The Anisotropic Etching of Silicon in CF₄, CF₄ + H₂ and CF_4-XCL_X Plasma

Abstract

Anisotropic etching of silicon in fluorine atom rich plasmas are practically impossible under most plasma etching condition because of rapid spontaneous chemical reaction between and Si. The main goal is to achieve the anisotropy of etching using mixtures of gases with physical and chemical treatment; sidewall protection etching is predominate there, The Cl atoms, however, are substantially lager than the F atom and have much greater difficulty forming a volatile silicon chloride molecule in absence of ion bombardment because activation energy of chlorine is high than activation energy of fluorine. Cl etches Si quite well, when ion bombardment is added to chemical fluxes (halogen size effect).The ion bombardment causes not only the sputtering of material but also activated chemical processes such as polymerization, etching and makes condition to the intermixing between surface atom and atoms from the bulk.