Quantitative charged particle beam tool alignment

Abstract

A method, a non-transitory computer readable medium that stores a set of instructions that is executable by at least one processor of a computing device, and an apparatus including a memory storing a set of instructions and at least one processor configured to execute the set of instructions to cause the apparatus to perform operations are disclosed. The method and instructions are for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool and includes obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot; comparing beam spot displacement based on the altering; and calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.

Description

QUANTITATIVE CHARGED PARTICLE BEAM TOOL ALIGNMENTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 720,107 which was filed on November 13, 2024 and US application 63 / 733,407 which was filed on December 12, 2024 which are incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The embodiments provided herein relate to charged particle beam inspection tools, and more particularly to a method for aligning the components of a charged particle beam inspection tool to align the charged particle beam with a center position.BACKGROUND

[0003] In manufacturing processes of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as a scanning electron microscope (SEM) can be employed. As the physical sizes of IC components continue to shrink, accuracy and yield in defect detection become more important. Various metrology tools are developed and used to check whether the ICs are correctly manufactured.

[0004] A charged-particle beam (CPB) tool includes several components, including a tip, an aperture, and a lens. It is noted that a CPB tool may include other components. It is desirable to align the beam such that the beam passes through the center of the lens. This process includes aligning the components and aligning the beam with the components. A common method of beam alignment is to “wobble” the lens by changing the current of the lens such that the beam passes through the center of the lens. However, this method only aligns the lens and does not align the tip and the aperture. It is desirable to have the beam centered through the entire column of components of the CPB tool. For example, it is desirable to align the tip (for generating the beam), the aperture (to restrict the beam size), and the lens (to focus the beam). The CPB tool may be used in connection with an inspection system and a metrology system.SUMMARY

[0005] Some embodiments provide a method for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool. The method includes: obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot; comparing beam spot displacement based on the altering; and calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.

[0006] Some embodiments provide a non-transitory computer readable medium that stores a set of instructions that is executable by at least one processor of a computing device to cause the computing device to perform operations for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool. The operations include: obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot; comparing beam spot displacement based on the altering, wherein the comparing includes obtaining a second beam spot displacement after the altering and calculating a difference between the second beam spot displacement and the center position; and calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.

[0007] Some embodiments provide an apparatus for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool. The apparatus can include a memory storing a set of instructions and at least one processor configured to execute the set of instructions to cause the apparatus to perform operations. The operations include: obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot; comparing beam spot displacement based on the altering; calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position; and repeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.

[0008] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present invention.BRIEF DESCRIPTION OF FIGURES

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

[0010] Fig. 1 is a schematic diagram of a simplified charged-particle beam (CPB) tool, consistent with embodiments of the present disclosure.

[0011] Fig. 2 is a schematic diagram illustrating an example CPB system, consistent with embodiments of the present disclosure.

[0012] Fig. 3 is a schematic diagram illustrating an example charged-particle beam tool, consistent with embodiments of the present disclosure that may be a part of the example CPB system of Fig. 2.

[0013] Fig. 4 is a schematic diagram illustrating an example multi-beam tool, consistent with embodiments of the present disclosure that may be a part of the example CPB system of Fig.2.

[0014] Fig. 5 is a block diagram of an exemplary server, consistent with embodiments of the present disclosure.

[0015] Fig. 6 is an x-y plot of transversal beam motion, consistent with embodiments of the present disclosure.

[0016] Fig. 7 is an example of matrices used to describe beam movement and to transfer coordinates to different z-axis locations, consistent with embodiments of the present disclosure.

[0017] Fig. 8A is a diagram of the simplified CPB tool shown in Fig. 1 and example beams, consistent with embodiments of the present disclosure.

[0018] Fig. 8B is a top view of the CPB tool and example beams shown in Fig.8A along the z-axis, consistent with embodiments of the present disclosure.

[0019] Fig. 9 is a diagram of the simplified CPB tool shown in Fig. 1 and example beams and measurements to be taken based on the beams, consistent with embodiments of the present disclosure.

[0020] Fig. 10 a flowchart of an example method for minimizing a beam displacement from a center position in a CPB tool, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0021] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments as recited in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the disclosure is not so limited. Other types of charged-particle beams (e.g., including protons, ions, muons, or any other particle carrying electric charges) may be similarly applied. Furthermore, other imaging systems may be used, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0022] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings, the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described. As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component may include A or B, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or A and B. As a second example, if it is stated that a component may include A, B, or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0023] Electronic devices are constructed of circuits formed on a piece of semiconductor material called a substrate. The semiconductor material may include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium, or the like. Many circuits may be formed together on thesame piece of silicon and are called integrated circuits or ICs. The size of these circuits has decreased dramatically so that many more of them can be fit on the substrate. For example, an IC chip in a smartphone can be as small as a thumbnail and yet may include over 2 billion transistors, the size of each transistor being less than 1 / 1000th the size of a human hair.

[0024] Making these ICs with extremely small structures or components is a complex, timeconsuming, and expensive process, often involving hundreds of individual steps. Errors in even one step have the potential to result in defects in the finished IC, rendering it useless. Thus, one goal of the manufacturing process is to avoid such defects to maximize the number of functional ICs made in the process; that is, to improve the overall yield of the process.

[0025] One component of improving yield is monitoring the chip-making process to ensure that it is producing a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be carried out using a scanning charged-particle microscope (SCPM). For example, an SCPM may be a scanning electron microscope (SEM). An SCPM can be used to image these extremely small structures, in effect, taking a “picture” of the structures of the wafer. The image can be used to determine if the structure was formed properly in the proper location. If the structure is defective, then the process can be adjusted, so the defect is less likely to recur.

[0026] The working principle of an SCPM (e.g., an SEM) is similar to a camera. A camera takes a picture by receiving and recording intensity of light reflected or emitted from people or objects. An SCPM takes a “picture” by receiving and recording energies or quantities of charged particles (e.g., electrons) reflected or emitted from the structures of the wafer. Typically, the structures are made on a substrate (e.g., a silicon substrate) that is placed on a platform, referred to as a stage, for imaging. Before taking such a “picture,” a charged-particle beam may be projected onto the structures, and when the charged particles are reflected or emitted (“exiting”) from the structures (e.g., from the wafer surface, from the structures underneath the wafer surface, or both), a detector of the SCPM may receive and record the energies or quantities of those charged particles to generate an inspection image. To take such a “picture,” the charged-particle beam may scan through the wafer (e.g., in a line-by-line or zig-zag manner), and the detector may receive exiting charged particles coming from a region under charged particle-beam projection (referred to as a “beam spot”). The detector may receive and record exiting charged particles from each beam spot one at a time and join the information recorded for all the beam spots to generate the inspection image. Some SCPMs use a single charged-particle beam (referred to as a “single -beam SCPM,” such as a single-beam SEM) to take a single “picture” to generate the inspection image, while some SCPMs use multiple charged-particle beams (referred to as a “multi-beam SCPM,” such as a multi-beam SEM) to take multiple “sub-pictures” of the wafer in parallel and, in some cases, stitch them together to generate the inspection image. By using multiple charged-particle beams, the SCPM may provide more charged-particle beams onto the structures for obtaining these multiple “sub-pictures,” resulting in morecharged particles exiting from the structures. Accordingly, the detector may receive more exiting charged particles simultaneously and generate inspection images of the structures of the wafer with higher efficiency and faster speed.

[0027] As the physical sizes of IC components continue to shrink, accuracy and yield in defect detection become more important. Metrology and inspection tools can be used to determine whether the ICs are correctly manufactured by identifying a number of defects on each wafer, including at different levels of detail, such as a pattern level, an image (field of view) level, a die level, a care area level, or a wafer level.

[0028] An example of an inspection tool in provided in Fig. 1, which provides an example of a charged-particle beam (CPB) tool 100. The CPB tool 100 includes several components, including a tip 102 to generate a beam, an aperture 104 to restrict the beam size, and a lens 106 to focus the beam. It is noted that CPB tool 100 may include other components not shown in Fig. 1. It is noted that while some of the descriptions in the present disclosure relate to the CPB tool 100 being used in connection with inspection systems, it is to be understood that the CPB tool may also be used in connection with metrology systems and the operation of the systems and methods described herein apply equally, regardless of the use of the CPB tool.

[0029] When the beam passes through the magnetic center of the lens 106 exactly, there is no field. If the strength of the lens 106 is changed (e.g., by changing the excitation current of the lens 106) and no beam movement is seen on a downstream screen 108 (e.g., where the beam is projected), then the beam appears to be aligned (e.g., passing through the center of the lens 106). In conventional systems, the lens 106 may be “wobbled” by changing the excitation current of the lens 106 to determine whether the beam spot on the screen 108 moves (e.g., has jitter). If there is no jitter of the beam spot on the screen 108, then the beam is passing through the center of the lens 106. But wobbling the lens 106 can only align the lens 106 and has no impact on whether the tip 102 or the aperture 104 are aligned. So wobbling the lens 106 does not completely address the problem of aligning the tip 102, the aperture 104, and the lens 106.

[0030] If the beam offset can be measured on the screen, the beam offset with respect to the gun lens and the beam tilt angle can be derived at the aperture plane, which can be further linked to the relative position of the tip, the aperture, and the gun lens. With the relative positions known, the components of the CPB tool can be aligned from upstream to downstream (relative to the aperture) to more fully address the alignment problem.

[0031] Embodiments of the present disclosure can provide a method of minimizing a beam displacement from a center position in a CPB tool. Beam spot displacement may be measured on a wafer plane, relative to a CPB component and the center position. The beam spot displacement measurement may include a beam spot displacement in an x-y plane and a beam tilt angle relative to the center position. A rotation matrix and a focusing matrix may be used to describe the motion of thebeam. Based on the rotation matrix and the focusing matrix, an amount of adjustment of the beam spot toward the center position may be determined.

[0032] The CPB component may then be adjusted (e.g., moved) to shift the beam spot toward the center position. A similar process may be performed for each CPB component that affects the beam, starting from a tip (where the beam is generated) downward toward the wafer plane (where the beam spot “lands”). Several iterations of the process may be needed to align all the components such that the beam displacement from the center position is minimized. In some embodiments, the movement of the individual CPB components may be limited by the precision with which the CPB components can be adjusted. For example, if a proposed amount of movement of a CPB component is smaller than the precision with which the CPB component may be moved, then the component may not be moved.

[0033] Fig. 2 illustrates an exemplary charged-particle beam (CPB) system 200 consistent with embodiments of the present disclosure. CPB system 200 may be used for imaging. For example, CPB system 200 may use an electron beam for imaging. As shown in Fig. 2, CPB system 200 includes a main chamber 201, a load / lock chamber 202, a beam tool 204, and an equipment front end module (EFEM) 206. Beam tool 204 is located within main chamber 201. EFEM 206 includes a first loading port 206a and a second loading port 206b. EFEM 206 may include additional loading port(s). First loading port 206a and second loading port 206b receive wafer front opening unified pods (FOUPs) that contain wafers (e.g., semiconductor wafers or wafers made of other material(s)) or samples to be inspected (the terms “wafers” and “samples” may be used interchangeably). A “lot” is a plurality of wafers that may be loaded for processing as a batch.

[0034] One or more robotic arms (not shown) in EFEM 206 may transport the wafers to load / lock chamber 202. Load / lock chamber 202 is connected to a load / lock vacuum pump system (not shown) which removes gas molecules in load / lock chamber 202 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) may transport the wafer from load / lock chamber 202 to main chamber 201. Main chamber 201 is connected to a main chamber vacuum pump system (not shown) which removes gas molecules in main chamber 201 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is subject to inspection by beam tool 204. Beam tool 204 may be a single-beam system or a multi-beam system.

[0035] A controller 209 is electronically connected to beam tool 204. Controller 209 may be a computer that may execute various controls of CPB system 200. While controller 209 is shown in Fig.2 as being outside of the structure that includes main chamber 201, load / lock chamber 202, and EFEM 206, it is appreciated that controller 209 may be a part of the structure.

[0036] In some embodiments, controller 209 may include one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, aprogrammable 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 Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), and any type circuit capable of data processing. The processor may also be a virtual processor that includes one or more processors distributed across multiple machines or devices coupled via a network.

[0037] In some embodiments, controller 209 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes may include an operating system (OS) and one or more application programs (or “apps”) for specific tasks. The memory may also be a virtual memory that includes one or more memories distributed across multiple machines or devices coupled via a network.

[0038] Fig. 3 illustrates an example imaging system 300 consistent with embodiments of the present disclosure. Beam tool 204 of Fig.3 may be configured for use in CPB system 200. Beam tool 204 may be a single beam apparatus or a multi-beam apparatus. As shown in Fig. 3, beam tool 204 includes a motorized sample stage 301, and a wafer holder 302 supported by motorized sample stage 301 to hold a wafer 303 to be inspected. Beam tool 204 further includes an objective lens assembly 304, a charged-particle detector 306 (which includes charged-particle sensor surfaces 306a and 306b), an objective aperture 308, a condenser lens 310, a beam limit aperture 312, a gun aperture 314, an anode 316, and a cathode 318. Objective lens assembly 304, in some embodiments, may include a modified swing objective retarding immersion lens (SORIL), which includes a pole piece 304a, a control electrode 304b, a deflector 304c, and an exciting coil 304d. Beam tool 204 may additionally include an Energy Dispersive X-ray Spectrometer (EDS) detector (not shown) to characterize the materials on wafer 303.

[0039] A primary charged-particle beam 320 (or simply “primary beam 320”), such as an electron beam, is emitted from cathode 318 by applying an acceleration voltage between anode 316 and cathode 318. Primary beam 320 passes through gun aperture 314 and beam limit aperture 312, both of which may determine the size of charged-particle beam entering condenser lens 310, which resides below beam limit aperture 312. Condenser lens 310 focuses primary beam 320 before the beam enters objective aperture 308 to set the size of the charged-particle beam before entering objective lens assembly 304. Deflector 304c deflects primary beam 320 to facilitate beam scanning on the wafer. For example, in a scanning process, deflector 304c may be controlled to deflect primary beam 320 sequentially onto different locations of top surface of wafer 303 at different time points, to providedata for image reconstruction for different parts of wafer 303. Moreover, deflector 304c may also be controlled to deflect primary beam 320 onto different sides of wafer 303 at a particular location, at different time points, to provide data for stereo image reconstruction of the wafer structure at that location. Further, in some embodiments, anode 316 and cathode 318 may generate multiple primary beams 320, and beam tool 204 may include a plurality of deflectors 304c to project the multiple primary beams 320 to different parts / sides of the wafer at the same time, to provide data for image reconstruction for different parts of wafer 303.

[0040] Exciting coil 304d and pole piece 304a generate a magnetic field that begins at one end of pole piece 304a and terminates at the other end of pole piece 304a. A part of wafer 303 being scanned by primary beam 320 may be immersed in the magnetic field and may be electrically charged, which, in turn, creates an electric field. The electric field reduces the energy of impinging primary beam 320 near the surface of wafer 303 before it collides with wafer 303. Control electrode 304b, being electrically isolated from pole piece 304a, controls an electric field on wafer 303 to prevent microarching of wafer 303 and to ensure proper beam focus.

[0041] A secondary charged-particle beam 322 (or “secondary beam 322”), such as secondary electron beams, may be emitted from the part of wafer 303 upon receiving primary beam 320.Secondary beam 322 may form a beam spot on sensor surfaces 306a and 306b of charged-particle detector 306. Charged-particle detector 306 may generate a signal (e.g., a voltage, a current, or the like) that represents an intensity of the beam spot and provide the signal to an image processing system 350. The intensity of secondary beam 322, and the resultant beam spot, may vary according to the external or internal structure of wafer 303. Moreover, as discussed above, primary beam 320 may be projected onto different locations of the top surface of the wafer or different sides of the wafer at a particular location, to generate secondary beams 322 (and the resultant beam spot) of different intensities. Therefore, by mapping the intensities of the beam spots with the locations of wafer 303, the processing system may reconstruct an image that reflects the internal or surface structures of wafer 303.

[0042] Imaging system 300 may be used for inspecting a wafer 303 on motorized sample stage 301 and includes beam tool 204, as discussed above. Imaging system 300 may also include an image processing system 350 that includes an image acquirer 360, storage 370, and controller 209. Image acquirer 360 may include one or more processors. For example, image acquirer 360 may include a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, and the like, or a combination thereof. Image acquirer 360 may connect with a detector 306 of beam tool 204 through a medium such as an electrical conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, or a combination thereof. Image acquirer 360 may receive a signal from detector 306 and may construct an image. Image acquirer 360 may thus acquire images of wafer 303. Image acquirer 360 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquiredimage, and the like. Image acquirer 360 may perform adjustments of brightness and contrast, or the like of acquired images. Storage 370 may be a storage medium such as a hard disk, cloud storage, random access memory (RAM), other types of computer readable memory, and the like. Storage 370 may be coupled with image acquirer 360 and may be used for saving scanned raw image data as original images, post-processed images, or other images assisting of the processing. Image acquirer 360 and storage 370 may be connected to controller 209. In some embodiments, image acquirer 360, storage 370, and controller 209 may be integrated together as one control unit.

[0043] In some embodiments, image acquirer 360 may acquire one or more images of a sample based on an imaging signal received from detector 306. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image including a plurality of imaging areas. The single image may be stored in storage 370. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may include one imaging area containing a feature of wafer 303.

[0044] Fig. 4 illustrates a schematic diagram of an example multi-beam beam tool 204 (also referred to herein as apparatus 204) and an image processing system 490 that may be configured for use in CPB system 200 (Fig. 2), consistent with embodiments of the present disclosure.

[0045] Beam tool 204 comprises a charged-particle source 402, a gun aperture 404, a condenser lens 406, a primary charged-particle beam 410 emitted from charged-particle source 402, a source conversion unit 412, a plurality of beamlets 414, 416, and 418 of primary charged-particle beam 410, a primary projection optical system 420, a motorized wafer stage 480, a wafer holder 482, multiple secondary charged-particle beams 436, 438, and 440, a secondary optical system 442, and a charged-particle detection device 444. Primary projection optical system 420 can comprise a beam separator 422, a deflection scanning unit 426, and an objective lens 428. Charged-particle detection device 444 can comprise detection sub-regions 446, 448, and 450.

[0046] Charged-particle source 402, gun aperture 404, condenser lens 406, source conversion unit 412, beam separator 422, deflection scanning unit 426, and objective lens 428 can be aligned with a primary optical axis 460 of apparatus 204. Secondary optical system 442 and charged-particle detection device 444 can be aligned with a secondary optical axis 452 of apparatus 204.

[0047] Charged-particle source 402 can emit one or more charged particles, such as electrons, protons, ions, muons, or any other particle carrying electric charges. In some embodiments, charged-particle source 402 may be an electron source. For example, charged-particle source 402 may include a cathode, an extractor, or an anode, wherein primary electrons can be emitted from the cathode and extracted or accelerated to form primary charged-particle beam 410 (in this case, a primary electron beam) with a crossover (virtual or real) 408. For ease of explanation without causing ambiguity, electrons are used as examples in some of the descriptions herein. However, it should be noted that any charged particle may be used in any embodiment of this disclosure, not limited to electrons. Primary charged-particle beam 410 can be visualized as being emitted from crossover 408. Gunaperture 404 can block off peripheral charged particles of primary charged-particle beam 410 to reduce Coulomb effect. The Coulomb effect may cause an increase in size of probe spots.

[0048] Source conversion unit 412 can comprise an array of image-forming elements and an array of beam-limit apertures. The array of image-forming elements can comprise an array of micro-deflectors or micro-lenses. The array of image-forming elements can form a plurality of parallel images (virtual or real) of crossover 408 with a plurality of beamlets 414, 416, and 418 of primary charged-particle beam 410. The array of beam-limit apertures can limit the plurality of beamlets 414, 416, and 418. While three beamlets 414, 416, and 418 are shown in Fig. 4, embodiments of the present disclosure are not so limited. For example, in some embodiments, the apparatus 204 may be configured to generate a first number of beamlets. In some embodiments, the first number of beamlets may be in a range from 1 to 1000. In some embodiments, the first number of beamlets may be in a range from 200-500. In some embodiments, an apparatus 204 may generate 400 beamlets.

[0049] Condenser lens 406 can focus primary charged-particle beam 410. The electric currents of beamlets 414, 416, and 418 downstream of source conversion unit 412 can be varied by adjusting the focusing power of condenser lens 406 or by changing the radial sizes of the corresponding beam-limit apertures within the array of beam-limit apertures. Objective lens 428 can focus beamlets 414, 416, and 418 onto a wafer 430 for imaging, and can form a plurality of probe spots 470, 472, and 474 on a surface of wafer 430.

[0050] Beam separator 422 can be a beam separator of Wien filter type generating an electrostatic dipole field and a magnetic dipole field. In some embodiments, if they are applied, the force exerted by the electrostatic dipole field on a charged particle (e.g., an electron) of beamlets 414, 416, and 418 can be substantially equal in magnitude and opposite in a direction to the force exerted on the charged particle by magnetic dipole field. Beamlets 414, 416, and 418 can, therefore, pass straight through beam separator 422 with zero deflection angle. However, the total dispersion of beamlets 414, 416, and 418 generated by beam separator 422 can also be non-zero. Beam separator 422 can separate secondary charged-particle beams 436, 438, and 440 from beamlets 414, 416, and 418 and direct secondary charged-particle beams 436, 438, and 440 towards secondary optical system 442.

[0051] Deflection scanning unit 426 can deflect beamlets 414, 416, and 418 to scan probe spots 470, 472, and 474 over a surface area of wafer 430. In response to the incidence of beamlets 414, 416, and 418 at probe spots 470, 472, and 474, secondary charged-particle beams 436, 438, and 440 may be emitted from wafer 430. Secondary charged-particle beams 436, 438, and 440 may comprise charged particles (e.g., electrons) with a distribution of energies. For example, secondary charged-particle beams 436, 438, and 440 may be secondary electron beams including secondary electrons (energies < 50 eV) and backscattered electrons (energies between 50 eV and landing energies of beamlets 414, 416, and 418). Secondary optical system 442 can focus secondary charged-particle beams 436, 438, and 440 onto detection sub-regions 446, 448, and 450 of charged-particle detection device 444. Detection sub-regions 446, 448, and 450 may be configured to detect corresponding secondarycharged-particle beams 436, 438, and 440 and generate corresponding signals (e.g., voltage, current, or the like) used to reconstruct an inspection image of structures on or underneath the surface area of wafer 430.

[0052] The generated signals may represent intensities of secondary charged-particle beams 436, 438, and 440 and may be provided to image processing system 490 that is in communication with charged-particle detection device 444, primary projection optical system 420, and motorized wafer stage 480. The movement speed of motorized wafer stage 480 may be synchronized and coordinated with the beam deflections controlled by deflection scanning unit 426, such that the movement of the scan probe spots (e.g., scan probe spots 470, 472, and 474) may orderly cover regions of interest on the wafer 430. The parameters of such synchronization and coordination may be adjusted to adapt to different materials of wafer 430. For example, different materials of wafer 430 may have different resistance-capacitance characteristics that may cause different signal sensitivities to the movement of the scan probe spots.

[0053] The intensity of secondary charged-particle beams 436, 438, and 440 may vary according to the external or internal structure of wafer 430, and thus may indicate whether wafer 430 includes defects. Moreover, as discussed above, beamlets 414, 416, and 418 may be projected onto different locations of the top surface of wafer 430, or different sides of local structures of wafer 430, to generate secondary charged-particle beams 436, 438, and 440 that may have different intensities. Therefore, by mapping the intensity of secondary charged-particle beams 436, 438, and 440 with the areas of wafer 430, image processing system 490 may reconstruct an image that reflects the characteristics of internal or external structures of wafer 430.

[0054] In some embodiments, image processing system 490 may include an image acquirer 492, a storage 494, and a controller 496. Image acquirer 492 may comprise one or more processors. For example, image acquirer 492 may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, or the like, or a combination thereof. Image acquirer 492 may be communicatively coupled to charged-particle detection device 444 of beam tool 204 through a medium such as an electric conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, or a combination thereof. In some embodiments, image acquirer 492 may receive a signal from charged-particle detection device 444 and may construct an image. Image acquirer 492 may thus acquire inspection images of wafer 430. Image acquirer 492 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, or the like. Image acquirer 492 may be configured to perform adjustments of brightness and contrast of acquired images. In some embodiments, storage 494 may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer-readable memory, or the like. Storage 494 may be coupled with image acquirer 492 and may be used for saving scanned raw image data as original images, and postprocessed images. Image acquirer 492 and storage 494 may be connected to controller 496. In someembodiments, image acquirer 492, storage 494, and controller 496 may be integrated together as one control unit.

[0055] In some embodiments, image acquirer 492 may acquire one or more inspection images of a wafer based on an imaging signal received from charged-particle detection device 444. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image comprising a plurality of imaging areas. The single image may be stored in storage 494. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of wafer 430. The acquired images may comprise multiple images of a single imaging area of wafer 430 sampled multiple times over a time sequence. The multiple images may be stored in storage 494. In some embodiments, image processing system 490 may be configured to perform image processing steps with the multiple images of the same location of wafer 430.

[0056] In some embodiments, image processing system 490 may include measurement circuits (e.g., analog-to-digital converters) to obtain a distribution of the detected secondary charged particles (e.g., secondary electrons). The charged-particle distribution data collected during a detection time window, in combination with corresponding scan path data of beamlets 414, 416, and 418 incident on the wafer surface, can be used to reconstruct images of the wafer structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of wafer 430, and thereby can be used to reveal any defects that may exist in the wafer.

[0057] In some embodiments, the charged particles may be electrons. When electrons of primary charged-particle beam 410 are projected onto a surface of wafer 430 (e.g., probe spots 470, 472, and 474), the electrons of primary charged-particle beam 410 may penetrate the surface of wafer 430 for a certain depth, interacting with particles of wafer 430. Some electrons of primary charged-particle beam 410 may elastically interact with (e.g., in the form of elastic scattering or collision) the materials of wafer 430 and may be reflected or recoiled out of the surface of wafer 430. An elastic interaction conserves the total kinetic energies of the bodies (e.g., electrons of primary charged-particle beam 410) of the interaction, in which the kinetic energy of the interacting bodies does not convert to other forms of energy (e.g., heat, electromagnetic energy, or the like). Such reflected electrons generated from elastic interaction may be referred to as backscattered electrons (BSEs). Some electrons of primary charged-particle beam 410 may inelastically interact with (e.g., in the form of inelastic scattering or collision) the materials of wafer 430. An inelastic interaction does not conserve the total kinetic energies of the bodies of the interaction, in which some or all of the kinetic energy of the interacting bodies convert to other forms of energy. For example, through the inelastic interaction, the kinetic energy of some electrons of primary charged-particle beam 410 may cause electron excitation and transition of atoms of the materials. Such inelastic interaction may also generate electrons exiting the surface of wafer 430, which may be referred to as secondary electrons (SEs). Yield or emission rates of BSEs and SEs depend on, e.g., the material under inspection and the landing energy of theelectrons of primary charged-particle beam 410 landing on the surface of the material, among others. The energy of the electrons of primary charged-particle beam 410 may be imparted in part by its acceleration voltage (e.g., the acceleration voltage between the anode and cathode of charged-particle source 402 in Fig. 4). The quantity of BSEs and SEs may be more or fewer (or even the same) than the injected electrons of primary charged-particle beam 410.

[0058] Fig. 5 is a block diagram of an example server 500, consistent with embodiments of the disclosure. As shown in Fig.5, server 500 can include processor 502. When processor 502 executes instructions described herein, server 500 can become a specialized machine. Processor 502 can be any type of circuitry capable of manipulating or processing information. For example, processor 502 can include any combination of any number of a central processing unit (“CPU”), a graphics processing unit (“GPU”), a neural processing unit (“NPU”), a microcontroller unit (“MCU”), 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 Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), or the like. In some embodiments, processor 502 can also be a set of processors grouped as a single logical component. For example, as shown in Fig.5, processor 502 can include multiple processors, including processor 502a, processor 502b, and processor 502n.

[0059] Server 500 can also include memory 504 configured to store data (e.g., a set of instructions, computer codes, intermediate data, or the like). For example, as shown in Fig. 5, the stored data can include program instructions and data for processing. Processor 502 can access the program instructions and data for processing (e.g., via bus 510), and execute the program instructions to perform an operation or manipulation on the data for processing. Memory 504 can include a highspeed random-access storage device or a non-volatile storage device. In some embodiments, memory 504 can include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or the like. Memory 504 can also be a group of memories (not shown in Fig.5) grouped as a single logical component.

[0060] Bus 510 can be a communication device that transfers data between components inside server 500, such as an internal bus (e.g., a CPU-memory bus), an external bus (e.g., a universal serial bus port, a peripheral component interconnect express port), or the like.

[0061] For ease of explanation without causing ambiguity, processor 502 and other data processing circuits are collectively referred to as a “data processing circuit” in this disclosure. The data processing circuit can be implemented entirely as hardware, or as a combination of software, hardware, or firmware. In addition, the data processing circuit can be a single independent module or can be combined entirely or partially into any other component of server 500.

[0062] Server 500 can further include network interface 506 to provide wired or wireless communication with a network (e.g., the Internet, an intranet, a local area network, a mobile communications network, or the like). In some embodiments, network interface 506 can include any combination of any number of a network interface controller (NIC), a radio frequency (RF) module, a transponder, a transceiver, a modem, a router, a gateway, a wired network adapter, a wireless network adapter, a Bluetooth adapter, an infrared adapter, a near-field communication (“NFC”) adapter, a cellular network chip, or the like.

[0063] In some embodiments, optionally, server 500 can further include peripheral interface 508 to provide a connection to one or more peripheral devices. As shown in Fig.5, the peripheral device can include, but is not limited to, a cursor control device (e.g., a mouse, a touchpad, or a touchscreen), a keyboard, a display (e.g., a cathode-ray tube display, a liquid crystal display, or a light-emitting diode display), a video input device (e.g., a camera or an input interface coupled to a video archive), or the like.

[0064] In the CPB tool, movement of the beam is described by beam dynamics. The beam motion is defined by a set of differential equations, but first order equations and a matrix may be used to describe the beam motion. Using a linear model to describe the linear motion of the beam simplifies the mathematics needed to describe the beam motion. As shown in Fig.6, an x-y plot 600 is looking at the beam from the top (e.g., from the tip 102 towards the screen 108, as shown in Fig. 1) so only the transversal beam motion is visible in the x-y plane. The beam is moving into the plot, along the z-axis. If the beam is located at an origin 602 of the x-y plot 600, then beam is perfectly aligned. But the beam is not usually perfectly aligned; the beam has transversal motion. The transversal motion of the beam includes a rotation movement 604, which is motion of the beam along an arc with the same radius and a focusing movement 606, which is motion of the beam from the rotation location back toward the origin 602 (e.g., radial motion from a point on the arc back towards the origin 602).

[0065] The rotation movement 604 and the focusing movement 606 can each be described by a matrix. The status of the beam can be described by a vector (x, x', y, y'), where (x, y) is an x-y offset of the beam from the origin in the x-y plane (e.g., the x-y plot 600 of Fig.6). But because the beam is moving into the x-y plane, it has a tilt (e.g., an angle relative to the z-axis). In the vector, (x', y') is used to describe the tilt angle of the beam, where x' = Ax / Az and y' = Ay / Az. The vector (x, x', y, y') can provide a full description of the beam at any point along the z-axis.

[0066] For example, to transfer the coordinates of the beam at the aperture to a location on the screen (e.g., the beam coordinates on the screen may be represented by a vector(xw, xw', yw, yw')), a matrix may be used because the beam motion is linear. The matrices may be used to connect the states of the beam at different locations along the z-axis. For example, as shown in Fig. 7, a rotation matrix (MR) 700 describes the rotation movement and the changes to all four coordinates x, x', y, and y', where 0 is the rotation angle of the beam in the x-y plane. A focusing matrix (MF) 702 describes the focusing movement as a harmonic oscillation in phase space, which is a rotation in x, x' space, where 0 is therotation angle of the beam in the x-y plane and g is a parameter related to the axial magnetic flux density. The total matrix (M) 712 to describe the beam offset is determined by multiplying the focusing matrix 702 and the rotation matrix 700, M = MF X MR.

[0067] To determine the coordinates at the screen, the equation 710 may be used. The vector at the screen 716 (xw, xw', yw, yw') may be determined as a product of the total matrix 712 and the vector at the aperture 714(xt, xt', yt, yt'). The beam offset and the beam tilt angle at each component of the CPB tool along the z-axis (e.g., each component along the beam path from the tip 102 to the screen 108) may be determined using the equation 710.

[0068] Using Fig. 1 as an example, to take the measurements to determine the vector at the aperture and the vector at the screen, assume that the beam from the tip 102 passes through the aperture 104 with a tilt angle and is not centered as it passes through the aperture 104. If using a fixed aperture 104 as a reference point, then it is possible to write a beam state vector (xt, xt', yt, yt'), e.g., the vector at the aperture 714. The screen 108 is where the beam “lands” and a camera may be positioned below the screen 108 such that the camera is pointing up toward the screen 108 to view the beam spot on the screen 108. At the screen 108, it is possible to write out the beam state vector (xw, xw', yw, yw'), e.g., the vector at the screen 716, by measuring x and y on the screen 108.

[0069] Because the matrix M between the aperture (t) and the screen (w) is known, it is possible to write out two equations:Equation (1)Equation (2)where xt, xt', yt, and yt' represent the beam state at the aperture.

[0070] To determine additional equations, the current of the lens 106 may be changed (also referred to as “varying the lens”). The matrix M will then change, but the unknowns (xt, xt', yt, yt') will not change because the initial beam state at the aperture 104 will not change, because the aperture 104 is located between the tip 102 and the lens 106. But xw and yw will change, so it is possible to obtain another pair of equations because the constants have changed. By repeating this process (e.g., changing the lens current), it is possible to obtain many equations, which may then be statistically solved for xt, xt', yt, and yt' at the aperture precisely.

[0071] Fig. 8A is a diagram of the simplified CPB tool 100 and example beams, consistent with embodiments of the present disclosure. A beam 800 is generated at the tip 102 and passes through the aperture 104. At the aperture 104, the beam 800 may be described by the beam state vector 714 (xt, xt', yt, yt'). When the beam 800 passes through the lens 106, the beam is deflected and exits the lens 106 as beam 802 which is visible on the screen 108. At the screen 108, the beam 802 may be described by the beam state vector 716 (xw, xw', yw, yw').

[0072] Fig. 8B is a top view of the CPB tool 100 and example beams 800, 802 shown in Fig. 8A along the z-axis, consistent with embodiments of the present disclosure. The view in Fig.8B is an extrapolation of how the beams 800, 802 would appear on the screen 108 if both beams 800, 802 reached the screen 108. It is noted that only beam 802 would be visible on the screen 108. The circles in Fig. 8B represent beam spots generated by the beams 800, 802 and are described by the vectors 714, 716. The purpose of Fig. 8B is to show how the beams 800, 802 are not centered at the origin of the x-y plot.

[0073] The goal with alignment is to make the beam offset equal to zero (e.g., to center the beam at the origin of the x-y plot shown in Fig.8B). It is noted that the terms “beam offset” and “beam displacement” may be used interchangeably in the present disclosure. After the beam offset and the beam tilt angle are known, to align the tip, the tilt angle is set to zero, so it is known that the beam will exit the tip 102 as shown by beam path 902 in Fig.9. The distance (L) from the aperture 104 to the screen 108 is known and the beam rotation angle 0 is known. The lens 106 is turned off (e.g., no current is applied to the lens 106) and the beam will follow beam path 902 to a spot 904a on the screen 108. Because both L and 0 are known, dx can be calculated, which is the distance the beam has to move if the tip 102 and the aperture 104 are perfectly aligned. The tip 102 is moved while watching the beam 902 on the screen 108. The beam 902 needs to move from spot 904a to spot 904b for the beam to be aligned (e.g., the beam path 902 will move to beam path 906). After the beam follows beam path 906 to spot 904b, the tip 102 is aligned to the center of the aperture 104.

[0074] The next step is to align the lens 106. Because the beam offsets as defined by (xw, yw) are solved, it is relatively simple to move the lens 106. The lens 106 is set to a certain current and the beam follows the beam path 902 to the spot 904a on the screen 108. It is noted that the beam path 902 and the spot 904a are used for purposes of explanation and clarity of illustration of Fig. 9. When the current is applied to the lens 106, the beam path 902 and the spot 904a may be different than that shown in Fig. 9 (e.g., the beam path 902 and the spot 904a do not need to be the same beam path and spot on the screen as used in connection with aligning the tip 102 and the aperture 104). The lens 106 is then moved to shift the beam from the beam path 902 and the spot 904a to the beam path 906 and the spot 904b.

[0075] After aligning the tip 102, the aperture 104, and the lens 106, the values of x' and y' may have changed (e.g., increased). To correct for this additional change in x' and y', the process of aligning the tip, the aperture, and the lens may be repeated. It may be necessary to perform a few iterations of the alignment process to correctly align the tip, the aperture, and the lens. For example, the process may be repeated until x' and y' are within a precision of 10-5. In some embodiments, the process may be repeated for a predetermined number of iterations. For example, the beam offset and the beam tilt angle may be evaluated and the process may stop when the beam offset and the beam tilt angle reach the micron level, which is about as precise as the tip, the aperture, and the lens may be able to bemoved. In some embodiments, the beam offset and the beam tilt angle may be compared to a threshold and once the beam offset and the beam tilt angle reach the threshold, the process may stop.

[0076] In some embodiments, the process may stop when certain limitations are reached. For example, measurement limitations or camera resolution limitations may limit how finely aligned the components can be. As another example, the precision of moving the CPB tool components may limit the adjustments (e.g., the process may stop when the suggested adjustment is finer than the precision with which the components may be moved).

[0077] In some embodiments, movements of the CPB tool components (e.g., the tip, the aperture, and the lens) may be automatically adjusted such that after the calculations are performed, the components may be automatically moved to achieve a precise alignment.

[0078] In some embodiments, the results of the calculations may be written out to a user interface to be displayed and viewed by an operator of the CPB tool. In some embodiments, the operator may initiate (e.g., by interacting with a user interface element) aligning the components based on the displayed results.

[0079] Fig. 10 is a flowchart of an example method 1000 for minimizing a beam displacement from a center position in a CPB tool, consistent with embodiments of the present disclosure. In some embodiments, the method 1000 may be performed by image processing system 250 of Fig.2 or by server 500 of Fig.5.

[0080] At step 1002, a beam spot displacement on a wafer plane in relation to a CPB component is obtained. For example, beam spot 904a on screen 108 may be obtained, as described in connection with Fig.9.

[0081] At step 1004, the CPB component is altered to shift the beam spot toward the center position. For example, the beam spot may be moved by moving the beam toward a central beam axis of the CPB tool, as shown by moving the beam from beam path 902 and beam spot 904a to beam path 906 and beam spot 904b.

[0082] At step 1006, the beam spot displacement based on the altering is compared. For example, the beam spot 904b may be compared to the beam spot 904a to determine whether the beam has been moved closer to the center position.

[0083] At step 1008, CPB component characteristics are calculated for minimizing the beam spot displacement from the center position. For example, the new position of the tip, the aperture, or the lens may be recorded to indicate the position of the CPB components in which the beam displacement is minimized.

[0084] A non-transitory computer readable medium may be provided that stores instructions for a processor of a controller (e.g., controller 209 of Fig. 2) to carry out, among other things, image inspection, image acquisition, stage positioning, beam focusing, electric field adjustment, beam bending, condenser lens adjusting, activating charged particle source, beam deflecting, and operations shown in Figs.7-9 and method 1000. Common forms of non-transitory media include, for example, afloppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0085] The embodiments may further be described using the following clauses:LA method of minimizing a beam displacement from a center position in a charged particle beam (CPB) tool, including:obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.2. The method of clause 1, wherein the center position is a central beam axis of the CPB tool. 3. The method of clauses 1 or 2, wherein obtaining the beam spot displacement on the wafer plane includes:measuring a first beam vector at the first CPB component, the first beam vector indicating a first beam displacement and a first beam tilt angle;measuring a second beam vector at the wafer plane, the second beam vector indicating a second beam displacement and a second beam tilt angle;obtaining a matrix based on motion of the beam;calculating the first beam vector based on the matrix and the second beam vector.4. The method of clause 3, wherein obtaining the matrix includes:calculating a rotation matrix based on a rotation of the beam in an x-y plane; calculating a focusing matrix based on moving the beam toward an origin point in the x-y plane; andcalculating the matrix by multiplying the rotation matrix and the focusing matrix.5. The method of clause 4, wherein the focusing matrix is defined aswherein:0 is a rotation angle of the beam in the x-y plane; andg is a parameter related to the axial magnetic flux density.6. The method of clause 4, wherein the rotation matrix is defined aswherein 0 is a rotation angle of the beam in the x-y plane.7. The method of any one of clauses 1-6, wherein altering the first CPB component includes moving the first CPB component to shift the beam toward the center position.8. The method of any one of clauses 1-7, wherein comparing beam spot displacement based on the altering includes:obtaining a second beam spot displacement after the altering; andcalculating a difference between the second beam spot displacement and the center position.9. The method of any one of clauses 1-8, wherein the calculating includes determining an amount to move the first CPB component for minimizing the beam displacement from the center position. 10. The method of any one of clauses 1-9, further including:repeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.11. The method of clause 10, wherein the predetermined threshold is based on a precision of movement of the first CPB component.12. The method of any one of clauses 1-11, further including:repeating the obtaining, the altering, the comparing, and the calculating for each component of the CPB tool that affects the beam.13. The method of clause 12, wherein the CPB components include a tip, an aperture, and a lens. 14. The method of any one of clauses 1-13, further including:obtaining a beam spot displacement on a wafer plane in relation to a second CPB component; altering the second CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, second CPB component characteristics for minimizing beam displacement from the center position.15. The method of clause 14, further including:obtaining a beam spot displacement on a wafer plane in relation to a third CPB component; altering the third CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, third CPB component characteristics for minimizing beam displacement from the center position.16. A non-transitory computer readable medium that stores a set of instructions that is executable by at least one processor of a computing device to cause the computing device to perform operations for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool, the operations including:obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering, wherein the comparing includes: obtaining a second beam spot displacement after the altering; andcalculating a difference between the second beam spot displacement and the center position; andcalculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.17. The non-transitory computer readable medium of clause 16, wherein the center position is a central beam axis of the CPB tool.18. The non-transitory computer readable medium of clauses 16 or 17, wherein obtaining the beam spot displacement on the wafer plane includes:measuring a first beam vector at the first CPB component, the first beam vector indicating a first beam displacement and a first beam tilt angle;measuring a second beam vector at the wafer plane, the second beam vector indicating a second beam displacement and a second beam tilt angle;obtaining a matrix based on motion of the beam;calculating the first beam vector based on the matrix and the second beam vector.19. The non-transitory computer readable medium of clause 18, wherein obtaining the matrix includes:calculating a rotation matrix based on a rotation of the beam in an x-y plane; calculating a focusing matrix based on moving the beam toward an origin point in the x-y plane; andcalculating the matrix by multiplying the rotation matrix and the focusing matrix.20. The non-transitory computer readable medium of clause 19, wherein the focusing matrix is defined aswherein:0 is a rotation angle of the beam in the x-y plane; andg is a parameter related to the axial magnetic flux density.21. The non- transitory computer readable medium of clause 19, wherein the rotation matrix is defined aswherein 0 is a rotation angle of the beam in the x-y plane.22. The non-transitory computer readable medium of any one of clauses 16-21, wherein altering the first CPB component includes moving the first CPB component to shift the beam toward the center position.23. The non-transitory computer readable medium of any one of clauses 16-22, wherein the calculating includes determining an amount to move the first CPB component for minimizing the beam displacement from the center position.24. The non-transitory computer readable medium of any one of clauses 16-23, wherein the operations further include:repeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.25. The non-transitory computer readable medium of clause 24, wherein the predetermined threshold is based on a precision of movement of the first CPB component.26. The non-transitory computer readable medium of any one of clauses 16-25, wherein the operations further include:repeating the obtaining, the altering, the comparing, and the calculating for each component of the CPB tool that affects the beam.27. The non-transitory computer readable medium of clause 26, wherein the CPB components include a tip, an aperture, and a lens.28. The non- transitory computer readable medium of any one of clauses 16-27, wherein the operations further include:obtaining a beam spot displacement on a wafer plane in relation to a second CPB component; altering the second CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, second CPB component characteristics for minimizing beam displacement from the center position.29. The non-transitory computer readable medium of clause 28, wherein the operations further include:obtaining a beam spot displacement on a wafer plane in relation to a third CPB component; altering the third CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, third CPB component characteristics for minimizing beam displacement from the center position.30. An apparatus for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool, including:a memory storing a set of instructions; andat least one processor configured to execute the set of instructions to cause the apparatus to perform operations including:obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering;calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position; andrepeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.31. The apparatus of clause 30, wherein the center position is a central beam axis of the CPB tool. 32. The apparatus of clauses 30 or 31, wherein obtaining the beam spot displacement on the wafer plane includes:measuring a first beam vector at the first CPB component, the first beam vector indicating a first beam displacement and a first beam tilt angle;measuring a second beam vector at the wafer plane, the second beam vector indicating a second beam displacement and a second beam tilt angle;obtaining a matrix based on motion of the beam;calculating the first beam vector based on the matrix and the second beam vector.33. The apparatus of clause 32, wherein obtaining the matrix includes:calculating a rotation matrix based on a rotation of the beam in an x-y plane; calculating a focusing matrix based on moving the beam toward an origin point in the x-y plane; andcalculating the matrix by multiplying the rotation matrix and the focusing matrix.34. The apparatus of clause 33, wherein the focusing matrix is defined aswherein:0 is a rotation angle of the beam in the x-y plane; andg is a parameter related to the axial magnetic flux density.35. The apparatus of clause 33, wherein the rotation matrix is defined aswherein 0 is a rotation angle of the beam in the x-y plane.36. The apparatus of any one of clauses 30-35, wherein altering the first CPB component includes moving the first CPB component to shift the beam toward the center position.37. The apparatus of any one of clauses 30-36, wherein comparing beam spot displacement based on the altering includes:obtaining a second beam spot displacement after the altering; andcalculating a difference between the second beam spot displacement and the center position.38. The apparatus of any one of clauses 30-37, wherein the calculating includes determining an amount to move the first CPB component for minimizing the beam displacement from the center position.39. The apparatus of any one of clauses 30-38, wherein the predetermined threshold is based on a precision of movement of the first CPB component.40. The apparatus of any one of clauses 30-39, wherein the operations further include:repeating the obtaining, the altering, the comparing, and the calculating for each component of the CPB tool that affects the beam.41. The apparatus of clause 40, wherein the CPB components include a tip, an aperture, and a lens.42. The apparatus of any one of clauses 30-41, wherein the operations further include: obtaining a beam spot displacement on a wafer plane in relation to a second CPB component; altering the second CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, second CPB component characteristics for minimizing beam displacement from the center position.43. The apparatus of clause 42, wherein the operations further include:obtaining a beam spot displacement on a wafer plane in relation to a third CPB component; altering the third CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, third CPB component characteristics for minimizing beam displacement from the center position.

[0086] Block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In some embodiments, a non-transitory computer-readable medium is provided and can include instructions to perform the functions described in connection with any one or more of Figs. 6-10. In this regard, each block in a schematic diagram may represent certain arithmetical or logical operation processing that may be implemented using hardware such as an electronic circuit. Blocks may also represent a module, segment, or portion of code that comprises one or more executable instructions for implementing the specified logical functions. It should be understood that in some alternative implementations, functions indicated in a block may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed or implemented substantially concurrently, or two blocks may sometimes be executed in reverse order, depending upon the functionality involved. Some blocks may also be omitted. It should also be understood that each block of the block diagrams, and combination of the blocks, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

[0087] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments, and other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the technology disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims.

Claims

CLAIMS1. A non-transitory computer readable medium that stores a set of instructions that is executable by at least one processor of a computing device to cause the computing device to perform operations for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool, the operations comprising:obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering, wherein the comparing includes:obtaining a second beam spot displacement after the altering; andcalculating a difference between the second beam spot displacement and the center position; andcalculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position.

2. The non-transitory computer readable medium of claim 1, wherein the center position is a central beam axis of the CPB tool.

3. The non-transitory computer readable medium of claim 1, wherein obtaining the beam spot displacement on the wafer plane includes:measuring a first beam vector at the first CPB component, the first beam vector indicating a first beam displacement and a first beam tilt angle;measuring a second beam vector at the wafer plane, the second beam vector indicating a second beam displacement and a second beam tilt angle;obtaining a matrix based on motion of the beam; andcalculating the first beam vector based on the matrix and the second beam vector.

4. The non-transitory computer readable medium of claim 3, wherein obtaining the matrix includes:calculating a rotation matrix based on a rotation of the beam in an x-y plane;calculating a focusing matrix based on moving the beam toward an origin point in the x-y plane; and calculating the matrix by multiplying the rotation matrix and the focusing matrix.

5. The non-transitory computer readable medium of claim 4, wherein the focusing matrix is defined aswherein:0 is a rotation angle of the beam in the x-y plane; andg is a parameter related to the axial magnetic flux density.

6. The non-transitory computer readable medium of claim 4, wherein the rotation matrix is defined aswherein 0 is a rotation angle of the beam in the x-y plane.

7. The non-transitory computer readable medium of claim 1, wherein altering the first CPB component includes moving the first CPB component to shift the beam toward the center position.

8. The non-transitory computer readable medium of claim 1, wherein the calculating includes determining an amount to move the first CPB component for minimizing the beam displacement from the center position.

9. The non-transitory computer readable medium of claim 1, wherein the operations further comprise:repeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.

10. The non-transitory computer readable medium of claim 9, wherein the predetermined threshold is based on a precision of movement of the first CPB component.

11. The non-transitory computer readable medium of claim 9, wherein the operations further comprise:repeating the obtaining, the altering, the comparing, and the calculating for each component of the CPB tool that affects the beam.

12. The non-transitory computer readable medium of claim 11, wherein the CPB components include a tip, an aperture, and a lens.

13. The non-transitory computer readable medium of claim 1, wherein the operations further comprise:obtaining a beam spot displacement on a wafer plane in relation to a second CPB component; altering the second CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, second CPB component characteristics for minimizing beam displacement from the center position.

14. The non-transitory computer readable medium of claim 13, wherein the operations further comprise:obtaining a beam spot displacement on a wafer plane in relation to a third CPB component; altering the third CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering; andcalculating, based on the comparison, third CPB component characteristics for minimizing beam displacement from the center position.

15. An apparatus for minimizing a beam displacement from a center position in a charged particle beam (CPB) tool, comprising:a memory storing a set of instructions; andat least one processor configured to execute the set of instructions to cause the apparatus to perform operations comprising:obtaining a beam spot displacement on a wafer plane in relation to a first CPB component; altering the first CPB component in a manner that shifts the beam spot;comparing beam spot displacement based on the altering;calculating, based on the comparison, first CPB component characteristics for minimizing beam displacement from the center position; andrepeating the obtaining, the altering, the comparing, and the calculating for the first CPB component until the beam displacement from the center position is less than a predetermined threshold.

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