Inductively coupled plasma reactive ion etching of ZnO using C2F6 and NF3-based gas mixtures

Inductively coupled plasma reactive ion etching (ICP RIE) of ZnO film using C2F6 and NF3-based gas mixtures was investigated as a function of ICP power, bias power, pressure, and plasma chemistry. An etch rate of about 410 nm min(-1) in the case of C2F6 plasma and about 380 nm min(-1) in the case of NF3 plasma was obtained at the optimum condition, with vertical sidewalls and smooth surfaces, which is about 30% higher than the etch rates obtained in the previous reports on ICP RIE of ZnO using CH4 or chlorine-related gas mixtures. Basically no chamber contamination and corrosion was observed, indicating that fluorine plasmas are more suitable for ZnO dry etching than previously studied CH4 or BCl3 plasma. The addition of 40% or more CH4 to the C2F6 plasma improved the etch rate and sidewall verticality of the etched mesas, but resulted in rough surface morphology.