Charged particle detection system

Abstract

Apparatuses, methods, and systems for ultrafast beam conditioning for charged particle detection systems include a charged particle source configured to emit charged particles to scan a sample, and an emission enhancer configured to illuminate the charged particle source with electromagnetic radiation to enhance the emission of charged particles in a first period of a scanning operation of the charged particle detection system, and to cease the illumination of electromagnetic radiation in a second period of the scanning operation.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application 62 / 951,950, filed on December 20, 2019, the entirety of which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to the field of charged particle detection systems, and in particular to beam conditioning for charged particle detection systems. Background Technology

[0004] In the manufacturing process of integrated circuits (ICs), both completed and unfinished circuit components are inspected to ensure they are manufactured according to design and free of defects. Inspection systems using optical microscopes typically have a resolution of a few hundred nanometers, and this resolution is limited by the wavelength of light. As the physical size of IC components continues to shrink to less than 100 nanometers or even less than 10 nanometers, inspection systems with higher resolution than optical microscopes are needed.

[0005] Charged particle (e.g., electron beam) microscopy, such as scanning electron microscopy (SEM) or transmission electron microscopy (TEM), with resolutions reduced to less than nanometers, serves as a practical tool for inspecting IC components with feature sizes smaller than 100 nanometers. Using SEM, electrons from a single primary charged particle beam or multiple primary charged particle beams can be focused onto a location of interest on the wafer being inspected. The primary electrons interact with the wafer and can be backscattered or cause the wafer to emit secondary electrons. The intensity of the electron beam, including backscattered and secondary electrons, can vary based on the properties of the wafer's internal and external structures, thereby indicating whether the wafer has defects. Summary of the Invention

[0006] Embodiments of this disclosure include apparatus, systems, and methods for beam conditioning of charged particle detection systems, such as ultrafast beam conditioning. In some embodiments, the charged particle detection system may include a charged particle source configured to emit charged particles to scan a sample. The apparatus may also include a emission intensifier configured to irradiate the charged particle source with electromagnetic radiation during a first cycle of scanning operation of the charged particle detection system to enhance charged particle emission, and to stop irradiating the electromagnetic radiation during a second cycle of scanning operation.

[0007] In some embodiments, the charged particle detection system may include a charged particle source configured to emit charged particles. The device may also include an emission intensifier configured to irradiate the charged particle source with electromagnetic radiation to enhance charged particle emission. The device may further include a beamforming unit configured to form a charged particle beam using the charged particles. The device may also include a scanning unit configured to guide the charged particle beam to scan the sample line by line. The device may further include a controller including circuitry configured to control the emission intensifier to irradiate electromagnetic radiation during a first scan cycle of the charged particle beam and to stop irradiating electromagnetic radiation during a second scan cycle of the charged particle beam.

[0008] In some embodiments, a method may include emitting charged particles using a charged particle source of a charged particle detection system to form a charged particle beam. The method may further include guiding the charged particle beam to scan a sample line by line using a scanning unit of the charged particle detection system. The method may further include: irradiating the charged particle source with electromagnetic radiation using an emission intensifier of the charged particle detection system during a first scan cycle of the charged particle beam to enhance charged particle emission, and stopping the irradiation of electromagnetic radiation during a second scan cycle of the charged particle beam.

[0009] In some embodiments, a non-transitory computer-readable medium may store an instruction set executable by at least one processor of a charged particle detection system to cause the system to perform a method. The method may include emitting charged particles using a charged particle source of the charged particle detection system to form a charged particle beam. The method may also include guiding the charged particle beam to scan a sample line by line using a scanning unit of the charged particle detection system. The method may further include: irradiating the charged particle source with electromagnetic radiation using an emission intensifier of the charged particle detection system during a first scan cycle of the charged particle beam to enhance charged particle emission, and stopping the irradiation of electromagnetic radiation during a second scan cycle of the charged particle beam. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam detection (EBI) system consistent with embodiments of the present disclosure.

[0011] Figure 2 This is a schematic diagram illustrating an exemplary multi-bundle tool consistent with embodiments of this disclosure, which may be... Figure 1 It is part of an exemplary EBI system.

[0012] Figure 3 This is an exemplary graph showing the production of secondary electrons relative to the landing energy of primary electrons, consistent with embodiments of the present disclosure.

[0013] Figure 4AThis is a schematic diagram illustrating the voltage contrast response of a wafer conforming to an embodiment of the present disclosure.

[0014] Figure 4B This is an illustration of an exemplary voltage contrast image over a time series, consistent with embodiments of this disclosure.

[0015] Figure 5 This is a schematic diagram illustrating an exemplary beam tool with ultrafast beam conditioning capability consistent with embodiments of the present disclosure.

[0016] Figure 6 This is an illustration of an exemplary scan frame showing scan lines consistent with embodiments of the present disclosure.

[0017] Figure 7A This is an illustration of an exemplary scanning frequency of a beam tool consistent with embodiments of this disclosure.

[0018] Figure 7B It is consistent with the embodiments of this disclosure. Figure 7A An illustration of an exemplary irradiation frequency of the emission enhancer of the beam tool.

[0019] Figure 8 This is a flowchart of an exemplary method for defect detection in a charged particle detection system, consistent with embodiments of this disclosure.

[0020] Figure 9 This is a flowchart of another exemplary method for defect detection in a charged particle detection system, consistent with embodiments of this disclosure. Detailed Implementation

[0021] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the drawings, wherein the same numerals in different drawings denote the same or similar elements unless otherwise indicated. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with this disclosure. Rather, they are merely examples of devices and methods consistent with aspects relevant to the subject matter described in the appended claims. For example, although some embodiments are described in the context of utilizing charged particle beams (e.g., electron beams), this disclosure is not limited thereto. Other types of charged particle beams can also be applied similarly. Furthermore, other imaging systems, such as optical imaging, light detection, X-ray detection, etc., can be used.

[0022] Electronic devices are made up of circuits formed on a silicon wafer called a substrate. Many circuits can be formed together on the same silicon wafer, called an integrated circuit or IC. The size of these circuits has been greatly reduced so that more circuits can be mounted on the substrate. For example, the IC chip in a smartphone can be represented by a scaled-down image. Figure 1It may be small, but it could contain more than 2 billion transistors, each less than one-thousandth the size of a human hair.

[0023] Manufacturing these very small ICs is a complex, time-consuming, and expensive process, typically involving hundreds of individual steps. Even a mistake in one step can lead to a defect in the finished IC, rendering it useless. Therefore, one goal of the manufacturing process is to avoid these defects in order to maximize the number of functional ICs manufactured in the process; that is, to improve the overall yield of the process.

[0024] A key component of increasing yield is monitoring the chip manufacturing process to ensure it produces a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip's circuit structure at each stage of its formation. Inspection can be performed using a scanning electron microscope (SEM). An SEM can be used to image these extremely small structures, essentially taking a "photograph" of the wafer structure. This image can be used to determine if the structure is properly formed in the correct location. If a defect is found in the structure, the process can be adjusted so that the defect is less likely to recur.

[0025] A Sequencing Electron Microscope (SEM) works similarly to a camera. A camera takes a picture by receiving and recording the brightness and color of light reflected or emitted from a person or object. A SEM takes a "picture" by receiving and recording the energy or number of electrons reflected or emitted from a structure. Before taking such a "picture," an electron beam can be provided to the structure, and as electrons are reflected or emitted ("ejected") from the structure, the SEM's detector can receive and record the energy or number of these electrons to generate an image. To take such "pictures," some SEMs use a single electron beam (referred to as "single-beam SEM"), while others use multiple electron beams (referred to as "multi-beam SEM") to take multiple "pictures" of the wafer. By using multiple electron beams, the SEM can provide more electron beams to the structure to obtain these multiple "pictures," thus causing more electrons to eject from the structure. Therefore, the detector can receive more ejected electrons simultaneously and generate images of the wafer structure with greater efficiency and faster speed.

[0026] Detecting buried defects in vertically high-density structures such as 3D NAND flash memory devices can be challenging. One approach to detecting buried or surface electrical defects in such devices is using voltage contrast in SEM. In this method, differences in conductivity within a sample's material, structure, or region result in contrast differences in its SEM image. In the context of defect detection, electrical defects beneath the sample surface can cause charge changes on the sample surface, thus allowing detection via contrast in the SEM image of the sample surface. To enhance voltage contrast, a process called pre-charging or flooding can be employed, where the region of interest in the sample is exposed to a large beam current before detection using a small beam current but with high imaging resolution. Some advantages of flooding for detection include reducing wafer charging to minimize image distortion due to charging, and in some cases, increasing wafer charging to enhance the difference between defects and surrounding non-defect features in the image.

[0027] One method for identifying voltage contrast defects is to rapidly switch between different beam currents so that the electron beam scans the wafer multiple times. Multiple voltage contrast images can be generated and compared to identify voltage contrast defects.

[0028] One challenge with existing SEM designs is the inability to regulate the beam current ultra-fast during inspection, causing the voltage contrast response in the defect region to recede before beam current regulation is complete. For example, when interconnects are manufactured below standard and the electron beam has a low current, external electrons may be ejected. If ejection occurs faster than beam current regulation, an abnormal voltage contrast response will not appear in the voltage contrast image. Similarly, when insulators are manufactured below standard and the electron beam has a high current, external electrons may accumulate rapidly, leading to electrical breakdown and ejection. If ejection occurs faster than beam current regulation, an abnormal voltage contrast response will not appear in the voltage contrast image. Because the beam current cannot be regulated ultra-fast during inspection, voltage contrast defects can be difficult to identify.

[0029] The disclosed embodiments provide apparatus, systems, and methods that allow for ultrafast beam current modulation during the detection process. Charged particle detection systems (e.g., SEM) can be equipped with emission intensifiers configured to illuminate a charged particle source. Due to photoelectric or photoradiative effects, the energy of the light may be transferred to electrons in the atoms of the material of the charged particle source, facilitating their escape from the atoms. Such transfer can occur in an ultrafast time. Therefore, the transferred energy can promote electron emission in an ultrafast time. When electron emission is enhanced, the electron beam may have a large current. When electron emission is not enhanced, the electron beam may have a low current. The electron emission of the emission intensifier can be synchronized with the scanning operation of the charged particle detection system, allowing the system to rapidly switch between high and low currents for the electron beam used for scanning. Accordingly, two “versions” of voltage contrast images can be generated from the scan, one generated at a high current and the other at a low beam current. By comparing the characteristics (e.g., brightness) of the voltage contrast images generated at different beam currents, the voltage contrast response (e.g., the rate of change of exiting electrons) at different beam currents can be identified. If the voltage contrast response is abnormal, potential voltage contrast defects can be identified without difficulty in a short period of time.

[0030] For clarity, the relative dimensions of the components in the figures may be exaggerated. In the following description of the figures, the same or similar reference numerals denote the same or similar components or entities, and only the differences with respect to the various embodiments are described.

[0031] As used herein, unless otherwise specified, the term "or" includes all possible combinations except where impractical. For example, if a statement declares that a component may include A or B, then unless otherwise specified or impractical, the component may include A or B, or A and B. As a second example, if a statement declares that a component may include A, B, or C, then unless otherwise specified or impractical, the component may include A or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0032] Figure 1 An exemplary electron beam detection (EBI) system 100 consistent with embodiments of this disclosure is shown. The EBI system 100 can be used for imaging. Figure 1As shown, the EBI system 100 includes a main chamber 101, a loading / locking chamber 102, a beam tool 104, and a device front-end module (EFEM) 106. The beam tool 104 is located within the main chamber 101. The EFEM 106 includes a first loading port 106a and a second loading port 106b. The EFEM 106 may include additional loading ports. The first loading port 106a and the second loading port 106b receive a front-open wafer transfer cassette (FOUP), which contains wafers to be inspected (e.g., semiconductor wafers or wafers made of other materials) or samples (wafers and samples can be used interchangeably). A "batch" is a group of wafers that can be loaded together for processing.

[0033] One or more robotic arms (not shown) in EFEM 106 can transport the wafer to loading / locking chamber 102. Loading / locking chamber 102 is connected to a loading / locking vacuum pump system (not shown), which removes gas molecules from loading / locking chamber 102 to achieve a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) can transport the wafer from loading / locking chamber 102 to main chamber 101. Main chamber 101 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules from main chamber 101 to achieve a second pressure below the first pressure. After reaching the second pressure, the wafer is detected by beam-collecting tool 104. Beam-collecting tool 104 can be a single-beam system or a multi-beam system.

[0034] The controller 109 is electronically connected to the beam tool 104. The controller 109 may be a computer configured to perform various controls of the EBI system 100. Although the controller 109 is... Figure 1 The controller 109 is shown outside the structure including the main chamber 101, the loading / locking chamber 102 and the EFEM 106, but it is understood that the controller 109 may be part of the structure.

[0035] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a general-purpose or specialized electronic device capable of manipulating or processing information. For example, a processor may include any number of central processing units (or “CPU”), graphics processing units (or “GPU”), optical processors, programmable logic controllers, microcontrollers, microprocessors, digital signal processors, intellectual property (IP) cores, programmable logic arrays (PLAs), programmable array logic (PALs), general-purpose array logic (GALs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), system-on-a-chip (SoCs), application-specific integrated circuits (ASICs), and any combination of circuits of any type capable of data processing. The processor may also be a virtual processor, comprising one or more processors distributed across multiple machines or devices coupled via a network.

[0036] In some embodiments, controller 109 may further include one or more memories (not shown). The memories can be general-purpose or specific electronic devices capable of storing processor-accessible code and data (e.g., via a bus). For example, the memories can include any number of random access memory (RAM), read-only memory (ROM), optical discs, magnetic disks, hard disks, solid-state drives, flash drives, secure digital cards (SD cards), memory sticks, compact flash (CF) cards, or any combination of any type of storage device. The code can include an operating system (OS) and one or more applications (or “apps”) for a specific task. The memories can also be virtual memory, which includes one or more memories distributed across multiple machines or devices coupled via a network.

[0037] Figure 2 A schematic diagram of an exemplary multi-bundle tool 104 (also referred to herein as device 104) and an image processing system 290 according to an embodiment of the present disclosure is shown. The image processing system 290 can be configured for use in an EBI system 100 ( Figure 1 )middle.

[0038] The beam tool 104 includes a charged particle source 202, a gun aperture 204, a focusing lens 206, a primary charged particle beam 210 emitted from the charged particle source 202, a source conversion unit 212, multiple fine beams 214, 216, and 218 of the primary charged particle beam 210, a main projection optics system 220, a motorized wafer stage 280, a wafer support 282, multiple secondary charged particle beams 236, 238, and 240, an auxiliary optics system 242, and a charged particle detection device 244. The main projection optics system 220 may include a beam splitter 222, a deflection scanning unit 226, and an objective lens 228. The charged particle detection device 244 may include detection sub-regions 246, 248, and 250.

[0039] The charged particle source 202, ejector orifice 204, focusing lens 206, source conversion unit 212, beam splitter 222, deflection scanning unit 226, and objective lens 228 can be aligned with the main optical axis 260 of the device 104. The auxiliary optical system 242 and the charged particle detection device 244 can be aligned with the auxiliary optical axis 252 of the device 104.

[0040] Charged particle source 202 can emit one or more charged particles, such as electrons, protons, ions, muons, or any other charged particles. In some embodiments, charged particle source 202 can be an electron source. For example, charged particle source 202 can include a cathode, extractor, or anode, wherein primary electrons can be emitted from the cathode and extracted or accelerated to form a primary charged particle beam 210 (in this case, a primary electron beam) having a cross (virtual or real) 208. For ease of explanation and without ambiguity, electrons are used as examples in some descriptions herein. However, it should be noted that any charged particle, not limited to electrons, can be used in any embodiment of this disclosure. The primary charged particle beam 210 can be visualized as being emitted from the cross 208. The ejector orifice 204 can block peripheral charged particles of the primary charged particle beam 210 to reduce the Coulomb effect. The Coulomb effect can lead to an increase in probe spot size.

[0041] The source conversion unit 212 may include an array of imaging elements and an array of beam-limiting apertures. The array of imaging elements may include a micro-deflector or microlens array. The array of imaging elements can form multiple parallel images (virtual or real) at an intersection 208 with multiple fine beams 214, 216, and 218 of the primary charged particle beam 210. The array of beam-limiting apertures can limit the multiple fine beams 214, 216, and 218. Although in Figure 2Three fine beams 214, 216, and 218 are shown, but embodiments of this disclosure are not limited thereto. For example, in some embodiments, device 104 may be configured to generate a first number of fine beams. In some embodiments, the first number of fine beams may be in the range of 1 to 1000. In some embodiments, the first number of fine beams may be in the range of 200-500. In an exemplary embodiment, device 104 may generate 400 fine beams.

[0042] The focusing lens 206 can focus the primary charged particle beam 210. The current of the fine beams 214, 216, and 218 downstream of the source conversion unit 212 can be changed by adjusting the focusing power of the focusing lens 206 or by changing the radial size of the corresponding beam-limiting apertures in the array of beam-limiting apertures. The objective lens 228 can focus the fine beams 214, 216, and 218 onto the wafer 230 for imaging, and can form multiple probe points 270, 272, and 274 on the surface of the wafer 230.

[0043] Beam splitter 222 can be a Wien filter-type beam splitter that generates electrostatic dipole fields and magnetic dipole fields. In some embodiments, if they are applied, the force exerted by the electrostatic dipole field on the charged particles (e.g., electrons) of the thin beams 214, 216, and 218 on the thin beams 214, 216, and 218 can be substantially equal in magnitude and opposite in direction to the force exerted by the magnetic dipole field on the charged particles. Therefore, the thin beams 214, 216, and 218 can pass directly through beam splitter 222 with zero deflection. However, the total dispersion of the thin beams 214, 216, and 218 generated by beam splitter 222 can also be non-zero. Beam splitter 222 can separate secondary charged particle beams 236, 238, and 240 from the thin beams 214, 216, and 218 and guide the secondary charged particle beams 236, 238, and 240 toward the auxiliary optical system 242.

[0044] Deflection scanning unit 226 can deflect fine beams 214, 216, and 218 to scan probe points 270, 272, and 274 on the surface region of wafer 230. In response to the incident of fine beams 214, 216, and 218 at probe points 270, 272, and 274, secondary charged particle beams 236, 238, and 240 can be emitted from wafer 230. Secondary charged particle beams 236, 238, and 240 can include charged particles (e.g., electrons) with an energy distribution. For example, secondary charged particle beams 236, 238, and 240 can be a secondary electron beam including secondary electrons (energy ≤ 50 eV) and backscattered electrons (energy between 50 eV and the landing energy of fine beams 214, 216, and 218). The auxiliary optical system 242 can focus the secondary charged particle beams 236, 238, and 240 onto the detection sub-regions 246, 248, and 250 of the charged particle detection device 244. The detection sub-regions 246, 248, and 250 can be configured to detect the respective secondary charged particle beams 236, 238, and 240 and generate corresponding signals (e.g., voltage, current, etc.) for reconstructing an image of the surface region of the wafer 230.

[0045] The generated signals can represent the intensity of the secondary charged particle beams 236, 238, and 240, and can be provided to an image processing system 290 that communicates with the charged particle detection device 244, the main projection optics system 220, and the motorized wafer stage 280. The movement speed of the motorized wafer stage 280 can be adjusted to regulate the time interval between successive beam scans of regions on wafer 230. Because different materials on wafer 230 have different resistivity-capacitance characteristics, it may be necessary to adjust the time interval, thus exhibiting different sensitivities to imaging timing.

[0046] The intensities of the secondary charged particle beams 236, 238, and 240 can vary depending on the external or internal structure of the wafer 230, and thus can indicate whether the wafer 230 contains defects. Furthermore, as described above, the fine beams 214, 216, and 218 can be projected onto different locations on the top surface of the wafer 230, or onto different sides of the wafer 230 at specific locations, to generate secondary charged particle beams 236, 238, and 240 of varying intensities. Therefore, by mapping the intensities of the secondary charged particle beams 236, 238, and 240 to regions of the wafer 230, the image processing system 290 can reconstruct an image reflecting features of the internal or external structure of the wafer 230.

[0047] In some embodiments, the image processing system 290 may include an image acquirer 292, a memory 294, and a controller 296. The image acquirer 292 may include one or more processors. For example, the image acquirer 292 may include a computer, server, mainframe, terminal, personal computer, any type of mobile computing device, or a combination thereof. The image acquirer 292 may be communicatively coupled to the charged particle detection device 244 of the beam tool 104 via a medium such as a conductor, fiber optic cable, portable storage medium, IR, Bluetooth, the Internet, wireless network, radio, or a combination thereof. In some embodiments, the image acquirer 292 may receive signals from the charged particle detection device 244 and may construct an image. Thus, the image acquirer 292 may acquire an image of the wafer 230. The image acquirer 292 may also perform various post-processing functions, such as generating contours, overlaying indicators on the acquired image, etc. The image acquirer 292 may be configured to perform brightness and contrast adjustments on the acquired image. In some embodiments, the memory 294 may be a storage medium, such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer-readable storage, etc. The memory 294 may be coupled to the image acquirer 292 and may be used to save scanned raw image data as raw images and post-processed images. The image acquirer 292 and the memory 294 may be connected to the controller 296. In some embodiments, the image acquirer 292, the memory 294, and the controller 296 may be integrated together as a single control unit.

[0048] In some embodiments, image acquisition unit 292 may acquire one or more images of the wafer based on imaging signals received from charged particle detection device 244. The imaging signals may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image comprising multiple imaging regions. The single image may be stored in memory 294. The single image may be an original image that can be divided into multiple regions. Each region may include an imaging region containing features of wafer 230. The acquired images may include multiple images of a single imaging region of wafer 230 sampled multiple times over a time series. Multiple images may be stored in memory 294. In some embodiments, image processing system 290 may be configured to perform image processing steps on multiple images of the same location on wafer 230.

[0049] In some embodiments, the image processing system 290 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of detected secondary charged particles (e.g., secondary electrons). Charged particle distribution data collected during a detection time window, combined with corresponding scan path data of the fine beams 214, 216, and 218 incident on the wafer surface, can be used to reconstruct an image of the inspected wafer structure. The reconstructed image can be used to reveal various features of the internal or external structure of the wafer 230, and thereby can be used to reveal any defects that may be present in the wafer.

[0050] In some embodiments, the charged particles can be electrons. When electrons from the primary charged particle beam 210 are projected onto the surface of wafer 230 (e.g., probe points 270, 272, and 274), the electrons of the primary charged particle beam 210 can penetrate to a certain depth into the surface of wafer 230 and interact with the particles of wafer 230. Some electrons from the primary charged particle beam 210 can elastically interact with the particles of wafer 230 (e.g., in the form of elastic scattering or collision) and can be reflected or bounced off the surface of wafer 230. The elastic interaction preserves the total kinetic energy of the interacting objects (e.g., electrons from the primary charged particle beam 210 and particles of wafer 230), wherein the kinetic energy of the interacting objects is not converted into other forms of energy (e.g., thermal energy, electromagnetic energy, etc.). Such reflected electrons produced by elastic interaction can be called backscattered electrons. Some electrons from the primary charged particle beam 210 can inelastically interact with the particles of wafer 230 (e.g., in the form of inelastic scattering or collision). Inelastic interactions do not preserve the total kinetic energy of the interacting objects; some or all of the kinetic energy is converted into other forms of energy. For example, through inelastic interactions, the kinetic energy of some electrons in the primary charged particle beam 210 can lead to electron excitation and transitions in the atoms of the particles. This inelastic interaction can also produce electrons that leave the surface of wafer 230, which can be called secondary electrons (SEs). The production or emission rate of BSEs and SEs depends, for example, on the material being detected and the landing energy of the electrons of the primary charged particle beam 210 landing on the material surface. The energy of the electrons in the primary charged particle beam 210 can be partially converted through its accelerating voltage (e.g., Figure 2 The accelerating voltage between the anode and cathode of the charged particle source 202 is used to transfer the electrons. The number of BSE and SE can be more or less (or even the same) than the injected electrons of the primary charged particle beam 210.

[0051] Images generated by SEM can be used for defect detection. For example, a generated image capturing a test device area of ​​a wafer can be compared with a reference image capturing the same test device area. The reference image can be predetermined (e.g., by simulation) and does not include known defects. If the difference between the generated image and the reference image exceeds a tolerance level, a potential defect can be identified. As another example, SEM can scan multiple areas of a wafer, each including test device areas designed to be identical, and generate multiple images capturing these manufactured test device areas. These multiple images can be compared with each other. If the difference between the multiple images exceeds a tolerance level, a potential defect can be identified.

[0052] Voltage contrast defects are one type of defect. Test device regions on a wafer can be designed and fabricated in three dimensions, for example, with different layers. Some test device regions on different layers can be designed to be electrically interconnected, for example, connected via conductive contacts (“interconnectors”). Some test device regions on different layers can be designed to be electrically insulated, for example, by filling the spaces between them with non-conductive or insulating material (“insulators”) (i.e., no interconnects are designed between them). However, due to variations in the manufacturing process, designed interconnects may be fabricated to be non-conductive or substandard (e.g., conductive but with high resistance). Similarly, designed insulators may be fabricated to be conductive (e.g., forming undesigned interconnects) or substandard (e.g., insulating but with low breakdown voltage). When subjected to testing, these defects can be sensitive to the energy of the charged particle beam reaching the surface of the test device region (“landing energy”), the number of charged particles in the charged particle beam (“beam current”), or other testing conditions. Different landing energies or beam currents of charged particle beams can cause different responses (“voltage contrast responses”) in defect regions, such as varying rates of ejected charged particle production or variations in these rates. Different voltage contrast responses can result in different contrast levels in the generated image. Contrast levels can make a defect appear brighter or darker than its surroundings, or indistinguishable from them. Therefore, such defects are called “voltage contrast defects,” and images displaying voltage contrast responses are called “voltage contrast images.”

[0053] When interconnects are manufactured as designed, and a beam of charged particles is projected onto a surface connected to an underlying layer via the interconnect, the underlying layer can act as an electrical ground (“good ground”) to expel external charged particles brought into the wafer by the beam. However, when interconnects are manufactured as non-conductive or below standard, the underlying layer may not be well grounded, and external charged particles may not be expelled at all, or not as quickly as in a well-grounded case. Similarly, when insulators are manufactured as designed, a beam of charged particles is projected onto a surface insulated from the underlying layer, and the underlying layer can be well insulated and will not expel external charged particles. However, when insulators are manufactured as conductive or below standard, the underlying layer may be fully grounded or have a low breakdown voltage, and external charged particles may be expelled immediately or after reaching the low breakdown voltage. Defective interconnects or insulators may cause abnormal voltage contrast responses compared to normal interconnects or insulators, and the voltage contrast image of defective interconnects or insulators may differ from that of normal interconnects or insulators (e.g., brighter or darker).

[0054] Figure 3 An exemplary graph illustrating the production rate of secondary electrons relative to the landing energy of a primary electron beam is shown, consistent with embodiments of this disclosure. The graph illustrates multiple beams of a primary charged particle beam (e.g., Figure 2 The landing energy of the primary charged particle beam 210 and its multiple fine beams 214, 216 and 218, and the secondary charged particle beam (e.g., Figure 2 The relationship between the yield of secondary charged particle beams (236, 238, and 240) is shown. Yield represents the number of secondary electrons generated in response to the impact of primary electrons. For example, a yield greater than 1.0 indicates that more secondary electrons may be generated than the number of primary electrons that have landed on the wafer. Similarly, a yield less than 1.0 indicates that fewer secondary electrons may be generated in response to the influence of primary electrons.

[0055] like Figure 3 As shown, when the landing energy of primary electrons is in the range of E1 to E2, more electrons may leave the wafer surface than land on it, which can result in a positive potential on the wafer surface. In some embodiments, defect detection can be performed within the aforementioned landing energy range, which is referred to as "positive mode." In positive mode, secondary electrons leaving the surface can be attracted by the positive potential of the surface. The more positive the surface potential, the more electrons reach the detection device (e.g., ...). Figure 2 The fewer secondary electrons in the detection device 244, the better, and the fewer beam tools (e.g., Figure 2 The multi-beam tool (104) can generate darker images of the surface being inspected.

[0056] When the landing energy is below E1 or above E2, fewer electrons may leave the wafer surface, resulting in a negative potential on the wafer surface. In some embodiments, defect detection can be performed within this landing energy range, which is referred to as "negative mode." In negative mode, secondary electrons leaving the surface are repelled by the negative potential of the surface. The more negative the surface potential, the more secondary electrons can reach the detection device, and the brighter the image that the beam tool can produce on the inspected surface.

[0057] In some embodiments, the landing energy of the primary charged particle beam can be controlled by the total bias or voltage between the charged particle source and the wafer.

[0058] Figure 4A A schematic diagram of the voltage contrast response of a wafer consistent with embodiments of the present disclosure is shown. In some embodiments, a beam tool (e.g., Figure 2 The multi-beam tool 104 can be used to transmit signals through multiple fine beams (e.g., using a primary charged particle beam) via a primary charged particle beam. Figure 2 The wafer is irradiated with multiple fine beams 214, 216, and 218 of a primary charged particle beam 210, and the wafer's voltage contrast response to the irradiation is measured to detect the wafer (e.g., Figure 2 Defects in the internal or external structure of the wafer 230. In some embodiments, the wafer may include a test device region 420 fabricated on a substrate 410. The substrate 410 may be conductive and grounded. In some embodiments, structure 420 may include multiple conductive structures, including structures 430 and 440 separated by an insulating material 450. For example, test device region 430 may be conductively connected to the substrate 410. Conversely, test device region 440 is separated from the substrate 410 by an insulating material 450, such that an insulating test device region 470 (e.g., oxide) exists between test device region 440 and substrate 410.

[0059] Beam tools can be used by multiple thin beams (e.g., a primary charged particle beam) Figure 2 Multiple fine beams 214, 216, and 218 of the primary charged particle beam 210 scan the surface of the test device region 420, generating secondary electrons (e.g., ...) from the surface of the test device region 420. Figure 2 The secondary charged particle beams 236, 238, and 240). As described above, when the landing energy of the primary electrons is between E1 and E2 (i.e., in positive mode), more electrons may leave the wafer surface than land on it, thus generating a positive potential on the wafer surface.

[0060] like Figure 4AAs shown, a positive potential can accumulate on the wafer surface. For example, after beam tool scanning of test device region 420, test device region 440 can retain more positive charge because test device region 440 is insulated from substrate 410, thereby generating a positive potential at the surface of test device region 440. Conversely, primary electrons with the same landing energy (i.e., the same yield) applied to test device region 430 can result in less positive charge remaining in test device region 430 because substrate 410 can supply electrons to test device region 430 to neutralize the positive charge through the conductive contact between them.

[0061] Bundle tools (e.g., Figure 2 Image processing systems (e.g., multi-beam tool 104) Figure 2 The image processing system 290 can generate images showing the voltage contrast response (“voltage contrast images”), such as voltage contrast images 435 and 445 corresponding to test device regions 430 and 440, respectively. For example, due to its conductive interconnection with the substrate 410 (i.e., as ground), test device region 430 may retain little positive charge and repel more secondary electrons during detection. Therefore, voltage contrast image 435 can be a bright image. Conversely, due to its insulation from the substrate 410 or any other ground, test device region 440 may retain an accumulation of positive charge, which may result in test device region 440 repelling fewer secondary electrons during detection. Therefore, voltage contrast image 445 can be a dark image.

[0062] In some embodiments, the beam tool may pre-scan the surface of the wafer to provide electrons to establish a potential on the wafer surface. The pre-scan may use a high-current primary charged particle beam. After the pre-scan, the beam tool may use a low-current primary charged particle beam to obtain images of multiple dies within the wafer. Because the dies may include the same test device area, defects can be detected by comparing the differences in voltage contrast images from multiple dies; this is known as a die-to-die (“D2D”) inspection method. For example, if the voltage contrast response (e.g., image brightness) of one image differs from the voltage contrast responses of other images, the die corresponding to the different voltage contrast responses may have a potential defect.

[0063] Pre-scanning can be applied to wafers under the assumption that the electrical surface potential established on the wafer surface during pre-scanning will be retained during detection and will remain above the detection threshold of the beam tool. However, in some cases, the level of surface potential accumulated during detection may change due to the effects of electrical breakdown or tunneling, which may result in the inability to detect voltage contrast defects.

[0064] For example, the test device region 440 (e.g., a tungsten plug) and the substrate 410 (the source or drain region of a field-effect transistor (FET)) can be designed with a conductive interconnect similar to that of the test device region 430 and the substrate 410. However, due to variations in the manufacturing process (e.g., defective etching processes), the test device region 440 can be fabricated below standard, where an insulating test device region 470 (e.g., a thin oxide layer) can be formed between the test device region 440 and the substrate 410. For example, the oxide layer can be a cobalt silicide layer (e.g., CoSi, CoSi2, Co2Si, Co3Si, etc.) thinner than 10 nanometers. This is a defect that needs to be detected. However, during pre-scanning, a high voltage may be applied to the thin insulating test device region 470 and cause electrical breakdown, where leakage current may flow through the thin insulating test device region 470 (i.e., electrons in the substrate 410 may be discharged into the test device region 440 through the below-standard insulating test device region 470), and the test device region 440 may be neutralized. Therefore, the voltage contrast image 445 can be brighter than expected. If the electron ejection process is fast enough, the test device region 440 may have been neutralized after the pre-scan and before the imaging process, which may result in the voltage contrast image 445 being indistinguishable from the voltage contrast image 435. Due to the rapid electron ejection, if the beam tool cannot adjust the beam current more quickly (e.g., quickly switch from pre-scan to imaging), the defect test device region 440 may not be detected.

[0065] Voltage contrast images 445, 446, and 447 illustrate different voltage contrast responses of the defect test device region 440 in a scenario where the beam tool provides ultrafast beam current conditioning. The beam tool can image the test device region 440 multiple times. Figure 4A As shown, over time, the test device region 440 gradually neutralizes, and the resulting voltage contrast image gradually brightens. After a certain period of time, the voltage contrast image 447 may become indistinguishable from the voltage contrast image 435.

[0066] One challenge in detecting this voltage contrast defect is that existing beam tools may not be able to modulate the beam quickly enough during the aforementioned pre-scanning and imaging processes. In existing beam tools, the beam current can be supplied by a source of charged particles (e.g., Figure 2 The charged particle source 202 in the middle) and the ejector hole (e.g., Figure 2 The beam current can be controlled by adjusting the size of the ejector orifice (204). The beam current can be adjusted by adjusting the size of the ejector orifice, the emissivity of the charged particle source, or both. However, such adjustment of the ejector orifice or the charged particle source can be very slow. Moreover, such adjustment cannot be performed during imaging. Due to the inability to provide ultrafast beam current adjustment, existing beam tools may not offer the ability to detect the aforementioned voltage contrast defects in a timely and cost-effective manner.

[0067] Those skilled in the art will understand that the bright and dark appearance of an image can be altered or reversed depending on the actual processing of the test device area or the beam tool settings.

[0068] Figure 4B An exemplary voltage contrast image over a time series consistent with embodiments of this disclosure is shown. Figure 4B This illustrates the pre-scanning and imaging processes in wafer inspection, including a pre-scanning stage 452 and an inspection stage 454. During the pre-scanning stage 452, a beam tool (e.g., Figure 2 The EBI (Electronic Biology Inspection) system (EBI 104) applies electrons to a surface region of a wafer to establish a potential on the surface region (referred to as "charging" for simplicity). A beam tool can charge the surface region using one or more high-current beams and construct a voltage contrast image of the surface region based on its voltage contrast response. During the detection phase 454, the EBI system can construct one or more voltage contrast images of the surface region using one or more low-current beams for scanning. This scanning can be repeated multiple times to produce a series of voltage contrast images that show the voltage contrast response of the surface region in chronological order. The EBI system can detect changes in potential over time on the surface region by comparing multiple voltage contrast images of the same surface region at different times, which can indicate the presence of device defects.

[0069] In some embodiments, the voltage contrast image can be constructed by a multi-beam EBI system. For example, a motorized platform can position the wafer such that the primary charged particle beam (e.g., Figure 2 A first fine beam of the primary charged particle beam (210) can pre-scan the surface region of the wafer at time Tpre1. Then, a motorized platform can position the wafer such that a second fine beam of the primary charged particle beam can pre-scan the same surface region of the wafer at time Tpre2. The first and second fine beams can have high currents. At Tpre1 and Tpre2, the potential of the surface region may be insufficient to display any region with a detectable voltage contrast response, as shown in voltage contrast images 456 and 458 constructed using the first and second fine beams, respectively. At the end of the pre-scan stage 452, a motorized stage can position the wafer such that a third fine beam of the primary charged particle beam (e.g., also having a high current) can pre-scan the surface region at time Tpre3. A voltage contrast image 460 can be constructed using the third fine beam. As shown in voltage contrast image 460, dark voltage contrast (DVC) regions 460a, 460b, and 460c can appear at the end of the pre-scan stage 452.

[0070] After the pre-scanning phase 452, the fourth, fifth, sixth, seventh, eighth, or more fine wavebeams of the primary charged particle beam can scan the same pre-charged surface region at times T1, T2, T3, T4, and T5, respectively. For example... Figure 4B As shown, the beam tool can use the fourth, fifth, sixth, seventh, and eighth fine beams to construct voltage contrast images 462, 464, 466, 468, and 470, respectively. While this example illustrates the use of eight or more fine beams, it is understood that fewer than eight fine beams can be used. For example, it is understood that a single fine beam can capture multiple images of a surface area.

[0071] At time T1, voltage contrast image 462 shows three DVC regions 460a, 460b, and 460c present on the wafer surface. DVC regions 460a, 460b, and 460c can represent the electrical surface potentials established in the device structure within the pre-scanned surface region. At times T2 and T3, voltage contrast images 464 and 466 show DVC regions 464a, 464b, and 464c, which can indicate that the accumulated positive charge remains within the device structure and does not change from times Tpre3 and T1.

[0072] At times T4 and T5, voltage contrast images 468 and 470 show that DVC region 464b has disappeared, while DVC regions 464a and 464c still exist. This indicates that the corresponding device structure for DVC region 464b may have lost accumulated positive charge due to leakage current, thereby causing the surface potential of DVC region 464b to drop to an undetectable level (e.g., due to electrical breakdown). For example, due to defects in the thin device structure (see example...). Figure 4A The positive charge accumulated in the corresponding device structure for the DVC region 464b (insulator structure 470) may have been neutralized.

[0073] The beam tool can adjust the time interval (e.g., the time span between T1 and T2) so that the fine beam of the primary charged particle beam can scan the surface region of the wafer more or less frequently. For example, the time interval can be as short as 5 ns, allowing signal differences from minute voltage contrast defects to be obtained, thereby increasing the sensitivity of voltage contrast wafer detection. Advantageously, the beam tool can compare voltage contrast images 456, 458, 460, 462, 464, 466, 468, 470 or more of the same surface region of the wafer to detect changes in the DVC region over time and identify device structural defects.

[0074] although Figure 4B Three pre-scan voltage contrast images and five detection voltage contrast images obtained from the beam tool are shown, but it can be understood that any number of images can be used to detect device structure defects in a wafer. Furthermore, although Figure 4B The voltage contrast image shown uses a detection mechanism of dark voltage contrast, but it should be understood that bright voltage contrast can also be used when the beam tool is operating in the negative mode. For example, in some embodiments, since the beam tool is operating in the positive mode (e.g., E1 < landing energy < E2), the wafer can have a positive surface potential. In some embodiments, since the beam tool is operating in the negative mode (e.g., landing energy < E1 or landing energy > E2), the wafer can have a negative potential.

[0075] As Figure 4B One challenge during the pre-scan and imaging processes shown is that it is difficult to switch the beam current from a high current to a low current between the pre-scan stage 452 and the detection stage 454. That is, the current switching between Tpre3 and T1 may take a long time. In this case, the surface potential of some regions (e.g., the DVC region 464b) may drop to an undetectable level between Tpre3 and T1, becoming undetectable from the detection stage (e.g., detection stage 454).

[0076] Figure 5 is a schematic diagram showing an exemplary beam tool 500 with an ultrafast beam current regulation ability consistent with embodiments of the present disclosure. The beam tool 500 can be a single-beam tool (e.g., a single-beam SEM) or a multi-beam tool (e.g., Figure 2 the beam tool 104 in ). For example, the beam tool 500 can include a beam shaping unit. The beam shaping unit can focus and form a single electron beam, or can focus and form multiple electron beams (or "fine beams"). For example, the beam shaping unit can be or can include a source conversion unit 212 for forming multiple beams. For the sake of concise illustration, Figure 5 not every component of the beam tool 500 is shown, and components with the same numbers as Figures 1 to 2 represent the same or similar components with the same or similar functions as those described previously, including a controller 109, a charged particle source 202, an injector aperture 204, a bunching lens 206, a primary charged particle beam 210, a deflection scanning unit 226, an objective lens 228, and a wafer 230. It should be noted that the beam tool 500 can include more components, such as a detection system (e.g., including an auxiliary optical system 242 and a detection device 244), an imaging processing system (e.g., an image processing system 290), other components of the main optical system (e.g., the main projection optical system 220), etc. It should also be noted that the beam tool 500 can arrange the components in a different order. For example, the deflection scanning unit 226 can be upstream (as Figure 2 ) or downstream (as Figure 5 ) of the objective lens 228. The present disclosure does not limit the number, type, or arrangement of the components of the beam tool 500.

[0077] The beam tool 500 also includes a emission enhancer 502. The controller 109 can control the emission enhancer 502 and the deflection scanning unit 226 to enable the beam tool 500 to perform ultrafast beam conditioning.

[0078] exist Figure 5 In this embodiment, charged particle source 202 can be configured to emit electrons. In some embodiments, the charged particle source can be a thermionic charged particle source or a cold field emission charged particle source. Emission enhancer 502 can irradiate charged particle source 202 with electromagnetic radiation 504 to promote electron emission. Electromagnetic radiation 504 can be electromagnetic waves with wavelengths, such as radio waves (e.g., long waves, short waves, or microwaves), infrared radiation, visible light, ultraviolet light, X-rays, gamma rays, etc. In some embodiments, electromagnetic radiation 504 can be one or more directional rays of electromagnetic waves (e.g., visible beams). In some embodiments, electromagnetic radiation 504 can be a laser. For example, charged particle source 202 can include a photocathode that can emit more electrons under irradiation by electromagnetic radiation 504 due to photoelectric or photoemission effects. In some embodiments, emission enhancer 502 can be a laser generator configured to irradiate a laser (e.g., an Nd:YAG laser). In some embodiments, the laser can be a free electron laser (FEL). In some embodiments, the laser can be a pulsed laser (e.g., each pulse has a duration of less than 100 nanoseconds, such as a femtosecond laser). For example, a laser generator can be configured to irradiate a photocathode with a laser to increase the electrons emitted by the photocathode. In some embodiments, when the laser generator irradiates the photocathode with a laser, the laser can enhance electron emission over an ultrafast time (e.g., within 100 nanoseconds, such as 10, 20, 40, 60 nanoseconds, etc.). Controller 109 can control emission enhancer 502 to irradiate electromagnetic radiation 504, while simultaneously controlling deflection scanning unit 226 to scan a sample (e.g., wafer 230). For example, controller 109 can control emission enhancer 502 to irradiate electromagnetic radiation 504 during a first cycle of scanning operation of deflection scanning unit 226 and to stop irradiating electromagnetic radiation 504 during a second cycle of scanning operation. The first cycle of scanning operation can occur before or after the second cycle of scanning operation.

[0079] In some embodiments, the deflection scanning unit 226 may guide the primary charged particle beam 210 (or a plurality of fine beams 214, 216 and 218 of the primary charged particle beam 210) to perform frame scanning, wherein a region (e.g., a rectangular region) of the wafer 230 may be scanned line by line. Figure 6This is an illustration of an exemplary frame 600 showing scan lines consistent with embodiments of the present disclosure. Frame 600 may be a region on the surface of wafer 230 and may include multiple scan lines, including lines 602-612. In some embodiments, frame 600 may be scanned in a raster manner. For example, deflection scan unit 226 may guide primary charged particle beam 210 to scan from left to right along line 602. After completing scan line 602, deflection scan unit 226 may guide primary charged particle beam 210 back to the left end and prepare to begin scanning to the right along line 602 (e.g., for repeating a line scan) or line 604 (e.g., for a new line scan). In some embodiments, frame 600 may be scanned in a "head-to-tail" manner. For example, deflection scan unit 226 may guide primary charged particle beam 210 to scan from left to right along line 602. After completing scan line 602, deflection scan unit 226 can prepare to guide the primary charged particle beam 210 to begin a right-to-left scan along line 602 (e.g., for repeated line scans) or line 604 (e.g., for new line scans). It should be noted that this disclosure does not limit the scanning method used for frame scanning.

[0080] In some embodiments, the controller 109 can control the emission enhancer 502 to scan the same row of the sample in the first and second cycles (e.g., Figure 6 (row 602 in the image). That is, the deflection scanning unit 226 can guide the primary charged particle beam 210 onto the scan line 602 twice, the first time with enhanced electron emission from the charged particle source 202, and the second time without enhanced electron emission. In some embodiments, the controller 109 can control the emission enhancer 502 to scan the first row of the sample in a first period and the second row of the sample in a second period. For example, the first row and the second row can be adjacent rows of frames used for scanning, such as... Figure 6 Rows 602 and 604 in the image. That is, the deflection scanning unit 226 can guide the primary charged particle beam 210 to scan the rows of frame 600 in an alternating manner with enhanced electron emission turned on and off.

[0081] In some embodiments, the length of the first period can be substantially equal to the length of the second period. For example, the scanning frequency of the primary charged particle beam 210 can be constant. Figure 7A This is an illustration of an exemplary scanning frequency of a beam tool 500 consistent with embodiments of this disclosure. Figure 7A In the diagram, the horizontal axis represents the timeline including timestamps t1 to t4 and t1', and the vertical axis represents the deflection voltage of the deflection scanning unit 226. Figure 7AThe diagram illustrates the relationship between deflection voltage and time when the scanning mode is raster mode. For example, from t1 to t1', the deflection voltage increases, and the deflection scanning unit 226 can guide the primary charged particle beam 210 to scan along line 602 from left to right. From t1' to t2, the deflection voltage decreases, and the deflection scanning unit 226 can guide the primary charged particle beam 210 back to the left end. When the controller 109 is configured to control the emission intensifier 502 to scan the same row of the sample in the first and second periods (e.g., ...), ... Figure 6 When scanning line 602, during the same time interval between t1' and t2, the deflection scanning unit 226 can guide the primary charged particle beam 210 back to the left end. Between t2 and t3, the deflection scanning unit 226 can guide the primary charged particle beam 210 to scan along line 602 from left to right and move back to the left end. When the controller 109 is configured to control the emission enhancer 502 to scan the first line (e.g., line 602) in the first cycle (e.g., from t1 to t2) and the second line (e.g., line 604) in the second cycle (e.g., from t2 to t3), during the same time interval between t1' and t2, the motorized wafer stage (e.g., motorized wafer stage 280) can move the wafer 230 away by one line to prepare for scanning line 604, and the deflection scanning unit 226 can guide the primary charged particle beam 210 back to the left end. From t2 to t3, the deflection scanning unit 226 can guide the primary charged particle beam 210 to scan from left to right along line 604 and move back to the left end. It should be noted that although the above description assumes scanning from left to right, the actual scanning direction can be along any direction and is not limited to the example described.

[0082] In some embodiments, the deflection scanning unit 226 can guide the primary charged particle beam 210 to perform raster scans with substantially equal periods. For example, (t2-t1), (t3-t2), and (t4-t3) can be substantially equal, wherein the differences between them can be less than or equal to a threshold time difference (e.g., 10, 20, 40, 60 nanoseconds, etc.). Figure 7A As can be shown, the amount of time (e.g., t2-t1) used to scan the first row (e.g., row 602) can be substantially equal to the amount of time (e.g., t3-t2) used to scan the second row (e.g., row 604). In some embodiments, raster scanning can be performed in unequal periods. For example, scanning the first row at a high current can be faster than scanning the second row at a low current, or scanning the first row at a high current can be slower than scanning the second row at a low current.

[0083] Figure 7B This is an illustration of an exemplary illumination frequency of the emission enhancer 502 consistent with embodiments of this disclosure. Figure 7AIn the diagram, the horizontal axis represents the timeline including timestamps t1 to t4, and the vertical axis represents the operating voltage of the emission enhancer 502 (e.g., a pulsed laser generator). From t1 to t2, the operating voltage can be turned on, and the emission enhancer 502 can irradiate the charged particle source 202 with electromagnetic radiation 504. From t2 to t3, the operating voltage can be turned off, and the emission enhancer 502 can stop irradiating the charged particle source 202 with electromagnetic radiation 504. When the emission enhancer 502 irradiates the charged particle source 202 with electromagnetic radiation 504, the primary charged particle beam 210 can have a high current due to photoelectric or photoemission effects. When the emission enhancer 502 stops irradiating the charged particle source 202 with electromagnetic radiation 504, the primary charged particle beam 210 can have a low current.

[0084] In some embodiments, such as Figures 7A to 7B As shown, controller 109 can synchronize the electron emission of emission intensifier 502 with deflection scanning unit 226, such that the electron beam has a high current when it begins (e.g., at t1) scanning the first row (e.g., row 602), and a low current when it begins (e.g., at t2) scanning the second row (e.g., row 604). Regardless of whether the first and second rows are scanned with substantially equal or unequal periods, controller 109 can synchronize the electron emission of emission intensifier 502 with the start time of these periods to irradiate electromagnetic radiation 504 or to stop irradiating electromagnetic radiation 504, such that any row of frame 600 can be scanned entirely by either a high-current beam or a low-current beam.

[0085] In some embodiments, the controller 109 may control the emission intensifier 502 to stop irradiating electromagnetic radiation 504 in the third cycle of the scanning operation, and may control the deflection scanning unit 226 to scan the same line of the sample in the second and third cycles. For example, the controller 109 may control the emission intensifier 502 and the deflection scanning unit 226 to scan line 602 with a high current in the first cycle t1 to t2, and to scan line 602 again with a low current in the second cycle t2 to t3, as... Figures 7A to 7B As shown and described. In the third cycle t3 to t4, controller 109 can control the emission enhancer 502 and the deflection scanning unit 226 to scan line 602 again with a low current (as shown and described). Figures 7A to 7B (Not shown in the image). That is, the controller 109 can control the emission enhancer 502 to stop irradiating electromagnetic radiation 504 during the third cycle t3 to t4. In some embodiments, for the same row, a high-current scan can be followed by multiple low-current scans. From the multiple low-current scans, a series of voltage contrast images for defect detection can be generated, for example... Figure 4B Voltage contrast images 462-470.

[0086] A detection system associated with beam tool 500 (e.g., including auxiliary optics system 242 and detection device 244) can generate a signal in response to receiving electrons (e.g., secondary electrons or backscattered electrons) exiting from a sample (e.g., wafer 230). This signal may include a first type of signal when the primary charged particle beam 210 has a high current, and a second type of signal when the primary charged particle beam 210 has a low current. An imaging processing system associated with beam tool 500 (e.g., image processing system 290) can generate an indication of a test device region of the sample (e.g., [missing information]) based on this signal. Figure 4A An image of the test device region 430 or 440 (in the image). For example, the image processing system can generate a first image (“high current image”) based on a first type of signal and a second image (“low current image”) based on a second type of signal. The first and second images can be voltage contrast images indicating voltage contrast response. Due to different beam currents, the voltage contrast response in the generated voltage contrast images may differ. By comparing the generated voltage contrast images, voltage contrast defects in the test device region can be identified effortlessly.

[0087] For example, such as Figure 6 As shown, controller 109 is configured to control emission enhancer 502 to scan a first row (e.g., row 602) in a first cycle (e.g., from t1 to t2) and a second row (e.g., row 604) in a second cycle (e.g., from t2 to t3). Lines 602, 606, and 610 can be scanned using a high-current beam (indicated by thick lines), while lines 604, 608, and 612 can be scanned using a low-current beam (indicated by thin lines). A detection system can receive exiting electrons (e.g., secondary electrons or backscattered electrons) from lines 602-612 and generate signals that can be classified into at least two types: a first type including signals corresponding to those generated by lines 602, 606, and 610, and a second type including signals corresponding to those generated by lines 604, 608, and 612. An image processing system can receive the first type of signal and generate a high-current image, and receive the second type of signal and generate a low-current image. Figure 6 In this process, the lines of frame 600 are scanned alternately under high and low beam current. Accordingly, the resulting high-current and low-current images can be interlaced scan images.

[0088] In another example, controller 109 can be configured to control emission enhancer 502 to scan the same line (e.g., line 602) in a first period (e.g., from t1 to t2) and a second period (e.g., from t2 to t3). Each line (e.g., lines 602-612 of frame 600) can be scanned first using a high-current beam and second using a low-current beam. A detection system can receive exiting electrons (e.g., secondary electrons or backscattered electrons) from each scan and generate signals that can be classified into at least two types, a first type including signals corresponding to those generated by the high-current beam scan and a second type including signals corresponding to those generated by the low-current beam scan. An image processing system can receive the first type of signal and generate a high-current image, and receive the second type of signal and generate a low-current image. Each line of frame 600 can be scanned under both high and low beam currents before scanning the next line. Accordingly, the generated high-current and low-current images can be progressive scan images. It should be noted that this disclosure does not limit the generated images to interlaced or progressive scan images.

[0089] Due to the ultrafast response of the photoelectric or photoemission effect, the beam current of the primary charged particle beam 210 can be modulated in an ultrafast time (e.g., on the order of nanoseconds) by using the emission intensifier 502 (e.g., a laser generator), which greatly reduces the time required for beam current modulation in existing beam tools. Alternatively, the beam current of the primary charged particle beam 210 can be modulated in a slower time (e.g., on the order of microseconds, milliseconds, etc.). By synchronizing the emission intensifier 502 with the deflection scanning unit 226, the illumination of the electromagnetic radiation 504 can be synchronized with the scanning frequency of the deflection scanning unit 226, wherein each line of the frame scan can be fully scanned under a beam with the same current (e.g., high current or low current). With this scanning method, high-current images and low-current images can be generated in an ultrafast time under ultrafast beam current modulation, greatly improving the detection of voltage contrast defects.

[0090] In some embodiments, the controller 109 can detect voltage contrast defects by comparing high-current and low-current images. For example, the controller 109 can determine the presence of a voltage contrast defect associated with the test device region based on changes in the grayscale levels of the same region indicating the test device region in the high-current and low-current images. If the change exceeds a predetermined threshold, the controller 109 can further determine the presence of a voltage contrast defect based on factors such as... Figure 4A The associated principle determines that the test device area includes potential voltage contrast defects.

[0091] In some embodiments, controller 109 may generate a fused image indicating a region of the test device based on high-current and low-current images for use in other defect detection, such as D2D inspection or chip-to-database (“D2DB”) inspection. For example, controller 109 may implement an exposure fusion technique to generate a high dynamic range (HDR) image using the high-current and low-current images. The HDR image may have a higher dynamic range than the high-current and low-current images. Compared to the high-current or low-current images, the HDR image has a wider range of intensity detail and lower noise, providing more information for defect detection.

[0092] In some embodiments, the emission enhancer 502 can be configured to provide at least two levels of power for the electromagnetic radiation 504. For example, by setting an operating voltage or current, the emission enhancer 502 (e.g., a pulsed laser generator) can provide a first level of power and a second level of power for the electromagnetic radiation 504, where the first level of power is higher than the second level of power. Accordingly, at the first level 504 of electromagnetic radiation power, the charged particle source 202 can be enhanced to emit more electrons than it would under the second level 504 of electromagnetic radiation power. Thus, the primary charged particle beam 210 can have three beam current levels: a first high current corresponding to the first power level, the second power level, and a first high current corresponding to the emission enhancer 502 under off-state conditions, a second high current below the first high current, and a low current, respectively. By providing more levels of beam current, the beam tool 500 can provide more images indicating more variations in the voltage contrast response, thereby providing more information for voltage contrast defect detection. It should be noted that this disclosure does not limit the number of levels that the power emission enhancer 502 can provide.

[0093] Figures 8 to 9 These are flowcharts of exemplary methods 800 and 900 for defect detection in a charged particle detection system according to embodiments of the present disclosure. Methods 800 and 900 can be performed by a charged particle detection system (e.g., Figure 1 EBI system 100 or Figure 5 The controller executes the beam tool 500. The controller may include a circuit system (e.g., memory and processor) programmed to implement methods 800 and 900. For example, the controller may be an internal controller coupled to the charged particle detection system or an external controller (e.g., ...). Figures 1 to 2 and Figure 5 (Controller 109 in the middle). Methods 800 and 900 can be used with... Figures 3 to 7B Connect the operations and steps shown and described.

[0094] exist Figure 8 In step 802, the controller (e.g., Figure 5 The controller 109 in the middle can control the charged particle detection system (e.g., Figure 5 Charged particle sources (e.g., beam tool 500) Figure 5 The charged particle source 202 in the middle emits electrons to form an electron beam (e.g., Figure 5 (The primary charged particle beam 210 in the example). In some embodiments, the charged particle source may be a thermionic charged particle source. In some embodiments, the charged particle source may be a cold field emission charged particle source. In some embodiments, the charged particle source may include a photocathode. The charged particle source may be any component that can be configured to emit electrons. Although the disclosed method utilizes a charged particle source to emit electrons, it will be understood that the method may more generally utilize a charged particle source to emit charged particles.

[0095] In step 804, the controller can control the scanning unit of the charged particle detection system (e.g., Figure 5 The deflection scanning unit 226 in the middle guides the electron beam to perform line-by-line scanning. For example, it can be used to scan a sample (e.g., Figure 5 The wafer 230 in the middle performs a line-by-line scan.

[0096] In step 806, the controller can control the emission enhancer of the charged particle detection system (e.g., Figure 5 The emission enhancer 502 in the electron beam (e.g., in the first scan cycle of the electron beam) is used to enhance the electromagnetic radiation (e.g., Figure 5 Electromagnetic radiation (504) is irradiated onto a charged particle source to enhance electron emission, and the irradiation of the electromagnetic radiation is stopped during a second scan cycle of the electron beam. While the emission enhancer irradiates the charged particle source with electromagnetic radiation, the electron beam may have a first current (referred to as "high current"), and when the emission enhancer stops irradiating the charged particle source with electromagnetic radiation, the electron beam may have a second current (referred to as "low current") lower than the first current. In some embodiments, the emission enhancer may be a laser generator configured to irradiate a laser (e.g., a pulsed laser). For example, a controller may control the laser generator to irradiate the photocathode of the emission enhancer with laser light to increase the electrons emitted by the photocathode. The emission enhancement caused by electromagnetic radiation can be ultrafast. For example, when the laser generator irradiates the photocathode with laser light, the laser can enhance electron emission within 70 nanoseconds.

[0097] In some embodiments, the scanning unit may guide the electron beam to scan the same row of the sample in a first scan cycle and a second scan cycle. In some embodiments, the scanning unit may guide the electron beam to scan a first row of the sample in the first scan cycle and a second row of the sample in the second scan cycle. In some embodiments, the length of the first scan cycle may be substantially equal to the length of the second scan cycle. For example, as... Figure 7AAs shown, the time taken to scan the first row (e.g., row 602) can be (t2-t1), the time taken to scan the second row (e.g., row 604) can be (t3-t2), and (t2-t1) and (t3-t2) can be substantially equal, where the difference between them can be less than or equal to a threshold time difference (e.g., 10, 20, 40, 60 nanoseconds, etc.). Also, as... Figure 7B As shown, from t1 to t2, the electron beam scans the first line, and the emission intensifier irradiates electromagnetic radiation. From t2 to t3, the electron beam scans the second line, and the emission intensifier stops irradiating electromagnetic radiation. It should be noted that the time used to scan the first and second lines may not be equal, and lines scanned under high or low current conditions may have different scan speeds.

[0098] In some embodiments, the controller can synchronize the electron emission of the emission intensifier with the scanning unit, such that the electron beam has a first current when it begins scanning the first row, and a second current when it begins scanning the second row. For example, as... Figures 7A to 7B As shown, the primary charged particle beam 210 has a high current when scanning line 602 begins at timestamp t1, and a low current when scanning line 604 begins at timestamp t2.

[0099] In some embodiments, the controller can control the scanning unit to scan the sample in a progressive scan mode, in which each row of the sample can be scanned twice by a high-current beam and a low-current beam, respectively, before the electron beam is guided to scan the next row. In some embodiments, the controller can control the scanning unit to scan the sample in an interlaced scan mode, wherein each row of the frame can be scanned once alternately by a high-current beam and a low-current beam. For example, the first and second rows can be frames used for scanning (e.g., Figure 6 The adjacent lines of frame 600 in the middle (e.g., Figure 6 (Lines 602 and 604 in the text).

[0100] Figure 9 This is a flowchart of an exemplary method 900 for defect detection in a charged particle detection system, consistent with embodiments of this disclosure. Method 900 may be a standalone method or associated with method 800. For example, a controller may execute method 900 after performing step 806 of method 800.

[0101] In step 902, the controller (e.g., Figure 5 The controller 109 in the system controls the charged particle detection equipment of the charged particle detection system (e.g., Figure 2 The charged particle detection device 244 in the middle, so as to receive the charged particle detection device from the sample (e.g., Figure 5A signal is generated when electrons (e.g., secondary electrons or backscattered electrons) leave the wafer 230. In some embodiments, the charged particle detection device can generate a first type of signal when the electron beam has a first current (e.g., a high current) and a second type of signal when the electron beam has a second current (e.g., a low current). For example, as Figure 6 As shown, when the primary charged particle beam 210 scans at a high current scan line 602, the charged particle detection device can generate a first type of signal. When the primary charged particle beam 210 scans at a low current scan line 604, the charged particle detection device can generate a second type of signal.

[0102] In step 904, the controller can control the image processing system of the charged particle detection system (e.g., Figure 2 The image processing system 290 in the image processing system generates a test device area indicating the sample based on the signal (e.g., Figure 4A An image of the test device region 430 or 440 in the image. In some embodiments, the image processing system may generate a first image based on a first type of signal (e.g., as previously described in...). Figures 5 to 8 The high-current image described in [the previous text]), and a second image is generated based on the second type of signal (e.g., as previously described in [the previous text]). Figure 5-8 (The low current image described in the text). For example, it can be based on... Figure 6 The first image is generated based on the detection signals corresponding to lines 602, 606, and 610 in the diagram, and can be based on... Figure 6 The lines 604, 608, and 612 in the middle or with Figure 6 The detection signals corresponding to the second scans of lines 602, 606, and 610 are used to generate a second image.

[0103] In some embodiments, the image processing system may generate a third image indicating the area of ​​the test device based on the first and second images (e.g., as previously stated in...). Figures 5 to 8 (As described in the fused image). For example, the third image may have a dynamic range that is higher than that of the first image and the second image.

[0104] In some embodiments, the controller may also determine the presence of a voltage contrast defect associated with the test device region based on changes in the grayscale levels of the same region indicating the test device region in the first and second images. If the change exceeds a predetermined threshold, the controller 109 may determine the presence of a voltage contrast defect associated with the test device region based on changes in the grayscale levels of the same region indicating the test device region in the first and second images. Figure 4A The associated principle determines that the test device area includes potential voltage contrast defects.

[0105] The embodiments may be further described using the following terms:

[0106] 1. A charged particle detection system, the system comprising:

[0107] A charged particle source, configured to emit charged particles for scanning a sample; and

[0108] The emission enhancer is configured to irradiate the charged particle source with electromagnetic radiation during the first cycle of the scanning operation of the charged particle detection system to enhance the emission of charged particles, and to stop irradiating the electromagnetic radiation during the second cycle of the scanning operation.

[0109] 2. The system according to Clause 1, wherein the charged particle detection system is configured to scan the same row of the sample in the first and second cycles.

[0110] 3. The system according to Clause 1, wherein the charged particle detection system is configured to scan a first row of the sample in a first period and a second row of the sample in a second period.

[0111] 4. The system according to Clause 3, wherein the first and second rows are adjacent rows of frames used for scanning.

[0112] 5. A system according to any of the foregoing clauses, wherein the length of the first period is substantially equal to the length of the second period.

[0113] 6. The system according to any of the preceding clauses, wherein the charged particle detection system is configured to generate a charged particle beam for scanning a sample, wherein the charged particle beam is configured to have a first current when the emission intensifier irradiates the charged particle source with electromagnetic radiation, and a second current lower than the first current when the emission intensifier stops irradiating the charged particle source with electromagnetic radiation.

[0114] 7. The system according to Clause 6, wherein the charged particle emission of the emission enhancer is configured to synchronize with the scanning operation of the charged particle detection system, such that when the charged particle beam begins scanning the first row, the charged particle beam has a first current, and when the charged particle beam begins scanning the second row, the charged particle beam has a second current.

[0115] 8. A system according to any of the foregoing clauses, wherein the charged particle source is one of a thermionic charged particle source and a cold field emission charged particle source.

[0116] 9. A system according to any of the foregoing clauses, wherein the charged particle source includes a photocathode.

[0117] 10. The system according to Clause 9, wherein the emission enhancer includes a laser generator configured to irradiate a laser.

[0118] 11. The system according to Clause 10, wherein the laser generator is configured to irradiate a photocathode with a laser to increase the number of charged particles emitted by the photocathode.

[0119] 12. The system according to Clause 11, wherein when the laser generator irradiates the photocathode with a laser, the laser enhances the emission of charged particles within 70 nanoseconds.

[0120] 13. The system according to any of the preceding clauses, wherein the emission enhancer is further configured to stop irradiating electromagnetic radiation in the third cycle of the scanning operation, and the charged particle detection system is further configured to scan the same row of the sample in the second and third cycles.

[0121] 14. The system according to any one of clauses 1-13, wherein the charged particle detection system is a single-beam detection system.

[0122] 15. A system according to any one of clauses 1-13, wherein the charged particle detection system is a multi-beam detection system.

[0123] 16. A system according to any of the preceding clauses, wherein the charged particles include electrons.

[0124] 17. A charged particle detection system, the system comprising:

[0125] A charged particle source is configured to emit charged particles;

[0126] An emission enhancer is configured to irradiate a charged particle source with electromagnetic radiation to enhance the emission of charged particles.

[0127] The beamforming unit is configured to form a beam of charged particles using charged particles;

[0128] The scanning unit is configured to guide a beam of charged particles to scan the sample line by line; and

[0129] The controller includes circuitry configured to control the emission enhancer to irradiate electromagnetic radiation during a first scan cycle of the charged particle beam and to stop irradiating electromagnetic radiation during a second scan cycle of the charged particle beam.

[0130] 18. The system according to Clause 17, wherein the charged particle beam is configured to scan the same row of the sample in a first scan cycle and a second scan cycle.

[0131] 19. The system according to Clause 17, wherein the charged particle beam is configured to scan a first row of the sample in a first scan cycle and a second row of the sample in a second scan cycle.

[0132] 20. A system according to Clause 19, wherein the first and second rows are adjacent rows of frames used for scanning.

[0133] 21. A system according to any one of clauses 17-20, wherein the length of the first scan cycle is substantially equal to the length of the second scan cycle.

[0134] 22. A system according to any one of clauses 17-21, wherein the charged particle beam is configured to have a first current when the emission enhancer irradiates the charged particle source with electromagnetic radiation, and a second current lower than the first current when the emission enhancer stops irradiating the charged particle source with electromagnetic radiation.

[0135] 23. A system according to any one of clauses 17-22, wherein the charged particle emission of the emission enhancer is configured to be synchronized with the scanning unit such that the charged particle beam has a first current when it begins scanning the first row, and has a second current when it begins scanning the second row.

[0136] 24. A system according to any one of clauses 17-23, wherein the charged particle source is one of a thermionic charged particle source and a cold field emission charged particle source.

[0137] 25. A system according to any one of clauses 17-24, wherein the charged particle source includes a photocathode.

[0138] 26. The system pursuant to Clause 25, wherein the emission enhancer includes a laser generator configured to irradiate a laser.

[0139] 27. A system according to Clause 26, wherein the laser generator is configured to irradiate a photocathode with a laser to increase the number of charged particles emitted by the photocathode.

[0140] 28. A system pursuant to Clause 27, wherein when a laser generator irradiates a photocathode with a laser, the laser enhances the emission of charged particles within 70 nanoseconds.

[0141] 29. The system pursuant to any one of clauses 17-28 also includes:

[0142] Charged particle detection equipment is configured to generate a signal in response to receiving charged particles exiting a sample; and

[0143] The image processing system is configured to generate an image of the test device area indicating the sample based on the signal.

[0144] 30. The system pursuant to Clause 29, wherein when the charged particle beam has a first current, the signal includes a first type of signal, and when the charged particle beam has a second current, the signal includes a second type of signal.

[0145] 31. The system according to Clause 30, wherein the image processing system is further configured to generate a first image based on a first type of signal and a second image based on a second type of signal.

[0146] 32. The system according to Clause 31, wherein the image processing system is further configured to generate a third image indicating the area of ​​the test device based on the first image and the second image.

[0147] 33. The system according to Clause 32, wherein the third image has a dynamic range that is greater than the dynamic range of the first image and the dynamic range of the second image.

[0148] 34. In a system pursuant to Clause 31, the controller is further configured to:

[0149] Based on the change in gray level of the same area indicating the test device region in the first and second images, it is determined whether there is a voltage contrast defect associated with the test device region.

[0150] 35. A system according to any one of clauses 17-34, wherein the beamforming unit is further configured to form a plurality of charged particle beams using charged particles.

[0151] 36. A system according to any one of clauses 17-34, wherein the beamforming unit is configured to form a plurality of charged particle beams.

[0152] 37. A system according to any one of clauses 17-36, wherein the emission enhancer is further configured to stop irradiating electromagnetic radiation during a third scan cycle of the charged particle beam, and the charged particle beam is further configured to scan the same row of the sample during the second and third scan cycles.

[0153] 38. A system according to any one of clauses 17-37, wherein the charged particles include electrons.

[0154] 39. A method comprising:

[0155] A charged particle source using a charged particle detection system emits charged particles to form a charged particle beam.

[0156] The scanning unit of the charged particle detection system guides the charged particle beam to perform line-by-line scanning; and

[0157] During the first scan cycle of the charged particle beam, the emission enhancer of the charged particle detection system irradiates the charged particle source with electromagnetic radiation to enhance charged particle emission; and

[0158] Electromagnetic radiation is stopped during the second scan cycle of the charged particle beam.

[0159] 40. The method according to Clause 39, wherein guiding the charged particle beam to perform line-by-line scanning includes:

[0160] The charged particle beam is guided to scan the same row of the sample in the first and second scan cycles.

[0161] 41. The method according to Clause 39, wherein guiding the charged particle beam to perform line-by-line scanning includes:

[0162] The charged particle beam is guided to scan the first row of the sample in the first scan cycle and the second row of the sample in the second scan cycle.

[0163] 42. The method according to Clause 41, wherein the first row and the second row are adjacent rows of a frame used for scanning.

[0164] 43. The method according to any one of clauses 39-40, wherein the length of the first scan cycle is substantially equal to the length of the second scan cycle.

[0165] 44. The method according to any one of clauses 39-42, wherein the charged particle beam is configured to have a first current when electromagnetic radiation irradiates the charged particle source, and a second current lower than the first current when electromagnetic radiation stops irradiating the charged particle source.

[0166] 45. The method pursuant to any one of clauses 39-44 further includes:

[0167] The emission enhancer is synchronized with the scanning unit such that when the charged particle beam begins scanning the first row, the charged particle beam has a first current, and when the charged particle beam begins scanning the second row, the charged particle beam has a second current.

[0168] 46. ​​The method according to any one of clauses 39-45, wherein the charged particle source is one of a thermionic charged particle source and a cold field emission charged particle source.

[0169] 47. The method according to any one of clauses 39-46, wherein the charged particle source includes a photocathode.

[0170] 48. The method according to Clause 47, wherein the emission enhancer includes a laser generator configured to irradiate a laser.

[0171] 49. The method pursuant to Clause 48 also includes:

[0172] A laser generator is used to irradiate a photocathode with a laser to increase the number of charged particles emitted by the photocathode.

[0173] 50. The method according to Clause 49, wherein when the laser generator irradiates the photocathode with laser light, the laser enhances the emission of charged particles within 70 nanoseconds.

[0174] 51. The method pursuant to any one of clauses 39-50 further includes:

[0175] When the charged particle detection device receives charged particles emitted from the sample, the charged particle detection device of the charged particle detection system generates a signal; and

[0176] An image processing system using a charged particle detection system generates an image of the test device region of the sample based on the signal.

[0177] 52. The method according to clause 51, wherein generating the signal includes:

[0178] A first type of signal is generated when the charged particle beam has a first current, and a second type of signal is generated when the charged particle beam has a second current.

[0179] 53. The method according to clause 52, wherein generating the image includes:

[0180] A first image is generated based on a first type of signal, and a second image is generated based on a second type of signal.

[0181] 54. The method according to clause 53, wherein generating the image includes:

[0182] A third image is generated based on the first and second images to indicate the area of ​​the test device.

[0183] 55. The method according to Clause 54, wherein the third image has a dynamic range that is higher than that of the first image and the second image.

[0184] 56. The method pursuant to Clause 53 also includes:

[0185] Based on the change in gray level of the same area indicating the test device region in the first and second images, it is determined whether there is a voltage contrast defect associated with the test device region.

[0186] 57. The method pursuant to any one of clauses 39-56 further includes:

[0187] Electromagnetic radiation is stopped during the third scan cycle of the charged particle beam.

[0188] 58. The method according to Clause 55, wherein guiding the charged particle beam to perform line-by-line scanning includes:

[0189] The charged particle beam is guided to scan the same line of the sample in the second and third cycles.

[0190] 59. The method according to any one of clauses 39-58, wherein the charged particle detection system is a single-beam detection system.

[0191] 60. The method according to any one of clauses 39-58, wherein the charged particle detection system is a multi-beam detection system.

[0192] 61. A system according to any one of clauses 39-59, wherein the charged particles include electrons.

[0193] 62. A non-transitory computer-readable medium storing an instruction set executable by at least one processor of a charged particle detection system to cause the system to perform a defect detection method, the method comprising:

[0194] A charged particle source using a charged particle detection system emits charged particles to form a charged particle beam.

[0195] The scanning unit of the charged particle detection system guides the charged particle beam to perform line-by-line scanning; and

[0196] In the first scan cycle of the charged particle beam, the emission enhancer of the charged particle detection system is used to irradiate the charged particle source with electromagnetic radiation to enhance the emission of charged particles, and the irradiation of electromagnetic radiation is stopped in the second scan cycle of the charged particle beam.

[0197] According to embodiments of the present invention, a non-transitory computer-readable medium can be provided, which stores information for use according to the above. Figures 8 to 9 An exemplary flowchart of a controller for defect detection (e.g., Figure 1 and Figure 5 Instructions of the processor of the controller (109). For example, instructions stored in a non-transitory computer-readable medium can be executed by the circuitry of the controller, either in method 800 or 900. Common forms of non-transitory media include, for example, floppy disks, hard disks, solid-state drives, magnetic tape or any other magnetic data storage media, optical disc read-only memory (CD-ROM), any other optical data storage media, any physical media with a perforated pattern, random access memory (RAM), programmable read-only memory (PROM) and erasable programmable read-only memory (EPROM), flash memory—EPROM or any other flash memory, non-volatile random access memory (NVRAM), caches, registers, any other memory chips or cassettes and their networked versions.

[0198] It will be understood that embodiments of this disclosure are not limited to the exact structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. This disclosure has been described in conjunction with various embodiments, and other embodiments of the invention will be apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A charged particle detection system, the system comprising: A charged particle source is configured to emit charged particles for scanning a sample; as well as An emission enhancer is configured to irradiate the charged particle source with electromagnetic radiation during a first cycle of a scanning operation of the charged particle detection system to enhance the emission of charged particles, and to stop irradiating the electromagnetic radiation during a second cycle of the scanning operation. The charged particle detection system is configured to scan the entire first row of the sample frame during the first period and the entire second row of the sample frame during the second period.

2. The system of claim 1, wherein the first row and the second row comprise the same row of the sample in the first period and the second period.

3. The system of claim 1, wherein the first row and the second row comprise different rows of the frame of the sample.

4. The system of claim 3, wherein the first row and the second row are adjacent rows of the sample frame.

5. The system of claim 1, wherein the length of the first period is substantially equal to the length of the second period.

6. The system of claim 1, wherein the charged particle detection system is configured to generate a beam of charged particles for scanning the sample, wherein the charged particle beam is configured to have a first current when the emission intensifier irradiates the charged particle source with electromagnetic radiation, and a second current lower than the first current when the emission intensifier stops irradiating the charged particle source with electromagnetic radiation.

7. The system of claim 6, wherein the charged particle emission of the emission enhancer is configured to synchronize with the scanning operation of the charged particle detection system, such that when the charged particle beam begins scanning the first row, the charged particle beam has the first current, and when the charged particle beam begins scanning the second row, the charged particle beam has the second current.

8. The system according to claim 1, wherein the charged particle source is one of a thermionic charged particle source or a cold field emission charged particle source.

9. The system according to claim 1, wherein the charged particle source comprises a photocathode.

10. The system of claim 9, wherein the emission enhancer includes a laser generator configured to irradiate a laser.

11. The system of claim 10, wherein the laser generator is configured to irradiate the photocathode with the laser to increase the number of charged particles emitted by the photocathode.

12. The system of claim 11, wherein when the laser generator irradiates the photocathode with the laser, the laser enhances the emission of charged particles within 70 nanoseconds.

13. The system of claim 1, wherein the emission enhancer is further configured to stop irradiating the electromagnetic radiation during a third cycle of the scanning operation, and the charged particle detection system is further configured to scan a second row of the sample during the second and third cycles.

14. The system according to claim 1, wherein the charged particle detection system is a single-beam detection system.

15. A non-transitory computer-readable medium storing an instruction set executable by at least one processor of a charged particle detection system to cause the system to perform a method of defect detection, the method comprising: Using the charged particle source of the charged particle detection system, charged particles are emitted to form a charged particle beam. Using the scanning unit of the charged particle detection system, the charged particle beam is guided to perform line-by-line scanning; and In the first scan cycle of the charged particle beam, electromagnetic radiation is irradiated onto the charged particle source using the emission enhancer of the charged particle detection system to enhance the emission of charged particles, and the irradiation of electromagnetic radiation is stopped in the second scan cycle of the charged particle beam. The entire first row of the sample frame is scanned during the first scan cycle, and the entire second row of the sample frame is scanned during the second scan cycle.

Images