WO2018131500A1 - 多結晶シリコンの製造方法 - Google Patents
多結晶シリコンの製造方法 Download PDFInfo
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- WO2018131500A1 WO2018131500A1 PCT/JP2017/047200 JP2017047200W WO2018131500A1 WO 2018131500 A1 WO2018131500 A1 WO 2018131500A1 JP 2017047200 W JP2017047200 W JP 2017047200W WO 2018131500 A1 WO2018131500 A1 WO 2018131500A1
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- silicon
- chlorosilane
- filter
- fine powder
- polycrystalline silicon
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
- C01B33/03—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent
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- the present invention relates to a method for producing polycrystalline silicon.
- Polycrystalline silicon is suitably used as a raw material for semiconductor elements and solar power generation batteries, for which further development and demand are expected.
- a reaction furnace for producing polycrystalline silicon from a mixed gas of chlorosilanes and hydrogen and a circulation type in which hydrogen gas is extracted from exhaust gas generated in the reaction furnace and reintroduced into the reaction furnace.
- a polycrystalline silicon manufacturing apparatus equipped with a purification system is used.
- a polycrystalline silicon manufacturing method includes a step of removing silicon fine powder that causes piping blockage.
- it has been proposed to remove the silicon fine powder by passing exhaust gas generated from a reaction furnace for producing polycrystalline silicon through a filter (for example, Patent Document 1).
- a filter for example, Patent Document 1
- By removing the silicon fine powder from the exhaust gas in this way it is possible to prevent the silicon fine powder from being deposited on the piping and the separation device in the post-process of the filter and to prevent the pump from being damaged due to the blockage.
- the filter In the production of polycrystalline silicon, if the operation is continued for a long time and the filter is clogged with fine silicon powder, the filter needs to be regenerated. However, there was a risk of ignition from the filter when the filter was opened to the open air to perform this regeneration work. This is because the exhaust gas contains silane oligomers (Si x H y Cl z ) in addition to silicon fine powder, and in the filter treatment, not only the silicon fine powder but also the silane oligomers adhere to the filter. The cause is. That is, the silane oligomer exhibits a very dangerous property that ignites in air.
- silane oligomers Si x H y Cl z
- Patent Document 2 proposes the following method as a method for producing polycrystalline silicon that can reduce the risk of ignition even when the filter is closed, even if the filter is opened to the outside air. That is, in the reaction vessel, chlorosilanes and hydrogen are reacted under heating to precipitate silicon, and exhaust gas containing hydrogen, silane oligomers, and silicon fines is discharged. Step 2 for transporting exhaust gas while maintaining the temperature at 105 ° C. or higher, the exhaust gas transported from Step 2 is supplied to the filter at a temperature of 105 ° C. or higher, and discharged from the filter device at a temperature of 105 ° C. or higher.
- Step 3 for removing silicon fine particles from the exhaust gas to obtain a mixed gas containing hydrogen and silane oligomers, Step for cooling the mixed gas obtained in Step 3 and separating hydrogen from the mixed gas as a gas 4 is a method for producing polycrystalline silicon. According to this method, since the exhaust gas supplied to the filter is maintained at the temperature of 105 ° C. or higher, the adhesion of the contained silane oligomer to the filter can be kept low. As a result, even if the filter is opened to the outside air at the time of blockage, the fear of ignition can be greatly reduced.
- the present invention has been made in view of the above problems, and its object is to remove silicon fine powder contained in exhaust gas with a filter, and to arrange a silicon fine powder in a separation apparatus and piping arranged in a process following the filter.
- a method for highly suppressing the adhesion of the silane oligomer to the filter is realized by a simple method.
- the present inventors have conducted extensive research. As a result, after separating the exhaust gas generated in the reactor into a chlorosilane condensate containing silicon fines and a gas component, the chlorosilane condensate is separated. By passing through the filter, it was found that the separation device of the process following the filter, the accumulation of silicon fine powder in the piping and the damage of the pump can be prevented, and the adhesion of the silane oligomer to the filter can be suppressed to a high degree. It came to complete. That is, the present invention includes the following methods.
- a method for producing polycrystalline silicon according to an embodiment of the present invention includes a silicon deposition step of depositing polycrystalline silicon by reacting a chlorosilane compound and hydrogen, and an exhaust gas discharged from the silicon deposition step.
- the silicon fine powder contained in the chlorosilane condensate is filtered and separated by filtering the chlorosilane condensate through the filter.
- the silane oligomer is dissolved in the chlorosilane condensate. For this reason, adhesion of the silane oligomer to the filter can be suppressed to a high degree, and the removability of the silicon fine powder when the filter is closed is excellent. As a result, the opening operation for exchanging or regenerating the filter can be performed more safely and easily.
- a method for producing polycrystalline silicon according to an embodiment of the present invention includes a silicon precipitation step in which polycrystalline silicon is precipitated by reacting a chlorosilane compound and hydrogen;
- the exhaust gas (gas component A) discharged from the deposition step is a chlorosilane condensate containing silicon fine powder (hereinafter referred to as “chlorosilane condensate A”) and a gas component (hereinafter referred to as “gas component B”).
- chlorosilane condensate A chlorosilane condensate containing silicon fine powder
- gas component B gas component
- a fine powder removing process of removing the silicon fine powder by passing the chlorosilane condensate A containing the fine silicon powder through a filter.
- FIG. 1 is a schematic view showing each step in the production of polycrystalline silicon.
- Silicon deposition process 1> This production method has a silicon deposition step 1 in which polycrystalline silicon is deposited by reacting a chlorosilane compound with hydrogen. In the silicon deposition step 1, the gas component A10 is discharged as exhaust gas.
- the structure and reaction conditions of the reactor used in the silicon deposition step 1 are not particularly limited, and known reactors and reaction conditions can be employed.
- the silicon deposition step 1 can be performed by, for example, the Siemens method (Bergger method), the melt deposition method (VLD method, Vapor to Liquid Deposition method), or the like.
- the Siemens method is as follows. First, a polycrystalline silicon core wire is installed as a heating substrate in a reactor (bell jar), and the polycrystalline silicon core wire is energized and heated to a temperature equal to or higher than the polycrystalline silicon deposition temperature. Next, a raw material gas containing a chlorosilane compound and hydrogen is brought into contact with the heated polycrystalline silicon core wire. Thereby, polycrystalline silicon is deposited on the surface of the polycrystalline silicon core wire, and as a result, a grown polycrystalline silicon rod is obtained.
- the temperature of the polycrystalline silicon core wire heated by electric current is not particularly limited as long as it is equal to or higher than the polycrystalline silicon deposition temperature, but preferably 600 ° C. to 1250 in order to precipitate polycrystalline silicon efficiently. ° C, more preferably 900 ° C to 1200 ° C.
- the melt precipitation method includes a sequential method and a continuous method as follows.
- the sequential method first, the base material installed in the reactor is heated to a high temperature (for example, 600 ° C. or higher) higher than the polycrystalline silicon deposition temperature. Next, it is made to contact by distribute
- the continuous method first, the substrate placed in the reactor is heated to a high temperature (for example, 1450 ° C.
- the silicon deposition step 1 is preferably performed by the Siemens method in order to precipitate polycrystalline silicon efficiently.
- a chlorosilane compound means a compound containing a chlorine element and a silicon element.
- examples of the chlorosilane compound contained in the raw material gas include trichlorosilane and dichlorosilane.
- the chlorosilane compound 16 obtained from the distillation step 7 described later can be used as the chlorosilane compound contained in the raw material gas, but the shortage is supplied by a known method. Can be used (not shown).
- the trichlorosilane that can be used as the chlorosilane compound can be generally produced by a known reaction between metal silicon and hydrogen chloride. In order to remove impurities such as boron and phosphorus from trichlorosilane obtained by distilling the product of the reaction, it is preferable to further distill the trichlorosilane. By distillation, high-purity trichlorosilane can be obtained.
- the trichlorosilane used in the silicon deposition step 1 preferably has a purity of 99.9% or more from the viewpoint of obtaining high-purity polycrystalline silicon.
- the supply amount of hydrogen as a raw material gas is not particularly limited as long as it is excessive with respect to the chlorosilane compound, but in order to precipitate polycrystalline silicon efficiently, it is added to 1 mol of the chlorosilane compound.
- the amount is preferably 3 mol or more.
- the hydrogen contained in the source gas can be supplemented by the hydrogen gas 19, but hydrogen (not shown) obtained by a known manufacturing method can be used for the shortage.
- hydrogen can be produced by electrolysis of water. Specifically, water is supplied by passing an electric current through an aqueous electrolyte solution containing an inorganic acid metal salt and / or metal hydroxide as an electrolyte (ie, an aqueous solution containing an inorganic acid metal salt and / or metal hydroxide as a solute). It is possible to disassemble.
- the hydrogen is preferably washed with water and further passed through a mist filter.
- the hydrogen By passing the hydrogen through a water wash and a mist filter, it is possible to obtain hydrogen substantially free of metal impurities.
- the hydrogen preferably does not contain gaseous impurities such as oxygen and water vapor.
- gaseous impurities such as oxygen and water vapor.
- a known method known for obtaining industrial hydrogen can be employed.
- the hydrogen used in the silicon deposition step 1 preferably has a purity of 99.99 vol% or more from the viewpoint of obtaining high-purity polycrystalline silicon.
- Separation process 2> This manufacturing method has the separation process 2 which isolate
- the gas component A10 contains a chlorosilane compound, hydrogen, hydrogen chloride and silicon fine powder, and may further contain a silane oligomer.
- the chlorosilane compound contained in the gas component A10 comprises a pyrolysis product of the chlorosilane compound contained in the raw material gas and an unreacted chlorosilane compound. For example, tetrachlorosilane, trichlorosilane, dichlorosilane, monochlorosilane, hexachlorodisilane. And one or more of pentachlorodisilane and the like.
- the hydrogen contained in the gas component A10 includes hydrogen generated by thermal decomposition of the chlorosilane compound contained in the raw material gas and unreacted hydrogen.
- Hydrogen chloride contained in the gas component A10 is hydrogen chloride by-produced from the precipitation reaction of polycrystalline silicon.
- concentration of hydrogen chloride in the gas component A10 is, for example, 0.1 mol% to 6 mol%, particularly 0.2 mol% to 3 mol%.
- silicon fine powder means silicon fine particles having a particle diameter of 40 ⁇ m or less, preferably 3 to 30 ⁇ m.
- the average particle size of the silicon fine powder is usually 5 to 15 ⁇ m.
- the silane oligomers contained in the gas component A10 are by-produced during the production process of the polycrystalline silicon, and specifically include Si 2 HCl 5 , Si 2 H 2 Cl 4 and Si 2 Cl 6. It is done. In addition, these boiling points are higher than tetrachlorosilane, and it is easy to condense.
- the chlorosilane condensate A11 obtained in the separation step 2 can contain silicon fine powder.
- the content of silicon fine powder in the chlorosilane condensate A11 may be 0.01% by mass to 0.3% by mass, particularly 0.05% by mass to 0.2% by mass.
- the chlorosilane condensate A11 may be supplied to a process such as a hydrogen chloride removing process 6 described later, or may be used for applications other than the present manufacturing method.
- the gas component B17 obtained in the separation step 2 contains hydrogen gas and hydrogen chloride as main components.
- the gas component B17 further contains a chlorosilane compound remaining as a chlorosilane condensate A11 without being condensed and separated in an amount of about several volume%, and although it is a very small amount, boron and phosphorus derived from metal silicon. Can be included.
- the gas component A10 is preferably cooled.
- the temperature of the gas component A10 is usually 200 to 270 ° C. immediately after being discharged from the silicon deposition step 1. If the piping which transfers this is not specially provided with a heating part for maintaining the temperature as in Patent Document 2, the temperature drops to less than 105 ° C. when supplied to the separation step 2. It is common. Therefore, when an attempt is made to remove the silicon fine powder contained in the exhaust gas by arranging a filter in the middle of the pipe connecting the silicon precipitation process 1 to the separation process 2, the adhesive properties at the low temperature together with the silicon fine powder. Increased adhesion of silane oligomers also causes significant results.
- the cooling temperature of the gas component A10 is not particularly limited as long as it is equal to or lower than the temperature at which the chlorosilane compound is condensed, and can be appropriately determined in consideration of the cooling capacity of the cooling device used. The lower the cooling temperature, the higher the condensation effect of the chlorosilane compound.
- the cooling temperature of the gas component A10 is preferably ⁇ 10 ° C. or less, more preferably ⁇ 30 ° C. or less, from the viewpoint of more efficiently and effectively separating the chlorosilane condensate A11 and the gas component B17. is there.
- the cooling temperature of the gas component A10 is preferably higher than ⁇ 60 ° C. from the viewpoint of production cost.
- the separation method used in the separation step 2 is not particularly limited as long as it can be separated into the chlorosilane condensate A11 and the gas component B17, but the condensation removal method is preferably used.
- the condensation removal method is a method of separating the chlorosilane condensate A11 and the gas component B17 by condensing the chlorosilane compound by cooling the gas component A10.
- the cooling method used when cooling the gas component A10 in the separation step 2 is not particularly limited as long as the gas component A10 can be cooled to the above-described cooling temperature, and a known cooling method may be used. Is possible. Specifically, such a cooling method is a cooling method in which the gas component A10 is cooled by passing it through a cooled heat exchanger, or a cooling method in which the gas component A10 is cooled by the condensed and cooled condensate. Etc. These methods can be employed alone or in combination.
- the separation step 2 is then preferably performed under high pressure, for example in a pressure vessel.
- the pressure in the separation step 2 is not particularly limited as long as the chlorosilane compound can be sufficiently removed, and can be appropriately determined in consideration of the ability of the condensation removal apparatus to be used.
- the pressure is preferably 400 kPaG or more, and more preferably 500 kPaG or more in order to enhance the separation effect between the chlorosilane condensate A11 and the gas component B17.
- a pressurizer can be installed prior to the separation step 2 for the purpose of increasing the pressure of the gas component A10 supplied to the separation step 2.
- Fine powder removal step 5> This manufacturing method has the fine powder removal process 5 which removes this silicon fine powder by letting the chlorosilane condensate A11 containing silicon fine powder pass to a filter. By applying the chlorosilane condensate A11 to the filter, the silicon fine powder contained in the chlorosilane condensate A11 is filtered and separated by the filter. As a result, it is possible to prevent the silicon fine powder from being delivered to the subsequent stage, and to prevent deposition on the separation apparatus and piping in the process following the filter and damage to the pump.
- the fine powder removing step 5 is performed after the separating step 2.
- the silane oligomer is dissolved in the chlorosilane condensate. For this reason, adhesion of the silane oligomer to the filter can be suppressed.
- Silane oligomers are extremely dangerous compounds because they ignite in the air, and when they adhere to the filter, they adhere and cannot be removed easily. According to the present invention, since the adhesion to the filter can be suppressed to a high degree as described above, the open cleaning of the filter can be performed more safely and simply.
- the chlorosilane condensate A11 may contain a chlorosilane compound, a silane oligomer and silicon fine powder.
- the chlorosilane compound contained in the chlorosilane condensate A11 is not particularly limited, and examples thereof include trichlorosilane, dichlorosilane, and tetrachlorosilane.
- silane oligomer and silicon fine powder contained in the chlorosilane condensate A11 are the same substances as described in the silicon deposition step 1.
- the type of filter is not particularly limited as long as it can collect silicon fine powder, and an element or a cyclone can be used without limitation.
- the pore size of the filter is preferably 1 ⁇ m to 5 ⁇ m, particularly 2 ⁇ m to 4 ⁇ m, taking into consideration the particle size and removal rate of the silicon fine powder contained in the chlorosilane condensate A11.
- the material of the filter may be a polyolefin resin such as polypropylene and polyethylene, a resin material such as a polystyrene resin, an acrylic resin, and a fluororesin, or a metal material such as stainless steel from the viewpoint of heat resistance and corrosion resistance.
- polypropylene is more preferable.
- this manufacturing method it is preferable to arrange a plurality of filters (not shown) in parallel in order to perform replacement without stopping the manufacturing when the performance of the filter deteriorates due to long-term use. By switching these filter devices, the filter can be replaced.
- the slurry pump 4 does not break down and the chlorosilane condensate can be delivered to the filter.
- the content of silicon fine powder in the chlorosilane condensate A11 may be 0.01% by mass to 0.3% by mass, and particularly 0.05% by mass to 0.2% by mass.
- the concentration of the silicon fine powder is lower than the solid content concentration (about 1 to 5% by mass) of the slurry normally applied to the slurry pump, but when the chlorosilane condensate A11 is delivered using a normal pump.
- the pump member is worn by silicon fine powder and is easily damaged early. For this reason, although the solid content concentration is lower than the concentration applied to a normal slurry pump, it is preferable to apply the slurry pump because there is no need to worry about the above problem.
- the slurry pump 4 is not particularly limited as long as it is a pump for transferring a mixture of a solid and a liquid or a viscous liquid, and a known pump may be used.
- Examples of the slurry pump 4 include a canned pump and a centrifugal pump.
- This configuration is preferable because the pump can be operated without any trouble even when the filter is clogged.
- the chlorosilane condensate after passing through the filter described later may be circulated, it is more effective to circulate the chlorosilane condensate before passing through the filter when the filter is clogged. preferable.
- the apparatus used in the separation step 2 can be cleaned. For example, by spraying a part of the chlorosilane condensate in the form of a shower, the solid matter attached to the apparatus used in the separation step 2 can be washed away.
- the chlorosilane condensate A11 it is more preferable to deliver the chlorosilane condensate A11 to the slurry pump 4 after passing through the strainer 3.
- the coarse silicon particles and coarse foreign matters other than silicon contained in the chlorosilane condensate A11 can be removed in advance, and then the chlorosilane condensate A11 can be delivered to the slurry pump 4. Therefore, damage to the slurry pump 4 can be prevented.
- the strainer 3 is a strainer for removing foreign matters larger than silicon fine powder.
- the strainer 3 is not particularly limited as long as it is coarser than the filter used in the fine powder removing step, and may be selected according to the size of foreign matter that is acceptable for the pump to be used.
- the hole diameter of the strainer 3 is preferably 0.1 mm to 0.25 mm, and more preferably 0.1 mm to 0.2 mm.
- chlorosilane condensate A11 after passing through the strainer 3 is expressed as chlorosilane condensate A12
- chlorosilane condensate A11 after passing through the slurry pump 4 is expressed as chlorosilane condensate A13
- the obtained chlorosilane condensate is represented as chlorosilane condensate B14.
- Hydrogen chloride removal step 6> This manufacturing method may have the hydrogen chloride removal process 6 which removes hydrogen chloride by making gas component B17 contact with a chlorosilane liquid, and obtains gas component C18.
- the chlorosilane liquid used in the hydrogen chloride removing step 6 is a liquid containing a chlorosilane compound.
- the chlorosilane compound is not particularly limited, and examples thereof include trichlorosilane, dichlorosilane, and tetrachlorosilane.
- the chlorosilane liquid used in the hydrogen chloride removal step 6 may also contain a part of the chlorosilane condensate A11 obtained in the separation step 2. Further, the chlorosilane liquid used in the hydrogen chloride removing step 6 may include the chlorosilane condensate B14 obtained from the fine powder removing step 5.
- hydrogen chloride contained in the gas component B17 is removed by absorbing the hydrogen chloride contained in the gas component B17 into the chlorosilane liquid to be contacted.
- the hydrogen chloride removing step 6 it is preferable to use a cooled chlorosilane liquid in order to efficiently remove hydrogen chloride from the gas component B17.
- the temperature of the chlorosilane liquid is preferably ⁇ 40 ° C. or lower, and more preferably ⁇ 50 ° C. or lower in order to efficiently remove hydrogen chloride from the gas component B17.
- the amount of chlorosilane compound contained in the chlorosilane liquid brought into contact with the gas component B17 is the total amount of silane contained in the chlorosilane compound in order to efficiently remove hydrogen chloride.
- the amount is preferably 130 mol or more, more preferably 140 mol or more, with respect to 1 mol of hydrogen chloride contained therein.
- the total amount of the chlorosilane compound from the viewpoint of reducing running cost, the total amount of silane contained in the chlorosilane compound is 150 mol or less with respect to 1 mol of hydrogen chloride contained in the gas component B17. It is preferable.
- the method of bringing the gas component B17 into contact with the chlorosilane liquid is not particularly limited, and for example, a known method such as a bubbling method, a packed tower method, or a shower method can be employed. Further, the hydrogen chloride removing step 6 can be performed by a known facility such as a gas-liquid contact tower.
- the gas component after bringing the gas component B17 into contact with the chlorosilane liquid is referred to as a gas component C18.
- the gas component C18 obtained in the hydrogen chloride removing step 6 contains hydrogen gas as a main component.
- the gas component C18 further contains a chlorosilane compound in an amount of about several volume% and also contains hydrogen chloride remaining without being removed.
- the concentration of hydrogen chloride contained in the gas component C18 is preferably 1 ppm or less, and more preferably 0.1 ppm or less.
- the production method preferably includes a distillation step 7 in which the chlorosilane compound 16 obtained by distilling the chlorosilane condensate B14 that has undergone the fine powder removal step 5 is circulated to the silicon deposition step 1. Thereby, the chlorosilane compound 16 obtained after distillation can be reused as a raw material for the silicon deposition step 1.
- the chlorosilane condensate C15 that has undergone the hydrogen chloride removal step 6 may be distilled.
- a purification step may be provided if necessary.
- Hydrogen purification step 8> This manufacturing method may have the hydrogen purification process 8 which obtains the hydrogen gas 19 by making the gas component C18 contact with activated carbon, and removing a chlorosilane compound.
- the hydrogen purification step 8 is performed, for example, by supplying the gas component C18 to an activated carbon layer or an adsorption tower packed with activated carbon. By bringing the gas component C18 into contact with the activated carbon in the adsorption tower, the chlorosilane compound in the gas component C18 is adsorbed and removed by the activated carbon, and as a result, the hydrogen gas 19 can be obtained.
- the activated carbon used in the hydrogen purification step 8 is not particularly limited as long as it is an activated carbon capable of removing the chlorosilane compound from the gas component C18, and a known activated carbon can be used.
- Activated carbon generally tends to adsorb moisture in the air.
- the moisture may react with the chlorosilane compound in the gas component C18 to produce silicon oxide on the activated carbon. Formation of silicon oxide on activated carbon is not preferable because problems such as blockage of pipes or contamination occur. Therefore, the activated carbon used in the hydrogen purification step 8 is preferably subjected to the hydrogen purification step 8 after removing the adsorbed moisture.
- a method for removing moisture at least one of a decompression process and a heat treatment can be used.
- the pressure reduction treatment is performed by maintaining the pressure at a reduced pressure of 1 ⁇ 10 4 Pa or less, more preferably 1 ⁇ 10 3 Pa or less for a certain time as an absolute pressure. It can be carried out.
- the heat treatment can be performed by holding at 80 ° C. to 130 ° C. for a certain period of time in order to sufficiently remove moisture in the activated carbon.
- This heat treatment is preferably performed under a flow of inert gas or under reduced pressure in order to sufficiently remove moisture in the activated carbon.
- the inert gas used include nitrogen, helium and argon.
- the preferred degree of decompression when performed under reduced pressure is the same as the degree of decompression in the decompression treatment.
- the decompression treatment and the heat treatment it is preferable to perform both the decompression treatment and the heat treatment until moisture in the activated carbon is sufficiently removed. Whether moisture has been sufficiently removed can be confirmed by measuring the dew point of the atmosphere.
- the water removal is preferably performed until the dew point of the atmosphere is ⁇ 30 ° C. or lower, more preferably ⁇ 40 ° C. or lower in order to sufficiently remove the water in the activated carbon.
- the adsorption temperature and the adsorption pressure when the chlorosilane compound is adsorbed and removed by bringing the gas component C18 into contact with activated carbon are not particularly limited as long as the chlorosilane compound is sufficiently adsorbed and removed.
- the adsorption temperature is preferably ⁇ 30 ° C. to 50 ° C., more preferably ⁇ 10 ° C. to 40 ° C.
- the adsorption pressure is preferably 1300 kPaG or more, and more preferably 1500 kPaG or more. If the adsorption temperature and adsorption pressure are within the above ranges, the chlorosilane compound can be sufficiently adsorbed and removed from the gas component C18.
- the speed at which the gas component C18 passes through the activated carbon layer or the adsorption tower packed with activated carbon is a speed at which the chlorosilane compound in the gas component C18 can be sufficiently adsorbed and removed. If it is, it will not restrict
- the passing speed of the gas component C18 in the hydrogen purification step 8 is preferably 50Hr ⁇ 1 to 500Hr ⁇ 1 and more preferably 50Hr ⁇ 1 to 150Hr ⁇ 1 as a space velocity (SV).
- the gas component C18 may contain a trace amount of hydrogen chloride, but the trace amount of hydrogen chloride is adsorbed on the activated carbon together with the chlorosilane compound in the hydrogen purification step 8.
- the hydrogen gas 19 obtained in the hydrogen purification step 8 is preferably a hydrogen gas having a purity of 99.99% by volume or more.
- the content of the chlorosilane compound contained in the hydrogen gas 19 obtained in the hydrogen purification step 8 is preferably 3 ppm or less, more preferably 1 ppm or less, based on the total amount of silane.
- the hydrogen gas 19 obtained in the hydrogen purification step 8 is a high-purity hydrogen gas, it can be recycled as it is as a raw material for the silicon deposition step 1. Further, the hydrogen gas 19 can be used as hydrogen used in the reduction reaction from tetrachlorosilane to trichlorosilane or as a hydrogen source in the production of silica using tetrachlorosilane as a raw material (not shown).
- This production method preferably includes a step of circulating the hydrogen gas 19 obtained from the hydrogen purification step 8 to the silicon deposition step 1. According to the above configuration, since hydrogen gas is reused, it is possible to provide a method for producing polycrystalline silicon that has a low environmental load and low production costs.
- An embodiment of the present invention may have the following configuration.
- a method for producing polycrystalline silicon comprising: a separation step; and a fine powder removal step of removing the silicon fine powder by passing the chlorosilane condensate containing the silicon fine powder through a filter.
- the chlorosilane compound obtained by distilling the chlorosilane condensate that has undergone the fine powder removal step is circulated to the silicon precipitation step, according to any one of [1] to [6] A method for producing polycrystalline silicon.
- Example 1 Polycrystalline silicon was manufactured according to the steps shown in FIG.
- silicon deposition step 1 polycrystalline silicon was deposited by the Siemens method.
- a bell jar (reactor) having an internal volume of 10 m 3
- 50 sets of inverted U-shaped polycrystalline silicon core wires were installed on electrodes provided on the bottom panel.
- the temperature in the bell jar was adjusted by the amount of current applied to the polycrystalline silicon core wire so that the temperature of the polycrystalline silicon core wire was maintained at about 1000 ° C.
- polycrystalline silicon was deposited by supplying hydrogen gas A19 and gaseous chlorosilane compound 16 as a raw material gas to a hydrogen ratio of 7 in the bell jar.
- most of the chlorosilane compound 16 was trichlorosilane.
- gas component A10 was obtained from the bell jar in an amount of 24000 Nm 3 / hour.
- the temperature at the time of discharge from the bell jar of the gas component A10 was 230 ° C.
- the gas component A10 was sent to the separation step 2 in a state where the temperature was lowered to 100 ° C. Next, the gas component A10 was cooled to ⁇ 15 ° C. by a chiller (cooler) to obtain a gas component B17 having a composition shown in Table 1 and a chlorosilane condensate A11.
- the compositions other than silicon fine powder in the gas component B17 and the chlorosilane condensate A11 are values obtained by analysis by gas chromatography. In addition, the presence of silicon fine particles having a particle size of 40 ⁇ m or less was confirmed by laser diffraction. As a result, those in the range of 3 to 30 ⁇ m were present as shown in Table 1 (average particle size of 10 ⁇ m).
- TCS represents trichlorosilane
- STC represents tetrachlorosilane (silicon tetrachloride)
- DCS represents dichlorosilane.
- the filter through which the chlorosilane condensate A13 containing the silicon fine powder obtained in the separation step 2 was passed was a polypropylene filter medium (manufactured by Fuji Filter Industry Co., Ltd.) having a pore size of 3 ⁇ m.
- the liquid temperature of the chlorosilane condensate A13 supplied to the filter was ⁇ 15 ° C.
- a canned pump was used as the slurry pump for supplying the chlorosilane condensate A11 to the filter.
- Example 1 (Comparative Example 1) In Example 1, the fine powder removing step 5 was operated in the same manner as in Example 1 except that it was provided not in the flow path of the chlorosilane condensate A13 but in the middle of the flow path of the gas component A10 discharged in the silicon deposition process 1. . In the production of polycrystalline silicon, the temperature of the gas component A10 supplied to the filter was 100 ° C.
- the present invention can be suitably used for a method for producing polycrystalline silicon.
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Abstract
Description
本製造方法は、クロロシラン化合物と水素とを反応させることによって多結晶シリコンを析出させるシリコン析出工程1を有する。シリコン析出工程1では、排ガスとしてガス成分A10が排出される。
本製造方法は、シリコン析出工程1から排出される排ガス(ガス成分A10)を、クロロシラン凝縮液A11とガス成分B17とに分離する分離工程2を有する。
本製造方法は、シリコン微粉を含有するクロロシラン凝縮液A11をフィルターへ通すことによって該シリコン微粉を除去する微粉除去工程5を有する。クロロシラン凝縮液A11をフィルターにかけることで、クロロシラン凝縮液A11中に含有されるシリコン微粉がフィルターで濾過分離される。その結果、シリコン微粉が後段まで配送されることを防ぎ、かつ、フィルターの後に続く工程の分離装置および配管への堆積およびポンプの破損を防止することができる。
本製造方法は、ガス成分B17をクロロシラン液と接触させることによって塩化水素を除去して、ガス成分C18を得る塩化水素除去工程6を有していてもよい。
本製造方法は、微粉除去工程5を経たクロロシラン凝縮液B14を蒸留して得られたクロロシラン化合物16をシリコン析出工程1へと循環させる蒸留工程7を含んでいることが好ましい。これにより、蒸留後に得られたクロロシラン化合物16をシリコン析出工程1の原料として再利用することができる。蒸留工程においては、図1に示すように、塩化水素除去工程6を経たクロロシラン凝縮液C15を蒸留してもよい。
本製造方法は、ガス成分C18を活性炭と接触させてクロロシラン化合物を除去することによって、水素ガス19を得る水素精製工程8を有していてもよい。
本発明の一実施形態は、以下のような構成であってもよい。
図1に示した各工程に従って多結晶シリコンを製造した。シリコン析出工程1では、シーメンス法により多結晶シリコンの析出を行った。内容積10m3のベルジャー(反応器)内には、逆U字型の多結晶シリコン芯線50セットを底盤に設けられた電極に設置した。前記ベルジャー内の温度は、多結晶シリコン芯線の温度が約1000℃で維持されるように、多結晶シリコン芯線への通電量により調整された。前記条件下で、ベルジャー内に、原料ガスとして、水素ガスA19およびガス状にしたクロロシラン化合物16を、水素比7となるように供給することによって、多結晶シリコンの析出を行った。ここで、クロロシラン化合物16の大部分は、トリクロロシランであった。
実施例1において、微粉除去工程5を、クロロシラン凝縮液A13の流路ではなく、シリコン析出工程1で排出されたガス成分A10の流路の途中に設ける以外、該実施例1と同様に操作した。なお、この多結晶シリコンの製造において、フィルターに供給されるガス成分A10の温度は100℃であった。
2 分離工程
3 ストレーナ
4 スラリーポンプ
5 微粉除去工程
6 塩化水素除去工程
7 蒸留工程
8 水素精製工程
10 ガス成分A
11、12、13 クロロシラン凝縮液A
14 クロロシラン凝縮液B
15 クロロシラン凝縮液C
16 クロロシラン化合物
17 ガス成分B
18 ガス成分C
19 水素ガス
Claims (7)
- クロロシラン化合物と水素とを反応させることによって多結晶シリコンを析出させるシリコン析出工程と、
前記シリコン析出工程から排出される排ガスを、シリコン微粉を含有するクロロシラン凝縮液とガス成分とに分離する分離工程と、
前記シリコン微粉を含有するクロロシラン凝縮液をフィルターへ通すことによって該シリコン微粉を除去する微粉除去工程と、を含むことを特徴とする多結晶シリコンの製造方法。 - 前記クロロシラン凝縮液をスラリーポンプによって前記フィルターへ配送することを特徴とする、請求項1に記載の多結晶シリコンの製造方法。
- 前記スラリーポンプから排出されたクロロシラン凝縮液の一部を前記分離工程に循環させる工程を含むことを特徴とする、請求項2に記載の多結晶シリコンの製造方法。
- 前記クロロシラン凝縮液をストレーナに通した後に、前記スラリーポンプへ配送することを特徴とする、請求項2または3に記載の多結晶シリコンの製造方法。
- 前記シリコン微粉を含有するクロロシラン凝縮液において、シリコン微粉の含有量が0.01質量%~0.3質量%であることを特徴とする、請求項1~4のいずれか1項に記載の多結晶シリコンの製造方法。
- 前記フィルターの孔径は、1μm~5μmであることを特徴とする、請求項1~5のいずれか1項に記載の多結晶シリコンの製造方法。
- 前記微粉除去工程を経たクロロシラン凝縮液を蒸留して得られたクロロシラン化合物をシリコン析出工程へと循環させることを特徴とする、請求項1~6のいずれか1項に記載の多結晶シリコンの製造方法。
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