JPH07291781A - Method for growing single crystal - Google Patents

Abstract

PURPOSE:To improve the production yield of a single crystal by subjecting the seed crystal housing part of a crucible to specific constitution in single crystal growth by a perpendicular slow cooling method, thereby stably maintaining the shape of a solid-liquid boundary at a projecting state. CONSTITUTION:The following means are used in the method for growing the single crystal from a seed crystal by putting the seed crystal and raw materials for the single crystal into the crucible and gradually lowering temp. after once melting the raw materials for the single crystal: A heat sink 6 is mounted at the part of the crucible where the seed crystal 2 is housed and the spacing between this part where the seed crystal is housed and the heat sink 6 is filled with low melting metals (e.g.: Pb, Au, Ga, Sn, In, Al, etc.) 7.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a vertical gradual cooling method (VGF).
Method, Vertical Gradient Freezing), and more particularly to a method for growing a compound semiconductor single crystal.

[0002]

2. Description of the Related Art A vertical slow cooling method (VG) for growing a single crystal by solidifying a semiconductor melt in a crucible from the lower part to the upper part.
The F method) has attracted attention as a method for growing a III-V compound semiconductor single crystal because it can produce a single crystal with a relatively large diameter and low dislocation.

The growth of a III-V group compound semiconductor single crystal by the conventional VGF method will be described below by taking the VGF furnace shown in FIG. 1 as an example.

A seed crystal 2 is placed in a crucible 1 having a funnel-shaped bottom.
Then, the polycrystalline raw material is charged, supported by a boron nitride susceptor 3, and vacuum-sealed in a quartz ampoule 4. Then, this is placed in a furnace having a cylindrical heater 5, and power is supplied to the heater 5 to form a temperature gradient such that the upper part of the seed crystal 2 is above the melting point, and the temperature is gradually lowered to form a single crystal. It grows.

By the way, as a method for supporting the crucible, a susceptor for accommodating the entire bottom of the crucible is generally used. This type of susceptor has good thermal conductivity in order to form the heat flow in the crucible in the vertical direction.

However, in the above-mentioned susceptor, since the heat flow flows through the susceptor when the melt in the increased diameter portion of the crucible solidifies, the solid-liquid interface is likely to be concave with respect to the melt. If the solid-liquid interface becomes concave during crystal growth, dislocations are likely to accumulate in the central part of the crystal, and if they are densely integrated, the crystal becomes polycrystal from that position. In order to obtain a single crystal, it is desirable that the solid-liquid interface be flat or convex with respect to the melt. However, it was difficult to do so by the conventional growth method for the above reasons.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and improve the production yield of single crystals by maintaining the solid-liquid interface shape in a stable and convex state. is there.

[0008]

Means and Actions for Solving the Problems That is, according to the present invention, a seed crystal and a single crystal raw material are placed in a crucible, the single crystal raw material is once melted, and then the temperature is gradually lowered. In the method of growing a single crystal from the crystal side, a heat sink is attached to the seed crystal containing portion of the crucible, and the space between the seed crystal containing portion and the heat sink is filled with a low melting point metal. It provides a growth method.

The low melting point metal is Pb, Au, Ga, Sn, I.
It is intended to provide a single crystal growth method characterized by using an alloy of any one of n, Al, Ge, Cu, Ag, and Sc or two or more of them.

In the present invention, as shown in FIG. 2, a metal 7 having a low melting point is provided between the heat sink 6 and the seed crystal accommodating portion of the crucible.
Since it is filled with, there is no gap between the crucible and the heat sink, and heat can be efficiently transferred to the heat sink. Therefore, the heat flow as a whole goes toward the seed crystal side, and the solid-liquid interface becomes convex with respect to the melt.

[0011]

Example A GaAs single crystal was grown using a VGF apparatus filled with Ga between a seed crystal accommodating portion of a crucible and a heat sink made of graphite. The crucible used is p
Made of BN, diameter φ80 mm, total length 180 mm, and the charge amount of the raw material GaAs polycrystal is 1500 g. Set the crucible into which the raw material was placed in a quartz ampoule and set it to 1 x 10
^It was evacuated to ^-6 Torr and capped with a quartz cap. The ampoule was set in the furnace, a temperature gradient was formed in the furnace in the vertical direction, and the raw material was melted. Then, it was cooled at a growth rate of 2 mm / h with a temperature gradient of 5 ° C./cm.

As the grown crystal, a complete single crystal was obtained from the seed crystal over the entire length of 80 mm. Further, when this crystal was cut vertically and etched, and the solid-liquid interface shape was examined from the growth fringes, it was confirmed that the crystal had a convex shape with respect to the melt in all regions.

In the above embodiment, G is used as the low melting point metal.
Although a is used, it is not limited to this, but Pb, Au, Ga, Sn, In, Al, G
Any one of e, Cu, Ag, and Sc, or any two or more alloys can be used.

[0014]

According to the present invention, the solid-liquid interface shape can be constantly controlled to be convex with respect to the melt, so that crystal defects can be prevented from entering and a single crystal having excellent crystallinity can be obtained. Further, since it is possible to prevent polycrystallization caused by the accumulation of dislocations, it is possible to grow a single crystal with a high yield.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a conventional single crystal growth apparatus by a vertical slow cooling method.

FIG. 2 is a diagram showing an example of a single crystal growth method according to the present invention.

Claims (2)

[Claims] 1. A method for growing a single crystal from the seed crystal side by placing a seed crystal and a single crystal raw material in a crucible, melting the single crystal raw material once, and then gradually lowering the temperature. A single crystal growth method, characterized in that a heat sink is attached to a seed crystal housing portion of a crucible, and a space between the seed crystal housing portion and the heat sink is filled with a metal having a low melting point. 2. The low melting point metal is Pb, Au, Ga, Sn, In, A.
The single crystal growth method according to claim 1, wherein the single crystal growth method is an alloy of any one of l, Ge, Cu, Ag, and Sc or any two or more thereof.