JP2014073943A - Polycrystalline silicon production device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device contributing to the cost reduction of polycrystalline silicon production.SOLUTION: The connection between a metallic electrode 10 and an adaptor 14 made of a material with a high melting point metal as the main element of the composition is screw connection in which a female screw part formed at the bottom of the adaptor 14 and a male screw part formed at the tip part of the metallic electrode 10 are screwed, and the connection between the adaptor 14 and a core wire holder 13 made of carbon is by the insertion of a taper-shaped projecting part formed at the bottom part of the core wire holder 13 made of carbon into a taper-shaped hole part formed at the tip part of the adaptor 14. Since the core wire holder 13 made of carbon is thrown away only by use for single time, it is preferable that its shape is made simple as possible and its large-sizing and thickening are suppressed as possible. Thus, it has an almost columnar shape, the upper part is provided with a hole part for inserting the silicon core wire 11, and on the other hand, the lower part has a taper shape to be inserted into a hole part with a taper shape provided at the tip part of the adaptor 14.

Description

  The present invention relates to a manufacturing apparatus for manufacturing polycrystalline silicon rods by depositing polycrystalline silicon on the surface of a heated silicon core wire, and more particularly to an apparatus that contributes to reducing the cost of manufacturing polycrystalline silicon.

  A Siemens method is known as a method for producing polycrystalline silicon as a raw material for single crystal silicon for semiconductors or silicon for solar cells. The Siemens method is a method in which a source gas containing chlorosilane is brought into contact with a heated silicon core wire, and polycrystalline silicon is vapor-phase grown on the surface of the silicon core wire using a CVD (Chemical Vapor Deposition) method.

  The reactor for vapor-phase growth of polycrystalline silicon by the Siemens method is a vertical furnace with two silicon core wires in a space composed of an upper structure called a bell jar and a lower structure (bottom plate) called a base plate. One torii type is assembled, and both ends of the torii type silicon core wire are fixed to a pair of metal electrodes disposed on the base plate via a pair of carbon core wire holders. This configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 2012-82128.

  The electrode passes through the base plate with an insulator interposed therebetween, and is connected to another electrode through wiring, or connected to a power source arranged outside the reactor. In order to prevent polycrystalline silicon from precipitating during vapor phase growth, the electrode, base plate and bell jar are cooled using a coolant such as water.

  When a silicon core wire is heated to a temperature range of 900 ° C. or higher and 1200 ° C. or lower in a hydrogen atmosphere by passing a current from the electrode, a mixed gas of, for example, trichlorosilane and hydrogen is supplied from a gas nozzle into the reactor as a source gas. Silicon is vapor-grown on the core wire, and a polycrystalline silicon rod having a desired diameter is formed in an inverted U shape.

  For the purpose of improving the productivity of polycrystalline silicon, the produced polycrystalline silicon rods tend to increase in size from 120 mmφ to 150 mmφ and 1.5 m to 3 m in length, and the weight is also 100 kg to 250 kg. The weight is increasing. Along with this, a metal electrode or core wire holder that plays a role of supporting such a heavy polycrystalline silicon rod in a reaction furnace is required to have a strength that can withstand this. Against this background, there has also been proposed an improved core wire holder so that troubles such as overturning do not occur during the polycrystalline silicon manufacturing process even if the polycrystalline silicon rod is enlarged (Patent Document 2: Japanese Patent Laid-Open No. 2005-209867). 2011-195438).

  The electrode and the core wire holder may be directly joined, but an adapter is provided between the electrode and the core wire holder for the following purpose. The adapter is provided, for example, to reduce the amount of heat that escapes from the polycrystalline silicon rod, which becomes a high temperature of 900 ° C. to 1200 ° C. during the reaction, to the metal electrode cooled by the refrigerant through the core wire holder. Further, an adapter may be provided to prevent heavy metal contamination of polycrystalline silicon due to high temperature of the metal electrode. Furthermore, an adapter is provided for the purpose of preventing damage deterioration of the metal electrode and adjusting the height of the core wire holder (Patent Document 3: Japanese Patent Application Laid-Open No. 2002-338226). It goes without saying that such adapters are also required to have higher strength due to the higher weight of the polycrystalline silicon rod for the reasons described above.

  As the material of the metal electrode, as shown in Patent Document 4 (Japanese Patent Laid-Open No. 2011-517734), in consideration of electric resistivity, copper (Cu), white copper (Cu-Ni), nickel (Ni), stainless steel, etc. are generally selected. As a material of the adapter, as shown in Patent Document 3, carbon is generally selected from the viewpoint of electrical resistivity, impurity contamination level, heat resistance characteristics, and the like. Further, as shown in Patent Document 1, carbon is usually selected as the material for the core wire holder from the viewpoints of electrical resistivity, impurity contamination level, heat resistance, easiness of silicon surface deposition, and the like. The

  As shown in Patent Document 1, the core wire holder is taken out of the reaction furnace in an integrated state with the polycrystalline silicon rod after the polycrystalline silicon precipitation reaction step. It is difficult to separate and reuse the crystalline silicon rod, and in most cases, one core holder is discarded every time one polycrystalline silicon rod is grown. For this reason, the cost of the core wire holder in the manufacturing cost of the polycrystalline silicon rod is not small.

JP 2012-82128 A JP 2011-195438 A JP 2002-338226 A JP 2011-517734 A JP-A-3-150298

  As described above, conventionally, a carbon material has been generally used for the adapter and the core wire holder. However, the strength of carbon materials is low compared to metals. For example, when compared with tensile strength, which is a representative strength index, copper (Cu) is about 250 MPa (20 ° C.), whereas carbon is about It is only about 25 MPa.

  On the other hand, since the diameter and weight of polycrystalline silicon rods are increasing, adapters and core wire holders are required to have strength that can withstand this weight increase. In order to secure it, it is necessary to increase the size and thickness. However, since the carbon material is difficult to use repeatedly, the increase in production cost is caused without increasing the size and thickness.

  The present invention has been made in view of such problems, and the object of the present invention is to ensure the strength that can cope with an increase in the diameter and weight of a polycrystalline silicon rod, and then repeat the adapter. An object of the present invention is to provide an apparatus that contributes to the cost reduction of the production of polycrystalline silicon by minimizing the increase in size and thickness of the carbon core holder as much as possible.

  In order to solve the above-described problem, the polycrystalline silicon manufacturing apparatus according to the present invention is configured to deposit polycrystalline silicon on the surface of the silicon core wire by supplying a raw material gas to the silicon core wire heated in the reaction furnace. An apparatus for producing polycrystalline silicon, comprising: a carbon core wire holder for holding the silicon core wire; a metal electrode for energizing the silicon core wire; and the core wire holder for placing the core wire holder on the metal electrode An adapter, and the metal electrode is inserted and supported in a through-hole formed in the bottom plate portion of the reactor, and has a cooling channel for circulating cooling water therein, the adapter It is characterized by comprising a material having a refractory metal as a main element of the composition.

  The refractory metal element is preferably one or more elements selected from the group consisting of tantalum (Ta), tungsten (W), molybdenum (Mo), and zirconium (Zr).

  The adapter is, for example, a metal, a metal mixture, or an alloy containing the refractory metal element as a main element of the composition.

  Preferably, the adapter includes a fitting portion with a top portion of the metal electrode at a bottom portion and a tapered hole portion into which the carbon core wire holder is fitted at a top portion.

  Preferably, the carbon core wire holder has a substantially cylindrical shape, a hole portion for inserting the silicon core wire is provided in an upper portion, and a lower portion is a tapered hole portion provided in a top portion of the adapter. It has a taper shape that is fitted in.

  According to the present invention, the adapter for placing the core wire holder on the metal electrode is formed of a material having a refractory metal as a main element of the composition, so that the strength is higher than that of an adapter made of a carbon material. As a result, the increase in size and thickness of the carbon core holder can be suppressed as much as possible, and the adapter can be used repeatedly.

  In addition, since the shape of the carbon core wire holder is simplified and the lower shape is a tapered shape that is fitted into the tapered hole provided at the top of the adapter, the concentration of stress during the production of polycrystalline silicon is alleviated. As a result, the increase in size and thickness of the carbon core holder can be suppressed as much as possible.

  As described above, according to the present invention, it is possible to repeatedly use the adapter while ensuring the strength capable of dealing with an increase in diameter and weight of the polycrystalline silicon rod, and an increase in the size of the carbon core holder. In addition, an apparatus that contributes to reducing the cost of manufacturing polycrystalline silicon is provided by minimizing the increase in thickness and thickness.

It is a schematic explanatory drawing which shows an example of a structure of the reaction furnace of the polycrystalline silicon manufacturing apparatus which concerns on this invention. It is the schematic of the assembly 1st example of a metal electrode, an adapter, and a carbon core wire holder in the present invention. It is the schematic of the 2nd assembly example of the metal electrode in this invention, an adapter, and a carbon core wire holder. It is the schematic of the assembly example of the conventional metal electrodes and carbon core wire holders. It is the schematic of the assembly example of the conventional metal electrodes, carbon adapters, and carbon core wire holders.

  Hereinafter, a polycrystalline silicon manufacturing apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a reaction furnace 100 of a polycrystalline silicon manufacturing apparatus according to the present invention. The reaction furnace 100 is an apparatus for obtaining a polycrystalline silicon rod 12 by vapor-phase growing polycrystalline silicon on the surface of the silicon core wire 11 by the Siemens method, and is composed of a base plate 5 and a bell jar 1.

  The base plate 5 is provided with a metal electrode 10 that supplies a current to the silicon core wire 11. The silicon core wire 11 is placed on the metal electrode 10 while being held by a carbon core wire holder 13. Between the holder 13 and the metal electrode 10, an adapter 14 made of a material having a refractory metal as a main element of the composition is provided.

  The base plate 5 is further provided with a gas nozzle 9 for supplying a process gas such as nitrogen gas, hydrogen gas, trichlorosilane gas, and an exhaust port 8 for exhausting the exhaust gas. Further, the base plate 5 has a refrigerant inlet 6 and an outlet 7 for cooling itself.

  The bell jar 1 has a refrigerant inlet portion 3 and an outlet portion 4 for cooling itself, and further has a viewing window 2 for visually confirming the inside from the outside.

  FIG. 2 is a schematic view of a first assembly example of the metal electrode 10, the adapter 14, and the carbon core wire holder 13 in the present invention. As described above, the metal electrode 10 is supported by being inserted into a through-hole formed in the base plate (bottom plate portion) 5 of the reaction furnace 100, and an inlet (10a) and an outlet (10b) for a coolant such as cooling water. And has a cooling flow path through which the refrigerant flows.

  In the example according to FIG. 2, the connection between the metal electrode 10 and the adapter 14 is a screw connection in which a female screw portion formed at the bottom of the adapter 14 and a male screw portion formed at the top of the metal electrode 10 are fitted. The adapter 14 and the carbon core wire holder 13 are connected to the tapered hole formed at the bottom of the carbon core wire holder 13 to the tapered hole formed at the top of the adapter 14. By insertion.

  Since the carbon core wire holder 13 is disposable after a single use, it is preferable to minimize the increase in size and thickness by making the shape as simple as possible. In the example shown in this figure, a substantially cylindrical shape is provided, and a hole for inserting the silicon core wire 11 is provided in the upper part, while the lower part is formed in a tapered shape that is fitted into a tapered hole provided in the top part of the adapter 14. Yes. The size of the carbon core wire holder 13 is such that the precipitation of the polycrystalline silicon rod is not hindered even in the final stage of the precipitation reaction of the polycrystalline silicon, and the strength does not cause an accident such as the falling of the polycrystalline silicon rod. Designed to be as small as possible.

  FIG. 3 is a schematic view of a second assembly example of the metal electrode 10, the adapter 14, and the carbon core wire holder 13 in the present invention. In the example shown in FIG. 3, the metal electrode 10 and the adapter 14 are connected by inserting a tapered convex portion formed at the bottom of the adapter 14 into a tapered concave portion formed at the top of the metallic electrode 10. I am letting. Further, the connection between the adapter 14 and the carbon core wire holder 13 is made by inserting a tapered convex portion formed at the bottom of the carbon core wire holder 13 into a tapered hole portion formed at the top of the adapter 14.

  Also in this embodiment, the carbon core wire holder 13 has a substantially cylindrical shape, and a hole portion for inserting the silicon core wire 11 is provided in the upper portion, while the lower portion is fitted into a tapered hole portion provided in the top portion of the adapter 14. It has a tapered shape.

  In the aspect shown in FIG. 3, since the female screw part is not formed in the adapter 14, the assembly time is shortened and maintenance such as cleaning is easy as compared with the aspect shown in FIG. There are advantages.

  The adapter 14 is made of a material having a refractory metal as a main element of the composition. Here, the refractory metal element is, for example, one or more elements selected from the group of tantalum (Ta), tungsten (W), molybdenum (Mo), and zirconium (Zr). It is made of a material such as a metal, a metal mixture, or an alloy having a metal element as a main element of the composition.

  A material having a composition having a refractory metal element as a main element is excellent in strength and heat resistance, and can also suppress metal contamination of polycrystalline silicon (for example, Patent Document 5: Japanese Patent Laid-Open No. 3-150298). Publication).

  Since the adapter 14 made of such a material can be used repeatedly and its size can be reduced, it contributes to a reduction in the manufacturing cost of polycrystalline silicon.

  The shape of the adapter 14 is preferably a cylindrical shape or a polygonal column so that maintenance during repeated use is easy. In this case, the diameter of the upper portion may be smaller than that of the lower portion. Moreover, even if the top part is flat, it may be processed into a curved surface shape so that the center becomes high, and in the case of a polygonal column, the corner part of the side surface may be processed into a curved surface shape.

  In the embodiment shown in FIGS. 2 and 3, all of the shape portions where stress tends to concentrate are all on the adapter 14 side so that the carbon core wire holder 13 is not loaded as much as possible even when the polycrystalline silicon rod to be grown is heavy. The shape of the carbon core wire holder 13 is simplified.

  Specifically, the concave portion is not formed in the connection portion with the adapter 14, and the lower portion of the carbon core holder 13 where the polycrystalline silicon rod 12 is not deposited is formed in a simple cylindrical shape or a slightly tapered cone. Shaped. With such a simple shape, the amount of carbon material used can be reduced. In addition, from the viewpoint of ensuring the bending strength of the carbon core wire holder 13, the cross-sectional shape may be rectangular, but from the viewpoint of processing cost and the like, the cross-sectional shape is preferably circular.

  In the present invention, the adapter 14 for placing the carbon core wire holder 13 on the metal electrode 10 is made of a material having a refractory metal as a main element of the composition, so that it is compared with an adapter made of a carbon material. As a result, the strength is increased, and the increase in the size and thickness of the carbon core holder can be suppressed as much as possible, and the adapter can be used repeatedly.

  Moreover, since the shape of the carbon core wire holder 13 is simplified and the lower shape is a tapered shape fitted into a tapered hole provided at the top of the adapter, the concentration of stress during the production of polycrystalline silicon is reduced, This also suppresses the increase in size and thickness of the carbon core wire holder as much as possible.

  FIG. 4 is a schematic view of a conventional assembly example of a metal electrode and a carbon core wire holder. In this embodiment, no adapter is used, and the carbon core wire holder 23 is directly screw-connected to the metal electrode 20.

  According to the study by the present inventors, it has been found that in such an aspect, when the polycrystalline silicon rod 12 is increased in weight, the portion of the carbon core wire holder 23 indicated as BK in the figure is likely to be damaged. .

  FIG. 5 is a schematic view of an assembly example of a conventional metal electrode, carbon adapter, and carbon core wire holder. The connection between the metal electrode 20 and the carbon adapter 24 is a screw connection in which a female screw portion formed at the bottom of the carbon adapter 24 and a male screw portion formed at the top of the metal electrode 20 are fitted. The carbon adapter 24 and the carbon core holder 23 are connected to the tapered hole formed at the top of the carbon adapter 24 at the bottom of the carbon core holder 23. Depending on the insertion of the part.

  According to the study by the present inventors, it has been found that in such an embodiment, when the polycrystalline silicon rod 12 is increased in weight, the portion of the carbon adapter 24 indicated as BK in the figure is easily damaged.

  In order to prevent damage in the embodiment shown in FIGS. 4 and 5, it is necessary to secure the strength by making the carbon core wire holder 23 and the carbon adapter 24 large or thick. This means an increase in the manufacturing cost of polycrystalline silicon.

  On the other hand, in the present invention, the carbon core wire holder 23 and the carbon adapter 24 are not enlarged and thickened, and the strength capable of supporting the increase in the diameter and weight of the polycrystalline silicon rod. Can be secured.

[Example]
In the embodiment shown in FIG. 2, the metal electrode 10, the adapter 14, and the carbon core wire holder 13 were assembled, and a polycrystalline silicon rod having a diameter of 160 mmφ, a length of 2 m, and a weight of 100 kg was grown. The adapter 14 is made of 100% molybdenum metal and has a cross-sectional diameter of 80 mmφ.

  When the adapter 14 was taken out after growing the polycrystalline silicon rod and inspected after cleaning, it was confirmed that the adapter 14 could be reused without damage.

[Comparative Example 1]
The metal electrode 20 and the carbon core wire holder 23 were assembled in the manner shown in FIG. 4, and a polycrystalline silicon rod having a diameter of 160 mmφ, a length of 2 m, and a weight of 100 kg was grown. The cross-sectional diameters of the metal electrode 20 and the carbon core wire holder 23 are both 80 mmφ.

  The carbon core wire holder 23 is complicated in shape as compared with the carbon core wire holder 13 of the embodiment, and it is necessary to increase the size in order to ensure sufficient contact strength with the metal electrode 20. Compared with the core wire holder 13, the cost is about twice as high.

  According to the present invention, the adapter for placing the core wire holder on the metal electrode is formed of a material having a refractory metal as a main element of the composition, so that the strength is higher than that of an adapter made of a carbon material. As a result, the increase in size and thickness of the carbon core holder can be suppressed as much as possible, and the adapter can be used repeatedly.

  In addition, the shape of the carbon core wire holder is simplified, and the lower shape is a tapered shape that fits into the tapered hole provided at the top of the adapter, reducing stress concentration during the production of polycrystalline silicon. As a result, the increase in size and thickness of the carbon core holder can be suppressed as much as possible.

  As described above, according to the present invention, it is possible to repeatedly use the adapter while ensuring the strength capable of dealing with an increase in diameter and weight of the polycrystalline silicon rod, and an increase in the size of the carbon core holder. In addition, an apparatus that contributes to reducing the cost of manufacturing polycrystalline silicon is provided by minimizing the increase in thickness and thickness.

1 Berja 2 Peep window 3 Refrigerant inlet (Berja)
4 Refrigerant outlet (Berja)
5 Base plate 6 Refrigerant inlet (base plate)
7 Refrigerant outlet (base plate)
8 Reaction exhaust gas outlet 9 Source gas supply nozzle 10, 20 Metal electrode 10a, 20a Refrigerant inlet (metal electrode)
10b, 20b Refrigerant outlet (metal electrode)
11 Silicon core wire 12 Polycrystalline silicon rods 13 and 23 Core wire holders 14 and 24 Adapter 100 Reactor

Claims (5)

A polycrystalline silicon production apparatus for depositing polycrystalline silicon on the surface of the silicon core wire by supplying a raw material gas to the silicon core wire heated in a reaction furnace,
A carbon core wire holder for holding the silicon core wire, a metal electrode for energizing the silicon core wire, and an adapter for placing the core wire holder on the metal electrode,
The metal electrode is inserted and supported in a through hole formed in the bottom plate portion of the reaction furnace, and has a cooling flow path for circulating cooling water therein.
The adapter is made of a material having a refractory metal as a main element of the composition, and manufacturing apparatus for polycrystalline silicon.   The polycrystalline silicon manufacturing apparatus according to claim 1, wherein the refractory metal element is one or more elements selected from the group consisting of tantalum (Ta), tungsten (W), molybdenum (Mo), and zirconium (Zr). .   The polycrystalline silicon manufacturing apparatus according to claim 2, wherein the adapter is a metal, a metal mixture, or an alloy containing the refractory metal element as a main element of the composition.   4. The adapter according to claim 1, wherein the adapter includes a fitting portion with a top portion of the metal electrode at a bottom portion and a tapered hole portion into which the carbon core wire holder is fitted at a top portion. The polycrystalline silicon manufacturing apparatus described in 1.   The carbon core wire holder has a substantially cylindrical shape, and a hole portion for inserting the silicon core wire is provided in an upper portion, and a lower portion is a taper fitted into a tapered hole portion provided in a top portion of the adapter. The polycrystalline silicon manufacturing apparatus according to claim 4, which has a shape.

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