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 SiO2 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.

Organosilicon polymers have found many uses in the electronics industry in the last 25 years due to their low-dielectric constant and water-repelling properties. These uses include insulators and encapsulating materials (RTV) for electronic parts. More recently, siloxanes have been incorporated into polyimides for the purpose of increasing the water resistance, improving mechanical properties, and preventing atomic oxygen attack of polyimides [R.

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