Audible vibration diagnostics of thermo-elastic residual stress in multi-crystalline silicon wafers

This paper presents audible vibratory mode data obtained by mechanically exciting acoustic modes in multi-crystalline silicon wafers with various levels and distributions of residual stress. Natural frequency data from the silicon wafers is found to correlate with residual stress optical polariscopy measurements. The data is fit with both linear and quadratic models with correlation coefficients of 0.8. The results reveal a dependence of wafer audible mode frequencies on residual stress level that may be useful for solar cell mechanical quality control and breakage inspection.