Thick oxidized porous silicon layer as thermo-insulating material for high temperature operating thin and thick film gas sensors

Thick oxidized porous silicon layers (OPS), with thickness ranging from 5 to 35 μm, have been realized on p⁺ Si substrates using Si anodization followed by thermal oxidation. A mesoporous Si structure with a 55% porosity has been selected as starting material. Phosphorus implantation of a patterned p⁺ Si substrate has been performed to take advantage of the selective anodization of p⁺ vs. n⁺ Si. After the oxidation, the stoichiometry of the oxidized PS layer has been evaluated using RBS and the EDAX microanalysis techniques. Patterned wafers with hundreds of thin or thick oxidized PS islands show a consistent wafer warpage after thermal oxidation