JPH0649569B2 - Method and apparatus for producing trichlorosilane - Google Patents

Description

TECHNICAL FIELD The present invention relates to silicon tetrachloride (SiC) at high temperature without producing impurities.
The present invention relates to a method and an apparatus for producing trichlorosilane which converts l ₄ ) into trichlorosilane (SiHCl ₃ ) and has excellent durability of a production reactor.

<Technical background> When hydrogen-reducing and pyrolyzing trichlorosilane at high temperature to produce semiconductor-grade high-purity polycrystalline silicon, a large amount of silicon tetrachloride is inevitably produced as a by-product. Directly from the silicon tetrachloride,
It is possible to manufacture polycrystalline silicon, but it is necessary to react at a higher temperature than that using trichlorosilane as a raw material, and the yield is poor. Therefore, in order to improve the production efficiency of polycrystalline silicon, it is indispensable to convert the above-mentioned silicon tetrachloride into trichlorosilane for effective use. Silicon tetrachloride, which is a by-product of the above semiconductor-grade polycrystalline silicon manufacturing process, has very few impurities by itself.
Using this silicon tetrachloride as a raw material, trichlorosilane containing very few impurities can be produced.

Conventionally, as a method for producing trichlorosilane from silicon tetrachloride and hydrogen, a method has been known in which a raw material gas is passed through a fluidized bed of metallic silicon to cause a catalytic reaction. However, this method has a problem that the trichlorosilane produced by the impurities contained in the metallic silicon powder is contaminated. Further, even when the fluidized bed of metallic silicon is not used, there are the following problems due to the material of the reaction furnace. That is, as the material of the reaction furnace, carbon, silicon carbide, silica, alumina, etc., which have corrosion resistance to high temperature hydrogen, silicon tetrachloride, and hydrogen chloride gas, have been conventionally selected. Of these, carbon is a high-purity and relatively large-sized member that can be manufactured. Also, if fibrous carbon is used, the heat insulating effect is great, and it is a suitable member as a furnace component. When exposed to the above high temperatures, organic impurities are generated and the generated trichlorosilane is contaminated. On the other hand, with respect to silicon carbide, organic impurities are hardly generated at temperatures up to 1000 ° C, but it is difficult to manufacture large members with high purity. Also, SiO ₂ , Al ₂ O
₃ also has a problem in use because it is not durable against hydrogen, hydrogen chloride and silicon tetrachloride at high temperatures above 1000 ° C. In addition to the above-mentioned members, there is high-purity silicon as a member containing no harmful impurities. It is known that in a mixed gas of silicon tetrachloride and hydrogen, silicon is kept in an equilibrium state by being precipitated or etched due to the mutual relationship between Cl ₂ , H ₂ , and Si partial pressures in the gas and temperature. . However, when the mixture molar ratio of silicon tetrachloride and hydrogen (4CS: H ₂ ) is 1:20 or less, silicon is etched at a temperature of 900 ° C or less and corrosion resistance is not obtained. For this reason, it was thought that it was not suitable as a constituent material of a reactor in which the temperature distribution from low temperature to high temperature is unavoidable.

<Structure of the Invention> The present invention makes it possible to convert silicon tetrachloride to trichlorosilane at a high temperature without producing impurities by providing a coating of silicon or a silicon compound in a portion exposed to a high temperature in a furnace. This is a solution to the conventional problem.

According to the present invention, a heater in the furnace and a reaction furnace in which silicon or a silicon compound is coated on the high temperature portion of the furnace wall are used,
There is provided a method for producing trichlorosilane, which comprises heating a raw material gas obtained by mixing silicon tetrachloride and hydrogen to produce trichlorosilane.

Further, as a preferred embodiment thereof, the raw material gas has a mixed molar ratio of silicon tetrachloride and hydrogen of 2: 1 to 1:30, and the raw material gas is heated to 600 to 1100 ° C. A method for producing the coating layer while keeping the thickness of the coating layer constant by changing the mixing molar ratio of the silicon tetrachloride and hydrogen is provided. Further, there is provided a manufacturing method for recovering the thickness of the coating layer by using a mixed gas of trichlorosilane and hydrogen in place of the silicon tetrachloride. As an apparatus for carrying out these manufacturing methods, silicon tetrachloride and hydrogen are used. In a reaction furnace having a feed port for a mixed raw material gas and an exhaust port and having a heater in the furnace, silicon or a silicon compound is coated on the heater and the portion exposed to the high temperature in the furnace. A manufacturing apparatus characterized by the above is provided.

In the present invention, a mixed gas of silicon tetrachloride and hydrogen is heated to a high temperature to convert silicon tetrachloride into trichlorosilane. Conventionally, the production of trichlorosilane using silicon tetrachloride as a raw material has been carried out in a temperature range of 500 to 1100 ° C. in an externally heated reaction tube as disclosed in JP-A-48-47500. The reason is that silicon tetrachloride, trichlorosilane,
This is because corrosive gases such as hydrogen chloride are used, so there is no material that can withstand this at high temperatures, and at temperatures above 1100 ° C, it is not advantageous because precipitation of trichlorosilane formed into silicon begins. Further, the method disclosed in Japanese Patent Laid-Open No. 48-95396 discloses that a mixed gas of SiHCl ₃ , SiCl ₄ , H ₂ and HCl, which is in a reaction equilibrium at a temperature of 600 to 1200 ° C., is heated to 300 ° C.
It is rapidly cooled to obtain trichlorosilane. As described above, various methods for converting silicon tetrachloride into trichlorosilane have been conventionally known, but there is a problem with the material constituting the reaction furnace, the raw materials used, and the like, and none of them has a semiconductor-grade purity.

According to the present invention, by coating silicon or a silicon compound on the high temperature portion including the heater in the furnace, the durability of the furnace and the contamination of impurities at high temperature are prevented.

An example of the device configuration according to the present invention is shown in FIG.

The reaction furnace 10 has a cylindrical shape, and an appropriate number of heaters 11 are provided inside the reaction furnace 10. The heater 11 is held by an electrode 16 provided on the upper surface of the reaction furnace 10, and protrudes from the upper part of the furnace toward the lower part. The heater 11 may be heated directly by electric current as shown in the figure, or may be heated by a method such as high frequency heating. The reactor 10
A source gas supply port 12 is provided on the lower side wall of the furnace, and the dispersion plate 1 for partitioning the inside of the furnace is further provided above the supply port 12.
3 is attached. A large number of small holes 14 are formed in the dispersion plate 13, and the raw material gas introduced into the furnace through the supply port 12 is uniformly dispersed and flows upward in the furnace. On the other hand, an appropriate number of exhaust ports 15 are provided in the upper part of the furnace 10, and a mixed gas of trichlorosilane, hydrogen chloride, unreacted hydrogen, and silicon tetrachloride is taken out through the exhaust ports 15.

Main body of the reaction furnace 10, heater 11, dispersion plate 13
Carbon is used as the material. Of course, other heat resistant materials can be used. Silicon or a silicon compound is coated on the high temperature portion inside the reaction furnace.
That is, the silicon compound is coated on the heater and the inner wall of the furnace at the portion A heated to 800 to 1000 ° C. from the dispersion plate 13 to the vicinity of the central portion of the carbon heater 11. Silicon carbide is suitable as the silicon compound. Besides, silicon nitride or the like can be used. The thickness of the coating layer may be such that carbon of the furnace material is not exposed, and in consideration of durability, it may be about 1 to 2 mm. High-purity silicon is coated on the heater and the inner wall of the furnace in the portion B of the reaction furnace 10 heated to 1000 ° C. or higher, that is, in the range from the central part of the heater 11 to the upper part of the furnace. The thickness of the silicon coating may be about 1 to 30 mm, preferably about 15 mm. If the silicon layer is too thick, the coating layer may crack due to the difference in thermal expansion coefficient between the inner wall of the furnace and silicon. On the other hand, if it is too thin, the silicon coating layer may be consumed during the reaction, exposing the underlying furnace material. Silicon does not deposit on the substrate at temperatures below 900-1000 ° C, so it is coated at high temperatures above 1000 ° C.

Another example of the device configuration according to the present invention is shown in FIGS. 2 and 3.

As shown in the figure, the reaction furnace 20 has a cylindrical shape.
An appropriate number of source gas supply ports 21 are provided on the lower side wall of 0. Further, an exhaust pipe 22 is provided at the center of the upper surface of the reaction furnace 20, and the exhaust pipe 22 projects from the upper surface of the furnace into the furnace and extends to the lower part of the furnace. A cylindrical heater 23 is provided in the furnace so as to surround the exhaust pipe 22.
3 is held by an electrode 24 provided at the bottom of the furnace, and stands upright toward the upper part of the furnace. A gap is formed between the heater 23 and the upper surface of the furnace as a flow path for the raw material gas. Further, a cylindrical partition wall 25 surrounding the heater 23 is provided in the passage. An opening 26 is formed along the cylinder at the upper part of the partition wall 25.
Is provided and forms a flow path for the raw material gas. The partition wall 25 plays a role of uniform distribution of the raw material gas and a heat transfer surface, and the raw material gas flowing into the furnace from the supply port 21 rises along the partition wall 25 and the heater 23 is installed through the opening 26. Flows into the central part of the furnace. The raw material gas flows down from the upper part of the furnace to the lower part along the heater 23, and after reaction, is guided to the outside through the exhaust pipe 22. The reaction furnace 20
In the same manner as in the reaction furnace 10 shown in FIG. 1, silicon or a silicon compound is coated on a high temperature portion in the furnace including a heater. That is, silicon carbide is coated on a portion of the furnace where the temperature is 800 ° C. or higher, and silicon is coated on the inner and outer upper portions of the partition wall 25 where the temperature is 1000 ° C. or higher, the heater 23, and the exhaust pipe 22. It

In the above device configuration, a mixed gas of silicon tetrachloride and hydrogen is introduced into the furnace through the supply port and flows on the heater surface along the longitudinal direction thereof. The heater is heated to 800 to 1300 ° C, and the raw material gas comes into contact with the heater and the heat transfer surface in the furnace heated by the heater to be heated to about 600 to 1100 ° C to generate trichlorosilane according to the following formula. To do.

SiCl ₄ + H ₂ → SiHCl ₃ + HCl At the same time, hydrogen chloride and silicon are by-produced according to the following formula.

2SiHCl ₃ → Si ＋ SiCl ₄ ＋ 2HCl SiHCl ₃ ＋ H ₂ → Si ＋ 3HCl In this case, the generated trichlorosilane is immediately removed from the high temperature heater and the heat transfer surface in the furnace by the gas flow, so it is better than the decomposition of trichlorosilane to silicon. A large amount of silicon chloride is converted to trichlorosilane, and trichlorosilane can be efficiently produced. In this case, the mixing molar ratio of silicon tetrachloride and hydrogen in the source gas is preferably in the range of silicon tetrachloride: hydrogen = 2: 1 to 1:10. If the molar ratio of silicon tetrachloride to hydrogen is 2: 1 or less, the rate of wear with the previously coated silicon is high, and the underlying carbon or silicon carbide may be exposed. Increased and not economical. On the other hand, hydrogen chloride reacts with silicon due to the by-product of hydrogen chloride, and the reaction of producing trichlorosilane secondarily proceeds.

_{Si + 3HCl → SiHCl 3 + H} 2 at this time, there are cases where silicon is Kotengu high temperature portion in the furnace reduces the thickness of the consumed Kotengu layer. Therefore, if the mixing molar ratio of silicon tetrachloride and hydrogen of the raw material gas is changed to adjust silicon tetrachloride: hydrogen = 1: 4 to 1:30 and the mixing amount of hydrogen is increased, the reaction between silicon and hydrogen chloride It is suppressed and, conversely, silicon is generated by decomposition of trichlorosilane or hydrogen reduction, and the thickness of the silicon coating layer can be recovered. In addition, the composition of the raw material gas is changed, trichlorosilane and hydrogen are mixed instead of silicon tetrachloride, and the mixing molar ratio of trichlorosilane and hydrogen is set to trichlorosilane: hydrogen = 1: 2 to 1:20. By adjusting, the thickness of the silicon coating layer can be recovered.

<Effects of the Invention> According to the present invention, since the high temperature portion in the furnace is coated with silicon or a silicon compound, it is possible to obtain high-purity trichlorosilane without contamination of impurities due to the furnace material. That is, for example, when carbon is used for the material of the furnace body or the heater, the carbon is conventionally exposed directly on the inner wall of the furnace, and when exposed to a high temperature of 800 ° C or higher, the carbon of the furnace material becomes hydrogen of the source gas. There is a problem that the reaction produces methane, and the trichlorosilane produced is contaminated by this methane and silicon organic compounds.
However, in the present invention, as described above, methane is not generated as in the conventional case, and extremely high-purity trichlorosilane can be produced.

Further, in the present invention, by adjusting the relative molar ratio of the raw material gas, silicon tetrachloride gas, and hydrogen, the silicon coating layer in the furnace can be maintained at a predetermined thickness to continue the production, and can be stably produced for a long time. It has the advantage of being manufacturable.

<Examples and Comparative Examples> A carbon fiber heat insulating material having an inner diameter of 180 mmφ and a furnace height on a gas distribution plate of 1200 mmh was installed inside a stainless steel cylindrical container, and four carbon heaters of 1000 mml and 26 mmφ protruded from the upper portion. The present invention was carried out under the conditions shown in the following examples and comparative examples using a reactor as shown in FIG.

Example 1 SiC coating was applied to the inner wall of the furnace and the heater above 150 mm above the gas dispersion plate to a thickness of 0.5 mm. Further, Si coating was applied at a thickness of 5 mm to the furnace inner wall portion 400 mm above the gas dispersion plate and the portion 800 mm 1 above the heater. Silicon tetrachloride 4 purified as a raw material gas in the above reaction furnace
Supply a mixed gas of 20 mol / h and hydrogen 2100 mol / h,
The production of trichlorosilane was carried out for about 180 hours. S at this time
The temperature of the iC coating part is about 700-900 ℃,
The temperature of the Si coating was about 900-1200 ℃.

When the reaction product gas was passed to -60 ° C and collected as a condensate, chlorosilane was analyzed by gas chromatography, and no organic impurities were detected. When non-condensed gas was analyzed by the same method, the methane concentration was 0.1pp
It was less than m and no other organic impurities were detected.

Example 2 When the production of Example 1 was continued for 160 hours, 0.2 ppm of methane was detected in the reaction product gas. Therefore, the mixing molar ratio of the raw material gas is 420 mol / hour of silicon tetrachloride and 2100 hydrogen.
Mol / h (4CS: H ₂ = 1: 5) to 210 mol / mol of silicon tetrachloride
Hour, change to hydrogen 2100 mol / hour (4CS: H ₂ = 1: 10),
When the reaction was continued, methane in the reaction product gas was not detected in about 0.5 hours. Furthermore, 4CS: H ₂ = 1: 10
The reaction was continued for 4.5 hours at a mixed molar ratio of.

After that, the molar ratio of 4CS: H ₂ = 1: 5 was restored and the reaction was continued. After 115 hours, 0.2 p of methane was added to the produced gas.
pm has been detected. Therefore, after reacting at a molar ratio of 4CS: H ₂ = 1: 10 for 5 hours, then reacting at a molar ratio of 4CS: H ₂ = 1: 5 for 100 hours, and further changing to 4CS: H ₂ = 1: 10 for 5 hours. After the reaction, the operation of returning to 4CS: H ₂ = 1: 5 was repeated again. As a result, methane was not detected in the reaction product gas for a long period of time, and there was no contamination with other organic impurities. I was able to get it.

Comparative Example 1 Trichlorosilane was produced by supplying a mixed gas of 420 mol / hr of purified silicon tetrachloride and 2100 mol / hr of hydrogen as a raw material gas to the above reaction furnace not coated with silicon and silicon carbide. At this time, the temperature distribution of the inner wall of the furnace and the heater was almost the same as in the case of Example 1.

When the reaction product gas was cooled to −60 ° C. and chlorosilane recovered as a condensate was analyzed by gas chromatography, 50 ppm of methyltrichlorosilane was detected. When non-condensed gas was analyzed by the same method,
240 ppm of methane was detected.

Comparative Example 2 In a reactor in which 150 mm above the gas dispersion plate and 0.5 mm in thickness of the inner wall of the furnace and the heater were coated with SiC, and where no other Si coating was applied, silicon tetrachloride was used as a source gas.
Supplying a mixed gas of 420 mol / hour and hydrogen 2100 mol / hour,
Trichlorosilane was produced. At this time, the temperature distributions of the inner wall of the furnace and the heater were almost the same as in Example 1.

When the reaction product gas was cooled to −60 ° C. and the cross silane collected as a condensate was analyzed by gas chromatography, methyltrichlorosilane at a concentration of 3 ppm was detected. When non-condensed gas was also analyzed by the same method, 8 ppm concentration of methane was detected.

[Brief description of drawings]

1 to 3 relate to the position of the present invention, FIG. 1 is a schematic perspective view of one embodiment thereof, FIG. 2 is a schematic vertical sectional view of another embodiment, and FIG. 3 is a schematic view of the apparatus. FIG. In the drawing, 10, 20 ... Reactor, 11, 23 ... Heater, 12, 21 ... Supply port, 14 ... Dispersion plate, 15, 2
2 ... Exhaust port, 16, 24 ... Electrode, 25 ... Partition wall.

Claims (7)

[Claims] 1. A trichlorosilane is produced by heating a raw material gas in which silicon tetrachloride and hydrogen are mixed using a reactor in which a heater and a high temperature portion of a furnace wall are coated with silicon or a silicon compound. And a method for producing trichlorosilane. 2. A raw material gas in which silicon tetrachloride and hydrogen are mixed in a molar ratio of 2: 1 to 1:30, and the raw material gas is 600 to 1100.
The production method according to claim 1, wherein trichlorosilane is produced by heating to ° C. 3. The production method according to claim 1, wherein trichlorosilane is produced while keeping the thickness of the coating layer constant by changing the mixing molar ratio of the raw material gas of silicon tetrachloride and hydrogen. 4. A heater in the furnace and a reactor in which high temperature portions of the furnace wall are coated with silicon or a silicon compound are used to heat a raw material gas in which silicon tetrachloride and hydrogen are mixed to produce trichlorosilane, while trichlorosilane is produced. A method for producing trichlorosilane, which comprises supplying a mixed gas of silane and hydrogen, and recovering the coating layer thickness by thermal decomposition or hydrogen reduction of the mixed gas. 5. A reactor equipped with a heater for supplying a raw material gas mixture of silicon tetrachloride and hydrogen and an outlet, and is exposed to the high temperature of the heater and the furnace. An apparatus for producing trichlorosilane, characterized in that silicon or a silicon compound is coated on a portion thereof. 6. The manufacturing apparatus according to claim 5, wherein silicon carbide is coated in a high temperature portion of 800 to 1000 ° C. of the reaction furnace. 7. The manufacturing apparatus according to claim 5, wherein silicon is coated in a high temperature portion of 1000 ° C. or higher of the reaction furnace.