METHOD OF PREPARING HIGH-PURITY SILICON Russian patent published in 1999 - IPC

FIELD: silicon production. SUBSTANCE: in a process including removing impurities from starting material, evacuation, degassing, and subsequent directional crystallization in pot of carbon-glass material placed in chamber and final removal of surface impurities from polycrystal, evacuation in the chamber is conducted to maintain the level of residual pressure 10 Pa during the whole process time and purification of starting material is carried out in three heating steps: removal of water at 120-190 C, removal of the rest of impurities excepting carbon at temperature from 1000 C to temperature close to melting point of silicon, and removal of carbon under silicon melting conditions. In the latter operation, melt is centrifuged to impart reverse motion on crystallization pot. Silicon product is characterized by purity of 99.99993-99.9995%. EFFECT: increased purity. 4 cl, 1 dwg, 1 tbl