JPS6131059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a compound semiconductor single crystal. FIG. 1 shows a conventionally commonly used manufacturing method. That is, a round horizontal quartz boat 2 is arranged in a round reaction vessel 1, and a melt of a compound semiconductor such as GaAs is contained in the horizontal quartz boat 2 to produce a single crystal.

However, when a round quartz boat as shown in FIG. 1 is used, there is a lot of waste when the single crystal is cut out as a wafer, resulting in a low utilization rate of the single crystal.

Therefore, it has been proposed to use a square quartz boat as shown in FIG. It is true that if a quartz boat is made into a square shape and a square single crystal is obtained,
When used as wafers, the utilization rate is high, but in reality there are difficult problems. In other words, the melting point of compound semiconductors is quite high; for example, GaAs is 1238°C, and in order to obtain this melt, it is necessary to raise the temperature to 1238°C or higher. In addition, the reaction vessel must be economical and have a structure that can withstand internal pressure.
The inner surface must necessarily be circular.

Furthermore, the horizontal quartz boat 2 softens at about 1200° C., and as a result, the quartz boat 2 sags and deforms as if leaning against the inner wall of the reaction vessel 1 during the manufacturing process.

This phenomenon was also observed in the case of Figure 1, but it was not enough to warrant special attention, but in the case of the square boat shown in Figure 2, the deformation was so significant that it could be considered fatal. Ta.

There is also a plan to consider new materials, dimensions, shapes, etc. for boats that do not deform, but even round boats are disposable after one or at most 10 single crystal productions, so there is no need for these. Comparatively speaking, very expensive boats may have somewhat good characteristics but are not practical.

On the other hand, there has been a demand for larger single crystal wafers in recent years, and it would be a great achievement if large single crystal production using a square boat could be realized.

In view of this situation, the present invention aims to provide a method for manufacturing a compound semiconductor single crystal in which the prismatic quartz boat is not deformed during the manufacturing process.

The configuration of the present invention will be specifically explained with reference to FIG. 3 showing one embodiment.

In FIG. 3, reference numeral 1 denotes a round reaction vessel, within which a rectangular horizontal quartz boat 2 is arranged, and within the horizontal quartz boat 2 a compound semiconductor melt 3 is accommodated.

A heat insulating deformation prevention device 4 is provided between the inner wall of the reaction vessel 1 and the outer wall of the horizontal quartz boat 2.

It goes without saying that the structure of the deformation prevention device 4 should be matched to the size and shape of the boat being used.For example, for a square boat as shown in Fig. 2, it is necessary to adjust the structure of the deformation prevention device 4 to prevent the opening end of the boat from widening. In particular, deformation prevention means are provided on both sides of the boat, and deformation prevention means are also provided at the bottom of the boat to prevent the bottom wall from sagging.

In Figure 3, the sides and bottom of the boat are integrated to prevent deformation of both sides.

Quartz is the most convenient material for reasons such as heat resistance, purity, and chemical stability, but other materials satisfying the above characteristics, such as graphite, boron nitride, alumina, etc., may also be used.

However, it is desirable that the thermal conductivity is 10 ^-2 cal/cm・deg・sec or less, and 10 ^-1 cal/cm・deg・sec.
Good conductors of heat of sec or more must be avoided. This is because if there is a large difference in thermal conductivity between the upper part and the lower part (side) of the compound semiconductor melt, it will have a negative effect on the properties of the obtained single crystal, and the deformation prevention tool 4 has a heat insulating property. This is necessary to ensure the properties of the single crystal.

The present invention will be explained in detail below using experimental examples.

[Experiment example] The crystal growth furnace accommodates a horizontal quartz boat, and a high-temperature furnace and a GaAs melt are produced in the boat.
A two-temperature zone system consisting of a low-temperature furnace to control the As pressure was used. The horizontal quartz boat has a rectangular cross section as shown in Figure 3, and the width of the opening end is 60 mm.
mm, depth 30mm, total length 280mm, and the wall thickness is approximately equal throughout, 2mm. On the outer periphery of the boat, a quartz device was installed as a deformation prevention device whose inner wall shape was almost the same as the outer wall shape of the horizontal quartz boat and whose outer wall shape was almost the same as the inner wall shape of the reaction vessel. Both the quartz boat and the deformation prevention device were sandblasted to prevent thermal compression bonding between the quartz boat and the deformation prevention device.
A quartz boat having the shape described above, in which 800 g of Ga, 160 mg of Si as a dopant, and a seed crystal are installed at one end of the quartz reaction vessel, is placed in the deformation prevention tool of the boat described above. Put 880g of As into the other end, 5x
After evacuating to 10 ^-6 torr or less, it was sealed and placed in the electric furnace. The low temperature furnace is maintained at approximately 610°C, and the As pressure in the quartz reaction vessel is maintained at 1 atm. The high-temperature furnace performs the GaAs synthesis reaction at around 1200℃, and then further raises the temperature to adjust the temperature gradient in the growth axis direction of the seed crystal to 1238℃ to 0.5℃/cm, and then performs seeding to 1.7℃/cm. Cooling down at a rate of 20 hr
The whole thing solidified in time. Thereafter, it was cooled to room temperature at a rate of about 100°C/hr, and the crystals were taken out. As a result of the above, 1640 g of GaAs single crystal with a length of 280 mm was obtained. When I took out the boat after it had grown and looked at it, no deformation had occurred at all.

[Comparative example]

The electric furnace, boat shape, amount of raw materials installed, and growth conditions were the same as in the experimental example, and when GaAs crystal was grown without installing a boat deformation prevention device, the width of the boat opening widened by about 10 mm in one growth. The bottom wall of the boat sagged approximately 10 mm at the center of the boat's longitudinal direction.

The resulting crystal becomes polycrystalline from the middle,
The desired single crystal could not be obtained. Also, as a matter of course, it was impossible to use this boat a second time or later.

Although the present invention has been described so far only to prevent deformation of the part of the boat where the melt is located, it is also possible to use the deformation prevention device around the seed crystal stand, which has an outer bottom wall at a position higher than the bottom of the boat. It's not a hindrance.

As is clear from the above explanation, according to the manufacturing method of the present invention, deformation of horizontal quartz boats can be almost completely prevented, and even inexpensive thick-walled quartz boats can be used repeatedly. When the quartz boat is worn out due to a reaction or the like, it is only necessary to replace the quartz boat while leaving the deformation prevention device as is, which is extremely economical. In addition, it is now possible to use square quartz boats, which previously had problems with deformation.
This facilitates the production of large-sized single crystals.

Although the present invention is intended to put square quartz boats into practical use, boats with flat bottoms, although not square, have the same problems as conventional boats, and the present invention is effective against these. It is something.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a conventional compound semiconductor single crystal manufacturing method, and FIG. 3 is a cross-sectional view showing an embodiment of the present invention. 1...Reaction vessel, 2...Horizontal quartz boat, 3...
...Compound semiconductor melt, 4...Deformation prevention tool.

Claims (1)

[Scope of Claims] 1. A method for obtaining a single crystal from a compound semiconductor melt contained in a horizontal quartz boat by disposing a horizontal quartz boat in a reaction vessel having a circular cross section, wherein the quartz boat has a flat bottom surface. A boat is used, and a heat insulating deformation prevention device for preventing deformation of the quartz boat is provided between the inner wall of the reaction vessel and the outer wall of the quartz boat so as to be in contact with the entire surface of the outer wall of the quartz boat. A method for manufacturing compound semiconductor single crystals. 2. The method for manufacturing a compound semiconductor crystal according to item 1, wherein the cross-sectional shape of the inner wall of the horizontal quartz boat is approximately trapezoidal.