JP2003002626A - Reaction apparatus for producing silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing silicon having a silicon precipitation zone and a silicon dropping zone and suitable for recovery of fused silicon liquid as drops from the precipitation zone. SOLUTION: The manufacturing apparatus has the tip part of a dropping zone made of silicon nitride for dropping deposited silicon in a deposition zone, in order to recover fused silicon liquid as drops.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor for producing silicon. More specifically, the present invention relates to a reactor for producing silicon for recovering silicon as molten droplets. [0002] Conventionally, various methods for producing silicon used as a raw material for semiconductors or wafers for photovoltaic power generation have been known, and some of them have already been industrially practiced. For example, one of them is a method called a Siemens method, in which a silicon rod heated to a deposition temperature of silicon by energization is placed inside a bell jar, and trichlorosilane (SiHCl ₃ , hereinafter, referred to as TCS) is placed therein.
And monosilane (SiH ₄ ) together with a reducing gas such as hydrogen to precipitate silicon. [0003] This method is characterized in that high-purity silicon can be obtained, and it is practiced as the most general method. However, since the deposition is of a batch type, the seeding silicon rod is installed and the silicon rod is There is a problem that extremely complicated procedures such as heating, deposition, cooling, removal, and cleaning of the bell jar must be performed. As another method, Japanese Patent Application Laid-Open No. Sho 59-162117 discloses that a matrix composed of silicon nitride particles heated to a temperature equal to or higher than the melting point of silicon is prepared, and a silicon-containing gas mixture is flowed into the matrix to form silicon nitride particles. A method for depositing molten silicon on a surface is disclosed. The publication states that silicon nitride is a suitable material for depositing silicon at a temperature higher than the melting point of silicon, and that silicon nitride is wetted by silicon, so that silicon flows down through the silicon nitride particle bed and reacts. It is disclosed that it can be collected at the bottom of the vessel. [0004] An object of the present invention is to provide a silicon production reactor used in a method for producing silicon different from the conventional method as described above.
Another object of the present invention is to provide a reaction apparatus for producing silicon, which is provided with a heating element of silicon, and allows silicon produced by the heating element to flow down as a melt and be recovered as droplets. . Still other objects and advantages of the present invention will become apparent from the following description. According to the present invention, the above object and advantages of the present invention are to provide a heating element that reacts chlorosilanes with hydrogen to produce silicon, and that causes the produced silicon to flow down as a melt and drop from the lower end. The present invention is attained by a silicon production reactor provided with a silicon nitride as a material of a lower end portion of the heating body. The production apparatus of the present invention includes a heating element that reacts chlorosilanes with hydrogen to generate silicon, causes the generated silicon to flow down as a melt, and drops from the lower end thereof. As a typical example of the reaction apparatus for producing silicon of the present invention, an apparatus as shown in FIG. 1 of the accompanying drawings, which uses a cylindrical vessel as a heating element, can be mentioned. That is, the reactor for producing silicon shown in FIG. 1 has (1) a cylindrical container 1 having an opening 2 at the lower end thereof serving as a silicon outlet, and (2) a cylindrical container 1 having an arbitrary height from the lower end of the cylindrical container 1. Heating means 3 for heating the inner wall to a temperature equal to or higher than the melting point of silicon; (3) chlorosilane provided so as to open downward in a space 4 surrounded by the inner wall heated to a temperature equal to or higher than the melting point of silicon And a seal gas supply pipe 7 for supplying a seal gas to a space inside the cylindrical container above the opening position of the chlorosilanes supply pipe 5. As will be described in detail later, the cylindrical container 1 has an opening 2 through which silicon precipitated and melted can fall out of the container by natural flow as described later in detail.
What is necessary is just a structure which has. Accordingly, the cross-sectional shape of the cylindrical container 1 is circular,
Any shape such as a polygon can be adopted. In addition, the cylindrical container 1 may be formed in a straight body shape having the same sectional area as shown in FIG.
In order to increase the residence time of the reaction gas and improve the conversion rate of chlorosilanes to silicon (hereinafter, also simply referred to as conversion rate), a part of the cross section may be formed to have a shape larger than other parts. It is suitable. On the other hand, the manner of opening the opening 2 in the cylindrical container 1 may be either a straight opening as shown in FIG. 1 or a narrowed portion formed such that the diameter gradually decreases downward. But it's fine. [0008] In the above device, the opening 2 of the cylindrical container 1
Corresponds to the lower end of the heating element. The heating element is a cylindrical container 1
Is formed by heating the inner wall from the lower end to an arbitrary height above the melting point of silicon, where silicon is generated and flows down as a melt. The apparatus of the present invention is characterized in that a lower end of the heating body is made of silicon nitride. The lower end of the heating element is made of silicon nitride, as shown in FIG. 2, the lower end 2 ′ of the cylindrical container 1, or as shown in FIG. And '' only. In the embodiment shown in FIG. 2, a lower end 2 'of the cylindrical container 1 is provided.
The upper portion 4 'and in the embodiment of FIG. 3 the outer wall 4''can be of any suitable material other than silicon nitride, for example silicon carbide or carbon. By forming the lower end of the heating element using silicon nitride as a raw material, the silicon melt flowing down the heating element can be easily collected and allowed to fall as droplets to be collected. When the lower end 2 'of the cylindrical container 1 is made of silicon nitride and the upper part 4' is made of another material, the deposition of silicon is promoted on the wall surface of the upper part 4 'and the lower end 2' is made of silicon nitride. The silicon precipitated from the portion 2 'can be reliably dropped as a molten droplet. In addition, as shown in FIGS. 1 to 3, silicon can be obtained as droplets without any problem in a mode in which the opening portion of the cylindrical container 1 is configured so that the peripheral edge thereof is horizontal as shown in FIGS. In this embodiment, the peripheral edge is inclined, and further, the peripheral edge is formed in a wavy shape as shown in FIG. 5, thereby making it easier for silicon droplets to fall from the peripheral edge of the opening 2. This is preferable because the droplets of the silicon melt can be aligned and the particle size of the silicon particles can be adjusted to be smaller and more uniform. The heating element of the cylindrical container 1 is heated to 1430 ° C. or higher, and its inner wall comes into contact with chlorosilanes or a silicon melt. It is desirable to select a material that can withstand the above in order to stably produce silicon for a long period of time. Such materials are partially described above. For example, carbon materials such as graphite, silicon carbide (SiC), silicon nitride (Si
₃ N ₄ ), boron nitride (BN), aluminum nitride (Al
Single materials or composite materials of ceramic materials such as N). Among these, silicon nitride or boron nitride is particularly good in the ease of flowing down the silicon melt because these materials have poor wettability to the silicon melt. In the reactor for producing silicon shown in FIG.
The cylindrical container 1 is provided with a 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 to form a heating body. The width for heating 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 depends on the size of the cylindrical container, the heating temperature, and
What is necessary is just to determine suitably considering the amount of chlorosilanes supplied, etc. As the heating means 3, any known means can be employed without particular limitation as long as it can heat the inner wall of the cylindrical container to the melting point of silicon or more, that is, 1430 ° C. or more. As a specific heating means, as shown in FIG. 1, there is a method of heating the inner wall of the cylindrical container by external energy. More specifically, there are a method using a high frequency, a method using a heating wire, a method using an infrared ray, and the like. Of these methods, the method using high frequency is simple while simplifying the shape of the heating coil that emits high frequency.
Because the cylindrical container can be heated to a uniform temperature,
It is suitable. In the reactor for producing silicon shown in FIG.
The chlorosilanes supply pipe 5 is provided in the space 4 surrounded by the inner wall existing in the heating body of the cylindrical container 1.
And is provided so as to open downward in the space 4. The term “downward” indicating the opening direction of the chlorosilanes supply pipe 5 is not limited to the vertical direction, but includes all modes in which the supplied chlorosilanes are opened so as not to come into contact with the opening again. But,
The most preferred embodiment is an embodiment that opens in a direction perpendicular to a plane. The chlorosilanes supply pipe 5 is provided in the space 4.
Cooling means 6 for cooling the inner wall of the tube to a temperature lower than the self-decomposition temperature of the chlorosilane so that the inside of the tube is heated so that silicon is not deposited due to thermal decomposition of the chlorosilane.
It is preferable to have The cooling mode may be any mode as long as the object can be achieved. For example, as shown in FIG. 1, a flow path 6 through which a refrigerant liquid such as water or heat transfer oil can pass.
A liquid jacket method of providing and cooling, not shown, a double pipe nozzle or more is provided in the chlorosilanes supply pipe, a chlorosilane is supplied from the center, and a cooling gas is purged from the outer pipe nozzle. An air-cooled jacket system that cools the center nozzle is exemplified. The cooling temperature of the chlorosilanes supply pipe may be set to a temperature lower than the decomposition temperature of the chlorosilanes to be supplied.
When iCl ₄ (hereinafter referred to as STC) is used as a raw material, it is preferably 800 ° C. or less, more preferably 600 ° C.
The temperature is most preferably set to 500 ° C. or less.
As the material of the chlorosilanes supply pipe 5, in addition to the same material as that of the cylindrical container 1, quartz glass, iron, stainless steel, or the like can be used. The seal gas supply pipe 7 is provided for supplying a seal gas to a space above the opening position of the chlorosilane supply pipe 5. The chlorosilanes supplied as a raw material to the cylindrical container are used to prevent solid silicon from being deposited in the cylindrical container due to decomposition of the chlorosilanes before reaching the space for precipitation and melting. The chlorosilanes are directly supplied to the high-temperature space. At this time, the temperature gradient from the melting temperature of silicon to a temperature lower than the deposition temperature of silicon on the wall surface located above the opening position of the supply pipe 5 for the chlorosilanes. When chlorosilanes or a mixed gas of chlorosilanes and hydrogen described below is reached, silicon precipitates and grows at a temperature where silicon is deposited in a solid state, and a silicon production reactor In long-term operation of
The problem of closing the device arises. To solve the above problem, the seal gas is provided above the opening position of the chlorosilanes supply pipe 5 so that the seal gas fills the space where the temperature gradient exists, and the chlorosilanes or chlorosilanes are described later. Of mixed gas with hydrogen can be prevented, and the deposition of the solid silicon can be effectively prevented. The sealing 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 produce silicon and does not adversely affect the production of silicon in a region where chlorosilanes exist. Specifically, an inert gas such as argon or helium, hydrogen, or the like can be used, but hydrogen, which is one of the raw materials, is preferable. In this case, it is sufficient that the supply amount of the sealing gas is such that the pressure that always fills the space where the temperature gradient exists is maintained. To reduce the supply amount, the entire space or the lower part of the space is required. The shape of the cylindrical container 1 or the shape of the outer wall of the chlorosilane supply pipe may be determined so as to reduce the cross-sectional area. In the reactor for producing silicon of the present invention, hydrogen provided for a precipitation reaction together with chlorosilanes is
As described above, the supply is preferably performed from the seal gas supply pipe 7, but a supply pipe is provided separately from the chlorosilanes supply pipe 5, which is opened at a position where the supply can be performed to the space 4 of the cylindrical container 1. It is also possible. The chlorosilanes used in the present invention include TCS, STC, dichlorosilane (SiH ₂ Cl ₂ ), monochlorosilane (Si
H ₃ Cl) and hexachlorodisilane (Si ₂ C)
chlorodisilanes typified by l _6), more chlorotrimethylsilane silanes represented by octa chlorotrifluoroethylene silane (Si ₃ Cl ₈₎ can be suitably used. These chlorosilanes can be used alone or as a mixture with one another. Of these chlorosilanes, the use of chlorosilanes containing TCS or STC as a main component can reduce the generation of silicon fine powder and ignitable high-boiling silanes (polymers) which adversely affect the gas downstream region. ,
This is preferable because stable operation can be performed for a longer time. FIG.
In the reactor for producing silicon of the above, the opening 2 at the lower end of the cylindrical container 1 is provided with a drop zone composed of a space cut off from the outside air for recovering the silicon melt that melts and falls without contacting the outside air. Has a room to give. The space 22 into which the silicon melt falls is connected to a gas discharge port 26 and, if necessary, a cooling recovery chamber 20 provided with an outlet 31 for the silicon solidified by cooling. The cooling / recovering chamber 20 can be provided directly at the opening 2 of the cylindrical container 1. However, a temperature gradient is generated from such a connection point, and a point where the temperature at which solid silicon is deposited at the upper part of the cooling / recovering chamber is reached. Is likely to be present. However, the chlorosilanes present in the gas discharged from the cylindrical container 1 are approaching a stable gas composition in which no more silicon is deposited, and the amount of chlorosilanes even if deposited is small. However, in order to almost completely prevent solid silicon from being deposited in the cooling recovery chamber 20 and to enable continuous operation for an extremely long period of time, as shown in FIG. By setting the connection portion to the upper part to a position covering the heating means 3 of the cylindrical container 1, the lower end of the heated cylindrical container 1 and the inner wall of the cooling and collecting chamber 20 are provided apart from each other, It is preferable that the seal gas supply pipe 21 is provided in a space above the opening position of the opening 2 of the cylindrical container 1 to supply the seal gas. The type and supply amount of the sealing gas can be determined in the same manner as when the sealing gas is supplied to the sealing gas supply pipe 7. In particular, in order to sufficiently exert 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, and most preferably 0.1 m / s. / S or more. As the material of the cooling / recovering chamber 20, any of metal, ceramic, glass and the like can be suitably used. Further, it is more preferable that the inside of the metal recovery chamber is lined with silicon, Teflon (registered trademark), quartz glass or the like. Silicon particles can be spread on the bottom of the cooling and recovery chamber 20. 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 that has melted and dropped from the cylindrical container 1 falls down in the space 22 of the cooling / recovery chamber 20, accumulates as silicon 23 that has been cooled and solidified, and is accumulated in the lower part of the chamber, and is cooled to a temperature that is easy to handle. When the cooling space is set to be long, solidified silicon is obtained, and when the cooling space is short, solid silicon plastically deformed by the impact of drop is obtained. In the present invention, it is possible to obtain silicon in any shape, but it is preferable to obtain silicon in a small particle form for ease of handling. In order to promote the above cooling,
Providing a cooling gas supply pipe 32 is a preferred embodiment. The cooling and recovery chamber 20 may be provided with an outlet 31 for extracting solidified silicon continuously or intermittently as required. In order to more effectively cool the silicon, it is preferable to provide a cooling jacket 24 in the cooling recovery chamber 20.
Cooling is performed by passing a coolant liquid such as water, heat medium oil, or alcohol through the cooling jacket 24. When the cooling recovery chamber 20 is extended to the upper part to cover the heating means as in the embodiment shown in FIG. 1, the cooling medium 27 such as a heat transfer oil may be circulated in an appropriate jacket structure to protect the material. You can also
If the material has heat resistance, a heat insulating material may be provided to keep the temperature in order to enhance the heat effect. While the apparatus of the present invention has been described above with respect to the embodiment using a cylindrical container forming a cylindrical heating element, the apparatus of the present invention has an inverted conical, rod, U-shaped, V-shaped heating element. The present invention can be applied to a device having a heating element having an arbitrary shape such as a letter shape, and it is needless to say that the same effect is exerted. The silicon production conditions using the silicon production reactor of the present invention are not particularly limited, but chlorosilanes and hydrogen are supplied to the silicon production reactor, and the conversion of the chlorosilanes to silicon is increased. Is 20%
As described above, the supply ratio, supply amount, residence time, and the like of chlorosilanes and hydrogen are determined so as to generate silicon under a condition of preferably 30% or more. It can be effectively prevented and is preferable. For example, the molar fraction of the chlorosilanes in the feed gas is 0.1 to 200 mol%, preferably 5 to 50 mol%, so that the economical silicon production rate with respect to the size of the reaction vessel can be improved. Preferred to obtain.
A higher reaction pressure has the advantage that the apparatus can be reduced in size, but a reaction pressure of about 0 to 1 MPaG is preferable because it is easy to carry out industrially. The residence time varies depending on the conditions of pressure and temperature for a reaction vessel having a fixed volume. Under the reaction conditions, the average residence time of the gas in the cylindrical vessel which is the reaction vessel is as follows. 0.001 to 60 seconds, preferably 0.1 to 60 seconds.
If the time is set to 01 to 10 seconds, a sufficiently economical conversion rate of chlorosilanes can be obtained. As will be understood from the above description, according to the present invention, silicon is generated in a heating element, and the generated silicon is used as a melt to improve liquid drainage from the lower end thereof.
Drops can be reliably dropped and collected as droplets, and a method for continuously producing silicon can be stably performed over a long period of time. It is extremely useful industrially and its value is extremely high. EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Example 1 The reactor for producing silicon shown in FIG. 1 was manufactured as described below to continuously obtain granular silicon. A cross-sectional structure shown in FIG. 2 having an inner diameter of 25 mm, a length of 50 cm, and an opening 2 in the lower part (2 ′ including the lower end of the heating body is made of silicon nitride,
Other portions 4 'are made of silicon carbide. ) Cylindrical container 1
(However, the periphery of the lower end was formed as shown in FIG. 4).
A high-frequency heating coil was installed. A stainless steel chlorosilanes supply pipe 5 having an outer diameter of 17 mm and having a jacket structure capable of passing liquid as shown in FIG. 1 was inserted to a height of 15 cm from the upper end of the cylindrical container. The cooling recovery chamber 20 was made of stainless steel having an inner diameter of 500 mm and a length of 3 m. Water is passed through the cooling jacket of the chlorosilanes supply pipe to maintain the inside of the pipe at a temperature of 50 ° C. or lower, and water is also passed through the lower jacket of the cooling and recovery chamber 20.
5 L of hydrogen gas was supplied from the hydrogen gas supply pipe 7 at the upper part and the seal gas supply pipe 21 at the upper part of the cooling / recovery chamber 20 respectively.
After the circulation, the high-frequency heating device was activated to heat the cylindrical container 1 to 1500 ° C. The pressure in the vessel was approximately atmospheric. Trichlorosilane was supplied to the chlorosilane supply pipe 5 and hydrogen was supplied from the seal gas supply pipe 7 to produce silicon. As a result of the production of silicon by the above method, the size of the droplet falling from the lower end of the heating element is extremely uniform, and does not grow excessively, and is approximately 5 mm.
Droplets of the size Furthermore,
After the reaction was continued for 50 hours, the operation was stopped and the inside of the apparatus was observed open. As a result, no clogging with silicon occurred. Comparative Example 1 Silicon was produced in the same manner as in Example 1 except that the material of 2 ′ including the lower end of the heating element in the cylindrical container was changed from silicon nitride to silicon carbide. As a result, there is some variation in the size of the silicon melt droplet that falls from the lower end of the heating body,
Droplets which grew abnormally to about mm and fell were observed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing a typical embodiment of a reactor for producing silicon of the present invention. FIG. 2 is a conceptual diagram showing a typical mode of a cross-sectional structure of a lower end portion of a cylindrical container of the reactor for producing silicon of the present invention. FIG. 3 is a conceptual diagram showing another representative embodiment of the cross-sectional structure of the lower end of the cylindrical container of the reactor for producing silicon of the present invention. FIG. 4 is a conceptual diagram showing a shape of a peripheral edge of a lower end of a cylindrical container of the reactor for producing silicon of the present invention. FIG. 5 is a conceptual diagram showing a shape of a peripheral edge of a lower end of a cylindrical container of the reactor for producing silicon of the present invention. [Description of Signs] 1 Cylindrical container 3 Heating means 5 Chlorosilane supply pipe 6 Cooling means 7, 21 Seal gas supply pipe (hydrogen gas supply pipe) 20 Cooling recovery chamber 24 Cooling jacket 26 Gas exhaust line 31 Silicon outlet 32 Cooling Gas supply pipe

Claims (1)

Claims: 1. A reaction apparatus for producing silicon comprising a heating element for reacting chlorosilanes with hydrogen to produce silicon, flowing down the produced silicon as a melt, and dropping it from a lower end. A reaction apparatus for producing silicon, wherein a material of a lower end portion of the heating body is silicon nitride.