Comparison of CH4/H2 and C2H6/H2 inductively coupled plasma etching of ZnO

CH4/H2-based discharges are attractive for dry etching of single crystal ZnO because of their non-corrosive nature. We show that substitution of C2H6 for CH4 increases the ZnO etch rate by approximately a factor of 2 both with and without any inert gas additive. The C2H6/H2/Ar mixture provides a strong enhancement over pure Ar sputtering, in sharp contrast to the case of CH4/H2/Ar. The threshold ion energy for initiating etching is 42.4 eV for C2H6/H2/Ar and 59.8 eV for CH4/H2/Ar. The etched surface morphologies were smooth, independent of the chemistry and the Zn/O ratio in the near-surface region was unchanged within experimental error after etching with both chemistries. The plasma etching improved the band-edge photoluminescence intensity and suppressed the deep level emission from the bulk ZnO under our conditions, due possibly to removal of surface contamination layer.