SUMMARY

The goal of this research was to investigate an experimental infrared transmission technique to extract the full stress components of the in-plane residual stresses in thin multi crystalline silicon wafer, and try to meet the need of photovoltaic industry to in situ measure residual stress for large cast wafers. Previous research has built a circular polariscope system to measure the maximum shear stress in silicon wafers. The error of the system was analyzed and the resolution of the system was about 1.2 MPa. In this research, a new polariscope system has been designed and built. The system is capable of measuring wafers as large as 156×156mm. Anisotropic stress optic law was proposed in this research and stress optic coefficients were calibrated for different grain orientations and stress orientations. The variation of the maximum stress optic coefficients is about 1.7 times of the minimal ones. System ambiguity at the boundaries was resolved completely by introducing a new function. Shear different method was used to obtain full stress components by integrating the shear stress map from the boundaries. The integration error was about 1 MPa within 10mm from the starting point of the integration, which was verified by a four point bending CZ single crystal wafer beam.