Effect of iodotrifluoromethane plasma for reducing ultraviolet light irradiation damage in dielectric film etching processes

Iodotrifluoromethane (CF₃ I) gas is one of the environmentally conscious perfluorocarbon gases because it has a very low global warming potential. The authors have found that CF₃ I gas plasma drastically reduces ultraviolet (UV) photon irradiation of ∼4.0 eV, which corresponds to the excitation energy at silicon dioxide (SiO₂) /silicon (Si) interfaces, in comparison with octafluorocyclobutane (C₄ F ₈) gas. This results in reducing UV irradiation damage in dielectric film etching processes, which was experimentally confirmed by evaluating charge-pumping currents in metal insulator semiconductor field effect transistors fabricated by using CF₃ I gas etching. They have also demonstrated that a novel etching method using pulse-time modulation of CF ₃ I gas plasma for the first time further reduced UV light irradiation damage.