OXYGEN-TRANSPORT MECHANISM IN SI MELT DURING SINGLE-CRYSTAL GROWTH INTHE CZOCHRALSKI SYSTEM

Silicon single crystals were grown in crucibles with and without a car bon sheet at the bottom to investigate how oxygen dissociates from the crucible and transfers to the crystals. Oxygen concentration in the c rystals grown in the sheet-attached crucible was lower than that of cr ystals grown in the sheetless crucible when crucible rotation rate was high. A three-dimensional numerical simulation clarified that with a high crucible rotation rate, about 20% of the oxygen in the grown crys tals was transferred by convection in the melt from the bottom of the crucible. For a low crucible rotation rate, a melt with a small oxygen concentration was directly transferred from the gas-melt interface to the crystal-melt interface; therefore, oxygen concentration in crysta ls grown at a low crucible rotation rate was lower than that for cryst als grown at a high rotation rate.