Origin mechanism of residual stresses in porous silicon film

摘要

In this article, a metallographic microscopy, an atomic force microscopy and a field emitting scanning electronic microscopy was used to investigate the surface and the cross-sectional morphology of porous silicon films, respectively. Simple micro-structure and micro-mechanical models are established to explain the origin mechanism of residual stresses in the porous silicon. Experimental results reveal that the residual stresses have close relation with the micro-structure of the porous silicon and consist of the lattice mismatch stress, capillary stress, oxidation stress, Van der Walls force and so on. Combining micro-Raman spectroscopy with x-ray diffraction measurements, we get the total residual stress of 900MPa, and its components of the lattice mismatch stress is about of 815.8MPa, the capillary stress of 13.2MPa and the oxidation stress of 71MPa for a chemical etched porous silicon sample with a certain porosity. It can be seen that the lattice mismatch between the porous layer and the Si substrate is a major source (about 91%) for the total residual stress of the porous silicon.