JP3042097B2 - Apparatus and method for growing single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to semiconductors such as Si and Ge, III-V compound semiconductor single crystals such as GaAs and InP, II-VI compound semiconductors such as CdTe, BSO and LB.
The present invention relates to an apparatus and a method for growing a single crystal such as an oxide such as O by a vertical Bridgman method or a vertical gradient freezing method.

[0002]

2. Description of the Related Art The above-mentioned single crystal has been conventionally grown by a vertical Bridgman method, a horizontal Bridgman method, a vertical slow cooling method, a pulling method, or the like. The vertical Bridgman method is a method of arranging a vertical container containing a raw material melt in a temperature gradient furnace, cooling and solidifying from below the raw material melt by moving the container downward, and growing a single crystal. is there. The vertical gradient freezing method is a method of growing a single crystal by controlling a heater of a furnace so as to move a temperature gradient inside a furnace upward instead of moving a vertical container downward by a vertical Bridgman method. is there. Each of these methods has an advantage that a columnar crystal along the side wall of the vertical container can be easily grown. However, in these methods, it is difficult to control the temperature distribution of the raw material melt, and it is difficult to obtain a single crystal having excellent crystallinity.

[0003] In Japanese Patent Publication No. 3-21511, the vertical container has a double wall structure to suppress the influence of temperature fluctuations on the outer wall, and a heat outflow promoting means is attached to the bottom of the container, and the inner surface of the wall is It has been proposed to suppress the generation of crystal nuclei.

In Japanese Patent Publication No. Hei 3-21511,
It has been proposed to provide a gap consisting of a plurality of channels in the inverted conical bottom support of a vertical container to control the heat flow from said bottom.

Further, Japanese Patent Application Laid-Open No. 64-56392 proposes that a metal identical to a single crystallized metal is interposed between a crucible and a support of a vertical Bridgman apparatus to promote the dissipation of heat flow. I have.

[0006]

In these devices, it is difficult to control the heat flow radiated from the bottom of the vertical container, and it is necessary to control the temperature distribution of the raw material melt and the shape of the solid-liquid interface with the crystal without fail. Could not do. Therefore, the present invention
In a device that grows a single crystal by the vertical Bridgman method or the vertical gradient freezing method, the above disadvantages are solved, the heat flow that flows downward from the bottom of the vertical container can be controlled, and the shape of the solid-liquid interface with the crystal It is an object of the present invention to provide a single crystal growing apparatus and a single crystal growing method that can be easily controlled.

[0007]

Means for Solving the Problems The present invention has succeeded in solving the above problems by employing the following constitution. (1) An apparatus for growing a single crystal by cooling and solidifying a raw material melt from below, comprising a vertical container for accommodating a raw material melt and a furnace for forming a temperature gradient in the vertical container. Inverted conical cooling of the cooling body, parallel to the inverted conical bottom of the vessel
An apparatus for growing a single crystal, wherein the surfaces are arranged with a gap . (2) An apparatus for growing a single crystal by cooling and solidifying a raw material melt from below, comprising a vertical container for accommodating the raw material melt and a furnace for forming a temperature gradient in the vertical container. The distance between the inverted conical bottom surface of the container and the inverted conical cooling surface of the cooling body is 1
(1) Symbol placement of a single crystal of growth apparatus characterized in that it is a to 10 mm. (3) A small-diameter cylindrical portion protrudes from the tip of the inverted conical bottom surface of the vertical container, a hole is formed in the center of the cooling body, and the cylindrical portion is inserted into the hole. 1) or
(2) single crystal growing apparatus according. (4) The temperature control means is provided to the cooling body to cool and solidify the raw material melt while controlling the temperature of the cooling body based on the temperature difference between the inverted conical bottom surface and the inverted conical cooling surface of the vertical container. how to grow a single crystal by using the growth apparatus of the single crystal according to any one of the above (1) to (3), wherein.

In the above apparatus, the support of the vertical container is
It is also possible to mount a small-diameter cylindrical container protruding from the tip of the inverted conical bottom in the hole in the center of the cooling body, but it is necessary to raise the vertical container upward without directly contacting the vertical container and the cooling body. It is also possible to support it by hanging from it. It is also possible to control the temperature by burying a circulation pipe in the cooling body to flow the refrigerant, or burying a heater in the inverted conical cooling surface to heat the cooling body.

[0009]

[Function] Heat transfer can be roughly divided into convection, heat conduction, and radiant heat transfer. However, convection is difficult to solve because the Navier-Stokes equation is difficult to solve, and heat conduction is easy to handle. However, it is difficult to estimate the magnitude of the heat flow because the heat radiation from the container to the support during crystal growth varies depending on the state of contact between the two. The radiant heat transfer follows Stephen-Bolsoman's law, and the transfer of heat between two objects arranged in parallel has a view factor of 1, making it easy to estimate the heat flow and relatively reliable. Therefore, the present inventors have studied control of crystal growth by detecting radiation heat transfer. That is,
According to the present invention, the cooling surface of the cooling body is arranged so as to be parallel to the inverted conical bottom surface of the vertical container, and the cooling means and the heating means in the cooling body are controlled based on the difference between the two surface temperatures. Thereby, the heat flow from the container to the cooling body is controlled. Since the change in the temperature of the bottom of the container due to the temperature adjustment of the cooling body is negligible, if the temperature of the bottom of the container is measured in advance, the temperature of the cooling body should be controlled only by measuring the surface temperature of the cooling body. Can be.

FIG. 1 is a conceptual view of a single crystal growing apparatus according to one embodiment of the present invention. In the chamber 1 in which the heat insulating material 2 is lined, heaters 3 to 6 are vertically arranged to form a temperature gradient furnace, and a vertical container 7 is arranged in the center thereof. The container 7 has an inverted conical bottom and a small-diameter cylindrical portion 8 at the end thereof, and is inserted into a hole of the cooling body 9 to support the container 7. The cooling body 9 is 1 to 10 mm with respect to the inverted conical bottom surface of the vertical container.
An inverted conical cooling surface of the cooling body 9 is arranged so as to be parallel at intervals of, and a thermocouple 12 is provided on the cooling surface. Vs. 12
The temperature is controlled by the measured value of. The raw material melt 13 in the vertical container 7 is cooled and solidified from below while controlling the heat flow from the container 7 to the cooling body 9 in the temperature gradient formed by the heater, and the single crystal 14 is grown. You.

When the heat flow from the raw material melt cannot be sufficiently dissipated downward during the growth of the single crystal at the inverted conical bottom of the vertical container, the flow of the heat flow as shown by the arrow in FIG. Since the ambient temperature decreases, the solid-liquid interface of the crystal becomes convex downward, and defects generated on the inner wall of the container are taken into the crystal, making single crystallization difficult. In the apparatus shown in FIG. 1, the small-diameter cylindrical portion 8 provided at the bottom end of the vertical container 7 is inserted into the cooling body 9, so that the heat flow from the raw material melt can be sufficiently radiated downward. Since the flow of the heat flow as shown by the arrow is shown, and the solid-liquid interface of the crystal is also maintained in the upwardly convex state, the single crystal can be easily grown. That is, when growing a single crystal at the inverted conical bottom of the vertical container, if the heat flow can be controlled dominantly by the heat transfer from the small-diameter cylindrical portion, the flow of the heat flow as shown in FIG. 3 can be easily secured. it can. Since the radiant heat transfer is proportional to the fourth power of the temperature and the heat conduction is proportional to the temperature gradient, the surface temperature of the cooling body may be set to a temperature slightly lower than the melting point of the raw material melt.

[0012]

EXAMPLE A single crystal of CdTe was grown by the vertical Bridgman method using the apparatus shown in FIG. 400 g of CdTe polycrystal was charged into a quartz vertical vessel having a diameter of 85 mm, and the inside of the vessel was evacuated to 1 × 10 ⁻⁶ torr, and then covered with a quartz cap. The small-diameter cylindrical portion at the bottom of the vessel is inserted into the cooling body to support it, and the inside of the chamber is evacuated. After that, a vertical temperature gradient is formed by four heaters. Was melted. Then, about 1 ° C / m
A single crystal was grown by moving the container downward at a rate of 3 mm / hr in a temperature gradient of m. Cooling body surface temperature is C
Starting from the dTe melting point of 1092 ° C., the temperature was lowered according to a preset program, and finally lowered to 950 ° C. The output of the lowermost heater of the temperature gradient furnace was appropriately adjusted to improve the controllability of the temperature control of the cooling body. The program of the surface temperature of the cooling body was optimized by estimating the excess or deficiency of the downward heat flow from the shape of the swelling of the longitudinal section of the obtained CdTe single crystal. As a result, a CdTe single crystal having excellent crystallinity could be obtained over the entire crystal, and the reproducibility was good, and stable crystal growth was enabled.

[0013]

According to the present invention, by adopting the above structure, the control of the heat flow flowing downward from the vertical container becomes easy, and the small diameter cylindrical portion at the bottom end of the vertical container is inserted into the cooling body. When supported, the shape of the solid-liquid interface can be more easily controlled, and as a result, a single crystal having excellent crystallinity can be stably grown.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a single crystal growing apparatus as one specific example of the present invention.

FIG. 2 is a diagram for explaining a relationship between a heat flow and a solid-liquid interface when a heat flow flowing downward from a vertical container is insufficient.

FIG. 3 is a diagram for explaining a relationship between a heat flow flowing downward from a vertical container and a solid-liquid interface when the apparatus of FIG. 1 is used.

Claims (4)

(57) [Claims] An apparatus for growing a single crystal, comprising: a vertical container for accommodating a raw material melt; and a furnace for forming a temperature gradient in the vertical container, wherein the raw material melt is cooled and solidified from below to grow a single crystal. The inverted circle of the cooling body is parallel to the inverted conical bottom of the vertical container.
An apparatus for growing a single crystal, wherein a conical cooling surface is arranged with a gap . 2. An apparatus for growing a single crystal, comprising: a vertical container containing a raw material melt; and a furnace for forming a temperature gradient in the vertical container, wherein the raw material melt is cooled and solidified from below to grow a single crystal. vertical distance inverted conical cooling face of the inverted conical bottom the cooling body of the container, growth apparatus of claim 1 Symbol <br/> mounting of the single crystal, characterized in that a 1 to 10 mm. 3. A small-diameter cylindrical portion is projected from a tip of an inverted conical bottom surface of the vertical container, and a hole is formed in the center of the cooling body.
3. The apparatus for growing a single crystal according to claim 1, wherein said cylindrical portion is inserted into said hole. 4. A temperature control means is provided to the cooling body, and the raw material melt is cooled and solidified while controlling the temperature of the cooling body based on the temperature difference between the inverted conical bottom surface and the inverted conical cooling surface of the vertical container. how to grow a single crystal by using the growth apparatus of the single crystal according to any one of claims 1-3, characterized in that.