Etching Characteristics and Mechanisms of TiO2 Thin Films in CF4 + Ar, Cl2 + Ar and HBr + Ar Inductively Coupled Plasmas

Abstract

The comparative study of etching characteristics and mechanisms for TiO2 thin films in CF4 + Ar, Cl2 + Ar and HBr + Ar inductively coupled plasmas was carried out. The etching rates for TiO2, Si and photoresist were measured as functions of gas mixing ratios at fixed gas pressure (10 mTorr), input power (800 W) and bias power (300 W). It was found that the maximum TiO2 etching rate of ~130 nm/min correspond to pure CF4 plasma while an increase in Ar fraction in a feed gas results in the monotonic non-linear decrease in the TiO2 etching rates in all three gas mixtures. Plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling supplied the data on the densities of plasma actives specie as well as on particle and energy fluxes to the etched surface. It was concluded that, under the given set of experimental conditions, the TiO2 etching kinetics in all gas systems correspond to the ion-assisted chemical reaction with a domination of the chemical etching pathway. It was found also that the differences in the absolute TiO2 etching rates correlate with the energy thresholds for TiO2 + F, Cl or Br reaction, and the reaction probabilities for F, Cl and Br atoms exhibit the different changes with the ion energy flux according to the volatility of corresponding etching products.