JP2007210817A - Silicon single crystal manufacturing apparatus and manufacturing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon single crystal manufacturing apparatus with which the cooling speed of a silicon single crystal being pulled can be increased so as to make the size of COP (Crystal Originated Particle) small, when a silicon single crystal is manufactured by a Czochralski method; and to provide a silicon single crystal manufacturing method. <P>SOLUTION: The apparatus has a tubular cooling chamber 33 which is arranged so as to surround a silicon single crystal 13 being pulled and is forcibly cooled by a cooling medium. As the cooling medium, a liquid, such as silicone oil having a vaporization temperature higher than that of water is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for manufacturing a silicon single crystal by a chocolate ski method (hereinafter referred to as CZ method) and a manufacturing method using the same.

High purity dislocation-free silicon single crystals are mainly used for semiconductor element substrates. In general, the CZ method is used as the manufacturing method.
FIG. 2 is a schematic longitudinal sectional view showing an example of a silicon single crystal manufacturing apparatus according to the prior art.
In the silicon single crystal manufacturing apparatus using the CZ method, a quartz crucible 3 is installed in the center of a chamber 1 so as to be movable up and down as shown in FIG. The quartz crucible 3 is accommodated in the carbon crucible 5.
In growing a silicon single crystal, first, bulk polycrystalline silicon is loaded into a quartz crucible 3, and polycrystalline silicon is formed by a main heater 7 and a lower heater 9 provided so as to surround the quartz crucible 3 and the carbon crucible 5. Is melted by heating to obtain a silicon melt 11. Then, a seed crystal (seed) having a desired crystal orientation is immersed in the silicon melt 11 to adjust to the melt temperature. When familiar, the seed is pulled upward to grow the silicon single crystal 13 to a predetermined diameter and length.

In recent years, as device miniaturization technology advances, control of so-called Grown-in defects such as COP (Crystal Originated Particle) that occur during the growth of a silicon single crystal is required. This is because it has been clarified that the presence of the Grown-in defect deteriorates the oxide film breakdown voltage characteristic of the semiconductor device.
Non-Patent Document 1 reports the temperature conditions for forming this Grown-in defect. According to this document, the COP formation temperature is 1080-1110 ° C. for nitrogen non-doped crystals and 1040-1090 ° C. for nitrogen-doped crystals. The COP formation temperature zone transit time when pulling the silicon single crystal has an influence on the COP density and size. That is, when the passage time is short, the COP density increases but the size decreases. Conversely, if the passage time is long, the COP density decreases but the size increases.

  Generally, in an annealed wafer that is subjected to heat treatment in an inert gas atmosphere to form a denuded zone (hereinafter referred to as a DZ layer), if the COP size after pulling the silicon single crystal is small, the COP in the region that becomes the DZ layer should be excluded. Is easy. Therefore, in order to suppress COP of the final wafer product, it is desirable to shorten the COP formation temperature zone passage time as much as possible during the growth of the silicon single crystal. That is, it is required to improve the single crystal cooling rate when pulling up the silicon single crystal.

Conventionally, the improvement of the single crystal cooling rate at the time of pulling the silicon single crystal has been studied mainly from the viewpoint of increasing the productivity by increasing the crystal pulling rate. As a method therefor, many inventions characterized in that a cooling chamber called a cooling cylinder or an aftercooler is provided so as to surround the silicon single crystal when pulled up.
For example, Patent Document 1 discloses an invention in which a cooling cylinder is provided that extends from at least the ceiling of the main chamber toward the surface of the raw material melt so as to surround the single crystal that is being pulled up and is forcibly cooled by a cooling medium. . This cooling cylinder can improve the single crystal cooling rate.
Further, for example, in Patent Document 2, an aftercooler is installed so as to surround the single crystal being pulled, and the amount of cooling water supplied to the aftercooler is set at a certain rate until at least the single crystal grows to a predetermined length. The invention is characterized in that it is gradually increased. By using this after cooler, the single crystal cooling rate can be improved.
WO01 / 057293 Publication JP-A-11-92272 Ono et al., Kansai branch seminar of the Japan Society of Applied Physics, 2000 1st seminar abstract, pp. 38-39

In the prior art, water is generally used as a cooling medium for the cooling chamber because it is inexpensive and can be stably supplied.
However, the use of water as a cooling medium in the vicinity of the melt exceeding 1000 ° C. has a risk of inducing a steam explosion due to vaporization and expansion. That is, it is conceivable that when the cooling chamber approaches a high-temperature melt or a single crystal that is being pulled, water as the cooling medium exceeds the vaporization temperature and a steam explosion occurs in the cooling chamber. It is also conceivable that a water vapor explosion in the furnace may occur due to leakage of water into the furnace caused by breakage of the cooling chamber caused by use in the furnace exposed to high temperatures.
In order to avoid the danger of these steam explosions, the prior art has suppressed the temperature rise of the water by ensuring the distance between the cooling chamber and the melt or single crystal. Alternatively, the cooling chamber itself is made thick so as to suppress the temperature rise of the cooling medium water and prevent the cooling chamber from being damaged.
However, increasing the distance between the cooling chamber and the melt or single crystal results in a decrease in cooling efficiency. In addition, increasing the thickness of the cooling chamber itself also reduces the cooling efficiency because the heat exchange action is reduced. Therefore, these measures are a great limitation in increasing the cooling rate of the pulled single crystal.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a silicon single crystal manufacturing apparatus capable of increasing the cooling rate of a pulled silicon single crystal and a manufacturing method using the same. There is to do.

An apparatus for producing a silicon single crystal of one embodiment of the present invention includes:
A silicon single crystal manufacturing apparatus using a chocolate lasky method (CZ method),
It has a cylindrical cooling chamber that is arranged so as to surround the silicon single crystal that is being pulled up and is forcedly cooled with a cooling medium,
The cooling medium is a liquid having a higher vaporization temperature than water.

The method for producing a silicon single crystal of one embodiment of the present invention includes:
A silicon single crystal manufacturing apparatus using a chocolate lasky method (CZ method),
It has a cylindrical cooling chamber that is arranged so as to surround the silicon single crystal that is being pulled up and is forcedly cooled with a cooling medium,
A silicon single crystal is manufactured using a silicon single crystal manufacturing apparatus, wherein the cooling medium is a liquid having a vaporization temperature higher than that of water.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the silicon single crystal manufacturing apparatus which can raise the cooling rate of a pulling silicon single crystal, and a manufacturing method using the same.

  Hereinafter, a silicon single crystal manufacturing apparatus and a silicon single crystal manufacturing method using the same according to the present invention will be described with reference to the accompanying drawings.

(Silicon single crystal manufacturing equipment)
FIG. 1 is a schematic longitudinal sectional view of an embodiment of a silicon single crystal manufacturing apparatus according to the present invention.
The silicon single crystal manufacturing apparatus shown in FIG. 1 is similar to the single crystal manufacturing apparatus of the prior art, in which crucibles 3 and 5 filled with polycrystalline silicon as a raw material are heated and melted to melt silicon melt 11. A main heater 7 and a lower heater 9 are housed in the chamber 1, and a pulling mechanism (not shown) for pulling up the grown silicon single crystal 13 is provided in the upper portion of the chamber 1.
A pulling wire 15 is unwound from a pulling mechanism attached to the upper portion of the chamber 1, and a seed holder (not shown) for attaching a seed crystal (not shown) is connected to the tip of the pulling wire 15. .

The crucibles 3 and 5 are composed of a quartz crucible 3 that directly stores the silicon melt 11 inside, and a carbon crucible 5 for supporting the quartz crucible 3 outside. The crucibles 3 and 5 are supported by a crucible shaft 17 that is rotatable up and down by a rotational drive function (not shown) attached to the lower part of the silicon single crystal manufacturing apparatus.
A main heater 7 and a lower heater 9 are arranged so as to surround the crucibles 3 and 5, and the heat from the main heater 7 is prevented from being directly radiated to the chamber 1 outside the main heater 7. A first heat insulating material 19 and a second heat insulating material 21 are provided so as to surround the main heater 7. In addition, a third heat insulating material 23 and a fourth heat insulating material 25 for preventing heat from the silicon melt 11 and the crucibles 3 and 5 from being directly radiated to the chamber 1 are provided. Then, the heat from the silicon melt 11 and the crucibles 3 and 5 does not hinder the cooling of the single crystal 13 or the silicon melt 11 scattered when the raw material melts adheres to the cooling chamber described later. In order to prevent this, a radiation shield 27 is provided between the silicon melt 11, the crucibles 3, 5 and the silicon single crystal 13. In addition, about the material of the heat insulating materials 19 and 21, it is desirable to use what is especially excellent in heat retention, and a shaping | molding heat insulating material is normally used. As the material of the heat insulating materials 23 and 25, for example, a molded heat insulating material, carbon, or a material whose surface is covered with silicon carbide is used. The radiation shield 27 plays the role of adjusting the radiation heat. For example, a metal such as molybdenum, tungsten, or tantalum, carbon, carbon whose surface is coated with silicon carbide, and a molded heat insulating material are installed inside these. Used.
The chamber 1 is made of a metal having excellent heat resistance and thermal conductivity, such as stainless steel, and is water-cooled through a cooling pipe (not shown).

  Further, a cylindrical cooling chamber 33 extends from the ceiling of the chamber 1 to the surface of the silicon melt 11 so as to surround the silicon single crystal 13 being pulled up. The information of the cooling chamber 33 is provided with a cooling medium inlet (not shown) for introducing a cooling medium for forcibly cooling the cooling chamber 33. The material of the cooling chamber 33 is not particularly limited as long as it has heat resistance and excellent thermal conductivity, but specifically, iron, nickel, chromium, copper, titanium, molybdenum, tungsten, or these metals It can be made from an alloy containing The metal or alloy may be covered with titanium, molybdenum, tungsten, or a platinum-based metal.

The silicon single crystal manufacturing apparatus according to the present invention is characterized in that a liquid having a higher vaporization temperature than water is used as a cooling medium.
Note that any liquid can be used as long as it has a higher vaporization temperature than water, but oil (oil) is used from the viewpoint of stability at high temperature and ease of handling. Is preferred. Here, the oil (oil) is a liquid that is liquid at room temperature, insoluble in water, viscous, and has a specific gravity smaller than that of water. Examples thereof include synthetic oil, mineral oil, animal oil, and vegetable oil. Furthermore, considering the high vaporization temperature of 250 ° C. or more, the influence of contamination in the furnace in the event of leakage, or the heat capacity and viscosity of silicone oil, the heat capacity effect is superior, resulting in a circulation pump. It is more preferable to use silicone oil from the viewpoint of reducing the load on the oil.

(Silicon single crystal manufacturing method)
Next, a method for manufacturing a silicon single crystal according to the present invention using the silicon single crystal manufacturing apparatus will be described with reference to FIG.
First, the raw material polycrystalline silicon is loaded into the quartz crucible 3, and the raw material polycrystalline silicon is melted by heating with the main heater 7 and the lower heater 9 while introducing an inert gas such as argon gas from the upper part of the chamber. Let it be the liquid 11. By introducing the inert gas, impurities generated in the furnace by heating can be discharged out of the furnace, and high purity of the pulled silicon single crystal can be realized.

After the polycrystalline silicon melts and the silicon melt 11 is generated, a seed crystal (not shown) having a desired crystal orientation attached to the tip of the pulling wire 15 is immersed in the silicon melt 11 to melt the melt. Acclimate with temperature. When familiar, the rod-shaped silicon single crystal 13 is grown by gently pulling it upward while rotating the seed crystal by a pulling mechanism (not shown). At this time, a so-called dash neck method is performed in order to remove dislocations generated when the seed crystal contacts the melt. This is because the crystal diameter is once narrowed to about 3 to 5 mm at the time of pulling, and when the dislocations are removed from the crystal, the crystal diameter is expanded to a desired size, and the silicon single crystal 13 is maintained up to a predetermined length while maintaining this diameter. Nurturing
Also, while pulling up the seed crystal by the pulling mechanism, the crucible is raised using the crucible shaft 17 so that the height of the melt surface is always kept constant in order to obtain a desired crystal quality.

  The silicon single crystal 15 pulled up from the silicon melt 11 is efficiently cooled by the cooling chamber 33 provided inside the chamber 1 so as to surround the silicon single crystal. A liquid having a higher vaporization temperature than water, for example, silicone oil, is introduced into the cooling chamber 33 as a cooling medium from a cooling medium inlet (not shown), and this liquid circulates in the cooling chamber 33 to circulate the cooling chamber. After forcibly cooling 33, it is discharged to the outside.

(effect)
In the prior art, water having a low vaporization temperature of 100 ° C. is used as a cooling medium for the cooling chamber 33, so there is a risk of steam explosion. For this reason, it is necessary to take measures to reduce the cooling efficiency, such as securing the distance between the cooling chamber 33 and the silicon melt 11 or the silicon single crystal 33 or increasing the thickness of the cooling chamber 33 itself.
In the present invention, a liquid having a higher vaporization temperature than water is used as the cooling medium. Therefore, as compared with the case of using water, measures such as reducing the distance between the cooling chamber 33 and the silicon melt 11 or the silicon single crystal 33 or reducing the cooling chamber 33 itself to improve the cooling efficiency. Is possible.
Specifically, for example, the cooling chamber 33 can be extended in the direction of the silicon melt 11 and the inner diameter of the cooling chamber 33 can be made smaller than in the prior art.
Furthermore, when oil is used as the liquid having a higher vaporization temperature than water, it is particularly effective in improving cooling efficiency from the viewpoint of stability at high temperature and ease of handling.
If silicone oil is used as the liquid having a higher vaporization temperature than water, the heat capacity is more effective when the heat capacity and viscosity of the silicone oil are taken into consideration. As a result, the load on the circulation pump is small. Even if it leaks, the main component is Si, so that the contamination remains relatively light. Therefore, it is more effective in improving the cooling efficiency.
As described above, according to the present invention, the cooling efficiency can be improved as compared with the conventional case, and the crystal pulling speed can be increased. Therefore, as a result, the COP formation temperature zone passage time at the time of crystal growth is shortened, and the COP can be miniaturized.
Further, by increasing the crystal pulling speed, it is possible to improve the productivity and reduce the cost of manufacturing the silicon single crystal.

  The embodiments of the present invention have been described above with reference to specific examples. In the description of the embodiment, the description of the silicon single crystal manufacturing apparatus, the silicon single crystal manufacturing method, etc. that is not directly necessary for the description of the present invention is omitted, but the required manufacturing apparatus and manufacturing method are omitted. Etc. can be appropriately selected and used.

  In addition, all silicon single crystal manufacturing apparatuses and silicon single crystal manufacturing methods that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

A first embodiment of the present invention will be described below with reference to FIG.
(Example)
A silicon single crystal was grown by the CZ method using the silicon single crystal manufacturing apparatus shown in FIG. At this time, a cooling chamber 33 made of SUS having an inner diameter of 280 mm and silicone oil was used as a cooling medium. The internal diameter of the cooling chamber is reduced by about 20% from that normally used in a silicon single crystal manufacturing apparatus using water as a cooling medium. The lower end of the cooling chamber 33 was installed 70 mm vertically above the melt surface.
Then, a polycrystalline silicon raw material was put into a quartz crucible 3 having a diameter of 600 mm, and a silicon single crystal having a diameter of 200 mm was grown.
At this time, the temperature of the inner surface lower end of the cooling chamber 33 was measured.
(Comparative example)
A silicon single crystal having a diameter of 200 mm was grown with a manufacturing apparatus configuration similar to that of the example, using the cooling medium as water.

(result)
In the case of the comparative example using water as the cooling medium, the liquid temperature rose to 75 ° C. when the length of the straight body portion of the silicon single crystal 13 being pulled reached 100 mm. For this reason, pulling up had to be interrupted to avoid a steam explosion.
On the other hand, when silicone oil was used as the cooling medium, the liquid temperature rose to 100 ° C when the length of the straight body reached 100mm, but it was raised because there was a margin of nearly 100 ° C to the vaporization temperature of the silicone oil. Continued. Thereafter, the maximum liquid temperature reached 120 ° C., but the vaporization temperature had a sufficient margin, so that the pulling could be completed.
From the above results, it has been found that by using silicone oil as the cooling medium, it is possible to reduce the inner diameter of the cooling chamber 33 by about 20% from the conventional level and increase the cooling rate.

The second embodiment of the present invention will be described below with reference to FIG.
(Example)
A silicon single crystal was grown by the CZ method using the silicon single crystal manufacturing apparatus shown in FIG. At this time, a cooling chamber 33 made of SUS having an inner diameter of 280 mm and silicone oil was used as a cooling medium. The lower end of the cooling chamber 33 was installed 200 mm vertically above the melt surface. The internal diameter of the cooling chamber is reduced by about 20% from that normally used in a silicon single crystal manufacturing apparatus using water as a cooling medium.
Then, a polycrystalline silicon raw material was put into a quartz crucible 3 having a diameter of 600 mm, and a silicon single crystal having a diameter of 200 mm was grown.
At this time, the fastest pulling speed at which bending deformation of the silicon single crystal 13 did not occur was confirmed. The pulling speed was measured for five pulls, and the average speed was obtained and used as the average crystal pulling speed.
(Comparative example)
Although the manufacturing apparatus configuration is the same as that of the example, a silicon single crystal having a diameter of 200 mm was grown using the conventional inner diameter of the cooling chamber 33 of 360 mm and the cooling medium as water.
The same measurement as in the example was performed, and the average crystal pulling rate was obtained.

(result)
Evaluation was made by dividing the average crystal pulling rate obtained from the example in the case of using silicone oil by the average crystal pulling rate obtained from the comparative example in the case of using water. As a result, it was found that in the example using silicone oil, it was possible to pull up the single crystal without bending deformation at a speed 1.3 times that of the comparative example.

It is a typical longitudinal section of the silicon single crystal manufacturing device of an embodiment. It is a typical longitudinal cross-sectional view which shows an example of the silicon single crystal manufacturing apparatus by a prior art.

Explanation of symbols

1 Chamber 3 Quartz crucible 5 Carbon crucible 7 Main heater
9 Lower heater
11 Silicon melt 13 Silicon single crystal 17 Crucible shaft 19 First heat insulating material 21 Second heat insulating material 23 Third heat insulating material 25 Fourth heat insulating material 27 Radiation shield 33 Cooling chamber

Claims (4)

A silicon single crystal manufacturing apparatus using a chocolate lasky method (CZ method),
It has a cylindrical cooling chamber that is arranged so as to surround the silicon single crystal that is being pulled up and is forcedly cooled with a cooling medium,
The silicon single crystal manufacturing apparatus, wherein the cooling medium is a liquid having a higher vaporization temperature than water.   The silicon single crystal manufacturing apparatus according to claim 1, wherein the liquid having a higher vaporization temperature than water is oil.   3. The silicon single crystal manufacturing apparatus according to claim 2, wherein the oil is silicone oil. A silicon single crystal manufacturing method using the silicon single crystal manufacturing apparatus according to claim 1 to manufacture a silicon single crystal.

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