JP2005255437A - Single crystal production apparatus and single crystal production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal production apparatus which is one for growing a single crystal by pulling a seed crystal from a melt, wherein single crystals can be produced in improved productivity by preventing crack by controlling the temperature of a crystal by realizing a heat-insulation material structure suited for growth and a heat-insulation structure suited for cooling, which are incompatible with each other, in a continuous growth process and to provide a single crystal production method. <P>SOLUTION: In a method for producing a single crystal by heating a melt in a crucible, bringing a seed crystal into contact with the melt, and pulling the seed crystal from the melt, the single crystal production apparatus has a mechanism for continuously and automatically or manually adjusting the opening degree of the upper opening of a refractory and a mechanism for simultaneously controlling the opening degree of the opening and the output from a high-frequency electric source. The single crystal production method is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to production of a single crystal, particularly an oxide single crystal, and relates to a production apparatus and a production method that do not cause cracks in the crystal. Furthermore, the present invention relates to a manufacturing method that saves power.

  In general, in a single crystal manufacturing apparatus, the structure of the heat insulating material is the same during both single crystal growth and cooling. Patent Document 1 proposes a method of covering the opening, but the temperature of the crystal cannot be controlled. In addition, there is a method of heating the upper part of the crystal with an after heater, but the Czochralski method using a high frequency power source requires a larger electric power.

JP-A-4-313270

The main cause of cracks in the crystal is that a large temperature difference occurs in the single crystal and cracks are generated due to the thermal stress.
If the lid is completely closed at the start of cooling as in the prior art described above, some or all of the crystal or crucible exceeds the melting point and melts. Further, when the lid is closed during the cooling, the upper low temperature gas flows by that time, or the heat radiation of the crystal is large and there is no crack prevention effect. In addition, in the almost closed state from the beginning, the temperature gradient at the solid-liquid interface becomes small, and the growth time becomes long because the crystal growth is slow. In addition, a new heat source is required, the structure of the apparatus is complicated, and more electric power is required.
The present invention provides a single crystal manufacturing apparatus and a manufacturing method for obtaining a single crystal in which power is reduced and cracks do not occur in a short time without adding a new heat source.

The present invention relates to the following inventions.
<1> In the method of heating the melt in the crucible, bringing the seed crystal into contact with the melt and pulling it up to produce a single crystal, the upper opening of the refractory can be opened or closed automatically or manually. A single crystal manufacturing apparatus having a mechanism for continuously adjusting and a mechanism for simultaneously controlling an opening / closing amount of an opening and an output of a high-frequency power source.
<2> The single crystal manufacturing apparatus according to <1>, wherein the crystal temperature or the furnace temperature is measured, and the opening / closing amount of the opening and the output of the high-frequency power source are simultaneously adjusted according to the measured temperature.
<3> In the above item <1>, an appropriate opening / closing amount of the opening and the output of the high-frequency power source are obtained in advance by calculation or experiment, and the opening / closing amount of the opening and the output of the high-frequency power source are simultaneously adjusted automatically or manually. Crystal production method.
<4> A method for producing a single crystal according to the above <1>, which has a function of obtaining the same cracking prevention effect as that of long-time cooling in a short time by a combination of rapid cooling, removal cooling, and rapid cooling.
<5> A single crystal produced by the apparatus or method of <1> to <4> above.

  According to the present invention, in a single crystal manufacturing apparatus, a heat insulating material structure suitable for conflicting growth and a heat insulating material structure suitable for cooling are realized in a continuous growth process, and the temperature of the crack is controlled. This has the effect of preventing generation and improving productivity.

  The movable refractory above the refractory is retracted during crystal growth. At the time when crystal growth is completed and the crystal is separated from the raw material melt, the movable refractory is moved to the upper part of the fixed heat insulating part, restricting the inflow and outflow of gas near the upper part of the fixed heat insulating part, and blocking the inflow of low-temperature airflow from the outside. Blocks outflow of hot airflow from the inside. Furthermore, heat radiation from the crystal is suppressed and the inside of the refractory is heated. However, when the state is almost closed, the crystal or crucible having a high temperature exceeds the melting point, so that the output of the high-frequency power source is lowered. Alternatively, the moving amount of the movable refractory can be adjusted to prevent the melting of the crystal or the crucible from exceeding the melting point.

Embodiments of the present invention will be described below with reference to FIGS. 1, 2, 3, and 4. FIG.
FIG. 1 is a sectional view of an embodiment to which the present invention is applied. The conductive crucible 1 is surrounded by a refractory 6 such as zirconia. A high frequency coil 10 is wound around the outside of the refractory 6. A high frequency power source 11 is connected to the high frequency coil 10. In the crucible 1, there is a liquid in which the raw material 2 is melted, and the seed crystal 4 is pulled up while being rotated by the holder 5 to generate a crystal 3.

  At the time of crystal growth, the movable refractory 8 is retracted outside or above the fixed refractory 7, and heat is dissipated from above the fixed refractory 7 to promote crystal growth. When the output of the high-frequency power source 11 is cooled as indicated by A in FIG. 2 in a state where the fixed refractory 7 is wide open, the shoulder temperature of the crystal 3 changes as indicated by C in FIG. On the other hand, as shown in FIG. 1, when the upper part of the fixed refractory 7 is closed with the movable refractory 8 simultaneously with the start of cooling, the shoulder temperature of the crystal 3 is increased as shown in FIG. At this time, the crystal 3 or the crucible 1 may partially or completely exceed the melting point and melt.

  Therefore, when the cooling refractory 8 is closed with the movable refractory 8 at the same time as cooling is started as shown in FIG. 1 and the output of the high-frequency power source 11 is changed stepwise as shown in FIG. The shoulder temperature of FIG. 3 shows a temperature change equivalent to the standard state as shown in FIG. At this time, since the movable refractory 8 closes the upper part of the fixed refractory 7, the surrounding cold gas inflow is blocked, and the outflow of hot gas inside the refractory is blocked. Further, the temperature is prevented from being lowered by heat radiation from the crystal 3, and in particular, the shoulder of the crystal 3 is heated to prevent the occurrence of cracks.

  Further, in the process of decreasing the output of the high frequency power supply 11 linearly, the movable refractory 8 is closed as necessary so that the crystal temperature does not exceed the melting point based on the measurement value of the radiation thermometer 12. As a result, the entire crystal is soaked and cracks are prevented from occurring.

  Further, in the process of decreasing the output of the high-frequency power source 11 linearly, the movable refractory 8 is closed by a predetermined amount based on experimental values so that the crystal temperature does not exceed the melting point. The whole is soaked to prevent cracks.

  FIG. 4 shows another embodiment. In order to prevent cracks generated in the process of cooling the crystal 3, the rate of decrease in the output of the high-frequency power supply 11 is reduced, and cooling is performed over a long time. According to experiments, there is a temperature region where cracks are likely to occur in the crystal, and if only this temperature interval is slowly cooled, the same effect can be obtained even if the rate of decrease in the high-frequency power output in other intervals is increased. Thereby, it becomes possible to obtain a crack-free crystal with a small electric power in a short time.

It is sectional drawing of the single crystal pulling apparatus of the Example of this invention. It is explanatory drawing 1 of the Example of this invention. It is explanatory drawing 2 of the Example of this invention. It is explanatory drawing 3 of the Example of this invention.

Explanation of symbols

1: crucible 2: raw material 3: crystal 4: seed crystal 5: holder 6: pedestal refractory 7: fixed refractory 8: movable lid refractory 9: furnace body 10: high frequency coil 11: high frequency power supply 12: radiation thermometer

Claims (5)

In the method of heating the melt in the crucible, bringing the seed crystal into contact with the melt and pulling it up to produce a single crystal, the upper opening of the refractory is automatically or manually opened and closed continuously. A single crystal manufacturing apparatus having a mechanism for adjusting, and a mechanism for simultaneously controlling an opening / closing amount of an opening and an output of a high-frequency power source. The single crystal manufacturing apparatus according to claim 1, wherein the single crystal manufacturing apparatus has a function of measuring a crystal temperature or a furnace temperature and simultaneously adjusting an opening / closing amount of an opening and an output of a high-frequency power source according to the measured temperature. 2. The method for producing a single crystal according to claim 1, wherein an appropriate opening / closing amount of the opening and an output of the high-frequency power source are obtained in advance by calculation or experiment, and the opening / closing amount of the opening and the output of the high-frequency power source are simultaneously adjusted automatically or manually. . The method for producing a single crystal according to claim 1, wherein the single crystal has a function of obtaining an effect of preventing cracking equivalent to long-time cooling in a short time by a combination of rapid cooling, cooling removal, and rapid cooling. The single crystal manufactured by the apparatus or method of Claims 1-4.

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