Field emission electron source and preparation method thereof

Abstract

The invention relates to the technical field of electronic optical equipment and micro-nano machining, and discloses a field emission electron source. The field emission electron source is mainly composed of a filament base, a binding post, a welding post, a welding groove, a tungsten sheet, an emission tungsten needle and the like. During welding, the tungsten sheet is in direct contact with the side wall of the welding groove, so that original point contact between the tungsten filament and the welding column is replaced by surface contact by contact between the tungsten sheet and the side wall of the welding groove, the welding area is increased, the conditions of pseudo soldering, unsoldering and the like are reduced, and the welding quality and reliability are greatly improved; and two or more tungsten sheet welding structures can disperse thermal stress generated in the heating process to a plurality of welding spots, deformation of a single welding spot due to stress concentration can be avoided, the position offset of the emission tungsten needle is prevented, and then the emission stability of the electron source can still be ensured in a long-term heating environment.

Description

Technical Field

[0001] This application relates to the field of electron optical equipment and micro / nano fabrication technology, and in particular to a field emission electron source and a method for preparing the electron source. Background Technology

[0002] Thermo-field emission electron source is a high-performance electron source that generates an electron beam through the principle of thermo-field emission. It combines the advantages of thermo-emission and field emission, and can achieve high brightness and high stability electron emission at relatively low temperatures. It is widely used in high-end scientific instruments such as transmission electron microscopes, scanning electron microscopes, electron beam lithography and semiconductor manufacturing. The working principle is based on the quantum tunneling effect. The cathode material (usually tungsten or lanthanum hexaboride) is made into a fine needle tip. Under the action of a strong electric field, electrons tunnel out from the surface of the needle tip to form an electron beam.

[0003] In existing field emission electron sources, a connection method is used to directly weld tungsten needles onto tungsten wires, achieving an indirect connection between the tungsten needles and the electron source base to meet the basic structural requirements for electron emission. However, in the fabrication of field emission electron sources, a point-to-point method is mainly used to weld the tungsten wires onto the terminals. Since the tungsten wires and the welding terminals are in point contact, the contact area is small, making it prone to issues such as incomplete soldering and detachment. Furthermore, the position of the tungsten needles changes when heated, and this offset directly causes changes in the electron emission angle and beam instability, leading to emission instability. Ultimately, this affects the microscopic analysis accuracy and micro / nano fabrication quality of the FIB-SEM dual-beam system. Therefore, the point-to-point welding structure not only increases the difficulty of welding operations but also reduces the yield rate of electron source production. To address this, a field emission electron source and its fabrication method are proposed. Summary of the Invention

[0004] This application proposes a field emission electron source and a method for preparing the electron source, which has the advantages of reducing poor soldering and desoldering, and preventing the positional deviation of the emission tungsten needle, thereby solving the technical problems mentioned in the background art.

[0005] To achieve the above objectives, this application adopts the following technical solution: a field emission electron source, including a filament holder, characterized in that: two terminals for connecting to an external power supply are fixedly connected inside the filament holder; the top ends of the two terminals penetrate the top surface of the filament holder; the bottom ends of the two terminals penetrate the bottom surface of the filament holder; two symmetrically arranged exhaust channels are opened on the bottom surface of the filament holder; welding posts for welding are fixedly connected to the bottom ends of the two terminals; welding grooves for easy welding are opened on the side of each welding post; and the same tungsten sheet is welded to the sidewalls of the two welding grooves.

[0006] Furthermore, the tungsten sheet is L-shaped, and the bend of the tungsten sheet is at the center of the tungsten sheet. An emitting tungsten needle for emitting an electron beam is fixedly welded to the bend of the tungsten sheet, and the resistance value of the tungsten sheet is the same as the resistance value of the emitting tungsten needle.

[0007] Furthermore, a zirconium oxide coating is provided at the tip of the tungsten needle.

[0008] Furthermore, the filament holder is made of ceramic.

[0009] A method for preparing a field emission electron source, characterized by the following specific preparation steps: The first step is to select polycrystalline tungsten as the raw material, and then process the polycrystalline tungsten raw material through laser and chemical etching methods to process the polycrystalline tungsten into tungsten sheets. The second step is to weld the tungsten needle onto the processed tungsten sheet, and the tungsten needle should be welded to the center of the tungsten sheet. The third step is to use precision cutting technology to open the welding grooves on the welding columns so that the welding grooves on the two welding columns are parallel and symmetrical. The fourth step is to weld the tungsten sheet and the emitting tungsten needle together. Then, weld the two leads of the emitting tungsten needle away from the tungsten sheet to the welding grooves on the welding pillar. The relative distance between the welding position of the emitting tungsten needle and the tungsten sheet and the welding position at the welding groove must strictly match the original electronic source size to ensure that after the tungsten sheet is welded, the tip of the emitting tungsten needle is always on the same axis as the center of the filament holder.

[0010] This application provides a field emission electron source and a method for preparing the electron source. By designing a welding tank and tungsten sheet, the tungsten sheet is in direct contact with the sidewall of the welding tank during welding. This replaces the point contact between the tungsten wire and the welding column with a surface contact between the tungsten sheet and the sidewall of the welding tank, thereby increasing the welding area, reducing incomplete welding and desoldering, and greatly improving the quality and reliability of welding.

[0011] By designing welding grooves, the thickness of the tungsten sheet after welding is made equal to the radius of the welding column. This allows the tungsten sheet to keep the emitting tungsten needle always at the center of the filament holder. Furthermore, the two-point or more tungsten sheet welding structure can disperse the thermal stress generated during heating to multiple welding points, preventing deformation of a single welding point due to stress concentration and preventing the emitting tungsten needle from shifting position. As a result, the electron source can still maintain emission stability under long-term heating conditions. Attached Figure Description

[0012] The accompanying drawings, which form part of this specification, illustrate embodiments disclosed in this application and, together with the specification, serve to explain the principles disclosed in this application.

[0013] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein: Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the welding column and tungsten sheet structure of the present invention; Figure 3 This is a schematic diagram of the tungsten sheet and emitting tungsten needle structure of the present invention.

[0014] The components include: 1. Filament holder; 2. Terminal block; 3. Exhaust channel; 4. Welding post; 5. Welding groove; 6. Tungsten sheet; 7. Tungsten emitting needle. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] Please see Figures 1-3 A field emission electron source and its preparation method are disclosed. The source includes a filament holder 1. Two terminals 2 for connecting to an external power supply are fixedly connected inside the filament holder 1. The top ends of the two terminals 2 penetrate the top surface of the filament holder 1, and the bottom ends of the two terminals 2 penetrate the bottom surface of the filament holder 1. Two symmetrically arranged exhaust channels 3 are opened on the bottom surface of the filament holder 1. Welding posts 4 for welding are fixedly connected to the bottom ends of the two terminals 2. Welding grooves 5 for easy welding are opened on the side of each welding post 4. The same tungsten sheet 6 is welded to the side wall of the two welding grooves 5.

[0017] Please see Figures 1-3 The tungsten sheet 6 is L-shaped, and the bend of the tungsten sheet 6 is the center position of the tungsten sheet 6. The bend of the tungsten sheet 6 is fixedly welded with an emitting tungsten needle 7 for emitting an electron beam. The resistance value of the tungsten sheet 6 is the same as the resistance value of the emitting tungsten needle 7. The current is transmitted to the emitting tungsten needle 7 on the tungsten sheet 6 through the terminal 2, so that an electric field is formed at the emitting tungsten needle 7, which attracts electrons to be emitted, thereby forming an electron beam.

[0018] Please see Figures 1-3 The tip of the tungsten needle 7 is coated with a zirconium oxide coating, which reduces the electron work function of the electron beam emitted by the tungsten needle 7.

[0019] Please see Figures 1-3 The filament holder 1 is made of ceramic and serves to provide dimensional positioning and heat insulation.

[0020] The first step is to select polycrystalline tungsten as the raw material, but it is not limited to tungsten. It can be other high-temperature resistant metals, such as molybdenum (100 mm in length, 100 mm in width, and 0.15 mm in thickness). Then, the polycrystalline tungsten raw material is processed by laser and chemical etching methods to process the polycrystalline tungsten into tungsten sheets 6.

[0021] The second step is to weld the tungsten needle 7 onto the processed tungsten sheet 6, and the tungsten needle 7 should be welded to the center of the tungsten sheet 6.

[0022] The third step involves using precision cutting technology to create welding grooves 5 on welding pillars 4, so that the welding grooves 5 on the two welding pillars 4 are parallel and symmetrical.

[0023] Fourth step: After the tungsten sheet 6 and the emitting tungsten needle 7 are welded, the two pins of the emitting tungsten needle 7 away from the tungsten sheet 6 are welded to the welding groove 5 on the welding post 4. The relative distance between the welding position of the emitting tungsten needle 7 and the tungsten sheet 6 and the welding position at the welding groove 5 strictly matches the original electronic source size, ensuring that after the tungsten sheet 6 is welded, the tip of the emitting tungsten needle 7 is always on the same axis as the center of the filament holder 1.

[0024] Working principle: Polycrystalline tungsten is processed into tungsten sheet 6 through laser etching. Then, the emitting tungsten needle 7 is welded to the center of the bend of the tungsten sheet 6. After the emitting tungsten needle 7 is welded, the two leads of the tungsten sheet 6 are welded to the welding grooves 5 on the two welding pillars 4. Through the above design of the tungsten sheet 6, the welding of the original tungsten wire is transformed into the welding of the tungsten sheet 6. This increases the contact area between the tungsten sheet 6 and the welding position, reduces the welding difficulty, and reduces the probability of cold solder joints and desoldering. Secondly, multiple welding points can avoid deformation of the tungsten sheet 6 caused by stress concentration at a single welding point, and prevent the deformation of the tungsten sheet 6 from changing the position of the emitting tungsten needle 7. This effectively suppresses the positional displacement of the emitting tungsten needle 7, so that the electron source can still maintain stability under long-term heating environment.

Claims

1. A field emission electron source, comprising a filament holder (1), characterized in that: The filament holder (1) is internally fixedly connected to two terminals (2) for connecting to an external power source. The top ends of the two terminals (2) penetrate the top surface of the filament holder (1), and the bottom ends of the two terminals (2) penetrate the bottom surface of the filament holder (1). The bottom surface of the filament holder (1) has two symmetrically arranged exhaust channels (3). The bottom ends of the two terminals (2) are fixedly connected to welding posts (4) for welding. Each welding post (4) has a welding groove (5) on its side for easy welding. The side walls of the two welding grooves (5) are welded with the same tungsten sheet (6).

2. The field emission electron source according to claim 1, characterized in that, The tungsten sheet (6) is L-shaped, and the bend of the tungsten sheet (6) is the center position of the tungsten sheet (6). A emitting tungsten needle (7) for emitting an electron beam is fixedly welded to the bend of the tungsten sheet (6). The resistance value of the tungsten sheet (6) is the same as the resistance value of the emitting tungsten needle (7).

3. A field emission electron source according to claim 2, characterized in that, The tip of the tungsten needle (7) is coated with a zirconium oxide coating.

4. A field emission electron source according to claim 1, characterized in that, The filament holder (1) is made of ceramic.

5. A method for preparing a field emission electron source, characterized in that, The specific preparation steps are as follows: The first step is to select polycrystalline tungsten as raw material, and then process the polycrystalline tungsten raw material by laser and chemical etching methods to process the polycrystalline tungsten into tungsten sheets (6). The second step is to weld the tungsten needle (7) onto the processed tungsten sheet (6), and the tungsten needle (7) should be welded to the center of the tungsten sheet (6); The third step is to use precision cutting technology to open the welding groove (5) on the welding column (4) so ​​that the welding groove (5) on the two welding columns (4) are parallel and symmetrical; In the fourth step, after the tungsten sheet (6) and the emitting tungsten needle (7) are welded, the two pins of the emitting tungsten needle (7) away from the tungsten sheet (6) are welded to the welding groove (5) on the welding pillar (4). The relative distance between the welding position of the emitting tungsten needle (7) and the tungsten sheet (6) and the welding position at the welding groove (5) strictly matches the original electronic source size, ensuring that after the tungsten sheet (6) is welded, the tip position of the emitting tungsten needle (7) is always on the same axis as the center of the filament holder (1).

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