System and method for cooling an objective lens of a charged particle beam system

Abstract

Disclosed are systems and methods for cooling an objective lens of a charged particle beam system. According to certain embodiments, the method for cooling an objective lens of a charged particle beam system includes receiving a fluid via a fluid input port of a spool, circulating the fluid that has absorbed heat generated by a plurality of electromagnetic coils of the objective lens via a plurality of channels distributed in the spool, and distributing the fluid circulated by the plurality of channels via a fluid output port of the spool. The spool may further include a bottom flange proximate to a wafer and a top flange distal to the wafer. The spool having a plurality of channels may include an additively manufactured monolithic structure.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 62 / 773,972 filed on November 30, 2018, and the above application is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments provided herein disclose an objective lens structure for a charged particle beam system, and more particularly disclose systems and methods for cooling the objective lens structure, for example, to minimize thermal drift in the charged particle beam system. Background Art

[0004] During the manufacture of integrated circuits (ICs), unfinished or completed 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 scanning electron microscopes (SEMs), may be employed. As the physical size of IC components continues to shrink, the accuracy and yield of defect detection become increasingly important. Multiple charged beams may be employed to meet inspection throughput requirements; however, the imaging resolution of multiple charged beam systems may be compromised, rendering the inspection tools inadequate for their intended use.

[0005] Related art systems face limitations, for example, in imaging resolution and beam-spot positioning accuracy due to substantial thermal drift caused by significant current flowing through the electromagnetic coils of the objective assembly. Further improvements in the cooling of objective assemblies of charged particle beam systems are desired in the art. Summary of the invention

[0006] In one aspect, the present disclosure relates to a bobbin for cooling an objective lens of a charged particle beam system. The bobbin may include a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the bobbin and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels. The bobbin may further include a bottom flange close to a wafer in the charged particle beam system and a top flange away from the wafer. The plurality of channels include an inlet channel configured to circulate the fluid received from the fluid inlet port, an outlet channel configured to guide the circulating fluid to the fluid outlet port, and an intermediate channel connected to the inlet channel and the outlet channel fluid. The circulated fluid may absorb heat generated by a plurality of electromagnetic coils wound around at least a portion of the bobbin. The fluid may include one of a liquid, a coolant, a gas, a compressed gas, or a mixture thereof. The plurality of channels may include a liquid having a power of 20-2000 W.m -1.K -1 The material may include aluminum, titanium, copper, graphite, aluminum carbide, aluminum nitride, plastic, composite, or alloy. The spool with multiple channels may include a monolithic structure or multiple parts coupled together. The monolithic structure may be an additively manufactured monolithic structure. The additively manufactured monolithic structure may include at least one of a metal, a metal alloy, a ceramic, or a ceramic composite.

[0007] In another aspect, the present disclosure relates to a method of creating a computer-readable three-dimensional model suitable for use in manufacturing the spool, the spool comprising a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the spool and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels. The method may include inputting data representing the spool into a computer and using the data to represent the spool as a three-dimensional model suitable for use in manufacturing the spool.

[0008] In yet another aspect, the present disclosure relates to an objective lens structure. The objective lens structure may include a plurality of electromagnetic coils and a bobbin configured to circulate a fluid to absorb the heat generated by the plurality of electromagnetic coils. The bobbin may include a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the bobbin and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels. The objective lens structure may further include a thermal insulation layer disposed circumferentially between the plurality of electromagnetic coils and the ferromagnetic housing of the objective lens. The thermal insulation layer may include a fluid channel configured to absorb the heat generated by the plurality of electromagnetic coils.

[0009] In yet another aspect, the present disclosure relates to a method for cooling an objective lens of a charged particle beam system. The method may include receiving a fluid via a fluid inlet port of a bobbin, circulating a fluid that absorbs the heat generated by a plurality of electromagnetic coils of the objective lens via a plurality of channels distributed in the bobbin, and distributing the fluid circulated by the plurality of channels via a fluid outlet port of the bobbin. The plurality of channels may include an inlet channel configured to circulate the fluid received from the fluid inlet port, an outlet channel configured to guide the circulating fluid to the fluid outlet port, and an intermediate channel connected to the inlet channel and the outlet channel fluid. The circulated fluid may absorb the heat generated by a plurality of electromagnetic coils wound around at least a portion of the bobbin. The method may further include circulating a second fluid in a fluid channel of a thermal insulation layer disposed circumferentially between the plurality of electromagnetic coils and the ferromagnetic shell of the objective lens. Each of the first fluid and the second fluid may include one of a liquid, a coolant, a gas, a compressed gas, or a mixture thereof.

[0010] In yet another aspect, the present disclosure relates to a computer-readable storage medium storing data representing a spool capable of being printed on a 3D printer. The spool represented by the stored data may include a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the spool and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels.

[0011] In yet another aspect, the present disclosure relates to a computer-readable three-dimensional model of a physical spool capable of being printed on a 3D printer, which spool may include a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the spool and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system in accordance with an embodiment of the present disclosure.

[0013] Figure 2 It is a diagram showing the embodiment of the present disclosure that can be used as Figure 1 A schematic diagram of an exemplary electron beam tool that is a portion of an exemplary electron beam inspection system.

[0014] Figure 3 A cross-sectional view of an exemplary objective lens structure of a charged particle beam system according to an embodiment of the present disclosure is illustrated.

[0015] Figure 4A cross-sectional view of an exemplary objective lens structure of a charged particle beam system according to an embodiment of the present disclosure is illustrated.

[0016] Figure 5 is a schematic diagram illustrating an exemplary bobbin for cooling an objective lens of a charged particle beam system according to an embodiment of the present disclosure.

[0017] Fig. 6A and Figure 6B A cross-sectional view of an exemplary spool illustrating fluid passages therein is illustrated in accordance with an embodiment of the present disclosure.

[0018] Figure 7 is a schematic diagram illustrating the direction of fluid flow in an exemplary spool according to an embodiment of the present disclosure.

[0019] Figure 8 is a schematic diagram illustrating the direction of fluid flow in an exemplary spool according to an embodiment of the present disclosure.

[0020] Fig. 9 A cross-sectional view of an exemplary objective lens structure of a charged particle beam system according to an embodiment of the present disclosure is illustrated.

[0021] Fig.10 is a process flow chart of an exemplary method for cooling an objective lens of a charged particle beam system according to an embodiment of the present disclosure.

[0022] Fig.11 is a schematic diagram showing a system for generating a three-dimensional model of an exemplary spool. DETAILED DESCRIPTION

[0023] 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, wherein, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments given in the following description of exemplary embodiments do not represent all embodiments according to the present invention. On the contrary, they are merely examples of devices and methods according to aspects related to the present invention as recorded in the attached claims. For example, although some embodiments are described in the context of utilizing electron beams, the present disclosure is not limited thereto. Other types of charged particle beams may be similarly applied. In addition, other imaging systems may be used, such as optical imaging, photoelectric detection, X-ray detection, and the like.

[0024] By significantly increasing the packaging density of circuit components such as transistors, capacitors, diodes, etc. on IC chips, it is possible to achieve increased computing power of electronic devices while reducing the physical size of the devices. For example, in a smart phone, an IC chip (which is the size of a fingernail) can include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair. Not surprisingly, semiconductor IC manufacturing is a complex process with hundreds of individual steps. Even an error in one step can significantly affect the functionality of the final product. Even a "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 achieve a 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%.

[0025] Although high process yields are desired in IC chip manufacturing plants, it is also essential to maintain high wafer throughput, which is defined as the number of wafers processed per hour. High process yields and high wafer throughput can be affected by the presence of defects, especially when there is operator intervention. Therefore, detection and identification of micron and nanometer-sized defects by inspection tools such as SEM is essential to maintaining high yields and low costs.

[0026] In charged particle beam imaging or inspection systems such as SEM, charged particle beam systems can be focused on the wafer using an electromagnetic lens having an electromagnetic coil (e.g., a coil in a ferromagnetic base) surrounding the lens. The electric current through the electromagnetic coil can produce a magnetic field that causes the charged particle beam to focus or lose focus. The amount of heat generated can be proportional to the number of electric current and coils through the coil. When the electromagnetic coil is close to the wafer, among other problems, conduction or radiation heat loss can cause the wafer temperature to rise locally.

[0027] When manufacturing computer chips or integrated circuits, in some examples, extremely small structures are formed on a silicon wafer. These structures can include transistors, capacitors, diodes, etc., which do the "thinking" of the computer chip, as well as metal wires that can be used to connect the transistors. These structures are extremely small, for example, 10,000 metal wires placed side by side can fit within the width of a human hair, each wire being about 10 nm wide. A computer chip can have several layers of metal wires that connect structures in a horizontal or vertical plane. A metal wire on a first layer can be connected to a metal wire on a second layer through a contact hole cut between the two layers and the contact hole cut is filled with metal so that the metal on the first layer is connected to the bottom side of the metal in the contact hole, which passes vertically through the insulating layer and connects to the second layer on the top side of the contact hole metal. As can be imagined, due to the incredibly small size of these wires and contact holes, they must be placed (also called aligned) very accurately, otherwise they will not line up correctly in the final product. Even the smallest amount of misalignment can cause a first connection to fail through the contact metal to connect to a second connection, which can render the entire computer chip defective.

[0028] Exposing the wafer to excessive heat for a long time can cause the wafer to expand, and the structure on the wafer eventually drifts away from the target position due to the expansion of the wafer. In one example, the structure drifts away from the target position at a rate of 8nm per minute, which is disadvantageously higher than the allowed limit. This high thermal drift rate of the wafer may cause fatal errors when manufacturing computer chips or locating defects on the wafer. Even slight changes in temperature can cause the region of interest to drift outside the field of view of the SEM image, making it challenging to obtain images and analyze data from the area, thereby adversely affecting throughput and inspection output. In addition, thermal exposure to adjacent optoelectronic components such as position sensors, mirrors, motors, etc. may cause platform positioning errors and beam placement accuracy errors.

[0029] Thermal management issues can be exacerbated in multi-beam inspection tools. While it is useful to increase wafer inspection throughput by inspecting wafers using multiple beams, where each beam can image a different point on the wafer, multi-beam inspection tools can be plagued by excessive heat generation. Focusing multiple beams can require a greater number of electromagnetic coils or require higher currents to pass through the electromagnetic coils, both of which necessitate improved heat dissipation systems and methods.

[0030] In one aspect of the present disclosure, an objective lens structure includes a plurality of electromagnetic coils, and a bobbin can be used to cool an objective lens of a charged particle beam system. The bobbin can include a fluid inlet port configured to receive a fluid, and a plurality of channels distributed in the bobbin configured to circulate a fluid received by the fluid inlet port. The circulating fluid can absorb the heat generated by the passage of electric current through the electromagnetic coil. The circulating fluid can then be distributed to the outlet port through an outlet channel. The bobbin with a plurality of channels can be a monolithic structure of additive manufacturing, in particular, such as manufactured by a 3D printing process. Some advantages of using additive manufacturing bobbin can be effective heat dissipation from the electromagnetic coil, effective space utilization, compatible materials and design flexibility, improved reliability and manufacturability of the objective lens.

[0031] In the context of this disclosure, low thermal conductivity materials can be defined as materials having thermal conductivity values ​​in the range of 1-10 W.m under standard measurement conditions. -1 .K -1 High thermal conductivity materials can be defined as materials with thermal conductivity values ​​in the range of 20-2000 W.m under standard measurement conditions. -1 .K -1 Materials within the range.

[0032] The relative sizes of the components in the drawings may be exaggerated for clarity. In the following description of the drawings, identical or like reference numerals refer to identical or like components or entities, and only the differences with respect to individual embodiments are described.

[0033] As used herein, unless otherwise specifically indicated, the term "or" includes all possible combinations, except those that are not feasible. For example, if it is indicated that a database may include A or B, then unless otherwise specifically indicated or not feasible, the database may include A, or B, or A and B. As a second example, if it is indicated that a database may include A, B, or C, then unless otherwise specifically indicated or not feasible, the database may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C.

[0034] Reference now Figure 1 , which illustrates an exemplary electron beam inspection (EBI) system 100 according to an embodiment of the present disclosure. Figure 1 As shown, the charged particle beam inspection system 1 includes a main chamber 10 , a loading / locking chamber 20 , an electron beam tool 100 , and an equipment front end module (EFEM) 30 . The electron beam tool 100 is located inside the main chamber 10 .

[0035] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include additional loading ports (multiple). The first loading port 30a and the second loading port 30b receive wafer front opening unified pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other (multiple) materials) or samples to be inspected (wafers and samples are collectively referred to as "wafers" hereinafter). One or more robot arms (not shown) in the EFEM 30 transport the wafers to the loading / locking chamber 20.

[0036] The loading / locking chamber 20 is connected to a loading / locking chamber vacuum pump system (not shown), which removes air molecules in the loading / locking chamber 20 to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robot 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 in the main chamber 10 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by an electron beam tool. Although the present disclosure provides an example of a main chamber 10 containing an electron beam inspection tool, it should be noted that aspects of the present disclosure are not limited to chambers containing electron beam inspection tools in their broadest sense. On the contrary, it should be appreciated that the above principles can also be applied to other chambers.

[0037] Reference now Figure 2 , which illustrates a diagram showing that an embodiment of the present disclosure can be used as Figure 1 Schematic diagram of an exemplary electron beam tool as part of an exemplary electron beam inspection system of FIG. The electron beam tool 100 (also referred to herein as an apparatus) includes an electron source 101, a gun hole plate 171 with a gun hole 103, a beam collecting lens 110, a source conversion unit 120, a primary projection optical system 130, a sample platform ( Figure 2 ), a secondary optical system 150, and an electron detection device 140. The primary projection optical system 130 may include an objective lens 131. The electron detection device 140 may include a plurality of detection elements 140_1, 140_2, and 140_3. The beam splitter 160 and the deflection scanning unit 132 may be placed inside the primary projection optical system 130. It can be appreciated that other known components of the electron beam tool 100 may be appropriately added / omitted.

[0038] The electron source 101, the aperture plate 171, the condenser lens 110, the source conversion unit 120, the beam splitter 160, the deflection scanning unit 132 and the primary projection optical system 130 can be aligned with the primary optical axis 100_1 of the device 40. Many components of the electron beam tool 100 can be partially or completely positioned within the vacuum chamber. For example, the primary projection optical system 130 can be partially or completely positioned in a vacuum chamber such as Figure 1 The secondary optical system 150 and the electron detection device 140 may be aligned with the secondary optical axis 150_1 of the electron beam tool 100 .

[0039] The electron source 101 may include a cathode, an extractor or an anode, wherein primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 102 forming a cross (virtual or real) 101s. The primary electron beam 102 may be visualized as being emitted from the cross 101s.

[0040] The source conversion unit 120 may include an image forming element array ( Figure 2 The array of image forming elements may comprise a plurality of micro-deflectors or micro-lenses to form a plurality of parallel images (virtual or real) of intersections 101s of a plurality of primary beamlets of the primary electron beam 102. Figure 2 Three sub-bundles 102_1 , 102_2 , and 102_3 are shown as an example, and it is to be appreciated that the source conversion unit 120 may handle any number of sub-bundles.

[0041] The condenser lens 110 can focus the primary electron beam 102. The current of the sub-beams 102_1, 102_2 and 102_3 downstream of the source conversion unit 120 can be changed by changing the focusing ability of the condenser lens 110 or by changing the radial size of the corresponding beam limiting holes in the beam limiting hole array. The objective lens 131 can focus the sub-beams 102_1, 102_2 and 102_3 onto the sample for inspection, and can form three detection spots 102_1s, 102_2s and 102_3s on the surface of the sample 109. The gun hole plate 171 can block the peripheral electrons of the unused primary electron beam 102 to reduce the Coulomb effect. The Coulomb effect can amplify the size of each of the detection spots 102_1s, 102_2s and 102_3s, and thus deteriorate the inspection resolution.

[0042] The beam splitter 160 may be a Wien filter type beam splitter, which includes generating an electrostatic dipole field E1 and a magnetic dipole field B1 (neither of which is present in the Figure 2If they are applied, the electrostatic force exerted by the electrostatic dipole field E1 on the electrons of the sub-beams 102_1, 102_2, and 102_3 is equal in magnitude but opposite in direction to the electrostatic force exerted by the magnetic dipole field B1 on the electrons. Therefore, the sub-beams 102_1, 102_2, and 102_3 can pass through the beam splitter 160 in a straight line with a zero deflection angle.

[0043] The deflection scanning unit 132 can deflect the sub-beams 102_1, 102_2, and 102_3 to scan the detection spots 102_1s, 102_2s, and 102_3s on three small scanning areas in a section of the surface of the sample. In response to the sub-beams 102_1, 102_2, and 102_3 being incident on the detection spots 102_1s, 102_2s, and 102_3s, three secondary electron beams 102_1se, 102_2se, and 102_3se can be emitted from the sample. Each of the secondary electron beams 102_1se, 102_2se, and 102_3se may include electrons having an energy distribution, and the above energy distribution includes secondary electrons (energy ≤ 50eV) and backscattered electrons (energy is between 50eV and the landing energy of the sub-beams 102_1, 102_2, and 102_3). The beam splitter 160 can direct the secondary electron beams 102_1se, 102_2se, and 102_3se toward the secondary optical system 150. The secondary optical system 150 can focus the secondary electron beams 102_1se, 102_2se, and 102_3se onto the detection elements 140_1, 140_2, and 140_3 of the electron detection device 140. The detection elements 140_1, 140_2, and 140_3 can detect the corresponding secondary electron beams 102_1se, 102_2se, and 102_3se and generate corresponding signals, which are used to construct an image of the corresponding scanned area of ​​the sample.

[0044] Reference now Figure 3 , which illustrates a charged particle beam system (such as Figure 1 1 ) is a cross-sectional view of an exemplary objective lens structure 300 of a charged particle beam inspection system 1). The 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 including an inlet channel 335, an electromagnetic coil 340, and a magnetic field guide 350. The objective lens structure 300 may include Figure 3 Other components related to the function of the objective lens structure 300 that are not shown in the figure, such as the objective lens assembly, the electromagnetic coil isolator, the thermal gap filler, the thermal sensor, etc.

[0045] The objective housing 310 may be configured to house at least a portion of the objective 131. In some embodiments, the objective housing 310 may house the entire objective 131. Figure 2 The objective lens 131 may be an electromagnetic compound lens, wherein the sample may be immersed in the magnetic field of the objective lens 131. In some embodiments, the objective lens 131 includes a magnetic lens and an electrostatic lens (not shown). The magnetic lens may be configured to direct a charged particle beam or a multi-beam device (such as Figure 2 Each primary beamlet in the electron beam tool 100 in the embodiment of the present invention is focused with relatively low aberration, thereby generating a relatively small detection spot on the sample. The electrostatic lens can be configured to affect the landing energy of the charged particle beam or each primary beamlet, thereby ensuring that the primary charged particles land on the sample with relatively low kinetic energy and pass through the device with relatively high kinetic energy. In some embodiments, the objective lens 131 can be configured as an "immersion lens". As a result, the sample can be immersed in the electrostatic field E of the electrostatic lens (electrostatic immersion) and the magnetic field B of the magnetic lens (magnetic immersion). Electrostatic immersion and magnetic immersion can reduce the aberration of the objective lens 131. As the electrostatic field and magnetic field become stronger, the aberration of the objective lens 131 can become smaller. However, the electrostatic field E should be limited to a safe range in order to avoid discharge or arcing on the sample. Due to this limitation of the field strength of the electrostatic field E, a further increase in the magnetic field strength in the immersion configuration can allow the aberration of the objective lens 131 to be further reduced, thereby improving the image resolution.

[0046] In some embodiments, the objective lens housing 310 can accommodate at least a portion of the coil 340, a portion of the bobbin 320, and the channel 330. The objective lens housing 310 can include a ferromagnetic material, which includes but is not limited to cobalt, nickel, iron, chromium dioxide, or an alloy thereof. Ferromagnetic materials as described herein can refer to materials with a large positive susceptibility to an external magnetic field. Ferromagnetic materials exhibit a strong attraction to magnetic fields and can retain their magnetic properties after the external magnetic field has been removed.

[0047] In certain embodiments, the lens housing 310 may include a material with low thermal conductivity, including but not limited to ceramic materials, such as ceria, silicon dioxide, fused silica, quartz, zirconium dioxide, etc. In certain embodiments, the lens housing 310 may include a material coated with a low thermal conductivity material, such as ceria as an example. This low thermal conductivity material may be useful in minimizing the heat loss from the lens structure 300 to adjacent components, such as a platform positioning module, a bottom (metro) frame of a supporting platform positioning module, a mirror block, a high voltage board, a fixture, etc. In certain embodiments, a part of the lens housing 310 may include a reflective coating to reduce the heat loss due to radiation. Other suitable techniques may also be used to reduce heat loss and heat transfer.

[0048] In some embodiments, the objective housing 310 may include an inner wall 312 close to the primary optical axis 100_1 and an outer wall 314 away from the primary optical axis 100_1. Based on design considerations and applications, the inner wall 312 and the outer wall 314 may include different materials, the same material coated with different materials, and the like. For example, the inner wall 312 may include a ferromagnetic material (e.g., iron) configured to concentrate the magnetic field generated by the current passing through the coil 340, while the outer wall 314 may include a low thermal conductivity material (e.g., ceria) configured to minimize heat loss to the external environment. Other suitable materials and material combinations may be used as needed.

[0049] In some embodiments, the objective housing 310 may include a cylinder having a central hole 316 configured to receive the objective 131. Figure 3 As shown, the central hole 316 is defined by the boundaries of the inner surface of the inner wall 312 and can be designed to conform to the shape and contour of the objective lens 131 .

[0050] like Figure 3 As shown in the cross-sectional view in FIG. 3 , the bobbin 320 may be disposed in an area between the inner wall 312 and the outer wall 314 of the objective housing 310. In some embodiments, at least a portion of the bobbin 320 may be coupled to a portion of the outer wall 314 or a portion of the inner wall 312, or other portions of the objective housing 310 by welding, heat pressing, bonding, mechanical coupling, etc. Other fastening techniques may be employed based on the material and application.

[0051] In some embodiments, the objective lens structure 300 may include a spool 320 having a channel 330 or a plurality of channels 330. As referred to herein, a channel may be a path through which a fluid may travel or circulate, and may include more than one channel. In some embodiments, the spool 320 includes a plurality of channels 330 through which a fluid may circulate. The fluid may include a cooling fluid, including but not limited to a coolant, a cooling liquid, water, a gas, a compressed gas, or a mixture thereof. It should be appreciated that channel, a plurality of channels, channel(s), and cooling channel may be used interchangeably herein.

[0052] In some embodiments, the bobbin 320 with cooling channels 330 may include a single material having a thermal conductivity in the range of 20-2000 W.m-1.K-1 under standard measurement conditions, such as, but not limited to, aluminum, titanium, copper, graphite, aluminum nitride, aluminum carbide, metal alloys, metal-ceramic composites, etc. In some embodiments, the bobbin 320 with cooling channels 330 may include more than one material having different thermal conductivities and machinability, for example, a portion of the bobbin 320 may include aluminum and the cooling channels 330 may include titanium. Other combinations are also possible.

[0053] In some embodiments, the spool 320 with multiple channels 330 may include a monolithic structure. A monolithic structure as referred to herein may be defined as a structure made from a single piece of material. For example, a monolithic structure may be formed by a subtractive manufacturing process or an additive manufacturing process. A subtractive manufacturing process is a process that creates a three-dimensional (3D) object by successively removing material from a single piece of material, either manually or using computer numerical control (CNC). An additive manufacturing process is a process that creates a three-dimensional part by depositing superimposed layers of material under computer-guided control, such as 3D printing.

[0054] In some embodiments, the spool 320 with channel 330 may include a monolithic structure of additive manufacturing. The additively manufactured spool 320 with channel 330 may include a single metal, such as aluminum or titanium, as an example. In such a configuration, heat transfer or heat dissipation can be more efficient due to the uniformity of the thermal conductivity of the structure. Higher heat transfer efficiency can minimize the thermal drift effect on the wafer 190, and can also minimize the exposure of heat sensitive components such as mirror blocks, platform positioning modules, etc. at high temperatures. The additively manufactured spool 320 with channel 330 can have multiple advantages over existing spools for cooling objective lens structures in charged particle beam systems. In particular, the additively manufactured spool can have some or all of the advantages discussed herein.

[0055] i. Efficient heat transfer - The efficiency of heat transfer can be further improved by the proximity of the channel 330 to the heat source (e.g., the electromagnetic coil 340). Figure 3 As shown in , the channel 330 can be adjacent to or in close proximity to the electromagnetic coil 340, through which a large current can be delivered to generate a magnetic field for the objective lens 131. At least a portion of the channel 330 can provide a thermal barrier for the wafer 190, the objective lens 131 placed in the central hole 316, or the stage positioning module, thereby maintaining the performance and accuracy of the charged particle beam system by dissipating heat more efficiently through the channel 330.

[0056] ii. Enhanced Cooling Capabilities - 3D printing spools with a large number of fluid channels can allow for enhanced cooling capabilities because a larger volume of fluid can pass through multiple channels. Additionally, having more fluid channels can reduce heat buildup and pressure drop within the channels, minimizing thermomechanical stresses. 3D printing can also support complex fluid channel configurations within the spool as needed.

[0057] iii. Enhanced structural integrity and reliability - the occurrence of mechanical failures such as leaks, cracks, material fatigue, deformation, stress due to mismatch in thermal expansion coefficients, etc., can be minimized or eliminated, as examples.

[0058] iv. Efficient Space Utilization - The additively manufactured bobbin 320 may provide more efficient space utilization in a charged particle beam system. For example, the cooling channels 330 may be configured to be disposed within the bobbin, which eliminates the need for external cooling tubes, thereby facilitating a compact structure.

[0059] v. Flexibility in materials and design - Additive manufacturing involves the deposition of successive layers under computer guidance, which allows different materials to be selected for one or more layers within the structure. In the context of the present disclosure, for example, a spool having an aluminum body with titanium channels (such as titanium alloys) disposed within the aluminum spool can be constructed. Figure 4 ).

[0060] vi. Higher Throughput and Lower Costs—The improved reliability and structural integrity of the additively manufactured spool 320 may result in higher inspection throughput and lower maintenance costs due to reduced maintenance and service downtime.

[0061] vii. Reduced Flow-Induced Vibration - 3D printing spools with multiple channels can support better designs with respect to flow-induced vibrations due to lower flow velocities through the channels and the natural flow patterns in the design. High fluid velocities and sharp edges can be associated with varying forces due to turbulent or unstable flow. Turbulence and instabilities in the fluid flow can cause vibrations in the spool, which can have an impact on the measurement and focusing of the charged particle beam.

[0062] In some embodiments, the channel 330 may be disposed on the outer surface of the spool 320 and may be arranged vertically or horizontally, or circumferentially around the spool 320. In some embodiments, the channel 330 may be disposed within the spool 320 (e.g., Figure 4 ), and may be arranged vertically, horizontally, or circumferentially within the spool 320. Other channel layouts and configurations may be used as appropriate.

[0063] In some embodiments, the spool 320 may include an inlet channel 335 configured to circulate a fluid through the channel 330. As referred to herein, the fluid may include, among other things, a liquid, a coolant, a cooling liquid, a gas, a compressed gas, or a mixture thereof. The fluid may be configured to absorb heat generated by the large current passing through the electromagnetic coil 340 (discussed later). The fluid may be circulated through the channel 330 before being dispensed through the outlet channel (not shown).

[0064] The channel 330 may include a single loop around the bobbin 320. In some embodiments, based on the application and system cooling requirements, the channel 330 may include multiple loops around the bobbin 320. In some embodiments, the channel 330 may include one or more input channels and a single output channel. For example, in a multi-beam device where more than one area of ​​the objective structure 300 may require temperature control, additional inlet channels 335 may be used. In some embodiments, the channel 330 may include a single input channel and multiple output channels. Other numbers and configuration combinations of input channels and output channels may be appropriately designed and employed.

[0065] In some embodiments, the surface forming the channel 330, also referred to as the external surface of the channel 330, can have surface features, such as micro-indentations, nano-indentations, protrusions, rough textures, etc., for increasing the surface area for enhanced heat transfer. In some embodiments, the external surface features can be introduced after the bobbin 320 having the channel 330 is manufactured or produced. Alternatively, the external surface features can be integrated into the original design before additive manufacturing using a 3D printer.

[0066] In some embodiments, the channel 330 may include a closed path, for example, a channel with a circular or elliptical cross section and a wall thickness. The shape of the cross section and the area of ​​the cross section may be determined based on the cooling requirements of the application, space availability, material compatibility, or system. In some embodiments, for example, the channel 330 with 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. The channel 330 may include a uniform or non-uniform wall thickness. It should be appreciated that the size, shape, cross section, area, total volume, and other relevant dimensions of the channel 330 may be determined and designed as needed.

[0067] In some embodiments, the objective lens structure 300 may include an electromagnetic coil 340 configured to adjust the focus of a single or multiple charged particle beams on the wafer 190. The electromagnetic coil 340 may include an electrical conductor, such as a wire in the shape of a coil, spiral, helix, etc. An electric current may be passed through the electromagnetic coil 340 to generate a circulating magnetic field around the conductor. Figure 3 In the illustrated coil configuration, the electrical conductor may be wound multiple times around the bobbin 320 to increase the magnetic field density of the objective lens 131 disposed in the central hole 316. The electromagnetic coil 340 may include an electrical conductor including, but not limited to, copper, aluminum, silver, and the like.

[0068] In some embodiments, the electromagnetic coil 340 may include a fine focusing coil 340_1 and a coarse focusing coil 340_2, which are configured to focus the charged particle beam 102_1. The fine focusing coil 340_1 and the coarse focusing coil 340_2 may include different materials or different sizes. Alternatively, the amount of current passing through the fine focusing coil 340_1 and the coarse focusing coil 340_2 can be adjusted to change the generated magnetic field to control the overall beam focus. In some embodiments, an electrical conductor wire such as a copper wire can be encapsulated with an insulating material. Due to the large amount of heat generated by the current passing through the electromagnetic coil 340, a thermal gap filler can be applied between each layer of the coil. The thermal gap filler can include a 1W.m -1 .K -1 or higher thermal conductivity thermal gap filler gel, putty or gasket to dissipate local heat, and 5×10 2 Ohms or higher electrical impedance to provide electrical insulation between the two layers of conductor coils. It will be appreciated that other suitable thermal gap fillers may also be used.

[0069] In some embodiments, the objective lens structure 300 may include Figure 3The magnetic field guide 350 shown is configured to guide the magnetic field generated by the electromagnetic coil 340 toward the objective lens 131. In some embodiments, the magnetic field guide 350 can be configured to minimize the exposure of the wafer 190 to the magnetic field created in the electromagnetic coil 340 or other stray magnetic fields. The magnetic field guide 350 can be clamped or coupled to the outer wall 314 of the objective lens housing 310 or the bobbin 320 using appropriate coupling techniques, including but not limited to welding, bonding, mechanical fastening, epoxy bonding, brazing, ultrasonic welding, soldering, etc.

[0070] In some embodiments, the bobbin may be configured or optimized to be located in a vacuum chamber. In a vacuum, the dominant heat transfer mechanism is radiation. Thus, it may be advantageous to be able to cool the portion of the bobbin that radiates toward the thermal element. For example, it may be advantageous to embed channels 330 that radiate toward the wafer near the bobbin surface, thereby cooling the surface and thus reducing the amount of heat radiated from the bobbin 320 to the wafer.

[0071] Some techniques for manufacturing spools do not facilitate the creation of channels in desired or optimal locations of a spool that is configured to be located in a vacuum chamber. For example, while it may be possible to machine channels in certain locations of the spool, such as the outer surface, it may not be practical to machine channels in other locations of the spool. An additively manufactured monolithic spool can create a spool that is configured or optimized to be located in a vacuum chamber. As a result of the manufacturing process, the channel 330 can be located in any desired location to cool the portion of the spool 320 that radiates toward the thermal element. Further, the monolithic nature of the spool 320 improves its performance in a vacuum, such as by supporting more efficient cooling of the portion of the spool that radiates heat and by maintaining a contaminant-free, superior vacuum. Spools having seams between materials / structures (e.g., seams between structures that are joined together to form the spool) may suffer from less effective cooling of the spool (such as due to reduced heat transfer at the material / structure interface), may suffer from poor vacuum (such as due to the seams between materials / structures), and may suffer from contamination (such as due to the materials used to join the multiple materials / structures of the spool together).

[0072] Reference now Figure 4 , which illustrates a charged particle beam system (such as Figure 1 1 ) is a cross-sectional view of an exemplary objective lens structure 400 of a charged particle beam inspection system 1 . The objective lens structure 400 may include a channel 330 disposed within a bobbin 320 , an inlet port 432 including at least a portion of an inlet channel 335 , and a cooling plate 420 including a cooling channel 430 .

[0073] In some embodiments, the cooling plate 420 can be coupled to the spool 320 so that the channel 330 and the cooling channel 430 are aligned to form a continuous channel for circulating fluid. The cooling plate 420 can be coupled to the spool 320 and the outer wall 314 of the objective housing 310. In some embodiments, the cooling plate 420 can be coupled to the spool 320 by a fastening mechanism 460, which includes but is not limited to mechanical fastening, welding, ultrasonic welding, soldering, bonding, epoxy bonding, brazing, etc. In particular, the cooling plate 420 can include a ferromagnetic material or a high thermal conductivity material. In a preferred embodiment, the cooling plate 420 and the spool 320 include similar materials so that the heat transfer loss caused by the mismatch of thermal coefficient and heat transfer capacity is minimized.

[0074] In some embodiments, the channel 330 can be disposed within the bobbin 320, and the cooling channel 430 can be disposed within the cooling plate 420, so that after assembly, the channel 330 and the cooling channel 430 are aligned to form a continuous circulation channel for the fluid. The cooling plate 420 with the cooling channel 430 can be additively manufactured using a 3D printer, or subtractively manufactured using a CNC machine.

[0075] In some embodiments, the inlet port 432 can be configured to receive fluid from a fluid source. The inlet port 432 may include at least a portion of the inlet channel 335. The inlet port 432 may be externally joined to the spool 320 using a mechanical fastening method. Alternatively, the inlet port 432 may be integrally connected to the spool 320. For example, the spool 320 including the inlet port 432 having the inlet channel 335 may be manufactured using a 3D printer. In some embodiments, the spool 320 including the inlet port 432 having the inlet channel 335 may be manufactured using a CNC machine or a lathe.

[0076] Reference now Figure 5 , which is a schematic diagram of an exemplary bobbin 320 for cooling an objective lens of a charged particle beam system according to an embodiment of the present disclosure. The bobbin 320 may include a top flange 510, a bottom flange 520, and a body portion 530 connecting the top flange 510 and the bottom flange 520. The bobbin 320 may be disposed on an objective lens structure (such as Figure 3 The objective lens structure 300 or Figure 4 The bottom flange 520 is close to the wafer (such as Fig. 9 190), and the top flange 510 is opposite to the bottom flange 520 and is far away from the wafer 190. In the context of the present disclosure, near and far refer to the distance along the longitudinal axis of the axis 320 with reference to the horizontal plane along which the wafer 190 or the wafer platform can be arranged. Fig. 9 As shown in (discussed later), the top flange 510 of the spool 320 is farther from the wafer (far away) while the bottom flange 520 of the spool 320 is closer to the wafer (closer). In some embodiments, the longitudinal axis of the spool 320 can be aligned with the main optical axis 100_1.

[0077] In some embodiments, the main body portion 530 may be a cylinder, a cone, or any other suitable shape. Figure 5 As shown in the figure, the end of the body portion 530 with a smaller diameter can be connected to the bottom flange 520, and the end of the cone body portion 530 with a larger diameter can be connected to the top flange 510. Other configurations can be used appropriately. In some embodiments, the shape of the body portion 530 can be determined based on the shape of the objective lens 131 used.

[0078] In some embodiments, the spool 320 may include an inlet port including a portion of an inlet channel 335, and an outlet port 532 including a portion of an outlet channel 535. The spool 320 may include a channel 330 distributed in the spool 320 and configured to circulate a fluid received by the inlet port 432, and an outlet port 532 configured to distribute the fluid circulated by the channel 330. The inlet channel 335 may be configured to circulate the fluid received from the inlet port 432, and the outlet channel 535 may be configured to direct the circulated fluid toward the outlet port 532. The outlet port 532 may be externally coupled to the spool 320 using a mechanical fastening method. Alternatively, the outlet port 532 may be integrally connected to the spool 320. For example, the spool 320 including the outlet port 532 having the outlet channel 535 may be additively manufactured using a 3D printer. In some embodiments, the spool 320 including the outlet port 532 having the outlet channel 535 may be subtractively manufactured using a CNC machine or a lathe.

[0079] Reference now Fig. 6A and Figure 6B , which illustrates an embodiment of the present disclosure Figure 5 330. The channel 330 may include an inlet channel 335, an outlet channel 535, and an intermediate channel 635. The inlet channel 335 may be configured to circulate the fluid received from the inlet port 432, the outlet channel 535 may be configured to direct the circulated fluid toward the outlet port 532, and the intermediate channel 635 may be configured to fluidly connect the inlet channel 335 and the outlet channel 535 and recirculate the fluid in a portion of the spool 320. In some embodiments, the inlet channel 335, the intermediate channel 635, and the outlet channel 535 may have a uniform cross-section and diameter throughout the channel 330.

[0080] like Figure 6B As shown in FIG. 4 , the inlet port 432 and the outlet port 532 are positioned adjacent to each other on the top flange 510. In some embodiments, the inlet port 432 and the outlet port 532 can be positioned away from each other, for example, diametrically opposite each other on the top flange 510, or spaced apart radially from each other on the top flange 510.

[0081] Figure 7 The diagram illustrates the direction of fluid flow in an exemplary spool according to an embodiment of the present disclosure. As illustrated, Figure 7 The spool 320 may include an inlet channel 335, an intermediate channel 635, and an outlet channel 535. The inlet channel 335 may be configured to receive fluid through an inlet port 432 (not shown) in the top flange 510 of the spool 320. The inlet channel 335 may also be configured to transport the received fluid from the top flange 510 to the bottom flange 520. The intermediate channel 635 may be configured to circulate the fluid in the bottom flange 520 and absorb heat generated by the electromagnetic coil 340 wrapped around the spool 320. The intermediate channel 635 may include concentric circles (such as Figure 7 ), in a spiral, in a sine wave pattern, etc. The intermediate channel 635 can be configured to fluidically connect the inlet channel 335 and the outlet channel 535. The outlet channel 535 can be configured to absorb heat and direct the circulated fluid from the intermediate channel 635 to the outlet port 532 (not shown). Figure 7 As illustrated in , the outlet channel 535 can be wrapped in a circumferential manner around the main body portion 530 and the top flange 510 of the spool 320 to distribute the circulated fluid into the outlet port 532.

[0082] In some embodiments, the inlet channel 335, the intermediate channel 635, and the outlet channel 535 may include channels having different materials, sizes, and cross-sections.

[0083] Figure 8 FIG. 2 illustrates the direction of fluid flow in an exemplary spool according to an embodiment of the present disclosure. Figure 8 As shown in FIG. 4 , a fluid may be introduced from a fluid source into the inlet channel 335 through the inlet port 432. The inlet channel 335 may be configured to carry the fluid from the top flange 510 to the bottom flange 520 through the inlet channel 335 extending longitudinally along the main body portion 530. The channel 330 disposed in the bottom flange 520 may include a portion of the inlet channel 335, a portion of the intermediate channel 635, a portion of the outlet channel 535, or a combination thereof.

[0084] In some embodiments, cooling of the objective lens by fluid flow in the spool 320 can be described as a multi-step process. It should be appreciated that the number and order of steps are exemplary and not limiting, and can be modified as desired.

[0085] Step 1 can include receiving fluid from the inlet port 432 in the inlet channel 335. The inlet channel 335 can extend from the top flange 510 through the body portion 530. In some embodiments, the inlet channel can extend to at least a portion of the bottom flange 520.

[0086] Large temperature gradients caused by thermal radiation between the spool 320 and the wafer 190 can cause several problems, including but not limited to thermal drift, local thermal expansion, microstructural defects, or hot spots on the wafer 190. Step 2 can include conditioning the bottom flange 520 by circulating the fluid immediately after receiving it from the fluid source through the inlet port 432. Conditioning the bottom flange 520 close to the wafer 190 can provide temperature stability and minimize the temperature gradient between the bottom flange 520 and the wafer 190 by providing a thermal barrier to radiation.

[0087] Step 3 may include directing the circulated fluid from the bottom flange 520 to the top flange 510 via the intermediate channel 635. The intermediate channel 635 may also be configured to circulate the fluid in channels radially disposed on the top flange 510 of the spool 320.

[0088] Step 4 may include directing fluid downward from the top flange 510 toward the bottom flange 520 through a plurality of channels disposed on the body portion 530 of the bobbin 320. Steps 3 and 4 as a combination may include cooling the objective lens structure 300 by absorbing heat generated by the electromagnetic coil 340.

[0089] Step 5 may include directing fluid from the plurality of downward channels into outlet channels 353 and dispensing the fluid through outlet ports 532 .

[0090] In some embodiments, thermal sensors can be used to monitor the temperature of the fluid circulating through the inlet channel 335, the intermediate channel 635, and the outlet channel 535. One or more thermal sensors can be disposed in the channel 330, on the spool 320, or at a remote location. In some embodiments, the amount of fluid flowing through the channel 330 can be determined using one or more flow meters. Other sensors and fluid control switches and valves can be installed as needed.

[0091] Fig. 9The cross-sectional view of an objective lens structure 900 of a charged particle beam system according to an embodiment of the present disclosure is shown. The objective lens structure 900 may include a thermal insulation layer 910 and a high voltage plate 920 configured to accelerate or decelerate a charged particle beam incident toward a wafer 190 .

[0092] In some embodiments, a thermal insulation layer 910 can be disposed in a circumferential manner between the electromagnetic coil 340 and the outer wall 314 of the objective housing 310. The thermal insulation layer 910 can prevent heat loss to the external surrounding environment and can concentrate heat in the heat transfer area to be absorbed by the fluid circulating through the channel 330 of the spool 320. The channel 330 and the thermal insulation layer 910 as a combination can surround the electromagnetic coil 340 and thus help limit the heat generated by the current passing through the electromagnetic coil 340 to generate a magnetic field for the objective 131.

[0093] In some embodiments, the thermal insulation layer 910 may include any material with good thermal insulation properties, such as but not limited to gas, vacuum, thermal gap filler gel, silicone, ceramic, etc. In some embodiments, the thermal insulation layer 910 may include a fluid channel configured to receive and circulate a fluid to absorb heat. In such a configuration, the electromagnetic coil 340 may be significantly thermally insulated from the surrounding environment, minimizing heat transfer due to radiation toward the wafer 190 and heat transfer to adjacent components, including but not limited to the bottom (metro) frame, platform positioning module, mirror block, sensor, etc.

[0094] Fig.10 is a process flow chart of an exemplary method for cooling an objective lens of a charged particle beam system according to an embodiment of the present disclosure. The method for cooling an objective lens and an objective lens structure can be performed by warping a linear axis (e.g., Figure 3 of the spool 320) (e.g., Figure 3 The channel 330) circulates fluid to perform.

[0095] In step 1010, a fluid may be introduced into the fluid via a fluid inlet port (e.g., Figure 4 The fluid may be received by an inlet port 432 of the invention. The fluid may be partially disposed in an inlet channel (e.g., Figure 3 The fluid may include a cooling fluid, including but not limited to a liquid, a coolant, a cooling liquid, water, a gas, a compressed gas, a solvent, or a mixture thereof. In some embodiments, the temperature of the fluid entering the inlet channel may be equal to or less than the temperature of the substrate or wafer (e.g., Fig. 9 The desired temperature set point for the wafer 190 shown in FIG.

[0096] In some embodiments, the channel 330 may include a closed path, such as a channel with a circular or elliptical cross section and wall thickness. The shape of the cross section and the area of ​​the cross section may be determined based on the cooling requirements of the application, space availability, material compatibility, or the system. In some embodiments, for example, the channel 330 with 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. The channel 330 may include a uniform or non-uniform wall thickness. It should be appreciated that the size, shape, cross section, area, total volume, and other relevant dimensions of the channel 330 may be determined and designed as needed.

[0097] In step 1020, a fluid may be circulated through one or more channels distributed in the spool. The fluid may absorb the liquid formed by the objective lens (e.g., Figure 2 The electromagnetic coil (e.g., Figure 3-4 As described above, the bobbin may include one or more channels, which are collectively referred to herein as channels.

[0098] The channel may include an inlet channel configured to circulate a fluid received from a fluid source through the inlet port. In some embodiments, the channel may also include an intermediate channel (e.g., FIG. 6A to FIG. 8 an intermediate channel 635), and an outlet channel (e.g., Figure 5-8 In some embodiments, the intermediate channel can receive fluid from the inlet channel and be located at a top flange (e.g., Figure 5 The top flange 510 of the spool) or the bottom flange of the spool (e.g., Figure 5 The bottom flange 520 of the spool) or the main body of the spool (e.g., Figure 5 The fluid is circulated in the main body portion 530).

[0099] In some embodiments, the intermediate channels distributed in the spool can be configured to circulate fluid in a pattern based on the application and requirements, including but not limited to radial, longitudinal, spiral, circumferential, helical, latitudinal, or a combination thereof.

[0100] In some embodiments, the intermediate channel distributed in the spool can be configured to circulate fluid in a predefined flow direction. For example, after receiving the fluid from the inlet channel through the inlet port, the intermediate channel can circulate the fluid in the bottom flange, and then the circulating fluid flows upward to the top flange. In the top flange, the fluid can be circulated radially along the circumference of the top flange, while a part of the fluid is directed downward to the bottom flange of the spool through multiple intermediate channels or fluid paths. The fluid can be circulated in at least a portion of the bottom flange and directed to an outlet channel, which is configured to receive the circulated fluid after absorbing the heat generated by the current flowing through the electromagnetic coil to generate a magnetic field for the object lens. Other flow directions and flow routes can be appropriately adopted to effectively absorb and dissipate heat from a wafer or a heat-sensitive component, and the above-mentioned heat-sensitive component includes but is not limited to a mirror block, a platform positioning module, a bottom (metro) frame, an object lens structure, etc.

[0101] At step 1030, the fluid circulated by the plurality of channels, such as the inlet channel, the intermediate channel, and the output channel, can be discharged through an outlet port (e.g., Figure 5 In some embodiments, the outlet port may be configured to further recirculate the fluid into the inlet port after the fluid is processed and cooled to a predetermined temperature suitable for introduction into the inlet port.

[0102] In some embodiments, the outlet port can be connected to a suction device such as a vacuum pump to create a negative pressure in at least a portion of the outlet channel. Negative pressure in the outlet channel can be useful when dispensing the circulating fluid.

[0103] The disclosed spool can be manufactured using conventional techniques, such as, for example, techniques generally referred to as additive manufacturing or additive fabrication. Conventional techniques such as casting, molding, and the like can be utilized where desired. For example, known additive manufacturing / fabrication processes include techniques such as, for example, 3D printing. 3D printing is a process in which material can be deposited in successive layers under computer control. A computer controls an additive fabrication device to deposit successive layers based on a three-dimensional model (e.g., a digital file in an additive manufacturing format (AMF) or stereolithography (STL) format), the three-dimensional model being configured to be converted into a plurality of slices, such as substantially two-dimensional slices, each slice defining a cross-sectional layer of the spool 320, in order to manufacture or fabricate the spool 320. In one instance, the disclosed spool 320 will be a raw component, and the spool 320 will be manufactured using a 3D printing process.

[0104] refer to Fig.11, the three-dimensional model 1101 used to represent the original spool 320 can be stored on a computer-readable storage medium 1102, such as, for example, magnetic storage, including floppy disks, hard disks, tapes; semiconductor storage, such as solid-state disks (SSDs) or flash memory; optical disk storage; magneto-optical disk storage; cloud storage; or any other type of physical storage that can store information or data readable by at least one processor. The computer-readable storage medium 1102 can be used in conjunction with a commercially available 3D printer 1106 to manufacture or produce the spool 320. Alternatively, the three-dimensional model can be electronically transmitted to the 3D printer 1106 in a streaming manner, and is not permanently stored at the location of the 3D printer 1106. In either case, the three-dimensional model constitutes a digital representation of the spool 320 suitable for use in manufacturing the spool 320.

[0105] The three-dimensional model can be formed in a variety of known ways. Typically, the three-dimensional model is created by inputting data 1103 representing the spool 320 into a computer or processor 1104, such as a cloud-based software operating system. The data can then be used as a three-dimensional model representing the physical spool 320. The three-dimensional model is intended to be suitable for use in manufacturing the spool 320. In an exemplary embodiment, the three-dimensional model is suitable for use in manufacturing the spool 320 by additive manufacturing technology.

[0106] In some embodiments, Fig.11As shown in , the input of data can be implemented using a 3D scanner 1105. The method can involve contacting the spool via a contact and data receiving device, and receiving data from the contact to generate a three-dimensional model. For example, the 3D scanner 1105 can be a contact scanner. The scanned data can be input into a 3D modeling software program to prepare a digital data set. In some embodiments, the contact can be carried out via direct physical contact using a coordinate measuring machine, which measures the physical structure of the spool 320 by contacting the probe with the surface of the spool 320 to generate a three-dimensional model. In some embodiments, the 3D scanner 1105 can be a non-contact scanner, and the method can include directing a projected energy such as light or ultrasonic energy onto the spool 320 to be replicated, and receiving reflected energy. Based on the reflected energy, a computer can generate a computer-readable three-dimensional model for use in manufacturing the spool 320. In various embodiments, a plurality of 2D images can be used to create a three-dimensional model. For example, 2D slices of a 3D object can be combined to create a three-dimensional model. Instead of a 3D scanner, the input of data can be completed using computer-aided design (CAD) software. In this case, the three-dimensional model may be formed by using CAD software to generate a virtual 3D model of the disclosed spool 320. The three-dimensional model will be generated from the CAD virtual 3D model in order to manufacture the spool 320.

[0107] The additive manufacturing processes utilized to create the disclosed spool 320 may involve materials such as metals, ceramics, metal alloys, ceramic composites, etc. In some embodiments, additional processes may be performed to create the finished product. Such additional processes may include, for example, one or more of cleaning, hardening, heat treating, material removal, or polishing. Other processes necessary to complete the finished product may be performed in addition to or in lieu of these identified processes.

[0108] The embodiments may be further described using the following terms:

[0109] 1. A bobbin for cooling an objective lens of a charged particle beam system, the bobbin comprising:

[0110] a fluid inlet port configured to receive a fluid;

[0111] a plurality of channels distributed in the spool and configured to circulate fluid received by the fluid inlet port; and

[0112] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0113] 2. The spool according to clause 1, further comprising:

[0114] a bottom flange proximate to a wafer in the charged particle beam system; and

[0115] Keep away from the top edge of the wafer.

[0116] 3. The spool of any one of clauses 1-2, wherein the plurality of channels comprises:

[0117] an inlet passage configured to circulate fluid received from the fluid inlet port; and

[0118] An outlet passage is configured to direct the circulated fluid toward the fluid outlet port.

[0119] 4. The spool of clause 3, wherein the plurality of channels further comprises an intermediate channel fluidly connected to the inlet channel and the outlet channel.

[0120] 5. The spool of any of clauses 1-4, wherein the circulated fluid absorbs heat generated by electromagnetic coils wrapped around at least a portion of the spool.

[0121] 6. The spool according to any of clauses 1-5, wherein the fluid comprises one of a liquid, a coolant, a gas, a compressed gas or a mixture thereof.

[0122] 7. A spool according to any one of clauses 1 to 6, wherein the plurality of channels comprises a plurality of channels having a power source in the range of 20-2000 W.m. -1 .K -1 Materials with thermal conductivity within the range.

[0123] 8. The spool of clause 7, wherein the material of the plurality of channels comprises aluminum, titanium, copper, graphite, aluminum carbide, aluminum nitride, plastic, composite or alloy.

[0124] 9. The bobbin of any of clauses 1-8, wherein the bobbin having the plurality of channels comprises a monolithic structure.

[0125] 10. The spool of clause 9, wherein the monolithic structure comprises an additively manufactured monolithic structure.

[0126] 11. The spool of clause 10, wherein the additively manufactured monolithic structure comprises at least one of a metal, a metal alloy, a ceramic, or a ceramic composite.

[0127] 12. The spool of any of clauses 1-8, wherein the spool having a plurality of channels comprises a plurality of sections coupled together.

[0128] 13. A method of creating a computer readable three-dimensional model suitable for use in manufacturing the spool of clause 1, the method comprising:

[0129] inputting data representing the spool into a computer; and

[0130] The data is used to represent the spool as a three-dimensional model suitable for use in manufacturing the spool.

[0131] 14. An objective lens structure, comprising:

[0132] a plurality of electromagnetic coils; and

[0133] A spool configured to circulate a fluid to absorb heat generated by the plurality of electromagnetic coils, the spool comprising:

[0134] a fluid inlet port configured to receive a fluid;

[0135] a plurality of channels distributed in the spool and configured to circulate fluid received by the fluid inlet port; and

[0136] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0137] 15. An objective lens structure according to clause 14, wherein the plurality of electromagnetic coils are wound around at least a portion of the bobbin.

[0138] 16. The objective lens structure according to any one of clauses 14 and 15, wherein the bobbin further comprises:

[0139] a bottom flange proximate to a wafer in the charged particle beam system; and

[0140] Keep away from the top edge of the wafer.

[0141] 17. An objective lens structure according to any one of clauses 14 to 16, wherein the plurality of channels comprises:

[0142] an inlet passage configured to circulate fluid received from the fluid inlet port; and

[0143] An outlet passage is configured to direct the circulated fluid toward the fluid outlet port.

[0144] 18. The objective lens structure according to clause 17, wherein the plurality of channels further comprises an intermediate channel fluidically connected to the inlet channel and the outlet channel.

[0145] 19. The objective lens structure according to any one of clauses 14-18, wherein the fluid comprises one of a liquid, a coolant, a gas, a compressed gas or a mixture thereof.

[0146] 20. An objective lens structure according to any one of clauses 14-19, wherein the plurality of channels comprises a plurality of channels having a power level of 20-2000 W.m. -1 .K -1 Materials with thermal conductivity within the range.

[0147] 21. The objective lens structure according to clause 20, wherein the material of the plurality of channels comprises aluminum, titanium, copper, graphite, aluminum carbide, aluminum nitride, plastic, composite or alloy.

[0148] 22. The objective lens structure according to any of clauses 14-21, further comprising a thermal insulation layer arranged in a circumferential manner between the plurality of electromagnetic coils and the ferromagnetic housing of the objective lens.

[0149] 23. The objective lens structure according to clause 23, wherein the thermal insulation layer comprises a fluid channel configured to absorb heat generated by the plurality of electromagnetic coils.

[0150] 24. An objective structure according to any of clauses 14-23, wherein the bobbin having the plurality of channels comprises a monolithic structure.

[0151] 25. An objective lens structure according to clause 24, wherein the monolithic structure comprises an additively manufactured monolithic structure.

[0152] 26. The objective lens structure according to clause 25, wherein the additively manufactured monolithic structure comprises at least one of a metal, a metal alloy, a ceramic or a ceramic composite.

[0153] 27. Objective structure according to any of clauses 14-23, wherein the bobbin having a plurality of channels comprises a plurality of parts coupled together.

[0154] 28. A method for cooling an objective lens of a charged particle beam system, comprising:

[0155] receiving a fluid via a fluid inlet port of the spool;

[0156] circulating through a plurality of channels distributed in the bobbin so that the fluid can absorb heat generated by a plurality of electromagnetic coils of the objective lens; and

[0157] Fluid circulated by the plurality of channels is distributed via a fluid outlet port of the spool.

[0158] 29. The method according to clause 28, wherein the spool further comprises:

[0159] a bottom flange proximate to a wafer in the charged particle beam system; and

[0160] Keep away from the top edge of the wafer.

[0161] 30. The method according to any of clauses 28 and 29, wherein the plurality of channels comprises:

[0162] an inlet passage configured to circulate fluid received from the fluid inlet port;

[0163] an outlet passage configured to direct the circulated fluid toward the fluid outlet port; and.

[0164] An intermediate channel is fluidly connected to the inlet channel and the outlet channel.

[0165] 31. The method of any of clauses 28-30, wherein the circulated fluid absorbs heat generated by electromagnetic coils wrapped around at least a portion of the spool.

[0166] 32. The method according to any of clauses 28-31, wherein the fluid comprises one of a liquid, a coolant, a gas, a compressed gas, or a mixture thereof.

[0167] 33. A method according to any one of clauses 28-32, wherein the plurality of channels comprises a plurality of channels having a power source in the range of 20-2000 W.m. -1 .K -1 Materials with thermal conductivity within the range.

[0168] 34. The method of clause 33, wherein the material of the plurality of channels comprises aluminum, titanium, copper, graphite, aluminum carbide, aluminum nitride, plastic, composite or alloy.

[0169] 35. The method according to any of clauses 28-34, further comprising circulating a second fluid in a fluid channel of a thermal insulation layer circumferentially disposed between the plurality of electromagnetic coils and the ferromagnetic housing of the objective lens.

[0170] 36. The method of clause 35, wherein the second fluid comprises one of a liquid, a coolant, a gas, a compressed gas, or a mixture thereof.

[0171] 37. The method of any of clauses 28-36, wherein the bobbin having the plurality of channels comprises a monolithic structure.

[0172] 38. The method of clause 37, wherein the monolithic structure comprises an additively manufactured monolithic structure.

[0173] 39. The method of clause 38, wherein the additively manufactured monolithic structure comprises at least one of a metal, a metal alloy, a ceramic, or a ceramic composite.

[0174] 40. The method of any of clauses 28-36, wherein the spool having a plurality of channels comprises a plurality of sections coupled together.

[0175] 41. A computer readable storage medium storing data representing a spool capable of being printed on a 3D printer, the spool comprising:

[0176] a fluid inlet port configured to receive a fluid;

[0177] a plurality of channels distributed in the spool and configured to circulate fluid received by the fluid inlet port; and

[0178] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0179] 42. A computer-readable three-dimensional model of a physical spool capable of being printed on a 3D printer, the spool comprising:

[0180] a fluid inlet port configured to receive a fluid;

[0181] a plurality of channels distributed in the spool and configured to circulate fluid received by the fluid inlet port; and

[0182] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0183] 43. A bobbin for cooling an objective lens of a charged particle beam system, the bobbin comprising:

[0184] a fluid inlet port configured to receive a fluid;

[0185] a plurality of channels distributed in the spool, the channels configured to reduce heat radiated from a portion of the spool toward the thermal element in a vacuum environment and configured to circulate the fluid received by the fluid inlet port; and

[0186] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0187] 44. The spool of clause 43, wherein the thermal element is a wafer, further comprising:

[0188] a portion of the channel being positioned proximate a bottom flange of the wafer in the charged particle beam system at a location of the spool for cooling a portion of the bottom flange proximate the wafer to facilitate reduction of heat radiated from the spool and toward the wafer in a vacuum environment; and

[0189] Keep away from the top edge of the wafer.

[0190] 45. A computer readable storage medium storing data representing a spool capable of being printed on a 3D printer, the spool comprising:

[0191] a fluid inlet port configured to receive a fluid;

[0192] a plurality of channels distributed in the bobbin, the plurality of channels being configured to reduce heat radiated from the bobbin toward the thermal element in a vacuum environment and being configured to circulate the fluid received by the fluid inlet port; and

[0193] A fluid outlet port is configured to distribute fluid circulated by the plurality of channels.

[0194] 46. ​​The medium of clause 45, wherein the thermal element is a wafer.

[0195] 47. A medium according to clause 45, wherein the channel is configured to reduce heat radiated from the spool toward the thermosensitive element in a vacuum environment, including: the channel is positioned on the spool at a location to cool a portion of the spool that radiates heat toward the thermosensitive element.

[0196] A non-transitory computer readable medium may be provided that stores instructions for a processor (e.g., processor 1104) to perform thermal sensing, flow sensing, image inspection, image acquisition, stage positioning, beam focusing, electric field adjustment, cleaning, hardening, heat treatment, material removal, polishing, etc. For example, common forms of non-transitory media include floppy disks, flexible disks, hard disks, solid state disks, magnetic tapes, or any other magnetic data storage medium; compact disk read-only memory (CD-ROM), any other optical data storage medium, any physical medium with a pattern of holes, 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, or any other memory chip or cartridge, and networked versions thereof.

[0197] The block diagrams in the accompanying drawings illustrate the architecture, functions and operations of possible implementations of the system, method and computer hardware or software product according to various exemplary embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a module, segment or part of a code, which includes one or more executable instructions for implementing a specified logical function. It should be understood that in some alternative embodiments, the functions indicated in the box can occur in an order different from that shown in the figure. For example, depending on the function involved, the two boxes shown in succession can be executed or implemented substantially at the same time, or the two boxes can sometimes be executed in reverse order. Some boxes can also be omitted. It should also be noted that each box in the block diagram and the combination of boxes can be implemented by a system based on special-purpose hardware that performs a specified function or action, or by a combination of special-purpose hardware and computer instructions.

[0198] It will be appreciated that the embodiments of the present disclosure are not limited to the exact configurations described above and illustrated in the accompanying drawings, and that various modifications and variations may be made without departing from the scope thereof. The present disclosure has been described in conjunction with various embodiments, but other embodiments of the present invention will be apparent to those skilled in the art by consideration of the specification and practice of the invention disclosed herein. The specification and examples are intended to be considered exemplary only, with the actual scope and spirit of the present invention being indicated by the appended claims.

[0199] The above description is intended to be illustrative rather than limiting. It will therefore be apparent to those skilled in the art that modifications may be made as described without departing from the scope of the appended claims.

Claims

1. A bobbin for cooling an objective lens of a charged particle beam system, the bobbin comprising: a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the spool, the channels configured to reduce heat radiated from a portion of the spool toward a thermal element in a vacuum environment and configured to circulate a fluid received by the fluid inlet port; and a fluid outlet port configured to distribute fluid circulated by the plurality of channels, The bobbin having the plurality of channels comprises a monolithic structure.

2. The spool of claim 1, wherein the thermal element is a wafer, the spool further comprising: a bottom flange proximate to the wafer in the charged particle beam system, a portion of the channel being positioned at a location of the bobbin to cool a portion of the bottom flange proximate to the wafer to facilitate reduction of heat radiated from the bobbin and toward the wafer in a vacuum environment; and away from the top edge of the wafer.

3. The spool of any one of claims 1-2, wherein the plurality of channels comprises: an inlet channel configured to circulate fluid received from the fluid inlet port; and An outlet channel is configured to direct the circulated fluid toward the fluid outlet port.

4. The spool of claim 3, wherein the plurality of channels further comprises an intermediate channel fluidly connected to the inlet channel and the outlet channel.

5. The spool of any one of claims 1, 2 and 4, wherein the circulating fluid absorbs heat generated by a plurality of electromagnetic coils wrapped around at least a portion of the spool.

6. The spool of any one of claims 1, 2, and 4, wherein the fluid comprises one of a liquid, a coolant, a gas, or a mixture thereof, wherein the gas comprises a compressed gas.

7. The spool of any one of claims 1, 2 and 4, wherein the plurality of channels comprises a plurality of channels having a power source in the range of 20-2000 W.m. -1 .K -1 range of thermal conductivity materials.

8. The spool of claim 7, wherein the material of the plurality of channels comprises aluminum, titanium, copper, graphite, aluminum carbide, aluminum nitride, plastic, composite, or alloy.

9. The spool of claim 1 wherein the monolithic structure comprises an additively manufactured monolithic structure.

10. The spool of claim 9, wherein the additively manufactured monolithic structure comprises at least one of a metal, a metal alloy, a ceramic, or a ceramic composite.

11. The spool of any one of claims 1, 2, 4, and 8, wherein the spool having the plurality of channels comprises a plurality of sections coupled together.

12. A computer-readable storage medium storing data representing a spool capable of being printed on a 3D printer, the spool comprising: a fluid inlet port configured to receive a fluid; a plurality of channels distributed in the bobbin, the channels being configured to reduce heat radiated from the bobbin toward a thermal element in a vacuum environment and configured to circulate the fluid received by the fluid inlet port; and a fluid outlet port configured to distribute the fluid circulated by the plurality of channels, The bobbin having the plurality of channels comprises a monolithic structure.

13. The medium of claim 12, wherein the thermal element is a wafer.

14. The medium of claim 12, wherein the channel is configured to reduce heat radiated from the bobbin toward the thermal element in the vacuum environment comprises: The channel is positioned on the bobbin at a location that cools a portion of the bobbin that radiates heat through the vacuum environment toward the thermal element.

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