JPH08198699A - Method for growing single crystal and apparatus for producing single crystal - Google Patents

Abstract

PURPOSE: To obtain a single crystal which is small in transition density in the crystal and is long-sized by controlling the height of a heat retaining cylinder under specific conditions at the time of growing the single crystal by an LEC method. CONSTITUTION: The height of the heat retaining cylinder is adjusted in the following manner in the growth of the single crystal by the LEC method. Namely, the top end of the inside wall of the heat retaining cylinder 3 is so set as to be made higher than the conical plane (shown by a dotted line) regulated by the solid-liquid boundary between the raw material melt 5 in a crucible and a pulled up crystal and the top end of the crucible 10 at the time of starting the growth of the straight cylindrical part of the crystal 4 and to be made lower than the conical plane regulated by the solid-liquid boundary between the raw material melt in the crucible and the pulled up crystal and the top end of the crucible at the time of ending the growth of the straight cylindrical part of the crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal growth method and a single crystal manufacturing apparatus, and more particularly to a liquid sealed Czochralski (LE).
The present invention relates to a method and a manufacturing apparatus for manufacturing a compound semiconductor single crystal by the method C).

[0002]

2. Description of the Related Art As a method for producing a single crystal of a III-V group compound semiconductor such as GaAs or InP, a crucible containing a raw material and a sealant is heated to bring a seed crystal into contact with the surface of the raw material melt. A liquid-encapsulated Czochralski (LEC) method is known in which a single crystal is grown by gradually pulling it while rotating it.

In the growth of a single crystal in the liquid-encapsulated Czochralski (LEC) method, in order to suppress the occurrence of crystal defects such as single crystallization, twinning, and dislocation, and to stably form the single crystal, the pull-up method is used. The temperature gradient at the solid-liquid interface between the crystal and the raw material melt and its shape are important parameters. The solid-liquid interface shape between the pulled crystal and the raw material melt must be convex downward, and if the solid-liquid interface is convex upward upward, polycrystal formation does not occur. Cause. Further, if the temperature gradient in the pulled crystal is too large, the dislocation density in the crystal becomes large, and if the temperature gradient near the solid-liquid interface of the crystal is too small, decomposition of the pulled crystal surface in compound semiconductors such as GaAs and InP and The solid-liquid interface shape easily deteriorates.

[0004]

When trying to elongate a single crystal in the LEC method, the temperature distribution inside the furnace, the crystal and the melt becomes complicated, and it becomes very difficult to control these parameters, so that a high quality is obtained. There is a problem that a long single crystal cannot be obtained. Therefore, the present invention has been made to solve the above problems, the dislocation density in the crystal is small by the LEC method, and a single crystal growth method and a single crystal suitable for producing a long single crystal To provide a manufacturing apparatus.

[0005]

MEANS FOR SOLVING THE PROBLEMS AND ACTIONS The present inventors have studied by paying attention to the height of the heat insulating cylinder in order to achieve the above object. In order to satisfy the heat retention capacity of the single crystal production equipment and to maintain a good downward convex convex crystal and the solid-liquid interface shape of the raw material melt without the temperature gradient in the crystal becoming too large, the height of the heat retention cylinder is required. However, on the other hand, in order to keep the temperature gradient in the crystal not too small and to maintain a good solid-liquid interface shape between the pulling crystal and the raw material melt, the vicinity of the growth interface of the crystal and the inner wall of the high-pressure vessel It is necessary to prevent the heat insulation tube from interfering with the radiant heat transfer between the two. As a result, the heat-retaining capacity of the single crystal production apparatus is satisfied, and the temperature gradient in the crystal does not become too large. Found the height.

That is, according to the present invention, a crucible containing a raw material and a sealant is installed in a high-pressure container, and the raw material and the sealant are heated by a heater surrounded by a heat insulating cylinder in the high-pressure container. To grow a single crystal by gradually pulling it while contacting and rotating a seed crystal on the surface of the raw material melt, the upper end of the inner wall of the heat-retaining cylinder, at the start of crystal straight body portion growth. Is higher than the conical surface defined by the solid-liquid boundary between the raw material melt in the crucible and the pulled crystal, and the conical surface defined by the upper end of the crucible. A single crystal growth method characterized in that it is lower than a conical surface defined by a liquid boundary and an upper end of the crucible, and a crucible for containing a raw material melt and a sealant, and a lower portion for supporting the crucible. Axis and above A heater provided around the heater, an upper shaft having a seed crystal attached to a lower end thereof for pulling a single crystal out of the melt and capable of rotating up and down, and a heat-retaining tube arranged around the heater. In the crystal manufacturing apparatus, the height of the outer wall of the heat insulating cylinder is higher than the height of the inner wall of the heat insulating cylinder. Furthermore, in the single crystal manufacturing apparatus, the upper end of the heat insulating cylinder is multi-staged.

[0007]

EXAMPLE FIG. 1 shows a schematic view of an apparatus for growing a single crystal by the LEC method. Since the inside of the pulling furnace in which the crucible 10 containing the raw material and the sealant is placed is pressurized to a high pressure such as 20 atm, the vessel 2 constituting the furnace should have a water-cooled high pressure jacket structure made of metal such as stainless steel. used. The container 2 is composed of a base portion 2A, a body portion 2B and a lid base portion 2C. Further, a heater 14 for melting the raw material and the sealant is provided inside the furnace, and the heater 14 allows the crucible 10 to be melted.
Is heated above the melting point of the grown crystal. On the other hand, since the container constituting the furnace must be protected from high temperatures, the heat insulating cylinder 3 is arranged around the heater 14 and cooling water is flown around the container. From above the crucible 10, a pulling shaft 7 having a seed crystal 6 at its lower end is rotatably and vertically movable. A displacement sensor 8 for detecting the amount of displacement of the pulling shaft and a weight sensor 9 such as a load cell used for controlling the diameter of the crystal are attached to the pulling shaft 7. Crucible 10 is a crucible shaft 11 that can rotate and move up and down.
The crucible shaft 11 is supported by a displacement sensor 12 for measuring the amount of displacement of the crucible shaft 11. The atmosphere inside the furnace can be controlled by the gas supply device 16, the gas exhaust device 17, and the pressure sensor 18.

First, a crucible 10 containing a raw material of a compound semiconductor single crystal and a sealant is set in a furnace, and the air in the furnace is exhausted by a vacuum pump (not shown in the figure), and then an inert gas is supplied to the furnace. It is introduced inside and pressure of several tens of atmosphere is applied. After that, power is supplied to the heater 14 to heat the crucible 10, and the sealing agent 13 in the crucible 13 is heated.
And melt the raw material. Then, the seed crystal is used as a raw material while controlling the electric power of the heater 14 so that the furnace temperature has a predetermined temperature distribution (a temperature environment in which the solid-liquid interface shape between the crystal and the melt is convex downward). The single crystal and the crucible to be formed are brought into contact with the melt 5 and the crucible is gradually pulled up while rotating in the opposite direction or the same direction.

The grown single crystal is a process in which the diameter of the single crystal is small and increases (crystal shoulder growth), and a process in which the diameter of the single crystal reaches a certain size and the crystal diameter is kept constant (crystal The straight body portion is grown), and finally the crystal diameter is reduced (the crystal tail portion is grown). The number of rotations of the crucible and the number of rotations of the crystal are controlled according to each stage. In the present invention, at the start of growing the crystal straight body after growing the crystal shoulder, as shown in FIG. 2 (a), the height of the inner wall of the heat insulating cylinder 3 is raised to form a solid-liquid boundary between the crystal 4 and the raw material melt 5. 10 is higher than the conical surface defined by the upper end, and at the end of growing the crystal straight body part, as shown in FIG. 2 (b), the height of the inner wall of the heat retaining tube 3 is increased to increase the crystal 4 and the raw material melt 5. The single crystal is grown so that it becomes lower than the conical surface defined by the solid-liquid boundary and the upper end of the crucible 10. If the height of the inner wall of the heat-retaining cylinder 3 is lower than the conical surface defined by the solid-liquid boundary between the pulled crystal 4 and the raw material melt 5 and the upper end of the crucible 10 at the start of growing the crystal straight body, The temperature gradient becomes excessive and the dislocation density increases. In addition, the heat retention is poor and the heater power becomes large. The height of the inner wall of the heat insulating cylinder 3 is set so that the crystal 4 pulled up at the end of the growth of the crystal straight body part
If it is higher than the conical surface defined by the solid-liquid boundary of the raw material melt 5 and the upper end of the crucible 10, the temperature gradient in the crystal becomes small,
The solid-liquid interface shape deteriorates. Further, the thermal decomposition of the grown single crystal becomes severe, which is not preferable. The pulled crystal 4 and the raw material melt 5
The conical surface defined by the solid-liquid boundary and the upper end of the crucible is
The pulled crystal 4, the raw material melt 5, and the sealant 13 as shown in FIG.
Is a conical surface defined by the line connecting the three points of the solid-liquid boundary and the upper end of the crucible.

The heat insulating cylinder is a cylinder made of graphite or graphite felt, and its upper end is horizontal (Fig. 3).
(c)). The upper end of the heat retaining cylinder may be horizontal, but if the slope is such that the outer wall is higher and the inner wall is lower, the heat retaining cylinder does not interfere with radiative heat transfer between the crystal growth interface and the inner wall of the high pressure vessel. Therefore, the heat retaining property of the heat retaining cylinder is maximized, which is preferable. This inclination is preferably linear as shown in FIG. 3 (a), but may be multi-stepped as shown in FIG. 3 (b) when processing costs are difficult.

A GaAs single crystal was grown using a single crystal manufacturing apparatus. 25 in a pBN crucible 10 with a diameter of 300 mm
2.5 kg of high-purity GaAs raw material and 2.5 kg of B ₂ O ₃ as the sealant 13 were set and set, and then the air in the furnace was evacuated by a vacuum pump (not shown in the figure), and the atmosphere was 20 atm of Ar gas. . Then, the crucible 10 is heated by supplying power to the heater 14 to melt the sealant 13 and the raw material in the crucible. Then, the seed crystal is melted while controlling the electric power of the heater 14 so that the furnace temperature has a predetermined temperature distribution (a temperature environment in which the solid-liquid interface shape between the crystal and the melt is convex downward). Contact the liquid,
The crystal pulling shaft 7 is rotated clockwise at 6 rpm, and the crucible shaft 11 is rotated counterclockwise at 20 rpm.
A GaAs single crystal with a diameter of 110 mm and a growth orientation of <100> was grown at a pulling rate of.

Crystals were grown under the condition that the height of the inner wall of the heat insulating cylinder was as follows. At the start of growing the crystal straight body part, it should be higher than the conical surface defined by the solid-liquid boundary and the upper end of the crucible, and at the end of growing the crystal straight body part, lower than the conical surface defined by the solid-liquid boundary and the upper end of the crucible. Yes (number of crystal growth times: 8 times). At the start of growing the crystal straight body, it should be higher than the conical surface defined by the solid-liquid boundary and the upper end of the crucible, and at the end of growing the crystal straight body, higher than the conical surface defined by the upper end of the crucible and the crucible. Yes (number of crystal growth: 5 times). Lower than the conical surface defined by the solid-liquid boundary and the upper end of the crucible at the start of the crystal straight body growth, and lower than the conical surface defined by the solid-liquid boundary and the upper end of the crucible at the end of the crystal straight body growth. Yes (number of crystal growth: 5 times). Here, at the start of growing the crystal straight body part, when the diameter of the single crystal becomes 110 mm in forming the shoulder part of the crystal, at the end of growing the crystal straight body part, the amount of the raw material melt decreases and the temperature is increased. At the start of growing the crystal tail (single crystal diameter; 110 mm).

As a result, under the condition of, all the obtained crystals were not polycrystallized, and the length of the straight body part was 350 to 450 mm.
A single crystal of was obtained. The dislocation densities of these crystals were measured and found to be 1 × 10 ^{4 to} 7 × 10 ⁴ / cm ² .
On the other hand, under the conditions of 1, all the obtained crystals decomposed violently, and polycrystals were generated, and the length of the single crystal part was 10
It was 0 to 150 mm. Furthermore, under the conditions of, a single crystal having a straight body length of 350 to 450 mm was obtained, but the dislocation density was 1 × 10 ⁵ to
It was higher than the condition of 2 × 10 ⁵ / cm ² .

As described above, the height of the inner wall of the heat retaining tube is set higher than the conical surface defined by the solid-liquid boundary and the upper end of the crucible at the start of growing the crystal straight body portion, and at the end of growing the crystal straight body portion. By growing the crystal under the condition that it is lower than the conical surface defined by the liquid boundary and the upper end of the crucible, it is possible to grow a long single crystal whose dislocation density is the same as before without crystal decomposition. Is possible.

Although the production of GaAs single crystal has been described in the above embodiments, the present invention is not limited to GaAs single crystal and is also applicable to the production of other compound semiconductor single crystals such as InP, InAs and GaSb. It is possible.

[0016]

As described above, the height of the heat-retaining cylinder of the single crystal manufacturing apparatus 1 is set higher than the conical surface defined by the solid-liquid boundary and the upper end of the crucible at the start of growing the crystal straight body, and At the end of growing the body, if the temperature is set to be lower than the conical surface defined by the solid-liquid boundary and the upper end of the crucible, the temperature gradient in the crystal will be an appropriate size and the solid-liquid interface shape will be ideally convex downward. A long single crystal having a dislocation density of less than 1 × 10 ⁵ / cm ² is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an example of an LEC method single crystal production apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a range of height of an inner wall of a heat insulating cylinder. (a) shows the start of growing the crystal straight body part, and (b) shows the end of growing the crystal straight body part.

3 (a) and 3 (b) are diagrams showing an example of the upper end of the heat insulating cylinder of the present invention, FIG. 3 (a) having a linearly inclined upper end, and FIG. It is shown that the upper end is inclined in multiple steps. (c) is the figure which showed the example of the upper end of the conventional heat insulation cylinder, and the upper end is horizontal.

FIG. 4 is a diagram showing a conical surface defined by a solid-liquid boundary between a pulled crystal 4 and a raw material melt 5 and an upper end of the crucible.

[Explanation of symbols]

 1; Single crystal manufacturing apparatus 2; Container 2A; Base part 2B; Body part 2C; Lid base part 3; Insulation part 4; Pulling crystal 5; Raw material melt 6; Seed crystal 7; Pulling axis 8; Displacement sensor 9; Weight sensor 10; crucible 11; crucible shaft 12; displacement sensor 13; sealant 14; heater 15; surveillance camera 16; gas supply device 17; gas exhaust device 18; pressure sensor 18

Claims (3)

[Claims] 1. A crucible containing a raw material and a sealant is placed in a high-pressure container, and the raw material and the sealant are melted by heating with a heater surrounded by a heat-retaining cylinder in the high-pressure container. In the method of growing a single crystal by gradually pulling this while contacting a seed crystal to the surface of the raw material melt and rotating it, the upper end of the inner wall of the heat retaining tube is
At the start of crystal straight body part growth, higher than the conical surface defined by the solid-liquid boundary between the raw material melt in the crucible and the pulled crystal, and the top of the crucible, and at the end of crystal straight body part growth, the crucible A single crystal growth method, characterized in that it is lower than the conical surface defined by the solid-liquid boundary between the internal raw material melt and the pulled crystal and the upper end of the crucible. 2. A crucible for containing a raw material melt and a sealant,
A lower shaft supporting the crucible, a heater arranged around the crucible, an upper shaft having a seed crystal attached to the lower end for pulling a single crystal from the melt and capable of rotating up and down, and a periphery of the heater 1. A single crystal manufacturing apparatus comprising: a heat insulating cylinder arranged in the heat insulating cylinder, wherein the height of the outer wall of the heat insulating cylinder is higher than the height of the inner wall of the heat insulating cylinder. 3. An apparatus for producing a single crystal, wherein an upper end of the heat insulating cylinder according to claim 2 has a multistage shape.