JPH1081594A - Apparatus for producing cz silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the heat quantity leaking from electrodes to the lower part of a chamber by interposing and arranging specific members in the electrodes in an apparatus for growing a silicon single crystal from a polycrystalline silicon according to a Czochralski process. SOLUTION: This apparatus is equipped with a crucible 3 filled with a polycrystalline silicon 7, a heater 9 for heating the crucible 3 and electrodes 13 for energizing the heater 9. In the apparatus, low-thermal conduction members 17 capable of suppressing the thermal conduction in the shaft direction are interposed and arranged in the electrodes 13. The electrodes 13 are preferably composed of carbon electrodes and the low-thermal conduction members 17 are preferably formed of carbon-fiber reinforced composite materials having high strength properties and the electric resistivity equal to that of carbon in the carbon electrodes 13. The electrodes 13 are preferably formed of carbon- fiber reinforced composite materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CZ silicon single crystal manufacturing apparatus for growing a silicon single crystal from polycrystalline silicon by the Czochralski method, and more particularly to a CZ silicon single crystal manufacturing apparatus for manufacturing large-diameter single crystal silicon. It concerns the device.

[0002]

2. Description of the Related Art As a method of growing a silicon single crystal from a polycrystalline silicon lump or granular polycrystalline silicon, a Czochralski method (hereinafter, referred to as "CZ method") is generally known. The production of a silicon single crystal using the CZ method is performed as follows. A polycrystalline silicon lump or granular polycrystalline silicon is filled in a quartz crucible provided in a chamber, and the quartz crucible is rotated at a predetermined speed. Next, a heater provided around the quartz crucible is energized by electrodes supporting the heater to generate heat. The quartz crucible is heated by the heat generated by the heater. By continuously energizing the electrode heater, the temperature in the quartz crucible reaches the melting point of silicon (1412 ° C.) or more due to the heating from the heater. Thereby, the polycrystalline silicon in the quartz crucible is melted. A seed crystal is brought into contact with the melted polycrystalline silicon (silicon melt) from the top of the chamber,
Adjust the power of the heater so that it is in thermal equilibrium. Then, with the power slightly lowered, the seed crystal 3
When 08 is raised at a predetermined speed by the pulling wire 319 while rotating at a predetermined speed, a silicon single crystal 321 is grown at the lower end of the drawn portion having a diameter of 2 to 3 mm. The maximum diameter of a silicon single crystal industrially mass-produced by a conventional silicon single crystal manufacturing apparatus using such a CZ method is about 20
0 mm.

Here, since the electrode supports the heater, a high strength is required as a material of the electrode. Moreover, since it is exposed to a high temperature of 1000 ° C. or more, high heat resistance is also required. Further, since a current of several thousand A flows through the heater, high electrical conductivity is also required. For this reason, a carbon electrode having high strength, high heat resistance, and high electrical conductivity is generally used as an electrode used in a silicon single crystal manufacturing apparatus.

[0004]

The carbon electrode is excellent in that it has high strength and high heat resistance, but also has the property of having high thermal conductivity. For this reason, the calorie of the heater is transmitted to the carbon electrode and further to the lower metal shaft along the axial direction of the electrode. here,
Since the metal shaft is cooled with water, the amount of heat generated from the heater leaks from the metal shaft to the outside. It is known that this heat loss is about 10% of the total heat generated from the heater.

When a silicon single crystal having a small diameter of about 200 mm is manufactured, only a small amount of polycrystalline silicon is required to fill the crucible, and the crucible does not require a large capacity. For this reason, the heater provided around the crucible and for heating the crucible needs a small diameter, and the calorific value of the heater required for melting the polycrystalline silicon is small.
Therefore, when a small-diameter silicon single crystal is manufactured by a conventional silicon single-crystal manufacturing apparatus, the amount of heat leaking from the lower portion of the chamber is within an error range, and the temperature inside the crucible is reduced due to heat loss. It rarely dropped below the melting point.

On the other hand, in recent years, attempts have been made to produce large-diameter silicon single crystals having a diameter of 12 inches or more. However, when manufacturing a large-diameter silicon single crystal, the amount of polycrystalline silicon to be melted becomes large, and the capacity of the crucible increases accordingly.Therefore, the heater surrounding the crucible becomes large in diameter and increases in weight. In order to support this weight, the electrode supporting the electrode must necessarily have a large diameter. Further, in order to melt a large amount of polycrystalline silicon, a large amount of heat from a heater is required. Therefore, the heat loss of about 10% exceeds the range of the error, and the amount of leaked heat makes it impossible to maintain the temperature in the crucible above the melting point of silicon. When the temperature in the crucible drops below the melting point of silicon, polycrystalline silicon cannot be melted, and therefore, it becomes impossible to produce a silicon single crystal.Therefore, the calorific value of the heater is increased, and the temperature in the crucible is reduced. It must be kept above the melting point of silicon. For this reason, when a large-diameter silicon single crystal is manufactured using a conventional silicon single crystal manufacturing apparatus, the durability of the heater and power cost become problems due to an increase in the thermal load of the heater, and the manufacturing cost increases. become. For this reason, there is a problem that it is more difficult to manufacture a large-diameter silicon single crystal in terms of manufacturing cost as compared with a small-diameter silicon single crystal.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem. In the case of producing a large-diameter silicon single crystal, the amount of heat leaking from an electrode to a lower portion of a chamber is suppressed, so that the heat generated by the heater is reduced. It is an object of the present invention to provide a silicon single crystal manufacturing apparatus capable of reducing the amount.

[0008]

In order to achieve the above object, the invention according to claim 1 comprises a crucible for filling polycrystalline silicon, a heater for heating the crucible, and an electrode for energizing the heater. A CZ silicon single crystal manufacturing apparatus, wherein a low heat conduction member for suppressing heat conduction in an axial direction is interposed in the electrode.

The present invention is a CZ silicon single crystal manufacturing apparatus having an electrode having a low heat conductive member interposed therebetween, and the amount of heat leaking from the electrode to the lower part of the chamber can be reduced by the low heat conductive member.

In the present invention, the electrode is provided with a low heat conducting member for suppressing heat conduction in the axial direction. Here, “suppressing heat conduction in the axial direction” means reducing or blocking heat transfer between the upper and lower electrodes. Further, "being interposed and arranged" means that the low heat conductive member is arranged in a sandwich shape on the electrode over the entire cross section of the electrode. Therefore, when the heater generates heat, a part of the amount of heat from the heater is transmitted to the electrode, but since the low heat conductive member is interposed in the electrode like a heat partition, the low heat conductive member is less than the low heat conductive member of the electrode. Also, heat conduction from the upper part to the part lower than the low heat conductive member is suppressed. Therefore, heat conduction in the axial direction of the electrode is reduced,
As a result, the amount of heat leaking from the lower part of the electrode to the outside is reduced.

Here, the configuration of the low heat conductive member is not particularly limited as long as it is interposed in the electrode as described above. For example, a disk-shaped low heat conductive member can be replaced with an arbitrary one of the columnar electrodes. It can be configured by being arranged in a sandwich shape at an axial position. Further, the low heat conduction member may be arranged at a plurality of axial positions of the electrode.

As described above, since the amount of heat leaking from the lower part of the electrode to the outside can be reduced by disposing the low thermal conductive member between the electrodes, the amount of heat applied to the polycrystalline silicon in the crucible is maintained, and the temperature in the crucible is reduced. It can be maintained at or above the melting point of silicon. In other words, the amount of heat leaking from the lower part of the electrode to the outside is reduced by the low heat conductive member interposed in the electrode, so that a large amount of heat generated by the heater is not required in consideration of the heat loss. As a result, even when a large-diameter silicon single crystal is manufactured, the manufacturing power cost is reduced.

The material of the electrode is not particularly limited as long as it has heat resistance and conductivity, but it has high strength because it supports a large-diameter and heavy-weight heater. It is preferably a material. As an electrode of such a material, for example, a carbon electrode can be used.

The low thermal conductive member is not particularly limited as long as it is made of a material having lower thermal conductivity than the electrode, but forms a part of the electrode that supports a large-diameter and heavy heater. For this reason, it is preferable that the material has high strength as well as low thermal conductivity. Also, the low heat conductive member is
It is desirable that the electrical resistivity does not greatly differ from the electrical resistivity of the material forming the electrode main body because it constitutes a part of the electrode to which the heater is energized. It is also possible to use one having an electrical resistivity that is ten and several percent higher than the resistivity. For example, when the electrode is a carbon electrode, a carbon fiber reinforced composite material having high strength and an electrical resistivity equal to that of the electrode carbon (about ± 10%) is used as the low thermal conductive member. Thus, the effects of the present invention can be achieved.

According to a second aspect of the present invention, in the apparatus for manufacturing a CZ silicon single crystal according to the first aspect, the electrode is formed of a carbon electrode, and the low thermal conductive member is provided with a carbon fiber reinforced interposed in the carbon electrode. Provided is an apparatus for manufacturing a CZ silicon single crystal, which is formed of a composite material.

In the present invention, the electrode is made of carbon, and the low heat conductive member is made of a carbon fiber reinforced composite material, so that the electrode maintains high strength and low heat conductivity. When manufacturing large-diameter silicon single crystals,
The capacity of the crucible increases, and therefore the heater also has a large diameter and a large weight. Therefore, the electrode supporting the heater needs to have a large diameter and high strength to support the heater. Further, in order to maintain the high strength of the electrode, it is necessary that the low thermal conductive member interposed in the electrode also has high strength. In addition, since the electrodes are used to supply current to the heater, the electrical resistivity of the low thermal conductive member disposed between the electrodes needs to be not much different from the electrical resistivity of the electrodes. In the present invention, a carbon electrode is adopted as an electrode having high strength, and a carbon fiber reinforced composite material having high strength and having an electrical resistivity equivalent to carbon is adopted as a low thermal conductive member. I have. For this reason, when manufacturing a large-diameter silicon single crystal, the amount of heat leaking from the lower part of the electrode to the outside can be reduced while maintaining high strength, and as a result, the manufacturing cost of the silicon single crystal is reduced. be able to.

Since the carbon fiber reinforced composite material has high strength and the same electrical resistivity as carbon, not only is it interposed in the carbon electrode, but the electrode itself is made of the carbon fiber reinforced composite material. May be.

That is, according to a third aspect of the present invention, in the CZ silicon single crystal manufacturing apparatus according to the first aspect, the electrode is formed of a carbon fiber reinforced composite material. Provide equipment.

In the present invention, the electrode itself is made of a carbon fiber reinforced composite material having a high strength and an electrical resistivity equivalent to that of carbon, so that the electrode has a high strength and It maintains low thermal conductivity. For this reason, when manufacturing a large-diameter silicon single crystal, the amount of heat leaking from the lower part of the electrode to the outside can be reduced while maintaining high strength, and as a result, the manufacturing cost of the silicon single crystal is reduced. be able to.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a CZ silicon single crystal manufacturing apparatus according to one embodiment of the present invention. FIG. 2 is a perspective view of a heater and electrodes used in the CZ silicon single crystal manufacturing apparatus according to one embodiment of the present invention.

The CZ silicon single crystal manufacturing apparatus according to this embodiment is configured as a pulling furnace 1 having a quartz crucible 5, a crucible rotating shaft 15, a heater 9, and an electrode 13.

A quartz crucible 5 for filling polycrystalline silicon is placed inside the chamber of the pulling furnace 1.
It is fitted and supported inside. The quartz crucible 5 has a diameter of at least 12 inches or more in order to produce a large-diameter silicon single crystal. The graphite crucible 3 holding the quartz crucible 5 is supported on a turntable on a crucible rotation shaft 15 which is connected and arranged on a metal shaft 19.
The crucible rotation shaft 15 is rotatably driven via a metal shaft 19, and the quartz crucible 5 and the graphite crucible 3 are configured to be rotatable around the crucible rotation shaft 15 as a center axis. Around the quartz crucible 5 and the graphite crucible 3, a heater 9 for melting the raw material polycrystalline silicon charged in the quartz crucible 5 is provided. The heater 9 is supported by a furnace body via a support 12 by electrodes 13 for supplying electricity to the heater. In addition, the code | symbol 22 of FIG.
These are insulating slits that form the Miranda shape of the heater 9.

Further, the electrode 13 is provided on a metal shaft 20, and the inside of the metal shaft 20 is cooled by water. Here, the electrode 13 is a carbon electrode made of a carbon material.
As a low heat conduction member to suppress heat conduction in the axial direction,
A disk-shaped carbon fiber reinforced composite material 17 is interposed and arranged so as to be sandwiched between the carbon members of the electrodes from above and below. The seed crystal holder 10 is suspended from the polycrystalline silicon in the quartz crucible 5 by a pulling wire 25, and the seed crystal 8 is held in the seed crystal holder 10. The seed crystal 8 can be raised and lowered and rotated around an axis (hereinafter referred to as “rotation”) by the pulling wire 25.

Next, a method for manufacturing a silicon single crystal using the apparatus for manufacturing a silicon single crystal of the present embodiment will be described.

First, a raw material polycrystalline silicon is placed in a quartz crucible 5.
After filling the inside, the quartz crucible 5 is rotated at a predetermined speed. Next, electricity is supplied from the electrode 13 to the inside of the heater 9 to cause the heater 9 to generate heat. Thus, the quartz crucible 5 surrounded by the heater 9 is heated.
By continuously energizing the heater 9 by the electrode 13, the polycrystalline silicon in the quartz crucible 5 has a melting point (14).
(12 ° C.), the polycrystalline silicon in the quartz crucible melts. Next, the seed crystal 8 is lowered by the pulling wire 25 and immersed in the melted polycrystalline silicon (silicon melt) 7, and then the heater 9 is thermally equilibrated.
Adjust the power of Thereafter, the pulling of the seed crystal 8 is started at a predetermined speed by the pulling wire 25 while rotating the seed crystal 8 at a predetermined speed while the power is slightly lowered. As a result, the silicon single crystal 6 having a large diameter is grown following the drawn portion having a diameter of 2 to 3 mm.

Here, the heater 9 is turned on by energizing the electrode 13.
Generates heat, and the amount of heat generated by the heater 9 is transmitted to the graphite crucible 3 and the quartz crucible 5 and also to the electrode 13. Of these, the amount of heat transmitted from the heater 9 to the electrodes moves from the upper part to the lower part of the electrode 13 by conduction along the axial direction. Here, in the present embodiment, since the carbon fiber reinforced composite material 17 as the low heat conductive member is interposed in the middle of the electrode 13,
The amount of heat is less likely to conduct and move below the carbon fiber reinforced composite material 17. Therefore, the amount of heat leaking from the lower part of the chamber to the outside via the electrode 13 is reduced, and accordingly, the temperature drop in the quartz crucible 5 is suppressed. Therefore, unlike the related art, it is not necessary to excessively increase the calorific value of the heater 9 in consideration of heat leakage. Can be fulfilled.

[0027]

As described above, in the silicon single crystal manufacturing apparatus according to the present invention, a large-diameter silicon single crystal is provided because a low heat conducting member for suppressing heat conduction in the axial direction is interposed in the electrode for supplying electricity to the heater. Even when manufacturing, it is possible to suppress the amount of heat leaking from the electrode to the lower part of the chamber, without excessively increasing the heat generation of the heater,
It is possible to suppress a decrease in the temperature in the crucible, to achieve an improvement in the durability of the heater and a reduction in power cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a CZ silicon single crystal manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a heater and electrodes used in the CZ silicon single crystal manufacturing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 1: Lifting furnace 3: Graphite crucible 5: Quartz crucible 6: Silicon single crystal 7: Silicon melt 8: Seed crystal 9: Heater 10: Seed crystal holder 11: Heat shielding material 12: Heater support 13: Electrode 15: Crucible rotating shaft 17: Carbon fiber reinforced composite member (low heat conducting part) 19, 20: Metal shaft 21: Observation window 22: Insulating slit 23: Optical system 25: Pulling wire

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Norihisa Machida 1-4-2 Marunouchi, Chiyoda-ku, Tokyo Inside the Super Silicon Research Laboratories (72) Inventor Hiroshi Shiraishi 1-4-2 Marunouchi, Chiyoda-ku, Tokyo Stock Company Inside Super Silicon Laboratories (72) Inventor Junichi Matsubara 1-4-2 Marunouchi, Chiyoda-ku, Tokyo Co., Ltd. Inside Super Silicon Laboratories (72) Inventor Tetsuhiro Iida 1-4-2 Marunouchi, Chiyoda-ku, Tokyo Super Co., Ltd. In Silicon Research Laboratory (72) Inventor Nobumitsu Takase 1-4-2 Marunouchi, Chiyoda-ku, Tokyo Super Silicon Research Laboratory

Claims (3)

[Claims] 1. A crucible for filling polycrystalline silicon, a heater for heating the crucible, and an electrode for energizing the heater, wherein the electrode is provided with a low heat conducting member for suppressing heat conduction in an axial direction. An apparatus for manufacturing a CZ silicon single crystal, wherein the apparatus is arranged. 2. The CZ silicon according to claim 1, wherein said electrode comprises a carbon electrode, and said low thermal conductive member is formed of a carbon fiber reinforced composite material interposed in said carbon electrode. Single crystal manufacturing equipment. 3. The CZ silicon single crystal manufacturing apparatus according to claim 1, wherein the electrode is formed of a carbon fiber reinforced composite material.