Measurement of Residual Stress in Bent Silicon Wafers by Means of Photoluminescence

The photoluminescence (PL) method was used to measure the residual stress in plastically-bent Si single crystal wafers. The bound-exciton PL line showed remarkable energy shift by the residual stress and the stresses measured from the PL shift agreed well with values of the stress deduced from the theory of plastic bending. It was found that the residual stress introduced by the plastic deformation is quite different in floating-zone (FZ) wafers from that in Czochralski (CZ) Si wafers, possibly because of the difference in the generation and multiplication processes of dislocations in the two crystals. Annealing of the bent specimen at 1000°C reduced the residual stress in the specimen, and the peak position of the bound-exciton PL line reverted to that before bending.