EVAPORATION OF OXYGEN-CONTAINING SPECIES FROM BORON-DOPED SILICON MELTS

Weight variations in boron-doped silicon melts due to the evaporation of oxygen-containing species from the free melt surface were measured by using the thermogravimetric method. Compared to the results obtaine d in the absence of doping, evaporation from boron-doped (10(21) cm(-3 )) silicon melts was much increased, and showed a strong pressure depe ndence when the temperature of the melt was high (1550 degrees C). How ever, a slight reduction of evaporation was observed for 1 X 10(18) at om/cm(3) boron doping under a pressure of 1 atm when the temperature o f the melt was low (1450C). Results of electron probe microanalysis of deposits from boron-doped melts and dissolution rates of silica rods being etched by silicon melts are also presented, and the influence of boron addition on evaporation and the oxygen transport in the melts i s discussed.