Patent ID: 8647432

Claim:
A method for making a large surface area filament usable in place of a solid rod silicon filament in a CVD reactor for the production of polysilicon, the method comprising: providing a CVD reactor having a power supply adjusted and configured for use with a solid rod silicon filament having a solid rod length, a solid rod impedance, a solid rod surface area, and a solid rod cross sectional area; determining a filament cross-sectional shape for a large surface area filament that will provide a filament surface area greater than the solid rod surface area, while also causing the large surface area filament to be usable with the CVD reactor without adjusting, reconfiguring, or replacing the power supply of the CVD reactor; heating silicon in a silicon melt pool to a molten state; growing the large surface area filament from said silicon in said molten state by an EFG method with a shaping die, said large surface area filament having said filament cross-sectional shape and having a uniform cross sectional shape over an axial length, all dimensions of said cross sectional shape being constant over said axial length to within a tolerance of 10%; installing the large surface area filament in the CVD reactor; and using the CVD reactor to produce polysilicon without adjusting, reconfiguring, or replacing the power supply of the CVD reactor.