Comparison of Phase Shifting Techniques for Measuring In-Plane Residual Stress in Thin, Flat Silicon Wafers

This paper reports on a comparison of the six- and ten-step phase shifting methods in digital transmission photoelasticity and the application of these methods to obtain the residual stresses in thin (200 μm), flat crystalline silicon wafers (156 mm square). The ten-step phase shifting technique is judged to be superior with reduced noise in the isoclinics and a resulting higher accuracy when dealing with the near-zero retardation prevalent in residual stress measurements of silicon wafers.