HF vapor phase wafer cleaning and oxide etching

This invention relates to processes for cleaning silicon substrates such as silicon wafers and for etching oxide layers on such wafers, and more particularly relates to wafer cleaning and oxide etching techniques employing hydrofluoric acid. The invention provides HF vapor process conditions that can be precisely controlled with a high degree of reproducibility for a wide range of starting wafer conditions. These HF vapor processes for, e.g., etching oxide on a semiconductor substrate, cleaning a contaminant on a semiconductor substrate, removing etch residue from a metal structure on a semiconductor substrate, and cleaning a metal contact region of a semiconductor substrate. In the HF vapor process, a semiconductor substrate having oxide, a contaminant, metal etch residue, or a contact region to be processed is exposed to hydrofluoric acid vapor and water vapor in a process chamber held at temperature and pressure conditions that are controlled to form on the substrate no more than a sub-monolayer of etch reactants and products produced by the vapor as the substrate is processed by the vapor. The sub-monolayer HF vapor process regime is defined in accordance with the invention to proceed under conditions wherein no more than about 95% of a monolayer of coverage of the substrate surface occurs.