On the Etching Characteristics and Mechanisms of HfO_2 Thin Films in CF_4/O_2/Ar and CHF_3/O_2/Ar Plasma for Nano-Devices

摘要

The study of etching characteristics and mechanisms for HfO_2 and Si in CF_4/O_2/Ar and CHF_3/O_2/Ar inductively-coupled plasmas was carried out. The etching rates of HfO_2 thin films as well as the HfO_2/Si etching selectivities were measured as functions of Ar content in a feed gas (0-50% Ar) at fixed fluorocarbon gas content (50%), gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). Plasma parameters as well as the differences in plasma chemistries for CF_4- and CHF_3-based plasmas were analyzed using Langmuir probe diagnostics and 0-dimensional plasma modeling. It was found that, in both gas systems, the non-monotonic (with a maximum at about 15-20% Ar) HfO_2 etching rate does not correlate with monotonic changes of F atom flux and ion energy flux. It was proposed that, under the given set of experimental conditions, the HfO_2 etching process is affected by the factors determining the formation and decomposition kinetics of the fluorocarbon polymer layer. These factor are the fluxes of CF_x (x = 1, 2) radicals, O atoms and H atoms.