JPH06172093A - Reactional furnace for producing semiconductor-grade polycrystalline silicon - Google Patents

Abstract

PURPOSE:To obtain a polycrystalline silicon rod free from defect of shape and having smooth surface in large amounts by providing discharge port of discharge gas in the upper part of a furnace above silicon core rods and make it possible to discharge gas out of the furnace without disturbing flown of raw material gas fed from the bottom of the furnace out of the furnace. CONSTITUTION:Raw material gas is fed from plural raw material gas feed nozzles 5 provided in the bottom of closed reactional furnace into the furnace. This raw material gas is raised so as to surround plural silicon core rods 3 erected in reverse U-shape by electrode holders 4 of the bottom of the furnace and brought into contact with red hot core rod and thermally decomposed to deposit silicon. After reaction, unreacted gas, etc., reaches the upper part of the furnace and discharged from a gas discharge port 2 provided in the ceiling part of the furnace to the outside. Consequently, a raw material gas flow is always fed on the surface of the core rods 3 without being disturbed by the discharge gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor grade polycrystalline silicon production reactor suitable for producing a polycrystalline silicon rod having a smooth surface with few defective shapes.

[0002]

2. Description of the Related Art Generally, semiconductor-grade polycrystalline silicon is supplied with a raw material gas from a nozzle provided at the bottom of a closed reaction furnace into a reaction furnace at high temperature, and the raw material gas is supplied to the surface of a red-hot silicon mandrel provided in the furnace. It is manufactured by thermally decomposing or reducing with hydrogen to deposit and grow polycrystalline silicon on the surface of the silicon mandrel. That is, a gas material that decomposes to deposit silicon, for example, a raw material gas composed of highly purified monosilane, disilane, trichlorosilane, silicon tetrachloride, or a mixture of these and hydrogen is applied to a highly pure silicon substrate at high temperature. To produce a silicon crystal by depositing it on the surface of the substrate.

Specifically, the reaction is generally carried out in a bell jar type furnace whose inside is hermetically sealed. A silicon mandrel is erected inside the reaction furnace, the lower end of which is supported by an electrode holder, and the silicon mandrel is energized so as to glow red during manufacturing. A nozzle is provided at the bottom of the reaction furnace, and the raw material gas is supplied into the furnace through the nozzle. The raw material gas supplied from the nozzle comes into contact with the red-hot silicon mandrel and is decomposed and reduced, so that polycrystalline silicon is deposited on the surface of the silicon mandrel.

Recently, as the demand for semiconductor-grade polycrystalline silicon has increased, the reactor has been enlarged in order to increase the production amount, and several tens of silicon mandrels have been installed in the reactor so that a large amount of silicon can be produced at a time. A method of depositing and growing crystalline silicon has been adopted. However, when the number of silicon mandrels installed in the furnace increases, it becomes difficult to stably supply the raw material gas to the surface of all silicon mandrels, which causes unevenness (popcorn) on the surface of the silicon rod, and The thickness is not uniform, resulting in defective shape. If unevenness is generated on the surface of the rod, abnormal growth is likely to occur, and the cleaning effect on the surface of the rod is significantly reduced, which is not preferable. In order to eliminate the irregularities on the rod surface, the surface temperature of the silicon mandrel may be lowered to moderate the precipitation reaction, but in this case, the precipitation rate of silicon is slowed and the productivity and energy efficiency are significantly reduced.

Therefore, the conventional reaction furnace is designed to supply the raw material gas based on the idea that, when a large number of silicon mandrels are provided, the gas flow in the furnace is agitated to improve the gas contact with the surface of the silicon mandrels. Many have a structure in which a nozzle and a gas exhaust port are provided in the central portion of the furnace bottom. In this structure, the source gas supplied to the furnace rises along the silicon mandrel,
After the reaction, it is inverted from the upper part of the furnace toward the central part of the bottom, and most of it is guided to the outside from the gas exhaust port, while a circulating flow in which new raw material gas rises is formed. However, in the above structure, when the reactor becomes larger, the gas supply to the inner part of the furnace is likely to be hindered by the circulation of the exhaust gas, and part of the exhaust gas inevitably rises together with the raw material gas.
As a result, the composition of the raw material gas supplied to the surface of the silicon mandrel is deteriorated, and the defective shape of the rod is likely to occur.

As described above, in the conventional method, when the production reactor is enlarged, there is a problem that a silicon rod having a smooth surface and no unevenness cannot be efficiently produced. The present invention is to solve such conventional problems,
It is an object of the present invention to provide a reactor suitable for producing a large-sized polycrystalline silicon rod having a smooth surface and no defective shape.

[0007]

In order to stably supply a raw material gas to a large number of silicon mandrels in a reaction furnace, the raw material gas supplied to the furnace at the time of reaction should flow uniformly to each silicon mandrel and the exhaust gas. Must be discharged outside the furnace without disturbing the flow of raw material gas. The inventors of the present invention have studied the relative arrangement of the electrode holder, the raw material gas supply nozzle, and the gas discharge port, and achieved the above object by reducing the gas circulation in the furnace. It was found that a polycrystalline silicon rod without defects can be manufactured.

That is, according to the present invention, a plurality of raw material gas supply nozzles are provided at the bottom of a closed reaction furnace, and polycrystalline silicon is placed on a plurality of silicon mandrels vertically erected by an electrode holder at the bottom of the furnace. In a reaction furnace for producing semiconductor-grade polycrystalline silicon that is deposited at high temperature, a plurality of gas outlets are evenly arranged on the upper furnace wall surface above the silicon mandrel, preferably on the furnace ceiling and / or furnace side wall. The present invention provides a semiconductor-grade polycrystalline silicon manufacturing reaction furnace characterized by the above.

The basic structure of the reactor of the present invention is a hermetically sealed reactor having a plurality of raw material gas supply nozzles and a plurality of electrode holders for vertically arranging a silicon mandrel in an inverted U shape at the bottom of the furnace. Yes, a plurality of gas outlets are provided in the upper part of the furnace above the silicon mandrel.

A normal nozzle can be used as the raw material gas supply nozzle, but the raw material gas is independently supplied to the upper and lower portions of the silicon mandrel to prevent the concentration of the raw material gas at the upper part of the silicon mandrel from decreasing. Nozzle to obtain, for example, multi-stage nozzle, different velocity nozzle, double nozzle, etc.
326976, Japanese Patent Application No. 3-326977, Japanese Patent Publication No. 57-12288, etc.)
May be used. By using these special nozzles, it is possible to manufacture a silicon rod having a better surface shape. Further, it is preferable that the raw material gas supply nozzle and the electrode holder arranged at the bottom of the furnace are arranged so that there is no excess or deficiency surface of the raw material gas supply with respect to the surface of the entire silicon mandrel.

In the conventional reactor, the gas outlet was arranged at the center of the bottom of the furnace as described above to facilitate the gas circulation in the furnace, but in the reactor of the present invention, The gas outlet is arranged in the upper part of the furnace, especially on the furnace wall surface above the uppermost part of the silicon mandrel to suppress gas circulation. The raw material gas supplied from the nozzle at the bottom of the furnace contacts the red-hot silicon mandrel and rises while precipitating silicon on the surface by thermal decomposition or hydrogen reduction. At the same time, reaction by-product gas is generated. The exhaust gas reaching the upper part of the furnace is
It is discharged to the outside of the furnace through a gas discharge port provided on the upper wall surface of the furnace without circulating inside the furnace. As a result, the gas circulation containing the exhaust gas is greatly reduced, and fresh raw material gas is always supplied to the surface of the silicon mandrel.

In order to minimize the gas circulation in the furnace, it is necessary to efficiently discharge the exhaust gas, and it is necessary to adjust the number of gas outlets, the location, the pipe diameter of the outlets, etc. Performed by. Regarding the number and location of the gas outlets, it is important to prevent uneven flow and short paths in the gas flow in the furnace. Therefore, in the present invention, the outlets are provided in the upper part of the furnace. In a specific apparatus configuration, the number of gas outlets, the pipe diameter, etc. are determined in consideration of the arrangement of the raw material gas supply nozzle and the silicon mandrel, but it is preferable to arrange them substantially evenly in the upper part of the furnace. Further, it is preferable that the pipe diameter of the discharge port is set large so that the discharge amount is not biased due to the pressure loss difference of the discharge pipe or the like. Also, the space between the silicon mandrel upper part and the furnace ceiling is
In order to improve the flow of gas to the discharge port and to allow the gas flow from the inlet nozzle to reach the top end of the silicon mandrel, it is preferable to make the space large.

[0013]

EXAMPLES A preferred embodiment of the reaction furnace of the present invention is one in which the gas outlet is provided in the furnace ceiling or one in which the gas outlet is provided on the upper side wall of the furnace. The present invention will be described in detail below with reference to the examples shown in the drawings, but the present invention is not limited thereto.

Example 1 FIG. 1 (a) is a schematic plan view of a furnace ceiling part showing a reaction furnace according to the present invention, and FIG. 1 (b) is a schematic vertical sectional view of a side surface of the furnace, in which 1 is a reaction. An inner wall of the furnace, 2 is a gas outlet, 3 is a silicon mandrel, 4 is an electrode holder for supporting the silicon mandrel, 5 is a nozzle for supplying a raw material gas, 6 is a furnace ceiling, and 7 is an exhaust pipe.
In the present embodiment, as shown in the figure, silicon mandrels 3 are concentrically arranged at equal intervals in a bell jar type closed reactor, and a raw material gas supply nozzle 5 is provided at the bottom of the furnace to supply the silicon mandrels 3 to each other. It is arranged alternately with the supporting electrode holders 4. The gas outlets 2 are evenly installed in the furnace ceiling portion 6, and the gas outlets 2 are provided substantially at the center of the furnace ceiling, at positions corresponding to the arrangement of multiple silicon mandrel arrays, and on the inner wall of the furnace. They are arranged along the respective positions. An exhaust pipe 7 is connected to each outlet. No gas outlet is provided at the bottom of the furnace.

In the present embodiment, the raw material gas supplied from the nozzle at the bottom of the furnace rises so as to surround the silicon mandrel 3, and during that time, the surface of the silicon mandrel comes into contact with the surface of the silicon mandrel that is heated red and the silicon is decomposed by heat or hydrogen reduction. To precipitate.
After the reaction, the unreacted gas and the by-product gas reach the upper part of the furnace and are discharged to the outside through the gas discharge port 2 provided in the furnace ceiling. Since a sufficiently large space is provided between the upper part of the silicon mandrel and the furnace ceiling, there is no uneven flow of exhaust gas in the upper part of the furnace, and the gas flow is smooth.

Therefore, since the exhaust gas reaching the upper part of the furnace is discharged without being inverted and circulated toward the lower part of the furnace, the raw material gas flow is not disturbed by the exhaust gas and the fresh raw material gas is always supplied to the surface of the silicon mandrel. As a result, large-sized polycrystalline silicon free of shape defects can be obtained.

Embodiment 2 FIG. 2 shows a reaction furnace according to another embodiment of the present invention. FIG. 2 (a) is a schematic plan view of the furnace ceiling, and FIG. 2 (b) is a schematic longitudinal sectional view thereof ( b). In this embodiment, as shown in the figure, the silicon mandrel 3 and the raw material gas supply nozzle 5 are arranged in the same manner as in Embodiment 1, but the gas discharge ports 2 are equidistantly arranged on the furnace side wall portion 8 near the furnace ceiling portion. It is provided in. In this embodiment, the raw material gas supplied from the nozzle 5 at the bottom of the furnace rises so as to surround the silicon mandrel 3, and during that time, it comes into contact with the surface of the silicon mandrel that is heated red and deposits silicon by thermal decomposition or hydrogen reduction. Let After the reaction, the unreacted gas and the by-product gas reach the upper part of the furnace and are discharged to the outside through a gas discharge port provided on the side wall of the furnace. In this embodiment, the gas discharge port is provided in the furnace side wall portion near the furnace ceiling portion, so that the same effect as that of the first embodiment is exhibited. Also, by taking sufficient space between the silicon mandrel upper part and the furnace ceiling part,
Similar to the first embodiment, the uneven flow of the exhaust gas in the upper part of the furnace is eliminated to further improve the gas flow.

[0018]

INDUSTRIAL APPLICABILITY The semiconductor grade polycrystalline silicon production reactor of the present invention can produce a large amount of polycrystalline silicon rods having a smooth surface with few defective shapes at one time.

[Brief description of drawings]

1A is a schematic plan view of a furnace ceiling portion of a reaction furnace of Example 1 according to the present invention, and FIG. 1B is a schematic vertical sectional view thereof.

2A is a schematic plan view of a furnace ceiling portion of a reaction furnace of Example 2 according to the present invention, and FIG. 2B is a schematic vertical sectional view thereof.

[Explanation of symbols]

 1 Reactor Inner Wall 2 Gas Outlet 3 Silicon Mandrel 4 Electrode Holder 5 Raw Material Gas Supply Nozzle 6 Furnace Ceiling 7 Gas Exhaust Pipe 8 Furnace Side Wall

Claims (3)

[Claims] 1. A polycrystalline silicon is deposited at a high temperature on a plurality of silicon mandrels, which have a plurality of raw material gas supply nozzles at the bottom of a closed reaction furnace and are vertically erected by an electrode holder at the bottom of the furnace. In the reactor for producing semiconductor-grade polycrystalline silicon, a plurality of gas outlets are evenly arranged in the upper part of the furnace above the silicon mandrel. 2. The semiconductor-grade polycrystalline silicon manufacturing reactor according to claim 1, wherein a plurality of gas outlets are evenly arranged on the furnace ceiling. 3. The semiconductor-grade polycrystalline silicon manufacturing reactor according to claim 1, wherein a plurality of gas outlets are evenly arranged on the side wall of the furnace upper part.