Full Field Stress Measurements in Thin Silicon Sheet

A full field near infrared polariscope has been designed and built for determination of in-plane residual stresses in thin multicrystalline silicon wafers. The technical issues that have been addressed are: wafer size (greater than 4 in times 4 in), wafer thickness (down to 100 mum), crystalline anisotropy, stress calibration and optical inaccuracies. Using this system, the in-plane residual stresses in thin edge-defined growth (EFG), cast and string ribbon wafers are compared