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 2eV and there are a small number of high-energy electrons. The plasma can only dissociate C-I bonds (2.0eV) 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 arc drastically improved. The iodofluorocarbon species are also alternatives to perfluorocarbon chemistries (PFCs) from an environmental standpoint.