Dislocation generation and propagation across the seed in seed Cast-Si ingots

We have studied the dislocation generation and propagation from the seed crystals during seed cast Si growth. The grown ingot was cut into a vertical wafer, followed by the dislocation imaging using X-ray topography and Secco etching. The dislocation behavior at the seed area was compared with the dislocation generation at the top surface due to the thermal stress during cooling. The dislocations at the seed/crystal interface have propagated on the {111} plane toward top. When the seed surface was not melted suffciently, the interface defect density became high, but no clear dislocation propagation was recognized. This suggests that the thermal shock at the seed/melt interface was not high enough to propagate dislocations to the growth direction. A certain amount of dislocations has been introduced from the top into the ingot according to the thermal stress. These observations suggest that optimizing the initial growth condition is important to dislocation control.