KR20110095754A - The methed of poly crystal control for increasing large caliber gaas single crystal yield - Google Patents

Abstract

PURPOSE: A method for controlling polycrystal for increasing the yield of GaAs single crystal with a large diameter is provided to minimize the temperature gradient of a crystal growing crucible by controlling the rising speed of a crucible. CONSTITUTION: GaAs solutions and boron oxide are put in a quartz crucible. A graphite heater(107) heats the quartz crucible. A heat insulator(103) is mounted around the quartz crucible to insulate heat from the quartz crucible. The diameter of a GaAs single crystal ingot grown in the quartz crucible is controlled. A quartz crucible support stand(108) is connected to a motor shaft to raise the crucible.

Description

The methed of poly crystal control for increasing large caliber GaAs single crystal yield}

The present invention relates to a gallium-arsenic large-diameter single crystal growth process method, due to the rapid change of the ingot diameter in the growth process of gallium-arsenic single crystal ingot using a liquid encapsulation method, the ingot dislocation and polycrystallization occurs a lot. In addition, boron oxide, a liquid encapsulant, has poor heat transfer characteristics, which causes a severe temperature gradient of the boron oxide melt, which is a major cause of polycrystallization when the grown ingot passes therethrough.

 In general, dislocations generated during gallium-arsenic single crystal growth occur and move at high temperatures. When a gallium-arsenic single crystal is grown, a cell structure of dislocation near the solid-liquid interface where the crystal is grown is formed, which is related to the upward movement of dislocation. Also, at 900-1000, the temperature at which the crystal exits the liquid encapsulant, slip lines occur in the crystal. To reduce this potential, 1) low temperature gradient near the liquid-liquid interface 2) flattening of the liquid-liquid interface 3) precise control of the gallium-arsenic chemical composition ratio 4) four necking methods are effective, but the effects of thermal stress As the largest, single crystal growth has been tried to reduce this thermal stress by reducing the temperature gradient inside.

A method of growing a gallium-arsenic single crystal by the liquid encapsulation method. Boron oxide, a liquid encapsulation agent, exists as a free solid at room temperature, but softens when heated, and has a viscosity in the temperature range utilized as a liquid encapsulation agent of gallium-arsenic. Becomes a high liquid phase. The viscosity of boron oxide decreases with increasing temperature, and it varies greatly with the amount of water in boron oxide in addition to the temperature, and the viscosity increases with decreasing amount of moisture in boron oxide. Specific gravity also changes depending on the water content in boron oxide. For example, in the case of boron oxide having a moisture content of 260 ppm, its specific gravity varies from 1.648 to 1.509 g / cm ³ at 500 ° C to 1200 ° C. The thermal conductivity of boron oxide

      K (W / m / k) = 0.237 + 0.0011 T (K)

Since the furnace is smaller than the compound crystal and the melt, the temperature gradient therein becomes very large. Although it is well known that the temperature gradient in the pulling direction in boron oxide is introduced into the crystal and affects the dislocation density, the radial temperature distribution in boron oxide also greatly influences the temperature distribution on the surface of the melt, and the gallium-arsenic single crystal growth is not allowed. It is an important parameter that influences.

 In order to solve the above problems, when the gallium-arsenic ingot grown by the liquid encapsulation method penetrates the boron oxide molten liquid, which is a liquid encapsulation agent, the diameter change of the ingot in the solid-liquid interface is caused by the rapidly changing temperature gradient. In this case, the conventional process method is to prevent the change in the diameter of the growing ingot when the temperature of the inside of the crystal growth furnace arbitrarily generated by the heating element, the graphite heater inside the crystal growth furnace.

Temperature change inside the crystal growth furnace is caused by the graphite heater, which is a heating element, and the temperature gradient inside the crystal growth furnace is intensified. Therefore, by controlling the diameter change of the growing ingot at the crucible ascent rate instead of temperature, the inside of the crystal growth furnace is controlled. The temperature gradient can be minimized.

In the process method of the present invention, when the gallium-arsenic ingot in the liquid encapsulation method penetrates the boron oxide melt, which is a liquid encapsulant, the diameter change of the ingot is controlled at the crucible ascent rate instead of the temperature control inside the crystal growth furnace to obtain a solid-liquid interface. It is characterized by preventing the formation of dislocations and polycrystallization of the ingot by minimizing the thermal stress of the ingot by low temperature gradient in the vicinity.

1 is a schematic diagram inside a gallium-arsenic single crystal growth apparatus.
Figure 2 shows the temperature and quartz crucible rising rate during gallium-arsenic single crystal growth according to the prior art.
3 is a temperature and quartz crucible rising rate during the growth of gallium-arsenic single crystal according to the present invention.

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

In the gallium-arsenic single crystal growth apparatus in the liquid encapsulation method, when the gallium-arsenic ingot penetrates the boron oxide molten liquid which is a liquid encapsulation agent, the diameter change of the ingot in the solid-liquid interface is caused by a rapid temperature gradient. It aims to prevent the generation of dislocations and polycrystallization of ingots by minimizing the thermal stress of ingots by controlling them at the crucible ascent rate rather than the internal temperature change.

As an exemplary embodiment of the present invention, FIG. 1 shows a gallium-arsenic single crystal growth apparatus as a schematic diagram of a gallium-arsenic single crystal growth apparatus by the liquid encapsulation method. The graphite heater 107 is a heating element, a gallium-arsenic melt. It consists of a quartz crucible 102 containing the 106, a thermal insulation material 103 to insulate the quartz crucible, and a quartz crucible support 108 connected to the motor shaft for raising the crucible.

       When explaining the crystal growth sequence for the growth of gallium-arsenic single crystal ingot in the single crystal ingot growth apparatus as described above,

Clean the inner wall, the heating element, and the graphite part of the growth furnace before cleaning the single crystal. In addition, in order to remove the adsorbed moisture and the arsenic element which did not disappear at the time of cleaning, it is burned off by heating to a temperature higher than the crystal growth temperature in vacuum. A quartz crucible, raw materials and a liquid encapsulant are charged into the growth equipment, and the inside of the growth furnace is evacuated to fill inert gas. The raw material solution is made by melting the raw material by heating the heating element. The seed 101, which is a seed fastened to the impression shaft, is lowered to reach the raw material solution and then pulled up while rotating. At this time, the diameter of the ingot is gradually grown while lowering the temperature of the solution. The direction of the growing ingot is determined by the direction of the seed. Once the ingot diameter target is reached, the ingot is continued while the temperature of the solution is finely adjusted to maintain the desired diameter. When the length of the ingot reaches the desired value, the melt temperature is raised, and the ingot diameter is made small to separate from the solution. Ingots are separated and placed on top of the liquid encapsulant. Slowly lower the temperature of the graphite heater to room temperature so as not to give thermal shock to the ingot, then extract the inert gas in the equipment and separate the ingot to complete the growth.

In the above process, the body step of raising the ingot while finely controlling the temperature of the raw material melt to maintain the diameter of the crystal increases ingot growth while increasing the surface area of the ingot. As the ingot surface area increases, the heat dissipated from the ingot surface area increases, and as the ingot penetrates through the boron oxide, a liquid encapsulant, a severe thermal gradient occurs to change the diameter of the ingot grown.

In the above situation, in the conventional process method to prevent the change of the diameter of the ingot through the fine adjustment of the temperature inside the single crystal growth by using the graphite heater as a heating element to prevent the change of the diameter of the ingot to the severe temperature gradient inside the single crystal growth. As a result, thermal stresses of the growing ingot are generated, and dislocation generation and polycrystallization of the ingot occur. Therefore, in order to minimize the temperature gradient inside the single crystal growth, the temperature inside the crystal growth furnace is maintained by using a graphite heater, which is a heating element, from the time when the ingot penetrates boron oxide, and the crucible ascending speed is controlled to prevent the ingot diameter change. And by minimizing the temperature gradient inside the crystal growth furnace it is possible to prevent the generation of dislocations and polycrystallization of the ingot.

101: seed seed 106: gallium-arsenic melt
102: quartz crucible 107: graphite heater
103: heat insulating material 108: quartz crucible support
104: boron oxide melt
105: gallium-arsenic ingot

Claims (3)

A quartz crucible for containing a gallium arsenide melt and boron oxide as a liquid encapsulating agent for the gallium arsenide melt;
A graphite heater for heating the quartz crucible around an edge of the quartz crucible;
A thermal insulation material mounted around the quartz crucible for thermal insulation of the quartz crucible;
Process method for diameter control of gallium-arsenic single crystal ingot grown inside the quartz crucible The method of claim 1,
Process method for maintaining the temperature inside the crystal growth furnace to minimize the temperature gradient inside the crystal growth furnace at the time when the ingot growing boron oxide, a liquid encapsulation agent passes. The method of claim 1,
Process method of adjusting the crucible ascending speed to prevent the change of the diameter of the ingot when the ingot growing boron oxide, a liquid encapsulation agent passes.

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