JPS61281009A - Apparatus for producing polycrystal silicon - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of cracks and reduce the heat loss, by forming a gold coating layer on the inner surface of a bell jar to give a specular surface in the titled apparatus having polycrystal silicon seed rods provided in the interior of a furnace consisting of a base and the bell jar. CONSTITUTION:A furnace 10 is constituted of a base 11 and a bell jar 12, and electrodes 14 for supporting polycrystal silicon seed rods 13, raw material gas inlet 15 and waste gas discharge outlet 15 are formed in the base 11. A gold coating layer 17 is formed on the inner surface of the bell jar 12 to give a specular surface. A current is then passed through the polycrystal silicon seed rods 13 to heat the seed rods 13 at about 1,050-1,150 deg.C. On the other hand, a mixed gas of chlorosilane and hydrogen is introduced from the inlet 15 into the furnace 10 to separate and deposit simple substance of silicon on the surface of the seed rods 13. The heat radiation through the bell jar 12 is suppressed by the specular surface due to the above-mentioned gold coating layer 17, and the temperature gradient in the furnace 10 is reduced. Thus, the temperature difference between the outer edge par and the central part is kept within a permissible range even when thick polycrystal silicon is grown and the heat loss is reduced to provide remarkable energy saving effect without causing cracks.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polycrystalline silicon manufacturing apparatus that has good durability and high heating efficiency.

<Prior Art> High-purity polycrystalline silicon, which is a raw material for semiconductors, is generally manufactured by an apparatus having a furnace consisting of a base and a bell jar placed on the top surface of the base. The base of the device is provided with an electrode, which is provided with a fixing hole. When manufacturing polycrystalline silicon, a polycrystalline silicon seed rod is attached to the fixed hole in the electrode, a plurality of the seed rods are set upright inside the furnace, and the seed rod is heated to about 1050 ° C. A mixed gas of chlorosilane and hydrogen is introduced into the furnace to deposit and grow polycrystalline silicon on the surface of the seed rod. Therefore, the furnace of the above manufacturing equipment is required to have as good a heating effect as possible, but in reality, due to the equipment configuration, heat loss due to heat radiation and heat transfer cannot be avoided.
Quartz has been used as the material for the bell jar that forms the reactor, but in recent years there has been a demand for larger furnaces to increase productivity, and metal bell jars have come to be used. In this case, it is usually necessary to prevent damage to the furnace due to overheating.
Cooling the outside of the furnace. Therefore, the heat loss is approximately 50 to 9
On the other hand, in order to produce high-quality polycrystalline silicon, it is necessary to make the temperature distribution in the furnace uniform and to uniformly grow polycrystalline silicon on the surface of the seed rod.

For this reason, conventionally, the inner surface of the bell jar is mirror-finished to reflect the radiant heat from the seed rod, thereby achieving a uniform heating effect and temperature distribution.

<Problems to be Solved by the Invention> Conventionally, in order to make the inner surface of a bell jar mirror-like, the surface of the stainless steel base material is thermally sprayed or plated with nickel, silver, chromium, etc., or the inner surface of the bell jar itself is coated. It is electrolytically polished and puff polished to a mirror finish. However, such a mirror surface has the disadvantage that it is inferior in durability, and furthermore, a bell jar whose inner surface is simply polished has a disadvantage that its reflectance is lower than that of a bell jar plated with silver.

When producing polycrystalline silicon in a furnace, not only silicon precipitates on the surface of the seed rod, but also silicon compounds adhere to the inside of the bell jar.While the seed rod is energized, there is no raw material gas or inert gas such as argon inside the furnace. Gas is supplied to prevent oxidation inside the furnace, but after manufacturing, when the bell jar is opened to take the grown polycrystalline silicon out of the furnace, outside air flows in and removes the silicon compounds that have adhered to the inside of the bell jar. Decomposes by oxidation. Alternatively, the remaining chlorosilane may oxidize and generate hydrochloric acid, which attacks the inner surface of the bell jar.
For this reason, the polished surface of bell jars polished to a mirror surface is directly corroded, and the plated surface of bell jars plated with silver or the like is corroded and peeled off, resulting in the mirror surface being damaged.

Means for Solving the Problems> The present invention solves the conventional problems by providing the inner surface of a belljar with a chemically extremely stable gold coating layer to give it a mirror surface.

<Structure of the Invention> According to the present invention, in a manufacturing apparatus for growing polycrystalline silicon on the seed rod by disposing a polycrystalline silicon seed rod inside a furnace consisting of a base and a bell jar, gold is provided on the inner surface of the bell jar. An apparatus for manufacturing polycrystalline silicon is provided, characterized in that a coating layer is provided to give a mirror surface.

Preferably, the gold coating layer is formed on the inner surface of the bell jar by thermal spraying, vapor deposition, or plating with gold, or the gold coating layer is formed on the inner surface of the bell jar with a gold coating plate. A manufacturing apparatus is provided, which is characterized in that it is formed by:

In the present invention, a gold coating layer is formed on the inner surface of the bell jar, and the inner surface is mirror-finished. The method for forming the gold coating layer may include forming the coating layer directly on the inner surface of the bell jar.

A gold-plated plate may be stretched over the inner surface.

To form a gold coating layer directly on the inner surface of the bell jar, gold is formed by thermal spraying, vapor deposition, or plating on the inner surface. For large-scale devices, the coating layer may be formed by thermal spraying, vapor deposition, brushing, or a gold-coated plate (
A gold-coated plate) may be pasted on the inner surface of the bell jar to give it a mirror surface. When using the gold-coated plate, it is easy to apply gold coating to the underlying plate by electroplating, etc., making it easy to form the coating layer. There are advantages. Of course, applying the gold coating to the underlying plate is not limited to the electroplating described above, but may also be done by other suitable methods. Incidentally, since the inside of the furnace is heated to about 1000° C., a steel plate or the like with high heat resistance is used as the base plate. Incidentally, the thickness of the gold coating layer is not particularly limited.

In order to affix the above-mentioned gold-coated plates to the inner surface of the bell jar, it is sufficient to laminate the adjacent gold-coated plates without any gaps so as to cover the inner surface of the bell-jar, and fix both ends of the gold-coated plates with screws or the like. , the inner surface of the bell jar is curved, but when a straight gold-coated plate is pasted together, a slight gap is created on the back side of the gold-coated plate, but the radiant heat inside the furnace is reflected by the gold-coated surface.
Furthermore, if fixing screws with good thermal conductivity are used, heat radiation and cooling from the outside can be effectively achieved through the fixing screws, so there is no particular problem.

Next, in both cases where the gold coating layer is directly formed on the inner surface of the belljar and when a gold coating plate is used, the gold coating layer may be formed only on the inner surface of the belljar inner surface excluding the ceiling surface. The seed rod, which is the heating element, is a long and thin rod-shaped member that is placed upright inside the furnace, so the radiant heat is large on the sides, and the radiation on the ceiling is not as large on the sides.Therefore, the inner surface of the bell jar is coated with gold. By providing a layer, the heating effect can be enhanced even if the ceiling surface is excluded, and the temperature inside the furnace can be sufficiently uniformized.

FIG. 1 shows an example of the furnace according to the present invention. As shown in the figure, the furnace 1O is formed of a base 11 and a bell jar 12 that covers the upper surface of the base 11, and a seed rod 13 is attached to the base 1. A suitable number of holding electrodes 144 are provided.Furthermore, the base 11 has an inlet 15 for supplying a mixed gas of chlorosilane and hydrogen, which is a raw material gas, into the furnace, and an exhaust port 16 for discharging the gas after the reaction. Note that some of these electrodes are shown in the figure and others are omitted.

A gold coating layer 17 is formed on the inner surface of the bell jar 12. The gold coating layer 17 is formed by fixing a large number of gold plated plates 17a to the inner surface of the bell jar with screws.

When manufacturing polycrystalline silicon, a seed rod 1 is attached to the electrode 14.
3, an appropriate number of seed rods are set upright in the furnace, and electricity is applied to the seed rods to heat them to about 1150°C. on the other hand,
A mixed gas of chlorosilane and hydrogen is supplied into the furnace through the inlet 15. The chlorosilane is reduced by hydrogen,
It decomposes into simple silicon, which precipitates and accumulates on the surface of the seed rod.

On the other hand, the gas after one reaction is discharged to the outside from the exhaust port 16.

<Effects of the Invention> In the present invention, since the inner surface of the furnace is mirror-finished with the gold coating layer, heat radiation through the bell jar is suppressed. As a result, the temperature gradient inside the furnace is reduced, and even when polycrystalline silicon grows thick, the temperature difference between the outer edge and the center remains within an allowable range, which not only prevents damage such as cracks but also Heat loss due to radiant heat transfer is reduced by 50 to 90%, resulting in a significant energy saving effect.

Incidentally, the coefficient of metal during heat dissipation is
is around 0.2, while gold (Au) is around 0°018~
It is 0.035. Therefore, it is possible to significantly improve heat loss.

Furthermore, since the inside surface of the bell jar is mirror-finished with a gold coating layer, it is chemically extremely stable, and even if outside air flows into the furnace after the furnace is opened, hydrochloric acid caused by residual gas and attached silicon compounds will not be removed. The mirror surface is not damaged even by foreign substances, and a good mirror state can be maintained for a long period of time.

<Examples and Comparative Examples> Example 1 Diameter 200mm +) Height 300mm, inner wall 5mm
A length of 20011 cm was placed inside the reactor plated with Au to a thickness of 1 L.
Two silicone rods were connected and installed in an inverted U shape, and H21
A mixed gas was supplied at a flow rate of 380 cc/win and 5iHCu, and the reaction was carried out at a reaction surface temperature of 1100° C., and the diameter of the silicon rod was set to 28 cm. In this case, the power consumption per 1 kg of silicon is 181 KIII
It was H.

Example 2 After reaction under the same conditions as in Example 1, the chlorosilane polymer adhering to the inner wall of the reactor and its hydrolysis products were washed away with pure water, and the reaction was carried out again under the same conditions to reduce the diameter of the silicon rod to 28.
It was set as Iφ. In this case, the power consumption per 1 kg of silicon was 159 KWH.

Comparative Example 1 Diameter 200mm $ Height 300an P cup 11. b'
, 5 IJS 304 Puff-polished two silicon rods were installed in a reactor, connected in an inverted U shape, and H2100u/sin, 5jHC1380cc/
The mixed gas was supplied at a flow rate of 5 in (7), and the reaction surface temperature was 1
The reaction was carried out at 100°C, and the diameter of the silicon rod was set to 28 layers. In this case, the power consumption per IKg of silicon is 21
0 K11)1.

Comparative Example 2 Diameter 200mtφ Height 300mg 4) and inner wall made of Ag
A silicon rod 2 with a length of 2001 layers is placed in a reactor plated with
The books are connected in an inverted U shape and set up, H2100 1 serving 1n
For SiHC, mixed gas was supplied at a flow rate of 60cc-/win.

Reaction surface temperature! ! The reaction was carried out at 00° C., and the diameter of the silicon rod was set to 28 amφ. In this case, the power consumption per IKg of silicon was 180 KW)I.

Comparative Example 3 After the reaction in Comparative Example 2, the chlorosilane polymer and its hydrolysis product adhering to the inner wall of the reactor were washed away with pure water, and the reaction was carried out again under the same conditions, and the diameter of the silicon rod was changed to 28 mm? And so. In this case, the power consumption per IKg of silicon is 188
It was KWH.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view schematically showing a furnace according to the present invention. In the drawing, 10-Furnace 11-Base 12-Belljar 13-Type rod 14-Electrode 15-Inlet port 16-Exhaust port 17-Gold coating It is a layer.

Claims (1)

[Claims] 1. A manufacturing apparatus in which a polycrystalline silicon seed rod is disposed inside a furnace consisting of a base and a bell jar, and the polycrystalline silicon of the seed rod is grown, in which a gold coating layer is applied to the inner surface of the bell jar. A manufacturing device for polycrystalline silicon, characterized in that it has a mirror surface. 2. The manufacturing apparatus according to claim 1, wherein the gold coating layer is formed by thermal spraying, vapor deposition, or plating of gold on the inner surface of the bell jar. 3. The manufacturing apparatus according to claim 1, wherein the gold coating layer is formed by stretching the gold coating layer on the inner surface of a bell jar.