IMPURITY TRANSIENTS IN MULTIPLE CRYSTAL-GROWTH FROM A SINGLE CRUCIBLEFOR EFG SILICON OCTAGONS

We present results of a study of impurity segregation in crystal growt h, where more than one crystal is grown from a single crucible with me lt replenishment taking place during growth of an individual crystal, The crystal is an octagonal-shaped hollow silicon tube, 4.6 m long and with 300 mu m wall thickness,and it is produced by the edge-defined f ilm-fed growth (EFG) technique. The full-length tube weighs 3 kg and h as eight 10 cm wide faces, which can be cut into 10 x 10 cm(2) wafers. Impurity segregation is studied indirectly by monitoring the solar ce ll efficiency of wafers made from individual tubes and by sampling imp urity levels at the ppb level using Deep Level Transient Spectroscopy (DLTS). We examine in detail two cases: a normal growth case, and a si tuation where there is accidental contamination entering the melt duri ng the replenishment process.