New Radical-Control Method for SiO2 Etching with Non-Perfluorocompound Gas Chemistries

To control radical generation in the etching of silicon dioxide, we propose a new radical control method using the iodofluorocarbon chemistries in ultra-high-frequency (UHF) plasma we developed. In the UHF plasma, the mean electron energy is about 2 eV and there are a small number of high-energy electrons. The plasma can only dissociate C-I bonds (2.0 eV) in the iodofluorocarbon plasma (CF3I, C2F5I) and it mainly generates CF3 and CF2 radicals. The ratio of each radical density can then be precisely controlled by changing the ratio of the mixture of CF3I and C2F5I. As a result, etching selectivity and microloading effects are drastically improved. The iodofluorocarbon species are also alternatives to perfluorocarbon chemistries (PFCs) from an environmental standpoint.