JPH11268991A - Production of silicon single crystal, and silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing silicon single crystal, capable of preventing a steep lowering of temperature, when a single crystal is separated from a melted liquid, and thereby capable of improving the productivity and yield of the silicon single crystal by gradually increasing the rate for pulling up the single crystal on the production of the tail portion of the single crystal after the production of the constant diameter portion of the single crystal on the growth of the silicon single crystal. SOLUTION: This method for producing silicon single crystal comprises growing a silicon single crystal by Czochralski method. Therein, on the production of the tail portion of the single crystal after the production of its constant diameter portion, a rate for pulling up the single crystal is gradually increased so that a pulling rate at the finish of the tail portion production is 1.1-5, when the pulling rate at the start of the tail portion production is 1. A method for accelerating the pulling rate may be either one of a method for accelerating the pulling rate in a quadric curve, a method for stepwisely accelerating the pulling rate and a method for linearly accelerating the pulling rate. It is further preferable that while the rate for pulling up the single crystal is gradually increased, a crucible receiving the melted liquid of a raw material is upward moved to moderate the steep lowering of a melted liquid level and thereby avoid the abrupt change of temperature.

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 tail portion in the growth of a silicon single crystal by the Czochralski method (CZ method), and a silicon single crystal produced by the method.

[0002]

2. Description of the Related Art Conventionally, in the production of a silicon single crystal by the CZ method, a silicon single crystal is used as a seed crystal, which is brought into contact with a silicon melt and then slowly pulled up while rotating to obtain a single crystal rod. Growing. At this time, a heater is provided on the outer periphery of the quartz crucible / graphite crucible holding the melt, and the single crystal is pulled while supplying heat to the crucible from the heater. In this case, after the seed crystal is brought into contact with the silicon melt, in order to eliminate dislocations propagating from slip dislocations generated at high density in the seed crystal due to thermal shock, the diameter is once reduced to about 3 mm and the constricted portion is formed. A so-called seed drawing (necking) is performed, and then the crystal is thickened to a desired diameter to form a cone portion, and a single crystal straight body portion having a predetermined diameter (hereinafter also referred to as a constant diameter portion) is formed. The silicon single crystal rod is grown at a pulling speed of.

When the length of the grown single crystal reaches a predetermined length, the end (tail) of the single crystal is cut off from the melt. At this time, the grown single crystal is simply cut off from the melt. In this case, a sudden drop in temperature occurs at the cut-off portion of the single crystal, and slip dislocations occur in the single crystal, which greatly lowers the single crystallinity (the yield of the fixed diameter portion where there is no problem with the quality of the single crystal). Would. Therefore, as a countermeasure, usually, after manufacturing a single crystal constant diameter part, gradually narrow the diameter gradually,
After the contact area between the single crystal and the melt is made sufficiently small, the single crystal is separated from the melt to prevent occurrence of slip dislocation. Usually, the part where the diameter is gradually narrowed is called a tail or rounding.

Conventionally, the tail portion has been formed by gradually increasing the diameter of the melt while gradually increasing the temperature of the melt by increasing the amount of heat supplied from the heater to the melt in the crucible.
However, in this method, since the melt temperature at the end of the tail step becomes high, the OSF (oxidation-induced stacking fault,
Oxidation Induced Stackin
g Fault) (hereinafter referred to as O fault).
Since the single crystal is easily cooled and the temperature change when the single crystal is separated from the melt is large, the single crystal is rapidly cooled, and a portion having an abnormally large amount of oxygen precipitated in the single crystal constant diameter portion (hereinafter, referred to as “the SF ring”). Abnormal oxygen precipitation portion).

In performing the rounding step, the pulling speed of the single crystal was sometimes increased. However, after the rounding was cut off or the single crystal constant diameter portion was completed, the speed was rapidly increased and the rounding was started. A sudden change in temperature occurs during the process, so that the single crystal is rapidly cooled to easily cause slip dislocation, and furthermore, there is a defect that an abnormal oxygen precipitation portion appears even in the single crystal constant diameter portion.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and prevents a sharp drop in temperature when a single crystal is separated from a melt in a final tail step in pulling a single crystal. Production of a silicon single crystal that suppresses the occurrence of an abnormally large amount of oxygen precipitation and an OSF ring in the constant diameter portion immediately adjacent to the tail portion, increases the single crystallization rate, and improves the productivity and yield of the silicon single crystal. It is a main object to provide a method and a silicon single crystal manufactured by the manufacturing method.

[0007]

According to a first aspect of the present invention, there is provided a method for growing a silicon single crystal by the Czochralski method, comprising the steps of: Is a method for manufacturing a silicon single crystal, characterized in that the speed of pulling a single crystal is gradually increased in manufacturing the silicon single crystal.

As described above, when pulling a silicon single crystal, the diameter of the single crystal is gradually reduced and narrowed until the single crystal is separated from the melt after the production of the fixed diameter portion of the single crystal. In the manufacturing method of the tail portion, which reduces the thermal shock at the time of separating by making the contact area sufficiently small, the pulling speed of the single crystal is gradually increased with reference to the pulling speed at the time of manufacturing the constant diameter portion, so that the tail portion is manufactured. With the formation of, the temperature rise of the tail portion is alleviated, and the occurrence of the OSF ring can be suppressed. Furthermore, the temperature of the melt does not need to be gradually increased as in the conventional technology. Even if the melt is finally cut off at a point contact point, the thermal shock is small, and the portion with an abnormally large amount of oxygen precipitation in the constant diameter portion near the tail part. Can be suppressed. Moreover, since the pulling speed is gradually increased, it is possible to improve the productivity and yield of silicon single crystal without being cut from the melt during the production of the rounded portion and without lowering the single crystallization ratio. it can.

In this case, as described in claim 2, when manufacturing the tail portion, if the pulling speed at the start of the tail portion production is set to 1, the pulling speed at the end of the tail portion production is 1.1. It is preferable to gradually increase the speed so as to reach ５5.

As described above, the pulling speed at the time of manufacturing the tail portion is gradually increased, and the pulling speed at the end of the tail portion is set within a range of 1.1 to 5 times the pulling speed at the start of manufacturing the tail portion. If the temperature of the tail part is reduced,
The occurrence of the OSF ring can be suppressed. Furthermore,
Even if the tail part is finally separated from the melt, a sharp temperature drop is avoided, so that a part with an abnormally large amount of precipitated oxygen can be suppressed. Also, if the pulling speed is rapidly increased, the tail tip and the melt may be separated during the manufacturing of the tail portion, but if the speed is gradually increased while being adjusted to fall within the above range, the tail can be increased. The formation of the site is easy, and a stable single crystal can be manufactured without being separated from the melt.

According to the third aspect of the present invention, in manufacturing the tail portion, the speed of pulling the single crystal is gradually increased, and at the same time, the crucible containing the raw material melt is moved upward. A method for producing a silicon single crystal, characterized in that:

As described above, when the tail portion is manufactured, if the single crystal pulling speed is gradually increased and the crucible containing the raw material melt is moved upward at the same time, a sharp decrease in the melt level can be prevented. As a result, the risk of separation during the formation of the tail portion is further reduced, rapid temperature changes are avoided, and abnormal oxygen precipitation is further prevented, contributing to improved productivity and yield of silicon single crystals. can do.

According to a fourth aspect of the present invention, there is provided a silicon single crystal manufactured by the manufacturing method according to the first to third aspects. A single crystal rod manufactured by such a method for manufacturing a tail portion has an abnormal oxygen precipitation portion particularly in a constant diameter portion immediately adjacent to the tail portion, and has an OSF.
Since the defect density is extremely low with almost no occurrence of rings, a high-quality silicon single crystal can be obtained over the entire length.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. The present inventors, when pulling the silicon single crystal, when the tail tip is separated from the melt in the final tail part manufacturing process, generated by thermal shock accompanied by a sharp temperature drop, in the constant diameter part immediately near the tail part After investigating and examining a method of manufacturing a tail part that suppresses the occurrence of OSF rings and the like due to abnormally high amounts of oxygen precipitation and sudden heating to a high temperature due to heating, the pulling rate of the single crystal was gradually increased when manufacturing the tail part. The inventors conceived that the speed should be increased, and scrutinized various conditions to complete the present invention.

First, the present invention is characterized in that in growing a silicon single crystal by the Czochralski method, the speed of pulling the single crystal is gradually increased when manufacturing the tail portion after manufacturing the constant diameter portion of the single crystal. Things.

As described above, when pulling a silicon single crystal, the diameter of the single crystal is gradually reduced until the single crystal is separated from the melt after the production of the fixed diameter portion of the single crystal. In the manufacturing method of the tail part, which has a sufficiently small contact area and reduces the thermal shock at the time of cutting, if the pulling speed of the single crystal is gradually increased based on the pulling speed at the time of manufacturing the constant diameter part, the melting Since it is not necessary to gradually raise the liquid temperature as in the prior art, the rise in the temperature of the tail portion is reduced,
The occurrence of the OSF ring can be suppressed. Then, even if the thermal shock is finally separated at a point contact, the thermal shock becomes small, and it becomes possible to suppress the appearance of the abnormal oxygen precipitation portion in the constant diameter portion immediately near the tail portion. Therefore, the productivity and yield of the silicon single crystal can be improved without deteriorating the quality of the constant diameter portion.

In this case, the speeding-up means that the pulling speed at the end of the tail portion production is set to 1.1 to 5 times when the pulling speed at the start of the tail portion production is set to 1 based on the pulling speed. It is preferable to accelerate gradually. in this way,
If the pulling speed at the time of tail part manufacturing is gradually increased, and the pulling speed at the time when the tail length reaches a predetermined tail length falls within a range of 1.1 to 5 times the pulling speed at the start of tail part manufacturing, It is possible to alleviate the rise in temperature of the tail part, suppress the occurrence of OSF rings, and avoid a sudden drop in temperature even when finally cut at the point contact part, and suppress the occurrence of abnormal oxygen precipitation. it can.

When the acceleration index of the pulling speed is less than 1.1, it is necessary to raise the temperature of the melt to some extent because the crystal cannot be sufficiently thinned to form a tail portion by the pulling speed alone. Therefore, the temperature of the crystal is also increased, and the temperature of the tail portion is rapidly lowered when the tail is separated, so that the prevention of abnormal oxygen precipitation may be insufficient. On the other hand, if the acceleration index of the pulling speed is higher than 5 when the speed is increased, the single crystal is easily separated from the surface of the melt during the production of the tail. Therefore, it is preferable to gradually increase the speed while adjusting to fall within the above range. .

FIG. 1 (a) shows an example of increasing the pulling speed during tail manufacturing. Here, to pull up to a tail length of 190 mm, the oxygen was accelerated to 4.7 times in a quadratic curve, and as a result, the oxygen precipitation concentration in the single crystal constant diameter portion (FIG. 1B)
Are almost uniform and there are no abnormally high areas. In the drawings of the single crystal shown in FIGS. 1 to 3, the scales of the vertical axis and the horizontal axis are shown differently.

As a method of accelerating the pulling speed, in addition to the method of accelerating in a quadratic curve as described above, substantially the same effect can be obtained by accelerating stepwise or linearly. . FIG. 2 (a) shows an example in which the pulling speed is changed to four steps to increase the tail length to 190 mm, and the pulling speed is increased to five times. 2
In (b)), a value almost equivalent to the method of accelerating in a quadratic curve is obtained.

Next, in the present invention, it is preferable that, when the tail portion is manufactured, the crucible containing the raw material melt is moved upward at the same time as the pulling speed of the single crystal is gradually increased. As described above, when manufacturing the tail portion, if the crucible containing the raw material melt is moved upward at the same time as the pulling speed of the single crystal is gradually increased, a sharp drop in the melt level can be mitigated. The risk of separation during the formation of the tail portion is further reduced, abrupt temperature changes are also avoided, and abnormal oxygen precipitation is further prevented, thereby contributing to improved productivity and yield of silicon single crystals. it can.

In the method of manufacturing a tail portion according to the present invention, the electric power of a heater for heating the raw material melt accommodated in the crucible at the time of manufacturing the tail is substantially equal to that at the time of manufacturing the constant diameter portion.
Alternatively, it is possible to sufficiently form the tail portion by increasing the amount by about 5% in the latter half of the tail production. Therefore, the thermal shock at the time of separating the tail tip can be reduced without increasing the temperature of the tail portion. When increasing the temperature at the same time as gradually increasing the pulling speed at the time of tail manufacturing, the raising width may be appropriately selected in consideration of the raising width of the pulling speed.

The silicon single crystal rod manufactured by the above-described method of manufacturing the tail portion has a slip dislocation, particularly at a constant diameter portion immediately adjacent to the tail portion, a portion having an abnormally large amount of precipitated oxygen, and an OSF ring. Since the defect density is very low with almost no occurrence, a high-quality silicon single crystal can be obtained over the entire length.

[0024]

EXAMPLES The present invention will now be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. The oxygen precipitation amount was determined by subjecting a wafer collected from each position of the constant diameter portion to a heat treatment at 650 ° C. × 2 hours in a nitrogen gas atmosphere and at 1000 ° C. × 16 hours in an oxygen gas atmosphere, and expressed as an ASTM '79 value. .

Example 1 A CZ single crystal having a diameter of a constant diameter portion of 150 mm and a length of a tail portion of 190 mm was produced. First, a constant-diameter portion having a diameter of 150 mm was prepared at a pulling rate of F mm / min, and then the process was shifted to the production of a tail portion as shown in FIG. When the pulling speed at the tail start was set to Fmm / min, the pulling speed at the tail portion manufacturing was gradually increased to 4.7 F at the end of the tail. On the other hand, when the tail start time is HkW, the heater power is 1.05H at the tail end, and the electric power at the end of the tail portion production is reduced by about 13% compared with the conventional method.
Could be lower. The oxygen precipitation concentration at this time is shown in FIG.
As shown in (b), when the constant diameter portion was measured from a position 8 cm before the start of the tail portion, it was 1c before the start of the tail.
It was almost uniform that the amount of precipitation increased very slightly at m.

Example 2 A CZ single crystal having a diameter of a constant diameter portion of 150 mm and a length of a tail portion of 190 mm was produced. First, a constant-diameter portion having a diameter of 150 mm was prepared at a pulling speed of F mm / min, and then the process was shifted to the production of a tail portion as shown in FIG. When the pulling speed at the start of the tail was set to Fmm / min, the pulling speed at the tail portion manufacturing was gradually increased stepwise so as to be 5.0 F at the end of the tail. On the other hand, when the tail start time was set to HkW, the heater power was 1.05 H at the tail end, and the power at the end of the tail portion fabrication could be reduced by about 13% compared to the conventional method. As shown in FIG. 2 (b), the oxygen precipitation concentration at this time was measured from a position 8 cm before the start of the tail portion with respect to the constant diameter portion. Was almost uniform.

Comparative Example A CZ single crystal having a diameter of a constant diameter portion of 150 mm and a length of a tail portion of 190 mm was produced. First, a constant-diameter portion having a diameter of 150 mm was formed at a pulling rate of F mm / min, and then the process was shifted to the production of a tail portion as shown in FIG. The pulling speed at the time of manufacturing the tail portion was set to Fmm / min at the start of the tail, and was kept constant until the end of the tail. On the other hand, in this case, the heater power continues to increase from about 4 cm after the tail starts, and the tail end 1
At 9 cm, it was 1.2 times that at the time of raising the constant diameter portion. As shown in FIG. 3B, the oxygen precipitation concentration at this time rapidly increased from the position 3 cm before the start of the tail portion for the constant diameter portion, and was 7.2 × 10 ¹⁷ atoms / s at the start of the tail portion.
cm ³ and increased abnormally.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, in the embodiment of the present invention, the diameter 15
Although a 0 mm (6 inch) silicon single crystal rod is grown, recent 200 mm (8 inch) to 400 mm (1 inch)
6 inches) or more.

The present invention is not limited to the ordinary Czochralski method, but also to the MCZ method (Magnetic Field Applied Czochralski Cry method) for applying a magnetic field when pulling a silicon single crystal.
It goes without saying that the term Czochralski method as used herein includes the MCZ method as well as the usual Czochralski method.

[0031]

As described above, according to the present invention,
Since the occurrence of OSF rings due to abnormal oxygen precipitation caused by thermal shock when the silicon single crystal tail part is separated and the sudden rise in temperature for producing the tail part is suppressed, the productivity, yield, and manufacturing cost of the silicon single crystal Can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing manufacturing conditions of a silicon single crystal tail portion of the present invention and the amount of oxygen precipitated in a single crystal constant diameter portion. (A) Pulling speed and heater power at the time of tail portion production, (b) Oxygen precipitation amount at single crystal constant diameter portion.

FIG. 2 is a graph showing manufacturing conditions of a silicon single crystal tail portion of the present invention and the amount of oxygen precipitated in a single crystal constant diameter portion. (A) The pulling speed changed in a stepwise manner at the time of manufacturing the tail portion, (b) The amount of precipitated oxygen in the single crystal constant diameter portion.

FIG. 3 is a graph showing a conventional silicon single crystal tail portion manufacturing condition and a single crystal constant diameter portion with oxygen precipitation. (A) Pulling speed and heater power at the time of tail portion production, (b) Oxygen precipitation amount at single crystal constant diameter portion.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tomohiko Ota 150 Odakura Odaikura, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Shin-Etsu Semiconductor Shirakawa Plant

Claims (4)

[Claims] 1. A method of growing a silicon single crystal by the Czochralski method, wherein a single crystal pulling speed is gradually increased in manufacturing a tail portion after manufacturing a constant diameter portion of the single crystal. Manufacturing method. 2. The method of manufacturing a tail part according to claim 1, wherein when the pulling speed at the start of the tail part manufacturing is set to 1, the pulling speed at the end of the tail part manufacturing is gradually increased to 1.1 to 5. The method for producing a silicon single crystal according to claim 1, wherein: 3. A crucible for accommodating a raw material melt is moved upward at the same time as the pulling speed of the single crystal is gradually increased when the tail portion is manufactured. 3. The method for producing a silicon single crystal described in 1. above. 4. A silicon single crystal manufactured by the manufacturing method according to claim 1.