High-density plasma etching of RF-sputtered indium-zinc-oxide films in Ar, Ar/Cl₂, and Ar/CH₄/H₂ chemistries

In this work, we investigate the potential of chlorine and methane/hydrogen plasma chemistries for the dry etching of rf-sputtered Indium-Zinc-Oxide (IZO) layers. The influence of the discharge chemistry on the postetched surface morphology and near-surface stoichiometry is also investigated. While the Cl₂-based plasma mixture showed little enhancement over physical sputtering in a pure argon atmosphere, the CH₄/H₂/Ar chemistry produced a strong increase of the IZO etch rate. The surface morphology of IZO films after etching in Ar and Ar/Cl₂ discharges is smooth, whereas that after etching in CH₄/H₂/Ar presents particle-like features resulting from the preferential desorption of In- And Ocontaining products. While the etch-induced damage in Ar and Ar/Cl₂ plasmas are constrained to the surface vicinity, etching in CH ₄/H₂/Ar produces a Zn-rich surface layer, whose thickness (~40 nm) is well-above the expected range of incident ions in the material (~1.5 nm). Auger electron spectroscopy measurements as a function of plasma exposure time indicate that diffusion of O, Zn and In atoms upon preferential desorption of volatile Oand In-containing reaction products is responsible for damage propagation.