JP3737863B2 - Method for producing granular polysilicon - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing granular polysilicon by depositing silicon on the surface of polysilicon particles by thermal decomposition reaction or reduction reaction of a silane compound using a fluidized bed reactor, and depositing and depositing on the inner wall of the reactor. The present invention relates to a method for producing granular polysilicon that can be continuously operated for a long period of time by efficiently removing the removed polysilicon.
[0002]
[Prior art]
Normally, granular polysilicon is produced by a method in which silicon is deposited on the surface of polysilicon particles by thermal decomposition reaction or reduction reaction of a silane compound in a fluidized bed reactor. In this method, silicon produced by the thermal decomposition reaction or reduction reaction of the silane compound is not only deposited on the surface of the polysilicon particles but also deposited on the inner wall of the reactor.
[0003]
In general, the inner wall of a fluidized bed reactor is made up of an insert tube to prevent contamination from impurities coming from the reactor body. If the material of this insert tube is quartz, the reaction will occur after polysilicon is deposited on the inner wall. When the operation is stopped, there arises a problem that the insert tube is broken due to a difference in thermal expansion coefficient between quartz as the inner wall material and deposited polysilicon.
[0004]
Even if the material is not damaged, the deposition of polysilicon on the inner wall causes the reactor to be clogged, resulting in a problem that long-term continuous operation becomes difficult.
[0005]
Conventionally, in order to solve the above problem, as a method for preventing polysilicon from depositing on the inner wall of the reactor, a raw material gas is supplied from the inner nozzle to the reactor using a double tube nozzle, and the annular outer nozzle is used. A method of supplying hydrogen, a method of blowing a polysilicon deposition suppressing gas from the inner wall of the reactor, a method of setting an inner cylinder in the reactor and advancing the reaction with the raw material gas inside the reactor, and further, the inner wall of the reactor inside the reactor A method of making the temperature lower than that of granular polysilicon is known.
[0006]
The method shown above aims to inhibit the source gas from reaching the inner wall of the reactor that supplies heat, and to slow down the deposition rate of polysilicon on the inner wall of the reactor. In the method using a nozzle, since the separately supplied raw material gas and hydrogen gas are immediately mixed by vigorous particle mixing in the fluidized bed in the reactor, the effect of inhibiting the raw material gas from reaching the inner wall is small, It is not possible to sufficiently suppress the deposition of polysilicon on the inner wall of the reactor. In the method in which the polysilicon deposition suppressing gas is blown from the inner wall of the reactor, there is a problem that the thermal efficiency is deteriorated and the granular polysilicon cannot be produced efficiently. In the method in which the inner cylinder is installed in the reactor and the reaction of the raw material gas proceeds inside, or in the method in which the temperature of the inner wall of the reactor is lower than the temperature of the granular polysilicon, the polysilicon is deposited on the inner cylinder or the inner wall of the reactor. It does not completely suppress the deposition of polysilicon on the inner wall of the reactor only by slowing down the speed, but eventually the inner wall is damaged due to the deposition and deposition of polysilicon on the inner wall of the reactor, or long-term due to clogging. Continuous operation becomes difficult.
[0007]
In addition, in order to prevent damage to the insert tube due to deposition of polysilicon on the inner wall of the fluidized bed reactor, a material having a thermal expansion coefficient close to that of polysilicon may be used, but when the material is graphite or silicon carbide, However, since the carbon derived from these materials is mixed into the granular polysilicon as an impurity, it becomes a serious problem particularly when the granular polysilicon is used for a semiconductor application. Therefore, the material of the insert tube is preferably polysilicon. It is. However, even when the material of the insert pipe is polysilicon, the deposition of polysilicon on the inner wall cannot be prevented, and as a result, the long-term continuous operation becomes difficult due to the blockage.
[0008]
In this case, as a method of removing polysilicon deposited on the inner wall of the fluidized bed reactor, the reaction is stopped when polysilicon is deposited to some extent on the reactor inner wall, and a mixed gas of hydrogen chloride and silicon tetrachloride is added to the reactor. An etching method is known that removes polysilicon deposited on the inner wall by supplying it into the inner wall. However, in this method, not only the polysilicon deposited on the inner wall is removed, but also the polysilicon insert constituting the inner wall. The overetching phenomenon that also removes the tube results in damage to the insert tube. Therefore, it is necessary to replace the damaged insert tube.
[0009]
[Problems to be solved by the invention]
Therefore, there is no damage to the inner wall of the fluidized bed reactor due to the removal of polysilicon deposited on the inner wall of the fluidized bed reactor, and there is no need to replace the insert tube in the long term, and the fluidized bed type reaction therefor A vessel has been sought.
[0010]
[Means for Solving the Problems]
As a result of earnest research to solve the above technical problem, the present inventor used a fluidized bed reactor in which an inner wall is constituted by a polysilicon insert tube having an oxide layer formed on the surface, and a halogen gas is formed on the inner wall. Alternatively, it has been found that polysilicon deposited on the inner wall can be removed without over-etching by contacting with a gas containing hydrogen halide, and the present invention has been completed.
[0011]
That is, according to the present invention, in a method for producing granular polysilicon by thermal decomposition reaction or reduction reaction of a silane compound using a fluidized bed reactor, an oxide layer is formed on the inner wall of the fluidized bed reactor. It is constituted by a polysilicon insert tube, and polysilicon is deposited on the inner surface of the insert tube by the reaction, and when deposited, the deposited polysilicon is brought into contact with a gas containing halogen gas or hydrogen halide. This is a method for producing granular polysilicon.
[0012]
The present invention also provides a fluidized bed reactor comprising an insert wall made of polysilicon having an inner layer formed on the inner wall of the fluidized bed reactor used in the production method.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
As the silane compound used in the present invention, silane such as monosilane and disilane or halogenated silane such as monochlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane, and hexachlorosilane can be used, and these can be used alone or in combination of two or more. May be. These silane compounds may be used as they are or diluted with other gases, but are preferably diluted with hydrogen and an inert gas such as argon, helium and nitrogen. The concentration of the compound is preferably 1 to 50%. If it is less than 1%, the precipitation reaction is slow, and if it is more than 50%, the precipitation reaction occurs rapidly.
[0014]
For the thermal decomposition reaction or reduction reaction of the silane compound for producing granular polysilicon in the present invention, a known method can be applied without any particular limitation. As the reaction conditions for these reactions, the conditions usually used can be adopted without any particular limitation. In general, the thermal decomposition reaction may be at or above the decomposition temperature of the silane compound, and the range of 600 to 700 ° C. is particularly suitable. The reduction reaction is generally performed by adding hydrogen, and the reaction temperature is preferably 900 to 1400 ° C, and particularly preferably 1100 to 1200 ° C.
[0015]
In the present invention, any known fluidized bed reactor can be used without any limitation. FIG. 1 shows a schematic configuration diagram of an apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a fluidized bed reactor, and an inner wall is constituted by a polysilicon insert tube 11. In the lower part of the fluidized bed reactor 1, a raw material introduction nozzle 2 for introducing a raw material silane compound, a hydrogen introduction nozzle 3, a nitrogen introduction nozzle 4 for purging the inside of the reactor with nitrogen, a product particle extraction nozzle 5, and an etching gas are introduced. A gas dispersion plate 7 on which an etching introduction nozzle 6 and an oxidant introduction nozzle 12 are disposed. The upper part of the fluidized bed reactor 1 includes a gas discharge pipe 8 and a polysilicon seed particle charging pipe 9 for charging polysilicon seed particles into the reactor. A heater 10 is provided above the gas dispersion plate 7 so as to surround the fluidized bed reactor 1.
[0016]
In the apparatus, the precipitation reaction is performed in a fluidized bed portion 13 formed in a fluidized bed reactor 1 whose inner wall is constituted by a polysilicon insert 11.
[0017]
A feature of the present invention resides in that the inner wall of the fluidized bed reactor is constituted by a polysilicon insert tube having an oxide layer formed on the surface thereof. By providing an oxide layer on the surface of the polysilicon insert tube, when the polysilicon deposited on the inner wall is removed by etching, over-etching of the insert tube is eliminated, and damage to the polysilicon insert tube can be prevented. .
[0018]
The material of the insert tube in the present invention is not particularly limited as long as it is a known polysilicon, but is preferably high-purity polysilicon in order to prevent contamination with impurities. The formation of the insert tube is not particularly limited, and may be an integral tube or a combination of a plurality of members. In this case, the shape of the inner surface is not particularly limited and may be a cylindrical shape or a rectangular tube shape. However, in order to remove the polysilicon deposited on the inner wall evenly, the cylindrical shape is preferable.
[0019]
In addition, the location of the insert tube as the inner wall of the fluidized bed reactor is not particularly limited. However, in the case of a system in which heat is applied from the outside of the reactor, the reactor and the insert tube are in close contact to improve heat conductivity. The method of installing and the method of installing by installing a member with good heat conductivity between the reactor and the insert tube are preferable.
[0020]
As a method for forming an oxide layer on the surface of the insert tube in the present invention, a known method can be applied without particular limitation. However, in order to prevent damage to the oxide layer, there is a temperature difference from the precipitation reaction temperature at the time of forming the oxide layer. The temperature is preferably within ± 50%, and the temperature difference from the precipitation reaction temperature is preferably maintained within ± 50% until the precipitation reaction is performed. That is, since there is a difference in the coefficient of thermal expansion between the polysilicon that is the material of the insert tube and the oxide layer formed on the polysilicon surface, the temperature difference from the deposition reaction temperature to the precipitation reaction is ±± By making it within 50%, breakage of the oxide layer can be prevented.
[0021]
The method of forming an oxide layer applicable to the present invention shown above is a method of contacting a gaseous oxidant such as oxygen, air, water vapor, nitrous oxide at 600 to 900 ° C., in a liquid oxidant such as nitric acid at room temperature. Examples of the method include immersion, and these methods may be used alone or in combination. The oxide layer may be formed after the insert tube is installed in the fluidized bed reactor or may be formed in advance before installation.
[0022]
In the present invention, the thickness of the oxide layer is preferably in the range of 0.01 to 100 μm. If the thickness of the oxide layer is less than 0.01 μm, it is preferable because the oxide layer is peeled off due to abrasion by granular polysilicon during the precipitation reaction, and the surface of the insert tube is over-etched when it comes into contact with a gas containing halogen gas or hydrogen halide. Absent. On the other hand, if it is thicker than 100 μm, the oxide layer is damaged due to the difference in thermal expansion coefficient between the oxide layer and the insert tube, which is not preferable. In addition, in order to prevent the oxide layer from being worn by the polysilicon particles during the precipitation reaction, silicon is generated in advance by a thermal decomposition reaction or reduction reaction of the silane compound before the precipitation reaction, and the surface of the oxide layer is covered with polysilicon. It is preferable to do this.
[0023]
In the present invention, the deposited polysilicon is removed by bringing a gas containing halogen gas or hydrogen halide (hereinafter referred to as etching gas) into contact with the surface of the insert tube. Halogen gas is preferably chlorine used in the present invention, the hydrogen halide Hydrogen chloride, bromide hydrogen. These etching gases may be used alone or in combination of two or more. The concentration of the halogen gas or hydrogen halide in the etching gas is not particularly limited, but is preferably 0.3 to 100% by volume. If the concentration is less than 0.3% by volume, the etching rate is slow, which is not preferable. As a gas for diluting the etching gas, a gas that does not impair the effects of the present invention can be used without any limitation, and hydrogen and inert gases such as argon, helium, and nitrogen are particularly preferable.
[0024]
In the present invention, the contact temperature between the etching gas and the insert tube is preferably 600 to 900 ° C. If the temperature is lower than 600 ° C., the reaction rate with chlorine or hydrogen halide in the etching gas is poor, and if it is higher than 900 ° C., over-etching occurs partially and uniform etching is not preferable. The contact temperature is preferably set to a temperature within ± 50% with respect to the precipitation reaction temperature. If the temperature change is more than ± 50%, the insert tube is damaged or the polysilicon deposited on the insert tube is peeled off.
[0025]
The flow rate of the etching gas in the fluidized bed reactor is preferably 0.01 to 200 cm / sec when empty. If the flow rate is less than 0.01 cm / second, the processing amount becomes small and is not practical. If the flow rate is larger than 200 cm / second, the reaction rate of chlorine or hydrogen halide is deteriorated, and as a result, a large amount of etching gas is required. It is not preferable.
[0026]
In the present invention, the timing when the inner surface of the fluidized bed reactor is brought into contact with the etching gas is not limited at all, and may be appropriately determined in consideration of production efficiency and etching efficiency. It is preferable to contact the etching gas when it reaches 1 to 20% of the inner capacity.
[0027]
In addition, the etching process is preferably performed by once stopping the precipitation reaction in consideration of the etching efficiency. If the granular polysilicon exists in the reactor, the granular polysilicon is also etched at the same time. It is preferable that the granular polysilicon in the vessel is once extracted and the inside of the reactor is emptied before etching.
[0028]
Furthermore, it is preferable to maintain within ± 50% of the precipitation reaction temperature and the etching treatment temperature until the etching treatment is performed after the precipitation reaction is stopped in order to prevent breakage of the insert tube.
[0029]
【The invention's effect】
According to the present invention, by using a reactor in which an inner wall is constituted by a polysilicon insert tube having an oxide layer formed on the surface, a gas containing halogen gas or hydrogen halide on the inner wall, which has been considered as a problem in the past, is used. By contacting, the overetching of the insert tube when removing the polysilicon deposited on the insert tube is eliminated, and it becomes possible to manufacture granular polysilicon without replacing the insert tube.
[0030]
【Example】
Examples of the present invention will be described below with reference to FIG. 1, but the present invention is not limited to these examples.
[0031]
Example 1
Using the fluidized bed reactor 1 whose inner wall is constituted by the insert tube 11 made of polysilicon and having a cylindrical inner surface, the reactor temperature is first heated to 700 ° C. using the heater 10, and then the oxidizing agent introduction nozzle The air was introduced into the reactor from No. 12, and the air was brought into contact with the surface of the insert tube for 5 hours to form an oxide layer on the surface of the insert tube. The thickness of the oxide layer formed by this oxide layer formation process was 0.1 μm.
[0032]
After forming the oxide layer, while maintaining the temperature in the reactor at 700 ° C., nitrogen is introduced from the nitrogen introduction nozzle 4 to replace the inside of the reactor with nitrogen, and hydrogen is further introduced from the hydrogen introduction nozzle 3 to react. The inside of the vessel was replaced with hydrogen.
[0033]
Next, the temperature of the reactor is set to 650 ° C., a predetermined amount of polysilicon seed particles are charged into the reactor from the polysilicon seed particle charging tube 9 to form the fluidized bed portion 13, and then the monosilane supply rate is set to 2 kg / hr, under the condition that the volume ratio of monosilane and hydrogen is 1: 9, monosilane is supplied from the raw material supply nozzle 2 provided in the gas dispersion plate 7 below the fluidized bed reactor 11, and hydrogen is supplied from the hydrogen introduction nozzle 3 to the fluidized bed. It was supplied to the mold reactor 1 and the precipitation reaction was performed for 300 hours.
[0034]
After the precipitation reaction, while maintaining the temperature in the reactor at 650 ° C., the particles in the reactor are extracted from the product particle extraction nozzle 5, then the temperature of the reactor is set to 690 ° C. by the heater 10, and the etching gas introduction nozzle From No. 6, hydrogen chloride gas having a concentration of 100% was introduced into the reactor under the condition of a flow rate of 16 cm / sec on the inner wall of the fluidized bed reactor when empty, and etching treatment was performed for 250 hours.
[0035]
When the insert tube 11 was taken out from the fluidized bed reactor 1 after the etching process was completed, the polysilicon deposited on the inner wall by the precipitation reaction was completely removed, and over-etching to the insert tube 11 was observed. Furthermore, there was no change in the weight of the insert tube 11.
[0036]
When the etching operation was not performed, the insert tube 11 was taken out and the weight was measured after completion of the reaction. As a result, 2.5% of the capacity of the polysilicon in the reactor was deposited on the inner wall of the polysilicon insert tube 11. Was.
[0037]
Example 2
The same operation as in Example 1 was performed except that the insert tube 11 was immersed in 70% nitric acid for 1 hour and then placed in the fluidized bed reactor 11. In this case, the thickness of the oxide layer was 5 μm.
[0038]
When the insert tube was taken out from the reactor after completion of etching, the polysilicon deposited on the inner wall by the precipitation reaction was completely removed, no over-etching on the insert tube was observed, and there was no change in the weight of the insert tube 11. It was.
[0039]
Comparative Example The same operation as in Example 1 was performed, except that the precipitation reaction of granular polysilicon was performed without forming an oxide layer on the surface of the insert tube.
[0040]
After completion of the etching operation, the reactor was opened and the insert tube was taken out. As a result, the polysilicon deposited on the inner wall by the precipitation reaction was removed, but part of the polysilicon insert tube 11 was over-etched, and the weight was reduced. Decreased by 0.3%.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.
1. 1. fluidized bed reactor 2. Raw material introduction nozzle 3. Hydrogen introduction nozzle 4. Nitrogen introduction nozzle Product particle extraction nozzle 6. 6. Etching gas introduction nozzle 7. Gas dispersion plate 8. Gas exhaust pipe 9. Polysilicon seed particle charging tube Heater 11. Insert tube 12. Oxidant introduction nozzle 13. Fluidized bed part

Claims (5)

  In a method for producing granular polysilicon by depositing silicon by thermal decomposition reaction or reduction reaction of a silane compound using a fluidized bed reactor, a polycrystal having an oxide layer formed on the inner wall of the fluidized bed reactor. Granular polysilicon comprising a silicon insert tube, polysilicon deposited on the inner surface of the insert tube, and contacting the deposited polysilicon with a gas containing halogen gas or hydrogen halide when deposited Manufacturing method.   The method for producing granular polysilicon according to claim 1, wherein the contact temperature with the gas containing halogen gas or hydrogen halide is 600 to 900 ° C. The method for producing granular polysilicon according to claim 1, wherein the contact temperature with the gas containing halogen gas or hydrogen halide is within ± 50% of the reaction temperature.   A fluidized bed reactor for producing granular polysilicon, characterized in that the inner wall is constituted by an insert tube made of polysilicon having an oxide layer formed on the surface thereof.   The fluidized bed reactor for producing granular polysilicon according to claim 4, wherein the oxide layer has a thickness of 0.01 to 100 µm.

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