US 12,269,747 B2
Method for producing polycrystalline silicon
Markus Wenzeis, Wurmannsquick (DE); Piotr Filar, Marktl (DE); and Thomas Schröck, Kastl (DE)
Assigned to Wacker Chemie AG, Munich (DE)
Appl. No. 17/617,704
Filed by Wacker Chemie AG, Munich (DE)
PCT Filed Jun. 11, 2019, PCT No. PCT/EP2019/065165
§ 371(c)(1), (2) Date Dec. 9, 2021,
PCT Pub. No. WO2020/249188, PCT Pub. Date Dec. 17, 2020.
Prior Publication US 2022/0234900 A1, Jul. 28, 2022
Int. Cl. C01B 33/035 (2006.01); C01B 33/02 (2006.01); C01B 33/021 (2006.01); C01B 33/027 (2006.01); C01B 33/03 (2006.01)
CPC C01B 33/035 (2013.01) [C01B 33/02 (2013.01); C01B 33/021 (2013.01); C01B 33/027 (2013.01); C01B 33/03 (2013.01)] 10 Claims
 
1. A method for producing polycrystalline silicon comprising introducing a reaction gas, which in addition to hydrogen contains silane and/or at least one halosilane, into a reaction space of a gas phase deposition reactor, wherein the reaction space comprises at least one heated filament rod upon which by deposition silicon is deposited to form a polycrystalline silicon rod, wherein during the deposition, to determine the morphology of the silicon rod,
at least one thermographic image of the surface of said rod comprising a measurement area Amax is generated,
by image processing a segmentation of the measurement area Amax into a first and a second area fraction is performed, wherein the first area fraction At corresponds to a relatively high temperature Tt compared to local average temperature values and the second area fraction Ap corresponds to a relatively low temperature Tp compared to local average temperature values, and
a morphology index M is determined according to

OG Complex Work Unit Math
wherein through variation of at least one parameter selected from the group comprising U, I, surface temperature TOF, reaction gas composition and volume flow the deposition is controlled such that for the production of polysilicon type B M has a value of 0.1 to 1, polysilicon type C M has a value of 1 to 3, or polysilicon type D M has a value of 3 to 5,
wherein U is in a range from 50 to 500 V, I is in a range from 500 to 4500 A, TOF is in a range from 950° C. to 1200° C., the volume flow is in a range from 1500 to 9000 m3/h and the reaction gas before entry into the reactor contains hydrogen in a proportion of 50% to 90%.