JPS6016060B2 - Cathode manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an electron emitting cathode useful in electron beam application equipment such as an electron microscope and an electron beam lithography apparatus.

Rare metal shelving materials are excellent electron-emitting materials, and are replacing conventional tungsten-based electron-emitting cathodes in the field of physical and chemical equipment that uses electron beams.

For example, six-shelf lanthanum (La&) has begun to be used as a thermionic emission cathode material with higher brightness than tungsten as an electron beam source for scanning electron microscopes and electron beam lithography devices.

Since shelved materials such as Buddha B6 have high reactivity with metals, carbon is generally used as a filament material for heating the shelved materials to high temperatures. The electron emitting cathode of electron beam application equipment is generally mounted on a stem with two metal supports 2 protruding from an insulator 1, as shown in Fig. 1, in order to facilitate the installation or replacement of the cathode. It consists of a structure in which material 3 and filament 4 are fixed.

In the case of a cathode using carbon as a filament material, various measures have been taken because carbon cannot be directly welded to a metal support. For example, as shown in Figure 2, 'a
}A method of pressing down the filament from the left and right sides using the spring force of a metal support, a method of fixing the filament with a 'b' screw, and a method of tying the filament with a metal band have been reported. However, with this method of fixing the filament using mechanical force, if the filament is heated with electricity and repeatedly heated and cooled, the fixing part loosens, and the electrical connection between the filament and the metal support becomes weak. This caused a problem in which the current could no longer flow stably. If the current flowing through the filament becomes unstable, the heating temperature of the cathode material fluctuates, making it impossible to obtain a stable electron beam. Conventionally, the method of fixing the carbon filament was not perfect, resulting in practical problems such as reduction in reliability and life of the cathode. The present invention has been made in view of these points, and its purpose is to provide a method for manufacturing a highly reliable cathode in which the carbon filament and the support are completely bonded.

The method for producing a cathode of the present invention is characterized by using a thermosetting resin as the material for the filament and support, fixing the cathode material in a predetermined position on the filament raw material, and then heating and carbonizing it in a non-oxidizing atmosphere. The filament and support have an integral structure made of carbon, and a portion of the support is fixed with an insulator.

Regarding a method for firmly attaching a cathode material to a carbon filament by fixing the cathode material to a resin filament and carbonizing it, the inventors of this case previously submitted a patent application (Method for manufacturing an electron emitting cathode, Showa 52 King, filed on April 18). In addition to firmly attaching the filament and the cathode material, the present invention aims to perfect the connection between the filament and the support that fixes it. According to the present invention, it is possible to manufacture a complete cathode consisting of an insulator, a support, a filament, and a cathode material. Furthermore, it can be attached to and detached from electron beam application equipment with the same ease as conventional tungsten cathodes.This makes it possible to effectively utilize the characteristics of rigid materials such as LaB6, which is an excellent cathode material. The present invention will be described in detail below with reference to Examples.

Example 1 0.0% to furfuryl alcohol. Cervical weight percent P-toluene.

Ethyl sulfonate was added as a catalyst to polymerize and harden to produce a resin mass. From this resin soul, width 0.8 willow, thickness 0.
I cut out a rectangular plate with 4 ribs and 10 columns in length, and a prism with a cross section of 3 antennae and 3 ribs in length. Next, a four-legged LaB6 single crystal was attached to the center of the rectangular plate at an elevation angle of 0.15 using a mixture of uncured resin and &C powder as a bonding agent. Furthermore, both ends of the rectangular plate were attached to resin prisms using the uncured resin as a bonding agent, as shown in FIG. 3a. After completely curing the joint, place it in a flat-bottomed graphite boat and hold it down with a graphite block at 1℃'m in vacuum.
up to 1000°C at a rate of in, then 10qC'min
The mixture was heated to 1,600°C at a rate of 1,600°C to carbonize it. The reason why the resin was heated while being pressed down with a graphite block was to prevent the resin from deforming during carbonization. Further, the length was isotropically shrunk by about 20% due to carbonization. Next, a ceramic insulator was attached to the center of the carbonized prism and bonded.

The La & single crystal was electrolytically polished in a 25 weight percent nitric acid aqueous solution to form a needle shape, thereby producing a cathode as shown in FIG. 3b. In Figure 3b, 5 is a LaB6 single crystal, 6
7 is a carbon filament, 7 is a carbon support, and 8 is a ceramic insulator. The operating temperature range of the La-string thermionic emission cathode is 1500 to 1650 q○, but the power required to heat it to this temperature was about 10 to 15 watts.

When this cathode was used as an electron beam source in an electron beam lithography system, it was able to operate stably for over 200 hours.
Example 2 Using a phenolic resin as a raw material, a hairpin-shaped support and a filament raw material as shown in FIG. 4a were produced.

The hairpin-shaped resin corresponding to the filament raw material has a plate shape with a thickness of 0.4 and a width of 0.8 around the tip, and a hole with an elevation angle of 0.12 is provided at the tip. Further, the side and lower portions of the hairpin-shaped resin corresponding to the support material are in the shape of a round rod on the third side. La &
The single crystal was fixed using a mixture of uncured phenol resin and La string powder as a bonding agent.

After the fixed part was heated and hardened, it was carbonized in the same manner as in Example 1. Next, a ceramic disc with two round holes inside was inserted into the bottom of the carbonized hairpin-shaped support and the two were fixed together using a bonding agent. A LaB single crystal was processed into a needle shape by electrolytic polishing to produce a cathode as shown in FIG. 4b. As is clear from the above examples, the present invention allows the cathode to be manufactured by a simple process.

In addition to being easy to manufacture, the cathode manufactured by the present invention has several characteristics, the main ones of which are listed below. '11 Since the filament and the support have an integral structure, the electrical and mechanical connections are perfect.

[21 The carbon obtained by carbonizing resin is glassy carbon, but this material has extremely low thermal conductivity, so when the filament is heated with electricity, the amount of heat that escapes through the support is small, making it difficult to heat the filament. It can be done effectively.

[3' The glassy carbon of the support material is hard and hard to wear,
Because of its high strength, the cathode can be attached and detached from electron beam application equipment with the same ease as a conventional tungsten cathode (having a metallic support).

According to the present invention, it is possible to solve the problem of the fixing method to a support, which was the biggest problem with cathodes using carbon filaments, and the reliability of the cathode can be improved.

For example, a shelved product such as LaB6, which is an excellent thermionic emission material, can be effectively used as a cathode material, resulting in the practical effect of improving the performance of electron beam application equipment.

[Brief explanation of the drawings] Figure 1 shows a conventional cathode commonly used in electron beam application equipment, Figure 2 shows a conventional cathode using carbon as a filament, and Figures 3 and 4 show the original cathode. FIG. 3 is a diagram showing a process of a method for manufacturing a cathode according to an embodiment of the invention and the state of the manufactured cathode. 1... Insulator, 2... Metallic support, 3...
...Cathode material, 4...Filament, 5
. . . Buddha B6 single crystal, 6 . . . Carbon filament, 7 . . . Carbon support, 8 . . . Ceramic insulator stem. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A filament and a portion corresponding to two supports supporting the filament are formed into an integral structure using a thermosetting resin that can be turned into carbon when heated in a non-oxidizing atmosphere, and the cathode material is added to the filament. After bonding in place, the thermosetting resin is heated and carbonized in a non-oxidizing atmosphere, and then the two supports are fixed with an insulator to form a carbon fiber in which the filament and the support supporting it are integrated. A method for producing a cathode, comprising forming a cathode consisting of: 2. The method for manufacturing a cathode according to claim 1, wherein the cathode material is a LaB_6 single crystal.