JP2936694B2 - Single crystal growing method and high frequency work coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention guides a high-frequency current generated from a high-frequency power supply to a work coil, and heats and melts a single crystal material installed in the work coil by the high-frequency current. The present invention relates to a method for growing a single crystal by a so-called high-frequency heating method for performing single crystallization and a high-frequency work coil used for the method.

[Conventional technology]

When growing a single crystal by the high frequency heating method, there are two methods for controlling the temperature of the raw material melt. The first method is to attach a thermocouple to a crucible for accommodating a raw material, thereby controlling a high-frequency current and controlling the temperature of the raw material melt in the crucible, and is called a thermocouple control method. , The control accuracy can be kept high. The second method is intended for a case where there is no room for using a thermocouple without using a crucible such as a floating zone method when there is no suitable thermocouple even if a crucible is used. Since the current is directly controlled, it is called a current control method. However, since the temperature control is indirect, the control accuracy is low.

[Problems to be solved by the invention]

Unlike the thermocouple control method, the current control method does not control the temperature of the raw material melt itself, but simply controls the high-frequency current to stay at a predetermined value. Even if the temperature changes due to change, external conditions, etc., there is no ability to restore it.
For example, when growing a single crystal by the floating zone method using the current control method, even if the growth is started by adjusting all conditions at the first start, the surrounding temperature changes with time, When the temperature of the growing portion changes due to a change in the flow of heat inside the formed crystal or the like, the diameter of the crystal becomes correspondingly thicker or thinner. This poses a serious problem such as a change in crystal composition as well as a change in diameter.

When growing a crystal by the current control method which is usually performed, it was examined how much temperature change occurs when the high-frequency current is kept at a constant value. FIG. 2 shows the configuration of the experiment, in which a thermocouple 2 for temperature detection was inserted into a quartz ampule 1, and tellurium 3 was vacuum-sealed as a raw material for melting. The ampoule 1 thus prepared was suspended in a high-frequency coil 4 connected to a high-frequency power supply (not shown). Next, high-frequency power was supplied to the high-frequency coil 4 so that the temperature indicated by a thermometer (not shown) to which the thermocouple 2 was connected was 460 ° C., which exceeded the melting point of tellurium, 450 ° C. As a result, the raw material tellurium 3 around the thermocouple 2 was melted and turned into a melt 5. The high-frequency current at this time was 65 A, but the high-frequency current extracted from the shunt for current control was 3.50 mV according to the instruction of the controller. The temperature was recorded for 24 hours after the temperature reached 500 ° C.

As a result, it was found that the shunt high-frequency current was 3.50 mV ± 0 mV and hardly changed, and was completely controlled by the controller.

On the other hand, the temperature indication by the thermocouple 2 was 460 ° C. ± 4 ° C. This change in temperature is due to an external factor, and is considerably larger than the temperature fluctuation ± 0.5 ° C. normally allowed for single crystal growth.

An object of the present invention is to provide a single crystal growing method for performing temperature control with little temperature change particularly in a floating zone type crystal growing, and a high frequency work coil used in the single crystal growing method.

[Means for solving the problem]

In order to achieve the above object, a single crystal growing method according to the present invention includes a heating / melting step and a temperature controlling step, and performs single crystallization by high frequency heating using a high frequency work coil to which a high frequency current is applied. A method for growing a single crystal, wherein the high-frequency work coil has a pair of a heating work coil and a temperature control work coil, and the pair of work coils is supplied with a high-frequency current by the same high-frequency power supply. The heating / melting step is a step in which the single-crystal material is subjected to high-frequency heating with a heating work coil to which a high-frequency current is applied to form a single crystal, and the temperature control step is a temperature control step in which the high-frequency current is applied. In the work coil, the same reference material as the single crystal material is melted by high frequency heating and its melting point is detected with a thermocouple.
The value of the high-frequency current supplied to the heating work coil is adjusted based on the output of the thermocouple, and the temperature of the heating work coil is controlled.

In the high-frequency work coil according to the present invention,
A high-frequency work coil having a pair of a heating coil and a temperature control coil for heating a single crystal material at a high frequency. A high-frequency current is supplied to the pair of the heating coil and the temperature control coil by the same high-frequency power supply. The heating coil is disposed on the outer periphery of the crystal growth ampule, and heats the single crystal material in the crystal growth ampule from the outside with a high frequency. The crystal growth ampule includes a single crystal. The temperature control coil is arranged on the outer periphery of the temperature control ampule and heats the inside of the temperature control ampule from outside using a high frequency. A reference material of the same material is filled, and a thermocouple for detecting the temperature of the melting point of the reference material is incorporated.

[Action]

As shown in FIGS. 1 (a) and 1 (b), one heating coil 9 connected in series to a high-frequency power supply 12 has an outer periphery of a crystal growing ampoule 10 in which a single crystal material 8a is filled. The other temperature control coil 6 is disposed on the outer periphery of the temperature control ampule 7. The reference ampoule 7 is filled with a reference material 8b of the same material as the single crystal material 8a, and incorporates a thermocouple 2 for detecting the melting point of the reference material 8b.

In this state, a high-frequency current is supplied from the high-frequency power supply 12 to the coils 6 and 9 forming a pair, and the high-frequency current value is controlled by a temperature control method in which the thermocouple 2 controls the temperature of the reference material 8b. When there is no temperature change due to external factors, a constant current is supplied to the coils 6, 9 so that the melted reference material 8b, that is, the melt 11b is maintained at a predetermined temperature. If there is a temperature change due to an external factor, a current changed accordingly is supplied to the coils 6 and 9 based on the output of the thermocouple 2 in order to keep the heating temperature of the coils 6 and 9 constant. Since both coils 6, 9 are arranged close to each other, external influences are simultaneously and equally received. Therefore, the correction of the influence of the external factor is performed by the combination of the thermocouple 2 and the temperature control coil 6, and therefore, the current flowing through the heating coil 9 connected in series with the temperature control coil 6 is naturally affected by the external factor. In response to the influence, the temperature of the melt 11a of the crystal growth ampule 10 is controlled to a predetermined value, similarly to the melt 11b of the temperature control ampule 7.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1A is a plan view illustrating a high-frequency work coil according to the present invention, and FIG. 1B is a configuration diagram illustrating a state where single crystallization is performed using the high-frequency work coil according to the present invention. .

In the drawing, the high-frequency work coil according to the present invention has a pair of a heating coil 9 and a temperature control coil 6, and both coils 6 and 9 forming a pair are connected in series to a high-frequency power supply 12. It is.

The heating coil 9 is disposed on the outer periphery of the crystal growing ampule 10 filled with the single crystal material 8a, and heats the single crystal material 8a in the crystal growing ampule 10 from the outside by high frequency.

The temperature control coil 6 is disposed on the outer periphery of the temperature control ampule 7 and heats the inside of the ampule 7 from the outside with high frequency.

The temperature control ampule 7 is filled with a reference material 8b of the same material as the single crystal material 8a, and incorporates a thermocouple 2 for detecting the melting point of the reference material 8b.

In the present embodiment, the heating coil 9 and the temperature control coil 6 are formed by a copper pipe having a cross-sectional inner diameter of 6 mm and a cross-sectional outer diameter of 8 mm,
This was connected to the high frequency power supply 12. A temperature control ampule 7 into which the thermocouple 2 is inserted at the center is inserted into the temperature control coil 6.
A crystal growth ampoule 10 filled with the same compound material HgCdTe 8a was installed in the heating coil 9. In actual crystal growth, high-frequency power was applied so that the melt 11b maintained 500 ° C., and temperature was controlled by the thermocouple 2. After 10 days of floating zone crystal growth, the composition change in the length direction of the extracted crystal with a diameter of 15 mm and a length of 50 mm was examined. The composition deformation corresponds to a change in the temperature of the melt. As a result, the predetermined value of Cd composition
It was found that the variation was within the range of ± 0.5% against 22.0%. This value is sufficient for the device quality of HgCdTe. The temperature fluctuation during this crystal growth period
As a result of monitoring with thermocouple 2, it was recorded that the temperature was within the range of ± 1 ° C.

In this embodiment, the temperature control coil 6 and the heating coil 9 are connected in series when connected to the high-frequency power supply 12, but they may be connected in parallel.

〔The invention's effect〕

As described in detail above, according to the present invention, in the growth of a floating zone type crystal, which usually has to rely on current control having a large temperature variation because temperature control using a thermocouple cannot be performed, the temperature variation is small. Since the temperature can be controlled, a crystal having excellent composition uniformity can be grown.

[Brief description of the drawings]

1 (a) is a plan view showing a high-frequency work coil according to the present invention, and FIG. 1 (b) is a configuration diagram showing a state where single crystallization is performed using the high-frequency work coil according to the present invention. 2
The figure is a configuration diagram showing a state in which a temperature change is detected using a thermocouple while performing temperature control by a current control method. 2 thermocouple, 6 temperature control coil 7 temperature control ampule 8a single crystal material 8b reference material 9 heating coil 10 crystal growth ampule

Claims (2)

(57) [Claims] 1. A single crystal growing method comprising a heating / melting step and a temperature control step, wherein a single crystal is grown by high frequency heating using a high frequency work coil to which a high frequency current is applied. It has a pair of a heating work coil and a temperature control work coil, and the paired work coils are energized by a high-frequency current from the same high-frequency power supply. The single-crystal material is subjected to high-frequency heating by the heated heating work coil to be single-crystallized. The temperature control step is a temperature-controlling work coil to which high-frequency current is applied, and the same reference material as the single-crystal material Is melted by high-frequency heating, its melting point is detected by a thermocouple, and the value of the high-frequency current supplied to the heating work coil is adjusted based on the output of the thermocouple. A method for growing a single crystal, which comprises controlling the temperature of the single crystal. 2. A high-frequency work coil having a pair of a heating coil and a temperature control coil for high-frequency heating of a single crystal material, wherein the pair of the heating coil and the temperature control coil is the same high-frequency power supply. The heating coil is disposed on the outer periphery of the crystal growth ampule, and heats the single crystal material in the crystal growth ampule from the outside by high frequency. Is filled with a single crystal material.The temperature control coil is disposed on the outer periphery of the temperature control ampule, and heats the inside of the temperature control ampule with high frequency from the outside. A high-frequency work coil characterized by being filled with a reference material the same as the single crystal material and incorporating a thermocouple for detecting the temperature of the melting point of the reference material.