Reactive ion etching of diamond in CF4, O2, O2 and Ar-based mixtures

The reactive ion etching of diamond in O2, CF4/O2, CHF3/O2, O2/Ar discharges has been examined as a function of bias voltage, flow rate and composition of the gas mixtures. Etching in O2 and O2/Ar plasmas (with flow ratio of O2/Ar ≥ 25%) was characterised by a high etch rate (∼35 nm/min) and an increase in surface roughness with rising bias voltage. The CF4/O2 plasmas also produced a high etch rate (∼50 nm/min) but with only minor dependence of roughness on bias voltage. In comparison, the O2/Ar (with O2/Ar flow ratio <25%) and CHF3/O2 plasmas resulted in a low etch rate (7–10 nm/min). The high and low rate regimes were identified as ionenhanced chemical etching and physical sputtering respectively. Etching in the O2/Ar plasmas has been attributed to a combination of the two processes dependent on the O2 content.