Noble gas effect on ACL etching selectivity to SiO₂ films

Abstract

In this study, we investigated the effect of Ar/He mixing ratio in the tetrafluoromethane/perfluorocyclobutane/Ar/He gas mixture on plasma parameters, SiO2 etching kinetics, and etching selectivity with respect to the amorphous carbon layer (ACL) mask in the inductively coupled plasma system with the low frequency (2 MHz) bias source. It was found that the type of dominant carrier gas does influence the output process characteristics through changes in both ion flux and CFx/F ratio determining the plasma polymerizing ability. In particular, He‐rich plasmas exhibited better performance with respect to the faceting of ACL mask and SiO2/ACL etching selectivity.