Etching Kinetics and Mechanisms of SiC Thin Films in F-, Cl- and Br-Based Plasma Chemistries

The comparative study of SiC and SiO 2 etching kinetics as well as the evaluation of SiC etching mechanisms in CF 4 + Ar, Cl 2 + Ar and HBr + Ar gas mixtures in inductively coupled plasma reactor were carried out. For each binary gas system, the experiments (SiC and SiO 2 etching rates measurements, plasma diagnostic by Langmuir probes and optical spectroscopy) were conducted with variable fractional compositions of a feed gas at constant input power (700 W), bias power (300 W) and overall gas pressure (6 mTorr). The 0-dimensional (global) models for CF 4 + Ar, Cl 2 + Ar and HBr + Ar plasmas provided the information on the steady-state densities and fluxes for halogen atoms as well as on the ion energy flux to the treated surface. It was found that the transition toward Ar-rich plasmas in all investigated gas systems: (1) provides the non-monotonic (with a maximum at ~ 50–60% Ar) SiC etching rate; (2) leads to the monotonic decrease in both halogen atom density and flux; and (3) results in increasing both ion energy flux and effective probability for SiC + F, Cl or Br reactions. It was shown that absolute differences in effective reaction probabilities are in agreement with corresponding ion energy fluxes and reaction threshold energies.