Quantitative evaluation method for stress in crystal was established by photoelasticity. It consists of three procedures: measurement by plane polarized light, measurement by circularly polarized light, and piezo-optical coefficients calculation. The last method is indispensable for stress evaluation in crystal. Piezo-optical coefficients for silicon in the [110] ~lO] [001] and [112] ~10] [lllJ coordinate system were calculated from the values in the [100] [010][001] coordinate system measured by Giardini. Practical approximation was made to correlate each isochromatic line directly to the difference between two principal stresses. This method was applied to the evaluation of the stress in silicon semiconductor pellet caused in the mounting and molding process. Observation of isochromatic lines according to temperature was practical for determination of the zeroth order of retardation.
The effect of annealing on residual stress and dislocation propagation in silicon slices with a damaged layer induced by diamond scribing, laser scribing and diamond blade cutting was studied by infra-red photoelastic measurements and dislocation pit observations. Residual stress and dislocation propagation both showed clear annealing temperature dependence at temperatures above 500 ~ C, although the residual stress was greatly reduced by a small degree of dislocation propagation. The experimental results can be explained using the stress recovery theory by the model of the damaged layer with a mosaic crystal layer and a single crystal layer with micro-cracks and dislocations.
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