Etching characteristics of thin SiON filmsusing a liquefied perfluorocarbon precursorof C6F12O with a low global warmingpotential

Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has anegative effect on the global environment owing to its high global warming potential (GWP) value.An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventionalperfluorocarbon etching gases such as CHF₃ with C₆F₁₂O, which has a low GWP and is in a liquidstate at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched usinginductively coupled CF₄ +C₆F₁₂O+O₂ mixed plasmas. Subsequently, the etching characteristicsof the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated.A double Langmuir probe was used and optical emission spectroscopy was performed for plasmadiagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were usedto confirm the change in the surface properties of the etched SiON film surface. Consequently, theetching characteristics of the C₆F₁₂O mixed plasma exhibited a lower etching rate, higher SiON/Siselectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF₃ mixed plasma. In addition, the C₆F₁₂O gas can be recovered in the liquid state, thereby decreasingglobal warming. These results confirmed that the C₆F₁₂O precursor can sufficiently replace theconventional etching gas.