JP4692324B2 - High purity polycrystalline silicon production equipment - Google Patents

Description

  The present invention relates to an apparatus for producing high-purity polycrystalline silicon that is a raw material for silicon for semiconductors and silicon for solar cells.

  Polycrystalline silicon is used as a raw material for single crystal silicon for semiconductors and as a raw material for silicon for solar cells. In particular, in recent years, with the widespread use of solar cells, the demand for polycrystalline silicon as a raw material has also increased.

  However, as the polycrystalline silicon used as the raw material for silicon for solar cells, scrap products such as the crucible residue after pulling up the single crystal silicon for semiconductors and the cutting scrap of the single crystal silicon ingot are currently used. It is. Therefore, polycrystalline silicon used in solar cells is in a chronic shortage as a result of both the quality and quantity depending on the movement of the semiconductor industry.

Here, the Siemens method is mentioned as a typical manufacturing method of the high purity polycrystalline silicon used as the raw material of the single crystal silicon for semiconductors. In the Siemens method, high-purity polycrystalline silicon is obtained by hydrogen reduction of trichlorosilane (HSiCl ₃ ) (see, for example, Patent Document 1).

In the general Siemens method, a silicon seed rod 50 is installed in a water-cooled bell jar type reactor 30 as in the production apparatus 10 shown in FIG. The rod 50 is heated to about 1000 ° C., and trichlorosilane (HSiCl ₃ ) is placed in the reactor 30.
Then, hydrogen (H ₂ ) as a reducing agent is introduced from below to reduce silicon chloride, and the produced silicon selectively adheres to the surface of the seed rod 50, whereby rod-shaped polycrystalline silicon is obtained. In addition to the advantage that the raw material gas is vaporized at a relatively low temperature, this Siemens method has an advantage on the apparatus that the reactor 30 itself is water-cooled, so that the atmosphere can be easily sealed. Widely spread and adopted.

  However, in the Siemens method, since the seed rod 50 is heated by energization, the rod-like silicon grows due to the adhesion of polycrystalline silicon and the electrical resistance gradually decreases, so that it is necessary to pass excessive electricity for heating. Therefore, there is a growth limit due to the balance with the energy cost, and the production facility is operated batchwise. Therefore, there is a problem that the production efficiency is poor, and the power unit consumption of the product polycrystalline silicon is large.

  Also, the seed rod 50 itself is expensive because special equipment and techniques such as a dedicated reaction device, a single crystal pulling device, and a cutting device are required when producing the seed rod 50. .

As a method for producing polycrystalline silicon other than the Siemens method, for example, there is a method by reduction of silicon tetrachloride (SiCl ₄ ) using a metal reducing agent (see, for example, Patent Documents 2 and 3). Specifically, it is a method of growing polycrystalline silicon in a reactor by supplying silicon tetrachloride and zinc (Zn) gas into a quartz horizontal reactor heated to about 1000 ° C. .

In the above method, by-product zinc chloride (ZnCl ₂ ) is separated into zinc and chlorine by a method such as electrolysis, and the obtained zinc is used again as a reducing agent, and the obtained chlorine is reacted with inexpensive metal silicon. Therefore, if silicon tetrachloride can be synthesized and used as a raw material gas, a circulation type process is established, so that polycrystalline silicon may be manufactured at a low cost.

However, in this method, the polycrystalline silicon obtained by the reaction grows from the reactor wall, so that it is easily affected by contamination from the reactor material. In addition, in the case of this quartz horizontal reactor, the reactor In addition to the problem that it itself breaks due to the difference in thermal expansion coefficient from that of polycrystalline silicon, there is a problem that the production efficiency of polycrystalline silicon is poor.
Japanese Patent No. 2867306 JP 2003-34519 A JP 2003-342016 A

  The present invention has been made in view of the above circumstances, and a high-purity polycrystalline silicon manufacturing apparatus capable of manufacturing high-purity polycrystalline silicon continuously, in large quantities, and relatively inexpensively with a compact structure. It is intended to provide.

  The inventors of the present invention have made extensive studies in order to solve the above problems. As a result, a silicon chloride gas and a reducing agent gas are supplied into a specific vertical reactor, and polycrystalline silicon is generated at the tip of the silicon chloride gas supply nozzle, which is supplied from the tip of the nozzle. It has been found that the above problems can be solved by a method for producing high-purity polycrystalline silicon grown downward. And based on this knowledge, this invention which consists of the following structures was completed.

That is, the high purity polycrystalline silicon manufacturing apparatus according to the present invention is:
A vertical reactor having heating means on the outer peripheral surface;
A silicon chloride gas supply nozzle inserted downward from the top of the vertical reactor; and a reducing agent gas supply nozzle inserted downward from the top of the vertical reactor;
An exhaust gas extraction pipe connected to the reactor,
Polycrystalline at the tip of the silicon chloride gas supply nozzle by a gas phase reaction between the silicon chloride gas introduced from the silicon chloride gas supply nozzle and the reducing agent gas introduced from the reducing agent gas supply nozzle An apparatus for producing high-purity polycrystalline silicon for sequentially growing silicon,
Silicon is produced in the reactor by installing a plurality of the silicon chloride gas supply nozzles so as to surround the reducing agent gas supply nozzle and at a predetermined distance from the inner wall of the reactor. The crystal is attached to the tip of the silicon chloride gas supply nozzle, and then is cohered and grown in a tubular shape downward.

  According to the present invention having such a structure, the polycrystalline silicon grown at the tip of the silicon chloride gas supply nozzle grows substantially downward without contacting the vessel wall of the reactor. It can be manufactured continuously.

Furthermore, since a plurality of silicon chloride gas supply nozzles are installed, a large amount of polycrystalline silicon can be manufactured by efficiently using a limited space.
Here, the opening end of the reducing agent gas supply nozzle is preferably disposed above the opening end of the silicon chloride gas supply nozzle.

With such a configuration, the reducing agent gas can be sufficiently dispersed in the reactor due to the difference in specific gravity of the gas, so that the reducing agent gas can be efficiently reacted with the silicon chloride gas. Also, since the silicon chloride gas does not flow back to the tip of the reducing agent gas supply nozzle, silicon does not grow at the opening end of the reducing agent gas supply nozzle, and silicon is not formed at the opening end of the silicon chloride gas supply nozzle. Crystals can be aggregated and grown in a tubular shape.

In the present invention, it is preferable that gas guiding means for guiding the gas flow downward is processed at the opening end of the silicon chloride gas supply nozzle.
In such a configuration, the silicon chloride gas protruding from the plurality of nozzles is not affected by each other, and is jetted straight downward as a laminar flow. It can be continuously grown downward.

Further, the gas guiding means may be configured such that the inner peripheral surface of the nozzle is formed so as to be thinner toward the opening end surface.
With such a configuration, the gas flow discharged from the nozzle can be ejected straight down relatively easily.

  According to the production apparatus of the present invention, it is possible to continuously produce polycrystalline silicon agglomerated in a tubular shape directly below a silicon chloride gas supply nozzle installed above the reactor, and to form silicon. It can grow without touching the vessel wall. Accordingly, contamination through the vessel wall can be prevented and high-purity polycrystalline silicon can be produced.

  Further, in the manufacturing apparatus of the present invention, since polycrystalline silicon agglomerates in a tubular shape downward, nozzle clogging does not occur. The polycrystalline silicon obtained by the present invention can be grown to an appropriate length and then dropped by a mechanical method such as vibration or scraping.

  Further, according to the production apparatus of the present invention, since the polycrystalline silicon grows in a state where it does not contact the inner wall surface of the reactor and is hung from the nozzle, the material constituting the reactor is not restricted, It can be freely selected from materials that are resistant to the operating temperature range.

Furthermore, for the reasons described above, the obtained polycrystalline silicon has a high purity and can be used as a raw material for semiconductor silicon in addition to a raw material for silicon for solar cells.
Further, the reducing agent gas supply nozzle is disposed above the opening end of the silicon chloride gas supply nozzle so that the reducing agent gas does not grow on the opening end of the reducing agent gas supply nozzle. Can be efficiently reacted with silicon chloride gas.

  Further, if the guide means for guiding the silicon chloride downward is processed by forming the silicon chloride gas supply nozzle so as to be thinner toward the opening end of the silicon chloride gas supply nozzle, the silicon chloride gas is directed downward. When the reducing gas is supplied here, the polycrystalline silicon can be grown straight downward.

Hereinafter, an apparatus for producing high-purity polycrystalline silicon according to an embodiment of the present invention will be described in detail with reference to the drawings.
The high-purity polycrystalline silicon in the present invention is a polycrystalline silicon having a purity of 99.99% or more, preferably a purity of 99.999% or more, which can be used as a raw material for silicon for solar cells and further as a raw material for semiconductor silicon. Say.

FIG. 1 shows the basic structure of a high purity polycrystalline silicon manufacturing apparatus according to an embodiment of the present invention.
As shown in FIGS. 1A to 1E, the high purity polycrystalline silicon production apparatus 10 of the present embodiment employs a substantially cylindrical vertical reactor 1.

  A silicon chloride gas supply nozzle 2 and a reducing agent gas supply nozzle 3 are inserted from the upper part of the vertical reactor 1 downward, and an exhaust gas extraction pipe 4 is connected to the lower part of the reactor 1. ing. In addition, while maintaining the reactor 1 at a predetermined temperature, silicon chloride and a reducing agent are supplied into the reactor 1 through each nozzle, and a gas phase reaction is performed in the reactor 1. The polycrystalline silicon 20 gradually agglomerated in a tubular shape is grown downward at the opening end 2a of the silicon chloride gas supply nozzle 2. In particular, the silicon chloride gas supply nozzle 2 is particularly required to be disposed at a position away from the instrument wall 1a by a predetermined distance.

  As shown in FIG. 1B, the reducing agent gas supplied from the reducing agent gas supply nozzle 3 into the reactor 1 is filled while being diffused in the reactor 1 because of its small specific gravity. On the other hand, as shown in FIG. 1 (c), the silicon chloride gas supplied from the silicon chloride gas supply nozzle 2 has a large specific gravity, and is thus easily lowered straight.

  The opening end 2a of the silicon chloride supply nozzle 2 and the opening end 3a of the reducing agent gas supply nozzle 3 are set to substantially the same height as shown in FIGS. Then, the diffusion of the reducing agent such as zinc discharged from the reducing agent gas supply nozzle 3 becomes insufficient, and is not sufficiently used for the reaction with the silicon chloride gas, and remains unreacted from the lower exhaust gas extraction pipe 4. Easily discharged out of the reactor 1.

  For this reason, in the growth apparatus 10 of this embodiment, the open end 3a of the reducing agent gas supply nozzle 3 is connected to the silicon chloride gas supply nozzle 2 as shown in FIGS. 1 (d) and 1 (e). It is preferable to be disposed above the opening end 2a.

By setting the heights of the nozzles 2 and 3 in this way, it becomes possible to efficiently react a reducing agent gas such as zinc with a silicon chloride gas such as silicon tetrachloride.
If the reducing agent gas and the silicon chloride gas are reacted in a gas phase in the reactor 1, the polycrystalline silicon 20 obtained by the reaction is first applied to the open end 2 a of the silicon chloride supply nozzle 2 over time. And then grows downward to produce tubular aggregated polycrystalline silicon 20 (hereinafter referred to as tubular aggregated polycrystalline silicon). The tubular agglomerated polycrystalline silicon is in contact with the vessel wall 1a during the growth process extending downward because the silicon chloride gas supply nozzle 2 is installed at a position away from the vessel wall 1a by a predetermined distance in advance. There is no. Therefore, contamination from the vessel wall 1a is prevented, and high purity tubular aggregated polycrystalline silicon can be obtained.

  In the vertical reactor 1 used in the present invention, the reducing agent gas is evenly dispersed in the container, and the gas flow is controlled so that the silicon chloride gas is linearly lowered from the nozzle. Any material can be used without particular limitation as long as it can grow tubular agglomerated polycrystalline silicon. However, in consideration of the gas flow behavior, a vertical reactor or a top plate 1b provided with a silicon chloride gas supply nozzle 2 and a reducing agent gas supply nozzle 3 respectively on a circular top plate 1b. A vertical reactor having a dome shape and having the supply nozzles 2 and 3 on the dome-shaped ceiling 1b is preferable.

For example, in the vertical reactor 1, when the length of the reactor is increased, the silicon chloride gas descending in the reactor gradually diffuses as the reactor descends, and eventually spreads laterally to disturb the flow. . However, in this embodiment, since the tubular agglomerated polycrystalline silicon grows downward in the vertical reactor 1, the same effect as in the case where the tip position of the nozzle is extended downward with time is obtained.

  In the vertical reactor 1 used in this example, the diameter and thickness of the silicon chloride gas supply nozzle 2 and the insertion length into the reactor are not particularly limited. In consideration, as illustrated in FIG. 2A, the diameter G is 10 to 100 mm, the wall thickness t is 2 to 15 mm, and the insertion length H into the reactor is 0 to 500 mm longer than the tip of the reducing agent gas supply nozzle. It is preferable to do. Moreover, as a material of a nozzle, the thing similar to the material of a reactor can be illustrated.

  Further, the number of silicon chloride gas supply nozzles 2 is not particularly limited as long as the gases released from adjacent nozzles do not interfere with each other and disturb the flow. May be. Further, even if the nozzle 2 is branched from the middle and has two or more branches, or has two or more branches and a combination of different nozzle diameters, there are many nozzles when viewed over time. Crystalline silicon is similarly produced and grown. Therefore, the number of nozzles 2 is not limited by the combination of nozzle branching and nozzle diameter, and the number and interval of nozzles are appropriately set in consideration of the size of polycrystalline silicon to be grown and the size of the reactor. do it. FIG. 3 exemplifies the arrangement positions of the nozzles 2 and 3 when four silicon chloride gas supply nozzles 2 and one reducing agent gas supply nozzle 3 are installed.

  That is, as shown in FIG. 3, the reducing agent supply nozzle 3 is arranged at a substantially central portion in the radial direction of the reactor 1, and the reducing agent gas supply nozzle 3 is surrounded by the cylindrical reactor 1. The silicon chloride gas supply nozzles 2 are radially arranged so as to be separated from the inner wall 1a by a predetermined distance. If the silicon chloride gas supply nozzle 2 is installed in this way, four tubular agglomerated polycrystalline silicon grown on the opening end 2a of the nozzle can be grown downward simultaneously without contacting the vessel wall 1a.

Further, in this embodiment, as shown in FIG. 2, the gas guide means I for processing the silicon chloride gas flow downward is processed at the open end 2a of the silicon chloride gas supply nozzle 2.
Here, specifically, the gas guiding means I has a thin tapered inner peripheral surface of the opening end 2a as shown in FIG. 2 (a), or as shown in FIG. 2 (b). The opening edge is formed so as to be rounded. Thus, if an appropriate gas guiding means I is processed at the opening end 2a of the nozzle 2, the gas flow is guided downward more straightly than in the case of FIG. Therefore, the tubular aggregated polycrystalline silicon can be easily grown.

  The supply rate of the silicon chloride gas supplied from the silicon chloride gas supply nozzle 2 is not particularly limited as long as it does not cause turbulent flow. However, in consideration of the generation and growth of tubular aggregated polycrystalline silicon, the supply nozzle 2 When the discharge port diameter is 50 mm, the flow rate is preferably 2400 mm / s or less.

  The size of the vertical reactor used in the present invention is not particularly limited. From the viewpoint of the production and growth of tubular aggregated polycrystalline silicon described above, the width and depth are 250 mm or more, and the height is tubular aggregated polycrystalline. In order to prevent damage to the vertical reactor due to the drop impact of silicon, the thickness is preferably 500 to 5000 mm.

  In addition, the silicon chloride gas supply nozzle is perpendicular to the upper part of the reactor from the viewpoint of generation and growth of tubular agglomerated polycrystalline silicon, and the distance between the perpendicular and the reactor wall is 50 mm or more. It is preferable to be installed.

Furthermore, in the vertical reactor 1 used in this example, the diameter, thickness, and insertion length of the reducing agent gas supply nozzle 3 into the reactor are not particularly limited, and the silicon chloride gas shown in FIG. What is necessary is just to set substantially the same as the case of the supply nozzle 2. FIG. However, the insertion length of the reducing agent gas supply nozzle 3 is preferably about 150 mm shorter than the insertion length of the silicon chloride gas supply nozzle 2 as shown in FIG. Moreover, as a material of a nozzle, the thing similar to the material of a reactor can be illustrated.

  Further, the attachment position and the number of the reducing agent gas supply nozzles 3 are not particularly limited as long as the reducing agent gas can be sufficiently diffused into the container. It may be on the side surface or the bottom surface of the vessel 1 and may be one or two or more. However, in consideration of handling and the like, it is preferable to install it by dropping downward from the top plate 1b.

  In the vertical reactor 1 used in the present embodiment, the supply rate of the reducing agent gas supplied from the reducing agent gas supply nozzle 3 is not particularly limited as long as it does not disturb the flow of the silicon chloride gas in the reactor. However, from the viewpoint of not disturbing the flow of the silicon chloride gas in the reactor 1, the flow velocity at the outlet of the supply nozzle is preferably 1500 mm / s or less.

  If the shape and the diameter of the exhaust gas extraction pipe 4 installed at the lower part of the vertical reactor 1 of this embodiment can sufficiently exhaust the exhaust gas without intentionally disturbing the flow of the silicon chloride gas, There is no particular limitation. Further, the exhaust gas extraction pipe 4 is generally attached to the center of the lower part of the vertical reactor or an eccentric position, but if the reactor does not intentionally disturb the flow of silicon chloride gas, the reactor It may be attached to the side or top plate. Similarly, the number of the exhaust gas extraction pipes 4 is not particularly limited as long as it does not intentionally disturb the flow of the silicon chloride gas, and may be one or two or more.

  The length of the extraction pipe protruding into the reactor is required to some extent to prevent a short path of silicon chloride gas or reducing agent gas. However, as described above, it is necessary to control the flow of silicon chloride gas. There is no particular limitation as long as there is no significant influence.

The vertical reactor used in the present invention may be provided with a nozzle for supplying a carrier gas such as nitrogen gas.
The basic configuration of the high purity polycrystalline silicon production apparatus using the vertical reactor of the present invention is as described above, but the case where it is further incorporated into a practical production line will be described below.

  FIG. 4 is a schematic diagram showing an example of a polycrystalline silicon manufacturing facility in which the high purity polycrystalline silicon manufacturing apparatus according to the present invention is incorporated. However, the present invention is not limited to these descriptions, and includes a range in which a person skilled in the art can appropriately modify and the like based on the description of the entire specification.

  As shown in FIG. 4, the reducing agent A is gasified by the melting furnace 5 and the evaporation furnace 6 and the like, and the silicon chloride B is gasified by the vaporizer 8 and the like. The melting furnace 5 or the like may be unnecessary depending on the type and form of the raw material used. The gasified reducing agent A and the gasified silicon chloride B are heated to 800 to 1200 ° C., which is a temperature suitable for the reduction reaction, by the superheated furnace 7 in the previous stage of the reactor 1, and then are heated by the reactor heating furnace 9. Feed to reactor 1 heated to 800-1200 ° C. In addition, when using the reactor provided with the source gas heating zone, it is also possible to supply at a temperature lower than the said temperature and to heat up to the temperature suitable for reaction inside.

The silicon chloride gas supplied into the reactor 1 from the silicon chloride gas supply nozzle 2 is quickly reduced to silicon by the reducing agent gas supplied from the reducing agent gas supply nozzle 3. The generated silicon immediately adheres to the tip of the silicon chloride gas supply nozzle 2, and the silicon crystal grows below the nozzle while agglomerating into a tubular shape starting from the silicon chloride gas supply nozzle 2. When this tubular agglomerated polycrystalline silicon grows to a certain length, it drops off from the nozzle and falls to the bottom of the reactor due to its own weight or mechanical shock. Thereafter, when the raw material is further continuously supplied, new tubular agglomerated polycrystalline silicon grows on the silicon chloride gas supply nozzle 2.

  In the production apparatus of the above embodiment, the silicon chloride gas supply nozzle 2 and the reducing agent gas supply nozzle 3 are shown to be inserted one by one in the reactor 1, but actually As shown in FIG. 3, a plurality of silicon chloride gas supply nozzles 2 are installed around one reducing agent gas supply nozzle 3.

  Furthermore, in this embodiment, the silicon chloride gas supply nozzle 2 and the reducing agent gas supply nozzle 3 are inserted directly into the reactor 1 independently, but the present invention is not limited to this. For example, when a plurality of silicon chloride gas supply nozzles 2 are provided, as shown in FIG. 5, the upstream portion 2a can be shared, and only the downstream portion 2b can be branched into a plurality. That is, in the example of FIG. 5, a small chamber 1A is defined at the top of the reactor 1 by a partition wall 1c, and an upstream portion 2a of the silicon chloride gas supply nozzle 2 is opened in the small chamber 1A. A plurality of downstream portions 2b are opened in the reaction chamber 1B below the wall 1c. The downstream portion 2b is arranged radially with respect to the reducing agent gas supply nozzle 3 as shown in FIG.

  In this way, even if the downstream side of the silicon chloride gas supply nozzle 2 is branched and independent, tubular agglomerated polycrystalline silicon is produced at the tip of the downstream portion 2b of the silicon chloride gas supply nozzle 2. can do.

  The polycrystalline silicon C grown and dropped in the reactor 1 is cooled in the lower part of the reactor or in the cooling / pulverizing apparatus 10 and pulverized as necessary, and then provided in the bottom of the reactor or in the cooling / pulverizing apparatus 10. It can be discharged out of the reactor by a shutter-type valve. Alternatively, by heating the lower part of the reactor to 1420 ° C. or higher, which is the melting point of silicon, the silicon can be taken out of the reactor in a molten state (silicon melt state).

  The exhaust gas extracted from the exhaust gas extraction pipe 4 includes a reducing agent chloride (for example, zinc chloride), unreacted silicon chloride and a reducing agent, polycrystalline silicon generated in the exhaust gas extraction path, and the like. It is included. Therefore, these are used for reducing agent chloride D and unreacted silicon chloride E using, for example, reducing agent chloride recovery tank 11, silicon chloride condensing device (1) 12, silicon chloride condensing device (2) 13 and the like. The exhaust gas that cannot be reused is appropriately treated by the exhaust gas treatment facility F or the like.

  In the high purity polycrystalline silicon production apparatus of this embodiment, silicon chloride gas is supplied from the silicon chloride gas supply nozzle 2 and reducing agent gas is supplied from the reducing agent gas supply nozzle 3 into the vertical reactor 1. To do. Then, by these reactions, the tubular agglomerated polycrystalline silicon is generated at the tip 2a of the silicon chloride gas supply nozzle 2 without using a seed rod used in the Siemens method. Grow downward from the nozzle tip.

In this embodiment, the polycrystalline silicon grows in such a manner that the silicon crystals are aggregated in a tubular shape and hang from the silicon chloride gas supply nozzle 2 as shown in FIG. 1 (e) and FIG. Therefore, the tubular agglomerated polycrystalline silicon can be grown without contacting the inner wall surface 1a of the reactor. Therefore, high purity polycrystalline silicon can be obtained without being contaminated by the reactor material. For the above reasons, there is an advantage that the material constituting the reactor and the combination of the seal material and the constituent material are not greatly restricted. In addition, as a material of a reactor, the material which has tolerance in a use temperature range, for example, quartz, silicon carbide, etc. can be used.

The high-purity polycrystalline silicon in the present invention refers to polycrystalline silicon that can be used as a raw material for solar cell silicon and further as a raw material for semiconductor silicon.
In the manufacturing method of the present invention, the plane orientation in the crystal growth direction of polycrystalline silicon is the (111) plane. In this way, when the crystallized single crystal grows with anisotropy in a specific plane direction, impurities in silicon segregate at the crystal interface (surface). This is considered to be a factor that can be obtained.

  The tubular agglomerated polycrystalline silicon grown as described above becomes heavier as it grows and falls off the silicon chloride gas supply nozzle 2 by its own weight, so that the nozzle 2 is not clogged. It is also possible to drop tubular aggregated polycrystalline silicon grown to an appropriate length by a mechanical method such as vibration or scraping. The dropped polycrystalline silicon C is cooled in a cooling zone provided at the lower part of the reactor, or melted by heating the lower part of the reactor to a temperature higher than the melting point of silicon to form a silicon melt, and then reacted. It can be continuously taken out from the reactor bottom. This makes it possible to construct a process for continuously obtaining high-purity polycrystalline silicon without stopping operation, and to stably manufacture a large amount of inexpensive high-purity polycrystalline silicon.

The silicon chloride gas used in the present invention is described in Table 1 represented by Si _m H _n Cl _{2m + 2-n} (m is an integer of 1 to 3, and n is an integer of 0 or more not exceeding 2m + 2). Gases such as chlorosilane can be used, and among these, silicon tetrachloride gas is preferable because it is easily available and can be easily recovered without generating complicated by-products. As the reducing agent gas, metal reducing agent gas such as sodium (Na), potassium (K), magnesium (Mg), zinc (Zn), or hydrogen gas (H ₂ ) can be used. Then, zinc gas is preferable because it has a relatively low affinity with oxygen and can be handled safely.

  The supply amount of the silicon chloride gas and the reducing agent gas in the production method of the present invention is not particularly limited as long as the reduction reaction is sufficiently advanced. For example, silicon chloride gas: reducing agent gas = 1 in terms of molar ratio. : 10 to 10: 1, preferably 1: 4 to 4: 1. By supplying the silicon chloride gas and the reducing agent gas at a ratio within the above range, polycrystalline silicon can be stably generated and grown.

  The reaction between the silicon chloride gas and the reducing agent gas is performed in the range of 800 to 1200 ° C, preferably 850 to 1050 ° C. Therefore, it is preferable to supply the silicon chloride gas and the reducing agent gas heated to the temperature range in the reactor heated and controlled to be in the temperature range.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples.

Purity analysis of the obtained product silicon was conducted by analyzing metal elements (17 elements: Zn, Al, Ca, Cd, Cr, Cu, Co, Fe, Mn, Mo in the solution after silicon was decomposed and removed with HF / HNO _3. , Na, Ni, Pb, Sn, Ti, P, B) are quantified by high frequency induction plasma emission spectroscopy (ICP-AES: model, Nippon Jarrel Ash, model, IRIS-AP), 100
It was determined by subtracting the sum of the quantitative values of the 17 elements from%.

[Example 1]
In the flow constituted by the schematic diagram illustrated in FIG. 4, the inner peripheral surface of the open end of the silicon chloride gas supply nozzle was previously processed to be thin as shown in FIG. Two quartz silicon chloride gas supply nozzles and one reducing agent gas supply nozzle with an inner diameter of 55 mm, a wall thickness of 5 mm, and an insertion length of 100 mm are installed on the ceiling, and an exhaust gas extraction pipe is installed on the lower wall surface. A vertical cylindrical silicon carbide (SiC) reactor having an inner diameter of 800 mm and a length of 1800 mm was used. The reactor was heated by an electric furnace so that the whole was about 950 ° C. Next, in this reactor, silicon tetrachloride gas of 950 ° C. as silicon chloride gas and zinc gas of 950 ° C. as reducing agent gas are in a molar ratio of silicon tetrachloride: zinc = 0.7: 1. Thus, it supplied from each supply nozzle and reacted for 7.5 hours. As a result of calculation, the flow rate per nozzle outlet of silicon tetrachloride gas was 500 to 700 mm / s, and the flow rate of zinc gas nozzle outlets was 800 to 1200 mm / s.

  After the supply of silicon tetrachloride gas and zinc gas was stopped and the reactor was cooled, the lower part of the reactor was opened, and the generated polycrystalline silicon was peeled off by its own weight from the silicon chloride gas supply nozzle, and the reactor bottom plate I was on the top. The amount of polycrystalline silicon adhering to the reactor wall was negligible. The weight of the obtained polycrystalline silicon was 5.9 kg, and the purity was 99.999% or more.

[Example 2]
The same reactor as in Example 1 was used, and in the reactor, silicon tetrachloride gas at 1000 ° C. as a silicon chloride gas and zinc gas at 1000 ° C. as a reducing agent gas in a molar ratio of silicon tetrachloride: zinc = It was carried out in the same manner as in Example 1 except that the reaction was carried out for 8 hours by supplying from each supply nozzle so as to be 1.4: 1.

After the supply of silicon tetrachloride gas and zinc gas was stopped and the reactor was cooled, the lower part of the reactor was opened, and tubular agglomerated polycrystalline silicon adhered to the two silicon tetrachloride gas supply nozzles and hung down. It was confirmed. The amount of polycrystalline silicon adhering to the reactor wall was negligible. The weight of the obtained polycrystalline silicon was 5.7 kg, and the purity was 99.999% or more.
Example 3
Two quartz silicon chloride supply nozzles with an inner diameter of 25 mm are processed to have a rounded tip as shown in FIG. 2B on the ceiling, and the distance is 175 mm around one reducing gas supply nozzle with an inner diameter of 35 mm. A vertical cylindrical quartz reactor having an inner diameter of 500 mm and a length of 1500 mm, which was evenly arranged on the circumference and provided with an exhaust gas extraction pipe on the lower wall surface, was heated to 950 ° C. Next, 950 ° C. silicon tetrachloride gas as silicon chloride and 950 ° C. zinc gas as reducing gas were fed into the reactor so that the molar ratio was silicon tetrachloride: zinc = 0.8: 1. For 3 hours. As a result of the calculation, the flow rate per nozzle outlet of silicon tetrachloride gas was 800 to 1000 mm / s, and the flow rate of zinc nozzle outlet was 300 to 500 mm / s.

After the supply of the silicon tetrachloride gas and the zinc gas was stopped and the reactor was cooled, the lower part of the reactor was opened. As a result, 6 pieces of tubular agglomerated polycrystalline silicon each were supplied to the silicon tetrachloride gas supply nozzle at 650 to 700 mm. It was confirmed that it was attached to a certain length and was hanging down. Note that the adhesion of polycrystalline silicon to the reaction wall was negligible. The weight of the obtained polycrystalline silicon was 4.1 kg, and the purity was 99.999% or more.

[Comparative Example 1]
A quartz silicon chloride gas supply nozzle and a reducing agent gas supply nozzle made of quartz each having an inner diameter of 20 mm, a thickness of 5 mm, and an insertion length of 100 to 400 mm are installed at one end, and exhaust gas is provided at the other end. A horizontal cylindrical quartz reactor having an inner diameter of 310 mm and a length of 2835 mm, in which an extraction pipe was installed, was used. The reactor was heated by an electric furnace so that the whole became 950 ° C. Next, in the reactor, silicon tetrachloride gas at 950 ° C. as silicon chloride gas and zinc gas at 950 ° C. as reducing agent gas so that the molar ratio is silicon tetrachloride: zinc = 0.7: 1. The reaction was carried out for 80 hours by supplying from each supply nozzle.

  After the supply of silicon tetrachloride gas and zinc gas was stopped, the reactor was slowly cooled, and the reactor end was opened. Formation of tubular agglomerated polycrystalline silicon was not observed, and acicular polycrystalline silicon reacted. It grew up inside the vessel. The adhesion strength of polycrystalline silicon to the quartz reactor wall was high, and when the polycrystalline silicon was peeled off, the quartz surface was chipped, and many pieces of quartz were mixed in the recovered high-purity silicon. The weight of the obtained polycrystalline silicon was 12.5 kg.

  In this comparative example, after the experiment was completed, the quartz reactor was destroyed due to the difference in thermal expansion coefficient between the deposited polycrystalline silicon and quartz.

FIG. 1 is a schematic diagram showing the basic configuration of a high purity polycrystalline silicon production apparatus according to an embodiment of the present invention. FIG. 1 (a) is a schematic view of a vertical reactor, and FIG. FIG. 1 (c) is a schematic diagram showing the flow of the silicon chloride gas, and FIG. 1 (d) shows the reaction of the reducing agent gas with the silicon chloride gas. FIG. 1D is a schematic diagram showing a process in which tubular aggregated polycrystalline silicon is manufactured. FIG. 2 shows the gas guiding means provided at the opening end of the silicon chloride supply nozzle employed in the embodiment shown in FIG. 1, and FIG. 2 (a) shows the thickness of the opening end face. FIG. 2 (b) is a schematic view of the guide means configured to be rounded, and FIG. 2 (c) is a schematic illustration of the guide means. It is a schematic diagram of the nozzle tip portion when not. FIG. 3 is a plan view showing an example of an installation mode of the silicon chloride gas supply nozzle with respect to the reducing agent gas supply nozzle. FIG. 4 is a schematic configuration diagram of a manufacturing facility provided with the manufacturing apparatus of the present embodiment shown in FIG. FIG. 5 is a cross-sectional view of an essential part showing another embodiment of the polycrystalline silicon manufacturing apparatus according to the present invention. FIG. 6 is a schematic view of a manufacturing apparatus based on the Siemens method which has been widely used conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vertical type reactor 1a ... Wall 1c ... Partition wall 1A ... Small room 1B ... Reaction room 2 ... Silicon chloride gas supply nozzle 2a ... Open end 3. .... Reducing agent gas supply nozzle 3a ... Open end 4 ... Exhaust gas extraction pipe 5 ... Melting furnace 6 ... Evaporating furnace 7 ... Superheated furnace 8 ... Vaporizer 9 ... Reaction Reheating furnace 10 ... Cooling and grinding device 11 ... Reducing agent chloride recovery tank 12 ... Silicon chloride condenser (1)
13 ... Silicon chloride condenser (2)
20 ... Tubular agglomerated polycrystalline silicon 40 ... Manufacturing equipment A ... Reducing agent B ... Silicon chloride C ... Dropped polycrystalline silicon D ... Reducing agent chloride E ... Not yet Reactive silicon chloride F ... Exhaust gas treatment equipment G ... Diameter H ... Insertion length I ... Guide means t ... Thickness

Claims (4)

A vertical reactor having heating means on the outer peripheral surface;
A silicon chloride gas supply nozzle inserted downward from the top of the vertical reactor; and a reducing agent gas supply nozzle inserted downward from the top of the vertical reactor;
An exhaust gas extraction pipe connected to the reactor,
Polycrystalline at the tip of the silicon chloride gas supply nozzle by a gas phase reaction between the silicon chloride gas introduced from the silicon chloride gas supply nozzle and the reducing agent gas introduced from the reducing agent gas supply nozzle An apparatus for producing high-purity polycrystalline silicon for sequentially growing silicon,
Silicon is produced in the reactor by installing a plurality of the silicon chloride gas supply nozzles so as to surround the reducing agent gas supply nozzle and at a predetermined distance from the inner wall of the reactor. An apparatus for producing high-purity polycrystalline silicon, characterized in that a crystal is attached to the tip of the silicon chloride gas supply nozzle and then is coagulated and grown downward in a tubular shape.   2. The high purity polycrystalline silicon manufacturing apparatus according to claim 1, wherein an opening end of the reducing agent gas supply nozzle is disposed above an opening end of the silicon chloride gas supply nozzle.   The high purity polycrystalline silicon manufacturing apparatus according to claim 1 or 2, wherein gas guide means for guiding a gas flow downward is processed at an opening end of the silicon chloride gas supply nozzle.   4. The high purity polycrystalline silicon manufacturing apparatus according to claim 3, wherein the gas guiding means is configured such that the inner peripheral surface of the nozzle is formed so as to be thinner toward the opening end surface.

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