RU79882U1 - POLYCRYSTALLINE SILICON SPRAYING DEVICE - Google Patents

Abstract

The utility model relates to the production of polycrystalline silicon. A device for spraying polycrystalline silicon consists of a casing equipped with at least one flange made with cooling, a cuvette with molten aluminum is placed inside the casing, made with the possibility of heating it, a thermostatic substrate for the deposition of polycrystalline silicon is placed over the cuvette, the cuvette is provided with a lid , the reagent supply system is a coaxial burner consisting of three concentrically arranged nozzles, an external chloride supply nozzle aluminum (AlCl _3), the inner tube supplying the silicon tetrachloride (SiCl ₄₎ and the intermediate pipe supplying an inert gas, wherein the outer tube feeding aluminum chloride is connected to the cuvette, to provide a passage of the reactant gas between the surface of molten aluminum and a cover, wherein the device body , the cuvette, the outer and intermediate nozzles are made of aluminum oxide-based material, and the inner nozzle is made of silicon oxide-based material.

The device allows to obtain a polycrystalline silicon film of the required purity, suitable for photovoltaics. 1 n.a. and 7 z.p. f-ly, 1 ill.

Description

The invention relates to the production of polycrystalline silicon, in particular, to devices for the conversion of silicon tetrachloride to polycrystalline silicon and its deposition.

A device for the hydrogenation of silicon tetrachloride is known, which allows a process with a high degree of conversion of silicon tetrachloride to trichlorosilane (Patent RU 2278076, С01В 33/107, 2006.06.20), and a device for producing polycrystalline silicon from trichlorosilane by its hydrogen reduction at high pressure and with low output (Siemens - process) (US Patent No. 4102764, B01J 10/00; СВВ 33/02; СВВ 33/027, 1978.07.25; № 4102985, C01B 33/02; C01B 33/027; C01B 33/00, 1978.07 .25). These devices are extremely complex in design and operating modes, and do not allow to achieve a high degree of conversion of silicon tetrachloride in one pass. In addition, they require an additional large number of auxiliary equipment for their work, in particular, for the conversion of simultaneously generated silicon chlorides and hydrochlorides (chlorosilanes).

A device is known that is close in design to the claimed one, designed to recover silicon tetrachloride vapors using metal vapor, for example magnesium, sodium, supplied to the device from the outside. (US Patent 4,139,438 B01K 1/00; C01B 33/02, 1979.02.13).

The known device does not allow to obtain a film of polycrystalline silicon. The silicon obtained in the device is contaminated with sodium or magnesium chlorides formed during the reduction of silicon, since their boiling point exceeds the optimum temperature required for the formation of the required semiconductor characteristics of a polycrystalline silicon film.

The closest in technical essence to the claimed device is a device for producing polycrystalline silicon by the method of zincothermy (EP1550636, С01В 33/035, 2005.07.06), which has a reaction zone closed from the surrounding atmosphere and a reagent vapor supply system. The device gives a silicon yield close to 100%, but it does not provide the possibility of obtaining a film of polycrystalline silicon suitable for photovoltaics. Vapors of a reducing agent, in this case zinc having a boiling point of 907 ° C, also have a temperature above the optimum required to obtain a polycrystalline silicon film,

suitable for photovoltaics, enter the device from the outside, in contact with the walls of the housing and other structural elements, contaminating the final product with impurities from structural materials. For the implementation of the cleaning process requires additional remelting of silicon at reduced pressure, and, therefore, additional equipment, which leads to higher costs of the device and increase the cost of the final product - polycrystalline silicon. In addition, the return of the reducing metal to the process requires its electrolytic reduction from chloride — ZnCl ₂ in high-temperature salt electrolysis cells, which is associated with its contamination with electrolyte and electrode material. Increases the cost of the device and the need to use special materials for its manufacture, capable of withstanding the high temperature process.

The problem that the claimed utility model solves is to obtain a polycrystalline silicon film suitable for photovoltaics, and to reduce the cost of producing polycrystalline silicon.

The technical result is achieved by providing the possibility of synthesizing a gaseous reducing agent inside the device case, excluding its external supply, cheaper device, due to the production of polycrystalline silicon film of the required purity in one device and the use of traditional materials for the manufacture of the device, due to the reduction in temperature in the polycrystalline silicon deposition zone .

This object is achieved in that in a device for spraying polycrystalline silicon, comprising a housing with a feed and withdrawal system of reagents, heaters, a substrate for the deposition of polycrystalline silicon, according to the claimed solution, the housing is equipped with at least one flange made with cooling inside the housing at least one cuvette with molten aluminum, arranged to heat it and provided with a lid, a reagent supply system, is placed under the thermostated substrate represents a coaxial burner consisting of three concentrically arranged nozzles, an external nozzle for supplying aluminum chloride (AlCl ₃ ), an internal nozzle for feeding silicon tetrachloride (SiCl ₄ ) and an intermediate nozzle for supplying inert gas, and the outer nozzle for feeding aluminum chloride (AlCl ₃ ) is connected with a cuvette, with the possibility of ensuring the passage of a gaseous reagent between the surface of the molten aluminum and the lid, while the body of the device, the cuvette, the outer and intermediate nozzles are made of material and an aluminum oxide, and an inner pipe made of a material based on silicon oxide.

As a material for the manufacture of the device case, leucosapphire can be used.

The housing of the device can be made insulated in the middle part.

As a device heating a cell, heaters installed inside the housing can be used.

Induction emitters installed outside the housing can be used as a device for heating the cell.

As a device heating a cuvette, infrared emitters installed outside the housing can be used.

When placing more than one cuvette inside the body, they are placed one above the other.

The inner pipe for supplying silicon tetrachloride (SiCl ₄ ) can be made of quartz.

The essence of the claimed utility model is illustrated by the drawing, which schematically shows a device for spraying polycrystalline silicon.

The device consists of a housing 1, heaters 2, a cuvette with liquid aluminum 3 with a cover 4, a thermostatically controlled substrate 5 on a thermostat-holder 6, a coaxial burner 7, consisting of an external pipe 8 for supplying aluminum chloride, an internal pipe 9 for supplying silicon tetrachloride and an intermediate pipe 10 inert gas supply, reagent outlet pipe 11, flanges 12.

Through the inner pipe 9 of the coaxial burner 7, silicon tetrachloride (SiCl ₄ ) is introduced into the reaction zone. To protect the pipe 9 from exposure to aluminum chloride and to maintain the required reaction temperature, an inert gas, argon, is supplied through the coaxial pipe 10. Alumina chloride (AlCl ₃ ) is introduced through nozzle 8 into a cuvette 3 with liquid aluminum, which, interacting with the melt mirror, is reduced to aluminum subchloride, which is a mixture of aluminum mono-, di-, and trichloride with aluminum monochloride dominating in this mixture. The ratio between aluminum chlorides is determined by the temperature of the cell: the higher it is, the greater the mixture of aluminum monochloride in the mixture leaving the cell. In the reaction zone, the mixing of the three gas flows and the interaction of silicon chloride and aluminum subchloride. The reduced silicon deposits on a thermostated substrate 5, the temperature of which is maintained at the required level by the thermostat-holder 6 due to cooling from the inside with a gas or liquid coolant. A co-product of the chemical reaction - AlCl ₃ leaves the reaction space and the device as a whole through the pipe 11 in the upper flange 12.

The inventive design of the device provide the maximum possible completeness of the reaction:

SiCl ₄ + 2 / 3AlCl ₃ + 4 / 3Al → Si + 2AlCl ₃

Placing a cuvette with liquid aluminum inside the reaction chamber in the high temperature zone (in the middle of the chamber) provides the maximum distance to the cooled flanges and the minimum distance for the passage of aluminum subchloride (AlCl _x , x <3), the product of the interaction of aluminum chloride with a mirror of molten aluminum, to the reaction zone located between the coaxial burner, consisting of a set of concentrically arranged nozzles for supplying reagents: fuel (AlClx), oxidizing agent (SiCl ₄ ) and inert gas ballast (argon). In the reaction zone, mixing and a highly exothermic reaction between gas reagents (combustion) occurs.

The design of the device allows the most rational use of heat from the heaters, since this heat is used to preheat the initial components of the gas mixture and maintain the temperature of the aluminum mirror, where the endothermic reaction of the reduction of aluminum chloride to subchloride takes place.

To protect the reaction space from oxygen and nitrogen, air sealing flanges with nozzles for supplying and removing reagents are located in cold zones with a temperature of 180-200 ° C, which allows the use of traditional materials for the manufacture of flanges - stainless steel, fluorosilicon rubber, etc., and significantly reduce the cost of device cost. At this temperature, AlCl ₃ vapor enters and leaves the device without desublimation.

For the effective implementation of the synthesis of aluminum subchloride, the temperature of the aluminum in the cell is maintained by a separate heater in the range of 1000-1400 ° C. The outer pipe for supplying aluminum chloride (AlCl ₃ ) is connected to the cuvette, with the possibility of ensuring the passage of the gaseous reactant between the surface of the molten aluminum and the lid, which ensures long-term contact of AlCl ₃ with the surface of the molten aluminum. The execution of the case walls from an alumina-based material ensures the resistance of the case to the reducing agent, and the manufacture of the case, in particular, from leucosapphire, provides transparency and allows the temperature of the substrate to be controlled by an optical pyrometer, and the course of chemical reactions of combustion of aluminum subchloride in silicon tetrachloride vapors with a spectrometer.

Claims (8)

1. A device for spraying polycrystalline silicon, comprising a housing with a reagent supply and withdrawal system, heaters, a substrate for the deposition of polycrystalline silicon, characterized in that the housing is equipped with at least one flange made with cooling, inside the housing under a thermostated substrate is placed at least one cuvette with molten aluminum, made with the possibility of heating and provided with a lid, the reagent supply system is a coaxial burner, consisting of w of three concentric pipes, the outer pipe feeding aluminum chloride (AlCl _3), the inner tube supplying the silicon tetrachloride (SiCl ₄₎ and the intermediate pipe supplying an inert gas, wherein the outer tube feeding aluminum chloride (AlCl ₃₎ is connected to the cuvette to provide a passage gaseous reagent between the surface of the molten aluminum and the lid, while the body of the device, the cuvette, the outer and intermediate nozzles are made of material based on aluminum oxide, and the inner nozzle is made silicon oxide based material. 2. The device according to claim 1, characterized in that the housing of the device is made of leucosapphire. 3. The device according to claim 1, characterized in that the housing of the device is made insulated in the middle part. 4. The device according to claim 1, characterized in that the cell heaters are installed inside the housing. 5. The device according to claim 1, characterized in that the induction emitters installed outside the housing are used as the device heating the cell. 6. The device according to claim 1, characterized in that infrared emitters installed outside the housing are used as a device heating cell. 7. The device according to claim 1, characterized in that when placing more than one cuvette inside the casing, they are placed one above the other. 8. The device according to claim 1, characterized in that the inner pipe for supplying silicon tetrachloride (SiCl ₄ ) is made of quartz.