Comparison of ZnO Dry Etching in High Density Inductively Coupled CH{sub}4/H{sub}2 and C{sub}2H{sub}6/H{sub}2-based Chemistries

摘要

CH{sub}4/H{sub}2 and C{sub}2H{sub}6/H{sub}2-based discharges are attractive for dry etching of single crystal ZnO because of their non-corrosive nature. We show that substitution of C{sub}2H{sub}6 for CH{sub}4 increases the ZnO etch rate by approximately a factor of 2 both with and without any inert gas additive. The C{sub}2H{sub}6/H{sub}2/Ar mixture provides a strong enhancement over pure Ar sputtering, in sharp contrast to the case of CH{sub}4H{sub}2/Ar. The threshold ion energy for initiating etching is 42.4eV for C{sub}2H{sub}6/H{sub}2/Ar and 59.8eV for CH{sub}4/H{sub}2/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.