The results of multiparameter fitting of spectroscopic ellipsometric (
SE) spectra on porous silicon layers (PSL) were connected with the pro
cessing parameters (oxidation, etching time, porosity, argon implantat
ion dose). Two optically different types of silicon forms, a bulk-type
silicon (c-Si) and polycrystalline-like silicon with enhanced absorpt
ion in the grain boundaries (p-Si) needed to be mixed with voids in th
e appropriate ratio, and the PSL had to be divided in depth in several
different sections in order to obtain the best fit, The sectioning re
flects the effect of upper and lower interfaces or inhomogeneity in de
pth. The effective porosity and the sublayer thicknesses are determine
d with high precision. In the case of argon implantation, we used the
dielectric function of c-Si and implanted amorphous silicon (a-Si) mix
ed with voids. The regression analysis of SE spectra clearly shows the
effect of different doses of implantation. The sectioning reflects th
at to the full range of argon ions the porous silicon became amorphous
and denser. The overall thickness of the originally porous layer also
significantly reduced (from 670 nm to 320 nm) due to the argon implan
tation.