Etching mechanisms of (In, Ga, Zn)O thin films in CF4/Ar/O2 inductively coupled plasma

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The authors investigated the etching characteristics and mechanisms of (In, Ga, Zn)O (IGZO) thin films in CF4/Ar/O2 inductively coupled plasmas. The etching rates of IGZO as well as the IGZO/SiO2 and IGZO/Al2O3 etching selectivities were measured as functions of O2 content in a feed gas (0%–50%) and gas pressure (p = 4–10 mTorr) at fixed input power (Winp = 700 W) and bias power (Wdc = 200 W). It was found that the IGZO etching rate decreases monotonically toward O2 rich plasma but exhibits a maximum under gas pressure conditions. The zero-dimensional plasma model with Langmuir probe diagnostics data provided the information on plasma parameters and densities of plasma active species. The model-based analysis shows the dominance of the ion-flux-limited etching regime at p ≥ 6 mTorr as well as the noticeable influence of CFx radicals on the overall etching kinetics.