JP3958092B2 - Reactor for silicon production - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reactor for producing silicon for producing silicon by reaction of chlorosilanes with hydrogen. More specifically, the present invention relates to a silicon production reactor that recovers silicon produced by a reaction via a highly reactive silicon melt.
[0002]
[Prior art]
Conventionally, various methods for producing silicon used as a raw material for a semiconductor or a battery for photovoltaic power generation 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, and trichlorosilane (SiHCl ₃ , hereinafter referred to as TCS) or monosilane (SiH ₄ ) is placed on the silicon rod. ) In contact with a reducing gas such as hydrogen to deposit silicon.
[0003]
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, 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.
In JP-A-62-2619, a reaction flame of halogen and hydrogen is emitted toward a starting material having at least a surface of polycrystalline silicon or SiO ₂ , and a silicon raw material compound is supplied into the flame. A method for producing silicon is disclosed in which silicon is deposited on the surface of a starting material, and the deposited silicon is melted and dropped. Since molten silicon has a very high reactivity, in this publication, when trying to obtain high-purity silicon, not only the surface of the starting material but also the diffusion of impurities from the inside is prevented to prevent the entire starting material. Is preferably made of high purity silicon.
[0004]
In Japanese Patent Laid-Open No. 54-124896, silicon is formed by bringing a silicon molten bath into contact with a mixture of silane chloride and hydrogen, thereby replenishing the silicon molten bath, while the solidified state is increased from the bottom of the molten bath. A method for producing a high-purity polycrystalline silicon rod, in which crystalline silicon is drawn into a rod shape, is disclosed. As a material for a molten bath container, a material such as opaque quartz, silicon nitride or quartz, boron nitride, graphite or the like coated with silicon nitride or silicon oxynitride is disclosed.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to enable continuous operation for a long period of time, when a silicon is produced from chlorosilane and hydrogen via a silicon melt, and the portion in contact with the silicon melt is made of a material having low reactivity with the silicon melt. Is to provide a simple reaction apparatus.
Another object of the present invention is to provide a reaction apparatus capable of continuous operation for a long time, including a member suitable for high-frequency induction heating and having low reactivity with a silicon melt, particularly in a silicon production apparatus using high-frequency induction heating. There is.
Still other objects and advantages of the present invention will become apparent from the following description.
[0006]
[Means for Solving the Problems]
According to the present invention, the above-mentioned objects and advantages of the present invention are a reactor for generating silicon that reacts chlorosilanes with hydrogen to generate silicon, and recovers the generated silicon via a silicon melt, inner surface of the device in contact with the silicon melt is achieved by thermal decomposition coal hydrogenation Ranaru silicon generation reactor.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The silicon reaction apparatus of the present invention may be any type of reaction apparatus as long as it is a reaction apparatus for producing silicon by reacting chlorosilanes and hydrogen as starting materials. As the reaction apparatus of the present invention, an apparatus using high frequency induction heating is particularly preferable.
[0008]
Such a reactor is preferably
(1) A cylindrical container having an opening serving as a silicon outlet at the lower end;
(2) A heating means capable of heating the inner wall from the lower end of the cylindrical container to an arbitrary height to a temperature equal to or higher than the melting point of silicon,
(3) Provided with a cooling means provided so as to open downward in a space surrounded by the inner wall heated to a temperature equal to or higher than the melting point of the silicon, and maintaining the inner wall below the silicon deposition temperature. A chlorosilane supply pipe, and (4) a seal gas supply pipe for supplying a seal gas to the space inside the cylindrical container at a position above the opening of the chlorosilane supply pipe.
Silicon produced by the reaction of chlorosilanes and hydrogen flows down in a state where a part or all of the inner wall of the cylindrical container is melted, and falls from a silicon outlet located at the lower end.
[0009]
Hereinafter, it will be described in more detail with reference to the accompanying drawings.
In the silicon manufacturing apparatus of FIGS. 1 to 3, the cylindrical container 1 is deposited as the silicon outlet, as will be described in detail later. What is necessary is just a structure which has the opening part 2 which can fall in. Therefore, the cross-sectional shape of the cylindrical container 1 can take arbitrary shapes, such as circular shape and polygonal shape. Moreover, when enlarging a cylindrical container, in order to improve heating efficiency without increasing the distance between the wall surfaces used as a heating surface, it is a preferable aspect to make the cross-sectional shape flat.
In order to make the cylindrical container 1 easy to manufacture, the cylindrical container can be formed in a straight cylinder shape with the same cross-sectional area as shown in FIGS. 1 to 3, and the residence time of the reaction gas can be increased. In order to improve the conversion rate of chlorosilanes to silicon (hereinafter, also simply referred to as conversion rate), it is also preferable that a part of the longitudinal cross section as shown in FIG. 4 is made larger than the other part. is there.
[0010]
On the other hand, the opening method of the opening 2 in the cylindrical container 1 may be a mode in which the opening is straight as shown in FIG. 1 or a mode in which the throttle portion is formed so that the diameter gradually decreases downward. But you can.
In addition, the opening of the cylindrical container 1 obtains particulate silicon without any problem even in a configuration in which the periphery is horizontal, but in a configuration in which the periphery is inclined as shown in FIG. As shown in FIG. 6, it is possible to adjust the particle size of the silicon particles more uniformly by arranging the silicon melt droplets falling from the periphery of the opening 2 by arranging the periphery in a wave shape. This is preferable because it is possible.
[0011]
Furthermore, in any of the shapes of the peripheral edge of the opening described above, it is a more preferable embodiment that the melted silicon has a blade shape that gradually decreases in thickness toward the tip in order to improve the liquid drainage at the time of dropping. .
Since the cylindrical container 1 is heated to a temperature higher than the melting point of silicon and the inside thereof is in contact with chlorosilanes and silicon melt, it is long to select a material having high durability against these temperature conditions and contact objects. This is desirable for stable silicon production.
[0012]
In the present invention, the inner surface of the tubular container in contact with the silicon melt, pyrolysis coal hydrogenation Ranaru. That is, this material has high durability even in a high temperature environment where hydrogen, chlorosilanes, and silicon melt coexist, effectively preventing the silicon melt from penetrating into the carbon base material, and destroying the carbon base material. To prevent it. On the other hand, these materials are not suitable materials for high-frequency induction heating, and are preferably used in combination with a carbon material which is a suitable material. For example, the cylindrical container is made using a carbon material such as carbon or graphite as a base material, and at least an inner surface thereof is covered with the material. These inner surface materials can be directly coated on the carbon material by the CVD method. However, the inner surface material can be used by being inserted into the cylinder after being molded to match the inner wall of the cylindrical container. In consideration of permeation of the silicon melt, the inner surface material in contact with the silicon melt preferably has a thickness of 1 μm or more.
Pyrolytic carbon of the inner surface material, contamination of the silicon obtained is not very small.
[0013]
In the silicon manufacturing apparatus, 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. It can be determined as appropriate.
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. There are various views on the melting point of silicon, but it should be understood that it is generally in the range of 1410 ° C to 1430 ° C.
[0014]
As a specific example of the 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, a 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.
In the silicon manufacturing apparatus, 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 before and after the melting point of silicon. Are provided so as to open downward.
[0015]
The “downward direction” indicating the opening direction of the chlorosilane supply pipe 5 is not limited to the vertical direction, and includes all modes in which most of the supplied chlorosilanes are opened so as not to contact the opening again. In a preferred embodiment, for example, the opening angle of the supply pipe 5, that is, the opening wall of the supply pipe 5 is preferably opened so that the angle from the vertical direction upward in the vertical cross section is 0 to 60 °.
The chlorosilanes supply pipe 5 is provided for cooling the inner wall of the pipe below the chlorosilane self-decomposition temperature so that the inside of the pipe is heated in the space 4 and silicon deposition due to thermal decomposition of the chlorosilanes does not occur. It is necessary to have the cooling means 6.
[0016]
Any cooling mode 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.
Cooling temperature of the chlorosilane feed pipe, but determined to be less than the self-decomposition temperature of the supplied chlorosilanes, when using TCS or silicon tetrachloride (SiCl _4, hereinafter referred to as STC) as a raw material, preferably not more than 800 ° C. More preferably, it is 600 ° C. or less, and most preferably 500 ° C. or less.
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.
[0017]
In the silicon manufacturing apparatus, as shown in FIG. 4, in the aspect in which the enlarged portion is provided in a part of the cylindrical container, it is heated to provide the opening of the chlorosilanes supply pipe in the space of the enlarged portion. It is preferable because the opening can be separated from the inner wall, and cooling for preventing silicon deposition in the chlorosilane supply pipe can be performed more easily.
[0018]
The seal gas supply pipe 7 is provided to supply seal gas to a space existing above the opening position of the chlorosilane supply pipe 5. That is, the chlorosilanes supplied as raw materials to the cylindrical container are decomposed by thermal decomposition of the chlorosilanes until reaching the space for precipitation and melting, and solid silicon is deposited in the cylindrical container. In order to prevent this, chlorosilanes are directly supplied from the chlorosilane supply pipe 5 to the high-temperature space. At this time, on the wall surface located above the opening position of the chlorosilane supply pipe 5, the melting temperature of silicon is increased. There is a temperature gradient that reaches a temperature below the silicon deposition temperature, and there is a portion that is heated above the silicon deposition temperature and not heated above the melting point of silicon. Then, the silicon deposited in the portion grows without being melted, and there is a problem that the device is blocked during the long-term operation of the silicon manufacturing device.
[0019]
To solve the above problem, the seal gas supply pipe 7 is provided above the opening position of the chlorosilanes supply pipe 5, and the space that is not heated above the melting point of silicon and the surface of the base material are filled with the seal gas. It is possible to prevent the mixed gas of hydrogen and hydrogen, which will be described later, from entering, and to effectively prevent the precipitation of the solid silicon.
The seal gas supply pipe 7 is not particularly limited as long as it is above the opening position of the chlorosilane 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 the region where chlorosilanes are present. Specifically, an inert gas such as argon or helium, hydrogen described later, or the like is preferable.
Furthermore, in order to further enhance the effect of the sealing gas, it is a more preferable aspect that a gas capable of etching silicon, such as hydrogen chloride, is appropriately mixed with the sealing gas.
[0020]
In this case, it is sufficient that the seal gas is supplied to such an extent that the space that cannot be heated to the melting point of silicon or higher and the pressure that always fills the surface of the base material is maintained. What is necessary is just to determine the shape of the cylindrical container 1, the shape of the outer wall of a chlorosilanes supply pipe | tube, etc. so that the cross-sectional area of the whole space or the lower part may be made small.
In the silicon manufacturing apparatus, hydrogen used for the precipitation reaction together with the chlorosilanes can be supplied from the chlorosilanes supply pipe 5 by mixing the chlorosilanes in advance and independently from the cylindrical container 1 in the space 4. It is also possible to provide a hydrogen supply pipe 10 that opens at a position where it can be supplied to and supply from there.
[0021]
The hydrogen supply pipe 10 can be appropriately provided at a place where the reaction with the chlorosilane can be efficiently performed in consideration of the structure, size, etc. of the cylindrical container 1 constituting the silicon production apparatus.
Furthermore, part or all of the hydrogen used for the silicon deposition reaction can also be supplied as the sealing gas. As shown in FIG. 2, the hydrogen gas supply pipe 14 also serving as the seal gas supply pipe can be provided above the opening position of the chlorosilane supply pipe 5.
Of course, the amount of hydrogen supplied from the hydrogen supply pipe 14 also serving as the seal gas supply pipe is appropriately determined in consideration of the amount necessary for the reaction.
[0022]
As chlorosilanes used in the present invention, in addition to TCS and STC, chlorodisilanes represented by dichlorosilane (SiH ₂ Cl ₂ ), monochlorosilane (SiH ₃ Cl) and hexachlorodisilane (Si ₂ Cl ₆ ), Chlorotrisilanes represented by octachlorotrisilane (Si ₃ Cl ₈ ) can also be suitably used. These chlorosilanes can also be used alone or as a mixture with one another.
Among these chlorosilanes, the use of chlorosilanes mainly composed of TCS or STC can reduce the generation of silicon fine powder and ignitable high-boiling silanes (polymers) that adversely affect the gas downstream region. Time stable operation is possible, which is preferable.
[0023]
In the silicon manufacturing apparatus, the opening 2 at the lower end of the cylindrical container 1 is a chamber that provides a space that is shut off from outside air for recovering by cooling and solidifying the silicon melt that melts and falls without touching the outside air. Is preferable for industrially obtaining high-purity silicon.
That is, as described in FIG. 3 and FIG. 4 showing a typical aspect thereof, the cooling space 22 in which the silicon melt can fall is formed in the opening 2 corresponding to the silicon outlet of the cylindrical container 1, A silicon manufacturing apparatus to which the gas discharge port 26 and, if necessary, a cooling recovery chamber 20 provided with a silicon outlet 31 that is solidified by cooling is connected is preferable.
[0024]
The cooling recovery chamber 20 can be directly provided in the opening 2 of the cylindrical container 1, but a temperature gradient is generated from the connection location, and a temperature at which solid silicon is deposited at the upper portion of the cooling recovery chamber. Is likely to exist. However, the chlorosilanes present in the gas discharged from the cylindrical container 1 are approaching a stable gas composition that no longer deposits silicon, and even if deposited, the amount is small.
[0025]
However, in order to substantially prevent solid silicon from being deposited in the cooling recovery chamber 20 and to enable continuous operation over an extremely long period of time, as shown in FIGS. 3 and 4, the cylindrical container of the cooling recovery chamber 20 is used. 1 is set upward to a position that covers the heating means 3 of the cylindrical container 1, thereby providing the lower end of the heated cylindrical container 1 and the inner wall of the cooling recovery chamber 20 apart from each other, A mode in which the seal gas is supplied by providing the seal gas supply pipe 21 in a space above the opening position of the opening 2 of the cylindrical container 1 is preferable.
[0026]
The type, supply amount, and the like of the seal gas can be determined in the same manner as when the seal gas is supplied to the seal gas supply pipe 7.
In the above aspect, in order to sufficiently exhibit the effect of the seal gas, the linear velocity of the seal gas flowing around the cylindrical container 1 is at least 0.1 m / s, preferably 0.5 m / s, most preferably Is preferably 1 m / s or more.
As the material of the cooling recovery chamber 20, any of metal materials, ceramic materials, glass materials, and the like can be suitably used. However, in order to achieve both robustness as industrial equipment and recovery of high-purity silicon, It is more preferable to line the inside of the recovery chamber with silicon, heat-resistant ceramics, Teflon (registered trademark), quartz glass, or the like.
On the other hand, the exhaust gas after the reaction in the cylindrical container 1 is taken out from the gas outlet 26.
[0027]
The silicon that has been partially or wholly melted and dropped from the cylindrical container 1 is accumulated in the lower part of the chamber as the silicon 23 that is cooled and solidified while falling in the cooling space 22 of the cooling recovery chamber 20, and reaches a temperature that is easy to handle. To be cooled. In the case of silicon that is completely melted, granulated silicon is obtained when the cooling space is set long, and solid silicon that is plastically deformed by the impact of dropping is obtained when the cooling space is short. The silicon deposited on the lower part of the apparatus can be crushed into a granular material as necessary.
In order to promote cooling when the molten silicon falls, it is preferable to provide a cooling gas supply pipe 32.
Further, the cooling recovery chamber 20 may be provided with an outlet 31 for extracting the solidified silicon continuously or intermittently as required.
[0028]
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 FIGS. 3 and 4, when the cooling recovery chamber 20 is extended upward to cover the heating means, a cooling medium 27 such as a heat transfer oil is appropriately provided with a jacket structure for protecting the material. If the material has heat resistance, it can be kept warm by applying a heat insulating material to enhance the heat effect.
[0029]
The silicon production conditions using the silicon production apparatus of the present invention are not particularly limited, but chlorosilanes and hydrogen are supplied to the silicon production apparatus, and the conversion rate from the chlorosilanes to silicon is 10% or more, preferably Determining the supply ratio, supply amount, residence time, etc. of chlorosilanes and hydrogen so that silicon is generated under conditions of 30% or more effectively prevents the precipitation of solid silicon in the cooling recovery device This is preferable. For example, the molar fraction of chlorosilanes in the pre-feed gas is 1 to 90 mol%, preferably 5 to 50 mol% in order to obtain an economical silicon production rate with respect to the size of the reaction vessel. Is preferable.
Moreover, although the one where reaction pressure is higher has the merit that an apparatus can be reduced in size, about 0-1 MPaG is easy to implement industrially and preferable.
[0030]
The residence time varies depending on the pressure and temperature conditions with respect to a certain volume of the reaction vessel. Under the reaction conditions, the average residence time of the gas in the cylindrical vessel as the reaction vessel is 0.001 to 0.001. By setting the time to 60 seconds, preferably 0.001 to 10 seconds, particularly preferably 0.001 to 1 second, a sufficiently economical conversion rate of chlorosilanes can be obtained.
[0031]
【The invention's effect】
As understood from the above description, according to the present invention, an apparatus for producing high-purity silicon capable of continuous operation for a long period of time is provided. This device is extremely useful industrially and its value is extremely high.
[0032]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples.
[0033]
Example 1
The silicon manufacturing apparatus shown in FIG. 3 was used.
A carbon tubular container 1 coated with pyrolytic carbon with a thickness of 50 μm by CVD, having an inner diameter of 25 mm, a length of 50 cm, and a shape having an opening 2 in the lower part is placed around the upper 10 cm position to the lower end. A high frequency heating coil was installed as the heating means 3. 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 capable of passing liquid as shown in FIG. 2 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 150 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.
[0034]
Water is supplied to the cooling jacket 6 of the chlorosilane supply pipe 5 to maintain the inside of the pipe at 50 ° C. or lower, and is also supplied to the lower jacket 24 of the cooling recovery chamber 20 to supply hydrogen gas at the upper part of the cylindrical container 1. Hydrogen gas was circulated at 5 L / min from the pipe 14 and the seal gas supply pipe 21 at the top of the cooling recovery chamber 20, respectively, and then the high-frequency heating device was started to heat the cylindrical container 1 to 1,500 ° C. The pressure in the container was almost atmospheric pressure.
Reactive hydrogen and trichlorosilane were mixed and supplied to the chlorosilanes supply pipe 5 at a rate of 20 L / min and 10 g / min, respectively. As a result, silicon was obtained at a rate of about 0.6 g / min. In this case, the conversion rate of trichlorosilane was about 30%. After the reaction was continued for 50 hours, the operation was stopped and the carbon cylindrical container was observed, and there was no deterioration due to silicon.
Moreover, the contamination of silicon by pyrolytic carbon was extremely low at 1 ppm or less.
[0035]
Comparative Example 1
The operation was carried out under the same conditions as in Example 1 except that a carbon cylindrical container without coating was used on the cylindrical container of Example 1. After the reaction was continued for 50 hours, the operation was stopped and the carbon cylindrical container was observed. As a result, there was a portion where the thickness of the carbon cylindrical container was reduced by several micrometers due to deterioration.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a typical embodiment of a silicon manufacturing apparatus of the present invention.
FIG. 2 is a conceptual diagram showing another typical aspect of the silicon manufacturing apparatus of the present invention.
FIG. 3 is a conceptual diagram showing still another representative aspect of the silicon manufacturing apparatus of the present invention.
FIG. 4 is a conceptual diagram showing still another typical aspect of the silicon manufacturing apparatus of the present invention.
FIG. 5 is a conceptual diagram showing the shape of the periphery of the lower end of the cylindrical container of the silicon manufacturing apparatus of the present invention.
FIG. 6 is a conceptual diagram showing the shape of the periphery of the lower end of the cylindrical container of the silicon production apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical container 3 Heating means 5 Chlorosilane supply pipe 6 Cooling means 7, 21 Seal gas supply pipe 8, 14 Hydrogen gas supply pipe 20 Cooling recovery chamber 24 Cooling jacket 26 Gas discharge line 31 Silicon outlet 32 Cooling gas supply pipe

Claims (4)

Reactor for generating silicon by reacting chlorosilanes and hydrogen to generate silicon, and recovering the generated silicon via the silicon melt, and the inner surface of the device in contact with the silicon melt is thermally decomposed. coal hydrogenation Ranaru silicon generation reactor.   The apparatus of claim 1, wherein the inner surface is molded onto the surface of the carbon substrate. The apparatus of claim 1 the thickness of the pyrolytic carbon-containing constituting the inner surface is 1μm or more.   The apparatus according to claim 1, wherein the inner surface is formed by a CVD method.

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