Tri-Layer Mask Dry Etch Process Optimizing and Wet Effect for Straight Profile

Photoresist/SiARC/Spin-on-carbon (SOC) trilayer mask is widely used in high density micro-fabrication with high NA ArF lithography. For most applications, trilayer mask is etched with polymer rich chemistry for CD shrinkage, in which taper profile is preferred. And also some special schemes use trilayer mask need straight SOC profile without necking near SiARC/SOC interface. In this paper, we report a study of dry etch process optimization for straight profile and wet etch process was also introduced for necking improved near SiARC/SOC interface on the top of the via top. ICP process chamber with RF pulsing function is used for decoupled plasma density and ion bombardment energy control. Commonly used sidewall protection gas SO2, N2 and CH4 are added in O2 plasma for several split experiment conditions aim to sidewall passivation and bottom CD controlling capability study.