Refining of silicon during its solidification from a Si–Al melt

To develop a low-cost process for refining silicon for use in solar cell materials, we have studied a low-temperature refining technique referred to as “solidification refining of silicon with a Si–Al melt at low temperature”. To discuss the purification in the solidification process, the segregation ratios of impurity elements between solid silicon and the Si–Al melt were determined experimentally and evaluated by thermodynamic analysis. Since the determined values were much smaller than the segregation coefficients between solid and liquid silicon, the solidification of silicon from the Si–Al melt at low temperature is found to be more effective for purification than general silicon solidification. A new technique for agglomerating solidified silicon crystals during solidification of Si–Al alloy was established using induction heating. A refining test, by means of this agglomeration method, revealed the effective purification during silicon solidification from the Si–Al melt.