KR20120095755A - Method of preparing feed seed for granular polycrystalline polysilicon preparation - Google Patents

Abstract

PURPOSE: A method of manufacturing raw material seed for manufacturing granulated polycrystalline polysilicon is provided to optimize manufacturing facilities by preventing the oxidization and the pollution of silicon micropowder and omitting a pre-treating process. CONSTITUTION: A method of manufacturing raw material seed for manufacturing granulated polycrystalline polysilicon includes the following: silicon micropowder, generated from a granulated polycrystalline polysilicon manufacturing process using a fluidized bed reactor(1), is primarily filtered and secondarily filtered to separately collect silicon micropowder of different particle sizes; silicon micropowder of different particle sizes are transferred to each storing bath under an anti-oxidizing condition; the silicon micropowder is mixed under an anti-pollution condition; the mixed silicon micropowder is formed into a silicon molded body without a pre-treating process for eliminating surface oxide; and the silicon molded body is molten, sprayed, and re-crystallized to obtain silicon particles of 200-500um.

Description

Manufacturing method of raw material seed for granular polycrystalline polysilicon production {METHOD OF PREPARING FEED SEED FOR GRANULAR POLYCRYSTALLINE POLYSILICON PREPARATION}

The present invention relates to a method for producing a raw material seed for producing particulate polycrystalline polysilicon, and more particularly, by mixing silicon fine powders having different particle size distributions produced in the production of polysilicon using a fluidized bed reactor at an appropriate ratio and treating them under specific conditions. In addition, the present invention relates to a method for preparing a raw material seed for producing a particulate polycrystalline polysilicon capable of producing a high purity polysilicon raw material seed without increasing a molding density of silicon and omitting a pretreatment step for removing impurities.

In general, a silicon element-containing reaction gas, which has been purified to a very high purity for producing polycrystalline polysilicon, is pyrolyzed and hydrogen-reduced at a high temperature to generate silicon element particles, and the silicon element particles are continuously precipitated on the silicon particle surface. The method is mainly used.

Specifically, the Siemens method has been mainly used so far for commercial mass production of polycrystalline polysilicon. However, the polycrystalline polysilicon manufacturing method using the Siemens method has a fundamental limitation that the product cannot be continuously produced because the reaction surface area required for silicon deposition is small, the power consumption for silicon production is large, and the diameter of the rod that increases due to silicon precipitation is limited. However, there is a problem that the operation efficiency of the reactor is low.

In order to solve the problems of the Siemens method, a particulate polycrystalline polysilicon production apparatus and a manufacturing process using a fluidized bed reactor have been developed. Particle polycrystalline polysilicon manufacturing apparatus using a fluidized bed reactor provides a large reaction surface area for silicon deposition, discharges silicon deposited over a certain size, and introduces new particulate polysilicon seeds manufactured separately in several ways This allows for continuous reactor operation. Therefore, the fluidized bed reactor can reduce the energy consumed per unit mass through continuous reactor operation as compared with the Siemens method.

In the particulate polycrystalline polysilicon manufacturing process using the fluidized bed reactor, the silicon generated by the silicon element-containing reaction gas is decomposed, and the silicon is deposited on the seeds through various reaction mechanisms or is grown in the same species. However, at this time, about 10 to 15% (by weight) of silicon fine powder is not involved in the deposition reaction and is entrained in hydrogen and / or unreacted gas, which is a fluidizing gas, to be collected in a cyclone and a bag filter. In itself, it does not have enough basic physical properties necessary for molding, and there is a problem that impurities such as oxygen are combined and their purity decreases in the process of transporting and processing them. That is, there is no specific and economical alternative to the method of utilizing such silicon fine powders, which is a serious loss of the manufacturing process.

The present invention is to solve the problems of the prior art as described above, it is excellent in the molding density and physical properties of the molded silicon can be easily melted, high purity poly without a separate pre-treatment process to remove impurities of the silicon fine powder It is a technical object of the present invention to provide a method for preparing a raw material seed for preparing polysilicon, which may prepare a silicon raw material seed, and which may effectively utilize the silicon fine powder which is by-produced when producing the particulate polycrystalline polysilicon.

In order to achieve the above technical problem, the present invention a) by filtering the silicon fine powder produced during the production of particulate polycrystalline polysilicon using a fluidized bed reactor over the first and second, to separate the silicon fine powder having a different particle size distribution Collecting; b) transferring the first and second collected silicon micropowders to a reservoir in an environment where oxidation by air contact is prevented; c) mixing the transferred silicon fine powder in a state where contamination is prevented; d) directly preparing the mixed silicon fine powder into a silicon molded body without a pretreatment process for removing surface oxides; And e) melting, spraying, and recrystallizing the prepared silicon molded body to produce silicon particles having a size of 200 to 500 μm.

In another aspect of the present invention, there is provided a raw material seed for producing particulate polycrystalline polysilicon prepared by the above method.

According to the polysilicon raw material seed production method according to the present invention, by mixing the silicon micropowder having a different particle size distribution has the advantage of improving the molding density and physical properties of the silicone molded body and facilitate the melting of the manufactured silicone molded body.

In addition, the oxidation and contamination of the silicon micropowder is prevented, so that the pretreatment step is omitted, thereby optimizing the manufacturing equipment and providing a high purity polysilicon raw material seed.

In addition, it is possible to reuse the silicon fine powder by-produced in the production of the granular polycrystalline polysilicon as the raw material of the same process has the advantage that can significantly reduce the manufacturing cost and waste treatment cost.

Figure 1 schematically shows a process and apparatus for performing a polysilicon raw material seed manufacturing method according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

Method for producing a raw material seed for producing a particulate polycrystalline polysilicon according to the present invention is a) particle size distribution by filtering the silicon fine powder produced during the production of particulate polycrystalline polysilicon using the fluidized bed reactor (1) and secondary Separating and collecting different silicon fine powders; b) transferring the primary and secondary collected silicon micropowders to the reservoirs 6 and 5, respectively, in an environment in which oxidation by air contact is prevented; c) mixing the transferred silicon fine powder in a state where contamination is prevented; d) directly preparing the mixed silicon fine powder into a silicon molded body without a pretreatment process for removing surface oxides; And e) melting, spraying, and recrystallizing the prepared silicon molded body to produce silicon particles having a size of 200 μm to 500 μm. As used herein, "silicone micropowder" means silicon particles having a diameter of 50 µm or less.

a) silicon fine powder Capture  step

This step is a step of collecting and collecting the silicon fine powder having a different particle size distribution by filtering the silicon fine powder produced during the production of particulate polycrystalline polysilicon using the fluidized bed reactor (1) and the second.

First, various methods have been proposed for producing a raw material seed for use in the preparation of particulate polycrystalline polysilicon using the fluidized bed reactor 1, which has emerged as an alternative to the Siemens method. For example, U.S. Patent No. 4,691,866 discloses silicon for a fluidized bed reactor that selects only a desired particle size range by pulverizing silicon particles by accelerating silicon particles having a diameter of 300 to 2000 µm using an inert gas to collide with a silicon ingot target. Disclosed is a method for producing seed particles. In addition, US Patent No. 6,951,637 discloses a method for producing silicon seed particles for a fluidized bed reactor by spraying using ultrasonic waves. However, the above method is to use the seed particles prepared separately from the outside in the process irrespective of the polysilicon production process using the fluidized bed reactor (1), the present invention is polysilicon using the fluidized bed reactor (1) It is to prepare a polysilicon raw material seed used in the same process using the silicon fine powder produced or by-product produced in the manufacturing process itself.

Specifically, looking at the particulate polycrystalline polysilicon manufacturing process using the fluidized bed reactor (1) is as follows. First, a silicon seed 2 prepared in a size of 200 to 500 μm is introduced into a fluidized bed reactor 1, and then a reaction gas containing silicon (eg, silane) and hydrogen, which is a fluidizing gas, are disposed above the reactor 1. Flowing in the direction forms a fluidized bed through which the silicon particles flow by the supplied gas. Subsequently, the silicon-containing reaction gas introduced into the fluidized bed heated to a high temperature generates silicon element fine particles through a hydrogen reduction reaction and a pyrolysis reaction at a high temperature. Finally, as the generated silicon elemental particles are deposited in a polycrystalline state on the surface of the seed, the size of the silicon particles increases with time to finally form polysilicon.

In this step, about 10 to 15% of the silicon fine which is not involved in the deposition reaction and is entrained in the fluidized gas and / or unreacted gas in the preparation of particulate polycrystalline polysilicon using the fluidized bed reactor 1 is discharged from the reactor 1 The powder is first filtered using a device such as a cyclone (3), and the smaller silicon fine powder that has passed through this is secondly filtered using a bag filter (4) or the like, so that the particle size distribution is improved. Two different groups of silicon micropowders are separately collected.

In one embodiment, the particle size of the first collected silicon micropowder is d (0.5) 10 ~ 50㎛, the particle size of the second collected silicon fine powder is preferably d (0.5) 1 ~ 10㎛. When the particle size of the first trapped silicon fine powder and the second trapped silicon fine powder are in the above ranges, Minimizing the porosity when manufacturing the molded body can improve the mechanical properties such as molding density, and there is an effect that can be produced a molded body suitable for melting without using a binder.

b) transfer step

This step is to transfer the first and second collected silicon fine powder in the collecting step to each of the reservoir (6, 5) in an environment in which oxidation by air contact is prevented. Silicon fine powder generated by the existing Siemens method is inevitable contact with air during the recovery process, which oxidizes the silicon fine powder. Eventually, in order to use the oxidized silicon fine powder as a raw material seed, a separate pretreatment process was required to remove impurities. The present invention solves this problem and omits the pretreatment process, thereby optimizing the manufacturing equipment and manufacturing process while maintaining high purity poly It was made possible to provide a silicone molded body.

In this step, the transfer is performed in an environment in which impurities such as oxygen in the air are blocked to provide high purity silicon. In a preferred embodiment, it can be carried out in the atmosphere of (liquid) nitrogen and / or inert gas such as helium, argon, etc., while blocking contact with air.

The primary and secondary collected silicon fine powder is conveyed (eg, automatically conveyed) to respective reservoirs 6, 5, such as silos.

In one embodiment, before mixing each of the silicon fine powders transferred to the reservoirs 6, 5, with a meter 8, 7, for example each meter 8, 7 located below the reservoirs 6, 5. By precisely weighing by a fixed amount after the transfer, the mixing ratio in the mixing step described later can be set in advance.

c) mixing step

This step is a step of mixing with each other the silicon fine powder transferred in the transfer step in a state where contamination is prevented. By mixing two groups of silicon fine powders having different particle size distributions at an appropriate ratio in the mixer 9, the range of particle size distribution can be expanded to produce a silicone molded article having excellent physical properties. For example, when the fine powder collected by the cyclone 3 and the bag filter 4 is mixed and used at a predetermined ratio, the fine silicon particles collected by the bag filter 4 having a relatively small particle size are collected by the cyclone 3. By filling the voids between the relatively large silicon particles can be expressed to improve the molding density of the molded body.

In a preferred embodiment, the silicon fine powder collected in the cyclone (3): the silicon fine powder collected in the bag filter (4) is a weight ratio of 1: 1 to 3: 1 (eg, 1: 1, 2: 1, 3 : 1, etc.). When the weight ratio of the silicon fine powder collected in the cyclone 3 to the silicon fine powder collected in the bag filter 4 is less than 1, the content of the large silicon particles is too low, so that the molded body may be easily broken due to the decrease in density. If the weight ratio exceeds 3, the content of the small size silicon particles is too low to effectively fill the voids between the large size silicon particles, the physical properties of the molded body may be lowered.

The present invention focuses on the mixing of silicon fine powders having different primary and secondary collected particle size distributions, but the primary collected silicon fine powders or secondary collected silicon fine powders have independent particle sizes. As long as the void filling effect as described above can be exhibited by itself, it may be possible to mold each of these alone.

On the other hand, in order to omit the pretreatment process for removing impurities and to provide a high-purity polysilicon raw material seed, the silicon fine powder mixing of this step is also performed in a state of preventing various contamination.

In one embodiment, the silicon fine powder is mixed as described above is transferred to the reservoir 10 and again to the meter (11) to be weighed by a certain amount, the silicon powder molding apparatus 12 for the next step to manufacture the molded body Is transferred to.

d) forming step

This step is a step for easily melting the silicon fine powder mixed in the mixing step into a silicon molded body directly without a pretreatment process for removing the surface oxide. In the present invention, the preceding steps are performed in a state in which oxidation or contamination by air is prevented, and the silicon fine powder is molded directly into the silicon powder molding apparatus 12 without undergoing a separate pretreatment process for removing impurities. Can be prepared.

There is no particular limitation on the silicon powder molding apparatus 12 and the method which can be used, and it can shape | mold using the apparatus and method generally used in the art. For example, various methods such as a mechanical uniaxial load method, a high frequency induction heating sintering method, and a cold hydrostatic pressure molding method may be used, but cold isostatic pressing without using a binder to prevent impurities from flowing into the manufactured silicon molded body. Most preferably).

In addition, in the cold hydrostatic molding, the molding pressure is preferably 2,000 to 5,000 bar, more preferably 3,000 to 4,000 bar, from the viewpoint of improving the density and strength of the formed body.

e) melting, spraying and recrystallization steps

This step is a step of melting, spraying and recrystallizing the silicon molded product produced in the molding step to produce silicon particles with a size of 200 ~ 500㎛. In order to be used as the granular polycrystalline polysilicon raw seed, the silicon particles should have a size of about 200 to 500 μm, and the silicon particles finally prepared according to the present invention at 200 to 500 μm may be directly reused as raw material seeds of the same process. There is an advantage that it can.

In one embodiment, in this step, the silicone molded product produced in the molding step is continuously charged and melted in the crucible 13 attached to the high pressure spray and recovery device 14, and then contaminated through the nozzle with a high pressure inert gas. With lower recovery device equipped with prevention and cooling device Sprayed to recrystallize to finally produce the polysilicon raw seed.

In a preferred embodiment, the nozzle for spraying the melt uses a nozzle made of at least one of silicon carbide (SiC) and silicon nitride (Si ₃ N ₄ ). The silicon is melted at about 1410 ° C. The use of the material can minimize contamination of the impurities into the recrystallized raw material seed without contaminating the silicon even at such high temperatures.

On the other hand, according to another aspect of the present invention, there is provided a raw material seed for producing particulate polycrystalline polysilicon produced by the method of the present invention as described above. The polysilicon raw material seed of the present invention relates to a raw material seed used in a granular polycrystalline polysilicon manufacturing process, but may be applied as a raw material for producing a general polysilicon ingot if appropriate additional processing is performed.

1: fluid bed reactor
2: seed (hopper)
3: cyclone
4: bag filter
5: Bag filter capture fine powder storage silo
6: Cyclone Capture Fine Powder Storage Silos
7: Bag filter capture fine powder meter
8: Cyclone Capture Fine Powder Meter
9: mixer
10: Mixed fine powder storage silo
11: Mixed fine powder weighing machine
12: powder molding machine
13: crucible
14: high pressure spray and recovery device

Claims (10)

a) filtering the silicon fine powder produced in the preparation of particulate polycrystalline polysilicon using a fluidized bed reactor over the first and second steps to separate and collect the silicon fine powder having different particle size distributions;
b) transferring the first and second collected silicon micropowders to a reservoir in an environment where oxidation by air contact is prevented;
c) mixing the transferred silicon fine powder in a state where contamination is prevented;
d) directly preparing the mixed silicon fine powder into a silicon molded body without a pretreatment process for removing surface oxides; And
e) melting, spraying, and recrystallizing the prepared silicon molded body to produce silicon particles having a size of 200 to 500 μm.
Method for producing a raw material seed (seed) for producing a particulate polycrystalline polysilicon comprising a. The particle size of the first collected silicon micropowder is d (0.5) 10 ~ 50㎛, the particle size of the secondary collected silicon micropowder is d (0.5) 1 ~ 10㎛ A method for producing a raw material seed for producing a particulate polycrystalline polysilicon. The method of claim 2, wherein the primary collection is performed in a cyclone and the secondary collection is performed in a bag filter. The method of claim 1, wherein the step b) is carried out in a nitrogen or inert gas atmosphere. According to claim 3, wherein the step c) is a silicon micropowder collected in a cyclone: for producing a particulate polycrystalline polysilicon, characterized in that the mixed silicon fine powder collected in the bag filter in a weight ratio of 1: 1 ~ 3: 1. Process for preparing raw seed. The method of claim 1, wherein the step d) is performed by cold isostatic pressing without using a binder. The method of manufacturing a raw material seed for producing particulate polycrystalline polysilicon according to claim 6, wherein a molding pressure during cold hydrostatic molding is 2,000 to 5,000 bar. The method of claim 1, wherein the step e) is carried out in a crucible attached to the high-pressure spraying and recovering apparatus continuously, and then the contamination prevention and cooling device is installed through a nozzle with a high-pressure inert gas. A method for producing a raw material seed for producing particulate polycrystalline polysilicon, which is sprayed with a lower recovery device and recrystallized. The method of claim 8, wherein the nozzle is made of at least one of silicon carbide and silicon nitride. A raw material seed for producing particulate polycrystalline polysilicon prepared by the method of any one of claims 1 to 9.

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