JPH06191817A - Production of granular polycrystal silicon - Google Patents

Abstract

PURPOSE:To obtain coarse particles free from silicon fine powder and suitable for the production of a semiconductor by using the silicon fine powder classified and collected by supplying product silicon particles produced in a fluidized bad reactor to a separation pipe as seed silicon particles or the like in a fluidized bed method. CONSTITUTION:A silane compound 7 is supplied to the fiuidized bed reactor 1 and is thermally decomposed on the fluidizing 10 silicon particles. The silicon particles obtained from the reactor 1 as the product are supplied to the particle separation pipe 11. Then, fin grain silicon particles and coarse grain silicon particles are classified and collected respectively to a fine grain silicon drum 13 and a coarse grain silicon drum 12. The collected fine grain silicon particles in the drum 13 are used as the seed silicon particles 17 for supplying them to the reactor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing granular polycrystalline silicon by a fluidized bed method.

[0002]

2. Description of the Related Art High-purity polycrystalline silicon is used as a raw material for semiconductor devices, solar cells, and the like, which have become very popular in recent years. There is. This production is mainly carried out by the bell jar method, which is a method in which a thin silicon rod with a diameter of about 5 mm installed in a bell jar reactor is electrically heated,
In this method, a mixed gas of a gaseous silicon compound and hydrogen is introduced to deposit silicon on the surface of the silicon rod.
This method is suitable for the production of high-purity silicon, but its productivity is low due to its small reaction surface area, and it consumes a large amount of electricity due to the large heat radiation from the surface of the bell jar type reactor. There is a drawback that it is necessary to stop the reaction to replace the silicon rod every time it grows,
It cannot be said that the method is suitable for mass production.

On the other hand, the fluidized bed method has recently received attention as an energy-saving method for producing polycrystalline granular silicon. This method introduces a mixed gas of a gaseous silane compound and a diluent gas onto the surface of fluidized silicon particles, deposits silicon produced by thermal decomposition of the silane compound on the surface of the fluidized silicon particles, and It is a method of obtaining granular polycrystalline silicon with a purity. In this method, the reaction is carried out on the surface of the fluidized particles, so that the reaction surface area is large, the productivity is high, and the continuation is easy. Since it is easy, it can be said to be a method suitable for industrialization.

By the way, when granular polycrystalline silicon is produced using a fluidized bed reactor, silicon particles that have grown are extracted as a product outside the reactor. In this case, since the product silicon particles are extracted and collected from the inside of the fluidized bed in which the silicon particles are violently flowing, they are accompanied by fine particles and fine silicon particles having a particle size smaller than the intended particle size. Is. Since these fine silicon particles are unsuitable as a raw material for semiconductor production, it is necessary to separate small silicon particles smaller than fine particles from the silicon particles extracted from the fluidized bed and collected. However, since the separation of these small silicon particles is carried out in a special process provided for that purpose, there is the disadvantage that the product particles must be packed in a container and transported to that container, and the product particles must be packed into that container. There is a problem that silicon particles are easily contaminated.

In Japanese Patent Laid-Open Publication No. 57-140310, when the granular silicon produced in the fluidized bed is taken out of the system, hydrogen gas is fed in a countercurrent to the flow of the granular silicon taken out in the taking-out pipe. A method has been proposed. According to this method, the fine silicon particles accompanying the product silicon particles are returned to the fluidized bed again due to the strong hydrogen flow, so that the product silicon particles containing no fine silicon particles can be obtained. However, with this method, it is difficult to extract the silicon particles without changing the reaction conditions, which causes various inconveniences. That is, in this method, a large amount of driving gas for returning the fine particles accompanying the product particles into the reactor is blown into the reactor, so that the fluidized bed conditions, especially the reaction temperature and the movement of the fluidized silicon particles are The state fluctuates, and as a result, the amount of fine silicon generated increases, the dispersion plate is clogged, and the amount of fine silicon in the reactor increases due to the return of fine silicon into the reactor. There arises a problem that a large amount of fine powder is accumulated on the inner wall of the empty tower portion provided. Also in this method, 0.1 to 300 μm is contained in the product particles.
Since it contains undesired fine particles to some extent, it is necessary to separate and remove these in a later step.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a method for producing high-purity polycrystalline granular silicon by a fluidized bed method, wherein product particles extracted through a product particle extraction tube without changing the fluidized bed reaction conditions. Therefore, it is an object of the present invention to provide a method for efficiently separating undesired small silicon particles accompanying it.

[0007]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a silane compound is supplied to a fluidized bed reactor having a fluidized bed of silicon particles to thermally decompose the silane compound on the fluidized silicon particles, and seed silicon particles are placed in the reactor. In the feeding method, silicon particles obtained as a product from the reactor are fed to a particle separation tube (A) in which a driving gas is blown up, and fine silicon particles are added to the upper part of the particle separation tube (A). The fine-grained silicon drum (I) is used to classify and collect the coarse-grained silicon particles in the coarse-grained silicon drum (II) provided in the lower part of the particle separation tube (A), and the fine-grained silicon drum (I) is also collected. There is provided a method for producing granular polycrystalline silicon, characterized in that at least a part of the silicon particles therein is used as seed silicon particles supplied to the fluidized bed reactor.

Examples of the silane compound used as a raw material in the present invention include chlorinated silanes such as monochlorosilane, dichlorosilane and trichlorosilane, and silanes such as monosilane and disilane. The silane compound is
Usually, it is diluted with a gas. In this case, the diluent gas may be hydrogen, argon, neon or the like, but hydrogen is preferably used.

Next, the present invention will be described with reference to the drawings. FIG. 1 shows a system diagram of an apparatus used for implementing the present invention. In FIG. 1, reference numeral 1 is a cylindrical reactor, and above this reactor there is a superficial tower expansion part 4 equipped with a seed silicon supply pipe 2 and a gas discharge pipe 3. A gas dispersion plate 5 is provided at the bottom of the reactor 1, and a particle extraction pipe 9 is connected to the center of the gas dispersion plate 5 so as to penetrate the bottom plate.
Further, a heater 6 is provided outside the reactor 1 so as to wrap it.

The lower end of the particle extracting pipe 9 is connected to the intermediate portion of the particle separating pipe (A) 11. This particle separation tube (A) 11 has a fine-grain silicon drum (I) 13 at the top.
And a coarse grain silicon drum (II) 12 at the bottom. A particle extraction pipe 18 having a particle storage tank A at the lower end is connected to the bottom of the fine-grain silicon drum (I) 13, and a pipe 24 for communicating with a filter (not shown) is provided at the upper part of the drum (I). It is connected. An extraction pipe 19 is connected to the bottom of the coarse-grain silicon drum (II) 12. The particle storage tank A is for temporarily storing the silicon particles in the drum.

On the downstream side of the particle separation tube (A), there is arranged a particle separation tube (B) 16 having an intermediate particle silicon drum (III) 14 in the upper part and a large particle silicon drum (IV) 15 in the lower part. ing. The upper stage of the particle separation pipe (B) 16 and the particle extracting pipe 18 are connected by a connecting pipe 23, and the lower stage of the separation pipe (B) 16 and the particle extracting pipe 19 are connected by a connecting pipe 25. ing. Medium grain silicon drum (III)
A particle storage tank A is connected to the bottom of the drum 14, and a pipe 26 is connected to the upper portion of the drum. A particle extracting pipe 27 is connected to the bottom of the large grain silicon drum (IV) 15. A flow rate control valve is provided in the separation tubes A and B, and the silicon particles can be classified to a desired particle size by adjusting the valve opening degree, if necessary.

The pipe 20 is a driving gas pipe for the particle separation pipe (A) 11, and its tip is connected to the lower portion of the particle separation pipe (A). In addition, this drive gas pipe 20
A pipe 28 is connected between the particle extracting pipe 9 and the particle extracting pipe 9. The gas introduced into the separation pipe (A) 11 through the pipe 20 blows up the silicon particles that fall into the separation pipe (A) through the pipe 9 and classifies the silicon particles by the air sieving effect. The gas introduced into the pipe 9 through the pipe 28 exerts a buoyancy force on the silicon particles passing through the pipe and has an effect of facilitating the silicon particles to flow downward in the pipe.

The pipe 21 is a driving gas pipe for the particle separation pipe (B) 16, and the tip thereof is the particle separation pipe (B).
It is connected to the lower part of 16. The gas introduced into the lower part of the separation pipe (B) 16 through the pipe 21 blows up the silicon particles introduced into the separation pipe (B) 16 through the pipe 25, and further classifies by the air sieving effect. A fine-grain silicon drum (I) 13 is provided on the upper part of the separation tube (B) 16.
A pipe 23 for introducing at least a part of the silicon particles extracted from the inside of the separation pipe (B) 16 is connected, and the fine silicon particles are further classified in the upper part of the separation pipe (B) 16.

In the respective particle storage tanks A connected to the bottoms of the fine grain silicon drum (I) 13 and the medium grain silicon drum (III) 14, particle withdrawing pipes 30 and 31 for withdrawing particles as needed are provided. In addition to being connected to each other, the pipes 41 and 43 are also connected to each other. The pipes 41 and 43 are particle extraction pipes in the particle storage tank A. These pipes are connected to lines 45 arranged above the seed silicon drum 17 via pipes 42 and 44 in order to circulate silicon particles as seed silicon in the seed silicon drum 17. A pipe 29 is connected to the pipe 41 connected to the particle storage tank A of the fine grain silicon drum (I) 13. This pipe 29 is for feeding the particles extracted from the particle storage tank A of the fine-grain silicon drum (I) via the pipe 42 to the seed silicon drum 1.
7 is a drive gas pipe used to circulate the gas in No. 7. A pipe 32 is connected between the pipe 21 and a pipe 43 connected to the particle storage tank A of the medium-grain silicon drum (III) 14. This pipe 32 is also a drive gas pipe used for circulating the silicon particles to the seed silicon drum 17 via the pipe 44. The pipes 33, 34, and 35 are arranged to introduce a part of the driving gas in the pipe 21 into the pipes 23 and 25, respectively. The gas from these pipes 34 and 35 is the same as the pipes 23 and 25, respectively.
It has the effect of giving buoyancy to the silicon particles passing through it to facilitate the silicon particles flowing downward in the pipe.

In order to carry out the method of the present invention using the apparatus system described above, first, granular polycrystalline silicon having a desired average particle size is produced using the fluidized bed reactor 1. To this end, the silane compound is fed through the supply pipe 7 and the diluent gas is fed through the supply pipe 8 into the reactor 1 via the dispersion plate 5, respectively, whereby the silicon particles filled on the dispersion plate are supplied. Is fluidized to form the fluidized bed 10, and the fluidized bed is heated to a predetermined temperature by the heater 6. The silicon particles that have grown to a desired particle diameter are extracted to the outside of the reactor through the particle extraction tube 9, and the seed silicon is correspondingly seed silicon drum 17
Is supplied into the reactor through the pipe 2.

The silicon particles extracted through the particle tube 9 are supplied to the intermediate portion of the particle separation tube (A) 11. In this particle separation pipe (A) 11, an upward flow of driving gas hydrogen, argon gas, etc., which is supplied to the lower portion of the pipe through the pipe 20, is formed. Therefore, the silicon particles supplied to the middle of the particle separation tube (A) are classified according to the flow velocity of the driving gas, and the fine particles having a small particle diameter are collected in the fine particle silicon drum (I) 13. While meanwhile,
Coarse particles with a large particle size can be obtained by using the coarse particle silicon drum (II) 1
2 is captured. In the present invention, the particle separation tube (A)
The flow rate of the driving gas rising 11 is 300 μm or less, preferably 25 μm or less, in the fine-grain silicon drum (I) 13.
It is adjusted so that fine particles of 0 μm or less rise together with the driving gas and are introduced into the fine particle silicon drum (I) 13. In this case, the flow velocity can be adjusted by the size of the inner diameter of the particle separation tube (A) and the amount of driving gas supplied to the particle separation tube (A). On the other hand, coarse particles having a particle size larger than 300 μm descend in the particle separation tube A and are collected by the coarse particle silicon drum 12.

The driving gas introduced together with the silicon particles into the fine-grain silicon drum (I) 13 is extracted from the upper part of the drum (I) through the pipe 24 and then introduced into a filter (not shown). Then, the fine particles that accompany the driving gas are collected here. The particle size of the fine particles accompanying the driving gas from the drum (I) is determined by the flow velocity of the driving gas extracted from the drum. In this case, the gas flow rate can be adjusted by the inner diameter of the pipe 24 for extracting gas. In the present invention, the particle size of the fine particles accompanying the driving gas is preferably specified to be 80 μm or less or 50 μm or less. That is, fine grain silicon drum (I) 1
3 has a particle size of 50 to 300 μm, preferably 80 to 25
It is preferable to collect 0 μm silicon particles. The silicon particles collected in the drum (I) 13 are used as seed silicon particles, if necessary, via the particle storage tank A and the pipes 41 and 42, and further via the pipe 45, to the upper portion of the seed silicon filling drum 17. The particles are circulated in the provided particle storage tank A.

The particles collected in the coarse-grained silicon drum (II) 12 are coarse particles having a grain size of more than 300 μm and can be recovered as product silicon particles.
If necessary, in order to obtain large-sized product silicon particles,
It can be further classified. For this purpose, at least a part of the coarse silicon particles collected in the coarse silicon drum (II) 12 is supplied to the particle separation tube (B) 16.
In the particle separating pipe (B) 16, an upward flow of the second driving gas supplied to the lower portion of the pipe through the pipe 21 is formed. Therefore, the silicon particles supplied to the particle separation tube (B) are classified according to the flow rate of the driving gas, and the medium particles having a small particle size are collected by the medium particle silicon drum (III) 14, On the other hand, large particles having a large particle size are collected by the large silicon drum (IV) 15. In this case, the flow velocity of the driving gas rising in the particle separation tube (B) 16 is 100 in the large grain silicon drum (IV) 15.
It is adjusted so that particles having a large particle size of 0 μm or more, preferably 1500 μm or more are collected. Particle separation tube (B) 16
The flow velocity of the gas rising inside can be adjusted by the inner diameter of the tube and the amount of driving gas supplied to the particle separation tube (B). The silicon particles collected on the large-sized silicon drum (IV) 15 are collected as product particles. on the other hand,
Medium particles having a particle size of less than 1000 μm rise together with the driving gas and are collected by the medium silicon drum (III) 14.

The driving gas introduced together with the silicon particles into the medium-grain silicon drum (III) 14 is withdrawn from the upper portion through the pipe 26, and then introduced into a filter (not shown), where it is driven. Fine particles that accompany the working gas are collected. The particle size of the silicon particles flowing out from the drum (III) together with the driving gas is determined by the flow velocity of the driving gas extracted from the drum. In this case, the gas flow velocity can be adjusted by the inner diameter of the gas extraction pipe 26. Further, when the silicon particles are classified as described above, if necessary, some of the particles in the fine-grain silicon drum (I) 13 may be extracted through the pipe 18 and the pipe 23 to separate the particle separation pipe (B). ) 16 and can be further classified. Since the fine particles collected in the fine-grain silicon drum (I) may include large particles larger than the predetermined particles, the fine-grain drum (I) collects the fine particles as described above. The classified fine particles are again classified in the separation tube (B) 16 to obtain large silicon drums (IV) of large particles contained in the particles.
15 can be collected. On the other hand, the fine particles after the large particles have been classified are collected by the medium-sized silicon drum (III) 14. In addition to the above, classification of the large-grained silicon contained in the fine-grained silicon is performed by supplying the fine-grained silicon to the lower part of the separation pipe (B), for example, to guide it from the pipe 23 to the pipe 25, It can also be carried out by supplying it to the lower part of the separation tube (B) together with the coarse-grained silicon.

The medium-sized silicon particles collected in the medium-sized silicon drum (III) 14 are preferably passed through the particle storage tank A, the pipes 43 and 44, and further to the pipe 45 arranged above the seed silicon drum. It is circulated to the seed silicon drum 17 via the particle storage tank A.

[0021]

EXAMPLES Next, the present invention will be explained more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 A fluidized bed reactor equipped with a quartz inner cylinder having an inner diameter of 80 mm and a height of 1,100 mm inside a quartz outer cylinder having an inner diameter of 100 mm and a height of 1,200 mm was used. A high-purity polycrystalline granular silicon manufacturing apparatus was manufactured. In this apparatus, the annular heater 6 for heating the reactor was installed between 0 mm and 1000 mm from the horizontal plate of the gas dispersion plate.

Monosilane is supplied at a flow rate of 0.5 m / sec through the raw material gas introduction pipe 7, hydrogen is supplied through the dilution gas introduction pipe 8, and a mixed gas of these monosilane and hydrogen (hydrogen concentration of 20%) is supplied to the dispersion plate. Introduced into the reactor 1 through the No. 5 silicon particles on the dispersion plate (particle size 300 ~ 100
Siliconized fluidized bed 10 was formed by fluidizing 0 μm and an average particle diameter of 700 μm). In this case, the height of the fluidized bed was 3.5 times the inner diameter of the reaction tube. Further, the fluidized bed was heated to 700 ° C. by the heater 16. The product withdrawal rate from the fluidized bed reactor 1 is set to 500 to 1000 g / hr, and the seed silicon supply rate from the seed silicon drum 17 is set to 750 g / hr to produce granular silicon by the fluidized bed reaction. It was

The silicon particles withdrawn from the fluidized bed reactor 1 were sequentially classified using the particle separation tube (A) 11 and the particle separation tube (B) 16 shown in FIG. The operating conditions of the particle separation tube and the classification results in this case are shown below. (1) Operating conditions of the particle separation tube (A) 11 (i) Flow velocity of driving gas (hydrogen): 2.3 m / sec (ii) Particle size of particles collected in the fine-grain silicon drum (I) 13. Range: 100 to 300 μm, (iii) Particle size of particles collected in the coarse-grained silicon drum (II) 12: 270 to 2000 μm (2) Operating conditions of the particle separation tube (B) 16 (i) Driving gas (Hydrogen) flow rate: 7.5 m / sec (ii) Particle size range of particles collected on the medium-sized silicon drum (III) 14: 300 to 1000 μm, (iii) Collected on large-sized silicon drum (IV) 15 Particle size range of the formed particles: 1000-2000 μm In this experimental example, fine silicon drum (I) 13
Also, a part of the particles collected in the medium-grain silicon drum (III) 14 is used as seed silicon particles to form the seed silicon drum 1.
7 was recycled. When continuous operation was performed for 220 hours as described above, no trouble occurred in the reactor. Further, the particles collected by the large-sized silicon drum (IV) 15 had a smooth surface with no accompanying fine powder. Further, when the reaction was stopped after 220 hours and the inside of the reactor was inspected, the thickness of the silicon deposited on the inner wall of the reactor was only 2 to 3 mm at the most places, and the amount of silicon deposited on the periphery of the gas dispersion plate was small. The amount of fine silicon powder attached to the expanded portion of the superficial column was also extremely small.

Example 2 In Example 1, the fluidized bed temperature was 750 ° C., the monosilane flow rate was 0.6 m / sec, the silicon particle extraction rate from the reactor was 800-1500 g / hr, and seed silicon was supplied. An experiment was performed in the same manner as in Example 1 except that the speed was 150 g / hr. The operating conditions of the particle separation tube and the classification results in this case are shown below. (1) Operating conditions of the particle separation tube (A) 11 (i) Flow velocity of driving gas (hydrogen): 2.3 m / sec (ii) Particle size of particles collected in the fine-grain silicon drum (I) 13. Range: 100 to 300 μm, (iii) Particle size of particles collected on the coarse-grained silicon drum (II) 12: 250 to 2200 μm (2) Operating conditions of particle separation tube (B) 16 (i) Driving gas (Hydrogen) flow rate: 7.5 m / sec (ii) Particle size range of particles collected on the medium-sized silicon drum (III) 14: 300 to 1000 μm, (iii) Collected on large-sized silicon drum (IV) 15 Particle size range of the formed particles: 1000 to 2200 μm In this experimental example, fine silicon drum (I) 13
A part of the particles collected on the medium-grain silicon drum (III) was circulated to the seed silicon drum 17 as seed silicon particles. When continuous operation was performed for 220 hours as described above, no trouble occurred in the reactor.
Further, the particles collected by the large-sized silicon drum (IV) 15 had a smooth surface with no accompanying fine powder. Further, when the reaction was stopped after 220 hours and the inside of the reactor was inspected, the thickness of the silicon deposited on the inner wall of the reactor was only 2 to 3 mm at the most places, and the amount of silicon deposited on the periphery of the gas dispersion plate was small. The amount of fine silicon powder attached to the expanded portion of the superficial column was also extremely small.

Comparative Example 1 A fluidized bed reaction was carried out under the conditions shown in Example 1, and at the time of extracting silicon particles from the reactor, hydrogen gas was introduced into the silicon particle extracting tube so as to face the flow of silicon particles. Then, fine silicon powder (particle size 150 μm or less) that accompanies the silicon particles was returned into the reactor. When continuous operation was performed for 100 hours in this manner, the fluidized bed temperature fluctuates every time hydrogen gas is introduced into the silicon particle extraction pipe, so that the conversion rate of monosilane decreases and a smooth fluidized bed reaction can be performed. could not. Also, 100
After the operation was stopped for a certain period of time, the inside of the apparatus was inspected, and it was confirmed that a fine silicon layer of 5 to 8 mm was deposited on each wall of the empty tower expansion section 4 and its ceiling plate and the upper part of the reactor 1. It was

[0027]

According to the present invention, from the silicon particles extracted from the reactor through the silicon particle extraction tube,
Without changing the reactor conditions, fine silicon particles contained therein can be removed, and coarse particles containing no fine silicon particles suitable as a semiconductor manufacturing raw material can be obtained. Further, according to the present invention, since silicon particles in the range of 50 to 300 μm, which are not preferable as a raw material for semiconductor production, are circulated and used as seed silicon particles, it is not necessary to specially prepare seed silicon particles. Further, according to the present invention, since the fine powder silicon produced in the reactor can also be positively extracted from the reactor through the particle extracting pipe, various troubles caused by the fine powder silicon are caused. For example, it is possible to effectively prevent troubles such as accumulation of fine silicon powder on the inner wall of the upper portion of the reactor or the inner wall of the expanded empty column portion, clogging of the dispersion plate, and the like.

[Brief description of drawings]

1 is a systematic diagram of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylindrical reactor 2 Silicon feed pipe 3 Gas discharge pipe 4 Expanded tower 5 Gas dispersion plate 6 Heater 7 Raw material gas supply pipe 8 Diluting gas pipe 9 Silicon particle extraction pipe 10 Fluidized bed 11 Particle separation pipe A 12 Coarse particles Silicon Drum (I) 13 Fine Grain Silicon Drum (II) 14 Medium Grain Silicon Drum (III) 15 Large Grain Silicon Drum (IV) 16 Particle Separation Pipe (B) 17 Type Silicon Drum 18,30 Fine Grain Silicon Extraction Pipe 19 Coarse Grain Silicon extraction pipe 20,21 Driving gas supply pipe 27 Product particle extraction pipe 31 Medium grain silicon extraction pipe 23,24,25,26,28,29,32,33,3
4,35,41,42,43,44 Piping

Continuation of the front page (72) Kazutoshi Takatsuna 3-1, Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Tonen Chemical Co., Ltd. Technical Development Center (72) Yasuhiro Saruwatari 3, Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 Tonen Kagaku Co., Ltd. Technical Development Center (72) Inventor Nobuhiro Ishikawa 1 in the first place of Funami-cho, Minato-ku, Nagoya, Aichi Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor ▲ Hiro ▼ Daisuke Ta, 23 Toagosei Synthetic Chemical Industry Co., Ltd.Nagoya factory, 17 Showa-cho, Minato-ku, Nagoya city, Aichi prefecture

Claims (2)

[Claims] 1. A method of supplying a silane compound to a fluidized bed reactor having a fluidized bed of silicon particles, thermally decomposing the silane compound on the fluidized silicon particles, and supplying seed silicon particles into the reactor. In, the silicon particles obtained as a product from the reactor are supplied to the particle separation tube (A) in which the driving gas is blown up, and the fine silicon particles are provided in the upper part of the particle separation tube (A). In the granular silicon drum (I), coarse silicon particles are classified and collected in the coarse silicon drum (II) provided at the lower part of the particle separation tube (A), and the silicon in the fine silicon drum (I) is collected. A method for producing granular polycrystalline silicon, characterized in that at least a part of the particles is used as seed silicon particles supplied to the fluidized bed reactor. 2. A particle separation tube (B) in which a driving gas attached to a downstream side of the particle separation tube (A) blows up the coarse particle silicon particles classified and collected in the coarse particle silicon drum (II). And / or fine particles of silicon particles that have been classified and collected by the fine particles of silicon drum (I) are supplied to the particle separation tube (B) to further classify the silicon particles. The method for producing granular polycrystalline silicon according to claim 1.