Stress characterization of undoped and doped laser crystallized poly-Si on different substrates using Raman spectroscopy

Abstract 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 substrates. A second effect is observed in heavily doped samples. Additional shifts in this case are explained by the incorporation of smaller atoms into the lattice leading to additional tensile stress.