WO2024132806A1

WO2024132806A1 - Advanced charge controller configuration in a charged particle system

Info

Publication number: WO2024132806A1
Application number: PCT/EP2023/085702
Authority: WO
Inventors: Jian Zhang; Ning Ye; Xiaoyu JI; Xuerang Hu
Original assignee: Asml Netherlands B.V.
Priority date: 2022-12-20
Filing date: 2023-12-13
Publication date: 2024-06-27

Abstract

Systems, apparatuses, and methods for advanced charge controller configurations in a charged particle system. A system may include a light source configured to emit a light beam; and a mirror system configured to adjust an angle of incidence of the light beam on a sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

Description

ADVANCED CHARGE CONTROLLER CONFIGURATION IN A CHARGED PARTICLE SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63/434,037 which was filed on December 20, 2022 and which is incorporated herein in its entirety by reference.

FIELD

[0002] The description herein relates to the field of charged particle systems, and more particularly to advanced charge controller configurations in a charged particle system.

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. An inspection system utilizing an optical microscope typically has resolution down to a few hundred nanometers; and the resolution is limited by the wavelength of light. As the physical sizes of IC components continue to reduce down to sub- 100 or even sub- 10 nanometers, inspection systems capable of higher resolution than those utilizing optical microscopes are needed.

[0004] A charged particle (e.g., electron) beam microscope, such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), capable of resolution down to less than a nanometer, serves as a practicable tool for inspecting IC components having a feature size that is sub- 100 nanometers. With a SEM, electrons of a single primary electron beam, or electrons of a plurality of primary electron beams, can be focused on locations of interest of a wafer under inspection. The primary electrons interact with the wafer and may be backscattered or may cause the wafer to emit secondary electrons. The intensity of the electron beams comprising the backscattered electrons and the secondary electrons may vary based on the properties of the internal and external structures of the wafer, and thereby may indicate whether the wafer has defects.

SUMMARY

[0005] Embodiments of the present disclosure provide apparatuses, systems, and methods for advanced charge controller configurations in charged particle systems. In some embodiments, systems and methods may include a light source configured to emit a light beam; and a mirror system configured to adjust an angle of incidence of the light beam on a sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

[0006] In some embodiments, a system may include a module configured to emit a beam that illuminates an area on a sample; and a mirror system configured to adjust an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

[0007] In some embodiments, a system may include a module configured to emit a beam that illuminates an area on a sample; and a mirror system including a first mirror having an adjustable position for adjusting an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system, consistent with embodiments of the present disclosure.

[0009] Fig. 2A is a schematic diagram illustrating an exemplary multi-beam system that is part of the exemplary charged particle beam inspection system of Fig. 1, consistent with embodiments of the present disclosure.

[0010] Fig. 2B is a schematic diagram illustrating an exemplary single -beam system that is part of the exemplary charged particle beam inspection system of Fig. 1, consistent with embodiments of the present disclosure.

[0011] Fig. 3 is a schematic diagram illustrating an exemplary electron beam system, consistent with embodiments of the present disclosure.

[0012] Fig. 4 is an exemplary graph showing a yield rate of secondary electrons relative to landing energy of primary electron beamlets, consistent with embodiments of the present disclosure.

[0013] Fig. 5 is a schematic diagram illustrating an exemplary voltage contrast response of a wafer, consistent with embodiments of the present disclosure.

[0014] Fig. 6 is a schematic diagram of an exemplary charged particle system, consistent with embodiments of the present disclosure.

[0015] Fig. 7 shows a graph, consistent with embodiments of the present disclosure.

[0016] Fig. 8 is a flowchart illustrating an exemplary process, consistent with embodiments of the present disclosure.

DETAILED DESCRIPTION

[0017] 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 consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter 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 may be similarly applied. Furthermore, other imaging systems may be used, such as optical imaging, photodetection, x-ray detection, extreme ultraviolet inspection, deep ultraviolet inspection, or the like, in which they generate corresponding types of images.

[0018] Electronic devices are constructed of circuits formed on a piece of silicon called a substrate. Many circuits may be formed together on the same piece of silicon and are called integrated circuits or ICs. The size of these circuits has decreased dramatically so that many more of them can fit on the substrate. For example, an IC chip in a smart phone can be as small as a thumbnail and yet may include over 2 billion transistors, the size of each transistor being less than l/1000th the size of a human hair.

[0019] Making these extremely small ICs is a complex, time-consuming, 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.

[0020] One component of improving yield is monitoring the chip making process to ensure that it is producing a sufficient number of functional ICs. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection may be carried out using a scanning electron microscope (SEM). A SEM 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, and also if it was formed at the proper location. If the structure is defective, then the process can be adjusted so the defect is less likely to recur. Defects may be generated during various stages of semiconductor processing. For the reason stated above, it is important to find defects accurately and efficiently as early as possible.

[0021] The working principle of a SEM is similar to a camera. A camera takes a picture by receiving and recording brightness and colors of light reflected or emitted from people or objects. A SEM takes a “picture” by receiving and recording energies or quantities of electrons reflected or emitted from the structures. Before taking such a “picture,” an electron beam may be provided onto the structures, and when the electrons are reflected or emitted (“exiting”) from the structures, a detector of the SEM may receive and record the energies or quantities of those electrons to generate an image. To take such a “picture,” some SEMs use a single electron beam (referred to as a “single-beam SEM”), while some SEMs use multiple electron beams (referred to as a “multi-beam SEM”) to take multiple “pictures” of the wafer. By using multiple electron beams, the SEM may provide more electron beams onto the structures for obtaining these multiple “pictures,” resulting in more electrons exiting from the structures. Accordingly, the detector may receive more exiting electrons simultaneously, and generate images of the structures of the wafer with a higher efficiency and a faster speed.

[0022] When electron beams are directed at a sample, secondary electrons are emitted in response. An Advanced Charge Control (ACC) module may be employed to manipulate or control the response of the sample to the electron beam. For example, an ACC module may modulate the emission of secondary electrons by the sample by illuminating a light beam, such as a laser beam, on the sample which alters the emission of secondary electrons by the sample.

[0023] A multi-wavelength ACC module design may be used in inspection systems to modulate the emission of secondary electrons by the sample. For example, depending on the material or structure of the sample to be inspected, different wavelengths of light from the ACC module may exhibit different modulations of secondary electron emission. Typical ACC modules may use a MEMS mirror to steer one or more light beams of a certain size to a point on the sample at a certain angle of incidence. In some cases, the MEMS mirror may steer the light beams to an area of the sample to be scanned or undergoing a scan with an electron beam (e-beam). Typical ACC modules may use a dichroic mirror to combine a multi-wavelength light beam to stimulate different nano-structures of different sample surfaces.

[0024] Higher optical coupling efficiency between the light beams from the ACC module and the material of the inspected sample may improve the performance of the ACC module. The optical coupling efficiency may depend on the angle of incidence of the light beams on the sample. Different sample materials may exhibit higher optical coupling efficiency at different incident angles.

[0025] Typical ACC module configurations, however, suffer from constraints. Typical ACC module configurations have a limited range of incident angles between the light beams and the sample. In some cases, typical ACC module configurations have a fixed incident angle. While changing or combining the wavelengths of the ACC module light beams may increase optical coupling efficiency, doing so requires burdensome hardware modification (e.g., adding or removing mirrors, adding ACC modules, etc.). Therefore, optical coupling efficiency in typical ACC modules are limited.

[0026] The disclosed embodiments provide systems and methods that may address some or all of these disadvantages by providing an ACC module configuration that allows for a greater range of incident angles between light beams from the ACC module and a sample. The disclosed embodiments may provide a light source configured to emit a light beam and a mirror system configured to adjust an angle of incidence of the light beam on a sample during inspection of the sample without substantially adjusting a position of the light beam on the sample.

[0027] 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.

[0028] 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.

[0029] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing detectors and detection methods in systems utilizing electron beams. However, the disclosure is not so limited. Other types of charged particle beams may be similarly applied. Furthermore, systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0030] Fig. 1 illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. EBI system 100 may be used for imaging. As shown in Fig. 1, EBI system 100 includes a main chamber 101, a load/lock chamber 102, an electron beam tool 104, and an equipment front end module (EFEM) 106. Electron beam tool 104 is located within main chamber 101. EFEM 106 includes a first loading port 106a and a second loading port 106b. EFEM 106 may include additional loading port(s). First loading port 106a and second loading port 106b receive 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 (wafers and samples may be used interchangeably). A “lot” is a plurality of wafers that may be loaded for processing as a batch.

[0031] One or more robotic arms (not shown) in EFEM 106 may transport the wafers to load/lock chamber 102. Load/lock chamber 102 is connected to a load/lock vacuum pump system (not shown) which removes gas molecules in load/lock chamber 102 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) may transport the wafer from load/lock chamber 102 to main chamber 101. Main chamber 101 is connected to a main chamber vacuum pump system (not shown) which removes gas molecules in main chamber 101 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is subject to inspection by electron beam tool 104. Electron beam tool 104 may be a single-beam system or a multi-beam system.

[0032] A controller 109 is electronically connected to electron beam tool 104. Controller 109 may be a computer configured to execute various controls of EBI system 100. While controller 109 is shown in Fig- 1 as being outside of the structure that includes main chamber 101, load/lock chamber 102, and EFEM 106, it is appreciated that controller 109 may be a part of the structure.

[0033] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controllers, a microcontroller, a microprocessor, a digital signal processor, 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.

[0034] In some embodiments, controller 109 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes 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.

[0035] Embodiments of this disclosure may provide a single charged-particle beam imaging system (“single -beam system”). Compared with a single-beam system, a multiple charged-particle beam imaging system (“multi-beam system”) may be designed to optimize throughput for different scan modes. Embodiments of this disclosure provide a multi-beam system with the capability of optimizing throughput for different scan modes by using beam arrays with different geometries and adapting to different throughputs and resolution requirements.

[0036] Reference is now made to Fig. 2A, which is a schematic diagram illustrating an exemplary electron beam tool 104 including a multi-beam inspection tool that is part of the EBI system 100 of Fig- 1, consistent with embodiments of the present disclosure. In some embodiments, electron beam tool 104 may be operated as a single-beam inspection tool that is part of EBI system 100 of Fig. 1. Multi-beam electron beam tool 104 (also referred to herein as apparatus 104) comprises an electron source 201, a Coulomb aperture plate (or “gun aperture plate”) 271, a condenser lens 210, a source conversion unit 220, a primary projection system 230, a motorized stage 209, and a sample holder 207 supported by motorized stage 209 to hold a sample 208 (e.g., a wafer or a photomask) to be inspected. Multi-beam electron beam tool 104 may further comprise a secondary projection system 250 and an electron detection device 240. Primary projection system 230 may comprise an objective lens 231. Electron detection device 240 may comprise a plurality of detection elements 241, 242, and 243. A beam separator 233 and a deflection scanning unit 232 may be positioned inside primary projection system 230.

[0037] Electron source 201, Coulomb aperture plate 271, condenser lens 210, source conversion unit 220, beam separator 233, deflection scanning unit 232, and primary projection system 230 may be aligned with a primary optical axis 204 of apparatus 104. Secondary projection system 250 and electron detection device 240 may be aligned with a secondary optical axis 251 of apparatus 104. [0038] Electron source 201 may comprise a cathode (not shown) and an extractor or anode (not shown), in which, during operation, electron source 201 is configured to emit primary electrons from the cathode and the primary electrons are extracted or accelerated by the extractor and/or the anode to form a primary electron beam 202 that form a primary beam crossover (virtual or real) 203. Primary electron beam 202 may be visualized as being emitted from primary beam crossover 203.

[0039] Source conversion unit 220 may comprise an image-forming element array (not shown), an aberration compensator array (not shown), a beam-limit aperture array (not shown), and a pre-bending micro-deflector array (not shown). In some embodiments, the pre-bending micro-deflector array deflects a plurality of primary beamlets 211, 212, 213 of primary electron beam 202 to normally enter the beam-limit aperture array, the image-forming element array, and an aberration compensator array. In some embodiments, apparatus 104 may be operated as a single -beam system such that a single primary beamlet is generated. In some embodiments, condenser lens 210 is designed to focus primary electron beam 202 to become a parallel beam and be normally incident onto source conversion unit 220. The image-forming element array may comprise a plurality of micro-deflectors or micro-lenses to influence the plurality of primary beamlets 211, 212, 213 of primary electron beam 202 and to form a plurality of parallel images (virtual or real) of primary beam crossover 203, one for each of the primary beamlets 211, 212, and 213. In some embodiments, the aberration compensator array may comprise a field curvature compensator array (not shown) and an astigmatism compensator array (not shown). The field curvature compensator array may comprise a plurality of micro-lenses to compensate field curvature aberrations of the primary beamlets 211, 212, and 213. The astigmatism compensator array may comprise a plurality of micro-stigmators to compensate astigmatism aberrations of the primary beamlets 211, 212, and 213. The beam-limit aperture array may be configured to limit diameters of individual primary beamlets 211, 212, and 213. Fig. 2A shows three primary beamlets 211, 212, and 213 as an example, and it is appreciated that source conversion unit 220 may be configured to form any number of primary beamlets. Controller 109 may be connected to various parts of EBI system 100 of Fig. 1, such as source conversion unit 220, electron detection device 240, primary projection system 230, or motorized stage 209. In some embodiments, as explained in further details below, controller 109 may perform various image and signal processing functions. Controller 109 may also generate various control signals to govern operations of the charged particle beam inspection system.

[0040] Condenser lens 210 is configured to focus primary electron beam 202. Condenser lens 210 may further be configured to adjust electric currents of primary beamlets 211, 212, and 213 downstream of source conversion unit 220 by varying the focusing power of condenser lens 210. Alternatively, the electric currents may be changed by altering the radial sizes of beam-limit apertures within the beam-limit aperture array corresponding to the individual primary beamlets. The electric currents may be changed by both altering the radial sizes of beam-limit apertures and the focusing power of condenser lens 210. Condenser lens 210 may be an adjustable condenser lens that may be configured so that the position of its first principal plane is movable. The adjustable condenser lens may be configured to be magnetic, which may result in off-axis beamlets 212 and 213 illuminating source conversion unit 220 with rotation angles. The rotation angles change with the focusing power or the position of the first principal plane of the adjustable condenser lens. Condenser lens 210 may be an anti-rotation condenser lens that may be configured to keep the rotation angles unchanged while the focusing power of condenser lens 210 is changed. In some embodiments, condenser lens 210 may be an adjustable anti-rotation condenser lens, in which the rotation angles do not change when its focusing power and the position of its first principal plane are varied.

[0041] Objective lens 231 may be configured to focus beamlets 211, 212, and 213 onto a sample 208 for inspection and may form, in the current embodiments, three probe spots 221, 222, and 223 on the surface of sample 208. Coulomb aperture plate 271, in operation, is configured to block off peripheral electrons of primary electron beam 202 to reduce Coulomb effect. The Coulomb effect may enlarge the size of each of probe spots 221, 222, and 223 of primary beamlets 211, 212, 213, and therefore deteriorate inspection resolution.

[0042] Beam separator 233 may, for example, be a Wien filter comprising an electrostatic deflector generating an electrostatic dipole field and a magnetic dipole field (not shown in Fig. 2A). In operation, beam separator 233 may be configured to exert an electrostatic force by electrostatic dipole field on individual electrons of primary beamlets 211, 212, and 213. The electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted by magnetic dipole field of beam separator 233 on the individual electrons. Primary beamlets 211, 212, and 213 may therefore pass at least substantially straight through beam separator 233 with at least substantially zero deflection angles.

[0043] Deflection scanning unit 232, in operation, is configured to deflect primary beamlets 211, 212, and 213 to scan probe spots 221, 222, and 223 across individual scanning areas in a section of the surface of sample 208. In response to incidence of primary beamlets 211, 212, and 213 or probe spots 221, 222, and 223 on sample 208, electrons emerge from sample 208 and generate three secondary electron beams 261, 262, and 263. Each of secondary electron beams 261, 262, and 263 typically comprise secondary electrons (having electron energy < 50eV) and backscattered electrons (having electron energy between 50eV and the landing energy of primary beamlets 211, 212, and 213). Beam separator 233 is configured to deflect secondary electron beams 261, 262, and 263 towards secondary projection system 250. Secondary projection system 250 subsequently focuses secondary electron beams 261, 262, and 263 onto detection elements 241, 242, and 243 of electron detection device 240. Detection elements 241, 242, and 243 are arranged to detect corresponding secondary electron beams 261, 262, and 263 and generate corresponding signals which are sent to controller 109 or a signal processing system (not shown), e.g., to construct images of the corresponding scanned areas of sample 208.

[0044] In some embodiments, detection elements 241, 242, and 243 detect corresponding secondary electron beams 261, 262, and 263, respectively, and generate corresponding intensity signal outputs (not shown) to an image processing system (e.g., controller 109). In some embodiments, each detection element 241, 242, and 243 may comprise one or more pixels. The intensity signal output of a detection element may be a sum of signals generated by all the pixels within the detection element. [0045] In some embodiments, controller 109 may comprise image processing system that includes an image acquirer (not shown), a storage (not shown). The image acquirer may comprise one or more processors. For example, the image acquirer may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, and the like, or a combination thereof. The image acquirer may be communicatively coupled to electron detection device 240 of apparatus 104 through a medium such as an electrical conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, among others, or a combination thereof. In some embodiments, the image acquirer may receive a signal from electron detection device 240 and may construct an image. The image acquirer may thus acquire images of sample 208. The image acquirer may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, and the like. The image acquirer may be configured to perform adjustments of brightness and contrast, etc. of acquired images. In some embodiments, the storage may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer readable memory, and the like. The storage may be coupled with the image acquirer and may be used for saving scanned raw image data as original images, and post-processed images.

[0046] In some embodiments, the image acquirer may acquire one or more images of a sample based on an imaging signal received from electron detection device 240. 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 the storage. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of sample 208. The acquired images may comprise multiple images of a single imaging area of sample 208 sampled multiple times over a time sequence. The multiple images may be stored in the storage. In some embodiments, controller 109 may be configured to perform image processing steps with the multiple images of the same location of sample 208.

[0047] In some embodiments, controller 109 may include measurement circuitries (e.g., analog-to- digital converters) to obtain a distribution of the detected secondary electrons. The electron distribution data collected during a detection time window, in combination with corresponding scan path data of each of primary beamlets 211, 212, and 213 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 sample 208, and thereby can be used to reveal any defects that may exist in the wafer.

[0048] In some embodiments, controller 109 may control motorized stage 209 to move sample 208 during inspection of sample 208. In some embodiments, controller 109 may enable motorized stage 209 to move sample 208 in a direction continuously at a constant speed. In other embodiments, controller 109 may enable motorized stage 209 to change the speed of the movement of sample 208 over time depending on the steps of scanning process.

[0049] Although Fig. 2A shows that apparatus 104 uses three primary electron beams, it is appreciated that apparatus 104 may use one, two, or more number of primary electron beams. The present disclosure does not limit the number of primary electron beams used in apparatus 104. In some embodiments, apparatus 104 may be a SEM used for lithography. In some embodiments, electron beam tool 104 may be a single-beam system or a multi-beam system.

[0050] For example, as shown in Fig. 2B, an electron beam tool 100B (also referred to herein as apparatus 100B) may be a single -beam inspection tool that is used in EBI system 10, consistent with embodiments of the present disclosure. Apparatus 100B includes a wafer holder 136 supported by motorized stage 134 to hold a wafer 150 to be inspected. Electron beam tool 100B includes an electron emitter, which may comprise a cathode 103, an anode 121, and a gun aperture 122. Electron beam tool 100B further includes a beam limit aperture 125, a condenser lens 126, a column aperture 135, an objective lens assembly 132, and a detector 144. Objective lens assembly 132, in some embodiments, may be a modified SORIL lens, which includes a pole piece 132a, a control electrode 132b, a deflector 132c, and an exciting coil 132d. In an imaging process, an electron beam 161 emanating from the tip of cathode 103 may be accelerated by anode 121 voltage, pass through gun aperture 122, beam limit aperture 125, condenser lens 126, and be focused into a probe spot 170 by the modified SORIL lens and impinge onto the surface of wafer 150. Probe spot 170 may be scanned across the surface of wafer 150 by a deflector, such as deflector 132c or other deflectors in the SORIL lens. Secondary or scattered primary particles, such as secondary electrons or scattered primary electrons emanated from the wafer surface may be collected by detector 144 to determine intensity of the beam and so that an image of an area of interest on wafer 150 may be reconstructed.

[0051] There may also be provided an image processing system 199 that includes an image acquirer 120, a storage 130, and controller 109. Image acquirer 120 may comprise one or more processors. For example, image acquirer 120 may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, and the like, or a combination thereof. Image acquirer 120 may connect with detector 144 of electron beam tool 100B 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 120 may receive a signal from detector 144 and may construct an image. Image acquirer 120 may thus acquire images of wafer 150. Image acquirer 120 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, and the like. Image acquirer 120 may be configured to perform adjustments of brightness and contrast, etc. of acquired images. Storage 130 may be a storage medium such as a hard disk, random access memory (RAM), cloud storage, other types of computer readable memory, and the like. Storage 130 may be coupled with image acquirer 120 and may be used for saving scanned raw image data as original images, and post-processed images. Image acquirer 120 and storage 130 may be connected to controller 109. In some embodiments, image acquirer 120, storage 130, and controller 109 may be integrated together as one electronic control unit.

[0052] In some embodiments, image acquirer 120 may acquire one or more images of a sample based on an imaging signal received from detector 144. 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 that may contain various features of wafer 150. The single image may be stored in storage 130. Imaging may be performed on the basis of imaging frames.

[0053] The condenser and illumination optics of the electron beam tool may comprise or be supplemented by electromagnetic quadrupole electron lenses. For example, as shown in Fig. 2B, electron beam tool 100B may comprise a first quadrupole lens 148 and a second quadrupole lens 158. In some embodiments, the quadrupole lenses are used for controlling the electron beam. For example, first quadrupole lens 148 can be controlled to adjust the beam current and second quadrupole lens 158 can be controlled to adjust the beam spot size and beam shape.

[0054] Fig. 2B illustrates a charged particle beam apparatus in which an inspection system may use a single primary beam that may be configured to generate secondary electrons by interacting with wafer 150. Detector 144 may be placed along optical axis 105, as in the embodiment shown in Fig. 2B. The primary electron beam may be configured to travel along optical axis 105. Accordingly, detector 144 may include a hole at its center so that the primary electron beam may pass through to reach wafer 150.

[0055] Fig. 3 illustrates an electron beam system 300 consistent with embodiments of the present disclosure. As shown in Fig. 3, electron beam system 300 includes an electron beam tool 310 (e.g., electron beam tool 104 of Fig. 1, electron beam tool 104 of Fig. 2A, electron beam tool 100B of Fig. 2B), an ACC module 320 (e.g., ACC module), and a wafer holder 330 (e.g., motorized stage 209 of Fig. 2A, motorized stage 134 of Fig. 2B) on which a sample (e.g., sample 208 of Fig. 2A, wafer 150 of Fig. 2B, sample 605 of Fig. 6) to be inspected (e.g., a wafer 340) is disposed. Electron beam tool 310 may emit a primary electron beam 312 (e.g., plurality of beamlets 211, 212, or 213 of primary electron beam 202 of Fig. 2A; electron beam 161 of Fig. 2B; electron beam 607 of Fig. 6) onto an area of interest on wafer 340, and collect secondary electrons emanated from the wafer surface to form an image of the area of interest on wafer 340. ACC module 320 may include an ACC beam source that emits a light beam 322 (e.g., laser beam, light beam 601 of Fig. 6) onto wafer 340 and form a beam spot 342 (e.g., area 603 of Fig. 6) of light beam 322 on the wafer surface during inspection. Light beam 322 may be emitted at an angle of incidence 0 of light beam 322 on wafer 340. When primary electron beam 312 irradiates the area of interest on wafer 340, charges may be accumulated due to a large electron beam current. Light beam 322 emitted from ACC module 320 may be configured to regulate the accumulated charges due to photoconductivity or photoelectric effect, or a combination of photoconductivity and photoelectric effect, among others.

[0056] In some embodiments, wafer 340 may include a PN-junction diode or bulk semiconductor material. In some embodiments, the ACC beam source may be a light source.

[0057] In some embodiments, electron beam tool 310 may generate multiple primary electron beamlets to simultaneously scan multiple locations on wafer 340. In some embodiments, the beam projected by ACC module 320 may charge a location on wafer 340 large enough so that multiple primary electron beamlets may scan corresponding portions on wafer 340.

[0058] Fig. 4 illustrates an exemplary graph showing a yield rate of secondary electrons relative to landing energy of primary electron beamlets, consistent with embodiments of the present disclosure. The graph illustrates the relationship of the landing energy of a plurality of beamlets of a primary electron beam (e.g., plurality of beamlets 211, 212, or 213 of primary electron beam 202 of Fig. 2A; electron beam 161 of Fig. 2B; primary electron beam 312 of Fig. 3; electron beam 607 of Fig. 6) and the yield rate of secondary electron beams (e.g., secondary electron beams 261, 262, or 263 of Fig. 2A). The yield rate indicates the number of secondary electrons that are produced in response to the impact of the primary electrons. For example, a yield rate greater than 1.0 indicates that more secondary electrons may be produced than the number of primary electrons that have landed on the wafer. Similarly, a yield rate of less than 1.0 indicates that fewer secondary electrons may be produced in response to the impact of the primary electrons.

[0059] As shown in the graph of Fig. 4, when the landing energy of the primary electrons is within a range from Ei to Ez, more electrons may leave the surface of the wafer than land onto the surface of the wafer, which may result in a positive electrical potential at the surface of the wafer. In some embodiments, defect inspection may be performed in the foregoing range of landing energies, which is called “positive mode.” An electron beam tool (e.g., electron beam tool 104 of Fig. 2A; electron beam tool 100B of Fig. 2B) may generate a darker voltage contrast image of a device structure with a more positive surface potential since a detection device (e.g., detection device 240 of Fig. 2A; detector 144 of Fig. 2B) may receive fewer secondary electrons (see Fig. 5).

[0060] When the landing energy is lower than Ei or higher than Ez, fewer electrons may leave the surface of the wafer, thereby resulting in a negative electrical potential at the surface of the wafer. In some embodiments, defect inspection may be performed in this range of the landing energies, which is called “negative mode.” An electron beam tool (e.g., electron beam tool 104 of Fig. 2A; electron beam tool 100B of Fig. 2B) may generate a brighter voltage contrast image of a device structure with a more negative surface potential a detection device (e.g., detection device 240 of Fig. 2A; detector 144 of Fig. 2B) may receive more secondary electrons (see Fig. 5).

[0061] In some embodiments, the landing energy of the primary electron beams may be controlled by the total bias between the electron source and the wafer. [0062] Fig. 5 illustrates a schematic diagram of a voltage contrast response of a wafer, consistent with embodiments of the present disclosure. In some embodiments, physical and electrical defects in a wafer (e.g., resistive shorts and opens, defects in deep trench capacitors, back end of line (BEOE) defects, etc.) can be detected using a voltage contrast method of a charged particle inspection system. Defect detection using voltage contrast images may use a pre-scanning process (i.e., a charging, flooding, neutralization, or prepping process), where charged particles are applied to an area of the wafer (e.g., sample 208 of Fig. 2A; wafer 150 of Fig. 2B) to be inspected before conducting the inspection.

[0063] In some embodiments, an electron beam tool (e.g., electron beam tool 104 of Fig. 2A; electron beam tool 100B of Fig. 2B) may be used to detect defects in internal or external structures of a wafer by illuminating the wafer with a plurality of beamlets of a primary electron beam (e.g., plurality of beamlets 211, 212, or 213 of primary electron beam 202 of Fig. 2A; electron beam 161 of Fig. 2B; primary electron beam 312 of Fig. 3; electron beam 607 of Fig. 6) and measuring a voltage contrast response of the wafer to the illumination. In some embodiments, the wafer may comprise a test device region 520 that is developed on a substrate 510. In some embodiments, test device region 520 may include multiple device structures 530 and 540 separated by insulating material 550. For example, device structure 530 is connected to substrate 510. In contrast, device structure 540 is separated from substrate 510 by insulating material 550 such that a thin insulator structure 570 (e.g., thin oxide) exists between device structure 540 and substrate 510.

[0064] The electron beam tool may generate secondary electrons (e.g., secondary electron beams 261, 262, or 263 of Fig. 2A) from the surface of test device region 520 by scanning the surface of test device region 520 with a plurality of beamlets of a primary electron beam. As explained above, when the landing energy of the primary electrons is between Ei and Ez (i.e., the yield rate is greater than 1.0 in Fig. 4), more electrons may leave the surface of the wafer than land on the surface, thereby resulting in a positive electrical potential at the surface of the wafer.

[0065] As shown in Fig. 5, a positive electrical potential may build-up at the surface of a wafer. For example, after an electron beam tool scans test device region 520 (e.g., during a pre-scanning process), device structure 440 may retain more positive charges because device structure 540 is not connected to an electrical ground in substrate 510, thereby resulting in a positive electrical potential at the surface of device structure 540. In contrast, primary electrons with the same landing energy (i.e., the same yield rate) applied to device structure 530 may result in fewer positive charges retained in device structure 430 since positive charges may be neutralized by electrons supplied by the connection to substrate 510.

[0066] An image processing system (e.g., controller 109 of Fig. 2A; controller 109 of Fig. 2B) of an electron beam tool may generate voltage contrast images 535 and 545 of corresponding device structures 530 and 540, respectively. For example, device structure 530 is shorted to the ground and may not retain built-up positive charges. Accordingly, when primary electron beamlets land on the surface of the wafer during inspection, device structure 530 may repel more secondary electrons thereby resulting in a brighter voltage contrast image. In contrast, because device structure 540 has no connection to substrate 510 or any other grounds, device structure 540 may retain a build-up of positive charges. This build-up of positive charges may cause device structure 540 to repel fewer secondary electrons during inspection, thereby resulting in a darker voltage contrast image.

[0067] An electron beam tool (e.g., multi-beam electron beam tool 104 of Fig. 2A; electron beam tool 100B of Fig. 2B) may pre-scan the surface of a wafer by supplying electrons to build up the electrical potential on the surface of the wafer. After pre-scanning the wafer, the electron beam tool may obtain images of multiple dies within the wafer. Pre-scanning is applied to the wafer under the assumption that the electrical surface potential built-up on the surface of the wafer during prescanning will be retained during inspection and will remain above the detection threshold of the electron beam tool.

[0068] However, the built-up surface potential level may change during inspection due to the effects of electrical breakdown or tunneling, thereby resulting in failure to detect defects. For example, when a high voltage is applied to a high resistance thin device structure (e.g., thin oxide), such as an insulator structure 570, leakage current may flow through the high resistance structure, thereby preventing the structure from functioning as a perfect insulator. This may affect circuit functionality and result in a device defect. A similar effect of leakage current may also occur in a structure with improperly formed materials or a high resistance metal layer, for example a cobalt silicide (e.g., CoSi, CoSiz, CozSi, Co sSi, etc.) layer between a tungsten plug and a source or drain area of a field-effect transistor (FET).

[0069] A defective etching process may leave a thin oxide resulting in unwanted electrical blockage (e.g., open circuit) between two structures (e.g., device structure 540 and substrate 510) intended to be electrically connected. For example, device structures 430 and 440 may be designed to make contact with substrate 510 and function identically, but due to manufacturing errors, insulator structure 570 may exist in device structure 540. In this case, insulator structure 570 may represent a defect susceptible to a breakdown effect.

[0070] Reference is now made to Fig- 6, a schematic diagram of an exemplary charged particle system 600, consistent with embodiments of the present disclosure. Charged particle system 600 may include an inspection system or a metrology system.

[0071] In some embodiments, charged particle system 600 may include a light source LI (e.g., ACC module 320 of Fig. 3). Light source LI may be an ACC module that is configured to emit one or more light beams 601 (e.g., laser beams, light beam 322 of Fig. 3). For example, emitted light beams 601 may illuminate an area 603 of a sample 605 (e.g., sample 208 of Fig. 2A, wafer 150 of Fig. 2B, wafer 340 of Fig. 3), thereby adjusting or controlling the accumulated charge on the area of sample 605. In some embodiments, charged particle system 600 may include a mirror system configured to adjust an angle of incidence 0 (e.g., angle of incidence 0 of Fig. 3) of light beam 601 on a sample 605 during an inspection of sample 605 without substantially adjusting a position or area 603 of light beam 601 on sample 605 (e.g., adjusting a position or area of a light beam on a sample by 10pm or less). In some embodiments, the mirror system is configured to adjust angle of incidence 0 of light beam 601 (e.g., by adjusting a position of one or more mirrors of the mirror system) based on a material of sample 605.

[0072] In some embodiments, the mirror system may include a tiltable flat mirror (e.g., a flat mirror configured to tilt) Ml, a first parabolic mirror Pl, and a second parabolic mirror P2. In some embodiments, tiltable flat mirror Ml may be a MEMS mirror. In some embodiments, tiltable flat mirror Ml may be a motorized tiltable flat mirror. In some embodiments, one or both of first parabolic mirror Pl and second parabolic mirror P2 may be a spherical mirror. In some embodiments, tiltable flat mirror Ml may be configured to receive light beam 601 from light source LI and adjustably reflect light beam 601 to first parabolic mirror Pl. For example, tiltable flat mirror Ml may be adjusted such that light beam 601 emitted from light source LI may follow a range of different paths (e.g., path 611, path 612, etc.). In some embodiments, the adjustable reflection of light beam 601 may cause an adjustment to angle of incidence 0 of light beam 601 on sample 605.

Advantageously, in some embodiments, angle of incidence 0 may be adjusted by only adjusting tiltable flat mirror ML

[0073] In some embodiments, first parabolic mirror Pl may be configured to receive light beam 601 reflected off of tiltable flat mirror Ml and reflect light beam 601 to second parabolic mirror P2, and second parabolic mirror P2 may be configured to receive light beam 601 reflected off of first parabolic mirror Pl and reflect light beam 601 to sample 605. In some embodiments, first parabolic mirror Pl may extend to point 621 or point 622. In some embodiments, second parabolic mirror P2 may extend to point 631 or point 632. In some embodiments, second parabolic mirror P2 may be configured to provide an unobstructed path for an electron beam 607 (e.g., plurality of beamlets 211, 212, or 213 of primary electron beam 202 of Fig. 2A; electron beam 161 of Fig. 2B; primary electron beam 312 of Fig. 3) to land on sample 605.

[0074] In some embodiments, light beam 601 may be a plurality of light beams and first parabolic mirror Pl may be configured to collimate the plurality of light beams. In some embodiments, a distance between first parabolic mirror Pl and second parabolic mirror P2 may be adjusted without affecting the one or more light beams. In some embodiments, first parabolic mirror Pl may be configured to reflect light beam 601 through a window Wl, first parabolic mirror Pl being on a first side of window Wl and second parabolic mirror P2 being on a second side of window WL In some embodiments, the first side of window W 1 may be in an ambient environment and the second side of window W 1 may be in a vacuum environment.

[0075] In some embodiments, the position or area 603 of light beam 601 on sample 605 may coincide with a position or area of electron beam 607 on sample 605. In some embodiments, the configuration of charged particle system 600 may advantageously provide a smaller light beam spot on sample 605, thereby providing a higher light beam density (e.g., a light beam density that is ~10x greater than in typical systems) on sample 605.

[0076] Reference is now made to Fig- 7, an exemplary graph 700, consistent with embodiments of the present disclosure.

[0077] Graph 700 may include a dispersion curve L0 for a free space light beam emitted from an ACC module (e.g., ACC module 320 of Fig. 3, light source LI of Fig. 6). Graph 700 may also include dispersion curves SI, S2, and S3, which correspond to relationships between light beams (e.g., light beam 322 of Fig. 3, light beam 601 of Fig. 6) emitted from an ACC module and a sample (e.g., sample 208 of Fig. 2A, wafer 150 of Fig. 2B, wafer 340 of Fig. 3, sample 605 of Fig. 6). Dispersion curves SI, S2, and S3 may correspond to different sample materials, respectively.

[0078] Axis 701 of graph 700 may correspond to wavelengths co of light beams emitted from an ACC module. Axis 703 of graph 700 may correspond to momentum k_x in an “x” direction of light beams emitted from an ACC module, where the “x” direction is a direction along a surface of the sample from a top view of the sample.

[0079] A relationship between wavelength co and momentum k_x of the light beams emitted from the ACC module may be described by the following equation: co = c-k_x = c-k-sin(O) (1) where c is the speed of light, k is the free space momentum of light, and 0 is an angle of incidence 0 (e.g., angle of incidence 0 of Fig. 3, angle of incidence 0 of Fig. 6) of light beams on a sample. As shown in Equation (1) above, momentum k_x is related to angle of incidence 0.

[0080] The intersection of a dispersion curve of a sample material (e.g., dispersion curves SI, S2, or S3) with the dispersion curve L0 of a free space light beam is consistent with a higher optical coupling efficiency. Optical coupling efficiency may describe the number of photons (e.g., from light beam 322 of Fig. 3, light beam 601 of Fig. 6) that couple to a sample. That is, an angle of incidence that results in the dispersion curve of a sample intersecting with L0 may be indicative of a higher number of photons emitted from the ACC module that couple to the sample. In some embodiments, the angle of incidence may be adjusted to maximize or increase the number of photons emitted from the ACC module that couple to the sample.

[0081] Accordingly, the angle of incidence of light beams emitted from the ACC module may be adjusted to increase the optical coupling efficiency for different sample materials under inspection. [0082] Reference is now made to Fig. 8, illustrating an exemplary process 800, consistent with embodiments of the present disclosure. The steps of process 800 can be performed by a system (e.g., charged particle system 600 of Fig. 6) for purposes of illustration. It is appreciated that the illustrated process 800 can be altered to modify the order of steps and to include additional steps that may be performed by the system. [0083] At step 801, a light source (e.g., ACC module 320 of Fig. 3, light source LI of Fig. 6) may be configured to emit a light beam (e.g., laser beams, light beam 322 of Fig. 3, light beam 601 of Fig. 6). In some embodiments, the light source may be an ACC module that is configured to emit one or more light beams. For example, the emitted light beams may illuminate an area (e.g., area 603 of Fig. 6) of a sample (e.g., sample 208 of Fig. 2A, wafer 150 of Fig. 2B, wafer 340 of Fig. 3, sample 605 of Fig. 6), thereby adjusting or controlling the accumulated charge on the area of the sample.

[0084] At step 803, a mirror system may adjust an angle of incidence (e.g., angle of incidence 0 of Fig. 3, angle of incidence 0 of Fig. 6) of the light beam on the sample during an inspection of the sample without substantially adjusting a position or area of the light beam on the sample. In some embodiments, the mirror system is configured to adjust the angle of incidence of the light beam based on a material of the sample.

[0085] In some embodiments, the mirror system may include a tiltable flat mirror (e.g., a flat mirror configured to tilt, tiltable flat mirror Ml of Fig. 6), a first parabolic mirror (e.g., first parabolic mirror Pl of Fig. 6), and a second parabolic mirror (e.g., second parabolic mirror P2 of Fig. 6). In some embodiments, the tiltable flat mirror may be a MEMS mirror. In some embodiments, the tiltable flat mirror may be configured to receive the light beam from the light source and adjustably reflect the light beam to the first parabolic mirror. For example, the tiltable flat mirror may be adjusted such that the light beam emitted from the light source may follow a range of different paths (e.g., paths 611 612 of Fig. 6). In some embodiments, the adjustable reflection of the light beam may cause an adjustment to the angle of incidence of the light beam on the sample. Advantageously, in some embodiments, the angle of incidence may be adjusted by only adjusting the tiltable flat mirror.

[0086] In some embodiments, the first parabolic mirror may be configured to receive the light beam reflected off of the tiltable flat mirror and reflect the light beam to the second parabolic mirror, and the second parabolic mirror may be configured to receive the light beam reflected off of the first parabolic mirror and reflect the light beam to the sample. In some embodiments, the second parabolic mirror may be configured to provide an unobstructed path for an electron beam (e.g., plurality of beamlets 211, 212, or 213 of primary electron beam 202 of Fig. 2A; electron beam 161 of Fig. 2B; primary electron beam 312 of Fig. 3; electron beam 607 of Fig. 6) to land on the sample.

[0087] In some embodiments, the light beam may be a plurality of light beams and the first parabolic mirror may be configured to collimate the plurality of light beams. In some embodiments, a distance between the first parabolic mirror and the second parabolic mirror may be adjusted without affecting the one or more light beams. In some embodiments, the first parabolic mirror may be configured to reflect the light beam through a window (e.g., window W1 of Fig. 6), the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window. In some embodiments, the first side of the window may be in an ambient environment and the second side of the window may be in a vacuum environment. [0088] In some embodiments, the position or area of the light beam on the sample may coincide with a position or area of the electron beam on the sample. In some embodiments, the configuration of charged particle system may advantageously provide a smaller light beam spot on the sample, thereby providing a higher light beam density (e.g., a light beam density that is ~10x greater than in typical systems) on the sample.

[0089] A non-transitory computer readable medium may be provided that stores instructions for a processor of a controller (e.g., controller 109 of Fig. 1) for controlling the electron beam tool or a mirror (e.g., tiltable flat mirror Ml of Fig. 6) to adjust an angle of incidence of a light beam on a sample, consistent with embodiments in the present disclosure. These instructions may allow the one or more processors to carry out operations of an ACC module, operations of a mirror system, image processing, data processing, beamlet scanning, graphical display, operations of a charged particle beam apparatus, or another imaging device, or the like. In some embodiments, the non-transitory computer readable medium may be provided that stores instructions for a processor to perform the steps of process 800. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-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.

[0090] The embodiments may further be described using the following clauses:

1. A system comprising: a light source configured to emit a light beam; and a mirror system configured to adjust an angle of incidence of the light beam on a sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

2. The system of clause 1, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

3. The system of clause 2, wherein: the tiltable flat mirror is configured to receive the light beam from the light source and adjustably reflect the light beam to the first parabolic mirror, the adjustable reflection of the light beam causing an adjustment to the angle of incidence of the light beam on the sample, the first parabolic mirror is configured to receive the light beam reflected off of the tiltable flat mirror and reflect the light beam to the second parabolic mirror, and the second parabolic mirror is configured to receive the light beam reflected off of the first parabolic mirror and reflect the light beam to the sample. 4. The system of any one of clauses 2-3, wherein the light beam comprises a plurality of light beams and the first parabolic mirror is configured to collimate the plurality of light beams.

5. The system of any one of clauses 2-4, wherein the first parabolic mirror is configured to reflect the light beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

6. The system of clause 5, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

7. The system of any one of clauses 2-6, wherein the tiltable flat mirror is a MEMS mirror.

8. The system of any one of clauses 1-7, wherein the mirror system is configured to adjust an angle of incidence of the light beam based on a material of the sample.

9. The system of any one of clauses 1-8, wherein the position of the light beam on the sample coincides with a position of an electron beam on the sample.

10. A system comprising: a module configured to emit a beam that illuminates an area on a sample; and a mirror system configured to adjust an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

11. The system of clause 10, wherein the module comprises a light source.

12. The system of any one of clauses 10-11, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

13. The system of clause 12, wherein: the tiltable flat mirror is configured to receive the beam from the module and adjustably reflect the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, the first parabolic mirror is configured to receive the beam reflected off of the tiltable flat mirror and reflect the beam to the second parabolic mirror, and the second parabolic mirror is configured to receive the beam reflected off of the first parabolic mirror and reflect the beam to the sample.

14. The system of any one of clauses 12-13, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams.

15. The system of any one of clauses 12-14, wherein the first parabolic mirror is configured to reflect the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

16. The system of clause 15, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

17. The system of any one of clauses 12-16, wherein the tiltable flat mirror is a MEMS mirror. 18. The system of any one of clauses 10-17, wherein the mirror system is configured to adjust an angle of incidence of the beam based on a material of the sample.

19. The system of any one of clauses 10-18, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample.

20. A system comprising: a module configured to emit a beam that illuminates an area on a sample; and a mirror system including a first mirror having an adjustable position for adjusting an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

21. The system of clause 20, wherein the first mirror comprises a tiltable flat mirror and the mirror system further comprises: a first parabolic mirror; and a second parabolic mirror.

22. The system of clause 21, wherein: the tiltable flat mirror is configured to receive the beam from the module and adjustably reflect the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, the first parabolic mirror is configured to receive the beam reflected off of the tiltable flat mirror and reflect the beam to the second parabolic mirror, and the second parabolic mirror is configured to receive the beam reflected off of the first parabolic mirror and reflect the beam to the sample.

23. The system of any one of clauses 21-22, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams.

24. The system of any one of clauses 21-23, wherein the first parabolic mirror is configured to reflect the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

25. The system of clause 24, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

26. The system of any one of clauses 21-25, wherein the tiltable flat mirror is a MEMS mirror.

27. The system of any one of clauses 20-26, wherein the mirror system is configured to adjust the angle of the beam based on a material of the sample.

28. The system of any one of clauses 20-27, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample.

29. A non- transitory computer readable medium including a set of instructions that is executable by one or more processors of an apparatus, comprising a light source configured to emit a light beam, to cause the apparatus to perform a method comprising: adjusting a position of a mirror system to adjust an angle of incidence of the light beam on the sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

30. The non-transitory computer readable medium of clause 29, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

31. The non-transitory computer readable medium of clause 29, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform: receiving, by the tiltable flat mirror, the light beam from the light source and adjustably reflecting the light beam to the first parabolic mirror, the adjustable reflection of the light beam causing an adjustment to the angle of incidence of the light beam on the sample, receiving, by the first parabolic mirror, the light beam reflected off of the tiltable flat mirror and reflecting the light beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the light beam reflected off of the first parabolic mirror and reflecting the light beam to the sample.

32. The non-transitory computer readable medium of any one of clauses 30-31, wherein the light beam comprises a plurality of light beams and the first parabolic mirror is configured to collimate the plurality of light beams.

33. The non-transitory computer readable medium of any one of clauses 30-32, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform reflecting, by the first parabolic mirror, the light beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

34. The non-transitory computer readable medium of clause 33, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

35. The non-transitory computer readable medium of any one of clauses 30-34, wherein the tiltable flat mirror is a MEMS mirror.

36. The non-transitory computer readable medium of any one of clauses 29-35, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform adjusting, by the mirror system, an angle of incidence of the light beam based on a material of the sample.

37. The non-transitory computer readable medium of any one of clauses 29-36, wherein the position of the light beam on the sample coincides with a position of an electron beam on the sample.

38. A non-transitory computer readable medium including a set of instructions that is executable by one or more processors of an apparatus, comprising a module configured to emit a beam, to cause the apparatus to perform a method comprising: adjusting a position of a mirror system to adjust an angle of the beam that illuminates a sample without substantially adjusting a position of illumination of the beam on the sample.

39. The non-transitory computer readable medium of clause 38, wherein the module comprises a light source.

40. The non-transitory computer readable medium of any one of clauses 38-39, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

41. The non-transitory computer readable medium of clause 40, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform: receiving, by the tiltable flat mirror, the beam from the module and adjustably reflecting the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, receiving, by the first parabolic mirror, the beam reflected off of the tiltable flat mirror and reflecting the beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the beam reflected off of the first parabolic mirror and reflecting the beam to the sample.

42. The non-transitory computer readable medium of any one of clauses 40-41, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams.

43. The non-transitory computer readable medium of any one of clauses 40-42, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform reflecting, by the first parabolic mirror, the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

44. The non-transitory computer readable medium of clause 43, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

45. The non-transitory computer readable medium of any one of clauses 40-44, wherein the tiltable flat mirror is a MEMS mirror.

46. The non-transitory computer readable medium of any one of clauses 38-45, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform adjusting, by the mirror system, an angle of incidence of the beam based on a material of the sample.

47. The non-transitory computer readable medium of any one of clauses 38-46, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample. 48. A non- transitory computer readable medium including a set of instructions that is executable by one or more processors of an apparatus, comprising a module configured to emit a beam, to cause the apparatus to perform a method comprising: adjusting a position of a first mirror of a mirror system to adjust an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

49. The non-transitory computer readable medium of clause 48, wherein the first mirror comprises a tiltable flat mirror and the mirror system further comprises: a first parabolic mirror; and a second parabolic mirror.

50. The non-transitory computer readable medium of clause 49, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform: receiving, by the tiltable flat mirror, the beam from the module and adjustably reflecting the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, receiving, by the first parabolic mirror, the beam reflected off of the tiltable flat mirror and reflecting the beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the beam reflected off of the first parabolic mirror and reflecting the beam to the sample.

51. The non-transitory computer readable medium of any one of clauses 49-50, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams.

52. The non-transitory computer readable medium of any one of clauses 49-51, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform reflecting, by the first parabolic mirror, the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

53. The non-transitory computer readable medium of clause 52, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

54. The non-transitory computer readable medium of any one of clauses 49-53, wherein the tiltable flat mirror is a MEMS mirror.

55. The non-transitory computer readable medium of any one of clauses 48-54, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform adjusting, by the mirror system, the angle of the beam based on a material of the sample.

56. The non-transitory computer readable medium of any one of clauses 48-55, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample. 57. A non-transitory computer readable medium including a set of instructions that is executable by one or more processors of an apparatus, comprising a light source configured to emit a light beam, to cause the apparatus to perform a method comprising: adjusting a position of a first mirror, based on a material of a sample, to adjust an angle of incidence of the light beam on the sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

58. The non-transitory computer readable medium of clause 57, wherein the first mirror comprises a tiltable flat mirror of a mirror system and the mirror system further comprises: a first parabolic mirror; and a second parabolic mirror.

59. The non-transitory computer readable medium of clause 58, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform: receiving, by the tiltable flat mirror, the beam from the light source and adjustably reflecting the light beam to the first parabolic mirror, the adjustable reflection of the light beam causing an adjustment to the angle of incidence of the light beam on the sample, receiving, by the first parabolic mirror, the light beam reflected off of the tiltable flat mirror and reflecting the light beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the light beam reflected off of the first parabolic mirror and reflecting the light beam to the sample.

60. The non-transitory computer readable medium of any one of clauses 58-59, wherein the light beam comprises a plurality of light beams and the first parabolic mirror is configured to collimate the plurality of light beams.

61. The non-transitory computer readable medium of any one of clauses 58-60, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform reflecting, by the first parabolic mirror, the light beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

62. The non-transitory computer readable medium of clause 61, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

63. The non-transitory computer readable medium of any one of clauses 58-62, wherein the tiltable flat mirror is a MEMS mirror.

64. The non-transitory computer readable medium of any one of clauses 57-63, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform adjusting, by the mirror system, the angle of the light beam based on a material of the sample.

65. The non-transitory computer readable medium of any one of clauses 57-64, wherein the position of the light beam on the sample coincides with a position of an electron beam on the sample. 66. A method of an apparatus comprising a light source configured to emit a light beam, the method comprising: adjusting a position of a mirror system to adjust an angle of incidence of the light beam on the sample during an inspection of the sample without substantially adjusting a position of the light beam on the sample.

67. The method of clause 66, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

68. The method of clause 67 further comprising: receiving, by the tiltable flat mirror, the light beam from the light source and adjustably reflecting the light beam to the first parabolic mirror, the adjustable reflection of the light beam causing an adjustment to the angle of incidence of the light beam on the sample, receiving, by the first parabolic mirror, the light beam reflected off of the tiltable flat mirror and reflecting the light beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the light beam reflected off of the first parabolic mirror and reflecting the light beam to the sample.

69. The method of any one of clauses 67-68, wherein the light beam comprises a plurality of light beams and the first parabolic mirror is configured to collimate the plurality of light beams.

70. The method of any one of clauses 67-69, further comprising reflecting, by the first parabolic mirror, the light beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

71. The method of clause 70, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

72. The method of any one of clauses 67-71, wherein the tiltable flat mirror is a MEMS mirror.

73. The method of any one of clauses 66-72 further comprising adjusting, by the mirror system, an angle of incidence of the light beam based on a material of the sample.

74. The method of any one of clauses 66-73, wherein the position of the light beam on the sample coincides with a position of an electron beam on the sample.

75. A method of an apparatus comprising a module configured to emit a beam, the apparatus to method comprising: adjusting a position of a mirror system to adjust an angle of the beam that illuminates a sample without substantially adjusting a position of illumination of the beam on the sample.

76. The method of clause 75, wherein the module comprises a light source.

77. The method of any one of clauses 75-76, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

78. The method of clause 77 further comprising: receiving, by the tiltable flat mirror, the beam from the module and adjustably reflecting the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, receiving, by the first parabolic mirror, the beam reflected off of the tiltable flat mirror and reflecting the beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the beam reflected off of the first parabolic mirror and reflecting the beam to the sample.

79. The method of any one of clauses 77-78, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams.

80. The method of any one of clauses 77-79 further comprising reflecting, by the first parabolic mirror, the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

81. The method of clause 80, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

82. The method of any one of clauses 77-81, wherein the tiltable flat mirror is a MEMS mirror.

83. The method of any one of clauses 75-82 further comprising adjusting, by the mirror system, an angle of incidence of the beam based on a material of the sample.

84. The method of any one of clauses 75-83, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample.

85. A method of an apparatus comprising a module configured to emit a beam, the method comprising: adjusting a position of a first mirror of a mirror system to adjust an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

86. The method of clause 85, wherein the first mirror comprises a tiltable flat mirror and the mirror system further comprises: a first parabolic mirror; and a second parabolic mirror.

87. The method of clause 86 further comprising: receiving, by the tiltable flat mirror, the beam from the module and adjustably reflecting the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, receiving, by the first parabolic mirror, the beam reflected off of the tiltable flat mirror and reflecting the beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the beam reflected off of the first parabolic mirror and reflecting the beam to the sample.

88. The method of any one of clauses 86-87, wherein the beam comprises a plurality of beams and the first parabolic mirror is configured to collimate the plurality of beams. 89. The method of any one of clauses 86-88 further comprising reflecting, by the first parabolic mirror, the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

90. The method of clause 89, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment. 91. The method of any one of clauses 86-90, wherein the tiltable flat mirror is a MEMS mirror.

92. The method of any one of clauses 85-91 further comprising adjusting, by the mirror system, the angle of the beam based on a material of the sample.

93. The method of any one of clauses 85-92, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample. [0091] 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.

Claims

2. The system of claim 1, wherein the mirror system comprises: a tiltable flat mirror; a first parabolic mirror; and a second parabolic mirror.

3. The system of claim 2, wherein: the tiltable flat mirror is configured to receive the light beam from the light source and adjustably reflect the light beam to the first parabolic mirror, the adjustable reflection of the light beam causing an adjustment to the angle of incidence of the light beam on the sample, the first parabolic mirror is configured to receive the light beam reflected off of the tiltable flat mirror and reflect the light beam to the second parabolic mirror, and the second parabolic mirror is configured to receive the light beam reflected off of the first parabolic mirror and reflect the light beam to the sample.

4. The system of claim 2, wherein the light beam comprises a plurality of light beams and the first parabolic mirror is configured to collimate the plurality of light beams.

5. The system of claim 2, wherein the first parabolic mirror is configured to reflect the light beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

6. The system of claim 5, wherein the first side of the window is in an ambient environment and the second side of the window is in a vacuum environment.

7. The system of claim 2, wherein the tiltable flat mirror is a MEMS mirror.

8. The system of claim 1, wherein the mirror system is configured to adjust an angle of incidence of the light beam based on a material of the sample.

9. The system of claim 1, wherein the position of the light beam on the sample coincides with a position of an electron beam on the sample.

10. A non-transitory computer readable medium including a set of instructions that is executable by one or more processors of an apparatus, comprising a module configured to emit a beam, to cause the apparatus to perform a method comprising: adjusting a position of a first mirror of a mirror system to adjust an angle of the beam that illuminates the sample without substantially adjusting a position of illumination of the beam on the sample.

11. The non-transitory computer readable medium of claim 10, wherein the first mirror comprises a tiltable flat mirror and the mirror system further comprises: a first parabolic mirror; and a second parabolic mirror.

12. The non-transitory computer readable medium of claim 11, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform: receiving, by the tiltable flat mirror, the beam from the module and adjustably reflecting the beam to the first parabolic mirror, the adjustable reflection of the beam causing an adjustment to the angle of incidence of the beam on the sample, receiving, by the first parabolic mirror, the beam reflected off of the tiltable flat mirror and reflecting the beam to the second parabolic mirror, and receiving, by the second parabolic mirror, the beam reflected off of the first parabolic mirror and reflecting the beam to the sample.

13. The non-transitory computer readable medium of claim 11, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform reflecting, by the first parabolic mirror, the beam through a window, the first parabolic mirror being on a first side of the window and the second parabolic mirror being on a second side of the window.

14. The non-transitory computer readable medium of claim 10, wherein the set of instructions that is executable by one or more processors of the apparatus to cause the apparatus to further perform adjusting, by the mirror system, the angle of the beam based on a material of the sample.

15. The non-transitory computer readable medium of claim 10, wherein the position of the beam on the sample coincides with a position of an electron beam on the sample.