JPH0297483A - Apparatus for producing single crystal - Google Patents

Abstract

PURPOSE:To suppress the generation of crystal defects such as dislocation with a device for pulling up and growing a single crystal from a raw material melt on which a coracle is floated by dividedly forming the above-mentioned coracle to the upper part and to the lower part having the thermal conductivity higher than the thermal conductivity of this part. CONSTITUTION:The coracle 10 having >=1 communicating holes are floated on the part of the boundary between the raw material melt 7 and a liquid sealant 6 in a crucible 4 and the single crystal 3 is pulled up and grown from the melt 7 supplied into the coracle 10 through the above-mentioned communicating holes. The coracle 10 is divided and constituted to the lower part 10a which is held substantially immersed in the melt 7 and the upper part 10b which is positioned substantially above the melt 7. The material of the lower part 10a is formed of, for example, carbon having the thermal conductivity higher than the thermal conductivity of the upper part 10. The radiation of heat through the upper part 10b is suppressed in this way and the heating by the heat conduction through the wall surface of the coracle is mainly executed through the lower part 10a and, therefore, the heating is enhanced. As a result, the temp. gradient of the melt 7 in the coracle is optimized and the generation of crystal defects such as polycrystallization, twinning and dislocation is suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to m-v group compound semiconductors such as GaAs and InP, II-VI group compound semiconductors such as CdTe, Si
, Ge, etc., as well as LiNb0. .

The present invention relates to a manufacturing apparatus for pulling and growing a single crystal such as an oxide such as Bi125102g.

[Conventional technology] The diameter of a single crystal obtained by a pulling method is controlled to a constant value from the viewpoints of suppressing polycrystalization and twinning, suppressing the occurrence of crystal defects such as dislocations, and improving yield during wafer production. This is very important. Usually, the diameter of a single crystal is controlled by changing the rotational speed of the single crystal pulling shaft, the rotational speed of the crucible, the temperature of the raw material melt, the pulling speed of the single crystal, etc.

Furthermore, a method has been proposed in which the diameter of a single crystal is mechanically controlled by floating a coracle on the surface of the raw material melt and pulling the single crystal from the raw material melt inside the coracle. As the coracle, various shapes are used, such as a cylindrical shape, a disk shape, a cone shape, or a combination of these shapes.

FIG. 4 is a sectional view showing an example of a conventional single crystal manufacturing apparatus as disclosed in, for example, Japanese Patent Application Laid-Open No. 51-64482. The coracle 40 used in this conventional manufacturing apparatus has a vertical hole that slightly expands upward, and is floated above the raw material melt 37 in the crucible 34.

The single crystal 33 is pulled up from the vertical hole of this coracle 40 by the upper shaft 31. The coracle 40 is the raw material melt 3
7, the relative height of the solid-liquid interface and the coracle is always constant, resulting in a single crystal with a uniform diameter.

FIG. 5 is a cross-sectional view showing another example of a conventional single crystal manufacturing apparatus as disclosed in, for example, Japanese Patent Laid-Open No. 57-7897. The coracle 50 used in this manufacturing apparatus has a disk shape and has a circular hole in the center. A raw material melt 47 is placed in the crucible 44, and a liquid sealant 46 is provided above the raw material melt 1ff147.

The coracle 50 is floating between the liquid sealant 46 and the raw material melt 47. The single crystal 43 is pulled up from the central hole of the coracle 50 by the upper shaft 41 using the liquid-sealed Czochralski method. The diameter of the single crystal 43 to be pulled is determined by the diameter of the hole in the center of the coracle 50.

FIG. 6 is a cross-sectional view showing still another example of a conventional manufacturing apparatus as disclosed in, for example, Japanese Patent Laid-Open No. 62-288193. The coracle 60 used in this manufacturing apparatus has an inverted conical shape at the lower part, and by pushing down the raw material melt 57 in the crucible 54, the raw material melt is transferred into the coracle 60. There is. coracle 60
A single crystal is produced by pulling up the seed crystal 52 attached to the upper shaft 51 while holding the surface of the raw material melt in the crucible 54 so that it is located at least 8 mm or more lower than the surface of the raw material melt 57 in the crucible 54. 53 is pulled up for crystal growth.

In this manufacturing equipment, the coracle 60 is melted as a raw material (k, 57
By pushing the single crystal 53 down, it keeps the temperature of the single crystal 53 to be pulled, prevents the coracle 60 from sticking to the single crystal 53 due to an increase in the temperature of the outer peripheral surface of the raw material melt inside the coracle 60, and prevents the generation of growth nuclei from the coracle 60. We are trying to prevent this.

[Problems to be Solved by the Invention] FIG. 7 is a cross-sectional view showing the state of heat transfer within the conventional single crystal manufacturing apparatus shown in FIG. Coracle 60 is
Since it needs to be pushed down into the raw material melt 57,
In order to balance the force, a considerable part of the volume of the coracle 60 protrudes above the raw material melt 57. On the other hand, the temperature above the raw material melt 57 is such that the single crystal 53 In order to grow with good controllability, the temperature gradient is such that the temperature decreases towards the top.7th
In the figure, H indicates solidification heat generated with crystal growth. A shows the heat introduced by the raw material melt flowing in from the communication hole 60a of the coracle 60, and B shows the heat introduced by the raw material melt flowing through the communication hole 60a of the coracle 60.
It shows the heat supplied to the raw material melt within 0. Also, C
indicates the heat radiated through the seed crystal 52 and the upper shaft 51, and D indicates the heat radiated from the single crystal 53. Further, E indicates heat radiated through the coracle 60.

When a coracle made of a material with high thermal conductivity is used as the coracle 60, heat is radiated through the coracle 60)
AE increases, thereby cooling the outer circumference of the raw material melt inside the coracle 60. On the other hand, when a coracle made of a material with low thermal conductivity is used, the heat E radiated through the coracle 60 is suppressed, but at the same time, the heat B transferred through the wall surface of the coracle 60 is also suppressed. . Therefore, the raw material melt in the coracle 60 is mainly
It will be directly heated by the raw material melt 57 flowing into the inside through the communication hole 60a in the lower part of 0, and the heat A will be dominant. Therefore, also in this case, the temperature of the outer peripheral portion of the raw material melt inside the coracle 60 becomes relatively low.

As described above, in the conventional manufacturing apparatus, the raw material melt inside the coracle has a temperature distribution in which the temperature is high at the center and low at the outer periphery. When crystal growth is performed under such temperature distribution, the solid-liquid interface shape becomes a convex shape with the center swollen upward, as shown in FIG. 6, which tends to cause polycrystalization and twinning. Moreover, even if a single crystal is obtained, it is difficult to obtain one with good crystallinity due to many crystal defects such as dislocations.

An object of the present invention is to provide a single crystal manufacturing apparatus that can eliminate such conventional problems and suppress the occurrence of crystal defects such as polycrystalization, twinning, and dislocations.

[Means for Solving the Problems] In the single crystal manufacturing apparatus of the present invention, the coracle has a lower part that is substantially immersed in the raw material melt and an upper part that is substantially located above the raw material melt. It is characterized in that it is divided into parts, and the lower part is made of a material with higher thermal conductivity than the upper part.

Examples of the material with high thermal conductivity that forms the lower part include carbon. In addition, materials with low thermal conductivity that form the upper part include quartz, BN, and P.
Examples include BNSA Fu N and PBN coated carbon.

[Operation] The coracle used in the manufacturing apparatus of the present invention is divided into a lower part having relatively high thermal conductivity and an upper part having relatively low thermal conductivity.

The heat radiation E through the coracle shown in FIG. 7 is mainly performed through the upper part of the coracle, but in the present invention, since the upper part has low thermal conductivity, the heat radiation E through the coracle is suppressed. Furthermore, since the heating B due to heat conduction through the wall surface of the coracle shown in FIG. be enhanced. Further, the solidification heat H generated by crystal growth is mainly radiated by heat transfer of C and D. Furthermore, since the heating B through the wall surface of the coracle is increased, according to the manufacturing apparatus of the present invention, the temperature of the outer circumference of the raw material inside the coracle is higher than that of the conventional method. As a result, the shape of the solid-liquid interface of the grown crystal becomes flat or convex protruding downward. Such a solid-liquid interface shape is desirable for suppressing polycrystalization, twinning, and generation of dislocation defects.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention. In FIG. 1, the crucible 4 has an upper shaft 5 that rotates and has an elevator.
Supported by A raw material melt 7 is contained in the crucible 4, and a liquid sealant 6 is spread over it. A heater 8 for heating the raw material melt 7 and the liquid sealant 6 is provided in the mat 4, and the heat radiates outward around the heater 8. A heat insulating wall 9 is provided to prevent the loss of μJj.

A coracle 10 is floated at the interface between the raw material melt 7 and the liquid sealant 11 6. The coracle 10 is composed of a lower part 10a that is substantially immersed in the raw material melt 7, and an upper part 10b that is substantially located above the raw material melt. The lower part is made of a material with higher thermal conductivity than the upper part, and in this embodiment is made of carbon. Further, the upper portion 10b is made of quartz. The lower part 10 has an inverted conical shape, and a communication hole 10c is formed in the center thereof.

The upper part 10b has a donut shape and is fitted with the upper part 10a at its inner end.

An upper shaft 1 is provided above the lever 4.
A seed crystal 2 is attached to the tip.

The entire apparatus shown in FIG. 1 is housed in a 11JJ pressure vessel (not shown), and several tens of atm, for example, N2. An inert gas such as Ar is introduced.

The single crystal 3 is seeded by applying the seed crystal 2 attached to the upper shaft 1 to the surface of the raw material melt 7 in the coracle 10, rotating the upper shaft 1 in the direction of the arrow, and rotating the upper shaft 5 in the direction of the arrow. By rotating it, it is pulled up and J-grown.

In this invention, the coracle 10 is divided into a lower part 10a and an upper part 10b as in this embodiment. Lower part 1
0a is an inverted conical portion that sinks into the raw material melt 7 and is in direct contact with the raw material melt 7.

In this embodiment, the lower part is made of carbon and has high thermal conductivity, so that the heat of the raw material melt 7 is transmitted into the coracle 10 through its wall surface. For this reason, coracle 10
The outer periphery of the raw material melt inside becomes relatively high temperature. Upper part 10
b is a portion that comes out above the raw material melt 7 and adjusts the buoyancy of the coracle 10. The upper portion 10b is made of a material with relatively low thermal conductivity, and in this embodiment is made of quartz. Since the thermal conductivity is relatively low, heat dissipation through this upper part is suppressed, and therefore the temperature of the outer peripheral part of the raw material melt in the upper part of the coracle does not decrease as in the conventional case. As described above, according to the manufacturing apparatus of the embodiment according to the present invention, it is possible to increase the temperature of the outer periphery of the raw material melt in the coracle, so that the shape of the solid-liquid interface can be made flat or a convex shape protruding downward. It is possible to suppress the occurrence of polycrystalization, twinning, and dislocation defects.

The connecting part between the upper part and the lower part of the coracle may protrude above the raw material melt as in the embodiment shown in FIG.
It is preferable that the volume of that part be as small as possible. It may also be located below the raw material melt. The lower part of the coracle only needs to be substantially immersed in the raw material liquid, and it is not necessarily necessary that the entire part be immersed. Similarly, the two sides of the coracle only need to be located substantially above the raw material melt, and the entire coracle does not necessarily have to be located above the raw material melt.

The manufacturing apparatus shown in FIG. 1 is a single crystal manufacturing apparatus using the liquid sealing Czochralski method, but the present invention is also applicable to the Czochralski method without liquid sealing, in which case the liquid sealant 6 is removed. It can be realized with a similar configuration.

FIG. 2 is a sectional view showing another embodiment of the invention.

In the coracle 20 shown in FIG. 2, the bottom surface of the upper part 2ob is in contact with the edge of the upper outer peripheral part of the lower part 20a,
The contact surface of the connecting part is extremely small. Therefore, the heat radiated to the outside through the coracle (E shown in FIG. 7) can be further suppressed.

FIG. 3 is a sectional view showing still another embodiment of the invention. In the coracle 30 shown in FIG. 3, the thickness of the portion of the upper portion 30a that extends above the surface of the raw material melt is extremely thin. The upper part 30b is placed on this thin peripheral wall part. Even with such a configuration, the upper part 30
The contact area of the connecting portion between b and the lower portion 30a can be reduced, and heat radiation passing through this portion can be suppressed.

Generally, the thickness of the contact portion between the upper and lower parts of the coracle in the radial direction is preferably 1 mm or less. Furthermore, the thickness of the wall surface of the lower part of the coracle that protrudes above the surface of the raw material melt is preferably lrn'm or less.

In the above embodiments, only one communication hole was formed in the lower part of the coracle, but the number, diameter, direction, and position of the communication holes can be freely selected as appropriate. However, if the diameter is made too large, the raw material melt may not flow stably into the coracle, resulting in unstable crystal growth.

When the wall thickness of the coracle is 3 mm, if the diameter of the communicating hole is 6 mm or more, crystal growth becomes unstable, and crystal breakage or dendrite-like growth may occur.

Hereinafter, specific experimental examples using the manufacturing apparatus of the present invention will be explained. A GaAs single crystal was manufactured by the liquid-sealed Czochralski method using a manufacturing apparatus as shown in FIG. The lower part 10a of the coracle was made of carbon and had an inner diameter of 100 mrn, a bottom inclination angle of 30°, and a wall thickness of 3 mm. The upper part 10b of the coracle was made of quartz and had a donut-shaped disk shape with an inner diameter of 100 mm, an outer diameter of 140 mm, and a thickness of 5 mm. The total weight of the coracle upper part 10b and lower part 10a is 180 g, and the buoyancy is adjusted so that the upper end of the lower part 10a protrudes above the surface of the raw material melt 7 by about 5 ml11.

GaAS raw material 3 is placed in a quartz Ruppo 4 with an inner diameter of 150 mm.
kg and 8203300 g as a liquid sealant were put therein, the coracle 10 was set, and the mixture was heated and melted to start pulling the GaAs single crystal.

As the crystal 2, one with <111> orientation was used. When the crystal was grown at a pulling rate of 6 mm/hr, a single crystal with a diameter of 75 mm could be stably grown.

The obtained single crystal weighed 1700 g and had an etch pit density (EPD) of 3 to 3.
8×10 3 cm −2 , and a good crystal with low dislocation density was obtained.

For comparison, crystals were grown using a conventional coracle, that is, a single coracle made entirely of carbon. Note that the shape and weight of the coracle were almost the same as in the above example. As a result, we were able to grow a single crystal with a diameter of 75 rn m, but the resulting single crystal had twins in three places and an EPD of 5X10' to 2X10'cm-
2, indicating that the crystal had a high dislocation density.

[Effects of the Invention] As explained above, according to the manufacturing apparatus of the present invention, when growing a single crystal, the heat radiated through the coracle is reduced, and the temperature gradient in the radial direction of the raw material melt inside the coracle is reduced. The shape of the solid-liquid interface between the single crystal and the raw material melt can be made flat or convex protruding downward. Therefore, it is possible to suppress polycrystalization and twinning, suppress the generation of dislocation defects, and obtain a single crystal with uniform diameter and excellent crystallinity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a sectional view showing another embodiment of the invention. FIG. 3 is a sectional view showing still another embodiment of the invention. FIG. 4 is a sectional view showing an example of a conventional manufacturing apparatus. FIG. 5 is a sectional view showing another example of a conventional manufacturing apparatus. FIG. 6 is a sectional view showing still another example of the conventional manufacturing apparatus. FIG. 7 is a cross-sectional view showing the state of heat transfer within the conventional single crystal manufacturing apparatus shown in FIG. In the figure, 1 is the upper axis, 2 is the seed crystal, 3 is the single crystal, 4 is the crystal, 5 is the lower axis, 6 is the liquid sealing moon, 7 is the raw material melt, 8
is a heater, 9 is a heat insulating material, 10 is a coracle, 10a is a lower part, 10b is an upper part, 20 is a coracle, 20a is an F cloth, 20b is an upper part, 30 is a coracle, 30a is a lower part,
30b indicates the upper part. Figure 2 Figure 1 Figure 3

Claims (1)

[Claims] (1) A single crystal manufacturing apparatus in which a coracle having at least one communicating hole is floated on a raw material melt, and the single crystal is pulled up and grown from the raw material melt supplied into the coracle through the communicating hole, The coracle is divided into a lower part substantially immersed in the raw material melt and an upper part located substantially above the raw material melt, and the lower part is heated more than the upper part. Single crystal manufacturing equipment characterized by being made of a material with high conductivity.