JPS5957992A - Manufacture of single crystal of semiconductor of compound - Google Patents

Abstract

PURPOSE:To obtain a high quality single crystal of a semiconductor of a compound, by placing a reflecting plte made of pyrolytic boron nitride over the opening of a crucible to inhibit the radiation of heat from the crucible and a heater and to grow a crystal at a gentle temp. gradient. CONSTITUTION:Starting materials for a crystal and starting materials for a liq. sealant are charged into a crucible 3, and the crucible 3 is put in a pressure vessel 1. An inert gas is introduced under pressure at 30-70 deg.C from an introducing pipe 9, and the crucible 3 is heated with a heater 2 to melt the starting materials in the crucible 3. A reflecting plate 12 made of pyrolytic boron nitride placed over the opening of the crucible 3 inhibits the radiation of heat from the crucible 3 and the heater 2, so the temp. gradient of a part close to the interface between the liq. sealant 7 and the melt 8 is regulated to <=70 deg.C/cm. This gentle temp. gradient is suitable for crystal growth.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a single-crystalline compound semiconductor of the 1-V group by a liquid-sealed pulling method.

Among the tiI-v group compound semiconductors, gallium arsenide (Ga
A3) has a large electron and electron mobility and is being widely used as a material for high-speed integrated circuits and opto-electronic devices.

In order for GaAs to be used as a crystal substrate for integrated circuits, it must have high insulating properties with a resistivity of 1070, and must have a uniform distribution with few defects in the crystal to ensure uniform device characteristics. , it is easy to manufacture large wafers, etc. A method for growing Gaps crystals that meets these requirements is the liquid confinement pulling method (LEC method).
is attracting attention.

The liquid sealing pulling method is known as a low pressure sealing pulling method and a high pressure sealing pulling method. The low-pressure sealed pulling method uses GaAII polycrystals produced by the boat growth method as a raw material, so the purity of the raw material is low and chromium needs to be added to make it semi-insulating, which is not preferable.

In addition, the high-pressure sealing pulling method, which involves direct synthesis, does not require the addition of chromium, but since the crystal is created under high pressure, the yield of single crystals is high, but the interface between the crystal material melt and the sealant is Because of the large humidity gradient, stress was generated within the formed crystals, which caused the occurrence of inversions, a type of crystal defect.

On this note, a proposal to lower the atmospheric pressure in the high-pressure container or lower the position of the crucible in the container in order to create a low temperature gradient when creating GaAs crystals: Although it was criticized, it is a high-quality crystal with fewer defects. It is difficult to set the temperature distribution and atmospheric pressure suitable for the production of GaAs crystals with good reproducibility. In particular, when lowering the atmospheric pressure in the high-pressure container for the purpose of creating a low humidity gradient, if the pressure is lowered too much, As in the melt will scatter, making it impossible to obtain high-quality crystals with a predetermined composition ratio.

The purpose of the present invention is to provide a method for producing high-quality compound semiconductor single crystals in which crystals are grown under a low temperature gradient without reducing the atmospheric pressure in a high-pressure container during the process of producing expanded semiconductor crystals. There is a particular thing.

Hereinafter, the present invention will be described and explained based on the attached drawings. A high-pressure vessel equipped with an inert gas inlet pipe and an exhaust pipe 10 has a crucible 3 made of quartz, boron nitride, etc. supported by a carbon material. A heater is installed around the crucible 3 to heat and maintain the crucible at a predetermined temperature, and an insulating wall is further provided around the heater. Prevents heat radiation from the heater to the outside. A pulling shaft 5 with a seed crystal attached to the lower end is provided at the upper part of the crucible, and during pulling up, the shaft is configured to rotate in the same manner as the support shaft 6 and to move up and down IJ.

In the single-crystal manufacturing apparatus configured as described above, a reflector plate made of Vyrolithic boron nitride is placed above the opening surface of the crucible.
2 will be provided. This reflector plate/2 has the function of preventing heat radiation from the crucible 3 and the heater heater, and also of reflecting the heat toward the crucible as necessary.

For this reason, the shape of the reflector should be such that it covers the opening of the crucible, and the end of the reflector should be of such a size that it extends above the insulation @ia, thereby preventing the heat from the heater from going outward. Divergence can be effectively suppressed. Specific shapes of the reflector include disc-shaped, conical-shaped, curved walls that intensively reflect toward the crucible, and bell-shaped.
Examples include a heater with a shape like this, and one that covers the sides of an insulating wall. These reflectors may be fixed to the pulling shaft S, or, as shown in FIG. During the raw material synthesis process, the pulling shaft 5 is raised to lift the reflecting plate upward, and during the crystal pulling process, the reflecting plate is lowered as the pulling shaft descends to cover the opening surface of the crucible. A structure may be adopted in which crystal growth is performed in this manner.

In the single crystal manufacturing apparatus configured as described above, the crystal material raw material and the liquid sealant raw material are placed in the crucible 3, placed inside the high pressure container 1, and an inert gas is pressurized into the crucible 3. The temperature is IO ~ 70 atm, and the crucible is heated to a temperature higher than the melting temperature of the raw material.
1 and the sealant are melted. At this time, the crystal material melt g
The humidity gradient near the interface between the liquid sealant 7 and the liquid sealant 7 is more than 100 tym or stiff when there is no reflector, but
Providing a reflective plate does not only suppress the dissipation of heat from within the crucible or from the heater, but also reflects the heat toward the crucible, reducing the temperature near the interface between the liquid sealant and the melt. The Sf gradient should be below 70 c/o, resulting in a humidity gradient suitable for crystal growth.

In this way, when the crystal material raw material and the sealing II/agent raw material in the crucible are completely melted, the packed crystal // is brought into contact with the molten liquid g under a low humidity gradient, and a single crystal is manufactured by rotation and pulling operations. .

At this time, the inside of the high-pressure container may be kept in a high-pressure state, so that volatilization of the component elements from the crystal surface is suppressed, and a high-quality compound semiconductor heavy crystal can be obtained.

Target of the production method of this invention [1-V expansion
゛G (2As, GaP, In
Examples include P, InAl+, etc., and since the reflector is made of pyrolytic boron nitride, there is no elution of impurities, and an undoped (undoped) half-unilateral single crystal is obtained.

This light 1! As is clear from the above explanation, in the high-pressure liquid confinement pulling method using IJ, the crystals were grown under a high humidity gradient, so the resulting crystals had many dislocations, and the distribution within the crystals was uneven. Although it is easy to achieve uniform growth, in this invention, a reflective plate is provided to raise the temperature of the liquid sealant, and the crystal growth operation is performed by lowering the temperature gradient near the interface between the sealant and the crystal raw material melt. There is little volatilization of the component purple from the surface of the formed crystal, and a high quality ■-■ group compound semiconductor single crystal can be obtained with good reproducibility.

Next, the present invention will be specifically explained using a practical example.

Using a sheep crystal production apparatus having the structure shown in FIG. 2, 5001 parts of Ga and As were put into a crucible, and then 1601 parts of B206 was put therein as a sealant. This crucible is placed in a high-pressure container, the reflector is raised to the top, argon gas is pressurized to create a pressure of approximately 50 atmospheres, and a heater is used to heat the crucible to approximately 1,300 tons.
It was heated to 11'. As a result of the above heating, a B2O3 melt was formed in the upper layer and a GaAl melt was formed in the lower layer in the P crucible. At this time, the temperature gradient at the interface between the liquid sealant and the G(IA 11 melt) was approximately 1 [15 tT/eel.

Once the raw materials have been combined in this way, the humidity can be adjusted to 1238G.
The pressure was lowered to 10 atm, and then the pulling shaft was lowered, the reflector was set above the crucible open position, and the seed crystal was brought into contact with the GaAs+ melt.
pulled up at the speed of time. During this pulling operation, the seed crystal is moved clockwise 5 times for 1 minute, and the crucible is moved counterclockwise for 1 minute.
It was rotated at a rate of tJJ 20 times. During the crystal pulling operation, the reflector plate covered the opening of the crucible. Therefore, the temperature gradient at the interface was about 50C.

As a result of continuing the above crystal growth operation for about 8 hours, a cylindrical GaAs single crystal having a diameter of about 50 fins and a length of about 1001.1 mm and about 960 ff was obtained. The middle part of this cylindrical GαAs crystal was cut out and the dislocation density distribution in the radial direction was measured. As shown in P1, the center of the crystal was wide <1
It was a high quality GaAs single crystal with a specific resistance of 107Ω·(Mk or more).

[Brief explanation of drawings]

FIG. 201 is a schematic sectional view showing an example of a single crystal manufacturing apparatus for carrying out the present invention, FIG. 2 is a schematic sectional view of the main part,
FIG. 6 is a dislocation density distribution diagram of a single crystal obtained by the method of the present invention. In the figure, / is a high-pressure container, C is a heater/3-keel crucible, S is a pulling axis, 7 is a liquid sealing agent, gll-i crystal raw material melt, // is a seed crystal, and 7.2 is a foul Gi shows. Patent 1 Junnin Director of the Agency of Industrial Science and Technology 46

Claims (1)

[Claims] (1) t+ of Ill-V group compound semiconductor single crystal by liquid seal 11-pulling method! In the method, a reflective plate made of Bairolitech boron nitride is installed at the opening of the crucible [111] to suppress heat radiation from the crucible and heat from the heater, and to prevent the liquid sealant and crystal raw material in the crucible from dissipating. A method for producing a compound semiconductor single crystal, characterized in that crystal growth is performed near the interface with a melt under a low temperature gradient. (The method for manufacturing a compound semiconductor single crystal according to claim 1, wherein the 2+111-V group compound semiconductor single crystal is an additive-free semi-insulating gallium arsenide ready crystal.