Surface smoothing during plasma etching of Si in Cl2

Effects of initial roughness on the evolution of plasma-induced surface roughness have been investigated during Si etching in inductively coupled Cl2 plasmas, as a function of rf bias power or ion incident energy in the range Ei ≈ 20–500 eV. Experiments showed that smoothing of initially rough surfaces as well as non-roughening of initially planar surfaces can be achieved by plasma etching in the smoothing mode (at high Ei) with some threshold for the initial roughness, above which laterally extended crater-like features were observed to evolve during smoothing. Monte Carlo simulations of the surface feature evolution indicated that the smoothing/non-roughening is attributed primarily to reduced effects of the ion scattering or reflection from microscopically roughened feature surfaces on incidence.