Environmentally harmonized CF3I plasma for low-damage and highly selective low-k etching

Low-damage, high-rate, and highly selective low-k etching can be simultaneously satisfied using a plasma with an environmentally harmonized gas chemistry (CF3I). Such a CF3I plasma can drastically reduce the irradiation damage by ultraviolet (UV) photons during low-k etching, because the intensity of UV in CF3I plasma is much lower than that in conventional CF4 plasma. The etching selectivity of SiOCH to a photoresist can be drastically improved by using CF3I plasma because of reducing F radical generation. In addition, pulse-time-modulated CF3I plasma causes a drastic increase in the etching rate because a large amount of negative ions can be generated. These results show that CF3I plasma is a very promising candidate for low-damage and highly selective low-k etching.