Comparative study of CF4 + X + He (X = C4F8 or C4H2F6) plasmas for high aspect ratio etching of SiO2 with ACL mask

Abstract This work compared C 4 F 8 and C 4 H 2 F 6 gases (as third components in CF 4 + He gas mixture) for the high aspect ratio etching of SiO 2 through the amorphous carbon layer (ACL) mask. The research scheme included the study of gas‐phase plasma characteristics, etching kinetics, and etching profiles. It was found that CF4 + C4F8 + He and CF4 + C4H2F6 + He gas mixtures are featured by quite close plasma parameters, the kinetics of electron‐impact processes, and ion bombardment intensities. At the same, the use of C 4 H 2 F 6 provides a bit lower F atom density together with a bit higher polymerizing ability. All these factors cause lower absolute etching rates for both SiO 2 and ACL but provide better SiO 2 /ACL/ACL selectivity and profile features.