Process for producing refined metallurgical silicon ribbon

Claim 1

A process for the production of low-cost, multigrained refined metallurgical silicon ribbon from metallurgical grade silicon comprising: a. dissolving metallurgical grade silicon in a liquid metal solvent to form a metal solvent-silicon solution; b. cooling said solution to a temperature at which silicon platelets form; c. removing silicon platelets from said solution of metallurgical grade silicon in a liquid metal solvent, thereby recovering partially purified, essentially iron-free silicon platelets with adherent impurities derived from said metal solvent; d. melting said partially purified silicon platelets in contact with acid silica slag in a melting zone, the resulting slag oxidation removing residual and said adherent impurities from the silicon platelets; e. removing the silicon-slag melt from said melting zone in a unidirectional manner so as to directionally solidify said silicon; and f. pulling a silicon ribbon from a melt of the thus-refined silicon, the resulting refined metallurgical silicon ribbon comprising a multigrained silicon ribbon having a resistivity of from about 0.04 to about 0.2 ohm-cm, said silicon having impurity concentrations of up to, but not exceeding, about 1 ppm of aluminum, about 1 ppm of iron, about 2 ppm of titanium, about 2 ppm of boron, about 2 ppm of phosphorus, about 1 ppm of chromium, about 1 ppm of calcium and about 1 ppm of magnesium, whereby said, multigrained silicon ribbon is obtained having a substantially higher impurity level than in a conventional, high purity semiconductor grade silicon and suitable properties for solar cell applications.