Study on plasma characteristics and gas analysis before and after recovery using liquid-fluorocarbon precursor

Perfluorocarbon (PFC) gas is a representative greenhouse gas with high global warming potential (GWP) and is mainly used in the etching processes applicable to the manufacture of semiconductor devices. High capacity and high integration have been achieved in recent years as semiconductor device structures have been replaced by vertical layer structures, and the consumption of PFC gas has exploded due to the increase in high aspect ratio and patterning processes. In this study, the etching and recovery process were performed using C₅F₈ in L-FC which is in liquid phase at room temperature. This is because the ratio of F and C constituting C₄F₈, which is a PFC gas used for conventional etching, is similar. In addition, the recovered C₅F₈ was injected back into the chamber to confirm its reusability, and the electron temperature, plasma density, and ion energy distribution were analyzed. In addition, based on these data, the Si and SiO₂ etching process requiring high selectivity was applied using the gas obtained before and after recovery. An analysis of the surface composition of Si and SiO₂ after the etching process confirmed the possibility of recovering and reusing the exhaust gas during the process.