Abstract: The invention provides a process for producing polycrystalline silicon, including introduction of a reaction gas containing a silicon-containing component and hydrogen by means of one or more nozzles into a reactor including at least one heated filament rod on which silicon is deposited, wherein an Archimedes number Arn which describes flow conditions in the reactor, as a function of the fill level FL which states the ratio of one rod volume to one empty reactor volume in percent, for a fill level FL of up to 5% is within the range limited at the lower end by the function Ar=2000×FL?0.6 and at the upper end by the function Ar=17 000×FL?0.9, and at a fill level of greater than 5% is within a range from at least 750 to at most 4000.

Abstract: Brittle polysilicon rods having a rod cross-section of 80-99% available for electrical conduction and a flexural strength of 0.1 to 80 N/mm2 are produced by a process wherein the temperature of the bridge of polysilicon rods in the Siemens process is held at a high temperature and the flow rate of chlorosilanes is increased to the maximum within a short time. The rods are easily fragmented with low force, resulting in polysilicon with a low level of metallic impurities.

Abstract: The invention provides a process for producing polycrystalline silicon, including introduction of a reaction gas containing a silicon-containing component and hydrogen by means of one or more nozzles into a reactor including at least one heated filament rod on which silicon is deposited, wherein an Archimedes number Arn which describes flow conditions in the reactor, as a function of the fill level FL which states the ratio of one rod volume to one empty reactor volume in percent, for a fill level FL of up to 5% is within the range limited at the lower end by the function Ar=2000×FL?0.6 and at the upper end by the function Ar=17 000×FL0.9, and at a fill level of greater than 5% is within a range from at least 750 to at most 4000.

Abstract: Brittle polysilicon rods having a rod cross-section of 80-99% available for electrical conduction and a flexural strength of 0.1 to 80 N/mm2 are produced by a process wherein the temperature of the bridge of polysilicon rods in the Siemens process is held at a high temperature and the flow rate of chlorosilanes is increased to the maximum within a short time. The rods are easily fragmented with low force, resulting in polysilicon with a low level of metallic impurities.