The reactions of the two-membered Si-O ring with CF_n (n＝1～3) radicals have been studied by using density functional theory calculations at the UB3LYP/6-31G(d) level. Calculated results show that these reactions proceed via either the mechanism without C—F bond breakage or the mechanism with the C—F and Si—O bond breakages. The activation energies, reaction heats, and details of the potential energy surfaces for these reactions have been obtained. CF₂ radical was found to be the most effective etchant to Si—O bonds. This result is in good agreement with the corresponding experimental finding.

Key words: silicon dioxide, CF_n (n＝1～3), reaction mechanism, density functional theory