A Parametric Study of the Etching of Silicon in SF₆Microwave Multipolar Plasmas: Interpretation of Etching Mechanisms

A parametric study of the etching of silicon has been performed in a Microwave Multipolar Plasma using an Electron Cyclotron Resonance excitation. The evolution of the anisotropy and etch rate is measured as a function of the SF 6 pressure, ion energy (<100 eV) and ion current density collected on the silicon wafers. For a given ion current density and ion energy, perfect anisotropy is obtained below a critical SF 6 pressure whereas the etch rate, independent of ion energy and current density, increases proportionally with the SF 6 pressure in the domain investigated. These results, corroborated by the mass spectrometry analysis of the reaction products are explained through the diffusion model recently proposed for plasma etching.