Oxidizing agent concentration effect on metal-assisted electroless etching mechanism in HF-oxidizing agent-H2O solutions

The mechanism of metal-assisted electroless etching of silicon in HF-oxidizing agent-H2O etching system as a function of oxidizing agent concentration was studied. Three types of oxidizing agent were experimented namely Na2S2O8, K2Cr2O7 and KMnO4. Their concentrations were varied from 0.05 M to 0.3 M. The layers formed on silicon were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). It is shown that an insoluble solid-phase film (K2SiF6) form on silicon surface when concentration of K2Cr2O7 or KMnO4 increases in chemical solutions. On other hand, when Na2S2O8 concentration increases, the surface roughness decreases without any chemical complex formation.