JP5502294B2 - Polycrystalline body manufacturing apparatus and polycrystalline body manufacturing method - Google Patents

Description

  The present invention relates to an apparatus for producing a polycrystalline body, and more particularly to an apparatus for producing a polycrystalline body of a periodic table group 14 element.

In recent years, a semiconductor device having a polysilicon film formed by a CVD method (Chemical Vapor Deposition) has been reported as a method for producing polysilicon, which is a polycrystal of a group 14 element of the periodic table ( Patent Document 1).
Recently, a method for reducing silicon tetrachloride (SiCl ₄ ) has been reviewed, and Patent Document 2 describes a method for producing acicular crystalline silicon by a gas phase synthesis reaction of silicon tetrachloride and zinc (Zn). Yes. Further, Patent Document 3 describes a method for producing high-purity silicon in which a gas phase reaction between silicon tetrachloride and zinc metal is performed in zinc chloride gas.

Japanese Patent Application Laid-Open No. 07-183529 JP 2006-290645 A Japanese Patent Laid-Open No. 2004-210594

By the way, polysilicon, which is a polycrystal of a group 14 element of the periodic table, is expanding its application in fields such as solar cells and electronic materials. Therefore, a manufacturing method capable of high-speed synthesis of high-purity polysilicon is desired.
However, since the conventional CVD method is usually performed under a reduced pressure of several tens to several hundreds of pascals, there is a problem that the concentration of the source gas is extremely low and the crystal growth rate is slow. Further, in the gas phase synthesis reaction using the silicon tetrachloride reduction method, there is a problem in the recovery of the product and the separation of zinc chloride as a by-product, and the purity of the obtained polysilicon is insufficient.
The objective of this invention is providing the manufacturing apparatus and the manufacturing method of a polycrystal which can obtain the high purity polycrystal of the periodic table 14 group elements, such as a silicon | silicone, at high speed.

According to the present invention, there is provided an apparatus for producing a polycrystalline body, wherein a reaction vessel body for forming a supercritical fluid state of a halide of a group 14 element of the periodic table introduced therein, and an inside of the reaction vessel body Provided is an apparatus for producing a polycrystalline body, comprising: an electrode for performing plasma discharge; and a seed crystal that is provided inside a reaction vessel body and deposits silicon decomposed by plasma discharge on the surface. Is done.
Here, the polycrystalline body manufacturing apparatus to which the present invention is applied preferably has an external power supply for applying a predetermined voltage to the seed crystal.
The seed crystal is preferably composed of a silicon single crystal.

  Next, according to the present invention, there is provided a method for producing a polycrystal, which forms a supercritical fluid state of a halide of a periodic table group 14 element in a reaction vessel having an electrode and a seed crystal therein. A polycrystalline structure comprising: a fluid state forming step; and a crystal precipitation step of performing plasma discharge in the formed supercritical fluid state to deposit a polycrystal of a group 14 element of a periodic table on a seed crystal. A manufacturing method is provided.

Here, in the method for producing a polycrystalline body to which the present invention is applied, it is preferable that the pressure in the reaction vessel is maintained at 3 MPa or higher and the temperature in the reaction vessel is maintained at 80 K or higher.
Furthermore, in the method for producing a polycrystalline body to which the present invention is applied, it is preferable to introduce an inert gas into the reaction vessel in the supercritical fluid state forming step.
In this case, it is preferable to introduce 50 ml of an inert gas per 0.1 ml to 100,000 ml of the halide of the group 14 element of the periodic table.

In the crystal precipitation step, the seed crystal temperature is preferably maintained at 450K or higher.
Moreover, it is preferable that the periodic table group 14 element is selected from silicon (Si) and germanium (Ge). In this case, the halide of the group 14 element of the periodic table is preferably chloride or bromide. Furthermore, the halide of the group 14 element of the periodic table is preferably silicon tetrachloride.

  According to the polycrystalline body manufacturing apparatus of the present invention, it is possible to obtain a polycrystalline body of a periodic table group 14 element such as high-purity polysilicon with high purity and high speed.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. The drawings used are for explaining the present embodiment and do not represent the actual size.

(manufacturing device)
FIG. 1 is a diagram for explaining an example of a production apparatus for carrying out a method for producing a polycrystalline body to which the present embodiment is applied.
As shown in FIG. 1, the production apparatus I includes a reaction vessel (reaction vessel body) 10 having a pressure resistance capable of maintaining a supercritical fluid state of a halide of a periodic table 14 group element described later, A pair of electrodes 11 and 12 arranged in parallel to generate a plasma discharge in a supercritical fluid state formed by the above, and a raw material for storing a halide of a group 14 element of the periodic table supplied into the reaction vessel 10 A storage tank 21 and a carrier gas storage tank 22 for storing a carrier gas (inert gas) supplied into the reaction vessel 10 are provided.

  As shown in FIG. 1, a high-frequency power source 27 that supplies power for plasma discharge is connected to the electrodes 11 and 12 via a matching unit 26. In the present embodiment, the halide of the group 14 element of the periodic table stored in the raw material storage tank 21 opens the raw material supply valve 21a, is heated by the heater 23, and is passed through the raw material supply pipe 21L by the predetermined supply machine 24. It is supplied to the reaction vessel 10. The carrier gas stored in the carrier gas storage tank 22 is supplied to the reaction vessel 10 through the gas supply pipe 22L by opening the pressure adjustment valve 22a. The pressure in the reaction vessel 10 is adjusted by the exhaust pressure adjustment valve 25.

In the present embodiment, a seed crystal 30 is provided in the vicinity of the electrodes 11, 12 in the reaction vessel 10 for depositing a polycrystal of a group 14 element of the periodic table, and both ends of the seed crystal 30 are provided outside the reaction vessel 10. And an external power source 32 for applying a predetermined voltage to the carbon electrode 31 attached to the unit.
Although not shown, a heating device for heating the reaction vessel 10 to a predetermined temperature is provided. Examples of the heating device include a jacket type heater and a cartridge type heater using a predetermined heat medium. Moreover, you may install the reaction container 10 in a thermostat.

The material which comprises the electrodes 11 and 12 will not be specifically limited if it is a material which can perform plasma discharge. For example, the material constituting the pure metal electrode includes manganese, iron, cobalt, nickel, copper, zinc, silver, tin, aluminum, tungsten, platinum, gold, and the like. Examples of the material constituting the electrode to be plated include silver-plated iron, galvanized iron, and tin-plated iron. Examples of the material constituting the alloy electrode include brass, iron nickel alloy, iron cobalt alloy, and magnesium alloy. Among these, manganese, copper, zinc, platinum, gold, galvanized iron, and brass are preferable.
The distance between the electrodes 11 and 12 is appropriately selected depending on the temperature, pressure or discharge conditions in the reaction vessel 10 and is not particularly limited, but is usually set within a range of 0.002 mm to 5 mm.

  The material constituting the reaction vessel 10 is not particularly limited as long as the material can maintain the supercritical fluid state of the halide of the group 14 element of the periodic table. For example, stainless steel can be used. In this embodiment, Hastelloy C (registered trademark) is used in consideration of corrosion by chlorine gas.

As shown in FIG. 1, in this embodiment, the seed crystal 30 is attached so that both ends are fixed to the bottom of the reaction vessel 10 and the intermediate portion formed in an inverted U shape faces the electrodes 11 and 12 side. It has been. Carbon electrodes 31 are joined to both ends of the seed crystal 30, and these are electrically joined to an external power source 32 provided outside the reaction vessel 10.
The material constituting the seed crystal 30 is preferably a single crystal of a group 14 element of the periodic table to be deposited, and examples thereof include a silicon single crystal and a germanium single crystal. Further, silicon carbide (SiC) or the like can be used. As will be described later, the radicals of the group 14 element of the periodic table that have reached the surface of the seed crystal 30 are induced to crystallize by the seed crystal 30, and solid-phase epitaxial growth occurs, so that a polycrystalline body is finally obtained. .

  The size of the seed crystal 30 on which the periodic table group 14 element is deposited is not particularly limited, but in the present embodiment, a square column of about 5 mm in one piece is bent into an inverted U shape and formed to have a height of about 20 mm. ing. In addition, crystal grains having a particle size of about several nm to several hundred nm can be used as seed crystals.

  Although the material which comprises the carbon electrode 31 attached to the both ends of the seed crystal 30 is not specifically limited, In this Embodiment, the carbon electrode material is used.

  The seed crystal 30 is usually 450 K (473 ° C.) or higher, preferably 500 K (273 ° C.) or higher by applying a predetermined voltage to the carbon electrodes 31 attached to both ends of the seed crystal 30 using an external power source 32. ) It is kept at the above temperature. However, for example, when the group 14 element of the periodic table is silicon (Si), the temperature is kept at a temperature lower than the melting point of 1,687 K (1,414 ° C.) of polysilicon.

  The carrier gas is preferably inert to the halide of the Group 14 element used as a raw material, and examples thereof include helium, neon, and argon. In this embodiment, argon is used as the carrier gas.

(Halides of group 14 elements of the periodic table)
Next, the halide of the 14th group element of the periodic table used as a raw material in this Embodiment is demonstrated.
Examples of the halide of the group 14 element in the periodic table used in this embodiment include a halogenated carbon compound, a halogenated silicon compound, and a halogenated germanium compound. Among these, a halogenated silicon compound and a halogenated germanium compound are preferable, and a silicon halide compound is particularly preferable.

(Halogenated silicon compounds)
Examples of the silicon halide compound include silicon fluoride, silicon chloride, silicon bromide, and silicon iodide. Among these, silicon chloride and silicon bromide are preferable.
Examples of silicon chloride include silicon tetrachloride (SiCl ₄ ), hexachlorodisilane, octachlorotrisilane, decachlorotrisilane, dodecachloropentasilane, and the like. Further, silane derivatives such as chlorosilane (SiH ₃ Cl), dichlorosilane (SiH ₂ Cl ₂ ), and trichlorosilane (SiHCl ₃ ) can be given.
Examples of silicon bromide include silicon tetrabromide (SiBr ₄ ), disilicon hexabromide, trisilicon octabromide, tetrasilicon decabromide and the like.
Furthermore, silicon bromide trichloride, silicon dibromide dichloride, silicon tribromide chloride, silicon iodide trichloride, silicon chlorosulfide, hexachlorodisiloxane and the like can be mentioned.
Among these, silicon tetrachloride (SiCl ₄ ) is particularly preferable.

(Halogenated germanium compound)
Examples of the halogenated germanium compound include germanium fluoride, germanium chloride, germanium bromide, and germanium iodide. Among these, germanium chloride and germanium bromide are preferable.
Examples of germanium chloride include germanium dichloride and germanium tetrachloride. Examples of germanium bromide include germanium dibromide and germanium tetrabromide.

  In the present embodiment, when the halide of the group 14 element of the periodic table used as a raw material is solid, a solution in which the raw material is dissolved in a predetermined solvent is prepared in advance, and this solution is supplied to the reaction vessel 10. You can also. The solvent that can be used is not particularly limited as long as it can dissolve a halide of a group 14 element of the periodic table. Preferably, the material is selected from known materials in consideration of the critical temperature and critical pressure inherent to the solvent in the supercritical fluid state described later. Specific examples include carbon dioxide, trifluoromethane (fluoroform), ethane, propane, butane, benzene, methyl ether, chloroform and the like.

(Polycrystalline production method)
Next, a method for producing a polycrystal of a periodic table group 14 element using the production apparatus I described above will be described. In the present embodiment, an example in which polycrystalline silicon (polysilicon) is manufactured using silicon tetrachloride (SiCl ₄ ) as a halide of a group 14 element of the periodic table and argon as a carrier gas will be described.

  In the present embodiment, first, the pressure adjustment valve 22a is opened, and the argon stored in the carrier gas storage tank 22 is supplied to the reaction vessel 10 through the gas supply pipe 22L. Subsequently, the raw material supply valve 21a is opened, and silicon tetrachloride stored in the raw material storage tank 21 is supplied to the reaction vessel 10 by the supply device 24 via the raw material supply pipe 21L. In the present embodiment, a liquid feed pump is used as the feeder 24. Silicon tetrachloride is heated to a predetermined temperature by the heater 23 before being supplied to the reaction vessel 10. Thereby, it can pressurize rapidly to the target pressure and can stabilize a pressure. Although the temperature of silicon tetrachloride heated by the heater 23 is not particularly limited, in the present embodiment, it is usually 300 K (27 ° C.) to 570 K (297 ° C.), preferably 330 (57 ° C.) to 520 K (247). ° C) range.

  The ratio of silicon tetrachloride and argon supplied to the reaction vessel 10 is not particularly limited. Usually, silicon tetrachloride is 0.1 ml to 100,000 ml, preferably 10 ml to 5,000 ml, more preferably 50 ml of argon. 10 ml to 200 ml. If the ratio of silicon tetrachloride to argon is too small, the production rate of polysilicon tends to be slow. If the ratio of silicon tetrachloride to argon is excessively large, the plasma discharge tends to become unstable.

  Note that the pressure in the reaction vessel 10 to which silicon tetrachloride and argon are supplied is adjusted using the pressure regulating valve 22a and the exhaust pressure regulating valve 25. Although the pressure in the reaction vessel 10 is not particularly limited, in the present embodiment, it is usually adjusted in the range of 3 MPa to 20 MPa, preferably 5 MPa to 10 MPa.

Next, the reaction vessel 10 is heated using a predetermined heater (not shown) to form a supercritical fluid state of a mixture of silicon tetrachloride and argon supplied to the reaction vessel 10.
Here, the supercritical fluid state is defined as a non-condensable fluid that exceeds the gas-liquid critical temperature inherent to the substance. That is, when gas and liquid are present in the sealed container, the liquid thermally expands as the temperature rises, and its density decreases. On the other hand, the density of gas increases as the vapor pressure increases. And finally, the density of both becomes equal, and it becomes a uniform state indistinguishable from gas and liquid. In the temperature-pressure diagram (not shown) of the substance, the point at which such a state is reached is called the critical point, the critical point temperature is called the critical temperature (Tc), and the critical point pressure is called the critical pressure (Pc). A supercritical fluid state means that the temperature and pressure of a substance exceed a critical point.

In the present embodiment, silicon tetrachloride has a critical temperature (Tc) of 506.75 K (233.6 ° C.) and a critical pressure (Pc) of 3.73 MPa. The critical temperature (Tc) of argon is 87.45K (-185.7 ° C.), and the critical pressure (Pc) is 4.86 MPa.
In the case of a mixture of silicon tetrachloride and argon, the critical temperature (Tc) and critical pressure (Pc) of the mixture depend on the composition of silicon tetrachloride and argon, and the critical temperature (Tc) and critical pressure (Pc) of each substance. ) Can be adjusted accordingly.

  In the present embodiment, the temperature of the reaction vessel 10 is usually heated to 80K or higher, preferably 300K to 600K, more preferably 313K to 510K. Moreover, the pressure in the reaction vessel 10 is usually maintained in a range of 3 MPa or more, preferably 4.86 MPa to 40 MPa, more preferably 4 MPa to 10 MPa. Under such conditions, a supercritical fluid state of a mixture of silicon tetrachloride and argon is formed in the reaction vessel 10.

  Subsequently, electric power is applied between the electrodes 11 and 12 by the high frequency power supply 27 to generate plasma discharge. The discharge conditions for generating plasma discharge are appropriately selected depending on the distance between the electrodes 11 and 12 and the pressure in the reaction vessel 10, and are not particularly limited. In the present embodiment, for example, when the frequency of the power source is set to 13.56 MHz and the power is set to about 100 W to 200 W, it is appropriate that the plasma discharge time is about several seconds to several hours.

  As described above, silicon tetrachloride is decomposed and reacted by applying power between the electrodes 11 and 12 in a supercritical fluid state of a mixture of silicon tetrachloride and argon to generate plasma discharge. Then, the silicon radicals that have reached the surface of the seed crystal 30 made of a silicon single crystal provided in the reaction vessel 10 after decomposition are deposited on the surface of the seed crystal 30. Then, crystallization is induced by the silicon single crystal of the seed crystal 30, solid phase epitaxial growth occurs, and finally polysilicon is formed.

In this embodiment, by performing plasma discharge on silicon tetrachloride in a supercritical fluid state, high concentration silicon radicals are generated, and high density polysilicon can be formed.
In addition, since silicon tetrachloride in a supercritical fluid state has high diffusibility, silicon radicals can be efficiently supplied to the surface of the seed crystal 30 and the like. Furthermore, by forming a supercritical fluid state of a mixture of silicon tetrachloride and argon, the inside of the reaction system is maintained at a uniform concentration, and the denseness of the produced polysilicon is improved.
In addition, by using a silicon single crystal as the seed crystal 30, the growth of polysilicon is promoted.

In the present embodiment, the case where the high-frequency power source 27 is used when performing plasma discharge has been described, but a DC power source may be used instead.
Further, chlorine decomposed by plasma discharge in the supercritical fluid state is recovered by a predetermined chlorine gas recovery device (not shown). Furthermore, it is recovered by an unreacted silicon tetrachloride recovery device (not shown) and recycled to the raw material storage tank 21.

  Hereinafter, the present embodiment will be described in more detail based on examples. However, the present invention is not limited to these examples.

(Example)
Polysilicon is manufactured by the following operation using the manufacturing apparatus I shown in FIG.
As the reaction vessel 10, a pressure-resistant cell (internal capacity: 50 ml) made of Hastelloy C that can be energized is used. A liquid feed pump (manufactured by JASCO Corporation) as the feeder 24, a fully automatic pressure regulator valve (manufactured by JASCO Corporation) as the pressure regulating valve 22a, and a fully automatic drain pressure regulating valve (JASCO Corporation as the exhaust pressure regulating valve 25). Made).

As the electrodes 11 and 12, parallel plate electrodes each having a width of 10 mm and a length of 20 mm are attached to the reaction vessel 10. SUS is used as the material of the electrodes 11 and 12. The distance between the electrodes 11 and 12 is set to 0.01 mm. A seed crystal 30 made of a silicon single crystal is attached on the carbon electrode 31. The raw material storage tank 21 is filled with silicon tetrachloride having a purity of 99.9%. The carrier gas storage tank 22 is filled with argon gas having a purity of 99.9%.
As the high frequency power supply 27, an AC generator (Tokyo High Power Co., Ltd. PSG-1301), a high frequency generator (Tokyo High Power Co., Ltd. PA-150) and a DC converter (Tokyo High Power Co., Ltd. PS-330) are used. ) And HC-2000 manufactured by Tokyo High Power Co., Ltd. is used as the matching unit 26.

First, argon gas is supplied from the carrier gas storage tank 22 into the reaction container 10, and then silicon tetrachloride is supplied from the raw material storage tank 21 into the reaction container 10. Next, the pressure in the reaction vessel 10 is increased to 5 MPa, the temperature is raised to 308 K, a supercritical fluid state of a mixture of silicon tetrachloride and argon gas is formed, and the mixture is left for about 20 minutes.
Subsequently, in a supercritical fluid state of a mixture of silicon tetrachloride and argon gas, 100 W of power is applied to the electrodes 11 and 12 by the high frequency power supply 27 (13.56 MHz) for about 3 minutes to generate plasma discharge. Thereafter, the reaction vessel 10 is cooled, and the pressure in the reaction vessel 10 is reduced at a rate of 0.1 MPa / min.
After the reaction is completed, polysilicon is formed on the surface of the seed crystal 30 made of a silicon single crystal provided in the reaction vessel 10.

  FIG. 2 shows a plasma emission spectrum in a supercritical fluid state of a mixture of silicon tetrachloride and argon gas. According to the plasma emission spectrum shown in FIG. 2, peaks corresponding to silicon atoms (212.1 nm, 221.3 nm, 251.9 nm, and 288.4 nm) are observed. Among these, very strong peaks are detected at 221.3 nm and 251.9 nm. Thereby, it turns out that silicon tetrachloride has decomposed | disassembled into atomic form.

It is a figure explaining an example of the manufacturing apparatus for enforcing the manufacturing method of the polycrystal of the periodic table 14 group element to which this Embodiment is applied. The plasma emission spectrum in the supercritical fluid state of the mixture of silicon tetrachloride and argon gas is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Reaction container (reaction container main body), 11, 12 ... Electrode, 21 ... Raw material storage tank, 22 ... Carrier gas storage tank, 27 ... High frequency power supply, 30 ... Seed crystal, 31 ... Carbon electrode, 32 ... External power supply

Claims (9)

An apparatus for producing a polycrystalline body,
A supercritical fluid state of a mixture of a halide of a periodic table group 14 element selected from silicon (Si) and germanium (Ge) introduced into the inside and a carrier gas consisting of an inert gas selected from helium, neon, and argon A reaction vessel body for forming;
A carrier gas storage tank for storing the carrier gas supplied into the reaction vessel body;
An electrode provided inside the reaction vessel body for performing plasma discharge;
And a seed crystal that is provided inside the reaction vessel main body and precipitates on the surface the group 14 element of the periodic table decomposed by the plasma discharge.   The apparatus for producing a polycrystalline body according to claim 1, further comprising an external power source that applies a predetermined voltage to the seed crystal.   The said seed crystal is comprised from a silicon single crystal, The manufacturing apparatus of the polycrystalline body of Claim 1 or 2 characterized by the above-mentioned. A method for producing a polycrystal, comprising:
In a reaction vessel having an electrode and a seed crystal inside, an inert gas selected from helium, neon, and argon as a carrier gas, and a halide of a group 14 element in the periodic table selected from silicon (Si) and germanium (Ge) A supercritical fluid state forming step of forming a supercritical fluid state of a mixture of the inert gas and the halide of the group 14 element of the periodic table ;
A crystal precipitation step of performing plasma discharge in the formed supercritical fluid state to deposit a polycrystal of a group 14 element of the periodic table on the seed crystal.   The method for producing a polycrystalline body according to claim 4, wherein the pressure in the reaction vessel is maintained at 3 MPa or more and the temperature in the reaction vessel is maintained at 80 K or more. 5. The method for producing a polycrystalline body according to claim 4 , wherein 50 ml of an inert gas is introduced to 0.1 ml to 100,000 ml of a halide of a group 14 element of the periodic table. The method for producing a polycrystalline body according to any one of claims 4 to 6 , wherein, in the crystal precipitation step, the temperature of the seed crystal is maintained at 450K or higher. The method for producing a polycrystalline body according to any one of claims 4 to 7 , wherein the halide of the group 14 element of the periodic table is a chloride or bromide. The method for producing a polycrystalline body according to any one of claims 4 to 8 , wherein the halide of the group 14 element of the periodic table is silicon tetrachloride.

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