JPH0222039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a compound semiconductor crystal having a high decomposition pressure such as GaP, GaAs, or InP by controlling it into a predetermined shape and using a liquid capsule pulling method.

Compound semiconductor single crystal containing volatile substances
GaP single crystal is an important material as a substrate for visible light-emitting diodes, and is usually made under high pressure by the liquid encapsulation method (LEC method). In this method, the surface of a raw material melt of a compound is covered with an inert liquid such as B ₂ O ₃ , and then a single crystal is pulled while pressurizing the surface with an inert gas at a pressure higher than the decomposition pressure of the compound. Control of crystal diameter is also an important issue in the LEC method. Optical methods and gravimetric methods are commonly used as diameter control methods, and are applied to silicon and oxide single crystals. In addition to the LEC method, an X-ray method has also been proposed. However, with the LEC method, which uses a high-pressure container, the viewing window gradually becomes cloudy due to volatile substances, and the structure of the device makes it difficult to use the optical method or
The ray method is not suitable for industrial use because the equipment is not easy to install and handle, and the X-ray method has safety problems. On the other hand, the gravimetric method has fewer such problems and can be handled relatively easily. Bardsley et al.
czochralski growth of − compounds”
(Inst.Phys.Conf.Ser.No.24, 1975, P355) −
We have succeeded in controlling the diameter by gravimetric method by pulling single crystals of group compounds.

By the way, when pulling a single crystal, the thermal environment inside the crucible changes as the melt decreases, and in order to prevent it from adversely affecting crystal growth, it is necessary to raise the crucible from an appropriate point and at the same time reduce the crystal growth rate. A method has been used in which the pulling speed is also increased to keep it constant. This is often started at an appropriate point after the shoulder area has grown and the area has reached a constant diameter. For example, as shown in FIG. 1a, a crucible moving motor, which has been set in advance to a predetermined speed, is turned on, and then the pulling speed is increased as shown in FIG. 1b. However, the LEC method has a drawback in that the weight of the pulled crystal appears to fluctuate significantly at this time, as shown in Figure 1c. This affects automatic diameter control, and the temperature of the melt fluctuates greatly, resulting in a problem of deterioration of diameter control accuracy. Therefore, in order to perform more precise diameter control, it is necessary to eliminate this obstacle.

The present invention has been made in view of the above points,
The present invention provides a method for manufacturing compound semiconductor single crystals that eliminates the above drawbacks when manufacturing compound semiconductor single crystals by the LEC method, performs automatic diameter control smoothly, and manufactures compound semiconductor single crystals that are precisely controlled in a predetermined shape. be.

The outline of the present invention is as follows. The cause of the weight fluctuation of the pulled crystal is the liquid capsule.
This is thought to be due to the fact that B ₂ O ₃ has high viscosity even in its high-temperature molten state, and the entire pulled crystal is covered with _three layers of B ₂ O, so it is unable to follow the changes in crucible elevation and pulling speed and exerts force on the crystal. . Therefore, when the crucible rising speed and the pulling speed were slowly changed as shown in Figure 2 a and b, the weight fluctuation of the pulled crystal became sufficiently small as shown in Figure 2 c, and the diameter was automatically adjusted. It was found that this had no effect on control. The rise time was set in the range of several minutes to several tens of minutes, but at this time, the thermal environment during the crystal growth process changes more slowly, so it does not have a direct effect on the crystal growth. First, it was found that diameter accuracy could be improved by reducing weight fluctuations.

Therefore, in order to achieve the above object, the single crystal manufacturing method of the present invention is equipped with a crucible lifting speed and pulling speed control device, and when starting crucible lifting, the crucible lifting speed and pulling speed are synchronized and gradually set in advance. It is characterized by being able to change up to a certain value.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is an example of a GaP single crystal manufacturing apparatus equipped with the functions according to the present invention. In the figure, 1: GaP melt, 2: liquid capsule, 3: seed crystal, 4: GaP crystal, 5: crucible, 6: pulling shaft, 7: pulling motor, 8: pulling speed controller, 9: crucible raising axis ,
10: Crucible lifting motor, 11: Crucible lifting speed controller, 12: Program signal generator, 13: Distributor, 14: Weight detector, 15: Target weight setting device, 16: Diameter control device, 17: Heating device, 1
8: It is a heater. In crucible 5 with an inner diameter of 96mmφ
600g of GaP raw material 1 and liquid capsule (B ₂ O ₃ ) 2
After charging 180g, pressurize with nitrogen gas (~60
Kg/cm ² ) and melted. Next, the seed crystal 3 with the (100) orientation is brought into contact with the GaP melt 1, and the pulling rate is increased to 12
mm/h and then start pulling to the specified diameter of 52 mm/h.
The shoulder was grown to have a diameter of mmφ. Here, as shown in FIG. 1, the speed is set in advance to 3.5 mm/h by the crucible rising speed control device 11,
After shoulder development, the crucible begins to rise at t = t ₀ ,
At the same time, when the pulling speed was increased to 15.5 mm/h, the crystal weight varied from 0.5 to 1 gr/min.
When the diameter was controlled by the control system (14 to 18) as shown in Figure 3, the variation in the diameter of the crystal obtained was ±
It was 3mm.

On the other hand, as shown _in FIG.
Over t ₁ (t ₁ − _{t 0} = 15 minutes), the crucible lifting speed and pulling speed were synchronized and gradually increased, and when set to the final value, the crystal weight fluctuation was ~0.1gh/min.
It decreased to below. Then, when pulling was carried out in the same manner as before, the diameter variation of the obtained crystal was ±1 mm.
It became the following.

By the method explained above, diameter 52mmφ,
We were able to stably produce 500g of GaP single crystal. Furthermore, the method is not necessarily limited to the method of linearly increasing the speed as shown in the embodiments, but it is sufficient as long as it can substantially eliminate fluctuations in crystal weight that would be a hindrance to diameter control.

As described above, according to the present invention, in the LEC method,
It has the following effects.

(1) Extremely precise diameter control can be performed stably.

(2) Due to improved diameter accuracy, the yield of wafers from raw materials was improved by more than 10% compared to conventional methods.

(3) Productivity is improved by industrially applying the present invention.

Note that the method of the present invention can be applied to other single crystals to which the liquid capsule pulling method can be applied, such as GaAs, InP,
It can be similarly applied to GaSb etc.
The benefits are also great.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the operation of the conventional method, and FIG. 2 is a diagram for explaining the operation of the method of the present invention.
b and c indicate changes in the crucible lifting speed, pulling speed, and amount of change in crystal weight, respectively. FIG. 3 is a configuration diagram for explaining one embodiment of the present invention. 1: GaP melt, 2: liquid capsule, 3: seed crystal, 4: GaP crystal, 5: crucible, 6: pulling shaft,
7: Pulling motor, 8: Pulling speed controller,
9: Crucible lifting axis, 10: Crucible lifting motor,
11: Crucible rising speed controller, 12: Program signal generator, 13: Distributor, 14: Weight detector,
15: Target weight setting device, 16: Diameter control device, 1
7: heating device, 18: heater.

Claims (1)

[Claims] 1. When a seed crystal is brought into contact with the compound semiconductor raw material melt housed in a crucible via a B ₂ O ₃ liquid that is a liquid capsule and the seed crystal is pulled up to start crystal growth, the weight of the pulled crystal is In a method for producing a compound semiconductor single crystal in which pulling is performed while detecting The crucible is grown at a constant speed by synchronizing the rising speed and the pulling speed of the crucible from a preset point to the end of growth. A method for manufacturing compound semiconductor crystals.