ChemInform Abstract: The Role of Noble Gas Ion Bombardment in Etching Reactions

Abstract

Chemical etching of a solid involves the interaction of reactive species with a surface. Simultaneous exposure of the solid to low energy noble gas ion bombardment, such as occurs during plasma etching, influences this interaction to a large extent. A considerable enhancement or reduction of the etch rate may result. In this survey, we discuss some aspects of the role of ion bombardment in etch reactions with emphasis on the etch rate. The discussion starts with the well-known sputtering phenomena, which occur in the absence of incident reactive gas. The phenomena are used to compare various experimental data that have been obtained in reactive scattering studies, i.e. during simultaneous bombardment of silicon containing targets (Si, SiO 2 ) with noble gas ions and reactive gases (XeF 2 Cl 2 ). It will be argued that an important role of the ions in influencing the etch rate in the reactions observed is to promote three dimensional compound formation. This compound formation is associated with a surface binding energy for the various species formed. The values of these surface binding energies, which influence the etch-product ejection via a collision cascade-like process, determine whether an enhancement or reduction of the etch rate may be expected.