Formation of polymeric layer during silicon etching in CF2Cl2 plasma

Abstract

The reactive ion etching of silicon in a CF2Cl2 plasma was considered. Different kinetics of the etching process at energies of bombarding ions of 100 and 400eV were observed. The polymeric layer is formed in both cases. Compositions of polymeric layers were measured by X-ray photoelectron spectroscopy (XPS) to explain the kinetics of etching rates. Significant variations of composition of polymeric layers were observed. It was found that the variations of concentrations of free and reacted carbon and alternation of bonds type on the surface influence the etching rate. XPS measurements showed that C–CF and CF–CCl species form Teflon-like polymer in later stages of the etching process. The polymer formed suppresses the etching process at low ion energy. Energy of bombarding ions of 400eV is sufficient to destroy partially the polymer and to produce etching. A theoretical model was proposed to explain the kinetics of composition of polymeric layers.