PROCESS FOR THE PRODUCTION OF MEDIUM AND HIGH PURITY SILICON FROM METALLURGICAL GRADE SILICON

摘要

A PROCESS FOR PURIFYING LOW-PURITY METALLURGICAL GRADE SILICON, CONTAINING AT LEAST ONE CONTAMINANT AND OBTAINING A HIGHER-PURITY SOLID POLYCRYSTALLINE SILICON IS PROVIDED. THE PROCESS INCLUDES CONTAINING A MELT OF LOW-PURITY METALLURGICAL GRADE SILICON IN A MOULD HAVING INSULATED BOTTOM AND SIDE WALLS, AND AN OPEN TOP; SOLIDIFYING THE MELT BY UNIDIRECTIONAL SOLIDIFICATION FROM THE OPEN TOP TOWARDS THE BOTTOM WALL WHILE ELECTROMAGNETICALLY STIRRING THE MELT; CONTROLLING A RATE OF THE UNIDIRECTIONAL SOLIDIFICATION; STOPPING THE UNIDIRECTIONAL SOLIDIFICATION WHEN THE MELT HAS PARTIALLY SOLIDIFIED TO PRODUCE AN INGOT HAVING AN EXTERIOR SHELL INCLUDING THE HIGHER-PURITY SOLID POLYCRYSTALLINE SILICON AND A CENTER INCLUDING AN IMPURITY-ENRICHED LIQUID SILICON; AND CREATING AN OPENING IN THE EXTERIOR SHELL OF THE INGOT TO OUTFLOW THE IMPURITY-ENRICHED LIQUID SILICON AND LEAVE THE EXTERIOR SHELL WHICH HAS THE HIGHER-PURITY SOLID POLYCRYSTALLINE SILICON.