JPH05319990A - Production of granular silicon raw material - Google Patents

Abstract

PURPOSE:To obtain a high-purity granular silicon raw material by subjecting a granular silicon raw material containing impurities to purifying treatment. CONSTITUTION:A dissolving treating liquid 4 capable of dissolving both silicon and silicon dioxide is introduced into a cylindrical container 1 housing granular polysilicon 2 having >=0.1mum grain diameter and all the granular polysilicon is kept in a substantially immersed state to carry out the dissolving and washing treatment. The discharge of the dissolving treating liquid and introduction of the wash liquid are performed while maintaining the substantially immersed state of the granular silicon. The granular polysilicon is washed and then dried. Thereby, the granular polysilicon in its housed state in the cylindrical container is subjected to the purifying treatment to produce the objective granular silicon raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granular silicon raw material, particularly a granular polycrystal (poly) used as a raw material in the Czochralski method (hereinafter, CZ method) applied to the production of silicon wafers for semiconductor devices. The present invention relates to a method for manufacturing silicon.

[0002]

2. Description of the Related Art The production of a silicon single crystal by the CZ method is
For each ingot, a block of polysilicon is filled in a crucible, the block of polysilicon is heated and melted by a carbon heater or the like, a seed crystal is dipped in the melt and pulled up while rotating.

However, in order to prevent the crucible and the like from being increased in size with the increase in the diameter and length of the single crystal ingot, a large amount of massive polysilicon is filled in the crucible at one time. Attempts have been made to continuously feed 2-3 mm of granular polysilicon into a crucible and pull up a large single crystal ingot.

Such granular polysilicon raw material is generally manufactured by a fluidized bed reaction method. However, the granular polysilicon raw material manufactured by such a conventional manufacturing method has impurities such as dust adhering to the surface thereof, impurities in the natural oxide film that naturally occur on the surface of the raw material, and impurities existing inside the raw material. Therefore, many of the silicon single crystal ingots manufactured using such a polysilicon raw material have many impurities, and many crystal defects cannot be put to practical use. Therefore, it has been attempted to remove the impurities on the surface of a granular polysilicon raw material as a raw material by placing it in a container such as a beaker or a bucket and adding an acid such as hydrofluoric acid and stirring the mixture.

[0005]

However, such a conventional treatment hardly shows an improvement in the purity of the granular polysilicon raw material. Therefore, a high-purity granular silicon raw material has been required as a raw material for manufacturing a defect-free silicon single crystal ingot.

Therefore, an object of the present invention is to provide a method for producing a granular silicon raw material, which is capable of obtaining a high-purity granular silicon raw material by subjecting a granular silicon raw material containing impurities to a purification treatment.

[0007]

Means for Solving the Problem The means for solving the problem provided by the present invention is capable of dissolving both silicon and silicon dioxide in a cylindrical container containing granular silicon having a particle size of 0.1 μm or more. The dissolution treatment liquid is introduced, and all the contained granular silicon is immersed and subjected to the dissolution cleaning treatment, and then the dissolution treatment liquid is discharged and the cleaning liquid is introduced while maintaining the immersion state substantially for cleaning. The method for producing a granular silicon raw material is characterized in that the granular silicon is dried after the above.

Another solution to the problem provided by the present invention is that, in the method for producing a granular silicon raw material, an oxide film is grown on the surface of the granular silicon in a cylindrical container before the solution cleaning treatment. A method for producing a granular silicon raw material, which is characterized by performing a treatment.

Still another solution provided by the present invention is, in the method for producing a granular silicon raw material, a dry cleaning treatment is carried out by introducing hydrogen chloride gas into a cylindrical container before the dissolution cleaning treatment. A method for producing a granular silicon raw material characterized by the above.

In the present invention, an aqueous solution of a mixture of hydrofluoric acid and nitric acid (HF + HN) is used as a solution capable of dissolving both silicon and silicon dioxide used for the dissolution cleaning treatment.
O3 + H2O), or the one with hydrochloric acid added (H
An acid-based solution such as F + HNO3 + H2O + HCl) is preferably used.

In addition, when the granular silicon raw material is dried, it is preferable to introduce an inert gas or purified air into the cylindrical container from the viewpoint of cleaning and improving throughput. As these drying gases, high-purity nitrogen gas is preferable in terms of purity and preventing unnecessary growth of an oxide film on the surface of the silicon raw material. These drying gases can be heated if necessary before being introduced into the container, whereby the drying time can be shortened.

[0012]

In the above means, the high-purity granular silicon raw material is manufactured by being purified while being housed in the cylindrical container. It is preferable that the cylindrical container is substantially sealed. By sealing, it is possible to prevent contamination by dust in the air or formation of an oxide film containing impurities by oxygen in the air. Further, when performing a gas cleaning treatment with hydrogen chloride gas, it is necessary to hermetically seal.

By introducing a dissolution treatment liquid capable of dissolving both silicon and silicon dioxide into a cylindrical container accommodating the silicon raw material and substantially immersing the contained granular silicon raw material, the silicon raw material surface The native oxide film and a part of the silicon body under the oxide film are dissolved to remove impurities adhering to or contained in the silicon raw material. Then, the dissolution treatment liquid is discharged to the outside of the cylindrical container and the cleaning liquid is introduced into the container while the immersion state of the silicon raw material is substantially maintained. Thereby, the impurities eluted in the dissolution treatment liquid are discharged out of the container. This is achieved by introducing and discharging the cleaning liquid to the extent that impurities can be prevented from redepositing on the treated silicon raw material.

What is important here is that the treatment is started after the discharge of the dissolving treatment liquid or the introduction of the washing liquid until the liquid in the container is replaced with the washing liquid to the extent that re-adhesion of dissolved impurities can be prevented. That is, the silicon raw material is not exposed to air (atmosphere inside the container). When the silicon raw material is exposed to air, a natural oxide film is formed. Then, the impurities eluted into the solution by the solution cleaning process are taken into the natural oxide film, and it becomes impossible to manufacture a high-purity silicon raw material. Even if the atmosphere in the container is replaced with a non-oxidizing atmosphere, the impurities are also redeposited when exposed to the atmosphere and dried, so that a high-purity silicon raw material cannot be manufactured.

An oxide film growth treatment may be performed on the surface of the granular silicon raw material before the introduction of the dissolution treatment liquid. As a result, the impurities existing in the silicon raw material particles are trapped in the oxide film formed and grown by the oxide film growth process. By removing this oxide film by dissolution cleaning treatment, impurities existing not only on the surface but also inside the silicon raw material particles can be removed or reduced. The oxide film growth treatment can be performed by introducing heated clean air, preferably heated gas containing oxygen, into the cylindrical container.

Impurities such as Fe and Cr contained in the silicon raw material can be removed by introducing hydrogen chloride gas into the cylindrical container and performing a dry cleaning process before introducing the dissolution treatment liquid. ..

The oxide film growth treatment and the dry cleaning treatment may be carried out if necessary, but by carrying out both of them, it is possible to manufacture a silicon raw material of higher purity.

A heating device provided outside the cylindrical container may be used as a means for heating the gas introduced when the oxide film is grown, or the dry cleaning process is performed, or when the film is dried after washing, or the cylindrical container is used. For example, a Si plate having a plurality of holes may be housed in the upper part of the, and the Si plate may be heated by high-frequency heating to heat the introduced gas.

As a cylindrical container suitable for carrying out the present invention, a column-shaped container having a flow rate adjusting valve for discharging gas or liquid at the bottom of the container is used. The discharge port can also be used for discharging the processing gas in the oxide film growth process or the dry cleaning process.

Further, as the material of the cylindrical container, it is preferable to use a material which is not corroded by the dissolution treatment liquid and which can prevent contamination from the container. However, considering the cost and the easiness of achieving high purity, etc. , Quartz, Teflon, SiC, Si ₃ N ₄ ,
A material made of Si or Si-impregnated SiC is used.

In the dissolution cleaning treatment or the cleaning treatment of the present invention, the dissolution treatment liquid or the cleaning liquid may be retained in the cylindrical container for the treatment, or the discharge amount and the supply amount of the solution from the bottom of the container may be adjusted. The silicon raw material may be adjusted to maintain the immersion state. Also, as a method of discharging the dissolution treatment liquid and introducing the cleaning liquid while maintaining the substantially immersed state, a column having a discharge port with a valve at the bottom of the container is used, and the opening of the valve is adjusted while introducing the cleaning liquid. Then, a method of discharging the dissolution treatment liquid is used.

In the present invention, the final cleaning is completed,
It is unavoidable that a natural oxide film is formed when the silicon raw material is exposed to air after the cleaning liquid is discharged, but since the atmosphere is cleaned by the cleaning liquid, it is possible to minimize the uptake of impurities. it can.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a purifying apparatus used for carrying out a method for producing a granular silicon raw material according to an embodiment of the present invention.

Example 1 First, a column 1 (inner diameter: 40) made of high-purity quartz glass was used.
mm, length 160 mm, internal volume 200 ml)
g of granular polysilicon 2 (particle size 0.2 to 1.5 mm) was accommodated. A hydrofluoric acid-based solution is used as the dissolution treatment solution, and a required amount (100 ml) of the hydrofluoric acid-based dissolution treatment solution 4 supplied from an acid solution tank (not shown) through the liquid conduit 3 is injected from above the column 1, The flow rate adjusting valve 5 at the bottom of the column 1 is opened to allow the hydrofluoric acid-based dissolution treatment solution 4 to be used for the required time (1
After performing a dissolution cleaning process by adjusting so as to discharge in 0 minute), a required amount (100 ml) of pure water (cleaning liquid) supplied through a liquid conduit 3 from a pure water tank (not shown) is placed above the column 1. Was poured in, and all the pure water was discharged over the required time (10 minutes) to wash with water.

During the switching from the dissolution cleaning to the water cleaning, pure water is injected before the hydrofluoric acid-based dissolution treatment liquid 4 reaches the polysilicon layer so that the upper portion of the granular polysilicon 2 does not touch the air. Started.

Then, the cleaning water is discharged and is supplied from a gas tank (not shown) through the gas conduit 6 and is also installed in the gas conduit 6 and the heating device 8.
The N ₂ gas which had been dust-removed and heated (120 ° C.) was introduced from above the column 1 to dry the granular polysilicon 2.

The composition of the dissolution treatment liquid was changed as shown in Table 1,
The amount of impurities contained in the granular polysilicon obtained by the method for producing the granular silicon raw material is shown in Table 1 which also shows that of the granular polysilicon before purification.

[0028]

[Table 1]

Therefore, impurities, especially F
It can be seen that e and Ni can be greatly reduced.

Furthermore, 5 g of the granular polysilicon after the purification treatment was put into 100 ml of pure water, and when the number of suspended particles of 2.0 μm or more was measured with a submerged particle counter, it was 7; It was found that the dust can be significantly reduced, while the number is 1000.

Comparative Example 1 In the case of Example 1, except that when the dissolution cleaning was switched to the water cleaning in Example 1, pure water was injected after the dissolution processing solution was completely discharged from the cylindrical container. The procedure was repeated. In Comparative Example 1, the particulate polysilicon was exposed to air during the switching from the dissolution cleaning to the water cleaning.

The composition of the dissolution treatment liquid was changed as shown in Table 2, and the amount of impurities contained in the obtained granular polysilicon raw material is shown in Table 2.

[0033]

[Table 2]

The purity of the granular polysilicon raw material used is higher in Fe and Ni than that used in Example 1. Nevertheless, it can be seen that the purity of the treated granular silicon raw material is worse than that in Example 1. Moreover, it can be seen that, depending on the composition of the dissolution treatment liquid, the amount of impurities contained in the dissolution treatment liquid is higher than that before the treatment. It is thought that this is because impurities contained in the reagent were trapped by the silicon particles.

Further, in the conventional method using a bucket or beaker, in addition to the contact with air as in Comparative Example 1, the environment is open to impurities contained in dust floating in the air. The purity cannot be expected to improve.

Example 2 First, as in Example 1, a column 1 made of high-purity quartz glass was filled with 10 g of granular polysilicon 2 and then the porous Si stored in the upper part of the column 1 was filled. A disk (not shown) is heated to a temperature of 600 to 1000 ° C. by high frequency heating, the flow rate control valve 5 is opened, and clean air or oxygen removed from a gas tank (not shown) through the gas filter 7 of the gas conduit 6 is removed. An inert gas containing is introduced from above the column 1 through the Si disk,
An oxide film growth treatment was previously performed on the surface of the granular polysilicon particles to form an oxide film having a required thickness on the surface of the granular polysilicon particles.

Then, a required amount (100 ml) of the hydrofluoric acid-based dissolution treatment liquid 4 supplied from an acid solution tank (not shown) through the liquid conduit 3 is injected from above the column 1 and the time is required (80 minutes). After the liquid amount adjusting valve 5 of the column 1 is adjusted so as to discharge the solution and the column is dissolved and washed, the required amount supplied from the pure water tank (not shown) through the liquid conduit 3 so that the granular polysilicon 2 does not come into contact with the air ( 100 ml) of pure water (cleaning liquid) was injected from above the column 1, and the flow rate adjusting valve 5 was adjusted so that the dissolution treatment liquid 4 was discharged within a required time (50 minutes), followed by washing with water.

Finally, the cleaning water is discharged, and a gas filter 7 and a heating device 8 which are supplied from a gas tank (not shown) through the gas conduit 6 and are provided in the gas conduit 6 are also provided.
The granular polysilicon 2 was dried by introducing an inert gas such as N ₂ or Ar, which had been dust-removed and heated (120 ° C.) or clean air, from above the column 1.

The amount of impurities contained in the granular polysilicon obtained by this purification method is shown in Table 3 together with that of the granular polysilicon obtained by the method of Example 1.
It came to be shown in.

[0040]

[Table 3]

Therefore, it is understood that by forming an oxide film on the surface of the granular polysilicon particles before the dissolution cleaning, impurities in the particles are trapped in the oxide film, so that the purity can be further improved.

In each of the above embodiments, the case where the column is made of quartz glass has been described, but the present invention is not limited to this, and the column is made of Teflon, SiC, or Si that is not affected by the hydrofluoric acid-based solution. ₃ N ₄ , Si impregnated SiC
The same effect was obtained by using the one consisting of.

[0043]

As described above, according to the method for producing a granular silicon raw material of the present invention, since the granular silicon raw material is purified and produced while being housed in the cylindrical container, there is a chance of contamination. It is possible to obtain a high-purity product with a reduced amount of water, and it is possible to perform a large amount of processing relatively easily, and it is possible to automate without requiring skill in operation.
Further, by performing the oxide film growth process before the dissolution cleaning process, the impurities in the particles are trapped in the oxide film,
The purity can be further increased. Furthermore, by performing a dry cleaning process before the dissolution cleaning process, impurities such as Fe and Cr contained in the silicon raw material can be removed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a purifying device used for carrying out a method for producing a granular silicon raw material according to an embodiment of the present invention.

[Explanation of symbols]

 1 column (cylindrical container) 2 granular polysilicon 3 liquid conduit 4 dissolution treatment liquid 5 flow control valve 6 gas conduit 7 gas filter 8 heating device

Claims (3)

[Claims] 1. A dissolution treatment liquid capable of dissolving both silicon and silicon dioxide is introduced into a cylindrical container containing granular silicon having a particle size of 0.1 μm or more to remove all of the contained granular silicon. Granules characterized by performing a dissolution cleaning treatment in a substantially immersed state, then discharging the dissolution treatment solution and introducing a cleaning solution while maintaining a substantially immersed state to perform cleaning, and then drying the granular silicon. Manufacturing method of silicon raw material. 2. The method for producing a granular silicon raw material according to claim 1, wherein, before the dissolving and cleaning treatment, a treatment for growing an oxide film on the surface of the granular silicon in the cylindrical container is performed. Raw material manufacturing method. 3. The method for producing a granular silicon raw material according to claim 1, wherein hydrogen chloride gas is introduced into the cylindrical container to perform a dry cleaning treatment before the dissolution cleaning treatment. Production method.