Residual Stress on Surface and Cross-section of Porous Silicon Studied by Micro-Raman Spectroscopy

Surface and cross-sectional residual stresses of electrochemical etching porous silicon are investigated quantitatively by micro-Raman spectroscopy. The results reveal that a larger tensile residual stress exists on the surface and increase linearly with the porosity. On the other hand, across the depth direction perpendicular to the surface, the tensile residual stress decreases gradually from the surface to regions near the interface between the porous silicon layer and the Si substrate. However, a compressive stress appears at the interface near to the Si substrate for balancing with the tensile stress in the porous silicon layer. The cross-sectional residual stress profile is due to the porosity and lattice mismatch gradients existing in the cross-section and influencing each other. Furthermore, the presented residual stresses of the porous silicon have a close relation with its microstructure.