Generation of dislocations introduced by bending stress in a Si wafer

Distribution and morphology for dislocations introduced in (001) Si wafers subjected to bending stress at 800°, 900°, and 1100°C were investigated. For wafers bent around a [110] axis at 900° and 1100°C, straight dislocations appeared along the [110] direction only near the neutral plane, and were absent at the surfaces where bending stress is greatest. However, for wafers bent at 800 °C, such straight dislocations were not formed. Dependence of the dislocation distribution and morphology on heat treatment temperature is explained on the basis of interaction between bending stress and SiO₂ precipitates introduced in bulk. Also, it was found that the straight [110] dislocations remained still near the neutral plane, even when additional reverse bending stress was applied around an axis parallel to the dislocations, but were transfered toward the tensile surface by bending around an axis normal to the dislocation direction.