas for secondary charged particle beams on a detector.

[0015] FIG.4C is an example schematic of scanning areas for charged particle beam on a detector after anti-scanning of the secondary charged particle beams, consistent with embodiments of the present disclosure

[0016] FIG.5A is an example schematic of a charged particle system, consistent with embodiments of the present disclosure.

[0017] FIGs.5B-5I are example schematics of a behavior for a secondary charged particle beam resulting from anti-scanning deflection, consistent with embodiments of the present disclosure.

[0018] FIG. 6 is an example illustration of calculating a target adjustment for anti-scanning of a secondary charged particle beam, consistent with embodiments of the present disclosure.

[0019] FIG.7 is an example workflow for calculating a behavior for a secondary charged particle beam resulting from anti-scanning deflection, consistent with embodiments of the present disclosure.

[0020] FIG.8A is an example schematic of a charged particle beam system, consistent with embodiments of the present disclosure.

[0021] FIGs.8B-8E are example schematics of a behavior for a secondary charged particle beam resulting from scanning of a primary charged particle beam, consistent with embodiments of the present disclosure.

[0022] FIG.9 is an example illustration for calculating an optimized deflection setting for an antiscanning deflection unit in a charged particle system, consistent with embodiments of the present disclosure.

[0023] FIG. 10 is an example workflow for adjusting a secondary charged particle beam during operation of a charged particle system, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0024] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments as recited in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the disclosure is not so limited. Other types of charged-particle beams (e.g., including protons,2025P00060WQ 4ions, muons, or any other particle carrying electric charges) may be similarly applied. Furthermore, other imaging systems may be used, including but not limited to, optical imaging, photon detection, x-ray detection, ion detection, etc.

[0025] Electronic devices are constructed of circuits formed on a piece of semiconductor material called a substrate. The semiconductor material may include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium, or the like. Many circuits may be formed together on the same piece of silicon and are called integrated circuits or ICs. The size of these circuits has decreased dramatically so that many more of them can be fitted on the substrate. For example, an IC chip in a smartphone can be as small as a thumbnail and yet may include over 2 billion transistors, the size of each transistor being less than 1 / 1000th the size of a human hair.

[0026] Making these ICs with extremely small structures or components is a complex, timeconsuming, and expensive process, often involving hundreds of individual steps. Errors in even one step have the potential to result in defects in the finished IC, rendering it useless. Thus, one goal of the manufacturing process is to avoid such defects to maximize the number of functional ICs made in the process; that is, to improve the overall yield of the process.

[0027] One component of improving yield is monitoring the chip-making process to ensure that it is producing a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be carried out using an inspection tool such as, for example, a scanning charged-particle microscope (SCPM). For example, an SCPM may be a scanning electron microscope (SEM). A SCPM inspection tool can be used to image these extremely small structures, in effect, taking a “picture” of the structures of the wafer to generate an inspection image. The inspection image can be used to determine if the structure was formed properly in the proper location. If the structure is defective, then the process can be adjusted, so the defect is less likely to recur.

[0028] As the physical sizes of IC components continue to shrink, accuracy and yield in defect detection become more important. Inspection images such as SCPM images can be used for metrology measurements (e.g., to identify or classify defects) of the manufactured ICs. Measurements including, but not limited to, critical dimensions of the inspection image may be used to identify defects on the wafer. In order to perform metrology measurements more accurately, it is desired to obtain inspection images that are accurately focused, have high-quality contrast, and improved signal-to-noise ratios. One way to improve the quality of inspection images may be to monitor a focus and signal-to-noise ratio of a generated image and improve secondary charged particle collection on a corresponding detector during imaging.

[0029] For example, a SEM scans the surface of a sample with a focused beam of primary electrons. The primary electrons interact with the sample and generate secondary electrons. By scanning the sample with the focused beam and capturing the secondary electrons with a detector, the SEM creates an image of the scanned area of the sample. For high throughput inspection, some of the inspection2025P00060WQ 5systems use multiple focused beams of primary electrons. As the multiple focused beams can scan different parts of a sample at the same time, multi-beam inspection system can inspect a sample at a much higher speed than a single-beam inspection system.

[0030] In a SEM, primary electrons are generated by an electron gun (also called an electron source). In the source, the primary electrons are created using electron emission from the cathode tip; then, they are accelerated to the energies necessary for transporting them through the electron-optical system of SEM to the sample. The electron source may be of thermal emission, field emission, or Schottky (field enhanced thermionic) emission types, among others. To obtain high-quality images of the sample, it is desired to increase the efficiency of secondary electrons impacting the detector. Further, for a multi-beam charged particle system (e.g., a SEM), it is desired for different secondary electron beams to impact different and separate regions of the detector to avoid cross-talk and subsequent degradation in image quality. However, as a primary electron beam scans over a sample surface, the generated secondary electron beam moves with respect to the detector (e.g., a landing position of the secondary electron beam on the detector moves over time). An anti-scanning deflection unit may be provided in a secondary imaging system to compensate for this shift and to minimize image displacement on the detector. That is, as the primary electron beams are deflected by scanning, the secondary electron beams are deflected toward the detector by deflectors of the secondary imaging system by a process called “anti-scanning.” The anti-scanning deflection unit may help to maintain secondary electrons for each secondary electron beam impacting a respective region or detector cell on a detector (e.g., maintain a one-to-one correspondence between a secondary electron beam and a detector regio n / cell).

[0031] The secondary imaging system may be provided between the sample and the detector, and may include components that help to improve image quality. For example, there may be a zoom lens for adjusting magnification so that beam spots are formed with a proper size on a detector cell or region, an anti-rotation lens that adjusts beam rotational positions, an anti-scanning deflector to adjust a deflection of a secondary electron beam, and aberration compensation elements that compensate for various aberrations. An anti-scanning deflector may be used to deflect a secondary electron beam such that the secondary electron beam does not move on the detector during scanning of the primary electron beam. Accordingly, alignment of different components in the secondary imaging system is desired to achieve stable secondary electron beams and improve image quality. Existing methods of aligning components of the secondary imaging system involve a trial-and-error approach by manually adjusting knobs or controls while viewing a generated image until a desired image is obtained. A user may determine that a generated image of a sample is suboptimal (e.g., defocused, suboptimal brightness / contrast, etc.) or that an image of secondary electron beams on a detector is poorly aligned, and then adjust the knobs or controls for the secondary imaging unit to correct. However, existing methods are unable to be quantified and applied in a repetitive and standardized manner. For example, a user may not be able to define when an accurate alignment of a secondary electron beam on a2025P00060WQ 6detector is achieved and when to stop the alignment. Furthermore, existing methods may not be incorporated effectively into high volume manufacturing and inspection of ICs because the operation time for the manual alignment method may be too long for the desired manufacturing efficiency and yield goals. Accordingly, an automatic, rapid, accurate, and quantitative method for aligning a secondary charged particle beam during anti-scanning operation of a charged particle system is desired.

[0032] Embodiments of the disclosure may provide a method of quantifying an anti-scanning alignment of a secondary charged particle beam. In some embodiments, the present disclosure provides a method of calculating a behavior of a secondary charged particle beam in response to antiscanning, and determining a mathematical model to calculate a relationship between a setting for an anti-scanning deflection unit and the corresponding behavior of the secondary charged particle beam. In some embodiments, the mathematical model may enable predictions of how a secondary charged particle beam may respond to any setting or input signal provided to an anti-scanning deflection unit. Additionally, some embodiments of the present disclosure provide a method for quantifying an antiscanning alignment of a secondary charged particle beam during a scanning operation in a charged particle beam apparatus. A desired behavior of a secondary charged particle beam in response to antiscanning may be calculated to counteract an influence of scanning a primary charged particle beam. In some embodiments, a mathematical model may be determined to calculate a relationship between a scanning setting and a desired behavior of the secondary charged particle beam. The mathematical model may enable rapid and accurate generation of settings or input signals to be provided to a secondary imaging system for anti-scanning of secondary charged particle beams during scanning of a primary charged particle beam. Thus, embodiments of the disclosure may improve the quality of a generated image of a sample, reduce time associated with anti-scanning alignment, and provide a method to accurate calculate and quantify settings to optimize anti-scanning alignment.

[0033] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings, the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described. As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component may include A or B, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or A and B. As a second example, if it is stated that a component may include A, B, or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless clearly stated otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this disclosure, specify the presence of stated components, but do not preclude the presence or addition of one or more other components.2025P00060WQ 7

[0034] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing systems and methods in systems utilizing electron beams. However, the disclosure is not so limited. Furthermore, systems and methods related to anti-scanning may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc. Also, distortion control or beam projection may be applicable in other systems, such as lithography systems. Additionally, the term “beamlef ’ may refer to a constituent part of a beam or a separate beam extracted from an original beam. The term “beam” may refer to beams or beamlets.

[0035] FIG. 1 illustrates an example electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. EBI system 100 may be used for imaging. As shown in FIG.1, EBI system 100 includes a main chamber 101, a load / lock chamber 102, a beam tool 104, and an equipment front end module (EFEM) 106. Beam tool 104 is located within main chamber 101. EFEM 106 includes a first loading port 106a and a second loading port 106b. EFEM 106 may include additional loading port(s). First loading port 106a and second loading port 106b receive sample front opening unified pods (FOUPs) that contain samples (e.g., semiconductor wafers or wafers made of other material(s)). A “lot” is a plurality of samples that may be loaded for processing as a batch.

[0036] One or more robotic arms (not shown) in EFEM 106 may transport the samples to load / lock chamber 102. Load / lock chamber 102 is connected to a load / lock vacuum pump system (not shown) which removes gas molecules in load / lock chamber 102 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) may transport the sample from load / lock chamber 102 to main chamber 101. Main chamber 101 is connected to a main chamber vacuum pump system (not shown) which removes gas molecules in main chamber 101 to reach a second pressure below the first pressure. After reaching the second pressure, the sample is subject to inspection by beam tool 104. Beam tool 104 may be a single -beam system or a multi-beam system.

[0037] A controller 109 is electronically connected to beam tool 104. Controller 109 may be a computer configured to execute various controls of EBI system 100. Controller 109 may also include processing circuitry configured to execute various signal and image processing functions. While controller 109 is shown in FIG. 1 as being outside of the structure that includes main chamber 101, load / lock chamber 102, and EFEM 106, it is appreciated that controller 109 may be a part of the structure.

[0038] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controllers, a microcontroller, a microprocessor, a digital signal processor, a hardware accelerator, an intellectual property (IP) core, a Programmable Logic Array (PLA), a Programmable Array Logic (PAL), a Generic Array Logic (GAL), a Complex Programmable Logic2025P00060WQ 8Device (CPLD), a Field-Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), a neural processing unit (NPU), and any other type of circuit capable of data processing. The processor may also be a virtual processor that includes one or more processors distributed across multiple machines or devices coupled via a network.

[0039] In some embodiments, controller 109 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes and data may include an operating system (OS) and one or more application programs (or “apps”) for specific tasks. The memory may also be a virtual memory that includes one or more memories distributed across multiple machines or devices coupled via a network.

[0040] FIG.2 illustrates a schematic diagram of an example multi -beam tool 104 (also referred to herein as apparatus 104) and an image processing system 290 that may be configured for use in EBI system 100 (FIG. 1), consistent with embodiments of the present disclosure. Beam tool 104 comprises a charged-particle source 202, a gun aperture 204, a condenser lens 206, a primary charged-particle beam 210 emitted from charged-particle source 202, a source conversion unit 212, a plurality of beamlets 214, 216, and 218 of primary charged-particle beam 210, a primary projection optical system 220, a motorized stage 280, a sample holder 282, multiple secondary charged-particle beams 236, 238, and 240, and a secondary imaging system 245 comprising a secondary optical system 242 or a charged-particle detection device 244. Primary projection optical system 220 may comprise a beam separator 222, a deflection scanning unit 226, and an objective lens 228. Charged-particle detection device 244 may comprise detection sub-regions 246, 248, and 250.

[0041] Charged-particle source 202, gun aperture 204, condenser lens 206, source conversion unit 212, beam separator 222, deflection scanning unit 226, and objective lens 228 may be aligned with a primary optical axis 260 of apparatus 104. Secondary optical system 242 and charged-particle detection device 244 may be aligned with a secondary optical axis 252 of apparatus 104.

[0042] Charged-particle source 202 may emit one or more charged particles, such as electrons, protons, ions, muons, or any other particle carrying electric charges. In some embodiments, charged-particle source 202 may be an electron source. For example, charged-particle source 202 may include a cathode, an extractor, or an anode, wherein primary electrons may be emitted from the cathode and extracted or accelerated to form primary charged-particle beam 210 (in this case, a primary electron beam) with a crossover (virtual or real) 208. For ease of explanation without causing ambiguity, electrons are used as examples in descriptions herein. However, it should be noted that any charged particle may be used in any embodiment of this disclosure, which is not limited to electrons. Primary electron beam 210 may be visualized as being emitted from crossover 208. Gun aperture 204 may2025P00060WQ 9block off peripheral electrons of primary electron beam 210 to reduce Coulomb effect. The Coulomb effect may cause an increase in size of probe spots.

[0043] Source conversion unit 212 may comprise an array of image-forming elements and an array of beam-limit apertures. The array of image-forming elements may comprise an array of microdeflectors or micro-lenses. The array of image-forming elements may form a plurality of parallel images (virtual or real) of crossover 208 with a plurality of beamlets 214, 216, and 218 of primary electron beam 210. The array of beam-limit apertures may limit the plurality of beamlets 214, 216, and 218. While three beamlets 214, 216, and 218 are shown in FIG. 2, embodiments of the present disclosure are not so limited. For example, in some embodiments, beam tool 104 may be configured to generate a first number of beamlets. In some embodiments, the first number of beamlets may be in a range from 1 to 10000. Controller 109 may be connected to various parts of electron beam inspection system 100 of FIG. 1, such as, but not limited to, source conversion unit 212, electron detection device 244, primary projection optical system 220, or motorized stage 280. In some embodiments, controller 109 may perform various image and signal processing functions. Controller 109 may also generate various control signals to govern operations of the electron beam inspection system.

[0044] Condenser lens 206 may collimate primary electron beam 210. The electric currents of beamlets 214, 216, and 218 down-beam of source conversion unit 212 may be varied by adjusting the focusing power of condenser lens 206 or by changing the radial sizes of the corresponding beam-limit apertures within the array of beam-limit apertures. Objective lens 228 may focus beamlets 214, 216, and 218 onto a sample 230 for imaging, and may form a plurality of probe spots 270, 272, and 274 on a surface of sample 230.

[0045] Beam separator 222 may be a beam separator of Wien filter type generating an electrostatic dipole field and a magnetic dipole field. In some embodiments, if they are applied, the force exerted by the electrostatic dipole field on an electron of beamlets 214, 216, and 218 may be substantially equal in magnitude and opposite in a direction to the force exerted on the electron by magnetic dipole field. Beamlets 214, 216, and 218 may, therefore, pass straight through beam separator 222 with zero deflection angle. However, the total dispersion of beamlets 214, 216, and 218 generated by beam separator 222 may also be non-zero. Beam separator 222 may separate secondary electron beams 236, 238, and 240 from beamlets 214, 216, and 218 and direct secondary electron beams 236, 238, and 240 towards secondary optical system 242.

[0046] Deflection scanning unit 226 may deflect beamlets 214, 216, and 218 to scan probe spots 270, 272, and 274 over a surface area of sample 230. In response to the incidence of beamlets 214, 216, and 218 at probe spots 270, 272, and 274, secondary electron beams 236, 238, and 240 may be emitted from sample 230. Secondary electron beams 236, 238, and 240 may comprise electrons with a distribution of energies. For example, secondary electron beams 236, 238, and 240 may include secondary electrons (energies < 50 eV) and backscattered electrons (energies between 50 eV and2025P00060WQ 10landing energies of beamlets 214, 216, and 218). Secondary optical system 242 may focus secondary electron beams 236, 238, and 240 onto detection sub-regions 246, 248, and 250 of electron detection device 244. Detection sub-regions 246, 248, and 250 may be configured to detect corresponding secondary electron beams 236, 238, and 240 and generate corresponding signals (e.g., voltage or current) used to reconstruct an image of structures on or underneath the surface area of sample 230. The generated corresponding signals may also include a spectrum of frequencies, wherein a low-frequency regime contains information about larger features of sample 230 and a high-frequency regime contains information about finer (i.e., sharper) features of sample 230.

[0047] The generated signals may represent intensities of secondary electron beams 236, 238, and 240 and may be provided to image processing system 290 that is in communication with secondary imaging system 245 (e.g., with electron detection device 244), primary projection optical system 220, and motorized sample stage 280. The movement speed of motorized sample stage 280 may be synchronized and coordinated with the beam deflections controlled by deflection scanning unit 226, such that the movement of the scan probe spots (e.g., scan probe spots 270, 272, and 274) may orderly cover regions of interests on the sample 230. The parameters of such synchronization and coordination may be adjusted to adapt to different materials of sample 230. For example, different materials of sample 230 may have different resistance-capacitance characteristics that may cause different signal sensitivities to the movement of the scan probe spots.

[0048] The intensity of secondary electron beams 236, 238, and 240 may vary according to the external or internal structure of sample 230, and thus may indicate whether sample 230 includes defects. Moreover, as discussed above, beamlets 214, 216, and 218 may be projected onto different locations of the top surface of sample 230, or different sides of local structures of sample 230, to generate secondary electron beams 236, 238, and 240 that may have different intensities. Therefore, by mapping the intensity of secondary electron beams 236, 238, and 240 with the areas of sample 230, image processing system 290 may reconstruct an image that reflects the characteristics of internal or external structures of sample 230.

[0049] In some embodiments, image processing system 290 may include an image acquirer 292, a storage 294, and a controller 296. Image acquirer 292 may comprise one or more processors. For example, image acquirer 292 may comprise a computer, server, mainframe host, terminals, personal computer, any other appropriate mobile computing devices. Image acquirer 292 may be communicatively coupled to electron detection device 244 of apparatus 104 through a medium such as an electric conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, or wireless radio. In some embodiments, image acquirer 292 may receive a signal from electron detection device 244 and may construct an image. Image acquirer 292 may thus acquire SEM images of sample 230. Image acquirer 292 may also perform various post-processing functions, including, but not limited to, generating contours and superimposing indicators on an acquired image. Image acquirer 292 may be configured to perform adjustments of brightness and contrast of acquired2025P00060WQ 11images. In some embodiments, storage 294 may be a storage medium including, but not limited to, a hard disk, flash drive, cloud storage, random access memory (RAM), or other types of computer-readable memory. Storage 294 may be coupled with image acquirer 292 and may be used for saving scanned raw image data as original images and post-processed images. Image acquirer 292 and storage 294 may be connected to controller 296. In some embodiments, image acquirer 292, storage 294, and controller 296 may be integrated together as one control unit.

[0050] In some embodiments, image acquirer 292 may acquire one or more SEM images of a sample based on an imaging signal received from electron detection device 244. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image comprising a plurality of imaging areas. The single image may be stored in storage 294. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of sample 230. The acquired images may comprise multiple images of a single imaging area of sample 230 sampled multiple times over a time sequence. The multiple images may be stored in storage 294. In some embodiments, image processing system 290 may include circuitry configured to perform image processing steps with the multiple images of the same location of sample 230.

[0051] In some embodiments, image processing system 290 may include measurement circuitry (e.g., analog-to-digital converters) configured to obtain a distribution of the detected secondary electrons. The electron distribution data collected during a detection time window, in combination with corresponding scan path data of beamlets 214, 216, and 218 incident on the sample surface, may be used to reconstruct images of the sample structures under inspection. The reconstructed images may be used to reveal various features of the internal or external structures of sample 230, and thereby may be used to reveal any defects that may exist in the sample.

[0052] When electrons of primary electron beam 210 are projected onto a surface of sample 230 (e.g., probe spots 270, 272, and 274), the electrons of primary electron beam 210 may penetrate the surface of sample 230 for a certain depth, interacting with particles of sample 230. Some electrons of primary electron beam 210 may elastically interact with (e.g., in the form of elastic scattering or collision) the materials of sample 230 and may be reflected or recoiled out of the surface of sample 230. An elastic interaction conserves the total kinetic energies of the bodies (e.g., electrons of primary electron beam 210) of the interaction, in which the kinetic energy of the interacting bodies does not convert to other forms of energy (e.g., heat or electromagnetic energy). Such reflected electrons generated from elastic interaction may be referred to as backscattered electrons (BSEs). Some electrons of primary electron beam 210 may inelastically interact with (e.g., in the form of inelastic scattering or collision) the materials of sample 230. An inelastic interaction does not conserve the total kinetic energies of the bodies of the interaction, in which some or all of the kinetic energy of the interacting bodies converts to other forms of energy. For example, through the inelastic interaction, the kinetic energy of some electrons of primary electron beam 210 may cause electron excitation and2025P00060WQ 12transition of atoms of the materials. Such inelastic interaction may also generate electrons exiting the surface of sample 230, which may be referred to as secondary electrons (SEs). Yield or emission rates of BSEs and SEs may depend on the material under inspection and the landing energy of the electrons of primary electron beam 210 landing on the surface of the material, among other factors. The energy of the electrons of primary electron beam 210 may be imparted in part by its acceleration voltage (e.g., the acceleration voltage between the anode and cathode of electron source 202 in FIG.2). The quantity of BSEs and SEs may be more or fewer (or even the same) than the injected electrons of primary electron beam 210.

[0053] While FIG. 2 shows detection device 244 having several detection sub-regions aligned with secondary optical axis 252, it is appreciated that other multi-beam detector schemes may exist. For example, it is appreciated that a detector may correspond with each beamlet, such as a different detector for each of beamlets 214, 216, 218. It is appreciated that these different detectors may be positioned under the primary column corresponding to primary axis 260. For example, these different detectors could be positioned between primary projection optical system 220 and the sample stage. Additionally, while FIG.2 shows detection device 244 having several detection sub-regions contacting one another, it is appreciated that other multi-beam detector schemes may exist and be used such that detection sub-regions may be separated from one another.

[0054] Reference is now made to FIG. 3A, which is an example schematic of a primary charged particle beam scanning over a sample, consistent with embodiments of the present disclosure. FIG. 3 illustrates a top view of a sample 301 to be inspected in a charged particle beam apparatus. A probe spot (e.g., probe spot 270 in FIG.2) may be at a first position 302, which represents a position of a beam spot for a primary charged particle beam impacting a surface of sample 301. During a scanning operation of the charged particle beam apparatus, the probe spot may be scanned from first position 302 across the surface of sample 301 in a scanning direction 303 to a second position 304.

[0055] Reference is now made to FIG. 3B, which is an example schematic of secondary charged particles emitted during a scanning operation and may enter a secondary imaging system, consistent with embodiment of the present disclosure. FIG.3B illustrates a first group 305 of secondary charged particle beams, which may be emitted from sample 301 at first location 302 in FIG. 3A, and a second group 306 of secondary charged particle beams, which may be emitted from sample 301 at second location 304 in FIG. 3A. Because the probe spot was scanned across the surface of sample 301, second group 306 of secondary charged particle beams may be shifted relative to first group 305 of secondary charged particle beams. First group 305 of secondary charged particle beams and second group 306 of secondary charged particle beams may enter a secondary imaging system 307, which may comprise a secondary optical system 308 (e.g., secondary optical system 242 in FIG. 2) or a detector 309 (e.g., charged-particle detection device 244 in FIG. 2). Although FIG. 3B illustrates that both secondary optical system 308 and detector 309 are contained within secondary imaging system 307, embodiments of the present disclosure are not so limited. For example, secondary imaging2025P00060WQ 13system 307 may contain detector 309 or secondary optical system 308. Secondary optical system 308 may comprise an anti-scanning deflection unit 310, a zoom lens 311, and a projection lens 312. Antiscanning deflection unit 310 may be configured to deflect secondary charged particles and may include an anti-scanning deflector 313. Zoom lens 311 may include a plurality of electrostatic lenses. Projection lens 312 may include an electrostatic lens or a magnetic lens.

[0056] As seen in FIG.3B, secondary optical system 308 may include components that influence secondary charged particle beams travelling therethrough. Components in secondary optical system 308 may influence charged particle beamlets together. For example, common for all charged particle beamlets entering secondary optical system 308, anti-scanning deflection unit 310 may shift the incoming array of secondary charged particle beamlets (e.g., second group 306 of secondary charged particle beams) with respect to a secondary optical axis 314 or secondary charged particles beams in first group 305 with respect to secondary optical axis 314). Anti-scanning deflection unit 310 may be configured to minimize an image displacement on detector 309. Detector 309 may comprise a first sensor 309_l, a second sensor 309_2, and a third sensor 309_3. A secondary charged particle beam may impact a sensor in detector 309 at a one-to-one correspondence (e.g., one secondary charged particle beam for one sensor). Image displacement on detector 309 may originate from the motion of probe spots across the inspected area on a surface of a sample (e.g., sample 301 in FIG. 3A). Antiscanning deflection unit 310 may influence beams in step with a charged particle deflection scanning system of the primary charged particle beam. For example, anti-scanning deflection unit 310 may influence secondary charged particles in first group 305 of secondary charged particle beams and in second group 306 of secondary charged particle beams in step with a scanning deflection unit (e.g., scanning deflection unit 226 in FIG. 2). Detector 309 may detect charged particles coming as a plurality of the beamlets. Detector 309 may be assembled from individual sensors (e.g., first sensor 309_l, second sensor 309_2, third sensor 309_3) or may be implemented as one detector with a plurality of sensitive elements (e.g., detector segments or groups of sensitive elements, such as a group of small pixels). Each secondary beamlet may be configured to be projected onto the corresponding detector or the detector segment.

[0057] Reference is now made to FIG. 4A, which is an example schematic of a detector for secondary charged particle beams, consistent with embodiments of the present disclosure. FIG. 4A illustrates a surface of a detector 401 containing regions 402-410 (which may each correspond to an individual sensor or sensing element), each configured to receive a secondary charged particle beamlet. For example, a secondary charged particle beamlet (e.g., a beamlet from first group 305 of secondary charged particle beams in FIG. 3B) may impact region 402 and a different secondary charged particle beamlet (e.g., a beamlet from second group 306 of secondary charged particle beams in FIG. 3B) may impact region 405. After anti-scanning alignment, secondary charged particle beams may impact at respective regions 402-410 on detector 401 such that no cross-talk or overlap of2025P00060WQ 14secondary charged particle beams occurs. However, as discussed above, it may be difficult to achieve optimal alignment where no overlap or cross-talking occurs with reliable and standardized precision.

[0058] Performance of the secondary column in a multi-beam charged particle apparatus may be determined by two main parameters: collection efficiency and cross-talk. The collection efficiency of a single detector cell may be defined as a fraction of the secondary electrons emitted from a corresponding probe spot within one of the sub-regions of the inspected area and detected by the corresponding detection element. Collection efficiency may be initially defined for each detection element. In some embodiments, for characterization of the whole detector, the average value for the collection efficiency of all detection elements may be derived. In some embodiments, collection efficiency may be supplemented with numbers characterizing the spread of values between elements, such as minimum and maximum values across all elements of the detector.

[0059] Cross-talk may be defined as a fraction of the secondary electrons detected by an individual detector cell originating not from the corresponding sub-region of the scanned area but from neighboring sub-regions. Similar to the collection efficiency, the average, minimum, and maximum values across all elements of the detector may be calculated for characterization of the entire detector.

[0060] High collection efficiency and low cross-talk may be significant design parameters for achieving high resolution and high throughput for a multi-beam charged-particle apparatus to be utilized as defect inspection tools at semiconductor manufacturing fabs.

[0061] Reference is now made to FIG. 4B, which is an example schematic of scanning areas of secondary charged particle beams on a detector. FIG.4B illustrates a variable area in which secondary charged particle beams may scan over detector 401 because of scanning a primary charged particle beam on a sample (e.g., as seen in FIG.3A). For example, a secondary charged particle beam may scan over region 402 within a scan area 411, and a different secondary charged particle beam may scan over region 403 within a scan area 412. Because a secondary charged particle beam may impact detector 401 anywhere within the scan area (e.g., scan area 411), there may be portions of detector 401 where a signal may be indistinguishable from one secondary charged particle beam to a second secondary charged particle beam. FIG.4B illustrates this overlap as overlapping area 412, which represents a signal received from a secondary charged particle beam impacting region 402 and a different secondary charged particle impacting region 402.

[0062] Reference is now made to FIG. 4C, which illustrates aligned secondary charged particle beams on a detector by anti-scanning, consistent with embodiments of the present disclosure. FIG. 4C illustrates beam spots 413-421 for different secondary charged particle beams impacting regions 402-410 on detector 401. FIG.4C illustrates an optimal anti-scanning alignment in which secondary charged particle beams impact detector 401 at set locations (e.g., a one-to-one correspondence between a secondary charged particle beam and a region) and a desired beam spot size. For example, beam spots 413-421 may represent a smallest beam spot size for the secondary charged particle beams impacting detector 401.2025P00060WQ 15

[0063] In existing methods to align secondary charged particles onto a detector during anti-scanning, a user may observe an image such as FIG. 4B and adjust knobs or controls to obtain an image such as FIG.4C. However, the existing methods for anti-scanning alignment do not provide a way for the user to determine which knobs or controls to adjust and how much adjustment is needed to obtain an optimal alignment such as FIG.4C. Additionally, the user may not be able to determine if the resulting alignment image is optimal or accurate. Accordingly, the existing methods for anti-scanning alignment of secondary charged particle beams do not enable a user to quantify and streamline the alignment for improved efficiency and accuracy.

[0064] In contrast, embodiments of the present disclosure provide a method of quantifying an antiscanning alignment of a secondary charged particle beam. In some embodiments, the present disclosure provides a method of calculating a behavior of a secondary charged particle beam in response to anti-scanning and determining a mathematical model to calculate a relationship between a setting for an anti-scanning deflection unit and the corresponding behavior of the secondary charged particle beam. In some embodiments, the mathematical model may enable predictions of how a secondary charged particle beam may respond to any setting or input signal provided to an antiscanning deflection unit. Additionally, some embodiments of the present disclosure provide a method for quantifying an anti-scanning alignment of a secondary charged particle beam during a scanning operation in a charged particle beam apparatus. A desired behavior of a secondary charged particle beam in response to anti-scanning may be calculated to counteract an influence of scanning a primary charged particle beam. In some embodiments, a mathematical model may be determined to calculate a relationship between a scanning setting and a desired behavior of the secondary charged particle beam. The mathematical model may enable rapid and accurate generation of settings or input signals to be provided to a secondary imaging system for anti-scanning of secondary charged particle beams during scanning of a primary charged particle beam, which can improve not only processing but also throughput.

[0065] Reference is now made to FIG. 5A, which is an example schematic of determining a behavior of a secondary charged particle beam in response to anti-scanning in a charged particle beam system, consistent with embodiments of the present disclosure. FIG. 5A illustrates a controller 501 (e.g., controller 109 in FIG. 1 or controller 296 in FIG. 2) may send a signal to a primary projection optical system 502 (e.g., primary projection optical system 220 in FIG.2) such that a primary charged particle beam 503 does not scan across a surface of a sample 504. Secondary charged particle beams 505 may be emitted and collected by secondary imaging system 506 (e.g., secondary imaging system 245 in FIG.2 or secondary imaging system 307 in FIG. 3B). In some embodiments, secondary imaging system 506 may comprise a secondary optical system 507 (e.g., secondary optical system 242 in FIG. 2 or secondary optical system 308 in FIG.3B) or a detector 508 (e.g., detector 309 in FIG.3B, detector 401 in FIGs.4A-4C, or electron detection device 244 in FIG.2). Controller 501 may be communicatively connected to primary projection optical system 502, secondary imaging system 506,2025P00060WQ 16secondary optical system 507, or detector 508. Secondary optical system 507 may comprise antiscanning components such as an anti-scanning deflection unit. In addition to providing a signal to primary projection optical system 502, controller 501 may also send a signal to a secondary imaging system 506 such that secondary imaging system 506 does not perform anti-scanning on secondary charged particle beams 505. In some embodiments, controller 501 may send a signal to an antiscanning deflection unit in secondary imaging system 506 to not perform anti-scanning on secondary charged particle beams 505.

[0066] Reference is now made to FIGs.5B-5E, which are example schematics of calculating a behavior of a secondary charged particle beam in response to anti-scanning, consistent with embodiments of the present disclosure. FIG. 5B is an example schematic of a region 509 on detector 508 (FIG.5A). First position 510 (dotted outline) represents a beam spot of a secondary charged particle beam from secondary charged particle beams 505 impacting region 509 due to no antiscanning performed on the secondary charged particle beam. Controller 501 may apply a first target signal to an anti-scanning deflection unit to perform anti-scanning of the secondary charged particle beam impacting region 509. In some embodiments, the first target signal may represent a voltage or a current that can, for example, be applied to electrodes of anti-scanning deflection unit (or one or more drivers of anti-scanning deflection unit). In some embodiments, the first target signal may correspond to adjusting a parameter of the secondary charged particle beam by a first desired or target amount. In some embodiments, controller 501 may apply a first target signal to an anti-scanning deflection unit to change a parameter of a secondary charged particle beam by a first target adjustment by antiscanning. In some embodiments, the parameter of the secondary charged particle beam may correspond to a focus of the secondary charged particle beam. In some embodiments, the parameter of the secondary charged particle beam may be a beam spot location on a detector (e.g., region 509), a beam spread value, a beam spot size, or a beam spot shape of the secondary charged particle beam.

[0067] FIG.5B illustrates a first target adjustment 511 (e.g., an expected change) of a parameter of a secondary charged particle beam. First target adjustment 511 may correspond to controller 501 providing a first target signal to an anti-scanning deflection unit to perform anti-scanning. In some embodiments, the first target signal may be expected to cause first target adjustment 511 of a beam spot location of the secondary charged particle beam to a first target position 512 of the beam spot. In some embodiments, the first target signal may be expected to cause first target adjustment 511 in a first direction (e.g., an X-direction). However, a first adjustment of the beam spot may not match first target adjustment 511.

[0068] FIG.5C illustrates a first adjustment 513 (e.g., a resulting change) from first position 510 to a first adjusted position 514 of the secondary charged particle beam in response to anti-scanning (e.g., the first target signal being applied to an anti-scanning deflection unit). FIG.5C shows that first adjustment 513 may have different X and Y parameters from first target adjustment 511 in FIG. 5B, but embodiments of the present disclosure are not so limited. For example, first adjustment 513 may2025P00060WQ 17have a same Y parameter compared to first target adjustment 511 and a different X parameter (e.g., a smaller value). In some embodiments, controller 501 may measure first adjustment 513 and associate first adjustment 513 with the first target signal.

[0069] FIG.5D is an example schematic of region 509 in which controller 501 applies a second target signal to an anti-scanning deflection unit to perform anti-scanning of the secondary charged particle beam at first position 510. In some embodiments, the second target signal may represent a voltage or a current. In some embodiments, the second target signal may correspond to adjusting a parameter of the secondary charged particle beam by a second desired or target amount. In some embodiments, controller 501 may apply a second target signal to an anti-scanning deflection unit to change a parameter of a secondary charged particle beam by a second target adjustment by antiscanning. FIG.5D illustrates a second target adjustment 515 (e.g., an expected change) of a parameter of a secondary charged particle beam. Second target adjustment 515 may correspond to controller 501 providing a second target signal to an anti-scanning deflection unit to perform antiscanning. In some embodiments, the second target signal may be expected to cause second target adjustment 515 of a beam spot location of the secondary charged particle beam to a second target position 516 for the beam spot. In some embodiments, the second target signal may be expected to cause second target adjustment 515 in a second direction (e.g., a Y-direction). However, a second adjustment of the beam spot may not match second target adjustment 515.

[0070] FIG.5E illustrates a second adjustment 517 (e.g., a resulting change) from first position 510 to a second adjusted position 518 of the secondary charged particle beam in response to anti-scanning (e.g., the second target signal being applied to an anti-scanning deflection unit). FIG. 5E shows that second adjustment 517 may have different X and Y parameters from second target adjustment 515 in FIG.5D, but embodiments of the present disclosure are not so limited. For example, second adjustment 517 may have a same X parameter compared to second target adjustment 515 and a different Y parameter (e.g., a smaller value). In some embodiments, controller 501 may measure second adjustment 517 and associate second adjustment 517 with the second target signal.

[0071] In some embodiments, the parameter of the secondary charged particle beam to be adjusted by anti-scanning is a beam spread value. Reference is now made to FIGs.5F-5I, which are example schematics of calculating a behavior of a secondary charged particle beam in response to antiscanning, consistent with embodiments of the present disclosure.

[0072] FIG.5F is an example schematic of a region 519 on detector 508 (FIG.5A). First beam spread 520 (dotted outline) represents a beam spread of a secondary charged particle beam from secondary charged particle beams 505 impacting region 519 with no anti-scanning performed on the secondary charged particle beam. Controller 501 may apply a first target signal to an anti-scanning deflection unit to perform anti-scanning of the secondary charged particle beam impacting region 519.FIG.5F illustrates a first target adjustment 521 (e.g., an expected change) of a parameter of a secondary charged particle beam that corresponds to the first target signal. In some embodiments, the2025P00060WQ 18first target signal may be expected to cause first target adjustment 521 of a beam spread of the secondary charged particle beam to achieve a first target beam spread 522. In some embodiments, the first target signal may be expected to cause first target adjustment 521 in a first direction (e.g., an X-direction). However, a first adjustment of the parameter of the secondary charged particle beam may not match first target adjustment 521.

[0073] FIG.5G illustrates a first adjustment 523 (e.g., a resulting change) from first beam spread 520 to a first adjusted beam spread 524 of the secondary charged particle beam in response to antiscanning (e.g., the first target signal being applied to an anti-scanning deflection unit). FIG.5G shows that first adjustment 523 may have a different X parameter from first target adjustment 521 in FIG.5F, but embodiments of the present disclosure are not so limited. For example, first adjustment 523 may have a different Y parameter compared to first target adjustment 521 and a same X parameter, or a different Y and X parameter. In some embodiments, controller 501 may measure first adjustment 523 and associate first adjustment 523 with the first target signal.

[0074] FIG.5H illustrates an example schematic of region 519 in which controller 501 applies a second target signal to an anti-scanning deflection unit to perform anti-scanning of the secondary charged particle beam. In some embodiments, the second target signal may correspond to adjusting a parameter of the secondary charged particle beam by a second desired or target amount. In some embodiments, controller 501 may apply a second target signal to an anti-scanning deflection unit to change a parameter of a secondary charged particle beam by a second target adjustment by antiscanning. FIG.5H illustrates a second target adjustment 525 (e.g., an expected change) of a parameter of a secondary charged particle beam. Second target adjustment 525 may be an expected change caused by controller 501 providing a second target signal to anti-scanning deflection unit to perform anti-scanning. In some embodiments, the second target signal may be expected to cause second target adjustment 525 to achieve a second target beam spread 527. In some embodiments, the second target signal may be expected to cause second target adjustment 525 in a second direction (e.g., a Y-direction). However, a second adjustment of the parameter of the secondary charged particle beam may not match second target adjustment 525.

[0075] FIG.51 illustrates a second adjustment 528 (e.g., a resulting change) from second beam spread 526 to a second adjusted beam spread 529 of the secondary charged particle beam in response to anti-scanning (e.g., the second target signal being applied to an anti-scanning deflection unit). FIG.51 shows that second adjustment 528 may have a different Y parameter from second target adjustment 525 in FIG.51, but embodiments of the present disclosure are not so limited. For example, second adjustment 528 may have a same Y parameter as second target adjustment 525 and a different X parameter. In some embodiments, second adjustment 528 may have a different X and Y parameter compared to second target adjustment 525. In some embodiments, controller 501 may measure second adjustment 528 and associate second adjustment 528 with the second target signal.2025P00060WQ 19

[0076] Although FIGs. 5B-5I show a parameter of the secondary charged particle beam as a beam spot location or a beam spread, embodiments of the present disclosure are not so limited. For example, any of the above embodiments described for FIGs.5A-5I may be applicable and realized for adjusting other parameters of a secondary charged particle beam.

[0077] Reference is now made to FIG. 6, which is an illustration of an example workflow for calculating an optimal adjustment for anti-scanning of a secondary charged particle beam, consistent with embodiments of the present disclosure. FIG.6 illustrates a controller 601 (as described above) may build a mathematical model 606 using a first target signal 602, a first adjustment 603, a second target signal 604, and a second adjustment 605. The first target signal 602, first adjustment 603, second target signal 604, and second adjustment 605 may be as described above. Controller 601 may associate first target signal 602 with first adjustment 603 and second target signal 604 with second adjustment 605. Accordingly, mathematical model 606 may comprise a first formulation and a second formulation. In some embodiments, the first formulation comprises first target signal 602 and first adjustment 603. In some embodiments, the second formulation comprises second target signal 604 and second adjustment 605. Controller 601 may use mathematical model 606 to solve or calculate a signal 607 that corresponds to an optimal setting for anti-scanning alignment of a secondary charged particle beam. In some embodiments, mathematical model 606 may comprise a system of equations or any other mathematical function or system to solve two or more expressions with unknown variables. Signal 607 may then be provided to a secondary imaging system 608 (as described above) to provide an optimal adjustment 609 to a secondary charged particle beam during anti-scanning. In some embodiments, signal 607 may be provided to an anti-scanning deflection unit of secondary imaging system 608. In some embodiments, optimal adjustment 609 may be an adjustment to a parameter of a secondary charged particle beam as described above. It is appreciated that optimal adjustment 609 may be understood to include any adjustment a user wishes to obtain for a parameter of a secondary charged particle beam by inputting signal 607 for anti-scanning (e.g., a desired beam spot location or beam spread).

[0078] Reference is now made to FIG. 7, which is a flowchart of an example method 700 of calculating a behavior of a secondary charged particle beam in response to anti-scanning deflection in a charged particle beam apparatus, consistent with embodiments of the present disclosure. The steps of method 700 may be performed for a charged particle beam system, for example, as shown in FIGs.1, 2, and 5A, executing on or otherwise using the features of a computing device (e.g., controller 109 of FIG. 1, controller 296 of FIG. 2, controller 501 in FIG. 5A, or controller 601 in FIG. 6). It is appreciated that the illustrated method 700 may be altered to modify the order of steps and to include additional steps. The steps of method 700 may be applicable to embodiments as illustrated in FIGs. 3, 5A-5I, and 6.

[0079] In step S701, a parameter of a secondary charged particle beam is changed by providing a first target signal and a second target to an anti-scanning deflection unit. The parameter may be2025P00060WQ 20changed by the anti-scanning unit, by a first adjustment, according to the first target signal. The parameter may be changed by the anti-scanning unit, by a second adjustment, according to the second target signal.

[0080] In step S702, a mathematical model is determined based on the first target signal, the first adjustment, the second target signal, and the second adjustment. The mathematical model may comprise a first formulation and a second formulation. The first formulation may comprise the first target signal and the first adjustment. The second formulation may comprise the second target signal and the second adjustment. The mathematical model may comprise a system of equations or any other mathematical expression or function to solve two or more expressions with unknown variables. The mathematical model may be a model to determine an adjustment to the parameter for any target signal.

[0081] In step S703, a signal is calculated using the mathematical model for adjusting the parameter. The calculated signal may be provided to the anti-scanning deflection unit to cause the anti-scanning deflection unit to adjust the parameter of the secondary charged particle beam by the optimal adjustment.

[0082] Reference is now made to FIG. 8A, which is an example schematic for calculating an antiscanning behavior of a secondary charged particle beam in response to scanning a primary charged particle beam in a charged particle beam system, consistent with embodiments of the present disclosure. FIG.8 illustrates a controller 801 (e.g., controller 109 in FIG. 1 or controller 296 in FIG.2) may send a first scanning signal to a primary projection optical system 802 (e.g., primary projection optical system 220 in FIG. 2) such that a primary charged particle beam 803 scans a first probe spot 805 across a surface of a sample 804 in a first scanning direction 806 to a second probe spot 807. Controller 801 may also send a second scanning signal to primary projection optical system 802 such that primary charged particle beam 803 scans first probe spot 805 across a surface of sample 804 in a second scanning direction 808 to a third probe spot 809. Secondary charged particle beams 810 may be emitted and collected by secondary imaging system 811 (e.g., secondary imaging system 245 in FIG.2 or secondary imaging system 307 in FIG. 3B). In some embodiments, secondary imaging system 811 may comprise a secondary optical system 812 (e.g., secondary optical system 242 in FIG. 2 or secondary optical system 308 in FIG.3B) or a detector 813 (e.g., detector 309 in FIG.3B, detector 401 in FIGs.4A-4C, or electron detection device 244 in FIG.2). Controller 801 may be communicatively connected to primary projection optical system 802, secondary imaging system 811, secondary optical system 812, or detector 813. Secondary optical system 812 may comprise antiscanning components such as an anti-scanning deflection unit. In addition to providing a signal to primary projection optical system 802, controller 801 may also send a signal to a secondary imaging system 811 such that secondary imaging system 811 performs anti-scanning on secondary charged particle beams 810. In some embodiments, controller 801 may send a signal to an anti-scanning2025P00060WQ 21deflection unit in secondary imaging system 811 to perform anti-scanning on secondary charged particle beams 810.

[0083] Reference is now made to FIGs.8B-8E, which are example schematics of calculating an antiscanning behavior of a secondary charged particle beam in response to scanning a primary charged particle beam, consistent with embodiments of the present disclosure. FIG. 8B is an example schematic of a secondary charged particle beam impacting a region 814 on detector 813 (FIG.8A). FIG.8B illustrates a secondary charged particle beam parameter at first position 815 prior to scanning of primary charged particle beam 803 in first scanning direction 806. Controller 801 may provide a first scanning signal to primary projection optical system 802 to scan primary charged particle beam 803 in first scanning direction 806, which may cause the secondary charged particle beam parameter to change. In some embodiments, the secondary charged particle beam parameter may be a beam spot location. FIG. 8B illustrates a secondary charged particle beam spot that has shifted from first position 815 to a shifted position 817 by a first displacement 816, where first displacement 816 is due to first scanning direction 806 of primary charged particle beam 803. In some embodiments, controller 801 may calculate a first signal to apply to an anti-scanning deflection unit as described above (e.g., FIG. 6). In some embodiments, controller 801 may calculate a first signal for antiscanning deflection unit to deflect the secondary charged particle beam parameter by a first adjusted displacement 818 to account for first displacement 816. In some embodiments, the first signal may be calculated such that first adjusted displacement 818 is equal and opposite to first displacement 816. Accordingly, the anti-scanning deflection unit may deflect the secondary charged particle beam back to first position 815 during scanning of primary charged particle beam 803 in first scanning direction 806. Therefore, the secondary charged particle beam may not move in region 814 while primary charged particle beam 803 is scanning in first scanning direction 806.

[0084] FIG.8C illustrates a secondary charged particle beam parameter at first position 815 prior to scanning of primary charged particle beam 803 in second scanning direction 808. Controller 801 may provide a second scanning signal to primary projection optical system 802 to scan primary charged particle beam 803 in second scanning direction 808, which may cause the secondary charged particle beam parameter to change. In some embodiments, the secondary charged particle beam parameter may be a beam spot location. FIG.8C illustrates a secondary charged particle beam spot that has shifted from first position 815 to a shifted position 820 by a second displacement 819, where second displacement 819 is due to second scanning direction 808 of primary charged particle beam 803. In some embodiments, controller 801 may calculate a second signal to apply to an anti-scanning deflection unit as described above (e.g., FIG. 6). In some embodiments, controller 801 may calculate a second signal for anti-scanning deflection unit to deflect the secondary charged particle beam parameter by a second adjusted displacement 821 to account for second displacement 819. In some embodiments, the second signal may be calculated such that second adjusted displacement 821 is equal and opposite to second displacement 819. Accordingly, the anti-scanning deflection unit may2025P00060WQ 22deflect the secondary charged particle beam back to first position 815 during scanning of primary charged particle beam 803 in second scanning direction 808. Therefore, the secondary charged particle beam may not move in region 814 while primary charged particle beam 803 is scanning in second scanning direction 808.

[0085] In some embodiments, the secondary charged particle beam parameter comprises a beam spread. FIG.8D illustrates a secondary charged particle beam parameter having a first spread 822 prior to scanning of primary charged particle beam 803 in first scanning direction 806. Controller 801 may provide a first scanning signal to primary projection optical system 802 to scan primary charged particle beam 803 in first scanning direction 806, which may cause the secondary charged particle beam spread to change. FIG.8D illustrates a secondary charged particle beam spread that has shifted from first spread 822 to a shifted spread 823 (dotted outline) by a first displacement 824, where first displacement 824 is due to first scanning direction 806 of primary charged particle beam 803. In some embodiments, controller 801 may calculate a first signal to apply to an anti-scanning deflection unit as described above (e.g., FIG.6). In some embodiments, controller 801 may calculate a first signal for anti-scanning deflection unit to deflect the secondary charged particle beam parameter by a first adjusted displacement 825 to account for first displacement 824. In some embodiments, the first signal may be calculated such that first adjusted displacement 825 is equal and opposite to first displacement 824. Accordingly, the anti-scanning deflection unit may deflect the secondary charged particle beam back to first spread 822 during scanning of primary charged particle beam 803 in first scanning direction 806. Therefore, the secondary charged particle beam may not spread while primary charged particle beam 803 is scanning in first scanning direction 806.

[0086] FIG.8E illustrates a secondary charged particle beam parameter having first spread 822 prior to scanning of primary charged particle beam 803 in second scanning direction 808. Controller 801 may provide a second scanning signal to primary projection optical system 802 to scan primary charged particle beam 803 in second scanning direction 808, which may cause the secondary charged particle beam spread to change. FIG. 8D illustrates a secondary charged particle beam spread that has shifted from first spread 822 to a shifted spread 826 (dotted outline) by a second displacement 827, where second displacement 827 is due to second scanning direction 808 of primary charged particle beam 803. In some embodiments, controller 801 may calculate a second signal to apply to an antiscanning deflection unit as described above (e.g., FIG.6). In some embodiments, controller 801 may calculate a second signal for anti-scanning deflection unit to deflect the secondary charged particle beam parameter by a second adjusted displacement 828 to account for second displacement 827. In some embodiments, the second signal may be calculated such that second adjusted displacement 828 is equal and opposite to second displacement 827. Accordingly, the anti-scanning deflection unit may deflect the secondary charged particle beam back to first spread 822 during scanning of primary charged particle beam 803 in second scanning direction 808. Therefore, the secondary charged2025P00060WQ 23particle beam may not spread while primary charged particle beam 803 is scanning in second scanning direction 808.

[0087] Reference is now made to FIG. 9, which is an illustration of an example workflow for calculating an optimal adjustment for anti-scanning of a secondary charged particle beam during scanning of a primary charged particle beam, consistent with embodiments of the present disclosure.FIG.9 illustrates a controller 901 (as described above) may build a mathematical model 908 using a first scanning direction 902, a first displacement 903, a first signal 904, a second scanning direction 905, a second displacement 906, and a second signal 907. The first scanning direction 902, a first displacement 903, a first signal 904, a second scanning direction 905, a second displacement 906, and a second signal 907 may be as described above. In some embodiments, controller 901 may associate first scanning direction 902 (or a first scanning signal to cause first scanning direction 902) with first displacement 903 and first signal 904. In some embodiments, controller 901 may associate second scanning direction 905 (or a second scanning signal to cause second scanning direction 905) with second displacement 906 and second signal 907. Accordingly, mathematical model 908 may comprise a first formulation and a second formulation. In some embodiments, the first formulation comprises first scanning direction 902, first displacement 903, and first signal 904. In some embodiments, the second formulation comprises second scanning direction 905, second displacement 906, and second signal 907. Controller 901 may use mathematical model 908 to solve or calculate a signal 909 that corresponds to an optimal setting for anti-scanning alignment of a secondary charged particle beam during scanning of a primary charged particle beam in any direction. In some embodiments, mathematical model 908 may comprise a system of equations or any other mathematical function or system to solve two or more expressions with unknown variables. Signal 909 may then be provided to a secondary imaging system 910 (as described above) to provide an optimal anti-scanning alignment 911 to a secondary charged particle beam during scanning of a primary charged particle beam. In some embodiments, signal 909 may be provided to an anti-scanning deflection unit of secondary imaging system 910. In some embodiments, optimal anti-scanning alignment 911 may be an adjustment to a parameter of a secondary charged particle beam as described above. It is appreciated that optimal anti-scanning alignment 911 may be understood to include any adjustment a user wishes to obtain for a parameter of a secondary charged particle beam by inputting signal 909 for antiscanning (e.g., a desired beam spot location or beam spread).

[0088] Reference is now made to FIG. 10, which is a flowchart of an example method 1000 of adjusting a secondary charged particle beam during operation of a charged particle system, consistent with embodiments of the present disclosure. The steps of method 1000 may be performed for a charged particle beam system, for example, as shown in FIGs. 1, 2, 5A, and 8A, executing on or otherwise using the features of a computing device (e.g., controller 109 of FIG. 1, controller 296 of FIG.2, controller 501 in FIG.5A, controller 801 in FIG. 8A, or controller 901 in FIG. 9). It is appreciated that the illustrated method 1000 may be altered to modify the order of steps and to include2025P00060WQ 24additional steps. The steps of method 1000 may be applicable to embodiments as illustrated in FIGs.3, 5A-51, 6, 8A-8E, and 9.

[0089] In step SI 001, a primary charged particle beam is scanned in a first scanning direction and a second scanning direction on a sample. A secondary charged particle beam is generated from incidence of the primary charged particle beam on the sample. A controller may provide a first scanning signal and a second scanning signal to cause scanning of the primary charged particle beam in the first scanning direction and the second scanning direction, respectively.

[0090] In step SI 002, a first displacement of a parameter of the secondary charged particle beam is determined based on the first scanning direction and a second displacement of a parameter of the secondary charged particle beam is determined based on the second scanning direction. The parameter may be a beam spot size, beam spot location, beam spot shape, or beam spot spread of the secondary charged particle beam.

[0091] In step S1003, a first signal and a second signal to apply to an anti-scanning deflection unit for deflecting the secondary charged particle beam is calculated. The first signal is calculated to counteract the first displacement and the second signal is calculated to counteract the second displacement.

[0092] In step S1004, a mathematical model that comprises a first formulation and a second formulation is determined. The first formulation comprises the first signal, the first displacement of the parameter of the secondary charged particle beam, and the first scanning direction of the primary charged particle beam. The second formulation comprises the second signal, the second displacement of the parameter of the secondary charged particle beam, and the second scanning direction. The mathematical model may comprise a system of equations or any other mathematical expression or function to solve two or more expressions with unknown variables. The mathematical model may be a model to determine a relationship between a signal to an anti-scanning deflection unit and a scanning signal for scanning a primary charged particle beam.

[0093] In step SI 005, the mathematical model is used to calculate a signal to be provided to the antiscanning deflection unit to align a secondary charged particle beam generated from scanning the primary charged particle beam in a third scanning direction.

[0094] A non-transitory computer readable medium may be provided that may store instructions for a processor of a controller (e.g., controller 109 of FIG. 1, controller 296 of 2, controller 501 of FIG.5A, controller 601 of FIG. 6, controller 801 in FIG.8A, or controller 901 in FIG. 9) to calculate a target signal, a signal to cause a displacement or adjustment, generate a mathematical model, or calculate an optimal signal or adjustment, perform inspection image acquisition, activating charged particle source, method 700, method 1000, and other executable functions in the charged particle system relating to anti-scan alignment of a secondary charged particle beam. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-2025P00060WQ 25ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0095] The embodiments may further be described using the following clauses:1. A non- transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for calculating a behavior of a secondary charged particle beam resulting from anti-scanning deflection in a charged particle beam apparatus, the operations comprising:changing a parameter of the secondary charged particle beam, using an anti-scanning deflection unit, by a first adjustment according to a first target signal provided to the anti-scanning deflection unit and by a second adjustment according to a second target signal provided to the antiscanning deflection unit;determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first target signal and the first adjustment and the second formulation comprises the second target signal and the second adjustment; and calculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit for adjusting the parameter of the secondary charged particle beam.2. The non-transitory computer readable medium of clause 1, wherein the anti-scanning deflection unit comprises an anti-scanning deflector.3. The non-transitory computer readable medium of clause 1 or 2, wherein the first adjustment comprises adjusting the parameter of the secondary charged particle beam in a first direction.4. The non-transitory computer readable medium of any one of clauses 1 to 3, wherein the second adjustment comprises adjusting the parameter of the secondary charged particle beam in a second direction.5. The non-transitory computer readable medium of clause 3 or 4, wherein the first direction and the second direction are different from each other.6. The non-transitory computer readable medium of any one of clauses 3 to 5, wherein the first direction is in an X-direction.7. The non-transitory computer readable medium of any one of clauses 3 to 6, wherein the second direction is in a Y-direction.8. The non-transitory computer readable medium of any one of clauses 1 to 7, wherein the parameter of the secondary charged particle beam corresponds to a focus of the secondary charged particle beam on a surface of a detector.2025P00060WQ 269. The non-transitory computer readable medium of any one of clauses 1 to 8, wherein the parameter of the secondary charged particle beam comprises a beam spot location, a beam spread value, a beam spot size, or a beam spot shape of the secondary charged particle beam.10. The non-transitory computer readable medium of any one of clauses 1 to 9, wherein the first target signal comprises a first electrical signal.11. The non-transitory computer readable medium of any one of clauses 1 to 10, wherein the second target signal comprises a second electrical signal.12. The non-transitory computer readable medium of clause 10 or 11, wherein the first electrical signal and the second electrical signal are different from each other.13. The non-transitory computer readable medium of any one of clauses 1 to 12, wherein the first target signal represents a first voltage or a first current applied to the anti-scanning deflection unit.14. The non-transitory computer readable medium of any one of clauses 1 to 13, wherein the second target signal represents a second voltage or a second current applied to the anti-scanning deflection unit.15. The non-transitory computer readable medium of any one of clauses 1 to 14, wherein the charged particle beam apparatus is a multi-beam charged particle beam apparatus.16. A method of calculating a behavior of a secondary charged particle beam resulting from anti-scanning deflection in a charged particle beam apparatus, the method comprising the operations of any one of clauses 1-15.17. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for adjusting a secondary charged particle beam during operation of a charged particle beam apparatus, the operations comprising:scanning of a primary charged particle beam in a first scanning direction and a second scanning direction on a sample, wherein a secondary charged particle beam is generated from incidence of the primary charged particle beam on the sample;determining a first displacement of a parameter of the secondary charged particle beam based on the first scanning direction and a second displacement of a parameter of the secondary charged particle beam based on the second scanning direction;calculating a first signal and a second signal to apply to an anti-scanning deflection unit for deflecting the secondary charged particle beam, wherein the first signal is calculated to counteract the first displacement, and the second signal is calculated to counteract the second displacement;determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first signal, the first displacement, and the first scanning direction of the primary charged particle beam, and the second formulation comprises2025P00060WQ 27the second signal, the second displacement, and the second scanning direction of the primary charged particle beam; andcalculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit to align a secondary charged particle beam generated from scanning the primary charged particle beam in a third scanning direction.18. The non-transitory computer readable medium of clause 17, wherein the first scanning direction and the second scanning direction of the primary charged particle beam are different from each other.19. The non-transitory computer readable medium of clause 17 or 18, wherein the first scanning direction is in an X-direction.20. The non-transitory computer readable medium of any one of clauses 17 to 19, wherein the second scanning direction is in a Y-direction.21. The non-transitory computer readable medium of any one of clauses 17 to 20, wherein the first displacement comprises a first displacement direction.22. The non-transitory computer readable medium of any one of clauses 17 to 21, wherein the second displacement comprises a second displacement direction.23. The non-transitory computer readable medium of clause 21 or 22, wherein the first displacement direction and the second displacement direction are different from each other.24. The non-transitory computer readable medium of any one of clauses 21 to 23, wherein the first displacement direction is in an X-direction.25. The non-transitory computer readable medium of any one of clauses 21 to 24, wherein the second displacement direction is in a Y-direction.26. The non-transitory computer readable medium of any one of clauses 17 to 25, wherein the parameter of the secondary charged particle beam corresponds to a focus of the secondary charged particle beam on a surface of a detector.27. The non-transitory computer readable medium of any one of clauses 17 to 26, wherein the parameter of the secondary charged particle beam comprises a beam spot location, a beam spreading value, a beam spot size, or a beam spot shape of the secondary charged particle beam.28. The non-transitory computer readable medium of any one of clauses 17 to 27, wherein the first signal is calculated such that the anti-scanning deflection unit adjusts the parameter of the secondary charged particle beam in an opposite direction from the first displacement, and the second signal is calculated such that the anti-scanning deflection unit adjusts the parameter of the secondary charged particle beam in an opposite direction from the second displacement.29. The non-transitory computer readable medium of any one of clauses 17 to 28, wherein the first signal and the second signal are calculated such that the parameter of the secondary charged particle beam does not change during scanning of the primary charged particle beam.2025P00060WQ 2830. The non- transitory computer readable medium of any one of clauses 17 to 29, wherein the first signal comprises a first electrical signal.31. The non- transitory computer readable medium of any one of clauses 17 to 30, wherein the second signal comprises a second electrical signal.32. The non-transitory computer readable medium of clause 30 or 31, wherein the first electrical signal and the second electrical signal are different from each other.33. The non-transitory computer readable medium of any one of clauses 17 to 32, wherein the first signal represents a first voltage or a first current applied to the anti-scanning deflection unit.34. The non-transitory computer readable medium of any one of clauses 17 to 33, wherein the second signal represents a second voltage or a second current applied to the anti-scanning deflection unit.35. The non-transitory computer readable medium of any one of clauses 17 to 34, further comprising operations for calibrating the anti- scanning deflection unit for the calculating the first signal and the second signal to apply to the anti- scanning deflection unit for deflecting the secondary charged particle beam.36. The non-transitory computer readable medium of clause 35, wherein the calibrating of the anti-scanning deflection unit comprises no scanning of the primary charged particle beam on the sample.37. The non-transitory computer readable medium of clause 35 or 36, wherein the operations for calibrating comprises:changing the parameter of the secondary charged particle beam, using an anti-scanning deflection unit, by a first adjustment according to a first target signal provided to the anti-scanning deflection unit and by a second adjustment according to a second target signal provided to the antiscanning deflection unit;determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first target signal and the first adjustment and the second formulation comprises the second target signal and the second adjustment; and calculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit for adjusting the parameter of the secondary charged particle beam.38. The non-transitory computer readable medium of clause 37, wherein the first adjustment comprises adjusting the parameter of the secondary charged particle beam in a first direction.39. The non-transitory computer readable medium of clause 37 or 38, wherein the second adjustment comprises adjusting the parameter of the secondary charged particle beam in a second direction.2025P00060WQ 2940. The non-transitory computer readable medium of clause 38 or 39, wherein the first direction and the second direction are different from each other.41. The non-transitory computer readable medium of any one of clauses 38 to 40, wherein the first direction is in an X-direction.42. The non-transitory computer readable medium of any one of clauses 39 to 41, wherein the second direction is in a Y-direction.43. The non-transitory computer readable medium of any one of clauses 37 to 42, wherein the parameter of the secondary charged particle beam corresponds to a focus of the secondary charged particle beam on a surface of a detector.44. The non-transitory computer readable medium of any one of clauses 37 to 43, wherein the parameter of the secondary charged particle beam comprises a beam spot location a beam spread value, a beam spot size, or a beam spot shape of the secondary charged particle beam.45. The non-transitory computer readable medium of any one of clauses 37 to 44, wherein the first target signal comprises a first electrical signal.46. The non-transitory computer readable medium of any one of clauses 37 to 45, wherein the second target signal comprises a second electrical signal.47. The non-transitory computer readable medium of clause 45 or 46, wherein the first electrical signal and the second electrical signal are different from each other.48. The non-transitory computer readable medium of any one of clauses 37 to 47, wherein the first target signal represents a first voltage or a first current applied to the anti-scanning deflection unit.49. The non-transitory computer readable medium of any one of clauses 37 to 48, wherein the second target signal represents a second voltage or a second current applied to the antiscanning deflection unit.50. The non-transitory computer readable medium of any one of clauses 17 to 49, wherein the third scanning direction is a same direction as one of the first scanning direction or the second scanning direction.51. The non-transitory computer readable medium of any one of clauses 17 to 50, wherein the charged particle beam apparatus is a multi-beam charged particle beam apparatus.52. A method for adjusting a secondary charged particle beam during operation of a charged particle beam apparatus, the method comprising the operations of any one of clauses 17-51.

[0096] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments, other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be2025P00060WQ 30considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

2025P00060WQ 31CLAIMS1. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for calculating a behavior of a secondary charged particle beam resulting from anti-scanning deflection in a charged particle beam apparatus, the operations comprising:changing a parameter of the secondary charged particle beam, using an anti-scanning deflection unit, by a first adjustment according to a first target signal provided to the anti-scanning deflection unit and by a second adjustment according to a second target signal provided to the antiscanning deflection unit;determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first target signal and the first adjustment and the second formulation comprises the second target signal and the second adjustment; and calculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit for adjusting the parameter of the secondary charged particle beam.

2. The non-transitory computer readable medium of claim 1, wherein the anti-scanning deflection unit comprises an anti-scanning deflector.

3. The non-transitory computer readable medium of claim 1, wherein the first adjustment comprises adjusting the parameter of the secondary charged particle beam in a first direction.

4. The non-transitory computer readable medium of claim 1, wherein the second adjustment comprises adjusting the parameter of the secondary charged particle beam in a second direction.

5. The non-transitory computer readable medium of claim 3, wherein the first direction and the second direction are different from each other.

6. The non-transitory computer readable medium of claim 3, wherein the first direction is in an X-direction.

7. The non-transitory computer readable medium of claim 3, wherein the second direction is in a Y-direction.2025P00060WQ 328. The non-transitory computer readable medium of claim 1, wherein the parameter of the secondary charged particle beam corresponds to a focus of the secondary charged particle beam on a surface of a detector.

9. The non-transitory computer readable medium of claim 1, wherein the parameter of the secondary charged particle beam comprises a beam spot location, a beam spread value, a beam spot size, or a beam spot shape of the secondary charged particle beam.

10. The non-transitory computer readable medium of claim 1, wherein the first target signal comprises a first electrical signal.

11. The non-transitory computer readable medium of claim 1, wherein the second target signal comprises a second electrical signal.

12. The non-transitory computer readable medium of claim 10, wherein the first electrical signal and the second electrical signal are different from each other.

13. The non-transitory computer readable medium of claim 1, wherein the first target signal represents a first voltage or a first current applied to the anti-scanning deflection unit.

14. The non-transitory computer readable medium of claim 1, wherein the second target signal represents a second voltage or a second current applied to the anti-scanning deflection unit.

15. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for adjusting a secondary charged particle beam during operation of a charged particle beam apparatus, the operations comprising:scanning of a primary charged particle beam in a first scanning direction and a second scanning direction on a sample, wherein a secondary charged particle beam is generated from incidence of the primary charged particle beam on the sample;determining a first displacement of a parameter of the secondary charged particle beam based on the first scanning direction and a second displacement of a parameter of the secondary charged particle beam based on the second scanning direction;calculating a first signal and a second signal to apply to an anti-scanning deflection unit for deflecting the secondary charged particle beam, wherein the first signal is calculated to counteract the first displacement, and the second signal is calculated to counteract the second displacement;2025P00060WQ 33determining a mathematical model that comprises a first formulation and a second formulation, wherein the first formulation comprises the first signal, the first displacement, and the first scanning direction of the primary charged particle beam, and the second formulation comprises the second signal, the second displacement, and the second scanning direction of the primary charged particle beam; andcalculating, using the mathematical model, a signal to be provided to the anti-scanning deflection unit to align a secondary charged particle beam generated from scanning the primary charged particle beam in a third scanning direction.

Images