Selective plasma etching of silicon nitride in presence of silicon or silicon oxides using mixture of (CH3F or CH2F2) and CF4 and O2

摘要

A chemical downstream etching (CDE) that is selective to silicon nitrides (SiN) over silicon oxides (SiO) uses at least one of a CH3F/CF4/O2 recipe and a CH2F2/CF4/O2 recipe. Inflow rates are mapped for the respective components of the input recipe to find settings that provide both high nitride etch rates and high selectivity towards the SiN material. A pins-up scheme is used for simultaneously stripping away backside nitride with topside nitride.