Depth dependence of stress and porosity in porous silicon : a micro-Raman study

The elastic strain of porous silicon membranes for potential use in the microsensor technology has been investigated by means of micro-Raman spectroscopy. A depth distribution of the stress normal-to-the plane of formation has been measured with maximal stress value at the interface between the porous layer and the crystalline Si-substrate. The spectral characteristics of the first order Raman scattering (line shape, bandwidth and peak position) were analyzed according to the spatial correlation model in order to estimate the effects of phonon confinement and evaluate the stress. A compressive stress, attributed to the lattice mismatch between porous silicon and c-Si, has been found and shown to relax faster in samples of higher porosity.