WO2025172004A1 - Systèmes et procédés de filtrage et de détection à base d'énergie de particules chargées - Google Patents

Systèmes et procédés de filtrage et de détection à base d'énergie de particules chargées

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Publication number
WO2025172004A1
WO2025172004A1 PCT/EP2025/051452 EP2025051452W WO2025172004A1 WO 2025172004 A1 WO2025172004 A1 WO 2025172004A1 EP 2025051452 W EP2025051452 W EP 2025051452W WO 2025172004 A1 WO2025172004 A1 WO 2025172004A1
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WO
WIPO (PCT)
Prior art keywords
charged
energy
signal
particles
electrons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/051452
Other languages
English (en)
Inventor
Wei-Yu Chang
Xiaoyu JI
Weiming Ren
Hong Xiao
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ASML Netherlands BV
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ASML Netherlands BV
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Filing date
Publication date
Application filed by ASML Netherlands BV filed Critical ASML Netherlands BV
Publication of WO2025172004A1 publication Critical patent/WO2025172004A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/05—Electron or ion-optical arrangements for separating electrons or ions according to their energy or mass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/05—Arrangements for energy or mass analysis
    • H01J2237/053—Arrangements for energy or mass analysis electrostatic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/05—Arrangements for energy or mass analysis
    • H01J2237/055—Arrangements for energy or mass analysis magnetic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/05—Arrangements for energy or mass analysis
    • H01J2237/057—Energy or mass filtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/244—Detection characterized by the detecting means
    • H01J2237/24475—Scattered electron detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/244—Detection characterized by the detecting means
    • H01J2237/2448—Secondary particle detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/26—Electron or ion microscopes
    • H01J2237/28—Scanning microscopes

Definitions

  • the description herein relates to charged-particle detectors and detection methods, and more particularly, to bandpass energy filters, detectors and detection methods that may be applicable to backscattered charged-particles.
  • Detectors may be used for sensing physically observable phenomena.
  • charged particle beam tools such as electron microscopes, may comprise detectors that receive charged particles projected from a sample and that output detection signals.
  • Detection signals may be used to reconstruct images of sample structures under inspection and may be used, for example, to reveal defects in the sample. Detection of defects in a sample is increasingly important in the manufacturing of semiconductor devices, which may include large numbers of densely packed, miniaturized integrated circuit (IC) components. Inspection systems may be provided as dedicated tools for this purpose.
  • E- beam electron beam
  • L landing energy
  • High LE systems show great potential in applications such as trench/hole bottom inspection, buried defect/void detection, and overlay/see- through metrology, etc.
  • PEs primary electrons
  • BSEs backscattered electrons
  • Embodiments of the present disclosure provide systems and methods for defect detection and metrology based on charged particle beams.
  • One aspect of the disclosure is directed to a charged- particle beam apparatus comprising an energy discrimination device configured to filter incoming signal charged particles having a plurality of ranges of energy levels.
  • a charged-particle beam apparatus comprising an energy discrimination device configured to filter incoming signal charged particles having a plurality of ranges of energy levels.
  • the energy discrimination device comprises an electromagnetic charged-particle deflector configured to deflect a path of the incoming signal charged particles based on an energy level of the incoming signal charged particles, a charged-particle detector comprising a plurality of segments of a charged-particle sensitive material configured to detect signal charged particles, wherein each segment of the plurality of segments is configured to collect signal charged particles having a range of energy levels of the plurality of ranges of energy levels, and a control lens located upstream from the electromagnetic charged-particle deflector and configured to focus the incoming signal charged particles on the charged-particle detector.
  • Yet another aspect of the present disclosure is directed to a charged-particle beam apparatus comprising a first charged-particle beam deflector configured to deflect a portion of signal charged particles traveling in a first direction, a first energy discrimination device comprising a second charged-particle deflector configured to deflect the deflected portion of signal charged particles to enter the first charged-particle beam deflector in a second direction opposite the first direction, and a second energy discrimination device comprising a third charged-particle deflector configured to filter signal charged particles, after receiving the portion of signal charged particles exiting the first charged-particle beam deflector in a third direction and after deflection from the second direction to the third direction, based on an energy level of the portion of signal charged particles.
  • the energy discrimination device may comprise a control lens configured to focus incoming signal charged particles generated after interaction of a primary charged particles with a sample, an electromagnetic charged-particle deflector located downstream from the control lens and configured to deflect a path of the incoming signal charged particles based on an energy level of the incoming signal charged particles, and an aperture formed on an aperture plane, the aperture configured to allow a portion of the signal charged particles exiting the electromagnetic charged-particle deflector to pass through based on the deflection.
  • Yet another aspect of the present disclosure is directed to a method of imaging a sample using a charged-particle beam apparatus.
  • the method may comprise generating signal charged particles having a plurality of ranges of energy levels from the sample by irradiating with primary charged particles, filtering, using an energy discrimination device, the generated signal charged particles based on the plurality of ranges of energy levels, and forming an image of the sample based on the detected first portion of the generated signal charged particles.
  • the filtering may comprise focusing the generated signal charged particles on an aperture plane using a control lens, deflecting, using an electromagnetic charged-particle deflector, a path of a first portion and a path of a second portion of the generated signal charged particles based on a range of the plurality of ranges of energy levels, directing the first portion of the generated signal charged particles to pass through an aperture located along the aperture plane, and detecting, using a charged-particle detector, the first portion of the generated signal charged particles passing through the aperture.
  • Yet another aspect of the present disclosure is directed to a method of imaging a sample using a charged-particle beam apparatus.
  • the method may comprise generating signal charged-particles having a plurality of ranges of energy levels from the sample by irradiating with primary charged particles, deflecting, using a first charged-particle beam deflector, a path of a first portion of the generated signal charged particles traveling in a first direction, deflecting, using a second charged- particle beam deflector, a path of the deflected first portion of the generated signal charged particles to enter the first charged-particle beam deflector in a second direction opposite the first direction, filtering, after receiving by an energy discrimination device, the first portion of the signal charged- particles exiting the first charged-particle beam deflector in a third direction and after deflection from the second direction to the third direction, based on an energy level of the first portion of the signal charged particles, detecting the filtered first portion of the signal charged particles using a charged- particle detector, and forming an image
  • Fig. 2 is a schematic diagram illustrating an exemplary electron beam tool that can be a part of the exemplary electron beam inspection system of Fig. 1, consistent with embodiments of the present disclosure.
  • Fig. 9A illustrates a schematic diagram of an exemplary bandpass energy filter comprising a Wien filter and a segmented backscattered electron detector, consistent with embodiments of the present disclosure.
  • Figs. 15C, 15D, and 15E represent exemplary energy ranges of signal electrons within the energy spectra configured to be detected by an energy filter consistent with embodiments of the present disclosure.
  • Fig. 15F illustrates a schematic of exemplary images acquired or simulated, based on the energy range of signal electrons detected by a charged-particle detector of energy filter, consistent with embodiments of the present disclosure.
  • charged-particle beams e.g., including protons, ions, muons, or any other particle carrying electric charges
  • systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, or any imaging system.
  • Electronic devices are constructed of circuits formed on a piece of silicon called a substrate.
  • the semiconductor material may include, for example, silicon, gallium arsenide, indium phosphide, or silicon germanium, or the like.
  • Many circuits may be formed together on the same piece of silicon and are called integrated circuits or ICs. With advancements in technology, 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 fingernail and yet may include over 2 billion transistors, the size of each transistor being less than 1/1, 000 th the width of a human hair.
  • 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 electron microscope (SEM). A SEM can be used to image these extremely small structures, in effect, taking a “picture” of the structures. The image can be used to determine if the structure was formed properly and also if it was formed in the proper location. If the structure is defective, then the process can be adjusted so the defect is less likely to recur. To enhance throughput (e.g., the number of samples processed per hour), it is desirable to conduct inspection as quickly as possible.
  • SEM scanning electron microscope
  • a SEM image may be made up of pixels that correspond to locations irradiated by a primary electron beam as the beam scans across the surface of a sample in, e.g., a raster pattern.
  • a higher resolution of pixels e.g., the number of individual pixels that make up the image
  • structures of interest in ICs become smaller and smaller, it may be more important to produce SEM images with higher resolution to accurately observe structures.
  • a primary electron beam with high landing energy (LE) is used, resolution may be negatively affected.
  • Landing energy of primary electrons may be determined, for example, based on a difference between the source voltage and the sample voltage, among other things. For example, if the source is operated at -10 kV and the sample is applied -5 kV, the landing energy of primary electrons may be 5 keV. Typically, in a SEM, the landing energy may range from 0.2 keV to 50 keV, based on the application, material being studied, tool condition, among other factors. Some of the ways to change landing energy of the primary electrons of a primary electron beam may include adjusting the potential difference between cathode and extractor, adjusting the sample potential, or adjusting both simultaneously, among other techniques.
  • the electron source of the SEM may generate a primary electron beam with high LE that is projected onto the sample.
  • High energy electrons may be useful for imaging because they can penetrate deeper into the material of the sample and can reveal additional information about the sample.
  • High LE SEM systems may enable or enhance performance of inspections of the bottom of trenches or holes, detection of buried features such as defects or voids, and performing overlay metrology (e.g., analyzing the alignment of stacked structures).
  • overlay metrology e.g., analyzing the alignment of stacked structures.
  • the higher energy of the electrons in the primary electron beam means that the electrons may interact with a relatively large volume of material of the sample upon impinging the sample (i.e., the “interaction volume”).
  • a SEM image may be formed of pixels.
  • secondary particles such as secondary electrons (SEs) and backscattered electrons (BSEs) may be detected by a detector, and information gathered therefrom may be used for forming each pixel in the image.
  • the interaction volume in the sample may be increased.
  • the increase in interaction volume may encompass lateral regions (e.g., regions to the sides in the 2-dimensional plane that defines the image consisting of pixels).
  • Pixels may be formed based on information from detected electrons, but information from neighboring pixels may overlap.
  • the detected electrons corresponding to one pixel may include information relating to structures that would be more appropriately located in neighboring pixels. Such effects may cause the SEM image to have poor resolution, and the resulting image may be blurry.
  • the accuracy, reliability, and throughput of inspection of high-density IC chips using SEMs may depend on the image quality of the system, among other things.
  • One of several ways to obtain and maintain high image quality is to maximize the collection efficiency of signal-electrons, such as secondary (SE) and backscattered electrons (BSEs).
  • SE secondary
  • BSEs backscattered electrons
  • BSEs have higher energies and originate from deeper areas within the interaction volume, and thus provide information associated with composition and distribution of a material. Therefore, maximum detection of backscattered electrons may be desirable to obtain high quality images of underlying defects or metrology of vertical high aspect-ratio features.
  • a single BSE scan may include a range of BSE energies corresponding to the entire depth of the interaction volume of the primary beam with the sample and extracting information about the feature-of-interest at a certain depth may be challenging.
  • an energy filter may be employed to permit only a desired range of energy levels of BSEs emitted from a desired sample depth to pass through to the BSE detector.
  • a bottom BSE detector located between an objective lens and the sample may be desirable to enhance BSE collection efficiency.
  • an energy discrimination device such as a reflection type energy filter may be introduced in front of an in-lens detector to filter out (by reflecting back) the secondary electrons and allow BSEs to pass through a high-voltage grid electrode or a filtering grid electrode.
  • the potential of the high-voltage grid electrode may be set very high (e.g., >10 keV) to serve as a potential barrier for the BSE electrons.
  • energy filters may be useful in low landing-energy applications where the energy of secondary electrons is comparable with BSEs and BSEs have small polar emission angles, for high landing-energy applications, an energy filter with a grid electrode may negatively affect the collection efficiency of BSEs, thereby affecting the quality of images.
  • the voltage applied to the grid may need to be adjusted to collect images with different BSE energies, which renders simultaneous collection of multiple images impossible. This approach may negatively impact the inspection throughput, among other challenges.
  • an energy discrimination device such as a bandpass energy filter comprising a Wien filter.
  • the energy filter may include a control lens, or a control electrode configured to focus the incoming signal charged particles.
  • the Wien filter may be configured to disperse signal charged particles such as signal electrons based on the energy level.
  • the Wien filter may be further configured to receive a floating voltage signal configured to repel the lower energy electrons such that the lower energy electrons may be dispersed away from the Wien filter and the higher energy electrons may travel through the Wien filter towards an aperture located on an aperture plane.
  • the aperture may be formed by one or more movable knife edges located along an aperture plane.
  • the energy filter may further include a ground electrode located between the Wien filter and the movable knife edge and may be configured to provide an electric-field free region between the ground electrode and a charged-particle detector.
  • the charged-particle detector may comprise a backscattered electron detector or a segmented charged- particle detector.
  • the target range of energy level allowed to pass through the aperture to the charged- particle detector may be adjusted based on factors including, but not limited to, ratio of the electric field strength to the magnetic field strength of the Wien filter, the electric field strength and the magnetic field strength for a fixed ratio, an excitation signal of the control electrode, size of the aperture, location of the aperture, number of knife edges, or a combination thereof.
  • Objects and advantages of the disclosure may be realized by the elements and combinations as set forth in the embodiments discussed herein. However, embodiments of the present disclosure are not necessarily required to achieve such exemplary objects or advantages, and some embodiments may not achieve any of the stated objects or advantages. [0059] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing systems and methods in systems utilizing electron beams (“e-beams”). However, the disclosure is not so limited. Other types of charged particle beams may be similarly applied. Furthermore, systems and methods for wafer inspection or overlay measurement may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.
  • e-beams electron beams
  • systems and methods for wafer inspection or overlay measurement may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.
  • the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component includes 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 includes 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.
  • Expressions such as “at least one of’ do not necessarily modify an entirety of a following list and do not necessarily modify each member of the list, such that “at least one of A, B, and C” should be understood as including only one of A, only one of B, only one of C, or any combination of A, B, and C.
  • the phrase “one of A and B” or “any one of A and B” shall be interpreted in the broadest sense to include one of A, or one of B.
  • Fig- 1 illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure.
  • EBI electron beam inspection
  • charged particle beam inspection system 100 includes a main chamber 10, a load-lock chamber 20, an electron beam tool 40, and an equipment front end module (EFEM) 30.
  • Electron beam tool 40 is located within main chamber 10. While the description and drawings are directed to an electron beam, it is appreciated that the embodiments are not used to limit the present disclosure to specific charged particles.
  • EFEM 30 includes a first loading port 30a and a second loading port 30b.
  • EFEM 30 may include additional loading port(s).
  • First loading port 30a and second loading port 30b 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 are collectively referred to as “wafers” hereafter).
  • wafers wafer front opening unified pods
  • wafers e.g., semiconductor wafers or wafers made of other material(s)
  • wafers samples to be inspected
  • One or more robot arms (not shown) in EFEM 30 transport the wafers to loadlock chamber 20.
  • Load-lock chamber 20 is connected to a load/lock vacuum pump system (not shown), which removes gas molecules in load-lock chamber 20 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robot arms (not shown) transport the wafer from load-lock chamber 20 to main chamber 10.
  • Main chamber 10 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules in main chamber 10 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is subject to inspection by electron beam tool 40.
  • electron beam tool 40 may comprise a single-beam inspection tool.
  • Controller 50 may be electronically connected to electron beam tool 40 and may be electronically connected to other components as well.
  • Controller 50 may be a computer configured to execute various controls of charged particle beam inspection system 100. Controller 50 may also include processing circuitry configured to execute various signal and image processing functions. While controller 50 is shown in Fig. 1 as being outside of the structure that includes main chamber 10, load-lock chamber 20, and EFEM 30, it is appreciated that controller 50 can be part of the structure.
  • main chamber 10 housing an electron beam inspection system While the present disclosure provides examples of main chamber 10 housing an electron beam inspection system, it should be noted that aspects of the disclosure in their broadest sense, are not limited to a chamber housing an electron beam inspection system. Rather, it is appreciated that the foregoing principles may be applied to other chambers as well.
  • Fig- 2 illustrates a schematic diagram illustrating an exemplary configuration of electron beam tool 40 that can be a part of the exemplary charged particle beam inspection system 100 of Fig. 1, consistent with embodiments of the present disclosure.
  • Electron beam tool 40 may comprise an electron emitter, which may comprise a cathode 203, an extractor electrode 205, a gun aperture 220, and an anode 222. Electron beam tool 40 may further include a Coulomb aperture array 224, a condenser lens 226, a beam-limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. Electron beam tool 40 may further include a sample holder 236 supported by motorized stage 234 to hold a sample 250 to be inspected. It is to be appreciated that other relevant components may be added or omitted, as needed.
  • electron emitter may include cathode 203, an anode 222, wherein primary electrons can be emitted from the cathode and extracted or accelerated to form a primary electron beam 204 that forms a primary beam crossover 202.
  • Primary electron beam 204 can be visualized as being emitted from primary beam crossover 202.
  • the electron emitter, condenser lens 226, objective lens assembly 232, beam-limiting aperture array 235, and electron detector 244 may be aligned with a primary optical axis 201 of apparatus 40. In some embodiments, electron detector 244 may be placed off primary optical axis 201, along a secondary optical axis (not shown).
  • Objective lens assembly 232 may comprise a modified swing objective retarding immersion lens (SORIL), which includes a pole piece 232a, a control electrode 232b, a beam manipulator assembly comprising deflectors 240a, 240b, 240d, and 240e, and an exciting coil 232d.
  • SORIL modified swing objective retarding immersion lens
  • primary electron beam 204 emanating from the tip of cathode 203 is accelerated by an accelerating voltage applied to anode 222.
  • a portion of primary electron beam 204 passes through gun aperture 220, and an aperture of Coulomb aperture array 224, and is focused by condenser lens 226 so as to fully or partially pass through an aperture of beam-limiting aperture array 235.
  • the electrons passing through the aperture of beam- limiting aperture array 235 may be focused to form a probe spot on the surface of sample 250 by the modified SORIL lens and deflected to scan the surface of sample 250 by one or more deflectors of the beam manipulator assembly. Secondary electrons emanated from the sample surface may be collected by electron detector 244 to form an image of the scanned area of interest.
  • exciting coil 232d and pole piece 232a may generate a magnetic field.
  • a part of sample 250 being scanned by primary electron beam 204 can be immersed in the magnetic field and can be electrically charged, which, in turn, creates an electric field.
  • the electric field may reduce the energy of impinging primary electron beam 204 near and on the surface of sample 250.
  • Control electrode 232b being electrically isolated from pole piece 232a, may control, for example, an electric field above and on sample 250 to reduce aberrations of objective lens assembly 232 and control focusing situation of signal-electron beams for high detection efficiency, or avoid arcing to protect sample.
  • One or more deflectors of beam manipulator assembly may deflect primary electron beam 204 to facilitate beam scanning on sample 250.
  • deflectors 240a, 240b, 240d, and 240e can be controlled to deflect primary electron beam 204, onto different locations of top surface of sample 250 at different time points, to provide data for image reconstruction for different parts of sample 250. It is noted that the order of 240a-e may be different in different embodiments.
  • Backscattered electrons (BSEs) and secondary electrons (SEs) can be emitted from the part of sample 250 upon receiving primary electron beam 204.
  • a beam separator 240c can direct the secondary or scattered electron beam(s), comprising backscattered and secondary electrons, to a sensor surface of electron detector 244.
  • the detected secondary electron beams can form corresponding beam spots on the sensor surface of electron detector 244.
  • Electron detector 244 can generate signals (e.g., voltages, currents) that represent the intensities of the received secondary electron beam spots, and provide the signals to a processing system, such as controller 50.
  • the intensity of secondary or backscattered electron beams, and the resultant secondary electron beam spots can vary according to the external or internal structure of sample 250.
  • controller 50 may comprise an image processing system that includes an image acquirer (not shown) and a storage (not shown).
  • the image acquirer may comprise one or more processors.
  • 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 detector 244 of apparatus 40 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.
  • the image acquirer may receive a signal from electron detector 244 and may construct an image. The image acquirer may thus acquire images of regions of sample 250.
  • Detection and inspection of some defects in semiconductor fabrication processes may benefit from inspection of surface features as well as compositional analysis of the defect particle.
  • information obtained from secondary electron detectors and backscattered electron detectors to identify the defect(s), analyze the composition of the defect(s), and adjust process parameters based on the obtained information, among other things, may be desirable for a user.
  • Interaction of primary electrons with a sample generate secondary electrons and backscattered electrons, and a mechanism to differentiate the corresponding signals based on their energy is desired.
  • a high landing energy of the incident electrons may be desirable to measure critical dimension (CD) of buried structures, or image the sidewalls of high-aspect ratio (HAR) features.
  • CD critical dimension
  • HAR high-aspect ratio
  • the high landing energy allows a deeper penetration depth for metrology or defect detection. However, the deeper penetration depth increases the electron-sample interaction volume, resulting in low contrast backscattered electron image.
  • Fig. 3A illustrates an exemplary desirable energy range 2AE (El ⁇ AE) and a desirable energy level El of backscattered electrons which may be filtered through to the charged-particle detector to obtain information from a region of the sample corresponding to the selected energy band.
  • the desired energy width may be larger, i.e., 4AE (El ⁇ 2AE) to detect backscattered electrons from a larger interaction volume.
  • the desired energy level E2 of backscattered electrons may be different, as illustrated in Fig. 3C, to obtain information from a deeper or a shallower region of the area of interest. It is to be appreciated that although two energy levels and two energy ranges are illustrated in Figs. 3A-3C, other energy levels, energy ranges, and their possible combinations may be desirable, as appropriate.
  • Apparatus 400 may comprise an energy filter 402, signalelectron detectors 406 and 413, a compound objective lens 407, a scanning deflection unit comprising primary electron beam deflectors 408, 409, 410, and 411, and a control electrode 414.
  • energy filter 402 and signal-electron detector 406 may be in-lens electron detectors located inside the electron-optical column of a SEM and may be arranged radially around primary optical axis 400-1.
  • signal-electron detector 406 may be referred to as through- the-lens detector, immersion lens detector, upper detector, or a secondary electron detector.
  • apparatus 400 may further include an electron source such as a thermionic electron source configured to emit electrons upon being supplied thermal energy to overcome the work function of the source, or a field emission source configured to emit electrons upon being exposed to a large electrostatic field, among other electron sources.
  • the electron source may be electrically connected to a controller, such as controller 50 of Fig. 2, configured to apply and adjust a voltage signal based on a desired landing energy, sample analysis, source characteristics, among other things.
  • An extractor electrode may be configured to extract or accelerate electrons emitted from a field emission gun, for example, to form a primary electron beam that forms a virtual or a real primary beam crossover (not illustrated) along primary optical axis 400-1. Primary electron beam may be visualized as being emitted from the primary beam crossover.
  • controller 50 may be configured to apply and adjust a voltage signal to the extractor electrode to extract or accelerate electrons generated from electron source. An amplitude of the voltage signal applied to the extractor electrode may be different from the amplitude of the voltage signal applied to a cathode.
  • the difference between the amplitudes of the voltage signal applied to the extractor electrode and to the cathode may be configured to accelerate the electrons downstream along primary optical axis 400-1 while maintaining the stability of the electron source.
  • downstream along primary optical axis refers to a direction along the path of primary electron beam starting from the electron source towards sample 415.
  • downstream along primary optical axis refers to a position of an element located below or after another element, along the path of primary electron beam starting from the electron source
  • intermediately downstream along primary optical axis refers to a position of a second element below or after a first element along the path of primary electron beam such that there are no other active elements between the first and the second element.
  • signal-electron detector 413 is positioned immediately downstream of a pole piece of objective lens 407 such that there are no other optical or electron-optical elements placed between pole piece of compound objective lens 407 and signal-electron detector 413.
  • Apparatus 400 may further include signal-electron detector 406 which may be configured to detect substantially all secondary electrons and a portion of backscattered electrons based on the emission energy, emission polar angle, emission azimuthal angle of the backscattered electrons, among other things.
  • Signal-electrons having low emission energy (typically ⁇ 50 eV) or small emission polar angles, emitted from sample 415 may comprise secondary electron beam 400B4, and signal-electrons having high emission energy (typically > 50 eV) and medium emission polar angles may comprise backscattered electron beam 400B2.
  • secondary electron beam 400B4 may comprise secondary electrons, low-energy backscattered electrons, or high-energy backscattered electrons with small emission polar angles. It is appreciated that although not illustrated, a portion of backscattered electrons may be detected by signal-electron detector 406. In some overlay metrology and inspection applications, signal-electron detector 406 may be useful to detect secondary electrons generated from a surface layer and backscattered electrons generated from the underlying deeper layers, such as deep trenches or high aspect-ratio holes.
  • Apparatus 400 may further include compound objective lens 407 configured to focus primary electron beam on a surface of sample 415. Controller 50 may apply an electrical excitation signal to the coils of compound objective lens 407 to adjust the focusing power of compound objective lens 407 based on factors including, but not limited to, primary beam energy, application need, desired analysis, sample material being inspected, among other things.
  • Compound objective lens 407 may be further configured to focus signal-electrons, such as secondary electrons having low emission energies, or backscattered electrons having high emission energies, on a detection surface of a signalelectron detector (e.g., in-lens signal-electron detector 406).
  • signalelectron detector e.g., in-lens signal-electron detector 406
  • Compound objective lens 407 may be substantially similar to or perform substantially similar functions as objective lens assembly 232 of Fig- 2.
  • compound objective lens 407 may comprise an electromagnetic lens including a magnetic lens, and an electrostatic lens formed by control electrode 414, polepiece of objective lens, and sample 415.
  • a compound objective lens is an objective lens producing overlapping magnetic and electrostatic fields, both in the vicinity of the sample for focusing the primary electron beam.
  • a magnetic lens refers to an objective magnetic lens
  • a reference to an electrostatic lens refers to an objective electrostatic lens, unless stated otherwise.
  • Apparatus 400 may further include a scanning deflection unit comprising primary electron beam deflectors 408, 409, 410, and 411, configured to dynamically deflect primary electron beam on a surface of sample 415.
  • scanning deflection unit comprising primary electron beam deflectors 408, 409, 410, and 411 may be referred to as a beam manipulator or a beam manipulator assembly.
  • the dynamic deflection of primary electron beam may cause a desired area or a desired region of interest of sample 415 to be scanned, for example in a raster scan pattern, to generate secondary electrons and backscattered electrons for sample inspection.
  • One or more primary electron beam deflectors 408, 409, 410, and 411 may be configured to deflect primary electron beam in X-axis or Y-axis, or a combination of X- and Y-axes.
  • X-axis and Y-axis form Cartesian coordinates
  • primary electron beam propagates along Z-axis or primary optical axis 400-1.
  • Electrons are negatively charged particles and travel through the electron-optical column and may do so at high energy and high speeds.
  • One way to deflect the electrons is to pass them through an electric field or a magnetic field generated, for example, by a pair of plates held at two different potentials, or passing current through deflection coils, among other techniques.
  • Varying the electric field or the magnetic field across a deflector 408, 409, 410, or 411 may vary the deflection angle of electrons in primary electron beam based on factors including, but not limited to, electron energy, magnitude of the electric field applied, dimensions of deflectors, among other things.
  • Apparatus 400 may further include energy filter 402 configured to filter signal-electrons based on their emission energy before detection by an electron detector. Interaction of primary electron beam with sample 415 may cause emission of secondary electrons comprising secondary electron beam 400B4 and backscattered electrons comprising backscattered electron beam 400B2, among other charged particles.
  • Fig. 4B illustrates an exemplary energy filter 402 comprising a ground mesh 420, a high-voltage mesh 430, and a signal-electron detector 440.
  • High-voltage mesh 430 may be configured to repel the secondary electrons and allow backscattered electrons having an energy level within the allowable threshold limit to pass through to signal-electron detector 440.
  • Ground mesh 420 may be configured to minimize the influence of leakage field of high-voltage mesh 430. While energy filter 402 may provide energy range selection based on bandpass filtering to improve image contrast, the overall signal-electron collection efficiency is negatively impacted because the repelled or blocked signal-electrons such as secondary electrons and filtered out backscattered electrons are unutilized. Therefore, it may be desirable to provide systems and methods of energy filtering and detection of backscattered electrons to enhance backscattered electron image contrast while improving the signalelectron collection efficiency and maintaining the inspection throughput.
  • One of several ways to enhance image quality and signal-to-noise ratio may include detecting more backscattered electrons emitted from the sample.
  • the angular distribution of emission of backscattered electrons may be represented by a cosine dependence of the emission polar angle (cos(0), where 0 is the emission polar angle between the backscattered electron beam and the primary optical axis).
  • a signal-electron detector may efficiently detect backscattered electrons of medium emission polar angles, the large emission polar angle backscattered electrons may remain undetected or inadequately detected to contribute towards the overall imaging quality. Therefore, a signal-electron detector, such as backscattered electron (BSE) detector 413 of Fig. 4A may be used to capture large angle backscattered electrons.
  • BSE backscattered electron
  • signal-electron detector 413 may comprise a signal-electron detector located between signal-electron detector 406 and control electrode 414. In some embodiments, signalelectron detector 413 may be located immediately downstream and outside of polepiece of the objective lens, as shown in Fig. 4A. In a configuration where signal-electron detector 413 is outside the polepiece, it may be desirable to place signal-electron detector 413 closer towards compound objective lens 407 or farther from control electrode 414, but aligned with primary optical axis 400-1 to minimize the electrical damage to signal-electron detector 413 caused by arcing, for example. However, as can be appreciated from Fig.
  • Energy filter 500 may include a ground mesh 502, a control lens 505, an electromagnetic charged-particle deflector such as a Wien filter 510, a shield 512, a ground electrode 520, an aperture plate 525, a charged-particle detector 530.
  • signal charged-particle beam 503 comprising secondary electrons (i.e., lower energy electrons) and backscattered electrons (i.e., higher energy electrons) may travel along a secondary optical axis 501 and may enter energy filter 500.
  • exemplary energy filter 500 may include more components as well, as appropriate.
  • signal charged-particle beam 503 may be a collimated beam of signalelectrons.
  • a “collimated” beam of signal-electrons refers to a beam in which the signal-electrons of the beam travel substantially parallel to each other such that the angle of path of each signal-electron with respect to the angle of path of other signal-electrons of the beam is equal to or less than 0.2°.
  • a non-collimated beam of signal electrons refers to a beam in which the signal-electrons do not travel parallel to each other and the angle of path of each electron with respect to the path of other electrons is more than 0.2°.
  • the signal-electrons of a non-collimated beam may be incident on a ground mesh (e.g., ground mesh 502) at an incidence angle > 90.2° or ⁇ 89.8°.
  • Ground mesh 502 may be configured to minimize the influence of leakage electromagnetic field of Wien filter 510.
  • Ground mesh 502 may be disposed along a plane perpendicular to secondary optical axis 501. As illustrated, ground mesh 502 may be disposed along a plane at the entrance of energy filter 500.
  • Ground mesh 502 may be located upstream, along secondary optical axis 501, from control lens 505.
  • upstream along secondary optical axis refers to a direction along the path of signal-electrons originating from a sample after interaction of primary electrons with the sample.
  • upstream along secondary optical axis refers to a position of an element located before another element, along the path of signalelectrons emitted from the sample
  • intermediately upstream along secondary optical axis refers to a position of a second element above or before a first element along the path of signal-electron beam such that there are no other active elements between the first and the second element.
  • downstream along secondary optical axis refers to a direction along the path of signalelectrons originating from a sample after interaction of primary electrons with the sample.
  • downstream along secondary optical axis refers to a position of an element located below or after another element, along the path of signal-electrons emitted from the sample
  • intermediately downstream along secondary optical axis refers to a position of a second element below or after a first element along the path of signal-electron beam such that there are no other active elements between the first and the second element.
  • Energy filter 500 may further include control lens 505 configured to focus the incoming signal-electrons of signal charged-particle beam 503.
  • control lens 505 may be an electrostatic lens configured to focus, by influencing a path of the signal-electrons, the signalelectrons before entering Wien filter 510.
  • control lens 505 may be configured to focus signal-electrons of signal charged-particle beam 503 on an aperture plane 525P (discussed later) upstream of charged-particle detector 530 with respect to secondary optical axis 501.
  • Control lens 505 may be disposed between ground mesh 502 and Wien filter 510 along secondary optical axis 501.
  • Energy filter 500 further includes an electromagnetic charged-particle deflector such as Wien filter 510 configured to influence a path of the incoming signal-electrons based on the electron energy.
  • Wien filter 510 may be configured to disperse the incoming signalelectrons, by exposing the signal-electrons passing through to an electromagnetic field, based on the electron energy level.
  • Wien filter 510 may be configured to repel or block signal-electrons based on the electron energy level.
  • repelling or blocking signalelectron refers to a deflection or a change in direction of traversal of the signal-electrons to prevent the signal-electrons from entering the electromagnetic field of Wien filter 510.
  • Wien filter 510 may be configured to perform signal-electron dispersion as well as signal-electron repulsion, based on the energy of the incoming signal-electrons.
  • energy filter 500 may further comprise shield 512 configured to shield Wien filter 510 from fringe fields and external stray magnetic field.
  • Shield 512 may substantially prevent Wien filter 510 from exposure to undesirable external stray magnetic field by effectively “trapping” the external magnetic field.
  • Shield 512 may be made from a material with high magnetic permeability such as, but not limited to, mu-metal (p-Metal).
  • a floating voltage signal may be applied to Wien filter 510 to repel signal-electrons of signal charged-particle beam 503 having an energy level below the applied floating voltage.
  • floating voltage refers to a voltage that is not referenced to ground or any other fixed voltage level. In other words, it is an electrical potential that may be varied independent of other voltages in a circuit.
  • the floating voltage level may be used as a “threshold” energy level to enter the electromagnetic field of Wien filter 510.
  • the threshold energy level may be a predetermined energy level. As an example, the threshold energy level may be predetermined to be a sum of 50 eV and an acceleration voltage applied to the signalelectron beam.
  • Signal-electrons 503-2R emitted from the sample and having an energy level equal to or below the floating voltage (i.e., threshold energy level), may be repelled or blocked from entering the electromagnetic field of Wien filter 510.
  • an acceleration voltage e.g., 7000 Volts
  • a floating voltage of -7051 V may be applied to Wien filter 510 to filter-out signal-electrons (e.g., signal-electrons 503-2R or secondary electrons emitted from sample) from being incident on charged-particle detector 530, providing a high-pass energy-filter function.
  • signal-electrons e.g., signal-electrons 503-2R or secondary electrons emitted from sample
  • the dispersion of signal-electrons of signal charged-particle beam 503, caused by the electromagnetic field of Wien filter 510 may be used to perform a bandpass energyfilter function.
  • Dispersion of signal-electrons refers to a deviation of the path of signal-electrons caused by the electromagnetic field of an electromagnetic deflector such as a Wien filter.
  • FIG. 5A illustrates an exemplary dispersion of signal-electrons of signal charged-particle beam 503 passing through Wien filter 510 and having an energy level above the threshold energy level.
  • dispersion of signal-electrons of signal charged-particle beam 503 having an energy level above the floating voltage of Wien filter 510 may form dispersed signalelectron beams 503-1A and 503-1B (indicated by broken line arrows).
  • the electromagnetic field strength of Wien filter 510 may be adjusted, among other things, to adjust the dispersion of signal- electrons based on the energy levels, thus allowing selection of a target electron energy level to pass through to a charged-particle detector.
  • the target signal-electron energy beam 503- 1C to be incident on charged-particle detector 530 is substantially undispersed (indicated by solid lines).
  • dispersed signal-electron beams 503-1A and 503-1B, and target signal-electron energy beam 503-1C may comprise backscattered electrons and charged-particle detector 530 may comprise a backscattered electron detector.
  • dispersed signal-electron beams 503-1A and 503-1B, and target signal-electron energy beam 503-1C may include other types of signalelectrons such as Auger electrons, elastically and inelastically scattered electrons, among others.
  • energy filter 500 may include aperture plate 525 forming an aperture 527, also referred to as a slit herein, configured to allow the target signal-electron energy beam to pass through.
  • Wien filter 510 in combination with aperture plate 525, may be configured to perform a bandpass energy-filter function of the signal-electron beam exiting Wien filter 510.
  • Aperture plate 525 may be located between Wien filter 510 and charged-particle detector 530 with respect to secondary optical axis 501.
  • aperture plate 525 may comprise two knife edges 525-1 and 525-2, as illustrated in Fig. 5C, disposed along aperture plane 525P (also referred to as a slit plane) perpendicular to secondary optical axis 501.
  • Aperture plane 525P is indicated by an imaginary horizontal broken line for illustrative clarity only.
  • knife edges 525-1 and 525-2 may be movable independently of each other along X-Y axes to adjust the size, or the location of aperture 527 along aperture plane 525P with respect to secondary optical axis 501.
  • aperture plate 525 may be formed from a single monolithic plate and may comprise a plurality of apertures (e.g., aperture 527) having similar or dissimilar aperture sizes. Aperture plate 525 comprising a plurality of apertures may be disposed and movable along aperture plane 525P along X-Y axes to select a desired aperture size. In some embodiments, aperture plate 525 may comprise a single aperture and the size of the single aperture may be adjusted by adjusting the separation distance between the two knife edges.
  • energy filter 500 may further include ground electrode 520 disposed between Wien filter 510 and aperture plate 525 such that ground electrode 520 is located immediately upstream of aperture plate 525 with respect to secondary optical axis 501 and immediately downstream of Wien filter 510 with respect to secondary optical axis 501.
  • Wien filter 510 may be electrically floating at a non-zero floating voltage. This creates an electric potential difference between charged-particle detector 530, which is electrically grounded, thereby creating an electric field between Wien filter 510 and charged-particle detector 530.
  • the electric field between Wien filter 510 and charged-particle detector 530 may be influenced by the presence of aperture plate 525, which may in turn influence the trajectory of signal-electrons exiting Wien filter 510 towards charged-particle detector 530.
  • the influence of an electric field in the region between Wien filter 510 and charged-particle detector 530 on the trajectory of signal-electrons may cause unintended dispersion of signal-electrons, thereby negatively impacting the bandpass energy-filtering for signal detection.
  • Ground electrode 520 located between Wien filter 510 and aperture plate 525, may be configured to be electrically grounded such that the electrical potential difference between ground electrode 520 and charged-particle detector 530 is negligibly small or zero, thereby creating an electric field-free region 550, as illustrated in Fig. 5C.
  • ground electrode 520 may be configured to negate the effect of presence of aperture plate 525 on the electric field between Wien filter 510 and charged-particle detector 530.
  • Signal-electrons generated from a sample e.g., sample 415 of Fig. 4A
  • a control lens e.g., control lens 505 of Fig. 5A
  • an aperture plane e.g., aperture plane 525P of Fig. 5A
  • the signal-electrons of signal charged-particle beam 503 having an energy level below a set threshold level may be repelled or blocked by a floating voltage signal applied to Wien filter 510, thereby only allowing signal-electrons having an energy level above the set threshold level (e.g., backscattered electrons) to enter the electromagnetic field of Wien filter 510.
  • the signal-electrons passing through Wien filter 510 and traversing toward charged-particle detector 530 may be dispersed based on the electron energy.
  • the bandpass energy filtering of signal-electrons having a desired energy level may be further accomplished by adjusting the strength of the electromagnetic field, ratio of the electric field to the magnetic field, the excitation energy for control lens 505, using an adjustable aperture plate or movable knife edges, adjusting floating voltages, among other things.
  • Energy filter 600 may be substantially similar to and may perform substantially similar functions as energy filter 500 of Fig. 5A.
  • Energy filter 600 may comprise control lens 605, Wien filter 610, ground electrode 620, a charged-particle detector 630, a shield 612, among other things.
  • Control lens 605, analogous to control lens 505, may be configured to focus signal-electrons of signal charged-particle beam 603 on an aperture plane 625P (discussed with reference to Fig. 6D) or a slit plane along which an aperture plate (e.g., aperture plate 625) may be disposed.
  • Wien filter 610 may be configured to disperse the signal-electrons based on the energy of incoming signal-electrons of signal charged-particle beam 603.
  • Fig. 6B illustrates an exemplary signal-electron distribution profile 600B along a plane A-A' shown in Fig. 6A.
  • Signal-electron distribution profile 600B shows the distribution of signalelectrons in a signal charged-particle beam 603 before entering energy filter 600.
  • Signal charged- particle beam 603 may comprise signal-electrons emitted from sample and having an energy in the range of 0 eV - landing energy of primary electrons.
  • Fig. 6C illustrates an exemplary signal-electron distribution profile 600C along a plane B-B' shown in Fig. 6A.
  • Signal-electron distribution profile 600C shows the distribution of signal-electrons in a signal charged-particle beam 603 after exiting Wien filter 610 and along an imaginary plane (B- B') upstream of charged-particle detector 630.
  • control lens 605 may be configured to focus the signal-electrons on the imaginary plane and Wien filter 610 may be configured to disperse the signal-electrons with different energy based on the signal-electron energy. Wien filter 610 and control lens 605, working in combination, may create an astigmatic image and disperse the signal-electrons with different energy.
  • the landing energy of primary electrons may be 5 keV and Wien filter 610 may be electrically floating at -8 kV.
  • signal-electrons such as secondary electrons, backscattered electrons, Auger electrons, among other things, may be emitted from the sample.
  • the signal-electrons may be accelerated by an externally applied acceleration voltage of 7 kV, resulting in the signal-electrons having an energy in the range of 7 keV - 12 keV before entering energy filter 600.
  • the excitation signal applied to control lens 605 may be adjusted, by a controller (e.g., controller 50 of Fig. 2), thereby adjusting the lens strength, based on the target energy range of signal-electrons to be detected.
  • Signal-electrons having an energy in the range of 7 keV - 8 keV may be repelled or blocked by Wien filter 610 floating at -8 kV.
  • Wien filter 610 floating at -8 kV.
  • ratio of electric field to magnetic field among other things, signal-electrons having an energy in the range of 8 keV - 12 keV passing through Wien filter 610 may be dispersed to form an astigmatic image along the focal plane (imaginary plane B-B') of signal-electrons.
  • Signal-electron distribution profile 600C along plane B-B' may be divided into energy ranges or energy bands. Exemplary energy bands E1-E8 are shown in Fig. 6C. It is to be appreciated that the distribution of signal-electrons may be divided into fewer or more energy bands, as appropriate.
  • the target signal-electron energy range or the range width may be adjusted by adjusting the aperture size or location, electromagnetic field strength, ratio of electric field to magnetic field, excitation energy of control lens, among other things.
  • Fig. 6D illustrates an exemplary aperture plate 625 and charged-particle detector 630 arrangement 600D to detect a target signal-electron energy range, consistent with embodiments of the present disclosure.
  • An exemplary desired energy range E4 of dispersed signal-electrons may be allowed to pass through the aperture of aperture plate 625, which is disposed along aperture plane 625P.
  • aperture plane 625P also referred to as the slit plane
  • aperture plate 625 may be movable horizontally along aperture plane 625P to adjust the energy range or energy width of target signal-electrons to be allowed to pass through to be detected by charged-particle detector 630.
  • Figs. 7A-7D illustrate exemplary strategies to select desired target signal-electron energy for detection by a charged-particle detector, using a Wien filter type bandpass energy filter, consistent with embodiments of the present disclosure.
  • the two solid vertical lines placed symmetrically around secondary optical axis 701 are for illustrative purposes only and indicate the size and location of the aperture of an aperture plate.
  • the aperture may be formed by one or two knife edges placed along aperture plane and physically separated to a desired aperture size, or an aperture plate comprising one or more apertures having a desired size.
  • the aperture may be asymmetrically placed around secondary optical axis 701 as well.
  • the size and location of aperture may be fixed and the target signal-electron energy may be adjusted by adjusting a ratio between the electric field strength and the magnetic field strength of a Wien filter (e.g., Wien filter 610 of Fig. 6A).
  • a Wien filter e.g., Wien filter 610 of Fig. 6A
  • Fig. 7A illustrates an exemplary signal-electron distribution profile 700A in an astigmatic image formed along the aperture plane (e.g., aperture plane 625P of Fig. 6D).
  • the aperture indicated by two solid vertical lines symmetric around secondary optical axis 701 and separated by a distance, may be fixed in size and location.
  • signal-electrons having a desired target signal-electron energy level ETI with a predetermined energy width ⁇ AE may be filtered through to be detected by a charged-particle detector, as illustrated in Fig. 7A.
  • an adjustment of the ratio of electric field strength to magnetic field strength to a second ratio may result in an adjustment of the signal-electron distribution profile such that a target signal-electron energy level ETZ may pass through the aperture, as illustrated in Fig. 7B.
  • the electric field strength or the magnetic field strength of one of the first or the second e/m ratios may be adjusted to influence the dispersion characteristics of the signal electrons passing through Wien filter.
  • the e/m ratio may be reduced to reduce the target signal-electron energy level to be detected. As an example, if the e/m ratio is reduced such that the second e/m ratio is lower than the first e/m ratio, energy level ETZ may be lower than energy level ETI (ETZ ⁇ ETI).
  • the e/m ratio of the Wien filter electromagnetic field and the size and location of aperture may be fixed; and the electric field strength and magnetic field strength may be adjusted to adjust the width of target signal-electron energy level, thereby providing bandpass energyfilter function.
  • Fig. 7C illustrates a signal electron distribution profile 700C in an astigmatic image formed along the aperture plane (e.g., aperture plane 625P of Fig. 6D).
  • the aperture indicated by two solid vertical lines symmetric around secondary optical axis 701 and separated by a distance, may be fixed in size and location.
  • the aperture may be asymmetric around secondary optical axis 701 such that the opening on one side of secondary optical axis 701 is larger than the other side.
  • the signal electrons passing through Wien filter may be dispersed by an electromagnetic field having a first e/m ratio and a first location of aperture, resulting in signalelectrons having a desired target signal-electron energy level ET3 and a first width W i of target signalelectron energy level.
  • an adjustment of the electric field strength and the magnetic field strength without impacting the ratio between the two may result in an adjustment of the signal-electron distribution profile such that a target signal-electron energy level ET4 having a second width W2 may pass through the aperture, as illustrated in Fig. 7D.
  • the first width Wi and the second width W2 of the target signal -electron energy levels ET3 and ET4, respectively, may be different.
  • increasing the electric field strength and the magnetic field strength without changing the ratio between the two may reduce the width of the target signal-electron energy level (W2 ⁇ Wi).
  • the lens strength or the excitation energy of control lens may be adjusted based on the target energy of signal-electrons to be focused and detected.
  • the lens strength may be increased to focus signalelectrons having a higher energy as compared to signal-electrons having a lower energy.
  • an excitation signal of -6.0 kV may be applied to a control lens to focus signal electrons of 3000 eV emission energy and in comparison, an excitation signal of -5.0 kV may be applied to a control lens to focus signal electrons of 2000 eV emission energy. It is to be appreciated that the numbers are exemplary and non-limiting.
  • Figs. 8A-8D illustrate exemplary strategies to select desired target signal-electron energy for detection by a charged-particle detector, using a Wien filter type bandpass energy filter, consistent with embodiments of the present disclosure.
  • the two solid vertical lines placed symmetrically around secondary optical axis 801 in Figs. 8A and 8B are for illustrative purposes only and indicate the size and location of the aperture of an aperture plate.
  • the aperture may be formed by one knife edge (as discussed with reference to Fig. 8C) or two knife edges placed along aperture plane and physically separated to a desired aperture size, or an aperture plate comprising one or more apertures having a desired size.
  • the aperture may be asymmetrically placed around secondary optical axis 801 as well.
  • the size of aperture may be adjusted to adjust the target signal-electron energy range or width of the target signal-electron energy range.
  • an aperture plate may comprise two independently movable knife edges. In such cases, an adjustment of the separation distance between the knife edges may adjust the size of the aperture formed.
  • a first aperture 827A may be formed by placing two knife edges along an aperture plane and physically separated by a predetermined distance Al (not illustrated). The size of aperture 827A may be the pre-determined distance Al.
  • the target signal-electron energy range ETS may be based on the size of an aperture formed by the knife edges.
  • the set of conditions may include, but is not limited to, e/m ratio of the electromagnetic field of Wien filter, the electromagnetic field strength, excitation signal for control lens, size of aperture, location of aperture, among other things.
  • the size of aperture 827B may be larger than size of aperture 827 A, as illustrated in Fig. 8B.
  • Second aperture 827B may be formed by placing two knife edges along an aperture plane and physically separated by a pre-determined distance A2 (not illustrated), such that aperture 827B is larger than aperture 827 A. Because of the larger aperture size, the corresponding target signal-electron energy range Eie rnay be wider as well.
  • the first and the second set of conditions may be substantially similar except for the sizes of apertures 827A and 827B, respectively.
  • bandpass energy-filter function may be performed by using a single knife edge and a floating voltage applied to a Wien filter.
  • Fig 8C illustrates an exemplary arrangement 800C in an energy filter configured to perform bandpass energy-filter function, consistent with embodiments of the present disclosure.
  • Arrangement 800C includes an “aperture” or an allowable range of signal-electron energy formed by using a single knife edge 825 and by applying a floating voltage to a Wien filter (e.g., Wien filter 610 of Fig. 6A).
  • single knife edge 825 may be configured to determine the highest energy level of signal-electrons allowed to pass through to the charged-particle detector (e.g., charged-particle detector 630 of Fig. 6A).
  • signal-electrons having an energy level lower than the energy range of signal-electrons which single knife edge 825 is configured to block may pass through to the charged-particle detector.
  • the location of single knife edge 825 may be adjustable along a horizontal aperture plane (e.g., aperture plane 525P of Fig. 5A) to adjust the highest energy level of signal electrons allowed to pass through.
  • the floating voltage applied to a Wien filter may determine the lowest energy level of signal electrons (indicated by edge 840) allowed to pass through. Signal-electrons with energy lower than the applied floating voltage may be repelled or blocked from passing through.
  • Edge 840 indicates the lowest energy level of signal-electrons that will be allowed to pass through Wien filter.
  • signal-electrons having an energy lower than the floating voltage may be repelled or blocked from passing through.
  • the combination of an adjustable applied floating voltage to a Wien filter and an adjustable single knife edge position may form a window of allowed signal-electron energy range (signal electrons in the region between knife edge 825 and edge 840) to allow signal-electrons within the allowable range to pass through to the charged-particle detector, thus enabling bandpass energyfilter selection.
  • a three-dimensional image of a feature-of-interest may be formed by performing multiple scans.
  • each scan generates an image based on the BSE signal from BSEs of a certain energy and each scan may correspond to a certain depth range of the sample from which the BSEs are emitted.
  • a high-aspect ratio feature such as a via
  • multiple scans may be required to image the entire height or depth of the via and each scan may collect BSEs of a different energy corresponding to a different depth of the via and providing information about the portion of the via at or near that depth.
  • This approach has several disadvantages including increased exposure time of the feature to probe beams resulting in higher possibility of beam damage, low inspection throughput, among other issues.
  • FIG. 9A illustrates a schematic diagram of energy filter 900 comprising a Wien filter type bandpass energy filter and a segmented backscattered electron detector, consistent with embodiments of the present disclosure.
  • Energy filter 900 may include a ground mesh 902, a control lens 905, a Wien filter 910, a shield 912, and a segmented backscattered electron detector 930. Using a segmented backscattered electron detector may allow detection of signal electrons with multiple energy bands simultaneously, while maintaining the collection efficiency.
  • segmented backscattered electron detector 930 may comprise a plurality of detector segments 930-1, 930-2, 930-3, 930-4, 930-5, 930-6, 930-7, 930-8, 930-9 of charged-particle sensitive material separated by a non-sensitive material or substrate.
  • a top-view of an exemplary segmented backscattered electron detector 930 comprising nine detector segments is illustrated in Fig. 9B, consistent with some embodiments of the present disclosure. As shown in Fig. 9B, rectangular detector segments (detector segments 930-1 - 930-9) may be disposed horizontally along the dispersion direction of signal charged-particles.
  • the charged-particle sensitive material may be sensitive to charged particles, such as ionizing radiation, electrons, X-rays, or photons, among other charged particles such that it may be configured to detect an incident charged particle and generate a corresponding signal in response to the detection.
  • the non-sensitive material separating the concentric segments may comprise the substrate material of segmented backscattered electron detector 930 or any material having low detection sensitivity for charged particles. .
  • each segment of segmented backscattered electron detector 930 may be configured to detect backscattered electrons of different energy levels or backscattered electrons of different ranges of energy levels E1-E4, as illustrated in Fig. 9C.
  • segment 930-1 may be configured to detect backscattered electrons having an emission energy in the range El (2-5 keV)
  • segment 930-2 may be configured to detect backscattered electrons having an emission energy in the range E2 (5-10 keV)
  • segment 930-3 may be configured to detect backscattered electrons having an emission energy in the range E3 (10-20 keV)
  • segment 930-4 may be configured to detect backscattered electrons having an emission energy in the range E4 (20-50 keV).
  • the number of segments and the energy ranges detected by each segment are non-limiting examples, and segmented backscattered electron detector 930 may comprise fewer or more segments, and energy thresholds for each segment may be adjusted, as appropriate.
  • the width of each segment may be uniform or non-uniform.
  • segmented backscattered electron detector 930 may comprise a plurality of radially concentric segments, or vertically linear segments, or non-circular segments, as appropriate. In some embodiments, segments of segmented backscattered electron detector 930 may be configured to detect signal-electrons based on the signal-electron distribution on aperture plane (slit plane).
  • backscattered electron detection signals may be used to reconstruct images of sample structures under inspection or observation.
  • the images may be two-dimensional images, or three-dimensional images generated from multiple two-dimensional images.
  • a three-dimensional image may be formed from images generated by signals detected in each segment of segmented backscattered electron detector 930. Additionally, or alternatively, a three-dimensional image may be formed from multiple images generated from signals detected by a single segment. Signals detected by a single segment may represent backscattered electrons having an energy range, thereby emitted from a certain depth or a certain depth range.
  • signal-electron beam emitted from a sample may comprise a noncollimated beam in which the angle of signal-electrons in signal-electron beam before entering a bandpass energy filter may be greater than 0.2° with respect to each other. Due to the objective lens chromatic aberration, different backscattered electron energy components form a crossover above the sample plane at different Z-heights along primary optical axis, resulting in an exaggerated energy dispersion effect of signal electrons entering the energy filter with a small half-angle.
  • Apparatus 1000 may include a bottom backscattered electron detector 1013 configured to detect large emission angle backscattered electrons, a control electrode 1014 located between backscattered electron detector 1013 and sample 1015, an energy filter 1001 configured to filter signal electrons based on their emission energy and an incidence angle (collimation angle).
  • Signal-electron beams 1003-1 (indicated by solid lines) represent signal electrons having a high emission energy
  • signal-electron beams 1003-2 entering energy filter 1001 represent signal electrons having a lower emission energy.
  • Fig. 10B illustrates an exemplary energy filter 1001 of apparatus 1000.
  • Energy filter 1001 may be substantially similar to and may perform substantially similar functions as energy filter 500 of Fig. 5A. In comparison with signal charged-particle beam 503, signal-electron beam 1003 may be noncollimated.
  • Energy filter 1001 may further include signal charged-particle detector 1030 configured to detect small-angle backscattered electrons which may not be efficiently collected by backscattered electron detector 1013.
  • Backscattered electron detector 1013 may detect a vast majority of backscattered electrons emitted from the sample.
  • Backscattered electron detector 1013 may be an emission angle-selective charged-particle detector.
  • Signal charged-particle detector 1030 may be an energy- selective charged particle detector.
  • the ratio of backscattered electrons detected by backscattered electron detector 1013 to backscattered electrons detected by backscattered electron detector 1030 may be based on the landing energy of primary electrons.
  • Energy filter 1001 may be configured to perform bandpass energy-filter selection by adjusting the excitation signal of control lens 1005 and electromagnetic field characteristics of Wien filter 1010.
  • the characteristics of Wien filter 1010 may include, but are not limited to, e/m ratio, electric field strength, magnetic field strength, among other things.
  • the target signalelectron energy electrons may be focused on the aperture plane (slit plane) by adjusting the excitation signal for control lens 1005 and the electromagnetic field strength, and the non-target signal-electron energy electrons may be out-of-focus.
  • the out-of-focus signal-electrons may form the background signal (e.g., noise) on the aperture plane.
  • the excitation signal of control lens 1005 may be adjusted to focus signal-electrons in the energy range 2000 eV - 4000 eV on the aperture plane along which aperture plate 1025 may be disposed.
  • the signal-electrons outside the energy range 2000 eV - 4000 eV may constitute the background signal.
  • the signal-electrons having an energy below 50 eV are generally undetected and disregarded for analysis. Emitted electrons in the range of 0 eV - 50 eV may provide information associated with the material, the crystal orientation, and the surface layers, and therefore, the collection, filtering, and detection of secondary electrons (0 to 50 eV) may be desirable.
  • the emission energy of secondary electrons ranges from 0 eV - 50 eV and the energy distribution is narrower compared to backscattered electrons, rendering electron energy filtering for secondary electrons challenging.
  • An electrostatic deflector may provide a larger energy dispersion (Ay) compared to a magnetic deflector, which may seem more suitable for energy filtering of secondary electrons having a narrow energy distribution.
  • the direction of beam deflection is based on the velocity vector of the incident electrons. Electrons entering a magnetic deflector in opposite directions may be deflected in different directions, enabling interference-free electron dispersion.
  • Apparatus 1100 may include two energy filters 1101-1 and 1101-2.
  • Energy filter 1101-1 may be substantially similar to and may perform substantially similar functions as energy filter 500, 600, or 900, of Figs. 5A, 6A, or 9A, respectively.
  • an energy filter e.g., energy filters 500, 600, 900 of Figs. 5A, 6A, 9A, respectively
  • energy filter 1101-2 may include a secondary electron detector configured to detect low energy signal electrons such as secondary electrons.
  • energy filter 1101-2 may be a bandpass energy filter for secondary electrons.
  • Apparatus 1100 may include a first Wien filter 1135, also referred to as the main Wien filter 1135, configured to disperse incoming signal electrons emitted from the sample and traversing along secondary optical axis 1181 toward energy filter 1101-1.
  • An incoming signal electron beam 1103 may comprise low energy level signal electrons 1103-2 and high energy level signal electrons 1103-1.
  • the low energy level signal electrons may comprise secondary electrons having an energy in the range of 0-50 eV and the high energy signal electrons may comprise backscattered electrons having an energy greater than 50 eV, in some cases, up to the landing energy.
  • Apparatus 1100 may further include a first beam deflector 1140 located downstream from first Wien filter 1135 and configured to deflect signal electrons of incoming signal electron beam 1103 towards secondary optical axis 1181.
  • first beam deflector 1140 may be an electrostatic deflector, a magnetic deflector, or an electromagnetic deflector.
  • Apparatus 1100 may further include a second beam deflector 1145 located downstream from first beam deflector 1140 and configured to deflect a path of incoming signal electrons based on their energy.
  • Second beam deflector 1145 may comprise a magnetic deflector.
  • Second beam deflector 1145 may be configured to disperse low energy level signal electrons 1103-2 of incoming signal electron beam 1103 based on their energy and allowing high energy level signal electrons 1103-1 to pass through to Wien filter 1110.
  • the energy-dependent dispersion of low energy level signal electrons 1103-2 is illustrated in Fig. 11B.
  • Wien filter 1110 includes dispersion of incident low energy level signal electron beams 1103-2-1, 1103-2-2, and 1103- 2-3, along three different paths having a different radius of curvature based on the energy of signal electrons.
  • Wien filter 1110 may be configured to function as an electron mirror for low energy level signal electrons 1103-2.
  • an electron mirror refers to an electric or a magnetic system in which incident electrons slow down to a complete standstill before being accelerated away in the opposite direction.
  • An electron mirror may be electrostatic, or a magnetic, or a single-electrode electrostatic, or a multi-electrode electrostatic electron mirror.
  • Positions Pl, P2, and P3 correspond to landing positions of low energy level signal electron beams 1103-2-1, 1103-2-2, and 1103-2-3, respectively, on Wien filter 1110 configured to function as an electron mirror.
  • a floating voltage applied to Wien filter 1110 may repel or reflect substantially all low energy level signal electrons 1103-2 back toward second beam deflector 1145.
  • the reflected or repelled low energy level signal electrons 1103-2R may travel toward second beam deflector 1145 in a direction opposite to the incoming low energy level signal electrons 1103-2.
  • High energy level signal electrons 1103-1 may pass through Wien filter 1110 and be dispersed toward signal-electron detector 1130, based on their energy.
  • Repelled low energy level signal electrons 1103-2R exiting energy filter 1101-1 may enter second beam deflector 1145, which is further configured to disperse the repelled signal-electrons toward energy filter 1101-2, as illustrated in Figs. 11A and 11C.
  • repelled low energy level signal electrons 1103-2R may be further dispersed (for the third time) using a bandpass energy filter 1101-2, before being detected by a secondary electron detector of energy filter 1101-2.
  • the energy dispersion (Ay) of second beam deflector 1145 is smaller than an electrostatic deflector, the electron mirror functionality of Wien filter 1110 enables an increase in the energy dispersion distance within the space between Wien filter 1110 and second beam deflector 1145.
  • Fig. 12 illustrates a process flowchart representing an exemplary method 1200 of imaging a sample using a charged-particle beam apparatus such as apparatus 400 of Fig. 4A, consistent with embodiments of the present disclosure.
  • One or more steps of method 1200 may be performed by controller 50 of EBI system 100, as shown in Fig. 2, for example.
  • Controller 50 may instruct a module of a charged particle beam apparatus to activate a charged-particle source to generate charged particle beam (e.g., electron beam), apply electrical signals to beam deflectors, apply electrical signals to adjust the excitation of control lens, and carry out other functions.
  • a region of a sample is irradiated with a primary charged-particle beam.
  • the primary charged-particle beam may comprise a primary electron beam.
  • a controller e.g., controller 50 of Fig. 1
  • a controller is configured to apply a voltage signal to a cathode of an electron source configured to generate a plurality of primary electrons forming a primary electron beam.
  • the electron source may be activated remotely, for example, by using software, an application, or a set of instructions for a processor of a controller to power the electron source through a control circuitry.
  • Signal charged- particles are generated after interaction of the primary charged-particle beam with the sample.
  • step 1220 signal charged particles emitted from the sample after interaction with the primary electron beam are filtered using an energy discrimination device (e.g., an energy filter 500 of Fig. 5A) based on an energy level of the generated signal charged particles.
  • the signal charged- particles may have an emission energy range from 0 eV - landing energy of the primary charged particles. In some embodiments, the landing energy may be more than 5 keV, or more than 10 keV, or than 15 keV, or more than 20 keV, or any suitable landing energy desired.
  • the energy discrimination device also referred to herein as an energy filter or a bandpass energy filter includes a control lens (e.g., control lens 505 of Fig.
  • Filtering the signal charged-particles may include: (a) focusing the signal charged-particles entering the energy filter on to an aperture plane by adjusting an excitation signal of the control lens.
  • Adjusting the excitation signal of the control lens may include adjusting a voltage signal applied to the control lens to adjust the focusing strength of the control lens; (b) deflecting a first portion and a second portion of the generated signal charged-particles based on a range of the plurality of ranges of energy levels by an electromagnetic charged-particle beam deflector such as a Wien filter.
  • a first portion of signal charged-particles may include charged particles having an emission energy > 50 eV (e.g., backscattered electrons) and a second portion of signal charged- particles may include charged particles having an emission energy ⁇ 50 eV (e.g., secondary electrons).
  • the Wien filter may repel or block the second portion of signal charged-particles from entering the electromagnetic field of Wien filter based on a floating voltage applied to Wien filter.
  • the floating voltage may be configured to block secondary electrons from entering the Wien filter.
  • the first portion of signal charged-particles, such as backscattered electrons, may be dispersed based on the energy levels.
  • the dispersion of signal charged-particles may be based on electric field strength, magnetic field strength, ratio of the electric to magnetic field strengths, energy levels of the signal charged-particles, among other things; (c) directing the first portion of the generated signal charged-particles to pass through an aperture located along the aperture plane.
  • the signal charged-particles may be directed toward an aperture plate comprising an aperture configured to allow signal charged-particles having a desired target energy level to pass through.
  • the signal charged-particles outside the desired target energy range may be blocked by the aperture plate, thereby preventing them from being detected and providing an energyfilter function; and (d) detecting the first portion of the generated signal charged-particles passing through the aperture by a charged-particle detector such as a backscattered electron detector.
  • an image of the sample is formed based on the signal charged particles detected by the charged-particle detector.
  • a three-dimensional (3D) image may be formed, using an image processing technique, based on the detected signal charged-particles.
  • the 3D image formed may provide a high-quality image of the feature of interest in a single scan of the sample.
  • Fig. 13 illustrates a process flowchart representing an exemplary method 1300, which illustrates a process flowchart representing an exemplary method 1200 of imaging a sample using a charged-particle beam apparatus such as apparatus 400 of Fig. 4A, consistent with embodiments of the present disclosure.
  • controller 50 may instruct a module of a charged particle beam apparatus to activate a charged-particle source to generate charged particle beam (e.g., electron beam), apply electrical signals to beam deflectors, apply electrical signals to adjust the excitation of control lens, and carry out other functions.
  • charged particle beam e.g., electron beam
  • step 1320 signal charged particles emitted from the sample upon interaction with the primary electron beam are filtered using an energy discrimination device (e.g., an energy filter 500 of Fig. 5A) based on an energy level of the generated signal charged particles.
  • the signal charged- particles may have an emission energy range from 0 eV - landing energy of the primary charged particles. In some embodiments, the landing energy may be more than 5 keV, or more than 10 keV, or than 15 keV, or more than 20 keV, or any suitable landing energy desired.
  • the energy discrimination device also referred to herein as an energy filter or a bandpass energy filter includes a control lens (e.g., control lens 505 of Fig.
  • Filtering the signal charged- particles may include: (a) focusing the signal charged-particles entering the energy filter on to an aperture plane by adjusting an excitation signal of the control lens.
  • Adjusting the excitation signal of the control lens may include adjusting a voltage signal applied to the control lens to adjust the focusing strength of the control lens; (b) deflecting a first portion and a second portion of the generated signal charged-particles based on a range of the plurality of ranges of energy levels by an electromagnetic charged-particle beam deflector such as a Wien filter.
  • a first portion of signal charged-particles may include charged particles having an emission energy > 50 eV (e.g., backscattered electrons) and a second portion of signal charged-particles may include charged particles having an emission energy ⁇ 50 eV (e.g., secondary electrons).
  • the Wien filter may repel or block the second portion of signal charged-particles from entering the electromagnetic field of Wien filter based on a floating voltage applied to Wien filter.
  • the floating voltage may be configured to block secondary electrons from entering the Wien filter.
  • the first portion of signal charged-particles, such as backscattered electrons, may be dispersed based on the energy levels.
  • the dispersion of signal charged-particles may be based on electric field strength, magnetic field strength, ratio of the electric to magnetic field strengths, energy levels of the signal charged-particles, among other things; (c) detecting the first portion of the generated signal charged-particles using a segmented charged-particle detector comprising a plurality of segments of a charged-particle sensitive material, wherein each segment of the plurality of segments is configured to detect signal charged- particles in a sub-range of a plurality of sub-ranges of the first portion of deflected signal charged- particles.
  • a region of a sample is irradiated with a primary charged-particle beam.
  • the primary charged-particle beam may comprise a primary electron beam.
  • a controller e.g., controller 50 of Fig. 1
  • the electron source may be activated remotely, for example, by using software, an application, or a set of instructions for a processor of a controller to power the electron source through a control circuitry. Signal charged- particles are generated upon interaction of the primary charged-particle beam with the sample.
  • Step 1420 includes deflecting, using a first charged-particle beam deflector, a first portion of the generated signal charged-particles traveling in a first direction.
  • the first charged-particle beam deflector may be a magnetic deflector (e.g., charged-particle beam deflector 1145 of Fig. 11A).
  • the signal charged-particles emitted from the sample traveling toward an energy discrimination device may travel along secondary optical axis (e.g., secondary optical axis 1181).
  • the charged-particle beam magnetic deflector may be configured to disperse low energy signal charged-particles (e.g., charged-particles 1103-2) of incoming generated signal charged-particles (e.g., signal-electron beam 1103) based on their energy and allowing high energy level signal electrons (e.g., charged-particles 1103-1) to pass through.
  • low energy signal charged-particles e.g., charged-particles 1103-2
  • signal-electron beam 1103 incoming generated signal charged-particles
  • high energy level signal electrons e.g., charged-particles 1103-1
  • Step 1430 includes deflecting, using a second charged-particle beam deflector, the deflected first portion of the generated signal charged-particles to enter the first charged-particle beam deflector in a second direction opposite the first direction.
  • the second charged-particle beam deflector may be a Wien filter (e.g., Wien filter 1110 of Fig. 11A) or an electromagnetic charged-particle beam deflector.
  • the Wien filter may function as an electron mirror configured to reflect the incident signal charged- particles deflected by the magnetic deflector in a second direction opposite to the first direction.
  • the reflected signal charged-particles may be directed back toward the magnetic deflector along the secondary optical axis.
  • Step 1440 includes filtering, after receiving by an energy discrimination device, the first portion of the signal charged-particles exiting the first charged-particle beam deflector in a third direction after deflection from the second direction to the third direction, based on an energy level of the first portion of the signal charged-particles.
  • the signal charged-particles re-entering the magnetic deflector after being deflected by the Wien filter, may be deflected again by the magnetic deflector.
  • the deflection of charged-particles passing through a magnetic deflector is based on the velocity vector of the moving charged-particle.
  • Step 1450 includes detecting the first portion of the signal charged-particles (e.g., secondary electrons) using a charged-particle detector (e.g., secondary electron detector).
  • the magnetic deflector, first Wien filter, and a second Wien filter in the second energy-discrimination device may provide the bandpass energy-filter function desired to disperse a narrow band of energy of secondary electrons.
  • Step 1460 includes forming an image of the detected secondary electrons by the secondary electron detector.
  • Energy spectra 1500 is a graphical illustration of number of signal charged particles (e.g., electrons) shown in the y- axis as a function of energy of the signal charged particles shown in the x-axis. Energy of signal electrons generated from the sample may range from 0 eV to landing energy of the primary charged particles interacting with the sample. It is to be appreciated that although energy spectra 1500 is indicated to comprise secondary and backscattered electrons, it may further include auger electrons, and elastically and inelastically scattered electrons as well.
  • signal charged particles e.g., electrons
  • Apparatus 1510 may include, among other things, an energy filter 1501 substantially similar to and may perform substantially similar functions as energy filter 1001 of Fig. 10.
  • Low energy electrons of energy spectra 1500 may include electrons having an energy in the range of 0 -100 eV (e.g., secondary electrons).
  • High energy electrons may include elastically scattered electrons having an energy closer to the landing energy (LE) of the primary electrons on the sample. In this context, elastically scattered electrons may have an energy in the range between (LE - 100 eV) and LE.
  • the low energy electrons and the elastically scattered electrons originate substantially from the sample surface and may not be useful in imaging or inspection of structures, defects, features buried under the surface. Further, the signal of low energy electrons and the elastically scattered electrons may add to the undesirable background or the noise signal in backscattered electron images. Therefore, it may be beneficial to exclude low energy signal electrons and elastically scattered signal electrons to enhance the signal associated with buried structures and defects in band-pass backscattered electron images.
  • Figs. 15C, 15D, and 15E represent exemplary energy ranges of signal electrons within the energy spectra configured to be detected by an energy filter such as energy filter 1501.
  • energy filter 1501 analogous to energy filter 1001 of apparatus 1000, may include a Wien filter (not shown) configured to block or repel signal electrons having an energy equal to or less than El (illustrated in Fig. 15C). Signal electrons having an energy equal to or less than El may comprise low energy electrons, or secondary electrons.
  • the charged-particle detector of apparatus 1510 may be configured to detect signal electrons having an energy between El and landing energy, comprising elastically scattered electrons and backscattered electrons, providing information associated with surface and sub-surface features.
  • the charged-particle detector may be configured to detect small-angle backscattered electrons.
  • energy filter 1501 may function as a high-pass energy filter.
  • charged-particle detector of energy filter 1501 may be configured to detect signal electrons having an energy in the range AE, as indicated in Fig. 15D.
  • the target signal electron energy range e.g., range AE of Fig. 15D
  • the target signal electron energy range may be selected by adjusting one or more factors including, but not limited to, position of an aperture, e/m ratio of the electromagnetic field of Wien filter, electric field strength or magnetic field strength of Wien filter, excitation of control lens, among other things.
  • Signal electrons having an energy in the range AE closer to landing energy may comprise small-angle elastically scattered electrons providing information associated with surface features.
  • energy filter 1501 may function as a low-pass energy filter.
  • charged-particle detector of energy filter 1501 may be configured to detect signal electrons having an energy in the range from El to (LE-AE), as indicated in Fig. 15E.
  • energy filter 1501 may function as a bandpass energy filter, allowing signal electrons having an energy within a band or a range of energy, while blocking the signal electrons outside the energy range from being detected.
  • the detectable energy range may be adjusted to exclude signals from low energy electrons and high-energy small-angle elastically scattered electrons, both of which provide surface information but do not contribute to backscattered electron signal for underlying or sub-surface features.
  • controller 50 may comprise an image processing system that includes an image acquirer (not shown) and a storage (not shown).
  • the image acquirer may comprise one or more processors.
  • 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 charged-particle detector of energy filter 1501 of apparatus 1510 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.
  • the image acquirer may receive a signal from charged-particle detector of energy filter 1501 and may construct an image.
  • the image acquirer may thus acquire images of regions of interest of sample.
  • 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.
  • the acquired or processed images may be stored in 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.
  • Images 1520, 1530, 1540, and 1550 may be images acquired using the image acquirer of the image processing system controlled by controller 50.
  • Image 1520 may be formed based on detected signal electrons having an energy in the range of 0 eV to the landing energy of primary electrons, including low energy electrons, backscattered electrons, high energy elastically scattered electrons, among other things.
  • Image 1530 may be formed based on detected backscattered electrons having an energy in the range of El to landing energy.
  • Image 1540 may be formed based on backscattered electrons BSE1 having an energy in the range of VI to landing energy.
  • Image 1550 may be formed based on detected low angle, high-energy, elastically scattered electrons.
  • images 1520, 1530, 1540, and 1550 may be simulated images generated using trained models such as a Monte Carlo simulation model comprising computational algorithms.
  • a bandpass backscattered electron image 1560 may be simulated or generated using a trained model.
  • bandpass backscattered electron image 1560 may be formed by a mathematical operation (e.g., subtraction) performed on images 1540 and 1550.
  • subtracting the intensity of each pixel of image 1550 (BSE2 image) from the intensity of corresponding pixel of image 1540 (BSE1 image) may result in formation of bandpass backscattered electron image 1560.
  • One or both images 1540 and 1550 may be acquired using an image acquirer of image processing system or may be simulated using a trained simulation model such as a Monte Carlo simulation model.
  • a non-transitory computer -readable medium may be provided that stores instructions for a processor of a controller (e.g., a central processing unit or electronic control unit that is configured to control a charged particle beam apparatus) for performing a method according to the exemplary flowcharts or other methods consistent with embodiments of the present disclosure (e.g., flowcharts of Figs. 12, 13, and 14).
  • a controller e.g., a central processing unit or electronic control unit that is configured to control a charged particle beam apparatus
  • the instructions stored in the non-transitory computer-readable medium may be executed by the circuitry of the controller for performing the methods in part or in their entireties.
  • 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.
  • NVRAM Non-Volatile Random Access Memory
  • 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.
  • 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.
  • 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.
  • a charged-particle beam apparatus comprising: an energy discrimination device configured to filter incoming signal charged-particles having a plurality of ranges of energy levels, the energy discrimination device comprising: an electromagnetic charged-particle deflector configured to deflect a path of the incoming signal charged-particles based on an energy level of the incoming signal charged- particles; an aperture formed on an aperture plane, the aperture configured to allow a portion of the incoming signal charged-particles exiting the electromagnetic charged-particle deflector to pass through based on the deflection; and a control lens located upstream from the electromagnetic charged-particle deflector and configured to focus the incoming signal charged-particles on the aperture plane.
  • the energy discrimination device further comprises a charged-particle detector configured to detect the signal charged-particles passing through the aperture.
  • a first range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 0 electron-volts to 50 electron-volts (eV)
  • a second range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 51 eV to a landing energy of primary charged particles incident on a sample.
  • a degree of deflection of path of the signal charged- particles in the second range of energy level is based on a ratio between an electric field strength and a magnetic field strength in the electromagnetic charged-particle deflector.
  • an adjustment of a position of a knife edge relative to the other knife edge of the at least two knife edges is configured to adjust a target sub-range of energy levels of the plurality of sub-ranges of energy levels of the signal charged particles to pass through the aperture.
  • the aperture is formed by a knife edge placed along the aperture plane.
  • the knife edge is movable along the aperture plane to adjust a size of the aperture.
  • the plurality of ranges of energy levels comprises at least two ranges of energy levels of the incoming signal charged-particles.
  • a first range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 0 electron-volts to 50 electron-volts (eV)
  • a second range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 51 eV to a landing energy of primary charged particles incident on a sample.
  • the apparatus of clause 23, wherein the second range of energy level of the incoming signal charged-particles further comprises a plurality of sub-ranges of energy levels.
  • the electromagnetic charged-particle deflector is configured to repel the incoming signal charged-particles in the first range of energy level away from the electromagnetic charged-particle deflector based on the floating voltage signal.
  • the electromagnetic charged-particle deflector is configured to propel the incoming signal charged-particles in the second range of energy level toward the aperture based on the floating voltage signal.
  • a degree of deflection of path of the signal charged- particles in the second range of energy level is based on a ratio between an electric field strength and a magnetic field strength in the electromagnetic charged-particle deflector.
  • an adjustment of the ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of sub-ranges of energy levels of the signal charged particles to pass through the aperture.
  • an adjustment of the electric field strength and the magnetic field strength for a fixed ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of subranges of energy levels of the signal charged particles to pass through the aperture.
  • a charged-particle beam apparatus comprising: an energy discrimination device configured to filter incoming signal charged-particles having a plurality of ranges of energy levels, the energy discrimination device comprising: an electromagnetic charged-particle deflector configured to deflect a path of the incoming signal charged-particles based on an energy level of the incoming signal charged- particles; a charged-particle detector comprising a plurality of segments of a charged-particle sensitive material configured to detect signal charged-particles, wherein each segment of the plurality of segments is configured to collect signal charged-particles having a range of energy levels of the plurality of ranges of energy levels; and a control lens located upstream from the electromagnetic charged-particle deflector and configured to focus the incoming signal charged-particles on the charged-particle detector.
  • the plurality of ranges of energy levels comprises at least two ranges of energy levels of the incoming signal charged-particles.
  • a first range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 0 electron-volts to 50 electron-volts (eV)
  • a second range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 51 eV to a landing energy of primary charged particles incident on a sample.
  • the second range of energy level of the incoming signal charged-particles further comprises a plurality of sub-ranges of energy levels.
  • the apparatus of any one of clauses 39 and 40 further comprising a controller including circuitry to apply a floating voltage signal to the electromagnetic charged-particle deflector.
  • the apparatus of clause 41 wherein the electromagnetic charged-particle deflector is configured to repel the incoming signal charged-particles in the first range of energy level away from the electromagnetic charged-particle deflector based on the floating voltage signal.
  • a degree of deflection of path of the signal charged- particles in the second range of energy level is based on a ratio between an electric field strength and a magnetic field strength in the electromagnetic charged-particle deflector.
  • an adjustment of the ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of sub-ranges of energy levels of the signal charged particles to pass through the aperture.
  • an adjustment of the electric field strength and the magnetic field strength for a fixed ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of subranges of energy levels of the signal charged particles to pass through the aperture.
  • a charged-particle beam apparatus comprising: a first charged-particle beam deflector configured to deflect a portion of signal charged particles traveling in a first direction; a first energy discrimination device comprising a second charged-particle deflector configured to deflect the deflected portion of signal charged particles to enter the first charged-particle beam deflector in a second direction opposite the first direction; and a second energy discrimination device comprising a third charged-particle deflector configured to filter signal charged particles, after receiving the portion of signal charged- particles exiting the first charged-particle beam deflector in a third direction and after deflection from the second direction to the third direction, based on an energy level of the portion of signal charged particles.
  • the apparatus of clause 48 wherein the first charged-particle beam deflector comprises a magnetic charged-particle beam deflector.
  • the first energy discrimination device further comprises: an aperture formed on an aperture plane, the aperture configured to allow a portion of the signal charged particles exiting the second charged-particle deflector to pass through; a control lens located upstream from the second charged-particle deflector and configured to focus signal charged particles on the aperture plane; and a charged-particle detector configured to detect the portion of the signal charged particles passing through the aperture.
  • the second energy discrimination device further comprises: an aperture formed on an aperture plane, the aperture configured to allow a portion of the signal charged particles exiting the third charged-particle deflector to pass through; a control lens located upstream from the third charged-particle deflector and configured to focus signal charged particles on the aperture plane; and a charged-particle detector configured to detect the portion of the signal charged particles passing through the aperture.
  • the second charged-particle deflector is configured to deflect the deflected portion of the signal charged particles based on an applied first floating voltage.
  • the applied first floating voltage is configured to deflect signal charged particles having an energy level in a range of 0 electron volts (eV) to 50 eV.
  • each of the first and the second energy discrimination device comprises an electrically grounded electrode.
  • An energy discrimination device for use in a charged-particle beam apparatus, the energy discrimination device comprising: a control lens configured to focus incoming signal charged-particles generated after interaction of a primary charged-particles with a sample; an electromagnetic charged-particle deflector located downstream from the control lens and configured to deflect a path of the incoming signal charged-particles based on an energy level of the incoming signal charged particles; and an aperture formed on an aperture plane, the aperture configured to allow a portion of the signal charged-particles exiting the electromagnetic charged-particle deflector to pass through based on the deflection.
  • the energy discrimination device of clause 66 wherein the energy level of the incoming signal charged particles comprises at least two ranges of energy levels.
  • the energy discrimination device of clauses 67 wherein a first range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 0 electron-volts to 50 electron-volts (eV), and wherein a second range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 51 eV to a landing energy of primary charged particles incident on the sample.
  • the energy discrimination device of clause 68 wherein the second range of energy level of the incoming signal charged-particles further comprises a plurality of sub-ranges of energy levels.
  • the energy discrimination device of clause 69 wherein the electromagnetic charged-particle deflector is configured to receive a floating voltage signal.
  • the energy discrimination device of clause 70 wherein the electromagnetic charged-particle deflector is configured to repel the incoming signal charged particles in the first range of energy level away from the electromagnetic charged-particle deflector based on the floating voltage signal.
  • a degree of deflection of path of the signal charged-particles in the second range of energy level is based on a ratio between an electric field strength and a magnetic field strength in the electromagnetic charged-particle deflector.
  • an adjustment of the ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of sub-ranges of energy levels of the signal charged particles to pass through the aperture.
  • the energy discrimination device of clause 73 wherein an adjustment of the electric field strength and the magnetic field strength for a fixed ratio between the electric field strength and the magnetic field strength is configured to adjust a target sub-range of energy levels of the plurality of sub-ranges of energy levels of the signal charged particles to pass through the aperture.
  • a first range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 0 electron-volts to 50 electron-volts (eV)
  • a second range of energy level of the at least two ranges of energy levels of the incoming signal charged-particles is between 51 eV to a landing energy of primary charged particles incident on a sample.
  • An energy discrimination device for use in a charged-particle beam apparatus, the energy discrimination device comprising: a control lens configured to focus incoming signal charged-particles generated after interaction of a primary charged particles with a sample; an electromagnetic charged-particle deflector located downstream from the control lens and configured to deflect a path of the incoming signal charged particles based on an energy level of the signal charged particles; and a charged-particle detector comprising a plurality of segments of a charged-particle sensitive material configured to detect signal charged-particles, wherein each segment of the plurality of segments is configured to collect signal charged particles having a plurality of ranges of energy levels.
  • the energy discrimination device of clause 89 wherein segments of the plurality of segments are separated by a charged-particle non-sensitive material.
  • the energy discrimination device of clause 92 wherein a first range of energy level of the at least two ranges of energy levels of the incoming signal charged particles is between 0 electron-volts to 50 electron-volts (eV), and wherein a second range of energy level of the at least two ranges of energy levels of the incoming signal charged particles is between 51 eV to a landing energy of primary charged particles incident on a sample.
  • the energy discrimination device of clause 93 wherein the second range of energy level of the incoming signal charged particles further comprises a plurality of sub-ranges of energy levels.
  • the energy discrimination device of clause 94 wherein the electromagnetic charged-particle deflector is configured to receive a floating voltage signal.
  • the energy discrimination device of clause 95 wherein the electromagnetic charged-particle deflector is configured to repel the incoming signal charged particles in the first range of energy level away from the electromagnetic charged-particle deflector based on the floating voltage signal.
  • the electromagnetic charged-particle deflector is configured to propel the incoming signal charged-particles in the second range of energy level toward an aperture based on the floating voltage signal.
  • a method of imaging a sample using a charged-particle beam apparatus comprising: generating signal charged particles having a plurality of ranges of energy levels from the sample by irradiating with primary charged particles; filtering, using an energy discrimination device, the generated signal charged particles based on the plurality of ranges of energy levels, the filtering comprising: focusing the generated signal charged particles on an aperture plane using a control lens, deflecting, using an electromagnetic charged-particle deflector, a path of a first portion and a path of a second portion of the generated signal charged particles based on a range of the plurality of ranges of energy levels, directing the first portion of the generated signal charged particles to pass through an aperture located along the aperture plane, detecting, using a charged-particle detector, the first portion of the generated signal charged particles passing through the aperture; and forming an image of the sample based on the detected first portion of the generated signal charged particles.
  • the method of clause 102 further comprising adjusting an excitation signal of the control lens to focus a target range of energy level of the plurality of ranges of energy levels on the aperture plane.
  • the method of any one of clauses 102 and 103 further comprising applying a floating voltage signal to the electromagnetic charged-particle deflector, the applied floating voltage signal configured to repel the second portion of the generated signal charged particles away from the electromagnetic charged-particle deflector.
  • the method of any one of clauses 102-104 further comprising forming the aperture using at least two knife edges placed along the aperture plane.
  • the method of clause 105 wherein the at least two knife edges are movable along the aperture plane independent of each other to adjust a size or a location of the aperture.
  • the method of any one of clauses 105-106 further comprising placing a ground electrode between the electromagnetic charged-particle deflector and the at least two knife edges.
  • the method of clause 107 further comprising forming an electric-field free region between the charged-particle detector and the ground electrode.
  • the method of any one of clauses 102-108 wherein the first portion of the generated signal charged particles comprises signal charged particles having an energy in a range of 51 electron volts (eV) to a landing energy of primary charged particles incident on the sample.
  • a degree of deflection of the path of the first portion of the generated signal charged particles is based on a ratio between an electric field strength and a magnetic field strength in the electromagnetic charged-particle deflector.
  • the method of clause 111 further comprising adjusting the ratio between the electric field strength and the magnetic field strength in the electromagnetic charged-particle deflector to adjust a target range of energy levels of signal charged particles to pass through the aperture.
  • the method of clause 111 further comprising adjusting the electric field strength and the magnetic field strength for a fixed ratio between the electric field strength and the magnetic field strength in the electromagnetic charged-particle deflector to adjust a target range of energy levels of signal charged particles to pass through the aperture.
  • a method of imaging a sample using a charged-particle beam apparatus comprising: generating signal charged-particles having a plurality of ranges of energy levels from the sample by irradiating with primary charged-particles; filtering, using an energy discrimination device, the generated signal charged- particles based on the plurality of ranges of energy levels, the filtering comprising: focusing the generated signal-charged particles using a control lens, deflecting, using an electromagnetic charged-particle deflector, a path of a first portion and a path of a second portion of the generated signal charged-particles based on a range of the plurality of ranges of energy levels, and detecting the first portion of the generated signal charged-particles using a segmented charged-particle detector comprising a plurality of segments of a charged-particle sensitive material, wherein each segment of the plurality of segments is configured to detect signal charged-particles in a sub-range of a plurality of sub-ranges of the first portion of deflected
  • clause 122 further comprising adjusting an excitation signal of the control lens to focus a target range of energy level of the plurality of ranges of energy levels.
  • the method of any one of clauses 122 and 123 further comprising applying a floating voltage signal to the electromagnetic charged-particle deflector, the applied floating voltage signal configured to repel the second portion of the generated signal charged particles away from the electromagnetic charged-particle deflector.
  • eV electron volts
  • the method of clause 127 further comprising adjusting the electric field strength and the magnetic field strength for a fixed ratio between the electric field strength and the magnetic field strength in the electromagnetic charged-particle deflector to adjust a target range of energy levels of signal charged particles to be incident on the segmented charged-particle detector.
  • segments of the plurality of segments are separated by a charged-particle non-sensitive material.
  • the plurality of segments comprises a plurality of linearly arranged segments, a plurality of concentric segments, or a plurality of horizontally arranged segments.
  • the electromagnetic charged-particle deflector comprises a Wien filter.
  • a method of imaging a sample using a charged-particle beam apparatus comprising: generating signal charged-particles having a plurality of ranges of energy levels from the sample by irradiating with primary charged particles; deflecting, using a first charged-particle beam deflector, a path of a first portion of the generated signal charged particles traveling in a first direction; deflecting, using a second charged-particle beam deflector, a path of the deflected first portion of the generated signal charged particles to enter the first charged-particle beam deflector in a second direction opposite the first direction; filtering, after receiving by an energy discrimination device, the first portion of the signal charged-particles exiting the first charged-particle beam deflector in a third direction and after de
  • the method of any one of clauses 135-138, wherein the first portion of the generated signal charged particles comprises signal charged particles having an energy in a range of 0 electron volts (eV) to 50 eV.
  • the method of any one of clauses 135-139, wherein the deflected first portion of the generated signal charged particles comprises signal charged particles having an energy in a range of 0 electron volts (eV) to 50 eV.
  • the method of any one of clauses 135-144, wherein the charged-particle detector comprises a secondary electron detector.
  • the method of any one of clauses 135-145, wherein forming the image of the sample comprises forming a secondary electron image.
  • a non- transitory computer readable medium storing a set of instructions that is executable by one or more processors of a charged-particle beam apparatus to cause the charged-particle beam apparatus to perform operations comprising: activating a charged-particle source to generate primary charged particles to be incident on a sample; filtering signal charged particles generated from the sample after interaction with the incident primary charged particles and having a plurality of ranges of energy levels based on the plurality of ranges of energy levels, the filtering comprising: focusing the generated signal charged particles on an aperture plane, deflecting a first portion and a second portion of the generated signal charged particles based on a range of the plurality of ranges of energy levels, directing the first portion of the generated signal charged particles to pass through an aperture located on the aperture plane, detecting the first portion of the generated signal charged particles passing through the aperture; and forming an image of the sample based on the detected first portion of the generated signal charged particles.
  • a non- transitory computer readable medium storing a set of instructions that is executable by one or more processors of a charged-particle beam apparatus to cause the charged-particle beam apparatus to perform operations comprising: activating a charged-particle source to generate primary charged particles to be incident on a sample; filtering signal charged particles generated from the sample after interaction with the incident primary charged particles and having a plurality of ranges of energy levels based on the plurality of ranges of energy levels, the filtering comprising: focusing the generated signal charged particles, deflecting a first portion and a second portion of the generated signal charged particles based on a range of the plurality of ranges of energy levels, detecting the first portion of the generated signal charged particles using a segmented charged-particle detector comprising a plurality of segments of a charged- particle sensitive material, wherein each segment of the plurality of segments is configured to detect signal charged particles in a sub-range of a plurality of subranges of the first portion of deflected signal charged particles; and forming an image of
  • a non-transitory computer readable medium storing a set of instructions that is executable by one or more processors of a charged-particle beam apparatus to cause the charged-particle beam apparatus to perform operations comprising: activating a charged-particle source to generate primary charged particles to be incident on a sample; generating signal charged particles after interaction of the primary charged-particles with the sample, the signal charged particles having a plurality of ranges of energy levels; deflecting, using a first charged particle beam deflector, a first portion of the generated signal charged particles traveling in a first direction; deflecting, using a second charged-particle beam deflector, the deflected first portion of the generated signal charged-particles to enter the first charged-particle beam deflector in a second direction opposite the first direction; filtering the first portion of the signal charged-particles exiting the first charged- particle beam deflector in a third direction after deflection from the second direction to the third direction, based on an energy level of the first portion of the signal charged particles

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

Des systèmes et des procédés d'imagerie d'un échantillon à l'aide d'un appareil à faisceau de particules chargées sont divulgués. L'appareil à faisceau de particules chargées peut comprendre un dispositif de discrimination d'énergie configuré pour filtrer des particules chargées de signal entrant présentant une pluralité de plages de niveaux d'énergie. Le dispositif de discrimination d'énergie peut comprendre un déflecteur de particules chargées électromagnétiques conçu pour dévier un trajet des particules chargées de signal entrant sur la base d'un niveau d'énergie des particules chargées de signal entrant ; une ouverture formée sur un plan d'ouverture, l'ouverture étant configurée pour permettre à une partie des particules chargées de signal entrant sortant du déflecteur de particules chargées électromagnétiques de passer à travers sur la base de la déviation ; et une lentille de commande située en amont du déflecteur de particules chargées électromagnétiques et configurée pour focaliser les particules chargées de signal entrant sur le plan d'ouverture.
PCT/EP2025/051452 2024-02-16 2025-01-21 Systèmes et procédés de filtrage et de détection à base d'énergie de particules chargées Pending WO2025172004A1 (fr)

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Citations (1)

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US20160372304A1 (en) * 2015-03-24 2016-12-22 Kla-Tencor Corporation Method and System for Charged Particle Microscopy with Improved Image Beam Stabilization and Interrogation

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US20160372304A1 (en) * 2015-03-24 2016-12-22 Kla-Tencor Corporation Method and System for Charged Particle Microscopy with Improved Image Beam Stabilization and Interrogation

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ANONYMOUS: "Geschwindigkeitsfilter - Wikipedia", 25 September 2023 (2023-09-25), XP093269679, Retrieved from the Internet <URL:https://de.wikipedia.org/wiki/Geschwindigkeitsfilter> *
TSUNO K: "ELECTRON OPTICAL ANALYSIS OF A RETARDING WIEN FILTER FOR ELECTRON SPECTROSCOPIC IMAGING", REVIEW OF SCIENTIFIC INSTRUMENTS, AMERICAN INSTITUTE OF PHYSICS, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747, vol. 64, no. 3, 1 March 1993 (1993-03-01), pages 659 - 666, XP000355647, ISSN: 0034-6748, DOI: 10.1063/1.1144193 *

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