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

摘要

Iodotrifluoromethane (CF_3I) gas is one of the environmentally conscious perfluorocarbon gases because it has a very low global warming potential. The authors have found that CF_3I gas plasma drastically reduces ultraviolet (UV) photon irradiation of ～4.0 eV, which corresponds to the excitation energy at silicon dioxide (SiO_2)/silicon (Si) interfaces, in comparison with octafluorocyclobutane (C_4F_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 CF_3I gas etching. They have also demonstrated that a novel etching method using pulse-time modulation of CF_3I gas plasma for the first time further reduced UV light irradiation damage.