JP2005008430A - Production method for silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon production method wherein polycrystalline silicon is produced by reacting a raw material gas for silicon deposition containing a chlorosilane and hydrogen at 1,300°C or higher and a fine silicon powder is efficiently removed from an exhaust reaction gas containing the fine silicon powder. <P>SOLUTION: The silicon production method comprises a silicon deposition step for depositing silicon by bringing a raw material gas for silicon deposition containing a chlorosilane and hydrogen into contact with a reactor surface heated to 1,300°C or higher and a fine powder removal step for removing a fine silicon powder from an exhaust reaction gas containing the fine silicon powder generated in the silicon deposition step. At least a part of the exhaust reaction gas from which the fine powder has been removed in the fine powder removal step is used as a part of the raw material gas for silicon deposition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing polycrystalline silicon by reaction of chlorosilanes with hydrogen. More specifically, the present invention relates to a method for efficiently producing polycrystalline silicon by simply removing silicon fine powder contained in a reaction exhaust gas generated in a silicon precipitation step.
[0002]
[Prior art]
Conventionally, various methods for producing polycrystalline silicon used as a raw material for semiconductors or photovoltaic power generation batteries are known. For example, the surface of a silicon rod placed inside a bell jar is heated and mixed with trichlorosilane (SiHCl). ₃ Hereinafter referred to as TCS), monosilane (SiH) ₄ For example, a Siemens method in which polycrystalline silicon is deposited by contacting a silicon deposition source gas containing a chlorosilane such as hydrogen) and a reducing gas such as hydrogen.
[0003]
The Siemens method is characterized in that high-purity silicon can be obtained, and is the most common method. However, since the deposition is batch-type, the installation of a silicon rod as a seed, current heating, deposition There is a problem that extremely complicated procedures such as cooling, taking out, and cleaning of the bell jar must be performed.
[0004]
Further, in the conventional Siemens method or the like, in order to stably deposit silicon, it is usually performed at a temperature of 900 to 1250 ° C., substantially 900 to 1150 ° C. However, in such a temperature range, tetrachlorosilane (SiCl) which is chemically extremely stable with the silicon precipitation reaction. ₄ Hereinafter referred to as STC) as a by-product, the efficiency of the silicon precipitation reaction is significantly reduced.
[0005]
For this reason, in equipment that performs silicon deposition reaction on an industrial scale, part or all of the STC produced as a by-product during the silicon deposition reaction must be discharged to a nearby or remote processing facility. It was. On the other hand, a closed system has been proposed as a self-supporting process that reduces the amount of STC by-products and does not discharge STC (see, for example, Patent Document 1 and Patent Document 2). However, any of these methods can be realized only on an ideal system, and it is difficult to secure an industrially effective production amount.
[0006]
In order to keep the amount of STC produced as a by-product low and to secure an industrially advantageous production amount, it is extremely advantageous to cause silicon to precipitate by reacting TCS and hydrogen at a temperature of 1300 ° C. or higher. However, under such high temperature reaction conditions, it has been found that silicon fine powder is generated in a high temperature gas boundary film formed in the vicinity of the deposition surface.
[0007]
In other words, since silicon fine powder is contained in the reaction exhaust gas of the silicon deposition reaction carried out at a temperature of 1300 ° C. or higher, a process for treating the reaction exhaust gas and recirculating a part thereof to the silicon deposition reaction is provided. In such an exhaust gas treatment system, silicon fine powder adheres to piping, mechanical devices, etc., which may cause clogging of the piping and occurrence of defects in the mechanical devices, resulting in problems in operation.
[0008]
[Patent Document 1]
JP 52-133302 A
[Patent Document 2]
JP-A-10-287413
[0009]
[Problems to be solved by the invention]
An object of the present invention is to efficiently produce silicon fine powder from a reaction exhaust gas containing silicon fine powder in a method for producing polycrystalline silicon by reacting a silicon deposition source gas containing chlorosilanes and hydrogen at a temperature of 1300 ° C. or higher. Another object of the present invention is to provide a method for manufacturing silicon that can be removed.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors made silicon react by reacting chlorosilanes with hydrogen at a temperature of 1300 ° C. or higher, thereby suppressing the amount of by-produced STC to be low. In addition, the silicon fine powder contained in the reaction exhaust gas is efficiently removed, and a part of the reaction exhaust gas from which the silicon fine powder is removed is circulated as a raw material gas, so that the production efficiency of polycrystalline silicon can be greatly improved. A manufacturing method of silicon was established.
[0011]
That is, the method for producing silicon according to the present invention is as follows.
A silicon deposition step for depositing silicon by bringing a silicon deposition source gas containing chlorosilanes and hydrogen into contact with the reaction vessel surface heated to a temperature of 1300 ° C. or higher; and
Including a fine powder removing step of removing the silicon fine powder from a reaction exhaust gas containing the silicon fine powder generated in the silicon deposition step,
It is characterized in that at least a part of the reaction exhaust gas from which the fine powder has been removed in the fine powder removing step is used as a part of the silicon deposition raw material gas.
[0012]
In the method for producing silicon according to the present invention, in the fine powder removing step, it is preferable to remove the silicon fine powder from the reaction exhaust gas by passing the reaction exhaust gas containing the silicon fine powder through a filter provided in the exhaust gas line. .
[0013]
However, since the silicon fine powder captured by the filter is firmly attached to the filter, it is difficult to remove the silicon fine powder from the filter by backwashing with a normal gas. Further, the method of disassembling the filter and removing the silicon fine powder by alkali cleaning or the like not only causes the filter to be easily corroded or deteriorated, but also has a risk of ignition by the silicon fine powder.
[0014]
In order to solve such a problem, the present inventors have found that the silicon fine powder exhibits good dispersibility with respect to liquid chlorosilanes. Then, by washing the silicon fine powder fixed to the filter with a cleaning liquid composed of chlorosilanes, the silicon fine powder can be removed from the filter without disassembling the filter, and the silicon fine powder is not contaminated with the apparatus and the piping. It has been found that a part of the reaction exhaust gas from which the gas is removed can be reused as a raw material gas.
[0015]
That is, it is preferable that the method for producing silicon according to the present invention further includes a step of washing the filter capturing the silicon fine powder with a washing liquid composed of chlorosilanes.
[0016]
In addition, a plurality of filters are provided in parallel in the exhaust gas line, the filter with increased filtration pressure is disconnected from the exhaust gas line, the process of cleaning with the cleaning liquid consisting of chlorosilanes without disassembling the filter, and the filter after cleaning again It is desirable to further include a step of connecting to the exhaust gas line.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the silicon manufacturing method according to the present invention will be specifically described.
[0018]
The apparatus for producing silicon by the silicon production method of the present invention is not particularly limited, and for example, the apparatus shown in FIG. That is,
(1) A cylindrical reaction vessel 1 having an opening 2 at the lower end,
(2) A heating device 3 capable of heating the inner wall from the lower end of the cylindrical reaction vessel 1 to an arbitrary height to a temperature equal to or higher than the melting point of silicon,
(3) Supplying a raw material gas A containing chlorosilanes and hydrogen provided in the cylindrical reaction vessel 1 so as to open downward in a space 5 surrounded by an inner wall heated to 1300 ° C. or higher. Raw material gas supply pipe 4,
(4) a seal gas supply pipe 6 for supplying hydrogen gas as the seal gas B into a gap formed by the inner wall of the cylindrical reaction vessel 1 and the outer wall of the source gas supply pipe 4;
(5) The extraction pipe 12 from which the reaction exhaust gas D is discharged, and
(6) A silicon production apparatus including the recovery unit 9 that melts and drops the deposited silicon is included.
[0019]
Since the cylindrical reaction vessel 1 is heated to a temperature higher than the melting point of silicon and the inside thereof is in contact with chlorosilanes and silicon melt, it is possible to select a material that can sufficiently withstand such temperature conditions and contact objects. preferable. Examples of such a material include carbon materials such as graphite, and ceramic materials such as silicon carbide, silicon nitride, boron nitride, and aluminum nitride, with carbon materials being preferred. In addition, a carbon material whose surface is coated with silicon carbide, pyrolytic carbon, boron nitride or the like is particularly preferable in order to achieve improved durability of the reaction vessel and improved purity of the silicon product.
[0020]
The heating device 3 is not particularly limited as long as the inner wall of the cylindrical reaction vessel 1 can be heated to 1300 ° C. or higher. However, in view of energy efficiency, the heating device 3 is preferably heated by a high frequency coil.
[0021]
The raw material gas supply pipe 4 is for directly supplying a raw material gas containing chlorosilanes and hydrogen to a space 5 surrounded by the inner wall of the cylindrical reaction vessel 1. In addition to the same material as the cylindrical reaction vessel 1, quartz glass, iron and stainless steel can be used.
[0022]
The seal gas supply pipe 6 supplies the seal gas B to a gap formed by the inner wall of the cylindrical reaction vessel 1 and the outer wall of the source gas supply pipe 4 existing above the opening position of the source gas supply pipe 4. Provided for. Since the gap is a low temperature region where silicon can be precipitated but cannot be melted, filling the gap with a seal gas effectively prevents solid silicon from being precipitated in the low temperature region. Can do. As the material of the seal gas supply pipe 6, the same material as that of the raw material gas supply pipe 4 can be used.
[0023]
In the above apparatus, in order to efficiently collect the reaction exhaust gas discharged from the cylindrical reaction container 1, the tubular reaction container 1 and the recovery unit 9 are separated by a sealed container 7 provided with an extraction pipe 12 for the reaction exhaust gas D. It is preferable to cover.
[0024]
At that time, a seal gas supply pipe 11 is provided in a gap formed by the outer wall of the cylindrical reaction vessel 1 and the inner wall of the sealed vessel 7 to supply a seal gas C such as nitrogen, hydrogen, argon or the like. Is preferred.
[0025]
The method for producing silicon of the present invention includes a silicon precipitation step and a fine powder removal step, and uses at least a part of the reaction exhaust gas from which the fine powder has been removed as a part of the raw material gas for silicon precipitation.
[0026]
The silicon deposition step in the present invention is a cylindrical reaction in which a silicon deposition source gas containing chlorosilanes and hydrogen is heated to a temperature of 1300 ° C. or higher, preferably 1300 to 1700 ° C., more preferably 1350 to 1700 ° C. This is a step of bringing silicon into contact with the surface of the container 1.
[0027]
By setting the reaction temperature to 1300 ° C. or higher, the amount of STC by-produced in the silicon deposition step can be effectively reduced.
[0028]
Adjusting the molar ratio of chlorosilanes and hydrogen (hydrogen / chlorosilanes) to be used for the reaction to 10 or more, preferably 15 to 30 makes the amount of STC by-produced in the silicon deposition step more effective. It is preferable because it can be reduced. The pressure of the reaction is not particularly limited, but is generally normal pressure to 3 MPaG, preferably normal pressure to 1 MPaG.
[0029]
Examples of the chlorosilanes used as the silicon deposition source gas in the present invention include various known chlorosilanes. Specific examples include monosilane, dichlorosilane (hereinafter also referred to as DCS), TCS, and STC. Among these, monosilane or TCS is preferable because industrially high-purity products can be obtained in large quantities.
[0030]
The silicon deposited on the inner wall of the cylindrical reaction vessel 1 as described above becomes a silicon melt at the inner wall of the cylindrical reaction vessel when the cylindrical reaction vessel is heated to a temperature higher than the melting point of silicon, and flows down the inner wall. Since the liquid drops naturally as droplets 14 from the opening 2, the inside of the cylindrical reaction vessel can always be kept in an initial state without performing a periodic temperature raising operation.
[0031]
When the cylindrical reaction vessel 1 is heated to a temperature of 1300 ° C. or higher and lower than the melting point of silicon, when the silicon deposition amount reaches a certain level, the heating output is increased or the gas supply amount is reduced, Precipitation can be performed continuously by raising the cylindrical container to a temperature equal to or higher than the melting point of silicon, melting part or all of the precipitate, and dropping and collecting the precipitate.
[0032]
The silicon melt droplets or partially melted solid silicon falling from the cylindrical reaction vessel 1 are dropped into the lower silicon recovery unit 9 to be solidified and recovered.
[0033]
The silicon deposits that have fallen on the silicon recovery unit 9 may be taken out after the precipitation reaction is stopped, but it is preferable to take out the precipitate while continuing the precipitation reaction. As a specific method for carrying out the recovery while continuing the reaction, the temperature of the cylindrical reaction vessel 1 is once adjusted below the melting point of silicon to prevent the silicon melt from falling, and the precipitation reaction vessel and the recovery vessel The method of closing the valve installed between the two and opening the collection unit 9 or the crushing device installed in the collection unit 9 gives mechanical force to the silicon precipitate solidified in the collection unit 9 and pulverizes to some extent, For example, a method of intermittently removing silicon E from a silicon outlet 13 located further below the recovery unit 9 may be used.
[0034]
The fine powder removing step in the present invention is a step of removing silicon fine powder from the reaction exhaust gas containing the silicon fine powder generated in the silicon deposition step.
[0035]
Examples of a method for removing silicon fine powder contained in the reaction exhaust gas include a method of removing the silicon fine powder from the reaction exhaust gas by passing the reaction exhaust gas containing the silicon fine powder through a filter provided in the exhaust gas line.
[0036]
Although the equipment of the fine powder removal process in the present invention is not particularly limited, for example, the equipment shown in FIG. That is, the reaction exhaust gas D generated in the silicon deposition step is cooled as necessary and distributed to the gas filter device 16 so that the silicon fine powder in the reaction exhaust gas is captured by the filter 17 and the silicon fine powder is removed. The exhaust gas is supplied to a reaction exhaust gas purification facility.
[0037]
Examples of the filter 17 include a metal filter, a ceramic filter, a glass filter, a plastic filter, and a carbon filter. The opening of the filter 17 is 0.1 to 100 μm, preferably 1 to 30 μm in consideration of the particle size and removal rate of silicon fine powder contained in the reaction exhaust gas.
[0038]
Further, considering the stabilization of the operating conditions in the silicon deposition process and the operating efficiency of the entire silicon production facility, it is preferable to reduce the frequency of cleaning the filter. Therefore, the filtration area of the filter 17 is a reaction exhaust gas of 1 Nm that passes through the filter 17. ³ / 10cm per H ² Above, preferably 20cm ² Or more, more preferably 30 cm ² The above is desirable.
[0039]
As a method for removing fine powder captured by the filter 17 from the filter, it is common to perform backwashing with gas. However, since silicon fine powder adheres firmly to the filter 17, silicon is not suitable for backwashing with gas. It is difficult to remove fine powder from the filter 17.
[0040]
On the other hand, the silicon fine powder can be easily removed from the filter 17 by washing the filter 17 with a liquid chlorosilane that has been found to be a good dispersion medium for the silicon fine powder. Further, even if the chlorosilanes remaining in the gas filter device 16 are evaporated and mixed into the exhaust gas treatment system, since the same chlorosilanes as the raw material gas are used, the recirculated gas and devices are not contaminated. .
[0041]
That is, it is desirable that the method for producing silicon in the present invention further includes a step of cleaning the filter 17 capturing silicon fine powder with a chlorosilane cleaning solution F made of liquid chlorosilanes.
[0042]
As a method of cleaning the filter 17 with the chlorosilane cleaning liquid F, supplying the chlorosilane cleaning liquid F from the secondary side of the filter 17 (that is, the gas downstream side) to the filter 17 that has captured silicon fine powder further enhances the cleaning effect. Therefore, it is preferable. Further, by supplying from the secondary side of the filter, a backwash effect can be obtained at the same time.
[0043]
The temperature of the chlorosilane cleaning liquid F may be appropriately adjusted according to operating conditions, the composition of chlorosilanes, and the like so that the cleaning liquid is maintained as a liquid.
[0044]
The supply amount of the chlorosilane cleaning liquid F is 1 cm for the filtration area of the filter 17 in order to perform sufficient cleaning. ² In contrast, usually 10cm ³ Above, preferably 30cm ³ That's it. It is desirable from the viewpoint of cleaning efficiency that the amount of the chlorosilane cleaning solution F as described above is usually supplied for 10 to 600 seconds, preferably 30 to 300 seconds.
[0045]
After cleaning the filter 17 with the chlorosilane cleaning solution F, the filter 17 may be dried with a filter drying gas, for example, nitrogen gas G. Further, in order to sufficiently regenerate the filter 17, it is preferable to repeat washing with chlorosilanes and drying with a drying gas at least twice.
[0046]
In the fine powder removing step, it is preferable to provide a plurality of gas filter devices in parallel in the exhaust gas line so that the exhaust gas line can be switched. By doing so, when the filtration pressure of one gas filter device increases, the exhaust gas line is switched to the other gas filter device, the gas filter device with the increased filtration pressure is separated from the exhaust gas line and cooled, and the gas filter device is Washing with a cleaning liquid composed of chlorosilanes without disassembling, the cleaned filter device can be connected to the exhaust gas line again. Therefore, it is not necessary to stop the silicon precipitation reaction when cleaning the filter, and silicon can be produced efficiently.
[0047]
Examples of the chlorosilanes constituting the chlorosilane cleaning liquid F include those similar to the chlorosilanes used in the raw material gas, but those having a low boiling point need to be cooled, and therefore may be selected from DCS, TCS, and STC. preferable. You may use these individually by 1 type or in mixture of 2 or more types.
[0048]
The cleaning liquid containing the fine silicon powder after the filter cleaning is continuously or intermittently withdrawn from the cleaning liquid discharge port 18 installed at the lower part of the filter device 16 and collected in the liquid gas separation container 19, and silicon is used as necessary. After removing the fine powder, the purified chlorosilane solution can be reused as the washed solution by distillation purification of the washed solution.
[0049]
The reaction exhaust gas from which the silicon fine powder has been removed as described above contains hydrogen chloride and STC as by-products in addition to unreacted chlorosilanes and hydrogen. By removing a part of the chlorosilanes and bringing them into contact with the raw material silicon at 280 to 400 ° C., hydrogen chloride and the raw material silicon selectively react to generate TCS. Thus obtained TCS, unreacted chlorosilanes and hydrogen can be separated and used as part of the silicon deposition source gas.
[0050]
As said raw material silicon, the well-known metallurgical grade silicon generally used as a raw material for manufacture of silicon can be used.
[0051]
As the reactor used for the TCS generation reaction, an apparatus capable of contacting the raw material silicon and the reaction exhaust gas can be used. For example, a fluidized bed reactor that reacts gas and powder while fluidizing the raw silicon powder with gas is suitable for industrial implementation.
[0052]
In the TCS generation step, the temperature at which the reaction between silicon and hydrogen chloride starts is about 250 ° C., so the reaction temperature is preferably 250 ° C. or higher, and in order to improve the yield of TCS, it is 400 ° C. or lower. It is preferably performed at temperature. Therefore, in order to maintain the reaction stably industrially, the reaction temperature is preferably adjusted at 280 to 350 ° C.
[0053]
When the gas after reaction obtained in the TCS production step is circulated to the silicon deposition step, it is preferable to separate hydrogen and a part of chlorosilanes in order to increase purity. The method for separating hydrogen and chlorosilanes is not particularly limited, but can be easily achieved industrially by cooling the gas.
[0054]
As a method for cooling the gas, the gas may be simply passed through a cooled heat exchanger, or the gas may be cooled by a condensed and cooled condensate. These methods can be employed alone or in combination.
[0055]
The cooling temperature is not particularly limited as long as a part of the chlorosilanes is condensed. However, in order to achieve high purity of hydrogen, it is usually 10 ° C. or lower, more preferably −10 ° C. or lower, most preferably Preferably it is -30 degrees C or less. Thus, by removing a part of the chlorosilanes, most of impurities such as heavy metals, phosphorus, boron, etc. contained in the raw material silicon can be removed from hydrogen, and the deposited silicon can be highly purified. it can.
[0056]
A gas mainly composed of hydrogen from which a part of chlorosilanes has been separated is sufficiently high in purity as a raw material gas, but may contain a boron compound depending on the separation conditions. Therefore, it is preferable to remove the boron compound from the gas according to the required purity of the silicon product.
[0057]
The method for removing the boron compound is not particularly limited, but —NR ₂ (R is an alkyl group having 1 to 10 carbon atoms), -SO ₃ A method of bringing a substance having a functional group such as H, —COOH, and —OH into contact with the gas is preferable. Most simply, ion exchange resins having these functional groups can be used.
[0058]
On the other hand, since the gas mainly containing chlorosilanes separated as described above contains impurities such as heavy metal compounds, it is preferable to increase the purity of the chlorosilanes by purifying the gas by distillation.
[0059]
The residual components after separation of chlorosilanes by the distillation purification include heavy metal compounds and STC. The STC in this residual component may be reduced with hydrogen and converted to TCS. The remaining components obtained by separating and recovering most of the STC in this way are generally neutralized and discarded.
[0060]
When it is necessary to further remove the boron compound from the chlorosilanes recovered as described above, the solid or liquid compound having the functional group described above is brought into contact with the chlorosilanes and then distilled as necessary. It can be removed by purification.
[0061]
By separating and circulating hydrogen and chlorosilanes from the reaction exhaust gas as described above, it is possible to effectively use at least part of the reaction exhaust gas from which silicon fine powder has been removed as part of the silicon deposition raw material gas. it can.
[0062]
【The invention's effect】
According to the silicon production method of the present invention, by reacting chlorosilanes and hydrogen at a temperature of 1300 ° C. or higher to precipitate silicon, the amount of by-produced STC is kept low and contained in the reaction exhaust gas. Polycrystalline silicon can be produced by efficiently removing silicon fine powder and circulating a part of the reaction exhaust gas from which the silicon fine powder has been removed as a raw material gas.
[0063]
In addition, since polycrystalline silicon can be produced without causing piping clogging due to adhesion of silicon fine powder or failure of mechanical devices, production efficiency of polycrystalline silicon can be greatly improved.
[0064]
Furthermore, according to the silicon production method of the present invention, the silicon fine powder can be removed from the filter without disassembling the filter that has captured the silicon fine powder, thereby reducing the equipment cost and work cost and improving the safety. can do.
[0065]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by these Examples.
[0066]
[Example 1]
The silicon precipitation reaction was performed using a silicon deposition apparatus similar to that shown in FIG. The cylindrical reaction vessel 1 is made of isotropic carbon having a wall thickness of 15 mm, and has a reaction zone I having an inner diameter of 50 mm and a length of 300 mm, as shown in FIG. A high frequency coil that generates a high frequency of 8 kHz was installed as the heating device 3 so as to surround the cylindrical reaction vessel 1. The source gas supply pipe 4 is made of stainless steel and has a source gas outlet 15 having an inner diameter of 4 mm. The sealed container 7 was made of stainless steel having an inner diameter of 1000 mm.
[0067]
The fine powder contained in the reaction exhaust gas was removed using a fine powder removing facility as shown in FIG. The gas filter device 16 is a carbon steel gas filter device having an internal volume of 20 L. As a filter 17, about 600cm ² A sintered stainless steel filter having a filtration area of 10 μm and an opening of 10 μm was used.
[0068]
While heating the inner surface of the cylindrical reaction vessel 1 to 1300 to 1400 ° C. with a high-frequency coil, hydrogen and trichlorosilane were supplied from the source gas supply pipe 4 as a silicon deposition source gas A to 28 Nm, respectively. ³ / H and 9 kg / H were supplied to perform silicon precipitation reaction. The reaction pressure was 50 kPaG. The reaction was continued while the inner surface of the cylindrical reaction vessel 1 was raised to 1450 ° C. or higher once per hour for about 5 minutes, and the precipitate was intermittently melted and dropped. The polycrystalline silicon recovered by the recovery unit 9 was maintained at a high purity.
[0069]
The reaction exhaust gas generated in the precipitation reaction was cooled to 300 ° C. or lower by a water-cooled heat exchanger and then passed through the gas filter device 16, and silicon fine powder contained in the reaction exhaust gas was captured by the filter 17.
[0070]
24 hours after the start of the precipitation reaction, the filtration pressure of the gas filter device 16 increased by 50 kPa from the filtration pressure before the start of the reaction, so the gas flow was switched to a spare gas filter device having similar performance.
[0071]
After cooling the gas filter apparatus with increased filtration pressure to about room temperature, a chlorosilane cleaning solution F of 30 ° C. composed of about 90 wt% STC and about 10 wt% TCS is supplied from the secondary side of the filter 17 at a feed rate of 35 L. For 1 minute. At this time, the supplied chlorosilane cleaning liquid was continuously discharged from the cleaning liquid discharge port 18 at the lower part of the gas filter device 16 and collected in the liquid gas separation container 19.
[0072]
Subsequently, after supplying the nitrogen gas G instead of the chlorosilane cleaning solution F to dry the filter 17, the filtration pressure of the filter device 16 was measured, and it was almost restored to the initial state.
[0073]
Since the chlorosilane cleaning liquid recovered in the liquid gas separation container 19 contained a brown suspension, the chlorosilane liquid of the fraction was colorless and transparent when purified by distillation using a chlorosilane cleaning liquid processing facility.
[0074]
The reaction exhaust gas after the fine powder was removed was purified by a reaction exhaust gas purification facility and used as part of the raw material gas. In addition, adhesion of silicon fine powder was not seen in piping, an apparatus, etc. in the reaction exhaust gas processing system after the fine powder removing step.
[0075]
[Comparative Example 1]
After performing the silicon precipitation reaction using the same equipment as in Example 1, the cleaning of the filter 17 with an increased filtration pressure was changed from cleaning with the chlorosilane cleaning solution F to back cleaning with nitrogen gas G. As backwashing with nitrogen gas G, a pressure increase of about 1 MPaG and a rapid depressurization operation were performed 10 times with nitrogen gas, but the recovery of the filtration pressure was about 20%.
[Brief description of the drawings]
FIG. 1 is a schematic view of a silicon manufacturing apparatus used in the present invention.
FIG. 2 is a schematic view of a cylindrical reactor in the silicon production apparatus used in the present invention.
FIG. 3 is a schematic view of a fine powder removing facility according to the present invention.
[Explanation of symbols]
1 cylindrical reaction vessel
2 opening
3 Heating device
4 Raw material gas supply pipe
5 space
7 Sealed container
8 Silicon
9 Collection Department
12 Extraction piping
16 Gas filter device
17 Filter
19 Liquid gas separation container
A Source gas
D Reaction exhaust gas
F Chlorosilane cleaning solution
G Nitrogen gas

Claims (5)

A silicon deposition step of depositing silicon by bringing a silicon deposition source gas containing chlorosilanes and hydrogen into contact with the reaction vessel surface heated to a temperature of 1300 ° C. or higher, and a reaction including silicon fine powder generated in the silicon deposition step Including a fine powder removal step of removing the silicon fine powder from the exhaust gas,
A method for producing silicon, wherein at least part of the reaction exhaust gas from which fine powder has been removed in the fine powder removing step is used as part of the raw material gas for silicon deposition. The method for producing silicon according to claim 1, wherein in the fine powder removing step, the silicon fine powder is removed from the reaction exhaust gas by passing the reaction exhaust gas containing the silicon fine powder through a filter provided in the exhaust gas line. The method for producing silicon according to claim 2, further comprising a step of cleaning the filter capturing the silicon fine powder with a cleaning liquid composed of chlorosilanes. A plurality of filters are installed in parallel in the exhaust gas line, the filter with increased filtration pressure is disconnected from the exhaust gas line, and the filter is cleaned with a cleaning solution consisting of chlorosilanes without disassembling the filter. The method for producing silicon according to claim 2, further comprising a step of connecting to the substrate. The method for producing silicon according to claim 3 or 4, wherein the chlorosilane constituting the cleaning liquid is at least one selected from the group consisting of tetrachlorosilane, trichlorosilane, and dichlorosilane.

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