JPH03137084A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To solidify the solid-liq. interface in a shape protruding to the melt side and to prevent polycrystallization and dislocation at the time of growing a compd. semiconductor single crystal by the horizontal boat method by placing a heat reflecting plate formed to radiate only the radiant heat at the center of a boat on the boat in its longitudinal direction. CONSTITUTION:The horizontal boat 2 contg. the raw material is placed in a reaction tube 5 and arranged in a furnace core tube 1. The boat is heated by a heater arranged outside the furnace core tube 1 to form a temp. distribution in the longitudinal direction of the boat 2 to transiently melt the raw material in the boat 2, the heater and boat 2 are relatively moved to gradually move the solid-liq. interface of the raw material in the boat 2 from one end to the other end, and a compd. semiconductor single crystal is grown. In this case, the heat reflecting plate 9 formed to radiate only the radiant heat at the center of the boat 2 is placed on the boat 2 in its longitudinal direction. Consequently, since more heat is radiated at the center of the boat 2 than at its periphery, the solid-liq. interface is solidified in the shape protruding to the melt side.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to single crystal manufacturing technology and crystal growth technology using a horizontal boat method, and is used for growing compound semiconductor single crystals with low thermal conductivity such as CdTe, for example. Regarding effective techniques.

[Prior Art] Conventionally, the horizontal Bridgman method (HB method) and the horizontal temperature gradient method (HGF method) are known as single crystal manufacturing methods using a horizontal boat. In either method, in order to improve the single crystallization rate and the quality of the single crystal, it is necessary to direct the growth of the single crystal from the center of the free surface of the melt toward the wall and bottom of the boat. It is desirable that the solid-liquid interface progresses in a convex shape toward the melt as shown in FIG. 4(A).

[Problems to be Solved by the Invention] By the way, when manufacturing a ■-■ group compound semiconductor single crystal such as CdTe in a crystal growth apparatus using the horizontal boat method as described above, CdTe is a common boat material. Thermal conductivity is 1 compared to certain graphite and pBN.
More than an order of magnitude smaller.

In this way, when a compound semiconductor single crystal with particularly low thermal conductivity is grown in a boat, it becomes difficult for the latent heat of solidification to travel through the crystal and escape, resulting in a large proportion of the heat escaping through the boat.

As a result, the solid-liquid interface shape becomes concave toward the melt side, as shown in Figure 4 (B), so that nuclei are formed in the area in contact with the boat, resulting in polycrystalization and dislocations such as lineage and cell structures. The disadvantage was that it encouraged the occurrence of

Therefore, as a means for obtaining a solid-liquid interface shape that is convex toward the melt side as shown in FIG. 4(A), the following method has been proposed. The first is the special public service in 1983-4.
In the method shown in No. 1958, the heater near the solid-liquid interface is divided into four parts: top, bottom, left and right, and the temperature distribution in the radial direction is optimized.

The second method is to use heat radiation holes provided in the upper part of the furnace body.The heat radiation holes are variable and the solid-liquid interface moves together with the growth (Japanese Patent Application Laid-open No. 62-270486). (Japanese Patent Application Laid-Open No. 61-227984)
No. 1), and one in which the amount of heat radiation in the left and right directions is controlled by moving the heat radiation holes left and right (Japanese Patent Laid-Open No. 63-45196). Thirdly, there is a method in which a cooling gas supply device is provided in place of the heat radiation hole in the upper part of the furnace body (Japanese Patent Application Laid-Open No. 64-33090), and a method in which a cooling gas supply pipe is provided directly above the melt surface (Japanese Patent Application Laid-Open No. 64-72983).
) is also available. However, all of the above methods have the drawback of complicating the structure of the furnace body and causing a rise in equipment costs.

The present invention was made in view of the above-mentioned problems, and its purpose is to reduce Cd by the horizontal boat method.
When growing a compound semiconductor single crystal with low thermal conductivity such as Te, the purpose is to improve the single crystallization rate and reduce the occurrence of dislocations using simple and inexpensive equipment.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a reaction tube that houses a horizontal boat containing raw materials in a furnace core tube, and a heater arranged outside the furnace core tube. to form a desired temperature distribution along the length of the boat, melt the raw material in the boat, and then move the heater and boat relative to each other to move the solid-liquid interface of the raw material in the boat from one end to the other. In growing a compound semiconductor single crystal by gradually moving the boat toward the boat, a heat reflecting plate was placed on top of the boat along its longitudinal direction so that only the radiant heat from the center of the boat could be emitted.

[Function] According to the above means, heat radiation due to radiation from the melt near the wall of the boat is suppressed, and the amount of heat radiation is relatively larger in the center of the boat than in the periphery.

As the solid-liquid interface becomes convex toward the melt side and solidification progresses,
It is possible to suppress polycrystalization and reduce the occurrence of dislocations.

[Example] FIGS. 1 to 3 schematically show the structure of a crystal growth apparatus in which the present invention is applied to a two-temperature horizontal Bridgman method, which is one of the horizontal boat methods.

In this embodiment, a boat 2 filled with raw materials, a quartz reaction tube 5 in which a vapor pressure control element 3 and a convection prevention plate 4 are vacuum-sealed are inserted into the furnace core tube 1, and the outside of the furnace core tube 1 is A divided heater 6 is disposed at , and the heater 6 is configured to form two soaking zones T, , T, along the axial direction within the furnace core tube 1 . The quartz reaction tube 5 is initially arranged so that the boat 2 loaded with raw materials is located in the high-temperature soaking zone T8, and the element 3 for vapor pressure control is located in the low-temperature soaking zone T. The high-temperature soaking zone T1 has a temperature slightly higher than the melting point of the raw materials in the boat 2, and the low-temperature soaking zone T has a temperature so that the inside of the reaction tube 5 has a desired pressure due to the vapor pressure of the element 3. controlled.

In the single crystal growth apparatus of this embodiment, a heat reflecting plate 9 is formed on the boat 2 so that only the central part can emit radiant heat.
is placed. Along with this, although not particularly limited, a quartz reaction tube 5 is installed in the furnace core tube 1 via a heat insulating material 7 covering the bottom plate 8 and the bottom surface of the boat 2.

FIG. 5(A) shows an example of the structure of the heat reflecting plate 9. The heat reflecting plate 9 is made of quartz and has a horizontally long U-shape, and its surface is sandblasted to scatter the radiant light and prevent radiant heat radiation from the melt surface near the boat wall. Only the formed slit 9a can radiate heat. The heat reflecting plate 9 that has been sandblasted is placed in the first
No. 5 on top of the carbon-coated quartz boat 2 of the device shown in the figure.
A CdTe crystal was placed as shown in Figure (B) and grown using the horizontal Bridgman method. As a result, a solid-liquid interface with a convex shape on the melt side as shown in FIG.
0'cm-'). In addition, the number of grain boundaries and twins that were generated from the boat wall surface was reduced, and the single crystallization rate was improved. Since the shape of the solid-liquid interface cannot be directly observed, the shape of the solid-liquid interface was confirmed by doping Zn to about 3 at% and examining the segregation distribution within the crystal.

FIG. 6 shows the distribution of intracrystalline Zn isoconcentration curves.

Places where the Zn concentration is equal are considered to be places where solidification occurred at the same time, so the Zn isoconcentration curve represents the shape of the solid-liquid interface. For comparison, a CdTe crystal was also grown using the apparatus shown in FIG. 1 without using a heat reflecting plate. That crystal Z
The n isoconcentration curve is shown in FIG. In this case, the solid-liquid interface had a concave shape as shown in FIG.

In this example, growth of CdTe was attempted, but the present invention
The present invention is not limited to Te, and can be applied to the growth of other ■-■ group compound semiconductors and ■-V group compound semiconductor crystals, and similar effects can be expected. Furthermore, the crystal growth method is not limited to the horizontal Bridgman method, but can also be applied to crystal growth using the horizontal temperature gradient method.

In the above embodiment, a U-shaped heat reflecting plate whose entire surface was sandblasted was used, but instead of forming the notch 9a in the center, the notch 9a in Fig. 3 was used.
It may be a rectangular quartz heat reflecting plate in which only the portion corresponding to the area is transparent and the periphery thereof is sandblasted. Further, the material of the heat reflecting plate 9 is not limited to quartz, but may be made of any material as long as it has heat resistance, does not transmit radiant heat, and does not become a source of impurities even at high temperatures.

Furthermore, in the above embodiment, since the heat insulating material 7 is interposed between the boat 2 and the quartz reaction tube 5, heat radiation due to conduction from the bottom of the boat can also be suppressed, and the center of the melt surface is lower than the bottom of the melt. is preferable because it allows faster cooling.

[Effects of the Invention] As explained above, the present invention has a reaction tube that houses a horizontal boat containing raw materials in the furnace core tube, and a heater is arranged outside the furnace core tube, so that the longitudinal direction of the boat can be adjusted. After forming the desired temperature distribution along the direction and melting the raw material in the boat, the heater and the boat are moved relative to each other, and the solid-liquid interface of the raw material in the boat is gradually moved from one end to the other. When growing compound semiconductor single crystals, a heat reflecting plate was placed on top of the boat along its longitudinal direction so that only the radiant heat from the center of the boat could be emitted, and the crystal was grown. , heat release due to radiation from the melt close to the wall of the boat is suppressed, and the amount of heat dissipated in the center of the boat is relatively larger than in the periphery, and the solid-liquid interface becomes convex toward the melt. Since solidification progresses, polycrystallization can be suppressed and the occurrence of dislocations can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view showing the main parts of an embodiment of a compound semiconductor single crystal manufacturing apparatus to which the method of the present invention is applied, and FIG.
Figure 3 is a cross-sectional front view showing the entire crystal growth apparatus using the horizontal boat method; Figures 4 (A) and (B) show the desirable shape of the solid-liquid interface during crystal growth. FIGS. 5(A) and 5(B) are plan views showing an example of a heat reflecting plate and its usage state. FIGS. 6(A) and (B) are plan views showing an example of a heat reflecting plate obtained by the method of the present invention. Cd
A plan view and a front view showing Zn isoconcentration curves of Te crystals.
FIG. 2 is an explanatory plan view and an explanatory front view showing a Zn isoconcentration curve of an e-crystal. l...Furnace tube, 2...Boat, 5...Reaction tube, 6...Hinita, 7...Insulation material, 9...
heat reflector. Figure 1 (A) (B) Figure 5 (A) (8)

Claims (1)

[Claims] (1) A reaction tube containing a horizontal boat containing raw materials is installed inside the furnace core tube, and a heater is placed outside the furnace core tube to form the desired temperature distribution along the longitudinal direction of the boat. ,
In growing the compound semiconductor single crystal by once melting the raw material in the boat and moving the heater and the boat relative to each other, the solid-liquid interface of the raw material in the boat is gradually moved from one end to the other. 1. A method for manufacturing a compound semiconductor single crystal, comprising placing a heat reflecting plate formed so as to radiate only radiant heat from the center of the boat along its longitudinal direction on top of the boat.