Medium purity metallurgical silicon and method for preparing same
AssigneeFerropem
InventorsGerard Baluais, Yves Caratini
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Abstract
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.
Claims10
A process for making medium-purity silicon, as a raw material for making photovoltaic quality or electronic quality silicon, the process comprising:
- producing a liquid silicon with a low content of boron, by carbothermal reduction of silica in a submerged electric are furnace, wherein a power density used expressed as a (Pe/Do3)/3 ratio is between 2 and 3 MW/m3, and a weighted average specific area S of reduction agents used is between 20 and 40 m2/g;
- refining the liquid silicon with oxygen or chlorine;
- treating the refined liquid silicon under low pressure between 10 and 100 Pa with injection of neutral gas;
- and
- solidifying the treated liquid silicon by segregated solidification.
Dependencies are inferred from the claim text.