Stress in undoped and doped laser crystallized poly-Si

Raman measurements were performed on laser crystallized poly-Si on different substrates. Observed shifts of the Si LO-TO phonon peak are caused by stress originating from the film-substrate interface. The principal cause of the stress is the difference in the thermal expansion coefficients of substrate and film. Consequently, the amount of thermal stress critically depends on the choice of substrate. In the case of undoped samples on quartz, profiler and x-ray measurements confirmed the occurrence of tensile stress in the films. In the case of heavily doped samples, the change of the lattice parameter determined by x-rays is probably to a significant extend responsible for additional Raman shifts. (C) 2002 American Institute of Physics.