Kinetics of electrochemical corrosion of silicon wafers in dilute HF solutions

An extensive experimental study of the factors influencing the electrochemical characteristics of the silicon/DHF junction has been undertaken, and leads to reproducible and reliable values of the electrochemical kinetics of the corrosion reactions. The usual model of electron and hole transfers between a semiconductor and an electrolyte solution should include an additional term due to the generation of h(+) and e(-) charges resulting from the dual redox reactions on anodic and cathodic sites. Then, in a narrow range of potential near the corrosion conditions, the classical Butler-Volmer electrochemical equations apply. The values of open circuit voltage and corrosion current have been obtained using n- and p-type silicon with different doping levels, in contact with deoxygenated or oxygen-saturated DHF solution, in the dark and tinder illumination. These data were used to characterize the electrochemical reaction kinetics leading to the corrosion rate expressed in atoms per square centimeter per second of different Si substrates. In addition, we derived an estimation of the exchange current density of the hydrogen evolution reaction on the Si surface.