Methods and equipment for cooling scanning electron microscope columns

Abstract

The device, system, and method for transferring heat from a component in a vacuum environment are revealed. In some implementations, heat pipes are used to transfer heat from the heat collector to a heat exchanger located outside the vacuum chamber. The implementations of the present invention provide a device or system that is more maintainable and reduces the risk of damaging the electronics or vacuum in the charged particle beam device. In some implementations, the efficiency of heat transfer or cooling can be improved.

Description

COOLING METHOD AND APPARATUS OF SCANNING ELECTRON MICROSCOPE COLUMNCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 591,067 which was filed on October 17, 2023 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The embodiments provided herein disclose an apparatus, a system, and a method for transferring heat from a heat collecting component in a vacuum, and more particularly, an apparatus, a system, and a method for transferring heat in a vacuum chamber without supplying coolant fluid into the vacuum chamber.BACKGROUND

[0003] In manufacturing processes of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as a scanning electron microscope (SEM) can be employed. As the physical sizes of IC components continue to shrink, accuracy and yield in defect detection become more and more important. Multiple charged-beams may be employed to address the inspection throughput requirements; however, imaging resolution of multiple charged-beam systems may be compromised, rendering the inspection tools inadequate for their desired purpose.

[0004] Thus, related art systems face limitations in, for example, image resolution and beam-spot positioning accuracy due to large thermal drifts caused by significant electric current through the electromagnetic coils of the objective lens assembly. Further improvements in the art for cooling the objective lens assembly of a charged-particle beam system are desired.SUMMARY

[0005] The embodiments provided herein disclose an apparatus, a system, and a method for transferring heat from a heat collecting component in a vacuum, and more particularly, an apparatus, a system, and a method for transferring heat in a vacuum chamber without supplying coolant fluid into the vacuum chamber.

[0006] Some embodiments of the present disclosure provide a system for transferring heat in a vacuum. The system comprises a vacuum chamber configured to provide a vacuum environment, a heat collecting component positioned within the vacuum chamber, a heat exchanger positioned outside of the vacuum chamber, and a heat pipe coupled to the heat collecting component and the heat exchanger and configured to transfer heat from the heat collecting component to the heat exchanger.

[0007] In some embodiments, a non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for transferring heat from a charged particle beam apparatus is provided. The operations comprise sending a signal that causes a component of the charged particle beam apparatus to generate heat, wherein the heat is absorbed via a heat pipe, causing a coolant fluid to be supplied to a heat exchanger positioned outside of the charged particle beam apparatus, and causing heat to be transferred from the heat pipe to the coolant fluid, wherein the absorbed heat is transferred without an externally supplied fluid flow in the heat pipe.

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

[0009] FIG. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system, consistent with embodiments of the present disclosure.

[0010] FIG. 2 is a schematic diagram illustrating an exemplary electron beam tool that can be a part of the exemplary electron beam inspection system of Fig. 1, consistent with embodiments of the present disclosure.

[0011] FIG. 3 illustrates a cross-section view of an exemplary objective lens structure of a charged- particle beam system, consistent with embodiments of the present disclosure.

[0012] FIG. 4 illustrates a cross-section view of an exemplary objective lens structure of a charged- particle beam system, consistent with embodiments of the present disclosure.

[0013] FIG. 5 is a schematic diagram illustrating an example fluid pipe attached in a channel of a bobbin in a conventional system or apparatus.

[0014] FIG. 6 is an illustration of an example heat transfer component coupled to a heat collecting component of a charged particle system, consistent with embodiments of the present disclosure.

[0015] FIG. 7A is an example schematic of a heat transfer component coupled to a heat collecting component, consistent with embodiments of the present disclosure.

[0016] FIG. 7B is a cross-sectional view of a heat transfer component coupled to a heat collecting component and to a cooling component of a charged particle system, consistent with embodiments of the present disclosure.

[0017] FIG. 7C is an illustration of a cross-sectional view of various configurations of a heat transfer component coupled to a heat collecting component and to a cooling component of a charged particle system, consistent with embodiments of the present disclosure.

[0018] FIG. 8 is an example flow diagram illustrating a method 800 for cooling a component of a charged particle beam apparatus, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0019] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the invention. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the invention as recited in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the disclosure is not so limited. Other types of charged particle beams may be similarly applied. Furthermore, other imaging systems may be used, such as optical imaging, photo detection, x-ray detection, etc.

[0020] The enhanced computing power of electronic devices, while reducing the physical size of the devices, can be accomplished by significantly increasing the packing density of circuit components such as, transistors, capacitors, diodes, etc. on an IC chip. For example, in a smart phone, an IC chip (which is the size of a thumbnail) may include over 2 billion transistors, the size of each transistor being less than l / 1000th of a human hair. Not surprisingly, semiconductor IC manufacturing is a complex process, with hundreds of individual steps. Errors in even one step have the potential to dramatically affect the functioning of the final product. Even one “killer defect” can cause device failure. The goal of the manufacturing process is to improve the overall yield of the process. For example, for a 50-step process to get 75% yield, each individual step must have a yield greater than 99.4%, and if the individual step yield is 95%, the overall process yield drops to 7%.

[0021] While high process yield is desirable in an IC chip manufacturing facility, it is also essential to maintain a high wafer throughput, defined as the number of wafers processed per hour. High process yields, and high wafer throughput can be impacted by the presence of defects, especially when operator intervention is involved. Thus, detection and identification of micro and nano-sized defects by inspection tools, such as a SEM, may be essential for maintaining high yields and low cost.

[0022] In a charged-particle beam imaging or inspection system, such as a SEM, the charged-particle beam may be focused on the wafer using an electromagnetic lens having electromagnetic coils circled around the lens (e.g., the coils being inside a ferromagnetic base). An electric current through the electromagnetic coils may generate a magnetic field that focuses or defocuses the charged-particle beam. The amount of heat generated may be proportional to the electric current passing through the coils and to the number of coils. In cases where the electromagnetic coils are near to the wafer, conductive and radiative heat losses may cause, among other problems, the wafer temperature to rise locally.

[0023] When manufacturing a computer chip or an integrated circuit, in some examples extremely small structures are formed on a silicon wafer. These structures may include transistors, capacitors, diodes, etc., which do the “thinking” of the computer chip, and metal wires that may be used toconnect the transistors. These structures are extremely small, for example, 10,000 metal wires, each wire approximately 10 nm wide, placed side by side can fit within the width of a human hair. A computer chip can have several layers of metal wires, connecting the structures in horizontal or vertical planes. A metal wire on a first layer may be connected to a metal wire on a second layer by a contact hole cut between the two layers and that is filled with metal, so that the metal on the first layer connects to the bottom side of the metal in the contact hole, which runs vertically through an insulation layer and connects on the top side of the contact hole metal to the second layer. As you might imagine, with the incredibly small dimension of these wires and contact holes, they must be placed (also referred to as aligned) very precisely, or they will not line up properly in the final product. Even the smallest amount of misalignment may cause the connection from the first wire to the second wire via the contact hole metal to fail, which may render the entire computer chip defective.

[0024] Exposing the wafer to excessive heat for extended periods of time may cause the wafer to expand, with structures on the wafer resultantly drifting away from a target position due to the expansion of the wafer. In an example, the structures drifted away from a target position at a rate of ~ 8 nm every minute, detrimentally higher than an allowable limit. Such high thermal drift rates of the wafer can cause fatal errors when manufacturing the computer chip or locating a defect on the wafer. Even slight changes in temperature can cause the area of interest to rapidly drift out of the field of view of a SEM image, making it challenging to acquire images and analytical data from the area, thus adversely affecting the throughput and inspection yield. In addition, heat exposure to neighboring opto-electric components, such as position sensors, mirrors, motors, etc. can cause stage positioning error and beam placement accuracy error.

[0025] Thermal management issues may be accentuated in a multi-beam inspection tool. Though useful in increasing the wafer inspection throughput by using multiple beams to inspect a wafer, where each beam may image a different point on the wafer, multi-beam inspection tools may be plagued by excessive heat generation. Focusing multiple beams may require a larger number of electromagnetic coils or higher electric current to be passed through the electromagnetic coils, necessitating improved heat dissipation systems and methods.

[0026] During SEM operation, an objective lens may generate an excessive amount of heat. Temperature increases of the objective lens may cause expansion of materials within the objective lens and alter the conductive and magnetic effects of the lens. This may result in aberrations in the charged-particle beam and negatively impact focus. Thus, inspection throughput may be decreased, or image resolution may be decreased due to improper heat dissipation in the SEM. Conventional methods to cool the objective lens involve flowing water in the SEM and around the objective lens assembly via a pipe to remove heat generated from the objective lens. However, this poses the risk of water leaking inside the SEM, destroying electronics and vacuum, and necessitating a lengthy and costly repair. Further, conventional methods and systems bond the water pipe to the objective lens byusing a thermal glue to ensure good contact between a water pipe and the objective lens. However, thermal glue may have suboptimal thermal conductivity, thereby reducing the capacity to dissipate heat generated in the objective lens. An improved heat dissipation method and system is thus desired.

[0027] In some aspects of the present disclosure, an objective lens structure including a plurality of electromagnetic coils and a bobbin may be used to cool an objective lens of a charged-particle beam system. The bobbin may include a heat pipe to transfer heat from the bobbin to a cooling plate positioned outside of the charged particle beam system. The heat pipe may contain a phase change material to transfer heat between the bobbin and the cooling plate. The heat pipe may also not contain water, and thus avoid water leaking into the charged particle beam system. In some embodiments, the heat pipe may be buried in the bobbin or may be soldered to the bobbin, both of which may improve heat conductivity between the bobbin and the heat pipe. The phase change material within the heat pipe may absorb the heat generated by passing electric current through the electromagnetic coils. The phase change material may then be dispensed to the cooling plate, in which the absorbed heat may be removed with an external coolant. Some of the advantages of using a heat pipe coupled with the bobbin may be efficient heat dissipation from the electromagnetic coils, efficient space utilization, compatible material and design flexibility, and improved reliability and manufacturability of objective lens, while avoiding coolant fluid from leaking in the charged particle system.

[0028] In the context of this disclosure, a low thermal conductivity material may be defined as a material having thermal conductivity values in the range of 1-10 W.m '.K1under standard measurement conditions. A high thermal conductivity material may be defined as a material having thermal conductivity values in the range of 20-2000 W.m1. K1under standard measurement conditions.

[0029] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings, the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described.

[0030] As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a database may include A or B, then, unless specifically stated otherwise or infeasible, the database may include A, or B, or A and B. As a second example, if it is stated that a database may include A, B, or C, then, unless specifically stated otherwise or infeasible, the database may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0031] FIG. 1 illustrates an example electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. EBI system 100 may be used for imaging. As shown in FIG.1, EBI system 100 includes a main chamber 101, a load / lock chamber 102, a beam tool 104, and an equipment front end module (EFEM) 106. Beam tool 104 is located within main chamber 101. EFEM 106 includes a first loading port 106a and a second loading port 106b. EFEM 106 may includeadditional loading port(s). First loading port 106a and second loading port 106b receive wafer front opening unified pods (FOUPs) that contain wafers (e.g., semiconductor wafers or wafers made of other material(s)) or samples to be inspected (wafers and samples may be used interchangeably). A “lot” is a plurality of wafers that may be loaded for wafer processing as a batch.

[0032] One or more robotic arms (not shown) in EFEM 106 may transport the wafers to load / lock chamber 102. Load / lock chamber 102 is connected to a load / lock vacuum pump system (not shown) which removes gas molecules in load / lock chamberl02 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) may transport the wafer from load / lock chamber 102 to main chamber 101. Main chamber 101 is connected to a main chamber vacuum pump system (not shown) which removes gas molecules in main chamber 101 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is subject to inspection by beam tool 104. Beam tool 104 may be a single-beam system or a multi-beam system.

[0033] A controller 109 is electronically connected to beam tool 104. Controller 109 may be a computer configured to execute various controls of EBI system 100. While controller 109 is shown in FIG. 1 as being outside of the structure that includes main chamber 101, load / lock chamber 102, and EFEM 106, it is appreciated that controller 109 may be a part of the structure.

[0034] In some embodiments, controller 109 may include one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a Programmable Logic Array (PLA), a Programmable Array Logic (PAL), a Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field- Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), and any type circuit capable of data processing. The processor may also be a virtual processor that includes one or more processors distributed across multiple machines or devices coupled via a network.

[0035] In some embodiments, controller 109 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes and data may include an operating system (OS) and one or more application programs (or “apps”) for specific tasks. The memory may also be a virtual memory that includes one or more memories distributed across multiple machines or devices coupled via a network.

[0036] FIG. 2 illustrates a schematic diagram of an example multi-beam tool 104 (also referred to herein as apparatus 104) and an image processing system 290 that may be configured for use in EBI system 100 (FIG. 1), consistent with embodiments of the present disclosure.

[0037] Beam tool 104 comprises a charged-particle source 202, a gun aperture 204, a condenser lens 206, a primary charged-particle beam 210 emitted from charged-particle source 202, a source conversion unit 212, a plurality of beamlets 214, 216, and 218 of primary charged-particle beam 210, a primary projection optical system 220, a motorized wafer stage 280, a wafer holder 282, multiple secondary charged-particle beams 236, 238, and 240, a secondary optical system 242, and a charged- particle detection device 244. Primary projection optical system 220 can comprise a beam separator 222, a deflection scanning unit 226, and an objective lens 228. Charged-particle detection device 244 can comprise detection sub-regions 246, 248, and 250.

[0038] Charged-particle source 202, gun aperture 204, condenser lens 206, source conversion unit 212, beam separator 222, deflection scanning unit 226, and objective lens 228 can be aligned with a primary optical axis 260 of apparatus 104. Secondary optical system 242 and charged-particle detection device 244 can be aligned with a secondary optical axis 252 of apparatus 104.

[0039] Charged-particle source 202 can emit one or more charged particles, such as electrons, protons, ions, muons, or any other particle carrying electric charges. In some embodiments, charged- particle source 202 may be an electron source. For example, charged-particle source 202 may include a cathode, an extractor, or an anode, wherein primary electrons can be emitted from the cathode and extracted or accelerated to form primary charged-particle beam 210 (in this case, a primary electron beam) with a crossover (virtual or real) 208. For ease of explanation without causing ambiguity, electrons are used as examples in some of the descriptions herein. However, it should be noted that any charged particle may be used in any embodiment of this disclosure, not limited to electrons. Primary charged-particle beam 210 can be visualized as being emitted from crossover 208. Gun aperture 204 can block off peripheral charged particles of primary charged-particle beam 210 to reduce Coulomb effect. The Coulomb effect may cause an increase in size of probe spots.

[0040] Source conversion unit 212 can comprise an array of image-forming elements and an array of beam-limit apertures. The array of image-forming elements can comprise an array of micro-deflectors or micro-lenses. The array of image-forming elements can form a plurality of parallel images (virtual or real) of crossover 208 with a plurality of beamlets 214, 216, and 218 of primary charged-particle beam 210. The array of beam-limit apertures can limit the plurality of beamlets 214, 216, and 218. While three beamlets 214, 216, and 218 are shown in FIG. 2, embodiments of the present disclosure are not so limited. For example, in some embodiments, the apparatus 104 may be configured to generate a first number of beamlets. In some embodiments, the first number of beamlets may be in a range from 1 to 1000. In some embodiments, the first number of beamlets may be in a range from 200-500. In an exemplary embodiment, the apparatus 104 may generate 400 beamlets.

[0041] Condenser lens 206 can focus primary charged-particle beam 210. The electric currents of beamlets 214, 216, and 218 downstream of source conversion unit 212 can be varied by adjusting the focusing power of condenser lens 206 or by changing the radial sizes of the corresponding beam-limit apertures within the array of beam-limit apertures. Objective lens 228 can focus beamlets 214, 216, and 218 onto a wafer 230 for imaging, and can form a plurality of probe spots 270, 272, and 274 on a surface of wafer 230.

[0042] Beam separator 222 can be a beam separator of Wien filter type generating an electrostatic dipole field and a magnetic dipole field. In some embodiments, if they are applied, the force exerted by the electrostatic dipole field on a charged particle (e.g., an electron) of beamlets 214, 216, and 218 can be substantially equal in magnitude and opposite in a direction to the force exerted on the charged particle by magnetic dipole field. Beamlets 214, 216, and 218 can, therefore, pass straight through beam separator 222 with zero deflection angle. However, the total dispersion of beamlets 214, 216, and 218 generated by beam separator 222 can also be non-zero. Beam separator 222 can separate secondary charged-particle beams 236, 238, and 240 from beamlets 214, 216, and 218 and direct secondary charged-particle beams 236, 238, and 240 towards secondary optical system 242.

[0043] Deflection scanning unit 226 can deflect beamlets 214, 216, and 218 to scan probe spots 270, 272, and 274 over a surface area of wafer 230. In response to the incidence of beamlets 214, 216, and 218 at probe spots 270, 272, and 274, secondary charged-particle beams 236, 238, and 240 may be emitted from wafer 230. Secondary charged-particle beams 236, 238, and 240 may comprise charged particles (e.g., electrons) with a distribution of energies. For example, secondary charged-particle beams 236, 238, and 240 may be secondary electron beams including secondary electrons (energies < 50 eV) and backscattered electrons (energies between 50 eV and landing energies of beamlets 214, 216, and 218). Secondary optical system 242 can focus secondary charged-particle beams 236, 238, and 240 onto detection sub-regions 246, 248, and 250 of charged-particle detection device 244. Detection sub-regions 246, 248, and 250 may be configured to detect corresponding secondary charged-particle beams 236, 238, and 240 and generate corresponding signals (e.g., voltage, current, or the like) used to reconstruct an SCPM image of structures on or underneath the surface area of wafer 230.

[0044] The generated signals may represent intensities of secondary charged-particle beams 236, 238, and 240 and may be provided to image processing system 290 that is in communication with charged-particle detection device 244, primary projection optical system 220, and motorized wafer stage 280. The movement speed of motorized wafer stage 280 may be synchronized and coordinated with the beam deflections controlled by deflection scanning unit 226, such that the movement of the scan probe spots (e.g., scan probe spots 270, 272, and 274) may orderly cover regions of interests on the wafer 230. The parameters of such synchronization and coordination may be adjusted to adapt to different materials of wafer 230. For example, different materials of wafer 230 may have differentresistance-capacitance characteristics that may cause different signal sensitivities to the movement of the scan probe spots.

[0045] The intensity of secondary charged-particle beams 236, 238, and 240 may vary according to the external or internal structure of wafer 230, and thus may indicate whether wafer 230 includes defects. Moreover, as discussed above, beamlets 214, 216, and 218 may be projected onto different locations of the top surface of wafer 230, or different sides of local structures of wafer 230, to generate secondary charged-particle beams 236, 238, and 240 that may have different intensities. Therefore, by mapping the intensity of secondary charged-particle beams 236, 238, and 240 with the areas of wafer 230, image processing system 290 may reconstruct an image that reflects the characteristics of internal or external structures of wafer 230.

[0046] In some embodiments, image processing system 290 (which may be part of controller 109) may include an image acquirer 292, a storage 294, and a controller 296. Image acquirer 292 may comprise one or more processors. For example, image acquirer 292 may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, or the like, or a combination thereof. Image acquirer 292 may be communicatively coupled to charged-particle detection device 244 of beam tool 104 through a medium such as an electric conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, or a combination thereof. In some embodiments, image acquirer 292 may receive a signal from charged- particle detection device 244 and may construct an image. Image acquirer 292 may thus acquire SCPM images of wafer 230. Image acquirer 292 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, or the like. Image acquirer 292 may be configured to perform adjustments of brightness and contrast of acquired images. In some embodiments, storage 294 may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer-readable memory, or the like. Storage 294 may be coupled with image acquirer 292 and may be used for saving scanned raw image data as original images, and post-processed images. Image acquirer 292 and storage 294 may be connected to controller 296. In some embodiments, image acquirer 292, storage 294, and controller 296 may be integrated together as one control unit.

[0047] In some embodiments, image acquirer 292 may acquire one or more SCPM images of a wafer based on an imaging signal received from charged-particle detection device 244. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image comprising a plurality of imaging areas. The single image may be stored in storage 294. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of wafer 230. The acquired images may comprise multiple images of a single imaging area of wafer 230 sampled multiple times over a time sequence. The multiple images may be stored in storage 294. In someembodiments, image processing system 290 may be configured to perform image processing steps with the multiple images of the same location of wafer 230.

[0048] In some embodiments, image processing system 290 may include measurement circuits (e.g., analog-to-digital converters) to obtain a distribution of the detected secondary charged particles (e.g., secondary electrons). The charged-particle distribution data collected during a detection time window, in combination with corresponding scan path data of beamlets 214, 216, and 218 incident on the wafer surface, can be used to reconstruct images of the wafer structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of wafer 230, and thereby can be used to reveal any defects that may exist in the wafer.

[0049] In some embodiments, the charged particles may be electrons. When electrons of primary charged-particle beam 210 are projected onto a surface of wafer 230 (e.g., probe spots 270, 272, and 274), the electrons of primary charged-particle beam 210 may penetrate the surface of wafer 230 for a certain depth, interacting with particles of wafer 230. Some electrons of primary charged-particle beam 210 may elastically interact with (e.g., in the form of elastic scattering or collision) the materials of wafer 230 and may be reflected or recoiled out of the surface of wafer 230. An elastic interaction conserves the total kinetic energies of the bodies (e.g., electrons of primary charged-particle beam 210) of the interaction, in which the kinetic energy of the interacting bodies does not convert to other forms of energy (e.g., heat, electromagnetic energy, or the like). Such reflected electrons generated from elastic interaction may be referred to as backscattered electrons (BSEs). Some electrons of primary charged-particle beam 210 may inelastically interact with (e.g., in the form of inelastic scattering or collision) the materials of wafer 230. An inelastic interaction does not conserve the total kinetic energies of the bodies of the interaction, in which some or all of the kinetic energy of the interacting bodies convert to other forms of energy. For example, through the inelastic interaction, the kinetic energy of some electrons of primary charged-particle beam 210 may cause electron excitation and transition of atoms of the materials. Such inelastic interaction may also generate electrons exiting the surface of wafer 230, which may be referred to as secondary electrons (SEs). Yield or emission rates of BSEs and SEs depend on, e.g., the material under inspection and the landing energy of the electrons of primary charged-particle beam 210 landing on the surface of the material, among others. The energy of the electrons of primary charged-particle beam 210 may be imparted in part by its acceleration voltage (e.g., the acceleration voltage between the anode and cathode of charged-particle source 202 in FIG. 2). The quantity of BSEs and SEs may be more or fewer (or even the same) than the injected electrons of primary charged-particle beam 210.

[0050] The images generated by SCPM may be used for defect inspection. For example, a generated image capturing a test device region of a wafer may be compared with a reference image capturing the same test device region. The reference image may be predetermined (e.g., by simulation) and include no known defect. If a difference between the generated image and the reference image exceeds a tolerance level, a potential defect may be identified. For another example, the SCPM may scanmultiple regions of the wafer, each region including a test device region designed as the same, and generate multiple images capturing those test device regions as manufactured. The multiple images may be compared with each other. If a difference between the multiple images exceeds a tolerance level, a potential defect may be identified.

[0051] Reference is now made to FIG. 3, which illustrates a cross-section view of an exemplary objective lens structure 300 of a charged-particle beam system (such as, charged-particle beam inspection system 1 of FIG. 1), consistent with embodiments of the present disclosure. Objective lens structure 300 may include an objective lens housing 310 having an inner wall 312 and an outer wall 314, a bobbin 320, a channel 330 comprising an inlet channel 335, electromagnetic coils 340, and a magnetic field guide 350. Objective lens structure 300 may include other components, not shown in FIG. 3, such as an objective lens assembly, electromagnetic coil isolators, thermal gap fillers, thermal sensors, etc., relevant to the functioning of objective lens structure 300.

[0052] Objective lens housing 310 may be configured to house at least a portion of objective lens 131. In some embodiments, objective lens housing 310 may house the entire objective lens 131. To obtain a higher resolution of images formed by a charged-particle beam (such as, primary electron beam 202 of FIG. 2) objective lens 131 may be an electromagnetic compound lens in which the sample may be immersed in the magnetic field of objective lens 131. In some embodiments, objective lens 131 includes a magnetic lens and an electrostatic lens (not illustrated). The magnetic lens may be configured to focus the charged-particle beam, or each primary beamlet in a multi-beam apparatus (such as, electron beam tool 104 of FIG. 2), at relatively low aberrations to generate relatively small probe spots on a sample. The electrostatic lens may be configured to influence the landing energy of the charged-particle beam or each primary beamlet to ensure that the primary charged-particles land on the sample at a relatively low kinetic energy and pass through the apparatus with a relatively high kinetic energy. In some embodiments, objective lens 131 may be configured to be an “immersion lens.” As a result, the sample may be immersed both in an electrostatic field E (electrostatic immersion) of the electrostatic lens and a magnetic field B (magnetic immersion) of the magnetic lens. Electrostatic immersion and magnetic immersion may reduce aberrations of objective lens 131. As electrostatic and magnetic fields get stronger, the aberrations of objective lens 131 may become smaller. Electrostatic field E, however, should be limited to within a safe range in order to avoid discharging or arcing on the sample. Due to this limitation of the field strength of electrostatic field E, further enhancement of the magnetic field strength in an immersion configuration may allow a further reduction in the aberrations of objective lens 131, and thereby improve image resolution.

[0053] In some embodiments, objective lens housing 310 may house at least a portion of coils 340, a portion of bobbin 320, and channel 330. Objective lens housing 310 may comprise a ferromagnetic material including, but not limited to, cobalt, nickel, iron, chromium dioxide, or alloys thereof. Ferromagnetic materials, as described herein, may refer to materials that have a large, positive susceptibility to an external magnetic field. Ferromagnetic materials exhibit a strong attraction tomagnetic fields and are able to retain their magnetic properties after the external field has been removed.

[0054] In some embodiments, objective lens housing 310 may comprise a material having low thermal conductivity including, but not limited to, ceramic materials such as cerium oxide, silica, fused silica, quartz, zirconium dioxide, etc. In some embodiments, objective lens housing 310 may comprise a material coated with a low thermal conductivity material, such as, for example, cerium oxide. The low thermal conductivity materials may be useful in minimizing heat loss from objective lens structure 300 to neighboring components, for example, stage positioning module, metro-frame supporting the stage positioning module, mirror-block, high voltage plates, clamps, etc. In some embodiments, a portion of objective lens housing 310 may comprise a reflective coating to reduce heat loss due to radiation. Other suitable techniques to reduce heat loss and heat transfer may be applied as well.

[0055] In some embodiments, objective lens housing 310 may comprise inner wall 312 proximal to primary optical axis 100_l and outer wall 314 distal from primary optical axis 100_l. Inner wall 312 and outer wall 314 may comprise different materials, the same material coated with different materials, etc., based on the design considerations and the application. For example, inner wall 312 may comprise a ferromagnetic material (e.g., iron) configured to concentrate the magnetic field generated by passing electric current through coils 340, and outer wall 314 may comprise a low thermal conductivity material (e.g., cerium oxide) configured to minimize heat loss to the external surroundings. Other suitable materials and combination of materials may be used, as needed.

[0056] In some embodiments, objective lens housing 310 may comprise a cylinder having a central bore 316, configured to receive objective lens 131. As shown in FIG. 3, central bore 316 is defined by boundaries of inner surface of inner wall 312 and may be designed to conform to the shape and contours of objective lens 131.

[0057] As illustrated in the cross-section in FIG. 3, bobbin 320 may be disposed in an area between inner wall 312 and outer wall 314 of objective lens housing 310. In some embodiments, at least a portion of bobbin 320 may be coupled to a portion of outer wall 314, or a portion of inner wall 312, or other portions of objective lens housing 310 by welding, hot-pressing, gluing, mechanical coupling, etc. Other fastening techniques may be employed based on the materials and application.

[0058] In some embodiments, objective lens structure 300 may comprise bobbin 320 having channel 330 or a plurality of channels 330. A channel, as referred to herein, may be a path through which a fluid may pass or circulate, and may include more than one channel. In some embodiments, bobbin 320 comprises a plurality of channels 330 through which a fluid may circulate. The fluid may comprise a cooling fluid including, but not limited to, a coolant, a cooling liquid, water, gas, compressed gas, or mixtures thereof. In conventional apparatuses and systems, the cooling fluid generally used is water. It should be appreciated that channel, plurality of channels, channels and cooling channels may be interchangeably used herein.

[0059] In some embodiments, bobbin 320 having cooling channels 330 may comprise a single material having thermal conductivity in the range of 20-2000 W.m '.K1under standard measurement conditions, for example, materials including but not limited to aluminum, titanium, copper, graphite, aluminum nitride, aluminum carbide, metal alloys, metal-ceramic composites, etc. In some embodiments, bobbin 320 having cooling channels 330 may comprise more than one material having different thermal conductivities and machinability, for example, a portion of bobbin 320 may comprise aluminum and cooling channels 330 may comprise titanium. Other combinations may be possible as well.

[0060] In some embodiments, channels 330 may be disposed on the outer surface of bobbin 320 and may be arranged vertically, or horizontally, or circumferentially around bobbin 320. In some embodiments, channels 330 may be disposed within bobbin 320 (as shown in FIG. 4), and may be arranged vertically, or horizontally, or circumferentially within bobbin 320. Other channel layouts and configurations may be suitably used.

[0061] Bobbin 320 may comprise inlet channel 335 configured to circulate a fluid through channel 330. A fluid, as referred to herein, may comprise, among others, a liquid, a coolant, a cooling liquid, a gas, a compressed gas, or mixtures thereof. The fluid may be configured to absorb heat generated by passing large electric current through electromagnetic coils 340 (discussed later). The fluid may be circulated through channel 330 before dispensing out via outlet channel (not illustrated).

[0062] Channel 330 may comprise a single loop around bobbin 320. In some embodiments, channel 330 may comprise multiple loops around bobbin 320, based on the application and system cooling requirements. In some embodiments, channel 330 may comprise one or more input channels and a single output channel. For example, in a multi-beam apparatus, where more than one region of objective lens structure 300 may require temperature control, an additional inlet channel 335 may be used. In some embodiments, channel 330 may comprise a single input channel and multiple output channels. Other combinations of numbers and configurations of input channels and output channels may be suitably designed and employed.

[0063] A surface forming channel 330, also referred to as the external surface of channel 330, may have surface features, for example, micro-indentations, nano-indentations, protrusions, roughening texture, etc. to increase the surface area for enhanced heat transfer. The external surface features may be introduced after bobbin 320 having channel 330 is manufactured or fabricated. Alternatively, the external surface features may be incorporated in the original design prior to being additively manufactured using a 3D printer.

[0064] Channel 330 may comprise an enclosed path, for example, a channel having a circular or an elliptical cross-section, and a wall thickness. The shape of the cross-section and the area of the crosssection may be determined based on the application, space availability, material compatibility, or cooling requirements of the system. For example, channel 330 having a circular cross-section may have an outer diameter of 4 mm, a uniform wall thickness of 0.5 mm, and an inner diameter of 3 mm.Channel 330 may comprise uniform or non-uniform wall thicknesses. It should be appreciated that the size, shape, cross-section, area, total volume and other relevant dimensions of channel 330 may be determined and designed, as needed.

[0065] Objective lens structure 300 may comprise electromagnetic coils 340 configured to adjust the focus of a single or multiple charged-particle beams on wafer 190. Electromagnetic coils 340 may comprise an electrical conductor, such as a wire in the shape of a coil, spiral, helix, etc. An electric current may be passed through electromagnetic coils 340 to produce a circular magnetic field around the conductor. In a coil configuration, such as illustrated in FIG. 3, the electrical conductor may be wound around bobbin 320 multiple times to increase the magnetic field density of objective lens 131 placed in central bore 316. Electromagnetic coils 340 may comprise an electrical conductor including, but no limited to, copper, aluminum, silver, etc.

[0066] Electromagnetic coils 340 may comprise a fine focus coil 340_l and a coarse focus coil 340_2 configured to focus charged-particle beam 102_l. Fine focus coil 340_l and coarse focus coil 340_2 may comprise different materials or different dimensions. Alternatively, the amount of electric current passed through fine focus coil 340_l and coarse focus coil 340_2 may be adjusted to vary the magnetic field generated to control the overall beam focus. The electrical conductor wire, such as copper wire, may be encapsulated with an insulating material. Due to the large amount of heat generated by passing electrical current through electromagnetic coils 340, a thermal gap filler material may be applied between each layer of coils. The thermal gap filler material may comprise thermal gap filler gels, putty, or pads having a thermal conductivity of 1 W.m '.K1or higher, to dissipate the local heat and electrical resistance of 5 x 1012ohms or higher to provide electrical insulation between two layers of conductor coil. It should be appreciated that other suitable thermal gap filler materials may be used as well.

[0067] Objective lens structure 300 may comprise magnetic field guide 350, as shown in FIG. 3, configured to guide the magnetic field generated by electromagnetic coils 340 towards objective lens 131. Magnetic field guide 350 may be configured to minimize exposure of wafer 190 to magnetic field created in electromagnetic coils 340 or other stray magnetic field. Magnetic field guide 350 may be clamped or coupled to outer wall 314 of objective lens housing 310 or bobbin 320 using suitable coupling techniques including, but not limited to, welding, gluing, mechanical fastening, epoxy bonding, brazing, ultrasonic welding, soldering, etc.

[0068] Reference is now made to FIG. 4, which illustrates a cross-section view of an exemplary objective lens structure 400 of a charged-particle beam system (such as, charged-particle beam inspection system 1 of FIG. 1). Objective lens structure 400 may include channel 330 disposed within bobbin 320, an inlet port 432 comprising at least a portion of inlet channel 335, cooling plate 420 comprising a cooling channel 430.

[0069] Cooling plate 420 may be coupled with bobbin 320 such that channel 330 and cooling channel 430 are aligned to form a continuous channel for circulating the fluid. Cooling plate 420 may becoupled with bobbin 320 and outer wall 314 of objective lens housing 310. Cooling plate 420 may be coupled with bobbin 320 by a fastening mechanism 460 including, but not limited to, mechanical fastening, welding, ultrasonic welding, soldering, gluing, epoxy bonding, brazing, etc. Cooling plate 420 may comprise, among others, a ferromagnetic material or a high thermal conductivity material. Cooling plate 420 and bobbin 320 may comprise similar material to minimize heat transfer losses due to a mismatch in thermal coefficients and heat transfer capacity.

[0070] Channel 330 may be disposed within bobbin 320, and cooling channel 430 may be disposed within cooling plate 420 such that, upon assembling, channel 330 and cooling channel 430 are aligned to form a continuous circulation path for the fluid. Cooling plate 420 having cooling channel 430 may be additively manufactured using a 3D printer, or subtractively manufactured using a CNC machine.

[0071] Inlet port 432 may be configured to receive the fluid from a fluid source. Inlet port 432 may comprise at least a portion of inlet channel 335. Inlet port 432 may be externally attached to bobbin 320 using mechanical fastening methods. Alternatively, inlet port 432 may be integrally connected with bobbin 320. For example, bobbin 320 including inlet port 432 having inlet channel 335 may be additively manufactured using a 3D printer. In some embodiments, bobbin 320 including inlet port 432 having inlet channel 335 may be subtractively manufactured using a CNC machine or a lathe.

[0072] Reference is now made to FIG. 5, which is an illustration of an example fluid pipe attached in a channel of a bobbin in a conventional system or apparatus. FIG. 5 illustrates a portion of a bobbin 501 (e.g., bobbin 320 in FIG. 3 and FIG. 4) in which a fluid pipe 503 is placed within a channel 502 (e.g., channel 330 in FIG. 3 and FIG. 4). Coolant fluid (e.g., water) may be passed through fluid pipe 503 to absorb heat generated from the charged particle system as described above. During manufacturing of bobbin 501, thermal glue 504 is applied around fluid pipe 503 to contact fluid pipe 503 to bobbin 501. Thermal glue 504 may also fill a portion of channel 502 to ensure fluid pipe 503 is securely coupled to bobbin 501. However, thermal glue 504 has an undesirably low thermal conductivity and may limit heat transfer to only the contact area between bobbin 501 and fluid pipe 503. Additionally, application of thermal glue 504 may be difficult to control and may result in bubbles 505 that are trapped within thermal glue 504. An excess of bubbles 505 may impact how securely fluid pipe 503 is attached to bobbin 501 and may further reduce heat transfer from bobbin 501 to fluid pipe 503.

[0073] Because conventional apparatuses and systems use fluids as a coolant fluid, there may be a significant risk of the fluid (e.g., water) leaking at an inlet channel or an inlet port of the bobbin (e.g., inlet channel 335 and inlet port 432 of FIG. 3 and FIG. 4, respectively). Furthermore, there is a risk of a fluid pipe bursting and leaking coolant fluid. Leakage of fluid coolant may damage any electronics in the charged particle system and compromise vacuum. If leakage of fluid coolant occurs, maintenance or repair may be a time consuming and difficult process. The vacuum in the system may need to be vented to atmospheric pressure, the charged particle system may need to be fully disassembled, and the bobbin (e.g., bobbin 320 of FIG. 3 and FIG. 4) may need to be removed toexpose the fluid channel (e.g., channel 330 of FIG. 3 and FIG. 4). This may significantly reduce throughput for IC inspection and high- volume manufacturing (HVM) of ICs. Moreover, conventional apparatuses and systems are limited in cooling capacity because contact between the fluid pipe and the fluid channel of the bobbin is facilitated by thermal glue. However, thermal glue has limited thermal conductivity, and application of the thermal glue to the fluid pipe / fluid channel may create bubbles in the glue. This may be difficult to control during manufacturing of a charged particle beam system, and further result in inconsistent cooling capacity for the system.

[0074] Reference is now made to FIG. 6, which is an illustration of an example heat transfer component coupled to a heat collecting component of a charged particle system, consistent with embodiments of the present disclosure. FIG. 6 illustrates a heat transfer component 603 coupled to a heat collecting component 601. In some embodiments, heat collecting component 601 may be a bobbin (e.g., bobbin 320 in FIG. 3 and FIG. 4). The term “heat collecting component” may be understood to include any surrounding or adjacent housing, covering, container, shield, or the like for a heat generating component in a vacuum. In some embodiments, the term “heat collecting component” may be understood to include any surrounding or adjacent housing, covering, container, shield, or the like for a heat generating component (e.g., magnetic coil 340 in FIG. 3 and FIG. 4) in a charged particle beam apparatus (e.g., beam tool 104 of FIG. 2) In some embodiments, heat transfer component 603 may be a cooling component that does not include water. In some embodiments, heat transfer component 603 may be a heat pipe. Heat transfer component 603 may be coupled to heat collecting component 601 via soldering. FIG. 6 illustrates a solder 604 that may connect heat transfer component 603 and heat collecting component 601. In some embodiments, solder 604 may be a lead- free solder. In some embodiments, solder 604 may be a lead-free tin solder. Solder 604 may improve a contact area between heat transfer component 603 and heat collecting component 601 (e.g., compared to a contact area between fluid pipe 503 and bobbin 501 in FIG. 5). FIG. 6 illustrates heat transfer component 603 may be soldered within a channel 602 of heat collecting component 601 (e.g., a bobbin). However, embodiments of the present disclosure are not so limited, and it is appreciated that heat transfer component 603 may be coupled to an outside surface of heat collecting component 601, an inside surface of heat collecting component 601, or any other surface of heat collecting component 601 such that heat transfer component 603 is securely attached. It is further appreciated that FIG. 6 is not drawn to scale, and any amount of solder 604 may be applied to couple heat transfer component 603 to heat collecting component 601.

[0075] In some embodiments, heat transfer component 603 may be a heat pipe and may contain a phase change material to absorb heat. In some embodiments, the heat pipe may be made from copper, stainless steel, aluminum, or any other high thermal conductivity material. In some embodiments, the heat pipe may be made from copper, stainless steel, or aluminum. In some embodiments, the phase change material within the heat pipe may include liquid nitrogen, liquid ammonia, or any other material that may not damage electronics or a vacuum environment within a charged particle beamsystem. In some embodiments, the heat pipe may be a sealed component without any fluid supplied from an external source. In some embodiments, the heat pipe may transfer heat without a fluid flow supplied from an external source. In some embodiments, the heat pipe may transfer heat without an applied liquid flow from an external source. In some embodiments, the heat pipe may have a thickness of at least about 2.5 mm, at least about 3 mm, at least about 3.5 mm, at least about 4 mm, at least about 4.5 mm, or at least about 5 mm. In some embodiments, the heat pipe may have a thickness of which the heat pipe may sufficiently absorb and transfer heat. In some embodiments, the heat pipe may be a standard, constant conductance heat pipe, a vapor chamber heat pipe, a flat heat pipe, a planar heat pipe, a variable conductance heat pipe, a pressure controlled heat pipe, a diode heat pipe, a thermosyphon, a rotating heat pipe, a loop heat pipe, an oscillating heat pipe, a pulsating heat pipe, or any other heat pipe designed for transferring heat via phase transition.

[0076] Reference is now made to FIG. 7A, which illustrates an example schematic of a heat transfer component coupled to a heat collecting component, consistent with embodiments of the present disclosure. Heat collecting component 701 may be a bobbin in an objective lens assembly, as described above. Heat transfer component 703 may be coupled to heat collecting component 701 such that heat transfer component 703 is buried within heat colleting component 701 (e.g., within a channel of heat collecting component 701 as described in FIG. 6). In some embodiments, heat transfer component 703 may be coupled to an exterior surface or an interior surface of heat collecting component 701. FIG. 7A illustrates an example heat transfer component 703 (e.g., a heat pipe) that may be configured as a concentric circle within or surrounding heat collecting component 701. However, it is appreciated that any number of heat transfer component 703 may be coupled to heat collecting component 701. For example, in some embodiments, a plurality of heat transfer components 701 may be coupled to an upper portion of heat collecting component 701 (e.g., a top flange of a bobbin), a middle portion of heat collecting component 701 (e.g., a middle portion of a bobbin), or a lower portion of heat collecting component 701 (e.g., a bottom flange of a bobbin).

[0077] Reference is now made to FIG. 7B, which is a cross-sectional view of a heat transfer component coupled to a heat collecting component and to a heat exchanger outside of a charged particle system, consistent with embodiments of the present disclosure. FIG. 7B illustrates an example heat transfer component 703 that may be positioned within a column 704 of a charged particle beam apparatus (e.g., multi-beam tool 104 in FIG. 2) and coupled to a heat collecting component (e.g., heat collecting component 601 in FIG. 6 and 701 in FIG. 7A). Column 704 may include a central bore 705 (e.g., central bore 316 in FIG. 3). FIG. 7B also illustrates heat transfer component 703 being coupled to a heat exchanger 706. Heat exchanger 706 may be located outside of column 704 (e.g., outside of beam tool 104 in FIG. 1). Heat transfer component 703 may be coupled to column 704 and heat exchanger 706 by soldering. In some embodiments, the soldering may be via lead-free tin. In some embodiments, heat transfer component 703 and heat exchanger 706 may be an integrated component (e.g., 3-D printed).

[0078] Heat exchanger 706 may be a high thermal conductivity material. In some embodiments, heat exchanger 706 is a metal (e.g., stainless steel, copper, or aluminum). In some embodiments, heat exchanger 706 may be a cooling plate. Heat exchanger 706 may include heat exchanger line 707. In some embodiments, heat exchanger line 707 may supply coolant fluid to heat exchanger 706. In some embodiments, the coolant fluid is water. In some embodiments, heat transfer component 703 may be a heat pipe. Heat transfer component 703 may absorb heat from column 704 and transfer the absorbed heat outside of column 704 to heat exchanger 706, effectively cooling column 704. Heat exchanger 706 may conduct the absorbed heat from heat transfer component 703 to heat exchanger line 707. Heat exchanger 706 may facilitate simultaneous cooling of heat transfer component 703 via heat exchanger line 707. Heat transfer component 703 may then absorb heat from column 704 and continue to cool column 704. Thus, exchanger line 707 may be positioned outside of column 704 and away from any electronics or vacuum contained within. There is no possibility of a coolant fluid (e.g., water) in exchanger line 707 leaking in column 704.

[0079] It is appreciated that heat exchanger 706 may be in physical contact with column 704 or may be physically separated from column 704. In some embodiments, heat exchanger 706 may be coupled to an exterior surface of column 704. In some embodiments, heat exchanger 706 may be soldered to an exterior surface of column 704. It is appreciated that any number of exchanger lines 707 may be supplied to heat exchanger 706, and embodiments of the present disclosure are not so limited as illustrated in FIG. 7B.

[0080] It is further appreciated that exchanger line 707 may have a coolant fluid flow supplied from an external source. FIG. 7B illustrates a flow of coolant fluid through exchanger line 707, which may be provided to heat exchanger 706 (e.g., through a channel on or in heat exchanger 706). The coolant fluid flowing through exchanger line 707 may be supplied from an external source (e.g., a water pump) to create a coolant fluid flow. In comparison, heat transfer component 703 may be a sealed component and transfer heat without a supplied fluid flow from an external source. In some embodiments, heat transfer component 703 may transfer heat via phase transformation (e.g., liquid nitrogen vaporizing into a gas). The arrows for heat component 703 in FIG. 7B illustrate a direction of heat transfer. A phase change material (e.g., liquid nitrogen) in heat transfer component 703 may absorb heat from column 704 and undergo a phase transformation (e.g., vaporize into a gas). The vaporized liquid may increase a vapor pressure within heat transfer component 703, which may transfer the gas to a cooler portion of heat transfer component 703. This may be a portion of heat transfer component 703 located outside of column 703 and coupled to heat exchanger 706. Thus, heat transfer component 703 may have an internally driven fluid flow, whereas exchanger line 707 may have an externally supplied flow of coolant fluid. Heat transfer component 703 may have no fluid flow supplied from an external source.

[0081] Reference is now made to FIG. 7C, which is an illustration of a cross-sectional view of various configurations of a heat transfer component coupled to a heat collecting component and to acooling component of a charged particle system, consistent with embodiments of the present disclosure. FIG. 7C indicates that heat transfer component 703 may be any shape or configuration (e.g., circular, rectangular, triangular, hexagonal, or any other polygon) within column 704. In some embodiments, a heat transfer component with a straight section or portion may have improved thermal conductivity. In some embodiments, a heat transfer component with a straight section or portion may be easier to manufacture. Furthermore, it is appreciated that heat transfer component 703 may be any length in a horizontal direction, a vertical direction, or a combination thereof in a heat collecting component (e.g., column 704). Any number of heat transfer component 703 may be incorporated to transfer heat from a heat collecting component to a heat exchanger.

[0082] Reference is now made to FIG. 8, which is an example flow diagram illustrating a method 800 for cooling a component of a charged particle beam apparatus, consistent with embodiments of the present disclosure. The steps of method 800 may be performed by a computing device that includes, e.g., processor 109 of FIG. 1, or controller 296 of FIG. 2. It is appreciated that the illustrated method 800 may be altered to modify the order of steps and to include additional steps.

[0083] In step 801, heat from a heat collecting component of the charged particle beam apparatus may be absorbed via a heat transfer component. In some embodiments, the heat transfer component (e.g., heat transfer component 603 of FIG. 6 or heat transfer component 703 in FIGS. 7A-C) may be a heat pipe. The heat pipe may be any shape, configuration, thickness, or material as described above. In some embodiments, the heat collecting component may be a column (e.g., column 704 in FIG. 7B and FIG. 7C) of a charged particle beam apparatus. In some embodiments, the heat collecting component may be an objective lens assembly (e.g., objective lens 228 in FIG. 2). In some embodiments, the heat collecting component may be a bobbin (e.g., bobbin 320 in FIG. 3 or FIG. 4).

[0084] In step 802, a coolant fluid may be supplied to a heat exchanger positioned outside of the heat collecting component. The heat exchanger may be thermally connected to the heat transfer component. In some embodiments, the heat exchanger (e.g., heat exchanger 706 in FIG. 7B and FIG. 7C) is coupled to an exterior surface of the heat collecting component. In some embodiments, the heat exchanger is soldered to an exterior surface of the heat collecting component. In some embodiments, the heat exchanger is soldered to the heat transfer component. In some embodiments, the heat exchanger is a high thermally conducting material. In some embodiments, the heat exchanger is copper, aluminum, or stainless steel. A coolant fluid may be supplied to a heat exchanger via an exchanger line (e.g., exchanger line 707 in FIG. 7B and FIG. 7C). In some embodiments, coolant fluid may be water, and the coolant fluid may not enter the charged particle beam apparatus. A computing device or a processor (e.g., processor 109 in FIG. 1) may measure a temperature of the heat collecting component and adjust a flow rate of cooling fluid through exchanger line 707 to heat exchanger 706.

[0085] In step 803, the absorbed heat in the heat transfer component is transferred to the coolant fluid via the heat exchanger. In some embodiments, the heat exchanger may facilitate conduction of heatabsorbed in the heat transfer component to the coolant fluid. The coolant fluid may then be removed from the heat exchanger, and the heat transfer component may continue to absorb heat from the heat collecting component.

[0086] A benefit provided by embodiments of the present disclosure may be an apparatus or a system to transfer heat from a heat collecting component in a vacuum chamber. In some embodiments, a heat transfer component is used to transfer heat from a heat collecting component to a heat exchanger positioned outside of the vacuum chamber. In some embodiments, the heat transfer component may be a heat pipe. In some embodiments, the heat exchanger may be a cooling plate with coolant fluid supplied to the heat exchanger. In some embodiments, the heat collecting component may be cooled without supplying coolant fluid into the vacuum chamber. Embodiments of the present disclose provide an apparatus or system that may be easier to maintain and reduce the risk of damaging electronics or vacuum within a charged particle beam apparatus. In some embodiments, efficiency of heat transfer or cooling may be improved by soldering a heat pipe to the heat collecting component. In some embodiments, a method is provided to transfer heat from a component within a vacuum chamber. Some embodiments of the present disclosure may increase throughput of IC manufacturing by ensuring safer operation of an inspection or metrology tool. Some embodiments of the present disclosure may provide a method to maintain defect inspection accuracy and yield of defect-free devices throughout HVM.

[0087] A non-transitory computer readable medium may be provided that may store instructions for a processor of a processor of an charged-particle beam tool (e.g., charged-particle beam tool 104 of FIG. 2 or multi-beam charged-particle beam tool 104 of FIG. 3) to perform method 800 of FIG. 8, to carry out thermal sensing, flow sensing, and other executable functions relating to transferring heat from a heat collecting component in a vacuum chamber to a heat exchanger positioned outside the vacuum chamber. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0088] The embodiments may further be described using the following clauses:1. A system for transferring heat in a vacuum, the system comprising: a vacuum chamber configured to provide a vacuum environment; a heat collecting component positioned within the vacuum chamber; a heat exchanger positioned outside of the vacuum chamber; and a heat pipe coupled to the heat collecting component and the heat exchanger and configured to transfer heat from the heat collecting component to the heat exchanger.2. The system of clause 1, wherein the heat pipe is sealed.3. The system of clause 1 or 2, wherein the heat pipe is coupled to the heat collecting component by soldering.4. The system of any one of clauses 1 to 3, wherein the heat pipe is coupled to the heat exchanger by soldering.5. The system of clause 3 or 4, wherein the soldering is a lead-free tin soldering.6. The system of any one of clauses 1 to 5, wherein the heat pipe comprises a phase change material.7. The system of clause 6, wherein the phase change material is liquid nitrogen or ammonia.8. The system of clause 6 or 7, wherein the heat pipe does not have a supplied fluid flow of the phase change material.9. The system of any one of clauses 1 to 8, wherein the heat pipe has a thickness of at least 2.5 mm.10. The system of any one of clauses 1 to 9, wherein the heat pipe has a polygonal shape or a circular shape.11. The system of any one of clauses 1 to 10 wherein the heat pipe comprises a high thermal conductivity material.12. The system of any one of clauses 1 to 11, wherein the heat pipe comprises a metal.13. The system of clause 12, wherein the metal is copper or stainless steel.14. The system of any one of clauses 1 to 13, wherein the heat exchanger comprises a high thermal conductivity material.15. The system of any one of clauses 1 to 14, wherein the heat exchanger comprises a metal.16. The system of clause 15, wherein the metal comprises copper, stainless steel, or aluminum.17. The system of any one of clauses 1 to 16, wherein the heat exchanger comprises a cooling plate.18. The system of any one of clauses 1 to 17, wherein the heat exchanger further comprises a coolant fluid.19. The system of clause 18, wherein the coolant fluid is water.20. The system of any one of clauses 1 to 19, wherein the heat collecting component is a component of a charged particle beam apparatus.21. The system of clause 20, wherein the charged particle beam apparatus is a scanning electron microscope.22. The system of clause 20 or 21, wherein the heat collecting component is an objective lens.23. The system of any one of clauses 20 to 22, wherein the heat collecting component is a bobbin.24. A system for transferring heat from a charged particle beam apparatus, the apparatus comprising: a heat exchanger positioned outside of the charged particle beam apparatus; and a heat pipe coupled to the charged particle beam apparatus and the heat exchanger wherein the heat pipe is configured to transfer heat from the charged particle beam apparatus to the heat exchanger.25. The system of clause 24, wherein the heat pipe is sealed.26. The system of clause 24 or 25, wherein the heat pipe is coupled to the charged particle beam apparatus by soldering.27. The system of any one of clauses 24 to 26, wherein the heat pipe is coupled to the heat exchanger by soldering.28. The system of clause 26 or 27, wherein the soldering is a lead-free tin soldering.29. The system of any one of clauses 24 to 28, wherein the heat pipe comprises a phase change material.30. The system of clause 29, wherein the phase change material is liquid nitrogen or ammonia.31. The system of clause 29 or 30, wherein the heat pipe does not have a supplied fluid flow of the phase change material.32. The system of any one of clauses 24 to 31, wherein the heat pipe has a thickness of at least 2.5 mm.33. The system of any one of clauses 24 to 32, wherein the heat pipe has a polygonal shape or circular shape.34. The system of any one of clauses 24 to 33 wherein the heat pipe comprises a high thermal conductivity material.35. The system of any one of clauses 24 to 34, wherein the heat pipe comprises a metal.36. The system of clause 35, wherein the metal is copper or stainless steel.37. The system of any one of clauses 24 to 36, wherein the heat exchanger comprises a high thermal conductivity material.38. The system of any one of clauses 24 to 37, wherein the heat exchanger comprises a metal.39. The system of clause 38, wherein the metal comprises copper, stainless steel, or aluminum.40. The system of any one of clauses 24 to 39, wherein the heat exchanger comprises a cooling plate.41. The system of any one of clauses 24 to 40, wherein the heat exchanger further comprises a coolant fluid.42. The system of clause 41, wherein the coolant fluid is water.43. The system of any one of clauses 24 to 42, wherein the charged particle beam apparatus is a scanning electron microscope.44. The system of any one of clauses 24 to 43, wherein the heat pipe is coupled to an objective lens assembly of the charged particle beam apparatus.45. The system of any one of clauses 24 to 44, wherein the heat pipe is coupled to a bobbin.46. A method for transferring heat from a charged particle beam apparatus, the method comprising: absorbing, via a heat pipe, heat from a heat collecting component of the charged particle beam apparatus; supplying a coolant fluid to a heat exchanger positioned outside of the charged particle beam apparatus; and transferring absorbed heat from the heat pipe to the coolant fluid, wherein the absorbed heat is transferred without an externally supplied fluid flow in the heat pipe.47. The method of clause 46, wherein the heat pipe is sealed.48. The method of clause 46 or 47, wherein the heat pipe is coupled to the charged particle beam apparatus and the heat exchanger.49. The method of clause 48, wherein the heat pipe is coupled to the heat collecting component and the heat exchanger.50. The method of clause 48 or 49, wherein the heat pipe is coupled to the charged particle beam apparatus by soldering.51. The method of any one of clauses 48 to 50, wherein the heat pipe is coupled to the heat exchanger by soldering.52. The method of clause 50 or 51, wherein the soldering is a lead-free tin soldering.53. The method of any one of clauses 46 to 52, wherein the heat pipe comprises a phase change material.54. The method of clause 53, wherein the phase change material is liquid nitrogen or ammonia.55. The method of clause 53 or 54 wherein the heat pipe does not have a supplied fluid flow of the phase change material.56. The method of any one of clauses 46 to 55, wherein the heat pipe has a thickness of at least 2.5 mm.57. The method of any one of clauses 46 to 56, wherein the heat pipe has a polygonal shape or a circular shape.58. The method of any one of clauses 46 to 57 wherein the heat pipe comprises a high thermal conductivity material.59. The method of any one of clauses 46 to 58, wherein the heat pipe comprises a metal.60. The method of clause 59, wherein the metal is copper or stainless steel.61. The method of any one of clauses 46 to 60, wherein the heat exchanger comprises a high thermal conductivity material.62. The method of any one of clauses 46 to 61, wherein the heat exchanger comprises a metal.63. The method of clause 62, wherein the metal comprises copper, stainless steel, or aluminum.64. The method of any one of clauses 46 to 63, wherein the heat exchanger comprises a cooling plate.65. The method of any one of clauses 46 to 64, wherein the coolant fluid is water.66. The method of any one of clauses 46 to 65, wherein the heat collecting component is an objective lens.67. The method of clause 66, wherein the heat collecting component is a bobbin.68. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for transferring heat from a charged particle beam apparatus, the operations comprising: sending a signal that causes a component of the charged particle beam apparatus to generate heat, wherein the heat is absorbed via a heat pipe; causing a coolant fluid to be supplied to a heat exchanger positioned outside of the charged particle beam apparatus; and causing heat to be transferred from the heat pipe to the coolant fluid, wherein the absorbed heat is transferred without an externally supplied fluid flow in the heat pipe.69. The non-transitory computer readable medium of clause 68, wherein the heat pipe is sealed.70. The non-transitory computer readable medium of clause 68 or 69, wherein the heat pipe is coupled to the charged particle beam apparatus and the heat exchanger.71. The non-transitory computer readable medium of clause 70, wherein the heat pipe is coupled to a heat collecting component and the heat exchanger.72. The non-transitory computer readable medium of clause 70 or 71, wherein the heat pipe is coupled to the charged particle beam apparatus by soldering.73. The non-transitory computer readable medium of any one of clauses 70 to 72, wherein the heat pipe is coupled to the heat exchanger by soldering.74. The non-transitory computer readable medium of clause 72 or 73, wherein the soldering is a lead-free tin soldering.75. The non-transitory computer readable medium of any one of clauses 68 to 74, wherein the heat pipe comprises a phase change material.76. The non-transitory computer readable medium of clause 75, wherein the phase change material is liquid nitrogen or ammonia.77. The non-transitory computer readable medium of clause 75 or 76 wherein the heat pipe does not have a supplied fluid flow of the phase change material.78. The non-transitory computer readable medium of any one of clauses 68 to 77, wherein the heat pipe has a thickness of at least 2.5 mm.79. The non-transitory computer readable medium of any one of clauses 68 to 78, wherein the heat pipe has a polygonal shape or a circular shape.80. The non-transitory computer readable medium of any one of clauses 68 to 79, wherein the heat pipe comprises a high thermal conductivity material.81. The non-transitory computer readable medium of any one of clauses 68 to 80, wherein the heat pipe comprises a metal.82. The non-transitory computer readable medium of clause 81, wherein the metal is copper or stainless steel.83. The non-transitory computer readable medium of any one of clauses 68 to 82, wherein the heat exchanger comprises a high thermal conductivity material.84. The non-transitory computer readable medium of any one of clauses 68 to 83, wherein the heat exchanger comprises a metal.85. The non-transitory computer readable medium of clause 84, wherein the metal comprises copper, stainless steel, or aluminum.86. The non-transitory computer readable medium of any one of clauses 68 to 85, wherein the heat exchanger comprises a cooling plate.87. The non-transitory computer readable medium of any one of clauses 68 to 86, wherein the coolant fluid is water.88. The non-transitory computer readable medium of any one of clauses 68 to 87, wherein the component that generates heat is an objective lens.89. The non-transitory computer readable medium of any one of clauses 71 to 88, wherein the heat collecting component is a bobbin.

[0089] The block diagrams in the figures 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 aflowchart or block diagram may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions. It should be understood that in some alternative implementations, functions indicated in a block may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed or implemented substantially concurrently, or two blocks may sometimes be executed in reverse order, depending upon the functionality involved. Some blocks may also be omitted. It should also be understood that each block of the block diagrams, and combination of the blocks, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

[0090] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

[0091] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A system for transferring heat in a vacuum, the system comprising: a vacuum chamber configured to provide a vacuum environment; a heat collecting component positioned within the vacuum chamber; a heat exchanger positioned outside of the vacuum chamber; and a heat pipe coupled to the heat collecting component and the heat exchanger and configured to transfer heat from the heat collecting component to the heat exchanger.

2. The system of claim 1, wherein the heat pipe is sealed.

3. The system of claim 1, wherein the heat pipe is coupled to the heat collecting component by soldering.

4. The system of claim 1, wherein the heat pipe is coupled to the heat exchanger by soldering.

5. The system of claim 1, wherein the heat pipe comprises a phase change material.

6. The system of claim 5, wherein the phase change material is liquid nitrogen or ammonia.

7. The system of claim 5, wherein the heat pipe does not have a supplied fluid flow of the phase change material.

8. The system of claim 1, wherein the heat pipe has a thickness of at least 2.5 mm.

9. The system of claim 1, wherein the heat pipe has a polygonal shape or a circular shape.

10. The system of claim 1, wherein the heat pipe comprises a high thermal conductivity material.

11. The system of claim 1, wherein the heat exchanger comprises a high thermal conductivity material.

12. The system of claim 1, wherein the heat exchanger comprises a cooling plate.

13. The system of claim 1, wherein the heat exchanger further comprises a coolant fluid.

14. The system of claim 13, wherein the coolant fluid is water.

15. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for transferring heat from a charged particle beam apparatus, the operations comprising: sending a signal that causes a component of the charged particle beam apparatus to generate heat, wherein the heat is absorbed via a heat pipe; causing a coolant fluid to be supplied to a heat exchanger positioned outside of the charged particle beam apparatus; and causing heat to be transferred from the heat pipe to the coolant fluid, wherein the absorbed heat is transferred without an externally supplied fluid flow in the heat pipe.

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