On the residual stress and fracture strength of crystalline silicon wafers

This letter reports on residual stress measurement in thin crystalline silicon wafers with a full-field near-infrared polariscope. Residual stress is analyzed in combination with observed surface defects, and the results are related to measured fracture strength variation in the wafers. Measurements indicate that there is a sawing process-related residual stress in the as-cut wafers, and that etch-removal of ∼5 μm from the wafer surface eliminates a damage layer that can significantly reduce the residual stress in the wafer, and therefore increases the observed fracture strength. There is a corresponding 2 to 3 μm reduction in the observed characteristic defect size after etching. Fracture strength anisotropy observed in the wafers is related to defect orientation (scratching grooves and microcracks) caused by the sawing process.