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 (CF 3 I, C 2 F 5 I) and it mainly generates CF 3 and CF 2 radicals. The ratio of each radical density can then be precisely controlled by changing the ratio of the mixture of CF 3 I and C 2 F 5 I. 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.