JPS5938189B2 - Single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing single crystals of semiconductors such as germanium silicon and metals.

In general, in the floating zone method, Czochralski method, pedestal method, etc., which are methods for producing single crystals from melt, in order to obtain a dislocation-free single crystal with a large diameter, the seed crystal is brought into contact with the melt, and then the crystal is The diameter of the constriction part is 1~
The Dash neck method is used in which the crystal is made thinner to 4 mm, further grown to a length of about 30 to 100 mm, and then the crystal is gradually thickened to obtain a dislocation-free single crystal of the desired diameter.

In this method, dislocations introduced into the seed crystal due to thermal shock during seeding are propagated into the crystal as the crystal grows.
This is based on the fact that the thin part of the crystal (the narrow part) is where most of the material is extracted outside the crystal.

When dislocations are completely removed at the constriction of the crystal, the crystal grows without dislocations, and a dislocation-free crystal with a desired diameter can be obtained.

The important point for this conventional dislocation-free technology is how to make the grown crystal thinner (longer) after seeding, and this process requires a very high level of skill in controlling temperature and growth rate. There is a drawback that it does.

Furthermore, (not all dislocations are necessarily removed in the constricted part, the dislocation-free rate is therefore low, and since the constricted part is created, application to large diameter crystals is difficult. There are many problems with this dislocation-free technology.

An object of the present invention is to provide a method for producing a single crystal that obtains a dislocation-free crystal without using the conventional dislocation-free technology that requires special skills and has the problems described above.

In order to achieve the above object, the method for growing a dislocation-free crystal according to the present invention uses auxiliary heating means to melt the tip of the seed crystal, and then brings the melt into contact with the melted portion of the tip of the seed crystal.

By doing this, the generation of dislocations when the seed crystal comes into contact with the melt is completely prevented, and by gradually increasing the thickness of the crystal without growing the constricted part, a large diameter dislocation-free crystal can be easily obtained. .

The principle of the present invention is based on the new fact discovered by the inventors that dislocations do not occur when a seed crystal is melted.

The effects of the present invention will be explained below using an example in which the present invention is applied to silicon crystal growth using the floating zone method, which requires the highest level of skill to grow dislocation-free crystals and is difficult to achieve dislocation-free crystal growth using conventional methods. do.

FIG. 1 shows a vertical cross-sectional view of the dislocation-free silicon IJ seed crystal with a diameter of 4 mm immediately after it has melted, and FIG. 2 shows a cross-sectional view taken along line A-A in FIG. has been done.

In FIG. 1, reference numeral 1 indicates an induction heating coil having a flat ring shape, and reference numeral 2 indicates a seed crystal preheating heater made of molybdenum and having an inner diameter of 6 mm in diameter and an open ring shape.

3 is a preheating heater holder, which is partially made of quartz glass for electrical and thermal insulation.

The inner diameter of the induction heating coil 1 is a large diameter (for example, 80 mm
) In order to stably grow the crystal, it is necessary to make it as large as 30 mm ± 5 mm. Therefore, since the electromagnetic coupling with the seed crystal 4 is weak, it is not possible to heat and melt the seed crystal 4 directly with the induction heating coil 1. It's impossible.

Therefore, in this embodiment, the seed crystal 4 is heated by radiant heat from the preheating heater 2.

According to experiments, as the seed crystal 4 is heated to a high temperature, the specific resistance decreases and the electromagnetic coupling with the induction heating coil 1 becomes stronger, so when the output of the oscillator exceeds a certain value, the seed crystal 2 is heated by induction. It absorbed the energy radiated from coil 1 and melted.

Of course, the preheating heater 2 must be removed from the space below the induction heating coil 1 by rotating the holder 3 about the holder rotating shaft 3' as shown in FIG. 2 before starting crystal growth.

FIG. 3 is an X-ray diffraction microphotograph image of the seed crystal 4 whose tip portion has been once melted and then solidified, and FIG. 4 is a schematic representation of FIG. 3.

In FIG. 4, 8 is the unmelted part of the seed crystal 4, and 9
, the 10' part is the part that solidified after being melted once,
11 indicates the interface between the two.

The upper tip is the last solidified part, and the shaded part 10 corresponds to the part shown in white in FIG. 3, and is a region where dislocations exist.

These dislocations are the result of dislocations that occurred in the last solidified area backing up into the solidified area.

No dislocations exist in the unmelted portion of the seed crystal 4, at the interface, or about two degrees above the interface.

In other words, dislocations do not occur simply by melting the crystal.

FIG. 5 shows an example in which a dislocation-free crystal with a diameter of 50 mm was grown by the Dash method (after growing the fin part 12, it was gradually thickened) after the seed crystal melting part 7 and the polycrystal melting part 6 were brought into contact with each other. FIG. 6 is an X-ray diffraction microphotograph image of the seed crystal 8 and the fin portion 12 in FIG. 6, and FIG. 6 is a schematic representation of FIG.

FIG. 5 shows that the seed crystal 4 and the waist portion 12 are completely dislocation-free, clearly demonstrating the effect of seed crystal melting according to the present invention.

As explained above, according to the present invention, by melting the seed crystal in advance, it has been confirmed that dislocations do not occur during seeding, which requires a high degree of skill and is a hindrance to the production of large diameter crystals. The advantage of the Dash neck method is that a dislocation-free single crystal with a large diameter can be easily produced without creating fins.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. Microphotograph image, Figure 4 is the 3rd
Figure 5 is an X-ray diffraction micrograph of the fins of the grown crystal, and Figure 6 is a schematic diagram of Figure 5. 1... Induction heating Coil, 2... Preheating heater, meter
・Preheating heater holder, 3′... Holder rotation axis, 4° 8... Seed crystal, 5... Polycrystal, 6, 7... Melting part, 9... Melting part of the seed crystal Post-solidified part, 10.
... Part where dislocations exist among 9, 11 ... Interface, 1
2. The part of the fin.

Claims (1)

[Claims] 1. In a method of growing a single crystal downward using a seed crystal from a melt formed by heating the lower end of a desired crystalline substance, the upper end of the seed crystal is previously melted using an auxiliary heating means, and then A method for producing a single crystal, characterized in that a dislocation-free crystal is grown by seeding the melt and the molten upper end of the seed crystal in this state and starting the growth.