JP2525300B2 - Method for producing silicon single crystal - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon single crystal in the Czochralski method. More specifically, silicon by the Czochralski method has been improved by improving the growth method of the seed drawn portion between the seed crystal and the shoulder portion of the silicon single crystal rod, and enabling the pulling of a large-weight silicon single crystal easily. The present invention relates to a method for producing a single crystal.

[0002]

2. Description of the Related Art A method for producing a silicon single crystal by the Czochralski method is to bring a seed crystal into contact with a silicon melt,
Next, perform seed drawing of a specific diameter and pull up the seed drawing part,
This is a method in which the single crystal in the seed drawn portion is made dislocation-free, and then the crystal is thickened to the intended diameter of the silicon rod, and the dislocation-free silicon single crystal rod is pulled up.

Generally, since crystal dislocations tend to grow in a direction perpendicular to the growth interface, it is said that dislocations are likely to escape when the growth interface is convex downward (F.SHIM).
URA, Semiconductor Silicon Crystal Technology, Aca
demic Press Inc. P.140). Therefore, in order to first pull up the dislocation-free seed drawn portion, it is necessary to slow down the growth rate of the seed drawn portion, that is, the pulling speed, because the interface shape needs to be convex downward.

Further, when the crystal orientation is (100), for example, it is said that the diameter of the seed-thinned portion is as thin as possible, and that the slowing down of the growth rate is a condition for making dislocation-free (W). .Zulehner and D.Huber, Czochralski-Grow
n Silicon. Crystals 8: Silicon Chemical Etcing P.
7 Springer-Verlag, Berlin and New York, 1981). Therefore, it was necessary to make the diameter of the seed-thinned portion as small as possible and slow the growth pulling rate of this portion.

From such conventional knowledge, it has been noted that the conventional method is such that the seed drawing portion is thinned and pulled up slowly. In the conventional method called the Dash neck method, the seed crystal is made into silicon. In order to grow dislocation-free crystals by allowing dislocations introduced by heat shock when brought into contact with the melt to escape to the outside of the crystal from the sufficiently narrowed seed-throttled portion, it is usually necessary to use a seed-throttled portion with a diameter of 3 mm or less. The crystalline silicon was being pulled up.

[0006]

However, the diameter of the thin seed diaphragm used in the conventional method is not sufficient for pulling a large weight silicon single crystal. .

In recent years, there has been a demand in the industry for a larger diameter silicon single crystal, but the thin seed-thinned portion by the conventional Dash neck method is a silicon single crystal with a diameter of at most 150 mm (6 inches) and a total length of 100 cm. Only pulling up can deal with strength. For example, 200mm diameter
When pulling a silicon single crystal with a large diameter (8 inches) or the like, in addition to increasing the weight, the crystal growth rate of the silicon single crystal rod is slow, and the seed drawing part is kept at high temperature and high stress for a long time. Because of the sagging, dislocations are generated in the seed drawing portion and the crystal is more likely to be cut in this portion, which may lead to a serious accident such as dropping of a silicon single crystal in the pulling process.

Therefore, according to the conventional method, it is difficult to pull up a large-diameter silicon single crystal having a large overall length and a specific length while only holding the seed drawn portion extending from the seed crystal, and there is a risk of falling. In order to prevent this, it is necessary to newly install a special crystal support device for holding the silicon single crystal, and to pull up the silicon single crystal with a special shape. was there. According to the present invention, a silicon single crystal produced by the Czochralski method has an increasing risk of a crystal falling at the time of pulling a single crystal along with the tendency of the industry to have a large diameter and a large weight. Based on the current situation, its purpose is to meet the demand of industry to prevent such a serious accident due to crystal falling.

[0009]

The present invention was created as a result of intensive studies to solve the above problems, and based on an idea completely different from the common sense of the conventional method, with a diameter above 4.5 mm, Taneshibo
The Czochralski method has succeeded in solving all of the above problems by producing a silicon single crystal by increasing the pulling rate at 4 mm / min or more to produce a low dislocation or substantially no dislocation. A method for producing a silicon single crystal is provided.

That is, according to the present invention, in pulling a silicon single crystal by the Czochralski method, the diameter of the seed narrowing portion during the growth of the silicon single crystal is 4.5 mm or more and 10 m.
iris seed performs species aperture so that the range of m
The pulling speed at that time is 4 mm / min or more, which is a method for producing a silicon single crystal by the Czochralski method.

In the pulling of a silicon single crystal by the Czochralski method, the diameter of the seed drawing portion during the growth of the silicon single crystal is in the range of 4.5 mm or more and 10 mm or less and the seed drawing is performed. 4 mm for seed aperture
It is a method for producing a silicon single crystal, which is characterized by pulling in the range of from min to 6 mm / min.

[0012]

The present invention will be described in detail below with reference to the accompanying drawings. In FIG. 1, the seed drawing portion 2 of the present invention refers to a constricted portion located between the seed crystal 1 and the shoulder portion of the silicon single crystal ingot 3, and has a diameter 5 defined in the present invention,
To narrow down the range from 4.5 mm to 10 mm,
Start pulling the seed crystal. Then, after narrowing down to a predetermined diameter prescribed in the present invention, while maintaining the diameter, the seed narrowing portion is grown at a specific pulling rate to perform seed narrowing, and then a silicon single crystal ingot 3 having a desired diameter is obtained. Are grown to the desired full length and pulled up.

In order to obtain the diameter of the seed drawing portion specified in the present invention, the seed crystal is gradually pulled up from the molten silicon and narrowed down to a predetermined diameter value specified in the present invention.
Normally, the pulling speed up to the specified diameter value is 2 mm / min.
Perform at the following low speed, and then smoothly 4 mm
/ Min The temperature is controlled so that it can be transferred at a high speed, for example, the temperature of the solid-liquid interface which is higher by 10 ° C than the single crystal rod pulling temperature of 1420 ° C, and the narrowing is performed until a predetermined diameter value is reached. The diameter value of the seed diaphragm portion is usually measured by visual observation using a scale, or when further accuracy is required, measured by a CCD camera.

Further, in order to obtain a seed diaphragm portion having a predetermined minimum diameter value, a seed crystal having a certain size or more may be used. For example, in order to reliably obtain a seed-thinned portion having a minimum diameter of 5 mm, a seed crystal of 15 mm square or more or 15 mmφ or more is used, although it depends on conditions such as the pulling speed until the narrowing.

To produce a silicon single crystal having a low dislocation rate or a substantially dislocation-free state in which a desired pulling rate is appropriately determined while maintaining the diameter corresponding to a predetermined diameter of the seed drawn portion. You can FIG. 2 is a graph clarified by the present inventor and is a graph showing the relationship between the dislocation-free rate of the silicon single crystal and the growth rate (pulling rate) of the seed-thinned portion at the minimum diameter of the specific seed-thinned portion. But
When the minimum diameter value of the seed drawn portion is 4 mm or less, dislocation-free silicon single crystal is produced regardless of the growth rate, but when it is 4.5 mm or more, the dislocation-free rate is proportional to the growth rate. Suggests a finding that
For example, the minimum diameter value of the seed narrowing portion is 4.5 mm to 10
In case of mm, the pulling speed of the seed throttle part is 4 mm / m
In-process produces a substantially dislocation-free silicon single crystal, without the risk of dropping a large-weight, large-diameter silicon single crystal at the seed drawing part, and without using another crystal support device. In addition, it is possible to pull up while maintaining the shape of the conventional silicon single crystal ingot.

As described above, the pulling rate (growth rate) of the seed drawn portion is appropriately determined by the minimum diameter value of 4.5 mm or more, and the preferable lower limit value is the desired dislocation-free rate of the silicon single crystal. From this relationship, it is appropriately determined within a range that does not impair the effects of the present invention, and the upper limit value is similarly determined. The growth rate does not need to be higher than the achievable growth rate for the purpose of producing a silicon single crystal having a desired dislocation-free rate, and is selected within a range in which narrowing does not occur frequently. Be done.

For example, the minimum diameter of the seed diaphragm is 4.5 m.
In the case of m, the growth rate of the seed drawn portion is 4 mm / min or more from the viewpoint of dislocation-free rate,
From the viewpoint of reducing the occurrence of squeezing, 6 mm /
It is a preferred embodiment of the present invention to be pulled up at a value of min or less.

The pulling rate of the seed-thinned portion having a predetermined minimum diameter value that can safely pull up a silicon single crystal having a low dislocation rate or substantially no dislocation is the crystal orientation. And the size of the seed crystal, the pulling time until narrowing down, and other conditions. It should be noted that if the diameter of the seed drawn portion exceeds 10 mm, it becomes difficult to manufacture a dislocation-free silicon single crystal.

Normally, the total length of the seed drawn portion is grown from 30 mm to 200 mm, but the preferred range in the present invention is 50 mm to 200 mm.

The pulling growth of the silicon single crystal ingot having the desired diameter and the entire length after the pulling up of the seed drawn portion is completed, and the pulling up growth of the silicon single crystal rod can be performed safely without falling within a range not impairing the effect of the present invention. A silicon single crystal ingot is manufactured by the Czochralski method provided with an arbitrary pulling rate for pulling the crystal, a rotation speed of the crystal and the crucible, and other conditions.

[Example 1] A seed crystal having a seed crystal orientation (100) and a thickness of 15 mm square was left for 10 minutes on the silicon melt in a crucible, and the temperature of the seed crystal was sufficiently raised. Was immersed in a silicon melt. After soaking the seed crystal into the melt until the fusion ring is visible,
The seed crystal was pulled up and grown. At this time, the initial growth rate was within the range of 2 mm / min, and the diameter was reduced from the seed crystal of 15 mm square to the target diameter value of 5 mmφ of the seed narrowing portion. Then, while maintaining the diameter of the seed drawn portion, the seed drawn portion was grown by pulling up at a growth rate of 4 mm / min or more. Subsequent to the seed drawing step described above, the diameter of the seed drawing portion of 5 mmφ pulls up a large-diameter silicon single crystal ingot with a crystal diameter of up to 208 mm, grows up to 50 cm, and then rounds,
A dislocation-free silicon single crystal having a diameter of up to 208 mm could be pulled and manufactured.

[Example 2] A seed crystal having a crystal orientation (111) was produced in exactly the same manner as in Example 1 and had a diameter of 208 mm.
The silicon single crystal ingot was pulled up and a dislocation-free silicon single crystal was manufactured by the Czochralski method.

[0023]

According to the present invention, compared to the conventional method, the risk of falling during pulling growth can be prevented and a larger weight silicon single crystal can be manufactured. Further, according to the present invention, it is possible to pull a large-diameter silicon single crystal over the same length as the conventional one, and it is possible to improve the yield and the productivity. According to the present invention, a silicon single crystal having low dislocation density or substantially no dislocation can be manufactured. Furthermore, since no special crystal holding device is required, it is possible to avoid an increase in the cost of the pulling device.
In addition, since it is not necessary to pull up a silicon single crystal having a special shape in order to prevent crystal falling as in the conventional case, pulling can be performed very easily, and a silicon single crystal free from crystal disorder due to the special shape can be manufactured. .

In the present invention, the risk of crystal falling during pulling up of a single crystal increases with the tendency of the industry that the silicon single crystal produced by the Czochralski method becomes larger in diameter and heavier. In view of the current situation, it is an epoch-making invention that meets the demand of the industrial world to prevent such a serious accident due to crystal falling.

[Brief description of drawings]

FIG. 1 is an external view of a silicon single crystal showing a seed diaphragm portion of the present invention.

FIG. 2 is a graph showing the relationship between the growth rate of the seed-thinned portion and the dislocation-free rate of the silicon single crystal with respect to the diameter value of the seed-thinned portion.

[Explanation of symbols]

 1 seed crystal 2 seed drawing part 3 silicon single crystal 4 seed crystal diameter 5 diameter of seed drawing part

Claims (3)

(57) [Claims] 1. A pulling of the silicon single crystal by the Czochralski method, when the diaphragm type with a diameter of the seed diaphragm portion during silicon single crystal growth performed seeds aperture to be in the range of 4.5mm or more 10mm or less Pulling speed of 4
A method for producing a silicon single crystal, which is characterized in that it is set to mm / min or more . 2. The pulling speed of the seed drawing portion having a diameter of 4.5 mm or more and 10 mm or less is 4 mm / min to 6 m.
The method for producing a silicon single crystal according to claim 1, which is in the range of m / min. 3. The method for producing a silicon single crystal according to claim 1, wherein the seed-throttled portion having a diameter of 4.5 mm or more and 10 mm or less has a total length in the range of 30 mm to 200 mm.