Mechanism of oxygen plasma etching of polydimethyl siloxane films

We have used x-ray photoelectron spectroscopy and multiple internal reflection infrared spectroscopy to study the etching of polysiloxane films in an rf oxygen plasma. The results indicate that a structurally strained SiO 2 layer, ∼1 nm thick, is formed on the film exposed to oxygen plasma. For a given rf power input this oxidized overlayer recedes with the etching front in a steady state fashion, acting as a protective layer for the underlying polysiloxane film. The etching mechanism is effectively a combination of two competitive processes, namely, ion sputtering and oxidation.