KR101672796B1 - Method for producing high purity trichlorosilane for poly-silicon using chlorine gas or hydrogen chloride - Google Patents

Abstract

The present invention relates to a process for producing high purity trichlorosilane (TCS, SiHCl ₃ ), and more particularly to a process for the production of silicon tetrachloride (STC, SiCl ₄ ) in a reactor such as a fluidized bed reactor or a fixed bed reactor, , Metallic silicon (MG Si), hydrogen (H ₂ ) and chlorine (Cl ₂ ) or hydrogen chloride (HCl) to produce trichlorosilane. The method for producing trichlorosilane of the present invention can utilize silicon tetrachloride and hydrogen, which are byproducts generated in the course of silicon precipitation, and can obtain a chlorination effect caused by additional chlorine, The effect of increasing the conversion rate of trichlorosilane is higher than that occurring. According to the present invention, high purity trichlorosilane as a raw material of polycrystalline silicon can be produced economically and effectively.

Metallic silicon, silicon tetrachloride, hydrogen, chlorine, hydrogen chloride, trichlorosilane, polycrystalline silicon

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of producing high-purity trichlorosilane as a raw material for producing polycrystalline silicon by using chlorine gas or hydrogen chloride,

The present invention relates to a process for the production of trichlorosilane (TCS, SiHCl ₃ ), and more particularly to a process for the production of silicon tetrachloride (STC, SiCl ₄ ) (MG Si), hydrogen (H ₂ ), chlorine (Cl ₂ ) or hydrogen chloride (HCl).

High purity trichlorosilane (TCS) is used in the production of polycrystalline silicon used in the photovoltaic industry or in the semiconductor industry's epicutlex process. In the production of polycrystalline silicon for solar cells using trichlorosilane, a method of reducing trichlorosilane gas with hydrogen gas or precipitating silicon by pyrolysis is mainly used.

A Bell jar reactor or a fluidized bed reactor is typically used for the silicon deposition method. In the method using a bell-shaped reactor, trichlorosilane and hydrogen gas are placed in a vertical type reactor and the silicon rod is heated to a high temperature by using electricity to precipitate silicon. In the method using a fluidized bed reactor, silicon particles having a small size are injected into a reactor by using a reaction gas, heated while being fluidized, and silicon seed particles are continuously supplied to the reactor to precipitate silicon from the surface of the silicon seed particles Thereby obtaining polycrystalline silicon having a larger size. In both of the above methods, hydrogen chloride and silicon tetrachloride are produced and discharged as unreacted trichlorosilane and by-products, and the discharged trichlorosilane is separated and used again as a raw material for producing polycrystalline silicon.

At this time, it is necessary to be able to produce trichlorosilane, which is a raw material for producing polycrystalline silicon, by using silicon tetrachloride, which is a by-product, so that the efficiency of silicon production can be increased. As a result, polycrystalline silicon can be economically manufactured and thus a competitive power can be obtained.

Therefore, a lot of studies have been conducted to produce trichlorosilane from hydrochloric acid from tetrachlorosilane (STC) in the process of producing trichlorosilane.

U.S. Patent No. 3,565,590 discloses a method for producing trichlorosilane by reacting hydrogen chloride, which is one of the byproducts produced after semiconductor-grade silicon deposition, with metallic silicon, and another by-product, tetrachlorosilane, by heating with a burner to produce fumed silica / RTI >

However, despite the high TCS selectivity of over 75% and the advantage of recycling the by-product silicon tetrachloride to reduce the amount of waste, this method uses silicon tetrachloride, a by-product, in the manufacture of fumed silica, There is a disadvantage that the utilization efficiency of the silicon raw material is inferior to that used in the production of silane, and further, there is a disadvantage in that a separate process for producing fumed silica is required for the treatment of silicon tetrachloride as a by-product.

U.S. Patent No. 4,117,094 discloses a method in which metallic silicon is reacted with silicon tetrachloride at a temperature of about 1300 ° C to form a dichlorosilane, and hydrogen chloride is added to the formed dichlorosilane at a ratio of about 1: 1, followed by cooling to about 800 ° C Discloses a method of synthesizing trichlorosilane through a two step reaction.

However, this method requires a two-step reaction, which complicates the production process of trichlorosilane and also requires a large amount of energy to be dissipated at a high temperature.

U.S. Patent No. 4,165,363 discloses a method for converting silicon tetrachloride to trichlorosilane by reacting silicon tetrachloride and hydrogen at an elevated temperature of 600 to 1200 ° C under an activated carbon catalyst. However, this method also has a drawback that the reaction temperature is high.

In addition to the disadvantage of economical disadvantages due to the high energy consumption, high reaction temperatures as in the conventional techniques described above cause undesired by-products such as dichlorosilane (DCS, SiH ₂ Cl ₂ ), silicon tetrachloride, and high boiling materials in addition to trichlorosilane There is a problem that the conversion rate to trichlorosilane is lowered.

U.S. Patent No. 2,595,620 discloses a method of converting silicon tetrachloride to trichlorosilane by reacting silicon tetrachloride with metallic silicon and hydrogen gas at 400 ° C under a copper catalyst. This method has a disadvantage in that the conversion temperature of silicon tetrachloride to trichlorosilane is low and the copper catalyst is used in an amount of about 10% by weight, though the energy consumption is low because the reaction temperature is low to 400 to 600 ° C.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to utilize silicon tetrachloride and hydrogen as byproducts generated in the polycrystalline silicon precipitation process, The chlorination reaction can be carried out at the same time so that the conversion rate of the high temperature trichlorosilane can be obtained as compared with the hydrochlorination reaction and the thermal energy generated during the chlorination reaction can be used. Therefore, the hydrochlorination reaction can be performed at a relatively low temperature It is an object of the present invention to provide an economical and effective method for producing high purity trichlorosilane as a raw material of polycrystalline silicon.

According to the present invention, there is provided a process for the production of a catalyst, characterized by reacting silicon tetrachloride (SiCl ₄ ), metallurgical silicon (MG Si), hydrogen (H ₂ ), and chlorine (Cl ₂ ) or hydrogen chloride A process for producing trichlorosilane (TCS) is provided.

The reaction of silicon tetrachloride and hydrogen with metallic silicon to convert silicon tetrachloride to trichlorosilane is an endothermic reaction requiring 3 to 6 Kcal / mol of thermal energy. On the other hand, the reaction in which hydrogen is reacted with metallic silicon in the presence of chlorine or hydrogen chloride to produce trichlorosilane is an exothermic reaction proceeding by emitting heat energy of 50 Kcal / mol. Therefore, in the present invention, since chlorine or hydrogen chloride is introduced into the hydrochlorination reaction using metallic silicon, silicon tetrachloride, and hydrogen, the heat generated in the exothermic reaction by the chlorination reaction can be immediately supplied to the endothermic reaction, It is possible to produce trichlorosilane with thermal efficiency.

Hereinafter, the present invention will be described in more detail.

The process for preparing the trichlorosilane of the present invention is carried out in a conventional reactor such as a fluidized bed reactor or a fixed bed reactor, and is more preferably carried out in a fluidized bed reactor.

In the method for producing trichlorosilane of the present invention, the reaction is preferably carried out at a temperature of 400 to 700 ° C, more preferably 450 to 650 ° C. When the reaction temperature is lower than 400 ° C., the reaction does not proceed smoothly and the rate of conversion of silicon tetrachloride (STC) to trichlorosilane (TCS) is low. When the temperature exceeds 700 ° C., a lot of energy is consumed and many by- It is uneconomical.

In the method for producing trichlorosilane of the present invention, the reaction is preferably carried out under a pressure of 1 to 40 bar, more preferably 5 to 15 bar. If this pressure condition is less than 1 bar, it is difficult for the reaction to proceed smoothly and the transition of the input STC to TCS is very low. Also, in order for the pressure to exceed 30 bar, a very special reactor is required, which is expensive because the reactor must be made of a special material.

Further, in the method for producing trichlorosilane of the present invention, the residence time of the reactants in the reactor is 3 to 30 seconds, and the preferable reaction time is 5 to 15 seconds.

As the catalyst used in the process for producing trichlorosilane of the present invention, a catalyst which can be used for the reaction to convert silicon tetrachloride to trichlorosilane can be used without any particular limitation, and from the viewpoint of the conversion and selectivity into trichlorosilane, Among them, copper (Cu) metal, or copper halide such as copper (I) (CuCl) or copper (II) chloride (CuCl ₂ ) is more preferably used. There is no particular limitation on the amount of the catalyst to be used, but 0.5 to 5% by weight, more preferably 1 to 3% by weight, of the total amount of the reactants is preferably used in view of the reaction and overall process efficiency.

In the method for producing trichlorosilane of the present invention, the metallic silicon (Si (MG)) used as the starting material of the reaction is a compound having a purity of about 98 to 99% prepared by reacting a silicon dioxide (SiO ₂ ) As the silicone, a particle size of preferably 20 to 500 mu m, more preferably 50 to 250 mu m is used. If the size of the metallic silicon particles is less than 20 占 퐉, the metallic silicon tends to escape from the reactor without participating in the reaction due to fluidization in the reactor. On the other hand, if it exceeds 500 mu m, effective fluidization can not be performed, and it is difficult to effectively disperse the reaction heat generated by chlorine (Cl ₂ ) injection.

In the present invention, since metallic silicon is filled in the fluidizing reactor and the raw material gases (silicon tetrachloride, hydrogen, chlorine, etc.) are injected from the lower portion of the reactor to react the metallic silicon particles while fluidizing the metallic silicon in the reactor, It may be present in excess of the quantitative reaction.

Further, in the method for producing trichlorosilane of the present invention, the amount of hydrogen (H ₂ ) used as a starting material for the reaction is preferably 1 to 10 moles, more preferably 2 to 4 moles, per 1 mole of silicon tetrachloride. When the amount of hydrogen used per 1 mole of silicon tetrachloride is less than 1 mole, there is a problem that the efficiency of STC conversion into TCS is low. When it exceeds 10 moles, too much energy is used to heat an excessive amount of hydrogen.

The amount of chlorine (Cl ₂ ) or hydrogen chloride (HCl) used as a starting material in the reaction of the present invention is preferably 0.025 to 2 mol, more preferably 0.05 to 2 mol, per mol of silicon tetrachloride. 1 mole.

In the method for producing trichlorosilane of the present invention, the starting materials of the reaction, silicon tetrachloride, hydrogen, and, if necessary, hydrogen chloride may be supplied separately from the outside, or may be used as a by- It may be mixed with recycled materials supplied from the outside. However, chlorine is not produced in the reaction process itself but supplied from the outside.

As described above, when silicon tetrachloride, hydrogen and, if necessary, hydrogen chloride, which are generated as byproducts in the polycrystalline silicon production process, are recycled and used in the production of trichlorosilane, the process of treating exhaust gas in the production of polycrystalline silicon can be simplified , The silicon source can be utilized to its full advantage, which is economically advantageous.

Hereinafter, the present invention will be described in more detail with reference to FIG.

FIG. 1 is a schematic view of one embodiment of a process for producing polycrystalline silicon including a process for producing trichlorosilane according to the present invention, wherein hydrogen (H ₂ ) and hydrogen chloride (hydrogen) recovered in the process of producing polycrystalline silicon HCl), and silicon tetrachloride is recycled to the process of preparing trichlorosilane.

1, the reaction for converting silicon tetrachloride to trichlorosilane is carried out in a fluidized bed reactor (FBR), and a mixture of metallic silicon (MG Si) and a copper-based catalyst, such as copper (I) chloride, (STC), hydrogen (H ₂ ), or hydrogen chloride (HCl) is introduced into the fluidized bed reactor (FBR) from the outside and is circulated in the reaction process as an exhaust gas generated during the production of polycrystalline silicon, do. Chlorine (Cl ₂ ) is injected into the fluidized bed reactor from outside the polycrystalline silicon manufacturing process.

The temperature in the fluidized bed reactor is maintained at 400 to 700 ° C and the pressure is maintained at 1 to 40 bar. The reaction product is reacted in the reactor for 3 to 30 seconds to prepare trichlorosilane (TCS). After the reaction is completed, in addition to the reaction product, trichlorosilane, unreacted hydrogen, chlorine and silicon tetrachloride, a byproduct dichlorosilane (DCS) and a high boiling point material (HB) such as hexachlorodisiloxane and hexachlorodisilane are present in the mixture Substances other than the trichlorosilane are removed by passing through additional separation columns (C1 to C3), and a high purity trichlorosilane is finally obtained which can be used for the production of polycrystalline silicon. The hydrogen recovered in the separation column C1 and the silicon tetrachloride recovered in the separation column C2 are recycled to the fluidized bed reactor and the silicon tetrachloride recovered in the separation column C3 is reintroduced into the separation column C2. The high purity trichlorosilane thus obtained is introduced into a bell-shaped reactor, where it reacts with hydrogen to produce polycrystalline silicon. The gas discharged from the bell-shaped reactor contains silicon tetrachloride, trichlorosilane, hydrogen chloride, and hydrogen. The exhaust gas is separated into individual components in the separation column C4, and silicon tetrachloride and trichlorosilane are re-introduced into the separation column C2 , Hydrogen is recycled to the bell-shaped reactor, and hydrogen chloride is separated and sold as gas at high purity or used for other purposes.

According to the present invention, it is possible to utilize silicon tetrachloride and hydrogen, which are byproducts generated in the silicon precipitation process, to perform the reaction at a relatively low temperature and to effectively utilize the heat generated by the chlorine reaction due to the addition of chlorine Therefore, a high purity trichlorosilane as a raw material of polycrystalline silicon can be produced economically and effectively.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 6

0.25 to 2.5 g of copper (I) (CuCl) as a catalyst (0.5 to 5 wt% of the total weight of the reactants) and 50 g of metallic silicon having a particle size of 53 to 212 μm as a reactant were placed in a SUS 316 reactor having a length of 23 cm, Nitrogen gas was flowed to remove metallic silicon and moisture in the reactor. Next, the temperature of the reactor was maintained as shown in Table 1, and silicon tetrachloride, hydrogen, and chlorine were charged in the molar ratios shown in Table 1 below, and reacted for 3 to 30 seconds in the reactor. The pressure in the reactor was maintained at about 10 bar. Silicon tetrachloride, hydrogen, and chlorine were preheated in a preheater maintained at 450 ° C and then introduced into the reactor to prevent the reactor temperature from dropping sharply. The dosing of silicon tetrachloride was carried out using a metering pump. Mass flow controller (MFC) was used.

After completion of the reaction, the resultant mixture was analyzed by gas chromatography connected to the reactor on-line, and the results are shown in Table 1 below.

Examples 7 to 14

(I) (CuCl) were used as catalysts as shown in the following Table 2, and the temperature of the reactor was maintained as shown in Table 2, and silicon tetrachloride, hydrogen and chlorine were added in the molar ratios shown in Table 2 The reaction was carried out in the same manner as in Example 1 to prepare trichlorosilane.

The results are shown in Table 2 below.

Comparative Examples 1 to 2

The reaction was carried out in the same manner as in Example 1 except that chlorine was not used to prepare trichlorosilane. The reactor temperature was maintained as shown in Table 3 below.

The results are shown in Table 3 below.

Comparative Examples 3 to 6

The reaction was carried out in the same manner as in Example 2, except that chlorine was not used, to prepare trichlorosilane. The reactor temperature was maintained as shown in Table 4 below and copper (I) chloride (CuCl) was used as catalyst as shown in Table 4 below.

The results are shown in Table 4 below.

As can be seen from the results shown in Tables 1 to 4, in the case of the embodiments of the present invention, the amount of the dichlorosilane and the high-boiling substance in the mixture is substantially the same as that of the corresponding Comparative Examples 1 to 6, Of the total population increased to a significant level.

1 is manufactured of a further input to trichlorosilane hydrogen (H ₂₎ and hydrogen chloride (HCl) and the number of silicon tetrachloride were charged into a manufacturing process of trichlorosilane, and chlorine (Cl ₂₎ generated in a polycrystalline silicon manufacturing process outside the FIG. 3 is a schematic view showing one embodiment of a polycrystalline silicon manufacturing process including a manufacturing process of trichlorosilane according to the present invention, showing the structure of a reaction system for increasing efficiency.

[Description of reference numerals shown in the drawings]

MG Si: Metallurgical silicon

STC: silicon tetrachloride

DCS: dichlorosilane

TCS: trichlorosilane

HB: High boiler material

Poly Si: polycrystalline silicon

FBR: Fluidized Bed Reactor

C1 to C4: separation column

BJR: Bell Jar Reactor

Claims (7)

In a fluid bed reactor, silicon tetrachloride, metallic silicon, hydrogen, and chlorine are used in a ratio of 2 moles of hydrogen per mole of silicon tetrachloride and 0.025 to 0.075 moles of chlorine in the presence of a CuCl catalyst corresponding to 1 to 2.5 wt% And the reaction is carried out for 3 to 30 seconds. The process for producing trichlorosilane according to claim 1, wherein the reaction is carried out at a temperature of 400 to 700 ° C. The process for producing trichlorosilane according to claim 1, wherein the reaction is carried out under a pressure of 1 to 40 bar. delete The process for producing trichlorosilane according to claim 1, wherein silicon tetrachloride and hydrogen are generated as a by-product in the hydrochlorination process and the polycrystalline silicon production process and recycled. delete delete

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