JP2531875B2 - Method for producing compound semiconductor single crystal - 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 compound semiconductor single crystal by a liquid-sealed cairoporous method (hereinafter referred to as LEK method).

[0002]

2. Description of the Related Art Generally, GaP, GaAs, InP, C
III-V and II-VI group compound semiconductors such as dTe are
Because of the high vapor pressure near the melting point, B
_A single crystal is grown by a liquid sealing method in which it is covered with a liquid sealing agent layer made of ₂ O ₃ or the like. Currently, this liquid sealing method includes liquid sealing Czochralski method (LEC method) and L method.
The EK method and the like are known. The LEC method is a method in which the seed crystal is pulled up as the crystal grows. Since the crystal orientation can be controlled by seeding and a high-purity crystal can be easily obtained, it is industrialized, but the diameter control is difficult and uniform. It is difficult to obtain a straight body, and since the temperature gradient in the melt during crystal growth is large, the thermal stress is large and the dislocation density is large.

On the other hand, the LEK method is a method in which a seed crystal is brought into contact with a raw material melt covered with a sealant and rotated while the crystal is not pulled up, and crystal growth is performed in a refractory crucible. The diameter of the grown crystal depends on the inner diameter of the crucible. Therefore, it is easy to control the diameter, and the temperature gradient in the melt during crystal growth is several degrees centigrade / cm, which is an order of magnitude smaller than that of the LEC method. Therefore, thermal stress is low and dislocation density is low. Have

[0004]

However, in the conventional general LEK method, like the LEC method, all the raw materials in the crucible are melted before crystal growth. Therefore, it has been found that there is a problem that convection occurs in the raw material melt, temperature fluctuations increase, and polycrystals and twins are likely to occur. The present invention has been made in view of the above problems, and in the production of a compound semiconductor single crystal by the LEK method, it is possible to prevent the generation of polycrystals or twins and improve the single crystallization rate. It is an object of the present invention to provide a method for producing such a compound semiconductor single crystal.

As a technique similar to the method of the present invention,
In the LEK method, an invention has been proposed in which crystal growth is started in a state in which a part of the raw material melt is melted, and the melt zone of the raw material is moved downward as the crystal grows (Japanese Patent Application Laid-Open No. HEI 2). -243585). However, the invention of this prior application is aimed at homogenizing the impurity concentration in the crystal due to segregation of impurities, and is not essential to the present invention aimed at preventing the generation of polycrystals or twins due to temperature fluctuations in the melt. Are different.

[0006]

In order to achieve the above object, the present invention covers a raw material melt in a refractory crucible placed in a high-pressure vessel with a liquid sealant layer to form a seed crystal in the raw material melt. In a method for producing a compound semiconductor single crystal in which a single crystal is grown by immersion, a raw material melt zone is formed by melting only a part of the raw material, and the temperature is adjusted so that the thickness of the raw material melt zone is 40 mm or less. While controlling the above, the raw material melt zone is gradually moved downward from the interface side with the liquid sealant layer to grow a single crystal.

[0007]

According to the above means, the thickness of the raw material melt zone is 4
Since the temperature is controlled to be 0 mm or less, the convection in the raw material melt can be reduced and the temperature fluctuation can be suppressed to ± 1.0 ° C. or less, which improves the single crystallization rate. The above object can be achieved. Also, the crystal growth rate can be controlled by controlling the moving speed of the raw material melt zone. Furthermore, by controlling the temperature during the crystal growth so that the thickness of the raw material melt zone is 20 mm or less, the temperature fluctuation can be suppressed to ± 0.5 ° C. or less, which further increases the single crystallization rate. Can be improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a crystal growth apparatus used for carrying out the method of the present invention. That is, this crystal growth apparatus is configured such that a cylindrical heater 2 is provided in a closed type high pressure vessel 1.
a and 2b are provided, and a refractory crucible 3 is provided at the center of the heaters 2a and 2b. The crucible 3 is rotatably supported by a support shaft 4 fixed to the lower end of the crucible 3. And in this crucible 3, G
A raw material 5 such as aAs is contained, and B is placed on the raw material 5.
A sealant 6 such as ₂ O ₃ is placed.

On the other hand, from the upper side of the crucible 3, the high-pressure container 1
A crystal pulling shaft 7 is vertically rotatably and rotatably hung inside the crystal pulling shaft 7, and the crystal pulling shaft 7 can hold a seed crystal and bring it into contact with the surface of the raw material melt in the crucible 3. . Further, a gas introduction pipe 8 for introducing a high-pressure inert gas is connected to the upper side wall of the high-pressure container 1 so that the pressure inside the high-pressure container 1 can be set to a predetermined pressure. . Furthermore, in the crystal growth apparatus of this embodiment, the heater 2b is vertically movable.

First, 1.1 kg of InP polycrystal and B ₂ O ₃ having a thickness of 10 mm when melted are put into a crucible 3 made of quartz having an inner diameter of 60 mm, and a heater 2 b is used as a heater as shown in FIG. Heater 2 in a state in which it is positioned below and away from 2a.
a was heated to melt B ₂ O ₃ . Then heater 2
After heating b to melt the InP polycrystal to form the raw material melt 5, the heater 2b is moved upward as shown in FIG. 2 to eliminate the gap between the melt and the crucible and the raw material InP. Solidified the bottom of. At this time, an inert gas such as argon gas was introduced from the gas introduction pipe 8 to make the inside of the high-pressure vessel 1 an argon gas atmosphere of 50 atm.

Next, as shown in FIG. 3, the crystal pulling shaft 7
The seed crystal on the surface of the raw material melt 5 ′ by lowering the temperature of the raw material melt 5 ′, and after sufficiently blending it, the heater 2b is moved downward at a speed of 5 mm / hr while rotating the crucible 3 and the crystal pulling shaft 7. As shown in FIG. 4, crystals were grown while gradually moving the raw material melt zone 5 ′ downward while keeping its thickness substantially constant. At this time, the crystal pulling shaft 7 was rotated at 6 rpm, and the crucible 3 was rotated at 3 rpm. During the above crystal growth, the thickness of the raw material melt zone 5'is almost constant at 40 mm,
The temperature fluctuation in the melt was about ± 1 ° C. After the raw material melt has solidified to the bottom of the crucible, the growth of crystals is completed, the crystals 9 are pulled up from the crucible 3, and slowly cooled to about 1000 ° C. in the high-pressure vessel 1 at a rate of 5 ° C./hr. 500 ° C /
It was cooled to room temperature at a rate of hr. When the crystals thus obtained were taken out and examined, all the crystals were single crystals.

By the same method as above, during the crystal growth, the thickness of the raw material melt zone 5'is 70 mm, 60 mm and 50 m, respectively.
The experiment of repeating the crystal growth by moving the raw material melt zone 5 ′ downward while controlling the m, 35 mm, 30 mm, 20 mm, 15 mm and 10 mm to be constant was repeated. When the temperature fluctuation during the crystal growth was measured, the results shown in FIG. 5 were obtained.

From FIG. 5, in order to suppress the temperature fluctuation to ± 1.0 ° C. or less, the thickness of the raw material melt zone is 40 during the crystal growth.
It can be seen that the temperature should be controlled so that it is less than mm. In addition, in order to suppress the temperature fluctuation within ± 0.5 ° C,
It is understood that the temperature may be controlled so that the thickness of the raw material melt zone becomes 20 mm or less during the crystal growth. By the way,
When the temperature fluctuation is suppressed to ± 1.0 ° C. or less, the single crystallization rate becomes 60% or more, and when the temperature fluctuation is suppressed to ± 0.5 ° C. or less, the single crystallization rate becomes 90% or more.

In the above embodiment, the heater was controlled so as to keep the thickness of the raw material melt zone constant during crystal growth.
The thickness may vary as long as the thickness of the raw material melt zone is 40 mm or less. Further, if the crystal pulling axis is slightly pulled up in accordance with the increase in volume accompanying the crystal growth, the stress inside the crystal can be relaxed. Further, in the above-mentioned embodiment, the heater 2b is moved to move the raw material melt zone, but the heater is multi-divided and the power supply target is changed so that the heater is not moved and only the raw material melt zone is moved. It can also be moved. In the above embodiment, In
Although the growth of P single crystal has been described as an example, the present invention is not limited to this, and can be applied to general growth of GaAs single crystal and other single crystals by the LEK method.

[0015]

As described above, according to the method for producing a compound semiconductor single crystal of the present invention, the raw material melt in the refractory crucible placed in the high-pressure vessel is covered with the liquid sealant layer to melt the raw material. In a method for producing a compound semiconductor single crystal in which a seed crystal is immersed in a liquid to grow a single crystal, a raw material melt zone is formed by melting only a part of the raw material, and the raw material melt zone has a thickness of 40.
While the temperature was controlled so that the temperature became less than or equal to mm, the raw material melt zone was gradually moved downward from the interface side with the liquid sealant layer to grow the single crystal. The internal convection can be reduced, and the temperature fluctuation can be suppressed to ± 1.0 ° C. or less, which has the effect of improving the single crystallization rate. In addition, the growth rate of the crystal can be controlled by controlling the moving speed of the raw material melt zone, whereby the dislocation density and the like can be reduced and the quality of the crystal can be improved. Furthermore, during crystal growth,
By controlling the temperature so that the thickness of the raw material melt zone is 20 mm or less, the temperature fluctuation can be suppressed to ± 0.5 ° C. or less, which can further improve the single crystallization rate.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an example of a crystal growth apparatus used for carrying out the method of the present invention.

FIG. 2 is a front sectional view showing the state of the crystal growth apparatus immediately before the start of crystal growth (seeding) according to the method of the present invention.

FIG. 3 is a front sectional view showing the state of the crystal growth apparatus at the start of crystal growth according to the method of the present invention.

FIG. 4 is a front sectional view showing a state of a crystal growth apparatus during crystal growth according to the method of the present invention.

FIG. 5 is a graph showing the relationship between the thickness of the raw material melt zone and the temperature fluctuation when growing an InP single crystal by the method of the present invention.

[Explanation of symbols]

 1 High-pressure container 3 Crucible 5'Raw material melt zone 6 Liquid sealant 7 Crystal pulling shaft 9 Crystal

Claims (1)

(57) [Claims] 1. A compound semiconductor single crystal in which a raw material melt in a refractory crucible placed in a high-pressure vessel is covered with a liquid sealant layer and a seed crystal is immersed in the raw material melt to grow a single crystal. In the manufacturing method, a raw material melt zone formed by melting only a part of the raw material is formed, and the raw material melt zone is controlled by controlling the temperature so that the thickness of the raw material melt zone is 40 mm or less. A method for producing a compound semiconductor single crystal, characterized in that the single crystal is grown by gradually moving downward from the interface side with the layer.