System and method for reducing particle contamination in a charged particle beam system

Abstract

A system and method for increasing a gas flow across a substrate in a charged particle beam apparatus are disclosed. The apparatus may include a vacuum chamber comprising: a first gas inlet fluidly connected to a charged particle beam optical element array and configured to guide a first gas flow downstream toward a substrate within the charged particle beam optical element array at a first flow rate; and a second gas inlet configured to guide a second gas flow toward the substrate at a second flow rate. The first and second gas flows are merged to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than either the first or second flow rate.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Application 63 / 608,004, filed December 8, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This article describes charged particle beam devices, and more specifically, systems and methods for mitigating particle contamination during the operation of vacuum systems. Background Technology

[0003] In the manufacturing process of integrated circuits (ICs), both completed and unfinished circuit components are inspected to ensure they are manufactured according to the design and free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes (such as scanning electron microscopy (SEM)) can be employed. As the physical dimensions of IC components continue to shrink and their structures continue to become more complex, particle contamination on critical surfaces poses a significant challenge to improving production volume, yield, and cost efficiency.

[0004] Particle contamination, generated by particle suspension or resuspension on surfaces operating in a vacuum environment, is detrimental to the system and the final product manufactured using such a system. For example, a stable high-voltage environment is desirable for the proper operation of SEM inspection equipment. The stability of the electron source can be affected by the presence of pre-existing or internally generated contaminants or unwanted particles. Contaminants can cause electrostatic discharge (ESD), which can interfere with system voltage output and electric field strength and may generate contaminants, further deteriorating system stability. Besides ESD, particulate contaminants can cause other problems including aperture blockage, lens damage, and wafer yield loss. Summary of the Invention

[0005] Embodiments of this disclosure provide systems and methods for mitigating particle contamination in charged particle beam systems during vent-up cycles. One aspect of this disclosure relates to a charged particle beam apparatus including a vacuum chamber. The vacuum chamber may include: a first gas inlet fluidly connected to a column of charged particle beam optics and configured to guide a first gas flow downstream toward a substrate in the column of charged particle beam optics at a first flow rate; and a second gas inlet configured to guide a second gas flow toward the substrate at a second flow rate. The first gas flow and the second gas flow are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than either the first or the second flow rate.

[0006] Another aspect of this disclosure relates to a method for increasing a gas flow across a substrate in a charged particle beam apparatus. The method may include causing a first gas flow to flow downstream toward a substrate in a vacuum chamber at a first flow rate; and causing a second gas flow to flow toward the substrate at a second flow rate, wherein the first gas flow and the second gas flow merge to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than either the first or the second flow rate.

[0007] Another aspect of this disclosure relates to a charged particle beam apparatus, comprising: a first gas inlet fluidly connected to a charged particle beam optical element array and configured to guide a first gas flow downstream toward a substrate within the charged particle beam optical element array at a first flow rate; a second gas inlet located upstream of the substrate and configured to guide a second gas flow toward the substrate at a second flow rate; and a third gas inlet located downstream of the substrate and configured to guide a third gas flow toward the substrate at a third flow rate. The first, second, and third gas flows are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than the first, second, or third flow rate.

[0008] Another aspect of this disclosure relates to a non-transitory computer-readable medium storing an instruction set executable by one or more processors of a charged particle beam apparatus to cause the charged particle beam apparatus to perform a method of increasing a gas flow across a substrate within the charged particle beam apparatus. The method may include: causing a first gas flow to flow downstream in a vacuum chamber toward a substrate at a first flow rate; and causing a second gas flow to flow toward the substrate at a second flow rate, wherein the first gas flow and the second gas flow merge to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than either the first or the second flow rate.

[0009] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit the claimed disclosed embodiments. Attached Figure Description

[0010] The above and other aspects of this disclosure will become more apparent from the description of exemplary embodiments in conjunction with the accompanying drawings.

[0011] Figure 1A This is a schematic representation of an exemplary charged particle beam inspection system according to an embodiment of the present disclosure.

[0012] Figure 1B The illustrations are based on embodiments of this disclosure. Figure 1A A schematic diagram of an exemplary wafer loading sequence in a charged particle beam inspection system.

[0013] Figure 2 The illustrations provided are schematic diagrams of exemplary charged particle beam tools according to embodiments of the present disclosure. The exemplary charged particle beam tool may be... Figure 1A This is part of an exemplary charged particle beam inspection system.

[0014] Figure 3A The illustrations are schematic diagrams of portions of an exemplary charged particle beam device and a gas flow during vacuum breaking, according to embodiments of the present disclosure.

[0015] Figure 3B The illustrations are based on embodiments of this disclosure. Figure 3A A schematic illustration of an exemplary protective gas blanket formed on a critical surface in a charged particle beam device.

[0016] Figure 4A The illustration is a schematic diagram of a portion of a charged particle beam apparatus including an exemplary purge ring, according to an embodiment of the present disclosure.

[0017] Figure 4B According to embodiments of this disclosure Figure 4A A schematic top view of the purge ring.

[0018] Figure 5A The illustration is a schematic diagram of a portion of a charged particle beam apparatus including an exemplary purge ring, according to an embodiment of the present disclosure.

[0019] Figure 5B The illustration shows a portion of a charged particle beam device according to an embodiment of the present disclosure along... Figure 5A Top view of section A-Aʹ.

[0020] Figure 5C This is a schematic diagram of a portion of a charged particle beam apparatus including two purge rings according to an embodiment of the present disclosure.

[0021] Figure 6A This is a schematic diagram of a portion of a charged particle beam apparatus including an exemplary purge ring, according to an embodiment of the present disclosure.

[0022] Figure 6B The illustration shows a portion of a charged particle beam device according to an embodiment of the present disclosure along... Figure 6A Top view of section A-Aʹ.

[0023] Figure 6C This is a schematic diagram of a portion of a charged particle beam apparatus including two purge rings according to an embodiment of the present disclosure.

[0024] Figure 7This is a flowchart illustrating an exemplary vacuum-breaking sequence of a charged particle beam device including one or more purge rings according to an embodiment of the present disclosure.

[0025] Figure 8 This is a flowchart illustrating an exemplary method for increasing a gas flow across a substrate in a charged particle beam apparatus according to an embodiment of the present disclosure. Detailed Implementation

[0026] Reference will now be made specifically to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which, unless otherwise indicated, the same reference numerals in different drawings denote the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations of the invention. Rather, they are merely examples of apparatuses, systems, and methods according to aspects relating to the subject matter that may be recited in the appended claims. Without limiting the scope of this disclosure, some embodiments may be described in the context of providing detection systems and methods in systems utilizing electron beams (“e-beams”). However, this disclosure is not limited thereto. Other types of charged particle beams (e.g., including protons, ions, muons, or any other charged particles) may be applied similarly. Furthermore, other imaging systems, such as optical imaging, photoelectric detection, X-ray detection, extreme ultraviolet inspection, deep ultraviolet inspection, etc., may be used.

[0027] Electronic devices are constructed from circuits formed on a silicon wafer called a substrate. Semiconductor materials can include, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), or silicon germanium (SiGe). Many circuits can be formed together on the same silicon wafer and are called integrated circuits (ICs). With technological advancements, the size of these circuits has been significantly reduced, allowing even more circuits to be integrated onto the substrate. For example, the IC chip in a smartphone can be as small as a fingernail, yet can include more than 2 billion transistors, each smaller than one-thousandth the width of a human hair.

[0028] Manufacturing these tiny ICs is a complex, time-consuming, and expensive process, typically involving hundreds of individual steps. Even a mistake in one step can result in a defective IC that renders it useless. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs manufactured in the process, i.e., to improve the overall yield of the process.

[0029] A component of improving 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 it at various stages of chip circuit structure formation. Inspection can be performed using a scanning electron microscope (SEM). SEM can be used to image these extremely small structures, essentially taking "photographs" of them. The images can be used to determine if the structure is formed correctly and in the correct location. If a defect is found, the process can be adjusted, making it less likely for the defect to recur. Defects can be generated at various stages of semiconductor processing. For the reasons mentioned above, accurate, efficient, and early defect detection is crucial. To increase throughput (e.g., the number of samples processed per hour), inspection as quickly as possible is desirable.

[0030] 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 Sequencing Electron Microscope (SEM) takes a "picture" by receiving and recording the energy or quantity of electrons reflected or emitted from a structure. Before taking such a "picture," an electron beam can be applied to the structure, and as electrons are reflected or emitted ("emission") from the structure, the SEM's detector receives and records the energy or quantity of these electrons to generate an image. To take such "pictures," some SEMs use a single electron beam (called a "single-beam SEM"), while others use multiple electron beams (called a "multi-beam SEM") to take multiple "pictures" of the wafer. By using multiple electron beams, the SEM can apply more electron beams to the structure to obtain these multiple "pictures," resulting in more electrons being emitted from the structure. Therefore, the detector can receive more emitted electrons simultaneously and generate images of the wafer's structure with greater efficiency and faster speed.

[0031] With continued miniaturization and increasing design and process complexity, the demand for semiconductor manufacturing process control is growing. This demand requires not only advanced methodologies and more capable tools, but also additional on-wafer, inter-wafer, and cross-batch sampling to capture process deviations and / or variations in process characteristics. Integrated circuits (ICs) are expected to perform more complex tasks with greater efficiency and faster processing speeds at each new process technology node, requiring complex device architectures to accommodate higher densities of active devices. In the context of the semiconductor device industry (e.g., "10 nm"), a "technology node" refers to the smallest dimension of a feature (such as the gate of a transistor or half-pitch of a metal line) that can be repeatedly printed on a semiconductor wafer.

[0032] As the size of features fabricated on semiconductor wafers shrinks, particle contamination in charged particle beam systems presents a greater challenge. In some cases, contaminants or unwanted particles may be larger than the entire device itself, and the suspension of such particles on the wafer during fabrication can render the device unusable. In other cases, particle contamination can also affect the performance and stability of critical components of the device, such as, but not limited to, the electron source in an electron beam apparatus or the mask in a lithography apparatus. As an example, a stable high-voltage environment is desirable for the proper operation of an electron source in a SEM configured to generate electrons or electron beams to inspect wafer surfaces. Any disturbance to the electric field strength or system voltage (such as due to contamination at the tip of the electron source) can affect the output of the electron source, thereby affecting the quality, throughput, or secondary electron images generated by the SEM. Furthermore, particulate contamination near high-field regions can induce arcing, which can damage or degrade the SEM system or the samples being inspected by the SEM system.

[0033] Whether particles are pre-existing in the system due to a lack of proper and regular cleaning procedures, or generated by internal sources, they can pose numerous challenges, such as electric arcing, dielectric breakdown, or electrostatic discharge (ESD), depending on the type of particle, its location, or both. Electric arcing can occur when conductive contaminants (e.g., moisture, conductive dust, debris) form low-resistance paths between surfaces with different voltages (e.g., in electrodes of an SEM). The ionized air created by the arc can conduct extremely high currents, leading to electrical failures, mechanical damage, or both. In some cases, high currents can generate excessive localized heat to melt the electrodes and release particles or debris, and may prolong the arc due to cascading contamination effects. In addition to pre-existing particles in the vacuum system, the pump-down and vent-up mechanisms of the vacuum chamber can also introduce particulate contamination. Changes in gas flow and pressure can lead to particulate contamination, which can take the form of suspended particles from the incoming gas flow or resuspended particles from pre-existing particles due to strong turbulent inflows.

[0034] One of several ways to protect critical surfaces, such as wafer surfaces, from particle suspension during a system vacuum breaking procedure may include placing the substrate (e.g., the wafer) below an electron optics array (i.e., a SEM module). Gas flow through the SEM module can form a protective gas cover, also referred to herein as a gas curtain, over the wafer surface. This protective gas cover can deflect incoming airborne contaminants or particles, thus protecting the wafer surface from particle suspension. However, such venting designs can encounter several challenges. The effectiveness of the formed protective gas cover can be determined based on the flow rate or velocity of the venting gas configured to form the gas cover. While a stronger gas flow through the electron optics array of the SEM may contribute to a stronger gas cover, the turbulence of the strong gas flow can cause pre-existing particles to be resuspended on surfaces within the electron optics array, on the wafer surface, or both, which can be detrimental to process and product yield. Therefore, it is desirable to provide a system and method for vacuum breaking a vacuum system that can provide a robust protective gas cover over critical surfaces while mitigating the risk of particle resuspension or contamination within the electron optics array.

[0035] Some aspects of this disclosure address some of the aforementioned challenges by providing an additional exhaust gas source to allow the formation of a robust protective gas coating over the wafer surface while preventing particle contamination within the electron optics array of a vacuum system such as a SEM, caused by the resuspension of pre-existing particles. In some embodiments, the system may include: a first gas flow configured to cause a vacuum break in the electron optics array; and a second gas flow configured to form a protective gas coating over the top surface of the wafer. The first gas flow may be directed downstream through the electron optics array, and the second gas flow may be directed downstream or upstream toward the top surface of the wafer. The two gas flows may be combined to form a lateral gas flow over the top surface of the wafer, and the lateral gas flow may be directed radially outward to push the gas toward the edge of the substrate (or critical surface). The velocity of the combined lateral gas flow may be higher than the individual velocity of the first or second gas flow. The second gas flow may be configured to flow through a purge ring mounted within a shield (e.g., a high-voltage shield) above the substrate (e.g., the wafer) or within a substrate holder below the substrate. The flow rate or velocity of the first gas flow and the second gas flow can be controlled independently by a controller configured to regulate the gas flow through a gas flow control mechanism.

[0036] The objectives and advantages of this disclosure can be achieved through the elements and combinations set forth in the embodiments discussed herein. However, the embodiments of this disclosure are not necessarily required to achieve such exemplary objectives or advantages, and some embodiments may not achieve any of the stated objectives or advantages.

[0037] The relative dimensions of the components in the accompanying drawings may be exaggerated for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and differences are described only with respect to individual embodiments. As used herein, unless specifically stated otherwise, the term "or" covers all possible combinations unless impractical. For example, if a stated component includes A or B, then unless specifically stated otherwise or impractical, the component may include A, or B, or A and B. As a second example, if a stated component includes A, B, or C, then unless specifically stated otherwise 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, B, and C. Expressions such as "at least one of..." do not necessarily modify the entire following list, nor do they necessarily modify each member of the list, such that "at least one of A, B, and C" should be understood to include only one of A, only one of B, only one of C, or any combination of A, B, and C. The phrase “one of A and B” or “either of A and B” should be interpreted in the broadest sense to include either A or B.

[0038] Now for reference Figure 1A , Figure 1A An exemplary charged particle beam inspection system 100 (e.g., an electron beam inspection (EBI) system) according to an embodiment of the present disclosure is illustrated. The EBI system 100 can be used for imaging or measurement. Figure 1A As shown, the charged particle beam inspection system 100 includes a main chamber 10, a loading and locking chamber 20, an electron beam tool 40, and an equipment front-end module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. Although the description and figures are directed to electron beams, it should be understood that the embodiments are not intended to limit this disclosure to specific charged particles.

[0039] EFEM 30 includes a first loading port 30a and a second loading port 30b. EFEM 30 may include additional loading ports(s). The first loading port 30a and the second loading port 30b receive a front-opening standard wafer cassette (FOUP), which contains a wafer (e.g., a semiconductor wafer or a wafer made of other materials(s)) or a sample to be inspected (wafers and samples are collectively referred to as “wafers” hereinafter). In some embodiments, a semiconductor wafer may be referred to as a substrate. One or more robotic arms (not shown) in EFEM 30 transport the wafer to a loading locking chamber 20.

[0040] A loading / locking chamber 20 is connected to a loading / locking vacuum pump system (not shown), which removes gas molecules from the loading / locking chamber 20 to achieve a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the wafer from the loading / locking chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules from the main chamber 10 to achieve a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single-beam inspection tool.

[0041] The controller 50 can be electrically connected to the electron beam tool 40 and can also be electrically connected to other components. The controller 50 can be a computer configured to perform various controls of the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is... Figure 1A The controller 50 is shown outside the structure including the main chamber 10, the loading and locking chamber 20 and the EFEM 30, but it should be understood that the controller 50 may be part of the structure.

[0042] In some embodiments, controller 50 may include one or more processors (not shown). A processor may be a general-purpose or special-purpose electronic device capable of manipulating or processing information. For example, a processor may include any number 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), neural network processing units (NPUs), and any combination of any type of circuitry capable of data processing. A processor may also be a virtual processor, including one or more processors distributed across multiple machines or devices coupled via a network.

[0043] In some embodiments, controller 50 may also include one or more memories (not shown). The memory can be a general-purpose or special-purpose electronic device capable of storing code and data accessible by a processor (e.g., via a bus). For example, the memory may include any number of random access memory (RAM), read-only memory (ROM), optical discs, magnetic disks, hard disks, solid-state drives, flash memory drives, secure digital cards (SD cards), memory sticks, compact flash memory (CF cards), or any combination of any type of storage device. The code may include an operating system (OS) and one or more applications (or "apps") for a specific task. The memory may also be virtual memory, including one or more memories distributed across multiple machines or devices coupled via a network.

[0044] While this disclosure provides an example of a main chamber 10 housing an electron beam inspection system, it should be noted that this disclosure is not limited, in its broadest sense, to chambers housing electron beam inspection systems. Rather, it should be understood that the foregoing principles can also be applied to other chambers.

[0045] Now for reference Figure 1B , Figure 1B The illustration shows an embodiment according to the present disclosure. Figure 1A This is a schematic diagram of an exemplary wafer loading sequence in a charged particle beam inspection system 100. In some embodiments, the charged particle beam inspection system 100 may include a robotic arm 11 located in an EFEM 30 and a robotic arm 12 located in a main chamber 10. In some embodiments, the EFEM 30 may also include a pre-aligner 60 configured to accurately position the wafer before it is transported to the loading locking chamber 20.

[0046] In some embodiments, for example, the first loading port 30a and the second loading port 30b can receive a wafer FOUP containing the wafer. The robotic arm 11 in the EFEM 30 can transport the wafer from either loading port to a pre-aligner 60 for positioning assistance. The pre-aligner 60 can position the wafer using mechanical or optical alignment methods. After pre-alignment, the robotic arm 11 can transport the wafer to the loading locking chamber 20.

[0047] After the wafer is transported to the loading and locking chamber 20, a loading and locking vacuum pump (not shown) removes gas molecules from the loading and locking chamber 20 to achieve a first pressure below atmospheric pressure. Once the first pressure is reached, the robotic arm 12 can transport the wafer from the loading and locking chamber 20 to the wafer stage 80 of the electron beam tool 40 in the main chamber 10. The main chamber 10 can be connected to a main chamber vacuum pump system (not shown), which removes gas molecules from the main chamber 10 to achieve a second pressure below the first pressure. Once the second pressure is reached, the wafer can be inspected by the electron beam tool.

[0048] In some embodiments, the main chamber 10 may include a parking station 70 configured to temporarily store wafers prior to inspection. For example, when the inspection of a first wafer is complete, the first wafer can be unloaded from the wafer stage 80, and then the robotic arm 12 can transport a second wafer from the parking station 70 to the wafer stage 80. Subsequently, the robotic arm 12 can transport a third wafer from the loading locking chamber 20 to the parking station 70 for temporary storage until the inspection of the second wafer is completed.

[0049] In some embodiments, to improve the overall throughput of the inspection system, the charged particle beam inspection system 100 may perform thermal conditioning of the wafer before loading it onto the wafer stage 80. This pre-inspection thermal conditioning may occur in the pre-aligner 60, the loading locking chamber 20, the parking station 70, or any other location suitable for thermal conditioning of the wafer before moving it onto the wafer stage 80.

[0050] Now for reference Figure 2 , Figure 2 The illustration shows a schematic diagram according to an embodiment of the present disclosure, illustrating an exemplary configuration of an electron beam tool 40, which may be... Figure 1AThis is a part of an exemplary charged particle beam inspection system 100. An electron beam tool 40 (also referred to herein as apparatus 40) may include an electron emitter, which may include a cathode 203, an extractor electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 may also include a coulomb aperture array 224, a converging lens 226, a beam-limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. The electron beam tool 40 may also include a sample holder 236 supported by a motorized stage 234 to hold the sample 250 to be inspected. It should be understood that other relevant components may be added or omitted as needed.

[0051] In some embodiments, the electron emitter may include a cathode 203 and an anode 222, wherein primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 204, which forms a primary beam cross 202. The primary electron beam 204 can be considered as being emitted from the primary beam cross 202.

[0052] In some embodiments, the electron emitter, converging lens 226, objective lens assembly 232, beam-limiting aperture array 235, and electron detector 244 may be aligned with the primary optical axis 201 of the device 40. In some embodiments, the electron detector 244 may be positioned outside the primary optical axis 201 along a secondary optical axis (not shown).

[0053] In some embodiments, objective assembly 232 may include a modified oscillating decelerated immersion objective (SORIL) comprising a pole piece 232a, a control electrode 232b, a beam manipulator assembly (including deflectors 240a, 240b, 240d, and 240e), and an excitation coil 232d. During general imaging, a primary electron beam 204 emanating from the tip of cathode 203 is accelerated by an accelerating voltage applied to anode 222. A portion of the primary electron beam 204 passes through the apertures of gun aperture 220 and coulomb aperture array 224 and is focused by converging lens 226, thereby passing completely or partially through the aperture of beam-limiting aperture array 235. Electrons passing through the aperture of beam-limiting aperture array 235 can be focused by the modified SORIL lens to form probe spots on the surface of sample 250 and deflected by one or more deflectors of the beam manipulator assembly to scan the surface of sample 250. Secondary electrons emitted from the sample surface can be collected by electron detector 244 to form an image of the scanned region of interest.

[0054] In objective assembly 232, excitation coil 232d and electrode 232a can generate a magnetic field. A portion of sample 250 scanned by primary electron beam 204 can be immersed in the magnetic field and charged, which in turn creates an electric field. This electric field can reduce the energy of the primary electron beam 204 impacting the surface of and near sample 250. Control electrode 232b, electrically isolated from electrode 232a, can control, for example, the electric field above and over sample 250 to reduce aberrations in objective assembly 232 and control the focusing of the signal electron beam to achieve high detection efficiency, or to avoid arcing to protect the sample. One or more deflectors in the beam manipulator assembly can deflect the primary electron beam 204 to facilitate beam scanning on sample 250. For example, during scanning, deflectors 240a, 240b, 240d, and 240e can be controlled to deflect the primary electron beam 204 to different locations on the top surface of sample 250 at different time points, thereby providing data for image reconstruction of different portions of sample 250. It should be noted that the order of 240a-240e may differ in different embodiments.

[0055] Backscattered electrons (BSE) and secondary electrons (SE) can be emitted from a portion of the sample 250 upon receiving the primary electron beam 204. A beam splitter 240c can guide the secondary or scattered electron beam(s), including backscattered and secondary electrons, to the sensor surface of the electron detector 244. The detected secondary electron beam can form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 can generate a signal (e.g., voltage, current) representing the intensity of the received secondary electron beam spot and provide the signal to a processing system, such as a controller 50. The intensity of the secondary electron beam or backscattered electron beam and the resulting secondary electron beam spot can vary depending on the external or internal structure of the sample 250. Furthermore, as described above, the primary electron beam 204 can be deflected to different positions on the top surface of the sample 250 to generate secondary or scattered electron beams (and the resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot to the position of the sample 250, the processing system can reconstruct an image reflecting the internal or external structure of the sample 250.

[0056] In some embodiments, controller 50 may include an image processing system comprising an image acquirer (not shown) and a storage device (not shown). The image acquirer may include one or more processors. For example, the image acquirer may include a computer, server, mainframe, terminal, personal computer, any kind of mobile computing device, or a combination thereof. The image acquirer may be communicatively coupled to the electronic detector 244 of device 40 via a medium such as an electrical conductor, fiber optic cable, portable storage medium, IR, Bluetooth, Internet, wireless network, radio, or a combination thereof. In some embodiments, the image acquirer may receive signals from the electronic detector 244 and may construct an image. The image acquirer may thus acquire an image of a region of sample 250. The image acquirer may also perform various post-processing functions, such as generating contours, overlaying indicators on the acquired image, etc. The image acquirer may be configured to perform adjustments such as brightness and contrast on the acquired image. In some embodiments, the storage device may be a storage medium such as a hard disk, flash memory drive, cloud storage device, random access memory (RAM), other types of computer-readable storage, etc. The storage device can be coupled to the image acquisition device and can be used to save the scanned raw image data as the original image, as well as to save the post-processed image.

[0057] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons and backscattered electrons. The electron distribution data collected during the detection time window, combined with corresponding scan path data of the primary electron beam 204 incident on the surface of the sample (e.g., a wafer), can be used to reconstruct an image of the structure of the wafer under inspection. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 250, and thereby can be used to reveal any defects that may be present in the wafer.

[0058] In some embodiments, the controller 50 may control the motorized stage 234 to move the sample 250 during the examination. In some embodiments, the controller 50 may enable the motorized stage 234 to continuously move the sample 250 at a constant speed in one direction. In other embodiments, the controller 50 may, depending on the steps of the scanning process, enable the motorized stage 234 to change the speed of movement of the sample 250 over time.

[0059] As is known in the art, the interaction of charged particles (such as electrons in a primary electron beam) with a sample can generate signal electrons, which contain compositional and morphological information related to the region of the sample being probed. Secondary electrons (SEs) can be identified as signal electrons with low emission energy, and backscattered electrons (BSEs) can be identified as signal electrons with higher emission energy. Due to their low emission energy, the objective lens assembly can guide the SEs along the electron path and focus them onto the detection surface of an in-microscope electron detector placed inside the SEM column. BSEs traveling along the electron path can also be detected by the in-microscope electron detector. In some cases, BSEs with large emission angles may, however, be detected using an additional electron detector (such as a backscattered electron detector), or remain undetected, resulting in the loss of sample information needed to examine the sample or measure critical dimensions.

[0060] The detection and inspection of defects in semiconductor manufacturing processes (such as buried particles during photolithography, metal deposition, dry etching, or wet etching) can benefit from the inspection of surface features and the compositional analysis of defect particles. In such scenarios, information obtained from secondary electron detectors and backscattered electron detectors may be desirable for users in order to identify (multiple) defects, analyze the composition of (multiple) defects, and adjust process parameters based on the obtained information.

[0061] Now for reference Figure 3A , Figure 3A This is a schematic diagram of a portion of an exemplary charged particle beam tool 300 according to an embodiment of the present disclosure. The charged particle beam tool 300 (also referred to as apparatus 300) may include a charged particle source, such as an electron source, configured to emit primary electrons from a cathode and extracted using extractor electrodes to form a primary electron beam along a primary optical axis. Apparatus 300 may also include an anode (not shown for simplicity), a converging lens, a beam-limiting aperture array, a signal electron detector, a compound objective, a scanning deflection unit including a primary electron beam deflector, and control electrodes. In the context of this disclosure, the signal electron detector may be an in-lens electron detector located within an electron optics array 310 and may be arranged rotationally symmetrically about the primary optical axis. In some embodiments, the signal electron detector(s) may be referred to as a through-lens detector, an immersion lens detector, an upper detector, or a secondary electron detector. It should be understood that components may be added, omitted, or reordered as needed.

[0062] The electron source (not shown) may include: a thermionic source configured to emit electrons when supplied with thermal energy to overcome the source's operating function; a field emission source configured to emit electrons when exposed to a large electrostatic field, etc. In the case of a field emission source, the electron source may be electrically connected to a controller (such as...). Figure 1A The controller 50 is configured to apply and adjust a voltage signal based on desired landing energy, sample analysis, source characteristics, etc. The extractor electrode can be configured to extract, for example, electrons emitted from a field emission gun or to accelerate electrons to form a primary electron beam that forms a virtual or real primary beam cross (not shown) along the primary optical axis. The primary electron beam can be considered as being emitted from the primary beam cross. In some embodiments, the controller 50 can be configured to apply a voltage signal to the extractor electrode and adjust the voltage signal to extract electrons generated from the electron source or to accelerate electrons. The amplitude of the voltage signal applied to the extractor electrode may differ from the amplitude of the voltage signal applied to the cathode. In some embodiments, the difference between the amplitudes of the voltage signals applied to the extractor electrode and the cathode can be configured to accelerate electrons downstream along the primary optical axis while maintaining the stability of the electron source.

[0063] Device 300 may include vacuum chambers 301 and 302. Vacuum chamber 301 may include an array of electro-optical devices 310. Vacuum chamber 302 may include a control electrode 320, a shield 330, a substrate 340 placed on a substrate holder 350, and a substrate stage 360. It should be understood that, although not illustrated, vacuum chambers 301 and 302 may include more elements. It should also be understood that, in some embodiments, device 300 may include a single vacuum chamber instead of two vacuum chambers.

[0064] Electron optics array 310, also known as charged particle beam optics array, may include charged particle sources (such as electron sources) that may be sensitive to particle contamination, multiple aperture arrays, electromagnetic or electrostatic lens arrays, converging lenses, objective lens assemblies, micro-astigmatism reducers, micro-deflectors, charged particle detectors, etc. In the context of this disclosure, components or surfaces sensitive to particulate contamination are referred to as “critical” components or surfaces. As an example, the control electrode 320, substrate 340, substrate holder 350, and internal surfaces of electron optics array 310 may include critical components or critical surfaces. A component or surface may be “critical” if its function is affected by the presence of contaminants (such as, but not limited to, dust particles, debris, or any airborne contaminants).

[0065] As used in the context of this disclosure, "downstream" refers to a direction along the path of the primary electron beam from the electron source toward the substrate 340. Reference is made to charged particle beam devices (e.g., Figure 3AIn the device 300), the positioning of elements, "downstream" can refer to the position of an element located below or after another element along the path of the primary electron beam from the electron source, and "immediately downstream" refers to the position of a second element located below or after the first element along the path of the primary electron beam such that there are no other active elements between the first and second elements. For example, as... Figure 3A As shown, substrate 340 can be positioned immediately downstream of shield 330 or control electrode 320 such that no other optical or electro-optical elements are placed between substrate 340 and shield 330. As used in the context of this disclosure, "upstream" can refer to the location of an element above or before another element along the path of the primary electron beam from the electron source, and "immediately upstream" refers to the location of a second element above or before the first element along the path of the primary electron beam such that no other active elements are placed between the first and second elements. As an example, control electrode 320 or shield 330 can be placed immediately upstream of substrate 340. As used herein, "active element" can refer to any element or component whose presence can modify the electromagnetic field between the first and second elements by generating an electric, magnetic, or electromagnetic field.

[0066] Apparatus 300 may include a gas inlet 305, which is fluidly connected to a vacuum chamber 301 or an electron-optical array 310. The gas inlet 305 may be configured to introduce exhaust gas 315 into the vacuum chamber 301 or the electron-optical array 310 to break the vacuum in the electron-optical array 310 from a vacuum environment to atmospheric pressure. During operation of a charged particle beam apparatus (e.g., SEM) for inspection or measurement purposes, the electron-optical array 310 or the vacuum chamber 301 may be maintained in a vacuum environment. Breaking the vacuum in a system or vacuum chamber (e.g., an electron-optical array or SEM module) refers to the process of restoring the internal pressure of the chamber from a vacuum or near-vacuum to atmospheric pressure. Evacuating the system or vacuum chamber refers to the process of reducing the internal pressure of the system or vacuum chamber from atmospheric pressure to a vacuum operating state.

[0067] Typically, the vacuum breaking process of the entire system (e.g., device 300) includes vacuum breaking of the electron optics array 310 (placed in vacuum chamber 301) and vacuum breaking of vacuum chamber 302. Vacuum breaking of the electron optics array 310 (also referred to here as the SEM module) involves injecting ultra-clean dry air (XCDA) or nitrogen (N2) into the electron optics array 310 via gas inlet 305. The exhaust gas flows downstream (e.g., ...). Figure 3A(Indicated by the dashed arrow) Proceeding toward vacuum chamber 302, which is fluidly connected to vacuum chamber 301. Vacuum chamber 302 may include a recessed substrate stage 360 ​​and a substrate holder 350 for holding substrate 340. Although not shown, vacuum chamber 302 may also include an intake mechanism configured to inject exhaust gas into vacuum chamber 302. The flow of exhaust gas 315 in the electron optical device array 310 or vacuum chamber 301 serves two functions: breaking the vacuum in electron optical device array 310 and generating overpressure in electron optical device array 310. Overpressure prevents contaminated gas from flowing into electron optical device array 310 and minimizes the risk of critical components in electron optical device array 310 being exposed to contaminants or airborne particles. In the context of this disclosure, “overpressure” in the system refers to a positive internal pressure above atmospheric pressure, or a higher internal pressure of the system relative to the pressure of other connected systems.

[0068] Particle contamination is one of the major challenges facing the semiconductor industry, and this challenge becomes increasingly severe as technology nodes shrink. Unintentionally present particles or contaminants can become a hazard in equipment manufacturing, equipment inspection, wafer metrology, and other aspects of semiconductor equipment manufacturing. Particles on critical surfaces, whether pre-existing in the system due to insufficient cleaning procedures or generated by internal sources or processes, can lead to functional impairment of the system or the equipment produced using that system. For example, a stable high-voltage environment is desirable for efficient operation of electron sources in SEMs, and the presence of unwanted particles can cause electrostatic discharge (ESD), which can interfere with system voltage and electric field strength. In some cases, ESD can also generate particles by causing localized heating of electrodes to release particles from molten metal surfaces, which in turn can create more weak spots for ESD. Particle contamination can therefore degrade and destabilize high-voltage systems. Other examples of functional impairment caused by particle contamination include, but are not limited to, aperture blockage, lens assembly damage, wafer yield loss, machine downtime, or equipment production loss. Therefore, minimizing particulate contamination is desirable in every aspect of semiconductor equipment manufacturing, including pre-manufacturing, during-manufacturing, and post-manufacturing inspections.

[0069] One source of particulate contamination in vacuum systems used in semiconductor device manufacturing is particle resuspension caused by internal pressure changes, such as during vacuuming or devastating. As previously mentioned, critical surfaces can be sensitive to particulate contamination because contaminants can alter one or more of the surface's optical, mechanical, electrical, chemical, structural, or desired functions. For example, dust particles or debris on critical surfaces (e.g., wafer surfaces) during device manufacturing can cause physical or electrical defects, rendering the final device inoperable. To "drive away" or "push away" contaminants that have settled on critical surfaces, increasing the lateral gas flow across the critical surface may be desirable. Increasing the lateral gas flow may include increasing the flow through SEM electron optics arrays (e.g., Figure 3A The gas flow (e.g., the flow of exhaust gas 315) in the electron optical device row 310. However, increasing the gas flow of exhaust gas 315 may cause turbulence 318 inside the electron optical device row 310, resulting in increased resuspension of contaminants in the electron optical device row 310. In the context of this disclosure, transverse gas flow across a surface refers to a direction in which gas flows radially outward and is substantially parallel to a horizontal plane extending from the surface. Figure 3A In the image, the direction indicated by arrow 319 indicates the lateral gas flow of exhaust gas 315 across the top surface of substrate 340 (e.g., a wafer placed on a substrate / wafer holder).

[0070] Figure 3B The diagram illustrates the relationship between... Figure 3A Similar to system 370, system 300 includes vacuum chambers 375 and 378 fluidly connected to each other. Vacuum chamber 375 may be a vacuum chamber housing a substrate holder 350, and vacuum chamber 378 may include a robotic arm chamber. Due to the relatively strong incoming exhaust flow from a chamber exhaust inlet (not shown), the gas flow in the robotic arm chamber or vacuum chamber 378 may be significantly stronger and more turbulent than the exhaust gas flow (e.g., exhaust gas 315) in vacuum chamber 375. In some cases, a stronger gas flow in vacuum chamber 378 may be desirable for faster vacuum breaking in system 370.

[0071] The risk of particle resuspension during vacuum breaking in a SEM apparatus may be related to the shear rate of the exhaust gas. For example, for average shear rates, particle resuspension during vacuum breaking is negligible (e.g., less than 0.0001% of 4 µm particles can be moved by the gas flow). Although shear rate may be affected by the control electrodes (e.g., Figure 3AThe higher concentration of particles on a smaller area of ​​the surface of the control electrode 320 may potentially cause resuspension of larger particles, but this risk can be mitigated by appropriate cleaning procedures or by using a particle-free exhaust gas flow in the SEM module. The wafer stage or substrate holder (which may be a critical surface) can be positioned such that it is substantially perpendicular to the downstream flow of the exhaust gas. In such a scenario, the substrate holder (e.g., [missing information]) that has direct, normal-angle contact with the exhaust gas flow from the SEM module... Figure 3A The top surface of the substrate holder 350 may experience the highest shear rate of the exhaust gas, and therefore, particles in the SEM exhaust gas may be deposited or trapped on the top surface of the substrate holder. As another example, as previously mentioned, the robotic arm chamber (e.g., Figure 3B The gas flow in the vacuum chamber 378 is significantly more turbulent and stronger due to the relatively strong incoming exhaust gas flow from the chamber exhaust inlet. The vacuum manipulator (not shown) can also be a source of particle contamination using exposed moving parts (such as, but not limited to, joints, bearings, or hydraulic lifting systems). Therefore, the turbulent environment around a relatively dirty manipulator can lead to significant particle resuspension, which can contaminate critical surfaces as the gas flow leaves the manipulator chamber and flows downstream.

[0072] During the vacuum breaking process of a SEM apparatus (e.g., system 370), it may be desirable to hold critical surfaces (such as substrate holder 350 or substrate 340) below the electron optics array 310 to protect them from particle contamination. In some existing systems, the flow of exhaust gas 315 downward through the electron optics array 310 may form a protective gas covering 380 (also referred to herein as a “gas curtain”) over the top surface of substrate 340. The gas covering 380 may be formed on control electrodes (e.g., Figure 3A The protective gas curtain 380 is positioned below the control electrode 320 and above the substrate 340 or substrate holder 350 (if the substrate is not placed on the substrate holder). The protective gas curtain 380 can be configured to protect portions of the control electrode 320 and the shield 330 in addition to protecting the substrate 340 placed on the substrate holder 350. Within the protective gas curtain 380, a gas flow diffuses from the control electrode 320 toward the edge of the substrate 340 (or substrate holder 350) and deflects the exhaust gas flow from the vacuum chamber 378 around critical surfaces. If the exhaust gas flow from the vacuum chamber 378 is stronger, such as for faster vacuum breaking, a stronger gas curtain may be desired to handle the more intense exhaust flow from the vacuum chamber 378, which is expected to cause more airborne contaminants.

[0073] One of several ways to form an effective protective gas cover 380 over a critical surface in vacuum chamber 375 may include providing a high-velocity exhaust gas 315 through vacuum chamber 375 to increase lateral gas flow across the critical surface. In this context, velocity refers to the distance a gas travels in a given time frame and may be expressed in meters per second (m / s), centimeters per second (cm / s), or millimeters per second (mm / s). However, if the velocity of the exhaust gas 315 passing through the electro-optics array 310 is too high, the risk of particle resuspension and surface contamination may be higher. In some existing systems, providing increased lateral gas flow across the critical surface may include increasing the exhaust gas flow through the electro-optics array. While increased lateral gas flow across the critical surface can reduce particle suspension on the critical surface, it may also cause particle resuspension on the critical surface within the electro-optics array 310 during its passage. Therefore, it is desirable to provide systems and methods that increase gas flow across the critical surface while minimizing contaminant resuspension on other critical surfaces to reduce contaminants settling on the critical surface.

[0074] Now for reference Figure 4A , Figure 4A An exemplary system 400 is illustrated, which includes an electron optics array 410, control electrodes 420, a purge ring 425, a shield 430, a substrate 440 placed on a substrate holder 450, and a substrate stage 460. Although not illustrated, it should be understood that the system 400 may also include one or more vacuum chambers (such as...). Figure 3B Vacuum chambers 375 and 378), vacuum breaking and vacuum pumping mechanisms, etc. Electro-optical device array 410 can be connected with... Figure 3A The electron optical device array 310 is substantially similar and can perform substantially similar functions. The electron optical device array 410 can be placed in a vacuum chamber or connected to a vacuum chamber.

[0075] In some embodiments, shielding 430 may include magnetic shielding configured to mitigate or prevent the charged particle beam from being exposed to stray magnetic fields that may cause magnetic interference. For example, in charged particle beam devices such as SEMs, an electron beam may be projected onto the surface of a substrate. Magnetic lenses may be used to focus or deflect the electron beam onto the substrate surface by magnetic force using a magnetic field. The electrons in the electron beam interact with the magnetic field through a magnetic Lorentz force and may be susceptible to magnetic interference. Furthermore, in some systems, the actuator of the substrate positioning device may be a magnetic actuator. Such actuators generate stray magnetic fields that may affect the electron beam in the SEM upon actuation. The interaction of the stray magnetic field with the electron beam may result in a loss of electron beam accuracy, a loss of device productivity, or both. Shielding 430 may be configured to reduce the effects of stray magnetic fields toward the propagation path of the electron beam and toward the magnetic lenses in the electron optics array 410. In some embodiments, shielding 430 may be configured to provide shielding against high-voltage effects, thermal effects, etc. The shielding element 430 may be made of μ alloy, a material with high magnetic permeability, or any other suitable material. The shielding element 430 may be in the form of a plate, a dish, a tube, or any suitable form.

[0076] Figure 4B The diagram shows... Figure 4A The diagram shows a corresponding top view of an exemplary shield 430 used in system 400. Shield 430 may include a central opening 432 configured to allow a primary charged particle beam to propagate through to the substrate 440. Shield 430 may be positioned such that the central opening 432 of shield 430 surrounds control electrode 420. In some embodiments, the geometric center of the central opening 432 of shield 430 and the center of control electrode 420 may be aligned with the primary optical axis 401 of system 400. In some embodiments, control electrode 420 and shield 430 may be coplanar or substantially coplanar. In this context, "coplanar" means that two or more components are positioned such that their respective centers of gravity lie on the same plane, and "substantially coplanar" means that two or more components are positioned such that their respective centers of gravity are approximately on the same plane. As an example, shield 430 and control electrode 420 may be coplanar or substantially coplanar such that their respective centers of gravity lie on a virtual two-dimensional plane 430P. It should be understood that plane 430P is a fictional virtual plane shown only for visual aids and illustration purposes.

[0077] In some embodiments, in addition to the exhaust gas 415 provided through gas inlet 405, system 400 may include a purge ring 425 configured to provide exhaust gas 422 during vacuum breaking of system 400 (e.g., a SEM tool). Purge ring 425 may include a second gas inlet configured to direct exhaust gas 422 to substrate 440. Gas inlet 405 and purge ring 425 may be configured to direct exhaust gas 415 and exhaust gas 422 toward substrate 440, respectively, such that the two gas flows merge to form a lateral flow across the top surface of substrate 440. The merged lateral flow (by...) Figure 4A (Indicated by the curved arrow in the image) the gas is pushed radially outward toward the edge of substrate 440 to minimize particle contamination on critical surfaces that may result from particle retention, suspension, or resuspension.

[0078] In some embodiments, the purge ring 425 may be mechanically coupled to the shield 430. In some embodiments, the shield 430 may include an opening configured to receive the purge ring 425, such that the purge ring 425 is partially or completely contained within the opening. The opening in the shield 430 for receiving the purge ring 425 may be a recessed portion having an aperture or hole to allow exhaust gas 422 to pass through. In some embodiments, the purge ring 425 may be held in place by a coupling mechanism (such as, but not limited to, welding, flexible coupling, rigid coupling, etc.). Although Figure 4A Although not illustrated, it should be understood that system 400 may include one or more gas flow regulating mechanisms. For example, the gas flow through gas inlet 405 or purge ring 425 may be controlled by a controller (e.g., Figure 2 The controller 50) controls individual flow valves for regulation. One or more flow valves can be individually activated or deactivated via the controller to regulate the gas flow during vacuum breaking in system 400.

[0079] The purge ring 425 can be configured to provide additional exhaust gas 422 during vacuum breaking in system 400. The gas flow of exhaust gas 422 can form a gas curtain (e.g., Figure 3BA gas curtain 380 is formed to protect one or more critical surfaces from particle contamination. The flow rate of the exhaust gas 422 can be individually adjusted. In this context, gas flow rate refers to the volumetric flow or volume of gas passing through a cross section within a specific time frame and can be expressed as nanoliters per minute (nL / min) or milliliters per minute (ml / min). The ability to individually adjust the flow rate of the exhaust gas 422 through the purge ring 425 can serve two functions: to form a stronger gas curtain to protect one or more critical surfaces, and to enable the system 400 to break the vacuum more quickly without increasing the risk of particle resuspension. Faster vacuum breaking can allow for increased production or overall system availability. In some embodiments, the flow rate of the exhaust gas 422 from the purge ring 425 can be higher or substantially higher than the flow rate of the exhaust gas 415, resulting in a stronger gas curtain and correspondingly better protection against particle contamination. This can be achieved without affecting or increasing the risk of particle resuspension within the electro-optics array 410, because the exhaust gas 422 is configured to flow through physically separate and individually controlled purge rings 425.

[0080] As previously mentioned, in some existing systems, the flow rate of the exhaust gas through the electron optics array may be restricted to maintain a laminar gas flow, thereby minimizing particle resuspension. A gas curtain formed by a slow-flowing exhaust gas may be insufficient to provide protection against particle resuspension on critical surfaces, such as the substrate or substrate holder. One of the problems with vacuum breaking procedures in existing systems is that the exhaust gas through the electron optics array is configured to form a gas curtain to protect critical surfaces from particle contamination, and to maintain a laminar gas flow within the electron optics array to minimize particle resuspension on critical surfaces within the array. Providing additional exhaust gas via purge ring 425 can overcome one or more of the problems associated with particle resuspension on critical surfaces.

[0081] In some embodiments, the additional exhaust gas supplied via purge ring 425 can allow the "SEM module overpressure" function to be decoupled from the "gas curtain" function. In the context of this disclosure, "SEM module overpressure" refers to a relative positive pressure within the SEM module compared to the external gas pressure. SEM module overpressure may be desirable to prevent gas from flowing upstream from an adjacent positive pressure region, including, for example, a vacuum chamber 378, into the SEM module. "Gas curtain" refers to a gas covering or layer formed by a layered, radially outward flow of exhaust gas directly above a critical surface, such as a substrate or substrate holder. In some existing systems, exhaust gas from the SEM module (i.e., an electron optics array) is used to create SEM module overpressure and form a gas curtain. However, as discussed herein, using purge ring 425 to provide additional exhaust gas (e.g., exhaust gas 422) can allow the SEM module overpressure function to be decoupled from the gas curtain function. A low flow rate of exhaust gas 415 can be maintained within the SEM module (e.g., Figure 3A Electro-optical devices 310 and Figure 4A In the electron optics array 410, a laminar gas flow is maintained to minimize particle resuspending and to maintain overpressure to prevent gas backflow into the SEM module. The high-flow-rate exhaust gas 422 via the purge ring 425 can be directed to the substrate to form a powerful gas curtain (e.g., Figure 3B The gaseous covering 380 protects critical surfaces from particle contamination.

[0082] In some embodiments, the composition of the exhaust gas 422 may include, as needed, ultra-clean dry air (XCDA), nitrogen (N2), ionized gas, or inert gas, or mixtures thereof. In some embodiments, the composition of the exhaust gas 422 may be substantially similar to that of the exhaust gas used to break the vacuum in the vacuum chamber 378 or the robotic arm chamber. In some embodiments, the amount of exhaust gas 422 passing through the purge ring 425 may be relatively small compared to the amount of exhaust gas used to break the vacuum in the vacuum chamber 378. In such a scenario, the composition of the exhaust gas 422 may include nitrogen. In some embodiments, the purge ring 425 may be used to introduce ionized gas to regulate the charge present on the surface of a substrate (e.g., a wafer). For example, in applications including wafer inspection using a SEM apparatus, the exhaust gas 422 may include a mixture of ionized gas and purge gas directed to the wafer before or after wafer inspection. It should be understood that in such applications for wafer charge control, the gas flowing through the purge ring 425 may not necessarily be used to break the vacuum in the system; instead, it may be used to regulate the charge present on the substrate.

[0083] In some embodiments, the temperature of the exhaust gas 422 flowing through the purge ring 425 can be adjusted based on the thermal regulation of the substrate or substrate holder (e.g., an electrostatic chuck). The gas flowing through the purge ring 425 can be heated or cooled to compensate for temperature mismatch between the substrate (e.g., a wafer) and the substrate holder (e.g., an electrostatic chuck). For example, a wafer introduced from a loading lock into the vacuum chamber 375 may be cold due to the thermal load caused by rapid evacuation in the loading lock. Temperature mismatch between a cold wafer and a chuck configured to receive the wafer can cause wafer deformation, resulting in image distortion during wafer inspection. In such scenarios, it may be desirable to adjust the temperature of the chuck to minimize the temperature mismatch between the incoming wafer and the chuck. The exhaust gas 422 flowing through the purge ring 425 can be pre-cooled to a predetermined temperature before being introduced into the gas supply mechanism. In some embodiments, the temperature of the substrate (e.g., a wafer) or substrate holder can be increased during wafer inspection or metrological measurements. Temperature increases can cause undesirable thermal drift, as it can affect image quality. Pre-cooled purge gas can be introduced through purge ring 425 to provide controlled cooling of the substrate or substrate holder to compensate for temperature rise.

[0084] System 400 may include a substrate stage 460, which is also referred to herein as a mirror block or encoder block. If the position of the substrate stage 460 is determined based on an interferometer position measurement system, the substrate stage may be referred to as a mirror block. If the position of the substrate stage 460 is determined based on an encoder position measurement system, the substrate stage 460 may be referred to as an encoder block. In some embodiments, a substrate holder 450 may be placed in a recess of the substrate stage 460, and a substrate 440 may be placed on top of the substrate holder 450. In some embodiments, a vacuum may be formed in the space between the substrate stage 460 and the substrate holder 450, and in the space between the substrate holder 450 and the substrate 440, such that the substrate 440 and the substrate holder 450 are held in place by atmospheric pressure above the substrate 440. In some embodiments, the recess in the substrate stage 460 may be slightly larger than the substrate holder 450 and the substrate 440 to accommodate variations in substrate size and placement. The difference in size between the recess and the substrate holder 450 or the substrate 440 may form a narrow groove or trench around the edge of the substrate 440 (see reference). Figure 5A and Figure 5B Let's discuss.

[0085] Now for reference Figure 5A , Figure 5AAn exemplary system 500 is illustrated, which includes an electro-optical array 510, control electrodes 520, a purge ring 525, a shield 530, a substrate 540 placed on a substrate holder 550, and a substrate stage 560. Although not illustrated, it should be understood that the system 500 may also include one or more vacuum chambers (such as...). Figure 3B Vacuum chambers 375 and 378), vacuum breaking and vacuum pumping mechanisms, etc. Electro-optical device series 510 can be connected with... Figure 3A The electron optical device array 310 is substantially similar and can perform substantially similar functions. The electron optical device array 510 can be placed in a vacuum chamber or connected to a vacuum chamber.

[0086] In some embodiments, the substrate holder 550 may include a purge ring 525. For example... Figure 5A As shown, the purge ring 525 can be placed within the substrate holder 550 such that the exhaust gas 522 is released in the trench 555 toward the inner wall of the recess of the substrate stage 560, traveling upward and radially outward toward the edge of the substrate 540. The exhaust gas 515 traveling downward toward the top surface of the substrate 540 through the electro-optics array 510 can be combined with the exhaust gas 522 from the purge ring 525 located inside the substrate holder 550 to form a transverse flow above the top surface of the substrate 540 and be guided radially outward to minimize or prevent particle suspension on the top surface of the substrate 540. The flow rate of the exhaust gas 515 can be low to maintain a laminar flow through the electro-optics array 510. In some embodiments, the flow rate of exhaust gas 515 may be less than 1 nl / min (nanoliths per minute), or less than 0.9 nl / min, or less than 0.8 nl / min, or less than 0.7 nl / min, or less than 0.6 nl / min, or less than 0.5 nl / min, or less than 0.4 nl / min, or less than 0.3 nl / min, or less than 0.2 nl / min, or within a suitable range to avoid turbulence, and thereby avoid increasing the risk of particle resuspending on critical surfaces inside the electron-optical device array 510. The flow rate of exhaust gas 522 through purge ring 525 may be significantly higher than the flow rate of exhaust gas 515. The high flow rate of exhaust gas 522 allows for the formation of a strong protective gas coating (e.g., ...) above the top surface of substrate 540. Figure 3B (Gas covering 380). The low flow rate of exhaust gas 515 can maintain a positive internal pressure to substantially prevent backflow of exhaust gas 522 or the chamber exhaust gas inside the electro-optical device array 510.

[0087] Figure 5B The illustrations depict some embodiments of the present disclosure along... Figure 5AThe figure shows a top view of system 500 (A-Aʹ). As shown, a purge ring 525 may be located within and on the outer edge of the substrate holder 550 to allow exhaust gas 522 to be directly introduced into the trench 555. In some embodiments, the purge ring 525 may be radially inwardly positioned toward the center of the substrate holder 550. In such cases, a path (e.g., conduit or passage) for the exhaust gas 522 may be provided to guide the exhaust gas from the purge ring 525 to the trench 555. In some embodiments, the width 555w and depth of the trench 555 may be uniform around the edge of the substrate 540 or the substrate holder 550. In some embodiments, the trench width 555w may be fixed or constant along the depth of the trench. In this context, the trench width refers to the horizontal distance between the inner wall of the recess of the substrate stage and the edge of the substrate or substrate holder, and the trench depth refers to the vertical distance between the top surface of the substrate or substrate holder (if no substrate is present) and the base of the recess of the substrate stage. In some embodiments, the depth of the trench (e.g., trench 555) may be substantially similar to the depth of the recess of the substrate stage (e.g., substrate stage 560). In some alternative embodiments, the depth of the trench may be greater than or less than the depth of the recess of the substrate stage.

[0088] In some embodiments, the substrate holder 550 may include more than one purge ring 525 (not shown). For example, a first purge ring may be configured to introduce a mixture of ionized gas and inert gas, and a second purge ring may be configured to introduce an exhaust gas, such as, but not limited to, XCDA or nitrogen. It should be understood that the size of the purge ring(s), the number of purge rings, the position of the purge ring(s), the spacing between the purge rings, the manufacturing material, or the gas introduced through the purge ring(s) may be adjusted as needed. It should also be understood that, although in Figure 5B The middle substrate stage is circular, but it can also be rectangular or have any desired shape.

[0089] Now for reference Figure 5C , Figure 5CAn exemplary system 500_2 comprising multiple purge rings according to some embodiments of the present disclosure is illustrated. Compared to system 500, system 500_2 includes an additional purge ring 525_2 located within a shield 530. In some embodiments, a downward or downstream gas flow may be combined with an upward or upstream gas flow to form a lateral gas flow across a critical surface. The downward or downstream gas flow may include an exhaust gas flow 515 toward a substrate 540 via an electro-optics array 510, or an exhaust gas flow 522_2 toward the substrate 540 from a purge ring 525_2 located within the shield 530, or both. The upward gas flow may include a purge gas flow 522 toward the substrate 540 from a purge ring 525 located within a substrate holder 550. In some embodiments, exhaust gas 522_2, exhaust gas 515, and exhaust gas 522 may be combined to form a lateral gas flow across the top surface of the substrate 540. The combined lateral gas flow can have a higher velocity than any individual gas flow. The combined gas flow can form a protective gas coating over critical surfaces (e.g., the top surface of substrate 540 or substrate holder 550 in the absence of a substrate) to prevent particle suspension or contamination of the critical surface. In some embodiments, the exhaust gas 515 can have a lower velocity to maintain a laminar gas flow downward through the electro-optics array 510, thereby minimizing particle resuspension and maintaining overpressure to prevent backflow of the exhaust gas. The flow rates of exhaust gases 522_2 and 522 can be adjusted individually and separately to adjust the exhaust velocity or the protective gas coating (e.g., Figure 3B The intensity of the gas covering (380), or both.

[0090] Now for reference Figure 6A , Figure 6A An exemplary system 600 is illustrated, which includes an electron optics array 610, a control electrode 620, a purge ring 625, a shield 630, a substrate 640 placed on a substrate holder 650, and a substrate stage 660. Although not illustrated, it should be understood that the system 600 may also include one or more vacuum chambers (such as...). Figure 3B Vacuum chambers 375 and 378), vacuum breaking and vacuum pumping mechanisms, etc. Electro-optical device series 610 can be connected with... Figure 3A The electron optical device array 310 is substantially similar and can perform substantially similar functions. The electron optical device array 610 can be placed in a vacuum chamber or connected to a vacuum chamber.

[0091] A purge ring 625 may be located inside the substrate stage 660 and around the trench 655, such that the purge ring 625 can directly introduce exhaust gas 622 into the trench 655. In some embodiments, the purge ring 625 may be configured to provide exhaust gas 622 through an opening in the inner vertical wall of the recess of the substrate stage and through an opening in the horizontal base of the recess. The exhaust gas 622 flowing upward toward the substrate 640 may be combined with the exhaust gas 615 flowing downward through the electro-optical device array 610 to form a transverse gas flow across the top surface of the substrate 640. The transverse gas flow across the top surface of the substrate 640 may act as a gas covering (e.g., Figure 3B A gas covering 380 is used to prevent or mitigate particle suspension. Particles can be pushed towards the outer edge and away from any critical surfaces by a radially outward-directed lateral gas flow. In some embodiments, the substrate stage 660 may include more than one purge ring 625 (not shown). For example, a first purge ring may be configured to introduce a mixture of ionized gas and inert gas, and a second purge ring may be configured to introduce an exhaust gas, such as, but not limited to, XCDA or nitrogen. It should be understood that the size of the purge ring(s), the number of purge rings, the position of the purge ring(s), the spacing between the purge rings, the manufacturing material, or the gas introduced through the purge ring(s) may be adjusted as needed. Figure 6B The diagram illustrates a portion of system 600 along... Figure 6A The top view of section A-A' shown.

[0092] Now for reference Figure 6C , Figure 6CAn exemplary system 600_2 comprising multiple purge rings according to some embodiments of the present disclosure is illustrated. Compared to system 600, system 600_2 includes an additional purge ring 625_2 located within a shield 630. In some embodiments, a downward or downstream gas flow may be combined with an upward or upstream gas flow to form a lateral gas flow across a critical surface. The downward or downstream gas flow may include a flow of exhaust gas 615 toward a substrate 640 via an electro-optics array 610, or a flow of exhaust gas 622_2 toward a substrate 640 from a purge ring 625_2 located within the shield 630, or both. The upward gas flow may include a purge gas flow 622 toward a substrate 640 from a purge ring 625 located within a substrate stage 660. In some embodiments, exhaust gas 622_2, exhaust gas 615, and exhaust gas 622 may be combined to form a lateral gas flow across the top surface of the substrate 640. The combined lateral gas flow can have a higher velocity than any individual gas flow. The combined gas flow can form a protective gas coating over critical surfaces (e.g., the top surface of substrate 640 or substrate holder 650 in the absence of a substrate) to prevent particle suspension or contamination of the critical surface. In some embodiments, the exhaust gas 615 can have a lower velocity to maintain a laminar gas flow downward through the electro-optics array 610, thereby minimizing particle resuspension and maintaining overpressure to prevent backflow of the exhaust gas. The flow rates of exhaust gases 622_2 and 622 can be adjusted individually and separately to adjust the exhaust velocity or the protective gas coating (e.g., Figure 3B The intensity of the gas covering (380), or both.

[0093] Now for reference Figure 7 , Figure 7 The illustration shows an exhaust sequence 700 of an exemplary system including one or more purge rings according to some embodiments of the present disclosure. In this context, an exhaust sequence refers to a sequence of steps or functions performed by the system to break the system from a negative internal pressure (i.e., vacuum) to a positive internal pressure (atmospheric pressure or higher). It should be understood that while the exemplary vacuum system may include SEM inspection or measurement tools, the exhaust sequence can also be applied to other vacuum systems.

[0094] In step 710, controller 50 may be configured to activate one or more valves to allow exhaust gas to flow through the electron optics array of a charged particle beam device (e.g., SEM). Figure 3A Electro-optical devices, Series 310, Figure 4A Electro-optical devices, Series 410, Figure 5A Electro-optical devices, Series 510 or Figure 6AThe exhaust gas from the electro-optical device array (610) can create overpressure while simultaneously causing a vacuum breach in the electro-optical device array. The controller 50 can also be configured to adjust the flow rate or velocity of the exhaust gas allowed through a corresponding valve to maintain non-turbulent flow through the electro-optical device array. This non-turbulent flow of the exhaust gas allows for a vacuum breach in the electro-optical device array without the risk of particle re-suspending on critical surfaces within the array.

[0095] In step 720, the controller 50 can be configured to activate one or more valves to allow exhaust gas to flow through the corresponding purge ring (e.g., Figure 4A purge ring 425, Figure 5A 525 purge rings Figure 5C purge ring 525_2, Figure 6A purge ring 625 or Figure 6C (Purge ring 625_2). In some embodiments, controller 50 may also be configured to induce a first delay 715 between steps 710 and 720. In some embodiments, the first delay may be in the range of 0.5 seconds to 5.0 seconds, or 0.5 seconds to 4.5 seconds, or 0.5 seconds to 4.0 seconds, or 0.5 seconds to 3.5 seconds, or 0.5 seconds to 3.0 seconds, or 0.5 seconds to 2.5 seconds, or 0.5 seconds to 2.0 seconds, or 0.5 seconds to 1.5 seconds, or 0.5 seconds to 1.0 seconds, or any suitable time range. In some preferred embodiments, the first delay may be between 1.5 seconds and 2 seconds. The first delay may allow overpressure (through the positive internal pressure of the electro-optics array) to be generated by the exhaust gas flow through the electro-optics array, thereby minimizing the backflow of purge gas into the electro-optics array through one or more purge rings. The controller 50 can also be configured to adjust the flow rate or velocity of the exhaust gas flowing through one or more purge rings, such that the flow rate is higher than the flow rate of the exhaust gas passing through the electro-optical array. A higher flow rate of exhaust gas through one or more purge rings allows for the formation of a more robust protective gas coating (e.g., Figure 3B A gas covering 380 is used to minimize particle suspension or retention on critical surfaces such as wafers. In some embodiments, the flow rate through one or more purge rings can also be adjusted to adjust the vacuum breaking rate of the system. In some embodiments, more than one purge ring can be used to break the vacuum of the system (e.g., Figure 5C System 500_2 or Figure 6C The system (600_2) controller can be configured to individually adjust the flow rate, the timing of activation or deactivation of corresponding valves, or the selection of the gas flowing through the purge ring.

[0096] In step 730, the controller can be configured to activate the valve to allow exhaust gas to pass through the robotic arm chamber (e.g., Figure 3B The exhaust gas flows within the vacuum chamber 378. The exhaust gas introduced into the robotic arm chamber can break the vacuum in the robotic arm chamber to atmospheric pressure or higher. The controller 50 can also be configured to adjust the flow rate or velocity of the exhaust gas to adjust the exhaust speed. In some embodiments, the controller 50 can also be configured to induce a second delay 725 between steps 720 and 730. In some embodiments, the second delay can be less than 0.5 seconds, or less than 0.45 seconds, or less than 0.40 seconds, or less than 0.35 seconds, or less than 0.30 seconds, or less than 0.25 seconds, or less than 0.2 seconds, or less than 0.15 seconds, or any suitable time range. In some preferred embodiments, the second delay can be 0.1 seconds.

[0097] Now for reference Figure 8 , Figure 8 The illustration shows a process flow diagram according to an embodiment of the present disclosure, the process flow diagram illustrating the process in a charged particle beam device (such as...) Figure 3A An exemplary method 800 for increasing gas flow across a substrate in an apparatus 300.

[0098] In step 810, the controller (e.g., Figure 2 The controller 50 can activate one or more valves to cause a first gas to be released in the vacuum chamber (e.g., Figure 3A The gas flowing through the electron optical device array 310 may include exhaust gas configured to break the vacuum of the electron optical device array from the operating vacuum pressure to atmospheric pressure or higher (e.g., Figure 3A (Exhaust gas 315). Some examples of exhaust gases include, but are not limited to, XCDA, nitrogen, or gas mixtures suitable for causing vacuum break in the vacuum system. The controller may also be configured to adjust the flow rate or velocity of the exhaust gas passing through the electro-optics array. In some embodiments, the flow rate or velocity may be adjusted to maintain laminar (non-turbulent) flow of the exhaust gas. Non-turbulent flow can cause vacuum break in the electro-optics array while mitigating particle contamination on critical surfaces, such as lens surfaces within the electro-optics array.

[0099] In step 820, the controller may activate one or more valves to cause the second gas to flow toward the substrate at a second flow rate. In some embodiments, the valve configured to regulate the flow of the second gas may be different from the valve configured to regulate the flow of the first gas. The second gas may flow through a purge ring (e.g., Figure 4A purge ring 425 or Figure 5A The purge ring 525 is used to purge the exhaust gas. In some embodiments, the purge ring may be located on the shield (e.g., Figure 4A High voltage shield 430) inside or substrate retainer (e.g., Figure 5A The high-voltage shield 530 is located inside the substrate. In some embodiments, the second gas (e.g., exhaust gas) can flow simultaneously from both purge rings to the substrate, such as... Figure 5C System 500_2 and Figure 6C As illustrated in system 600_2. In some embodiments, the second flow rate may be higher than the first flow rate.

[0100] In some embodiments, the first gas flow and the second gas flow are merged to form a cross-substrate (e.g., Figure 3A A transverse gas flow on the top surface of the substrate 340. The transverse gas flow can be directed radially outward and provide a protective gas covering (e.g., Figure 3B A gas coating 380 is used to mitigate particle contamination on critical surfaces (e.g., the top surface of a substrate or wafer, or a substrate holder). The lateral gas flow, guided radially outward, can have a velocity higher than a first or second flow rate.

[0101] In some embodiments, the second gas flow can be guided downstream or downward from a purge ring (e.g., purge ring 425) located inside the shield to the top surface of the substrate, such as... Figure 4A As illustrated. In some embodiments, the second gas flow can be guided upstream or upward toward the top surface of the substrate from a purge ring (e.g., purge ring 525) located inside the substrate holder (e.g., substrate holder 550), such as... Figure 5A As illustrated. In some embodiments, one or more purge rings may be used to introduce exhaust gas to form a protective gas coating over the top surface of the substrate. For example, as shown... Figure 5C As illustrated, exhaust gas can be introduced through purge ring 525 located in the substrate holder and purge ring 525_2 inside the shield to break the vacuum in the system.

[0102] In some embodiments, the controller may be configured to activate a first valve to introduce exhaust gas flowing through the electro-optical device array (e.g., Figure 3A Exhaust gas 315, Figure 4A Exhaust gas 415, Figure 5A Exhaust gas 515, Figure 6A The time delay is caused between the exhaust gas (615) and the exhaust gas that is activated to introduce the second valve through the purge ring.

[0103] Non-transitory computer-readable media may be provided, storing instructions for a processor of a controller (e.g., a central processing unit or electronic control unit configured to control a charged particle beam device) to perform methods according to exemplary flowcharts or other methods according to embodiments of this disclosure. For example, instructions stored in a non-transitory computer-readable medium may be executed by circuitry of the controller to perform the methods in part or in whole. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tape, or any other magnetic data storage media, optical disc read-only memory (CD-ROM), any other optical data storage media, any physical media with a perforated pattern, random access memory (RAM), programmable read-only memory (PROM) and erasable programmable read-only memory (EPROM), FLASH-EPROM or any other flash memory, non-volatile random access memory (NVRAM), cache, registers, any other memory chip or tape cartridge, and networking versions thereof.

[0104] The block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block in the diagram may represent certain arithmetic or logical operations that can be implemented using hardware such as electronic circuits. A block may also represent a module, segment, or code portion including one or more executable instructions for implementing the specified logical function. It should be understood that in some alternative implementations, the functions indicated in the blocks may not occur in the order shown in the figures. For example, two blocks shown consecutively may be executed or implemented substantially concurrently, or the two blocks may sometimes be executed in reverse order depending on the functions involved. Some blocks may also be omitted. It should also be understood that each block in the block diagram, and combinations of blocks, may be implemented by a system based on dedicated hardware that performs the specified function or action, or by a combination of dedicated hardware and computer instructions.

[0105] The embodiments may also be described using the following terms: 1. A charged particle beam device, comprising: Vacuum chamber, the vacuum chamber comprising: A first gas inlet, fluidly connected to a charged particle beam optical element array, and configured to guide a first gas flow downstream toward a substrate within the charged particle beam optical element array at a first flow rate; and A second gas inlet, configured to guide a second gas flow toward the substrate at a second flow rate. The first gas flow and the second gas flow are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than the first flow rate or the second flow rate. 2. The apparatus according to Clause 1, wherein the first flow rate is lower than the second flow rate. 3. The apparatus according to any one of clauses 1 and 2, wherein the first gas flow is configured to cause the charged particle beam optical element array to break the vacuum. 4. The apparatus according to any one of clauses 1 to 3 further includes a shield located immediately upstream of the substrate, the shield including an opening configured to receive the second gas inlet. 5. The apparatus according to Clause 4, wherein the second gas inlet includes a purge ring mechanically coupled to the shield via a coupling mechanism. 6. The apparatus according to Clause 5 further includes a substrate chamber configured to house the substrate, the substrate chamber being fluidly connected to the charged particle beam optical element array. 7. The apparatus according to Clause 6 further includes a third gas inlet configured to guide a third gas flow inside the substrate chamber to break the vacuum in the substrate chamber. 8. The apparatus according to Clause 7 further includes a controller, the controller including circuitry configured to: Activate the first valve, which is configured to regulate the flow of the first gas through the first gas inlet; Activate the second valve, which is configured to regulate the flow of the second gas through the second gas inlet; and Activate the third valve, which is configured to regulate the flow of the third gas through the third gas inlet. 9. The apparatus according to Clause 8, wherein: Activation of the first valve allows the first gas flow to pass through the array of charged particle beam optical elements. Activation of the second valve allows the second gas flow to pass through the purge ring, and Activation of the third valve allows the third gas flow to enter the substrate chamber. 10. The apparatus according to any one of clauses 8 and 9, wherein the controller, including the circuit means, is further configured to cause a first time delay between the activation of the first valve and the activation of the second valve. 11. The device according to Clause 10, wherein the controller, including the circuitry, is further configured to cause a second time delay between the activation of the second valve and the activation of the third valve. 12. The apparatus according to Clause 11, wherein the first delay and the second delay are predetermined. 13. The apparatus according to any one of clauses 11 and 12, wherein the first delay is longer than the second delay. 14. The apparatus according to any one of clauses 7 to 13, wherein the gas composition of the second gas stream is substantially similar to that of the third gas stream. 15. The apparatus according to Clause 14, wherein the gas composition of the second gas stream is different from that of the third gas stream. 16. The apparatus according to any one of Clauses 14 and 15, wherein the gas composition of the second gas stream comprises nitrogen, ultra-clean dry air (XCDA), an inert gas, or an ionized gas. 17. The apparatus according to any one of clauses 1 to 5, wherein the purge ring is located downstream of the substrate. 18. The apparatus according to Clause 17 further includes a substrate holder configured to support the substrate. 19. The apparatus according to Clause 18 further includes a substrate stage, wherein the substrate holder is placed in a recess in the substrate stage. 20. The apparatus according to Clause 19, wherein when the substrate holder is placed in the recess, a trench is formed between the edge of the substrate holder and the inner wall of the substrate stage forming the recess. 21. The apparatus of claim 20, wherein the substrate holder includes the purge ring configured to guide the second gas flow in the trench. 22. The apparatus of claim 20, wherein the substrate stage includes the purge ring configured to guide the second gas flow in the trench. 23. The apparatus according to any one of clauses 2 to 22, wherein the lateral gas flow is directed radially outward. 24. The apparatus according to any one of clauses 2 to 23, wherein the first gas flow and the second gas flow increase the gas pressure in the vacuum chamber. 25. A method for increasing a gas flow across a substrate in a charged particle beam apparatus, the method comprising: This causes a first gas flow to flow downstream toward the substrate in the vacuum chamber at a first flow rate; and This causes a second gas flow to flow toward the substrate at a second flow rate. The first gas flow and the second gas flow are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than the first flow rate or the second flow rate. 26. The method according to Clause 25, wherein the first flow rate is lower than the second flow rate. 27. The method according to any one of clauses 25 and 26, wherein the first gas flow is configured to cause a vacuum break in the charged particle beam optical element array. 28. The method according to any one of clauses 25 to 27, wherein causing the first gas flow downstream comprises: guiding the first gas flow using a first gas inlet fluidly connected to a charged particle beam optical element array, and wherein causing the second gas flow to flow toward the substrate comprises: guiding the second gas flow using a second gas inlet, the second gas inlet being different from the first gas inlet. 29. The method according to Clause 28, wherein the second gas inlet includes a purge ring located upstream of the substrate. 30. The method according to Clause 29, wherein the purge ring is mechanically coupled to the shield via a coupling mechanism. 31. The method according to Clause 30 further comprises: causing a third gas flow through a third gas inlet, and the third gas flow being configured to break a vacuum in a substrate chamber housing the substrate, wherein the substrate chamber is fluidly connected to the charged particle beam optical element array. 32. The method according to Clause 31, wherein: Inducing the first gas flow includes: activating a first valve, the first valve being configured to regulate the first gas flow through the first gas inlet; Inducing the second gas flow includes: activating a second valve, the second valve being configured to regulate the second gas flow through the second gas inlet; and Inducing the third gas flow includes activating a third valve configured to regulate the third gas flow through the third gas inlet. 33. The method described according to Clause 32, wherein: Activating the first valve allows the first gas flow to pass through the charged particle beam optical element array toward the substrate; Activating the second valve allows the second gas flow to pass through the purge ring towards the substrate; and Activating the third valve allows the third gas flow to enter the substrate chamber. 34. The method according to any one of clauses 32 and 33 further includes: inducing a first time delay between activating the first valve and activating the second valve. 35. The method according to Clause 34 further includes: inducing a second time delay between activating the second valve and the third valve. 36. The method according to Clause 35, wherein the first delay is longer than the second delay. 37. The method according to any one of clauses 31 to 36, wherein the gas composition of the second gas stream is substantially similar to that of the third gas stream. 38. The method according to any one of clauses 31 to 36, wherein the gas composition of the second gas stream is different from that of the third gas stream. 39. The method according to any one of Clauses 37 and 38, wherein the gas composition of the second gas stream includes nitrogen, ultra-clean dry air (XCDA), an inert gas, or an ionized gas. 40. The method according to Clause 28, wherein the second gas inlet includes a purge ring located downstream of the substrate. 41. The method according to Clause 40, wherein the purge ring is located inside the substrate holder, the substrate holder is configured to support the substrate, and wherein the substrate holder is placed in a recess of the substrate stage. 42. The method according to Clause 41, wherein the substrate holder is placed in the recess to form a groove between the edge of the substrate holder and the inner wall of the substrate stage forming the recess. 43. The method according to Clause 42, wherein the purge ring is configured to guide the second gas flow in the trench. 44. The method according to Clause 42, wherein the purge ring is located inside the substrate stage and is configured to guide the second gas flow in the trench. 45. The method according to any one of clauses 25 to 44, wherein the transverse gas flow is directed radially outward. 46. ​​The method according to any one of clauses 25 to 45, wherein the first gas flow and the second gas flow increase the gas pressure in the vacuum chamber. 47. A charged particle beam device, comprising: A first gas inlet is fluidly connected to a charged particle beam optical element array and is configured to guide a first gas flow downward toward the substrate in the charged particle beam optical element array at a first flow rate. A second gas inlet, located upstream of the substrate, is configured to guide a second gas flow toward the substrate at a second flow rate; and A third gas inlet, located downstream of the substrate, is configured to direct a third gas flow toward the substrate at a third flow rate. The first gas flow, the second gas flow, and the third gas flow are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than the first flow rate, the second flow rate, or the third flow rate. 48. The apparatus according to Clause 47, wherein the first flow rate is lower than the second flow rate or the third flow rate. 49. The apparatus according to any one of clauses 47 and 48, wherein the first gas flow is configured to cause the array of charged particle beam optical elements to break a vacuum. 50. The apparatus according to any one of clauses 47 to 49 further includes a shield located immediately upstream of the substrate, the shield including an opening configured to receive the second gas inlet. 51. The apparatus according to clause 50 further includes: A substrate holder, the substrate holder being configured to support the substrate; and A recessed substrate stage, wherein the substrate holder is placed in the recess of the substrate stage. 52. The apparatus according to clause 51, wherein when the substrate holder is placed in the recess, a trench is formed between the edge of the substrate holder and the inner wall of the substrate stage forming the recess. 53. The apparatus according to Clause 52, wherein the second gas inlet includes a first purge ring mechanically coupled to the shield via a coupling mechanism, and wherein the third gas inlet includes a second purge ring configured to guide the third gas flow in the trench. 54. The apparatus according to Clause 53, wherein the second purge ring is located inside the substrate holder. 55. The apparatus according to Clause 53, wherein the second purge ring is located inside the substrate stage. 56. The apparatus according to Clause 55 further includes a substrate chamber configured to house the substrate, the substrate chamber being fluidly connected to the array of charged particle beam optical elements. 57. The apparatus according to Clause 56 further includes a fourth gas inlet configured to direct a fourth gas flow inside the substrate chamber to break the vacuum in the substrate chamber. 58. The apparatus according to clause 57 further includes a controller, the controller including circuitry configured to: Activate the first valve, which is configured to regulate the flow of the first gas through the first gas inlet; Activate the second valve, which is configured to regulate the flow of the second gas through the second gas inlet; Activate the third valve, which is configured to regulate the flow of the third gas through the third gas inlet; and Activate the fourth valve, which is configured to regulate the flow of the fourth gas through the fourth gas inlet. 59. The apparatus according to clause 58, wherein: Activation of the first valve allows the first gas flow to pass through the array of charged particle beam optical elements; Activation of the second valve allows the second gas flow to pass through the first purge ring; Activation of the third valve allows the third gas flow to pass through the second purge ring; and Activation of the fourth valve allows the fourth gas flow to enter the substrate chamber. 60. The device according to Clause 59, wherein the controller, including the circuitry, is further configured to cause a first time delay between the activation of the first valve and the activation of one of the second or third valve. 61. The device according to Clause 60, wherein the controller, including the circuitry, is further configured to cause a second time delay between activation of the second valve or the third valve and activation of the fourth valve. 62. The apparatus according to Clause 61, wherein the first delay and the second delay are predetermined. 63. The apparatus according to any one of clauses 61 and 62, wherein the first delay is longer than the second delay. 64. The apparatus according to any one of Clauses 47 to 63, wherein the gas composition of the second gas stream or the gas composition of the third gas stream comprises nitrogen, ultra-clean dry air (XCDA), an inert gas, or an ionized gas. 65. The apparatus according to any one of clauses 47 to 64, wherein the lateral gas flow is directed radially outward. 66. The apparatus according to any one of clauses 47 to 65, wherein the first gas flow and the second gas flow increase the gas pressure in the vacuum chamber. 67. A non-transitory computer-readable medium storing an instruction set executable by one or more processors of a charged particle beam apparatus to cause the charged particle beam apparatus to perform a method of increasing a gas flow across a substrate within the charged particle beam apparatus, the method comprising: This causes a first gas flow to flow downstream toward the substrate in the vacuum chamber at a first flow rate; and This causes a second gas flow to flow toward the substrate at a second flow rate. The first gas flow and the second gas flow are combined to form a transverse gas flow across the top surface of the substrate, the transverse gas flow having a flow rate higher than the first flow rate or the second flow rate. 68. The non-transitory computer-readable medium according to Clause 67, wherein the first flow rate is lower than the second flow rate. 69. A non-transitory computer-readable medium according to any one of clauses 67 and 68, wherein causing the first gas flow downstream comprises: guiding the first gas flow using a first gas inlet fluidly connected to a column of charged particle beam optical elements, and wherein causing the second gas flow to flow toward the substrate comprises: guiding the second gas flow using a second gas inlet different from the first gas inlet. 70. The non-transitory computer-readable medium according to Clause 69, wherein the second gas inlet includes a purge ring located upstream of the substrate, and wherein the purge ring is mechanically coupled to a shield via a coupling mechanism. 71. The non-transitory computer-readable medium according to Clause 70, wherein the method further comprises: inducing a third gas flow through a third gas inlet, and the third gas flow being configured to break a vacuum in a substrate chamber housing the substrate, wherein the substrate chamber is fluidly connected to the charged particle beam optical element array. 72. The non-transitory computer-readable medium as described in Clause 71, wherein: Inducing the first gas flow includes: activating a first valve, the first valve being configured to regulate the first gas flow through the first gas inlet; Inducing the second gas flow includes: activating a second valve, the second valve being configured to regulate the second gas flow through the second gas inlet; and Inducing the third gas flow includes activating a third valve configured to regulate the third gas flow through the third gas inlet. 73. The non-transitory computer-readable medium as described in Clause 72, wherein: Activating the first valve allows the first gas flow to pass through the charged particle beam optical element array toward the substrate; Activating the second valve allows the second gas flow to pass through the purge ring towards the substrate; and Activating the third valve allows the third gas flow to enter the substrate chamber. 74. The non-transitory computer-readable medium according to any one of clauses 72 and 73, wherein the method further comprises: A first time delay is caused between activating the first valve and activating the second valve, and A second time delay is caused between activating the second valve and activating the third valve. 75. The non-transitory computer-readable medium according to Clause 74, wherein the first delay is longer than the second delay. 76. A non-transitory computer-readable medium according to any one of clauses 71 to 75, wherein the gas composition of the second gas stream is substantially similar to that of the third gas stream. 77. A non-transitory computer-readable medium according to any one of clauses 71 to 75, wherein the gas composition of the second gas stream is different from that of the third gas stream. 78. The non-transitory computer-readable medium according to any one of clauses 76 and 77, wherein the gaseous components of the second gas stream include nitrogen, ultra-clean dry air (XCDA), an inert gas, or an ionized gas. 79. The non-transitory computer-readable medium according to Clause 69, wherein the second gas inlet includes a purge ring located downstream of the substrate. 80. The non-transitory computer-readable medium according to Clause 79, wherein the purge ring is located inside a substrate holder configured to support the substrate, and wherein the substrate holder is placed in a recess of a substrate stage. 81. The non-transitory computer-readable medium according to Clause 80, wherein the substrate holder is placed in the recess in a groove formed between the edge of the substrate holder and the inner wall of the substrate stage forming the recess. 82. The non-transitory computer-readable medium according to Clause 81, wherein the purge ring is configured to guide the second gas flow in the trench. 83. The non-transitory computer-readable medium according to Clause 81, wherein the purge ring is located inside the substrate stage and is configured to guide the second gas flow in the trench. 84. The non-transitory computer-readable medium according to any one of clauses 67 to 83, wherein the lateral gas flow is directed radially outward. 85. A non-transitory computer-readable medium according to any one of clauses 67 to 84, wherein the first gas flow and the second gas flow increase the gas pressure in the vacuum chamber.

[0106] It should be understood that the embodiments of this disclosure are not limited to the precise constructions already described above and illustrated in the accompanying drawings, and various modifications and alterations 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 from consideration of the specification disclosed herein and from practice of the invention. It is intended that the specification and examples be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims. The foregoing description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the description herein without departing from the scope of the set forth claims.

Claims

1. A charged particle beam device, comprising: a vacuum chamber, the vacuum chamber comprising: a first gas inlet fluidly connected with a column of charged particle beam optical elements and configured to direct a first gas flow downstream in the column of charged particle beam optical elements towards a substrate at a first flow rate; and a second gas inlet configured to direct a second gas flow towards the substrate at a second flow rate, wherein the first gas flow merges with the second gas flow to form a lateral gas flow across a top surface of the substrate, the lateral gas flow having a flow rate higher than the first flow rate or the second flow rate.

2. The device of claim 1, wherein the first flow rate is lower than the second flow rate.

3. The device of claim 1, wherein the first gas flow is configured to cause the column of charged particle beam optical elements to break vacuum.

4. The device of claim 1, further comprising a shield located immediately upstream of the substrate, the shield comprising an opening configured to receive the second gas inlet.

5. The device of claim 4, wherein the second gas inlet comprises a purge ring mechanically coupled to the shield by a coupling mechanism.

6. The device of claim 5, further comprising a substrate chamber configured to house the substrate, the substrate chamber fluidly connected to the column of charged particle beam optical elements.

7. The device of claim 6, further comprising a third gas inlet configured to direct a third gas flow inside the substrate chamber to break vacuum of the substrate chamber.

8. The device of claim 7, further comprising a controller comprising circuitry configured to: activate a first valve configured to regulate the first gas flow through the first gas inlet; activate a second valve configured to regulate the second gas flow through the second gas inlet; and activate a third valve configured to regulate the third gas flow through the third gas inlet.

9. The device of claim 8, wherein: activation of the first valve enables the first gas flow through the column of charged particle beam optical elements, activation of the second valve enables the second gas flow through the purge ring, and activation of the third valve enables the third gas flow into the substrate chamber.

10. The device of claim 8, wherein the controller comprising circuitry is further configured to cause a first time delay between activation of the first valve and activation of the second valve.

11. The device of claim 10, wherein the controller comprising circuitry is further configured to cause a second time delay between activation of the second valve and activation of the third valve.

12. The device of claim 11, wherein the first time delay and the second time delay are predetermined.

13. The device of claim 11, wherein the first time delay is longer than the second time delay. ​ 14. The apparatus of claim 7, wherein a gas composition of the second gas stream is substantially similar to a gas composition of the third gas stream.

15. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method of increasing a gas flow across a substrate in a charged particle beam device, the method comprising: causing a first gas stream to flow downstream in a vacuum chamber towards a substrate at a first flow rate; and causing a second gas stream to flow towards the substrate at a second flow rate, wherein the first gas stream merges with the second gas stream to form a lateral gas flow across a top surface of the substrate, the lateral gas flow having a flow rate higher than the first flow rate or the second flow rate.

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