Russia-based Valen-Si-A has created a new production method for solar polysilicon production called UM-technology.
The production method involves using filaments to produce profiled crystals for gas-phase deposition of intermediate silicon with different sections ranging from 5 mm to 9 mm in diameter. Filament production speed reaches 40 to 45 mm/min, reducing polysilicon consumption to 1.2 kg of polysilicon for 1 kg of filaments, the company says.
A polysilicon rod measuring 50 mm to 80 mm in diameter is fixed to a wire rope or a stock in a loading chamber. It is then brought to an inductor, where it is heated to melting temperatures. The melted silicon is then drawn through a form-building unit to a receiving chamber, where it crystallizes.
Silicon is doped with thermodonors that are partially removed from the crystal latitude of silicon during the filament breakdown, while the remaining thermodonors are removed from the silicon when it is reprocessed at Czochralski units. According to Valen-Si-A, this technology allows for the production of filaments that are not contaminated with metals, which, in turn, increases the purity of the polysilicon.