JPS5812227B2 - Single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for producing a single crystal, more specifically a method for producing a single crystal by pulling, which aims to shorten the process time.

When producing dog-shaped crystals of semiconductor silicon, etc. using the Czyok-2-Ruski method, in which a seed crystal is brought into contact with a raw material melt in a crucible and grown by rotation and pulling, conventionally, nodules are generated at the end of crystallization. The lower end was squeezed into a conical shape to suppress the thermal shock caused by the pulling of the crystal and the residual melt, and to prevent the generation of crystal defects due to crystal strain introduced from the lower end of the crystal.

Since the crystal is formed into a conical shape upon completion of crystal growth, there is a drawback that the process of forming the conical shape requires a considerable amount of time.

FIG. 1 is a schematic diagram of a crystal produced by such a conventional method, and in the figure, 1 indicates a seed crystal, 2 a shoulder portion, 3 a constant diameter portion, and 4 a lower end portion.

As is clear from Fig. 1, the crystal rotated and pulled up by the seed crystal 1 first forms a shoulder portion 2, then forms a constant diameter portion 3, and then shapes the lower end into a conical shape to prevent crystal growth. However, extra time is required to form the length of the conical lower end 3.

The present invention aims to eliminate such drawbacks.

Specifically, it is an object of the present invention to provide a method for manufacturing a single crystal without forming a conical lower end as in the conventional method and without generating crystal defects due to thermal shock.

Therefore, in the single crystal manufacturing method according to the present invention, in which a single crystal is pulled from a raw material melt using a seed crystal, the single crystal and the raw material melt are heated while heating the vicinity of the lower end of the crystal at the end of crystal growth. It is characterized by separating.

According to the method for manufacturing a single crystal according to the present invention, since the single crystal and the melt are separated while heating the vicinity of the lower end of the crystal, crystal defects due to thermal shock do not occur, and it is necessary to form a conical lower end. This makes it possible to shorten manufacturing time.

To explain the present invention in more detail, the method for producing a single crystal according to the present invention separates the crystal from the melt while heating the lower end of the crystal, that is, the vicinity of the terminal end of the crystal, at the end of crystal growth.

Figure 2 shows the temperature distribution within the crystal (curve A) at the end of the constant diameter deafening of a 7.62 cmφ silicon crystal, and after the formation of the conical lower end.
This is a graph showing the intracrystal distribution (curve B) immediately after the single crystal is separated from the residual melt.As is clear from the graph, when the single crystal is separated from the residual melt,
Exposure to temperature differences of ~300°C acts as a thermal shock, inducing crystal distortion and resulting in crystal defects.

Therefore, when separating the melt from the single crystal, if the vicinity of the lower end of the single crystal is auxiliary heated to around the melting point of the raw material, the intracrystal distribution immediately after separation from the single crystal and the melt becomes like curve C, and the single crystal and melt Thermal shock during liquid separation is eliminated.

Specifically, it is preferable to control the temperature of the entire single crystal growth system, lower the amount of heat generated by the electric furnace for keeping the raw material in the crucible as a melt, and auxiliary heat the vicinity of the lower end of the single crystal.

This is because if the calorific value of the electric furnace is not reduced, defects may occur in the crystal.

The auxiliary heating means for heating the lower end of the single crystal is not limited in the present invention, and for example, an auxiliary heating device consisting of an insulating support, a conductive support rod, or a ring-shaped heating element can be used.

Next, an example will be described.

Example 1 FIG. 3 is a schematic cross-sectional view of an apparatus for implementing the single crystal manufacturing method according to the present invention, in which 31 is a seed crystal, 32 is a seed crystal, and 32 is a seed crystal.
3 is a single crystal, 33 is a crucible, 34 is a residual melt, 35 is an insulating support, 36 is a conductive support rod, 37 is a ring-shaped heating element, 3
Sun is the lead line.

As is clear from FIG. 3, the lower end of the single crystal 32 grown at the tip of the seed crystal 31 is in contact with the residual melt 34 in the crucible 33, and is further insulated just above the residual melt 34 near this lower end. A ring-shaped heating element 37 supported by a support body 35 and a conductive support rod 36 is provided.

In this apparatus, silicon was used as the seed crystal 31, and a wet silicon single crystal 32 with a diameter of γ62 was grown.

When separating the residual melt 34 and the silicon single crystal 32,
Electric power was supplied from the lead wire 38 to the ring-shaped heating element 37 to generate electricity.

At this time, the calorific value of the electric furnace (not shown) together with the ring-shaped heating element 37 is adjusted so that the temperature distribution within the crystal is as shown by curve C in FIG. The temperature at the lower end of the crystal 32 was set near the melting point of silicon, and the single crystal and the residual melt 34 were separated.

The shape of this single crystal 32 is shown in FIG.

In FIG. 4, 41 is a seed crystal, 42 is a shoulder portion, and 4 is a constant diameter portion.

As is clear from this FIG.
(Fig. 1).

When forming the conical bottom end by the conventional method, it took about 2.5 hours to separate, but in this example, it was possible to separate within about 0.5 hours.

Example 2 A silicon single crystal 32 with a diameter of 12.7 m was placed in a residual melt 34.
separated.

If a conical lower end is formed as in the conventional method, the electric furnace body is large and the temperature of the single crystal growth system does not rise easily.
Moreover, since the lower end of the conical shape is longer, it took about 5 hours to physically perform the lower end, but in this example, it was completed in about 0.5 to 0.6 hours by increasing the auxiliary heating power.

As explained above, since the auxiliary heating is limited to the lower end of the crystal and the surface of the residual melt, the process progresses efficiently and the time required can be shortened to less than 20% of the conventional time. It is effective in increasing productivity.

While conventional methods require longer processing time as the crystal size increases, the method for producing single crystals according to the present invention
Since the processing time can be kept short by increasing the power for auxiliary heating, we believe that this will be more and more advantageous in increasing the size of crystals in the future.

As described above, the time reduction is remarkable even in silicon with a high crystal growth rate, so the method of the present invention is even more effective in the case of large crystals with a low growth rate and whose lower end needs to be formed into a conical shape. It is clear that there is.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a single crystal produced by a conventional method, Figure 2 is the temperature distribution within the single crystal at the end of crystal growth, and Figure 3 is an apparatus for carrying out the single crystal manufacturing method according to the present invention. FIG. 4 is a schematic cross-sectional view of a single crystal produced by the method for producing a crystal in accordance with the present invention. 1, 31. 41 Seed crystal, 2, 42 River shoulder, 3, 43
2 constant diameter parts, 4 lower end parts, 32...single crystal, 33 crystal crucible, 3
42 residual melt, 35-insulating support, 362 conductive support rods, 37...ring-shaped heating element, wings...lead wire.

Claims (1)

[Claims] 1 In a single crystal manufacturing method in which a single crystal is pulled from a raw material melt using a seed crystal, at the end of crystal growth, the core single crystal and the raw material melt are heated while heating the vicinity of the lower end of the crystal to near the melting point of the raw material. A single crystal production method characterized by separation.