Plasma atomic layer etching of SiO₂ with a low global warming potential fluorocarbon precursor (C₆F₆)

Reducing greenhouse gas emissions from semiconductor manufacturing has been attracting enormous interest in both industry and academia as global warming issues have increased in significance year by year. Among various strategies, the search for etch precursors that have low global warming potential is actively underway worldwide to reduce the use of conventional precursors with high global warming potential. In this paper, we explore the use of C6F6, a promising candidate to replace the widely utilized perfluorocarbon precursor C4F8, for plasma atomic layer etching (ALE) of SiO2. In situ ellipsometry results indicated that acceptable ALE characteristics were obtained with C4F8 and C6F6 each in their own specific ALE window, while C6F6 showed superior ALE performance. Investigation into the ALE performance with different precursors was then conducted based on plasma diagnostics for radical density, electron density, and plasma potential, and the results of which showed that the difference in the radical composition between precursors significantly affected the resulting ALE trends and also that the excellent ALE performance with C6F6 might originate from its significant polymeric characteristics. We expect the present findings to contribute to the wider adoption of low global warming potential precursors in the etching process.