JPH06100312A - Device for extracting granular polycrystalline silicon - Google Patents

Abstract

PURPOSE:To provide a device for drawing out granular polycrystalline silicon produced by fluidized bed method, having no complicated structure, not contaminating the extracted granular polycrystalline silicon. CONSTITUTION:A device for extracting granular polycrystalline silicon has a piping 11 for drawing out granular polycrystalline silicon produced from a silane as a raw material by a fluidized bed method extending downward from the bottom of a reactor 7, then sending in the horizontal direction and having a riser 16 on the extended part of the bending part. An inner wall of the piping for extracting the granular polycrystalline silicon in the extracting device comprises a material not contaminating polycrystal line silicon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for extracting high-purity granular polycrystalline silicon produced by a fluidized bed method from a reactor without impairing its purity.

[0002]

2. Description of the Related Art Siemens method and Komatsu method are typical methods for producing polycrystalline silicon. In these methods, a silicon rod placed in a bell jar furnace is electrically heated, and gaseous chlorosilane (Siemens method) or monosilane (Komatsu method) is circulated through the silicon rod to generate silicon by thermal decomposition and reduction of the silanes. Then, polycrystalline silicon is deposited on the silicon rod. The silicon rod is grown to a predetermined size and then collected to obtain a product. Currently, most of polycrystalline silicon is manufactured by these methods, and it is relatively easy to maintain high purity of products. However, since these methods are basically batch operations, the production efficiency is low, and in mass production, it is necessary to increase the number of bell jars to deal with, the equipment cost is high, and the energy supplied is large. It has drawbacks such as that part of it becomes heat and is dissipated.

Under such circumstances, the recent development is the production of polycrystalline silicon by the fluidized bed method. In this method, polycrystalline silicon particles are used as seed crystals and silicon is deposited on the surface of the polycrystalline silicon particles in a cylindrical reactor using an apparatus as shown in FIG. In this method, normally, the reactor 1 is heated by the external heater 2, the seed silicon particles 3 are supplied from the upper part of the reactor, and the source gas containing silanes of the source is supplied from the lower source gas supply line 4. It The silicon particles in the reactor are fluidized by the raw material gas rising in the reactor to form the fluidized bed 5. The raw material gas is heated by the heater and the silicon particles while passing through the reactor, is thermally decomposed to generate silicon, and is deposited on the surface of the fluidized silicon particles to grow polycrystalline silicon. The production of granular polycrystalline silicon by the fluidized bed method is not only suitable for industrialization because it can be operated continuously and is easy to scale up,
Since a heat-insulated reactor can be used, heat dissipation is 1/10 or less that of the Siemens method, which is energy-saving, and since the surface area of granular polycrystalline silicon is significantly larger than that of rods, productivity is also high. This is an extremely advantageous method. In addition, the granular polycrystalline silicon produced by this method has less labor for transportation, crushing, packing, etc. compared to the rod-shaped one produced by the Siemens method, and further, the particles have fluidity. Therefore, it is easy to supply to the crucible, which is performed at the time of manufacturing single crystal silicon, the packing density in the crucible can be increased, and continuous supply is easy. Have advantages.

[0004]

As described above, in the production of granular polycrystalline silicon by the fluidized bed method, the granular polycrystalline silicon is continuously operated and therefore stably operated, and the quality of the granular polycrystalline silicon of the product is improved. In order to make the product uniform, it is important to control and control the amount of product granular polycrystalline silicon extracted from the reactor. In general, as a device for extracting solid particles, in a normal pipe, for the purpose of adjusting the amount of extraction, valves such as butterfly valves, gate valves, rotary valves, screw feeders, table feeders, belt feeders, vibration feeders, etc. There are devices equipped with feeders that use mechanical principles. However, when the above-mentioned device is adopted as a device for extracting granular polycrystalline silicon, any of the above devices includes a sliding portion, and its shape is complicated, and contact with a product inside the device for extracting, It is liable to wear, and therefore impurities in the materials such as pipes and valves that make up the extraction device easily mix into the granular polycrystalline silicon of the product, especially heavy metals such as chromium, iron and nickel, or boron, phosphorus and carbon. And the like are easily mixed. Granular polycrystalline silicon requires high-purity products because it is used as a raw material for semiconductor materials.
It is difficult to employ the above-mentioned device as a device for extracting granular polycrystalline silicon, since the impurity concentration in the product is usually in the range of 1/100 billion.
There is also a method to prevent contamination by lining the inside of the equipment with a material that is less contaminated with granular polycrystalline silicon, but it is difficult to process with these materials due to the complicated structure of these equipment. It is something.

In order to solve such a problem, in US Pat. No. 4,806,317, silicon, silicon carbide, silicon nitride, etc., which are considered to contain less impurities in the granular polycrystalline silicon of the product, are used. A granular polycrystal, which is used as a material constituting the device, has a meandering flow path, and performs extraction control by utilizing the repose angle of granular polycrystalline silicon and the collapse of the repose angle due to gas injection. A silicon extraction device has been proposed. Since this device is characterized by the flow path structure inside the device, it requires advanced processing when manufacturing the device, and in reality, the device material due to impurities from tools, jigs, etc., during processing and assembly. However, it is difficult to say that it is sufficient to prevent contamination of impurities when the granular polycrystalline silicon of the product is extracted.

The present inventors do not need to have a complicated structure as an apparatus for extracting granular polycrystalline silicon, can extract it by a simple method, and can produce high-purity granules extracted from a reactor. In order to find an extraction device that does not contaminate the polycrystalline silicon, the inventors have made diligent studies.

[0007]

Means for Solving the Problems In order to solve the above problems, the present inventors have found that a pipe for extracting granular polycrystalline silicon particles has a specific structure, and the material of the inner wall of the pipe. The present invention has been found to be effective in selecting

That is, according to the present invention, a pipe for withdrawing granular polycrystalline silicon produced by the fluidized bed method from silane as a raw material extends downward from the bottom of the reactor and then bends. Granular polycrystalline silicon extraction device characterized by having a rising portion on the extension of, and the inner wall of the pipe is a non-contaminating material for polycrystalline silicon, preferably silicon carbide treated with silicon, silicon, The present invention relates to a granular polycrystalline silicon extracting device characterized by being made of quartz, Teflon, or a combination thereof. Hereinafter, the present invention will be described in detail.

The granular polycrystalline silicon extracting device of the first invention is a pipe for extracting granular polycrystalline silicon (hereinafter simply referred to as a product) of a product manufactured by a fluidized bed method from a reactor (hereinafter simply referred to as a pipe). ) Has a structure that extends downward from the bottom of the reactor, preferably vertically downward and then horizontally bent. The bending direction of the pipe does not have to be a horizontal direction in a strict sense, and may be slightly deflected upward or downward with respect to the true horizontal direction.
The bend in the pipe makes it easier for product particles to stop in the pipe when the product is withdrawn from the reactor. The bending angle of the bent portion is not particularly limited, but it is preferable that the product extracted into the pipe by its own weight without being pressurized from the reactor is naturally angled so that it is a gentle J-shape. It is usually preferable to make it into a shape.

The extraction device of the present invention has a rising portion on the extension of the bent portion of the pipe. The rising portion is upward with respect to the extension direction of the bent portion,
It can be provided by drawing a right angle or a gentle arc. When the pipe has only a bent portion, when stopping the product being withdrawn, it becomes difficult to stop the withdrawal due to the pressure fluctuations in the reactor and the pipe, and it is necessary to control and manage the withdrawal amount of the product. It will be difficult.

A gas supply line is installed in these pipes in order to replace the inside of the pipes with an inert gas or the like, and to supply gas into the pipes when the product is extracted to enhance the fluidity of the product. Preferably. Finally the piping connects with the product reservoir for storing the product. In the product tank,
It is preferable to have a device for pressure adjustment in order to adjust the withdrawal and stoppage of the product due to the pressure difference with the reactor. As the gas supplied into the pipe or the gas for adjusting the pressure of the product storage tank, an inert gas such as nitrogen or argon, or hydrogen can be used.

When a product is extracted using the extraction device of the present invention, a gas is supplied from a gas supply line to a pipe, a product storage tank is depressurized to a pressure lower than the reactor internal pressure, or a combination of these methods is used. Thus, the flow of product particles in the pipe is promoted to extract the product. Products can be withdrawn intermittently or continuously. When stopping the withdrawal of the product, a method of stopping the gas supply to the pipe, a method of increasing the pressure of the pipe or the product storage tank to the same as or higher than the pressure in the reactor, or a combination of these methods Depending on the method, the withdrawal of the product is stopped. By these methods, it is possible to prevent the mixed gas containing the silane gas from flowing out from the inside of the reactor to the pipe.

A second aspect of the present invention is that the inner wall of the pipe according to the first aspect is made of a non-polluting material with respect to polycrystalline silicon. As the non-polluting material, various materials can be used as long as they are non-polluting to polycrystalline silicon, and silicon carbide is treated with silicon (hereinafter referred to as SiC.
/ Si), silicon, quartz or Teflon, or a combination thereof.
Examples of SiC / Si include those in which silicon carbide is coated with silicon by a chemical vapor deposition method, those in which silicon carbide is impregnated with silicon, and the like. The preferred materials for the inner wall of the pipe are those commonly used as reactor materials, such as Teflon frequently used as a pipe material in chemical factories and SiC / Si generally used in semiconductor factories. Is. As a method of configuring the inner wall of the pipe with a non-contaminating material for polycrystalline silicon, a method of coating the inside of the pipe such as steel with a non-contaminating material, or a tube made of a non-contaminating material in the pipe A general method such as mounting can be adopted. By configuring the material inside the pipe with a non-polluting material for polycrystalline silicon, contact with the pipe during product extraction,
It is possible to prevent impurities from being mixed into the product due to wear.

FIG. 2 shows an example of the product extracting device of the present invention. Reference numeral 7 is a reactor having an inner surface made of quartz, and 8 is a product buffer / product cooling container having an inner surface made of quartz. Cooling water is supplied from a cooling water inlet 9 and discharged from a cooling water outlet 10 to cool 8 To do. When the pipes 11 and 16 are Teflon-lined steel pipes whose inner walls are coated with resin, the coolers are provided so that the resin inside the pipes will not melt due to high-temperature product particles. When the material of the inner wall of the extraction pipe is made of a material having high heat resistance such as SiC / Si, the material is not affected by the sensible heat of the product particles, so that cooling is not necessary. Reference numeral 8 is connected to a J-shaped bent pipe 11, and an extension of the pipe 11 is connected to a pipe 16 having a rising portion. A gas supply line 12 is connected to the pipe 11 and a gas supply line 14 is connected to the pipe 16. Pressure gauges 13 and 15 are installed on the gas supply lines 12 and 14, respectively, in order to control the amount of product extracted. The valve 17 is an emergency valve for closing the emergency. When replacing the entire line with an inert gas or the like, close the valve of the valve 19 and
An inert gas or the like is supplied from the gas supply line 12 and / or the gas supply line 14, and the gas is exhausted from the exhaust line 18 to be replaced. Since the products are sufficiently cooled in the parts where the valves 17 and 19 are installed,
It is sufficient to use a Teflon lined valve. The piping is finally connected to the product storage tank 20. The product storage tank 20 has a pressure gauge 22 for adjusting the pressure inside the product storage tank,
A pressure adjusting line 21 for air supply / exhaust is installed.

[0015]

The present invention will be described in more detail with reference to the following examples. {Example 1} A granular polycrystalline silicon production apparatus comprising the reaction apparatus shown in FIG. 1 and the product extraction apparatus shown in FIG. 2 was used. As for the pipes 11 and 16, the bent portion has an R of 70 m.
A pipe having a diameter of m and an inner wall of a steel pipe having an inner diameter of 17.5 mm was lined with Teflon for 3 mm was used. The superficial pressure of the reactor 7 was set to 0.3 kg / cm ² as a gauge pressure, and a mixed gas consisting of silane and hydrogen was supplied to the reactor in this state to produce granular polycrystalline silicon by the fluidized bed method. . During 40 minutes from the start of the reaction, hydrogen gas is supplied from the line 21 into the product storage tank 20 to pressurize the inside to 0.4 kg / cm ² with a gauge pressure, and the gas supply line 12
Or from 14, no gas was supplied. After reacting for 40 minutes, the inside of the product storage tank 20 was replaced with nitrogen gas, and the inside of the product storage tank was checked. As a result, the granular polycrystalline silicon, which is the product, could not be extracted due to the pressure balance, and the product was stored in the product storage tank. No outflow was observed.
After that, the pressure in the product storage tank 20 is set to 0.15 as a gauge pressure.
At the same time as reducing the pressure to kg / cm ² , the gas supply line 12
20 and hydrogen gas at a flow rate of 15 L / min from 14 and 14.
After feeding for 2 seconds, the inside of the product storage tank was replaced with nitrogen, and when the inside of the product storage tank was checked, about 250 g of the product was extracted. 5 g of the extracted product is dissolved in an aqueous solution consisting of 40 mL of 50 wt% hydrofluoric acid aqueous solution and 40 mL of 68 wt% nitric acid aqueous solution, and IPCS-10 manufactured by Shimadzu Corporation
The concentration of impurities in the product was measured by IPC emission spectrometry using 00III. The result is shown in No. 1 of Table 1. Shown in 1. Then, after operating for 4 hours under the operating condition that seed silicon particles are charged from the upper part of the reactor at an rate of about 50 g every hour, and the product is extracted every about 40 minutes in the same manner as described above, The impurity concentration was measured in the same manner as above. The result is shown in No. 1 of Table 1. 2 shows. Further, after operating for 80 minutes under the same conditions, the impurity concentration in the product was measured in the same manner as above. The result is shown in No. 1 of Table 1. 3 shows.

[0016]

[Table 1]

Example 2 The reactor shown in FIG. 1 and FIG.
An apparatus for producing granular polycrystalline silicon, which comprises the product extracting apparatus shown in FIG. As the pipes 11 and 16, SiC / Si having a bent portion R of 70 mm and an inner diameter of 17.5 mm
A steel pipe with a pipe made inside was used. The pressure in the empty space of the reactor 7 was set to 0.3 kg / cm ² as a gauge pressure, and in this state, a mixed gas of silane and hydrogen was supplied to the reactor to start the reaction. After the reaction starts, at the same time keeping the product storage tank 20 at a gauge pressure of ^{0.3kg / cm 2, 0.33~0.35kg / cm} 2 pressure gauge 13 is a gauge pressure, the pressure gauge 15
Was fed from the gas supply lines 12 and 14 so that the gauge pressure was 0.34 to 0.36 kg / cm ² . It was confirmed that 400 g of the product was withdrawn almost continuously per hour in the product storage tank, although small variations in the form of slip sticks were observed. The impurity concentration in the product extracted after the 40-minute reaction was measured in the same manner as in Example 1, and the results are shown in Table 2. Shown in 1. Further, the impurity concentration in each product was measured in the same manner as in Example 2 after 4 hours (No. 2 in Table 2) and after 80 minutes (No. 3 in Table 2). The above results are shown in Table 2.

[0018]

[Table 2]

Comparative Example 1 The reaction was carried out under the same conditions as in Example 2 except that as the pipes 11 and 16, stainless steel (SUS304TP) pipes having a bent portion R of 70 mm and an inner diameter of 17.5 mm were used. The extraction condition was almost the same as that of the second embodiment. 40 minutes after the start of the reaction (No. 1 in Table 3), 4 hours after this (No. 2 in Table 3), and 80 minutes after this (No. 3 in Table 3) The results of measuring the impurity concentration in the same manner as in Example 2 are shown in Table 3. The impurity concentration in the extracted product is high, and it is difficult to use for semiconductors.

[0020]

[Table 3]

[0021]

The granular polycrystalline silicon extracting device of the present invention does not have a complicated structure and therefore does not require any special processing for manufacturing the device, and the product can be extracted by a simple method. Moreover, since the inner wall of the pipe constituting the device is made of a non-polluting material for polycrystalline silicon and has no sliding part, the product particles can be extracted from the reactor without being contaminated. The product purity can be maintained at the same level as the granular polycrystalline silicon in the reactor. Therefore, according to the present invention, the purity of the product, which is the most important issue in the production of granular polycrystalline silicon for semiconductors, can be kept at an extremely high semiconductor grade purity by using an inexpensive apparatus. The effects of application and implementation are extremely large.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a reactor for producing granular polycrystalline silicon by a fluidized bed method.

FIG. 2 is a schematic view showing an embodiment of the present invention.

[Explanation of symbols]

 1: Fluidized Bed Reactor 2: Heater 3: Seed Silicon Particles 4: Raw Material Gas Supply Line 5: Bed Particles 6: Extraction Line 7: Fluidized Bed Reactor 8: Product Buffer / Cooler 9: Cooling Water Inlet 10 : Cooling water outlet 11: Piping 12: Gas supply line 13: Pressure gauge 14: Gas supply line 15: Pressure gauge 16: Piping 17: Emergency valve 18: Exhaust line 19: Replacement shutoff valve 20: Product storage tank 21: Pressure Adjustment line 22: Pressure gauge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Komatsu 3-1, Chidori-cho, Kawasaki-ku, Kanagawa Prefecture Tonen Chemical Co., Ltd. Technology Development Center (72) Masaaki Ishii 3 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 Tonen Chemical Co., Ltd. Technology Development Center (72) Inventor Kazutoshi Takatsuna 3-1, Chidori-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Tonen Chemical Co., Ltd. Technical Development Center (72) Inventor Yasuhiro Saruwatari Kawasaki, Kanagawa Prefecture 3-1, Chidori-cho, Kawasaki-ku, Tonen Chemical Co., Ltd. Technology Development Center

Claims (2)

[Claims] 1. A pipe for withdrawing granular polycrystalline silicon produced by a fluidized bed method from silane as a raw material extends downward from the bottom of the reactor and then bends in the horizontal direction. A granular polycrystalline silicon extracting device having a rising portion on the extension. 2. The granular polycrystalline silicon extracting device according to claim 1, wherein the inner wall of the pipe for extracting the granular polycrystalline silicon is made of a non-polluting material with respect to polycrystalline silicon.