A comparative study of CF4, Cl2 and HBr + Ar inductively coupled plasmas for dry etching applications

This work discusses the plasma characteristics and chemistry in CF4 + Ar, Cl2 + Ar and HBr + Ar gas systems in a comparative scale under one and the same operating condition. The investigation was carried out using the combination of plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling in the planar inductively coupled plasma reactor at constant gas pressure (1.33 Pa), input power (800 W) and bias power (300 W), but with variable (0-80%) Ar fraction in a feed gas. The study was focused on the parameters influencing the kinetics of ion-assisted chemical reaction and thus, determining the output characteristics of the etching process (etching rate, anisotropy). These parameters are the fluxes of F, Cl or Br atoms, ion bombardment energy, ion energy flux and neutral/charged species ratio. The differences between CF4 + Ar, Cl2 + Ar and HBr + Ar plasmas which seem to be important for the correct choice of the working gas for the particular etched material were discussed and explained in the framework of formation-decay kinetics of neutral and charged species.