Origin of SiC Impurities in Silicon Crystals Grown from the Melt in Vacuum

A main source of high carbon levels in silicon crystals grown from melt under reduced pressures and contained in silica crucibles upported by graph-ite retainer/susceptor has been identified by thermodynamic analysis. The calculations have been verified by experimental results and the carbon level can be reduced by approximately 50 % with the use of molybdenum retainers. The heat exchanger method (HEM) developed to grow large sapphire crystals (1-3) has been extended to the growth of silicon crystals (4). In this method the seed is placed at the bottom of the crucible and the temperature in the melt increases upwards. This sup-presses convection that causes temperature and con-centration fluctuations at the solid-liquid interface (5). Early experiments indicated that SiC particles were found in crystals solidified by the HEM (6). However