JPH01122995A - Growth of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To accomplish growth of the above single crystal in high quality and yield using the LEC process, by facing the upper end of the outer circumference of a graphite crucible and the inner circumference of a thermal insulating plate each other and carrying out pulling of single crystal. CONSTITUTION:An inner crucible 8 made of PBN is put in a graphite crucible 2, and a raw material for GaAs growth and a sealer are put in the inner crucible 8. Thence, a pressure vessel 1 is evacuated to vacuum followed by introducing Ar gas into said vessel 1 to effect pressurization. The crucibles are heated by a heater 4 to melt the raw material and sealer into raw melt 9 and liquid sealer 10 respectively, followed by allowing the pulling shaft to descend to bring a seed crystal into contact with the surface of the raw melt 9 and performing pulling growth of a GaAs single crystal 11 by a specified operation. This process will reduce variation in the diameter of the single crystal, enhance the single crystal yield and enable high-quality crystal growth in high reproducibility. This process can also be applied to the other group III to V compound semiconductors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for growing a compound semiconductor single crystal by a liquid-sealed pulling method.

[Conventional technology]

Compound semiconductors such as GaAS have a resistivity higher than that of Si semiconductors,
It has high electron mobility and light emission probability, and has been developed in recent years as an IC and light emitting device.

Among the methods for manufacturing such compound semiconductor single crystals, the liquid encapsulation pulling method (hereinafter abbreviated as LEC method) is often used as the most industrial production means.

This LEC method uses a pressure-resistant container (1
), the rotating shaft (3) is fixed to the bottom, and 5iOz
Alternatively, a cylindrical graphite crucible (2) with an inner crucible (8) made of PBN is provided, and a graphite crucible heating heater (4) is provided around the outer periphery of the side surface of the crucible (2), and above the heater. Using a device equipped with an annular heat insulating plate (7) that prevents thermal convection of the atmospheric gas due to the heat of the heater,
A raw material for growth is placed in an inner crucible (8) made of SiO2 or PAN, and the top thereof is covered with a sealant such as 8203.

Next, after evacuating the inside of the pressure container (1), an inert gas such as Ar is introduced and pressurized to about 5 to 100 K'J/cd.
A heating heater (4) melts the growth raw material and the sealant to form a melt raw material (9) and a liquid sealant (10), respectively. Thereafter, a seed crystal (6) of the desired single crystal is attached to the lower end of a pulling shaft (5) that penetrates from the upper surface of the pressure container (1) and can move up and down and freely rotate. )
The seed crystal (6) descends from above and penetrates the liquid sealant (10) layer to contact the melt raw material (9), and then the pulling shaft (5)
While rotating, the temperature of the solution, the pulling speed of the seed crystal (6), etc. are controlled to grow a crystal having the same crystal orientation as the seed crystal (6). Note that (12) in the figure is a peephole for observation.

[Problem that the invention seeks to solve]

In crystal growth using the LEC method as described above, thermal convection above the melt in the container is large due to the influence of pressure applied during crystal growth, and temperature fluctuations in the atmosphere become large.

This causes fluctuations in the solid phase growth rate at the growth interface, which tends to cause variations in crystal diameter or generation of foreign crystals due to non-uniformity at the interface, which has become a problem.

[Means for Solving the Problems] In view of this, and as a result of various studies, the present invention provides a method for growing single crystals with high quality and high yield by the LEC method, which eliminates the above-mentioned drawbacks using a simple method. It is.

That is, a graphite crucible with a rotating shaft on the bottom is provided in a pressure-resistant container, a heater for heating the graphite crucible is provided around the outer periphery of the side surface of the crucible, and an annular heat insulating plate is provided above the heater to heat the graphite crucible. In a method of melting a compound semiconductor and growing a single crystal by liquid-sealed pulling, the single crystal is pulled by aligning the upper end of the outer peripheral surface of a graphite crucible with the inner peripheral surface of a heat insulating plate. The length of the vertical overlap between the upper end of the outer circumferential surface of the graphite crucible and the inner circumferential surface of the heat insulating plate is 1, and the length of the vertical overlap between the upper end of the outer circumferential surface of the graphite crucible and the inner circumferential surface of the heat insulating plate is A good method is to pull a single crystal while satisfying the following equation (1), where d is the gap width with respect to the surface.

! ≧ 3d (1) [Function] This arrangement of the upper end of the outer peripheral surface of the graphite crucible and the inner peripheral surface of the heat insulating plate is caused by heating with a heater. This is to prevent the thermal convection of the atmospheric gas from directly affecting the space above the crucible and to improve the temperature stability of the atmosphere.

Furthermore, the reason why the relationship between the vertical overlapping length 1 of the opposing surfaces and the gap width d is defined as in equation (1) above is because the atmospheric gas heated by the heater passes over this gap. This is because it acts as a run-up section when flowing in the direction, and causes a rectifying effect on the upward flow, thereby increasing the effect of stabilizing the ambient temperature above the melt surface, which is necessary for crystal growth. On the other hand, if the dimension of 1 is O~3d, the flow of atmospheric gas from the above-mentioned opposed parts becomes turbulent, and the upper end of the outer circumferential surface of the graphite crucible and the inner circumferential surface of the heat insulating plate are placed opposite each other. This will reduce the temperature stabilizing effect caused by this.

(Example〕 An embodiment of the present invention will be explained with reference to FIG.

(1) is a pressure-resistant container, (2) is a cylindrical graphite crucible with a rotating shaft (3) fixed to the bottom, (4) is an 11-hole thermal heater installed around the side of the graphite crucible (2), and (5) is Ga at the bottom end
This is a vertically movable and rotatable pulling shaft to which an AS single crystal seed crystal (6) is attached, and an annular heat insulating plate (7) is provided above the heater (4). 7) and the graphite crucible (2) were configured as shown in FIG. In other words, the length (i) of the vertical overlap between the upper end of the outer circumferential surface of the graphite crucible (2) and the inner circumferential surface of the heat insulating plate (7) is calculated as follows:
2), the gap width between the outer circumferential surface and the inner circumferential surface of the heat insulating plate (7) was 4 times the gap width (d>), thus maintaining a relationship that satisfied the condition of equation (1).

In such a device, an inner crucible (8) of PBNUH is installed inside the graphite crucible (2), raw materials for GaAS growth and a sealant are put in, and after the inside of the pressure container (1) is evacuated, Ar gas is evacuated. was introduced and pressurized. Next, the crucible was heated with a heating heater (4), and the raw material and sealant inside were melted to form a melt raw material (9) and a liquid sealant (10), respectively. After that, the pulling shaft (5) was lowered, the seed crystal was brought into contact with the surface of the melt raw material (9), and a GaAS single crystal (11) was pulled and grown by a predetermined operation. Diameter fluctuations have been reduced, the single crystallization rate has been improved, and high-quality crystal growth with excellent reproducibility has become possible.

Although the above is an example for GaAS, the method of the present invention can also be applied to other Ⅰ-v group compound semiconductors.

(Effects of the Invention) As described above, according to the present invention, the variation in the diameter of the grown crystal can be significantly reduced through crystal growth using the LEC method, and single crystals can be grown with high yield and good reproducibility, resulting in remarkable industrial effects. It is.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged view of section A in FIG. 1, and FIG. 3 is a side sectional view showing a conventional example. 1......Pressure vessel 2...Cylindrical graphite crucible 3...Rotating shaft 4...Heating heater 5... ..... Pulling shaft 6 ..... Seed crystal 7 ..... Annular heat insulating plate 8 .....
...Inner crucible 9...Melt raw material 10...Liquid sealant 11...GaAS single crystal Fig. 1 Fig. 2

Claims (2)

[Claims] (1) A graphite crucible with a rotating shaft on the bottom is provided in a pressure-resistant container, a heater for heating the graphite crucible is provided around the outer periphery of the side surface of the crucible, and a heat insulating plate is provided in an annular shape above the heater. In a method of melting a compound semiconductor in a graphite crucible and growing a single crystal using a liquid-sealed pulling method, the single crystal is pulled by aligning the upper end of the outer peripheral surface of the graphite crucible with the inner peripheral surface of the heat insulating plate. A method for growing a compound semiconductor single crystal, characterized in that: (2) The length of the vertical overlap between the upper end of the outer circumferential surface of the graphite crucible and the inner circumferential surface of the heat insulating plate, and the length of the vertical overlap between the outer circumferential surface of the graphite crucible and the inner circumferential surface of the heat insulating plate. 2. The method for growing a compound semiconductor single crystal according to claim 1, wherein the single crystal is pulled while satisfying the following relationship, where d is the gap width. l≧3d