JPH09118975A - Device and method for evaporating metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal evaporating device which prevents leakage of the molten metal when the temperature excessively rises, and generates the metallic vapor with excellent thermal efficiency. SOLUTION: A metal evaporating device is provided with a vacuum container 1, a crucible 2 arranged in the vacuum container 1, a metallic material 4 (uranium U) which is an evaporating material placed in the crucible 2, and the electron beam 5 to generate the metallic vapor 6 of U through irradiation of the surface of the uranium material 4, a film which forms an outer wall to surround a side surface and a lower surface of the uranium member 4 is formed of a stable compound 14 (UO2 ) which contains the metal (U) as the composition and whose melting point is higher than that of U, and a heat insulation material 15 consisting of the powder of UO2 is charged between the uranium material 4 and the crucible 2. The molten uranium is sealed by the film made of the stable compound, and the temperature is kept by the heat insulation material, and the film can be re-generated by the heat insulation material even when the film is broken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for heating and evaporating a metal material in a crucible by heating means in a vacuum container, and more particularly to evaporating a large amount of a metal material, such as a metal thin film or metal coating. The present invention relates to a metal evaporation device and a metal evaporation method suitable as an evaporation source used for vacuum deposition or laser isotope separation.

[0002]

2. Description of the Related Art A conventional metal evaporation apparatus and method for heating and evaporating a metal material in a crucible in a vacuum container by a heating means will be described with reference to FIG. The metal evaporator comprises a crucible 2 placed in a vacuum container 1 and an electron gun 3 as a heating means. A metal material 4 as a raw material is arranged in the crucible 2, and the surface of the metal material 4 is irradiated with a deflected electron beam 5 from an electron gun 3. Thereby, the metal material 4 is heated and the metal vapor 6 is generated. In order to prevent thermal deformation of the crucible 2 and reaction between the crucible 2 and the metal material 4, a cooling pipe 7 through which a coolant such as water passes is incorporated in the crucible 2.

Among the above-described metal evaporation devices and evaporation methods, a metal evaporation device and evaporation method for increasing the evaporation amount of a metal material while keeping the energy used for heating constant in order to evaporate the metal material inexpensively This will be described below.

In the evaporation method described in Japanese Patent Application Laid-Open No. 2-107725, the metal material 4 is heated to become a liquid, and convection in the crucible 2 suppresses an increase in heat loss to the crucible 2. In addition, the crystal grain 8 of the refractory metal is mixed with the metal material 4. Since the crystal grains 8 of the refractory metal suppress the convection, a large amount of heat is accumulated in the metal material 4, the temperature of the metal material surface increases, and the evaporation amount increases.

Further, the crucible for melting a metal disclosed in JP-A-62-129132 will be described with reference to FIG. In this crucible, in order to reduce heat loss, a carbon material 9 having a thermal conductivity lower than that of the metal material 4 is arranged inside, and zirconium having a lower thermal conductivity is disposed outside the carbon material 9. Graphite material 1 in which material 10 is arranged and cooling tube 7 is provided outside zirconium material 10
It is configured by arranging 1. When the crucible material is not a metal such as copper, but a material having a low thermal conductivity is used, heat transfer to the crucible due to heat conduction is suppressed, and a large amount of heat is accumulated in the metal material 4. And the amount of evaporation increases.

[0006]

In the above-mentioned conventional technique, the movement of heat in the crucible 2 is suppressed, the temperature of the metal material 4 is raised, and the evaporation amount of the metal material 4 is increased. When wrapping a metal material in such a material with low thermal conductivity (for heat insulation), it is most preferable to use ceramic powder such as oxides, carbides and nitrides or a sintered body with high porosity as a heat insulating material. desirable. However, in the above-mentioned prior art, it was not considered whether the metal material 4 is a liquid or a solid. Therefore, when the metal material 4 is held at its melting point or higher, the use of the ceramic powder or the sintered body having a high porosity, which is optimal as the heat insulating material, can prevent the metal from seeping into the ceramics. There was a problem that I could not.

It is an object of the present invention that, when a metal material is held above its melting point, the metal permeates into the ceramics by using an excellent ceramic powder or a sintered body having pores as a heat insulating material. It is an object of the present invention to provide a metal evaporation device and an evaporation method capable of preventing the above-mentioned phenomenon and efficiently evaporating a metal material.

[0008]

In order to achieve the above-mentioned object, a metal evaporation apparatus of the present invention comprises a vacuum container, a crucible arranged in the vacuum container, and an evaporation material contained in the crucible. A metal member and a heating means for irradiating the metal member with energy to melt and vaporize the metal are provided, and the element contains the element of the metal as a component and has a melting point of the metal so as to surround the side surface and the lower surface of the metal member. An outer wall made of a higher stable compound is provided, and a heat insulating material is interposed between the outer wall and the crucible.

And, in the metal evaporator of the present invention,
It is preferable that the heat insulating material is composed of a powder or a sintered body having the same components as the stable compound. The outer wall of the stable compound is preferably formed as a film on the surface of the metal member. The stable compound here is a metal oxide, carbide or nitride.

The outer wall of the stable compound that surrounds the side surface and the lower surface of the metal member has a powder of an unstable compound which is composed of the same element as the constituent element of the stable compound and has a melting point lower than that of the stable compound, around the metal member. It is preferable that the powder of the unstable compound is decomposed by heating through the metal member to form a film of the stable compound.

In the above metal evaporation device, when the metal member, which is the evaporation material, is irradiated with energy by the heating means, the metal member is melted, and a large amount of metal vapor is generated particularly from the portion irradiated with energy. Usually, the outer wall made of a stable compound has a higher melting point than the metal member, so that the molten metal is confined in the outer wall and does not seep into the heat insulating material.

Further, since the stable compound is a compound containing a metal constituting the metal member as a component, even if atoms move from the stable compound at the interface between the outer wall of the stable compound and the molten metal, deterioration of the purity of the molten metal can be suppressed. . Further, a stable compound composed of an oxide, a carbide or a nitride of the metal, when it reaches the surface of the molten metal when moving from the interface, oxygen,
Carbon or nitrogen becomes a gas and is removed from the vacuum container,
It is possible to suppress a decrease in the purity of metal vapor.

The heat insulating material insulates the heat transmitted from the molten metal through the outer wall of the stable compound to maintain the temperature of the molten metal,
The metal material can be efficiently evaporated by the input power from the heating means. Further, if the heat insulating material is made of the same material as the stable compound of the outer wall, the heat insulating material regenerates the outer wall even when the temperature of the molten metal rises excessively and the outer wall is broken, and the leakage of the molten metal is prevented.

Further, the outer wall of the stable compound surrounding the metal member is preliminarily surrounded by a powder of an unstable compound which contains, as a component, a metal constituting the vaporizing metal member and which is thermally decomposed at a temperature lower than the melting point of the stable compound. The stable compound can be decomposed by heating the metal member to form a stable compound film on the surface of the metal member, so that the stable compound can be used without using other special equipment. It can be easily formed using a metal evaporator.

In order to achieve the above object, the metal evaporation method of the present invention uses the above metal evaporation apparatus, wherein the metal member as an evaporation material is higher than the melting point of the metal and higher than the melting point of the stable compound. It is characterized in that it is kept in a low temperature range to evaporate the metal.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of a metal evaporation device according to a first embodiment of the present invention. The metal evaporation apparatus of the first embodiment includes a vacuum container 1 exhausted by a vacuum exhaust device 12, a crucible 2 placed in the vacuum container 1, a metal material 4 loaded in the crucible 2, and a metal material 4. Equipped with an electron gun 3 as a heating means for heating a part of the surface of
Further, an outer wall of the stable compound 14 which covers the side surface and the lower surface except the upper surface is formed as a film on the metal material 4, and a heat insulating material 15 is provided around the outer wall so as to be interposed between the heat insulating material 15 and the crucible 2. The stable compound 14 is a compound of a metal that is a component of the metal material 4 and has a melting point higher than that of the metal and is stable. A cooling pipe 7 is embedded in the crucible 2 for water cooling.

The heating means is composed of the electron gun 3 and the electron gun power source 13, and the surface of the metal material 4 is irradiated with the deflected electron beam 5. As a result, the temperature of the metal material 4 is raised, and particularly the temperature of the portion irradiated with the electron beam 5 is higher than that of the other surface, and evaporation occurs only at the irradiation position to generate the metal vapor 6. In the first embodiment, about 600 grams of uranium (U) was used as the metal material 4. Further, uranium dioxide (UO ₂ ) was used as the stable compound 14, and the surface of the metal uranium was coated with this. Further, as the heat insulating material 15, yttrium oxide (Y ₂ O ₃ ) powder was used.
When the output of the electron gun 3 of 4 kW was applied, the temperature of the electron beam irradiation part reached about 3500 ° C. Also, metal material 4
The temperature at the interface between (U) and the stable compound 14 (UO ₂ ) is higher than the melting point of uranium (1102 ° C.) and the melting point of UO ₂ (2760).
2000 ° C., which is lower than the temperature (° C.). Therefore, the liquid uranium could be confined by the UO ₂ film, and the uranium did not seep into the heat insulating material. At this time, due to the effect of using the heat insulating material, although the input power was ⅓ of that when the heat insulating material was not used, the temperature of the electron beam irradiation part was about 300 ° C. higher, so the evaporation amount was about 7 Doubled. Therefore, the evaporation efficiency (energy used for evaporation / input power) was improved about 20 times.

Next, a method for forming a UO ₂ film around uranium which is the metal material 4 will be described with reference to FIG. First, as shown in FIG. 2A, a uranium high-order oxide (U ₃ O ₈ ) 16 containing uranium as a component and thermally decomposed into UO ₂ is installed around the uranium. A powder 15 of UO ₂ was placed on the outside thereof. When the surface of the uranium is heated by the electron gun in this state, the temperature of U ₃ O ₈ rises and is thermally decomposed to generate UO ₂ and oxygen. Since lower than the melting point of the metal temperature UO _2, UO ₂ as shown in FIG. 4 (b)
Forms a film around uranium as a solid. On the other hand, since oxygen is a gas, it is exhausted by a vacuum exhaust device. According to this method, it is possible to form a stable compound film by using the evaporation device of the first embodiment without using a special device.

Next, a metal evaporation device according to a second embodiment of the present invention will be described. The structure of this metal evaporator is the same as in FIG. However, as the heat insulating material 15, powder of stable compound UO ₂ was used instead of yttrium. The advantage of the device of the second embodiment is that even if the power of uranium (U) is raised higher than the melting point of UO ₂ and the UO ₂ coating 14 is broken, the heat insulating material is erroneously applied. The reaction between the uranium (U) soaked in 15 and the heat insulating material 15 (UO ₂ ) is to autonomously reform the UO ₂ film around the uranium. In the second embodiment, the power of 8 kW was deliberately applied to destroy the UO ₂ film 14 formed first. After that, when the operation of the electron gun was stopped once and the state of uranium was confirmed, the film was re-formed by UO ₂ of the heat insulating material 15. Evacuate again and use the electron gun 3 to move the uranium 4
When was heated to evaporate, when the input power was set to 4 kW, the amount of evaporation was about 7 times as much as in the case of not using the heat insulating material 15 as in the device of the first embodiment.
Therefore, the evaporation efficiency was also improved about 20 times. That is,
In the device of the second embodiment, even if the film of the stable compound is destroyed, the film of the stable compound can be formed autonomously by reducing the power applied once.

Next, an embodiment in which a carbide is used as a stable compound will be described. Uranium monocarbide (UC) was used as the stable compound. The melting point of uranium monocarbide is 252.
Since it is 5 ° C., uranium can be kept at 2000 ° C. as in the case of using uranium dioxide (UO ₂ ). Further, higher order carbide (U ₂ C ₃ ) was used as the unstable compound used for forming the film.

In each of the above embodiments, powder was used as the heat insulating material, but it is also possible to use a sintered body having a high porosity.

[0022]

According to the present invention, a metal member, which is an evaporation material, is provided with an outer wall made of a stable compound having a melting point higher than that of the metal and containing the metal, and the evaporation material is further interposed with a heat insulating material interposed. Since it is placed in a crucible, the metal can be confined by the outer wall to prevent leakage and the purity of the molten metal can be prevented from decreasing, and the molten metal of the vaporized material can be easily maintained at a predetermined temperature by the heat insulating material, and efficient metal vapor generation You can

Further, by making the heat insulating material the same material as the stable compound constituting the outer wall, the outer wall can be regenerated in the case of damage to the outer wall.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a metal evaporation device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a method for forming a stable compound film on a metal material.

FIG. 3 is a configuration diagram of a conventional metal evaporation device.

FIG. 4 is a configuration diagram of another conventional metal evaporation device.

[Explanation of symbols]

 1 Vacuum Container 2 Crucible 3 Electron Gun 4 Metal Material 5 Electron Beam 6 Metal Vapor 7 Cooling Tube 12 Vacuum Evacuation Device 13 Electron Gun Power Supply 14 Stable Compound 15 Insulation Material 16 Unstable Compound

Claims (10)

[Claims] 1. A vacuum container, a crucible arranged in the vacuum container, a metal member as an evaporation material placed in the crucible, and the metal member is irradiated with energy to melt and vaporize the metal. In a metal evaporation device provided with a heating means, an outer wall surrounding a side surface and a lower surface of the metal member and including a stable compound having a metal that is a constituent element of the metal member as a component and a melting point higher than that of the metal. A metal evaporation device, characterized in that a heat insulating material is provided between the outer wall and the crucible. 2. The metal evaporation device according to claim 1, wherein the heat insulating material is made of powder having the same components as the stable compound. 3. The metal evaporation device according to claim 1, wherein the heat insulating material is made of a sintered body having the same components as the stable compound. 4. The metal evaporation device according to claim 1, wherein the outer wall of the stable compound is formed as a film on the surface of the metal member. 5. The metal evaporation device according to claim 1, wherein the stable compound is an oxide of a metal that is a component of the metal member. 6. The metal evaporation device according to claim 1, wherein the stable compound is a carbide of a metal that is a component of the metal member. 7. The metal evaporation device according to claim 1, wherein the stable compound is a nitride of a metal that is a component of the metal member. 8. The outer wall of the metal member has, around the metal member, a powder of an unstable compound which is composed of the same element as that of the stable compound and has a melting point lower than that of the stable compound. The metal evaporation device according to claim 4, wherein the powder of the unstable compound is decomposed by heating through the metal member to form a film of the stable compound. 9. The metal evaporation device according to claim 8, wherein the stable compound is an oxide, a carbide, or a nitride of a metal that is a component of the metal member. 10. The metal evaporation device according to claim 1, wherein the metal member as the evaporation material is kept in a temperature range higher than the melting point of the metal and lower than the melting point of the stable compound. And a method for evaporating a metal, which comprises evaporating a metal.