JPH01264991A - Apparatus for producing single crystal - Google Patents

Abstract

PURPOSE:To improve the uniformity of the crystal in the radial direction and to stably grow the high-quality single crystal which has a large diameter and less crystal defects with good controllability with the title apparatus by providing small apertures to the specific positions in the sloped side wall part or bottom part of a coracle to be immersed into a raw material melt. CONSTITUTION:The raw material melt 2 and, if necessary, a liquid sealing material are housed into a crucible 1 which is constituted rotatably and liftably and is supported on a lower shaft. The coracle 3 which has the sloped side wall part decreased in the diameter toward the lower part and is provided with >=1 pieces of the small apertures to the sloped side wall part or the bottom part near the outside circumference of the straight cylindrical part of the pulled up crystal 5 is immersed into the above-mentioned raw material melt 2 and while the raw material melt 2 is introduced through the small apertures, the single crystal 5 is pulled up by the single crystal pull up shaft 4 which is attached with a seed crystal and is rotatable and liftable.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to m-v group compound semiconductors such as GaAs and lnP, n-vr group compound semiconductors such as CdTe, Si, Ge
This invention relates to an apparatus for producing single crystals of semiconductors such as LNO1BSO and oxides by the Czochralski method.

(Prior Art) Conventionally, a coracle is inserted into the raw material melt to adjust the amount of the raw material melt in the coracle to control the diameter of the grown crystal.

FIG. 2 is a conceptual diagram of a conventional single crystal manufacturing apparatus using a coracle. (Refer to Japanese Patent Application Laid-Open No. 62-2H193.) This device uses an inverted conical coracle 7 having one small opening at the bottom. The raw material melt 2 is stored in the container, and the coracle 7 is immersed in the melt using a support. (The support for the coracle is not shown.) Next, the upper shaft 4 with the seed crystal attached is lowered, and the raw material melt 2 in the coracle 7 is lowered.
After immersing the seed crystal in the water, the single crystal 5 is pulled up. The above device is intended to control the diameter of the pulled crystal by adjusting the diameter of the surface of the melt in the coracle 7.

(Problem to be Solved by the Invention) However, in the above device, since there is only one small opening at the bottom for introducing the raw material melt into the coracle, the raw material melt is transferred to the second
It flows from the center to the periphery of the solid-liquid interface as shown by the arrow in the figure. As a result, the shape of the solid-liquid interface 6 becomes upwardly convex, which facilitates the generation of crystal nuclei in the periphery, causing polycrystalization.

In addition, since there is resistance to the inflow of the melt into the small opening, when the diameter of the pulled crystal increases, the inflow of the raw material melt cannot keep up, which poses an obstacle to increasing the size of the crystal.

The present invention eliminates the drawbacks of the coracle, smoothes the flow of the raw material melt into the coracle, and uses a coracle that flattens or convexes the solid-liquid interface. The present invention aims to provide a single-crystal manufacturing apparatus that enables the manufacture of high-quality single crystals.

(Means for Solving the Problems) The present invention provides a crucible that accommodates a raw material melt or a raw material melt and a liquid sealant, a lower shaft that supports the crucible so that it can rotate up and down,
A heater placed around the crucible, a single crystal pulling shaft equipped with a seed crystal that can be rotated up and down, a coracle having an inclined side wall whose diameter decreases toward the bottom, and a coracle that uses the inclined side wall to convert the raw material melt into In a single crystal production apparatus equipped with a support for supporting a coracle so as to be immersed, one or more crystals are provided near the outer periphery of the straight body of the pulled crystal on the inclined side wall or bottom of the coracle that is immersed in the raw material melt. This is a single crystal manufacturing device characterized by having a small opening.

Note that the number of openings in the coracle may be one, but it is better to have multiple openings in symmetrical positions, and the diameter of the opening is 2 to 6 mm.
is desirable. In addition, coracles are carbon, quartz, BN,
pBN, AIN, pBN coated carbon, 5iN
s It can be manufactured from SiC, ZrO, ^1,03, etc.

(Function) FIG. 1 is a conceptual diagram of a single crystal manufacturing apparatus which is a specific example of the present invention. This device uses a coracle 3 in which a plurality of small openings are provided in the inclined side wall near the outer periphery of the straight body of the pulled crystal. A coracle 3 is immersed in the raw material melt 2 in the crucible 1, the raw material melt 2 is introduced into the coracle 3 through a small opening, and the single crystal 5 is pulled up from there. The arrows in the figure indicate how the raw material melt 2 flows into the coracle 3. The temperature distribution of the raw material melt inside the coracle is higher in the vicinity of the small opening outside the coracle into which the high-temperature melt flows, and relatively lower in the center. As a result, the shape of the solid-liquid interface 6 is either flat or downwardly convex as shown in the figure. Although it is preferable to provide a plurality of small openings at symmetrical positions as described above, since the pulled crystal is rotated, the melt temperature is also averaged to some extent. At this time, instead of rotating the pulled crystal, it is also possible to rotate the coracle.

Figures 3 and 4 show cross-sectional views of various coracles that can be used with the present invention.

FIG. 3 shows an example of a coracle with a wide bottom and a small opening provided at the bottom. Note that the coracle does not necessarily have a bottom (a cross-sectional shape as shown in FIG. 4 may also be adopted).

(Example) Using the apparatus shown in Fig. 1, GaAs with a diameter of 3 inches in the straight body part was
A single crystal was produced. The coracle has a cylindrical part with a diameter of +00, a flat bottom with a diameter of 50M, and a sloped side wall with a height of 30mm, and small openings with a diameter of 4m1I+ are provided at 4 force points every 90' on the sloped sidewall with an inner diameter of 75M. The material is pBN.

First, 4 kg of GaAs is placed in a crucible, melted, and then held so that the coracle is submerged slightly above the small opening. - The rotation speed of the L axis was 5 rpm, the pulling speed was 10 mm/hr, and the crucible was rotated in the opposite direction at a rotation speed of 20 rpm.

As a result, although the crystal had a large diameter of 3 inches, it was possible to pull it up stably. Moreover, the shape of the solid-liquid interface was extremely flat.

When crystal growth was performed using the coracle shown in Figure 2 under the same conditions as above, it was possible to stably pull the crystal up to a diameter of 2 inches, but the shape of the solid-liquid interface was concave toward the center. change was observed. Further, when trying to make the diameter 3 inches, a sudden decrease in diameter or cutting occurred.

(Effects of the Invention) By adopting the above configuration, the present invention makes it possible to pull a crystal with a large diameter, and also makes it possible to make the shape of the solid-liquid interface of the pulled crystal flat or downwardly convex.
The radial uniformity of the crystal has been significantly improved, making it possible to stably grow high-quality single crystals with few crystal defects with good controllability.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a single crystal manufacturing apparatus which is a specific example of the present invention, FIG. 2 is a conceptual diagram of a conventional apparatus, and FIGS. 3 and 4 are cross-sectional views of a coracle used in the present invention. Figure 1 Figure 2

Claims (1)

[Claims] A crucible that accommodates a raw material melt or a raw material melt and a liquid sealant, a lower shaft that supports the crucible so that it can be rotated up and down, a heater placed around the crucible, and a unit that can be rotated up and down that is equipped with a seed crystal. In a single crystal manufacturing apparatus, comprising a crystal pulling shaft, a coracle having an inclined side wall portion whose diameter decreases toward the bottom, and a support supporting the coracle such that the inclined side wall portion is immersed in a raw material melt. An apparatus for producing a single crystal, characterized in that one or more small openings are provided near the outer periphery of the straight body of the pulled crystal in the inclined side wall or bottom of the coracle that is immersed in the raw material melt.