JP4099322B2 - Method for producing silicon - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for producing silicon. Specifically, in a reactor equipped with a heating body heated to a melting point of silicon or more, when silicon is generated and recovered as a silicon melt from the heating body, silicon is prevented from being precipitated as a solid in the apparatus. This is a silicon manufacturing method for this purpose.
[0002]
[Prior art]
Conventionally, various methods for producing silicon used as a raw material for semiconductors or photovoltaic power generation batteries are known, some of which have already been industrially implemented.
For example, one of them is a method called a Siemens method, in which a silicon rod heated to the deposition temperature of silicon by energization is placed inside a bell jar, where trichlorosilane (SiHCl ₃ , hereinafter referred to as TCS) or monosilane (SiH ₄ ). Is deposited with a reducing gas such as hydrogen to deposit silicon.
This method is characterized in that high-purity silicon can be obtained, and is implemented as the most general method, but since precipitation is batch-type, the installation of a silicon rod as a seed, the current heating of the silicon rod, There is a problem that extremely complicated procedures such as precipitation, cooling, taking out, and cleaning of a bell jar must be performed.
[0003]
In contrast to the above method, there is a deposition method using a fluidized bed as a method for continuously producing silicon. In this method, a fluidized bed is used, while supplying silicon fine particles of about 100 μm as precipitation nuclei, supplying the above-mentioned silanes to deposit silicon on the silicon fine particles, and continuously extracting the silicon particles as 1-2 mm. Is the method. This method is characterized in that it is not necessary to stop the reaction in order to extract silicon, and a relatively long continuous operation is possible.
[0004]
However, in an embodiment that is industrially implemented by this method, since monosilane having a low precipitation temperature is used as a silicon raw material, generation of fine silicon by thermal decomposition of the monosilane or reaction even at a relatively low temperature range Silicon deposition or the like tends to occur on the vessel wall, and it is necessary to periodically clean or replace the reaction vessel. In addition, since the silicon particles in the middle of precipitation in a fluidized state violently contact and rub against the reactor wall for a long time, there remains a problem in the purity of the produced silicon.
As a continuous silicon production method capable of avoiding problems in the fluidized bed method, there is a method in which silicon is generated and deposited on the surface of a heating body, and the silicon is continuously recovered from the heating body as a melt. .
[0005]
For example, in Japanese Patent Application Laid-Open No. 11-314996, a high frequency coil is disposed opposite to the lower surface of a heating element, the heat generating solid is induction-heated by the high frequency coil, and silicon source gas is blown thereto to deposit silicon. And an apparatus for producing silicon crystals by forming a molten liquid and dropping or flowing a silicon molten liquid. In addition, an outer cylinder surrounding the heating element is provided along the periphery of the side surface of the heating element, an inert gas is allowed to flow as a sealing gas between the heating element and the outer cylinder, and the silicon deposition temperature on the heating element or its surrounding wall There has also been disclosed a device for preventing polycrystalline silicon precipitation caused by a raw material gas flowing around a portion (hereinafter also referred to as a low temperature portion) having a temperature lower than the melting point of silicon.
[0006]
Although this technique can reduce the precipitation of polycrystalline silicon at low temperature sites, it is difficult to completely prevent silicon precipitation. For example, due to the drift of the seal gas and the insufficient flow rate of the seal gas, the raw material gas circulates to the low temperature region, and once silicon is deposited, it grows, causing problems such as blocking of the raw material gas supply nozzle.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing silicon that can prevent silicon from being deposited in a low temperature region of the reactor and can produce silicon industrially and stably.
Other objects and advantages of the present invention will become apparent from the following description.
[0008]
[Means for Solving the Problems]
According to the present invention, the above objects and advantages of the present invention are to produce silicon by supplying chlorosilanes and hydrogen to the heating body in a reactor equipped with a heating body heated to a melting point of silicon or higher. When the produced silicon is recovered as a melt from the heating body, a reaction agent capable of reacting with silicon is continuously or intermittently applied to a portion of the apparatus that is higher than the silicon deposition temperature and lower than the melting point of silicon. It is achieved by a method for producing silicon characterized in that it is introduced.
That is, according to the method of the present invention, even when silicon is deposited at a low temperature site, it is possible to remove a part or all of the deposited silicon by introducing a reaction reagent described later into the site, Silicon precipitation and growth at the low temperature region can be effectively prevented, and silicon can be produced industrially stably.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, silicon is produced by reacting chlorosilanes with hydrogen in a reaction apparatus including a heating body heated to a melting point of silicon or higher, and the produced silicon is recovered as a melt from the heating body. It can be applied to the method to do.
The reactor is provided with a specific example which will be described later, and includes a heating body heated to a melting point of silicon or higher, and supplies the heating body with chlorosilanes and hydrogen, which are source gases for generating silicon. Those having the means to do are used without particular limitation.
[0010]
Examples of the chlorosilanes include trichlorosilane (SiHCl ₃ ), silicon tetrachloride (SiCl ₄ ), dichlorosilane (SiH ₂ Cl ₂ ), monochlorosilane (SiH ₃ Cl), and hexachlorodisilane (Si ₂ Cl ₆ ). Preferable examples include chlorodisilanes represented by chlorodisilanes and octachlorotrisilane (Si ₃ Cl ₈ ). These chlorosilanes can be used alone or as a mixture with one another.
In the method of the present invention, the raw material chlorosilanes and hydrogen are supplied to a heating body heated to a temperature equal to or higher than the melting point, and react with the surface to produce silicon, and the silicon melts the inner wall of the heating body. Then, it falls from the lower end and is collected.
[0011]
And when manufacturing silicon using the above-mentioned device, a low-temperature site always exists in the device. That is, the boundary between the part heated by the heating means and the part not heated exists on the inner wall of the apparatus, and the vicinity of this part becomes a low temperature part. Usually, a seal gas is supplied to such a portion to prevent the raw material gas from coming into contact with the inner wall. However, as described above, when the supply of the seal gas to the low temperature portion is insufficient or cut off due to some cause, silicon may be deposited due to the wraparound of the raw material gas.
If the reaction apparatus is operated for a long time in this state, a problem such as blocking of the supply lines for the source gas such as the chlorosilanes supply pipe and the hydrogen supply pipe is likely to occur due to the deposition of solid silicon at a low temperature site. .
[0012]
In the present invention, a reaction reagent capable of reacting with the solid silicon produced at a low temperature site in the reaction system is introduced into the reaction system to cause the silicon to react with the reaction reagent, and as a result, the solid silicon enters the nozzle portion of the reactor. Inconveniences such as deposition and clogging can be avoided.
Examples of the reaction agent that can react with silicon include hydrogen chloride (HCl) and silicon tetrachloride. Hydrogen chloride is diluted with, for example, hydrogen gas, and preferably introduced into a reaction system having a hydrogen chloride concentration of 0.01 to 100% by volume, and the following reaction:
Si + 3HCl → SiHCl ₃ + H ₂
To convert solid silicon (Si) into gas (SiHCl ₃ ). In order for this reaction to proceed smoothly, the hydrogen chloride concentration in the gas atmosphere in the reaction system is maintained at a concentration such that the etching rate is greater than the silicon deposition rate.
[0013]
When silicon tetrachloride (SiCl ₄ ) is mixed with hydrogen, the rate of precipitation reaction is high when the hydrogen molar ratio is large, and the rate of etching reaction is high when the hydrogen molar ratio is low. Moreover, since the value also changes depending on the reaction temperature, it is desirable to use the temperature and the concentration properly depending on the purpose.
In the case of giving priority to etching, at a reaction temperature of 1,400 ° C., for example, diluted with hydrogen gas, and preferably introduced into the reaction system as a mixed gas having a silicon tetrachloride concentration of 30 to 50% by volume, the following reaction:
Si + 3SiCl ₄ + 2H ₂ → 4SiHCl ₃
Similarly, silicon is converted into a gas. Also in this case, the silicon tetrachloride concentration is maintained at such a concentration that the etching rate is higher than the silicon deposition rate so that the reaction proceeds smoothly.
[0014]
The reaction reagent capable of reacting with silicon is continuously or intermittently introduced into the reaction system in consideration of the concentration used, the deposition rate of silicon at low temperature sites, and the like.
The means for introducing the reaction system into the reaction system may be provided with a separate pipe for introducing the reaction reagent into the reaction system in the reaction apparatus, or a seal gas supply pipe for gas-sealing the low-temperature part. It is also possible.
Further, when the reaction reagent is intermittently supplied, the time when the deposited silicon does not interfere with the flow path of the sealing gas, that is, the thickness of the silicon deposited on the inner wall of the reaction apparatus is 10 mm, preferably 2 mm, more preferably 0. It is preferable to introduce the reaction reagent at a time not exceeding 2 mm.
[0015]
The present invention will be described in more detail according to a preferred embodiment of the reactor used in the present invention. FIG. 1 of the accompanying drawings showing one embodiment of the above,
(1) A cylindrical container 1 having an opening 2 serving as a silicon outlet at the lower end;
(2) Heating means 3 for heating the heating body made of the cylindrical container 1 to a temperature equal to or higher than the melting point;
(3) A chlorosilanes supply pipe 5 provided so as to open downward in the space 4 surrounded by the inner wall, and (4) the inside of the cylindrical container above the opening position of the chlorosilanes supply pipe 5 Seal gas supply pipe 7 for supplying seal gas to the space
The reactor comprised from more is shown.
[0016]
In the reactor shown in FIG. 1, a cylindrical container 1 serving as a heating body has, as a silicon outlet, an opening 2 through which silicon deposited and melted can fall out of the container due to natural flow, as will be described in detail later. Have
Since the cylindrical container 1 is heated to 1,430 ° C. or more and the inside thereof is in contact with chlorosilanes or silicon melt, it is long to select a material that can sufficiently withstand these temperature conditions and contact objects. It is desirable for manufacturing silicon with a stable period.
In the silicon manufacturing apparatus of the present invention, the cylindrical container 1 is provided with heating means 3 for heating the peripheral wall from the lower end to an arbitrary height to a temperature equal to or higher than the melting point of silicon. The width to be heated to the above temperature, that is, the height at which the heating means 3 is provided from the lower end of the cylindrical container 1 takes into account the size of the cylindrical container, the heating temperature, and the amount of chlorosilanes to be supplied. What is necessary is just to determine suitably.
[0017]
Any known means can be used as the heating means 3 as long as the inner wall of the cylindrical container can be heated to the melting point of silicon or higher, that is, 1430 ° C. or higher.
As an example of a specific heating means, as shown in FIG. 1, there is a method of heating the inner wall of the cylindrical container with energy from the outside. More specifically, there are a method using high frequency, a method using heating wire, a method using infrared rays, and the like.
Among these methods, the method using high frequency is preferable because the cylindrical container can be heated to a uniform temperature while simplifying the shape of the heating coil that emits high frequency.
[0018]
In the silicon manufacturing apparatus of the present invention, the chlorosilanes supply pipe 5 is for directly supplying the chlorosilanes 11 to the space 4 surrounded by the inner wall of the cylindrical container 1 heated to the melting point of silicon or more. 4 is provided so as to open downward.
The “downward direction” indicating the opening direction of the chlorosilanes supply pipe 5 is not limited to the vertical direction, and includes all modes in which the supplied chlorosilanes are opened so as not to contact the openings again. However, the most preferable mode is a mode in which the aperture opens in the direction perpendicular to the plane.
[0019]
The chlorosilanes supply pipe 5 is cooled to cool the inner wall of the pipe below the self-decomposition temperature of chlorosilane so that the inside of the pipe is heated in the space 4 and silicon does not precipitate due to the thermal decomposition of the chlorosilanes. Means 6 are preferably provided.
Any mode of cooling may be used as long as the object can be achieved. For example, as shown in FIG. 1, a liquid jacket method for cooling by providing a flow path through which a refrigerant liquid such as water or heat transfer oil can be passed inside, although not shown, a chlorosilanes supply pipe is a double pipe An air cooling jacket system in which the above-described multiple ring nozzle is provided, chlorosilanes are supplied from the center, and a cooling gas is purged from the outer ring nozzle to cool the center nozzle.
[0020]
What is necessary is just to set the cooling temperature of a chlorosilanes supply pipe | tube below the self-decomposition temperature of the chlorosilanes supplied. Specifically, when trichlorosilane or silicon tetrachloride (SiCl ₄ , hereinafter referred to as STC) is used as a raw material, it is preferably 800 ° C. or lower, more preferably 600 ° C. or lower, and most preferably 500 ° C. or lower. .
As a material of the chlorosilanes supply pipe 5, in addition to the same material as the cylindrical container 1, quartz glass, iron, stainless steel, and the like can be used.
It is preferable to open the chlorosilanes supply pipe so that the chlorosilanes of the raw material gas are supplied to a high temperature portion of the cylindrical container, that is, a portion where the temperature can be higher than the melting point of silicon.
[0021]
The seal gas supply pipe 7 is not particularly limited as long as it is above the opening position of the chlorosilanes supply pipe 5, but is preferably provided on the wall surface of the cylindrical container where the heating means 3 does not exist. The seal gas supplied from the seal gas supply pipe 7 is preferably a gas that does not generate silicon and does not adversely affect the generation of silicon in a region where chlorosilanes are present. Specifically, an inert gas such as argon or helium, hydrogen described later, or the like is preferable.
A part or a front part of hydrogen which is one of the source gases can be introduced into the reaction system from the seal gas supply pipe 7.
[0022]
In the above reaction apparatus, the terminal part of the reactor wall such as the holding part of the cylindrical container has a large heat dissipation and the temperature tends to decrease. For this reason, on the wall surface close to the holding part, there is a low temperature region in a temperature gradient from the melting temperature of silicon to a temperature lower than the deposition temperature of silicon. And, when the mixed gas of chlorosilanes or chlorosilanes and hydrogen described later reaches such a location due to insufficient supply of the sealing gas, etc., silicon is likely to precipitate and grow, and in the long-term operation of the silicon production apparatus The problem of blocking the device arises.
[0023]
In the apparatus shown in FIG. 1, the problem is likely to occur in a gap formed by the inner wall of the cylindrical heating body and the outer wall of the chlorosilane supply pipe. In this case, by introducing into the reaction system a reaction reagent capable of reacting with silicon from the annular seal gas supply pipe 7 for supplying the seal gas to such a portion together with the seal gas or independently of the seal gas. Precipitation can be prevented. That is, the reaction reagent can be mixed with the sealing gas and continuously supplied, or can be intermittently supplied by switching to the sealing gas.
In the above reaction apparatus, when a low temperature site exists outside the cylindrical container, a reaction reagent capable of reacting with silicon can be introduced from a seal gas supply pipe 21 or a cooling gas supply pipe 32 described later.
[0024]
In the silicon manufacturing apparatus of the present invention, the opening 2 at the lower end of the cylindrical container 1 has a space that is shut off from the outside air for recovering by cooling and solidifying the silicon melt that melts and falls without coming into contact with the outside air. It is preferable to connect the feeding chambers in order to obtain high-purity silicon industrially. As shown in FIG. 1, such a preferable manufacturing apparatus forms a cooling space 22 in which the silicon melt can fall in the opening 2 corresponding to the silicon outlet of the cylindrical container 1, and a gas discharge port 26. And the cooling recovery chamber 20 which provided the extraction port 31 of the silicon | silicone solidified by cooling as needed is provided.
[0025]
In order to prevent the precipitation of solid silicon in the cooling recovery chamber 20 and to enable continuous operation over an extremely long period of time, as shown in FIG. The connecting portion is set upward to a position that covers the heating means 3 of the cylindrical container 1, so that the lower end of the heated cylindrical container 1 and the inner wall of the cooling recovery chamber 20 are spatially separated from each other, At the same time, it is preferable to supply the seal gas by providing the seal gas supply pipe 21 in a space above the opening position of the opening 2 of the cylindrical container 1.
[0026]
When the seal gas is introduced from the seal gas supply pipe, in order to fully exhibit the effect of the seal gas, the linear velocity of the seal gas flowing around the cylindrical container 1 is at least 0.01 m / s, preferably 0.05 m / s, most preferably 0.1 m / s or more.
As a material of the cooling recovery chamber 20, for example, any of a metal material, a ceramic material, a glass material, and the like can be suitably used. It is more suitable to line the inside of the metal recovery chamber with silicon, Teflon (registered trademark), quartz glass, etc. in order to achieve both robustness as industrial equipment and recovery of high-purity silicon. is there.
[0027]
On the other hand, the exhaust gas after the reaction in the cylindrical container 1 is taken out from the gas outlet 26.
The molten silicon melted and dropped from the cylindrical container 1 is accumulated in the lower part of the chamber as the silicon 23 cooled and solidified while falling in the cooling space 22 of the cooling recovery chamber 20 and to a temperature at which it can be easily handled. To be cooled. In the present invention, silicon can be obtained in any shape, but it is preferable to obtain it in a granular form for ease of handling.
In order to promote the cooling, it is preferable to provide a cooling gas supply pipe 32.
[0028]
In addition, the cooling recovery chamber 20 can be provided with an outlet 31 for continuously or intermittently extracting the solidified silicon, if necessary.
In order to cool the silicon more effectively, it is preferable to provide a cooling means 24 in the cooling recovery chamber 20. As the cooling mode, for example, as shown in FIG. 3, a method using a liquid jacket that cools by providing a flow path through which a refrigerant liquid such as water, heat transfer oil, alcohol, etc. can be passed is most preferable.
As shown in FIG. 1, when the cooling recovery chamber 20 is extended upward to cover the heating means, a cooling medium 27 such as heat transfer oil is circulated in an appropriate jacket structure to protect the material. If the material is heat resistant, heat insulation can be applied to keep the heat effective.
[0029]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples.
[0030]
Example 1
The silicon manufacturing apparatus shown in FIG. 1 was used.
A high-frequency heating coil was installed as a heating means 3 around a carbon cylindrical container 1 having an inner diameter of 25 mm and a length of 50 cm and having an opening 2 in the lower part, from the position of the upper part 10 cm to the lower end. A stainless steel chlorosilane supply pipe 5 having an inner diameter of 4 mm and an outer diameter of 20 mm having a jacket structure 6 capable of passing liquid was inserted from the upper end of the cylindrical container to a height of 15 cm. The cooling recovery chamber 20 was made of stainless steel having an inner diameter of 50 mm and a length of 3 m. In addition, the periphery of the lower end of the said cylindrical container was made into the shape shown in FIG.
[0031]
Water is passed through the cooling jacket of the chlorosilane supply pipe to maintain the inside of the pipe at 50 ° C. or lower, and is also passed through the lower jacket of the cooling recovery chamber 20 from the hydrogen gas supply pipe 7 at the upper part of the cylindrical container 1. After mixing and circulating hydrogen gas 5 L / min and hydrogen chloride gas 0.03 L / min, the high-frequency heating apparatus was started and the cylindrical container 1 was heated to 1,500 ° C. The pressure in the container was almost atmospheric pressure.
When trichlorosilane was supplied to the chlorosilanes supply pipe 5 at a rate of 10 g / min, silicon was obtained at a rate of about 0.6 g / min. In this case, the conversion of trichlorosilane was 30%.
After the reaction was continued for 50 hours, the operation was stopped and the outside of the carbon cylindrical container was observed. As a result, no silicon was deposited.
[0032]
Comparative Example 1
The operation was performed under the same conditions as in Example 1 except that the supply of hydrogen chloride gas from the hydrogen gas supply pipe 7 of Example 1 was stopped. After the reaction was continued for 50 hours, the operation was stopped and the outside of the carbon cylindrical container was observed. As a result, silicon deposition was observed.
[0033]
Example 2
Instead of hydrogen and hydrogen chloride gas, a mixed gas of silicon tetrachloride and hydrogen (1% by volume of silicon tetrachloride, 99% by volume of hydrogen) is allowed to flow from the hydrogen gas supply pipe 7 of Example 1 and from the chlorosilane particle supply pipe 5 The operation was performed under the same conditions as in Example 1 except that 15 L / min of hydrogen gas and trichlorosilane were mixed and supplied. After the reaction was continued for 50 hours, the operation was stopped and the outside of the carbon cylindrical container was observed. As a result, no silicon was deposited.
[0034]
Example 3
After performing the same reaction as in Comparative Example 1, 10 volume% of hydrogen chloride gas was added to the hydrogen gas supplied from the Si removal gas supply pipe 21 and the reaction was continued for 5 hours. When the outside of the cylindrical container was observed, no silicon deposition was observed.
[0035]
【The invention's effect】
According to the present invention, it is possible to prevent the nozzle part of the reaction apparatus from being blocked by silicon generated by the reaction between chlorosilanes and hydrogen, and to continue to manufacture silicon smoothly industrially.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a typical aspect of a silicon manufacturing apparatus used in the practice of the present invention. FIG. 2 is a conceptual diagram showing the shape of the peripheral edge of a cylindrical container at the bottom of a silicon manufacturing apparatus according to the present invention. Schematic diagram showing the shape of the periphery of the lower end of the cylindrical container of the silicon manufacturing apparatus in the present invention
DESCRIPTION OF SYMBOLS 1 Cylindrical container 3 Heating means 5 Chlorosilane supply pipe 6 Cooling means 7, 21 Seal gas supply pipe 20 Cooling recovery chamber 24 Cooling jacket 26 Gas discharge line 31 Silicon outlet 32 Cooling gas supply pipe

Claims (2)

In a reactor equipped with a heating body heated to a melting point of silicon or higher, chlorosilanes and hydrogen are supplied to the heating body to generate silicon, and the generated silicon is recovered as a melt from the heating body. A method for producing silicon, wherein a reaction reagent capable of reacting with silicon is continuously or intermittently introduced into a portion of the apparatus that is not lower than the silicon deposition temperature and lower than the melting point of silicon. The method according to claim 1, wherein the reaction agent capable of reacting with silicon is hydrogen chloride or silicon tetrachloride.

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