JPH04160099A - Method for growing inp single ctystal - Google Patents

Abstract

PURPOSE:To inhibit the formation of a twin due to a facet at the shoulder of a crystal and to enhance the yield of single crystallization by adopting a specified method when an InP single crystal is grown by a flat top system with a liq. sealed pulling device. CONSTITUTION:When an InP single crystal of 2 in diameter is grown by a flat top system with a liq. sealed pulling device, polycrystalline InP as starting material is melted in a crucible, the tip of a seed is immersed in the resulting melt and crystal growth is started. A crystal is grown on the seed while controlling the dropping of temp. and the number of rotations of the crucible and the grown crystal is further grown in the transverse direction. At the time when the crystal attains to 30-40mm square, the rate of dropping of temp. is regulated to 0.13-0 deg.C/min and crystal growth in the transverse direction is stopped. After a meniscus appearing at the interface between the crystal and melt becomes stable, the crystal is pulled up at >=7mm/hr rate of pulling to obtain an InP single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for growing a compound semiconductor single crystal, particularly an InP single crystal growth method that is less likely to generate twins.

[Conventional technology]

Generally, InP single crystals are pulled by a liquid confinement pulling method (hereinafter referred to as LEC method)4.

InP single crystal has a small stacking fault energy and is a material that is very likely to generate twins.
When pulling P using an LEC device, we proposed that the generation of twins could be suppressed by flattening the upper end surface of the pulled crystal and pulling the crystal in a cylindrical shape. That is, it was proposed that it would be easy to obtain an InP single crystal by pulling the crystal with a flat top. In this method, after a seed is immersed in an InP melt, the temperature of the melt is stepped down by about 6 to 10 degrees Celsius, the crystal is grown in a square shape laterally to the seed, and the temperature drop rate is further reduced by 0.2 to 0. , 9° C./win, the temperature is lowered at a constant rate, the square crystal is further enlarged, and the crystal is pulled up when it reaches a predetermined diameter.

[Problem to be solved by the invention]

In growth using the flat top method, we have already mentioned that it is important to expand the crystal shape laterally into a square shape at the initial stage of growth. The shape of the shoulder, which is the main part of the body, was not clearly defined. However, if even a small amount of facet planes, which are stable growth planes for P or In, are exposed at the crystal shoulders, twins are likely to occur, and the single crystallization yield will be poor. Therefore, a method for controlling the shape of the crystal shoulder is an important issue for increasing the single crystallization yield.

[Means to solve the problem]

In view of this, and as a result of various studies, the present invention has developed an InP single crystal growth method that can suppress the generation of twins from the shoulder of the crystal and improve the single crystallization yield.

That is, in the present invention, when growing an InP single crystal with a diameter of 2 inches by a flat top method using the LEC method, the crystal at the initial stage of growth is grown in the lateral direction of the surface of the InP melt, and the crystal on the surface of the melt is grown. When the size reaches 30 to 40 mm square, the temperature drop rate of the melt is set to 0.13 to b to stop the lateral growth of the crystals, and the meniscus at the solid-liquid interface grows all around the melt surface. The single crystal is pulled up at a pulling speed of 7 mm/h+ or more at the point when the entire area becomes visible, thereby preventing facets from forming at the shoulders of the crystal.

[For production]

As described above, the present invention involves growing an InP single crystal with a diameter of 2 inches by a flat top method using an LEC device, by melting an InP poly raw material and immersing a seed tip in it.
After holding this state for 15 minutes, crystal growth begins. At this time, a crystal is grown as a seed by controlling the temperature drop and crucible rotation speed, and this crystal is grown laterally.

When the crystal size reaches 30 to 40 mm square, the temperature drop rate is set to 0.13 to b to stop crystal growth. When the lateral growth begins to stop, a meniscus (a concave shape due to interfacial tension at the interface between the melt and the crystal) appears at the interface between the crystal and the melt.

When this meniscus shape becomes stable, crystal pulling is started.

Therefore, the temperature drop rate when stopping the crystal diameter is 0.
The reason for having a width of 13° C. to 7 m1n is to increase the temperature drop rate when the melt temperature reaches a high level when the crystal diameter stops, thereby preventing the crystal diameter from becoming thinner after the start of pulling. Furthermore, when the melt temperature has settled down to a low level, the temperature drop rate is made smaller so that it approaches 0° C./min. When the meniscus shape is stabilized in this way, the crystal is pulled at a pulling speed of 7 mm/br or more, so that the pulled crystal becomes a single crystal without facets appearing at the shoulders.

〔Example〕

The present invention will be described below with reference to Examples.

InP single crystal growth was performed using the LEC apparatus shown in FIG. In the figure, (1) is a high pressure chamber, (2)
is the hot zone, (3) is the heater, (4) is the crucible, (
5) is the pulling shaft, (6) is the inert gas, (7) is the seed, (8) is B2O3, (91 is the InP poly raw material, (11)
is the crucible axis, (1υ is the thermocouple, (12) is the electrode,
Charged InP poly raw material - 1.2kg1B203
was 200 g, a 4-inch quartz crucible was used, and an InP seed with a (001) orientation was used. The heater is a wine cup heater, the inert gas introduced into the high pressure chamber is Ar or N2, and the gas pressure is 3.
It is 5 kg/cd.

First, the InP poly raw material (9) is melted (
The melt temperature is about 1070° C.), and after an InP melt is formed, the tip of the seed (7) is immersed in the melt and held in this state for about 15 minutes, after which crystal growth is started. Figure 2 shows how the temperature decreases and the crucible rotational speed changes over time. That is, first, the melt temperature is lowered by 8° C. (7 to 10° C. is suitable) to create supercooling, and then crystals are grown as seeds.

A temperature drop rate is applied so that the crystals grow in a square shape, and the crucible rotation speed is gradually increased. When the size of the crystals reached 30 to 40 degrees, the temperature drop rate was controlled to 0.13 to 0.05 mm to stop crystallization in the lateral direction on the melt surface. And at this time, the crucible rotation speed is -1
5 It was assumed to be constant at pm.

When the horizontal growth of the crystal on the surface of the melt begins to stop, the crystal (14) and the melt (13) start to stop as shown in Figure 3.
) A meniscus (4) appears at the interface (25 to 35 minutes after the melt temperature is lowered by 8°C).

8 mm/hr when the meniscus shape can be seen stably over the entire circumference of the crystal on the melt surface.
The pulling of the crystal was started at a speed of .

The crystal pulled in this manner had a flat top shape as shown in FIG. 4, had no facets on the shoulder (16), and had twin crystals (single crystal 64).

Note that when the degree of supercooling at the initial stage of growth is large (the step-down width of the temperature at the initial stage of growth is 15° to 10° C.), the temperature drop rate is kept at zero from the beginning and is raised when it becomes stable. On the other hand, if the degree of supercooling is small, it will be approximately 0.2℃/
It is preferable to give a temperature drop rate of min and pull the crystal at a pulling rate of about 1Own/h+.

Although the above explanation was made for a 1nP single crystal, this method
It can be applied to single crystal growth of strongly anisotropic semiconductors such as rb and InSb.

〔Effect of the invention〕

One of the biggest problems in single crystallization using the flat top method is to suppress the generation of twins at the shoulder, but according to the present invention, the generation of facets at the shoulder can be suppressed, and twin crystals can be prevented. This has the remarkable effect of significantly improving the yield of InP single crystallization.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the LEC device used in the embodiment of the present invention,
Figure 2 is an explanatory diagram showing how to lower the melting temperature at the start of crystal growth according to the present invention and changes in crucible rotation over time. Figure 3 shows the meniscus that appears at the solid-liquid interface when the crystal diameter is stabilized according to the present invention. The perspective view and FIG. 4 are side views showing the vicinity of the shoulder when the crystal is pulled up with a flat top according to the present invention. 1... High pressure chamber 2... Hot zone 3.
... Heater 4 ... Crucible 5 ... Pulling shaft 6 ... Inert gas 7 ... Seed
8...B2039...InP poly raw material 1
G... Crucible axis 11... Thermocouple 12.
... Electrode 13 ... Melt 14 ... Crystal 15 ... Meniscus 16 ... Shoulder part Figure 1 Weight detection

Claims (1)

[Claims] When growing an InP single crystal with a diameter of 2 inches using the flat top method using the liquid-sealed pulling method, the crystal at the initial stage of growth is grown in the lateral direction of the InP melt surface, and the crystal size on the melt surface is When the area reaches 30 to 40 mm square, the temperature drop rate of the melt is reduced to 0.13 to 0°C/min.
When the lateral growth of the crystal is stopped and the meniscus at the solid-liquid interface becomes visible over the entire circumference of the melt surface, the crystal is pulled at a pulling speed of 7 mm/hr or more. A method for growing an InP single crystal, which is characterized in that the single crystal is pulled up without facets at the shoulders of the crystal.