JPH0829924B2 - Method for crushing high-purity silicon - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for crushing high-purity silicon.

[Conventional technology]

A crushed product of high-purity silicon grows silicon crystal particles by depositing silicon on the surface while keeping the silicon crystal particles in a fluidized state by injecting an inorganic silane gas or an inorganic silane gas and hydrogen gas and / or an inert gas. In the method (fluidized bed method), it is used as seed silicon crystal particles. or,
It is also used as a raw material for single crystals by the Czochralski method.

A method for producing high-purity silicon by the fluidized bed method is disclosed in US Pat.
It is publicly known as shown in 2,861, 3,012, 861 and the like.
As one of the typical methods, a reduction reaction or thermal decomposition of the precursor gas is performed on the surface of silicon crystal particles held in a fluid state by hydrogen gas or an inert gas and a precursor gas such as chlorosilane gas or monosilane gas. There is a method of depositing silicon by reaction to grow silicon crystal grains. According to this method, the reaction surface is granular silicon as compared with the conventional bell jar reaction method, so that there is an advantage that the surface area per unit reaction volume is enormously increased and the productivity is remarkably improved. Further, if seed silicon particles having a small particle diameter are continuously supplied and the grown silicon particle having a large particle diameter is continuously extracted, continuous operation becomes possible and the production efficiency is remarkably improved. Furthermore, since the produced silicon is granular, it has an advantage that when it is melted for single crystallization, it can be used as it is without the need of a crushing step which may cause contamination. As described above, the production of granular silicon by the fluidized bed method is expected to have various advantages, and thus vigorous development and research have been carried out at various places and numerous proposals have been made.

However, the method for producing high-purity silicon by the fluidized bed method includes some problems that must be solved.

One of them is how to produce seed silicon particles having a small particle size used for one of them, and in particular, how to obtain seed silicon particles of a small particle analyzer from silicon particles having a large particle size. Conventionally, as a method of obtaining small particle size silicon from large particle size silicon, a method of mechanically crushing large particle size silicon with a roll crusher to classify the obtained powder or granules with a sieve or in a jet gas atmosphere There is known a method in which silicon particles having a large particle diameter are charged and pulverized by violent collision of particles, and the obtained powder or granules are classified by a wind sieving method.

Further, a method of producing high-purity silicon by the bell jar method is a method of supplying a mixture of chlorosilanes and hydrogen or monosimmon gas to a bell jar type reactor to deposit and grow silicon on rod-shaped silicon that has been electrically heated to obtain rod-shaped silicon. The rod-shaped silicon thus obtained is pulverized to an appropriate size and used as high-purity silicon seed particles as a raw material for producing a single crystal by the Czochralski method. As a conventional crushing method used in the production of these seed particles, a method such as a hammer is used to mechanically apply a violent shock to crush, or a method of rapidly crushing rod-shaped silicon heated to high temperature with water. Is known.

However, these methods have a problem in that the silicon particles are abraded by the violent contact between the apparatus and the apparatus during the crushing and classification, and the product cannot be contaminated. Furthermore, in the conventional method, it is difficult to completely separate the fine particles generated during the crushing process. Therefore, the residual fine powder particles having a large unit area play a bad role as a messenger of impurities to the product.

Further, in the quenching and crushing method using water, reaction of silicon heated to a high temperature with water or dissolved oxygen in water is caused, and product contamination due to oxygen uptake cannot be avoided. Furthermore, contamination by other elements contained in water can be a problem.

[Object of the Invention]

It is an object of the present invention to provide a method for crushing high-purity silicon that minimizes product contamination that occurs during crushing as described above and does not generate fine powder particles.

[Disclosure of Invention]

The present invention is a method for crushing high-purity silicon, which comprises heating heated high-purity silicon in contact with a liquid inert cooling medium to rapidly cool and crush, and preferably heating temperature of high-purity silicon 500 ° C. To a temperature range of 1,600 ° C., preferably a method in which heated high-purity silicon is in the form of particles or a molten liquid, and more preferably a liquid inert cooling medium is a liquefied gas, and Preferably, the method is characterized in that the liquid inert cooling medium is selected from helium, neon, argon, nitrogen and hydrogen.

More specifically, the embodiment of the present invention is 500 ° C.
To high-purity silicon particles, which are particles or a molten liquid heated to a high temperature of about 1,600 to 1,600, are charged into a liquid inert medium, preferably liquid nitrogen or liquid argon, or conversely, to high-purity silicon heated to a high temperature. A method of crushing silicon particles by spraying a liquid inert medium, preferably liquid nitrogen or liquid argon, and quenching. As the silicon particles before crushing used here, product particles manufactured by the fluidized bed method or rod-shaped silicon or crushed silicon manufactured by the bell jar method are used.

The present invention will be described below with reference to the accompanying drawings. FIG. 1 is an apparatus suitable for implementing the present invention. First, high-purity silicon (particles in this case) 2 as a crushing raw material is charged into a heating container 3 in the figure from a supply port 4, and heated by a heating device, for example, a heater 6 for heating. In order to prevent the product from being contaminated, the heating container used is preferably made of silicon silicon carbide, glassy carbon, quartz or silicon nitride, at least the inner surface of which is coated with a high-purity silicon layer. In the present invention, high-purity silicon particles are heated to a high temperature, but the heating drop rate is 500
℃ to 1600 ℃ can be applied. Therefore, more preferably, it is 800 ° C. to the melting temperature of silicon particles. When heated above the melting temperature of silicon, the raw material silicon will of course melt and become liquid. If the heating temperature is lower than 500 ° C, the crushing effect due to rapid cooling cannot be expected, and conversely, if it exceeds 1600 ° C,
The energy required for heating only increases unnecessarily, which is not economically preferable. The use of even higher heating temperatures is free. In addition, 1 is an inlet of an inert gas such as argon gas, and 5 is an outlet.

Then, when the high-purity silicon particles 2 are heated to the above-mentioned predetermined temperature, the opening / closing plate 9 is operated to remove the heated silicon particles 2 from the silicon particle extracting pipe 7 into the liquid inert cooling medium 8. It is dropped into the filled receiver 10 and brought into contact with the liquid inert cooling medium to quench it. In addition, 12 is the inert medium inlet. Of course, when the heating temperature is equal to or higher than the melting temperature of silicon, the silicon particles are molten and are dropped as droplets. The liquid inert cooling medium used here is preferably a liquefied gas and is selected from liquefied gases such as liquid helium, neon, argon, nitrogen and hydrogen. Argon and nitrogen are preferable in view of economy.
In addition, 11 is an inert gas outlet.

Thus, the particles of high-purity silicon or the molten liquid that have been dropped and contacted with the liquid inert cooling medium are rapidly cooled (in the case of a molten liquid, cooled and solidified), and immediately crushed into small-diameter particles.

Incidentally, in some cases, some particles that are not crushed to particles of a small diameter remain, but according to the present invention, cracks due to rapid cooling are contained inside the particles, and a slight impact after removal from the receiver, for example, a fluidized bed The silicon particles can be easily crushed into small particles only by keeping the silicon particles in a fluidized state by an inert gas or the like.

Further, FIG. 2 shows an example of heating in the heating container 23 to a temperature above the melting temperature of silicon as described above. Molten silicon 22 is dropped from the nozzle 29 as droplets 33, It shows the state of rapid crushing. The other reference numerals in FIG. 2 correspond to corresponding portions in FIG. 1 and will not be particularly described.

The method shown in FIGS. 1 and 2 is merely an example,
Of course, the present invention is not limited to these.

〔effect〕

Although the method of the present invention is much simpler in equipment and operation as compared with the conventional method, the obtained crushed particles are also particles of high purity with substantially no contamination from the crushing step. That is why.

Further, in the obtained small particle size silicon after crushing, there is substantially no fine powder particle silicon, so when used as seed particles in the fluidized bed method, it is necessary to classify with a sieve or a wind sieve. There is no.

(Example-1) As shown in FIG. 1, a heating container 3, a receiver 10, a silicon particle extracting pipe 7, and silicon carbide whose inner surface was coated with high-purity silicon.
The opening / closing plate 9 was created and used. The specifications of the main equipment are shown below.

Heating container 30 mm inside diameter, 500 mm high height Receiver 100 mm inside diameter, 500 mm high height Silicon extraction tube 10 mm inside diameter, 100 mm height Product silicon particles manufactured by the fluidized bed method, 200 g of silicon particles with a particle size of 800 μm to 1300 μm from the supply port 4 A heating container was charged, and the gas inside the heating container was replaced by supplying argon gas from the inlet 1. Then, the heating heater 6 was used to heat the silicon particles until the temperature of the silicon particles reached 900 ° C. Argon is supplied to the receiver as a liquid at a dose of about 1/3 of the receiver volume, and after confirming the gas replacement in the silicon particle extraction tube 7 and the receiver, the opening / closing plate 9
Was operated to extract 200 g of silicon particles in about 30 minutes, dropped into liquid argon and rapidly crushed. Liquid argon was replenished several times on the way to adjust the level. As a result of measuring the particle size of the dropped silicon particles, most of them (170 g) were crushed into particles of 100 μm to 300 μm, and 30 g of particles of 300 μm or more were present. Therefore, by further placing the particles of 300 μm or more in a jet flow state with argon gas for 10 minutes, all the particles were easily made to be 100 μm to 300 μm.

(Example-2) A crushed rod-shaped silicon produced by the bell jar method has a particle size of 800.
The same experiment was conducted except that 200 g of silicon particles having a size of 1 μm to 1300 μm was used. As a result of measuring the particle size of the crushed silicon particles, most of the particles (180 g) are 100 μm to 300 μm.
It was crushed to a size of μm, but there were 20 g of particles of 300 μm or larger. Therefore, by further placing the particles of 300 μm or more in a jet flow state with argon gas for 10 minutes, all the particles easily became 100 μm to 300 μm.

(Example-3) The same experiment as in Example-1 was carried out except that the heating temperature of the particles in the heating container was 1,200 ° C. After crushing the crushed silicon particles with argon gas for 10 minutes under a jet flow condition, the particle size of the silicon particles was measured, and all the particles were 100 μm to 300 μm.
It was crushed to m.

(Embodiment 4) A heating container 23, a receiver 30, a molten silicon extraction pipe 27, and a nozzle port 29 as shown in FIG. 2 were manufactured and used with silicon carbide whose inner surface was coated with high-purity silicon. The main equipment specifications were a nozzle diameter of 2.0 mm, a molten silicon extraction tube inner diameter of 10 mm, and a length of 100 mm. The other device specifications were the same as in Example-1. Product made by fluidized bed method Silicon particles with a particle size of 800 μm to 1,300
100 g of silicon particles of μm were charged into the heating container 23 through the supply port 24, and the gas inside the heating container was replaced by supplying argon gas from 21. Thereafter, the heating heater 26 was used to heat the silicon particles to 1,500 ° C. to melt them. The molten silicon becomes droplets 33 from the nozzle port 29, passes through the molten silicon extraction pipe 27 sufficiently replaced with nitrogen gas, and receives the liquid nitrogen 28 in the receiver 30.
It was dripped at and rapidly crushed. Liquid nitrogen was replenished several times on the way to adjust the level of liquid nitrogen in the receiver. After the dropped silicon particles were placed in a jet flow state with argon gas for 10 minutes, the particle size of the silicon particles was measured. As a result, all the dropped particles were crushed to 100 μm to 300 μm.

[Brief description of drawings]

1 and 2 are schematic diagrams showing an apparatus suitable for carrying out the present invention.

Claims (8)

[Claims] 1. A method for crushing high-purity silicon, which comprises bringing heated high-purity silicon into contact with a liquid inert cooling medium, rapidly cooling and crushing. 2. The heating temperature of high-purity silicon is 500 ° C. to 1,600 ° C.
The crushing method according to claim 1, wherein the crushing method is in the temperature range of. 3. The method according to claim 1, wherein the heated high-purity silicon is in the form of particles. 4. The method according to claim 1, wherein the heated high-purity silicon is a molten liquid. 5. The method according to claim 1, wherein the liquid inert cooling medium is a liquefied gas. 6. The liquid inert cooling medium is helium, neon,
A method according to claim 5 selected from argon, nitrogen and hydrogen. 7. The method of claim 6 wherein the liquid inert cooling medium is argon or nitrogen. 8. A method according to claim 1, wherein the crushed silicon particles are suitable for use as seed silicon crystal particles.