The interaction between conventional and highly porous SiOCH with CF4, O2, and H2 plasma has been investigated. The highly porous SiOCH film has porosity about 40% and a k value about 2.2. The pristine SiOCH film has 19% of porosity and k value of 2.7. All experiments were performed at room temperature in a downstream plasma reactor. It was found that (i) the CF4 plasma etches the SiOCH film without bulk material modification (however, the etch rate was higher in the case of the SiOCH film with increased porosity); (ii) the O2 plasma oxidizes the SiOCH film converting the top layer to a hydrophilic SiO2-like porous material, the SiOCH film with increased porosity suffers more severely from this kind of plasma; (iii) the CF4/O2 plasma mixture has an optimal O2 concentration at which the etch rate is maximal; and (iv) the H2 plasma does not interact with the SiOCH film and can be a promising candidate for the resist stripping. © 2002 American Vacuum Society.