Invensil

Ferropem

Gerard Baluais

Yves Caratini

Yves Delannoy

Christian Trassy

The invention concerns a silicon designed in particular for making solar cells containing a total of impurities ranging between 100 and 400 ppm, a boron content ranging between 0.5 and 3 ppm, a phosphorus/boron content ratio ranging between 1 and 3, and a content of metal elements ranging between 30 and 300 ppm. The invention also concerns a method for making such a silicon from an oxygen- or chorine-refined metallurgical silicon containing at least 500 ppm of metal elements, and comprising: refusion under neutral atmosphere of the refined silicon, in an electric furnace equipped with a hot crucible; transferring the molten silicon, to provide a plasma refining, in an electric furnace equipped with a hot crucible; plasma refining with as plasma-forming gas a mixture of argon and of at least a gas belonging the group consisting of chlorine, fluorine, HCI and HF; casting under controlled atmosphere in an ingot mold wherein is produced segregated solidification.

High purity metallurgical silicon and method for preparing same

The invention concerns a method for producing a medium purity silicon comprising: preparing, by carbothermic reduction of silica in a submerged arc-furnace a silicon with low boron content; refining the liquid silicon with oxygen or chlorine; treating the refined silicon under reduced pressure from 10 to 100 Pa with neutral gas injection; segregated solidification. The invention also concerns a medium purity silicon designed to serve as raw material for making silicon of electronic or voltaic quality, and having (in weight fractions): a total of impurities ranging between 100 and 400 ppm, with the content in metallic elements ranging between 30 and 300 ppm; a boron content from 1 to 10 ppm; a phosphorus/boron ratio ranging between 0.5 and 1.5.

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Chedde, France

Gerard Baluais