3D stress reconstruction from birefringence measurement for photovoltaic Si ingots

Residual stress or other defects in silicon CZ ingot can lead to cracks in wafers cut from that ingot, themselves resulting in PV modules to perform poorly or even to fail. The ability to detect high levels of stress or crystallographic defects before processing an ingot would help reduce cost and improve reliability. However, analyzing stress in an ingot is a difficult problem. In this paper, we present a way of using birefringence measurement to build a 3D reconstruction of the ingot. This method allows a better understanding of residual stress distribution in a given ingot and will assist, we hope, the PV industry in the growing of silicon ingot.