Electrochemical Investigation into the Dissolution Mechanism of Anodic Oxide Films on Silicon

摘要

Electropolishing of p-type silicon has been investigated over a wide range of HF concentrations (0.01-11 wt.%) by potentiodynamic polarization. Oxide dissolution rates were determined from the plateau current densities observed in the electropolishing region during the reverse sweeps; i.e. where the growth and dissolution rates of the anodic oxide film are believed to be equal. Based on the shape of the CV curves the oxide dissolution process was treated as a corrosion process controlled by the dissolution of a salt film, that is its rate controlled by removal of dissolved products away from the surface rather than reactants to the surface as previously proposed. Although a contribution from HF from bulk to surface cannot be completely ruled out, because the removal of the initial dissolution product can be by either mass transport or further chemical reaction with HF species in solution this mechanism is capable of explaining the dependence of the dissolution rate on HF concentration for the whole range investigated.