Wacker Chemie Ag

Christian Gossmann

Hanns Wochner

Herbert Lindner

Wolfgang Stoiber

Polysilicon fragments are purified to remove metal contaminates by contacting the fragments with a purifying liquid at a flow rate &#x3e;100 mm/sec. Effective removal without abrasion is accomplished.

Method for purifying polycrystalline silicon

In a method for recovering acid from an aqueous etching mixture containing HF, HNO, HSiFand HNOwhich has been used for purifying polycrystalline silicon, the used etching mixture is distilled progressively so that approximately from 20 to 50 wt. % of the mixture is distilled off as dilute acid containing more than 90 wt. % of the silicon dissolved as hexafluorosilicic acid in a first fraction, and the water contained in the used etching mixture having been reduced by approximately 10-30 wt. %, this water-depleted mixture is then concentrated by evaporation to a residue of about 1 to 5 wt. % of the initial amount of used etching mixture during which a second fraction is distilled off, and the residue is disposed of.

Method for processing an etching mixture which is formed during the production of highly pure silicon

The present invention relates to a method for cleaning polycrystalline silicon fragments to a metal content of &#x3c;100 ppbw, wherein a polysilicon fraction is added to an aqueous cleaning solution containing HF and HO, this aqueous cleaning solution is removed and the polycrystalline fraction thereby obtained is washed with highly pure water and subsequently dried.

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Emmerting, Germany

Christian Gossmann