JPH0375320A - Crucible for electron beam vaporizing apparatus - Google Patents

Abstract

PURPOSE:To surely enable ground of a crucible without going out of electron beam orbit from the crucible by arranging part, where erosion resistant coating is not applied, at a part of inner face and outer face in the crucible and executing the electric ground at the above position in the outer part. CONSTITUTION:The position 16, where the erosion resistant coating 11 is not applied, is arranged at the bottom face of crucible 6 to enable the electric conducting between molten metal 7 for vaporizing and the crucible 6. At the outer face of crucible 6, too, the position 16', where the erosion resistant coating 11' is not applied, is arranged and an electric conductor of spring 18, etc., is set in a groove hole 17 of water cooled copper case 9, etc., for supporting the crucible 6 and the compressive force is given to these with dead wt. of the crucible 6 to bring the crucible 6 into close contact with the water cooled copper case 9 of the ground potential. By this method, thermoelectron 2 discharged from an electron gun unit 5 and accelerated does not go out from heating center 10. Further, as the position 16, where the erosion resistant coating 11 is not applied, is a stagnated range, where is directly exposed to convection of molten metal, this is not eroded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a crucible for an electron beam evaporation device used for vacuum melting or vapor deposition of metals.

(Prior art) Conventionally, in an electron beam evaporation device used for vacuum melting or vapor deposition of metals, a metal for evaporation is placed in a crucible, and an electron beam accelerated by an electron gun is deflected by a magnetic field. The energy generated when it collides with metal is used as a heating source. Figure 2 shows an example of this.A current is passed through a filament 1 made of tungsten or the like to heat it, and thermionic electrons 2 are emitted between a Wehnelt electrode 3 at a negative potential and an anode electrode 4 at a ground potential. It is accelerated and flies out from the electron gun unit 5. The ejected thermoelectrons 2 then collide with the evaporating metal 7 placed in the crucible 6, which is deflected by a magnetic or electric field (not shown), and their kinetic energy is converted into thermal energy. Evaporation metal 7
When heated sufficiently, it becomes molten in the crucible 6,
Vapor 8 of metal 7 for evaporation is generated. At this time, the crucible 6 is cooled by a jig such as a water-cooled copper case 9 that supports the crucible.

(Problem to be solved by the invention) However, as mentioned above, in the conventional technology, thermionic 2
Convection occurs within the crucible 6 because of the large temperature difference between the heating center lO, where the evaporating metal 7 impinges on the crucible 6, and the crucible 6, which is being cooled. Normally, this convection flows along the liquid surface from the heating center 10 toward the inner wall of the crucible 6, which is being cooled, and then goes around downward and flows toward the heating center 10 again. At this time, if the metal for evaporation 7 is a highly corrosive active metal, the high temperature molten metal comes into contact with the inner wall of the crucible 6 due to convection, so that the inner wall of the crucible is gradually corroded. To prevent this, a corrosion-resistant coating 11 that has extremely low reactivity to the metal for evaporation is generally applied to the inner wall of the crucible 6, and also to the outer wall of the crucible 6, which is not directly exposed to the molten metal, to improve heat insulation and ensure uniform melting. This is done to increase thermal efficiency.

This corrosion-resistant coating 11 is suitably one that has a high melting point and is low in reactivity to the molten metal for evaporation as described above, but most of these are electrically insulating oxide ceramics.

When this coating is applied, the evaporating metal 7 and the crucible 6 float electrically, so the electron beam 12
If the electron beam (
In addition to the diffusion of the electron beam 3, there are serious problems such as the spot of the electron beam 2 continuing to move unsteadily around the crucible 6 while repeating charge accumulation and discharge. In order to prevent this, there is a method of attaching a ground wire 14 or a ground rod 15 made of a high-melting point metal as shown in Fig. 5 or 6, respectively. In the case of strongly active metals, they are easily cut by convection at the liquid level boundary. Further, impurities such as the ground wire 14 or the ground rod 15 may enter the crucible 6, which is undesirable. Further, when the crucible is used multiple times, it is impossible to insert or attach the ground wire 14 or the ground rod 15 since a solidified -like liquid surface is formed on the crucible from the second time onward.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a crucible for use in an electron beam evaporation device, in which the trajectory of the electron beam does not deviate from the crucible, and the crucible can be reliably grounded.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above technical problem, a corrosion-resistant, non-conductive oxide coating is not applied to the lower half of the inner surface of the crucible, which is not directly exposed to convection. Set up a place. In addition, if the outer surface is also coated, a part of the crucible is similarly provided with an electrically conductive point, and the crucible is grounded through this point.

(Function) With this configuration, the crucible is grounded at a portion where no metal for evaporation is present, so there is no breakage of the grounding wire, and the crucible can be maintained reliably and permanently.

(Example) Hereinafter, an example of a crucible for an electron beam evaporator according to the present invention will be described with reference to FIG.

A current is passed through a filament 1 made of tungsten or the like to heat it, and the emitted thermoelectrons 2 are accelerated between a Wehnelt electrode 3 at a negative potential and an anode electrode 4 at a ground potential and ejected from an electron gun unit 5. Thermionic electron 2 that jumped out
is then deflected by a magnetic or electric field (not shown) and impinges on the evaporating metal 7 placed in the crucible 6;
That kinetic energy is converted into thermal energy. When the metal for evaporation 7 is sufficiently heated, it becomes molten in the crucible 6, and vapor 8 of the metal for evaporation 7 is generated.

At this time, the crucible 6 has a water-cooled steel case 9 that supports the crucible.
It is cooled by a jig such as

The inner and outer surfaces of the crucible 6 are coated with a corrosion-resistant coating 11.11- made of oxide ceramics or the like.

A portion 1B-, which is directly exposed to the convection of the evaporation metal and is not coated with the anti-corrosion coating 11, is provided on the bottom surface of the lukewarm 6, and is melted to establish electrical continuity between the evaporation metal 7 and the lukewarm 6. Area 16 where coating is not applied to the outer surface of crucible 6
An electric contact such as a spring or a brush 18 is installed in the slot 17 of the water-cooled copper case 9 or the like that supports the crucible 6 in advance, and the weight of the crucible 6 applies compressive force to these. Then, the crucible 6 is brought into close contact with the water-cooled steel case 9 at ground potential.

As a result, the thermionic electrons 2 emitted and accelerated by the electron gun unit 5 collide without deviating from the heating center 10 on the evaporation metal 7 and the crucible 6, which are at ground potential, and convert their kinetic energy into thermal energy. It converts and returns to earth as a current. At that time, corrosion-resistant coating I
The area l6 where I is not applied is not eroded because it is in a stagnation area that is not directly exposed to convection.

[Effects of the Invention] According to the present invention, since the metal for evaporation and the crucible are reliably brought to earth potential, the trajectory of the electron beam does not deviate from the crucible, and the state does not change due to corrosion.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a crucible for an electron beam evaporator according to an embodiment of the present invention, and FIGS. 2 to 6 are views showing conventional crucibles for an electron beam evaporator. 1... Filament 2... Thermionic 3...
Wehnelt electrode 4... Anode 5... Electron gun unit 6... Crucible 7... Metal for evaporation
8...Steam 9...Water-cooled steel case IO
...Heating center 11, 11--Corrosion-resistant coating 12, 13...Electron beam 14...Earth wire 15...Earth rod 18, 18--...Position where coating is not applied 17.
・Groove hole

Claims (1)

[Claims] It has a shape with an open top to store the metal for evaporation, and a corrosion-resistant coating is applied to all but a part of the inner surface that contacts the metal for evaporation and a part of the outer surface, and electrical grounding is applied to the part of the outer surface that does not have the corrosion-resistant coating. A crucible for an electron beam evaporation device characterized by: