Method for determining a charged particle beam spot size and sample

Abstract

Samples and methods for determining beam spot size include scanning a pattern on a sample with a charged particle beam to generate an image. The pattern can include at least one sloped side edge and a top surface. The at least one sloped side edge can have a slope angle controlled during fabrication of the sample to be between about 40 to 80 degrees. The beam spot size can be determined based on an imaged profile of the at least one sloped side edge, the imaged profile being derived based on the image.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Application 63 / 611,078, filed December 15, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This specification generally relates to methods and samples for measuring the main beam size or resolution of charged particle beams in charged particle beam apparatus. Background Technology

[0003] In the manufacturing process of integrated circuits (ICs), unfinished or completed circuit elements are inspected or measured to ensure that features are manufactured according to the design and without defects. Inspection and / or measurement systems utilizing charged particle (e.g., electron) beam microscopy, such as scanning electron microscopy (SEM), can be employed. As the feature size of IC components continues to shrink, determining the resolution of the particle beam (e.g., electron beam) becomes important, for example, for the accurate determination of feature size. Summary of the Invention

[0004] Some embodiments provide a method for determining a beam spot size. The method may include scanning a pattern on a sample using a charged particle beam to generate an image. The pattern may include at least one sloping side edge and a top surface. The at least one sloping side edge may have a tilt angle controlled during sample fabrication to be between about 40 and 80 degrees. The method may further include determining the beam spot size based on an imaging profile of the at least one sloping side edge, the imaging profile being derived from the image.

[0005] Some embodiments provide a method for determining a beam spot size. The method may include scanning a pattern on a sample using a charged particle beam to generate an image. The pattern may include at least one sloping side edge and a top surface. The at least one sloping side edge has a sloping angle between about 40 and 80 degrees and a ramp width greater than or equal to about 2.3 times the estimated beam spot size based on simulation. The method may further include determining the beam spot size based on an imaging profile of the sloping side edge in the at least one sloping side edge, the imaging profile being derived from the image.

[0006] Some embodiments provide a sample for determining the beam spot size of a charged particle beam. The sample may include a substrate formed of a conductive material and a pattern disposed on the substrate. The pattern may be formed of a conductive material and may include at least one sloping side edge and a top surface. The at least one sloping side edge may have a tilt angle controlled during sample fabrication to be between about 40 and 80 degrees.

[0007] Some embodiments provide a non-transitory computer-readable medium storing an instruction set executable by at least one processor of a computing device to cause the computing device to perform a method for determining a beam spot size. The method may include scanning a pattern on a sample using a charged particle beam to generate an image. The pattern may include at least one tilted side edge and a top surface. The at least one tilted side edge may have a tilt angle controlled during sample fabrication to be between about 40 and 80 degrees. The method may further include determining the beam spot size based on an imaging profile of the at least one tilted side edge, the imaging profile being derived from the image.

[0008] Other advantages of the embodiments of this disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, which illustrate certain embodiments of the invention by way of illustration and example. Attached Figure Description

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

[0010] Figure 1 This is a schematic diagram of an exemplary charged particle beam inspection or measurement system consistent with some embodiments of this disclosure.

[0011] Figure 2A This is a schematic diagram of an exemplary multi-beam tool, which can be Figure 1 It is part of a charged particle beam inspection system.

[0012] Figure 2B This is a schematic diagram of an exemplary single-beam tool, which can be Figure 1 It is part of a charged particle beam inspection system.

[0013] Figure 3A This is a schematic diagram of a main electron beam falling on a sample surface, consistent with some embodiments of this disclosure.

[0014] Figure 3B The illustration shows an exemplary relationship between the secondary electron yield of a sample and the landing angle of the main electron beam on the sample, consistent with some embodiments of this disclosure.

[0015] Figure 4A This is a schematic diagram of secondary electron yield when an exemplary pattern is scanned on a single electron-scanned sample, consistent with some embodiments of this disclosure.

[0016] Figure 4B This is a schematic diagram of the secondary electron yield signal when the primary electron beam scans an exemplary pattern on a sample, consistent with some embodiments of this disclosure.

[0017] Figure 4C It is consistent with some embodiments of this disclosure. Figure 4B A schematic diagram of the resolution of secondary electron yield signal measurement.

[0018] Figure 5A The illustration shows a cross-sectional view of an exemplary resolution measurement sample with an exemplary pattern having slanted edges.

[0019] Figure 5B The diagram shows... Figure 5A The effect of the width of the tilted edge in the sample on resolution and measurement error.

[0020] Figure 6 This is an illustration of the edge proximity effect when the main electron beam falls on the tilted edge of a pattern, consistent with some embodiments of this disclosure.

[0021] Figure 7A This is a schematic diagram of an exemplary resolution measurement sample with multiple patterns, consistent with some embodiments of this disclosure.

[0022] Figures 7B to 7C This is an illustration of an exemplary resolution measurement sample with various patterns, consistent with some embodiments of this disclosure.

[0023] Figures 8A to 8D The illustration shows a top-down view of a resolution measurement sample having exemplary patterns arranged in different orientations, consistent with some embodiments of this disclosure.

[0024] Figures 9A to 9B An exemplary resolution measurement sample with exemplary patterns arranged in two orthogonal orientations is illustrated, consistent with some embodiments of this disclosure.

[0025] Figure 10A An exemplary resolution measurement sample having multiple patterns arranged in a field of view (FOV) is illustrated, consistent with some embodiments of this disclosure.

[0026] Figure 10B The illustration shows an exemplary pattern being scanned in a scanning direction different from the pattern edge direction, consistent with some embodiments of this disclosure.

[0027] Figures 11A to 11B An exemplary resolution measurement sample, consistent with some embodiments of this disclosure, is illustrated, configured to measure the beam size at different locations within a field of view (FOV).

[0028] Figures 12A to 12D An exemplary resolution measurement sample with a dense layout of patterns arranged in different orientations in the field of view is illustrated, consistent with some embodiments of this disclosure.

[0029] Figures 13A to 13C An exemplary resolution measurement sample with a dense group of patterns arranged in different orientations in a field of view, consistent with some embodiments of this disclosure, is illustrated.

[0030] Figure 13B The illustration shows an exemplary resolution measurement sample of a dense group of patterns arranged in the same orientation in a field of view, consistent with some embodiments of the present disclosure.

[0031] Figures 14A to 14F The illustrations show some exemplary shapes of patterns consistent with some embodiments of this disclosure.

[0032] Figures 15A to 15D The illustration shows an exemplary resolution measurement sample with different types of patterns arranged in a field of view (FOV), consistent with some embodiments of this disclosure.

[0033] Figure 16A This is a flowchart illustrating an exemplary method for manufacturing a resolution measurement sample consistent with some embodiments of this disclosure.

[0034] Figure 16B This is a flowchart illustrating an exemplary method for measuring resolution and beam size using a resolution measurement sample, consistent with some embodiments of this disclosure. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, where the same numerals in different drawings denote the same or similar elements unless otherwise indicated. The embodiments set forth in the following exemplary description do not represent all embodiments. Rather, they are merely examples of apparatus and methods relating to aspects of the disclosed embodiments as described in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, this disclosure is not limited thereto. Other types of charged particle beams (e.g., including protons, ions, muons, or any other charged particles) can be applied similarly. Furthermore, other imaging systems, such as optical imaging, photon detection, X-ray detection, ion detection, etc., can also be used.

[0036] Electronic devices consist of circuits formed on a wafer of semiconductor material called a substrate. Semiconductor materials can include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium. Many circuits can be formed together on the same silicon wafer, called an integrated circuit or IC. The size of these circuits has drastically decreased, allowing more of them to fit on a substrate. For example, the IC chip in a smartphone can be as small as a thumbnail, but can also include more than 2 billion transistors, each smaller than one-thousandth the size of a human hair.

[0037] Manufacturing these ICs with extremely small structures or components is a complex, time-consuming, and expensive process, typically involving hundreds of individual steps. Even an error in one step can lead to a defect in the completed IC, rendering it malfunctioning. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs manufactured in the process; that is, to improve the overall yield of the process.

[0038] One component of improving yield is monitoring the chip manufacturing process to ensure that a sufficient number of functional integrated circuits are produced. One method of monitoring the process is to inspect it at various stages of chip circuit structure formation. Inspection can be performed using a scanning charged particle microscope (“SCPM”). For example, SCPM could be a scanning electron microscope (SEM). SCPM can be used to image these extremely small structures, essentially taking “pictures” of the wafer's structure. This image can be used to determine if the structure is correctly formed in the correct location. If the structure is defective, the process can be adjusted, so the defect is less likely to recur.

[0039] As the physical size of IC components continues to shrink, the accuracy and throughput of defect detection become increasingly important. In the context of SEM (Series Electron Microscopy) used for inspection in semiconductor manufacturing, resolution refers to the microscope's ability to distinguish and display fine details in an observed sample. Resolution is often described as spatial resolution, which is the smallest distance between two points on a sample surface that can be distinguished as separate entities in an SEM image. SEM resolution is a critical performance parameter in the semiconductor industry, where extremely small features need to be accurately characterized. As feature sizes continue to shrink, accurately measuring the resolution of electron beam apparatuses is crucial to ensuring that the equipment can provide the level of detail required for a specific application and to ensuring accurate measurement of feature sizes. Conventional methods for measuring the resolution of electron beam apparatuses involve measurements on samples with patterns of lines or particles (e.g., nanoparticles) with sharp edges on a substrate. However, these samples may be inaccurate and unsuitable for measuring resolution in some applications. For example, data measured on such samples may not correspond satisfactorily to known resolutions due to the shape and configuration of the particles and lines. Therefore, the error in resolution measurements using such samples can be significant. Embodiments of this disclosure provide methods and samples for accurately measuring the resolution of an electron beam in an electron beam apparatus (or a particle beam in a particle beam apparatus).

[0040] The relative dimensions of components in the accompanying drawings may be enlarged for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and differences are described only with respect to the various embodiments. Other objects and advantages of this disclosure may be achieved by the elements and combinations set forth in the embodiments discussed herein. However, embodiments of this disclosure are not necessarily required to achieve these exemplary objects or advantages, and some embodiments may not achieve any of the stated objects or advantages.

[0041] As used herein, unless otherwise specified, the term "or" covers all possible combinations, unless impractical. For example, if a component is described as including A or B, then unless otherwise specified or impractical, the component may include A, or B, or A and B. As a second example, if a component is described as including A, B, or C, then unless otherwise specified or impractical, 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. Expressions such as "at least one of..." do not necessarily modify the entire following list, nor do they necessarily modify each member of the list, such that "at least one of A, B, and C" should be understood to include only one of A, only one of B, only one of C, or any combination of A, B, and C. The phrase "one of A and B" or "any one of A and B" should be interpreted in the broadest sense as including one of A or one of B.

[0042] All relative terms such as “about,” “generally,” “approximately,” etc., indicate a possible variation of ±10% (unless otherwise stated or specified). For example, a feature disclosed as having a width (or length, thickness, etc.) of approximately “w” units may vary in width between (w-0.1w) and (w+0.1w) units. Similarly, a width within the range of approximately A to B units may have a width between (A-10%) and (B+10%). Furthermore, widths varying between or from A to B units include the endpoints (i.e., A and B). In some cases, the specification and / or drawings provide context for some of the relative terms used.

[0043] Figure 1 An exemplary electron beam inspection (EBI) system 100 consistent with embodiments of this disclosure is illustrated. The EBI system 100 can be used for imaging. Figure 1 As shown, the EBI system 100 includes a main chamber 101, a loading / locking chamber 102, a beam tool 104, and a device front-end module (EFEM) 106. The beam tool 104 is located within the main chamber 101. The EFEM 106 includes a first loading port 106a and a second loading port 106b. The EFEM 106 may include (multiple) additional loading ports. The first loading port 106a and the second loading port 106b receive a front-open unified wafer cassette (FOUP) containing a wafer to be inspected (e.g., a semiconductor wafer or a wafer made of (multiple) other materials) or a sample (wafers and samples are interchangeable). A “batch” is a group of wafers that can be loaded for processing.

[0044] One or more robotic arms (not shown) in EFEM 106 can transfer the wafer to loading / locking chamber 102. Loading / locking chamber 102 is connected to a loading / locking vacuum pump system (not shown), which removes gas molecules from loading / locking chamber 102 to achieve a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) can transfer the wafer from loading / locking chamber 102 to main chamber 101. Main chamber 101 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules from main chamber 101 to achieve a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by beam tool 104. Beam tool 104 can be a single-beam system or a multi-beam system.

[0045] Controller 109 is electrically connected to clamping tool 104. Controller 109 may be a computer configured to perform various controls of EBI system 100. Although controller 109 is... Figure 1 The controller 109 is shown as being located outside the structure including the main chamber 101, the loading / locking chamber 102 and the EFEM 106, but it should be understood that the controller 109 may be part of the structure.

[0046] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a general-purpose or special-purpose electronic device capable of manipulating or processing information. For example, a processor may include any number and any combination of the following: a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a programmable logic array (PLA), a programmable array logic (PAL), a general-purpose array logic (GAL), a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a system-on-a-chip (SoC), an application-specific integrated circuit (ASIC), and any circuitry capable of performing data processing. A processor may also be a virtual processor, comprising one or more processors distributed across multiple machines or devices coupled via a network.

[0047] In some embodiments, controller 109 may also include one or more memories (not shown). Memory can be a general-purpose or special-purpose electronic device capable of storing processor-accessible (e.g., via a bus) code and data. For example, memory can include any number and any combination of the following: random access memory (RAM), read-only memory (ROM), optical disc, magnetic disk, hard disk, solid-state drive, flash drive, secure digital card (SD card), memory stick, compact flash (CF) card, or any type of storage device. Code and data can include an operating system (OS) and one or more applications (or “apps”) for a specific task. Memory can also be virtual memory, comprising one or more memories distributed across multiple machines or devices coupled via a network.

[0048] Figure 2A The illustration shows a schematic diagram of an example multi-beam tool 104A (also referred to herein as apparatus 104A) and an image processing system 290 consistent with embodiments of the present disclosure, which can be configured for use in EBI system 100 ( Figure 1 Used in ).

[0049] The beam tool 104A includes a charged particle source 202, a gun aperture 204, a converging lens 206, a main charged particle beam 210 emitted from the charged particle source 202, a source conversion unit 212, multiple sub-beams 214, 216, and 218 of the main charged particle beam 210, a main projection optics system 220, a motorized wafer stage 280, a wafer holder 282, multiple secondary charged particle beams 236, 238, and 240, a secondary optics system 242, and a charged particle detection device 244. The main projection optics system 220 may include a beam splitter 222, a deflection scanning unit 226, and an objective lens 228. The charged particle detection device 244 may include detection sub-regions 246, 248, and 250.

[0050] The charged particle source 202, the gun aperture 204, the converging lens 206, the source conversion unit 212, the beam splitter 222, the deflection scanning unit 226, and the objective lens 228 can be aligned with the primary optical axis 260 of the device 104A. The secondary optical system 242 and the charged particle detection device 244 can be aligned with the secondary optical axis 252 of the device 104A.

[0051] Charged particle source 202 can emit one or more charged particles, such as electrons, protons, ions, muons, or any other charged particles. In some embodiments, charged particle source 202 can be an electron source. For example, charged particle source 202 can include a cathode, extractor, or anode, wherein main electrons can be emitted from the cathode and extracted or accelerated to form a main charged particle beam 210 (in this case, a main electron beam) with a cross-spot (virtual or real) 208. For ease of explanation and without ambiguity, some descriptions herein use electrons as examples. However, it should be noted that any charged particle, not limited to electrons, can be used in any embodiment of this disclosure. The main charged particle beam 210 can be considered to be emitted from the cross-spot 208. The aperture 204 can block peripheral charged particles of the main charged particle beam 210 to reduce the Coulomb effect. The Coulomb effect can cause an increase in the size of the detection spot.

[0052] The source conversion unit 212 may include an imaging element array and a beam-limiting aperture array. The imaging element array may include a micro-deflector or a microlens array. The imaging element array can utilize multiple sub-beams 214, 216, and 218 of the main charged particle beam 210 to form multiple parallel images (virtual or real) of the cross-spot 208. The beam-limiting aperture array can limit the multiple sub-beams 214, 216, and 218. Although Figure 2A Three sub-bundles 214, 216, and 218 are shown, but embodiments of this disclosure are not limited thereto. For example, in some embodiments, device 104A may be configured to generate a first number of sub-bundles. In some embodiments, the first number of sub-bundles may be in the range of 1 to 1000. In some embodiments, the first number of sub-bundles may be in the range of 200 to 500.

[0053] The converging lens 206 can focus the main charged particle beam 210. The currents of the sub-beams 214, 216, and 218 downstream of the source conversion unit 212 can be changed by adjusting the focusing capability of the converging lens 206 or by changing the radial size of the corresponding limiting aperture within the limiting aperture array. The objective lens 228 can focus the sub-beams 214, 216, and 218 onto the wafer 230 for imaging, and can form multiple probe spots 270, 272, and 274 on the surface of the wafer 230.

[0054] Beam splitter 222 can be a Wien filter type beam splitter that generates electrostatic dipole fields and magnetic dipole fields. In some embodiments, if these fields are applied, the force exerted by the electrostatic dipole field on the charged particles (e.g., electrons) of sub-beams 214, 216, and 218 can be substantially equal in magnitude to the force exerted by the magnetic dipole field on the charged particles, and opposite in direction. Therefore, sub-beams 214, 216, and 218 can pass directly through beam splitter 222 with zero deflection. However, the total dispersion of sub-beams 214, 216, and 218 generated by beam splitter 222 may also be non-zero. Beam splitter 222 can separate secondary charged particle beams 236, 238, and 240 from sub-beams 214, 216, and 218, and guide secondary charged particle beams 236, 238, and 240 toward secondary optical system 242.

[0055] Deflection scanning unit 226 can deflect sub-beams 214, 216, and 218 to scan probe spots 270, 272, and 274 on the surface region of wafer 230. In response to the incident of sub-beams 214, 216, and 218 at probe spots 270, 272, and 274, secondary charged particle beams 236, 238, and 240 can be emitted from wafer 230. Secondary charged particle beams 236, 238, and 240 can include charged particles (e.g., electrons) with an energy distribution. For example, secondary charged particle beams 236, 238, and 240 can be secondary electron beams, including secondary electrons (energy ≤ 50 eV) and backscattered electrons (energy between 50 eV and the landing energy of sub-beams 214, 216, and 218). The secondary optical system 242 can focus the secondary charged particle beams 236, 238, and 240 onto the detection sub-regions 246, 248, and 250 of the charged particle detection device 244. The detection sub-regions 246, 248, and 250 can be configured to detect the corresponding secondary charged particle beams 236, 238, and 240, and generate corresponding signals (e.g., voltage, current, etc.) used to reconstruct an inspection image of the structure on or below the surface region of the wafer 230.

[0056] The generated signals can represent the intensity of the secondary charged particle beams 236, 238, and 240, and can be provided to an image processing system 290 that communicates with the charged particle detection device 244, the main projection optics system 220, and the motorized wafer stage 280. The movement speed of the motorized wafer stage 280 can be synchronized and coordinated with the beam deflection controlled by the deflection scanning unit 226, so that the movement of the scanning probe spots (e.g., probe spots 270, 272, and 274) orderly covers the region of interest on the wafer 230. Such synchronization and coordination parameters can be adjusted to accommodate different materials of the wafer 230. For example, different materials of the wafer 230 can have different resistivity-capacitance characteristics, which can cause different signal sensitivities to the movement of the scanning probe spots.

[0057] The intensities of the secondary charged particle beams 236, 238, and 240 can vary depending on the external or internal structure of the wafer 230, thus indicating whether the wafer 230 contains defects. Furthermore, as described above, sub-beams 214, 216, and 218 can be projected onto different locations on the top surface of the wafer 230, or onto different edges of a local structure of the wafer 230, to generate secondary charged particle beams 236, 238, and 240 with varying intensities. Therefore, by mapping the intensities of the secondary charged particle beams 236, 238, and 240 to regions of the wafer 230, the image processing system 290 can reconstruct an image reflecting the characteristics of the internal or external structure of the wafer 230.

[0058] In some embodiments, the image processing system 290 may include an image acquisition unit 292, a storage device 294, and a controller 296. The image acquisition unit 292 may include one or more processors. For example, the image acquisition unit 292 may include a computer, server, mainframe, terminal, personal computer, any type of mobile computing device, or a combination thereof. The image acquisition unit 292 may be communicatively coupled to the charged particle detection device 244 of the beam tool 104A via a medium such as an electrical conductor, fiber optic cable, portable storage medium, IR, Bluetooth, the Internet, wireless network, radio, or a combination thereof. In some embodiments, the image acquisition unit 292 may receive signals from the charged particle detection device 244 and construct an image. The image acquisition unit 292 may thus acquire inspection images of the wafer 230. The image acquisition unit 292 may also perform various post-processing functions, such as generating contours, overlaying indicators on the acquired images, etc. The image acquisition unit 292 may be configured to perform adjustments to the brightness and contrast of the acquired images. In some embodiments, the storage device 294 may be a storage medium such as a hard disk, flash drive, cloud storage device, random access memory (RAM), other types of computer-readable storage, etc. Storage device 294 can be coupled to image acquisition unit 292 and can be used to save scanned raw image data as raw images and to save post-processed images. Image acquisition unit 292 and storage device 294 can be connected to controller 296. In some embodiments, image acquisition unit 292, storage device 294 and controller 296 can be integrated into a single control unit.

[0059] In some embodiments, the image acquisition unit 292 may acquire one or more inspection images of the wafer based on imaging signals received from the charged particle detection device 244. The imaging signals may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image comprising multiple imaging regions. The single image may be stored in the storage device 294. The single image may be an original image that can be divided into multiple regions. Each region may include an imaging region containing features of the wafer 230. The acquired images may include multiple images of a single imaging region of the wafer 230 sampled multiple times over time. The multiple images may be stored in the storage device 294. In some embodiments, the image processing system 290 may be configured to perform image processing steps using multiple images of the same location on the wafer 230.

[0060] When electrons from the main charged particle beam 210 are projected onto the surface of the wafer 230 (e.g., probe spots 270, 272, and 274), the electrons of the main charged particle beam 210 can penetrate to a certain depth into the surface of the wafer 230 and interact with the particles of the wafer 230. Some electrons of the main charged particle beam 210 can elastically interact with the material of the wafer 230 (e.g., in the form of elastic scattering or collisions) and can be reflected or bounced off the surface of the wafer 230. Elastic interactions conserve the total kinetic energy of the interacting body (e.g., electrons from the main charged particle beam 210), where the kinetic energy of the interacting body is not converted into other forms of energy (e.g., heat, electromagnetic energy, etc.). Such reflected electrons generated by elastic interactions can be called backscattered electrons (BSE). Some electrons of the main charged particle beam 210 can inelastically interact with the material of the wafer 230 (e.g., in the form of inelastic scattering or collisions). Inelastic interactions do not conserve the total kinetic energy of the interacting body, where some or all of the kinetic energy of the interacting body is converted into other forms of energy. For example, through inelastic interactions, the kinetic energy of some electrons in the main charged particle beam 210 can induce electronic excitation and transitions in the atoms of the material. This inelastic interaction can also generate electrons that leave the surface of the wafer 230; these electrons can be called secondary electrons (SEs). The yield or emission rate of BSEs and SEs depends on, for example, the material being examined and the landing energy of the electrons from the main charged particle beam 210 on the material surface. The energy of the electrons in the main charged particle beam 210 can be partially imparted by its accelerating voltage (e.g., ...). Figure 2A The accelerating voltage between the anode and cathode of the intermediate charged particle source 202. The number of BSE and SE may be more or less than (or even equal to) the injected electrons of the main charged particle beam 210.

[0061] In some embodiments, the image processing system 290 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of detected secondary charged particles (e.g., secondary electrons). Charged particle distribution data collected during the detection time window, combined with corresponding scan path data of sub-beams 214, 216, and 218 incident on the wafer surface, can be used to reconstruct an image of the inspected wafer structure. The reconstructed image can be used to reveal various features of the internal or external structure of the wafer 230, thereby revealing any defects that may be present in the wafer.

[0062] Now refer to Figure 2B Another example of a charged particle beam device is discussed. Beam tool 104B (also referred to herein as device 104B) can be an example of beam tool 104 and can be similar to... Figure 2A The beam tool 104A is shown. However, unlike the device 104A, the device 104B can be a single-beam tool, which uses only one main electron beam to scan one position on the wafer at a time.

[0063] like Figure 2B As shown, the apparatus 104B includes a wafer holder 136 supported by a motorized stage 134 to hold a wafer 150 to be inspected. The beam tool 104B includes an electron emitter, which may include a cathode 103, an anode 121, and a gun aperture 122. The beam tool 104B also includes a beam-limiting aperture 125, a converging lens 126, a column aperture 135, an objective lens assembly 132, and a detector 144. In some embodiments, the objective lens assembly 132 may be a modified SORIL lens, which includes a pole piece 132a, a control electrode 132b, a deflector unit 132c, and an excitation coil 132d. During inspection or imaging, an electron beam 161 emitted from the tip of the cathode 103 can be accelerated by the voltage of the anode 121, pass through the gun aperture 122, the beam-limiting aperture 125, and the converging lens 126, and is focused by the modified SORIL lens into a probe spot 170, impacting the surface of the wafer 150. The probe spot 170 can be scanned across the surface of the wafer 150 by deflectors (such as deflector unit 132c or other deflectors in a SORIL lens). Secondary or scattered particles emitted from the wafer surface, such as secondary electrons or scattered primary electrons, can be collected by detector 144 to determine the intensity of the beam, thus allowing an image of the region of interest on the wafer 150 to be reconstructed.

[0064] An image processing system 199 may also be provided, comprising an image acquisition unit 120, a storage device 130, and a controller 109. The image acquisition unit 120 may include one or more processors. For example, the image acquisition unit 120 may include a computer, server, mainframe, terminal, personal computer, any type of mobile computing device, or a combination thereof. The image acquisition unit 120 may be connected to the detector 144 of the beam tool 104B via a medium such as an electrical conductor, fiber optic cable, portable storage medium, IR, Bluetooth, Internet, wireless network, radio, or a combination thereof. The image acquisition unit 120 may receive signals from the detector 144 and construct an image. The image acquisition unit 120 may thus acquire an image of the wafer 150. The image acquisition unit 120 may also perform various post-processing functions, such as image averaging, contour generation, and overlaying indicators onto the acquired image. The image acquisition unit 120 may be configured to perform adjustments to the brightness and contrast of the acquired image. The storage device 130 may be a storage medium such as a hard disk, random access memory (RAM), cloud storage device, or other types of computer-readable storage. Storage device 130 can be coupled to image acquisition device 120 and can be used to save scanned raw image data as raw images and to save post-processed images. Image acquisition device 120 and storage device 130 can be connected to controller 109. In some embodiments, image acquisition device 120, storage device 130 and controller 109 can be integrated together as an electronic control unit.

[0065] In some embodiments, the image acquisition unit 120 may acquire one or more images of a sample based on imaging signals received from the detector 144. The imaging signals may correspond to a scanning operation for imaging charged particles. The acquired image may be a single image comprising multiple imaging regions that may include various features of the wafer 150. The single image may be stored in the storage device 130. Imaging may be performed on an imaging frame basis.

[0066] The focusing and illumination optics of an electron beam tool may include or be supplemented by an electromagnetic quadrupole electron lens. For example, such as Figure 2B As shown, the electron beam tool 104B may include a first quadrupole lens 148 and a second quadrupole lens 158. In some embodiments, the quadrupole lens can be used to control the electron beam. For example, the first quadrupole lens 148 can be controlled to adjust the beam current, and the second quadrupole lens 158 can be controlled to adjust the beam spot size and beam shape.

[0067] Figure 2B The illustration shows a charged particle beam device that can use a single main beam, configured to generate secondary electrons by interacting with a wafer 150. A detector 144 can be positioned along the optical axis 105, as shown. Figure 2BThe embodiment shown. The main electron beam can be configured to travel along the optical axis 105. Accordingly, the detector 144 may include a hole at its center so that the main electron beam can pass through to reach the wafer 150. Figure 2B An example of a detector 144 with a central opening is shown. However, some embodiments may use a detector placed off-axis relative to the optical axis, along which the main electron beam travels. For example, as discussed above. Figure 2A The illustrated embodiment may provide a beam splitter 222 to guide the secondary electron beam toward an off-axis detector. The beam splitter 222 may be configured to direct the secondary electron beam toward the electron detection device 244, such as... Figure 2A As shown.

[0068] Therefore, in embodiments of SEM-based electron beam devices, the sample (e.g.) Figure 2A Chip 230 and Figure 2B The image of the chip 150 is obtained by detecting the image of the focused master beam (e.g., Figure 2B The secondary electrons generated and emitted by the electron beam 161 scanning the sample are formed. Typically, the detection efficiency of detector 144 can exceed 90%, and in some embodiments, is very close to 100%. Image signal (I i ) is the current density distribution of the main electron beam spot or detector spot 170 on the wafer 150 and the secondary electron yield signal (I o The convolution of two signals is shown in equation (1) below. The convolution of two signals (denoted by the symbol "...") The "" indicates that the combination of two signals is a mathematical operation that produces a third signal. The current density distribution of the main electron beam spot (or probe spot 170) is called the point spread function (PSF) or beam profile. The PSF of the electron beam describes how the electron source is imaged onto the sample by the electron optics system of the microscope. It characterizes the blurring or diffusion of the main electrons in the electron source image. In electron microscopy, when the focused main electron beam interacts with the wafer 150 (or other sample), the electrons of the beam are scattered within the wafer and generate secondary electrons, which are detected to form an image of the wafer 150. However, due to the various Due to various physical and optical factors, the resulting image of the source is not a sharp point, but rather a diffused blotch. The secondary electron yield (PSF) is a mathematical description of how the source image is diffused and is a key factor in determining the achievable resolution of an electron microscope. For example, the PSF is used to determine the smallest feature that can be accurately resolved in an image of a sample. Secondary electron yield (δ) is a material property characterizing how many secondary electrons are emitted from a material when it is bombarded by primary electrons. For example, if a material has a secondary electron yield of 2, this means that for each primary electron striking the material, an average of two secondary electrons are emitted. The secondary electron yield signal (I0) is... oThe signal generated and detected in a microscope (e.g., by detector 144) is due to secondary electron emission. In other words, the secondary electron yield signal (I0) is the actual signal generated and detected by the microscope. o () is a signal indicating the number of secondary electrons emitted from the chip 150 in response to being bombarded by the main electrons. (Equation 1)

[0069] Based on Equation 1, the image signal (I) i ) and secondary electronic output signal (I o The similarity depends on the PSF. For example, if the PSF is a delta function (or a Dirac delta distribution), then I i Will with I o Same (i.e., I) i (x, y) = I o (x, y)). The delta function is a theoretical construct used to describe a spike or pulse at a point. It represents a spike that is infinitely high and thin at one point, and zero elsewhere. For the delta function, the area under the curve is always equal to 1. However, in reality, due to the non-zero size and non-zero energy diffusion of the main electron beam (e.g., due to geometric aberration coefficients, wave diffraction, electron interactions in the electron optics system of the device, etc.), all electrons are not focused at one location, and the PSF is not a delta function. If the PSF is known, it can be determined from the image signal (I i The PSF is deconvolved in the equation, and the secondary electron yield signal (I) is calculated from Equation 1. o Deconvolution is a mathematical operation used to reverse or undo the convolution of two signals. When two signals are convolved, their information is combined or mixed together. Deconvolution aims to separate the combined information and recover the original signal. (Equation 2)

[0070] Typically, the PSF of an electron optical system closely approximates a Gaussian distribution, as shown in equation (2) above. This property can be used to describe or quantify how the PSF diffuses. This property indicates that if a diameter equal to twice the beam radius (r) is drawn around the central peak of the PSF... b The integral intensity within a circle with a diameter of 2r will be approximately 63% of the total intensity of the PSF. In other words, the integral intensity within the circle will be approximately 63% of the total intensity of the PSF. b The circle contains approximately 63% of the current inside the PSF. In some embodiments, 2r b This can be used as the electron beam spot size for the PSF. In other embodiments, circles with different diameters can be used as the electron beam spot size. For example, in some embodiments, the diameter is equal to 1.916r. bFurthermore, a circle comprising approximately 60% of the current can be used as the electron beam spot size. In some embodiments, FWHM (full width at half maximum) is used as the electron beam spot size, which corresponds to a diameter equal to 1.664r. b And it includes a circle containing approximately 50% of the current.

[0071] Numerical simulations can be used to determine or predict the expected PSF (and resolution) of a SEM apparatus. For example, the design configuration of an electron optics system can be simulated, and the distribution of the main electron beam on the sample and the system's resolution can be determined based on the simulation. However, the actual resolution of an electron beam apparatus can differ from the value obtained from the simulation. For example, some electron optics components (e.g., lenses, deflectors, etc.) can have mechanical errors, and electronic components can have electronic noise and drift, which can cause differences between the actual resolution and the value predicted from the simulation. Furthermore, in some cases, electron optics components may not be aligned with the optical axis of the system (e.g., ...). Figure 2B The optical axis (105) is well aligned, which can also lead to differences. Therefore, it is desirable to experimentally measure the resolution of the electron optics system. However, since the PSF is very small, it is usually not possible to directly measure it experimentally to determine its resolution. However, since the secondary electron yield (δ) depends on the local tilt of the sample, in embodiments of this disclosure, the PSF can be indirectly measured from the secondary electron image based on the effect of the secondary electron yield (δ) on the local topographic contrast of the sample (e.g., local tilt). The secondary electron yield signal (I o The value of I is proportional to the secondary electron yield (δ) of the sample and can be simply considered as the secondary electron yield (δ). O ≈ δ. (Equation 3)

[0072] The secondary electron yield (δ) is strongly dependent on the landing energy and angle θ of the main electron beam on the sample, and for landing energies less than about 5 keV, it is slightly dependent on the sample material. Figure 3A As shown, the landing angle (θ) of the main electron beam 300 is measured relative to the surface normal of the landing position of the beam 300 on the sample 320. Equation 3 shows the relationship between the secondary electron yield (δ) of the sample and its surface morphology. Figure 3B This is a graph plotting the ratio of δ(θ) / δ(θ=0) against the landing angle (θ). In equation 3 and... Figure 3B In this context, "n" is a material parameter (describing the dependence of yield on angle). For light elements, n equals 1.3; for elements with atomic number 30, n equals 1; and for heavy elements, n equals 0.8. From... Figure 3B It is evident that the secondary electron yield (δ) is highly sensitive to the surface morphology of the sample.

[0073] Figure 3AThe sample 320 includes an exemplary pattern 340 or structure (e.g., lines, etc.) formed on the surface of a substrate 330 (wafer, die, etc.). As shown, the pattern 340 includes two slanted (or slanted) edges s1 and s2 located on opposite sides of a relatively flat top. Figure 4A The diagram schematically illustrates the secondary electron yield (δ) obtained when a single electron 300' (e.g., a dot) scans the pattern 340 on sample 320. Figure 4A As shown, the secondary electron yield (δ) follows a rectangular function relative to each pattern edge. Therefore, in the SEM image, the distribution of secondary electron yield (δ) indicates the cross-sectional profile of pattern 340.

[0074] Figure 4A The illustration shows the secondary electron yield (δ) obtained when a hypothetical single electron beam scans pattern 340. The total secondary electron yield (δ) is also shown when the main electron beam (comprising many electrons) scans pattern 340. t The total secondary electron yield (δ) will be the sum of the secondary electron yields (δ) of all electrons in the main beam. As mentioned earlier, the PSF is a mathematical description of the current density distribution of the main electron beam. Therefore, as shown in Equation 4 below, when the main electron beam scans pattern 340, the total secondary electron yield (δ) will be the sum of the secondary electron yields (δ) of all electrons in the main beam. t It is equal to the convolution of the PSF (Gaussian function) and the yield of a single secondary electron (δ) (rectangular function). Image signal I i With total secondary electronics production (δ) t It is proportional to δ and can be considered as being related to δ t same. (Equation 4)

[0075] Therefore, when the main electron beam scans pattern 340, Figure 4A In the outline, each step-shaped edge of the rectangular function distribution is blurred into an error function distribution, such as... Figure 4B As shown. By assuming that the distance (x3-x2) is large enough that the influence of the tilted edge s2 on the image signal of the tilted edge s1 is negligible, the image signal (I) of the tilted edge s1 of pattern 340 is... i The equation (5) below illustrates this. In equation (5), A0 depends on δ. 11 A1 depends on δ 12 -δ 11 And A2 depends on δ 12 -δ 13 . (Equation 5)

[0076] exist Figure 4B In the model, the sharpness of each blurred edge (s1, s2) depends on the PSF of the main electron beam 300. (Reference) Figure 4CWith the left slanted edge s1 of pattern 340 (corresponding to Figure 4C Taking the region marked p1 as an example, the resolution (or sharpness) of the image can be considered as the distance S2575 between the intensity of points I_25% (= I2+0.25 × (I1-I2)) and I_75% (= I2+0.75 × (I1-I2)) within the intensity range (I1-I2) from the maximum (I1) to the minimum (I2). For the image signal I in equation (5) i If the distance x2-x1 is sufficiently large compared to the PSF of the main electron beam 300 (e.g., r b (5.2X), then the image signal I i It can be mainly contributed by the first error function in equation (5). In this case, S2575 will be equal to 0.954r. b As shown in equation (6). (Equation 6)

[0077] From the SEM image of sample 320, the distance S2575 value can be directly measured from the signal profile of the edge (e.g., the slanted edge s1) of pattern 340, and r can be determined according to equation (6). b Value. In some embodiments, the determined distance S2575 can be considered as the system resolution, while r b (or r) b Multiples of, such as, for example, 2r b 1.916r b (etc.) can be considered as bundle size. In some embodiments, r b This can be considered as the system's resolution. The difference between the experimentally obtained resolution value and the value obtained from simulation can be used as feedback to adjust the SEM's electron optics system (e.g., adjust the electron optics equipment, improve system alignment, etc.) to reduce the difference between the measured and expected values.

[0078] In embodiments of this disclosure, a sample with a selected resolution measurement pattern having slanted edges with controlled contours is provided for accurate measurement of the beam size (e.g., PSF size, radius r) of an SEM-based electron beam apparatus. b or r b (multiples of) and resolution (e.g., distance S2575, etc.). Figure 5A A cross-sectional view of an exemplary sample 400 is illustrated, the sample 400 having a resolution measurement pattern 440 formed on a substrate 330. In a three-dimensional or perspective view, Figure 5A Pattern 440 will be presented as lines (see, for example, see...) Figure 14APattern 440 can be formed on substrate 330 using any known semiconductor manufacturing technique (deposition, photolithography, etching, etc.). Both substrate 330 and pattern 440 can comprise or be formed of a conductive material. Any conductive material can be used (e.g., metal, doped semiconductor with a surface resistivity <0.01 ohm-cm, etc.). Substrate 330 and pattern 440 can be made of the same conductive material or different conductive materials. For example, in some embodiments, substrate 330 and pattern 440 can both be formed of the same conductive material, such as, for example, a metal (e.g., copper) or doped silicon. In other embodiments, substrate 330 can be formed of a first conductive material (e.g., doped silicon), and pattern 440 can be formed of a different conductive material (e.g., a metal).

[0079] The geometry of the pattern 440 formed on the substrate 330 is designed so that when the electron beam 300 scans the pattern, the change in secondary electron yield (δ) caused by the edges is clear and obvious. For example... Figure 5A As shown, in some embodiments, the pattern 440 of sample 400 includes two sloping edges s1 and s2 located on opposite sides of a relatively flat top surface f1. As used herein, a relatively flat surface only indicates that the surface is not designed or intended to be sloping. However, it should be understood that surface f1 can still have sloping or non-flatness due to the manufacturing process used. The sloping edge s1 can be manufactured to have a sloping angle (φ) and a ramp width W1. The sloping angle (φ) is designed to be between approximately 40° and 80°. A sloping angle (φ) within this range makes the variation in secondary electron yield (δ) clear and pronounced, and mitigates strong edge effects. Secondary electron yield is affected by the landing angle (θ in Equation 3) and the edge effect of the pattern edge. It is preferred to use the landing angle effect rather than the edge effect. The larger the sloping angle (φ) of the pattern edge sidewall, the stronger the edge effect of the pattern edge. The ramp width W1 (its corresponding Figure 4A (X2-X1) can be based on PSF size (e.g., r) b ) is selected to make the second error function in equation (5) (i.e. The impact of this was reduced to, for example, an acceptable level.

[0080] Figure 5B This graph illustrates the effect of slope width W1 on the S2575 distance (sharpness, resolution, etc.) and measurement error. From this graph, it can be seen that when W1 is chosen to be greater than or equal to (≥) approximately 2.3r... b At that time, the error is less than about 10%. Therefore, to ensure S2575 (and r b If the difference is less than 10%, the width W1 of pattern 440 can be selected to be ≥ approximately 2.3r. b In some embodiments, to ensure that the measurement error is less than about 1%, W1 can be selected as about ≥3.8r. bSimilarly, in some embodiments, to ensure that the measurement error is less than about 0.1%, W1 can be selected to be ≥5r. b The combination of tilt angle (φ) and ramp width W1 can be selected to make the edge height H1 less than the depth of focus (DOF) of the electron beam. Depth of focus (DOF) refers to the range of distances along the optical axis from which the sample remains acceptablely focused.

[0081] In some embodiments, to ensure that signals from both inclined surfaces or edges s1 and s2 can be used for beam width measurement, similar to width W1 (see...), Figure 5A For the selection of the top surface width W2 and the slope width W3, both can be chosen to be ≥ approximately 2.3r. b To keep the measurement error less than about 10%, or selected as ≥ about 3.8r b To maintain a measurement error of <1%, or to be selected as ≥5r b To maintain a measurement error of <0.1%. Similarly, the tilt angle (φ') of the tilted surface s2 can also be selected between approximately 40° and 80° to make the change in secondary electron yield (δ) clear and obvious when the electron beam scans the tilted surface s2. However, this is not mandatory. For example, in some embodiments, only the tilt angle (φ) and width W1 can be selected within the above range (i.e., φ = approximately 40° to 80°, W1 ≥ approximately 2.3r). b or ≥ 3.8r b or ≥ 5r b In some embodiments, both W1 and W2, in addition to the tilt angle (φ) and W1, can be selected to be within the ranges described above. And in some embodiments, the tilt angles φ, φ', W1, W2, and W3 can each be selected to be within the ranges described above. It should be noted that while the tilt angle (φ') and slope width W3 of the tilted edge s2 can be the same as the tilt angle (φ) and slope width (W1) of the tilted edge s1, this is not mandatory.

[0082] like Figure 6 As schematically illustrated, when the main electron beam 300 is incident on the tilted edge s1 of pattern 440, in addition to the secondary electrons released from edge s1, secondary electrons can also be released from the opposite tilted edge s2 if the main electrons penetrate too deeply into the sample. Secondary electrons leaving the tilted edge s2 can also be detected by detector 144 (see [reference]). Figure 2BThis phenomenon can be referred to as edge crosstalk or edge proximity effect. When the main electron beam 300 scans the tilted edge s1, the influence of secondary electrons leaving the tilted edge s2 can cause errors in the measurement of beam size. For example, secondary electrons leaving the tilted edge s2 can increase the secondary electron yield in the recorded data of the tilted edge s1 and lead to errors in the determined beam size. Therefore, to avoid the adverse effects of edge crosstalk, in some embodiments, the width W2 of the sample 400 can be selected to be greater than the electron beam penetration depth. For example, if the pattern 440 is made of silicon and the energy of the main electron beam 300 is 2 keV, the width W2 can be selected to be greater than or equal to (≥) about 100 nm to avoid edge crosstalk. Similarly, if the electron beam has an energy of 5 keV, the width W2 can be selected to be ≥ about 400 nm to avoid edge crosstalk. Therefore, in some embodiments of this disclosure, in addition to the tilt angle (φ) and width W1 being selected within the ranges previously described (e.g., φ between about 40° and 80°, and W1 ≥ about 2.3r), b or ≥ 3.8r b or ≥ 5r b In addition to the above, the width W2 can be selected as the larger of the following: based on r b Determined value (see) Figure 5B (i.e., based on an acceptable measurement error, greater than or equal to 2.3r) b 3.8r b Or 5r b And values ​​determined based on the electron beam penetration depth. For example, a main electron beam 300 designed to measure a beam size of approximately 5 nm is used. b In an exemplary embodiment of a sample 400 having a silicon pattern 440 (e.g., simulated values), based on r b W2 can be determined to be ≥5r b (i.e., ≥25nm) to keep the measurement error less than 0.1%, and ≥400nm to minimize edge crosstalk. Therefore, in this exemplary embodiment, the width W2 can be selected to be greater than or equal to 400nm (the larger of 25nm and 400nm).

[0083] It should be noted that, although Figure 4A and Figure 5A The illustration shows a sample 400 with two opposing inclined edges s1 and s2, but this is merely exemplary. It is conceivable that in some embodiments, the pattern may have only one inclined edge (e.g., edge s1). For example, in some embodiments, the sample may include a pattern with a single inclined edge (e.g., in the form of a metal coating on a substrate) having an inclination angle (φ) between about 40° and 80° and ≥ about 2.3r. b or ≥ 3.8r bor ≥ 5r b The slope width W1 is determined based on acceptable measurement error. The coating width W2 can be substantially larger than its thickness (e.g., 1000 times), so that the width W2 is theoretically infinite.

[0084] Compared to the disclosed inclined edges with controlled profiles (e.g., with an inclination angle (φ) between approximately 40° and 80° and a slope width ≥ approximately 2.3r, based on acceptable measurement errors). b or ≥ 3.8r b or ≥ 5r b Compared to the pattern 440 of sample 400, conventional samples used for resolution measurements include gold particles on a substrate or line patterns with sharp edges formed on a substrate. See, for example, Chapter 4 of Peter W. Hawkes' "Scanning Electron Microscopy (2nd Edition)". However, for granular samples, due to the roundness of the particles, the single electron yield (δ) is not a rectangular function (as shown in the image). Figure 4A As shown), therefore, image signal I i (See equation (5)) will not be an error function distribution, and the sharpness S2575 will not be equal to 0.954 r. b (See equation (6)). For line patterns with sharp edges (see, for example, see...) Figure 4A The sharp right edge s2), due to the sharpness of the edge, the slope width ( Figure 4A x4-x3) and r b It is not large enough in comparison. Therefore, the secondary electron yield signal corresponding to this sharp edge (see...) Figure 4C There will be no flat top section (such as) Figure 4C The flat top portion (p2) of the signal corresponding to the sloping left edge (s1) divides regions p4 and p5. Therefore, the signals in regions p4 and p5 will merge, and the secondary electron yield (δ) will not be a rectangular function. Instead, the secondary electron yield (δ) for this sharp edge will be more similar to a delta function for the PSF, and thus the S2575 distance will be significantly less than 0.954. r b .

[0085] While an exemplary sample 400 with a single pattern 440 has been described above, this is merely exemplary. In some embodiments, the sample 400 may include multiple patterns thereon. For example, Figure 7A An exemplary sample 400 with two patterns 440A and 440B formed thereon is illustrated. When sample 400 contains multiple patterns, such as... Figure 7AAs illustrated, the spacing W4 between two adjacent patterns 440A and 440B can be chosen to be ≥2.3r. b To maintain a measurement error of <10%, or to be selected as ≥3.8r b To maintain a measurement error of <1%, or be selected as ≥5r b To maintain a measurement error of <0.1%, as per reference Figure 5B In some embodiments, the aspect ratio H / W4 of the pattern can be selected to be ≤1 to avoid secondary electrons generated from one pattern (e.g., pattern 440A) being blocked by adjacent patterns 440 (e.g., pattern 440B). This phenomenon can be called the pattern proximity effect. To avoid the potential influence of adjacent patterns, in some embodiments, W4 can also be selected to be greater than the penetration depth of the electron beam within the substrate 330. For example, if the substrate 330 is made of silicon and the main electron beam has an energy of 5 keV, W4 can be selected to be ≥400 nm to avoid the adverse effects of electron beam penetration. Therefore, in some embodiments, the spacing W4 between adjacent patterns 440A, 440B can be selected as the larger of the following: based on r b Determined values ​​(such as references) Figure 5B The values ​​are determined based on the pattern proximity effect (H / W4≤1) and the electron beam penetration depth. For example, in an exemplary sample, the expected (e.g., from simulation, etc.) beam size r is measured with an electron beam having an energy of 5 keV. b Approximately 5nm, W4 can be based on r b (e.g., 5r) b W4 is determined to be ≥25nm, or ≥50nm if H is designed to be 50nm, and ≥400nm in terms of electron beam penetration depth. Therefore, in such embodiments, W4 can be selected to be ≥400nm (i.e., the maximum of 25nm, 50nm, and 400nm).

[0086] Although Figure 5A and Figure 7A In the illustrated exemplary sample 400, the opposing edges s1 and s2 of patterns 440, 440A, and 440B are shown tilted in opposite directions, but this is merely exemplary. In some embodiments, such as Figure 7B and Figure 7C As illustrated, the opposite edges s1 and s2 can be tilted in the same direction. The reference has... Figure 5A and Figure 7A The above discussion regarding the configuration of the sample also applies to samples with... Figure 7B and Figure 7C Samples with the specified configuration. In some cases, it may be possible to manufacture samples with... Figure 7B and Figure 7C The samples with the configuration patterns 440, 440A, and 440B are manufactured with... Figure 5A and Figure 7A The pattern of the configuration is easier to sample. Figure 7B and Figure 7C The tilt angles (φ, φ') and widths W1, W2, and W4 of patterns 440, 440A, and 440B can be compared with reference. Figure 5A and Figure 7A The pattern 440 is selected in the same manner as described above. For example, if sample 400 is designed to measure a desired beam size r of approximately 4.5 nm. b (For example, determined by simulation, calculation, etc.), if the main electron beam energy is approximately 2keV, then W1 can be selected to be ≥22.5nm (e.g., 5r). b To maintain a measurement error of <0.1%, W2 can be selected as ≥100nm (based on r). b The larger of 22.5 nm and 100 nm based on the electron beam penetration depth of 2 keV. In this case, if the pattern height H is 50 nm and the tilt angle φ = 65°, then W1 = H / tan(φ) = 23.3 nm, which is > 22.5 nm. Therefore, in some embodiments, W2 can be selected as ≥ 100 nm, i.e., the larger of 23.3 nm and 100 nm. Therefore, in some embodiments, patterns 440A and 440B with a spacing P of approximately 750 nm and a pattern width W1 + W2 = 200 nm can be selected to meet the foregoing requirements.

[0087] As described above (e.g., reference) Figure 7A , Figure 7C In some cases, when scanning the first pattern 440A on sample 400, the adjacent second pattern 440B can have some influence on the signal recorded from the first pattern 440A. In some embodiments, to completely avoid the influence of adjacent patterns (or the proximity effect of adjacent patterns), adjacent patterns 440A, 440B on sample 400 can be separated by a large gap. For example, in some embodiments of the sample, a single pattern 440 or line can be provided in the scanning area or field of view (FOV) of the main electron beam. The field of view (FOV) refers to the area of ​​sample 400 that is imaged (or visible) by the main electron beam at any given time. Figure 8A The diagram shows Figure 5A The top view of the exemplary sample 400 shown in the figure. Note that... Figure 5A The illustration shows a cross-sectional view (e.g., in the XZ plane) of pattern 440 on sample 400, while Figure 8A The illustration shows its top-down view (e.g., in an orthogonal XY plane), illustrating pattern 440 as a line on substrate 330. Reference Figure 5A and Figure 8AThe direction perpendicular to pattern 440 (i.e., the line in the top-down view) and passing through its two relatively sloping edges s1 and s2 is referred to in this paper as the edge direction A of pattern 440. Figure 5A and Figure 8A In the example shown, pattern 440 is arranged such that edge direction A is aligned with the X-axis of sample 400, and the angle (α) between edge direction A and the X-axis is zero. Figure 8A As illustrated, in some embodiments of sample 400, a single pattern 440 may be provided in FOV 500.

[0088] In some embodiments, the scanning direction (or scanning direction B) of the main electron beam 300 can be aligned with the X-axis. For example, the electron beam 300 can start from one corner of the FOV 500, scanning the surface of the sample 400 horizontally along the X-axis. Once the beam 300 reaches the opposite end of the FOV 500, it moves slightly up and down (e.g., on the Y-axis) and begins scanning the next line. This process continues until the entire FOV 500 has been scanned with a series of parallel lines. Figure 8A (and Figure 5A In the example, electron beam 300 scans pattern 440 along edge direction A or parallel to edge direction A. As beam 300 scans pattern 440, the beam size in scanning direction B is measured. In some embodiments, the PSF of the main electron beam 300 may not be circular due to aberrations and manufacturing variations of SEM optics. To evaluate the size of the non-circular PSF in different directions, the main electron beam 300 can scan pattern 440 with different orientations along edge direction A, such as... Figure 9A and Figure 9B As shown. Figure 9A and Figure 9B Both show a cross-sectional view and a top-down view of the exemplary pattern 440. Figure 9A In the middle, pattern 440 extends along the Y direction as a line (similar to...). Figure 8A The configuration shown in the diagram), while Figure 9B In the example, pattern 440 extends as a line along the X direction. In both embodiments ( Figure 9A and Figure 9B In the pattern, the scanning direction B of beam 300 is along (or parallel to) the edge direction A of the pattern. For example, when beam 300 scans from left to right (or from right to left)... Figure 9A When measuring the size of sample 400 in one direction (left-right or X-axis), the scanning direction of beam 300 can be rotated to scan from top to bottom. Figure 9B Sample 400 was used to measure the size of the beam in another direction (the top-to-bottom direction of the Y-axis). Therefore, using... Figure 9A and Figure 9B The sample size 400 can measure the beam size in two orthogonal directions.

[0089] For reference Figure 8A The pattern 440 illustrates (this diagram is related to) Figure 9A (same pattern configuration) Figure 9A Pattern 440 is oriented such that the angle (α) between the edge direction A and the X-axis is zero. Figure 9B (It is illustrated in the diagram) Figure 8B (With the same configuration as the illustrated pattern), pattern 440 is oriented such that the angle (α) between the edge direction A and the X-axis is 90°. The sample 400 of this disclosure may also include pattern 440 oriented in other directions to measure beam size in other directions. For example, Figure 8C The illustration shows a sample 400 with pattern 440, oriented such that angle (α) is 45°, and Figure 8D The illustration shows a sample 400 with pattern 440, oriented such that angle (α) is 135°. Angle (α) can be measured (or defined) relative to any common axis (e.g., the X-axis). In some embodiments, such as... Figure 8D As illustrated, the common X-axis can be defined on the wafer (e.g., ( Figure 2B The wafer 150, on which a pattern 440 may be formed, extends along an axis between its center and a notch (or flat edge) disposed on the periphery of the wafer (e.g., as a reference point for alignment, processing, etc.). The electron beam 300 can scan using its scanning direction B, parallel to the edge direction A. Figures 8A to 8D The sample was used to measure the size of the beam 300 in different directions (e.g., arranged at 45° intervals). It should be noted that... Figures 8A to 8D The specific orientation illustrated is merely exemplary; typically, pattern 440 can be oriented in any direction (i.e., at any angle (α)). Regardless of its orientation, the tilt angles (φ, φ') and widths W1, W2, and W3 of pattern 440 can be selected as previously described (e.g., refer to...). Figure 5A ).

[0090] exist Figures 8A to 8D In the illustrated example samples, the patterns 440 on each sample are spaced apart, such that there is only one pattern 440 in the FOV 500, to avoid measurement errors caused by the proximity effect of adjacent patterns. In some embodiments, such as Figure 10A As illustrated, sample 400 may include a plurality of isolated patterns 440A to 440F (or lines) spaced apart within a single FOV 500. Figure 10AAs shown, patterns 440A to 440F can be oriented such that the edge direction A of each pattern forms a different angle (α) with the X-axis to measure the beam size in different directions during beam scanning at FOV 500. Regardless of the orientation of patterns 440A to 440F, the tilt angles (φ, φ') and widths W1, W2, W3, and W4 of patterns 440A to 440F can be selected as previously described (e.g., refer to...). Figure 5A and Figure 7A When the electron beam scans the FOV 500, in some cases, the scanning direction B of the beam may not be parallel to the edge directions of all patterns 440A to 440F in the FOV 500. In such cases, such as Figure 10B As shown, the beam size will be measured in the edge direction, but the pixel size in the SEM image will be in the scan direction B. Therefore, the pixel size may need to be converted to the edge direction A for each pattern 440A to 440F. Pixel size refers to the size of a single pixel in the final digital image and can be determined by the step size used during the scanning process. The pixel size (PS) can be converted from one direction (e.g., scan direction B) to another direction (e.g., edge direction A) based on the angle (β) between the two directions (e.g., PS). A =PS B cos(β)). It is also conceivable that in some such embodiments, as referenced... Figure 9A and Figure 9B The scanning direction B of the electron beam can be changed when it scans certain patterns 440A to 440F in the FOV 500 so that the scanning direction B is parallel to the edge direction A of each pattern 440A to 440F.

[0091] The resolution (e.g., S2575 distance) and beam size of the main electron beam may not be the same at all locations within a large field of view (FOV), such as, for example, 100 μm x 100 μm. In order to measure the resolution and beam size at all locations within the FOV 500, in some embodiments, isolated patterns may be provided at different locations within the FOV 500. Figure 11A and Figure 11B An exemplary sample 400 is illustrated that can be used to measure beam size at different locations within a large FOV 500. In some embodiments, such as Figure 11A As illustrated, pattern 440C can be provided at the center of the FOV 500, and patterns 440A, 440B, 440D, and 440E can be provided at each corner of the FOV to independently measure resolution and beam size at these locations using different patterns. It should be noted that... Figure 11A The specific location of the pattern illustrated is merely exemplary. Typically, the pattern can be provided anywhere within the field of view (FOV). Figure 11B In some embodiments, two patterns on the same side of the FOV are combined to form a single pattern (e.g. Figure 11A Patterns 440A and 440D are combined to form Figure 11B Pattern 440A, Figure 11A Patterns 440B and 440E are combined to form Figure 11B Pattern 440C). With Figure 11B Compared to sample 400, Figure 11A Sample 400 can be made easier because preparing the mask used to make this sample can be easier (such as taking less writing time, for example by using an electron beam writer).

[0092] To improve the signal-to-noise ratio, in some embodiments, a denser pattern layout can be provided in the FOV, and measurements (of bundle size) can be averaged across different patterns. Figures 12A to 12D An exemplary sample 400 is illustrated having a dense layout of patterns 440A to 440D with different orientations in a field of view (FOV) of 500. See reference... Figure 10A As explained, the electron beam size or PSF may not be circular. To measure the beam size in different directions, patterns 440A to 440D can be oriented such that the edge direction A of the pattern forms different angles (α) with the X-axis. Typically, if the FOV size is small (e.g., 10 μm x 10 μm), the beam size can be almost the same at all locations within the FOV, and an average beam size can be used (e.g., obtained by averaging results from all patterns in a dense patterned layout). For example, from Figure 12A The average beam size obtained from the four patterns 440A to 440D can be taken as the beam size in one direction, and from Figure 12B The average beam size obtained from the four patterns 440A to 440D can be taken as the beam size in the orthogonal direction. (See reference...) Figure 9A and Figure 9B The scanning direction B of the electron beam 300 can be used during its scanning... Figures 12A to 12D The pattern 440A to 440D is changed so that the scanning direction B is parallel to the edge direction A of the pattern 440A to 440D. Figures 12A to 12D In a denser pattern layout, the tilt angles (φ, φ') and widths W1, W2, W3, and W4 of patterns 440A to 440D can be selected as previously described (e.g., refer to...). Figure 5A and Figure 7A ).

[0093] In some embodiments, in order to evaluate the beam size in different directions within the FOV 500, such as Figure 13A As shown, sample 400 may comprise group 440' of more densely patterned patterns 440A to 440D in FOV 500 with different orientations (e.g., different angles α). In this case, as referenced above... Figure 10A and Figure 10B Similarly, the electron beam scanning direction B may not be parallel to the edge direction A of all patterns in the FOV 500. In such embodiments, the pixel size (in the scanning direction) can be converted to the pixel size in the edge direction based on the angle between the two directions. If the size of the FOV 500 is large enough that the beam size is non-uniform across the FOV, the beam size measurements can be averaged over local areas (e.g., the FOV center, FOV angles, etc.). For example, in some exemplary embodiments of sample 400, such as Figure 13B As shown, a denser group 440' of patterns 440A to 440D in one orientation (e.g., at an angle α) can be provided at different locations within the field of view, and the results for each location can be averaged. It should be noted that, although Figure 13B The illustration shows a sample of a group of patterns 440A to 440D oriented at angle α=0, but typically patterns 440A to 440D can be oriented at any angle (α). In some embodiments, to measure the beam size in different directions at different locations in the FOV500, such as Figure 13C As illustrated, sample 400 may include groups 440' of patterns 440A to 440F at different locations (e.g., center, corner, etc.) within FOV 500, and different patterns 440A to 440F in each group 440' may be oriented at different angles (α). Figure 13C In the embodiments, as referenced Figure 10A and Figure 10B The electron beam scanning direction B may not be parallel to the edge directions A of all patterns 440A to 440F in the pattern group. In such embodiments, as previously described, the pixel size of the SEM image (which is measured in scanning direction B) can be converted to the edge directions A of each pattern 440A to 440F based on the angle between the two directions. Figures 13A to 13C In the pattern layout, the tilt angles (φ, φ') and widths W1, W2, W3, and W4 of the pattern can be selected as previously described (e.g., refer to...). Figure 5A and Figure 7A ).

[0094] In the example patterns above, such as Figure 14A As illustrated, the shape (e.g., cross-sectional shape) of pattern 440 in a plane (e.g., the XZ plane) can be approximately trapezoidal with two opposing inclined edges, and the shape of the pattern in an orthogonal plane (e.g., the XY plane) is similar to a line. Furthermore, to measure the bundle size in different directions, the pattern is oriented such that the edge direction A of pattern 440 forms different angles (α) with respect to the X-axis. However, this pattern configuration is merely exemplary. In some embodiments, a pattern with multiple edges oriented in more than one direction can be used. For ease of description, such a pattern may be referred to herein as a two-dimensional or 2D pattern. Figure 14B An exemplary octagonal pattern 440 with multiple edges oriented in different directions is illustrated. Specifically, pattern 440 includes four pairs of opposing edges (s1 & s2, s3 & s4, s5 & s6, and s7 & s8), wherein each pair of edges is oriented in a different direction. For example, edges s1 & s2 are oriented along a first edge direction A1, edges s3 & s4 are oriented along a second edge direction A2, edges s5 & s6 are oriented along a third edge direction A3, and edges s7 & s8 are oriented along a fourth edge direction A4. In some embodiments, the tilt angle φ of each tilted edge and its slope width can be referenced as previously stated. Figure 5A The aforementioned selection is made. For example, the tilt angle (φ) of each tilted edge s1 to s8 can be between approximately 40° and 80° to make the variation in secondary electron yield (δ) clear and obvious and to mitigate strong edge effects, as previously referenced. Figure 5A The width of each of the inclined edges s1 to s8 (which corresponds to...) Figure 5A The distances between W1 and W3 and the relatively inclined edges (i.e., s1 & s2, s3 & s4, s5 & s6, and s7 & s8) can be chosen to be ≥ 2.3r. b To ensure that the measurement error is less than approximately 10%, or ≥3.8r b To ensure that the measurement error is less than approximately 1%, or ≥5r b To ensure that the measurement error is less than approximately 0.1%, the combination of tilt angle (φ) and ramp width can be selected such that the edge height is less than the depth of focus (DOF) of the electron beam. The beam size in different directions can be measured by scanning the pattern 440 with the electron beam in scanning directions parallel to (or along) different edge directions (A1, A2, A3, and A4). In some embodiments, the scanning direction of the beam can be changed to be parallel to different edge directions. However, as previously referenced... Figure 10A and Figure 10B As explained, in some embodiments, it may be impossible to make the scan direction parallel to all edge directions. In such embodiments, the pixel size (in the scan direction) may be converted to a non-parallel edge direction based on the angle between these edges and the scan direction.

[0095] It should be noted that Figure 14B The illustrated octagonal pattern 440 is merely exemplary. Typically, pattern 440 can include any polygonal shape (in the top-down view of the sample), where sloping edges form the sides of the polygonal shape. For example, Figures 14C to 14F The illustration shows some exemplary 2D patterns 440 with multiple slanted edges. Figure 14C The illustration shows a triangular pattern 440 with three slanted edges s1 to s3. Figure 14D The illustration shows a quadrilateral pattern 440 with four slanted edges s1 to s4. Figure 14E The illustration shows a hexagonal pattern 440 with six slanted edges s1 to s6. Figure 14F A heptagonal pattern 440 with seven sloping sides s1 to s7 is illustrated. It should be noted that these 2D pattern shapes are merely exemplary, and other pattern shapes (e.g., pentagons, nonagons, decagons, etc.) can also be conceived. The sloping angle (φ), slope width, and distance between opposite edges of each pattern 440 can be selected as previously described (e.g., referencing...). Figure 5A and Figure 7A As previously mentioned, in order to measure the beam size in different directions within a FOV 500, a 2D pattern 440 with multiple edges oriented in different directions can be provided within the FOV 500 (such as, for example...). Figures 14B to 14F Pattern 440). For example. Figure 15A An exemplary embodiment of sample 400 is illustrated, wherein an octagonal pattern 440 (as shown) is provided in FOV 500. Figure 14B (As shown). By using an electron beam parallel to different edge directions (A1 to A4, see...) Figure 14B The scanning pattern 440 of the beam direction can measure the beam size in different directions. The scanning direction can be made parallel to each edge direction by changing the beam scanning direction as it scans each pair of opposite edges. If it is not possible to make the scanning direction parallel to all different edge directions, refer to the reference... Figure 10A and Figure 10B The pixel size (in the scanning direction) can be converted to each non-parallel edge direction based on the angle between the edge direction and the scanning direction.

[0096] To account for the differences in beam size at different locations within the FOV, multiple multi-edge 2D patterns can be provided at different locations within the FOV 500. Figure 15B An exemplary sample 400 is illustrated, having an octagonal pattern 440B at the center and octagonal patterns 440A, 440C, 440D, and 440E at each corner of the field of view (FOV) 500. Figure 15B In some embodiments, the orientation of patterns 440A to 440E at each location in the FOV 500 can be the same. However, this is not required. In some embodiments, even if the same pattern configuration is used at different locations, the orientation of the patterns can be changed at different locations in the FOV 500. For example, Figure 15C An exemplary sample 400 is illustrated, having pentagonal patterns 440A to 440E with different orientations at different locations within a field of view (FOV) 500. Patterns with different configurations can also be provided at different locations within the FOV 500. For example, Figure 15DAn exemplary sample 400 is illustrated, which has an octagonal pattern 440C at the center of the field of view (FOV), two quadrilateral patterns 440A and 440B with different orientations at two FOV corners, a pentagonal pattern 440D at a third FOV corner, and a hexagonal pattern 440E at a fourth FOV corner. Each of these samples (e.g., Figures 15B to 15D In this context, the tilt angle (φ), slope width, distance between opposite edges, and spacing between adjacent patterns can be selected as previously described.

[0097] In this disclosure, electron beam size (e.g., r) is measured using a sample having a patterned edge profile with a known and controlled tilt angle and ramp width. b Using such samples to measure beam size is expected to improve measurement accuracy, for example, by up to 30% (see [reference]). Figure 5B Exemplary methods for manufacturing resolution measurement samples and methods for measuring resolution (S2575) and beam size using such samples will now be described.

[0098] Figure 16A An exemplary method 600 for fabricating an exemplary resolution measurement sample is illustrated. In step S610, the main electron beam size of the SEM (e.g., re) can be predicted or determined using, for example, simulation. b In some embodiments, the predicted (or estimated) electron beam (or beam spot) size may be a sharpness S2575 or a Gaussian radius. Any suitable simulation technique (e.g., Monte Carlo simulation, Gaussian beam model, finite element analysis, etc.) can be used in step S610 to predict the beam size. In step S620, a sample 400 with a pattern 440 having the controlled edge profile described above can be fabricated. For example, the tilt angle (φ) of the edges may be between approximately 40° and 80°, and the slope width of the tilted edges may be ≥ approximately 2.3r. b (Measurement error less than approximately 10%) or ≥3.8r b (Measurement error less than approximately 1%) or ≥5r b (Measurement error less than approximately 0.1%). As previously described, this controlled edge profile makes variations in secondary electron yield (δ) clear and pronounced, with minimal or even negligible influence from other surfaces of the pattern. In some embodiments, this pattern 440 may include having, for example, Figure 5A The lines representing the cross-sectional shape shown in the illustration extend across the surface of substrate 330. (Additional reference) Figure 5A The pattern 440 produced in step S620 may have a pair of inclined edges s1 and s2, each inclined edge having an inclination angle (φ, φ') between approximately 40° and 80° and a bundle size (r) approximately determined in step S610. bThe slope width (W1, W3) is 5 times that of the slope width. The pattern 440 can be fabricated in step S620 using known semiconductor manufacturing techniques. For example, the pattern 440 can be formed on the substrate using known photolithography techniques. Samples having any of the previously described patterns 440 can be fabricated using method 600.

[0099] Figure 16B An exemplary method 700 is illustrated, which measures the resolution (S2575) of the main electron beam of an SEM using an exemplary resolution measurement sample (e.g., a sample manufactured using method 600) and determines its beam size. In some exemplary embodiments, method 700 may be performed by ( Figure 1 Controller 109, ( Figure 2A , Figure 2B The image processing system 290, 199, or any other controller associated with the SEM system can be used to perform this step. In step S710, the main electron beam of the SEM can be used to scan a pattern 440 (e.g., ...). Figure 5A The illustrated pattern 440) measures the sample at a resolution to obtain a signal (see, for example, see...). Figure 4C Additional References Figure 4C and Figure 5A From the corresponding inclined edge s1 (with an inclination angle (φ) between approximately 40° and 80° and ≥ approximately 5r b The signal of the slope width (W1) can be used to measure the distance (i.e., resolution, sharpness, etc.) of S2575 as explained in the previous step S720. For example, the maximum and minimum values ​​of the vertical axis of the signal (I) can be obtained. max and I min ), and will correspond to I max -I min The difference between the 25% and 75% X-axis positions is measured as the S2575 distance. The bundle size (r) can then be determined in step S730 based on the measured S2575 distance. b In some embodiments, in step S730, r b It can be determined as S2575 / 0.954 (e.g., based on equation 6). In some embodiments, r b It can be determined to be equal to S2575 (i.e., S2575 / 1.0). Typically, r b It can be determined as S2575 / A, where A is any value between 0.9 and 1.0. It should be noted that although the bundle size is described as r... b However, this is just an example. Typically, the bundle size can be chosen as r. b Any multiple of, such as, for example, 2r b 1.916r b wait.

[0100] In some embodiments, instead of scanning the resolution measurement sample in step S710 to measure the S2575 distance (e.g., resolution) and determine the beam size, the SEM image of the resolution measurement sample can be used to determine the resolution and beam size. For example, the SEM image of the resolution measurement sample can be input into SEM image analysis software (e.g., ImageJ, FIJI, ImagePro Plus, DigitalMicrograph, AnalySIS, Avizo, etc.), and the SEM image (with a controlled tilt profile, such as a reference) Figure 5A The contour of the edge can be selected and used to measure the beam size and resolution (e.g., as described in steps S720 and S730 of method 700). In some exemplary embodiments, method 700 can be composed of ( Figure 1 Controller 109, ( Figure 2A , Figure 2B The image processing system 290, 199 or any other controller associated with the SEM system may be used to perform this operation.

[0101] In some embodiments, a non-transitory computer-readable medium may be provided, which stores information for a controller (e.g., Figure 1 The processor of the controller 109 executes instructions to perform image inspection, image acquisition, stage positioning, beam focusing, electric field adjustment, beam bending, converging lens adjustment, activation of charged particle sources, beam deflection, measurement of the resolution and beam size of the main electron beam, and methods 700 and 800, etc. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tape or any other magnetic data storage media, optical disc read-only memory (CD-ROM), any other optical data storage media, any physical media with a perforated pattern, random access memory (RAM), programmable read-only memory (PROM) and erasable programmable read-only memory (EPROM), FLASH-EPROM or any other flash memory, non-volatile random access memory (NVRAM), caches, registers, any other memory chips or cassette tapes, and their networked versions.

[0102] These embodiments may also be further described using the following terms: 1. A method for determining the size of a beam spot of a charged particle beam, comprising: An image is generated by scanning a pattern on a sample using a charged particle beam, wherein the pattern includes at least one tilted side edge and a top surface, wherein the at least one tilted side edge has a tilt angle controlled during the fabrication of the sample to be between approximately 40 and 80 degrees; and The size of the beam spot on the sample is determined based on the imaging profile of the at least one inclined side edge, the imaging profile being derived from the image. 2. The method according to Clause 1, wherein the at least one inclined side edge has a slope width that is greater than or equal to about 2.3 times the estimated size of the fascicle. 3. The method according to Clause 1, wherein the at least one inclined side edge has a slope width greater than or equal to about 3.8 times the estimated size of the fascicle. 4. The method according to Clause 1, wherein the at least one inclined side edge has a slope width that is greater than or equal to about 5 times the estimated size of the fascicle. 5. The method according to any one of clauses 2 to 4, wherein the estimated size of the beam spot is based on a predetermined value simulated. 6. The method according to any one of Clauses 1 to 4, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface. 7. The method according to Clause 6, wherein the first inclined side edge and the second inclined side edge have a slope width greater than or equal to about 2.3 times the estimated size of the fascicle. 8. The method according to any one of clauses 1 to 4, wherein the width of the top surface is greater than or equal to the larger of: (i) the penetration depth of the charged particle beam on the sample and (ii) about 2.3 times the estimated size of the beam spot. 9. The method according to Clause 8, wherein the sample comprises only a single pattern in the field of view of the charged particle beam. 10. The method according to any one of clauses 1 to 4, wherein the pattern is a first pattern, and the sample further comprises a second pattern spaced apart from the first pattern, the second pattern having a second inclined side edge with an inclination angle between about 40 and 80 degrees, wherein the first pattern and the second pattern are located in the field of view of the charged particle beam. 11. The method according to Clause 10, wherein the distance between the first pattern and the second pattern is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) approximately 5 times the estimated size of the beam spot. 12. The method according to Clause 11, wherein the second pattern is oriented differently on the sample than the first pattern. 13. The method according to any one of clauses 1 to 4, wherein in a top-down view of the sample, the pattern is polygonal in shape, and the at least one inclined side edge comprises a plurality of inclined side edges, wherein each of the plurality of inclined side edges forms an edge of the polygonal pattern. 14. The method according to Clause 13, wherein the pattern is a first pattern, and the sample further comprises a second pattern and a third pattern in the field of view of the charged particle beam, and wherein the second pattern and the third pattern are spaced apart from the first pattern by a distance greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) approximately 5 times the estimated size of the beam spot. 15. The method according to Clause 14, wherein at least one of the second pattern and the third pattern (a) is oriented differently on the sample from the first pattern, or (b) has a different number of edges than the first pattern. 16. A method for determining the size of a beam spot of a charged particle beam, comprising: An image is generated by scanning a pattern on a sample using a charged particle beam, wherein the pattern includes at least one sloping side edge and a top surface, wherein the at least one sloping side edge has a sloping angle between approximately 40 and 80 degrees and a ramp width greater than or equal to approximately 2.3 times the estimated size of the beam spot based on simulation; and The size of the beam spot is determined based on the imaging profile of the at least one inclined side edge, which is derived from the image. 17. The method according to Clause 16, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface. 18. The method according to Clause 16, wherein in a top-down view of the sample, the pattern is polygonal in shape, and the at least one sloping side edge comprises a plurality of sloping side edges, and wherein each of the plurality of sloping side edges forms an edge of the polygonal pattern. 19. The method according to any one of Clauses 16 to 18, wherein the width of the top surface is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) about 2.3 times the estimated size of the beam spot. 20. The method according to any one of Clauses 16 to 18, wherein the sample comprises the pattern formed on a substrate, wherein the substrate and the pattern comprise a conductive material, and wherein at least one of the substrate and the pattern comprises a metal or doped silicon. 21. A sample for determining the size of a beam spot of a charged particle beam, comprising: Substrate formed of conductive material, and A pattern disposed on the substrate, wherein the pattern is formed of a conductive material, and wherein the pattern includes at least one inclined side edge and a top surface, wherein the at least one inclined side edge has an inclination angle controlled during the manufacture of the sample to be between about 40 and 80 degrees. 22. The sample according to Clause 21, wherein the at least one inclined side edge has a slope width greater than or equal to about 2.3 times the estimated size of the beam spot based on simulation. 23. The sample according to Clause 21, wherein the at least one inclined side edge has a slope width greater than or equal to approximately 3.8 times the estimated size of the beam spot based on simulation. 24. The sample according to Clause 21, wherein the at least one inclined side edge has a slope width that is greater than or equal to about 5 times the estimated size of the beam spot based on simulation. 25. The sample according to any one of clauses 21 to 24, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface. 26. The sample according to Clause 25, wherein the first inclined side edge and the second inclined side edge have a ramp width greater than or equal to about 2.3 times the estimated size of the beam spot. 27. A sample according to any one of clauses 22 to 24, wherein the width of the top surface is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) about 2.3 times the estimated size of the beam spot. 28. The sample as described in Clause 27, wherein the sample comprises only a single pattern in the field of view of the charged particle beam. 29. A sample according to any one of clauses 22 to 24, wherein the pattern is a first pattern, and the sample further comprises a second pattern spaced apart from the first pattern, the second pattern having a second inclined side edge at an angle between about 40 and 80 degrees, wherein the first pattern and the second pattern are located in the field of view of the charged particle beam. 30. The sample according to Clause 29, wherein the distance between the first pattern and the second pattern is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) approximately 5 times the estimated size of the beam spot. 31. The sample according to Clause 30, wherein the second pattern is oriented differently on the sample from the first pattern. 32. A sample according to any one of clauses 22 to 24, wherein, in a top-down view of the sample, the pattern is polygonal in shape, and the at least one sloping side edge comprises a plurality of sloping side edges, wherein each of the plurality of sloping side edges forms an edge of the polygonal pattern. 33. The sample according to Clause 32, wherein the pattern is a first pattern, and the sample further comprises a second pattern and a third pattern in the field of view of the charged particle beam, wherein the second pattern and the third pattern are spaced apart from the first pattern by a distance greater than or equal to the greater of: (i) the penetration depth of the charged particle beam in the sample and (ii) approximately 5 times the estimated size of the beam spot. 34. The sample according to Clause 33, wherein at least one of the second pattern and the third pattern (a) is oriented differently on the sample from the first pattern, or (b) has a different number of edges than the first pattern. 35. A non-transitory computer-readable medium storing an instruction set executable by at least one processor of a computing device to cause the computing device to perform operations for determining the size of a beam spot of a charged particle beam, the operations comprising: An image is generated by scanning a pattern on a sample using a charged particle beam, wherein the pattern includes at least one tilted side edge and a top surface, wherein the at least one tilted side edge has a tilt angle controlled during the fabrication of the sample to be between approximately 40 and 80 degrees; and The size of the beam spot is determined based on the imaging profile of the at least one tilted side edge, the imaging profile being derived from the image. 36. The non-transitory computer-readable medium according to Clause 35, wherein the at least one inclined side edge has a ramp width greater than or equal to about 2.3 times the estimated size of the bundle spot. 37. The non-transitory computer-readable medium according to Clause 35, wherein the at least one inclined side edge has a ramp width greater than or equal to about 3.8 times the estimated size of the bundle spot. 38. The non-transitory computer-readable medium according to Clause 35, wherein the at least one inclined side edge has a ramp width greater than or equal to about 5 times the estimated size of the beam spot. 39. The non-transitory computer-readable medium according to any one of clauses 35 to 38, wherein the estimated size of the beam spot is based on a predetermined value from a simulation. 40. A non-transitory computer-readable medium according to any one of clauses 35 to 38, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface. 41. The non-transitory computer-readable medium according to Clause 40, wherein the first inclined side edge and the second inclined side edge have a ramp width greater than or equal to about 2.3 times the estimated size of the beam spot. 42. A non-transitory computer-readable medium according to any one of clauses 35 to 38, wherein the width of the top surface is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) about 2.3 times the estimated size of the beam spot. 43. The non-transitory computer-readable medium according to Clause 42, wherein the sample comprises only a single pattern in the field of view of the charged particle beam. 44. A non-transitory computer-readable medium according to any one of clauses 35 to 38, wherein the pattern is a first pattern, and the sample further comprises a second pattern spaced apart from the first pattern, the second pattern having a second inclined side edge at an angle between about 40 and 80 degrees, wherein the first pattern and the second pattern are located in the field of view of the charged particle beam. 45. The non-transitory computer-readable medium according to Clause 44, wherein the distance between the first pattern and the second pattern is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) approximately 5 times the estimated size of the beam spot. 46. ​​The non-transitory computer-readable medium according to Clause 45, wherein the second pattern is oriented differently on the sample from the first pattern. 47. A non-transitory computer-readable medium according to any one of clauses 35 to 38, wherein, in a top-down view of the sample, the pattern is polygonal in shape, and the at least one sloping side edge comprises a plurality of sloping side edges, wherein each of the plurality of sloping side edges forms an edge of the polygonal pattern. 48. The non-transitory computer-readable medium according to Clause 47, wherein the pattern is a first pattern, and the sample further comprises a second pattern and a third pattern in the field of view of the charged particle beam, wherein the second pattern and the third pattern are spaced apart from the first pattern by a distance greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) approximately 5 times the estimated size of the beam spot. 49. The non-transitory computer-readable medium according to Clause 48, wherein at least one of the second pattern and the third pattern is (a) oriented differently on the sample from the first pattern, or (b) has a different number of edges than the first pattern. 50. A non-transitory computer-readable medium storing an instruction set executable by at least one processor of a computing device to cause the computing device to perform operations for determining the size of a beam spot of a charged particle beam, the operations comprising: An image is generated by scanning a pattern on a sample using a charged particle beam, wherein the pattern includes at least one sloping side edge and a top surface, wherein the at least one sloping side edge has a sloping angle between approximately 40 and 80 degrees and a ramp width greater than or equal to approximately 2.3 times the estimated size of the beam spot based on simulation; and The beam spot size is determined based on the imaging profile of the at least one inclined side edge, which is derived from the image. 51. The non-transitory computer-readable medium according to Clause 50, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface. 52. The non-transitory computer-readable medium according to Clause 50, wherein in a top-down view of the sample, the pattern is polygonal in shape, and the at least one sloping side edge comprises a plurality of sloping side edges, wherein each of the plurality of sloping side edges forms an edge of the polygonal pattern. 53. A non-transitory computer-readable medium according to any one of clauses 50 to 52, wherein the width of the top surface is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam on the sample and (ii) about 2.3 times the estimated size of the beam spot. 54. A non-transitory computer-readable medium according to any one of clauses 50 to 52, wherein the sample comprises the pattern formed on a substrate, wherein the substrate and the pattern comprise a conductive material, and wherein at least one of the substrate and the pattern comprises a metal or doped silicon.

[0103] The block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products, based on various exemplary embodiments of this disclosure. In this regard, each block in the diagrams may represent certain arithmetic or logical operations, which can be implemented using hardware such as electronic circuits. Blocks may also represent modules, segments, or code portions comprising one or more executable instructions for implementing a specified logical function. It should be understood that in some alternative implementations, the functions indicated in the blocks may not occur in the order shown in the figures. For example, two blocks shown consecutively may be executed or implemented substantially simultaneously, or sometimes two blocks may be executed in reverse order depending on the functions involved. Some blocks may also be omitted. It should also be understood that each block in the block diagrams, and combinations of blocks, may be implemented by a dedicated hardware-based system performing the specified function or action, or by a combination of dedicated hardware and computer instructions.

[0104] It should be understood that the embodiments of this disclosure are not limited to the exact constructions illustrated in the foregoing description and drawings, and various modifications and changes can be made without departing from its scope. This disclosure has been described in conjunction with various embodiments, and other embodiments of the invention will be apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The specification and examples are intended to be illustrative only, and the true scope and spirit of the invention are indicated by the following claims.

Claims

1. A non-transitory computer-readable medium storing an instruction set executable by at least one processor of a computing device to cause the computing device to perform operations for determining the size of a beam spot of a charged particle beam, the operations comprising: A pattern on a sample is scanned using a charged particle beam to generate an image, wherein the pattern includes at least one tilted side edge and a top surface, wherein the at least one tilted side edge has a tilt angle controlled during the fabrication of the sample to be between about 40 and 80 degrees. as well as The size of the beam spot is determined based on the imaging profile of the at least one tilted side edge, the imaging profile being derived from the image.

2. The non-transient computer-readable medium of claim 1, wherein the at least one inclined side edge has a ramp width greater than or equal to about 2.3 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

3. The non-transitory computer-readable medium of claim 1, wherein the at least one inclined side edge has a ramp width greater than or equal to about 3.8 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

4. The non-transient computer-readable medium of claim 1, wherein the at least one inclined side edge has a ramp width greater than or equal to about 5 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

5. The non-transitory computer-readable medium of claim 1, wherein the at least one inclined side edge comprises a first inclined side edge and a second inclined side edge disposed on opposite sides of the top surface.

6. The non-transitory computer-readable medium of claim 5, wherein the first inclined side edge and the second inclined side edge have a ramp width greater than or equal to about 2.3 times the estimated size of the beam spot.

7. The non-transitory computer-readable medium of claim 1, wherein the width of the top surface is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam in the sample and (ii) about 2.3 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

8. The non-transitory computer-readable medium of claim 7, wherein the sample comprises only a single pattern in the field of view of the charged particle beam.

9. The non-transitory computer-readable medium of claim 1, wherein the pattern is a first pattern, and the sample further comprises a second pattern spaced apart from the first pattern, the second pattern having a second tilted side edge at an angle between about 40 and 80 degrees, wherein the first pattern and the second pattern are located in the field of view of the charged particle beam.

10. The non-transitory computer-readable medium of claim 9, wherein the distance between the first pattern and the second pattern is greater than or equal to the greater of: (i) the penetration depth of the charged particle beam in the sample and (ii) about 5 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

11. The non-transitory computer-readable medium of claim 10, wherein the second pattern is oriented differently on the sample from the first pattern.

12. The non-transitory computer-readable medium of claim 1, wherein in a top-down view of the sample, the pattern is polygonal in shape, and the at least one sloping side edge comprises a plurality of sloping side edges, wherein each of the plurality of sloping side edges forms an edge of the polygonal pattern.

13. The non-transitory computer-readable medium of claim 12, wherein the pattern is a first pattern, and the sample further comprises a second pattern and a third pattern in the field of view of the charged particle beam, wherein the second pattern and the third pattern are spaced apart from the first pattern by a distance greater than or equal to the greater of: (i) the penetration depth of the charged particle beam in the sample and (ii) about 5 times the estimated size of the beam spot, wherein the estimated size of the beam spot is based on a predetermined value from simulation.

14. The non-transitory computer-readable medium of claim 13, wherein at least one of the second pattern and the third pattern is (a) oriented differently on the sample from the first pattern, or (b) has a different number of edges than the first pattern.

15. A sample for determining the size of a beam spot of a charged particle beam, comprising: Substrate formed of conductive material, and A pattern disposed on the substrate, wherein the pattern is formed of a conductive material, and wherein the pattern includes at least one inclined side edge and a top surface, wherein the at least one inclined side edge has an inclination angle controlled during the manufacture of the sample to be between about 40 and 80 degrees.

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