Etching Characteristics of ZnO and Al-Doped ZnO in Inductively Coupled Cl₂/CH₄/H₂/Ar and BCl₃/CH₄/H₂/Ar Plasmas

Abstract

ZnO and Al-doped ZnO (AZO) were etched in Cl2/CH4/H2/Ar (Cl2-based) and BCl3/CH4/H2/Ar (BCl3-based), inductively coupled plasmas (ICPs) and their etching characteristics were compared by varying the Cl2/(Cl2+CH4) and BCl3/(BCl3+CH4) flow ratios, top electrode power and dc self-bias voltage (Vdc). The etch rates of both ZnO and AZO layers were higher in the Cl2-based chemistry than in the BCl3-based chemistry. The AZO and ZnO etch rates were increased and decreased, respectively, with increasing Cl2 or BCl3 flow ratio. Optical emission measurements of the radical species in the plasma and surface binding states by optical emission spectroscopy (OES) and X-ray photoelectron spectroscopy (XPS), respectively, indicated that, with increasing Cl2 or BCl3 flow ratio; the effective removal of Al in the AZO enhanced the AZO etch rate, whereas the reduced removal of Zn by the Zn(CHx)y products reduced the ZnO etch rate.