JPH05174699A - Long size cathode - Google Patents

Abstract

PURPOSE:To lower a temperature of a main body, and also reduce deflection, by joining an electron emitting member consisting of tantalum to the front a cathode main body consisting of tungsten, and emitting thermoelectrons from here, in an electron gun used as a heat source to vaporize metal in a vacuum by means of long size shape electron beams. CONSTITUTION:In a linear electron gun, a cathode 1 is positioned/arranged in the rear of an anode 7 and a grid 6, and both the ends are supported with a support mechanism 3. At this time, a main body 5 of the cathode 1 is constituted by combining a tungsten material and a tantalum material 4 to play a role of electron emission with each other, and the shape is formed in a long size shape. At this time, a recess part is bored in front of the main body 5, that is, in the central part of the electron emitting directional surface, and the tantalum material 4 is buried here, and electrons are emitted from here. By constituting in this way, even if the main body 5 and the tantalum material 4 are heated up to the same temperature, thermoelectrons are emitted mostly from the tantalum material 4 according to size of a work function, so that a temperature of the main body 5 can be lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long cathode in an electron gun used as a heat source for generating metal vapor in a vacuum.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional electron gun. This electron gun evaporates metal or the like in a vacuum by generating a long electron beam (hereinafter referred to as a linear electron gun). That is, in this linear electron gun, the anode 7,
A cathode 1 is arranged behind the grid 6, and a cathode heating filament 2 is arranged behind the cathode 1. The cathode 1 is made of a tungsten material or a tantalum material, and the cathode heating filament 2
They are heated to 2700 k and 2500 k, respectively, and emit thermoelectrons e. A positive high voltage is applied to the anode 7 by the acceleration power supply 9, and the emitted thermoelectrons e are accelerated. Grid 6
A negative voltage is applied by the grid power supply 8 to adjust the electron beam amount and the light collecting property. Furthermore, a uniform magnetic field B is formed in the direction perpendicular to the plane of the drawing.

Therefore, when the cathode 1 is heated by the cathode heating filament 2, the thermoelectrons e are generated from the cathode 1.
Are emitted and accelerated by an electric field from the anode 7 to become an electron beam 12, which is a uniform magnetic field B
It is deflected by the action of. Then, the electron beam 12 is focused on a target (evaporation source) 11 in the crucible 10 and is irradiated, whereby the target 11 is evaporated and metal vapor 13 is obtained.

Here, since the cathode 1 is made of a tungsten material or a tantalum material alone, 27
When heated up to 00k and 2500k, the cathode itself bends, causing bending. Therefore, the conventional cathode 1 cannot have a long span. Therefore, long span cathode 1
If a cathode is needed, as shown in FIG.
Both ends of the cathode must be supported by the both-end supporting mechanism 3 and the middle of the cathode 1 must be supported by the intermediate supporting mechanism 15. That is, a cathode with a long span is divided into a plurality of cathodes with a short span, the middle of these is supported by an intermediate support mechanism 15, and the cathodes with a short span are continuously arranged. The cathode heating filament 2 can be made longer by providing the intermediate support 14 or by providing split cathode heating filaments in series.

[0005]

In order to make the distribution density of the metal vapor 13 uniform in the longitudinal direction of the crucible 10 and form a uniform film thickness in that direction, the long cathode 1 is heated to a uniform temperature. At the same time, it is necessary to keep the length between the electrodes uniform. However, if a tungsten material or a tantalum material is used alone as the cathode 1, it is necessary to increase the electron emission area or raise the heating temperature in order to obtain the required radiation current density. For the former, the electron beam 12
There is a problem of deteriorating the light condensing property, and the latter has a problem that the strength decreases and creep deformation occurs.

Therefore, at present, the length of the long cathode is
When the upper limit is 150 mm and a longer cathode is required, as shown in FIG. 4, the intermediate support mechanism 15
However, there was no choice but to arrange the short-span cathodes continuously, but there was a problem of uneven temperature distribution or uneven distance between electrodes. The present invention has been made in view of the above-mentioned prior art, and combines a tungsten material as a cathode body serving as a structural material and a tantalum material as an electron emitting material serving as an electron emitting material, and has a small work function. An object of the present invention is to provide a long cathode which can be heated to a temperature at which a required emission current density can be obtained by using only a tantalum material and used.

[0007]

The structure of the present invention which achieves such an object is made of tungsten in an electron gun used as a heat source for evaporating a metal or the like in a vacuum by the generation of a long electron beam. An electron emission member made of tantalum is coupled to the front surface of the cathode body, and the tantalum is heated to a temperature at which thermoelectrons are emitted.

[0008]

With respect to the work function, since tantalum is smaller than tungsten, if these are heated to the same temperature, most of the thermoelectrons are emitted from tantalum. To obtain the required emission current density, for example 2 A / cm ² , tungsten needs to be heated up to about 2700 k, whereas for tantalum about 2500 k, a low temperature of 200 k is sufficient. Therefore,
The heating temperature can be lowered by using tantalum as a material that serves as electron emission. With respect to high temperature strength, since tungsten is larger than tantalum, by using tungsten as the cathode main body that serves as a structural material, it is possible to reduce the deflection at high temperature.

Since the tantalum material used as the electron emitting material can have any shape, the electron beam can have any shape. In particular,
By providing a part without tantalum in the center of the cathode,
It is possible to reduce the damage caused by the ion bomber. Further, as a method of joining the tungsten material and the tantalum material, diffusion joining in which they are pressure-welded in a high temperature vacuum or HIP (
Hot Isostation Press), HIP, CVP after spraying
There are methods such as vapor deposition by PVD and PVD.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 and 2 show a linear electron gun according to an embodiment of the present invention. As shown in both figures, in this linear electron gun, an anode 7 and a cathode 1 are arranged behind a grid 6. Both ends of the cathode 1 are supported by both end supporting mechanisms 3, and the structural material 5 is
The cathode 1 is supported so as to allow thermal expansion. The cathode 1 is a combination of a tungsten material as a cathode main body 5 serving as a structural member and a tantalum material as an electron emitting material 4 serving as an electron emitting material. That is, a long cathode main body 5 is made of a tungsten material, and a recess is formed in the front surface of the cathode main body 5, that is, in the center of the surface in the electron emission direction, and the electron emission made of a tantalum material is formed in the recess. The material 4 is integrally fitted.

Since the work function of tantalum is smaller than the work function of tungsten, when the cathode body 5 and the electron emitting material 4 are heated to the same temperature, most of the thermoelectrons e are emitted from tantalum which is the electron emitting material 4. .. Therefore,
To obtain the required emission current density, for example 2 A / cm ² , tungsten needs to be heated up to about 2700 k, whereas for tantalum about 2500 k, a low temperature of 200 k is sufficient. Therefore, tantalum is used as the electron-emitting material 4 as in the present invention.
As a result, the heating temperature can be lowered as compared with the case where only tungsten is used.

Since the high temperature strength of tungsten is higher than that of tantalum, the use of tungsten as the cathode body 5 reduces the deflection at high temperature as compared with the case of using only tantalum. be able to. On the other hand, a cathode heating filament 2 is arranged behind the cathode 1. Since the cathode heating filament 2 generally has a smaller cross-sectional area than the cathode 1 and is easily deformed by its own weight, the intermediate portion thereof is supported by the support mechanism 14. The cathode heating filament 2 is
The cathode 1 is uniformly heated in the length direction by a method such as heat conduction, radiation, or electron impact heating until the required radiant current density is obtained. Further, a positive high voltage is applied to the anode 7 by the acceleration power source 9, so that the emitted thermoelectrons are accelerated. In addition, a negative voltage is applied to the grid 6 by the grid power supply 8 to adjust the electron beam amount and the light collecting property. Furthermore, the uniform magnetic field B is perpendicular to the plane of the drawing.
Are formed.

Therefore, when the cathode 1 is heated to 2500 k by the cathode heating filament 2, thermoelectrons e are emitted from the tantalum, which is the electron emitting material 4, and the anode 7 is discharged.
The electron beam 12 is accelerated by the electric field due to the electron beam 12 and is deflected by the action of the uniform magnetic field B.
Then, the electron beam 12 is focused on a target (evaporation source) 11 in the crucible 10 and is irradiated, whereby the target 11 is evaporated and metal vapor 13 is obtained. Here, the cathode 1 is heated to 2500 k, which is 200 k lower than 2700 k, and since tungsten having the highest high-temperature strength is used as the cathode main body 5, the deflection due to its own weight is reduced. Therefore, the intermediate support mechanism 15 becomes unnecessary, and the length of the cathode 1 can be increased.

Next, another structure of the cathode 1 is shown in FIG. Similar to the above embodiment, FIG. 3 (a) shows a cathode main body 5 made of a tungsten material, in which a concave portion is formed in the center of the front surface, and an electron emitting material 4 which is a tantalum material is fitted in the concave portion. 3 (b) and 3 (c) each have a three-layer structure in which the upper and lower sides of the electron emitting material 4 are sandwiched by the cathode main body 5, but FIG. 3 (b) shows that the electron emitting material 4 is projected forward. On the other hand, in FIG. 3C, the cathode main body 5 projects forward. 3 (d) and 3 (e), the electron-emitting material 4 is formed on the entire front surface of the cathode body 5, but FIG. 3 (e) further shows that the electron emitting material 4 is formed on the rear surface of the cathode body 5. A concave portion is formed, and the cathode heating filament 2 is housed in this concave portion. 3 (f) and 3 (g), the electron-emitting material 4 is attached to a part of the front surface of the cathode main body 5, but the same FIG. 3 (f) is attached up and down. Figure (g) is attached to the center.

Those shown in FIGS. 3 (a) to 3 (c) are mainly manufactured by diffusion bonding, and those shown in FIGS. 3 (d) to 3 (g) are H after thermal spraying.
It is manufactured by IP processing. When the tantalum is thin as shown in FIGS. 3D to 3G, it can be manufactured by a coating method such as CVD or PVD. Figures 3 (a) (b) (g) are manufactured for the purpose of obtaining light-collecting properties, and Figures 3 (c) (f) are manufactured for the purpose of reducing damage due to ion bombardment and extending the life. Is done.

[0016]

As described above in detail with reference to the embodiments, the long cathode of the present invention is a combination of tungsten as a cathode body as a structural member and tantalum as an electron emitting material. The temperature can be reduced by about 200 k as compared with the case of using it alone, and the deflection during heating can be reduced as compared with the case of using tantalum alone. By reducing the cathode temperature as described above, the life due to evaporation can be extended and the cooling time of the electron gun can be shortened. Further, since the bending at a high temperature is small, it is possible to make the cathode longer without the need for an intermediate supporting mechanism. In particular,
Since the electron-emitting material can have an arbitrary shape, it is possible to improve the beam converging property and reduce the damage due to the ion bombardment. As described above, according to the present invention, a long linear electron gun with high performance and long life can be manufactured, and high-quality vapor deposition can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of a long cathode according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a linear electron gun using the long cathode shown in FIG.

3 (a) to 3 (g) are cross-sectional views showing another embodiment of the long cathode according to the present invention.

FIG. 4 is a perspective view of a conventional cathode supported by an intermediate support mechanism.

FIG. 5 is a configuration diagram of a conventional linear electron gun.

[Explanation of symbols]

 1 cathode 2 cathode heating filament 3 both ends support mechanism 4 electron emission material 5 cathode body 6 grid 7 anode 8 grid power supply 9 acceleration power supply 10 crucible 11 target 12 electron beam 13 metal vapor 14 filament support mechanism 15 intermediate support mechanism B uniform magnetic field e Thermoelectron

Front page continued (72) Inventor Takamasa Nakamura 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Kazuyuki Toki 3-1-2 Musashino, Akishima-shi, Tokyo Inside JEOL Ltd.

Claims (1)

[Claims] 1. In an electron gun used as a heat source for evaporating a metal or the like in a vacuum by generating a long electron beam, an electron emitting member made of tantalum is coupled to a front surface of a cathode body made of tungsten. A long cathode which is heated to a temperature at which thermionic electrons are emitted by tantalum.