Etching Characteristics and Mechanisms of MoS2 2D Crystals in O2/Ar Inductively Coupled Plasma

Etching characteristics and mechanism of MoS2 in O-2/Ar inductively coupled plasma were investigated by both experimental and modeling methods. It was found the under the given set of experimental conditions the MoS2 etching process appears in the layer-by layer steady-state regime while the MoS2 etching rate exhibits the non-monotonic but changes versus O-2/Ar mixing ratio. Plasma diagnostics by Langmuir probes and plasma modeling provided the data on plasma parameters, densities and fluxes of plasma active species. In order to reach the agreement between the changes of measured MoS2 etching rate and model-predicted fluxes of plasma active species versus O-2/Ar mixing ratio, gas pressure and input power, we proposed the multistep etching mechanism where the kinetics of the limiting stage is influenced by both physical sputtering and chemical etching by oxygen atoms. Within the proposed mechanism, the non-monotonic etching rate as a function of Ar fraction in a feed gas may be explained by the concurrence of physical and chemical etching pathways where the chemical pathway is also activated by physical factors, such as the energy fluxes from ions and UV photons.