Dry etching characteristics of Mo and Al2O3 films in O2/Cl2/Ar inductively coupled plasmas

• We investigated the etching characteristics and mechanisms of Mo and Al2O3 films.
• The Al2O3 is proving to be a promising substitute to be used as the gate dielectric.
• An increase in the O2 mixing ratio resulted in a non-monotonic Mo etching rate.
• The Al2O3 etching rate monotonically decreased with increasing O2 fraction.
• We also attempted a model-based analysis of the etching mechanisms.

An investigation of etching characteristics and mechanisms of thin Mo and Al2O3 films in O2/Cl2/Ar inductively coupled plasmas under the condition of fixed gas pressure (0.8 Pa), input power (700 W) and bias power (200 W) was carried out. It was found that an increase in the O2 mixing ratio resulted in a non-monotonic Mo etching rate (with a maximum of 320 nm/min at 40–45% O2) while the Al2O3 etching rate decreased monotonically. Plasma parameters and composition were investigated using a combination of a zero-dimensional plasma model and plasma diagnostics by double Langmuir probes. The analysis of etching kinetics involving model-predicted fluxes of plasma active species allows one to relate the non-monotonic Mo etching rate to the change in reaction probability.