Spatial Distribution of Full-Field Residual Stress and Its Correlation with Fracture Strength of Thin Silicon Wafers

28th European Photovoltaic Solar Energy Conference and Exhibition; 1474-1476
Residual stresses are a major concern in thin silicon wafers because of their potentially detrimental effect on mechanical properties during cell processing. Residual stresses are induced by crystal growth as well as wafering. This work investigates the correlation between the residual stress distribution in a mono-cast silicon wafer and its fracture strength variation. Full-field residual stress maps in 156 mm square as-cut mono-cast silicon wafers are measured using near infra-red polariscopy and correlated with the spatial variation of fracture strength measured using four-line bending. Results show that regions of the wafer with higher residual shear stress are correlated with lower fracture strength. Etching, which removes saw damage, shows a decrease in residual stress with a corresponding increase in fracture strength. The variation in residual stress and fracture strength in a given wafer also appears to be correlated with the grain structure in that region.