JP3152971B2 - Manufacturing method of high purity copper single crystal ingot - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity copper single crystal ingot.

[0002]

2. Description of the Related Art Conventionally, high-purity copper has been used not only for electronics such as bonding wires and metal / semiconductor contacts, but also for conductive materials such as superconducting, ultra-high voltage, ultra-high vacuum or acoustic equipment, and cryogenic equipment. It has been widely used as one of the materials governing its performance in many advanced technology fields such as a cooling medium or a high strength laser mirror. In recent years, while the demand for high-purity copper materials used for such uses has increased remarkably, the shapes required for these uses have been diversified.

[0003] Usually, when producing a single crystal ingot of pure metal, a pulling method (Czochralski method) in which a seed crystal is brought into contact with a molten metal and gradually raised while rotating the seed crystal,
There are known the Bridgeman method in which raw materials are put into a vertical or horizontal boat or a mold and a heat source for heating is gradually moved.

[0004] In order to produce a single crystal from the melt by these methods, the solidified melt must be cooled without being supercooled. This is because if supercooled, new crystal nuclei are generated. Further, in order to solidify the melt, the latent heat must be extracted and removed. That is, a heat escape path is required to remove heat from the crystal, while a heat source for supplying heat for melting the metal and maintaining the molten state for a predetermined time is also required. For this reason, the lifting speed in the lifting method is 5 to 10 mm / hr,
The moving speed of the heating source in the Bridgman method is 20 to 50 mm /
hr and both are very slow and therefore less productive,
Also, since there is no effective means for preventing supercooling in the device itself,
There is a drawback that polycrystals are easily formed.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and provides a high-purity copper single crystal ingot having a desired shape while maintaining high purity characteristics of a raw material. It is an object of the present invention to provide a novel method for producing a high-purity copper single crystal ingot that can be produced by the method described above.

[0006]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems. As a result, when high-purity copper is melted in a mold by high-frequency heating under a high vacuum, the distance between the mold and the crucible is reduced. The present inventors have found that the presence of a molten metal of copper as a means for preventing supercooling can prevent polycrystallization of high-purity copper in a mold.

That is, according to the present invention, high purity copper having a total content of silver and sulfur of 1 ppm or less and a purity of 99.999% or more is used as a raw material, and single crystal casting is performed in a high vacuum while maintaining the high purity characteristics of the raw material. In the method of producing a lump, a columnar graphite mold having a casting space with a bottom pointed in the shape of an inverted cone was fixed vertically in a graphite crucible, leaving a space between the mold and the crucible that could hold the molten copper. Thereafter, the copper raw material for producing a single crystal ingot is placed in a mold, and the same or different grades of heat insulation are provided in a space provided between the outer wall of the mold and the inner wall of the graphite crucible.
A copper material for heat transfer is filled, then the copper material and the copper material are melted by high-frequency heating, and the coil is moved at a rising speed of 0.1 to 20 mm / min while heating the mold with a high-frequency coil. The present invention relates to a method for producing a high-purity copper single crystal ingot, wherein a copper raw material is formed into a high-purity copper single crystal ingot.

[0008]

Generally, a purification technique for obtaining high-purity copper having a total content of silver and sulfur of 1 ppm or less and a purity of 99.999% (5N) or more has been almost completed. It is an object of the present invention to use such high-purity copper and to obtain a single-crystal ingot with good productivity while maintaining its high-purity characteristics.

The apparatus used in the method of the present invention includes:
As shown in FIG. 1, a male screw portion provided at the outer lower end portion of a columnar graphite mold 1 having the inner wall bottom portion pointed in an inverted cone shape is provided at the inner bottom portion of the graphite crucible 2 and fitted to the screw portion. By being combined, the one fixed in the graphite crucible 2 is used. In this way, the structure was such that the copper material 7 could be filled between the mold 1 and the graphite crucible 2, and this was fixed to the quartz support 3 in the quartz bell jar 4 installed vertically. The copper material 7 is not the same as the raw material high-purity copper material 6, but may be a normal copper material (4N or less). However, the structure of the apparatus is such that the upper surface of the copper material at the time of melting is in a mold. It is important that the top of the molten high-purity copper 6 is higher than the top, while the lower end is lower than the top of the mold. Next, the high-frequency coil 5 was installed outside the quartz bell jar 4 so as to be able to move up and down.

First, in the present invention, the high-frequency coil 5
Is set at a position surrounding the lower end of the mold 1 containing the high-purity copper material 6 as a raw material, and the output is increased to melt while heating.
After the dissolution, it was kept at that position for a while and heated sufficiently to dissolve both the high-purity copper material in the mold and the copper material 7 arranged outside the mold. Whether or not these copper materials 6 and 7 are actually melted can be confirmed by measuring the temperature with a thermocouple 8 installed below the mold 1.

In this case, since the effect of the high frequency extends only to the graphite crucible 2 located outside, the copper material 7 in contact with the inner wall of the crucible and the high-purity copper material 6 as a raw material in the mold 1 are formed.
Is dissolved by heat transfer. After sufficient heating, the coil is gradually raised at a speed of 0.1 to 20 mm / min, and after melting and solidification at the upper part of the mold is confirmed, heating is stopped. In the conventional Bridgman method, since the temperature of the mold 1 cannot be maintained during the above operation, the mold is easily cooled, resulting in overcooling and polycrystal formation. For this reason, it was necessary to prevent rapid cooling of the crystal by using an apparatus such as an after-heater, and to take care to keep the temperature gradient constant. In addition, there is a disadvantage that the moving speed of the coil must be sufficiently reduced in order to maintain such a balance of the amount of heat. In the method of the present invention, these drawbacks can be eliminated.

That is, in the method of the present invention, a high frequency is placed on the outer graphite crucible 2 to melt the copper material 7 disposed around the mold 1 by heat transfer, and then the high-purity copper material 6 in the mold 1 is transferred by the heat transfer. Dissolve. In this case, when the coil is raised, solidification starts from the molten metal below the mold, which is out of the range of influence of the coil. In the case of the conventional method, the part outside the influence of the coil does not supply heat from the heat source and only radiates heat to the outside, so supercooling occurs and causes new nucleation, but in the case of the method of the present invention, In this case, heat is supplied from the entire periphery of the mold by heat conduction from the molten copper even at a position outside the influence of the coil because copper having good thermal conductivity is dissolved around the mold 1 and exists. Since the high-purity copper 6 in the mold 1 can be indirectly cooled and solidified by heat transfer to the cooled and solidified copper material 7 instead of cooling by cooling by contacting the outer surface of the mold directly with the outside. Cooling can be prevented.

At this time, the temperature gradient is set so that the temperature of the molten metal in the portion where the coil is located is the highest, and the temperature of the tip of the mold is always the lowest. In addition, since the entire periphery of the mold is covered with a copper material having good thermal conductivity, the temperature does not locally increase or decrease, and furthermore, the latent heat generated when the copper material solidifies. Release also increases the effect of keeping and cooling the high-purity copper in the mold. By these effects, the moving speed of the coil can be made 20 times or more as compared with the conventional case, and the productivity can be increased.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

[0015]

Embodiment 1 A method for producing a high-purity copper single crystal ingot of the present invention using the production apparatus shown in FIG. 1 will be described below.

FIG. 1 is a cross-sectional view showing an apparatus used in the present embodiment. A graphite mold 1 having an internal shape made according to the shape of an ingot to be manufactured has an outer wall,
FIG. 4 shows a state in which the graphite crucible 2 is fixed in the graphite crucible 2 and is fixed to the graphite crucible 2 in such a size and shape that it can be covered with the copper material 7 for heat retention and heat transfer in a molten state. I have. The entire apparatus is covered by a quartz bell jar 4, and this quartz bell jar 4 is connected to an evacuation apparatus, so that the inside thereof can be made high vacuum. A high-frequency coil 5 is provided outside the quartz bell jar 4 so as to surround the bell jar, and the high-frequency coil 5 extends from the bottom of the graphite crucible 2 inside the quartz bell jar 4 to the top of the mold 1. It has a movable structure that can heat the space. At the bottom of the graphite crucible 2, a PR thermocouple 8 is provided.
The temperature at the bottom of the graphite crucible 2 can be measured. Reference numeral 9 indicates the direction of evacuation.

In this embodiment, first, about 500 g of high-purity copper having a purity of 99.999% or more and having a total content of silver and sulfur of 1 ppm or less.
Was placed in a graphite mold 1 and a sufficient amount of copper material 7 was put around the mold to fix the graphite crucible 2 to the support 3. Then, these were covered with a quartz bell jar 4 and connected to a vacuum exhaust device. Next, the degree of vacuum inside the quartz bell jar 4 is raised to 10 ^-5 to 10 ^-6 Torr by a vacuum exhaust device to maintain the vacuum, and the high-frequency coil 5 is placed at a position surrounding the upper part of the mold 1 containing the raw material. After heating and melting, it was held until it fell, and the coil was lowered at a speed of 20 mm / min while the high-frequency coil 5 was heated.

After confirming the dissolution by the PR thermocouple 8 when reaching the bottom, the coil is heated to 20 mm / min.
The heating was stopped after moving the coil up to the upper part of the mold at the speed of. When removed from the mold, a 1-inch φ × 100 mm single-crystal ingot with the high-purity characteristics maintained could be produced.

[0019]

Comparative Example 1 A high-purity copper ingot was produced in the same manner as in Example 1 except that a mold having no means for preventing supercooling was used. This ingot was a polycrystal having six crystals in cross section.

[0020]

According to the development of the present invention, a homogeneous high-purity copper single crystal having a desired shape can be produced while maintaining the high-purity characteristics of the raw material. Further, according to the present invention, even when expensive high-purity copper is used as a raw material, the high-purity single crystal can be manufactured at low cost because the high-purity characteristics of the raw material can be maintained and the loss is extremely small. Was. further,
Since the present invention can be easily implemented using a simple device, its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a high-purity copper single crystal manufacturing apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Graphite mold 2 Graphite crucible 3 Quartz support 4 Quartz bell jar 5 High frequency coil 6 High purity copper material 7 Copper material 8 PR thermocouple 9 Vacuum exhaust

Claims (1)

(57) [Claims] Claims: 1. The total content of silver and sulfur is 1 ppm or less,
In a method of producing a single crystal ingot in a high vacuum while maintaining the high purity characteristics of the raw material using high-purity copper with a purity of 99.999% or higher, a columnar shape with an inverted conical bottom-shaped casting space at the bottom After fixing the graphite mold vertically in a graphite crucible, leaving a space that can hold the molten copper between the mold and the crucible, put the single crystal ingot production copper raw material into the mold, The space provided between the inner wall of the graphite crucible is filled with the same or different grade of copper material for heat retention and heat transfer, and then the copper raw material and the copper material are melted by high frequency heating, and the mold is heated by a high frequency coil. 0.1 ~ 20m
A method for producing a high-purity copper single crystal ingot, characterized in that a copper material in a crucible in which a coil is moved at an ascending speed of m / min is made into a high-purity copper single crystal ingot.