Abstract: The invention relates to a method for producing polycrystalline silicon granulate in a fluidized bed reactor. The method comprises a fluidization of silicon seed particles by means of a fluidizing gas in a fluidized bed, which is heated by a heating device, wherein elemental silicon is deposited by pyrolysis on the silicon seed particles by the addition of a reaction gas containing hydrogen and silane and/or halosilane to form the polycrystalline silicon granulate. In a continuous process, waste gas is discharged from the fluidized bed reactor and hydrogen recovered from said waste to gas is again supplied to the fluidized bed reactor as a circulating gas. The circulating gas has a nitrogen content of less than 1000 ppmv. The invention further relates to polycrystalline silicon granulate having a nitrogen content of less than 2 ppba.

Abstract: The invention relates to a method for producing polycrystalline silicon granulate in a fluidized bed reactor. The method comprises a fluidization of silicon seed particles by means of a fluidizing gas in a fluidized bed, which is heated by a heating device, wherein elemental silicon is deposited by pyrolysis on the silicon seed particles by the addition of a reaction gas containing hydrogen and silane and/or halosilane to form the polycrystalline silicon granulate. In a continuous process, waste gas is discharged from the fluidized bed reactor and hydrogen recovered from said waste to gas is again supplied to the fluidized bed reactor as a circulating gas. The circulating gas has a nitrogen content of less than 1000 ppmv. The invention further relates to polycrystalline silicon granulate having a nitrogen content of less than 2 ppba.

Abstract: Contamination of fluidized bed-produced polycrystalline granules by phosphorus is reduced by employing as seals and/or packings, graphite containing <500 ppmw of phosphorus.

Abstract: Yield of products of increased purity from a fluidized bed reactor where silicon is produced or consumed is enhanced by purging with inert gas, purging with hydrogen gas, and purging with a chlorosilane-containing gas. The purging with hydrogen is conducted at an elevated temperature.

Abstract: Assembly of a fluidized bed reactor for the preparation of polycrystalline silicon granules by chemical vapor deposition of silicon onto seed particles and removal of polycrystalline silicon granules is facilitated without breakage and with gas tightness by a specific assembly sequence.

Abstract: A reactor for preparing granular polysilicon by deposition of polycrystalline silicon on silicon seed particles has a reaction vessel, an inner reactor tube for a fluidized bed comprising granular polysilicon and a reactor bottom within the reactor vessel, a heating device for heating the fluidized bed in the inner reactor tube, at least one bottom gas nozzle for introduction of fluidizing gas and at least one reaction gas nozzle for introduction of reaction gas, a feed device to introduce silicon seed particles, an offtake line for granular polysilicon, and a device for discharging reactor offgas from the reactor vessel, and has a cylindrical component which has openings on its cylindrical surface, with at least 5% and not more than 95% of the cylindrical surface being open located between the inner reactor tube and the heating device.

Abstract: Granular polysilicon is produced in a fluidized-bed reactor by fluidizing silicon particles by means of a gas flow in a fluidized bed heated to a temperature of 850-1100° C., adding a silicon-containing reaction gas by means of a nozzle and depositing of silicon on the silicon particles, wherein, in at least 56% of an axially symmetric region around a nozzle opening of the nozzle, the reaction gas concentration is greater than 75% of the maximum concentration of the reaction gas (10 to 50 mol %), the fluidized-bed temperature is greater than 95% of the fluidized-bed temperature outside the axially symmetric region (850-1100° C.) and the solids concentration is greater than 85% of the solids concentration at the edge of the fluidized bed (55 to 90% by volume).

Abstract: Assembly of a fluidized bed reactor for the preparation of polycrystalline silicon granules by chemical vapor deposition of silicon onto seed particles and removal of polycrystalline silicon granules is facilitated without breakage and with gas tightness by a specific assembly sequence.

Abstract: Contamination of fluidized bed-produced polycrystalline granules by phosphorus is reduced by employing as seals and/or packings, graphite containing <500 ppmw of phosphorus.

Abstract: Silicon deposited by CVD and/or silico dust is removed from a polycrystalline silicon deposition reactor component by abrasion with silicon-containing particles in a gas stream.

Abstract: Silicon deposited by CVD and/or silico dust is removed from a polycrystalline silicon deposition reactor component by abrasion with silicon-containing particles in a gas stream.

Abstract: A reactor for preparing granular polysilicon by deposition of polycrystalline silicon on silicon seed particles has a reaction vessel, an inner reactor tube for a fluidized bed comprising granular polysilicon and a reactor bottom within the reactor vessel, a heating device for heating the fluidized bed in the inner reactor tube, at least one bottom gas nozzle for introduction of fluidizing gas and at least one reaction gas nozzle for introduction of reaction gas, a feed device to introduce silicon seed particles, an offtake line for granular polysilicon, and a device for discharging reactor offgas from the reactor vessel, and has a cylindrical component which has openings on its cylindrical surface, with at least 5% and not more than 95% of the cylindrical surface being open located between the inner reactor tube and the heating device.

Abstract: Granular polysilicon is produced in a fluidized-bed reactor by fluidizing silicon particles by means of a gas flow in a fluidized bed heated to a temperature of 850-1100° C., adding a silicon-containing reaction gas by means of a nozzle and depositing of silicon on the silicon particles, wherein, in at least 56% of an axially symmetric region around a nozzle opening of the nozzle, the reaction gas concentration is greater than 75% of the maximum concentration of the reaction gas (10 to 50 mol %), the fluidized-bed temperature is greater than 95% of the fluidized-bed temperature outside the axially symmetric region (850-1100° C.) and the solids concentration is greater than 85% of the solids concentration at the edge of the fluidized bed (55 to 90% by volume).

Abstract: Yield of products of increased purity from a fluidized bed reactor where silicon is produced or consumed is enhanced by purging with inert gas, purging with hydrogen gas, and purging with a chlorosilane-containing gas. The purging with hydrogen is conducted at an elevated temperature.

Abstract: Silicon deposited by CVD and/or silico dust is removed from a polycrystalline silicon deposition reactor component by abrasion with silicon-containing particles in a gas stream.

Abstract: Granular polycrystalline silicon is disclosed, which has a convexity of 0.850-1.000 and a chlorine content of 10-40 ppmw. Also disclosed is a process for producing granular polycrystalline silicon in a fluidized bed reactor, which includes: (a) fluidization of silicon seed particles by gas flow in a fluidized bed heated by a heating apparatus, (b) addition of a silicon- and halogen-containing reaction gas resulting in pyrolytic deposition of elemental silicon on heated seed particle surfaces, (c) forming the granular polycrystalline silicon, (d) removing from the reactor particles and offgas containing hydrogen halide, and (e) metered addition of fresh seed particles. The hydrogen halide concentration in the offgas is determined as the controlled variable. The rate of metered addition of fresh seed particles and heating output of the heating apparatus are controlled as manipulated variables to keep the hydrogen halide concentration in the offgas within an above-defined range during operation.

Abstract: Granular polycrystalline silicon is disclosed, which has a convexity of 0.850-1.000 and a chlorine content of 10-40 ppmw. Also disclosed is a process for producing granular polycrystalline silicon in a fluidized bed reactor, which includes: (a) fluidization of silicon seed particles by gas flow in a fluidized bed heated by a heating apparatus, (b) addition of a silicon- and halogen-containing reaction gas resulting in pyrolytic deposition of elemental silicon on heated seed particle surfaces, (c) forming the granular polycrystalline silicon, (d) removing from the reactor particles and offgas containing hydrogen halide, and (e) metered addition of fresh seed particles. The hydrogen halide concentration in the offgas is determined as the controlled variable. The rate of metered addition of fresh seed particles and heating output of the heating apparatus are controlled as manipulated variables to keep the hydrogen halide concentration in the offgas within an above-defined range during operation.