JPH1149508A - Production with decreased waste of polycrystalline silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing polycrystalline silicon by decreasing wastes. SOLUTION: The high-purity polycrystalline silicon is produced with the decreased wastes by furnishing the entire amt. of the silicon tetrachloride considered necessary for the reaction of metal silicon 1 and hydrogen by the silicon tetrachloride 3 by produced at the time of producing the high-purity silicon 7 by the reaction of trichlorosilane 10 and the hydrogen 21 without supplying trichlorosilanes from outside. Heavy ends are extracted at a ratio at which <=250 kg is attained as the silicon per ton of the high-purity silicon in a distillation stage. A reaction product is brought into reaction with hydrogen chloride 13 before this product is subjected to distillation. The distillation of the reaction product is executed in multiple steps and the hydrogen chloride 13 is brought into reaction with the intermediate extract exclusive of the refined trichlorosilane and the refined silicon tetrachloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polycrystalline silicon with reduced waste. More specifically, the present invention relates to a method for producing semiconductor-grade high-purity polycrystalline silicon, which is a raw material of silicon for devices, with less waste.

[0002]

2. Description of the Related Art Semiconductor-grade polycrystalline silicon is generally manufactured by the following method. First, in the first step, crude trichlorosilane is produced by using metallurgical grade low-purity silicon (usually called metallic silicon because of its metallic luster) as a raw material and reacting it with hydrogen and chlorine in a reactor. You. Next, in a second step, the crude trichlorosilane produced in the first step is purified by a method such as distillation to obtain high-purity trichlorosilane and other chlorosilanes (e.g., silicon such as trichlorosilane and silicon tetrachloride). , Chlorine and / or hydrogen)
And impurities to be discarded. Next, in a third step, high-purity silicon is deposited by thermally decomposing and hydrogen-reducing the high-purity trichlorosilane obtained by distillation. In particular, a method for producing a rod-shaped precipitate is called a Siemens method, and is widely and generally performed. Since silicon tetrachloride is produced as a by-product of the precipitation reaction and is discharged out of the reaction system together with trichlorosilane not used in the reaction, these exhaust gases are liquefied in the next step and separated again by distillation or the like. Attached to Generally, the distillation separation step is performed by returning the liquefied exhaust gas to the second step.

As a method for producing trichlorosilane, a method in which metallic silicon is reacted with hydrogen chloride gas is generally used (see Japanese Patent Application Laid-Open No. 58-32011). Hereinafter, this reaction is referred to as a chlorination reaction. Further, when polycrystalline silicon is deposited in the deposition step, silicon tetrachloride is generated as a by-product. As a method of converting this silicon tetrachloride again into trichlorosilane useful for the deposition of silicon, there is known a method of reacting silicon tetrachloride with metallic silicon and hydrogen (see Japanese Patent Application Laid-Open No. 63-100015). Hereinafter, this reaction is referred to as a reduction reaction.

[0004] Conventional polycrystalline silicon production processes have been performed by a combination of processes of producing trichlorosilane by a chlorination reaction, purifying it, and depositing high-purity silicon (hereinafter, a combination of these processes). Is referred to as a process). However, in this process, it was necessary to discard 10 to 14 tons of silicon tetrachloride by-product in depositing 1 ton of high-purity silicon. As a countermeasure, a method has been proposed in which silicon tetrachloride by-produced by precipitation is used for other purposes, for example, silica production (US Pat. No. 4,5,5).
15,762). In this method, since two completely different processes are operated simultaneously, it is difficult to balance them. As a countermeasure, to balance the amount of silicon tetrachloride generated and the fluctuating usage,
It has been proposed as a process having a total of two types of reactors, which is provided with an auxiliary reduction reactor for recycling a part of silicon tetrachloride by-produced in the precipitation step to the production of trichlorosilane (US Patent No. 4,454,104).

[0005]

In the processes adopted up to now, large amounts of waste have been treated in separate processes. Therefore, for example, there is a disadvantage that the production amount of polycrystalline silicon depends on the production amount of the silica production process. For this reason, there has been a demand for the development of a production method with less waste for producing polycrystalline silicon without being affected by other processes.

Needless to say, in the process of producing polycrystalline silicon, it is ideal to supply only metal silicon as a raw material and discharge only high-purity silicon as a product. Therefore, in a near-ideal process, substances other than silicon, such as chlorine, circulate while changing the shape of the process,
In order to discharge impurities, it is desirable that the gas in the system be slightly purged but hardly purged outside.

There is no problem if the source of the silicon component to the process is silicon itself. However, when the silicon component is supplied in the form of chlorosilanes such as silicon tetrachloride, the chlorine component accompanying the silicon must be removed from the process. Must be discharged. In this case, it is discharged in the form of hydrogen chloride or the like. Since this is gaseous waste, parts that cannot be absorbed by abatement may cause air pollution.
When chlorosilanes are supplied from outside, impurities from outside are also taken in. In this case, the amount of chlorosilanes discharged out of the process to remove impurities also increases. In particular, impurities such as methylchlorosilane are not easily separated and removed by distillation or the like, so that the amount of gas to be discarded out of the system is significantly increased. In addition, since these impurities are difficult to separate, there is a danger that the purity of the polycrystalline silicon of the product is reduced. For these reasons, it is not preferable to supply a large amount of chlorosilanes into the process from outside.

[0008] In order to make the process closer to the ideal, a process in which no chlorination reactor is provided and all of the silicon tetrachloride by-produced in the deposition step is recycled in a reduction reactor is considered. However, in this process, it was difficult to balance the silicon balance for the following reasons. For example, assume that a process having only a reduction reactor is employed. The reduction reaction is a reaction that consumes silicon simultaneously with the reduction of silicon tetrachloride, and its reaction formula is represented by the following formula (1). _{Si + 2H 2 + 3SiCl 4 →} 4SiHCl 3 ...... (1) As can be seen from equation (1), the amount of metal silicon consumed is proportional to the amount of silicon tetrachloride reduction. Therefore, if the amount of silicon tetrachloride is small, the required amount of metallic silicon cannot be consumed.

This has already been studied and is disclosed in
No. 5811 discloses that when 10 to 20 mol of silicon is produced, only 24 to 26 mol of silicon tetrachloride can be by-produced. That is, 1-2 moles per mole of silicon
It is said that moles of silicon tetrachloride are by-produced. On the other hand, in the reduction reaction shown in the formula (1), 3 moles of silicon tetrachloride are required even in a stoichiometric amount to consume 1 mole of silicon. That is, in order to produce 10 to 20 mol of silicon without supplying chlorosilanes from the outside, 30 to 60 mol of silicon tetrachloride as a by-product is required.
Considering the discharge of impurities in the purification process, more silicon tetrachloride is required. For this reason, it was difficult to consider establishing the process without supplying chlorosilanes from the outside.

[0010]

Means for Solving the Problems The present inventors changed the viewpoint and studied a process of circulating silicon tetrachloride as much as the consumption of polycrystalline silicon. As a result, they have found that the amount of by-produced silicon tetrachloride can be intentionally adjusted to an optimum value by controlling the reaction conditions in the precipitation reaction using trichlorosilane. By utilizing this technology, the balance of silicon and chlorine in the entire process is adjusted, thereby enabling operation of the process with less waste.

It is, therefore, an object of the present invention to provide a method for producing polycrystalline silicon with less waste. Another object of the present invention is to provide a reaction between metallic silicon and hydrogen by using silicon tetrachloride by-produced when producing high-purity silicon by reacting trichlorosilane with hydrogen without supplying chlorosilanes from the outside. It is an object of the present invention to provide a method for producing high-purity polycrystalline silicon while reducing waste by covering all the necessary amount of silicon tetrachloride. Still other objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the above objects and advantages of the present invention include: (I) a step of reacting metallic silicon with hydrogen and silicon tetrachloride to produce a reaction product containing trichlorosilane; (I) A step of subjecting the reaction product obtained in (I) to distillation to separate it into purified trichlorosilane and purified silicon tetrachloride. (III) The purified trichlorosilane obtained in step (II) is reacted with hydrogen to obtain a highly purified product. Used in the step (I) in the method for producing high-purity silicon comprising the step of producing pure silicon and the step of (IV) circulating the by-product containing silicon tetrachloride in the step (III) to the distillation in the step (II) This is achieved by a method for producing polycrystalline silicon, wherein substantially all of silicon tetrachloride is covered by silicon tetrachloride by-produced in step (III).

As described above, the present invention basically comprises a step of reacting metallic silicon with hydrogen and silicon tetrachloride to produce a reaction product containing trichlorosilane (Step I, hereinafter referred to as a reaction step), A step of subjecting the reaction product obtained in step (I) to distillation to separate it into purified trichlorosilane and purified silicon tetrachloride (step II, hereinafter referred to as a distillation step), and a purification step obtained in step (II). It consists of three steps of reacting trichlorosilane with hydrogen to produce high-purity silicon (Step III, hereinafter referred to as a deposition step). In the step (III), silicon tetrachloride generated as a by-product in the deposition step is converted into a step ( This is a method for producing high-purity silicon, which is circulated to the distillation of II).

A reduction reaction is suitably employed in the reaction step of the method of the present invention. By not installing a reactor for the chlorination reaction, a process based on the recycling of chlorosilanes with less waste is established. In the method of the present invention, silicon tetrachloride used in the reaction step is mainly composed of high-purity silicon tetrachloride generated as a by-product in the precipitation step.
Although supplied once to the reduction reactor in the reaction step, it is sent to the distillation step as it is unreacted, and is again supplied to the reaction step as purified silicon tetrachloride. There is also substantially unreacted circulating silicon tetrachloride. I do. Circulating silicon tetrachloride is not treated here as silicon tetrachloride used in the reaction. On the other hand, it is assumed that all silicon tetrachloride generated in portions other than the reaction step in the process is included. For example, silicon tetrachloride and the like generated by the reaction of hydrogen chloride with trichlorosilane or dichlorosilane in an activated carbon adsorption tower in a hydrogen circulation facility are also included.

The silicon deposition conditions in the deposition step of the method of the present invention must be such that the reaction form of trichlorosilane is controlled. The present inventors have conducted research on the reaction form of trichlorosilane, and have determined the following method as a means for increasing the amount of silicon tetrachloride by-produced.
That is, a reaction that occurs when trichlorosilane and trichlorosilane collide, such as raising the temperature of the deposition gas, increasing the pressure of deposition, or increasing the concentration ratio of trichlorosilane to hydrogen, that is, conditions that promote a homogeneous reaction. I found that I should choose Preferably, the temperature of the deposition gas is 950-1200 ° C,
Deposition reaction conditions are employed, wherein the deposition pressure is from normal pressure to 1000 KPa and the molar ratio of hydrogen to trichlorosilane is from 1: 4 to 1:15. If the circulation amount of silicon tetrachloride is increased in the method of the present invention, the amount of silicon tetrachloride used for the reduction reaction naturally increases, and the silicon consumption increases in proportion thereto. If it is desired to reduce the amount of silicon tetrachloride by-produced in order to reduce the consumption of silicon, the reverse operation may be performed. By the above operation, 2.7 to 4.2 mol, preferably 3.0 to 4.2 mol of silicon tetrachloride per mol of precipitated silicon.
By producing 4.0 mol, more preferably 3.1 to 3.8 mol of by-product, the method of the present invention is established. As a result, chlorosilanes are not substantially supplied from the outside, that is, the amount is made 5% or less, more preferably 2% or less, especially 1% or less of the amount of silicon tetrachloride used in the reaction step. Substantially all of the silicon tetrachloride used is covered by silicon tetrachloride by-produced in the precipitation step, so that waste can be reduced by the method of the present invention. For this reason, 95% or more, more preferably 97% or more, and especially 99%
% Or more is preferably supplied to the reduction reactor in the reaction step. On the other hand, if a chlorination reactor is installed in the process, this is the same as supplying chlorosilanes from the outside.In this case, considering the balance of silicon and chlorine in the entire process, chlorine Ingredients become excessive and the amount of waste increases.

In the method in which the amount of silicon tetrachloride by-produced in the precipitation reaction is regulated, and the silicon tetrachloride which is a by-product of the precipitation reaction in the reduction reactor is completely recycled, there is no waste containing chlorine components. In this case, only the metal silicon needs to be supplied to this method. However, in practice, chlorination of impurities contained in the raw material silicon, such as iron and aluminum, purging of chlorosilanes accompanied by impurities in the course of distillation, chlorosilanes of high, low and medium boiling point to be discarded, or Some chlorine components are discharged out of the system by purging hydrogen chloride generated in the precipitation step. It is not preferable to supply too much chlorosilanes such as trichlorosilane and silicon tetrachloride to the process from the outside for the above-mentioned reason. Therefore, when replenishing chlorine components, it is preferable to replenish hydrogen chloride.

When the chlorine component is supplied into the plant in the form of hydrogen chloride, the method is not particularly limited. However, the supply to the reduction reactor causes local heat generation due to the reaction between metallic silicon and hydrogen chloride. There is a risk. Particularly in the case of a metal fluidized bed having a diameter of more than 50 cm, the reactor may be damaged by local heating due to poor flow. In particular, when the concentration of hydrogen chloride exceeds 0.5 mol with respect to 1 mol of silicon tetrachloride to be supplied, when flow failure occurs, the reactor is locally heated and melted, and a fire may occur. Therefore, hydrogen chloride can be mixed only at such a concentration that the temperature in the reactor hardly changes. The amount of hydrogen chloride is preferably at most 0.2 mol, more preferably at most 0.1 mol, per mol of silicon tetrachloride supplied.

As another method, a silicon compound such as trichlorosilane or a low-boiling chlorosilane such as SiH ₂ Cl ₂ or a high-boiling chlorosilane such as Si ₂ Cl ₆ is placed on a solid catalyst together with hydrogen chloride gas. It is also possible to select a method of further chlorinating the silicon compound and supplying chlorine into the system by a mild reaction to be passed. For example, it is possible to select a method in which the reaction product such as trichlorosilane, dichlorosilane, and the polymer obtained in the reaction step (I) is reacted with hydrogen chloride on the catalyst before subjecting to the distillation in the step (II). it can. Further, the distillation of the reaction product such as chlorosilanes obtained in the reaction step (I) in the step (II) is performed in multiple stages, and an intermediate product other than purified trichlorosilane and purified silicon tetrachloride, for example, dichlorosilane, hexachlorodisilane , Methyldichlorosilane, trichlorosilane, etc., hydrogen chloride is reacted therewith, and the method is returned to the distillation step (II). The intermediate extract may contain not only the reaction step but also chlorosilanes supplied from the precipitation step. Chlorosilanes having a low boiling point are obtained as light ends from the liquids withdrawn at the top of each distillation column in the distillation step (II). Further, chlorosilanes having a high boiling point can be obtained as heavy ends from a liquid extracted from the bottom of the distillation column. For multi-stage distillation, a plurality of distillation columns may be used in combination, or may be extracted from the middle of one distillation column. Hydrogen chloride to be reacted may be newly supplied from the outside, but hydrogen chloride discharged from the reaction step can be used for a part of the hydrogen chloride. For example, a by-product containing silicon tetrachloride in the precipitation step can be reacted with hydrogen chloride before being supplied to the distillation step. These methods generate less heat and have less trouble than the method of supplying hydrogen chloride to the reactor. Activated carbon is most preferably used as a solid catalyst for performing a reaction with hydrogen chloride, from the viewpoint of stable activity, low cost, and the like. When chlorosilanes reacted with hydrogen chloride are returned to the process, impurities mixed from hydrogen chloride, activated carbon, and the like may be introduced into the process. Therefore, it is preferable to supply the chlorosilanes before the distillation step.

The light end can be supplied to the precipitation step if there is no particular problem with the purity. It can also be supplied to a reaction step and converted into trichlorosilane.
In this case, since the light end component reacts with silicon tetrachloride, the silicon tetrachloride that consumes silicon decreases accordingly.
Therefore, the proportion of silicon tetrachloride generated in the deposition step must be selected in consideration of these factors.

Thus, almost all of the silicon tetrachloride used in the reaction step (I) is covered by the silicon tetrachloride by-produced in the precipitation step (III) to balance silicon and chlorine in the process, and to externally supply chlorosilanes. It is possible to realize a silicon production process that does not require supply of waste and has low waste. The main waste is the heavy end of the distillation process, which contains hydrogen chloride and silicon tetrachloride for dilution. By employing this method, hydrogen chloride can be reduced to a level at which almost no hydrogen chloride is released unless chlorosilanes are supplied from the outside. Silicon tetrachloride is extracted as heavy ends due to dilution of impurities, polymers, hexachlorodisilane, etc. However, since the balance of silicon in the process is adjusted, there is no need to extract silicon tetrachloride any more. The amount of heavy-end containing silicon tetrachloride is 250 kg of silicon per ton of high-purity silicon produced.
It can be suppressed to the following ratio.

Dichlorosilane, hexachlorodisilane,
The amount of chlorosilanes to be discarded can be further reduced by reacting chlorosilanes, which should be discarded out of the process, such as trichlorosilane containing intermediate boiling point impurities such as methylchlorosilane, with hydrogen chloride. As a result, it is possible to reduce the amount of waste to 100 kg or less, more preferably 50 kg or less, particularly 20 kg or less as silicon per ton of high-purity silicon produced. For the chlorination of chlorosilanes containing a large amount of impurities as described above, it is preferable to use activated carbon having a relatively large pore diameter, which can be easily regenerated. The pore radius is from 0.8 to 4.0 nm, and more preferably from 1.0 to 2.0 n.
m, especially those having a diameter of 1.2 to 1.5 nm are preferably used.
The water vapor adsorption method can be used for measuring the pore radius.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic process diagram of the process of the method of the present invention. 4 is a reduction reactor for performing the reaction step (I). Here, metal silicon, hydrogen and silicon tetrachloride are reacted to produce a reaction product containing trichlorosilane. Reference numeral 1 denotes the supplied metal silicon. 2 indicates hydrogen gas used for the reaction. Reference numeral 3 denotes the supplied silicon tetrachloride. 9
Is a reaction residue such as silicon powder discharged from the reactor. Reference numeral 5 denotes a distillation column for performing the distillation step (II). 10 shows the reaction product obtained in the step (I). 1
0 is distilled in the distillation column 5 and purified trichlorosilane 17
And purified silicon tetrachloride 11. Chlorsilanes 8 and 12 containing impurities are discharged from the distillation column 5.
12 is a low boiling component, that is, light end, and 8 is a high boiling and medium boiling component, that is, heavy end and middle end. The light end 12 can be supplied to the vaporizer 16 as a raw material 18 for reaction with hydrogen chloride, and reacted with hydrogen chloride. Also, a required amount can be supplied to the reduction reactor 4. Light end 1 supplied to the reactor 4
Almost all the dichlorosilane in 2 reacts. This is because it is converted to trichlorosilane by reaction with silicon tetrachloride. Since this reaction does not involve the consumption of metallic silicon, it must be taken into account in determining the silicon balance.

The heavy end 8 is either discarded or supplied to a vaporizer 16 as a raw material 18 for reaction with hydrogen chloride, mixed with hydrogen chloride 13 and then filled with activated carbon.
5 can be passed. The gas after passing is supplied to the distillation column 5 again. In order to avoid clogging of the vaporizer due to concentration of high-boiling impurities that do not vaporize, it is preferable to extract a part 14 of the liquid from the bottom of the vaporizer. The light end 12 can be used for the light end 12 in addition to the heavy end.

6 is a method of reacting the purified trichlorosilane 17 obtained in the distillation column 5 with hydrogen to produce high-purity silicon 7
It is a precipitation reactor for performing a precipitation step (III) for producing a. Almost all by-products generated when high-purity silicon is generated in the precipitation reactor 6 are sent to the five distillation columns. Reference numeral 19 denotes a device for cryogenically separating gas components from the precipitation reactor 6. The chlorosilanes separated at a low temperature are circulated to the distillation step (II), and the other components are led to the activated carbon adsorption tower 20. Hydrogen is circulated to the precipitation step (III) by 21, chlorosilanes 22 adsorbed and recovered are also circulated to the distillation step (II), and hydrogen chloride 23 is discarded. The silicon tetrachloride supplied from outside is indicated by 24.
This process can be carried out without substantially supplying external chlorosilanes in all steps. for that reason,
The amount of waste is smaller than that of a normal polycrystalline silicon production process.

[0025]

【Example】

Example 1 In the production process of polycrystalline silicon shown in FIG. 1, as deposition conditions in a step of producing high-purity silicon, the deposition pressure of silicon was 100 KPa, the deposition temperature was 1130 ° C., and the concentration of trichlorosilane in the supplied deposition gas was The ratio was set at 13.1% to control the ratio of the homogeneous reaction to the heterogeneous reaction. All the heavy ends 8 in the distillation process were discarded. Further, a part of the light end in the distillation step was supplied as a raw material to the vaporizer 16 and reacted with the hydrogen chloride 13 in the activated carbon tower 15. The remaining light end was supplied to the reduction reactor 4. Table 1 shows the balance of silicon at each measurement point at this time. Under these conditions, it was possible to balance silicon and chlorine in the process without supplying chlorosilanes from the outside.

Example 2 Under the manufacturing conditions of Example 1, the entire amount of the light end of the distillation step supplied to the vaporizer 16 was supplied to the reduction reactor 4. Instead, almost all of the heavy end 8 was supplied to a vaporizer 16 as a raw material 18 and reacted with hydrogen chloride in activated carbon 15. Table 1 shows the silicon balance at each measurement point.
Shown in The concentration of trichlorosilane in the deposition gas was 12.8.
%, A process with very low chlorine content released was realized.

Comparative Example 1 Table 1 shows the balance of silicon in the process when a chlorination reactor was used without using a reduction reactor in the reaction step. The waste from this process was slightly increased in hydrogen chloride and large amounts of chlorosilane were discarded out of the process.

Comparative Example 2 In the process of producing high-purity silicon, the concentration of trichlorosilane in the supplied gas was set to 10%, and the pressure was set to normal pressure.
The operation was performed under the same conditions as in Example 1 except that the deposition temperature was 950 ° C. Table 1 shows the silicon balance at each measurement point.
Shown in Under these operating conditions, the amount of silicon tetrachloride generated in the precipitation reactor 6 was reduced, so that the consumption of silicon in the reduction reactor 4 was reduced. In order to maintain the production of polycrystalline silicon, silicon tetrachloride was externally supplied.
The replenishment amount is 300 times the amount of silicon tetrachloride used in the reaction process.
%. Therefore, the amount of chlorosilanes discharged is
Approximately the same as Example 1, but a large amount of hydrogen chloride was discarded out of the process because the chlorine component in the process became excessive.

[0029]

[Table 1]

[0030]

According to the present invention, high-purity polycrystalline silicon can be manufactured without substantially supplying chlorosilanes from the outside.

[Brief description of the drawings]

FIG. 1 is a schematic process diagram of the process of the method of the present invention.

[Explanation of symbols]

1: Metal silicon supply amount 2: Hydrogen gas 3: Silicon tetrachloride supplied to the reactor 4: Reduction reactor 5: Distillation column 6: High-purity silicon production step 7: High-purity silicon produced 8: Extracted from the distillation step 9: Silicon fine powder discharged from the reactor 10: Chlorsilanes containing trichlorosilane and silicon tetrachloride 11: Purified silicon tetrachloride extracted from the distillation step 12: Light end component extracted from the distillation step 13: Hydrogen chloride 14: Chlorosilanes discharged from the process 15: Activated carbon packed tower 16: Vaporizer 17: Purified trichlorosilane extracted from the distillation process 18: Raw material supplied to the vaporizer 19: Cryogenic separation equipment 20: Activated carbon Adsorption tower 21: Circulating hydrogen 22: Recovered chlorosilanes in adsorption tower 23: Disused hydrogen chloride 24: Externally supplied silicon tetrachloride

Claims (7)

[Claims] (I) a step of reacting metallic silicon with hydrogen and silicon tetrachloride to produce a reaction product containing trichlorosilane; (II) a step of distilling the reaction product obtained in step (I). (III) reacting the purified trichlorosilane obtained in the step (II) with hydrogen to produce high-purity silicon; and (IV) the step (IV) In the method for producing high-purity silicon, which comprises recycling the by-product containing silicon tetrachloride to the distillation in step (II) in step III), almost all of the silicon tetrachloride used in step (I) is removed in step (III). A method for producing polycrystalline silicon, which is provided by silicon tetrachloride produced. 2. The method for producing polycrystalline silicon according to claim 1, wherein in the distillation step of the step (II), heavy ends are extracted at a rate of 250 kg or less as silicon per tonne of high-purity silicon. 3. The method for producing polycrystalline silicon according to claim 1, wherein the reaction product obtained in the step (I) is reacted with hydrogen chloride before subjecting the reaction product to distillation. 4. The distillation of the reaction product obtained in the step (I) is performed in multiple stages, and hydrogen chloride is reacted with an intermediate extract other than purified trichlorosilane and purified silicon tetrachloride, and then returned to the distillation step again. A method for producing polycrystalline silicon according to claim 1. 5. The method for producing polycrystalline silicon according to claim 1, wherein the by-product containing silicon tetrachloride in the step (III) is reacted with hydrogen chloride before being recycled to the distillation in the step (II). 6. The method for producing polycrystalline silicon according to claim 1, wherein 2.7 to 4.2 mol of silicon tetrachloride is by-produced per mol of high-purity silicon in the step (III). 7. The reaction of the step (III) is carried out at 950 to 1200
C., a reaction pressure of 100 KPa to 1000 KPa and a molar ratio of trichlorosilane to hydrogen of 1: 4 to
7. The method of claim 6, implemented as 1:15.