Electron gun cathode, preparation method thereof and electron gun

Abstract

The invention discloses an electron gun cathode, a preparation method thereof and an electron gun, and the preparation method of the cathode comprises the following steps: processing a boride material into a shape required by the electron gun cathode to obtain a base material; preparing a carbide coating layer on the surface of the base material by adopting a chemical vapor deposition method; and removing the carbide coating layer on the surface of the electron beam emitting surface of the base material to finish the preparation. According to the preparation method, the high-quality carbide coating layer can be prepared on the surface of the base material by adopting a chemical vapor deposition method, so that the base material can be effectively protected by utilizing the carbide coating layer, the base material is effectively prevented from being volatilized under high-temperature and high-vacuum conditions, and the electron beam current can be kept stable for a long time; when the material is used for preparing an electron gun of an electron beam exposure machine, the beam stability and the service life of the electron gun can be improved. Meanwhile, the preparation method has the advantages of being simple in process, convenient to operate, low in cost and the like, is suitable for large-scale preparation and is beneficial to industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor electron beam equipment, and relates to an electron gun cathode, a preparation method thereof, and an electron gun. Background Art

[0002] An electron beam lithography machine is an important basic equipment that uses a focused electron beam to generate, accelerate, focus, and deflect to perform high-precision exposure on materials to prepare micro-nano size graphic structures. Since the electron beam accelerated by high voltage has a small wavelength and can form a small beam spot, the electron beam lithography technology can effectively overcome the limitation of the light wave diffraction limit and achieve higher graphic precision exposure. In addition, compared with traditional lithographic exposure, the depth of focus of the electron beam is very deep and is not affected by the surface finish of the working sample, and devices that cannot be manufactured by optical exposure can be manufactured. Therefore, in the field of micro-nano processing technology, the electron beam lithography technology is a crucial process and one of the core technologies for realizing high-precision pattern making.

[0003] As one of the core components of an electron beam lithography machine, the electron gun is the generation and extraction part of the electron beam, and the quality and intensity of the electron beam largely determine the exposure precision and efficiency of the equipment. In order to obtain a higher beam current density to achieve efficient exposure drawing, the electron gun of the electron beam lithography machine generally uses an electron gun cathode generated by a thermal field, and its structural schematic diagram is as Figure 1 shown. Currently, the commonly used electron gun cathode materials are boride (such as LaB 6 , CeB 6 , GdB 6 or YB 6 ) filaments and tungsten (W) filaments, and because boride (such as LaB 6 , 2.7eV) filaments have a lower working temperature and electron emission work function than W (4.5eV) filaments, the electron gun cathode made of boride filaments (abbreviated as LaB 6 cathode) can obtain an electron beam current 10 times brighter than that of the W cathode at a lower temperature, and the LaB 6 cathode has a higher lifespan, usually 10 times that of the W cathode. Therefore, the LaB 6 cathode is the first choice for the cathode material of high-performance electron beam lithography machines.

[0004] In addition, in order to reduce the electron emission barrier of the electron gun cathode and ensure the beam current density of the electron beam, the electron gun cathode is usually designed in a needle tip shape. However, at high temperatures, the LaB 6 cathode is easily oxidized by oxygen in the air, so it must work under high vacuum conditions. Further, the LaB 6 cathode working under high vacuum conditions is easily volatilized, resulting in a reduction in the emission area (such as Figure 2As shown in the figure, it causes the instability of the electron beam current, affecting the accuracy and stability of the electron beam lithography machine. To address the above problems, the existing improvement method is to coat a layer of pyrolytic carbon on the LaB 6 cathode surface to inhibit the volatilization of LaB 6 , ensure the stability of the electron gun emission surface, and improve the stability of the beam current. However, the C coating layer will react with LaB 6 at high temperatures, corrode the matrix material, and since the C material has a large difference in thermal expansion coefficient, thermal stress is easily generated during the heating and cooling process, resulting in coating peeling. At the same time, due to the large thermal conductivity of the C material, it is easy to cause energy loss of the electron gun cathode, affecting the performance of the electron gun. In addition, since the LaB 6 material will almost react chemically with any metal at high temperatures, this also makes the connection between the LaB 6 cathode and the heating metal electrode another problem faced by the thermionic emission cathode. For this reason, the existing solution is to load the LaB 6 cathode into a water suspension adhesive ointment coated with a small amount of tantalum, cobalt, and tantalum carbide powder, and then perform vacuum sintering at 1800K, thereby forming a conductive isolation layer between the LaB 6 cathode and the metal electrode, but this preparation process is complex and there is a problem that the interface contact quality is difficult to control. Therefore, how to prepare a suitable coating layer on the surface of the electron gun cathode material to obtain an electron gun cathode with good working stability and long service life is of great significance for improving the performance of the electron beam lithography machine and promoting the wide use of the electron beam lithography machine. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an electron gun cathode with good working stability and long service life, its preparation method, and an electron gun.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A preparation method of an electron gun cathode, comprising the following steps:

[0008] S1. Process a boride material into the shape required for the electron gun cathode to obtain a matrix material; the boride material is one of LaB 6 , CeB 6 , GdB 6 , YB 6 ;

[0009] S2. Prepare a carbide coating layer on the surface of the matrix material by chemical vapor deposition; the carbide coating layer is one of TaC coating, HfC coating, and MoC coating;

[0010] S3. Remove the carbide coating layer on the surface of the electron beam emission surface of the substrate material to complete the preparation of the electron gun cathode.

[0011] In the preparation method, further improved, in step S1, the boride material is LaB 6 , CeB 6 One of them.

[0012] In the preparation method, further improved, in step S2, the carbide coating layer is one of TaC coating and HfC coating.

[0013] In the preparation method, further improved, the thickness of the carbide coating layer is 100 nm to 800 nm. Further preferably, the thickness of the carbide coating layer is 200 nm to 600 nm.

[0014] In the preparation method, further improved, in step S2, the carbide coating layer is prepared on the surface of the substrate material by chemical vapor deposition, including the following steps:

[0015] S2-1. Place the substrate material in the deposition furnace of the chemical vapor deposition equipment, evacuate to below 10 -4 Pa, first heat at a heating rate of 2 °C / min -1 ~5 °C / min -1 Heat to 400 °C, keep warm for 20 min to 60 min, and then heat at a heating rate of 10 °C / min -1 ~20 °C / min -1 Heat to 800 °C to 1000 °C;

[0016] S2-2. Use argon as the carrier gas, introduce the metal source and reaction gas into the deposition furnace for reaction, and deposit the carbide coating layer on the surface of the substrate material;

[0017] S2-3. After the reaction is completed, stop introducing the gas, heat to 1200 °C, keep warm for 1 h to 3 h, and complete the preparation of the carbide coating layer.

[0018] In the preparation method, further improved, in step S2-2, the metal source is TaCl 5 , HfCl 4 , MoCl 5 One of them; the reaction gas is a carbon source gas and hydrogen; the carbon source gas is CH 4 , C 2 H 4 , C 3 H 6at least one of; the volume fraction of argon in the reaction system is ≥ 40%; the reaction is carried out under the condition of a pressure of 10 Pa to 100 Pa; the reaction time is 10 min to 30 min.

[0019] In the preparation method, further improved, in step S1, the boride material is processed into the shape required for the electron gun cathode by mechanical processing to obtain the substrate material; the shape of the substrate material is a needle tip shape; the substrate material includes a cylinder and a cone located on the cylinder, and the diameter of the bottom surface of the cone is the same as that of the cylinder; the diameter of the cylinder is 500 μm to 2000 μm; the cone angle of the cone is 40° to 120°; the height of the substrate material is 1 mm to 5 mm; the (100) crystal plane of the substrate material is parallel to the cross-section of the cylinder.

[0020] In the preparation method, further improved, the cone angle of the cone is 90°.

[0021] In the preparation method, further improved, in step S3, removing the carbide coating layer on the electron beam emission surface of the substrate material includes the following steps:

[0022] S3-1. Remove the carbide coating layer at the tip of the substrate material by using a focused ion beam processing method to form a preliminary profile of the electron beam emission surface at the tip of the substrate material;

[0023] S3-2. Process the tip exposed at the electron beam emission end of the substrate material by using a mechanical polishing method until a frustum with a diameter of 0.5 μm to 1.5 μm is formed to obtain the electron gun cathode.

[0024] As a general technical concept, the present invention also provides an electron gun cathode, and the electron gun cathode is prepared by the above preparation method.

[0025] For the above electron gun cathode, further improved, the electron gun cathode is composed of a cylinder and a frustum, the frustum is located on the cylinder, and the diameter of the bottom surface of the frustum is the same as that of the cylinder; the surface of the cylinder and the side surface of the frustum are both coated with a carbide coating layer.

[0026] As a general technical concept, the present invention also provides an electron gun, and the electron gun includes the above electron gun cathode.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] The present invention provides a method for preparing an electron gun cathode. Using a boride material as the electron beam emission material, the boride material is first processed into the shape required for the electron gun cathode to obtain a substrate material. Then, a carbide coating layer is prepared on the surface of the substrate material by chemical vapor deposition. Finally, the carbide coating layer on the electron beam emission surface of the substrate material is removed, and an electron gun cathode with good working stability and long service life can be prepared. Compared with other preparation methods (vacuum sintering, magnetron sputtering, pulsed laser deposition), the chemical vapor deposition method is used to prepare the carbide coating layer in the present invention, which has the following advantages: not only can a highly dense carbide coating layer be prepared on the surface of the substrate material, but also the prepared carbide coating layer can firmly coat the surface of the substrate, and at the same time, the interface contact quality can be effectively regulated, so as to effectively protect the substrate material by using the high-quality carbide coating layer, and it has the advantages of high deposition efficiency and low cost. In addition, in the present invention, by preparing a high-quality carbide coating layer on the surface of the boride material, the following advantages are also achieved: (a) The prepared carbide coating layer has the characteristics of high melting point (such as the melting point of TaC is 3380 °C, and the melting point of HfC is 3890 °C) and low thermal conductivity (such as the thermal conductivity of TaC is 22 W·m -1 ·K -1 , and the thermal conductivity of HfC is 20 - 30 W·m -1 ·K -1 ), which can effectively avoid the volatilization of the substrate material (boride material) at high temperature and high vacuum during operation, and is beneficial to improving the stability and service life of the electron gun cathode; (b) The prepared carbide coating layer has a thermal expansion coefficient similar to that of the substrate material (such as the thermal expansion coefficient of TaC is 6.6×10 -6 °C -1 , the thermal expansion coefficient of HfC is 6.73×10 -6 °C -1 , and the thermal expansion coefficient of LaB 6 is 6.4×10 -6 °C -1), it can avoid the accumulation of interfacial thermal stress caused by temperature changes, effectively prevent the peeling of the carbide coating layer, and is conducive to improving the stability and service life of the electron gun cathode; (c) The prepared carbide coating layer has stable high-temperature performance and will not chemically react with the substrate material (boride material) at high temperatures to cause corrosion. Moreover, the electron work function of the carbide coating layer (such as the electron work function of HfC is 4 eV) is quite different from that of the substrate material, which can avoid the interference of the coating layer on the electron emission performance of the cathode material, thereby ensuring the stability of the beam current. Therefore, in the preparation method of the present invention, by using chemical vapor deposition to prepare a high-quality carbide coating layer on the surface of the substrate material, the substrate material can be effectively protected by the carbide coating layer, and further, the volatilization of the substrate material under high-temperature and high-vacuum conditions can be effectively avoided, so that the emission surface of the electron gun cathode can be ensured to maintain the set area for a long time, and finally, the beam current of the electron beam can be ensured to remain stable for a long time. Thus, when the prepared electron gun cathode is used to prepare the electron gun of an electron beam exposure machine, the beam current stability and service life of the electron gun can also be improved. At the same time, the preparation method of the present invention also has the advantages of simple process, convenient operation, low cost, etc., is suitable for large-scale preparation, and is conducive to industrial application. Description of the Drawings

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] Figure 1 It is a schematic structural diagram of an existing thermal field emission electron gun.

[0031] Figure 2 It is a change diagram of the cathode emission surface of an existing thermal field emission electron gun before and after use under high-temperature conditions.

[0032] Figure 3 It is a process flow chart for preparing the electron gun cathode in Embodiment 1 of the present invention.

[0033] Figure 4 It is a sectional structure change diagram of the electron gun cathode in the preparation process of Embodiment 1 of the present invention. Detailed Embodiments

[0034] The present invention will be further described below with reference to the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0035] Embodiment 1:

[0036] Existing high-performance thermal field emission electron gun cathode materials are prone to volatilization in high-temperature and high-vacuum working environments, resulting in unstable emission surfaces of the electron gun (such as Figure 2As shown in the figure, it seriously affects the stability and service life of the electron gun emission beam current, and the assembly process of the cathode and the metal heating electrode is complex. At the same time, there are many problems in the existing preparation methods of carbon-coated cathode materials. For example, C will react with the matrix material at high temperatures above 1000 °C. For example, C reacts with LaB 6 to form LaC 3 and elemental B. The working temperature of the cathode for thermionic emission is usually above 1300 °C. Therefore, the C coating will corrode the cathode matrix material during operation. Another example is that the C material has a thermal expansion coefficient (3 - 4×10 -6 °C -1 ) which is quite different from that of the LaB 6 material (6.4×10 -6 °C -1 ). During the heating and cooling process of the electron gun, large thermal stresses are likely to be generated at the interface, resulting in the peeling off of the coating and the loss of the protection function. Moreover, the C material has a relatively large thermal conductivity, which easily causes energy loss of the electron gun cathode and affects the performance of the electron gun, making it difficult to truly solve the existing problems of the thermionic emission LaB 6 electron gun. In view of the above problems, a creative preparation method of an electron gun cathode is proposed in the present invention. Using a boride material as the electron beam emission material, first process the boride material into the shape required for the electron gun cathode to obtain the matrix material, then use chemical vapor deposition to prepare a carbide coating on the surface of the matrix material, and finally remove the carbide coating on the electron beam emission surface of the matrix material, thus an electron gun cathode with good working stability and long service life can be prepared. Specifically: By using chemical vapor deposition to prepare a high-quality carbide coating on the surface of the matrix material, the carbide coating can be used to effectively protect the matrix material, thereby effectively avoiding the volatilization of the matrix material under high temperature and high vacuum conditions, ensuring that the emission surface of the electron gun cathode can maintain the set area for a long time, and ultimately ensuring that the electron beam current remains stable for a long time. At the same time, when this electron gun cathode is used to prepare the electron gun of an electron beam exposure machine, it can also improve the beam current stability and service life of the electron gun. In addition, the preparation method of the present invention also has the advantages of simple process, convenient operation, low cost, etc., is suitable for large-scale preparation, and is conducive to industrial application.

[0037] To facilitate understanding of the innovation of the present invention, a preparation method of an electron gun cathode is provided. Specifically, a single crystal LaB 6 material is used as the matrix material of the electron gun cathode, and a TaC coating is coated on the surface of the matrix material to form a core-shell structure. The process flow chart of its preparation is as Figure 3 shown, including the following steps:

[0038] S1. Using a single crystal LaB 6 material as the boride material, use mechanical processing to process the boride material into the shape required for the electron gun cathode to obtain the matrix material; asFigure 4 As shown in (a), the shape of the substrate material is needle-like. Specifically, the prepared substrate material includes a cylinder and a cone located on the cylinder, and the diameter of the bottom surface of the cone is the same as that of the cylinder. The diameter of the cylinder is 1000 μm. In other embodiments, the diameter of the cylinder is 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1100 μm, 1300 μm, 1500 μm, 1800 μm, 2000 μm. The cone angle of the cone is 90°. In other embodiments, the cone angle of the cone can also be 40°, 50°, 60°, 80°, 100°, 110°, 120°. In addition, the height of the substrate material is 3 mm. In other embodiments, the height of the substrate material is 1 mm, 2 mm, 2.5 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, and the (100) crystal plane of the substrate material is parallel to the cross-section of the cylinder.

[0039] In this step, the boride material can also be CeB 6 , GdB 6 , YB 6 One of them.

[0040] S2. As Figure 4 shown in (b), a carbide coating layer is prepared on the surface of the substrate material by chemical vapor deposition. The carbide coating layer is a TaC coating, specifically as follows:

[0041] S2-1. Place the substrate material processed into a set shape in step S1 in the deposition furnace of the chemical vapor deposition equipment, evacuate to below 10 -4 Pa, first heat it to 400 °C at a heating rate of 3 °C / min -1 (in other embodiments, the heating rate can also be 2 °C / min -1 , 2.5 °C / min -1 , 3.5 °C / min -1 , 4.5 °C / min -1 , 5 °C / min -1 ), keep it warm for 30 min (in other embodiments, the holding time can also be 20 min, 25 min, 35 min, 40 min, 50 min, 60 min), and then heat it at a heating rate of 15 °C / min -1 (in other embodiments, the heating rate can also be 10 °C / min -1 , 12 °C / min -1 , 13 °C / min -1 , 16 °C / min -1 , 18 °C / min -1 , 20 °C / min -1)Heat to 900 °C (in other embodiments, the heating temperature can also be 800 °C, 850 °C, 880 °C, 920 °C, 980 °C, 1000 °C).

[0042] S2-2: Using argon as the carrier gas, introduce the metal source and reaction gas into the deposition furnace for reaction. In the reaction system, control the volume fraction of argon ≥ 40%, for example, the volume fraction of argon is 40%. In other embodiments, the volume fraction of argon can also be 50%, 60%. And during the reaction process, control the pressure to be 10 Pa. In other embodiments, the pressure can also be 20 Pa, 30 Pa, 40 Pa, 50 Pa, 100 Pa. The reaction time is 30 min. Thus, deposit a carbide coating layer (TaC coating) with a thickness of 500 nm on the surface of the substrate material. The metal source is TaCl 5 , and the reaction gas is a carbon source gas and hydrogen. The carbon source gas is CH 4 .

[0043] In this step, the metal source can also be HfCl 4 , MoCl 5 One of them. The carbon source gas can also be C 2 H 4 , C 3 H 6 At least one of them.

[0044] S2-3: After the reaction is completed, stop introducing the gas, heat to 1200 °C, keep the temperature for 2 h, and then cool down to room temperature in the furnace under vacuum conditions to complete the preparation of the carbide coating layer.

[0045] In this step, the carbide coating layer can also be one of the HfC coating and the MoC coating.

[0046] S3: Remove the carbide coating layer on the surface of the electron beam emission surface of the substrate material to complete the preparation of the electron gun cathode, specifically as follows:

[0047] S3-1: Use the focused ion beam (FIB-SEM) processing method to remove the carbide coating layer on the surface of the electron beam emission surface of the substrate material (i.e., remove the TaC coating at the tip of the substrate material).

[0048] S3-2: As shown in Figure 4 (c), use the mechanical polishing method to process the tip exposed at the electron beam emission end of the substrate material until a frustum with a diameter of 0.8 μm is formed to obtain the electron gun cathode.

[0049] In this step, the focused ion beam (FIB-SEM) processing method is adopted, which can observe the coating processing situation on the surface in real time, ensure the accurate removal of the carbide coating at the cathode tip, and at the same time polish the electron beam emission surface by mechanical polishing until the required size to ensure the flatness and smoothness of the emission surface.

[0050] In this step, the diameter of the frustum can also be 0.5 μm, 0.6 μm, 0.7 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm.

[0051] An electron gun cathode prepared by the preparation method in the above-mentioned embodiment. The electron gun cathode is composed of a cylinder and a frustum. The frustum is located on the cylinder, and the diameter of the bottom surface of the frustum is the same as that of the cylinder. At the same time, the surface of the cylinder and the side surface of the frustum are both coated with a carbide coating layer. In this electron gun cathode, the cylinder and the frustum are single-crystal LaB 6 material, and the single-crystal LaB 6 material is used as the core electron beam emission material. At the same time, a TaC coating is coated on the surface of the single-crystal LaB 6 material to form a core-shell structure, so that the TaC coating can effectively protect the single-crystal LaB 6 material.

[0052] An electron gun includes the electron gun cathode prepared by the preparation method in the above-mentioned embodiment. The structure of the electron gun can be referred to Figure 1 .

[0053] In this embodiment, electron gun cathodes corresponding to different types of substrate materials are also prepared. Except for the different types of substrate materials, other parameters are the same, as shown in Table 1 specifically.

[0054] In this embodiment, electron gun cathodes corresponding to different types of carbide coating layers are also prepared. Except for the different types of carbide coating layers, other parameters are the same, as shown in Table 2 specifically.

[0055] In this embodiment, electron gun cathodes corresponding to different carbide coating layer thicknesses are also prepared. Except for the different thicknesses of the carbide coating layers, other parameters are the same, as shown in Table 3 specifically.

[0056] In this embodiment, electron gun cathodes corresponding to different frustum diameters are also prepared. Except for the different diameters of the frustum, other parameters are the same, as shown in Table 4 specifically.

[0057] The performance of the electron gun cathode prepared in the above-mentioned embodiment is tested, and the results are shown in Tables 1-4.

[0058] Table 1 Performance indicators of electron gun cathodes corresponding to different types of substrate materials

[0059]

[0060] Table 2 Performance indicators of electron gun cathodes corresponding to different types of carbide coatings

[0061]

[0062]

[0063] Table 3 Performance indicators of electron gun cathodes corresponding to different carbide coating thicknesses

[0064]

[0065] As can be seen from Table 3, as the thickness of the carbide coating increases, the service life of the cathode extends. When it reaches more than 600 nm, it is basically stable; further increasing the coating thickness will cause a change in the electric field distribution on the electron emission surface, affecting the stability of the beam current. Therefore, when the thickness of the carbide coating is 100 nm to 800 nm, especially when the thickness of the carbide coating is 200 nm to 600 nm, it can not only ensure that the cathode has a very long service life, but also obtain a stable beam current, with good working stability and a long service life.

[0066] Table 4 Performance indicators of electron gun cathodes corresponding to different frustum diameters

[0067]

[0068]

[0069] As can be seen from Table 4, the smaller the frustum diameter of the electron gun cathode, the more uniform the electric field distribution and the better the stability of the electron beam current; however, the smaller the diameter of the cathode, the faster the loss of the base material during use, resulting in a shorter service life. Considering various factors comprehensively, when the frustum diameter is 0.5 μm to 1.5 μm, especially 0.7 μm to 0.9 μm, the prepared cathode has the best performance.

[0070] In addition, as Figure 1 shown, when the thermal field emission electron gun is working, the electron gun cathode is heated to a certain temperature by the heating electrode, and then the electron beam is extracted from the cathode through the anode voltage. The grid is mainly used to suppress the generation of stray electrons from the cathode and improve the quality of the electron beam current.

[0071] Figure 2 In, (b) is the enlarged area of the tip of the electron gun cathode in the dashed box of (a), and the dashed line in Figure (b) is the tip corresponding before use, and the solid black line is the tip corresponding after use. At the same time, as Figure 2As shown, with the increase of the service time, the cathode material (substrate material) volatilizes continuously, resulting in the degradation of the area of the electron emission surface, the decrease of the emission area, and the instability of the electron beam current.

[0072] From the above results, it can be seen that compared with the cathode of the conventional electron gun, in the preparation method of the cathode of the electron gun of the present invention, a boride material is used as the electron beam emission material. First, the boride material is processed into the shape required for the cathode of the electron gun to obtain the substrate material. Then, a carbide coating layer is prepared on the surface of the substrate material by chemical vapor deposition. Finally, the carbide coating layer on the electron beam emission surface of the substrate material is removed, and an electron gun cathode with good working stability and long service life can be prepared. Specifically: by using chemical vapor deposition to prepare a high-quality carbide coating layer on the surface of the substrate material, the substrate material can be effectively protected by the carbide coating layer, and further, the volatilization of the substrate material under high temperature and high vacuum conditions can be effectively avoided, so that the emission surface of the electron gun cathode can be ensured to maintain the set area for a long time, and finally, the electron beam current can be ensured to be stable for a long time. At the same time, when the electron gun cathode is used to prepare the electron gun of the electron beam exposure machine, the beam current stability and service life of the electron gun can also be improved. In addition, the preparation method of the present invention also has the advantages of simple process, convenient operation, low cost, etc., is suitable for large-scale preparation, and is conducive to industrial application.

[0073] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, the improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an electron gun cathode, characterized in that: The following steps are involved: S1. Processing a boride material into a shape required for an electron gun cathode to obtain a matrix material; the boride material is one of LaB6, CeB6, GdB6, and YB6; S2. Preparing a carbide coating layer on the surface of the substrate material by chemical vapor deposition; the carbide coating layer is one of TaC coating, HfC coating and MoC coating; S3. Remove the carbide coating on the electron beam emitting surface of the substrate material to complete the preparation of the electron gun cathode.

2. The preparation method according to claim 1, characterized in that: In step S1, the boride material is one of LaB6 and CeB6; In step S2, the carbide coating layer is one of a TaC coating and a HfC coating; the thickness of the carbide coating layer is 100nm to 800nm.

3. The preparation method according to claim 2, characterized in that: In step S2, a carbide coating layer is prepared on the surface of the substrate material by chemical vapor deposition, which includes the following steps: S2-1. Place the substrate material in a deposition furnace of a chemical vapor deposition device and evacuate to 10 -4 Pa below, first heat at a rate of 2℃min -1 ~5℃min -1 Heat to 400℃, keep warm for 20min~60min, then heat at a rate of 10℃min -1 ~20℃min -1 Heating to 800℃~1000℃; S2-2, using argon as a carrier gas, introducing a metal source and a reaction gas into a deposition furnace for reaction, and depositing a carbide coating layer on the surface of the substrate material; S2-3. After the reaction is completed, stop introducing gas, heat to 1200°C, and keep warm for 1h to 3h to complete the preparation of the carbide coating layer.

4. The preparation method according to claim 3, characterized in that: In step S2-2, the metal source is one of TaCl5, HfCl4, and MoCl5; the reaction gas is a carbon source gas and hydrogen; the carbon source gas is at least one of CH4, C2H4, and C3H6; the volume fraction of argon in the reaction system is ≥40%; the reaction is carried out under a pressure of 10Pa to 100Pa; and the reaction time is 10min to 30min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step S1, a boride material is processed into a desired shape of an electron gun cathode by a mechanical processing method to obtain a base material; the base material is in the shape of a needle tip; the base material includes a cylinder and a cone located on the cylinder, and the diameter of the bottom surface of the cone is the same as that of the cylinder; the diameter of the cylinder is 500 μm to 2000 μm; the cone apex angle of the cone is 40° to 120°; the height of the base material is 1 mm to 5 mm; and the (100) crystal plane of the base material is parallel to the cross section of the cylinder.

6. The preparation method according to claim 5, characterized in that: The cone apex angle of the cone is 90°.

7. The preparation method according to any one of claims 1 to 4, characterized in that In step S3, removing the carbide coating layer on the electron beam emitting surface of the substrate material comprises the following steps: S3-1, using a focused ion beam processing method to remove the carbide coating at the tip of the base material, and forming a preliminary outline of the electron beam emission surface at the tip of the base material; S3-2. The tip exposed at the electron beam emission end of the base material is processed by mechanical polishing until a truncated cone with a diameter of 0.5 μm to 1.5 μm is formed to obtain an electron gun cathode.

8. An electron gun cathode, characterized in that: The electron gun cathode is prepared by the preparation method according to any one of claims 1 to 7.

9. The electron gun cathode according to claim 8, characterized in that The electron gun cathode is composed of a cylinder and a truncated cone. The truncated cone is located on the cylinder, and the diameter of the bottom surface of the truncated cone is the same as that of the cylinder. The surface of the cylinder and the side surface of the truncated cone are both coated with a carbide coating layer.

10. An electron gun, characterized in that: The electron gun comprises the electron gun cathode according to claim 8 or 9.

Images