Focusing lens device and cathode lens device

Abstract

The application relates to a focusing lens device and a cathode lens device. The focusing lens device comprises a pole shoe assembly, a spacing assembly and a coil assembly. The pole shoe assembly has a pole shoe gap and a mounting gap. The spacing assembly comprises a metal sealing piece arranged in the pole shoe assembly and sealingly matched with the inner wall of the cavity of the pole shoe assembly. The metal sealing piece is used for spacing the mounting gap and the pole shoe gap. The coil assembly is arranged in the mounting gap. The metal sealing piece overcomes the problem that the rubber sealing piece has a high self outgassing rate and affects the vacuum degree of the pole shoe gap. The metal sealing piece does not have the inherent defects of the rubber sealing piece, such as permanent deformation caused by the decrease of elasticity after long-term pressure and incomplete sealing caused by low-temperature hardening. Therefore, the metal sealing piece is favorable for effectively reducing the leakage risk, ensuring the long-term stability of the pole shoe gap under the super-high vacuum condition, and improving the reliability and use performance of the focusing lens device.

Description

Technical Field

[0001] This application relates to the field of cathode lens device technology, and in particular to a focusing lens device and a cathode lens device. Background Technology

[0002] For the focusing lens device of the cathode lens assembly, the coil assembly is made of cable conductors wrapped in insulating material. The magnetic field generated by the coil assembly is coupled to the pole piece assembly, exciting an enhanced magnetic field. The magnetic field overflows at the gap, forming the magnetic field distribution of the focused electron beam. Among them, the pole piece gap, as part of the particle beam channel, needs to maintain an ultra-high vacuum environment to ensure the cleanliness and stability of electron beam transmission.

[0003] To prevent the outgassing and heat generation of the coil assembly during use from affecting the vacuum environment of the pole shoe gap, related technologies often use rubber seals to separate the mounting gap for installing the coil assembly from the pole shoe gap. While this separation is beneficial for maintaining an ultra-high vacuum environment to some extent, the rubber seal itself has a relatively high outgassing rate. Under vacuum conditions, adsorbed gas molecules can still detach from the material and enter the pole shoe gap, affecting the vacuum environment and making it difficult to meet the ultra-high vacuum requirements. Summary of the Invention

[0004] Therefore, it is necessary to provide a focusing lens device and a cathode lens device to address the problem that when rubber seals are used to seal the installation gap and pole shoe gap inside the pole shoe assembly in related technologies, the inherently large outgassing rate of the rubber seals still affects the ultra-high vacuum environment of the pole shoe gap.

[0005] In one embodiment, a focusing lens device is provided, the focusing lens device comprising:

[0006] The pole shoe assembly has pole shoe clearance and mounting clearance;

[0007] The spacer assembly includes a metal seal disposed within the pole shoe assembly and sealingly fitted to the inner wall of the cavity of the pole shoe assembly. The metal seal is used to space the installation gap and the pole shoe gap.

[0008] The coil assembly is positioned within the mounting gap.

[0009] In one embodiment, a stepped surface is provided between the pole shoe clearance and the mounting clearance, and a metal seal is disposed on the stepped surface and seals with the stepped surface, thereby separating the mounting clearance and the pole shoe clearance.

[0010] In one embodiment, the metal seal is deformable, and the stepped surface for sealing with the metal seal has a first knife-edge structure. The metal seal is press-fitted onto the first knife-edge structure, and the metal seal deforms and embeds itself into the first knife-edge structure during the pressing process, thus sealing with the first knife-edge structure.

[0011] In one embodiment, the spacing component further includes:

[0012] The press-fit structure allows metal seals to be press-fitted onto the stepped surface.

[0013] In one embodiment, the pole shoe assembly further has a receiving gap for forming a particle beam channel, one end of the receiving gap extending into the pole shoe gap and the other end of the receiving gap extending to the outer periphery of the pole shoe assembly and forming an opening, the surface of the pole shoe assembly having the opening of the receiving gap having a second cutting edge structure for sealing with an external structure metal.

[0014] In one embodiment, the pole shoe assembly includes:

[0015] The upper pole shoe has an installation gap with an opening, and a spacer assembly is disposed on the upper pole shoe and seals the opening of the installation gap;

[0016] The lower pole shoe is located on one side of the upper pole shoe and together with the upper pole shoe forms the pole shoe gap. The spacer assembly is located within the pole shoe gap and is spaced apart from the lower pole shoe.

[0017] In one embodiment, the spacer component is spaced apart from the lower pole shoe, and the upper pole shoe is electrically isolated from the lower pole shoe.

[0018] In one embodiment, the pole shoe assembly further includes:

[0019] The upper and lower pole shoes are connected by a fixing component;

[0020] An insulating element is sealed between the upper and lower pole shoes by a fixing assembly. Both the fixing assembly and the insulating element are surface-treated with non-magnetic insulation and / or made of non-magnetic insulating material for electrically isolating the upper and lower pole shoes.

[0021] In one embodiment, the pole shoe assembly has an air extraction port, through which a vacuum pump communicates with the pole shoe gap to adjust the vacuum level within the pole shoe gap.

[0022] In one embodiment, a cathode lens device is provided, which includes a sample stage and the aforementioned focusing lens device. The mounting gap of the focusing lens device forms an outlet on the surface of the pole shoe assembly, and the sample stage is disposed below the outlet.

[0023] The aforementioned focusing lens device uses metal seals instead of the commonly used rubber seals in related technologies to isolate the mounting gap from the pole shoe gap, thereby achieving effective isolation of the coil assembly. Compared to rubber seals, metal seals not only prevent the heat and outgassing of the coil assembly from affecting the vacuum level of the pole shoe gap, but also overcome the problem of rubber seals affecting the vacuum level of the pole shoe gap due to their high outgassing rate. Furthermore, metal seals do not suffer from the inherent defects of rubber seals, such as permanent deformation due to decreased elasticity after long-term pressure and incomplete sealing due to low-temperature hardening. This effectively reduces the risk of leakage, ensures the long-term stability of the pole shoe gap under ultra-high vacuum conditions, and thus improves the reliability and performance of the focusing lens device. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the focusing lens device provided in one embodiment of this application;

[0025] Figure 2 A cross-sectional view of a focusing lens device provided in an embodiment of this application;

[0026] Figure 3 This is a schematic diagram of the structure of the upper pole shoe provided in an embodiment of this application;

[0027] Figure 4 This is a schematic diagram of the structure of the lower pole shoe provided in an embodiment of this application;

[0028] Figure 5 This is a schematic diagram of the structure of a spacer component provided in an embodiment of this application;

[0029] Figure 6 This is a schematic diagram of the structure of an insulating component provided in an embodiment of this application.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Focusing lens device;

[0032] 10. Pole shoe assembly; 101. Pole shoe gap; 102. Mounting gap; 1021. Guide path; 103. Stepped surface; 104. First knife-edge structure; 105. Accommodation gap; 106. Second knife-edge structure; 107. Evacuation port; 108. Ejection port; 109. Third knife-edge structure; 11. Upper pole shoe; 1101. Third mounting hole; 1102. Fourth mounting hole; 1103. Fifth mounting hole; 12. Lower pole shoe; 1201. Seventh mounting hole; 13. Insulator; 1301. Sixth mounting hole;

[0033] 20. Spacer assembly; 21. Metal seal; 22. Press-fit structure; 2201. First mounting hole; 2202. Second mounting hole;

[0034] 30. Coil assembly;

[0035] 2. Sample stage. Detailed Implementation

[0036] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0037] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0041] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0042] Rubber seals, commonly used in related technologies, release volatile substances such as vulcanizing agents, plasticizers, and low-molecular-weight greases left over from the rubber material and manufacturing process. These substances continuously release these substances into a vacuum environment, becoming the primary gas load. This not only prolongs the evacuation time of the pole shoe gap 101 but also affects and limits the ultimate vacuum level. Furthermore, the macromolecular structure of rubber seals cannot completely prevent the penetration of small-molecule gases such as helium and hydrogen, easily leading to minute leaks. On the other hand, ultra-high vacuum typically requires high-temperature baking to remove gases adsorbed on the cavity walls. However, conventional rubbers such as nitrile rubber can only withstand temperatures up to 120°C, and even high-performance fluororubber should not be baked above 150-200°C. Forced high-temperature baking can accelerate rubber aging or even decompose, thus affecting the vacuum environment. Moreover, rubber seals lose elasticity and undergo permanent deformation after prolonged pressure, leading to a decrease in sealing contact pressure and leakage. In low-temperature environments, common fluororubbers can harden, making it difficult to fully fill the sealing surface, resulting in incomplete or inadequate sealing and leakage. For the problems that rubber seals may cause, please refer to [reference needed]. Figure 1 and Figure 2 The present application provides a focusing lens device 1, which includes a pole shoe assembly 10, a spacer assembly 20, and a coil assembly 30. The pole shoe assembly 10 has a pole shoe gap 101 and a mounting gap 102. The spacer assembly 20 includes a metal seal 21 disposed within the pole shoe assembly 10 and sealingly fitted with the inner wall of the cavity of the pole shoe assembly 10. The metal seal 21 is used to space the mounting gap 102 and the pole shoe gap 101. The coil assembly 30 is disposed within the mounting gap 102.

[0043] The technical solution provided in this application embodiment uses a metal seal 21 instead of the commonly used rubber seal in related technologies to isolate the mounting gap 102 from the pole shoe gap 101, thereby achieving effective isolation of the coil assembly 30. Compared with the rubber seal, the metal seal 21 not only avoids the problem of heat generation and gas release during the operation of the coil assembly 30 affecting the vacuum degree of the pole shoe gap 101, but also overcomes the problem of the rubber seal affecting the vacuum degree of the pole shoe gap 101 due to its high gas release rate. Furthermore, the metal seal 21 does not suffer from the inherent defects of the rubber seal, such as permanent deformation due to decreased elasticity after long-term pressure and incomplete sealing due to low-temperature hardening. This effectively reduces the risk of leakage, ensures the long-term stability of the pole shoe gap 101 under ultra-high vacuum conditions, and thus improves the reliability and performance of the focusing lens device 1.

[0044] It is understandable that by designing a specific metal seal 21, its ultra-low outgassing rate can meet the requirements of the sample chamber entering an ultra-high vacuum range of ≤1E-10 mbar. In some embodiments, the coil assembly 30 is placed outside the pole shoe gap 101 by means of a full metal seal, thereby avoiding the impact of outgassing of polymer materials such as the insulation layer of the coil assembly 30 on the ultra-high vacuum, resulting in good vacuum compatibility, which can be less than 1E-11 mbar. Preferably, the coil assembly 30 is electrically connected to an external power source via wires, and the mounting gap 102 has at least one guide path 1021 for mounting the wires required for the electrical connection of the coil assembly 30. Figures 1 to 3 In the illustrated embodiment, two guide paths 1021 are symmetrically arranged. Specifically, the wires of the coil assembly 30 can be installed along the guide path 1021 inside the mounting gap 102, and led out to the outside of the mounting gap 102 without affecting the sealing effect through designs such as sealed joints or wire holes. In order to prevent the wires from interfering with the surrounding structure or affecting the magnetic field distribution, insulating sleeves or fixing clamps can be used to constrain the wires. The mounting gap 102 can also be provided with other discharge paths for timely heat dissipation and venting.

[0045] exist Figure 2 and Figure 3 In the illustrated embodiment, the pole shoe assembly 10 further includes a receiving gap 105 for forming a particle beam channel. One end of the receiving gap 105 extends into the pole shoe gap 101, and the other end extends to the outer periphery of the pole shoe assembly 10, forming an opening. The receiving gap 105 can serve as a particle beam channel itself or be used to limit the installation of other devices for forming a particle beam channel, depending on the actual situation. An exit port 108 is formed on the surface of the pole shoe assembly 10 by the mounting gap 102. In this embodiment, one end of the receiving gap 105 extends into the inner region of the exit port 108.

[0046] exist Figure 2 and Figure 4 In the illustrated embodiment, the pole shoe assembly 10 has a vacuum port 107. A vacuum pump is connected to the pole shoe gap 101 via the vacuum port 107 to adjust the vacuum level within the pole shoe gap 101. By evacuating the pole shoe gap, an unobstructed, clean channel is provided for the particle beam, reducing the scattering of gas molecules on the particle beam and preventing residual gas from decomposing and contaminating the pole shoe assembly and sample under the bombardment of the particle beam. Furthermore, the vacuum level of the pole shoe gap 101 can be maintained within a suitable range through the vacuum port 107, ensuring that the vacuum level is between that of the particle beam channel and the working chamber, i.e., the environment where the focusing lens device 1 is located. This helps guarantee imaging resolution and provides the necessary conditions for in-situ experiments under ultra-high vacuum conditions. It is understood that the number of vacuum ports 107 can be adaptively adjusted according to actual conditions; not all examples are provided here.

[0047] exist Figure 2 and Figure 3 In the illustrated embodiment, a stepped surface 103 is provided between the pole shoe gap 101 and the mounting gap 102. A metal seal 21 is disposed on the stepped surface 103 and seals against the stepped surface 103, while also spacing the mounting gap 102 and the pole shoe gap 101. This arrangement facilitates the positioning and installation of the metal seal 21, improving the convenience and reliability of the sealing installation.

[0048] exist Figure 2 , Figure 3 and Figure 5 In the illustrated embodiment, the metal seal 21 is deformable. The stepped surface 103, used for sealing with the metal seal 21, has a first knife-edge structure 104. The metal seal 21 is press-fitted onto the first knife-edge structure 104. During the pressing process, the metal seal 21 deforms and embeds itself into the first knife-edge structure 104, sealing with it. By setting the deformable metal seal 21 to cooperate with the first knife-edge structure 104 on the stepped surface 103, the metal seal 21 undergoes controllable plastic deformation and embeds itself into the knife-edge structure during the pressing process. The extremely high local pressure generated at the knife-edge tip forms a tight metal hard seal, effectively blocking the gas molecule permeation channel, achieving an extremely low leakage rate, and meeting the requirements of ultra-high vacuum environments. At the same time, the deformation of the metal seal 21 can automatically adapt to the microscopic unevenness of the knife-edge surface, reducing the dependence on the machining accuracy of the mating surface and ensuring long-term stability and consistency of the seal.

[0049] Preferably, the metal seal 21 is made of a relatively soft, ultra-high vacuum compatible metal material such as oxygen-free copper with a very low outgassing rate. The leakage rate of this type of metal seal is generally less than 1E-12 mbar L / s, which can meet the vacuum requirements of the ultra-high vacuum system.

[0050] exist Figure 2and Figure 5 In the illustrated embodiment, the spacer assembly 20 further includes a press-fit structure 22, through which the metal seal 21 is press-fitted onto the stepped surface 103. By setting the press-fit structure 22 to provide a controllable and uniform clamping force to the metal seal 21, stable and consistent plastic deformation and tight fit are ensured between it and the first knife-edge structure 104, thereby ensuring the reliability and repeatability of the seal. At the same time, the press-fit structure 22, as an independent force-applying element, facilitates its installation, positioning, and replacement with the metal seal 21, reducing assembly difficulty and improving maintenance efficiency. It also facilitates effective control of the deformation of the metal seal 21 by controlling the pressure, avoiding seal failure due to overpressure or bias pressure, and further ensuring the sealing stability for long-term use in ultra-high vacuum environments.

[0051] Preferably, the press-fit structure 22 is a sealing cover made of ultra-high vacuum compatible metal material, which can be connected to the stepped surface 103 by fasteners such as screws and adjust the press-fitting force, making it easy to disassemble and adjust the pressure.

[0052] exist Figure 2 In the illustrated embodiment, the surface of the pole shoe assembly 10 having the opening for receiving the gap 105 has a second knife-edge structure 106, which is used for a metal-sealed engagement with an external structure. The top of the pole shoe assembly 10 also has a third knife-edge structure 109, which is also used for a metal-sealed engagement with an external structure. This arrangement ensures that both the focusing lens device 1 itself and its seal with the external structure are metal-sealed, which improves the reliability and stability of the seal between the focusing lens device 1 and its external structure.

[0053] exist Figures 1 to 4 In the embodiment shown, the pole shoe assembly 10 includes an upper pole shoe 11 and a lower pole shoe 12. The upper pole shoe 11 has an installation gap 102 with an opening. A spacer assembly 20 is disposed on the upper pole shoe 11 and blocks the opening of the installation gap 102. The lower pole shoe 12 is disposed on one side of the upper pole shoe 11 and together with the upper pole shoe 11 forms a pole shoe gap 101. The spacer assembly 20 is located within the pole shoe gap 101. In this embodiment, the upper pole shoe 11 includes a seat and a cylindrical portion. The cylindrical portion is disposed at the center end of the seat and protrudes from the surface of the seat. The cylindrical portion has a receiving gap. The seat has an annular mounting gap 102 surrounding the cylindrical portion, and the opening of the mounting gap 102 faces the side of the cylindrical portion that protrudes from the seat. The lower pole shoe 12 is a conical seat with a conical cavity inside. The upper pole shoe 11 is disposed at the opening of the conical cavity and seals the opening. The end of the cylindrical portion is located inside the conical cavity. After the conical cavity is sealed, the pole shoe gap 101 is formed. The spacer assembly 20 can be directly disposed and seal the opening of the mounting gap 102. Its installation can be independent of the lower pole shoe 12. This arrangement facilitates the forming of the mounting gap 102 and the pole shoe gap 101.

[0054] In this embodiment, the spacer component 20 is an annular structure corresponding to the annular mounting gap 102, the metal seal 21 is an annular gasket structure, the sealing cover is an annular plate structure, the stepped surface 103 is directly formed at the opening of the mounting gap 102, and the sealing cover is press-fitted onto the surface of the upper pole shoe 11 that has the opening of the mounting gap 102. Specifically, in Figure 3 In the illustrated embodiment, the cylindrical portion has an inner ring hole group formed by a plurality of third mounting holes 1101, and the seat portion has an outer ring hole group formed by a plurality of fourth mounting holes 1102. Preferably, the two hole groups are located on the same surface. Figure 5 In the illustrated embodiment, the sealing cover has a plurality of first mounting holes 2201 corresponding to the inner ring hole group and a plurality of second mounting holes 2202 corresponding to the outer ring hole group. The third mounting hole 1101 and the fourth mounting hole 1102 are threaded holes, such as... Figure 2 As shown, during installation, the metal seal 21 is first positioned and installed on the stepped surface 103. Then, fasteners such as bolts or screws are passed through the first mounting hole 2201 and threadedly connected to the third mounting hole 1101, and through the second mounting hole 2202 and threadedly connected to the fourth mounting hole 1102, so as to gradually install the sealing cover. During the installation process, pressure is applied to the metal seal 21 to make it fit and seal with the first knife-edge structure 104.

[0055] Specifically, the spacer component 20 is spaced apart from the lower pole piece 12, and the upper pole piece 11 is electrically isolated from the lower pole piece 12. This configuration effectively cuts off the direct magnetic coupling path between the upper pole piece 11 and the lower pole piece 12, preventing the magnetic field lines from closing directly. This forces the magnetic field to overflow at a predetermined location, providing a structural basis for introducing an insulating magnetic gap into the magnetic circuit. This allows the lower pole piece 12 to also function as a deceleration electrode itself, performing primary deceleration on the incident electrode, and working in conjunction with the sample bias voltage to decelerate the entire incident electron.

[0056] Preferably, both the upper pole piece 11 and the lower pole piece 12 are made of permalloy. Due to its high relative permeability, it can achieve the ability to confine the magnetic field in a small space. After they are combined, they form a closed magnetic circuit and an insulating magnetic gap.

[0057] exist Figure 2 and Figure 6In the illustrated embodiment, the pole shoe assembly 10 further includes a fixing component and an insulating member 13. The upper pole shoe 11 and the lower pole shoe 12 are connected by the fixing component. The insulating member 13 is sealed between the upper pole shoe 11 and the lower pole shoe 12 by the fixing component. Both the fixing component and the insulating member 13 have non-magnetic insulating surface treatment and / or are made of non-magnetic insulating material for electrically isolating the upper pole shoe 11 and the lower pole shoe 12. In this embodiment, the position of the insulating magnetic gap is the location of the insulating member 13 between the upper pole shoe 11 and the lower pole shoe 12. The position of the insulating magnetic gap is relatively close to the position of the pole shoe gap 101, so it will not affect the pole shoe gap 101 and will have a low impact. The non-magnetic insulation design of the fixing component and the insulating component 13 can be adapted to the actual situation. It can be achieved by surface non-magnetic insulation treatment, by material limitation, or by other feasible methods. A single design or a combination of multiple designs can be used. As long as it is ensured that the two can electrically isolate the upper pole shoe 11 and the lower pole shoe 12 without affecting the magnetic field, the problem of the upper pole shoe 11 and the lower pole shoe 12 being connected through the fixing component and / or the insulating component 13 or the magnetic field being affected by the fixing component and / or the insulating component 13 is avoided.

[0058] Specifically, in this embodiment, the fixing component includes multiple fasteners such as screws or bolts, which facilitates disassembly and assembly. Figure 3 In the illustrated embodiment, the upper pole shoe 11 has a plurality of fifth mounting holes 1103 on the side facing the lower pole shoe 12. Figure 4 In the embodiment shown, the lower pole shoe 12 has a plurality of seventh mounting holes 1201 on the side facing the upper pole shoe 11. Figure 6 In the embodiment shown, the insulating member 13 is an annular member and has multiple sixth mounting holes 1301. The multiple sixth mounting holes 1301 correspond one-to-one with the multiple fifth mounting holes 1103 and the multiple seventh mounting holes 1201. The fifth mounting hole 1103 is a threaded hole. Fasteners such as bolts or screws pass through the seventh mounting hole 1201 and the sixth mounting hole 1301 in sequence and are threadedly connected to the fifth mounting hole 1103 to realize the connection between the upper pole shoe 11, the lower pole shoe 12 and the insulating member 13. Preferably, the insulating component 13 can be directly sealed to the upper pole shoe 11 and the lower pole shoe 12, or indirectly sealed to the upper pole shoe 11 and the lower pole shoe 12 through other sealing structures. When introducing other sealing structures, it can be determined whether the other sealing structures directly conduct electricity to the upper pole shoe 11 and the lower pole shoe 12, and whether they need to be electrically isolated like the fixing components and the insulating component 13. In this embodiment, the insulating component 13 is directly sealed to the upper pole shoe 11 and the lower pole shoe 12. Preferably, the insulating component 13 is made of a material that takes into account both structural strength and a certain elastic deformation capability, so that it can withstand a certain installation extrusion force and can deform under extrusion to adapt to the two opposing surfaces of the upper pole shoe 11 and the lower pole shoe 12, which helps to achieve tight fit and sealing.

[0059] Specifically, in this embodiment, the insulating component 13 is made of a non-magnetic insulating material with high resistivity, elastic deformation capability, and almost no effect on the magnetic field. For example, in one specific embodiment, the insulating component 13 can be made of epoxy resin composite material reinforced with aramid fiber or glass fiber. This material has extremely high resistivity and a relative permeability close to 1, which can ensure reliable electrical isolation between the upper pole shoe 11 and the lower pole shoe 12, allowing the lower pole shoe to be independently biased, without forming a low magnetic reluctance bypass. This ensures that the regulating effect of the insulating magnetic gap on the magnetic field distribution is not disrupted. At the same time, this material balances structural strength and small elastic deformation capability, enabling it to undergo small deformations under compression that contribute to tight bonding and sealing while ensuring the reliability and stability of the insulating component 13 structure. In addition, this material also has excellent voltage withstand characteristics, bending strength, and corrosion resistance. Its specific withstand voltage value can meet the insulation matching requirements of the ultra-high vacuum system according to the design thickness and structure of the insulating component, and can fully meet the requirements of thermal stress, mechanical stress, and sealing under ultra-high vacuum and high pressure environments. Furthermore, in this embodiment, the fixing components, i.e., fasteners such as bolts or screws, are made of non-magnetic insulating materials with high resistivity that have almost no effect on the magnetic field. For example, in a specific embodiment, the fasteners such as bolts or screws can be made of silicon nitride ceramic bolts or aramid ultra-high voltage insulating bolts made of the same material as the insulating component 13. Both of these materials are non-magnetic and have high insulation strength, and will not become part of the magnetic path.

[0060] Another embodiment of this application provides a cathode lens device, which includes a sample stage 2 and the aforementioned focusing lens device 1. The sample stage 2 is disposed below the exit port 108. Specifically, the sample stage 2 is used to hold a sample, which is the sample to be observed. The sample is required to be made of a relatively flat metal or semiconductor material. In some embodiments, the sample itself is connected to a negative high-voltage power supply, while the focusing lens device 1 and its auxiliary components are connected to ground potential. Therefore, an electrostatic field of approximately 2~20 kV / mm is formed between the sample and the focusing lens device 1. An electron beam with a specific kinetic energy is decelerated by this electrostatic field as it moves from the upper pole piece 11 to the lower pole piece 12 of the focusing lens device 1.

[0061] In summary, this application provides a focusing lens device 1 and a cathode lens device. By utilizing the magnetic field generated between the upper and lower pole pieces 11 and the electrostatic field formed between the lower pole piece 12 and the sample, very low spherical aberration and chromatic aberration coefficients can be achieved, solving the spatial resolution problem of cathode lens devices. Specifically, the electrical isolation between the upper and lower pole pieces 11 forms an insulating magnetic gap, allowing the lower pole piece 12 to act as a deceleration electrode itself, performing primary deceleration on the incident electrode. Combined with the sample bias voltage, this achieves the overall deceleration effect of the incident electrons, effectively reducing the required bias voltage for the sample and lowering the risk of discharge at high bias voltages. This reduces the requirements for sample selection, allowing for the observation of a wider variety of samples. Furthermore, this design enables compatibility with multiple operating modes. Specifically, when the lower pole piece 12 and upper pole piece 11 have the same potential, the electron beam is decelerated by biasing the sample; this mode is similar to the working principle of traditional LEEM / PEEM. When the voltage of the lower electrode 12 is between that of the upper electrode 11 and the sample, the electric field formed between the lower electrode 12 and the upper electrode 11 initially decelerates the electrons, and then a second deceleration occurs through the electric field between the lower electrode 12 and the sample, effectively reducing the field strength near the sample. When the voltage of the lower electrode 12 is higher than that of the upper electrode 11 and higher than the sample bias voltage, the incident electrons are accelerated through the electric field formed by the upper electrode 11 and the lower electrode 12, and then decelerated when passing through the electric field between the lower electrode 12 and the sample. This operating mode can further reduce aberrations and improve the spatial resolution of the device, making it suitable for scenarios with low sample discharge probability. On the other hand, the spacer assembly 20 achieves a full metal seal for the mounting gap 102 and the electrode gap 101, solving the problem of venting from the coil assembly 30 and the rubber seals affecting the vacuum level of the ultra-high vacuum environment.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A focusing lens device, characterized in that, The focusing lens device (1) includes: The pole shoe assembly (10) has a pole shoe clearance (101) and a mounting clearance (102). The spacer assembly (20) includes a metal seal (21) disposed within the pole shoe assembly (10) and sealingly fitted to the inner wall of the cavity of the pole shoe assembly (10), the metal seal (21) being used to space the mounting gap (102) and the pole shoe gap (101). The coil assembly (30) is disposed within the mounting gap (102).

2. The focusing lens device according to claim 1, characterized in that, There is a stepped surface (103) between the pole shoe gap (101) and the mounting gap (102), and the metal seal (21) is disposed on the stepped surface (103) and seals against the stepped surface (103) and spaced between the mounting gap (102) and the pole shoe gap (101).

3. The focusing lens device according to claim 2, characterized in that, The metal seal (21) is deformable, and the stepped surface (103) has a first knife-edge structure (104) on the surface for sealing with the metal seal (21). The metal seal (21) is press-fitted onto the first knife-edge structure (104). During the press-fitting process, the metal seal (21) deforms and embeds itself into the first knife-edge structure (104) and seals with the first knife-edge structure (104).

4. The focusing lens device according to claim 2, characterized in that, The spacer assembly (20) further includes: The metal seal (21) is pressed onto the stepped surface (103) by means of the press-fit structure (22).

5. The focusing lens device according to claim 1, characterized in that, The pole shoe assembly (10) also has a receiving gap (105) for forming a particle beam channel, one end of the receiving gap (105) extending into the pole shoe gap (101), and the other end of the receiving gap (105) extending to the outer periphery of the pole shoe assembly (10) and forming an opening. The surface of the pole shoe assembly (10) having the opening of the receiving gap (105) has a second knife-edge structure (106), which is used for sealing with an external structure metal.

6. The focusing lens device according to claim 1, characterized in that, The pole shoe assembly (10) includes: The upper pole shoe (11) has the mounting gap (102) having an opening, and the spacer assembly (20) is disposed on the upper pole shoe (11) and blocks the opening of the mounting gap (102); The lower pole shoe (12) is disposed on one side of the upper pole shoe (11) and together with the upper pole shoe (11) forms the pole shoe gap (101). The spacer assembly (20) is located within the pole shoe gap (101) and spaced apart from the lower pole shoe (12).

7. The focusing lens device according to claim 6, characterized in that, The spacer assembly (20) is spaced apart from the lower pole shoe (12), and the upper pole shoe (11) is electrically isolated from the lower pole shoe (12).

8. The focusing lens device according to claim 7, characterized in that, The pole shoe assembly (10) also includes: A fixing component is provided, through which the upper pole shoe (11) and the lower pole shoe (12) are connected; An insulating element (13) is sealed between the upper pole shoe (11) and the lower pole shoe (12) by means of the fixing assembly; Both the fixing component and the insulating component (13) are surface-treated with non-magnetic insulation and / or made of non-magnetic insulating material for electrically isolating the upper pole shoe (11) from the lower pole shoe (12).

9. The focusing lens device according to claim 1, characterized in that, The pole shoe assembly (10) has an air extraction port (107), and a vacuum pump is connected to the pole shoe gap (101) through the air extraction port (107) to adjust the vacuum level in the pole shoe gap (101).

10. A cathode lens device, characterized in that, The cathode lens device includes a sample stage (2) and a focusing lens device (1) according to any one of claims 1 to 9, wherein the mounting gap (102) of the focusing lens device (1) forms an outlet (108) on the surface of the pole shoe assembly (10), and the sample stage (2) is disposed below the outlet (108).

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