Effect of krypton addition on electron cyclotron resonance-radio frequency hybrid oxygen plasma for patterning diamond surfaces

Electron cyclotron resonance radio frequency (ECR-rf) hybrid krypton-diluted oxygen plasmas were used to pattern the surfaces of diamond films with the assistance of a physical mask, while optical emission spectroscopy was employed to characterize the plasmas. It was found that with krypton dilution the etching rate decreased, and also the aspect ratios of nanotips formed in micro-holes were significantly modified. The oxygen atomic densities were estimated by oxygen atom optical emission and argon actinometry. Under a microwave power of 300 W and rf bias of -300 V, the absolute density of ground-state oxygen atoms decreased from 1.3 x 10(12) cm(-3) to 1.4 x 10(11) cm(-3) as the krypton dilution ratio increased to 80%, accompanied by the decrease in the plasmas excitation temperature. It is concluded that oxygen atoms play a dominant role in diamond etching. The relative variations in the horizontal and vertical etching rates induced by the addition of krypton are attributed to the observations of thicker nanotips at a high krypton dilution ratio.