JPH0742194B2 - Single crystal manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to III-V group compound semiconductor single crystals such as GaAs and ZnT.
The present invention relates to an apparatus for producing II-VI group compound semiconductor single crystals such as e and CdTe, semiconductor single crystals such as Si and Ge, and oxide single crystals such as LiNbO ₃ and Bi ₁₂ SiO ₂₀ .

[Conventional technology]

In the raw material melt, a molded body having a wide top and a narrow bottom and a small opening at the tip is dipped to divide the raw material melt into two parts, and a single crystal is pulled from the raw material melt inside the molded body. , For example, in Japanese Patent Application No. 60-199377. This compact was intended to control the temperature distribution in the radial direction within the raw material melt, and was intended to flatten the solid-liquid interface of the pulled crystal.

However, depending on the material and shape of the molded body, the heat dissipation from the melt through the molded body is large, so that the shape of the solid-liquid interface of the pulling crystal tends to be upwardly convex (concave). This causes increase of crystal defects such as increase of dislocations and generation of lineage. Further, when the heat dissipation is remarkable, the crystal and the molded body may adhere to each other, which causes polycrystallization.

[Problems to be solved by the invention]

The present invention eliminates the drawbacks of the conventional single crystal production apparatus, prevents heat from escaping from the molded body, makes it possible to adjust the temperature of the molded body itself, temperature distribution of the raw material melt, and further pulling crystal An object of the present invention is to provide a single crystal manufacturing apparatus capable of controlling the shape of the solid-liquid interface.

[Means for solving problems]

The present invention is a crucible for containing a raw material melt or a raw material melt and a liquid sealant, and a lower shaft for supporting the crucible so that the crucible can be rotated up and down,
A raw material heating heater provided around the crucible, an upper shaft capable of rotating up and down and having a seed crystal attached to a lower end thereof, and a molded body having a wide upper portion, a narrow bottom portion and a small opening portion at a tip, In the apparatus for producing a single crystal, which is arranged so as to be immersed in the raw material melt, the forming body is provided with a heating means.

As a method of holding the heating means in the molded body, in addition to forming the molded body itself with a heating element, a heating body is integrally attached around the molded body, or the heating body is separated around the molded body. It can be attached in the state. Regarding heating of the molded body, resistance heating is excellent in controllability, but it is also possible to form the molded body from a conductive material and perform high frequency heating.

As the material properties of the molded body, it is required that it does not react with the raw material melt and that it has heat resistance, high purity workability, and low cost. Therefore, the material of the molded body that can be used differs depending on the crystalline material. Generally, carbon, quartz, P
Ceramics such as BN, BN, AlN, SiC, Si ₃ N ₄ and Al ₂ O ₃ can be used, and the surface can be coated if necessary. When forming a compact with a resistance heating element, carbon or
It is better to use SiC or the like.

FIG. 1 is a cross-sectional view of an apparatus for producing a single crystal which is a specific example of the present invention.

A crucible 4 containing the raw material melt 2 and the liquid sealant 3 is supported by a lower shaft 6 for rotation and elevation. Heater 7 around crucible 4
Is provided to heat and melt the raw material. A heat insulating material 8 is arranged outside the heater 7. A molded body 9 having a conical portion having a small opening at the tip is immersed in the raw material melt 2 at the lower part of the cylindrical portion, and the tip of the pulling shaft 5 is applied to the raw material melt 2 inside the molded body 9. The single crystal 1 is pulled up by immersing the seed crystal attached to. The feature of the present invention resides in that the molded body 9 is composed of a heating element. In the apparatus shown in FIG. 1, both upper ends of the molded body 9 are supported by the electrodes 10, and the molded body is energized from there. There is. In addition, the molded body has a lower thickness to increase the resistance value to increase heating, and an upper thickness to increase heat generation to prevent heat generation, and to increase mechanical strength for supporting the molded body. . It should be noted that temperature sensors 11 are provided on the bottom of the crucible 4, the heater 7 and the back side of the molded body 9 to detect the temperature of the raw material melt and the heating temperature of the heater and the molded body.

FIG. 2 is a view showing an example of a molded body composed of a resistance heating element made of carbon. The figure (a) is a perspective view of a molded object, and the figure (b) is a front view. (C) is an explanatory view of a heat generating circuit of the molded body, and a thick line portion is a heat generating portion. As shown in FIGS. 2 (a) and 2 (b), a slit is put in the molded body to form a heating circuit. The surface of the compact is entirely coated with PBN for insulation from the melt.

[Action]

FIG. 3 is a diagram showing the relationship between the compact and the pulled crystal.
The molded body has a bottom immersed in the raw material melt and an upper part exposed to the gas in the furnace. Since the gas temperature in the furnace is lower than the melt temperature, the exposed portion of the compact is significantly cooled. As a result, the heat of the melt escapes through the compact, the melt temperature near the wall surface of the compact is slightly lower than the temperature in the center of the compact, and the solid-liquid interface of the pulling crystal is convex upward. It becomes the shape.

The present invention can avoid the cooling of the molded body as described above by keeping the molded body with a heating means and maintaining it at a high temperature, and as a result, the solid-liquid interface of the pulled crystal can be flattened.
Crystal defects can be reduced.

〔Example〕

A GaAs single crystal was manufactured using the single crystal manufacturing apparatus of FIG. 1 incorporating the molded body of FIG.

The molded body had an inner diameter of 80 mmφ, an outer diameter of 90 mmφ and a small opening of 10 mmφ at the bottom. The overall height was 10 cm and the heater portion height was 6.5 cm, and a slit was inserted as shown in FIG. The material is made of carbon and the surface is coated with PBN.

About 1.2 kg of Andove GaAs raw material melt and 240 g of liquid encapsulant B ₂ O ₃ were placed in the crucible and pulled in the (100) direction using a seed crystal. Crystal rotation speed is 5 rpm, crucible rotation speed is 15 r
At pm, the rotation directions of both are opposite and the pulling speed is 6 mm / H,
The temperature gradient near the solid-liquid interface was 50 ° C / cm. Under the above-mentioned conditions, dislocation density was evaluated by X-ray topography and EPD for the crystal pulled up by heating the molded body and the crystal pulled up without heating.

The shape of the solid-liquid interface by X-ray topography was slightly flat when heated, while it was slightly flattened, whereas in the case where it was not heated, the crystals in the circumferential and central parts grew more downward, It was M type. The average dislocation density by EPD was 5 × 10 ³ cm ^-2 with heating and no lineage was observed, whereas the average value of dislocation density was 1 × 10 ⁴ cm ^-2 with no heating. Was given.

〔The invention's effect〕

According to the present invention, by adopting the above configuration, the temperature of the molded body itself can be adjusted, and the temperature distribution of the melt in the vicinity of the solid-liquid interface can be optimally restricted. As a result, the solid-liquid interface shape is flattened. It has become possible to manufacture high quality single crystals with few crystal defects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an apparatus for producing a single crystal which is a specific example of the present invention, FIG. 2 is a view showing an example of a molded body, FIG. 1 (a) is a perspective view, and FIG. FIG. 3C is an explanatory diagram of the heat generating circuit, and FIG. 3 is a diagram for explaining the relationship between the compact and the pulled crystal.

Claims (3)

[Claims] 1. A crucible for containing a raw material melt or a raw material melt and a liquid sealant, a lower shaft for supporting the crucible so as to be rotatable and vertically movable, a raw material heater provided around the crucible, and a rotatable and vertically movable unit. Apparatus for producing a single crystal comprising an upper shaft having a lower end to which a seed crystal is attached, and a compact having a wide upper portion, a narrow bottom portion and a small opening portion at the tip, arranged so as to be immersed in the raw material melt. 2. The apparatus for producing a single crystal, wherein the molded body is provided with a heating means. 2. The apparatus for producing a single crystal according to claim 1, wherein the compact is composed of a heating element, and a slit is inserted into the heating element to form a heating circuit. 3. A molded body made of carbon, the surface of which is PB
An apparatus for producing a single crystal according to claim 1 or 2, wherein the single crystal is coated with N.