JPS5933551B2 - Single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the pulling of single crystals by rotary pulling, and in particular to the production of long crystals and the production of crystals in succession.

The rotational pulling method is a method in which a seed crystal is immersed in molten crystal raw material in a crucible, and the seed crystal is pulled up at a predetermined speed while applying a predetermined rotation, thereby growing the crystal that has grown at the tip even larger. This is a method for growing single crystals.

The crystals obtained by this method include silicon,
There are many types including metal crystals and metal oxide crystals.

This method is excellent in that it can grow high-quality crystals in a relatively short time, and is regarded as important industrially.

As mentioned above, since the rotary pulling method uses a crucible, it is natural that a large crucible is required to produce large crystals, but when pulling long crystals, it is simply It will be limited by the volume of the crucible.

Recently, when pulling silicon single crystals, after the first crystal pulling, without lowering the temperature of the crucible,
Fill a crucible with silicon polycrystalline rods (raw material) and melt them.
A method has come to be used in which a long single crystal is obtained by repeatedly pulling a crystal from the terminal end of the crystal that has already been pulled.

However, applying this method to crystalline materials that are particularly susceptible to thermal shock, such as oxide crystals, is accompanied by many difficulties.

In addition, as crystal growth progresses, the liquid level of the melt in the crucible decreases, and the conditions for crystal growth change accordingly, making it difficult to continue pulling a single crystal depending on the type of crystal and pulling conditions. In some cases, the crystals may grow bent, and there are few (or no) obstacles to obtaining long crystals.

In the conventional rotary pulling method, in which once the single crystal has been pulled, it is separated from the melt and the crystal is recovered after the temperature is gradually lowered, the time required for cooling down takes up a considerable proportion of the entire process. This is also one of the reasons for the rise in crystal costs.

The present invention has been made to eliminate the drawbacks of the conventional rotary pulling method as described above, and to achieve the following objects.

(1) In order to obtain long crystals, it is desirable that the position of the melt surface is always within a certain range, regardless of the volume of the crucible. To make it possible to supply raw materials to

(2) To make it possible to sequentially connect and pull single crystals in order to minimize the chance of temperature drop in the crucible and to efficiently produce single crystals.

(3) Collecting the crystals whose temperature has gradually decreased, and supporting the crystals remaining in the pulling device system to continue rotating and pulling the crystals.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for supplying raw materials while pulling a single crystal, in order to achieve the above object (1).

A single crystal 1 grows at the tip of a seed crystal fixed to a pulling shaft 4.

The weight change is detected by the load detector 17'.

Using the output electric signal of this detector 7', the temperature of the heater 6 of the electric furnace 5 is controlled so that the crystal has a predetermined shape.

On the other hand, one load detector 7 detects a change in the amount of melt 2 in the crucible 3.

Based on the output signal of the detector 7, the amount of raw material 9 supplied from the hopper 8 is controlled by opening and closing the shank 8a so that the amount of the melt 2 is always within a certain range.

As a result, even as the pulling of the single crystal 1 progresses, the liquid level position of the melt 2 remains almost constant, and the length of the crystal is restricted by the volume of the crucible, or the crystal 1 grows bent. These problems have been resolved, and it has become possible to pull long crystals under stable conditions.

The shape of the raw material 9 shown in FIG. 1 is expected to be powder, granule, or block, but it may also be rod-shaped (or liquid).

FIGS. 3 to 6 are diagrams showing an embodiment of the present invention in which a single crystal is continuously pulled, the single crystals are connected, and the single crystals whose temperature has been lowered are sequentially recovered. Achieve the purpose of (3).

Adding Figure 2 to these figures and explaining, crystal 1 is as follows:
It grows on the tip of a seed crystal fixed to the pulling shaft 4.

Conventionally, when the required length has been grown, the crystal 1a is separated from the melt 2 as shown in FIG. (or/
(and the pulling speed is increased), the shape of the end portion of the crystal 1a is made thin, and this portion is used as it is as a seed crystal for the second crystal body 1b.

By repeating this process, the crystal is continuously pulled up (FIG. 3).

The temperature of these connected crystals decreases as they move away from the crucible.

The crystal body 1a, whose temperature has cooled to room temperature or close to it, is supported on its side by a support device 14a incorporated in a mechanism that rotates in synchronization with the pulling shaft 4, with its central axis coincident, and moves at the same speed. (Figure 4).

This support device 14a needs to be strong enough to support the weight of the crystal body 1b and the subsequent crystal body 1c connected thereto.

Next, the narrow diameter part between the crystal body 1a and the crystal body 1b is cut by the laser beam 16, and the crystal body 1a is pulled up by the pulling shaft 4.
Remove and collect.

After the crystal has been pulled a predetermined distance further, as shown in FIG. 5, if the side surface of the crystal 1c is supported by the same supporting device 14b as described above, the crystal 1b is lifted by the same operation as described above. It can be recovered.

Next, as shown in FIG. 6, the crystal body 1c supported by the support device 14b is transferred to the support device 14a, which had been supporting the crystal body 1b up until now, and continues to be rotated and pulled up. When the same situation (FIG. 6) is reached, the lower crystal body 1d is supported by the support device 14b as in the previous case.

By repeating the above-described operations, the crystals can be recovered one by one.

Here, cutting the narrow diameter part between the crystals is easy by using local heating with a laser beam or infrared beam, but it is also possible to cut by using a wire heated to red by passing an electric current, or by using a machine using a rotating grindstone such as a diamond cutter. There are various methods, and the selection is made taking into account the properties of the crystal material, the conditions of the crystal pulling apparatus, the atmosphere of the crystal pulling system, etc.

As is clear from the above description, the present invention, which departs from the conventional crystal growth method in which heating and cooling are reduced to pulling a single crystal, has many advantages.

The present invention makes it possible to pull crystals while supplying raw materials, realizing the long-held dream of pulling long crystals.

The supply of raw materials is not only to simply replenish raw materials for long crystals, but also to keep the amount of melt in the crucible almost constant at all times to prevent changes in crystal growth conditions and, as a result, to produce long crystals. It makes it easy to

Furthermore, in contrast to the conventional method in which a crucible temperature cooling process was required each time one crystal was pulled, the present invention enables the crystal to be pulled by connecting the crystals together. It naturally cools down as it moves away from the crucible,
Since forced cooling can be performed at a location away from the crucible, there is no need for a process to lower the temperature of the crucible during operation of the device.

This significantly reduces the manufacturing cost of single crystals, and has a significant economic effect.

Then, when the crystal has reached a predetermined length, a narrow diameter portion is formed to facilitate cutting and recovery, and can be used as a seed crystal for connecting the next crystal.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing how a single crystal is pulled while supplying raw materials into a crucible according to the present invention. Figure 2 is a cross-sectional view showing the conventional known crystal pulling method;
Figures 6 through 6 are cross-sectional views showing the crystal pulling method according to the present invention, in which the crystals are connected at their narrow diameter parts, pulled up continuously, the naturally cooled crystals are supported, and the crystals are sequentially recovered. It's raining. In Figures 1 to 6, the names corresponding to each number are as follows: 1 is single crystal (1a, including 1d), 2 is melt, and 3 is Crucible, 4 is a pulling shaft, 5 is an electric furnace, 6 is a heater, T, γ' is a load detection device ■, ■, 8 is a hopper, 8a is a shutter, 9
10 is a raw material, 10 is an auxiliary heater, 11 is a constant supply device, 14
a and 14b are support devices, 15 is a laser light source, and 16 is a laser beam.

Claims (1)

[Claims] 1. In a method for producing a single crystal by a rotational pulling method, a step in which a raw material is continuously or intermittently supplied to a crucible to maintain the liquid level of the melt of the raw material contained in the crucible within a substantially constant range. After the process of step 1 and growing a predetermined portion of the first crystal body, the crystal growth is continued without separating the first crystal body from the melt, and the rear end of the first crystal body is grown. A second process in which the diameter is controlled to be thin and a second crystal body is successively grown by connecting to this narrow diameter part, and a cooled crystal body which is kept away from the melt while continuously growing the crystal. A third process of newly supporting the crystal, applying a predetermined rotation to the crystal while supporting other crystals connected to the newly supported crystal, and continuing to pull the crystal at a predetermined speed; A fourth step of cutting the thin diameter portion above the newly supported crystal while continuing to grow, and recovering the crystal located above the cut point. A method for producing single crystals.