JP2014091670A - Manufacturing apparatus of single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing apparatus of a single crystal for manufacturing an oxide single crystal such as a sapphire single crystal that can improve a crucible life even when a graphite holding jig is used.SOLUTION: A manufacturing apparatus 10 of a single crystal manufactures an oxide single crystal 17 from melt 15 obtained by heating and melting a raw material in a crucible 14 in a Czochralski method (CZ method). The manufacturing apparatus 10 of a single crystal includes a heater 22 for heating the raw material in the crucible 14, and a main chamber 11 for housing the crucible 14, the crucible 14 being held by a graphite holding jig 18 via a sacrificial material 23 made of a high melting point metal.

Description

  The present invention relates to a single crystal manufacturing apparatus used when an oxide single crystal such as a sapphire single crystal is manufactured by a CZ method.

Various growth methods such as the EFG method, the Bridgman method, and the Kyropoulos method are used to manufacture a sapphire single crystal that is in great demand as an LED substrate.
In the Kyropoulos method which has become the mainstream recently, a sapphire single crystal is grown using a crucible of a refractory metal (tungsten, molybdenum, etc.), but a c-axis crystal necessary for an LED substrate cannot be obtained. After producing an a-axis crystal by this method, a process of obtaining a c-axis crystal by piercing the crystal from a right angle direction is necessary, and productivity and yield are extremely inferior.

  Therefore, the Czochralski method (CZ method) has recently attracted attention because it allows c-axis crystal growth, and various crystal growth methods have been attempted using high-frequency induction heating or resistance heating methods. In the CZ method using the high frequency induction heating method, a growth furnace is configured with an iridium crucible and a zirconia heat insulating material, and iridium is very expensive. ing. Therefore, it is expected that the crucible is made of a refractory metal (tungsten, molybdenum, etc.) that is cheaper and versatile than iridium, and the cost is reduced by repeated use.

JP 2008-7353 A

  Patent Document 1 discloses a method of supporting a molybdenum or tungsten crucible with an iridium crucible through a molybdenum or tungsten spacer. However, since an expensive iridium crucible is used, there is a limit to cost reduction.

For this reason, in a single crystal manufacturing apparatus, it is advantageous in terms of cost reduction and thermal conductivity to use a graphite material for the in-furnace component, and particularly to hold a refractory metal crucible with a graphite material.
However, in such an apparatus, since the refractory metal material is carbonized (carburized) below the melting point of the raw material such as alumina, the crucible is significantly deteriorated and deformed, and the life is reduced. Found them.

  Tungsten absorbs and carbides carbon at 850 ° C. to 1600 ° C., and molybdenum is carbonized at 1100 ° C. or higher. For this reason, even at a temperature lower than the melting point 2050 ° C. of aluminum oxide as a raw material, embrittlement and deformation due to carbonization cannot be avoided.

  The refractory metal crucible is made of a brittle material, but at a high temperature, the contact portion with the graphite material is accelerated in brittleness due to carbonization, and deterioration such as cracks becomes remarkable. Therefore, the number of times the crucible is used has been remarkably reduced, and the production cost has been remarkably deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an apparatus capable of improving the life of a crucible even when a graphite crucible holder is used in a single crystal manufacturing apparatus.

  In order to achieve the above object, the present invention is an apparatus for producing an oxide single crystal from a melt obtained by heating and melting a raw material in a crucible by the CZ method, and heating the raw material in the crucible And a main chamber in which the crucible is disposed, and the crucible is held by a refractory metal sacrificial material by a graphite holder. To do.

  In this way, if the crucible is held by a graphite holder through a refractory metal sacrificial material, the crucible will not directly contact the graphite holder, so that the crucible may be cracked due to carbonization. Deterioration can be suppressed, and the life of the crucible can be improved. Furthermore, the cost can be reduced by using a graphite holder. Therefore, it becomes an apparatus which can achieve the life improvement of a crucible simultaneously with cost reduction.

At this time, it is preferable that the material of the crucible is mainly composed of at least one of tungsten, molybdenum, and tantalum.
If it is such a crucible, since it is an inexpensive material, it becomes an apparatus which can reduce cost more.

At this time, the heater is preferably a resistance heater.
Such a resistance heater can be used in the apparatus of the present invention.

At this time, the sacrificial material of the refractory metal is preferably composed mainly of at least one of tungsten, molybdenum, and tantalum.
With such a sacrificial material, the device does not melt even at a high temperature and does not have a risk of contamination of the melt.

At this time, the oxide single crystal is preferably a sapphire single crystal.
The apparatus of the present invention can be an apparatus for the production of a sapphire single crystal.

At this time, the sacrificial material of the refractory metal preferably has a thickness of 2 mm or more.
If it is such thickness, it will become a device which can prevent carburization to a crucible certainly and can control degradation of a crucible more effectively.

  As described above, according to the present invention, crucible life improvement and device cost reduction can be achieved simultaneously.

It is the schematic which shows an example of the single crystal manufacturing apparatus of this invention. It is the figure which observed the deterioration condition of the bottom part of a crucible.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a schematic view of a single crystal production apparatus of the present invention.

The single crystal production apparatus 10 of the present invention shown in FIG. 1 is an apparatus for producing an oxide single crystal 17 such as a sapphire single crystal from a melt 15 obtained by heating and melting a raw material in a crucible 14 by a CZ method. It is.
The single crystal manufacturing apparatus 10 includes a heater 22 that heats the raw material in the crucible 14, a main chamber 11 in which the crucible 14 is disposed, and a pull chamber 13 that is connected to the main chamber 11 so as to be partitioned by a gate valve 12. It is provided.

  Further, as shown in FIG. 1, the apparatus 10 includes a gas introduction pipe 25 and a gas discharge pipe 26. For example, during normal times such as when a single crystal is grown, an inert gas or the like is supplied from above the pull chamber 13 into the furnace. The introduced gas can be discharged to the outside of the furnace from the gas discharge pipe 26 at the bottom of the main chamber 11 by a vacuum pump 27 or the like. On the other hand, when charging the raw material, the gate valve 12 is closed and the material charging operation is performed in the pull chamber 13, and then the inside of the pull chamber 13 is a gas exhaust pipe and a gas introduction pipe for a pull chamber (not shown). 25 can be used for gas replacement.

  In addition, the apparatus 10 supports a heat insulating material 16 such as a graphite-based felt material surrounding the crucible 14 and the heater 22, a pulling shaft 20 used for pulling up the single crystal 17, a seed holder 21 that holds a seed crystal, and the crucible 14. A graphite holder 18 and a crucible support shaft 19 that supports the crucible 14 via the graphite holder 18 are provided.

In the apparatus 10 of the present invention, the crucible 14 is held by a graphite holder 18 through a refractory metal sacrificial material 23. For example, the sacrificial material 23 is inserted and set between the bottom of the crucible 14 and the upper surface of the graphite holder 18.
Thus, if the crucible 14 is held by the graphite holder 18 via the refractory metal sacrificial material 23, the crucible 14 is held in a non-contact state by the graphite holder 18, and the crucible 14 Deterioration such as cracking due to carbonization can be prevented, and the life of the crucible 14 can be effectively improved. Furthermore, by making the holder 18 that holds the crucible 14 made of graphite using a graphite material, a carbon composite material, or the like, the thermal conductivity is good and the cost can be reduced. Accordingly, the life of the crucible 14 can be improved while reducing the cost. Here, even when the graphite holder 18 is held so as to surround the side surface of the crucible 14, not only the bottom surface of the crucible 14 but also the side surface thereof is not in direct contact with the graphite holder 18 by the sacrificial material 23. Hold on.

  FIG. 2 shows an image of the state of deterioration of the crucible when it comes into contact with the graphite holder at a high temperature. As shown in FIG. 2 (a), when the crucible was directly held by the graphite holder, cracks occurred on the bottom of the crucible, making it difficult to use repeatedly. Further, as shown in FIG. 2B, when the graphite holder was in contact with the side surface of the crucible, it reacted, expanded and deformed. In the present invention, such crucible deterioration can be effectively prevented.

Moreover, it is preferable that the heater 22 is a resistance heater, and the material of the crucible 14 is a metal crucible containing at least one of tungsten, molybdenum, and tantalum as a main component.
A high-frequency heater can be used as the heater 22 of the apparatus 10 of the present invention, and an iridium crucible can be used as the crucible 14, but in the present invention, an inexpensive crucible mainly composed of tungsten, molybdenum, or tantalum is used. Is preferred. In this case, since the oxidation resistance is lower than that of iridium, the carbon heat insulating material 16 is used. Since carbon is a good conductor, the high-frequency heating method has poor thermal efficiency, and a resistance heater may be used. preferable. Thereby, cost can be further reduced.

The refractory metal sacrificial material 23 is preferably composed mainly of at least one of tungsten, molybdenum, and tantalum.
Such a sacrificial material 23 does not melt even at high temperatures, and there is no fear of contamination of the melt 15. At this time, the sacrificial material 23 is preferably made of a material different from the material of the crucible 14. If the same material is used, the sacrificial material 23 may be fused (diffusion welding) to the bottom of the crucible due to the diffusion welding phenomenon, so that different materials can further improve the life of the crucible 14, and the sacrificial material 23 also It can be used repeatedly.

The refractory metal sacrificial material 23 can be, for example, a disc-shaped material, and preferably has a thickness of 2 mm or more, particularly 3 mm or more.
If it is such thickness, the carburizing to the crucible 14 can be prevented reliably and deterioration of the crucible 14 can be suppressed more effectively. At this time, the upper limit of the thickness of the sacrificial material 23 is not particularly limited. However, since the sacrificial material 23 needs to be replaced by observing the state of deterioration, for example, by setting the thickness to 20 mm or less, it is easy to handle. The increase in cost due to can be kept low.

  By producing an oxide single crystal such as a sapphire single crystal using the single crystal production apparatus of the present invention as described above, the crucible can be used repeatedly, so that the apparatus cost can be reduced and the production cost of the oxide single crystal can be reduced. Contribute to

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples and comparative examples)
Sapphire single crystals were produced using the single crystal production apparatus of the present invention shown in FIG.
As an example, a tungsten and molybdenum disc (thickness 2 mm) was inserted between the bottom of a tungsten crucible and a graphite holder, and a molybdenum and tungsten disc (thickness). 2 mm) was inserted between the bottom of the molybdenum crucible and the graphite holder, and the crucible was confirmed for deterioration.

  Further, as a comparative example, single crystal production was performed in the same manner as in Example except that the tungsten and molybdenum crucibles were directly held by a graphite holder, and deterioration of the crucible was confirmed.

  At this time, the crucible had an outer diameter of 250 mm and a height of 200 mm, and the sacrificial disk had an outer diameter of 160 mm and a thickness of 2 mm. Further, the disc was inserted between the crucible bottom and the graphite holder in consideration of concentricity.

  Table 1 shows the result of confirming the deterioration state of the crucible bottom for each combination of the material of the crucible and the material of the disc (sacrificial material) and the result of confirming the deterioration state of the crucible bottom in the comparative example.

In the case of the example held through the disc, when the state of the crucible bottom after the completion of the pulling was observed, no deterioration of the crucible bottom was observed.
In the case of the comparative example in which no disc was laid, the change in the bottom of the crucible was large even in one batch, and deterioration such as cracks and deformation was observed.

  In addition, when a molybdenum disc was inserted into the molybdenum crucible, the crucible was not deteriorated, but the disc was sometimes fused to the bottom of the crucible due to the diffusion welding phenomenon. Therefore, it can be seen that the crucible and the disc (sacrificial material) of different materials can be used stably.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

10 ... Single crystal manufacturing equipment, 11 ... Main chamber, 12 ... Gate valve,
13 ... Pull chamber, 14 ... Crucible, 15 ... Melt, 16 ... Insulating material,
17 ... oxide single crystal, 18 ... graphite holder, 19 ... crucible support shaft,
20 ... Single crystal pulling shaft, 21 ... Seed holder, 22 ... Heater, 23 ... Sacrificial material,
25 ... Gas introduction pipe, 26 ... Gas discharge pipe, 27 ... Vacuum pump.

Claims (6)

An apparatus for producing an oxide single crystal from a melt obtained by heating and melting a raw material in a crucible by a CZ method,
A heater for heating the raw material in the crucible, and a main chamber in which the crucible is arranged,
The crucible is held by a refractory metal sacrificial material by a graphite holder, and the single crystal manufacturing apparatus according to claim 1.   The single crystal manufacturing apparatus according to claim 1, wherein the material of the crucible is mainly composed of at least one of tungsten, molybdenum, and tantalum.   The single crystal manufacturing apparatus according to claim 1, wherein the heater is a resistance heater.   The single crystal manufacturing apparatus according to any one of claims 1 to 3, wherein the sacrificial material of the refractory metal contains at least one of tungsten, molybdenum, and tantalum as a main component. .   The single-crystal manufacturing apparatus according to any one of claims 1 to 4, wherein the oxide single crystal is a sapphire single crystal.   The single crystal manufacturing apparatus according to any one of claims 1 to 5, wherein the refractory metal sacrificial material has a thickness of 2 mm or more.

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