JP2001294416A - Device for producing polycrystalline silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide production device with which a polycrystalline silicon rod whose whole surface is smooth and which has small residual stress can be obtained. SOLUTION: In the production device for producing the polycrystalline silicon, silicon core rods are arranged in the standing state in a closed furnace, and a source gas is introduced into the furnace and at the same time, the core rods are heated to a high temperature, thereby, polycrystalline silicon formed by pyrolysis of the source gas is deposited on the surface of each core rod, the temperature in the furnace is made uniform by providing a heat-insulating material in the furnace in such a manner that the silicon rods are surrounded by the heat-insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a production furnace for depositing polycrystalline silicon on the surface of a red-heated silicon core rod, and to a polycrystalline silicon rod having good surface properties and low residual stress. It relates to a manufacturing device.

[0002]

2. Description of the Related Art The Siemens method is known as a method for producing high-purity polycrystalline silicon as a semiconductor material. In this method, a raw material gas such as a mixed gas of chlorosilane and hydrogen is brought into contact with a glowed silicon core rod, and silicon generated by thermal decomposition of the raw material gas is deposited on its surface.
This is a manufacturing method of growing a polycrystalline silicon rod having a gradually increasing diameter, and a manufacturing apparatus in which a number of silicon core rods are erected in a closed reaction furnace is used. Generally, this silicon core rod is formed in an inverted U-shape, and both ends thereof are fixed to electrodes installed on the bottom of the reaction furnace. During operation, electricity is passed from the electrodes at both ends to the silicon core rod, the silicon core rod is glowed to a high temperature by the resistance heat, and the generated silicon is deposited on the surface of the core rod. As the reaction of the raw material gas, hydrogen reduction of silicon tetrachloride or trichlorosilane at a high temperature or thermal decomposition of silane or chlorosilane is used.
It is heated to a high temperature of about 0 to 1150 ° C.

[0003]

A furnace wall of a reaction furnace is generally formed of a metal material such as stainless steel or a nickel-based alloy. However, since the inside of the furnace is heated to a high temperature, contamination of silicon by the metal material is prevented. For this purpose, the reaction furnace is provided with a water-cooling jacket for cooling the furnace wall. For this reason, the temperature inside the furnace becomes lower around the furnace wall than at the center of the furnace,
There is a problem that the quality of the silicon rod deteriorates due to such uneven furnace temperature. Specifically, since the temperature of the silicon rod placed near the furnace wall is low and the temperature of the silicon rod placed on the center side inside the furnace is high, controlling the furnace temperature based on the silicon rod on the furnace wall side will cause As the silicon rod on the side becomes hot and the reaction speed becomes faster, the surface becomes rough and rough. For this reason, the surface area of the rod becomes large, and impurities easily adhere to the gaps. Further, at the time of etching cleaning, the cleaning liquid hardly enters the gaps, and washing out of the adhered impurities tends to be insufficient. Further, the cleaning liquid or the like easily stays in the gap, which causes impurity contamination. On the other hand, if the furnace temperature is controlled on the basis of the silicon rod on the center side, the temperature on the furnace wall side becomes low, so that the thermal decomposition of the raw material gas becomes insufficient and the reaction efficiency decreases. This is not limited to the whole inside of the furnace, but also applies to individual silicon rods on the furnace wall side.Since the surface temperature on the furnace wall side and the surface temperature on the center side are different, silicon rods with uneven surface properties and large residual stress Become.

The present invention has solved the above-mentioned problems in the conventional manufacturing furnace. By making the furnace temperature uniform, a silicon rod having a smooth surface and small residual stress can be efficiently manufactured, and An object of the present invention is to provide a manufacturing apparatus capable of reducing the amount of power or the manufacturing cost.

[0005]

According to the manufacturing apparatus of the present invention, the temperature inside the furnace is made uniform by providing a heat insulating material in the furnace so as to surround the silicon rod. Is provided.

(1) A silicon core rod is erected in a closed furnace, a raw material gas is introduced into the furnace, and the core rod is heated to a high temperature. An apparatus for producing polycrystalline silicon, wherein silicon is deposited on the surface of said core rod, wherein the temperature inside the furnace is made uniform by providing a heat insulating material in the furnace so as to surround the silicon core rod. . (2) The manufacturing apparatus according to the above (1), wherein a heat insulating material is lined on a peripheral wall and a bottom surface in the furnace. (3) The manufacturing apparatus according to the above (1), wherein a heat insulating material is provided on a peripheral wall, a bottom surface, and a ceiling in the furnace. (4) The manufacturing apparatus according to (3) above, wherein a heat insulating material is lined on the ceiling surface or the heat insulating material is installed in the furnace so as to cover the ceiling. (5) The manufacturing apparatus according to the above (1), wherein a heat insulating material is coated on a peripheral surface and a ceiling surface in the furnace. (6) The production apparatus according to (1), wherein carbon, silicon nitride, quartz, silicon carbide, zirconium oxide, or a composite material thereof is used as the heat insulating material. (7) The manufacturing apparatus according to the above (1), using a heat insulating material coated with silicon on the surface.

As described above, the polycrystalline silicon of the present invention has a cooling means for a furnace wall, and a heat insulating material is provided so as to surround the silicon rod in a reactor in which a large number of silicon rods are erected in the furnace. In the furnace, the temperature inside the furnace, especially the temperature near the furnace wall, was made uniform and adjusted to the optimum temperature.
By this temperature control, it is possible to obtain a silicon rod in which the entire rod surface is smooth, has a small residual stress, and is not easily broken.

The heat insulating material has a certain effect if it is provided on the furnace inner peripheral surface so as to surround the furnace inner bottom surface and the silicon rod. Preferably, a heat insulating material is further provided on the ceiling portion so that the entire furnace interior is made of heat insulating material. It is good to form it in a covered state. This heat insulating material may be a plate-like member attached to a wall surface by a beam material or the like,
Alternatively, a liquid or powdery heat insulating material may be coated on the wall surface.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments shown in the drawings. FIG. 1 is a partially cutaway perspective view showing a schematic structure of a polycrystalline silicon production furnace, and FIGS. 2 to 6 are schematic longitudinal sectional views or schematic bottom views of a reaction furnace showing an apparatus configuration according to the present invention.

FIG. 1 shows a schematic structure of a polycrystalline silicon reactor. As shown in the drawing, the reaction furnace 10 is formed by a furnace base 11 and a bell-shaped bell jar 12 covering the furnace base. Cooling means (not shown) such as a water-cooled jacket is provided in the furnace base 11 and the bell jar 12 to prevent thermal damage. An electrode 14 for holding a silicon core 13 is provided on the furnace base 11.
Are protruded, and an inlet 15 for introducing the raw material gas into the furnace, and an exhaust port 1 for discharging the reacted gas out of the furnace.
6 are provided. The silicon core rod 13 is erected in the furnace by an electrode 14, and electricity is supplied to the silicon core rod 13 through the electrode 14 to heat the silicon rod to a state in which the entire silicon rod generates heat (red heat). The electrode 14 is provided with a cooling means (not shown). Silicon core 13 in the center of the furnace
There is provided a carbon rod 17 for heating the carbon rods so that they can be energized. A large number of silicon core rods 13 are concentrically arranged around the carbon rod 17. When the silicon core rod 13 is energized, the silicon core rod 13 has about 8
The raw material gas introduced into the furnace is heated to about 00 ° C. to 1150 ° C., and thermally decomposes by contacting the heated silicon core rod 13, and polycrystalline silicon is deposited on the surface thereof, and gradually grows thick to several tens. It becomes a polycrystalline silicon rod of centimeter diameter. As the raw material gas, silane, chlorosilane or a mixed gas of these and hydrogen is used. The arrangement and number of the silicon core rods, and the positions and numbers of the raw material gas inlets and exhaust ports are appropriately determined according to the size of the furnace.

In the above configuration, the manufacturing apparatus of the present invention comprises:
As shown in FIGS. 2 to 6, a heat insulating material 20 is lined on a furnace inner wall and a furnace bottom of the reaction furnace 10. It is preferable to provide an interval of 5 mm or more between the silicon rod 13 and the heat insulating material to prevent discharge. As a material of the heat insulating material, carbon, silicon nitride, quartz, silicon carbide, zirconium oxide, or a composite material thereof can be used. As for these heat insulating materials, a porous material having a large number of independent pores therein has a good heat insulating effect. Further, by using a heat insulating material other than silicon, such as carbon or silicon carbide, whose surface is coated with silicon, impurity contamination due to carbon or the like can be prevented.

To attach the plate-shaped heat insulating material 20 to the wall surface in the furnace, as shown in the figure, an L-shaped beam member 21 is provided on the wall surface, and the heat insulating material 20 is formed in a groove formed by the beam material 21. Can be inserted and fixed. The beam 21 is preferably made of the same material as the reaction furnace, and a cooling means is preferably provided.
As the cooling means, a method such as providing a flow path of cooling water inside the beam material can be used. When the heat insulating material 20 is provided separately, a net 22 made of a material having a high melting point such as molybdenum may be attached to the beam member 20, and the heat insulating material 20 may be supported by the net 22.

As shown in FIG. 2, the temperature inside the furnace can be made fairly uniform by lining the heat insulating material 20 on the inner bottom surface and the inner peripheral wall. In the device examples of FIGS. 1 and 2,
An elongated beam member 21 is provided so as to go around the inside of the furnace at the bottom of the furnace and at the corner of the peripheral wall, and at the boundary between the peripheral wall and the ceiling.
The upper and lower ends are fitted into and fixed to the grooves of the beam 21. As shown in FIG. 3, a heat insulating material 20 is laid on the bottom surface of the furnace, and the periphery thereof is
Has been fixed by.

As shown in FIG. 4 and FIG.
Is provided on the ceiling together with the furnace inner peripheral surface and the furnace inner bottom surface, whereby the furnace temperature can be made more uniform. Preferably, both ends of the heat insulating material 20 at the ceiling are fixed by beams 21 and supported by a net 22 of a high melting point material.

As shown in FIG. 5, a plurality of (five in the illustrated example) beam members 21 are attached to the ceiling surface of the reactor 10 and the heat insulating material 20 at the ceiling portion is used as the heat insulating material. The heat insulating material 20 may be fixed to the ceiling surface by pressing the end of the heat insulating material 20. Further, a net 22 made of a high melting point material is preferably attached to the beam 21 to support the heat insulating material 20.

Instead of the embodiment shown in FIGS. 2 to 5, a heat insulating material 20 may be coated on the inner wall of the furnace as shown in FIG. The coating method is not particularly limited as long as the layer of the heat insulating material 20 is formed on the wall surface.

[0017]

According to the manufacturing apparatus of the present invention, since the heat insulating material is provided so as to surround the silicon rod in the furnace, the furnace temperature is made uniform and controlled to the optimum temperature, so that the rod surface is smooth and smooth. A high quality silicon rod having excellent surface properties can be obtained. In addition, the silicon rod manufactured by the manufacturing apparatus of the present invention has a small residual stress, so that it is difficult to break, and a long rod can be stably obtained. Further, since the temperature in the furnace is uniformly controlled within the optimum range, the power cost can be reduced, and the economic efficiency of silicon rod production can be improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of a polycrystalline silicon manufacturing apparatus (furnace).

FIG. 2 is a schematic longitudinal sectional view of a manufacturing apparatus (furnace) according to the present invention.

FIG. 3 is a schematic cross-sectional view of the manufacturing apparatus (furnace) of FIG. 2;

FIG. 4 is a schematic longitudinal sectional view of another manufacturing apparatus (furnace) according to the present invention.

FIG. 5 is a schematic longitudinal sectional view of another manufacturing apparatus (furnace) according to the present invention.

FIG. 6 is a schematic longitudinal sectional view of another manufacturing apparatus (furnace) according to the present invention.

[Explanation of symbols]

10-reactor, 11-furnace base, 12-bell jar, 13-silicon core rod, 14-electrode, 15-source gas inlet, 16
-Exhaust port, 17-carbon rod, 20-thermal insulation, 21
-Beams, 22-net

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisayuki Takesue 5 Mitacho, Yokkaichi-shi, Mie Prefecture Inside Mitsubishi Materi AlPolysilicon Co., Ltd. (72) Inventor Mark Forest 1-5-1, Otemachi, Chiyoda-ku, Tokyo Material Co., Ltd. F term (reference) 4G072 AA01 BB12 GG04 HH01 NN01

Claims (7)

[Claims] 1. A silicon core rod is erected in a sealed furnace, a raw material gas is introduced into the furnace, and the core rod is heated to a high temperature. In the apparatus for producing polycrystalline silicon, wherein the temperature inside the furnace is made uniform by providing a heat insulating material in the furnace so as to surround the silicon core rod. 2. The manufacturing apparatus according to claim 1, wherein a heat insulating material is lined on a peripheral wall and a bottom surface in the furnace. 3. The manufacturing apparatus according to claim 1, wherein a heat insulating material is provided on a peripheral wall, a bottom surface, and a ceiling in the furnace. 4. The manufacturing apparatus according to claim 3, wherein a heat insulating material is lined on the ceiling surface or the heat insulating material is installed in the furnace so as to cover the ceiling. 5. The manufacturing apparatus according to claim 1, wherein a heat insulating material is coated on a peripheral surface and a ceiling surface in the furnace. 6. The manufacturing apparatus according to claim 1, wherein carbon, silicon nitride, quartz, silicon carbide, zirconium oxide, or a composite material thereof is used as the heat insulating material. 7. The manufacturing apparatus according to claim 1, wherein a heat insulating material coated with silicon on the surface is used.