ECR Plasma Etching with Heavy Halogen Ions

Abstract

It is shown that the ECR plasma, which contains heavy halogen ions and other light ions, is effective as a dry etching technique for fabrication of VLSI devices. The ion temperature, which is one of the most important parameters for etching fine features, is greatly reduced by using a Cl₂/He mixture gas and by controlling the pressure. By this method, strong anisotropic etching of poly-Si is realized with high selectivity to SiO₂. Hydrogen halide gases are suitable gases for the ECR plasma etching process, because they produce heavy halogen ions and protons. In particular, using HBr or HI gas produces a strong anisotropic feature with no micro-loading effects. The ion temperature of Br⁺ ions and I⁺ ions is 1.0∼1.1 eV, which is about half that of Cl⁺ ions.