The surface reaction of CF2 radicals on Si and fluorocarbon films was investigated in electron cyclotron resonance (ECR) Ar and H2/Ar downstream plasmas employing CF2 radical injection technique. The effects of Ar+ ions, Ar* metastable species and radiation from plasmas on the fluorocarbon film formation were evaluated in ECR Ar downstream plasma with CF2 radical injection. As a result, CF2 radicals with assistance of Ar+ ion bombardment were found to play an important role in the fluorocarbon film formation. The adsorptive reactions of CF2 radicals on the fluorocarbon film surface with and without Ar and H2/Ar plasma exposures were successfully investigated by in situ Fourier transform infrared reflection absorption spectroscopy and in situ x-ray photoelectron spectroscopy. It was found that the formation of fluorocarbon film in the plasma proceeded through the adsorptive reaction of CF2 radicals at a high probability on the active sites formed by the bombardment of Ar+ ions on the fluorocarbon film surface. © 1998 American Vacuum Society.